title: [Stereochemistry of benzanilides and N-methylbenzanilides].
abstract: Conformations of benzanilide , N-methylbenzanilide and those with a methyl group(s) ortho to the amide bond in solution and in the crystal have been studied. N-Methylbenzanilide exists in cis-amide (E) form in the crystal. In CDCl3 solution, cis-amide form is also predominant (99%), while benzanilide exists in trans-amide (Z) form in the crystal and in solution. In the crystal, all the methyl-substituted benzanilides exist in trans-amide conformation and the introduction of an ortho-methyl group(s) makes the interplanar angles of the aromatic rings and the amide group (Aramide) larger. N-Methylbenzanilides exist in cis form in the crystal except the compound which has four methyl groups ortho to the amide bond. For the N-methylbenzanilides, the effects of introduction of one or two ortho-methyl groups on the dihedral angles of Ar-amide are smaller than that for the secondary benzanilides. In solution, benzanilides exist exclusively in trans conformation except for the compound 12 which has a minor cis conformer (3%) in CDCl3, whereas N-methylbenzanilides exist in equilibrium between the major cis-form and the minor trans-form. The tetramethyl derivative exists in trans conformation in solution as observed in the crystal. For N-methylbenzanilides, an introduction of a methyl group(s) ortho to the amide bond seems to destabilize the cis-amide conformation in solution, resulting in an increased ratio of the trans-amide conformation.
authors.affiliation: Faculty of Pharmaceutical Sciences, University of Tokyo, Japan.
authors.forename: I
authors.initials: I
authors.lastname: Azumaya
authors.forename: K
authors.initials: K
authors.lastname: Yamaguchi
authors.forename: H
authors.initials: H
authors.lastname: Kagechika
authors.forename: S
authors.initials: S
authors.lastname: Saito
authors.forename: A
authors.initials: A
authors.lastname: Itai
authors.forename: K
authors.initials: K
authors.lastname: Shudo
mesh_terms: D000813:Anilides / Q000737:chemistry*; D003460:Crystallization; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D013237:Stereoisomerism
chemical_list: D000813:Anilides