Sulfides, trimethylsilyl alkyl

Trimethylsilyl alkyl and aryl sulfides were found to function as latent sources of a sulfide nucleophile when used in conjunction with allyl carbonates or vinyl epoxides with Pd catalysts (equation 64).223... 

Trimethylsilyl alkyl and aryl sulfides react with allyl carbonates and vinyl epoxides to deliver the alkyl or aryl sulfide to the allyl unit. These species show typical regioselectivities by (i) adding to the less substituted end of alkyl substituted allyls (equation 290) (ii) adding to the allyl terminus more distant from remote oxygen functionality (equation 291) and (iii) showing substantial endocyclic addition to methylenecyclohexane-derived allyls (equation 292).223... 

Reduction of a-silyl sulfides with tributylstannyllithium is also useful for the generation of a-silyl carbanions [251]. When a,a-bis(trimethylsilyl)alkyl phenyl sulfides 137 are treated sequentially with tributylstannyllithium and aldehydes, they give the corresponding alkenylsilanes (Scheme 2.87). This method has an advantage in that tributylstannyllithium is thermally stable and can be stored for several months. 

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],... 

The alkyl chain distribution of the base alcohol in alcohol sulfates is easily determined by gas chromatography. However, alcohol sulfates and alcohol ether sulfates are not volatile and require a previous hydrolysis to yield the free alcohol. The extracted free alcohol can be injected directly [306] or converted to its trimethylsilyl derivative before injection [307]. Alternatively, the alcohol sulfate can be decomposed by hydroiodic acid to yield the alkyl iodides of the starting alcohols [308]. A preferred method forms the alkyl iodides after hydrolysis of the alcohol sulfate which are analyzed after further extraction of the free alcohol, thus avoiding the formation of hydrogen sulfide. This latter method is commonly used to determine the alkyl chain distribution of alcohol ether sulfates. 

Sulfides having two silyl groups are also oxidized electrochemically in methanol to give the corresponding methyl esters (Scheme 11 [36, 37]. The alkylation of (phenylthio)bis(trimethylsilyl)methane with alkyl halides followed by the anodic oxidation provides a convenient access to esters with one-carbon... 

Different nucleophiles such as methanol, allylsilanes, silyl enol ethers, trimethylsilyl-cyanide, and arenes can be used in this process [62]. When the sulfide itself contains an unsaturated or aromatic fragment and the process is carried out in the absence of a nucleophile, an intramolecular anodic sub-stitution/cyclization might occur [61-63]. Methyl esters of 2-benzothiazolyl-2-alkyl or aryl-acetic acid, oxidized in MeOH/Et4 NCIO4 or H2SO4 in the presence of CUCI2, form 2,2-dimethoxy products (Eq. 7) [64]. 

Commercial polymers have been produced from methyl, ethyl, isopropyl, n-butyl, isotubtyl, t-butyl, stcaryl, benzyl and trimethylsilyl vinyl ethers. The polylmethyl vinyl ether) called PVM or Resyn is produced by the polymerization of the monomer by boron trifluoride in propane at —40°C in the presence of traces of an alkyl phenyl sulfide. The polymer may have isotactic, syndiotactic or stereoblock configurations depending on the solvent and catalyst used. 

The phenyl-substituted sulfide 91 (R = Ph) was used for the synthesis of various a-disubstituted phosphepines 93 via sequential deprotonation steps with Bu Li and subsequent treatment with trimethylsilyl chloride (TMS-C1), alkyl iodide, or benzyl bromide <2005TA3416>. 

Na(Hg) used in excess with Na2HP04 in MeOH was particularly efficient, and presented fewer drawbacks. It was possible to perform reductive desulfonylations of sulfones in the presence of alkyl phenyl sulfides. This procedure tolerates ethers, a trimethylsilyl group, esters, - ketones, - isolat double and triple bonds, ketals, - amides and lactones. A few examples are given in Scheme 14. 

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. ... 

Diazo(trialkylsilyl)acetates 1 can be prepared conveniently from an alkyl diazoacetate and a trialkylsilyltriflate in the presence of a tertiary amine (path A). Furthermore, metalation of ethyl diazoacetate with butyllithium at — 110 °C, followed by addition of chlorotrimethylsilane provides ethyl diazo(trimethylsilyl)acetate. Ethyl diazo(trimethylsilyl)acetate and the corresponding trimethylgermyl- and trimethylstannyl- substituted diazoacetate have been prepared from mercury bis(ethyl diazoacetate) and bis(trimethylsilyl-, germyl- or stannyl)sulfide (path B). Ethyl diazo(trimethylgermyl)- and ethyl diazo(trimethylstannyl)acetate were obtained from ethyl diazoacetate and diethylaminotrimethyltin or -germanium (path C). Similarly, the ethyl (trimethylplumbyl)diazoacetate was obtained from bis(trimethylsilyl)aminotrimethyl-lead. 2... 

In the presence of a Lewis acid, silyl enol ethers can be alkylated with reactive secondary halides, such as substituted benzyl halides, and with chloromethylphenyl sulfide (ClCH2SPh), an activated primary halide. Thus, reaction of the benzyl chloride 10 in the presence of zinc bromide with the trimethylsilyl enol ether derived from mesityl oxide allowed a short and efficient route to the sesquiterpene ( )-ar-turmerone (1.22). Reaction of ClCH2SPh with the trimethylsilyl enol ethers of lactones in the presence of zinc bromide, followed by 5-oxidation and pyrolytic ehmination of the resulting sulfoxide (see Section 2.2), provides a good route to the a-methylene lactone unit common in many cytotoxic sesquiterpenes (1.23). Desulfurization with Raney nickel, instead of oxidation and elimination, affords the a-methyl (or a-alkyl starting with RCH(Cl)SPh) derivatives. ... 

Carbon disulfide as the thio-analog of carbonyl compounds reacts with primary amines, resulting in the formation of alkyl isothiocyanates, which have slightly lower RIs than those of other derivatives of primary amines, including A -trimethylsilylated amines (Table 5). The sole product of this reaction is gaseous hydrogen sulfide ... 

Alkylation and hydroxyalkylation of allenic sulfides, 46 -(22) 4-Phenyl-l-butyne, 48 - (23) l-Chloro-5-hexyne, 48 - 24) 3-Buty-noic acid, 49 - (2S) 2,3-Pentadienedioic acid, 50 - (2S) 2-riethyl-2,3--pentadienedioic acid, 51 - (37) 3-Trimethylsilyl-l-heptyne, 52 - 23) 3-Ethynyl-l-hexanol, 53 - (29) 3-Phenyl-3-trimethylsilyl-l-propyne,... 

Direct alkylation has been achieved in special circumstances. Thus 2-(trimethylsilyl)ethyl sulfides, obtainable from alkylation of 2-(trimethylsilyl)ethanethiol or by radical addition of thiols to vinyl trimethylsilane, react with a-glycosyl bromide with the assistance of Ag(I) activation to offer a general synthesis of 8-thioglycosides. Yields generally vary (34-99%), and the fi a ratio can be quite high (eq 10). ... 

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