Crystal and molecular structure of the major products from the benzylation of 1-ethyl-4-phenylpiperidine and 1-isopropyl-4-phenylpiperidine

Abstract

The structures of the major isomers of 1-benzyl-1-ethyl-(1) and of 1-benzyl-1-isopropyl-4-phenylpiperidinium chloride (2), as determined by X-ray analysis, indicate that N-benzylation of piperidines normally occurs by preferential equatorial attack. Crystals of (1) are orthorhombic, space group Pbca, with Z= 8 in a unit-cell of dimensions: a= 9·41(3), b= 17·94(6), c= 20·47(6)Å. Crystals of (2) are monoclinic, space group C2/c, with Z= 8 in a unit-cell of dimensions a= 27·778(19), b= 9·483(7), c= 19·911(12)Å, β= 133·05(2)°. The structures were solved by the symbolic addition procedure and refined by block-diagonal least-squares methods to R 0·13 [(1), 2036 photographic data] and 0·048 [(2), 2089 diffractometer data].