Nitroacetamidation of dienes by indirect electrochemical nitration

Abstract

Solutions of nitronium tetrafluoroborate in acetonitrile were obtained by anodic oxidation of N₂O₄. The electrogenerated NO₂BF₄ efficiently nitroacetamidates conjugated dienes. Buta-1,3-diene, isoprene, 2,3-dimethylbutadiene, trans-penta-1,3-diene and trans-trans-hexa-2,4-diene give mixtures of products by 1,2- and 1,4-addition. Structures of the 1,2- and the 1,4-nitroacetamides are assigned on the basis of spectroscopic analysis and conversion of 1,2-nitroacetamides into dihydroimidazoles. The observed selectivity of 1,2-addition relative to 1,4-addition, regioselectivity, and stereoselectivity are compared with related electrophilic additions to conjugated dienes.