An efficient preparation of β-dimethylaminovinyl sulfone and sulfoximide, and investigation of their reactivity as dipolarophiles

Abstract

A simple reaction affording (E)‐1‐dimethylamino‐2‐phenylsulfonylethylene, and S‐((E)‐2‐(N',N'‐dimethylamino)ethenyl)‐S‐phenyl‐N‐(p‐tolylsulfonyl) sulfoximide in high yields is described. A reversal in regioselectivity was observed when the β‐dimethylaminovinyl sulfone was employed as a dipolarophile in cycloadditions with nitrile oxides. The sulfone gives rise mainly to 4‐substituted isoxazoles, after elimination of dimethyl amine. In comparison, phenyl vinyl sulfone cycloadds to give 5‐substituted isoxazolines. Although not showing comparable dipolarophilic activity in reactions with nitrile oxides and nitrile imides, the β‐dimethylaminovinyl sulfoximide was easily converted to S‐((E)‐(3‐ethoxycarbonyl)prop‐2‐enyl)‐S‐phenyl‐N‐(p‐tolylsulfonyl) sulfoximide. This allylic sulfoximide cycloadds in good yield to both benzonitrile oxide and diphenylnitrile imide, but no stereoselectivity was observed in the process; and only modest regioselectivity was detected in the case of benzonitrile oxide.