Synthesis of polynuclear heterocycles via the reaction of α-ester carbanions with quaternized nicotinamide salts. A facile stereoselective synthesis of sesbanine

α-Ester carbanions add to N-benzylnicotinamide salts to give C-4 and C-6 substituted primary products. The C-4 substituted dihydronicotinamides undergo a further reaction involving nucleophilic attack of the amide nitrogen on the carbonyl group of the ester. The resulting cyclization products can be oxidized and debenzylated to 1,2-dioxo-1,2,3,4-tetrahydro-2,7-naphthyridine derivatives. The sequence of reactions has been utilized in the synthesis of several heterocycles and in the stereoselective synthesis of the alkaloid sesbanine.