Bing-Feng Shi

Cobalt(III)-Catalyzed C2-Selective C–H Alkynylation of Indoles

A cobalt(III)-catalyzed C-2 selective C-H alkynylation of indoles using hypervalent iodine-alkyne reagents is described. A broad range of synthetically useful functional groups (-F, -Cl, -Br, -CO2Me, -CN) were tolerated, providing an efficient and robust protocol for the synthesis of C-2 alkynylated indoles. The pyrimidyl and silyl protecting groups could be easily removed to give the corresponding 2-ethynyl-1H-indole.

Cu(II)-mediated C-S/N-S bond formation via C-H activation: access to benzoisothiazolones using elemental sulfur.

A copper-mediated C-S/N-S bond-forming reaction via C-H activation that uses elemental sulfur has been developed. The addition of TBAI was found to be crucial for the success of this transformation. The method is scalable, shows excellent functional group tolerance, and is compatible with heterocycle substrates, providing efficient and practical access to benzoisothiazolones. The direct diversification of the benzoisothiazolone products into a variety of sulfur-containing compounds is also demonstrated.

Copper-Mediated Hydroxylation of Arenes and Heteroarenes Directed by a Removable Bidentate Auxiliary

A copper-mediated C-H hydroxylation of arenes and heteroarenes using our newly developed PIP directing group has been developed. This procedure is scalable and compatible with a wide range of functional groups and heteroarenes, providing an operationally simple protocol for the synthesis of o-hydroxybenzamides. The hydroxylation of nicotinamides gave 4-oxo-1,4-dihydropyridine-3-carboxamides selectively. Preliminary mechanistic studies implicate that a basic ligand-enabled, irreversible, rate-determining CMD step is most likely involved in this process.

Copper(II)-Catalyzed Direct Sulfonylation of C(sp2)–H Bonds with Sodium Sulfinates

A copper-catalyzed direct sulfonylation of C(sp(2))-H bonds with sodium sulfinates using a removable directing group is described. This reaction tolerates a wide range of functional groups, providing an efficient protocol for the synthesis of diverse aryl sulfones. Moreover, a series of 2,6-disubstituted benzamides could be synthesized via sequential C-H functionalization.

Indole Synthesis via Cobalt(III)-Catalyzed Oxidative Coupling of N-Arylureas and Internal Alkynes

A mild Co(III)-catalyzed oxidative annulation of N-arylureas and internal alkynes has been developed. The use of less electrophilic ureas other than acetamides as directing groups is crucial for the reaction. A broad range of synthetically useful functional groups are compatible with this reaction, thus providing a new opportunity for the synthesis of diverse indoles.

Rhodium(III)-Catalyzed Oxidative Olefination of Pyridines and Quinolines: Multigram-Scale Synthesis of Naphthyridinones

A Rh(III)-catalyzed oxidative olefination of pyridines and quinolines has been achieved. This method has a broad substrate scope and has been applied to the expeditious, multigram-scale synthesis of naphthyridinones.

Recent advances in copper-mediated chelation-assisted functionalization of unactivated C–H bonds

Transition metal-catalyzed direct functionalization of C–H bonds has recently emerged as a powerful strategy for the construction of carbon–carbon and carbon–heteroatom bonds. Among various metals employed, base metal copper has attracted significant attention owing to its relatively low cost, abundance, and versatile reactivity. This review aims to comprehensively summarize the recent advances in copper-mediated (both stoichiometric and catalytic) chelation-assisted functionalization of unactivated C–H bonds.

Copper/Silver‐Mediated Direct ortho‐Ethynylation of Unactivated (Hetero)aryl CH Bonds with Terminal Alkyne

A copper/silver-mediated oxidative ortho-ethynylation of unactivated aryl C-H bonds with terminal alkyne has been developed. The reaction uses the removable PIP directing group and features broad substrate scope, high functional-group tolerance, and compatibility with a wide range of heterocycles, providing an efficient synthesis of aryl alkynes. This procedure highlights the potential of copper catalysts to promote unique, synthetically enabling C-H functionalization reactions that lie outside of the current scope of precious metal catalysis.

Pd(II)-Catalyzed Direct Sulfonylation of Unactivated C(sp3)–H Bonds with Sodium Sulfinates

A Pd(II)-catalyzed sulfonylation of unactivated C(sp(3))-H bonds with sodium arylsulfinates using an 8-aminoquinoline auxiliary is described. This reaction demonstrates excellent functional group tolerance with respect to both the caboxamide starting material and the sodium arylsulfinate coupling partner, affording a broad range of aryl alkyl sulfones. Moreover, the late-stage modification of complex molecules was achieved via this sulfonylation protocol.

Site-Selective Alkenylation of δ-C(sp3)–H Bonds with Alkynes via a Six-Membered Palladacycle

Most chelation-assisted aliphatic C-H activation proceeds through a kinetically favored five-membered cyclometalated intermediate. Here, we report the first site-selective alkenylation of δ-C(sp(3))-H in the presence of more accessible γ-C(sp(3))-H bonds via a kinetically less favored six-membered palladacycle. A wide range of functional groups are tolerated, and the unique protocol can be applied to the synthesis of chiral piperidines. Moreover, mechanistic insights have been conducted to elucidate the origin of the unusual site-selectivity.