title: Conformation and stereodynamics of 2,2'-disubstituted N,N'-diaryl ureas.
abstract: Except in the most hindered of cases, N,N'-diaryl N,N'-dimethyl ureas adopt a conformation with the two aryl rings disposed cis to one another. Variable temperature NMR studies reveal the rate at which the Ar-N bonds rotate as well as the conformational preference of ortho disubstituted ureas in which more than one cis orientation is possible. In general, a conformation in which the aryl rings lie close in space but with their most bulky 2-substituents aligned anti is preferred, but with particularly bulky 2-substituents, conformations in which one of the aryl rings points away from the other may also be populated.
authors.affiliation: School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK. clayden@man.ac.uk
authors.forename: Jonathan
authors.initials: J
authors.lastname: Clayden
authors.forename: Loïc
authors.initials: L
authors.lastname: Lemiègre
authors.forename: Mark
authors.initials: M
authors.lastname: Pickworth
authors.forename: Lyn
authors.initials: L
authors.lastname: Jones
mesh_terms: D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D015394:Molecular Structure; D013237:Stereoisomerism; D013696:Temperature; D013816:Thermodynamics; D014508:Urea / Q000031:analogs & derivatives* / Q000737:chemistry*
chemical_list: D014508:Urea