Related Experiment Video
Updated: Jul 3, 2026

Facile Preparation of (2Z,4E)-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate
Published on: June 21, 2017
Conformation and stereodynamics of 2,2'-disubstituted N,N'-diaryl ureas
Jonathan Clayden1, Loïc Lemiègre, Mark Pickworth
1School of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, UK. clayden@man.ac.uk
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.
Related Concept Videos
Stereoisomerism of Cyclic Compounds
Diels–Alder Reaction Forming Cyclic Products: Stereochemistry
Stability of Conjugated Dienes
A comparison of the enthalpies of hydrogenation of dienes reveals that conjugated dienes release less heat on hydrogenation, rendering them more stable than their nonconjugated analogs.
Structure of Amines
Structure of Conjugated Dienes
Conjugated dienes are compounds characterized by the presence of alternating double and single bonds. In a conjugated system like 1,3-butadiene, the unhybridized 2p orbital on each carbon overlaps continuously, allowing the π electrons to be delocalized across the entire molecule. In contrast, this type of overlap does not occur in cumulated and isolated dienes, such as 2,3-pentadiene and 1,4-pentadiene, respectively. Instead, the π electrons remain localized between the double...
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction

