A simple and highly efficient metal-free method has been developed for hydroxyfluoroalkylation of indoles and imidazo­[1,2-a]­pyridines via TEMPO-mediated C­(sp3)–H and C­(sp2)–H bond cross-dehydrogenative coupling of fluorinated alcohols and indoles. The protocol showed broad substrate scope, afforded good yields of hydroxyfluoroalkylated products, and was amenable for scale-up. Mechanistic investigation indicated involvement of the radical pathway.

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Rhodium(III)-catalyzed dehydrogenative annulation of 2-aryl-imidazo[1,2-a]pyridines with maleimides is described. The reaction afforded 1H-benzo[e]pyrido[1',2':1,2]imidazo[4,5-g]isoindole-1,3(2H)-diones in high yields with wide range of functional group tolerance. The reaction proceeds through Rh(III)-catalyzed CÀ H bond activation, followed by maleimide insertion and intramolecular cyclization. Photophysical properties of 1H-benzo[e]pyrido[1',2':1,2]imidazo[4,5-g]isoindole-1,3(2H)-diones were studied with UVvisible and fluorescence spectroscopy and validated by quantum chemical calculations. All the annulated products showed large Stokes shift values with emission in the range of 530-618 nm, and moderate to high quantum yields.

A series of indolyl or imidazo­[1,2-a]­pyridinyl-substituted para-quinone methides (p-QMs) is prepared by a metal-free, TEMPO-mediated cross-dehydrogenative coupling of butylated hydroxytoluene (BHT) with indoles or imidazo­[1,2-a]­pyridines in good to high yields. Broad substrate scope with respect to indoles and imidazo­[1,2-a]­pyridines, good functional group tolerance, and acid/base-free conditions are advantageous feature of the developed protocol. The method was amenable for scale-up on the gram scale. Based on control experiments, a reaction mechanism is proposed to describe this transformation.

A simple and straightforward approach has been realized for the direct regioselective benzoylation of imidazoheterocycles by oxidative decarboxylation of arylglyoxylic acids in the presence of K2S2O8 as oxidant. Various functional...