Carbene-Promoted Multicomponent Reactions

David Monger Javier Iglesias-Siguenza and Elena Mas-Marza  

Nucleophilic carbenes, such as dimethoxycarbenes (Section 5.2.1) or N-heterocyclic carbenes (NHCs) (Section 5.2.2), are used as reagents in the synthesis of heterocycles, becoming part of the final molecule. These MCRs involve zwitterionic species generated by the addition of nucleophilic carbenes to multiple bonds and subsequent reactions with electrophilic compounds. 

Fischer carbene complexes (FCCs), organometaUic compounds, are used as reagents in MCRs. These species transfer the organic carbene moiety from the metal center to the final target (Section 5.2.3). 

Carbenes are employed as catalysts to drive the MCRs (Section 5.3). This section illustrates the formidable performance of NHCs as organocatalysts (Section 5.3.1) and ligands for organometaUic catalysts (Section 5.3.2) in MCRs. 

This chapter is not meant to be an exhaustive review of the literature but rather illustrates the main roles of carbenes in MCRs. 

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SCHEME 5.1 Different carbene-promoted multicomponent reactions. 

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