Convenient synthesis of N-benzyl-1,4-dihydropyridines, cyclohexenones, and bicyclo[3.3.1]nonan-3-one derivatives from 1-aza-1,3-butadienes

Readily available 1-aza-1,3-butadienes (enimines) react with methyl acetoacetate and acetylacetone in the presence of catalytic amounts of lithium iodide to form in high yields unsymmetrically substituted 1,4-dihydropyridines or cyclohexenones. The reaction pathway depends on the structure of the enimine used. This divergence was not observed when the enimines were reacted with dimethyl 1,3-acetonedicarboxylate to provide bicyclo[3.3.1]nonane-3-one derivatives in excellent yields in a remarkably stereoselective reaction.