The masking of carbonyl groups by 1,2-dimethyl-4,5-di(mercaptomethyl)benzene

Abstract

Many aldehydes and ketones, as well as aldehydo- and keto-acid derivatives, give stable odourless crystalline thioacetals and thioketals with 1,2-dimethyl-4,5-di(mercaptomethyl)benzene (I). The rate of this condensation differentiates between aldehydes and ketones, and between α-keto-acids and other keto-acids. α-Hydroxy-methylene-ketones and -esters react with (I) in the their aldehyde forms. The derivatives of (I) with α-hydroxymethylene-esters give, by reductive desulphuration, esters of the corresponding α-monomethyl acids. If the thioacetals and thioketals still contain keto or ester groups, they will react with Grignard reagents and lithium aluminium hydride, leading to αβ-unsaturated aldehydes.