Copper-catalyzed C-H ethoxycarbonyldifluoromethylation of imidazoheterocycles.

A regioselective copper-catalyzed ethoxycarbonyl-difluoromethylation of imidazo[1,2-a]pyridines has been developed through sp(2) C-H bond functionalization with BrCF2CO2Et under ambient air. A series of ethoxycarbonyldifluoromethylated imidazo[1,2-a]pyridines with broad functionalities have been synthesized. This methodology is also applicable to imidazo[2,1-b]thiazole and benzo[d]imidazo[2,1-b]thiazole.

Diversified Synthesis of Furans by Coupling between Enols/1,3-Dicarbonyl Compounds and Nitroolefins: Direct Access to Dioxa[5]helicenes.

A versatile method for the diversified synthesis of furans and arenofurans has been developed that proceeds through K2CO3-promoted cyclization between enols/1,3-dicarbonyl compounds and nitroolefins at reflux in EtOH. This facile method has been successfully employed in the synthesis of benzotrifuran derivatives, which are useful hole-transporting materials. This procedure also provides direct access to dioxa[5]helicenes. This reaction offers a broad substrate scope, uses an inexpensive base and environmentally benign solvent, and is operationally simple.

Metal-Free Thiocyanation of Imidazoheterocycles through Visible Light Photoredox Catalysis.

A visible light mediated, metal-free process for the thiocyanation of imidazoheterocycles has been developed using eosin Y as a photoredox catalyst under ambient air at room temperature. A library of 3-(thiocyanato)imidazo[1,2-a]pyridines with broad functionalities have been synthesized in high yields. This methodology is also applicable for the selenocyanation of imidazo[1,2-a]pyridine.

Regioselective synthesis of nitrosoimidazoheterocycles using tert-butyl nitrite.

A simple and practical method has been developed for the regioselective nitrosylation of imidazopyridines via C(sp(2))-H bond functionalization using tert-butyl nitrite under mild reaction conditions in a short time. A library of 3-nitrosoimidazopyridines with broad functionalities was synthesized in near quantitative yields. The present protocol is also applicable to imidazo[2,1-b]thiazole and benzo[d]imidazo[2,1-b]thiazole.

Regioselective Synthesis of Multisubstituted Furans via Copper-Mediated Coupling between Ketones and ß-Nitrostyrenes.

A copper-mediated intermolecular annulation of alkyl ketones and ß-nitrostyrenes has been developed for the regioselective synthesis of multisubstituted furan derivatives in good yields. This protocol is applicable to both cyclic and acyclic ketones.

Iodine-catalyzed regioselective thiolation of imidazo[1,2-a]pyridines using sulfonyl hydrazides as a thiol surrogate.

Iodine-catalyzed regioselective sulfenylation of imidazo[1,2-a]pyridines via C(sp(2))-H bond functionalization has been achieved using sulfonyl hydrazides as a thiol surrogate. A library of 3-sulfanylimidazopyridines with broad functionalities was synthesized under metal and oxidant-free practical reaction conditions. This methodology is also applicable for the regioselective sulfenylation of imidazo[2,1-b]thiazole and benzo[d]imidazo[2,1-b]thiazole.

Regioselective oxidative trifluoromethylation of imidazoheterocycles via C(sp2)-H bond functionalization.

Catalytic oxidative trifluoromethylation of imidazopyridines has been carried out at room temperature through the functionalization of the sp(2) C-H bond employing Langlois reagent under ambient air. A library of 3-(trifluoromethyl)imidazo[1,2-a]pyridines with broad functionalities have been synthesized regioselectively. This methodology is also applicable to imidazo[2,1-b]thiazole and benzo[d]imidazo[2,1-b]thiazole.

Copper-catalyzed regioselective synthesis of furan via tandem cycloaddition of ketone with an unsaturated carboxylic acid under air.

A catalytic decarboxylative annulation has been developed for the regioselective synthesis of trisubstituted furans by the cycloaddition of ketones with α,ß-unsaturated carboxylic acids under ambient air. A library of furan derivatives were obtained in good yields from the readily available substrates in the combination of a catalytic amount of Cu-salt and a stoichiometric amount of water. Water plays a crucial role in this catalytic transformation.

Unprecedented catalytic activity of Fe(NO3)3·9H2O: regioselective synthesis of 2-nitroimidazopyridines via oxidative amination.

A unique iron-catalyzed oxidative diamination of nitroalkene with 2-aminopyridine for the synthesis of 2-nitro-3-arylimidazo[1,2-a]pyridines with complete regioselectivity has been achieved under mild and aerobic reaction conditions. This is the first method for the synthesis of 2-nitroimidazo[1,2-a]pyridines. These scaffolds were also synthesized directly from styrenes.