Atropisomers of 1-(Acyl or Aroyl)-2-naphthylindolines. Isolation, X-Ray Crystal Structure and Conformational Analysis

Abstract

A series of pairs of stable diastereomeric atropisomers caused by restricted rotation around the Csp3–Csp2 bond of [2-(2-hydroxynaphthalen-1-yl)-3,3-dimethyl-2,3-dihydroindol-1-yl]-(3- or 4-substituted phenyl)-methanone or [2-(2-hydroxynaphthalen-1-yl)-3,3-dimethyl-2,3-dihydroindol-1-yl]-1-alkanone were isolated. The conformational analyses of the atropisomers were performed based on the X-ray crystallographic and ¹H-NMR spectral data. It became clear that rotation about the C2–naphthyl bond is restricted at room temperature, whereas the >NCO–Ar bond rotates freely.