Metal carbenes derived from transition metal-catalyzed decomposition of diazo compounds react with nucleophiles with heteroatoms, such as alcohols and amines, to generate highly active oxonium/ammonium ylides intermediates. These intermediates can be trapped by appropriate electrophiles to provide three-component products. Based on this novel trapping process, we have developed novel multicomponent reactions (MCRs) of diazo compounds, alcohols/anilines, and electrophiles. The nucleophiles were also extended to electron-rich heterocycles (indoles and pyrroles)/arenes, in which the resulting zwitterionic intermediates were also trapped by electrophiles. By employing efficient catalysis strategy, the reactions were realized with excellent stereocontrol and wide substrate scope. In this personal account, we introduce our breakthroughs in the development of novel asymmetric MCRs via trapping of the active ylides and zwitterionic intermediates with a number of electrophiles, such as imines, aldehyde, and Michael acceptors, under asymmetric catalysis. Transition metal/chiral Lewis acid catalysis, transition metal/Brønsted acid catalysis, and chiral transition-metal catalysis, enable excellent stereocontrolled outcomes. The methodologies not only provide experimental evidence to support the existence of protic onium ylides intermediates/zwitterionic intermediates and the stepwise pathways of carbene-induced O-H, N-H and C-H insertions, but also offer a novel approach for the efficient construction of chiral polyfunctional molecules.

Asymmetric functionalization of aromatic C-H bonds of N,N-disubstituted anilines with diazo compounds and imines is reported for the efficient construction of α,α-diaryl benzylic quaternary stereocenters in good yields with high diastereoselectivities and excellent enantioselectivities. This Rh(II)/chiral phosphoric acid cocatalyzed transformation is proposed to proceed through a metal-carbene-induced zwitterionic intermediate which undergoes electrophilic trapping. To the best of our knowledge, this is the first asymmetric example of metal carbene-induced intermolecular functionalization of aryl C-H bonds.

A novel enantioselective aminomethylation reaction of diazo compound, alcohol and α-aminomethyl ether enabled by asymmetric counteranion-directed catalysis is disclosed that offers an efficient and convenient access to furnish optically active α-hydroxyl-β-amino acids in high yield with high to excellent enantioselectivities. Control experiments and DFT calculations indicate that the transformation proceeds through trapping the in situ generated enol intermediate with methylene iminium ion, and the asymmetric induction was enabled by chiral pentacarboxycyclopentadiene anion via H-bonding and electrostatic interaction.

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Reaction trio: The title reaction delivers CH functionalized pyrrole derivatives in moderate to good yields. This novel three‐component reaction provides both syn‐ and anti‐pyrrole derivatives having two contiguous stereocenters with good regio‐, diastereo‐, and enantioselectivity. This process represents the first highly enantioselective palladium‐carbenoid‐mediated reaction.