Hydrolysis of Mustard Derivatives. Remarkable Tosylate/Chloride and Chloride/Dinitrophenolate Rate Ratios

摘要

Comparisons of leaving group solvolytic rate ratios for mustard derivatives with other substrate types reveals unusual OTs/Cl and Cl/ODNP rate ratios for mustards. A very tight transition state is suggested. Among primary alkyl chlorides, sulfur mustards show extraordinary reactivity resulting from neighboring group assistance by the beta sulfur (Scheme 1). We recently described another significant difference between mustards and other alkyl halides: rates of solvolysis of mustard chlorohydrin in aqueous ethanols, acetones, and trifluoroethanols cannot be satisfactorily correlated using four parameter extended Grunwald-Winstein equations. We describe here the remarkable observation that mustard derivatives show usually low tosylate/chloride solvolytic rate ratios but expected tosylate/dinitrophenolate rate ratios.