Rates of N-methylation of N-methylpyrazole, isothiazole and isoxazole and their 2,1- and 1,2-benzologues

Abstract

The rates of quaternization of N-methylpyrazole, isothiazole and isoxazole and of their 2,l- and 1,2-benzologues with methyl iodide in dimethyl sulphoxide and with dimethyl sulphate are reported. All compounds quaternized at 33º and a number of new compounds were isolated. The order of reactivity in each series is NMe > S > O. Benzofusion was shown to be rate-diminishing with one exception. 2,l-Benzisoxazole reacted faster than did isoxazole and the reason for this behaviour is discussed.