Synthesis of -Difluorinated Oxa/Azaspiro[2.4]heptanes via Palladium-Catalyzed Spirocyclopropanation.

A palladium-catalyzed spirocyclopropanation of -difluoroalkenes with π-allylpalladium 1,4-dipoles has been successfully developed, which gives a powerful and straightforward synthetic strategy for the construction of novel -difluorinated spirocyclic compounds, 6,6-difluoro-5-oxa/azaspiro[2.4]heptanes. The scope of -difluoroalkenes can be extended to styrenes, acrylic esters, and acrylamides to realize the installment of various functional groups and different heteroatoms on the spirocyclic skeletons, which could be converted to valuable compounds with potential biological activity.

Molybdenum-catalyzed deoxygenative heterocyclization of 2-nitroazobenzenes: a novel strategy for catalytic synthesis of 2-aryl-2-benzo[][1,2,3]triazoles.

A novel strategy for the catalytic synthesis of 2-aryl-2-benzo[][1,2,3]triazoles bearing a wide range of functional groups in good to excellent yields by non-noble molybdenum-catalyzed deoxygenative heterocyclization of 2-nitroazobenzenes is described. The salient features of the transformation include the use of readily available substrates, valuable products and ease of scale-up. The mechanistic study indicates that the reaction occurred double deoxygenation by the Mo(VI)/Mo(IV) catalytic cycle from 2-nitroazobenzene, through the formation of 2-aryl-2-benzo[][1,2,3]triazole--oxide or nitrene intermediates.

Asymmetric Dearomatization of Indole by Palladium/PC-Phos-Catalyzed Dynamic Kinetic Transformation.

A palladium-catalyzed intermolecular dynamic kinetic asymmetric dearomatization of 3-arylindoles with internal alkynes was developed with the use of achiral Xantphos and chiral sulfinamide phosphine ligand (PC-Phos) as the co-ligands. This method could deliver various spiro[indene-1,3'-indole] compounds in good yields (up to 95 % yield) with up to 98 % ee. The salient features of the transformation include the use of readily available substrates, ease of scale-up and the versatile functionalization of the products.

Pd-Catalyzed Enantioselective Heck Reaction of Aryl Triflates and Alkynes.

The first palladium-catalyzed asymmetric Heck reaction between aryl triflates and alkynes to give trisubstituted allenes with high er under mild reaction conditions is described. The key to the success is the discovery and fine-tuning of the different -substituents of , which ensure the enantioselectivity and reactivity. Synthetic transformation of the chiral allenes with high chirality transfer was also demonstrated.

Synthesis of 2-Amino-3-hydroxy-3H-indoles via Palladium-Catalyzed One-Pot Reaction of Isonitriles, Oxygen, and N-Tosylhydrazones Derived from 2-Acylanilines.

A cyanide-free one-pot procedure was developed to access 2-amino-3-hydroxy-3H-indoles, which involved: (1) in situ formation of ketenimines by the reaction of N'-(1-(2-aminophenyl)ethylidene)-p-tosylhydrazones with isonitriles; (2) the intramolecular nucleophilic attack of ketenimines by the amino in phenyl furnishing the ring closure leading to 2-aminoindoles; (3) the oxidation of 2-aminoindoles by O leading to 2-amino-3-hydroxy-3H-indoles. This strategy represents not only a key compliment to the sporadic synthetic methods toward 2-amino-3-hydroxy-3H-indoles but also progress in N-tosylhydrazone, isonitrile, and ketenimine chemistry.

Rhodium-Catalyzed Annulation of Primary Benzylamine with α-Diazo Ketone toward Isoquinoline.

Rhodium-catalyzed annulation of commercially available primary benzylamine with α-diazo ketone was developed, leading to isoquinolines in moderate to good yields. This procedure features the employment of primary benzylamine as starting material as well as high selectivity in the 3- and 4- position of isoquinoline, generating a key compliment to the previously developed annulation with internal alkyne.

Rh-catalyzed sequential oxidative C-H activation/annulation with geminal-substituted vinyl acetates to access isoquinolines.

The concise synthesis of 3-substituted or non-C3-substituted isoquinolines through Rh-catalyzed sequential oxidative C-H activation/annulation with geminal-substituted vinyl acetates was developed with good functional group tolerance. The protocol was successfully applied to the total synthesis of the natural product papaverine.

Diethylene Glycol Serving as Ethyne Equivalent: A Sustainable Approach toward 2,3-Disubstituted Furan.

In the presence of tert-butyl peroxide (TBHP), the copper-catalyzed annulation of 1,3-dicarbonyl compound with diethylene glycol was developed leading to 2,3-disubstituted furan. Diethylene glycol serves as a cheap and environmentally friendly equivalent of ethyne, with the release of H2O and alcohol as clean wastes. The procedure involves a sequential O- and C- functionalization of β-ketoester by diethylene glycol.

Copper-catalyzed N-cyanation of sulfoximines by AIBN.

The direct copper-catalyzed N-cyanation of sulfoximines was achieved by using AIBN as a safe cyanide source. It represents a simple and environmentally benign procedure for the construction of the N-CN bond. Furthermore, some sec-amines can also be tolerated well under this procedure.