Feijie Song

Rhodium or Ruthenium‐Catalyzed Oxidative CH/CH Cross‐Coupling: Direct Access to Extended π‐Conjugated Systems

Doubling up: a chemo- and regioselective oxidative cross-coupling between various N-heteroarene-containing arenes and heteroarenes has been carried out by rhodium- or ruthenium-catalyzed twofold C-H activation, to deliver an array of highly functionalized π-conjugated systems.

N‐Oxide as a Traceless Oxidizing Directing Group: Mild Rhodium(III)‐Catalyzed CH Olefination for the Synthesis of ortho‐Alkenylated Tertiary Anilines

Double role: A traceless directing group also acts as an internal oxidant in a novel Rh(III) -catalyzed protocol developed for the synthesis of ortho-alkenylated tertiary anilines. A five-membered cyclometalated Rh(III) complex is proposed as a plausible intermediate and confirmed by X-ray crystallographic analysis.

A general method to diverse cinnolines and cinnolinium salts.

Rhodium catalysis: A highly efficient and general method has been established to prepare cinnolines, cinnolinium salts, and polycyclic cinnolinium salts through the rhodium(III)-catalyzed oxidative C-H activation/cyclization of azo compounds with alkynes (see scheme). Key features of this methodology include the unprecedented capacity to create both cinnoline and cinnolinium frameworks.

Iron‐Catalyzed Oxidative CH/CH Cross‐Coupling: An Efficient Route to α‐Quaternary α‐Amino Acid Derivatives

Fully loaded: A coordinating activation strategy has been developed to furnish α-quaternary α-amino acids through the iron(III)-catalyzed oxidative functionalization of α-C(sp(3) )H bonds of α-tertiary α-amino acid esters. The reaction exhibits a broad substrate scope for both α-amino acids and nucleophiles (Nu) as well as good functional-group tolerance (see scheme, DTBP=di-tert-butyl peroxide, DCE=1,2-dichloroethane).

Pd-catalyzed oxidative C–H/C–H cross-coupling of pyridines with heteroarenes

We have developed for the first time a general, concise and highly selective method for the C2-heteroarylation of pyridines and related azines with a broad range of heteroarenes via a two-fold C–H activation, which streamlines the previous approaches that require the activated azine N-oxide as the coupling partner.

Palladium‐Catalyzed Direct Arylation of N‐Heteroarenes with Arylsulfonyl Hydrazides

Hydrazides applied: A palladium-catalyzed direct C-H arylation of heteroarenes, with arylsulfonyl hydrazides as the arylating reagents, has been developed. The reaction is chemoselective, in that arylsulfonyl hydrazides containing halogen substituents can be employed without participation of the halogen substituent in the reaction. The method offers a straightforward approach to a variety of aryl-heteroaryl compounds.

Gold-catalyzed C(sp3)-H/C(sp)H coupling/cyclization/oxidative alkynylation sequence: a powerful strategy for the synthesis of 3-alkynyl polysubstituted furans.

In sharp contrast to the gold-catalyzed reactions of alkynes/allenes with nucleophiles, gold-catalyzed oxidative cross-couplings and especially C-H/C-H cross-coupling have been under represented. By taking advantage of the unique redox property and carbophilic π acidity of gold, this work realizes the first gold-catalyzed direct C(sp(3))-H alkynylation of 1,3-dicarbonyl compounds with terminal alkynes under mild reaction conditions, with subsequent cyclization and in situ oxidative alkynylation. A variety of terminal alkynes including aryl, heteroaryl, alkenyl, alkynyl, alkyl, and cyclopropyl alkynes all successfully participate in the domino reaction. The protocol offers a simple and region-defined approach to 3-alkynyl polysubstituted furans.

Palladium-catalyzed C–H activation of anilides at room temperature: ortho-arylation and acetoxylation

Room-temperature ortho-arylation and acetoxylation of anilides have been achieved using cationic palladium (Pd[TFA]+) as catalyst and (NH4)2S2O8 as oxidant. Preliminary investigation of the mechanism suggests that palladium may have different oxidation states in the catalytic cycles of these two transformations.

Silver-catalyzed one-pot cyclization/fluorination of 2-alkynylanilines: highly efficient synthesis of structurally diverse fluorinated indole derivatives

Highly efficient approaches to obtain structurally diverse fluorinated indole derivatives have been realized through the Ag-catalyzed one-pot cyclization/fluorination of 2-alkynylanilines in the presence of NFSI or Selectfluor.

Transition‐Metal‐Catalyzed CH Bond Functionalizations: Feasible Access to a Diversity‐Oriented β‐Carboline Library

Diversification of the β-carboline skeleton has been demonstrated to assemble a β-carboline library starting from the tetrahydro-β-carboline framework. This strategy affords feasible access to heteroaryl-, aryl-, alkenyl-, or alkynyl-substituted β-carbolines at the C1, C3, or C8 position through three categorically different types of transition-metal-catalyzed CC bond-forming reactions, in the presence of multiple potentially reactive positions. These site-selective functionalizations include; 1) the Cu-catalyzed C1/C3-selective decarboxylative C sp 3C sp 2 and C sp 3Csp coupling of hexahydro-β-carboline-3-carboxylic acid with a CH bond of a heteroarene or terminal alkyne; 2) the chelation-assisted Pd-catalyzed C1/C8-selective CH arylation of hexahydro-β-carboline with aryl boron reagents; and 3) the chelation-assisted Pd-catalyzed C1/C3-selective oxidative CH/CH cross-coupling of β-carboline-N-oxide with arenes, heteroarenes, or alkenes. The saturated structural feature of the hexahydro-β-carboline framework can increase reactivity and control site selectivity. The robustness of these approaches has been demonstrated through the synthesis of hyrtioerectine analogues and perlolyrine. We believe that these strategies could provide inspiration for late-stage diversifications of bioactive core scaffolds.