No abstract

An efficient route to multisubstituted indoles has been developed through intramolecular oxidative C-H activation-amination of readily available 2-(het)aryl-3-(het)aryl/alkyl-3-(het)aryl/acylaminoacrylonitrile/enaminone precursors in the presence of either palladium acetate/cupric acetate catalytic system under oxygen atmosphere or palladium acetate/silver carbonate in the presence of pivalic acid as additive. The method is compatible with a diverse range of substituents on the aryl ring as well as at the 2- and 3-positions of the indole ring. The versatility of this method was further demonstrated by elaborating it for the synthesis of heterofused pyrroles such as thieno[2,3-b]pyrroles, thieno[3,2-b]pyrroles, pyrrolo[2,3-b]indoles, and pyrrolo[2,3-b]pyridines in good yields. Probable mechanisms for the formation of these indoles have been suggested.

An efficient straightforward synthesis of 2,5,4'-trisubstituted 4,5'-bisoxazoles via copper(I)-catalyzed domino reactions of 2-phenyl- and 2-(2-thienyl)-4-[(aryl/heteroaryl)methylene]-5-oxazolones with activated methylene isocyanides has been reported. The overall domino process comprised of formation of one C-C and two C-O bonds involves initial nucleophilic ring opening of oxazolones by cupriomethylene isocyanides followed by sequential construction of two oxazole rings in the presence of copper catalyst. The broad substrate scope and excellent functional group compatibility of the reaction has been demonstrated by employing a variety of heteroaryl- and aryl-substituted oxazolones and activated methylene isocyanides, yielding bisoxazoles with three potential points of diversity. A probable mechanism for this novel copper-catalyzed domino process has been proposed.

The title reaction provides a direct entry to a range of biologically relevant annulated pyrroles via a domino process involving a regioselective one-carbon homologation of cyclic ketones as the key step.