1,3‐Dipolar cycloaddition reactions of isothiazol‐3(2<i>H</i>)‐ones with nitrile oxides. An unexpected site selectivity of the carbonyl bond of 5‐benzoyl‐isothiazol‐3(2<i>H</i>)‐one

Abstract

Abstract 2,6‐Dichlorobenzonitrile oxide ( 2a ) reacts with isothiazolones 1a and 1b at the ethylenic double bond to give 4 via transformation of the primary cycloadducts 3 . Mesitonitrile oxide ( 2b ) adds preferentially to the carbonyl double bond of 1b yielding the monoadduct 5 and the bisadduct 6 .