DIRECT SYNTHESIS OF DITHIOKETALS FROM N,N-DIALKYLHYDRAZONES

Direct dithioketalisation of N,N-dialkylhydrazones promoted by BF3. Et 2O or p-TsOH and 1,2-ethanedithiol in dry medium affords the correspon ding dithiolanes in nearly quantitative yields. A variety of hydrazone s derived from several kinds of aldehydes (aliphatic, aromatic, and al pha,beta-unsaturated) and hydrazines [N, N-dimethylhydrazine, 1-aminop yrrolidine, and (S)-1-amino-2- (methoxymethyl)pyrrolidine (SAMP)] were reacted, indicating the generality of the method. The reaction was de monstrated to proceed without racemization of a particularly sensitive chiral substrate. (C) 1998 Elsevier Science Ltd. All rights reserved.