Quaternization and sodium borohydride reduction of N-(4-pyridylcarbonylamino)-1,2,3,6-tetrahydropyridine. Synthesis of N-amino-1,2,3,6-tetrahydropyridines

Reaction of N-(4-pyridylcarbonylamino)-1,2,3,6-tetrahydropyridine (2a) with methyl chloroformate afforded the quaternary salt 3a whereas reaction with methyl iodide gave a mixture of 3b and 6. Sodium borohydride reduction of 3a using methanol at −65 °C gave the N-methoxycarbonyl-1,2-dihydropyridine 4a whereas reduction using ethanol at 0 °C gave the 1,2,3,6-tetrahydropyridine 4b. Reduction of 3b and 6 gave rise to a mixture of 4c and 7. Catalytic hydrogenation of 4b and 4c afforded the respective piperidyl derivatives 10 and 11. The pharmacological activities of the products are presented.