Visible-light-promoted tandem decarboxylation coupling/cyclization of N-aryl glycines with quinoxalinones: Easy access to tetrahydroimidazo [1,5-a]quinoxalin-4(5H)-ones

A visible-light-promoted formal[2+2+1]cyclization of N-aryl glycines with quinoxalin-2(1H)-ones to synthesize tetrahydroimidazo[1,5-a]quinoxalin-4(5H)-ones have been developed.The protocol features operational simplicity,mild reaction conditions with blue LED light employing Ru(bpy)3Cl2.6H2O as a photoredox catalyst,a combination of O2 from air and Cu(OAc)2 as the oxidant and broad substrate applicability.

Visible-light-promoted sulfonylmethylation of imidazopyridines

The visible light promoted C-H sulfonylmethylation of imidazopyridines with easily accessible bromomethyl sulfones under mild reaction conditions was described.This protocol provides an effective and practical access to sulfonylmethylated imidazopyridines with good functional group tolerance.The desired products were provided in moderate to excellent yields for 50 examples at room temperature.The method could also be an attractive strategy to install a methyl group on imidazopyridines.

Rhodium(Ⅲ)-catalyzed intermolecular cyclization of anilines with sulfoxonium ylides toward indoles

Rhodium(Ⅲ)-catalyzed synthesis of indole derivatives has been realized via cascade reaction of C -H alkylation/nucleophilic cyclization starting from readily available N-phenylpyridin-2-amines and sulfoxonium ylides. Notably, this transformation could smoothly proceed with high yields, good regioselectivity, and feature broad group tolerance and under redox-neutral condition to avoid external oxidant. The titled products are potentially important building blocks in the organic synthesis through various chemical transformations.

A Highly Efficient Synthesis of Optically Active Ferrocenylethylamines via Hydride Reduction of Chiral Ferrocenylketimines

Due to using （R）- or （S）-a-methylbenzylamine as a chiral auxiliary, and low-temperature regime for reduction of the intermediate ferrocenyl-mono- or 1,1＇-bis-ketimines, the corresponding secondary mono- or 1,1＇-bis-amines were prepared with high diastereoselectivity. Removal of the a-methylbenzyl group afforded the optically active primary mono- and bis-ferrocenylethylamines in high yields. The absolute configuration of （R,R）-3a and （S,S）-3b was determined by X-ray single crystal diffraction.

Ring opening [3+2] cyclization of azaoxyallyl cations with benzo[d]-isoxazoles:Efficient access to 2-hydroxyaryl-oxazolines

A selective ring-opening [3+2] cyclization reaction of benzo[d]isoxazoles with 2-bromo-propanamides has been developed.The azaoxyallyl cation intermediates are employed as C^O 3-atom synthon to build oxa-heterocycles via the selectivity of suitable cyclization partners.This transformation provides rapid access to highly functionalized 2-hydroxyaryl-oxazolines under mild conditions and excellent regioselectivity.

Copper-catalyzed asymmetric propargylic substitution of anthrones and propargylic esters

Anthrones are key structural motifs in many natural products, bioactive compounds and pharmaceutical chemicals. Earth-abundant-metal-catalyzed asymmetric functionalization of anthrones has not proved to be viable. Herein, we disclosed a highly enantioselective propargylic substitution of anthrones with propargylic esters using copper salts with chiral N, N, P-ligand. This strategy is amenable to a broad range of substrates, uses readily available starting materials, provides excellent yields with remarkable enantioselectivity under mild conditions, and enables attractive products diversification routes.

Rhodium(Ⅲ)-catalyzed [4+2] annulation of N-arylbenzamidines with1,4,2-dioxazol-5-ones: Easy access to 4-aminoquinazolines via highly selective C-H bond activation

A novel approach for the synthesis of 4-aminoquinazolines has been developed via rhodium(Ⅲ)-catalyzed [4+2] annulation of N-arylbenzamidines with 1,4,2-dioxazol-5-ones.This reaction features excellent regioselectivity,broad substrate scope and high step economy,which would provide the refe rence for the construction of the fused 4-aminoquinazolines with biologically and pharmacologically active compounds.

Water and fluorinated alcohol mediated/promoted tandem insertion/aerobic oxidation/bisindolylation under metal-free conditions:Easy access to bis(indolyl)methanes

A green tandem reaction,including insertion/aerobic oxidation/bisindolylation,starting from indoles and diazo compounds has been developed.The combination of water and fluorinated alcohol plays dual roles as solvent and promoter in this chemical transformation.Molecular oxygen in the air acts as an oxidant.3,3’-Bis(indolyl)methanes with quaternary carbon were produced under metal-free conditions.No any catalyst and additive were required.N2 and water were released as sole by-products.Absence of water and fluorinated alcohol resulted in Wolff rearrangement product.

Ru(Ⅲ)-catalyzed construction of variously substituted quinolines from 2-aminoaromatic aldehydes(ketones)and isoxazoles:Isoxazoles as cyclization reagent and cyano sources

A Ru(Ⅲ)-catalyzed annulation reaction of 2-aminoaromatic aldehydes(ketones)and isoxazoles to afford diverse 3-cyanoquinolines has been developed.Notably,isoxazole acted as a cyclization reagent and nontoxic cyano source via N-O bond cleavage and fragmentation.Variously substituted(especially 6-or 7-substituted)quinolines could be easily afforded.This procedure features wide functional group compatibility,efficiency and avoiding toxic cyano source.Meanwhile,this protocol could be successfully applied to scale-up synthesis.Further chemical transformations of 3-cyanoquinoline could give some valuable skeletons,demonstrating its potential in synthetic application.

Cp^*Co(Ⅲ)-catalyzed C—H amidation of azines with dioxazolones

Cp^*Co(Ⅲ)-catalyzed direct C—H amidation of azines has been developed.This co nversion could proceed smoothly in the absence of external oxidants,acids or bases,with excellent regioselectivity and broad functional group tolerance,CO2 was released as the sole byproduct,thus providing an environmentally benign amidation process.The products obtained are important intermediates in organic synthesis.