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Geometry-Selective Synthesis of E or Z N-Vinyl Ureas (N-Carbamoyl Enamines)

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posted on 21.01.2011, 00:00 authored by Julien Lefranc, Daniel J. Tetlow, Morgan Donnard, Alberto Minassi, Erik Gálvez, Jonathan Clayden
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.