Development of a Novel Method for the Preparation of Dithioacetal in the Presence of Titanium(IV) Chloride/Zinc in Dimethoxymethane

We have developed a new synthetic method for the preparation of dithioacetal, which employs TiCl₄/Zn in DMM. Dithioacetals containing versatile functional groups, such as ether, ester, and amino group can be obtained cleanly. Investigations on applying this thioacetals and the mechanistic aspects are currently underway and will be reported in due course. Organosulfur compounds are important intermediates in organic synthesis. Since the pioneering report by Corey and Seebach, sulfur-stabilized carbanion has played an important role in organic synthesis. Recently, a new reaction method was developed that consists of a reductive lithiation of alkyl or arylthioesters and ring closing metathesis of titanium carbene complex prepared from thioacetals. In general, bis(methylthio)methane is used for the synthesis of ketene thioacetal by the reaction with aldehyde or ketone, and bis(phenylthio)methane is used for the synthesis of alkenes, ketones, allyic alchols and 1,3-dienes. In these reactions, only a few reagents, such as bis(methylthio)-methane and bis(phenylthio)methane, are used presumably because the reagents are commercially available and can be prepared under limited conditions. In spite of the importance of dithioacetals or sulfur-stabilized carbanions in organic synthetic chemistry, only a few synthetic methods were known