N-heterocyclic carbenes catalyzed umpolung reactions via homoenolates

Polarity inversion (umpolung or charge affinity inversion) of functional groups is widely recognized as a powerful and efficient synthetic method because it makes possible not only to offer strategic flexibilities but also to form carbon-carbon bonds in the design of complex molecules. Recently, the new approaches of carbonyl synthons employing N-heterocyclic carbene catalyzed homoenolate reactions have been utilized in a variety of applications. In this review, the chemistry highlight in development of the catalytic generation of homoenolates and their application to the novel carbon-carbon bond-forming process is described.