A novel RuII-catalyzed tandem C–H bond activation tool has been successfully developed involving allylation and oxidative cyclization of 2-phenyl indoles with allyl carbonates. This one-pot reaction is a new way to synthesize indolo[2,1-a]isoquinoline units via a simple and efficient process.

Diazo compounds play an important role as a coupling partner in the synthesis of unique π-conjugated 7-azaindole derivatives via rhodium(III)-catalyzed double C–H activation/cyclization.

Rhodium(III)-catalyzed N-directed ortho C–H activation reactions have been developed for the synthesis of unique heterocyclic benzoisothiazoles. Herein, this novel tandem annulation approach can efficiently construct benzoisothiazole compounds from free NH-sulfoximines and alkenes via C–H activation, olefination and subsequent intramolecular aza-Michael cyclization.

A new concise methodology was developed for the synthesis of the two vicinal quaternary centers of the natural product perophoramidine. Key steps involved the Morita–Baylis–Hillman reaction, reductive cyclization and allylic alkylation. Moreover, most conditions are simple and convenient with good yields.Download high-res image (97KB)Download full-size image

AbstractA highly efficient synthesis of polycyclic amides by a RhIII-catalyzed cascade cyclization of 3-phenyl-1,4,2-dioxazol-5-one and diphenylacetylene has been developed. This one-pot strategy expanded the application scope of directing groups to dioxazolones.

A novel decahydropyrene synthesis has been successfully developed involving a tandem rhodium-catalyzed C–H activation/intramolecular Diels–Alder reaction/1,3-dipolar cycloaddition cascade process by using diazole as a traceless directing group. The advantage of this one-pot strategy is a quite simple, efficient, highly stereoselective, and unique product structure.

A highly efficient iridium(III)-catalyzed C–H activation/tandem Grignard-type [3 + 2] annulation process was developed for the synthesis of novel spirocyclic phosphoramide derivatives. Compared with other transition-metal catalysts, [Cp*IrCl2]2 exhibited favorite efficiency and best selectivity in this cascade reaction. The strategy could be applied to further construct more complex heterocyclic compounds.

Various rhodium-catalyzed double C–H activations are reviewed. These powerful strategies have been developed to construct C–C bonds, which might be widely embedded in complex aza-fused heterocycles, polycyclic skeletons and heterocyclic scaffolds. In particular, rhodium(III) catalysis shows good selectivity and reactivity to functionalize the C–H bond, generating reactive organometallic intermediates in most of the coupling reactions. Generally, intermolecular, intramolecular and multi-component coupling reactions via double C–H activations with or without heteroatom-assisted chelation are discussed in this review.

Rhodium(III)-catalyzed N-directed ortho C–H activation and subsequent roll-over C–H activation represents an important strategy to synthesize fused polycyclic compounds. Herein, the novel methodology broadens the scope of the coupling partner to alkenes, which working smoothly with 7-azaindoles has been proven to be an efficient and atom-economical strategy to access complex π-conjugated 7-azaindole derivatives.

An efficient rhodium(III)-catalyzed C–H activation has been developed by using 7-azaindole as a directing group. A wide variety of olefinated 7-azaindole derivatives and N-naphthylazole derivatives have been selectively formed in moderate to excellent yields when alkenes or alkynes act as the C–H coupling partner.An efficient rhodium(III)-catalyzed C–H activation has been developed by using 7-azaindole as a directing group. A wide variety of olefinated 7-azaindole derivatives and N-naphthylazole derivatives have been selectively formed in moderate to excellent yields when alkenes or alkynes act as the C–H coupling partner.

Rhodium(III)-catalyzed double C–H activation involving N-directed ortho C–H activation and subsequent roll-over C–H activation of the heterocycle ring has been developed to form complex 7-azaindole derivatives in moderate to excellent yields. A broad scope of 7-azaindoles and internal alkynes has been demonstrated in this oxidative annulation reaction.

Tandem multi-site cyclization triggered by Rh(III)-catalyzed C–H activation has been achieved for highly efficient synthesis of spirocycle indolin-3-one (C2-cyclization), benzo[a]carbazole (C3-cyclization) and an unusual indoxyl core (N1-cyclization). In particular, the synthesis of pseudo-indoxyl is typically completed within 10 min, and the reaction tolerates air, water and a range of solvents.

In this paper, a simple and highly efficient ruthenium-catalyzed direct C3 alkylation of indoles with various α,β-unsaturated ketones without chelation assistance has been developed. This novel C–H activation methodology exhibits a broad substrate scope such as different substituted indoles, pyrroles, and other azoles. Further synthetic applications of the alkylation products can lead to more attractive 3,4-fused tricyclic indoles.

Ruthenium(II)-catalyzed oxidative coupling of NH protic amides with alkynes has been developed for the synthesis of a diversity of complex structures, such as N-acyl indole and tricyclic amide derivatives.

A simple approach for the direct synthesis of 1,2-dihydropyridines was developed involving a one-step rhodium-catalyzed [2+2+2] cycloaddition between N-sulfonyl ketimines and two terminal alkynes. Mechanistic studies suggested a stepwise reaction of an imine and alkyne with rhodium(III), followed by the insertion of a second alkyne.

Ru(II)-catalyzed one-pot synthesis of polysubstituted spirofluorene–indenes via [3 + 2] annulation and then intramolecular Friedel–Crafts alkylation has been achieved. The simple method provides a broad scope of aryl ketones and internal alkynes, achieving PAHs skeletons in moderate to good yields.

The N–S bond-based internal oxidant offers a distinct approach for the synthesis of highly functionalized pyridines. A novel Rh(III)-catalyzed one-pot process undergoes an efficient C–C/C–N bond formation along with desulfonylation under very mild conditions. The method is quite simple, general, and efficient.

Double C–H activations of C(5)–H and Csp2–H of 2-substituted N-vinyl- or arylimidazoles were realized without heteroatom-directing assistance by rhodium(III) catalyst. A subsequent oxidative annulation reaction with alkynes efficiently produced aza-fused heterocycles with high molecular complexity in low to excellent yields.

A simple approach for synthesis of novel aza-fused scaffolds such as pyrido[1,2-α]benzimidazoles and imidazo[1,2-α]pyridines was developed by Rh(III)-catalyzed direct oxidative coupling between alkenes and unactivated alkynes without an extra directing group. The method would allow a broad substrate scope, providing fused heterocycles with potential biological properties.

In this paper, a simple and highly efficient ruthenium-catalyzed direct C3 alkylation of indoles with various α,β-unsaturated ketones without chelation assistance has been developed. This novel C–H activation methodology exhibits a broad substrate scope such as different substituted indoles, pyrroles, and other azoles. Further synthetic applications of the alkylation products can lead to more attractive 3,4-fused tricyclic indoles.

Various rhodium-catalyzed double C–H activations are reviewed. These powerful strategies have been developed to construct C–C bonds, which might be widely embedded in complex aza-fused heterocycles, polycyclic skeletons and heterocyclic scaffolds. In particular, rhodium(III) catalysis shows good selectivity and reactivity to functionalize the C–H bond, generating reactive organometallic intermediates in most of the coupling reactions. Generally, intermolecular, intramolecular and multi-component coupling reactions via double C–H activations with or without heteroatom-assisted chelation are discussed in this review.

Tandem multi-site cyclization triggered by Rh(III)-catalyzed C–H activation has been achieved for highly efficient synthesis of spirocycle indolin-3-one (C2-cyclization), benzo[a]carbazole (C3-cyclization) and an unusual indoxyl core (N1-cyclization). In particular, the synthesis of pseudo-indoxyl is typically completed within 10 min, and the reaction tolerates air, water and a range of solvents.

Rhodium(III)-catalyzed N-directed ortho C–H activation and subsequent roll-over C–H activation represents an important strategy to synthesize fused polycyclic compounds. Herein, the novel methodology broadens the scope of the coupling partner to alkenes, which working smoothly with 7-azaindoles has been proven to be an efficient and atom-economical strategy to access complex π-conjugated 7-azaindole derivatives.

A simple approach for synthesis of novel aza-fused scaffolds such as pyrido[1,2-α]benzimidazoles and imidazo[1,2-α]pyridines was developed by Rh(III)-catalyzed direct oxidative coupling between alkenes and unactivated alkynes without an extra directing group. The method would allow a broad substrate scope, providing fused heterocycles with potential biological properties.

A novel cyclic N-phosphoryl ketimine structure can efficiently react with olefins as useful directing groups to construct a myriad of phosphate scaffolds via rhodium(III)-catalyzed ortho-alkenylation. This method provides a probability that the coupling products could be used as a building block to access more complex organic phosphorus compounds.

Diazo compounds play an important role as a coupling partner in the synthesis of unique π-conjugated 7-azaindole derivatives via rhodium(III)-catalyzed double C–H activation/cyclization.

Ruthenium(II)-catalyzed oxidative coupling of NH protic amides with alkynes has been developed for the synthesis of a diversity of complex structures, such as N-acyl indole and tricyclic amide derivatives.