Palladium-catalyzed allylic alkylation dearomatization of ß-naphthols and indoles with gem-difluorinated cyclopropanes.

A palladium-catalyzed allylic alkylation dearomatization of ß-naphthols and indoles with gem-difluorinated cyclopropanes has been developed. This reaction provided an efficient route to access 2-fluoroallylic ß-naphthalenones and indolenines bearing quaternary carbon centers in good yields with high Z-selectivity via C-C bond activation, C-F bond cleavage and the dearomatization process, benefiting from the wide substrate scope and good functional group tolerance. Moreover, 2-fluoroallylic furanoindoline and pyrroloindolines were achieved in good efficiency via cascade allylic alkylation, dearomatization and cyclization processes in the presence of Et3B.

Nickel-Catalyzed Reductive 1,2-Dialkynylation of Alkenes Bearing an 8-Aminoquinoline Directing Group.

An unprecedented nickel-catalyzed reductive 1,2-dialkynylation of alkenes bearing an 8-aminoquinoline directing group has been developed. This method proceeded through a migratory insertion/reductive-coupling process under mild conditions with a wide substrate scope and good functional group tolerance, providing direct access to the synthetically flexible 1,5-diynes. Moreover, the 1,2-dialkynylation products could be further converted to borate-ester- or azide-functionalized 1,5-dienes, ditriazole, ß-diyne primary amide, and trisubstituted benzene.

Synthesis of Indole-Fused Polycyclics via Rhodium-Catalyzed Undirected C-H Activation/Alkene Insertion.

A Rh(III)-catalyzed undirected C-H activation/alkene insertion to synthesize diversified indole-fused polycyclics has been developed. Intramolecular electrophilic cyclization generated a 3-indolyl rhodium species that went through an aryl-to-aryl 1,4-rhodium migration to realize the C-H activation. The subsequent [4 + 2] carboannulation or hydroarylation of alkenes could be achieved, respectively, by simply adjusting the additives of the reaction.

Pd-Catalyzed Alkyne Insertion/C-H Activation/[4 + 2] Carboannulation of Alkenes to the Synthesis of Polycyclics.

An unprecedented Pd-catalyzed alkyne insertion/C-H activation/intramolecular [4 + 2] carboannulation of alkenes has been reported. In this transformation, the C-H activation was triggered by an in situ generated alkenylpalladium species via the Pd-catalyzed cross-coupling reaction of aryl iodides and alkynes. Subsequently, the resulting five-membered C, C-palladacycle intermediates were added across the alkenes, providing a unique approach to access diversified polycyclics in good efficiency. Two new rings and three C-C bonds were formed in one pot.

Palladium-Catalyzed Cascade Heck Cyclization To Access Bisindoles.

A novel strategy for intercepting the σ-alkylpalladium species generated via a Heck reaction, enabling a palladium-catalyzed cyclization of o-ethynylanilines, has been described. This direct and operationally simple protocol provided a fundamental platform to synthesize bisindoles with high efficiency, involving one C-N bond and two C-C bond formations.

Controllable Rh(III)-Catalyzed Annulation between Salicylaldehydes and Diazo Compounds: Divergent Synthesis of Chromones and Benzofurans.

A Rh(III)-catalyzed annulation between salicylaldehydes and diazo compounds with controllable chemoselectivity is described. AgNTf2 favored benzofurans via a tandem C-H activation/decarbonylation/annulation process, while AcOH led to chromones through a C-H activation/annulation pathway. The reaction exhibited good functional group tolerance and scalability. Moreover, only a single regioisomer of benzofuran was obtained due to the in situ decarbonylation orientation effect.

Rh(III)-Catalyzed Cascade Annulation/C-H Activation of o-Ethynylanilines with Diazo Compounds: One-Pot Synthesis of Benzo[a]carbazoles via 1,4-Rhodium Migration.

A Rh(III)-catalyzed cascade annulation/C-H activation of o-ethynylanilines with diazo compounds has been developed. This concise method allows for the rapid formation of a number of benzo[a]carbazoles in high yields, exhibiting good functional group tolerance and scalability. The key to the success of this approach involves one C-N bond and two C-C bond formation, and an aryl-to-aryl 1,4-rhodium migration.

3-Aza π-allyl palladium derived from imino migration in palladium-carbene: MCRs toward multiple substituted indole skeleton.

Palladium-catalyzed multi-component reactions (MCRs) between 2-iodoaniline, aryl isonitrile, N-tosylhydrazones and solvent were developed. This procedure features the migration of the imino group in palladium-carbene to produce a 3-aza π-allyl palladium species. Then, intramolecular nucleophilic attack of the π-allyl palladium species by the amino group takes place facilely, thus producing a 1,2,3-trisubstitued indole skeleton, which has high diversity and complexity.

Iodine-catalyzed ammoxidation of methyl arenes.

The development of organic transformation using cheap and readily available substrates under mild conditions will be pivotal for green and sustainable synthetic organic chemistry. Concerning our continued interest in the cyanation reaction, a metal-free direct ammoxidation of readily available methyl arenes leading to nitriles was established under mild conditions. A series of aryl methanes especially heteroaryl methanes (30 examples) were applicable in moderate to good yields with good functionality tolerance.

tert-Butyl peroxybenzoate-promoted α-methylation of 1,3-dicarbonyl compounds.

A tert-butyl peroxybenzoate (TBPB)-promoted direct α-methylation of 1,3-dicarbonyl compounds has been developed, providing α-methyl derivatives in moderate to good yields. In this procedure, TBPB plays a dual role, serving as both the methyl source and radical initiator. This work represents a key complement to the traditional α-methylation of 1,3-dicarbonyl compounds using methyl iodide.

TBHP-promoted sequential radical silylation and aromatisation of aryl isonitriles with silanes.

The tert-butyl hydroperoxide (TBHP) promoted sequential silylation and aromatisation of isonitriles was developed, where the silyl group was regioselectively installed at the 6-position of phenanthridines. This procedure tolerates a series of functional groups, such as fluoro, chloro, acetyl, methoxy carbonyl, cyano and trifluoromethyl. The addition of a silyl radical to the isonitrile followed by an intramolecular aromatic cyclization was involved in this transformation.

The Bu4NI-catalyzed alfa-acyloxylation of ketones with benzylic alcohols.

The Bu4NI-catalyzed reaction of ketones with benzylic alcohols was achieved, leading to alfa-acyloxycarbonyl compounds in moderate to good yields. This metal-free procedure featured the employment of facilely and commercially available starting materials and TBHP as a clean oxidant with high atom economy.

The carbomethylation of arylacrylamides leading to 3-ethyl-3-substituted indolin-2-one by cascade radical addition/cyclization.

An FeCl2-promoted carbomethylation of arylacrylamides by di-tert-butyl peroxide (DTBP) is achieved, leading to 3-ethyl-3-substituted indolin-2-one in high yield. The reaction tolerates a series of functional groups, such as cyano, nitro, ethyloxy carbonyl, bromo, chloro, and trifluoromethyl groups. The radical methylation and arylation of the alkenyl group are involved in this reaction.