Crystal and molecular structures of atropisomeric N-aryl-1,2,3,4-tetrahydro-3,3-dimethyl-2,4-quinolinediones

The crystal structures of N-aryl-1,2,3,4-tetrahydro-3,3-dimethyl-2,4-quinolinediones bearing methoxy- (1), methyl- (2), and chloro- (3) substituents in 2′-position of the phenyl ring have been determined by X-ray crystal structure analysis. The heterocyclic ring in 1–3 adopts an envelope conformation, with the smallest ring puckering in the ortho-chloro derivative 3. The N-aryl ring is almost perpendicular with respect to the quinoline-2,4-dione ring. The corresponding dihedral angle values are 83.2(1)°, 80.0(9)°, and 83.4(2)° in 1, 2 and 3, respectively. The hydrogen bond of CH⋅⋅⋅O type joins the molecules of the ortho-methoxy derivative 1 into dimers. The supramolecular structure also contains two CH⋅⋅⋅π interactions that link the hydrogen-bonded dimers into sheets. In ortho-methyl derivative 2, one CH⋅⋅⋅π interaction generates infinite chains, whereas two CH⋅⋅⋅O hydrogen bonds and three CH⋅⋅⋅π interactions in the ortho-chloro derivative 3 form three-dimensional framework. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:325–331, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20436