Reaction of sulfene and dichloroketene with open‐chain <i>N,N</i>‐disubstituted α‐aminomethyleneketones. Synthesis of 4‐dialkylamino‐3,4‐dihydro‐5,6‐dimethyl‐1,2‐oxathiin 2,2‐dioxides and of 6,(5)(di)alkyl‐3‐chloro‐4‐methylphenylamino‐2<i>H</i>‐pyran‐2‐ones

Abstract

Abstract Cycloaddition of sulfene to N,N ‐disubstituted 4‐amino‐3‐methyl‐3‐buten‐2‐ones (III) occurred in fair to good yield only in the case of aliphatic N ‐substitution to give 4‐dialkylamino‐3,4‐dihydro‐5,6‐dimethyl‐1,2‐oxathiin 2,2‐dioxides, whereas N,N ‐disubstituted 1‐amino‐1‐penten‐3‐ones (II) did not react at all. Cycloaddition of dichloroketene to II, III and N,N ‐disubstituted 4‐amino‐3‐buten‐2‐ones occurred only in the case of the methylphenylamino derivative, giving in good to moderate yield 6,(5)(di)alkyl‐3,3‐dichloro‐3,4‐dihydro‐4‐methylphenylamino‐2‐ H pyran‐2‐ones, which were dehydrochlorinated with DBN to 6,(5)(di)alkyl‐3‐chloro‐4‐methylphenylamino‐2 H ‐pyran‐2‐ones.