A Rh­(III)-catalyzed regioselective redox-neutral cascade process of carbenoid functionalization followed by dephosphonylative annulation of benzoic acids with α-diazo-β-keto phosphonate has been realized, which led to the direct synthesis of a privileged 3-substituted isocoumarin scaffold. To the best of our knowledge, this is the first report of a complete redox neutral method to synthesize isocoumarins using C–H functionalization strategy. In the catalytic cycle of this reaction, there are two possible pathways for the C–C coupling between ortho-positioned carbon atom of benzoic acid and the diazo carbon atom: (i) concerted 1,2-aryl shift and (ii) stepwise metal–carbene formation followed by migratory insertion. DFT study has predicted that the concerted pathway has lower activation energy as compared to the stepwise pathway by 1.5 kcal/mol.

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Newly synthesized blue-emitting few-atom copper nanoclusters (CuNCs) have been successfully utilized for catalyzing C­(sp2)–C­(sp2) and C­(sp2)–N­(sp3) bond formations. Various substituted biphenyls and 2° aromatic amines have been synthesized in good yield using this copper catalyst at facile reaction conditions in dimethyl sulfoxide. The amount of required nanocatalysts is as low as merely 2 mol % for carrying out these reactions. These types of copper nanoclusters are promising as potential and cheap catalysts for replacing conventional metal nanoparticles and heavy-metal-ion-based organic catalysts. The optimized structure of Cu6(GS)2 [GS = C10H16N3O6S] from computational studies revealed the perfect arrangements of Cu atoms in CuNCs and their interactions with stabilizing ligands. It is evident from the structure that some free Cu sites are available in the nanocluster species. These kinds of coordinatively unsaturated sites are highly active toward the catalytic reactions. Matrix-assisted laser desorption ionization–time-of-flight (MALDI–TOF) analysis also supports the computational hypothesis. Interestingly, matrix-assisted laser desorption ionization–time-of-flight mass spectrometry (MALDI–TOF MS) and computational studies revealed the formation of several reaction key intermediates in catalyzing C­(sp2)–C­(sp2) bond formation.

The lack of directionality and the long-range nature of Coulomb interactions have been a bottleneck to achieve chemically precise C−H activation using ion-pairs. Recent report by Phipps and co-workers of the ion-pair-directed regioselective Iridium-catalyzed borylation opens a new direction toward harnessing noncovalent interactions for C−H activation. In this article, the mechanism and specific role of ion-pairing are investigated using density functional theory (DFT). Computational studies reveal that meta C−H activation is kinetically more favorable than the para analogue due to stronger electrostatic interactions between the ion-pairs in closer proximity [d(NMe 3The electrostatic interactions overwhelm the Pauli repulsion and distortion interactions incurred in bringing the oppositely charged ions in close contact for the rate-limiting meta transition state (TSP1 m ). Multiple linear regression shows that the free energies of activation correlate well with descriptors like the charge densities on the meta carbon and Ir atom along with that on the cation and anion with R 2 = 0.74. Tuned range-separated DFT calculations demonstrate accurately the localization of charge separation in the reactant complex and transition state for the meta selectivity.

Concerning environmentally benign catalysis with reduced chemical usage, less energy consumption, and waste minimization, metal-organic frameworks (MOFs) with spatially isolated task-specific functionalities not only execute atom-economic important reactions but also...