Patent ID: 8299293

Claim:
A method, comprising: a) reacting an aldehyde represented by R 1 CHO with at least two thiols represented by R 4 —S—H, to give a dithioacetal; b) reacting the dithioacetal with a carbonyl-containing electrophile in the presence of a strong base that comprises at least one member selected from the group consisting of n-butyllithium, tert-butyllithium, sodium amide, sodium hydride, potassium hydroxide, and potassium carbonate and hydrolyzing in a solvent represented by R 5 OH to give an α,α-(dithio)carboxylic acid or a derivative thereof represented by formula (III): c) converting the α,α-(dithio)carboxylic acid or derivative thereof represented by formula (III) by acid-catalyzed solvolysis in the presence of at least one molar equivalent of water with release of thiols of the formula R 4 SH to give at least one of an α-keto acid represented by formula (I) and a compound represented by formula (II) wherein R 1 is an optionally substituted, branched or straight-chain C 1 -C 18 -alkyl, C 5 -C 8 -cycloalkyl, vinyl, allyl, C 6 -C 10 -aryl-C 1 -C 4 -alkylene or C 4 -C 9 -heteroaryl-C 1 -C 4 -alkylene group, R 2 is —OR′″ or —NR′R″, in which R′ and R″ are the same or different and are each a hydrogen atom or a branched or straight-chain C 1 -C 6 -alkyl group, and R′″ is a hydrogen atom, a branched or straight-chain C 1 -C 8 -alkyl, C 5 -C 8 -cycloalkyl, allyl or a benzyl group, where the alkyl in R′, R″ and R′″ is optionally substituted, or R′″ is an alkaline metal ion, alkaline earth metal ion or a mono- or divalent transition metal ion, R 3 is the same or different and is a hydrogen atom, a branched or straight-chain C 1 -C 8 -alkyl, allyl or a benzyl group, where alkyl and/or benzyl is optionally substituted, or the two R 3 radicals together are C 2 -C 8 -alkanediyl and together form a ring, or the two R 3 and R′″ radicals together are part of a C 3 -C 8 -alkanetriyl group of the general formula —R 3 (CH—)R′″ and together form a bicyclic group, R 4 is a branched or straight-chain, optionally substituted C 1 -C 6 -alkyl, C 5 -C 8 -cycloalkyl, allyl or benzyl group, and R 5 is a hydrogen atom or a branched or straight-chain C 1 -C 6 -alkyl group, wherein the acid-catalyzed solvolysis in c) is carried out in the presence of a solvent that comprises at least one of: a diol represented by HO—R 7 —OH, wherein R 7 is a branched or straight-chain, optionally substituted C 2 -C 8 -alkanediyl group; a triol represented by HOR 8 (CHOH)R 9 OH, wherein the R 8 and R 9 radicals together are part of a branched or straight-chain, optionally substituted C 3 -C 8 -alkanetriyl group of the general formula —R 8 (CH—)R 9 ; and an amine represented by HNR 10 R 11 wherein R 10 and R 11 may be the same or different and are each a hydrogen atom or a branched or straight-chain C 1 -C 6 -alkyl group, with the proviso that R 10 and R 11 cannot both be a hydrogen atom.