Chemistry of aryl N‐(2‐pyridyl) thionocarbamates in basic media^†

Abstract

Three aryl N‐pyridylthionocarbamates were synthesized by thioacylation of 2‐aminopyridine and 2‐methylaminopyridine with the respective chlorothionoformates. Their hydrolysis mechanism was studied in aqueous basic media. The aryl N‐(2‐pyridyl)thionocarbamates are considerably less reactive than their oxo analogues, the aryl N‐(2‐pyridyl) carbamates, especially the N‐monosubstituted ones (1a‐b). Absence of significant buffer catalysis, isolation of the product resulting from trapping of the unsaturated intermediate with piperidine and the entropy of activation observed for the hydrolysis of compound 1b clearly indicate an E1cB mechanism for the N‐monosubstituted aryl N‐(2‐pyridyl)thionocarbamates. The experimental data suggest that the N,N‐disubstituted substrate (2) undergoes basic hydrolysis by a general base catalysed B_AC2 mechanism. Copyright © 2008 John Wiley & Sons, Ltd.