Photoinduced and thermal reactions of α-cyano-β-bromomethylcinnamide with 1-benzyl-1,4-dihydronicotinamide^†

The photoinduced reaction of a mixture of (Z)-α-cyano-β-bromomethylcinnamide (1) and (E)-α-cyano-β-bromomethylcinnamide (2) with 1-benzyl-1, 4-dihydronicotinamide produces a mixture of the (E)- and (Z)- isomers of α-cyano-β-methylcinnamide (3 and 4). Using spin-trapping technique for monitoring reactive intermediate, it is shown that the reaction proceeds via electron transfer-debromination-H abstraction mechanism. The thermal reaction of the same substrate with BNAH at 60°C in the dark gives three products: the (E)- and (Z)-isomers of α-cyano-β-methylcinnamide and a dehydrodimeric product; 2, 7-dicyano-3, 6-diphenylocta-2, 4, 6-trien-1, 8-dioic amide (7). Based on product analysis, scavenger experiment and cyclic voltammetry, an electron transfer-debromination-disproportionation mechanism is proposed.