Abstract
Reactions of 3, 4-dimethyl-5- (2-hydroxyethyl) thiazolium iodide (I) and 3-benzyl-4-methyl-5- (2-hydroxyethyl) thiazolium bromide (I') with diaryl carbodiimides afforded corresponding (1 : 1) adduct (III, III') and (1 : 2) cycloadduct (IV, IV'). Product distribution in these reactions was largely effect by a substituent of carbodiimide and of thiazolium nitrogen. For para substituent in carbodiimide in the reaction with (I), the product ratio IV/III was increased in the order Me<H<NO2, which suggested that the formation of zwitterion (VI) by deprotonation of (1 : 1) adduct is the rate determining step for the cycloaddition reaction. ortho substituent in carbodiimide markedly increased the formation of cycloadduct in the reaction both with I and with I', while thiazolium N-benzyl group in I' decreased the cycloadduct formation as compared to N-CH3 group.
