COMPARISON OF THE PARTITION BETWEEN POLAR AND SET PATHWAYS IN THE S(RN)1 MECHANISM FOR THE NITRONATE AND DIETHYLDITHIOCARBAMATE ANIONS - ANUNEXPECTED RESULT

Competition between S(RN)1 and S(N)2 mechanisms is discussed according to the stereochemical results in the alkylation of two anions by opti cally active alpha-chloroparanitrophenylethane 1. In the reaction of 1 with the ambident anion of 2-nitropropane 2, competing S(RN)1 and S(N )2 processes take place, giving C-alkylation 3 with complete racemizat ion and 0-alkylation 4 products respectively. On the other hand S-alky lation of the diethyldithiocarbamate anion 5 by the halide 1 involves also an S(RN)1-S(N)2 competition giving the same product 6 with an ind ication of a less important participation of the S(RN)1 pathway despit e the fact that dithiocarbamate is a better reducing agent than nitron ate. (C) 1997, Published by Elsevier Science Ltd.