Photoinduced Regioselective Decarbonylative and Decarboxylative C-O Bond Functionalizations: Approach toward Chemoselective Scissions of Isatoic Anhydride and Unraveling the Enroutes through Control Experiments and DFT Studies.

Distinctive, green, innovative, and well-organized photoinduced (metal- or photocatalyst-free) regioselective decarbonylative and decarboxylative C-O bond functionalization protocols to access aryl 2-aminobenzoates and 2-substituted benzoxazinone derivatives in excellent yields have been devised. These are achieved through the chemoselective scission of isatoic anhydride with ketones, diaryliodonium triflate, nitroalkene, phthalazinone, and phenol derivatives, which, in turn, served as the representative "electrophilic and nucleophilic" coupling partners. Control experiments and DFT calculations reveal that electrophilic radical-bearing coupling partners specifically follow the decarbonylation pathway, while nucleophilic radical-bearing conjugates facilitate the decarboxylation process.

Skeletal Reorganization Emanated via the Course of Heterocyclic N-N Bond Cleavage: Electrosynthetic Approach.

A unified method toward the synthesis of functionalized diazepines and quinazolines through reorganization of the molecular skeleton has been devised. The process is indulged by electrical energy via a domino N-N bond cleavage followed by concomitant ring closing, initiating from cinnolines and indazoles as designed precursors. Additionally, an intermolecular ring homologation has also been established to synthesize densely functionalized dihydroquinazolines from 2,3-diaryl-indazoles and acetonitrile involving the same electrochemical strategy.

Pragmatic Access to Hybrid Quinoxaline Scaffold Mediated by Elemental Sulfur Enabling Actualization to π-Extended and Aza-Annulated Heterocyclic Units.

A metal-free approach for synthesizing hybrid quinoxaline derivatives from sulfoxonium ylide and a 1,5-bis-nucleophilic N-heterocycle mediated by elemental sulfur is presented to illuminate the [5+1] cascade cyclization sequence. Large-scale synthesis and postsynthetic functionalizations for the annulative π-extension and intramolecular aza-annulation reactions reveal the potential utility and actualize the fabricated approach.

Harnessing the benzyne insertion consequence to enable π-extended pyrido-acridine and quinazolino-phenanthridine.

Distinct protocols have been devised for the preparation of hybrid heterocyclic scaffolds like π-extended pyrido-acridines and quinazolino-phenanthridines duly materialized through Rh(III)- and Pd(II)-mediated catalytic courses commencing from acridine and quinazolimine scaffolds. Interestingly, the parent compounds (acridines and quinazolimines) are actualized from 2-aminobenzonitrile and anthranilic acid, where 2-aminobenzonitrile acts as the 1,4-dipolarophilic species and anthranilic acid as the benzyne precursor. The molecular assembly of acridine suggests the participation of two benzyne units.

Fused Furan Moieties from Enol-like Compounds and β-Keto Sulfoxonium Ylides Involving sp C-H Activation and Concomitant Tandem C-O Annulation.

An efficient and fascinating protocol has been devised for the preparation of fused furan moieties involving a Rh(II) catalyzed one-pot C-H activation/concomitant tandem annulation process, employing an enolic compound and β-keto sulfoxonium ylide as the reacting conjugates. The developed technique demands only Rh(TFA) as the catalyst to proceed forward and is devoid of additional metallic or nonmetallic additives. The skeletal transformation of naphthoquinone fused furan to highly decorated naphthoquinone fused indolizines is a promising synthetic application.

Electrochemically Enabled C4-H and C3-H Functionalization of 2-Phenyl Quinazoline and Quinoxaline through Dehydrogenative C-H/C-H, C-H/P-H, and C-H/O-H Cross-Coupling.

Quinazoline moieties and particularly C4-substituted quinazoline scaffolds are widely distributed in biologically active molecules, and thus, direct C4-functionalization of quinazolines is the most convenient way to materialize new, straightforward, and sustainable strategies for the synthesis of useful medicinal targets. Retrospecting that, effort has been directed toward electrocatalytic C4-H bond diversification of quinazoline and related electron-deficient N-heterocycles (quinoxaline) offering C4 and C3 benzoyl-, acetyl-, phenol-, ether-, phosphonate-, and nitroalkane-incorporated N-heterocycles via a radical addition pathway under sacrificial oxidant- and additive-free conditions. Various coupling partners and quinazolines, as well as other structurally similar heterocyclic motifs, respond well, providing moderate to high yields of coupled products along with the gram-scale upgradation.

Access to π-Extended Heterocycles Containing Pyrrolo-Coumarin Cores Involving -COCH as a Traceless Directing Group and Materializing Two Successive spC-H/spN-H and spC-H/spN-H Activations.

An efficient protocol has been developed for the preparation of π-extended N-heterocycles involving a Rh(III)-catalyzed C-H activation reaction starting from 3-acetamidocoumarins and internal alkynes. The isolation of the intermediate pyrrolo-coumarin suggests that the -COCH group in acetamidocoumarins performs the role of a traceless directing group. Besides, the use of commercially available [Cp*RhCl] adds more importance as no additional modification of the catalyst is required.

"On water" palladium catalyzed diastereoselective boronic acid addition to structurally diverse cyclopropane nitriles.

An efficient palladium catalyzed diastereoselective addition of arylboronic acids to complex spirocyclopropyl dinitriles is developed in the presence of a catalytic amount of 4-dodecylbenzenesulphonic acid (DBSA) as a Brønsted acid surfactant in aqueous media. The protocol is also found to be highly effective when different types of nitrile compounds and organo-boron compounds are used. The overall reaction has been found to be very cost efficient since it requires low catalyst loading, mild thermal energy and short reaction time.