Geometry-Selective Synthesis of <i>E</i> or <i>Z</i> <i>N</i>-Vinyl Ureas (<i>N</i>-Carbamoyl Enamines)
作者:Julien Lefranc、Daniel J. Tetlow、Morgan Donnard、Alberto Minassi、Erik Gálvez、Jonathan Clayden
DOI:10.1021/ol1027442
日期:2011.1.21
N-Vinyl ureas are emerging as a valuable class of compounds with both nucleophilic and electrophilic reactivity. They may be made by capturing the enamine tautomer of an imine with an isocyanate, a reaction which in general leads to the E isomer of the vinyl urea. Deprotonation of such a vinyl urea, or of an allyl urea, generates a dipole stabilized Z-allyl anion which may be protonated to return the Z-vinyl urea. Isomerization of an allyl urea with a Ru complex provides an alternative route to E-vinyl ureas.
sato, Tatsunori; Chono, Noriko; Ishibashi, Hiroyuki, Journal of the Chemical Society. Perkin transactions I, 1995, # 9, p. 1115 - 1120
The condensation of deoxybenzoin, phenylacetone, dibenzylketone and ethyl phenyl ketone with primary aromatic amines results in imines, which tautomerize partially in solution with measurable rate to the corresponding enamines. The condensation with methylamine produces instantly the isomer composition. In several cases the imines show syn-anti-isomerism. The structural dependence of the imine-enamine-equilibrium