The kinetics and mechanism of the electrophilic substitution of heteroaromatic compounds. Part XLIII. The nitration of isothiazoles
Abstract
Whereas isothiazole and its 3- and 5-methyl derivatives are all nitrated solely as free bases, the 3,5-dimethyl analogue shows a mechanistic changeover to nitration as conjugate acid. The effects of methyl groups on the reactivity are discussed in comparison with hydrogen exchange.