Conformation and stereodynamics of 2,2'-disubstituted N,N'-diaryl ureas.
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.
Clayden
Jonathan
J
School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK. clayden@man.ac.uk
Lemiègre
Loïc
L
Pickworth
Mark
M
Jones
Lyn
L
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*
D014508:Urea