Stereospecific vicinal oxyamination of N-substituted 1,2,3,6-tetrahydropyridines and 1,2-dihydropyridines by N-chloro-N-metallocarbamates

Abstract

The vicinal oxyamination of 1-substituted 1,2,3,6-tetrahydropyridines (2) affords a mixture of the regioisomeric cis-hydroxycarbamates 3 and 4. The tert-butoxycarbonylamino and hydroxyl substituents for 3 and 4 assume the equatorial and axial orientations respectively, irrespective of the substituent position. Acid hydrolysis of 3a and 4a affords the cis-aminoalcohols 5 and 6. The regiospecific oxyamination of 1-methyoxycarbonyl-1,2-dihydropyridine occurs at the 5,6-olefenic bond to yield the hydroxycarbamates 15 and 16. Reduction of 15 or 16 with palladium on charcoal affords the same vicinal hydroxy and methoxycarbamates 17 to 20 which may arise via the aziridine intermediate 21.