Nitroacetamidation of styrenes

Reaction of styrenes with nitronium tetrafluoroborate in acetonitrile affords good yields of products of nitroacetamidation. In all cases addition is highly regioselective to give Markownikoff products. With trans-β-methylstyrene, conversion of the initial product of nitroacetamidation into epimeric imidazolines proves a cis-nitroacetamidation. In contrast the trans-addition to 1-phenylcyclohexene is proved by n.m.r. analysis of the epimeric nitroamides. trans-Stilbene gives only the threo-nitroamide by cis-addition but cis-stilbene gives a little of the erythro-nitroamide in addition to the threo-nitroamide. Products from the stilbenes are related to the known threo-1-acetamido-2-benzamido-1,2-diphenylethane. The course of these nitroacetamidations is compared with those of related additions. The nitroacetamidation of the less nucleophilic alkenes hex-1-ene, oct-1-ene, cyclohexene, and cyclo-pentene gives poor yields of nitroamides.