Two efficient iodine-mediated strategies, which are economical and one-pot, are described to access bis(imidazo[1,2-a]pyridin-3-yl)sulfanes and bis(imidazo[1,2-a]pyridin-3-yl)disulfanes in chloroform and acetic acid, respectively, by a direct oxidative homocoupling of imidazo-heterocycles using inexpensive sodium sulfide as a sulfur source. These strategies are scalable, and an array of substrates delivered their corresponding stable sulfur-bridged imidazo-heterocycles in excellent yields.

A concise cascade strategy for the synthesis of 6H‐chromeno[4,3‐b]quinolin‐6‐ones was developed from 4‐hydroxycoumarins and arylhydrazine hydrochlorides in DMSO. The synthetic strategy relies on dual role of ammonium acetate in generating 4‐aminophenyl coumarin from arylhydrazine via aryl radical formation, and Csp2‐H formylation of coumarin using DMSO as a methine source. The strategy is scalable, and an array of arylhydrazine hydrochlorides delivered chromene‐fused quinolinones in good to excellent yields.

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Direct ortho amidation at the phenyl ring of 2-phenylimidazo heterocycles with aryl isocyanates has been achieved via a chelation-assisted cationic ruthenium(II) complex catalyzed mechanism. The methodology provides a straightforward, high-yielding regioselective approach toward the synthesis of an array of ortho-amidated phenylimidazo heterocycles without prior activation of C(sp)-H. This also reports the first method for coupling of aryl isocyanates with the imidazo[1,2-a]pyridine system via a pentacyclometalated intermediate. The methodology is found to be easily scalable and could be applied toward the selective ortho amidation of 2-heteroarylimidazo[1,2-a]pyridine frameworks.

An efficient, one-pot Cu-catalyzed tandem synthesis of fluorescent 1-benzyl-2-phenyl-1,2-dihydro-5H-chromeno[4,3-d]pyrimidin-5-ones from 4-chloro-3-formylcoumarin and benzylamines was developed by in situ intramolecular cross-dehydrogenative C(sp3)-N bond formation in moderate-to-good yields under ligand-free ambient conditions. This synthesis was easily scalable, and the generality of the substrates was established. These coumarin-fused pyrimidines exhibited interesting photo-physical properties and high quantum yields, and would be potential candidates for facilitating suitable studies in medicinal chemistry and materials science.

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Direct oxidative homocoupling of 2‐arylimidazo heterocycles was achieved by using a phenyliodine diacetate‐mediated BF3·OEt2‐accelerated protocol at room temperature. A series of biimidazo heterocycles were synthesized under ambient conditions without prior activation of the C(sp2)–H bond. The desired biimidazo heterocycles were also obtained by using catalytic amounts of iodobenzene and m‐CPBA/AcOH in an organocatalytic fashion.

Fluorophores based on 4-triazolyl, 7-hydroxy-4-triazolylmethyl, 4-O-triazolylmethyl, and 7-O-triazolylmethyl coumaryl-tagged amino acids and dipeptides were synthesized by copper-catalyzed [3 + 2] cycloaddition reaction between azido- or alkynyl-functionalized coumarins with alkynyl- or azido-functionalized amino acid and dipeptides in good-to-excellent yields. Steady-state absorption and the fluorescence properties of the synthesized conjugates were studied. The chemical applicability of these amino acid and peptide-based fluorophores was successfully demonstrated by their linear elongation by further tagging them with appropriate C- or N-terminus amino acid.