Russian Chemical Bulletin, International Edition, Vol. 62, No. 5, pp. 1238—1243, May, 20131238

Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1238—1243, May, 2013.

1066�5285/13/6205�1238 © 2013 Springer Science+Business Media, Inc.

Base�induced rearrangement of 4�amidino�3�R�furoxansinto 1�substituted 3�(1�nitroalkyl)�5�R�1H�1,2,4�triazoles

S. I. Molotov,a A. S. Kulikov,a K. A. Lyssenko,b and N. N. Makhovaa

aN. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,47 Leninsky prosp., 119991 Moscow, Russian Federation.

Fax: +7 (499) 135 5328. E�mail: mnn@ioc.ac.rubA. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,

28 ul. Vavilova, 119991 Moscow, Russian Federation.Fax: +7 (495) 135 5085. E�mail: kostya@xrlab.ineos.ac.ru

A new base�induced rearrangement of furoxans, viz., a recyclization of 4�amidino�3�R�furoxans into 1�substituted 3�(1�nitroalkyl)�5�R�1H�1,2,4�triazoles in the presence of alkalimetal alkoxides and into 3�acyl�5�R�1H�1,2,4�triazoles in aqueous alkaline solutions, was found.

Key words: azole�azole rearrangements, base catalysis, 4�amidino�3�R�furoxans, 1,2,4�tri�azoles.

Among plethora of known methods for the construc�tion of heterocyclic compounds, there is a group of meth�ods, in which one heterocycle, as a rule, fairly available,serves as a starting compound for the preparation of otherheterocycles. The rearrangements proceeding with reten�tion of molecular composition can be considered as one ofthe versions of such reactions. For example, azole�azolerearrangements are studied well enough in azole series.They in one step lead to other heterocycles with a widerange of functional substituents, many of which can beobtained by traditional methods only in multi�step pro�cesses.1—6 These rearrangements can be initiated thermal�ly, photochemically, or by treatment with bases. A neces�sary structural condition for the possibility to accomplishan azole�azole rearrangement is the presence of a three�atom substituent in the molecule of azole, which in theSN

i�type reaction plays the role of a nucleophile with re�spect to one of the nitrogen atoms of the ring with subse�quent cleavage of the neighboring N—O bond and forma�tion of a new azole. These requirements are met, in partic�ular, by isoxazoles, 1,2,4� and 1,2,5�oxadiazoles (fur�azans). In a number of cases, these rearrangements can bereversible (Scheme 1).

Until recently, such azole�azole rearrangements offuroxans were largely studied for benzofuroxans (Boul�ton—Katrizky rearrangement).7—9 Significant contribu�tion to the studies of azole�azole rearrangements of unfusedfuroxan derivatives was made by our research group.10—18

The rearrangements of these furoxan derivatives were foundto have a number of specific features, which are notcharacteristic of other azoles. In particular, it appeared

(Scheme 2) that along with a classic version of the rear�rangement (cleavage of the N—O bond with the forma�tion of other heterocycle and liberation of a 1�nitroalkylfragment) (pathway A), furoxans are capable of giving therearrangement proceeding through the dinitrosoethyleneintermediate (pathway B), since the furoxan ring can un�dergo ring opening to form dinitrosoethylene19,20 (theserearrangements are thermally initiated). Besides, furoxanazo derivatives are capable of undergoing a cascade rear�rangement: two consecutive rearrangements proceedingin situ result in the liberation of the nitro group concealedin the furoxan ring, which form a bond with the carbonatom of the newly forming heterocycle (see Scheme 2,pathway C).

The purpose of the present work is to study the rear�rangement of 4�amidino�3�R�furoxans 1. It could havebeen expected that in this case the reaction would followa classic scheme with the formation of 3�(1�nitroalkyl)�5�R�1H�1,2,4�triazoles 2. To prepare the starting amidino�furoxans 1, we have chosen two approaches, which arecommonly used for the synthesis of amidines: 1) an acid�catalyzed reaction of nitriles with amines21 and 2) a pre�liminary synthesis of imino ethers by the reaction of amines

Scheme 1

New base�induced rearrangement of furoxans Russ.Chem.Bull., Int.Ed., Vol. 62, No. 5, May, 2013 1239

with orthoformates or orthoacetates,22 followed by involve�ment of the imino ethers formed in the reaction with vari�ous amines.23 4�Amino�3�R�furoxans 3a—c were taken asthe starting compounds in both cases. Based on the firstapproach, we studied the reaction of 4�aminofuroxans 3a—cwith trichloroacetonitrile under different conditions (a pro�longed heating of the reaction mixture with the simulta�neous passing of gaseous HCl or heating in the presence ofsulfuric acid). Unfortunately, we failed to find suitableconditions for the preparation of trichloromethylamid�ines 4 (Scheme 3).

Scheme 3

R1 = Me (3a, 4a), Ph (3b, 4b), COOMe (3c, 4c)

Reagents and conditions: i. Cl3CCN, H+, 75—80 C; ii. R2C(OEt)3,reflux, 24 h.

5 R1 R2 Yield of 5 (%)a Me H 90b Ph H 96c Ph Me 65d CO2Me H 72

The target amidinofuroxans 1 were successfully ob�tained starting from imino ethers 5a—d (Scheme 4), which,

in turn, were synthesized by reflux of aminofuroxans 3a—cin the excess of triethyl orthoformate or triethyl orthoace�tate (see Scheme 3).

Scheme 4

Reagents and conditions: i. R3NH2, CHCl3, reflux, 3 h; ii. R3NH2,H2O, 20 C, 12 h.

1 R1 R2 R3 Yield of 1 (%)a Me H 4�MeC6H4 75b Ph H 4�MeC6H4 97c Ph H 4�EtOC6H4 82d CO2Me H 4�MeC6H4 54e Ph H Me 64f Ph Me Me 47

To obtain amidines 1, the reaction of imino ethers5a—d was carried out with both aromatic and aliphaticamines. It appeared that out of aromatic amines onlyanilines with electron�donating substituents (R3 == 4�MeC6H4, 4�EtOC6H4) underwent the reaction, andit was enough to reflux a mixture of reagents in chloroformto obtain compound 1. Amidines 1a—d were prepared inhigh yields. The weakly nucleophilic 4�nitroaniline or

Scheme 2

Cat+ stands for cation.

Molotov et al.1240 Russ.Chem.Bull., Int.Ed., Vol. 62, No. 5, May, 2013

4�aminobenzoic acid failed to be involved in the reactionwith imino ethers. Aliphatic amines (only methylaminewas used) gave this reaction in water at room temperature.To prepare amidines of this type (1e,f), imino ethers 5b,csynthesized from 4�amino�3�phenylfuroxan 3b were used(see Scheme 4).

A possibility of rearrangement of synthesized amidi�nofuroxans 1a—f into 1�substituted 3�(1�nitroalkyl)�5�R�1H�1,2,4�triazoles 2 was studied for both the thermal andthe base induction. A possibility of thermally induced re�arrangement (in melt) was shown only for a single sub�strate, amidinofuroxan 1b. This reaction resulted in ob�taining a mixture of compounds, which gave the target3�(1�nitrobenzyl)�1,2,4�triazole 2b in 10% yield after iso�lation by preparative column chromatography. The base�induced rearrangement was studied under various condi�tions (heating in the presence of tertiary or secondaryamines, treatment with MeOK in methanol or ButOK indiverse solvents, reaction with aqueous solution of NaOH).It appeared that no expected reaction took place in thepresence of organic bases. The use of MeOK in methanolwas more successful and allowed us to involve amidines1a—d in the rearrangement even without heating to affordthe corresponding 3�(1�nitroalkyl)�5�R�1H�1,2,4�tri�azoles 2a—d in high yields (Scheme 5). Amidines 1e,fcontaining a methylamine moiety underwent the re�arrangement only upon heating with ButOK in DMF at100 C (see Scheme 5). The use of more drastic conditionsfor amidines 1e,f is necessary apparently because of the

lower acidity of the amidine fragment in these compounds,that interferes with the formation of the correspondinganion, which is the species attacking the nitrogen atomof furoxan.

In aqueous solution of NaOH, both types of amidinesunderwent the rearrangement (studied for 1b,f as an ex�ample), however, in both cases 3�benzoyl�1,2,4�triazoles6a,b were obtained as the reaction products, rather thanthe expected 3�(1�nitroalkyl)�5�R�1H�1,2,4�triazoles 2band 2f, besides, a partial decomposition of the startingamidines was observed (Scheme 6). It is obvious that theexpected rearrangement did occur, but the 1�nitroalkylderivatives 2b and 2f formed underwent hydrolysis underthese conditions to the corresponding ketones followingthe Nef reaction mechanism. Similar transformation wasdescribed earlier for 4�(1�nitroalkyl)�1,2,3�triazoles.12

Scheme 6

6 R1 R2 R3 Yield of 6 (%)a Ph H 4�MeC6H4 56b Ph Me Me 51

Yields, spectroscopic and physicochemical character�istics of synthesized 1,2,4�triazole derivatives 2a—f and6a,b are given in Tables 1 and 2, the starting imino ethers 5and amidines 1 are described in the Experimental section;the structure of compound 6a was additionally confirmedby X�ray diffraction studies (Fig. 1).

Scheme 5

Reagents and conditions: i. 1b, 145 C, 10 min; ii. for 2a—d: 1a—d,MeOK, MeOH, 20 C, 6 h; iii. for 2e,f: 1e,f, ButOK, DMF.

2 R1 R2 R3 Yield of 2 (%)a Me H 4�MeC6H4 86b Ph H 4�MeC6H4 92c Ph H 4�EtOC6H4 95d CO2Me H 4�MeC6H4 68e Ph H Me 70f Ph Me Me 58

Fig. 1. General view of molecule 6a in the representation ofatoms by ellipsoids of thermal vibrations (p = 50%).

C(12)C(8) C(7)

C(9)

C(10)

C(11)

C(6)

C(5)

N(2)C(3)

N(4)

C(15)

C(14)

C(13)

O(1)

N(1)

C(16)C(17)

C(18)

C(19)

New base�induced rearrangement of furoxans Russ.Chem.Bull., Int.Ed., Vol. 62, No. 5, May, 2013 1241

Table 1. Yields and some physicochemical characteristics of 1H�1,2,4�triazole derivatives 2a—f and 6a,b

Com� Yield M.p./C Rf Found (%) Molecular formulapound (%) (CHCl3) Calculated

C H N

2a 86 109—110 0.36 57.03 5.07 24.04 С11H12N4O256.89 5.21 24.12

2b 92 167—168 — 65.14 4.55 19.25 С15H14N4O2(10*) 65.30 4.79 19.04

2c 95 150—153 — 62.49 4.78 17.30 С16H16N4O362.95 4.97 17.27

2d 68 107—108 — 52.02 4.36 20.42 С12H12N4O452.17 4.38 20.28

2e 70 Oil 0.45 51.20 4.09 23.81 С10H10N4O251.28 4.30 23.92

2f 58 Oil 0.48 57.20 5.00 23.94 С11H12N4O256.89 5.21 24.12

6a 56 127—128 0.52 73.08 5.87 15.63 С16H13N3O72.99 4.98 15.96

6b 51 73—74 0.63 65.78 5.44 21.09 С11H11N3O65.66 5.51 20.88

* Thermally induced rearrangement.

X�ray diffraction analysis of compound 6a showed thatthe bond distances in the molecule statistically significantdid not differ from those in the known structures ofaryl�substituted 1,2,4�triazoles. Despite a possible con�jugation between the cyclic fragments and the carbon�yl group, the rings in the molecule are somewhat turnedwith respect to each other. Thus, the torsional anglesN(1)N(2)C(6)C(11), N(2)C(3)C(13)O(1), andO(1)C(13)C(14)C(19) in the crystal are equal to 17.1,20.6, and 21.4, respectively. The disturbed planarity ofthe molecule observed can be due to both the steric repul�sion (for example, of hydrogen atoms at C(7) and C(5)atoms) and the effects of the crystal packing. In fact, anal�ysis of the intermolecular interactions showed that a wholenumber of intermolecular interactions was present in thecrystal, including both the weak contacts CH...O and thestacking interactions of the triazole and the tolyl rings.

Experimental

NMR spectra were recorded on Bruker WM�250 (1H,250 MHz) and Bruker AM�300 (13C, 75.5 MHz and 14N,21.5 MHz) spectrometers in CDCl3, chemical shifts are given in scale. Chemical shifts in the 1H and 13C NMR spectra weremeasured relative to Me4Si as an internal standard, in the14N NMR spectra relative to MeNO2 as external standard. Massspectra were obtained on a Varian MAT CH 6 instrument (70 eV).Thin�layer chromatography was carried out on Silufol UV�254plates, a UV light was used for visualization. Preparative columnchromatography was performed on SiO2 (Merck, 70—230 meshASTM). 4�Amino�3�methyl� (3a), 3�phenyl� (3b), and 3�meth�oxycarbonylfuroxans (3c) were synthesized according to the

known procedures.24—26 X�ray diffraction studies were carriedout on a Bruker SMART APEX II CCD diffractometer.

Synthesis of imino ethers 5a—d (general procedure). A solu�tion of 4�amino�3�methylfuroxan (3a), (4�amino�3�phenylfurox�an (3b) or methyl 4�amino�3�furoxancarboxylate (3c)) (10 mmol) intriethyl orthoformate (5 mL) (or 3b (10 mmol) in triethyl ortho�acetate (5 mL)) was refluxed for 24 h. The reaction mixture was con�centrated, a dry residue was dissolved in some CHCl3 and sub�jected to flash�chromatography on a filter with silica gel (eluentCHCl3 (30 mL)). A solution obtained was concentrated and theproduct was recrystallized from light petroleum with b.p. 40—60 C.

4�Ethoxymethylideneamino�3�methylfuroxan (5a). The yieldwas 90%, m.p. 47—48 C. Found (%): C, 42.26; H, 5.40;N, 24.29. C6H9N3O3. Calculated (%): C, 42.10; H, 5.30; N, 24.55.MS, m/z: 171 [M]+. 1H NMR, : 1.39 (t, 3 H, CH3CH2); 2.12(s, 3 H, CH3C(4) in furoxan ring); 4.45 (q, 2 H, CH3CH2); 8.34,8.82 (both s, 1 H, EtOCH).

4�Ethoxymethylideneamino�3�phenylfuroxan (5b). The yieldwas 96%, m.p. 80—82 C. Found (%): C, 56.47; H, 4.81; N, 18.07.C11H11N3O3. Calculated %: C, 56.65; H, 4.75; N, 18.02. Massspectrum m/z: 233 [M]+. 1H NMR, : 1.37 (t, 3 H, CH3CH2);4.45 (q, 2 H, CH3CH2); 7.62—8.07 (m, 5 H in Ph); 8.52, 9.03(both s, 1 H, EtOCH).

4�1�(Ethoxyethylideneamino)�3�phenylfuroxan (5c). Theyield was 65%, m.p. 65—67 C. Found (%): C, 58.12; H, 5.47;N, 16.70. C12H13N3O3. Calculated (%): C, 58.29; H, 5.30;N, 16.99. MS, m/z: 247 [M]+. 1H NMR, : 1.35 (t, 3 H,CH3CH2); 2.22, 2.37 (both s, 3 H, CCH3); 4.45 (q, 2 H,CH3CH2); 7.46—8.10 (m, 5 H in Ph).

Methyl 4�(ethoxymethylideneamino)furoxan�3�carboxylate(5d). The yield was 72%, m.p. 50—51 C. Found (%): C, 39.04;H, 4.32; N, 19.71. C6H9N3O3. Calculated (%): C, 39.07; H, 4.22;N, 19.53. MS, m/z: 215 [M]+. 1H NMR, : 1.29 (t, 3 H,CH2CH3); 3.95 (s, 3 H, OCH3); 4.35 (q, 2 H, CH2CH3); 8.15,8.67 (both s, 1 H, EtOCH).

Molotov et al.1242 Russ.Chem.Bull., Int.Ed., Vol. 62, No. 5, May, 2013

Synthesis of amidines 1a—f (general procedure). A. A solutionof imino ether 5a,b,d (10 mmol) and 4�toluidine (1.18 g, 11 mmol)(or imino ether 5b (2.33 g, 10 mmol) and 4�ethoxyaniline (1.51 g,11 mmol)) in CHCl3 (10 mL) was refluxed for 3 h. The reactionmixture was concentrated, and the dry residue was recrystallizedfrom methanol.

B. A 20% aqueous MeNH2 (2 mL) was added to a solution ofimino ether 5b,c (10 mmol) in methanol (20 mL), and the mix�ture was stirred at room temperature for 12 h. The solvent wasevaporated, and the product was isolated by preparative columnchromatography on SiO2 (eluent CHCl3).

3�Methyl�4�[(4�methylphenylamino)methylideneamino]fur�oxan (1a) was obtained by method A. The yield was 75%, m.p.98—99 C. Found (%): C, 56.67; H, 5.13; N, 24.30. C11H12N4O2.Calculated (%): C, 56.89; H, 5.21; N, 24.12. MS, m/z: 232 [M]+.1H NMR, : 2.12 (s, 3 H, CH3C(4) in furoxan ring); 2.32 (s, 3 H,CH3—Ar); 7.25, 7.64 (both d, 4 H in Ar, J = 8.2 Hz); 8.32, 8.54(both s, 1 H, NCH=N).

4�[(4�Methylphenylamino)methylideneamino]�3�phenylfur�oxan (1b) was obtained by method B. The yield was 97%, m.p.140—141 C. Found (%): C, 65.01; H, 4.97; N, 19.22. C15H14N4O2.Calculated (%): C, 65.30; H, 4.79; N, 19.04. MS, m/z: 294 [M]+.1H NMR, : 2.36 (s, 3 H, CH3); 7.12—8.62 (m, 9 H, Ar); 8.70,8.83 (both s, 1 H, NCH=N).

4�[(4�Ethoxyphenylamino)methylideneamino]�3�phenylfur�oxan (1c) was obtained by method A. The yield was 82%, m.p.

130—131 C. Found (%): C, 62.78; H, 4.68; N, 17.45. C16H16N4O2.Calculated (%): C, 62.95; H, 4.97; N, 17.27. MS, m/z: 324 [M]+.1H NMR, : 1.29 (t, 3 H, CH2CH3); 3.97 (q, 2 H, CH2CH3);7.09—8.60 (m, 9 H, Ar); 8.64 (s, 1 H, NCH=N).

Methyl 4�[(4�methylphenylamino)methylideneamino]furoxan�3�carboxylate (1d) was obtained by method A. The yield was54%, m.p. 107—108 C. Found (%): C, 52.05; H, 4.46; N, 20.53.C12H12N4O4. Calculated (%): C, 52.17; H, 4.38; N, 20.28. MS,m/z: 276 [M]+. 1H NMR, : 2.37 (s, 3 H, CH3—Ar); 3.95 (s, 3 H,OCH3); 7.35, 7.72 (both d, 4 H in Ar, J = 7.9 Hz); 8.61 (s, 1 H,NCH=N).

4�[(Methylamino)methylideneamino]�3�phenylfuroxan (1e)was obtained by method B. The yield was 64%, oil, Rf = 0.37.Found (%): C, 51.11; H, 4.07; N, 23.60. C10H10N4O2. Calculat�ed (%): C, 51.28; H, 4.30; N, 23.92. MS, m/z: 218 [M]+. 1H NMR,: 2.98 (d, 3 H, CH3N); 7.44—8.77 (m, 6 H, 5 H in Ph, 1 H inNCH=N).

4�[1�(Methylamino)ethylideneamino]�3�phenylfuroxan (1f)was obtained by method B. The yield was 47%, oil, Rf = 0.37.Found (%): C, 56.94; H, 5.00; N, 24.36. C11H12N4O2. Calculat�ed (%): C, 56.89; H, 5.21; N, 24.12. MS, m/z: 232 [M]+. 1H NMR,: 2.32 (s, 3 H, CCH3); 3.00 (d, 3 H, CH3N); 7.52—8.87(m, 5 H, Ph).

Synthesis of 3�(1�nitroalkyl)�1�R3�5�R2�1H�1,2,4�triazoles2a—f upon treatment of furoxans with bases (general procedure).A. Potassium methoxide (0.77 g, 11 mmol) was added to a solu�

Table 2. 1H, 13C, and 14N NMR spectroscopic and mass spectrometric data for 1H�1,2,4�triazole derivatives 2a—f and 6a,b

Com� MS, 1H NMR, , J/Hz 13C NMR, pound (m/z) [M]+ [14N NMR, ]

2a 232 1.75 (d, 3 Н, СН3СН); 2.37 (s, 3 H, CH3Ar); [5.87 (NO2)]6.17 (q, 1 Н, СНCH3); 7.32, 7.80 (both d, 4 H in Ar,3J = 8.2); 8.58 (s, 1 Н, СН in triazole ring )

2b 294 2.47 (s, 3 H, CH3Ar); 6.17 (q, 1 Н, СНNO2); 21.06 (CH3), 87.61 (СNO2), 120.13, 128.63,7.25—7.82 (m, 9 Н in Ar); 8.61 (s, 1 Н, СН 129.58, 130.28, 131.92, 134.27, 138.84, in triazole ring) 141.84 (8 C in Ar), 156.02, 158.53 (C(4) and

С(5) in triazole ring) [3.67 (NO2)]

2c 324 1.29 (t, 3 H, CH2CH3); 4.15 (q, 2 Н, CH2CH3); 14.91 (CH3), (8 C, Ar), 63.97 (CH2)6.17 (q, 1 Н, СНNO2); 7.02—7.87 (m, 9 Н, Ar); 115.38, 121.90, 128.85, 129.59,8.54 (s, 1 Н, СН in triazole ring) 129.80, 130.08, 131.97, 141.87 (8 C),

158.44, 159.16 (C(4) and С(5) in triazole ring)[3.52 (NO2)]

2d 276 2.48 (s, 3 H, CH3Ar); 3.99 (s, 3 Н, ОСН3); [6.07 (NO2)]7.05, 7.87 (both d, 4 H in Ar, 3J = 8.0); 8.61 6.98 (s, 1 Н, СНNO2),(s, 1 H, СН in triazole ring)

2e 218 3.72 (s, 3 Н, СН3N); 6.87 (s, 1 Н, СНNO2); [3.36 (NO2)]7.35—7.82 (m, 5 Н, Ph); 8.34 (s, 1 H, СН in triazole ring)

2f 232 2.32 (s, 3 Н, СН3C); 3.92 (s, 3 Н, СН3N); [3.42 (NO2)]6.82 (s, 1 Н, СНNO2); 7.32—7.76 (m, 5 Н, Ph)

6a 263 2.41 (s, 3 H, CH3Ar); 7.45, 7.87 (both d, 4 H in Ar, —3J = 8.4); 7.56—8.39 (m, 5 Н in PhСО);9.22 (s, 1 H, СН in triazole ring)

6b 201 2.49 (s, 3 Н, СН3C); 3.89 (s, 3 Н, СН3N); 11.84 (СН3C), 35.78 (СН3N), 28.16, 130.57,7.45—8.29 (m, 5 Н in Ph) 1131.51, 133.12 (4 C in Ph), 153.53, 158.47

(C(4) and С(5) in triazole ring), 185.06 (CO)

New base�induced rearrangement of furoxans Russ.Chem.Bull., Int.Ed., Vol. 62, No. 5, May, 2013 1243

tion of amidinofuroxan 1a—d (10 mmol) in dry methanol(20 mL), and the mixture was stirred at room temperature for 6 h,then acidified with AcOH to рH 7. The solvent was evaporatedon a rotary evaporator, the residue was triturated with water andfiltered off.

B. Potassium tert�butoxide (1.23 g, 11 mmol) was added toa solution of amidine 1e,f (10 mmol) in anhydrous DMF (10 mL),and the mixture was stirred at 100 C for 6 h, then acidified withAcOH to рH 7. The solvent was evaporated on a rotary evapora�tor, the residue was washed with water and dried in air. Theproduct was isolated by preparative column chromatography onSiO2 (eluent CHCl3).

Synthesis of 3�(1�nitrobenzyl)�1�(4�tolyl)�1H�1,2,4�triazole(2b) by thermally induced rearrangement. A melt of furoxanyl�amidine 1b (2.94 g, 10 mmol) was heated at 145 C for 10 min.The product was isolated from the resin�like mass by preparativecolumn chromatography on SiO2 (eluent CHCl3).

Synthesis of 3�benzoyl�1�(4�tolyl)�1H�1,2,4�triazole (6a) and3�benzoyl�1,5�dimethyl�1H�1,2,4�triazole (6b) (general proce�dure). Sodium hydroxide (0.44 g, 11 mmol) was added toa suspension of amidinofuroxan 1b,f (10 mmol) in water (10 mL),and the mixture was stirred at room temperature for 4 h, thenacidified with AcOH to рH 7. The solvent was evaporated ona rotary evaporator. Products 6a,b were isolated by preparativecolumn chromatography on SiO2 (eluent CHCl3).

X�ray diffraction studies. Crystals 6a (C16H13N3O, M = 263.29)monoclinic, space group P21/c at 100 K: a = 11.2638(14),b = 10.9245(13), c = 11.5430(14) Å, = 114.350(3), V = 1294.0(3) Å3,Z = 4 (Z´ = 1), dcalc = 1.351 g cm–3, (MoK) = 0.88 cm–1,F(000) = 552. Intensities of 8279 reflections were measured ona Bruker SMART APEX II CCD diffractometer [(MoK) == 0.71072 Å, �scan mode, 2 < 54], and 2829 independentreflections (Rint = 0.0401) were used in further refinement. Thestructure was solved by direct method and refined by the full�matrix least squares method on F 2 in anisotropic�isotropic ap�proximation. Positions of hydrogen atoms H(C) were calculatedgeometrically. All hydrogen atoms were refined in isotropic ap�proximation using the riding model. The final Q�factor valuesfor: wR2 = 0.0873 and GOF = 1.051 for all independent reflec�tion (R1 = 0.0536 were calculated on F for 1732 observed reflec�tion with I > 2(I)). All calculation were carried out using theSHELXTL PLUS 5.0. The structure was deposited with the Cam�bridge Structural Database (CCDC 906682).

References

1. H. C. van der Plas, Ring Transformation of Heterocycles, Vols1, 2, Acad. Press., London—New York, 1973.

2. N. Vivona, G. Makaluso, V. Frenna, M. Russia, J. Hetero�cycl. Chem., 1983, 20, 931.

3. N. Vivona, S. Buscemi, V. Frenna, G. Gusmano, Adv.Heterocycl. Chem., 1993, 56, 49.

4. G. L´Abbé, Tetrahedron, 1982, 38, 3537.

5. G. L´Abbé, J. Heterocycl. Chem., 1984, 21, 627.6. G. L´Abbé, K. Buelens, J. Heterocycl. Chem., 1990, 27, 1993.7. A. J. Boulton, P. B. Ghosh, Adv. Heterocycl. Chem., 1969,

10, 1.8. A. J. Boulton, A. R. Katrizky, A. Majid�Hanid, J. Chem.

Soc. C, 1973, 2005.9. A. R. Katrizky, M. F. Gordeev, Heterocycles, 1993, 35, 483.

10. N. N. Makhova, T. I. Godovikova, Mendeleev Chem. J.(Engl. Transl.), 1997, 41, No. 2, 81 [Ross. Khim. Zh., 1997,41, No. 2, 54].

11. N. N. Makhova, A. N. Blinnikov, Mendeleev Commun., 1999,9, 17.

12. E. L. Baryshnikova, N. N. Makhova, Mendeleev Commun.,2000, 10, 190.

13. E. L. Baryshnikova, A. S. Kulikov, I. V. Ovchinnikov, V. S.Solomentsev, N. N. Makhova, Mendeleev Commun., 2001,11, 230.

14. S. I. Molotov, A. S. Kulikov, Yu. A. Strelenko, N. N. Ma�khova, K. A. Lyssenko, Russ. Chem. Bull. (Int. Ed.), 2003,52, 1829 [Izv. Akad. Nauk, Ser. Khim., 2003, 1734].

15. S. I. Molotov, A. S. Kulikov, N. N. Makhova, K. A. Lyssen�ko, Mendeleev Commun., 2003, 13, 188.

16. I. V. Ovchinnikov, M. A. Epishina, S. I. Molotov, Yu. A.Strelenko, K. A. Lyssenko, N. N. Makhova, Mendeleev Com�mun., 2003, 13, 272.

17. A. B. Sheremetev, N. N. Makhova, W. Friedrichsen, Adv.Heterocycl. Chem., 2001, 78, 66.

18. N. N. Makhova, I. V. Ovchinnikov, A. S. Kulikov, S. I.Molotov, E. L. Baryshnikova, Pure Appl. Chem., 2004,76, 1691.

19. L. I. Khmel´nitskii, T. I. Godovikova, S. S. Novikov, Khimiyafuroksanov. Stroenie i sintez [Chemistry of Furoxans. Structureand Synthesis], Nauka, Moscow, 1996, p. 382 (in Russian).

20. Л. I. Khmel´nitskii, T. I. Godovikova, S. S. Novikov, Khimiyafuroksanov. Reaktsii i primenenie [Chemistry of Furoxans.Reactions and Application], Nauka, Moscow, 1996, p. 430(in Russian).

21. F. Shaefer, in The Chemistry of the Cyano Group, Intersci.Publ., New York, 1970, p. 239.

22. V. G. Andrianov, E. N. Rozhkov, A. V. Eremeev, Chem.Heterocycl. Compd. (Engl. Transl.), 1994, 30, 470 [Khim.Geterotsikl. Soedin., 1994, 534].

23. M. Ruccia, N. Vivova, G. Cusmano, G. Macaluso, J. Chem.Soc., Perkin Trans. 1, 1977, 589.

24. A. Defilippi, G. Sorba, R. Calvino, A. Garrone, A. Gasco,M. Orsetti, Arch. Pharm., 1988, 321, 77.

25. A. R. Gagneux, R. Meier, Helv. Chim. Acta, 1970, 53, 1883.26. A. S. Kulikov, I. V. Ovchinnikov, S. I. Molotov, N. N. Ma�

khova, Russ. Chem. Bull. (Int. Ed.), 2003, 52, 1822 [Izv. Akad.Nauk, Ser. Khim., 2003, 1727].

Received December 10, 2012;in revised form February 28, 2013