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.