Stereoselective carbon carbon bond formation via …nopr.niscair.res.in/bitstream/123456789/43828/1/IJCB 57B...Indian Journal of Chemistry Vol. 57B, March 2018, pp. 327-339 Stereoselective

Indian Journal of Chemistry

Vol. 57B, March 2018, pp. 327-339

Stereoselective carbon–carbon bond formation via 1,2-asymmetric induction by a

β-substituent in the reaction of α-chloro sulfides with organozinc reagents

S Raghavan*a & L Raju Chowhana,b

a Natural Product Chemistry Division, CSIR-Indian Institute of Chemical Technology, Hyderabad 500 007, India b School of Chemistry, University of Hyderabad, Hyderabad 500 046, India

E-mail: [email protected]

Received 8 October 2016; accepted (revised) 8 May 2017

The stereoselectivity of C–C bond formation in the reaction of α-chlorosulfides with a variety of organozinc reagents has been investigated. The study reveals excellent 1,2-asymmetric induction by a β-siloxy substituent and moderate 1,2-induction by the β-methyl

substituent. The stereoselectivity is a function of the size of the organozinc reagents.

Keywords: α-Chlorosulfide, organozinc reagents, 1,2-asymmetric induction, chiral α-substituted sulfides

α-Chloro sulfides are versatile intermediates for the

stereocontrolled formation of C–C bonds. Normant1

reported the preparation of organomagnesium reagent

from α-chlorosulfides for C–C bond formation.

Takai and co-workers reported on the reaction of

organochromium reagents2, derived from α-chloro

sulfides, with aldehydes. More recently, Mitzel and

co-workers have prepared organoindium reagents3 from

chloro sulfides and utilized them for the preparation

of epoxy alkynes. α-Chloro sulfides are valuable as

reactive electrophiles for the alkylation of aromatics4,

alkenes5, enolates6, and silyl ethers of aldehydes, ketones7,

esters and lactones8. Chiral α-substituted sulfides are

useful synthons for the preparation of epoxydiynes9,

α,β-unsaturated acids10, allylic alcohols11, and allylic

amino derivatives12. The stereoselective synthesis of

α-substituted sulfides therefore assumes importance.

Results and Discussion

The reaction of the simplest α-chloro sulfide with

phenylmagnesium bromide was reported as early as

1936 by Bohme13. The generality of the reaction was

demonstrated by introducing α-alkyl/aryl substituents

on simple cyclic and acyclic chloro sulfides. There

were no reports however, on the diastereoselective

preparation of α-substituted sulfides prior to our

preliminary report, utilizing organozinc reagents for

stereoselective C–C bond formation from β-siloxy

α-chloro sulfides, Scheme I (Ref 14). Herein, we

provide details of the steric influence of alkyl

substituents attached to the β-carbon of siloxy sulfides

3 in the reaction of the derived chloro sulfides, with

various organozinc reagents. Also the stereoselectivity

of C–C bond formation by 1,2-asymmetric induction

as a function of the size of the alkyl group in β-methyl

α-chloro sulfides derived from sulfides 5 is explored.

The siloxy substrates 3a-d were readily prepared

by reaction of phenythiomethyl lithium15 obtained

from 7 with commercially available aldehydes 8a-d,

followed by silylation (Scheme II).

The α-chloro sulfides, prepared from sulfides 3 by reaction with N-chlorosuccinimide, were reacted with octynylzinc bromide 10a, vinylzinc bromide 10b and butylzinc bromide 10c to furnish syn-siloxy sulfides 4 in synthetically useful yields and diastereoselectivity.

The results are collected in Table I. The structures were assigned to the products based on the J values of the methine protons of the diastereoisomers and by comparison with product 2 (Ref 9,14). The stereoselecitvity of the reaction was determined by integration of the peaks of the diastereomers in the

crude 1H NMR spectrum. An inspection of Table I reveals that sterically bulky sp2 (10b) and sp3 (10c) hybridized nucleophiles reacted with substrates 3a-d uniformly with high selectivity to furnish the syn-isomers as the sole product. With the less bulky sp hybridized reagent 10a, the influence of the β-alkyl

substituent could be discerned. The sulfide 3d with a bulky t-butyl substituent afforded propargylic sulfide 4da as the sole product. Moderate selectivity only was observed in the case of substrates 3b and 3c (dr = 3:1), which was poorer than that observed for sulfide 1 (dr = 9:1).

INDIAN J. CHEM., SEC B, MARCH 2018

328

The diastereoselectivity in the reaction of the

chloro sulfide derived from 3a with 10a could not be

determined by examination of the 1H NMR of crude

product mixture. Thus a branching at the α- or even at

the β-position of the alkyl group is sufficient to

furnish substituted sulfides in good to excellent

diastereoselectivity.

Synthesis and reactions of β-methyl sulfides 5

The substrate 5a was prepared from the known16

alcohol 11a, by reaction with diphenyl disulfide using

Hata's protocol17 (Scheme III). The sulfide 5b, 5c and

5d were prepared using Hata's protocol from the

known alcohols 11b, 11c and 11d (Ref 18). To

comprehend the influence of the β-methyl substituent

relative to the siloxy substituent in the 1,2-asymmetric

induction, sulfides 5a-d were reacted with reagents

10a-c and the results are collected in Table II.

A cursory examination of Table II reveals that

the asymmetric induction by the β-methyl group is

inferior compared to the siloxy group. While substrate

3d afforded 4da as the only product even in the

reaction with the least bulky of the nucleophiles

10a, the chloro sulfide derived from 5d afforded

6da as a 9:1 mixture of isomers. Likewise, while

sulfide 1 afforded products in the reaction with

organozinc reagents 10a-c in excellent selectivity,

5c furnished syn-propargylic sulfide 6ca in a 56:44

ratio. The allylic and alkyl sulfides 6cb and 6cc

were obtained as roughly 3:1 ratio of isomers.

Interestingly, relative to 5c, sulfide 5b possesing an

isopropyl substituent, afforded products with a

better stereoseectivity; allylic sulfide 6bb and alkyl

sulfide 6bc were obtained as sole products and

propargylic sulfide 6ba was obtained in a 3:1 ratio.

The superior induction by the OTBS group is evident

by comparing entry 2, Table I with entry 1, Table II;

the alkyl sulfide 6ac is obtained in a 7:3 ratio

while 6ac was obtained as the sole product. The

influence of the size of the alkyl substituent at the

Scheme I — Stereoselective synthesis of α-substituted sulfides by asymmetric induction

Scheme II — Synthesis of β-siloxy sulfides 3a-d

RAGHAVAN & CHOWHAN: ASYMMETRIC INDUCTION BY β-SUBSTITUENT

329

β-position is evident in the methyl series as in the

OTBS series. The branching at the α-position of

the alkyl substituent is required for efficient

chiral induction. As observed with substrates 3,

vinyl sulfides were obtained in the reaction of

chlorosulfides prepared from 5 with butylzinc reagent.

The ratio of alkylated to eliminated products was

lower due to lower reactivity. It can be concluded

that an alkyl group with α-branching (5b) is required

for obtaining substituted sulfides with good selectivity

in the β-Me series.

Assignment of structure

The observed stereoselectivity of products can be

rationalized by invoking a model depicted in

Scheme IV, wherein the nucleophile (R3M) attacks

the sulfenium ion from the face opposite to the larger

alkyl group (R1), R2 being OTBS/Me groups.

The relative stereochemistry of the compound 5ca

has been assigned as shown in Scheme V, on the

basis of preferred conformations. Acyclic compounds

having vicinal stereogenic centers, each bearing

one hydrogen, normally exist predominantly in the

Table I

Entry Substrate Propargylic sulfide, Yield (dr) Allylic sulfide, Yield (dr) Alkyl sulfide, Yield (dr)

1

86% (90:10)

80% (>95:<5)

64%a (>95:<5)

2

78% (70:30)

75% (>95:<5)

50%a (>95:<5)

3

80% (78:22)

85% (>95:<5)

50%a (>95:<5)

4

75% (75:25)

75% (>95:<5)

45%a (>95:<5)

5

65% (>95:<5)

73% (>95:<5)

48%a (>95:<5)

a: Vinyl sulfide side product also obtained resulting in poor yields.


330

conformation having the hydrogens anti to minimize

gauche interactions19. The preferred conformations

of 5ca and its anti-diastereomer is depicted in

Scheme V. The substituent gauche to the phenyl group

resonates upfield due to the net shielding effect of

the aromatic ring. The observed chemical shifts for

–CH2-C≡C- of 5ca is δ 2.10 (dt, J = 6.7, 2.2 Hz, 2H)

and for the minor anti-diastereomer the signal is

observed at δ 2.18 (dt, J = 6.7, 2.2 Hz, 2H). The

signals for the vinyl group in 5cb appeared at δ 5.56

(m, 1H), 4.80 (d, 1H), 4.68 (d, 1H) and for the anti-

isomer the signals were observed at δ 5.71 (m, 1H),

4.94 (d, 1H) and 4.76 (d, 1H). The chemical shift

values for the major isomer were upfield relative to

the minor isomer. Based on the above, the relative

orientation of the Me- and -SPh groups in the major

Scheme III — Synthesis of β-methyl sulfides 5a-d

Table II

Entry Substrate Propargylic sulfide, Yield (dr) Allylic sulfide, Yield (dr) Alkyl sulfide, Yield (dr)

1

82% (64:36)

73% (75:25)

40% a (68:32)

2

80% (75:25)

80% (>95:<5)

44%a (70:30)

3

80% (56:44)

78% (80:20)

40%a (70:30)

4

73% (90:10)

70% (>95:<5)

55%a (>95:<5)

a: Vinyl sulfide side product also obtained resulting in poor yields.


331

product 5ca-5cc were assigned as syn- and anti- in the

minor isomers. relation. The stereochemistry of other

compounds were assigned based on analogy.

Experimental Section

Unless otherwise indicated, all reactions were

carried out with magnetic stirring and if air or

moisture sensitive, in flame-dried glassware under

nitrogen. Syringes used to transfer reagents and

solvents were purged with nitrogen prior to use. 1H

and 13C NMR spectra were recorded at 200, 300, 400

and 50, 75, 100 MHz respectively in CDCl3. Reactions

were monitored by thin layer chromatography (TLC).

Before use, all the Grignard reagents were titrated

with salicylaldehyde phenylhydrazone indicator.

1-(Phenylthio)octan-2-ol, 9a

To a solution of the mixture of thioanisole 7

(1.2 mL, 10 mmol), DABCO (1.1 g, 10 mmol)

in anhydrous THF (16 mL) was added n-BuLi

(7.3 mL, 1.5 M in Hexanes, 11 mmol) at 0°C. The

mixture was gradually allowed to warm to RT and

stirred for 2 h. The reaction mixture was then

cooled to 0°C, a solution of heptaldehyde 8a (1.4 mL,

10 mmol) in anhydrous THF (10 mL) was added and

the mixture stirred at the same temperature for 1 h.

The reaction mixture was quenched with saturated aq.

NH4Cl, the layers were separated and the aqueous

layer was extracted with EtOAc (3×10 mL). The

combined organic layers were washed with brine

(10 mL), dried over anhyd. Na2SO4, concentrated under

reduced pressure and purified by column chromatography

using 10% EtOAc/Hexanes (v/v) as the eluent to

afford the alcohol 9a (2.0 g, 8.5 mmol) in 85% yield as

a colourless oil. TLC (SiO2): Rf = 0.32 (10% EtOAc/

Hexanes); IR (neat): 3426, 2923, 1582, 1480, 1443,

1301, 1085, 1055, 740, 696 cm−1; 1H NMR (CDCl3,

300 MHz): δ 7.32 (d, J = 7.1 Hz, 2H), 7.24 (t, J = 7.1

Hz, 2H), 7.16 (t, J = 7.1 Hz, 1H), 3.64-3.56 (m, 1H),

3.06 (dd, J = 13.5, 3.3 Hz, 1H), 2.80 (dd, J = 13.5, 8.6

Hz, 1H), 1.49-1.40 (m, 2H), 1.36-1.22 (m, 8H), 0.87

(t, J = 6.7 Hz, 3H); 13C NMR (CDCl3, 75 MHz): δ

135.8, 128.9, 128.3, 125.5, 69.2, 41.0, 35.7, 31.4,

28.9, 25.2, 22.2, 13.7; ESI-MS: m/z 238 [M]+.

4-Methyl-1-(phenylthio)pentan-2-ol, 9b: Following

the procedure detailed above, thioanisole 7 (1.2 mL,

10 mmol) and isovaleraldehde 8b (1.1 mL, 10 mmol)

furnished the alcohol 9b (1.79 g, 8.5 mmol) in 85%

yield as a liquid. TLC (SiO2): Rf = 0.39 (10% EtOAc/

Hexanes); IR (neat): 3448, 2926, 2855, 1630, 1462,

1254, 1217, 1060, 837, 767, 687 cm−1; 1H NMR

(CDCl3, 300 MHz): δ 7.34 (d, J = 7.9 Hz, 2H), 7.25

(t, J = 7.9 Hz, 2H), 7.16 (t, J = 7.9 Hz, 1H), 3.74-3.65

(m, 1H), 3.06 (dd, J = 13.4, 3.5 Hz, 1H), 2.80 (dd,

J = 13.4, 8.4 Hz, 1H), 2.32 (s, 1H), 1.85-1.72 (m, 1H),

1.31-1.24 (m, 2H) 0.95-0.85 (m, 6H); 13C NMR

Scheme IV — Model to rationalize stereoselectivity

Scheme V — Assignment of relative configuration


332

(CDCl3, 75 MHz): δ 136.0, 129.6, 128.9, 126.2, 67.7,

45.3, 24.7, 23.4, 22.1, 14.2; ESI-MS: m/z 234 [M+Na]+.

3-Methyl-1-(phenylthio)butan-2-ol, 9c: Following

the procedure detailed above for the preparation 9a,

thioanisole 7 (1.2 mL, 10 mmol) and isobutanal 8c

(0.9 mL, 10 mmol) furnished sulfide 9c (1.5 g, 8.0

mmol) in 80% yield as a liquid. TLC (SiO2): Rf = 0.35

(10% EtOAc/Hexanes); IR (neat): 3426, 2923, 1582,

1480, 1443, 1301, 1085, 1055, 740, 696 cm−1; 1H NMR (CDCl3, 500 MHz): δ 7.34 (d, J = 7.8 Hz,

2H), 7.28 (t, J = 7.8 Hz, 2H), 7.18 (d, J = 7.8 Hz, 1H),

3.40-3.34 (m, 1H), 3.15 (dd, J = 13.6, 2.9 Hz, 1H),

2.80 (dd, J = 13.6, 5.8 Hz, 1H), 2.32 (s, 1H),

1.79-1.72 (m, 1H), 0.95 (d, J = 7.8 Hz, 3H), 0.94 (d,

J = 6.8 Hz, 3H); 13C NMR (CDCl3, 75 MHz): δ 135.5,

130.1, 129.2, 126.7, 73.9, 40.0, 34.0, 17.8, 17.2;

ESI-MS: m/z 234 [M+O+Na]+; ESI-HRMS: m/z

Calcd for C11H16O2SNa 235.0763. Found: 235.0756.

Note: The sulfide was oxidized to the sulfoxide while

recording the mass spectrum.

3,3-Dimethyl-1-(phenylthio)butan-2-ol, 9d: Following

the general procedure thioanisole 7 (1.2 mL, 10

mmol) and trimethylacetaldehyde 8d (1.1 mL, 10 mmol)

furnished the alcohol 9d (1.26 g, 6.0 mmol) in 60%

yield as a liquid. TLC (SiO2): Rf = 0.35 (10% EtOAc/

Hexanes); IR (neat); 3448, 2926, 2855, 1630, 1462,

1254, 1217, 1060, 837, 767, 697 cm−1; 1H NMR

(CDCl3, 500 MHz): δ 7.34 (d, J = 7.4 Hz, 2H), 7.26

(t, J = 7.4 Hz, 2H), 7.17 (t, J = 7.4 Hz, 1H), 3.25

(dd, J = 11.7, 1.9 Hz, 1H), 3.22 (dd, J = 13.6, 1.9 Hz,

1H), 2.70 (dd, J = 13.6, 11.7 Hz, 1H), 0.90 (bs, 9H); 13C NMR (CDCl3, 75 MHz): δ 135.3, 129.8, 129.0,

126.5, 76.3, 38.0, 34.7, 25.9; ESI-MS: m/z 249

[M+O+Na]+; ESI-HRMS: m/z Calcd for C12H18O2SNa

249.0919. Found: 249.0931. Note: The sulfide was oxidized

to the sulfoxide while recording the mass spectrum.

tert-Butyldimethyl(1-(phenylthio)octan-2-yloxy)

silane, 3a: To a solution of the alcohol 9a (2.0 g, 8.5

mmol) in anhydrous DCM (34 mL) cooled to 0°C was

added imidazole (867 mg, 12.7 mmol, 1.5 eq) followed

by TBS-Cl (1.4 g, 9.35 mmol, 1.1 eq). The mixture

was stirred at RT for a period of 2 h, then diluted

with DCM (30 mL), washed successively with

water (10 mL), brine (10 mL), dried over anhyd.

Na2SO4 and the solvent evaporated under reduced

pressure to yield the crude product which was purified

by column chromatography using hexanes to furnish

the product 3a (2.9 g, 8.2 mmol) in 97% yield as a

liquid. TLC (SiO2): Rf = 0.81 (Hexanes); IR (neat):

2953, 2927, 2855, 1582, 1470, 1252, 1094, 1008, 755,

737, 694 cm−1; 1H NMR (CDCl3, 500 MHz): δ 7.28 (d,

J = 7.8 Hz, 2H), 7.19 (t, J = 7.8 Hz, 2H), 7.08 (t,

J = 7.8 Hz, 1H), 3.77 (m, 1H), 2.95 (dd, J = 13.6, 5.8

Hz, 1H), 2.90 (dd, J = 13.6, 5.8 Hz, 1H), 1.71-1.62

(m, 1H), 1.51-1.44 (m, 1H), 1.32-1.24 (m, 8H),

0.91-0.86 (bs, 12H), 0.03 (s, 3H), 0.00 (s, 3H); 13C NMR (CDCl3, 75 MHz): δ 137.3, 129.3, 128.6,

125.7, 71.4, 40.9, 36.4, 31.9, 29.4, 25.9, 25.8, 22.8,

18.1, 14.2, -4.3, -4.5; ESI-MS: m/z 369 [M+O+H]+.

Note: The sulfide was oxidized to the sulfoxide while


tert-Butyldimethyl(4-methyl-1-(phenylthio)pentan-

2-yloxy)silane, 3b: Following the procedure detailed

above for the preparation of sulfide 3a, the alcohol 9b

(1.79 g, 8.9 mmol) furnished sulfide 3b (2.6 g, 8.2

mmol) in 92% yield as a liquid. TLC (SiO2): Rf = 0.82

(Hexanes); IR (neat): 2955, 2925, 2857, 1580, 1472,

1250, 1090, 1012, 758, 735, 697 cm−1; 1H NMR

(CDCl3, 500 MHz): δ 7.31 (d, J = 7.9 Hz, 2H), 7.22

(t, J = 7.9 Hz, 2H), 7.12 (t, J = 7.9 Hz, 1H), 3.85-3.79

(m, 1H), 2.97 (dd, J = 12.8, 4.9, Hz, 1H), 2.89 (dd,

J = 12.8, 6.9, Hz, 1H), 1.75-1.65 (m, 1H), 1.55-1.48

(m, 2H) 0.95-0.82 (m, 15H), 0.04 (s, 3H), 0.03 (s,

3H); 13C NMR (CDCl3, 75 MHz): δ 137.2, 129.7,

128.8, 126.0, 69.9, 46.1, 27.4, 26.1, 24.5, 23.7, 22.5,

18.4, -4.0, -4.4; ESI-MS: m/z 341[M+O+H]+. Note:

The sulfide was oxidized to the sulfoxide while


tert-Butyldimethyl(3-methyl-1-(phenylthio)butan-

2-yloxy)silane, 3c: Following the procedure detailed

for the preparation 3a, the alcohol 9c (1.5 g, 7.9 mmol)

furnished the product 3c (2.2 g, 7.3 mmol) in 92%

yield as a liquid. TLC (SiO2): Rf = 0.81 (Hexanes); IR

(neat): 2953, 2927, 2855, 1582, 1470, 1252, 1094,

1008, 755, 737, 694 cm−1; 1H NMR (CDCl3, 300

MHz): δ 7.24 (d, J = 7.5 Hz, 2H), 7.28 (t, J = 7.5 Hz,

2H), 7.18 (t, J = 7.5 Hz, 1H), 3.45-3.44 (m, 1H), 3.14

(dd, J = 9.2, 3.1 Hz, 1H), 2.80 (dd, J = 9.2, 3.1 Hz,

1H), 1.81-1.67 (m, 1H), 0.93 (d, J = 6.7 Hz, 3H), 0.9

(s, 9H), 0.79 (d, J = 6.7 Hz, 3H), 0.06 (s, 3H), 0.00 (s,

3H); 13C NMR (CDCl3, 75 MHz): δ 137.4, 129.2,

128.9, 125.9, 75.6, 38.1, 32.5 26.0, 25.8, 18.9, 16.4,

-4.0, -4.5; ESI-MS: m/z 362 [M+O2+NH4]+. Note: The

sulfide was oxidized to the sulfone while recording

the mass spectrum.


333

tert-Butyl(3,3-dimethyl-1-(phenylthio)butan-2-yloxy)

dimethylsilane, 3d: Following the procedure detailed

for the preparation of 3a, the alcohol 9d (1.18 g, 5.6

mmol) furnished the product 3d (1.55 g, 4.8 mmol) in

85% yield as a liquid. TLC (SiO2): Rf = 0.86

(Hexanes); IR (neat): 2953, 2927, 2855, 1582, 1470,

1252, 1094, 1008, 755, 737, 694 cm−1; 1H NMR

(CDCl3, 500 MHz): δ 7.38 (d, J = 7.5 Hz, 2H), 7.33

(t, J = 7.5 Hz, 2H), 7.22 (t, J = 7.5 Hz, 1H), 3.54

(dd, J = 6.5, 3.1 Hz, 1H), 3.31 (dd, J = 13.0, 3.1 Hz, 1H),

2.86 (dd, J = 13.0, 6.5 Hz, 1H), 1.01 (bs, 9H), 0.97

(bs, 9H), 0.12 (s, 6H); ESI-MS: m/z 325 [M+H]+.

tert-Butyldimethyl((7R,8RS)-8-(phenylthio)hexadec-

9-yn-7-yloxy)silane, 4aa

To a solution of 1-octyne (165 mg, 1.5 mmol) in

anhydrous THF (0.8 mL) cooled to −10°C was added

i-PrMgCl·LiCl (1 mL, 1.5 mmol, 1.5 M in THF) and

stirred for 30 min at the same temperature. To the

so generated Grignard reagent, ZnBr2 (1.1 mL, 1.65

mmol, 1.5 M in THF) was added at 0°C and stirred

for 30 min. To the above organozinc reagent cooled

to 0°C was added the solution of chloro sulfide

(0.5 mmol) in anhydrous benzene (5 mL), generated

from sulfide 3a (176 mg, 0.5 mmol). The reaction

mixture was stirred, gradually allowing it to attain

RT, and stirred further for a period of 7 h when TLC

examination indicated complete consumption of the

chlorosulfide. The reaction mixture was cooled to 0°C

and quenched by the addition of an aq. saturated

NH4Cl solution. It was allowed to warm to RT and

diluted with Et2O (5 mL), the layers were separated

and aqueous layer was extracted with Et2O (3×10 mL).

The combined organic layers were washed with brine

(5 mL), dried over anhyd. Na2SO4. The solvent was

evaporated under reduced pressure to afford a crude

compound which was purified by column chromatography

using hexanes as the eluent to afford the pure product

4aa (179 mg, 0.39 mmol) in 78% yield as a liquid.

TLC (SiO2): Rf = 0.88 (Hexanes); IR (neat): 3063,

2954, 2928, 2857, 1586, 1463, 1384, 1253, 1094, 837,

777, 695 cm−1; 1H NMR (CDCl3, 300 MHz): δ 7.45 (d,

J = 6.9 Hz, 2H), 7.30-7.18 (m, 3H), 3.87 (dt, J = 4.5,

2.2 Hz, 1H), 3.75-3.73 (m, 1H), 2.16 (dt, J = 6.7, 2.2

Hz, 2H), 1.78-1.69 (m, 2H), 1.50-1.20 (m, 16H), 0.92-

0.87 (bs, 15H), 0.01 (s, 3H), 0.0 (s, 3H); 13C NMR

(CDCl3, 75 MHz): δ 135.3, 132.1, 128.7, 127.1, 86.1,

77.5, 74.0, 46.3, 33.6, 31.8, 31.3, 29.3, 28.6, 28.4,

25.8, 25.1, 22.6, 22.5, 18.9, 18.1, 14.1, 14.0, −4.5,

−4.6; ESI-MS: m/z 483 [M+Na]+.

tert-Butyldimethyl((3RS,4RS)-3-(phenylthio)dec-

1-en-4-yloxy)silane, 4ab: Following the general

procedure detailed above, the α-chlorosulfide derived

from sulfide 3a (176 mg, 0.5 mmol) was reacted with

vinylzinc bromide (1.5 mmol) at RT (6 h) to afford

the crude product which was purified by column

chromatography using hexanes as the eluent to furnish

the pure product 4ab (141 mg, 0.37 mmol) in 75%


(neat): 3067, 2930, 2856, 1468, 1254, 1094, 840, 776

cm−1; 1H NMR (CDCl3, 300 MHz): δ 7.40 (d, J = 6.9

Hz, 2H), 7.30-7.16 (m, 3H), 5.90 (ddd J = 17.0, 10.2,

8.5 Hz, 1H), 5.15-5.01 (m, 2H), 3.87-3.8 (m, 1H), 3.60

(dd, J = 8.5, 4.1 Hz, 1H), 1.82-1.60 (m, 2H), 1.40-1.20

(bs, 8H), 0.90 (bs, 12H), 0.06 (s, 3H), 0.05 (s, 3H); 13C NMR (CDCl3, 75 MHz): δ 135.7, 132.2, 129.5,

128.7, 126.8, 116.7, 74.5, 43.8, 33.6, 29.3, 25.9, 25.7,

25.6, 22.6, 18.2, 14.1, -3.6, -4.4; ESI-MS: m/z 417

[M+O+Na]+. Note: The sulfide was oxidized to the

sulfoxide while recording the mass spectrum.

tert-Butyldimethyl((5RS,6RS)-5-(phenylthio)dodecan-

6-yloxy)silane, 4ac: Following the general procedure,

the α-chloro sulfide derived from sulfide 3a (176 mg,

0.5 mmol) was reacted with n-butylzinc bromide

(1.5 mmol) at RT (6 h) to afford the crude product

which was purified by column chromatography

using hexanes as the eluent to furnish the pure product

4ac (101 mg, 0.25 mmol) in 50% yield as a liquid.


2954, 2930, 2857, 1468, 1253, 1089, 837 cm−1; 1H NMR (CDCl3, 500 MHz): δ 7.38 (d, J = 8.0 Hz,

2H), 7.24 (t, J = 8.0 Hz, 2H), 7.18 (t, J = 8.0 Hz, 1H),

3.69-3.64 (m, 1H), 3.12 (dt, J = 6.0, 3.0 Hz, 1H),

1.92-1.84 (m, 1H), 1.83-1.77 (m, 1H), 1.67-1.58 (m,

1H), 1.44-1.20 (m, 13H), 0.94-0.88 (m, 6H), 0.85 (s,

9H), -0.09 (s, 3H), -0.10 (s, 3H); 13C NMR (CDCl3,

75 MHz): δ 136.6, 132.0, 128.8, 126.7, 74.1, 55.7,

32.0, 31.5, 30.4, 29.8, 29.4, 28.7, 26.7, 26.0, 22.8,

18.0, 14.3, 14.2, -4.3, -4.4; ESI-MS: m/z 380 [M]+.

tert-Butyldimethyl((4RS,5RS)-2-methyl-5-(phenylthio)

tridec-6-yn-4-yloxy)silane, 4ba: Following the

general procedure, the α-chlorosulfide prepared from

sulfide 3b (162 mg, 0.5 mmol) was reacted with

1-octynylzinc bromide (1.5 mmol) at RT (6 h) to

afford the crude product which was purified by

column chromatography using hexanes as the eluent

to furnish the pure product 4ba (172 mg, 0.4 mmol) in

80% yield as a liquid. TLC (SiO2): Rf = 0.86


334

(Hexanes); IR (neat): 3063, 2954, 2928, 2857, 1586,

1463, 1384, 1253, 1094, 837, 777, 695 cm−1; 1H NMR

(CDCl3, 500 MHz): δ 7.49 (d, J = 6.7 Hz, 2H), 7.30-7.20

(m, 3H), 3.89 (dt, J = 4.5, 2.2 Hz, 1H), 3.78 (td, J = 7.5,

5.2 Hz, 1H), 2.15 (dt, J = 5.2, 2.2 Hz, 2H), 1.80-1.70

(m, 2H), 1.52-1.25 (m, 12H), 0.97-0.91 (bs, 15H),

0.02 (s, 6H); 13C NMR (CDCl3, 75 MHz): δ 135.5,

132.3, 128.8, 127.2, 86.3, 77.5, 74.2, 46.5, 33.8, 32.0,

31.5, 29.5, 28.8, 28.6, 26.0, 25.3, 22.8, 19.1, 18.3,

14.2, −4.3, −4.4; ESI-MS: m/z 455 [M+Na]+;

ESI-HRMS: m/z Calcd for C26H44OSSiNa 455.2779.

Found: 455.2765.


hept-1-en-4-yloxy)silane, 4bb: Following the general

procedure, the α-chloro sulfide prepared from sulfide

3b (162 mg, 0.5 mmol) was reacted vinylzinc bromide


which was purified by column chromatography using

hexanes as the eluent to furnish the pure product 4bb

(148 mg, 0.42 mmol) in 85% yield as a liquid. TLC

(SiO2): Rf = 0.85 (Hexanes); 1H NMR (CDCl3, 500

MHz): δ 7.36 (d, J = 7.0 Hz, 2H), 7.24 (t, J = 7.0 Hz,

2H), 7.19 (t, J = 7.0 Hz, 1H), 5.92 (ddd, J = 17.0, 10.0,

8.0 Hz, 1H), 5.10-5.01 (m, 2H), 3.91 (td, J = 8.0, 4.0

Hz, 1H), 3.65 (dd, J = 8.0, 4.0 Hz, 1H), 1.73-1.65

(m, 1H), 1.59-1.53 (m, 1H), 1.44-1.38 (m, 1H), 0.94

(d, J = 7.0 Hz, 6H), 0.89 (bs, 9H), 0.02 (s, 3H), 0.01

(s, 3H); 13C NMR (CDCl3, 75 MHz): δ 135.6, 135.5,

132.4, 128.8, 126.9, 117.0, 72.7, 58.7, 42.6, 26.1,

24.4, 23.8, 22.2, 18.3, −4.1, −4.3; ESI-MS: m/z 373

[M+Na]+; ESI-HRMS: m/z Calcd for C20H34OSSiNa

373.1997. Found: 373.1986.


nonan-4-yloxy)silane, 4bc: Following the general

procedure, the α-chloro sulfide prepared from sulfide

3b (162 mg, 0.5 mmol) was reacted with n-butylzinc

bromide (1.5 mmol) at RT (6 h) to afford the crude product


hexanes as the eluent to furnish the pure product 4bc



MHz): δ 7.52 (d, J = 7.5 Hz, 2H), 7.42-7.31 (m, 3H),

3.87 (td, J = 5.2, 3.0, Hz, 1H), 3.14 (td, J = 6.0, 3.0

Hz, 1H), 2.08-1.95 (m, 1H), 1.84-1.66 (m, 2H),

1.53-1.33 (m, 4H), 1.15-0.97 (m, 20H), 0.0 (s, 3H),

-0.01 (s, 3H); 13C NMR (CDCl3, 75 MHz): δ 132.5,

129.2, 129.0, 127.0, 71.9, 40.6, 30.6, 28.5, 26.0, 24.5,

24.2, 22.9, 21.8, 18.2, 14.3, -4.3, -4.5; ESI-MS: m/z

419 [M+O+Na]+. Note: The sulfide was oxidized to

the sulfoxide while recording the mass spectrum.


dodec-5-yn-3-yloxy)silane, 4ca: Following the general

procedure, the α-chlorosulfide prepared from 3c (156

mg, 0.5 mmol) was reacted with the 1-octynylzinc

bromide at RT (6 h) to afford the crude product which

was purified by column chromatography using

hexanes as the eluent to furnish the pure product 4ca


(SiO2): Rf = 0.85 (Hexanes); IR (neat): 3062, 2955,

2926, 2855, 1587, 1462, 1385, 1252, 1090, 835, 776,

693 cm−1; 1H NMR (CDCl3, 300 MHz): δ 7.46 (d,

J = 7.5 Hz, 2H), 7.30-7.10 (m, 3H), 3.89 (dt, J = 4.9,

2.4 Hz, 1H), 3.62 (dd, J = 4.7, 2.4 Hz, 1H), 2.20-2.0

(m, 2H), 1.40-1.20 (m, 8H), 0.91-0.72 (m, 19H), 0.10

(s, 3H), 0.01 (s, 3H); 13C NMR (CDCl3, 75 MHz): δ

136.1, 131.9, 128.8, 126.9, 86.3, 79.3, 78.9, 45.7,

32.2, 31.5, 29.8, 28.7, 26.3, 22.7, 20.8, 19.1, 18.6,

17.5, 14.2, -3.6, -4.0; ESI-MS: m/z 441 [M+Na]+.


hex-5-en-3-yloxy)silane, 4cb: Following the general

procedure, the α-chlorosulfide prepared from 3c (156

mg, 0.5 mmol) was reacted with vinylzinc bromide



hexanes as the eluent to furnish the pure product 4cb



MHz): δ 7.34 (d, J = 6.8 Hz, 2H), 7.27-7.16 (m, 3H),

5.86 (ddd, J = 16.6, 9.7, 8.7 Hz, 1H), 4.94 (d, J = 9.7

Hz, 1H), 4.86 (d, J = 16.6 Hz, 1H), 3.65 (dd, J = 8.7,

4.8 Hz, 1H), 3.59 (t, J = 4.8 Hz, 1H), 2.04 (m, 1H),

0.99-0.93 (m, 15H). 0.10 (s, 3H), 0.05 (s, 3H); 13C NMR (CDCl3, 75 MHz): δ 136.9, 135.4, 132.3,

128.5, 126.7, 115.6, 79.5, 59.0, 32.1, 29.8, 26.3, 20.7,

17.9, −3.5, −3.8.


octan-3-yloxy)silane, 4cc: Following the general procedure,

the α-chlorosulfide prepared from 3c (156 mg, 0.5

mmol) was reacted with n-butylzinc bromide (1.5 mmol)

at RT (6 h) to afford the crude product which was

purified by column chromatography using hexanes as

the eluent to furnish the pure product 4cc (81 mg,

0.23 mmol) in 45% yield as a liquid. TLC (SiO2):

Rf = 0.83 (Hexanes); 1H NMR (CDCl3, 500 MHz): δ

7.38 (d, J = 7.1 Hz, 2H), 7.30-7.18 (m, 3H), 3.56 (dd,


335

J = 4.9, 3.2 Hz, 1H), 3.12-3.06 (m, 1H), 1.90-1.80

(m, 1H), 1.40-1.20 (m, 2H), 1.02-0.85 (m, 22H),

−0.01 (s, 3H), −0.03 (s, 3H); 13C NMR (CDCl3, 75

MHz): δ 137.3, 131.2, 128.8, 126.2, 78.4, 55.4, 31.2,

30.4, 29.7, 26.0, 25.6, 22.6, 21.5, 19.0, 14.0, −4.1, −4.2.

tert-Butyl((3RS,4RS)-2,2-dimethyl-4-(phenylthio)dodec-

5-yn-3-yloxy)dimethylsilane, 4da: Following the


sulfide 3d (162 mg, 0.5 mmol) was reacted with

octynylzinc bromide (1.5 mmol) at RT (6 h) to afford



the pure product 4da (140 mg, 0.32 mmol) in 65%


(neat): 3064, 2952, 2928, 2857, 1586, 1463, 1384,

1253, 1094, 837, 777, 695 cm−1; 1H NMR (CDCl3, 500

MHz): δ 7.46 (d, J = 7.7 Hz, 2H), 7.25-7.15 (m, 3H),

4.02 (dt, J = 3.7, 2.2 Hz, 1H), 3.71 (d, J = 3.7 Hz,

1H), 2.16 (td, J = 6.0, 2.2 Hz, 2H), 1.49-1.42 (m, 2H),

1.32-1.23 (m, 6H), 1.02 (s, 9H), 1.00 (s, 9H), 0.90

(t, J = 6.7 Hz, 3H), 0.27 (s, 3H), 0.11 (s, 3H); 13C NMR (CDCl3, 75 MHz): δ 137.0, 131.4, 128.6,

126.4, 84.6, 83.3, 82.2, 43.4, 37.0, 31.6, 29.9, 28.7,

27.2, 26.5, 22.8, 19.1, 14.3, −2.9, −4.5; ESI-MS: m/z

455 [M+Na]+; ESI-HRMS: m/z Calcd for

C26H44OSSiNa 455.2779. Found: 455.2765.

tert-Butyl((3RS,4RS)-2,2-dimethyl-4-(phenylthio)

hex-5-en-3-yloxy)dimethylsilane, 4db: Following

the general procedure, the α-chlorosulfide prepared

from sulfide 3d (162 mg, 0.5 mmol) was reacted with

vinylzinc bromide (1.5 mmol) at RT (6 h) to afford



the pure product 4db (127 mg, 0.36 mmol) in 73%

yield as a liquid. TLC (SiO2): Rf = 0.83 (Hexanes); 1H NMR (CDCl3, 500 MHz): δ 7.35-7.11 (m, 5H),

5.95 (ddd, J = 17.3, 10.5, 9.0 Hz, 1H), 4.88 (d, J = 10.5

Hz, 1H), 4.72 (d, J = 17.3 Hz, 1H), 3.75 (dd, J = 9.0,

2.2 Hz, 1H), 3.52 (d, J = 2.2 Hz, 1H), 0.97 (s, 9H),

0.92 (s, 9H), 0.15 (s, 3H), 0.04 (s, 3H); 13C NMR

(CDCl3, 75 MHz): δ 139.8, 132.4, 129.1, 128.8, 126.7,

114.8, 82.8, 57.2, 37.5, 27.6, 26.7, 19.1, −2.7, −3.8.

tert-Butyl((3RS,4RS)-2,2-dimethyl-4-(phenylthio)

octan-3-yloxy)dimethylsilane, 4dc: Following the


sulfide 3d (162 mg, 0.5 mmol) was reacted with

n-butylzinc bromide (1.5 mmol) at RT (6 h) to afford



the pure product 4dc (92 mg, 0.28 mmol) in 48%

yield as a liquid. TLC (SiO2): Rf = 0.84 (Hexanes); 1H NMR (CDCl3, 500 MHz): δ 7.26 (d, J = 7.5 Hz,

2H), 7.19 (t, J = 7.5 Hz, 2H), 7.06 (t, J = 7.5 Hz, 1H),

3.49 (s, 1H), 3.20 (dd, J = 8.8, 5.4 Hz, 1H), 1.82-1.72

(m, 1H), 1.69-1.56 (m, 2H), 1.28-1.20 (m, 6H) 0.98

(s, 12H), 0.94 (s, 9H), 0.10 (s, 3H), 0.03 (s, 3H); 13C NMR (CDCl3, 75 MHz): δ 138.3, 130.4, 128.8,

125.7, 81.1, 51.8, 36.8, 35.8, 30.6, 27.8, 26.6, 22.7,

19.1, 14.2, −2.9, −3.8.

(2-Methylpentyl)(phenyl)sulfane, 5a

To the mixture of the alcohol 11a (510 mg, 5

mmol) and diphenyl disulfide (1.2 g, 5.5 mmol) in

anhydrous THF (20 mL) cooled to 0°C was added

Bu3P (7.5 mL, 7.5 mmol, 1.5 M in EtOAc) drop-wise

and the mixture stirred for 4 h while allowing it to

warm to RT gradually. The reaction mixture was then

diluted with water (5 mL). The aqueous layer was

separated and extracted with EtOAc (3×15 mL). The

combined organic layer were washed with brine

(5 mL), dried over anhyd. Na2SO4 and concentrated

under reduced pressure to afford the crude sulfide


2% EtOAc/Hexanes (v/v) as the eluent to afford the

pure sulfide 5a as a viscous oil (824 mg, 4.25 mmol)

in 85% yield; TLC (SiO2): Rf = 0.81 (Hexanes); IR

(neat): 3445, 2955, 2927, 2855, 1580, 1470, 1252,

1094, 1006, 775, 694 cm−1; 1H NMR (CDCl3, 500

MHz): δ 7.26 (d, J = 7.4 Hz, 2H), 7.21 (t, J = 7.4 Hz,

2H), 7.09 (t, J = 7.4 Hz, 1H), 2.89 (dd, J = 12.8, 5.9

Hz, 1H), 2.74 (dd, J = 12.8, 7.9 Hz, 1H), 1.75-1.70

(m, 1H), 1.50-1.43 (m, 1H), 1.40-1.19 (m, 3H),

1.10 (d, J = 6.6 Hz, 3H), 0.89 (t, J = 7.1 Hz, 3H); 13C NMR (CDCl3, 75 MHz): δ 135.2, 128.9, 128.8,

125.6, 41.1, 38.6, 32.8, 20.1, 19.5, 14.4. ESI-MS: m/z

194 [M]+.

(2,3-Dimethylbutyl)(phenyl)sulfane, 5b: The

alcohol 11b (510 mg, 5 mmol) was converted into the

sulfide 5b by following the procedure detailed above.

The crude sulfide was purified by column

chromatography using 2% EtOAc/Hexanes (v/v) as

the eluent to afford the pure sulfide 5b as a viscous

oil (824 mg, 4.25 mmol) in 85% yield as a liquid.

TLC (SiO2): Rf = 0.84 (Hexanes); 3063, 2955, 2927,

2855, 1580, 1470, 1252, 1094, 1006, 775, 694 cm−1;

1H NMR (CDCl3, 500 MHz): δ 7.31 (d, J = 7.2 Hz,

2H), 7.25 (t, J = 7.2 Hz, 2H), 7.14 (t, J = 7.2 Hz, 1H),

3.01 (dd, J = 12.7, 5.4 Hz, 1H), 2.71 (dd, J = 12.7, 8.2


336

Hz, 1H), 1.85-1.78 (m, 1H), 1.68-1.62 (m, 1H), 1.01

(d, J = 6.3 Hz, 3H) 0.95 (d, J = 7.2, Hz, 3H), 0.90

(d, J = 6.3 Hz, 3H); 13C NMR (CDCl3, 75 MHz): δ

137.8, 129.0, 128.8, 125.5, 39.0, 38.6, 31.6, 20.5,

18.0, 15.4; ESI-MS: m/z 194 [M]+.

Phenyl(2-phenylpropyl)sulfane, 5c: Sulfide 5c

was prepared by from alcohol 11c (680 mg, 5 mmol)

following the general procedure. The crude sulfide

was purified by column chromatography using


pure sulfide 5c as a viscous oil (969 mg, 4.25 mmol)

in 85% yield as a liquid. TLC (SiO2): Rf = 0.84

(Hexanes); 3063, 2955, 2927, 2855, 1580, 1470,

1252, 1094, 1006, 775, 694 cm−1; 1H NMR (CDCl3,

500 MHz): δ 7.28-7.09 (m, 10H), 3.18 (dd, J = 12.8,

5.4 Hz, 1H), 3.12-2.92 (m, 2H), 1.39 (d, J = 6.4 Hz,

3H); 13C NMR (CDCl3, 125 MHz): δ 145.3, 136.8,

128.8, 128.7, 128.3, 126.8, 126.4, 125.6, 41.8, 39.2,

20.8; ESI-MS: m/z 245 [M+O+H]+.

Phenyl(2,3,3-trimethylbutyl)sulfane, 5d: Sulfide

5d was prepared by from alcohol 11d (580 mg,

5 mmol) following the general procedure. The crude

sulfide was purified by column chromatography using


pure sulfide 5d as a viscous oil (884 mg, 4.25 mmol)

in 85% yield as a liquid. TLC (SiO2): Rf = 0.84

(Hexanes); 3065, 2955, 2927, 2855, 1580, 1470,

1252, 1094, 1006, 775, 694 cm−1; 1H NMR (CDCl3,

300 MHz): δ 7.30-7.17 (m, 4H), 7.10 (t, J = 6.9 Hz,

1H), 3.20 (d, J = 12.2 Hz, 1H), 2.40 (dd, J = 12.5, 1.8

Hz, 1H), 1.49-1.39 (m, 1H), 1.02 (d, J = 6.6 Hz, 3H),

0.91-0.88 (bs, 9H); 13C NMR (CDCl3, 75 MHz): δ

137.7, 128.8, 128.6, 125.4, 42.7, 36.9, 33.2, 27.3,

14.2; ESI-MS: m/z 208 [M]+.

((4SR,5RS)-4-Methyltridec-6-yn-5-yl)(phenyl)sulfane,

6aa: Following the general procedure, the α-

chlorosulfide prepared from sulfide 5a (97 mg, 0.5

mmol) was reacted with 1-octynylzinc bromide



hexanes as the eluent to furnish the pure product 6aa

as a viscous oil (123 mg, 0.41 mmol) in 82% yield;


2954, 2928, 2857, 1586, 1463, 1384, 1253, 1094, 837,

777, 695 cm−1; 1H NMR (CDCl3, 500 MHz): δ 7.45

(d, J = 6.9 Hz, 4H), 7.25 (t, J = 7.9 Hz, 4H), 7.19

(t, J = 6.9 Hz, 4H), 3.84* (t, J = 1.9 Hz,1H), 3.75

(t, J = 1.9 Hz, 1H), 2.16 (dt, J = 6.9, 1.9 Hz, 4H),

1.82-1.76 (m, 2H), 1.72-1.66 (m, 2H), 1.50-1.42

(m, 6H), 1.38-1.22 (m, 16H), 1.09 (d, J = 5.9 Hz, 6H),

0.92 (t, J = 6.9, 6H), 0.89 (t, J = 6.9 Hz, 6H); 13C NMR (CDCl3, 75 MHz) 137.0, 136.4*, 132.0,

131.8*, 128.7*, 128.6, 127.1, 126.9*, 86.0*, 85.6,

78.8, 77.6*, 46.2, 45.2*, 37.6, 37.5*, 37.4, 36.9, 35.2,

31.4, 29.8, 28.8*, 28.5, 22.7, 20.5, 20.4*, 18.9, 14.4*,

14.2. Note: The signals for the minor diastereoisomer

are indicated by an asterisk mark.

((3SR,4SR)-4-Methylhept-1-en-3-yl)(phenyl)sulfane,

6ab: Following the general procedure, the α-chlorosulfide

prepared from sulfide 5a (97 mg, 0.5 mmol) was

reacted with vinylzinc bromide (1.5 mmol) at RT

(6 h) to afford the crude product which was purified

by column chromatography using hexanes as the

eluent to furnish the pure product 6ab as a viscous

oil (80 mg, 0.36 mmol) in 73% yield; TLC (SiO2): Rf

= 0.90 (Hexanes); IR (neat): 3067, 2930, 2856, 1468,

1254, 1094, 840, 776 cm−1; 1H NMR (CDCl3, 500

MHz): δ 7.29-7.21 (m, 10H), 5.78-5.70 (m, 2H), 4.94

(d, J = 9.0 Hz, 2H), 4.88 (d, J = 16.2 Hz, 1H), 4.84*

(d, J = 16.2 Hz, 1H), 3.55* (dd, J = 9.0, 5.0 1H), 3.51

(dd, J = 9.0, 5.0 Hz, 1H), 1.30-1.20 (m, 10H), 1.02

(d, J = 7.0 Hz, 3H), 1.00* (d, J = 7.0 Hz, 3H), 0.90

(t, J = 7.0, 6H); 13C NMR (CDCl3, 75 MHz): δ 137.4,

132.5*, 132.3, 129.0*, 128.6, 127.5, 127.1*, 126.8,

126.6*, 116.4*, 115.9, 59.4, 58.4*, 37.0, 35.9*, 29.7,

20.4, 20.2*, 17.2, 16.2*, 14.2. Note: The signals for

the minor diastereoisomer are indicated by an asterisk

mark.

((4SR,5SR)-4-Methylnonan-5-yl)(phenyl)sulfane,

6ac: Following the general procedure, the α-chlorosulfide

prepared from sulfide 5a (97 mg, 0.5 mmol) was

reacted with n-butylzinc bromide (1.5 mmol) at RT



eluent to furnish the pure product 6ac as a viscous oil

(100 mg, 0.45 mmol) in 90% yield in 40:45 ratio of

sulfide 6ac and vinyl sulfide; TLC (SiO2): Rf = 0.90

(Hexanes); IR (neat): 3063, 2954, 2930, 2857, 1468,

1253, 1089, 837 cm−1; 1H NMR (CDCl3, 500 MHz): δ

7.39 (t, J= 7.7 Hz, 4H), 7.26 (t, J = 7.7 Hz, 4H), 7.28

(t, J = 7.7 Hz, 2H), 3.12-3.07 (m, 2H) 1.70-1.44

(m, 8H) 1.40-1.20 (m, 17H), 0.96 (d, J= 6.8 Hz, 6H),

0.89 (t, J= 6.8 Hz, 12H); 13C NMR (CDCl3, 75 MHz):

δ 137.5, 128.7, 128.6, 125.4, 41.0, 38.4, 32.6, 29.9,

20.0, 19.9, 19.3, 19.2, 14.3, 14.2.


337

((3SR,4RS)-2,3-Dimethyldodec-5-yn-4-yl)(phenyl)

sulfane, 6ba: Following the general procedure, the

α-chlorosulfide prepared from sulfide 5b (97 mg,

0.5 mmol) was reacted with 1-octynylzinc bromide



hexanes as the eluent to furnish the pure product 6ba

as a viscous oil (113 mg, 0.37 mmol) in 80% yield;


2954, 2928, 2857, 1586, 1463, 1384, 1253, 1094, 837,

777, 695 cm−1; 1H NMR (CDCl3, 500 MHz): δ 7.4

(d, J = 7.1, 4H), 7.29-7.18 (m, 6H), 4.0-3.96* (m, 1H),

3.75-3.69 (m, 1H), 2.13 (td, J = 6.8, 2.2 Hz, 2H), 1.3-1.2

(m, 20H), 1.06 (d, J = 6.8 Hz, 6H), 0.95 (d, J = 6.7

Hz, 6H), 0.90 (t, J = 6.7 Hz, 6H), 0.85 (d, J = 6.7 Hz,

6H); 13C NMR (CDCl3, 75 MHz): δ 134.5, 132.3,

131.9*, 129.2, 128.6, 128.1*, 127.5*, 127.0, 85.5,

79.8, 44.9, 43.6, 43.4*, 31.6, 31.3*, 29.8, 28.7, 28.5,

22.6, 22.5*, 21.7, 21.1*, 19.3*, 18.9, 18.0*, 17.6,

14.5*, 14.1, 12.9*, 12.8; ESI-MS: m/z 302 [M]+.

Note: The signals for the minor diastereoisomer are

indicated by an asterisk mark.

((3SR,4SR)-4,5-Dimethylhex-1-en-3-yl)(phenyl)

sulfane, 6bb: Following the general procedure, the

α-chlorosulfide prepared from sulfide 5b (97 mg,

0.5 mmol) was reacted with vinylzinc bromide



hexanes as the eluent to furnish the pure product 6bb

as a viscous oil (88 mg, 0.4 mmol) in 80% yield; TLC

(SiO2): Rf = 0.90 (Hexanes); IR (neat): 3064, 2932,

2858, 1468, 1256, 1094, 842, 774 cm−1; 1H NMR

(CDCl3, 500 MHz): δ 7.27 (d, J = 6.9 Hz, 2H), 7.20-7.10

(m, 3H), 5.63 (ddd, J = 17.0, 9.8, 9.4 Hz, 1H), 4.78

(d, J = 9.8 Hz, 1H), 4.66 (J = 17.0 Hz, 1H), 3.42 (dd,

J = 9.4, 8.3 Hz, 1H) 1.90-1.80 (m, 1H) 1.50-1.40 (m,

1H), 0.97 (d, J = 6.7 Hz, 3H), 0.9 (d, J = 6.7 Hz, 3H),

0.74 (d, J = 6.6 Hz, 3H); 13C NMR (CDCl3, 75 MHz):

δ 138.7, 133.0, 128.7, 128.6, 126.9, 115.1, 58.7, 43.1,

29.9, 22.0, 17.2, 12.4; ESI-MS: m/z 237 [M+O+H]+.

((3SR,4SR)-2,3-Dimethyloctan-4-yl)(phenyl)sulfane,

6bc: Following the general procedure, the α-chlorosulfide

prepared from sulfide 5b (97 mg, 0.5 mmol) was

reacted with n-butylzinc bromide (1.5 mmol) at RT

(6 h) to afford the crude product which was purified by

column chromatography using hexanes as the eluent to

furnish the pure product 6bc as a viscous oil (116 mg,

0.47 mmol) in 40% yield, TLC (SiO2): Rf = 0.90

(Hexanes); IR (neat): 3063, 2954, 2930, 2857, 1468,

1253, 1089, 837 cm−1; 1H NMR (CDCl3, 500 MHz): δ

7.30-7.10 (m, 5H), 3.25-3.10 (m, 1H), 1.70-1.40

(m, 8H), 1.10 (d, J = 6.7 Hz, 3H), 1.05 (d, J = 6.7 Hz,

3H), 0.99-0.85 (m, 6H).

Phenyl((2SR,3RS)-2-phenylundec-4-yn-3-yl)sulfane,

6ca: Following the general procedure, the α-chlorosulfide

from sulfide 5c (114 mg, 0.5 mmol) was reacted with

1-octynylzinc bromide (1.5 mmol) at RT (6 h) to

afford the crude product which was purified by

column chromatography using hexanes as the

eluent to furnish the pure product 6ca as a viscous oil

(134 mg, 0.4 mmol) in 80% yield; TLC (SiO2):

Rf = 0.91 (Hexanes); IR (neat): 3065, 2956, 2930,

2855, 1584, 1462, 1384, 1253, 1094, 837, 777, 695

cm−1; 1H NMR (CDCl3, 500 MHz): δ 7.43-7.36

(m, 8H), 7.29-7.15 (m, 12H), 4.01 (dt, J = 4.5, 2.2 Hz,

1H), 3.95* (dt, J = 4.5, 2.2 Hz, 1H), 3.07 (q, J = 6.7

Hz, 1H), 2.98* (m, 1H), 2.17 (td, J = 6.7, 2.2 Hz, 2H),

2.08* (dt, J = 6.7, 2.2 Hz, 2H), 1.48 (d, J = 6.7 Hz,

6H), 1.37-1.18 (m, 16H), 0.9 (t, J = 6.0 Hz, 3H),

0.80* (t, J = 6.7 Hz, 3H); 13C NMR (CDCl3, 75

MHz): δ 144.1*, 143.0, 135.2*, 134.6, 132.4, 132.2*,

129.4, 129.2*, 128.9, 128.8*, 128.4, 128.0*, 127.7,

127.3*, 127.1, 126.9, 87.2, 86.9*, 78.7, 77.4*, 46.7,

46.6*, 44.0, 43.4*, 31.5, 28.8*, 28.7, 28.6, 22.7, 19.7,

19.1, 19.0, 17.3, 14.3; ESI-MS: m/z 336[M]+. Note:

The signals for the minor diastereoisomer are indicated

by an asterisk mark.

Phenyl((3SR,4SR)-4-phenylpent-1-en-3-yl)sulfane,

6cb: Following the general procedure the the

α-chlorosulfide prepared from sulfide 5c (114 mg,

0.5 mmol) was reacted with the organozinc reagent

prepared from vinylmagnesium bromide (1.5 mmol)

at RT (6 h) to afford the crude product which was


the eluent to furnish the pure product 6cb as a viscous


= 0.91 (Hexanes); IR (neat): 3064, 2932, 2856, 1468,

1254, 1094, 840, 776 cm−1; 1H NMR (CDCl3, 500

MHz): δ 7.42-7.21 (m, 20H), 5.75* (ddd, J = 16.9,

9.9, 9.0 Hz, 1H), 5.56 (ddd, J = 16.9, 9.9, 7.0 Hz, 1H),

4.95* (d, J = 9.9 Hz, 1H), 4.81 (d, J = 10.0 Hz, 1H),

4.77* (d, J = 16.9 Hz 1H), 4.68 (d, J = 16.9 Hz, 1H),

3.75* (dd, J = 6.7, 9.0 Hz, 1H), 3.71 (dd, J = 9.3, 7.0

Hz, 1H), 3.22* (q, J = 6.7 Hz, 1H), 3.01-3.11 (m, 1H),

1.48 (d, J = 6.7 Hz, 3H), 1.39* (d, J = 6.7 Hz, 3H); 13C NMR (CDCl3, 75 MHz): δ 137.2*, 136.7, 132.9,

132.8, 128.9, 128.8, 128.3*, 128.2, 127.9*, 127.86,


338

127.1, 126.7, 116.9*, 116.3, 60.0, 59.8*, 43.9, 43.7*,

29.8; 19.8; ESI-MS: m/z 254 [M]+.

Phenyl((2SR,3SR)-2-phenylheptan-3-yl)sulfane, 6cc:

Following the general procedure the α-chlorosulfide

prepared from sulfide 5c (114 mg, 0.5 mmol) was

reacted with the organozinc reagent prepared from n-

butyl bromide (1.5 mmol) at RT (6 h) to afford the

crude product which was purified by column


the pure product 6cc as a viscous oil (113 mg, 0.4

mmol) in 40% yield; TLC (SiO2): Rf = 0.90

(Hexanes); IR (neat): 30635, 2954, 2930, 2857, 1468,

1253, 1089, 837 cm−1; 1H NMR (CDCl3, 500 MHz): δ

7.5-7.2 (m, 20H), 3.39-3.34* (m, 1H), 3.14 (q, J = 6.7

Hz, 1H), 3.04* (q, J = 6.7 Hz, 1H), 2.95-2.85 (m, 1H),

1.65-1.60* (m, 1H), 1.55-1.47 (m, 1H), 1.42 (d, J = 6.7

Hz, 3H), 1.40 (d, J = 6.7 Hz, 3H), 1.25-1.15 (m, 12H),

0.97* (t, J = 6.7 Hz, 3H), 0.80 (t, J = 6.7 Hz, 3H);

13C NMR (CDCl3, 75 MHz): δ 131.7, 129.2, 129.0,

128.5, 128.2, 127.9, 127.6, 126.5, 57.6, 44.0, 42.5*,

33.2, 29.9*, 29.6, 25.3, 17.9*, 18.9, 14.1.

Phenyl((3SR,4RS)-2,2,3-trimethyldodec-5-yn-4-yl)

sulfane, 6da: Following the general procedure, the

α-chlorosulfide prepared from 5d (104 mg, 0.5 mmol)

was reacted with 1-octynylzinc bromide (1.5 mmol) at

RT (6 h) to afford the crude product which was


the eluent to furnish the pure product 6da as a viscous


= 0.93 (Hexanes); IR (neat): 3063, 2954, 2928, 2857,

1586, 1463, 1384, 1253, 1094, 837, 777, 695 cm−1; 1H NMR (CDCl3, 500 MHz): δ 7.44 (d, J = 7.2 Hz,

2H), 7.25-7.21 (m, 3H), 4.05 (d, J = 2.0 Hz, 1H), 2.10

(dt, J = 7.2, 2.0 Hz, 2H), 1.86-1.82 (m, 1H), 1.42-1.34

(m, 2H) 1.3-1.2 (m, 6H), 1.18 (d J = 7.2 Hz, 3H), 1.04

(bs, 9H), 0.88 (t, J = 7.2 Hz, 3H); 13C NMR (CDCl3,

75 MHz): δ 136.2, 131.9, 128.6, 126.8, 84.1, 81.9,

48.6, 43.0, 33.9, 31.5, 28.8, 28.8, 27.4, 22.7, 19.0,

14.2, 12.1; ESI-MS: m/z 316 [M]+.

Phenyl((3SR,4SR)-4,5,5-trimethylhex-1-en-3-yl)

sulfane, 6db: Following the general procedure, the


was reacted with vinylzinc bromide (1.5 mmol) at RT



eluent to furnish the pure product 6db as a viscous

oil (82 mg, 0.35 mmol) in 70% yield; TLC (SiO2):

Rf = 0.92 (Hexanes); IR (neat): 3067, 2930, 2856,

1468, 1254, 1094, 840, 776 cm−1; 1H NMR (CDCl3,

500 MHz): δ 7.30-7.08 (m, 5H), 5.85 (ddd J = 15.8,

9.8, 8.3 Hz, 1H), 4.78 (m, 2H), 3.76 (dd, J = 8.3, 1.7

Hz, 1H), 1.66-1.56 (m, 1H), 1.10-1.04 (m, 12H); 13C NMR (CDCl3, 75 MHz): δ 140.0, 136.2, 132.1,

128.7, 126.6, 113.9, 55.5, 47.7, 29.2, 28.8, 27.5; ESI-

MS: m/z 234 [M]+.

Phenyl((3SR,4SR)-2,2,3-trimethyloctan-4-yl)sulfane,

6dc: Following the general procedure, the


was reacted with n-butylzinc bromide (1.5 mmol) at

RT (6 h) to afford the crude product which was


the eluent to furnish the pure product 6dc as a viscous

oil (72 mg, 0.27 mmol) in 55% yield of sulfide 6dc;


2954, 2930, 2857, 1468, 1253, 1089, 837 cm−1; 1H NMR (CDCl3, 500 MHz) 7.33-7.10 (m, 5H), 3.37

(m, 1H), 1.65-1.55 (m, 7H), 1.13 (s, 9H), 1.01 (s, 3H),

1.0 (t, J = 6.6 Hz, 3H); 13C NMR (CDCl3, 75 MHz):

δ 137.5, 129.0, 128.9, 128.3, 44.9, 36.9, 30.0, 29.1,

28.5, 27.4, 22.7, 15.2, 14.1.

Conclusion

A general stereoselective route to α-substituted

sulfides has been developed taking advantage of

1,2-asymmetric induction. The asymmetric induction

by a β-siloxy substituent is better than the β-methyl

substituent. The products have useful handles for

further functionalization to synthetic intermediates.

Acknowledgements

LRC is thankful to CSIR, New Delhi for

fellowship. SR acknowledges funding from DST

(SR/S1/OC-5/2011) and CSIR, New Delhi as a part of

the XII five year plan programme under the title

ORIGIN (CSC-108).

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