Reaction of sulfene and dichloroketene with open‐chain <i>N,N</i>‐disubstituted α‐aminomethyleneketones. Synthesis of <i>N,N</i>‐disubstituted 4‐amino‐3,4‐dihydro‐(5‐methyl‐6‐phenyl)(5,6‐diphenyl)‐1,2‐oxathiin 2,2‐dioxides and of 4‐amino‐3‐chloro‐5‐methyl‐6‐phenyl‐2<i>H</i>‐pyran‐2‐ones

Abstract

Abstract Cycloaddition of sulfene to N,N ‐disubstituted 3‐amino‐2‐methyl‐1‐phenyl‐2‐propen‐1‐ones (I) and 3‐amino‐1,2‐diphenyl‐2‐propen‐1‐ones (II) occurred in good to moderate yield only in the case of aliphatic N ‐substitution to give 4‐dialkylamino‐3,4‐dihydro‐(5‐methyl‐6‐phenyl)(5,6‐diphenyl)‐1,2‐oxathiin 2,2‐dioxides. Polar 1,4‐cycloaddition of dichloroketene to I and II occurred only in the former case, giving in good to moderate yield N,N ‐disubstituted 4‐amino‐3,3‐dichloro‐3,4‐dihydro‐5‐methyl‐6‐phenyl‐2 H ‐pyran‐2‐ones which were dehydrochlorinated with DBN to N,N ‐disubstituted 4‐amino‐3‐chloro‐5‐methyl‐6‐phenyl‐2 H ‐pyran‐2‐ones. In the reaction of 2‐methyl‐1‐phenyl‐3‐diphenylamino‐2‐propen‐1‐one with dichloroketene, a product was isolated which was proven by uv, ir, nmr and chemical evidence to be the dipolar ion VI, the supposed intermediate of the polar 1,4‐cycloaddition of dichloroketene to N,N ‐disubstituted enaminones.