Vinyl thioethers, synthesis

Reaction of organolithium compounds with vinyl thioethers Synthesis of thioethers... 

Thiophenols undergo base-catalyzed, Michael addition to acetylenic acids and esters to give trans addition products. These vinyl thioethers have been used in the synthesis of thiochromones. " Recently, Undheim and Lie have shown that thiophenol adds to DMAD with concomitant cyclization to give benzo[6]thiophenes. 

Azine approach. Cyclization by oxidative formation of the S—N bond is frequently the final step in isothiazole syntheses. This approach can be used in the synthesis of the parent cation from the thioformyl precursor (129). 2-Substituted derivatives would require thioketone precursors and such compounds are more readily available as vinyl thioethers, e.g. (130). Bromine is used for the oxidative cyclization in this instance giving (13lj (73CC150). 

Vinyllithiums of type 663 (R2 = R3 = H) reacted with primary alkyl bromides, carbonyl compounds, carbon dioxide, DMF, silyl chlorides, stannyl chlorides, disulfides and phenylselenyl bromide142,970-979. Scheme 173 shows the synthesis of dihydrojasmone 669 from the corresponding 1,4-diketone. a-(Phenylsulfanyl)vinyllithium 665, prepared from phenyl vinyl thioether, reacted with hexanal and the corresponding adduct 666 was transformed into its acetoacetate. This ester 667 underwent a Carrol reaction to produce the ketone 668, which was transformed into the cyclopentenone 669 by deprotection either... 

Carey, F.A., and Court, A.S., Silicon-containing carbanions. Part 1. Synthesis of vinyl thioethers and vinylphosphonates via silicon-modified organolithium reagents, J. Org. Chem., 37, 939, 1972. 

Use of the methylsulphinyl carbanion as base is recommended for the synthesis of ethers from alcohols and alkyl halides. The catalysed formation of dimethyl ether from hydrogen and carbon dioxide has been reported. Carey has described the use of the silicon-modified organolithium reagent (73) in the preparation of vinyl thioethers (Scheme 151). In order to extend the scope of this reaction to include vinyl ethers themselves, an attempt was made to metalate trimethylsilylmethyl ether use of n-buty 1-lithium resulted in nucleophilic attack on silicon, whereas t-butyl-lithium abstracted the wrong proton, as shown in Scheme 151. 

SYNTHESIS OF VINYL THIOETHERS AND RELATED COMPOUNDS THROUGH THE FORMATION OF SULFUR-CARBON(sp2) BONDS... 

The fragmentation of a-chlorothioethers has been studied by use of the model reaction shown in Scheme 8, before application to the synthesis of vinyl thioether 42, a segment of trienomycin and mycotrienin macrolide antibiotics. ... 

A recently developed application of the Ramberg-Backlund reaction is the synthesis of C-glycosides. The required thioethers can be prepared easily by exchange with a thiol. The application of the Ramberg-Backlund conditions then leads to an exocyclic vinyl ether that can be reduced to the C-nucleoside.95 Entries 3 and 4 in Scheme 10.6 are examples. The vinyl ether group can also be transformed in other ways. In the synthesis of partial structures of the antibiotic altromycin, the vinyl ether product was subjected to diastereoselective hydroboration. 

Benzyloxynitromethane is a useful reagent in the synthesis of the precursors of some / -lactam antibiotic molecules. The nitrovinyl thioether (42.8) and others are thus synthesized, and may be cyclized with tetrabutylammonium fluoride, ozone and DBU (review of the chemistry of DBU [3364]. 2-Vinyl-thiopyridine forms a fused thiazolium ring on stirring with bromine-carbon tetrachloride [2811]. 

Autrey and Scullard used this fragmentation in a synthesis of corynantheine (11) from yohimban-l7-one (7). The synthesis also involved a novel desulfurization of the enol thioether (9) without reduction of the vinyl group. This step... 

Vinyl bromides react with copper(i) thiolates, both aliphatic and aromatic, to give vinyl sulphides. Vinyl bromides studied include ]8-bromostyrene and l-bromo-2-methyl-l-propene. This method of synthesis of thioethers is claimed to be superior to that using sodium thiolates and most other reported methods . 1,2-Dibromoethylene gives a mixture of cis (18%) and Irons (42%) 1,2-diphenylthioethylene with copper(i) benzene-thiolate, but with copper(i) ethanethiolate ethylthioacetylene is formed with the elimination of hy ogen bromide , ... 

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