A metal-free visible-light-induced phosphonylation of 2H-indazoles with diphenylphosphine oxide has been developed using rose bengal as an organophotoredox catalyst under ambient air at room temperature. A library of diphenyl(2phenyl-2H-indazol-3-yl)phosphine oxide with broad functionalities has been synthesized in high yields. The experimental result suggests the radical pathway of the reaction.

A mild and efficient method for the direct difluoromethylenephosphonation of imidazopyridines has been developed using rose bengal (RB) as a photoredox catalyst. Bis(pinacolato)diboron (B 2 pin 2 ) is found to be a crucial additive in the present reaction. The present methodology is also applicable to other heterocycles like imidazo[2,1-b]thiazole, benzo [d]imidazo-[2,1-b]thiazole, and indole. The reaction possibly proceeds through a single electron transfer (SET) process.

A Ru(II)-catalyzed facile and controllable protocol for C−H alkylation and spirocyclization of 2-arylquinoxalines with maleimides has been achieved under ambient air in high yields. Sequential ortho-C−H activation and C-annulation results in the formation of diverse polyheterocycles containing spiro[indeno[1,2b]quinoxaline-11,3′-pyrrolidine]-2′,5′-diones, which are of potent interest in medicinal chemistry. Mechanistic investigations suggest a reversible cleavage of the ortho-C−H bond in the turnover-limiting step.

A visible-light-promoted regioselective C­(sp2)–H/C­(sp3)–H cross-dehydrogenative coupling between 2H-indazoles and ethers has been achieved using a catalytic amount of rose bengal as an organophotoredox-catalyst and tert-butyl hydroperoxide (TBHP) as an oxidant at ambient temperature under aerobic conditions. A variety of C-3 oxyalkylated 2H-indazoles have been synthesized in moderate to good yields. Mechanistic studies suggest a radical pathway of the present reaction.

An environment-friendly method for the chlorination of imidazoheterocycles has been developed using chloramine-T, a novel chlorinating reagent. A bunch of C-3 chloro-substituted imidazo[1,2- a ]pyridines with variety of functionalities have been synthesized in good yields under neat condition at room temperature within very short time. This chlorination process is also applicable to imidazo[2,1- b ]thiazole scaffolds. The present methodology is relevant to gram-scale synthesis. The major advantages of this system such as wide applicability, easy availability of reactants, open-air and metal- and solvent-free reaction conditions, no need of work-up, and simple purification technique represent a green synthetic protocol.

The metal‐free sodium persulfate mediated direct selenylation of arenofurans with diaryl diselenides at room temperature was developed, and the products were obtained in high yields. The reaction was found to be applicable to a variety of naphthofurans, benzofurans, and furocoumarins. To the best of our knowledge, this is the first report of the metal‐free direct selenylation of arenofurans. The experimental results suggest that the reaction proceeds through an electrophilic substitution pathway.

A hitherto unreported aminomethylation occurs at C-3 of imidazopyridines with morpholine in the presence of (diacetoxyiodo)benzene at ambient temperature in short reaction times. This methodology is also applicable to indolizine, imidazo[2,1-b]thiazole, benzo[d]imidazo[2,1-b]thiazole, and indole. Interestingly, the aminomethylation involving morpholine as a source of methylene group is a new phenomenon. This protocol is of much potential for the synthesis of aminomethylated derivatives under mild reaction conditions.

A convenient and straightforward regioselective synthesis of pi‐conjugated pyrazolo[1, 5‐a]pyrimidines has been achieved via Brønsted acidic ionic liquid catalyzed tandem cyclization between 3‐aminopyrazole and chalcone derivatives in high yields. Task specific ionic liquid [1‐methyl‐3‐(4‐sulfobutyl)imidazolium‐4‐methylbenzenesulfonate] is found to be an effective catalyst for the cyclization, and the presence of both C2‐H of imidazolium moiety and acidic proton drastically enhance the catalytic activity. Substituted aminopyrazoles reacted with a wide range of functionalized α,β‐unsaturated ketones to variety of pyrazolo[1, 5‐a]pyrimidine derivatives. The present protocol offers a broad substrates scope, use of non‐hazardous reagent, metal‐free environmentally benign conditions and catalyst recyclability. Comparative photophysical studies have shown high quantum yields for certain derivatives.