Geometry-Selective Synthesis of E or ZN-Vinyl Ureas (N-Carbamoyl Enamines)
摘要:
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.
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.
Tandem β-Alkylation−α-Arylation of Amines by Carbolithiation and Rearrangement of <i>N</i>-Carbamoyl Enamines (Vinyl Ureas)
作者:Jonathan Clayden、Morgan Donnard、Julien Lefranc、Alberto Minassi、Daniel J. Tetlow
DOI:10.1021/ja1007992
日期:2010.5.19
an umpolung fashion to the beta-carbon of N-carbamoyl enamines (N-vinyl ureas). The reaction proceeds with syn diastereospecificity and provides urea-stabilized, configurationally defined organolithiums. Facilitated by coordinating solvents (THF or DMPU), these undergo intramolecular attack on an N'-aryl group, resulting in retentive arylation of the organolithium and hence overall addition of an alkyl