Isolation and Characterization of Atropisomers of Seven-Membered-Ring Benzolactams

The atropisomeric properties of seven-membered-ring benzolactams (<b>7a</b>–<b>c</b> and <b>8a</b>) [1,5-benzodiazepin-2-one (<b>a</b>), 1,5-benzothiazepin-4-one (<b>b</b>), and 1-benzazepin-2-one (<b>c</b>)] were examined. The atropisomers were isolated as the diastereomers with an (<i>S</i>)-phenethylamide moiety, which were characterized by X-ray crystallography, and the barriers to their interconversion were clarified.