Stereochemistry of 2,6-Dipyridine Substituted N-Benzyl-4-piperidone Mono- and Dicarboxylates and of the Corresponding Reduction Products f1]

Abstract

The alkyl N-benzy1-4-piperidone-3-carboxylate (1) is synthesized by a Mannich procedure from pyridine aldehyde, benzylamine and the monoester of acetonedicarboxylate: The corresponding diester 2 is formed by condensation of pyridine aldehyde, benzylamine and dimethyl 3-oxogluta-rate. Isomerism is observed with respect to keto-enol tautomerism and cis or trans substitution of the pyridines. The structure of the enol lb (C24H23N3O3) is determined by X-ray analysis: It crystallizes in the triclinic space group P1 with a = 9.965(2), b = 10.476(2), c = 10.838(2) A, a = 69.48(1),β= 81.56(1),γ = 79.09(1)°, Z = 2 and Dx= 1.29gcm-3. It is refined to R(unweighted) = 0.047 and R(weighted) = 0.045 using 1459 non-equivalent reflections. The structures of 1a/b and 2a/b were determined by 1H and l3C NMR data. MNDO calculations of 1a/b are discussed. The 11enols 1/2b are reduced by sodium borohydride. The configuration of the obtained alcohols is determined by NMR data. 0932-0776/89/0500-0565/$ 01.00/0. © 1989, Verlag der Zeitschrift für Naturforschung. All rights reserved.