Stereocontrolled formation of substituted imidazolidines in the reaction between N-metallated azomethine ylides and isocyanate.
Stereocontrolled formation of substituted imidazolidines in the reaction between N-metallated azomethine ylides and isocyanate. ARKIVOC. 2005, Vol. (ix), pp 189-199.
Abstract:Substituted imidazolidines (and not imidazolidin-4-ones) are the unexpected cycloadducts obtained in the reaction between imines and isocyanates. The reaction is shown to take place via stepwise [3+2] cycloaddition between the N-metallated azomethine ylide formed in situ and the starting imine, followed by nucleophilic addition of the resulting imidazolidine on the sphybridized carbon atom of the isocyanate. Density-Functional Theory calculations provide a model for the mechanism of this unusual reaction and for the origins of the observed regio- and stereoselectivity.