The rearrangement of 2‐benzyl‐5‐mesitoyl‐3(2<i>H</i>)‐isothiazolone to 2‐phenyl‐6‐mesitoyl‐3,4‐dihydro‐1,3‐thiazin‐4(2<i>H</i>)‐one

Abstract

Abstract 2‐Benzyl‐5‐mesitoyl‐3( 2H )‐isothiazolone ( 8 ) has been prepared from 3‐mesitoylpropionic acid ( 5 ). Reaction of the isothiazolone 8 with sodium ethoxide in ethanol has been found to yield an isomeric rearranged compound, which was characterized as 2‐phenyl‐6‐mesitoyl‐3,4‐dihydro‐1,3‐thiazin‐4( 2H )‐one ( 9 ). This unexpected rearrangement is attributed to the abstraction of a benzylic hydrogen atom from the N ‐benzyl group, followed by ring enlargement through cleavage of the isothiazolone SN bond.