Rhodium- and Iridium-Catalyzed Dehydrogenative Cyclization through Double C–H Bond Cleavages To Produce Fluorene Derivatives

Copper-mediated radical alkylarylation of unactivated alkenes with acetonitrile leading to fluorenes and pyrroloindoles

A Cu-mediated/catalyzed selective oxidative dual C–H bond cleavage of an arene and alkylnitrile or acetone is reported. This method provides an alternative method for designing new pharmaceutical frameworks and photoelectronic devices.

Iridium-Catalyzed ortho-Arylation of Benzoic Acids with Arenediazonium Salts

In the presence of catalytic [{IrCp*Cl2 }2 ] and Ag2 CO3 , Li2 CO3 as the base, and acetone as the solvent, benzoic acids react with arenediazonium salts to give the corresponding diaryl-2-carboxylates under mild conditions. This C-H arylation process is generally applicable to diversely substituted substrates, ranging from extremely electron-rich to electron-poor derivatives. The carboxylate directing group is widely available and can be removed tracelessly or employed for further derivatization. Orthogonality to halide-based cross-couplings is achieved by the use of diazonium salts, which can be coupled even in the presence of iodo substituents.

Synthesis of Indolo[1,2-a][1,8]naphthyridines by Rhodium(III)-Catalyzed Dehydrogenative Coupling via Rollover Cyclometalation

The rhodium-catalyzed dehydrogenative coupling of N-pyridylindoles with alkynes proceeds smoothly through rollover cyclometalation to produce indolo[1,2-a][1,8]naphthyridine derivatives. A number of tetra-, penta-, and hexacyclic N-containing heteroaromatics can also be readily constructed in a similar manner. The L-shaped π-conjugated molecules exhibit intense solid-state fluorescence.

Direct synthesis of N-H carbazoles via iridium(III)-catalyzed intramolecular C-H amination

The iridium-catalyzed dehydrogenative cyclization of 2-aminobiphenyls proceeds smoothly in the presence of a copper cocatalyst under air as a terminal oxidant through intramolecular direct C-H amination to produce N-H carbazoles. A similar iridium/copper system can also catalyze the unprecedented dimerization reaction of 2-aminobiphenyl involving 2-fold C-H/N-H couplings.

Ligand Design for Rh(III)-Catalyzed C-H Activation: An Unsymmetrical Cyclopentadienyl Enables a Regioselective Synthesis of Dihydroisoquinolones

We report the regioselective synthesis of dihydroisoquinolones from aliphatic alkenes and O-pivaloyl benzhydroxamic acids mediated by a Rh(III) precatalyst bearing sterically bulky substituents. While the prototypical Cp* ligand provides product with low selectivity, sterically bulky Cpt affords product with excellent regioselectivity for a range of benzhydroxamic acids and alkenes. Crystallographic evidence offers insight as to the source of the increased regioselectivity.

Cp*Rh(iii) and Cp*Ir(iii)-catalysed redox-neutral C–H arylation with quinone diazides: quick and facile synthesis of arylated phenols

Cp*Rh(iii)- and Cp*Ir(iii)-catalysed direct C–H arylation with quinone diazides provides a facile and redox-neutral access to arylated phenols.

Gold-catalyzed intermolecular oxidation of o-alkynylbiaryls: an easy and practical access to functionalized fluorenes

A novel gold-catalyzed intermolecular oxidation of o-alkynylbiaryls has been developed. A variety of functionalized fluorenes are readily accessed by utilizing this non-diazo approach, thus providing a viable alternative to synthetically useful fluorenes.

Cyclometalated [Cp*M(C^X)] (M = Ir, Rh; X = N, C, O, P) complexes

Isolated and well-defined cyclometalated iridium/rhodium complexes that contain a Cp*M–C (M = Ir, Rh) bond stabilised by the intramolecular coordination of neutral donor atoms (N, C, O or P), together with their applications, were summarized.