A wide range of N-arylated 2-amino-N-heterocycles were synthesized by a copper-catalyzed boronic acid cross coupling reaction at ambient temperature in air. This ligand and base free methodology is general and could provide rapid access to a diverse array of potential bioactive heterocyclic compounds.

A diverse array of benzimidazole-fused heterocycles was synthesized by in situ generated hypervalent iodine(iii) catalyzed intramolecular oxidative C–N bond formation in water and under ambient conditions.

An unprecedented Pd/Ag synergistic catalysis in the direct carbonylation of C(sp(2))-H bonds utilizing DMF as the carbon source under oxygen is described and demonstrated in the synthesis of pyrido-fused quinazolinone and phenanthridinone scaffolds. Control experiments indicated that the "C" of the carbonyl group is derived from the methyl group of DMF and "O" originates from oxygen as in the case of Ge's recent work. This transformation offers an alternative avenue for "CO-free" carbonylations.

A Cu (II)-catalyzed, inter/intramolecular C-N bond formation for the synthesis of various benzimidazole-fused heterocycles in a concise manner has been reported. The robustness of this reaction is demonstrated by the synthesis of a series of benzimidazole-fused heteroaromatics (e.g., pyrido[1,2-a] benzimidazole, benzimidazo[1,2-a]quinolines, benzimidazo [1,2-a]pyrazine, benzo[4,5] imidazo[2,1-b]thiazoles) directly from 2-aminoheteroarenens and 2-iodoarylboronic acids in one-pot. The novel cascade protocol for C-N bond formation operates via unique combination of Chan-Lam type coupling followed by Ullmann-type reaction.

A copper(II)-catalyzed selective C À NH 2 arylation of 2-aminobenzimidazoles and related Camino-NH-azoles was achieved in presence of 2,2'-bipyridine and cesium carbonate at 60 8C under open air conditions and this is first method for the coppercatalyzed selective C À NH 2 arylation in the presence of other reactive nucleophilic sites. Previously unexplored heteroaromatics possessing multiple nucleophilic sites that are selectively arylated at the C À NH 2 position are obtained, providing an exceptional tool for rapid delivery of a diverse array of medicinally important C À NH(aryl) derivatives of aminoazoles without any protection/deprotection of ring N À H bonds. It is first example for the selective C À NH 2 arylation of 5-aminoindazole, 4-aminopyrazole, 5-aminopyrazole, 9H-purine-6-amine, and 1H-pyrazolo[3,4-d]pyrimidin-4-amine derivatives.

Copper(ii)-catalyzed boronic acid promoted chemoselective N-arylation of unprotected aminophenols has been developed. Selective N-arylation of 3-aminophenol is achieved with a Cu(OAc)/AgOAc combination in MeOH at rt, whereas the chemoselective N-arylated products of 4-aminophenol can be obtained with a Cu(OAc)/CsCO system and benzoic acid as an additive. These ligand-free conditions and "open-flask" chemistry are robust and compatible with a wide range of functional groups. The mechanistic investigation for this selective N-arylation has been studied by considering Density Functional Theory (DFT) calculations.

A complementary set of Ni- and Cu-based catalyst systems for the selective N-arylation of 2-aminobenzimidazoles have been developed. Selective N-arylation of the primary amine (C-NH2) group was achieved by Ni-catalyzed, boronic acid promoted cross-coupling reactions in air, whereas, selective N-arylation of the azole nitrogen was achieved with Cu-catalysis and aryl halides. These protocols are general and give rapid access to an array of both the N-arylated isomers of 2-aminobenzimidazoles.

A novel method of transamidation of carboxamides with amines using catalytic amounts of H2SO4–SiO2 under solvent-free conditions has been developed. The scope of the methodology has been demonstrated with primary and secondary amines.