Trimethylsilyl sulfides

Various S-nucleophiles are allylated. Allylic acetates or carbonates react with thiols or trimethylsilyl sulfide (353) to give the allylic sulfide 354[222], Allyl sulfides are prepared by Pd-catalyzed allylic rearrangement of the dithio-carbonate 355 with elimination of COS under mild conditions. The benzyl alkyl sulfide 357 can be prepared from the dithiocarbonate 356 at 65 C[223,224], The allyl aryl sufide 359 is prepared by the reaction of an allylic carbonate with the aromatic thiol 358 by use of dppb under neutral condi-tions[225]. The O-allyl phosphoro- or phosphonothionate 360 undergoes the thiono thiolo allylic rearrangement (from 0-allyl to S -allyl rearrangement) to afford 361 and 362 at 130 C[226],... 

Another reagent system that has been recently employed in the Paal synthesis of thiophenes is the combination of bis(trialkyltin)- or bis(triaryltin) sulfides with boron trichloride. Known as the Steliou reagent,it has been utilized in the transformation of 1,4-diketone 11 to thiophene 12. Higher yields are obtained in shorter reaction times in contrast to the use of Lawesson s reagent. Additionally, others have noted the relative ease of the work-up procedure using the Steliou conditions, and the fact that the tributyltinchloride byproduct of the reaction is reusable. Similarly, the combination of the bis(trimethylsilyl)sulfide has been used in conjunction with trimethylsilyltriflate for the preparation of thiophenes in an analogous manner. ... 

Aldehydes can be converted into thioaldehydes by a similar reaction with bis(trimethylsilyl) sulfide catalyzed by BuLi (equation II). This disilyl sulfide has been used indirectly for conversion of aldehydes into thioaldehydes via boron trisulfide (11, 63). 

Capperucd and co-workers investigated the dimerization of a,/i-un saturated thioacylsilanes 224, which are generated in situ from 1-silylated alkoxyallenes 222 using bis(trimethylsilyl) sulfide and cobalt(II) chloride hexahydrate as reagents. The resulting 1,2-thiins 223 are isolated as major products in 29-65% yield [128] (Scheme 8.55). 

The reaction of tra i -[ Me3N(H)Al( j,-Se) 2] with N,N,N, N",N"-ptnia-methyldiethylenetriamine (PMEDTA) affords an interesting bicyclic compound with an AUScs (9.33b) skeleton the sulfur analogue of this bicycle 9.33a is obtained from the direct treatment of Me3N AIH3 with bis(trimethylsilyl) sulfide at 90 °C in toluene (Scheme 9.20). ... 

Treatment of bis(trimethylsilyl)sulfide (8) with bromine in anhydrous dichloromethane at - 78°C followed by addition of 1,2-disubstituted alkenes (9) to the reaction mixture at the same temperature gave the thiiranes (10) in about 30% yields (Scheme 5) (88TL4177). This synthesis is (i) highly selective, since only 1,2-disubstituted alkenes undergo the transformation to thiiranes and (ii) stereospecific since the stereochemistry of the alkene is retained in the thiirane. The nature of the reagents suggests that the silyl subsituted sulfenyl bromide (11), formed by attack of bromine on (8), is an intermediate. 

Methyl methylthiosulfinate (lg, 9 mmol) was dissolved in anhydrous chloroform and treated with bis(trimethylsilyl) sulfide (1.62 g, 9 mmol). The reaction mixture was heated to 60CC with stirring for 14 h, diluted with dichloromethane and washed several times with water. After work-up the crude material obtained was distilled under vacuum to obtain the pure trisulfide (830mg, 73%), b.p. 65-68°C725 torr. 

A solution of the aldehyde (1 mmol), the diene (1.5 mmol) and bis(trimethylsilyl) sulfide (2 mmol) in acetonitrile (0.5 ml) was treated at room temperature with a solution of CoC12.6H20 (0.2 mmol) in acetonitrile (2.5 ml). Progress of the reaction was monitored by GC/MS analysis. The reaction mixture was quenched with saturated ammonium chloride, extracted with ether and dried over sodium sulfate, and the solvent removed under vacuum. The crude reaction product was then purified by column chromatography or TLC on silica gel. For R1 = Ph a 94% yield was secured. 

Thiiranes can be formed directly and stereospecifically from 1,2-disubstituted alkenes by addition of trimethylsilylsulfenyl bromide, formed at -78 C from reaction of bromine with bis(trimethylsilyl) sulfide (Scheme 7).12 A two-step synthesis of thiiranes can be achieved by addition of succinimide-A/-sulfe-nyl chloride or phthalimide-A -sulfenyl chloride to alkenes followed by lithium aluminum hydride cleavage of the adducts (Scheme 8).13 Thiaheterocycles can also be formed by intramolecular electrophilic addition of sulfenyl chlorides to alkenes, e.g. as seen in Schemes 914 and 10.13 Related examples involving sulfur dichloride are shown in Schemes 1116 and 12.17 In the former case addition of sulfur dichloride to 1,5-cyclooctadiene affords a bicyclic dichloro sulfide via regio- and stereo-specific intramolecular addition of an intermediate sulfenyl chloride. Removal of chlorine by lithium aluminum hydride reduction affords 9-thiabicyclo[3.3.1]nonane, which can be further transformed into bicyclo[3.3.0]oct-1,5-ene.16... 

Another reagent with limited application in thionation reactions has been S2CI2, which afforded intermediates leading to 1,3,4-oxadithiolanes300. However, among the different thionating reagents developed in recent years the most successful has been bis(trimethylsilyl) sulfide, which in the presence of a catalyst affords thioaldehydes... 

Treatment of aryl and heteroaryl o-azidocarbaldehydes with bis(trimethylsilyl)sulfide and hydrochloric acid gave fused isothiazoles, via thionation of the formyl function followed by spontaneous decomposition at room temperature. Yield was dependent upon the nature of the heteroaromatic ring. [94CL1873, 94PS479]... 

An attractive reagent for the transformation of ketones into thioketones has been introduced by Degl Innocenti and co-workers [74, 75]. The commercially available bis (trimethylsilyl) sulfide works efficiently at room temperature, with catalysis of CF3S03SiMe3 in acetonitrile, for the production of aromatic thiobenzophenones, adamantanethione and 2-cyclenethiones. 

The thionation of aldehydes with bis(trimethylsilyl)sulfide and CoCl2.H20 in the presence of a 1,3-diene was applied to pyruvaldehyde (Table 3, entry 3). In the presence of TMSOTf a remarkable stereochemical effect was observed one equivalent of the Lewis acid leads to a 97 3 endo exo mixture, whereas two equivalents furnish selectively the exo isomer [74]. 

N,Ai-Dialkylaminoethyl tert-butyldimethylsilyl ether 2.B.12 2-iV,iV-Dialkylaminoethyl trimethylsilyl sulfide... 

RCOSi(CH3)3 — RCSSi(CH3)3.1 Acybi lanes by reaction with bis(trimethylsilyl) sulfid yield). The reaction is also applicable to al thioaldehydes, which can be trapped by diem... 

Dithiins 367 have been prepared in moderate yields by [4 + 2] cycloaddition of in situ formed thioenones with thiocarbonyl groups (Scheme 171) <2004SL2159, CHEC-III(8.11.9.2)824>. The thio compounds were generated from trialkylsilyl- or trialkylstannyl-tetrahydropyranyloxy allenes 366 using bis(trimethylsilyl)sulfide (HMDST) and CoC nbE O. 

Although sulfide species are commonly made from sulfur, alkali sulfides, or polysulfides, a useful procedure for converting oxoanions or alkoxides to sulfides is by use of trimethylsilyl sulfide, for example,... 

Sulfuration of 2,3-diaroylbicyclo[2.2.1]hepta-5-enes 50 using B2S3, which is generated in situ by reaction of BCI3 with bis-trialkyltin sulfide or with bis-trimethylsilyl sulfide, produces enthiols 51 and 52. Their cyclizations followed by [3,4] and [3,5] rearrangements afford dihydrothiophene 53 and thiophene 54, respectively (Scheme 12) <1997TL799>. 

Bis(trimethylsilyl) sulfide reacts with methyl, phenyl, or other thiosulfinates (disulfane oxides), R S(0)SR, in anhydrous chloroform at 60 °C to give the symmetrical trisulfane and hexamethyldisiloxane the latter is removed together with the solvent by vacuum distillation, leaving almost pure R2S3 (yields 70 90%). In a similar reaction,... 

Unsaturated thialdehydcs, generated from the corresponding aldehydes by treatment with bis(trimethylsilyl) sulfide in the presence of butyllithium, undergo intramolecular Diels-Alder reaction affording cycloadducts 3 as a mixture of cis- and trans-fused isomers62. 

Segi et al. reacted some aldehydes with bis(trimethylsilyl) sulfide in THF with n-BuLi as catalyst. The thioaldehydes (41) thus formed were trapped with cyclopentadiene to afford adducts 42 as a mixture of endo and exo isomers (88JA1976). French workers have recently reported a gas-phase synthesis of thioxoethanal (44) from precursor (43) 44 was detected as an intermediate by photoelectron spectroscopy and by the formation of adduct 45 (90JOC2596). 

Acylation of a simple thiol with an alkyl carboxylate is not a very suitable method for preparation of S-alkyl thiocarboxylates. Transesterification is, however, possible if either the thiol or the carboxylic ester is activated. The enhanced reactivity of boron, aluminum and silicon thiolates has been utilized for the synthesis of a large variety of thiocarboxylic S-esters, including hydroxy derivatives (from lactones). a,P-Unsaturated thiol esters, e.g. cinnamoyl or 2-butenoyl derivatives, are also accessible. Michael addition, an undesirable side reaction of thiols, is completely avoided if alkyl trimethylsilyl sulfides ortris(arylthio)boranes are applied. ... 

Interestingly, 0-trimethylsilyl carbothioates are formed if acyl chlorides react with trimethylsilyl sulfides (equation 44) 4-2J or N-trimethylsilylthioacetamide (equation 45)." This is obviously due to the... 

The synthesis of a-cyclocitral (161) in Scheme 39 illustrates further how trimethylsilyl sulfides can be synthesized and readily converted to aldehydes by the sila-Pununerer reaction. Compound (159) was prepared by a route involving a 2,3-sigmatropic rearrangement of the ylide derived from intermediate U )> The sila-Pummerer rearrangement of the sulfoxide derived from (158) occurred below room temperature. Unfortunately, however, the enhanced rate of the rearrangement to (160) conferred by the methyl substituent on the intermediate sulfoxide was accompanied by greater than normal difficulty in the (2,5-acetal hydrolysis step. 

Trifluoromethyl trimethylsilyl sulfide. This reagent is obtained by reaction of MCjSil with CFjSag in pyridine at 80°. It is a source of trifluoromethanethiolate for nucleophilic substitution of activated haloarenes. 

Trimethylsilyl sulfides are useful reagents for the synthesis of various organosulfur compounds such as thioacetals (eq (37)) [34] and thiolesters (eq (38)) [35]. 

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