Zhenxing Liu

Cross-Coupling Reactions Involving Metal Carbene: From C═C/C–C Bond Formation to C–H Bond Functionalization

Cross-coupling reactions involving metal-carbene are emerging as a new type of carbon-carbon bond-forming reaction. The aim of this JOCSynopsis is to provide an overview of the most recent development of these reactions, focusing on the use of diazo compounds (or in situ formed diazo compounds from N-tosylhydrazones) as carbene precursors. In addition, the integration of this type of reaction with C-H bond functionalization is also surveyed.

Rhodium(III)‐Catalyzed ortho Alkenylation of N‐Phenoxyacetamides with N‐Tosylhydrazones or Diazoesters through CH Activation

A coupling reaction of N-phenoxyacetamides with N-tosylhydrazones or diazoesters through Rh(III) -catalyzed CH activation is reported. In this reaction, ortho-alkenyl phenols were obtained in good yields and with excellent regio- and stereoselectivity. Rh-carbene migratory insertion is proposed as the key step in the reaction mechanism.

Formal carbene insertion into C-C bond: Rh(I)-catalyzed reaction of benzocyclobutenols with diazoesters.

A Rh(I)-catalyzed formal carbene insertion into C-C bond of benzocyclobutenols has been realized by employing diazoesters as carbene precursors. The product indanol derivatives were obtained in good yields and in diastereoselective manner under mild reaction conditions. All-carbon quaternary center is constructed at the carbenic carbon. This catalytic reaction involves selective cleavage of C-C bond, Rh(I) carbene insertion, and intramolecular aldol reaction.

Palladium-Catalyzed Diarylmethyl C(sp3)–C(sp2) Bond Formation: A New Coupling Approach toward Triarylmethanes

Palladium-catalyzed reductive coupling reactions between N-tosylhydrazones and aryl halides lead to the formation of C(sp(3))-C(sp(2)) bonds. This approach provides a general route for the synthesis of triarylmethanes.

Transition‐Metal‐Free Intramolecular Carbene Aromatic Substitution/Büchner Reaction: Synthesis of Fluorenes and [6,5,7]Benzo‐fused Rings

Intramolecular aromatic substitution and Büchner reaction have been established as powerful methods for the construction of polycyclic compounds. These reactions are traditionally catalyzed by Rh(II) catalysts with α-diazocarbonyl compounds as the substrates. Herein a transition-metal-free intramolecular aromatic substitution/Büchner reaction is presented. These reactions use readily available N-tosylhydrazones as the diazo compound precursors and show wide substrate scope.

Pd(0)-Catalyzed Carbene Insertion into Si-Si and Sn-Sn Bonds.

The first Pd(0)-catalyzed carbene insertion into Si-Si and Sn-Sn bonds has been realized by using N-tosylhydrazones as the carbene precursors. Geminal bis(silane) and geminal bis(stannane) derivatives were obtained in good to excellent yields under mild conditions. Migratory insertion of Pd carbene is supposed to be the key step for the reaction.

Pd-Catalyzed Cyclization and Carbene Migratory Insertion: New Approach to 3-Vinylindoles and 3-Vinylbenzofurans

A Pd-catalyzed stereoselective synthesis of 3-vinylindoles and 3-vinylbenzofurans has been developed. The reaction merges the alkyne-based Pd-catalyzed cyclization and Pd carbene migratory insertion in a single catalytic cycle, generating a C-C single bond and a C═C double bond in one operation.

Catalyst-Free Intramolecular Formal Carbon Insertion into σ-CC Bonds: A New Approach toward Phenanthrols and Naphthols†

The different reactivity of two kinds of carbonyl groups in keto aldehyde substrates has been exploited for the synthesis of phenanthrols, naphthols, and their heteroatom-containing analogues. Key to this highly efficient and robust methodology is the catalyst-free intramolecular formal diazo carbon insertion of N-tosylhydrazones into keto C-C bonds.

Rhodium(I)‐Catalyzed C−C Bond Activation of Siloxyvinylcyclopropanes with Diazoesters

The rhodium(I)-catalyzed C-C bond activation reaction of siloxyvinylcyclopropanes with diazoesters demonstrates a novel mode of C-C bond cleavage of siloxyvinvylcyclopanes. The alkene products were obtained as single E-configured isomers in good yields. A σ,η3 -allyl rhodium complex, which has been previously proposed as the key intermediate in rhodium(I)-catalyzed cycloaddition of vinylcyclopropanes, has been isolated and characterized by X-ray crystallography.