Contents
1.Introduction 1168
1.1.General structures of N-heterocyclic carbenes 1168
1.2.General properties of N-heterocyclic carbenes 1168
1.3.Major applications of NHCs in organocatalysis 1169
2.Activation of Aldehydes for Access to Breslow and Homoenolate Intermediates 1169
2.1.Characterization of the Breslow intermediate 1169
2.2.Progresses in the benzoin and Stetter reactions 1170
2.3.Hydroacylation of alkenes and alkynes 1172
2.4.Annulation reactions of homoenolate intermediates 1174
2.5.Non-annulation reactions of homoenolate intermediates 1175
2.6.Cooperative catalysis with NHC-bounded homoenolate intermediates 1176
3.Activation of Ketenes and Aldehydes for Access to Enolate, Dienolate, and α,β-Unsaturated Acylazolium Intermediates 1177
3.1.Activation of ketenes for access to enolate intermediates 1177
3.2.Activation of ketenes for access to dienolate intermediates 1178
3.3.Activation of aldehydes for access to enolate intermediates 1178
3.4.Activation of aldehydes for access to dienolate intermediates 1180
3.5.Activation of aldehydes for access to α,β-unsaturated acyl azolium intermediates 1181