Crystal structures of ten enanti-opure Schiff bases bearing a naphthyl group.

Using a general solvent-free procedure for the synthesis of chiral Schiff bases, the following compounds were synthesized and their crystal structures determined: (S)-(+)-2-{[(1-phenyl-eth-yl)imino]-meth-yl}naphthalene, C19H17N, (1), (S)-(+)-2-({[(4-methyl-phen-yl)eth-yl]imino}-meth-yl)naphthalene, C20H19N, (2), (R)-(-)-2-({[(4-meth-oxy-lphen-yl)eth-yl]imino}-meth-yl)naphthalene, C20H19NO, (3), (R)-(-)-2-({[(4-fluoro-phen-yl)eth-yl]imino}-meth-yl)naphthalene, C19H16FN, (4), (S)-(+)-2-({[(4-chloro-phen-yl)eth-yl]imino}-meth-yl)naphthalene, C19H16ClN, (5), (S)-(+)-2-({[(4-bromo-phen-yl)eth-yl]imino}-meth-yl)naphthalene, C19H16BrN, (6), (S)-(+)-2-({[1-(naphthalen-1-yl)eth-yl]imino}-meth-yl)naph-thalene, C23H19N, (7), (S)-(+)-2-{[(1-cyclo-hexyl-eth-yl)imino]-meth-yl}naph-tha-lene, C19H23N, (8), (S)-(-)-2-{[(1,2,3,4-tetra-hydro-naphthalen-1-yl)imino]meth-yl}naphthalene, C21H19N, (9), and (+)-2-({[(1S,2S,3S,5R)-2,6,6-tri-methylbi-cyclo-[3.1.1]hept-3-yl]imino}-meth-yl}naphthalene, C21H25N, (10). The moiety provided by the amine generates conformational flexibility for these imines. In the crystals, no strong inter-molecular contacts are observed, in spite of the presence of aromatic groups.