Base-catalysed hydrogen–deuterium exchange in some 2-substituted thiazoles: reactivity in the 5-position

Abstract

Kinetic data on the base-catalysed hydrogen deuterium exchange at the 5-position of some 2-substituted thiazoles in [²H₆]DMSO–CD₃OD (1 : 1 v/v) are reported. The reaction probably occurs via an anionic intermediate. Substituent effects give (using σ_m) a high ρ value (5.7). Only 2-NN-dimethylamino-3-methylthiazolium iodide shows an appreciable exchange reaction at the 4-position. The reactivity order for the three thiazole positions (5 2 4) is related to inductive effects and the presence of sulphur. The tautomerism of some 2-aminothiazoles is discussed.