One-Pot Synthesis of Dihydrobenzo[]fluorenes via Cascade C-H Annulation of Thiobenzamide with Alkynes.

We herein disclose a highly efficient one-pot synthetic strategy for dihydrobenzo[]fluorenes via cascade rhodium(III)-catalyzed -C-H activation/annulation of thiobenzamides with aryl ethynyl ketones and subsequently copper(II)-promoted intramolecular C-H/C-H cross-coupling reactions. Mechanistic investigations suggest that Cu(II) plays two crucial roles by serving as a sulfide scavenger to regenerate the Rh(III) catalyst and promoting the intramolecular C-H/C-H cross-coupling reaction. This protocol greatly streamlines accesses to a variety of appealing tetracyclic benzo[]fluorene skeletons, which may have potential biological activity and medicinal properties.

Nickel-Catalyzed 3,3-Dialkynylation of 2-Aryl Acrylamides: Direct Access to -Diethynylethenes via Double Vinylic C-H Bond Activation.

Direct access to -diethynylethenes is achieved by a Ni-catalyzed 3,3-dialkynylation of 2-aryl acrylamides with 1-bromotriisopropylsilylacetylene. The preliminary mechanism study reveals that the reaction goes through a sequential double vinylic C-H bond activation with the assistance of an 8-aminoquinolinyl directing group.

Rh(III)-Catalyzed Oxidative C-H Activation/Domino Annulation of Anilines with 1,3-Diynes: A Rapid Access to Blue-Emitting Tricyclic N,O-Heteroaromatics.

Disclosed herein is a rhodium-catalyzed oxidative C-H activation/domino annulation of -Boc-anilines with 1,3-diynes for the construction of tricyclic N,O-heteroaromatics. This reaction features easily available substrates, mild reaction conditions, high regioselectivity, mono/diannulation selectivity, and intra/intermolecular annulation selectivity. Moreover, this synthetic protocol enables the rapid assembly of a library of blue-emitting molecules with high quantum yields, among of which two fluorophores with pure blue-emission in toluene are discovered.

Direct C-H/C-H cross-coupling of benzimidates with heteroarenes to access biheteroaryl-2-carbonitriles.

A Rh-catalyzed C-H/C-H oxidative cross-coupling reaction of benzimidates with heteroarenes is developed, yielding biheteroaryl-2-carbonitriles directly after in situ dealcoholization. This protocol features high atom- and step-economy, and a broad substrate scope with good functional group tolerance.

Oxidative C-H/C-H Cross-Coupling of [1,2,4]Triazolo[1,5- a]pyrimidines with Indoles and Pyrroles: Discovering Excited-State Intramolecular Proton Transfer (ESIPT) Fluorophores.

A highly efficient Rh(III)-catalyzed oxidative C-H/C-H cross-coupling of [1,2,4]triazolo[1,5- a]pyrimidines (TAP) with indoles and pyrroles has been developed, which provides an opportunity to rapidly assemble a large library of novel excited-state intramolecular proton transfer (ESIPT) fluorophores. The resulting 7-(pyrrol-2-yl)TAPs only show the enol-form emission, while 7-(indol-2-yl)TAPs would undergo an ESIPT process and mainly exhibit the keto-form emission. In highly polar solvents, the enol-form emission of 7-(indol-2-yl)TAPs is enhanced significantly, thus showing the dual emission of enol and keto forms.

Tandem Rh(III)-Catalyzed C-H Heteroarylation of Indolyl Ketones and Cu(II)-Promoted Intramolecular Cyclization: One-Pot Access to Blue-Emitting Phenanthrone-Type Polyheterocycles.

Disclosed herein is a highly efficient one-pot synthetic strategy to phenanthrone-type polyheterocycles via tandem rhodium(III)-catalyzed ortho-C-H heteroarylation of indolyl ketones and copper(II)-promoted intramolecular cyclization. This protocol enables a library of blue-emitting fluorophores with high quantum yields and narrow full widths at half-maximum to be rapidly built from readily available substrates, among of which 6,6,7,9,12-pentamethyl-6,12-dihydro-5 H-benzofuro[2,3- a]carbazol-5-one (4a) exhibits pure blue emission with Commission Internationale de I'Eclairage coordinates of (0.15, 0.