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.

Synthesis of 1,2,3-Triazoles by Cycloadditions of Azides with Enol Ethers

“…10,14 Loss of the amino group from the 5-position can be slow, and decomposition of the triazoline ring frequently competes with triazole formation. Side reactions include aziridine formation 25,26 and diazonium ion rearrangements. 10 The use of enamides 8 (Y = NRAc) in place of enamines facilitates loss of the nitrogen in the 5position, 21 but enamides are typically less convenient to prepare than enamines.…”

“…In some cases cyclic enamines successfully react with azides to afford ring-fused triazoles, 16,17 while triazoline decomposition products predominate in other instances. 10,25,26 Most reactions in Table 1 were performed on less than a 10 mmol scale in sealed vials or pressure tubes. The reaction can be run on a large scale without resorting to heavywalled glassware and elevated pressures.…”