Thioacetals trifluoromethanesulfonate

Considerable efforts have been devoted to the stereoselective introduction of a /(-methyl function in intermediates for the synthesis of 1 jS-methylcarbapenems. While the trimethylsilyl trifluoromethanesulfonate catalyzed reaction of a 4-acetoxyazetidinone derivative with ketene acetals shows no selectivity, ketene thioacetals lead to stereoselective formation of the a-methyl isomer108. The zirconium enolate, however, shows high /(-methyl selectivity. 

The reaction of crotonaldehyde and methyl vinyl ketone with thiophenol in the presence of anhydrous hydrogen chloride effects conjugate addition of thiophenol as well as acetal formation. The resulting j3-phenylthio thioacetals are converted to 1-phenylthio-and 2-phenylthio-1,3-butadiene, respectively, upon reaction with 2 equivalents of copper(I) trifluoromethanesulfonate (Table I). The copper(I)-induced heterolysis of carbon-sulfur bonds has also been used to effect pinacol-type rearrangements of bis(phenyl-thio)methyl carbinols. Thus the addition of bis(phenyl-thio)methyllithium to ketones and aldehydes followed by copper(I)-induced rearrangement results in a one-carbon ring expansion or chain-insertion transformation which gives a-phenylthio ketones. Monothioketals of 1,4-diketones are cyclized to 2,5-disubstituted furans by the action of copper(I) trifluoromethanesulfonate. ... 

Vinyl Sulfides from Thioacetals with Copper Trifluoromethanesulfonate ... 

In some procedures, thioacetal cleavage occurs after alkylation at the sulfur atom with a reactive alkylating reagent such as methyl iodide, tnalkyloxonium tetrafluoroborate (Meerwein salt), or ethyl trifluoromethanesulfonate to give a tnalkylsulfonium salt. 

VINYL SULFIDES FROM THIOACETALS WITH COPPER(I) TRIFLUOROMETHANESULFONATE (Z)-2-METHOXY-l-PHENYLTHIO-l,3-BUTADIENE... 

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