BIOTIN. I. 2-ALKYLTHIOPHANE-3,4-DICARBOXYLIC ACIDS

[CONTRIBUTION FROM THE LEDERLE LABORATORIES]

BIOTIN. I. 2-ALKYLTHIOPHANE-3,4-DICARBOXYLIC ACIDS

B. R. BAKER, MERLE V. QUERRY, S. R. SAFIR, AND SEYMOUR BERNSTEIN

Received July 29, 1946

Interest in the little known field of functional derivatives of thiophane has been given incentive by the elucidation of the structure of biotin, 2-(&carboxy- butyl)-5-ketoimidazolido[4,5, clthiophane, by duVigneaud and his collaborators (la). In the course of the structure proof of biotin, the diethyl ester of thiophane-3,4-dicarboxylic acid (lb) was synthesized and converted to derivatives of 3,4-diaminothiophane by the Curtius degradati0n.l

In this communication is described the preparation of 2-propyl- and 2-(7- phenoxypropyl) thiophane-3,4-dicarboxylic acids (XI) by general methods, the separation of some of the isomers, and their behavior in the Curtius degradation.

When butylideneacetonitrile (IIa) was condensed with ethyl thioglycolate (I) in benzene in the presence of sodium ethoxide, the sulfhydryl group added to the conjugated double bond and the intermediate thio ether underwent a Dieckmann cyclization to form 2-propyl-3-cyano-4-ketothiophane (IVa). This nitrile, characterized by its crystalline semicarbazone, was converted to 2-propyl-3- carbethoxy-4-ketothiophane (Va) via the imino ether. However, the keto ester (Va) was more conveniently prepared by the condensation of ethyl thioglycolate and ethyl 2-hexenoate (IIIa) in boiling benzene in the presence of sodium ethoxide. In this reaction either 2-propyl-3-carbethoxy-4-ketothiophane (Ya) or 2-propyl-4-keto-5-carbethoxythiophane (VIa) or a mixture of the two may be formed depending upon which may the intermediate thio ester cyclizes. Identity of the semicarbazones of the keto esters, Va, prepared from either the nitrile, IVa, or ethyl 2-hexenoate (IIIa) showed that ring closure had taken place mainly to the desired 2-propyl-3-carbethoxy-4-ketothiophane (Ta) .?

The keto esters, Va and Vb, were further characterized by treatment with dilute sulfuric acid, which readily decarbalkoxylated them to the 2-alkyl-4- thiophanones, VII.

By the action of liquid hydrogen cyanide on 2-propyl-3-carbethoxy-4-ketothiophane (Va) a cyanohydrin, VIIIa, was formed in excellent yield and was smoothly hydrolyzed with hydrochloric acid to a non-crystalline mixture of isomeric 2-propyl-4-hydroxythiophane-3 ,4-dicarboxylic acids (IXa). Distilla- tion in vacuo from either 85% phosphoric acid or potassium bisulfate effected dehydration to 2-propyldihydrothiophene-3 ,.l-dicarbosylic acid (Xa) mainly in the form of its anhydride. The double bond, the position of which was un-

1 A different isomer was obtained in a second synthesis (2). The stereochemical configuration of these two forms is now described in an accompanying communication.

After this work was completed Woodward and Eastman (3) showed that Dieckmann cyclization of methyl &(carbomethoxymethylthio)propionate a t high temperature gave a keto ester, V (R=H), while low temperature favored the formation of the keto ester, VI (R = H).

138

BIOTIN. I 139

known, w a readily reduced with sodium amalgam in dilute alkali a t 70-80" to a mixture of

COOR'

CH? + SH

I

I \

I I II- 0

/ E \S,

I V

0

kLR v [I

COKHNH2 I

isomeric 2-pr0pylthiophane-3~4-dicarboxylic acids (XIa). One

CH-CN COOR' CH-COOR'

CHR I I1 \

CH2 + CH--R I1

SH

I1 1 I11 I

-------I 3 /I 0

I 0

- +

CN COOH

HO ' COOR' HO ' COOH __3

VI11 Lx

COOH J.

COOH I

c-- Co""2 (1) CHIN, h (2) N2H4 uIooH

\ S ,,-R

XI1 X I x

i "COO CaHs

I r' ,,,,I-ICOOC8H6 t ( 1 ) (2) soc12 NaNI

(3) CzHoOH

XI11

a series R = 72-C3H7-, R ' = CaH6- b series R = CBHLO-(CHa)a-, R' = CH3-

crystalline isomer, m.p. 156-157", was easily isolated, due to its insolubility in benzene.

The crystalline isomer was shown to have its carboxyl groups related by a

140 BAKER, QUERRY, SAFIR, AND BERXSTEIN

trans configuration as (a) i t was stable to heat at 250"; (b) it gave a diacid chloride with thionyl chloride; (c) i t formed a mixed anhydride when treated with acetyl chloride and the same acid was regenerated on hydrolysis; (d) i t was converted with boiling propionic anhydride to a mixture of isomeric cis anhydrides from which a crystalline cis diacid, m.p. 130-131", could be isolated. The carboxyl groups of the latter have a cis configuration as (a) acetyl chloride or thionyl chloride gave an inner anhydride which regenerated the same acid on treatment with water; (b) i t evolved water a t 150" to form an anhydride; (c) it formed a cyclic imide. Thus, two of the possible four racemic modifications of 2-propylthiophane-3,4-dicarboxylic acid (XIa) have been characterized, one cis and one trans.

The preparation of 2-(yphenoxypropyl) thiophane-3,4-carboxylic acid (XIb) followed the same reactions except that dehydration of the hydroxy acid, IXb, was accomplished by means of boiling acetic anhydride. Again a trans diacid, m.p. 183", was readily separated and mas convertible to the cis anhydrides with boiling propionic anhydride. One of the cis anhydrides, m.p. 105", was isolated and hydrolyzed to a cis diacid, m.p. 158". The cis and trans configurations were established in the same manner as for the 2-propylthiophane-3 ,4-dicarboxylic acids (XIa).

2-(y-Phenoxypropyl) thiophane-3,4-trans-dicarboxylic acid (XIb) was prepared by a second method. yPhenoxypropylmalonic acid (XIV) on chlorination with sulfuryl chloride followed by decarboxylation gave a mixture of 5-phenoxyvaleric acid, 5-chlorophenoxyvaleric acid, 2-chloro-5-phenoxyvaleric acid (XVI), and 2-chloro-5-chlorophenoxyvaleric acid. The mixture was treated with sodium hydrosulfide, then esterified. Cold alkaline extraction of an ethereal solution of the esters gave on acidification a mixture of methyl 2-mercapto-5-phenoxyvalerate (XVIII) and methyl 2-mercapto-5-chlorophenoxyvalerate, which mere separated by fractional distillation, in yields of 14% and 8% respectively based on the original malonic acid, XIV.

Condensation of the methyl 2-mercapto-5-phenoxyvalerate (XTTIII) with methyl acrylate in the presence of piperidine followed by Dieckmann cyclization with sodium methoxide in ether proceeded smoothly to 2-(yphenoxypropy1)-3- keto-4-carbomethoxythiophane (XIX). In this case the Dieckmann reaction can take place only as indicated, as formation of the isomeric 2-(y-phenoxypropyl)-2-carbomethoxy-3-ketothiophane would involve the elimination of methanol between a carbomethoxy group and a tertiary hydrogen, which takes place only with difficulty (4).

The keto ester, XIX,3 was converted to 2-(r-phenoxypropyl)thiophane-3,4- trans-dicarboxylic acid by the same series of reactions used for the isomeric 2-(y-phenoxypropyl)-3-carbomethoxy-4-ketothiophane (Vb). The crystalline trans acids obtained by both methods were identical, thus offering additional proof of the direction of ring closure in the preparation of the keto ester, Vb. The yield of crystalline trans diacid, m.p. 183", obtained on sodium amalgam

* After this work was completed Cheney and Piening (20) published 8 superior method for the preparation of the corresponding keto ethyl ester.

BIOTIN. I 141

reduction of XXII, was 29%. The isomers in the filtrate were esterified, treated with sodium methoxide to invert cis isomers to trans and then hydrolyzed. An- other 20% of the same crystalline trans acid was obtained. The filtrate from this material presumably contained a second trans isomer which did not crystallize. It was boiled with propionic anhydride in order to invert it back to the cis isomers, then esterified and reinverted back to the trans isomers by treatment

COOH COOH I

SOzclr + CeHaO(CH2)3CCOOH ---+ I

CaHsO (CHJSCHCOOH I

XIV

COOH

c1 xv

COOH

COOH 1

COOH

XXII XIb

with sodium methoxide. crystalline trans isomer was ~ b t a i n e d . ~

4 Since completion of this work, Grussner, Bourguin, and Schnider (21) have described the synthesis of the dimethyl ester of 2-(8-methoxybutyl)thiophane-3,4-dicarboxylic acid by a somewhat similar method. However, they did not isolate and characterize any of the isomers of the diacid.

In this way an additional 7%, a total of 56%) of the

142 BAKER, QUERRY, SAFIR, AND BERNSTEIN

The trans dicarboxylic acids, XI, were converted via the methyl esters to the trans dihydrazides, XII, which were in turn degraded by the Curtius method to the trand diurethans. The 2-(-y-phenoxypropyl)-3,4-trans-dicarbethoxylamino- thiophane (XIIIb) was prepared more easily and in better yield by treating the diacid chloride of the trans dicarboxylic acid, XI, with sodium azide in dilute acetone (6). However, when the esters of 2-propyl- or 2-(y-phenoxypropyl)- thiophane-3 , 4-cis-dicarboxylic acids were treated with hydrazine under a variety of conditions, no cis dihydrazides6 could be isolated, but inversion to the trans dihydrazides, XII , took place. Similarly when the imide (XXIII) or cyclic hydrazide (XXIV) of 2-propylthiophane-3 ) 4-cis-dicarboxylic acid was treated with hydrazine, the trans dihydrazide, XIIa, was formed. Apparently hydrazine is sufficiently alkaline to cause rearrangement of a cis diester or cis dihydrazide to the more stable trans configuration by enolization of the carbonyl groups in the same manner as sodium niethoxide.

NH NH-NH

CO"", co co I I / \ co co

O C & I , ----$ b C &

CONHNHi t-

cis

X X I I I

trans

XIIa

cis

XXIV

In view of these results it is highly probable that the 3,4-diaminothiophane of duvigneaud (lb) has a trans configuration. The diacid chloride-sodium azide procedure could not be applied to the cis diacids, as they were, as in the case of succinic acid (€9, converted to the anhydrides on treatment with thionyl chloride or oxalyl chloride. The method used for preparing succinyl chloride by long treatment of the acid with phosphorus pentachloride (9) was unsuccessful in the thiophane series as only dark tars were formed.

The Schmidt (10) hydrazoic acid degradation of either the cis or trans diacids failed to take place and no nitrogen was evolved. The thio ether linkage /3 to the carboxyl groups in the thiophane series may have an inhibitory effect on the course of the reaction.

It had been planned to hydrolyze simultaneously the urethan and phenoxy groups of 2-(yphenoxypropyl)-3 ,4-trans-dicarbethoxyaminothiophane (XIIIb) with 48% hydrobromic acid to form 2-(y-bromopropyl)-3,4-trans-diaminothiophane dihydrobromide (XXV). By blocking the amine groups followed by treatment with malonic ester, the side chain would have been completed to valeric acid.

6 Jones and Wallis (5) have demonstrated that the Curtius rearrangement takes place with retention of configuration. See also reference 7.

6 Buchman, Reims, Skei, and Schlatter (7) observed tha t in the cyclobutane series either a cis or trans dihydrazide of the 1,2-dicarboxylic acid could be prepared from the corresponding cis or trans diester.

BIOTIN. I 143

X I I I b

I xxv

XXVIII

Unfortunately, the preparation of 2-bromopropylthiophanes by this method was unsuccessful as ring closure to a sulfonium bromide took place readily. The ease with which this type of ring closure takes place was demonstrated by hydrolysis of 2- (y-phenoxypropyl) thi0phane-3~4-trans-dicarboxylic acid (XIb) . When the acid was refluxed with 48% hydrobromic acid for only twenty minutes a 5970 yield of the water-soluble 1 , 2-trimethylene-3,4-dicarboxythiophanium bromide (XXVIII)' was obtained.

The hydrolysis of the phenoxy urethan, XIIIb, appeared to give a mixture of 1 ,2-trimethylene-3,4-trans-diaminothiophanium bromide dihydrobromide (XXVII) and 3-aminopiperidino[3,2, blthiophane dihydrobromide (XXVI). The latter could be separated as its water-insoluble dibenzoate and the presence of the former was assumed by analogy with the hydrolysis of XIb as well as by the analytical data. The presence of the bromopropyldiamine, XXV, in the mixture could not be detected.

Acknowledgments. The authors wish to express their thanks to Dr. Y. SubbaRow for his helpful suggestions and to Messrs Louis Brancone and Louis Dorfman for the microanalyses.

EXPERIMENTAL

Butylideneacetonitrile (11). A mixture of 75 g. of butylidenecyanoacetic acid ( l l) , 75 cc. of quinoline, and 0.8 g. of copper oxide was heated in a 250 cc. modified Claisen flask at 125-140" (bath) for twenty-five minutes, when the evolution of carbon dioxide had practically ceased. The product was distilled out of the reaction mixture a t 15 mm. until the vapors reached 110". Redistillation gave in four runs 23.5-24.3 g. (4648%) of a water- white liquid, b.p. 57-59" (12 mm.).

Letch and Linstead (11) decarboxylated this acid by heating its mixture with sand, and

7 Bennet and Hock (22) have observed a similar type of ring closure on hydrobromic The product was l-(t-hydroxybutyl) - acid hydrolysis of bis-(6-benzyloxybutyl) sulfide.

thiophanium bromide and no bis-(t-bromobutyl) sulfide could be isolated.


reported that the yield vaned widely and never exceeded 40%. They record the boiling point 57-58' (11 mm.).

Ethyl thioglycolate. A mixture of 150 g. of thioglycolic acid, 200 cc. of absolute ethanol, 300 cc. of benzene, and 20 cc. of concentrated sulfuric acid was refluxed for sixteen hours under a Soxhlet apparatus containing about 90 g. of anhydrous magnesium sulfate in the thimble. The cooled mixture was washed twice with water, solvent removed through a Vigreux column, and the residue distilled; colorless liquid, b.p. 63' (20 mm.); yield, 174 g. (89yo). If water is not continuously removed, as in the ordinary esterification, the yield is about 60%.

The methyl ester may be prepared similarly using methanol and chloroform; yield,

This method (12) is used routinely for all esterifications of this type and has been found to give invariably higher yields than can be obtained without continuous drying.

Methyl 8-hezenoate. 2-Hexenoic acid was prepared from n-butyraldehyde and malonic acid according to Goldberg and Linstead (13), except that a 25% excess of aldehyde was employed and the reaction was allowed to proceed for seventeen hours a t room temperature; yield, 76% of product, m.p. 32'.

From 278 g. of 5-hexenoic acid, 300 cc. of methanol, 300 cc. of chloroform, and 30 cc. of concentrated sulfuric acid, using 90 g. of anhydrous magnesium sulfate for continuous drying as described above, was obtained 305 g. (98%) of the ester, b.p. 56-58' (13 mm.).

The ethyl ester was prepared in the same manner using ethanol and benzene, b.p. 72-73' (15 mm.); yield, 94%.

The esterification reaction of 2-hexenoic acid has been found by Thomas and Sudborough (14) to be sensitive t o water and they have shown that at equilibrium only 15% of the methyl ester is formed. The only esterification of this acid reported in the literature is that of Kon, Linstead, and MacLennan (15) who treated the silver salt with ethyl iodide. They record the b.p. 80" (22 mm.).

Methyl 6-phenozy-2-hezenoate ( I I Ib) . From 46 g. of 6-phenoxy-2-hexenoic acid (23), 5 cc. of concentrated sulfuric acid, 100 cc. of methanol, and 100 cc. of chloroform was obtained 42 g. (86%) of the ester by the continuous drying procedure; b.p. 135-138" (1 mm.).

7742%.

Anal . Calc'd for C13H1603: C, 70.8; H, 7.3. Found: C, 70.4; H, 6.8,

2-Propyl-S-cyano-~-ketothiophane ( I V a ) . To the dry sodium ethoxide from 8.3 g. of sodium and 150 cc. of absolute ethanol, obtained by evaporating the solution to dryness in vacuo, was added in a nitrogen atmosphere a solution of 42.5 g. of ethyl thioglycolate in 60 cc. of benzene. After most of the sodium ethylate had dissolved, a solution of 37.2 g. of butylideneacetonitrile in 30 cc. of benzene was added. The solution was refluxed for one hour on the steam-bath, during which the sodium salt of the product separated. The cooled mixture was extracted with ice-water, the extracts immediately acidified, and the oil which separated aas extracted with benzene. Distillation gave 31 g. (52%) of a yellow oil, b.p. 125-127' (1 mm.), n f 1.5118.

Anal.

The semicarbazone formed white crystals from dilute alcohol, m.p. 175-176'. Anal.

2-Propyl-8-carbethoxy-4-ketothiophane (Vu).

Calc'd for CSH11NOS: C, 56.7; H, 6.5; K, 8.3. Found: C, 56.4; H, 6.3; N, 7.8.

Calc'd for C ~ H I A N ~ O S : C, 47.8; H, 6.2; N, 24.8. Found: C, 48.1; H, 6.1; N, 25.2.

A. A mixture of 15 g. of 2-propyl-3-cyano4 ketothiophane (IVa) in 7 cc. of absolute alcohol was treated with dry hydrogen chloride until 3.3 g. had been absorbed. After two days in a stoppered flask, the mixture was diluted with water and benzene and stirred for twenty hours. The separated benzene layer was extracted twice with iced 5% sodium hydroxide and the extracts immediately acidified with acetic acid. The oily layer was taken up in benzene, then distilled, b.p. 108-111" (1 mm.), n: 1.4927; yield, 9 g. (47%).

BIOTIN. I 145

Anal. Calc'd for Cl~HlsOsS: C, 55.6; H, 7.4. Found: C, 55.4; H, 6.8.

The semicarbazone slowly formed in dilute alcohol and was purified by recrystallization

Anal. Calc'd for CuHlpNa03S: C, 48.3; H, 7.0; N, 15.4. Found: C, 48.3; H, 6.8; N, 15.0.

B . This ester was more conveniently prepared by refluxing for three hours a solution of sodium ethoxide (from 23 g. of sodium), 109 g. of ethyl thioglycolate, and 132 g. of ethyl 2-hexenoate in 300 cc. of benzene according to the procedure described for 2-propyl-3- cyano-4-ketothiophane (IVa); light yellow oil, b.p. 110-113° (1 mm.); yield, 130 g. (66%).

The semicarbazone formed white crystals from dilute alcohol, m.p. 162-164", alone or when mixed with semicarbazone described in part A .

The corresponding methyl ester was prepared analogously using the sodium methoxide from 57 g. of sodium, 227 g. of methyl thioglycolate and 297 g. of methyl 2-hexenoate; yield, 223 g. (52%) of oil, b.p. 112-114" (3 mm.), n: 1.4963.

from the same solvents, white crystals, m.p. 163-165'.

Anal. Calc'd for CsH1,03S: C, 53.4; H, 7.0. Found: C, 53.2; H, 6.6.

The semicarbazone melted at 156-158'. 2-(y-Phenoxypropyl) -S-carbomethoxy-4-ketothiophane (Vb). From 23 g. of sodium

methoxide (Mathieson Alkali Works), 32 g. of methyl thioglycolate, 63.4 g. of methyl 6-phenoxy-2-hexenoate (IIIb), and 150 cc. of benzene was obtained 60.5 g. (72%) of a non-distilled alkali-soluble fraction in the same manner as described for the corresponding propyl compound. This was sufficiently pure for the next step, but could be further purified by evaporative distillation a t a pressure of 1 micron and bath temperature of 110" as a light yellow oil with 90% recovery.

Anal. Calc'd for C l ~ H l ~ O ~ S : C, 61.3; H, 6.2. Found: C, 61.9; H, 6.0.

The semicarbazone formed white crystals from methanol, m.p. 143-144.5'. Anal. Calc'd for C1eHZ1N30(: C, 54.7; H, 6.0; N, 11.9.

Found: C, 54.9; H, 5.8; N, 11.5, 11.5. The keto ester could not be distilled a t 1 mm. as i t decomposed t o give 2-(?-phenoxy-

propyl)-4-ketothiophane (VIIb) and a large amount of tar. 2-Propyl-4-ketothiophane (VZZa). A mixture of 33.5 g. of 2-propyl-3-carbethoxy-4-

ketothiophane (Va), 40 cc. of acetic acid, 21 cc. of concentrated sulfuric acid, and 150 cc. of water was refluxed for six hours. The cooled mixture was extracted with benzene and the extract washed with 10% sodium hydroxide. Solvent was removed through a Vigreux column and the residue distilled; colorless liquid, b.p. 98" (12 mm.); yield, 17.8 g. (80%).

Anal. Calc'd for C7HI20S: C, 58.3; H, 8.3. Found: C, 58.5; H, 8.0.

The semicarbazone crystallized from dilute alcohol in the form of white plates, m.p. 161-162'.

Anal.

d-(y-Pheno.zypropy1)-4-ketothiophane (VIZb). This keto ester was prepared from 2-(?- phenoxypropyl) -3-carbomethoxy-4-ketothiophane in the same manner as described for the ketone above. The product was purified by distillation at 1 mm. in a two-bulbed flask follqwed by recrystallization from methanol or petroleum ether (b.p. 30-60') ; white crystals, m.p. 59-61'.

Calc'd for CaHlsNaOS: C, 47.7; H, 7.5; N, 20.9. Found: C, 47.7; H, 6.9; N, 20.9.

Anal. Calc'd for C1sHle02S: C, 66.2; H, 6.8. Found: C, 65.9; H, 6.3.

The semicarbazone formed white crystals from alcohol, m.p. 159-160'. Anal. Calc'd for ClrHlsNsOnS: C, 57.3; H , 6.5; N , 14.3.

Found: C, 57.1; H, 6.9; S, 14.0.


~-Propyl-3-carbethoxy-~-hydroxy-~-cyanothio~hane (VIIIa). It was not necessary to use anhydrous hydrogen cyanide in this reaction and therefore its method of preparation could be greatly simplified. Fifty per cent by volume sulfuric acid was dropped on potassium cyanide crystals, the vapors led to a vertical tube cooled in an ice-bath and the liquid caught in an ice-cooled graduated cylinder; yield about 70%.

To 30 cc. of liquid hydrogen cyanide and 0.3 cc. of 50% potassium hydroxide cooled in an ice-bath was added 100 g. of 2-propyl-3-carbethoxy-4-ketothiophane (Va) in portions, maintaining the temperature a t 10-15". After fifteen hours a t 0" the mixture was acidified with 0.6 cc. of 85% phosphoric acid. The excess hydrogen cyanide was removed in lracuo through an aqueous alkali trap and the residue distilled; yellow oil, b.p. 142-145" (1 mm.), nz 1.4911; yield, 107 g. (95%).

Anal. Calc'd for C ~ ~ H ~ T N O ~ S : C, 54.3; H, 7.0; N, 5.8. Found: C, 54.5; H, 6.6; N, 5.7.

The methyl ester was prepared in the same manner in 94% yield, b.p. 139-142" (1 mm.), n: 1.4968.

Anal.

If the excess acid is washed out of the cyanohydrin, then it dissociates back into i ts starting components on distillation.

2-Propyl-4-hydro~ythiophane-3~~-dicarboxylic acid (IXa). A mixture of 50 g. of 2-propyl- 3-carbetho:,y4-hydror:y-4-cyanothiophane (VIIIa), 100 cc. of acetic acid, and 250 cc. of concentrated hydrochloric acid was refluxed for twenty hours. The solution was diluted to 1 liter with water and clarified with Norit. After saturation with salt, the solution was extracted with three 250-cc. portions of ethyl acetate, the extracts dried with magnesium sulfate, then evaporated to dryness in vacuo. The product, a mixture of stereoisomers, was a gum; yield, 46.6 g. (97%).

Calc'd for C Q I I ~ ~ O & : C, 46.2; H, 6.0. Found: C, 46.6; H, 5.4.

Calc'd for CloHI6NO&3: C, 52.3; H, 6.2; N, 6.1. Found: C, 52.7; H, 6.3; N, 6.2.

Anal.

In later runs it was found advantageous to hydrolyze the crude cyanohydrin, VIIa, prior to distillation. The over-all yield from the keto ester was 90%.

Anal. Found: C, 46.0; H, 5.5. The dimethyl ester was formed in 74% yield by the usual continuous drying method with

methanol, chloroform, sulfuric acid, and anhydrous magnesium sulfate; light yellow oil, b.p. 135-138" (1 mm.), n: 1.4917.

Anal. Calc'd for CIIHl~OsS: C , 50.3; H, 6.9. Found: C, 50.3; H, 6.3.

&-Propyl-3-carbomethoxy-4-cyanodihydrothiophene. To a solution of 6 g. of 2-propyl-3- carbomethoxy4-hydroxy4-cyanothiophane in 10 cc. of dry pyridine was added 4.7 CC. of phosphorus oxychloride. The temperature was maintained a t 38-43" by occasional cooling until the temperature began to drop. After twenty hours at room temperature, the mixture was poured on iced hydrochloric acid and the oil extracted with benzene. The extract was washed with dilute hydrochloric acid and solvent removed. The residue distilled as a light yellow oil, b.p. 128-132' (1 mm.), n: 1.5225; yield, 3.9 g. (71%).

Anal. Calc'd for Cl~H13NOrS: C, 56.8; H, 6.2; N, 6.6. Found: C, 56.7; H, 5.6; N, 6.5.

The use of thionyl chloride in this dehydration (16) gave a product contaminated with much free sulfur and difficulty with emulsions was encountered in the work-up. The yield was about the same.

To a mixture of 60.5 g. of 2-(y-phenoxypropyl)-3-carbomethoxy-4-ketothiophane (Vb) and 35 cc. of liquid hydrogen cyanide cooled in an ice-bath was added 0.5 cc. of 50% potassium hydroxide. The mixture soon became homogeneous on swirling. After twenty-three hours a t &5", the mixture was acidified with 2 cc. of 85% phosphoric acid and the excess hydrogen cyanide removed in vacuo. The residual cyanohydrin was refluxed with 180 cc. of acetic acid, 450

&-(y-Phenoxypropyl)-~-hydroxyth~o~hane-3,~-dicarboxylic acid (IXb) .

BIOTIN. I 147

cc. of water, and 63 cc. of concentrated sulfuric acid for twelve hours, then diluted t o 2 1. with water. The oil was taken up in ethyl acetate and extracted with aqueous sodium bicarbonate solution. The ethyl acetate layer was washed with water and evaporated. The residue consisted of 10.5 g. (22%) of crude 2-(~-phenoxypropyl) -4-ketothiophane (VIIb), which was purified as previously described.

The sodium bicarbonate solution of acidic material was acidified, the oil extracted with ethyl acetate, and the latter washed twice with water containing a little salt.8 Evaporation of the ethyl acetate in vacuo gave 40 g. (60%) of product as a gummy mixture of stereoisomers which was used in the next step without further purification.

One of the isomers crystallized when a benzene solution of the mixture was allowed t o stand. It was purified by recrystallization from ethylene dichloride-acetone, then dilute acetic acid, white crystals, m.p. 200-202' dec.

Anal. Calc'd for ClsHlaOeS: C, 55.2; H, 5.5. Found: C, 55.2; H, 5.1.

When the cyanohydrin, VIIIb, was hydrolyzed with hydrochloric acid in acetic acid in the same manner as described for 2-propyl-3-carbethoxy4-hydroxy~-cyanothiophane (VIIIa), no product could be isolated except small amounts of phenol.

i?-PropyEdihydrothiophene-S,8-dicarboxylic acid ( X a ) and anhydride. A mixture of 19 g. of 2-propyl4-hydroxythiophane-3,4-dicarboxylic acid (IXa) and 0.1 cc. of 85% phosphoric acid was distilled a t 2-8 mm. and a bath temperature of 190-210". Redistillation gave 11.1 g. of an oil, b.p. 125-145' (1 mm.). Analyses indicated a mixture of the acid and anhydride. About the same results were obtained when 1 g. of potassium bisulfate was substituted for the phosphoric acid.

A mixture of 9.5 g. of the above distillate, 2 cc. of concentrated sulfuric acid, 40 cc. of methanol, and 60 cc. of chloroform was refluxed overnight with continuous drying in the usual manner. The 2-propyl-3,4-dicarbomethoxydihydrothiophene was obtained as an oil, b.p. 123-125' (1 mm.), n: 1.5018; yield, 8.4 g. (72%).

Anal. Calc'd for C,,H,aOS: C, 54.2; H, 6.6. Found: C, 54.2; H, 5.8.

A crystalline acid, m.p. 150-152', was obtained by treatment of the pyrolysis distillate

Anal. Calc'd for C O H ~ ~ O & : C, 50.0; H, 5.6. Found: C, 50.4; H, 5.4.

7-Phenozypropylmalonic acid ( X I V ) . This acid, prepared by methods described in the literature (17), has been reported as melting indefinitely between 70" and 100". This has been found to be due t o water of crystallization. The anhydrous material can be obtained by refluxing its solution in benzene, with or without the addition of ethyl acetate t o aid solubility, under a constant water separator until no more water is removed. On cooling, the solution deposits crystals of the anhydrous acid, m.p. 113-114' (20).

with water followed by crystallization from benzene.

Anal.

Methyl 2-mercapto-6-phenoxyvalerate (XVII I ) .

Calc'd for C12Hl406: C, 60.4; H, 5.9. Found: C, 60.2; H, 5.5.

To a refluxing solution of 160 g. of m h y - drous 7-phenoxypropylmalonic acid (XIV) in 640 cc. of chloroform was added dropwise over a period of twenty minutes 57 cc. of sulfuryl chloride. After being refluxed for ninety minutes more, the solution was evaporated t o dryness in vacuo. The residue waa heated with 1.6 g. of copper oxide at 145-160" until carbon dioxide evolution was complete which required twenty-five minutes.

The cooled residue was dissolved in 400 cc. of water containing 37 g. of anhydrous sodium carbonate and added to a solution of 54 g. of sodium hydroxide in 280 cc. of water saturated with hydrogen sulfide. After being heated on the steam-bath for ninety minutes, the solution was poured into a mixture of ice and 200 cc. of concentrated hydrochloric acid. The -~ ~~

8 I t is necessary to remove inorganic acids from the crude hydroxy acid, as traces cause acetylation instead of dehydration by acetic anhydride in the next step.


viscous oil was extracted with two 200-cc. portions of chloroform. The extracts were diluted with 200 cc. of methanol and 5 cc. of concentrated sulfuric acid, then refluxed for about fifteen hours under a Soxhlet apparatus containing anhydrous magnesium sulfate in the thimble. The solution, concentrated to turbidity in vacuo, was diluted with 500 cc. of ice-water and the esters extracted with ether. The latter was extracted with two 500-cc. portions of iced 3% sodium hydroxide and the extracts immediately run into iced hydrochloric acid. The mercaptans were extracted with benzene, washed with aqueous sodium bicarbonate and water, then the solvent was evaporated. The residue was fractionated through a Widmer column. The product (XVIII) was obtained as a colorless oil, b.p. 138-142' (1 mm.); yield, 22 g. (14%).

Anal. Calc'd for C ~ ~ H t 6 0 ~ S : C, 59.9; H, 6.7. Found: C , 59.7; H, 7.1.

The second fraction, b.p. 155-158" (1 mm.), consisted of 15 g. (8%) of methyl 2-mercapto-

Anal. Calc'd for C12H1&103S: C, 52.3; H, 5.5. Found: C, 52.3; H, 5.6.

A large number of variations of the halogenation were tried without increasing the yield. Bromine gave about the same yields as sulfuryl chloride.

Z-(y-Phenoxypropyl)-3-keto-~-carbomethoxythiophane ( X I X ) . To a mixture of 25.3 g. of methyl 2-mercapto-5-phenoxyvalerate (XVIII) and 0.2 cc. of piperidine was added 13 cc. of methyl acrylate, in portions with ice cooling, so that the temperature was 40-45". After five hours at room temperature, the mixture was dissolved in 150 cc. of dry ether and added to the dry sodium methoxide obtained by evaporating t o dryness in vacuo a solution of 2 g. of sodium in methanol. The sodium methoxide rapidly dissolved on swirling. The solution, after sixteen hours a t room temperature protected from moisture, was extracted three times with ice-water, the extracts being immediately run into iced hydrochloric acid. The oil was extracted with benzene, washed with aqueous sodium bicarbonate and water. Removal of the solvent in vacuo left the keto ester as a yellow-orange oil; yield, 22.7 g. (73%). The keto ester gave a purple color with alcoholic ferric chloride.

5-chlorophenoxyvalerate.

Anal. Calc'd for ClaH1804S: C, 61.3; H, 6.2. Found: C, 61.0; H, 6.5.

The semicarbazone was prepared in dilute methanol and recrystallized from aqueous

Anal. Calc'd for CleH21NsO~: C, 54.7; H, 6.0; N, 11.9. Found: C, 55.0; H, 6.7; K, 11.8.

8-(y-Chlorophenoxypropyl)-J-keto-~-carbomethoxythiophane. Prepared from methyl 2-mercapto-5-chlorophenoxyvalerate in the same manner as described for XIX, it was a n orange oil. The semicarbazone formed white crystals, m.p. 181-182", when recrystallized from dilute acetone.

Anal. Cslc'd for Cl~H~oClN30aS: C, 50.3; H, 5.2; N, 10.9. Found: C, 50.4; H, 5.6; K, 10.3.

2-(y-Phenoxypropyl) -3-hydroxythiophane-3, Q-dicarboxylic acid ( X X I ) . 2-(y-Phenoxy- propyl)-3-keto-4-carbomethoxythiophane (XIX) was converted t o the cyanohydrin and hydrolyzed with 20% sulfuric acid containing no acetic acid in the same manner as for the isomeric hydroxy acid, IXb. The mixture of isomers, obtained in 71% yield, did not crystallize.

Anal. Calc'd for C15H180eS: C, 55.2; H, 5.5. Found: C, 55.0; H, 5.6.

The intermediate cyanohydrin, XX, was also analyzed. Ana2. Calc'd for ClaHl&OaS: N, 4.4. Found: N, 3.9. b-(y-Phenoxypropyl)dihydro~hiophene-3,~-d~carboxylic acid. Preparation of Xb. A

mixture of 67 g . of 2-(y-phenoxypropyl) -4-hydroxythiophane-3,4-dicarboxylic acid isomers (IXb) and 330 cc. of acetic anhydride was refluxed for two hours. Most of the acetic anhydride was removed i n vacuo and the residue heated on the steam-bath with 900 cc. of water

acetone; urhite crystals, m.p. 160-161".

BIOTIN. I 149

for twenty minutes with occasional shaking. The oily acid was extracted with ethyl acetate, washed with dilute hydrochloric acid, and extracted in turn with aqueous sodium bicarbonate. Acidification gave an oil which was extracted with ethyl acetate. The extracts, dried with anhydrous sodium sulfate and clarified with Norit, were evaporated in vacuo to give 54 g. (85%) of an amber gum.

One of the isomers was obtained crystalline from benzene and was purified by recrystallization from the same solvent, white crystals, m.p. 133-136".

-4naE.

Preparation of X X I I .

Calc'd for C15Hl,0jS: C, 58.4; H, 5.2. Found: C. 58.6; H, 4.7.

From 23.1 g. of 2-(r-phenoxypropyl)-3-hydroxythiophane-3,4- dicarboxylic acid (XXI) and 120 cc. of acetic anhydride in the same manner as above was obtained 16.8 g. (77%) of an oily, somewhat impure product satisfactory for the next step.

A n d . Calc'd for C1jHl6O5S: C, 58.4; H, 5.2. Found: C, 57.8; H, 5.8.

2-Propylthiophane-J,~-trans-dicarboxylic acid ( X I a ) . A mixture of 10 g. of 2-propyldihydrothiophene-3,4-dicarboxylic acid (Xa) and its anhydride was warmed with 42 cc. of 10% sodium hydroxide and 55 cc. of water until solution was complete. The solution was stirred with 150 g. of 2% sodium amalgam at a bath temperature of 70-75" for two hours. The solution, decanted from the mercury, was acidified and the oil extracted with chloroform. The solvent was evaporated and the residue crystallized from benzene-heptane at 0'. The solid was collected on a filter and washed with benzene; yield, 2.9 g. (26%), m.p. 148-153'. For analysis a sample was purified by recrystallization from benzene containing a little acetone, white crystals, m.p. 156-157" which evolve no gas up to 250".

Anal. Calc'd for C8H1104S: C, 49.5; H, 6.4. Found: C, 49.6,49.8; H, 5.9, 5.9.

X-(~-Phenoxypropyl)thiophane-J,~-trans-dicarbozylic acid ( X I b ) . A . A solution of 54 g. of 2-(~-ph~noxypropyl)dihydrothiophene-3,4-dicarboxylic acid (Xb) in 350 cc. of water containing 15 g. of sodium hydroxide was stirred with 540 g. of 2% sodium amalgam in the same manner as described for the corresponding propyl compound, XIa, except that ethyl acetate was used for extraction. The crystalline trans acid was obtained when the mixture of isomers was triturated n-ith benzene, yield, 16.6 g. (31%), m.p. 169-175'. Recrystalliza- tion from acetone-ethylene dichloride gave white crystals, m.p. 182-183'.

A n d .

B . A solution of 16.8 g. of 2-(~-phenoxypropyl)dihydrothiophene-3,4-dicarboxylic acid (XXII) in dilute alkali was reduced with sodium amalgam in the same manner as A : yield, 4.9 g. (29%), m.p. 175-178'. A mixed m.p. with preparation A was 179-181'.

The benzene filtrate (about 100 cc.) was diluted with 50 cc. of absolute ethanol and 1 cc. of concentrated sulfuric acid and refluxed for fifteen hours under a Soxhlet apparatus containing anhydrous magnesium sulfate in the thimble. The solution was washed with water and evaporated in z'acuo. The residual diester was refluxed with 50 cc. of 1% methanolic sodium methoxide for two hours, then diluted with 10 g. of potassium hydroxide in 100 cc. of water and refluxed three hours more. Most of the methanol was evaporated, the solution diluted with water, acidified, and extracted with ethyl acetate. The ethyl acetate extract was worked up in the same manner as above. An additional 3.4 g. (20%) of trans diacid, m.p. 172-17S0 was obtained.

The benzene filtrate was evaporated. The residue consisted of 7 g. of an oil which was prohably mainly the second trans isomer. It was refluxed with 35 cc. of propionic anhydride for t,wo hours and the excess anhydride removed in vacuo. The residue was converted t o the dimethyl ester by the previously described continuous drying method. The dimethyl ester was then distilled in a two-bulbed distilling flask at 1 mm., b.p. 180-220". The dimethyl ester was rearranged and hydrolyzed t o the trans acids as above. Crystallization from benzene gave 1.2 g. (7%) of trans acid, m.p. 175-180". A mixed m.p. with preparation A was 178-181".

Calc'd for C l ~ H l ~ O ~ S : C, 58.1; H, 5.8. Found: C, 58.0; H, 5.5.

A mixture with preparation A melted a t 175-180'.


Thus, the total yield of one crystalline trans isomer in this reduction was 56%. I-Propylthiophane-S,4-cis-dicarboxylic acid (XZu). A solution of 1.07 g. of the corre-

sponding crystalline trans acid in 5 cc. of propionic anhydride was refluxed for two hours, then the excesa anhydride was distilled in vucuo. The residue was warmed with 10% aqueous sodium hydroxide until solution was complete. The solution, acidified and saturated with salt, was extracted with ethyl acetate. Removal of the ethyl acetate in vacuo left an oil which was crystallized from carbon tetrachloride, yield, 0.61 g. (57%) in two crops, m.p. 127-129" and evolving gas when heated to 150". Recrystallization from carbon tetrachloride-petroleum ether gave white crystals, m.p. 130-131".

Anal. Calc'd for CBHIIO~S: C, 49.5; I€, 6.4. Found: C, 49.2; H, 6.6.

2-(~-Phenoxypropyl)thiophane-S,~-cis-dicarboxylic anhydride. A solution of 500 mg. of 2-(~-phenoxypropyl)thiophane-3,4-trans-dicarboxylic acid (XIb, m.p. 182-183") in 2.5 cc. of acetic anhydride was refluxed for three hours and the solvent was evaporated in vacuo. The residue was distilled in a two-bulbed distilling flask a t 1 mm. The distillate partially crystallized. Recrystallization from benzene-petroleum ether gave 240 mg. of white crystals, m.p. 90-98". Further recrystallization raised the m.p. to 104-105".

Anal. Calc'd for ClsHleO8: C, 61.7; H, 5.5. Found: C, 62.4; H , 5.3.

2-(~-Phenoxypropyl)tl~iophaneS,~-czs-dicurboxylic aczd ( X l b ) . A. A warm solution of 50 mg. of pure 2-(~-phenoxypropyl)thiophane-3,4-cis-dicarboxylic anhydride in 10% aqueous sodium hydroxide was acidified. White crystals separated, m.p. 157-158", and evolved gas at 190'. The m.p. was unchanged on recrystallization from acetone-benzene- petroleum ether.

Anal. Calc'd for C15H1805S: C, 58.1; H, 5.8. Found: C, 58.2; H, 5.2.

B. A mixture of 22.8 g. of 2-(~-phenoxypropyl)thiophane-3,4-trans-dicarboxyIic acid (XIb, m.p. 169-175') and 160 cc. of propionic anhydride was refluxed for two hours, then excess anhydride removed m vucuo. The residue was warmed with 10% aqueous sodium hydroxide until solution was complete, treated with Norit, and acidified. The oil was extracted v,Tith ethyl acetate, the extract washed with dilute hydrochloric acid, and the solvent evaporated in vacuo. Trituration of the partially crystalline residue with hot benzene gave 7.7 g. (34%) of white crystals, m.p. 134-156'. The filtrate, on standing overnight, deposited 2.9 g. (13%) of crystals, m p. 140-143".

The czs diacid, when converted to the methyl ester with diazomethane and boiled with methanolic sodium methoxide, then hydrolyzed with potassium hydroxide, gave the trans diacid, m.p. and mixed m.p. 183-184'.

A , To a suspension of 2 g. of 2-propylthiophane-3,4-trans-dicarboxylic acid (XIa) in 20 cc. of ether was added an excess of ethereal diazomethane. The oily ester remaining after evaporation of th2 ether was refluxed with 15 cc. of methanol and 2 cc. of 55% hydrazine hydrate for one hour. Evap- oration in vacuo gave 2.1 g. (94%) of product, m.p. 225" dec. Recrystallization from 50% alcohol gave white crystals, m.p. 234" dec.

Calc'd for C9H18S10LS: C, 43.8; H, 7.4; N, 22.7. Found: C, 44.1; H, 6.7; N, 22.4.

2-Propylthiophane-S,4-trans-dicarboxh1~dra~ide ( X I I a ) .

Anal.

The configuration of the trans dihydrazide was demonstrated by hydrolysis with 6 N hydrochloric acid back t o 2-propylthiophane-3,4-trans-dicarboxylic acid (XIa), m.p. 152-154". A mixed m.p. was 154-156'.

B. A mixture of 1.05 g. of 2-propyl-3,4-cis-dicarbomethoxythiophane and 0.6 cc. of 100% hydrazine hydrate was heated on the steam-bath under reflux for one hour. Trituration with alcohol gave 0.47 g. (45%) of the trans dihydrazide, m.p. 203-210" dec.

A large number of experiments were run under various conditions of time, temperature, and solvents, but no cis dihydrazide was isolated. The only product which could be obtained was the trans dihydrazide in yields varying from 15% to 50% and melting points from

BIOTIN. I 151

203" to 230" dec. The identity with trans dihydrazide was ehown by mixed melting points in each case.

~-(~-Phenoxypropyl)thiophane-3,4-trans-dicarboxhydrazide (XIIb). A. A suspension of 350 mg. of 2-(-y-phenoxypropyl)thiophane-3,4-trans-dicarboxylic acid (XIb) in ether was treated with an excess of ethereal diazomethane. Evaporation left a crystalline methyl ester. It was refluxed for five hours with 10 cc. of Cellosolve and 0.4 cc. of 85% hydrazine hydrate. Removal of the solvent left the crystalline hydrazide which was triturated with benzene; yield, 300 mg. (7979, m.p. 202-204" after recrystallization from aqueous propanol.

Anal. Calc'd for C I ~ I ~ ~ ~ N ~ O S S : K, 16.6. Found: N, 16.5. When the trans dihydrazide was heated at 100" for twenty hours with 10% sulfuric acid,

the zrans diacid (XIb) separated, m.p. and mised m.p. 181-183". B. The dimethyl ester prepared from 0.47 g. of 2-(-pphenoxypropyl)thiophane-3,4-cis-

dicarboxylic acid, (XIb) and excess ethereal diazomethane was refluxed with 0.9 cc. of 85% hydrazine hydrate for six hours (bath 130-135"). The cooled mixture was triturated with methanol; yield, 0.17 g. (34%), m.p. 197-204". A mixed m.p. with preparation A showed them t o be identical.

No crystalline product other than the trans dihydrazide could be isolated by shorter heating periods with or without solvents.

2-Propyl-J,~-trans-dicarbethoxyaminothiophane (XIIIa). To a solution of 0.50 g. of 2- propylthiophane-3,4-trans-dicarboxhydrazide (XIIa) in 5 cc. of 1 N hydrochloric acid and 10 cc. of chloroform was added a t 20" dropwise with stirring a solution of 0.30 g. of sodium nitrite in 3 cc. of water over a period of five minutes. After being stirred an additional ten minutes, the chloroform layer was separated and the aqueous layer extracted with chloroform. The combined extracts were dried with calcium chloride at 0". After dilution with 10 cc. of absolute ethanol, the solution was refluxed one hour, then evaporated to dryness. The residue was triturated with carbon tetrachloride; yield, 0.22 g. (37%) of white crystals, m.p. 170-172". Recrystallization from ethyl acetate did not change the m.p.

ilnal. Calc'd for C ~ S H * ~ N ~ O & : C, 51.3; H, 7.9; N, 9.2. Found: C, 51.5; H, 7.5; N, 9.3.

When the diazotization was carried out a t 0" the yield was 30%. 2- (y -Ph enox yprop yl) th iophane-3 , 4-trans-dicarbethox yaminothiophane (XIIIb) . A. From

160 mg. of 2-(~-phenoxypropyl)thiophane-3,4-trans-dicarboxhydrazide was obtained 70 mg. (37%) of the diurethan, m.p. 172-173" in the same manner as described above for the corresponding 2-propyl compound.

dnal. Calc'd for CI~H&:O;S: C, 57.7; H, 7.1; N, 7.1. Found: C, 57.7; H, 6.5; N, 7.2.

R. A mixture of 2.8 g. of 2-(y-phenoxypropy1)thiophane-3,4-trans-dicarboxylic acid (Xlb), 10 cc. of benzene, 5 cc. of thionyl chloride, and 1 cc. of a solution of one drop of pyridine in 10 cc. of benzene was refluxed for fifteen minutes, gas evolution being complete in ten minutes. The solution was evaporated in vacuo, the residue dissolved in 20 CC. of benzene, and the evaporation repeated. A solution of the residue in 20 cc. of acetone was added dropwise over a period of five minutes t o a solution of 2.8 g. of sodium azide in 20 cc. of water at 15-20'. After being stirred one hour the mixture was diluted with 50 cc. of water and the oily azide estracted with chloroform. The extracts, dried with calcium chloride a t O D , were diluted with 25 cc. of absolute ethanol. refluxed thirty minutes, and evaporated. The crystalline residue was heated to boiling with 15 cc. of absolute ethanol, cooled to room temperature and the product collected on a filter; yield, 2.1 g. (58%), m.p. 169-170".

A mixture of 200 mg. of 2-(y-phenoxypropyl)-3,4-trans-dicarbethoxyaminothiophane (XIIb), one-half teaspoon of desulfurizing Raney nickel (IS), and 55 cc. of 75% alcohol was refluxed for thirty minutes. The nickel was removed by centrifugation and washed with 20 cc. of acetone. The combined solutions were evaporated t o dryness in vacuo. The residue was extracted with ace-

A mixed m.p. with preparation A was 170-171°. trans-4-Yethyl-5-(6-phenoxybutyl)-4,6-dihydro-2-imidazolone.

152 BAKER, QUERRY, SBFIR, AND BERNSTEIX

tone, separated from a little inorganic material, and evaporated. The residual colorless oil did not crystallize. It was refluxed with 0.5 g. of potassium hydroxide and 2 cc. of methanol for thirty minutes, then diluted with 20 cc. of water. The white crystals had the m.p. 145-147"; yield, S5 mg. (68%). Recrystallization from 50% alcohol raised the m.p. to 148-149". The ureide is only slightly soluble in hot acetone and contains no sulfur.

Anal. Calc'd for C1rHd?10: C, 67.7; H, 8.1; N, 11.3. Found: C, 67.6; H, S.4; N, 11.0.

Recently, Hafmann (19) described the same type of ring closure of a diurethan t o an imidazolone by mild hydrolysis.

2-Propylthiophane-8,4-cis-dzcarboximide (XXIII). A mixture of 0.50 g. of 2-propylthiophane-3,4-cis-dicarboxylic acid (XIa) and 5 cc. of acetyl chloride was refluxed for twenty minutes. After the addition of 1 cc. of 2S% ammonia water the solution was heated on the steam-bath for thirty minutes, then at 160" for one hour. The niivture m s cooled and diluted with water; yield 0.35 g. (77%), m.p. 86-90". Recrystallization from benzene-petroleum ether with the aid of Norit gave white crystals, m.p. 94-96'.

Evaporation in vacuo gave an oily anhydride.

Anal. Calc'd for CgHl3XO2S: N, 7.0. Found: K, 6.9. A solution of 170 mg. of the cis imide (XXIII) in 0.4 cc. of 85% hydrazine hydrate was

heated on the steam-bath under reflux for fifteen hours. The solid was triturated with methanol; yield, 110 mg., of 2-propylthiophane-3,4-trans-dicarboxhydrazide, m.p. 2.20' dec. which was identified by a mixed m.p.

Several attempted Hofmann degradations with aqueous or niethanolic sodium hypo- bromite gave no crystalline products.

2-Propylthiophane-S,4-czs-dzcarboxy-N, N'-monohydrazide (XXIV). To the anhydride from 0.50 g. of 2-propylthiophane-3,4-cis-dicarboxylic acid (XIa) prepared as above with acetyl chloride was added 0.5 cc. of S5% hydrazine hydrate. The solution was dissolved in 20 cc. of water, acidified with 2 cc. of acetic acid, and heated on the steam-bath for fifteen minutes. The cooled solution was extracted twice with benzene, the extracts Fashed with aqueous sodium bicarbonate, and concentrated t o 5 cc. Dilution with petroleum ether gave 0.25 g. (50%) of product. m.p. 76-79". Recrystallization from benzene-petroleum eLher gave white crystals, m.p. 81-82".

Anal. Calc'd for C9H1*02N2S: K, 13.1. Found: K, 13.2. The cyclic hydrazide structure (XXIV) was assigned on the basis of solubility in aqueous

alkali and insolubility in 1 AT hydrochloric acid or dilute sodium bicarbonste solution. A mixture of 120 mg. of the cyclic hydrazide (XXIV) and 0.4 cc. of 85% hydrazine hy-

drate was heated on the steam-bath for t n o hours. Trituration with methanol gave white crystals, m.p. 232" dec., identical with 2-propglthiophane-3,4-trans-dicarboxhydrazide (XIIa). When the same reaction was carried out in 5 cc. of butanol a t the b.p. as a solvent, starting material was the only compound which could be isolated.

2-PropyZ-S,4-trans-dia~inothiophane sulfate. To a filtered solution of 3 g. of barium hydroxide in 15 cc. of water was added 0.52 g. of 2-propyl-3,4-trans-dicarbethoxyaminothiophane (XIIIa) in 10 cc. of methanol. After being refluxed for twenty-four hours, the mixture vias just acidified with dilute sulfuric acid, and the filtered solution evaporated to dryness in vacuo. Trituration with acetone gave 0.28 g. (64%) of white crystals 11-hich were recrystallized from water. The sulfate gradually decomposes above 300" without melting.

Anal.

Action of 48% h ydrobTomic acid on 2-(7-phenoxypropyl)-S,Q-trans-dzcarbethoxya~ninothio- phane (XIIIb). A mixture of 1.7 g . of the urethan and 25 cc. of 48% hydrobromic acid was refluxed under an air condenser for two honrs, then evaporated to dryness in uacuo. The residue solidified on trituration with absolute alcohol; yield, 1.4 g . For analysis a sample of the bromide was dissolved in water and precipitated by the addition of absolute alcohol, m.p., gradually decomposes over 200".

Calc'd for C ~ H I ~ N ~ O ~ S Z : C, 32.6; H, 7.0; N, 10.8; Sod-, 37.2. Found: C, 32 9; H, 6.6; K, 10.8; SO*-, 36.8.

BIOTIS. I 153

Anal. Calc'd for C,HleBr2NzS (XXVI) : C, 26.3; H, 5.0; N, 8.8; Br-, 50.0. Calc'd for C7HI7Br3N2S (XXVII): C, 21.0; H, 4.3; N, 7.0; Br-, 59.8. Found: C, 22.9; H, 4.9; N, 7.4; Br-, 54.1, 54.7.

This material gave no water-insoluble derivatives when treated with (a) phosgene in aqueous sodium carbonate at 0"; (b) sodium acetate in acetic anhydride; (c) sodium acetate, acetic anhydride, and water; (d) aqueous sodium hydroxide and phenyl isothiocya- nate; (e) aqueous picric acid; (f) forniamide by fusion; or (9) benzoyl chloride in triethyl- amine.

Dibenzoyl derivative of 3-aminopiperidino [S, 8 , blthiophane ( X X V Z ) . To a solution of 410 mg. of the above mixture in 3 cc. of 10% sodium hydroxide was added 0.3 cc. of benzoyl chloride. The mixture was shaken at about 35" until the benzoyl chloride had reacted, then treated again with 3 cc. of 10% sodium hydroxide and 0.3 cc. of benzoyl chloride. The dibenzoyl derivative was removed by filtration and the filtrate treated twice more with alkali and benzoyl chloride. In this way a total of 240 mg. of product, m.p. 147-151' was obtained. I t x a s purified by recrystallizations from dilute alcohol, m.p. 165-166'. This compound contained no bromine.

Anal. Calc'd for CZ1H22N2O2S: C, 68.8; H, 6.0; N, 7.7; M.W., 366. Found: C, 68.4; H, 5.5; N, 7.8; M . W . (Rast), 357.

1,8-Trimethylene-S, 4-trans-dicarboxythiophanium bromide ( X X V Z I I ) . A solution of 0.20 g. of 2-(~-phenoxypropyl)thiophane-3,4-~runs-dicarboxylic acid (XIb) in 2 CC. of 48% hydrobromic acid was refluxed for twenty minutes, then evaporated t o dryness in vacuo. The evaporation was repeated with 5 cc. of water and then with 5 cc. of absolute ethanol. The residue, on trituration with acetone, crystallized t o a white solid, m.p. about 170" with decomposition; yield, 0.11 g. (59%). This compound is extremely soluble in water. No suitable solvent could be found for recrystallization.

Anal. Calc'd for CoH18Br04S: Br-, 26.9. Found: Br-, 28.0.

SUMMARY

Two isomeric methods of synthesizing 2-alkylthiophane-3 4-dicarboxylic acids have been described.

Curtius degradations of the 2-alkylthiophane-3 4-trans-dicarboxylic acids have led to derivatives of the corresponding 3,4-trans-diamines, but cis diamines could not be obtained from the cis diacids.

PEARL RIVER, N. Y.

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(2) KILMER AND MCKENNIS, J . Biol. Chem., 162, 103 (1944). (3) WOODWARD AND EASTMAN, J. Am. Chem. SOC., 66,849 (1944). (4) MCELVAIN, J. Bm. Chem. SOC., 61, 3124 (1929). (5) .TONES AND WALLIS, J. Am. Chem. S O C . , 48, 169 (1926). (6) SCHROTER, Ber., 42,3356 (1909); NAEGLI AND TYABJI, HeEv. Chim. Acta, 16, 349 (1933). (7) BUCHXAN, REIMS, SKEI, AND SCHLATTER, J. Am. Chem. SOC., 64,2696 (1942). (8) MYER, Monatsh., 32, 420 (1911). (9) VORLANDER, Ann., 280, 183 (1894).

BROWN, AND DUVIGNEAUD, J. Biol. Chem., 146, 495 (1942).

(10) SCHMIDT, Ber., 67,704 (1924); 68,2413 (1925); OESTERLIN, Angew. Chem., 46,536 (1932).

(11) LETCH AND LINSTEAD, J . Chem. SOC., 450 (1932). (12) BAKER, J. Am. Chem. soc., 66, 1577 (1943).

See also reference 7 .


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(15) KON, LINSTEAD, AND MACLENNAN, J. Chem. SOC., 2454 (1932). (16) LINSTEAD AND MILLIDGE, J . Chem. SOC., 478 (1936). (17) MERCHANT, WICKERT, AND ~XARDL, J. Am. Chem. Soc., 49, 1829 (1927); GABRIEL,

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BIOTIN. I. 2-ALKYLTHIOPHANE-3,4-DICARBOXYLIC ACIDS