Harekrishna Sahoo

Copper-Catalyzed 8-Amido Chelation-Induced Remote C-H Amination of Quinolines.

A copper-catalyzed 8-amide chelation-induced remote C-H amination of quinolines has been developed. This direct amination with readily available azodicarboxylates proceeded with perfect C5-regioselectivity offering amino-substituted 8-aminoquinolines, important bioactive molecular scaffolds, in very high yields (up to 96%). A single-electron transfer (SET)-mediated mechanism with kH /kD =1.1 was proposed after trapping of the radical intermediate.

Copper-Catalyzed 8-Aminoquinoline-Directed Selenylation of Arene and Heteroarene C-H Bonds.

An efficient copper-catalyzed/-mediated and 8-aminoquinoline-assisted arylselenylation of inert C-H bonds of (hetero)arenes with readily available diselenides has been reported. The reaction is scalable and tolerates a wide spectrum of functional groups to deliver diarylselenides in very high yields (up to 98%). Application of this methodology to the facile synthesis of thiophene-fused selenochromone was demonstrated.

Ruthenium(II)-Catalyzed ortho-C-H Chalcogenation of Benzoic Acids via Weak O-Coordination: Synthesis of Chalcogenoxanthones

A general protocol for direct chalcogenation of inert C-H bonds of (hetero)aromatic carboxylic acids is developed with a ruthenium(II) catalyst using readily available starting materials, offering densely substituted ortho-chalcogenyl aromatic acids in high yields (up to 96%). The strategy avoids the installation of an external directing group, use of metallic oxidants, and features operational simplicity with ample substrate scope. Synthetic application en route to biologically important chalcogenoxanthones is also demonstrated. This work represents the first example of ruthenium(II)-catalyzed direct C-H chalcogenation of benzoic acids.

Copper Catalyzed C–N Cross-Coupling Reaction of Aryl Boronic Acids at Room Temperature through Chelation Assistance

A copper-catalyzed selective C-N cross-coupling has been developed based on chelation-assisted amidation of readily available aryl boronic acids at room-temperature under open-flask conditions. The reaction is scalable and tolerates a wide spectrum of functional groups delivering fully substituted unsymmetrical amides in high yields (up to 96%). The C-N cross coupling also established with aryl silanes, extending the palette of coupling partners of this strategy.

Ruthenium(II)-Catalyzed Hydroarylation of Maleimides Using Carboxylic Acids as a Traceless Directing Group

An efficient Ru(II)-catalyzed hydroarylation of maleimides with ready-stock aryl carboxylic acids has been developed based on weak carboxylate-directed ortho-C-H alkylation and concomitant decarboxylation processes, fabricating 3-aryl succinimides, a recurrent scaffold in drug molecules, in high yields (up to 97%). The protocol features operational simplicity, avoids the need for precious metal additives/oxidants, and offers broad substrate scope with formal meta- and para-selectivities. It represents the first example of Ru(II)-catalyzed direct arylation of maleimides with unbiased benzoic acids.

Ru(II)-Catalyzed C–H Functionalization on Maleimides with Electrophiles: A Demonstration of Umpolung Strategy

The unconventional nucleophilic reactivity of maleimides, innate electrophiles, has been realized under Ru(II)-catalysis such that exposure to electrophiles delivered products of C-H chalcogenation and amidation in good yields (up to 94%). This protocol features mild conditions and operational simplicity with broad substrate scope, uses an inexpensive and air-stable catalyst, and also represents the first example of Ru(II) catalyzed C-H selenylation of alkenes.

Copper-mediated etherification of arenes with alkoxysilanes directed by an (2-aminophenyl)pyrazole group

An efficient copper-mediated etherification of inert C–H bonds of (hetero)arenes with reagent-amounts of alkoxysilanes and alkanols has been developed using (2-aminophenyl)pyrazole (2-APP) as a removable directing group. The reaction is scalable, rapidly proceeds under an open atmosphere, and tolerates diverse functional groups to provide alkyl aryl ethers in high yields (up to 87%). As an application, the formal synthesis of anti-emetic drug metoclopramide is accomplished.

Ru(II)-Catalyzed Oxidative Heck-Type Olefination of Aromatic Carboxylic Acids with Styrenes through Carboxylate-Assisted C–H Bond Activation

A straightforward synthesis of 2-styrylbenzoic acids from aryl carboxylic acids is disclosed through a carboxylate-assisted coupling under Ru(II) catalysis. This protocol is simple and exhibits broad scope with high tolerance of common organic functional groups, providing good to excellent yields of diverse olefinated products. The efficacy of this protocol has been showcased through sequential syntheses of isochromanone, isocoumarin, and formal synthesis of anacardic acid derivative in good yields.

Radical Cascade Reaction of Aryl Alkynoates at Room Temperature: Synthesis of Fully Substituted α,β-Unsaturated Acids with Chalcogen Functionality

A radical-based cascade reaction has been devised for oxidative difunctionalization of aryl alkynoates at room temperature to access stereodefined fully substituted α,β-unsaturated acids bearing a chalcogen functionality in high yields (up to 95%). The protocol is operationally simple, metal-free, scalable, and suppresses the usual CO2 exclusion phenomenon. The utility of this method was showcased in the synthesis of vinyl halides, vinyl selenides, and 3,3-disubstituted indanones.