Some reactions of 1,2-dihydropyridines with organic azides. Synthesis of diazabicylo[4.1.0]hept-4-enes, 1,2,5,6-tetrahydropyridylidene-2-cyan (sulfon, carbon) amides, and piperidylidene-2-cyan (sulfon, carbon) amides

Abstract

The regiospecific 1,3-dipolarcycloaddition reaction of 1,2-dihydropyridines 1 with organic azides 2 afford 2,7-diazabicyclo[4.1.0]hept-4-enes 4, whereas solutions of 1 also containing lithium hydroxide give predominately 4 along with the diazo product 6. In contrast, the dimeric product 7 was obtained from the reaction of 1a with hydrazoic acid. Catalytic hydrogenation of 4 gives rise to a tautomeric mixture of 9 and 10; when R2 is methanesulfonyl or p-aminobenzenesulfonyl only 9 was obtained. Treatment of 4 with neutral alumina gives rise to the 1,2,5,6-tetrahydropyridylidenes 8 which are likewise reduced to a mixture of 9 and 10 or 9.