Cp*Rh(III)- and Cp*Ir(III)-catalysed direct C-H arylation with quinone diazides as efficient coupling partners is disclosed. This redox-neutral protocol offers a facile, operationally simple and environmentally benign access to arylated phenols. The reaction represents the first example of Cp*Ir(III)-catalysed C-H direct arylation reaction.

A cobalt-catalyzed decarboxylative Negishi coupling reaction of redox-active aliphatic esters with organozinc reagents was developed. The method enabled efficient alkyl-aryl, alkyl-alkenyl, and alkyl-alkynyl coupling reactions under mild reaction conditions with no external ligand or additive needed. The success of an in situ activation protocol and the facile synthesis of the drug molecule (±)-preclamol highlight the synthetic potential of this method. Mechanistic studies indicated that a radical mechanism is involved.

Tandem catalysis by Rh(III)/Pd(II) was realized, enabling rapid access to two important N-heterocycles that bear a synthetically valuable vinyl substituent. The reaction occurred under mild reaction conditions and was easy to handle. Good substrate scope and high regioand stereoselectivities were observed. The vinyl group was demonstrated to be a reliable handle for functional group interconversions. The alkene effect was found to be the key factor for the success of this process.

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Cp*Co(III)-catalyzed annulations of 2-alkenylphenols with CO for the synthesis of coumarin derivatives have been developed. The reaction features mild reaction conditions, broad substrate scope, and good functional group tolerance. Preliminary mechanistic studies were conducted, suggesting that C-H activation is the turnover limiting step. Furthermore, the efficiency of this reaction was demonstrated by the rapid total synthesis of three natural products herniarin, xanthyletin, and seselin.

α‐Haloboronates are useful organic synthons that can be converted to a diverse array of α‐substituted alkyl borons. Methods to α‐haloboronates are limiting and often suffer from harsh reaction conditions. Reported herein is a photochemical radical C‐H halogenation of benzyl N‐methyliminodiacetyl (MIDA) boronates. Fluorination, chlorination, and bromination reactions were effective by using this protocol. Upon reaction with different nucleophiles, the C−Br bond in the brominated product could be readily transformed to a series of C−C, C−O, C−N, C−S, C−P, and C−I bonds, some of which are difficult to forge with α‐halo sp2‐B boronate esters. An activation effect of B(MIDA) moiety was found.

The direct trifluoromethylthiolation of arenes was realized via (pentamethylcyclopentadienyl)cobalt(III)‐catalyzed C(sp2)‐H activation and coupling with AgSCF3 under the assistance of a directing group. The reaction features redox‐neutrality, mild conditions, broad substrate scope, and good functional group tolerance. Preliminary mechanistic studies have been conducted.magnified image

Group 9 Cp*M­(III) (M = Co, Rh, Ir) complexes have been extensively investigated as catalysts in a variety of C–H activation reactions. Typically, late metal-based silver or copper salt was used (while needed) as oxidant in these catalytic systems. Herein, we report our discovery of a potentially general type of N–O bond-containing oxidants, which allowed the mild and efficient syntheses of isocoumarins, isoquinolines, isoquinolinone, and styrenes via C–H activation catalyzed by group 9 Cp*M­(III) complexes. By using Cp*Rh­(III)-catalyzed isocoumarin synthesis as a model reaction, experimental and theoretical mechanistic studies were conducted. The results concluded that the Rh­(III)–Rh­(I)–Rh­(III) rather than the Rh­(III)–Rh­(V)–Rh­(III) pathway is more likely involved in the mechanism, and both the C–H activation and oxidation of the Cp*Rh­(I) species were involved in the turnover-limiting step.