[82452-67-3] · C3H5LiS2 · Methyl Lithiodithioacetate · (MW 112.16)
(enolate equivalent, capable of reacting as a carbon or sulfur nucleophile)
Preparative Methods: colorless solutions of the reagent are prepared by addition of Lithium Diisopropylamide to an ether or THF solution of methyl dithioacetate at -78 °C; reaction is complete in minutes.
Methyl lithiodithioacetate gives aldol products with simple aldehydes.4 Selective conjugate addition is observed with enones (eq 1).5 The unexpected syn selectivity in the reaction arises from internal proton transfer to produce (1). Similar reactions conducted in the presence of Chlorotitanium Triisopropoxide (4 equiv) give exclusively the 1,2-addition product (eq 2).6 A variety of transformations possible for the products obtained from reactions with carbonyl compounds is described in a review article.1
Methyl lithiodithioacetate reacts exclusively as a sulfur nucleophile with a variety of alkyl halides,7 epoxides,8 and with Chlorotrimethylsilane.9 Presumably, C-allylation products can be obtained by the thio-Claisen rearrangement, examined in detail with aldol products derived from methyl lithiodithioacetate.4
Michael Rathke & Robert Elghanian
Michigan State University, East Lansing, MI, USA