Hemant Joshi

Herein, compositionally varied nickel-based nanocatalysts, namely Ni _0.85 Se, NiTe ₂ , and Ni nanoparticles (NPs), are employed to selectively control product formation in the α-alkylation of ketones with benzyl alcohols.

We report a palladium-catalyzed site-selective C-H nitration of 1-aryl-1H-indazoles enabled by newly developed Pd-organoselenium complexes. The protocol achieves highly efficient ortho-nitration of the aryl ring, delivering 1-(2-nitroaryl)-1H-indazoles in good to excellent yields and with selectivity complementary to previous indazole-C3, C4, and C7 nitration methods. Broad functional-group compatibility is observed across diverse substrates. Mechanistic studies indicate a ligand-controlled radical pathway responsible for the selectivity. The synthetic value of the nitrated products is demonstrated through their transformation into structurally diverse compounds, establishing this method as a practical route to valuable indazole scaffolds.

Subtle substituent modifications can significantly alter the photophysical behavior of organic luminogens in the aggregated state. In this work, the influence of minor alkoxy substitution on emission properties is investigated using two closely related carbohydrazide–salicylaldehyde derivatives bearing methoxy (CDMS) and ethoxy (CDES) substituents. Both compounds exhibit nearly identical UV–visible absorption characteristics in solution, confirming comparable electronic structures of the chromophoric core. However, their emission behavior differs markedly depending on the molecular environment. CDMS is strongly emissive in solution but quenched in the solid state, whereas CDES shows weak solution emission and strong solid-state emission. Aggregation studies in THF/water mixtures further validate this divergence, revealing progressive fluorescence quenching for CDMS but significant emission enhancement for CDES. Single-crystal X-ray diffraction and Hirshfeld surface analyses show that CDES forms a packing arrangement with a higher density of intermolecular contacts and hydrogen-bond interactions, whereas CDMS exhibits closer π–π interactions within the crystal lattice. These findings demonstrate that even minimal alkoxy chain elongation can modulate intermolecular packing and switch the emission response from aggregation-caused quenching (ACQ) to aggregation-induced emission (AIE).

Herein, we report the design, synthesis, and characterization of an Mn(I) complex (C1) coordinated with an SNS-type pincer ligand L1. Single-crystal X-ray diffraction studies confirms the pincer coordination mode and a distorted octahedral geometry around the metal center. Both the ligand and complex C1 are air-and moisture-stable, remaining intact at room temperature for over one month. The newly synthesized complex C1 was evaluated for the catalytic hydration of aryl and alkyl carbonitriles to the corresponding carboxamides.Optimization studies highlight the crucial role of the well-designed ligand framework in enabling efficient Mn(I)-mediated catalysis. Catalyst C1 exhibits broad substrate scope with excellent functional group tolerance, delivering up to 99% yield. Poisoning experiments indicate a homogeneous catalytic pathway, while radical scavenger tests exclude the involvement of radical intermediates. Based on experimental observations, control studies, and literature precedents, a plausible mechanism emphasizing the key role of metal-ligand cooperativity is proposed.

A SeNSe pincer ligand (L1) and its palladium(II) complex (C1) were synthesized and fully characterized by analytical and spectroscopic methods. Complex C1 displayed excellent catalytic efficiency for the regioselective C-4 arylation of thiophene derivatives, delivering the desired products in yields up to 91% under mild, room-temperature conditions. The method exhibits a broad substrate scope, including heteroarenes relevant to optoelectronic and pharmaceutical applications, and provides high regioselectivity while suppressing homocoupling and other side reactions. Under the standard conditions, unsubstituted thiophenes underwent selective C-3 arylation. A striking regioselectivity switch was observed in the arylation of benzothiophene, favoring C-3 arylation under milder, greener conditions compared to previously reported C-2 selective methods. Mercury-drop and triphenylphosphine poisoning tests confirmed homogeneous catalysis, while radical scavenger experiments excluded radical pathways. Control studies and high-resolution mass spectrometric analysis of reaction intermediates support the proposed catalytic cycle. These findings underscore the impact of ligand design and reaction parameters in directing site-selective C-H activation, establishing the SeNSe-Pd(II) pincer complex as a powerful catalyst for regioselective heteroarene functionalization.

Herein, we report a palladium(II)‐catalyzed dehydrogenative annulation of 2‐arylimidazo[1,2‐ a ]pyridines with maleimides, representing the first example of the regioselectivity reversal for this class of substrates. Notably, the transformation proceeds efficiently with a low catalyst loading (1.5 mol%). A plausible reaction mechanism is proposed, supported by control experiments and in situ HRMS analysis. Photophysical investigations of the annulated products reveal moderate to high quantum yields, highlighting their potential for optoelectronic applications. Furthermore, these molecules demonstrate promising sensitivity as picric acid‐sensing probes.

Here, we present a catalytic, regioselective synthesis of bisindolylmethanes through the reaction of indoles and benzyl alcohol derivatives mediated by metal‐ligand cooperative catalysis. The reaction is catalyzed by an earth‐abundant manganese‐NNSe pincer complex without the need for base, solvent, additives, or hydrogen acceptors yielding water and dihydrogen as environmentally friendly by‐products. Notably, C‐3 and N ‐alkylation of indole, commonly observed in similar reactions were not detected. Mechanistic studies suggest that metal‐ligand cooperative catalysis by the Mn(I)‐NNSe pincer complex initiates the conversion of benzyl alcohol to benzaldehyde through dihydrogen elimination, which subsequently facilitates the synthesis of bisindolylmethane derivatives. To highlight the practical utility of this method, a wide range of substrates can be activated with low catalyst loading under mild reaction conditions.