Gopal Chandru Senadi

Facile, selective, and regiocontrolled synthesis of oxazolines and oxazoles mediated by ZnI2 and FeCl3.

An expedient method for a direct approach to the selective and regiocontrolled synthesis of 2-oxazolines and 2-oxazoles mediated by ZnI(2) and FeCl(3) is described. A Lewis acid promoted cyclization of acetylenic amide with various functionalities was well tolerated to give 2-oxazolines and 2-oxazoles in good to excellent yields under mild reaction conditions.

I2–TBHP-Catalyzed Oxidative Cross-Coupling of N-Sulfonyl Hydrazones and Isocyanides to 5-Aminopyrazoles

I2-TBHP-catalyzed oxidative cross coupling of N-sulfonyl hydrazones with isocyanides has been realized for the synthesis of 5-aminopyrazoles through formal [4 + 1] annulation via in situ azoalkene formation. Notable features are the metal/alkyne-free strategy, C-C and C-N bond formation, atom economy, catalytic I2, broad functional group tolerance, good reaction yields, shorter time, and also applicability to one-pot methodology.

Metal-Free, Acid-Promoted Synthesis of Imidazole Derivatives via a Multicomponent Reaction

An expedient and metal-free synthetic route has been developed for the construction of tri- and tetrasubstituted imidazole derivatives via acid promoted multicomponent reaction methodology. The reaction proceeded smoothly with a range of functionalities to produce the imidazole scaffolds in good to excellent yields.

Palladium(0)-catalyzed single and double isonitrile insertion: a facile synthesis of benzofurans, indoles, and isatins.

A palladium(0)-catalyzed cascade process consisting of isonitrile insertion and α-Csp(3)-H cross-coupling can be achieved for the synthesis of benzofurans and indoles. The construction of isatins by a Pd-catalyzed cascade reaction incorporating double isonitrile insertion, amination, and hydrolysis has also been achieved. The key features of this work include diverse heterocycle synthesis, phosphine-ligand-free reaction conditions, a one-pot procedure, simple and commercially available starting materials, broad functional-group compatibility, and moderate to good reaction yields.

Discovery, Synthetic Methodology, and Biological Evaluation for Antiphotoaging Activity of Bicyclic[1,2,3]triazoles: In Vitro and in Vivo Studies

Novel bicyclic[1,2,3]triazoles (4, 7, 11, 15) have been synthesized using a one-pot metal free strategy with high structural diversity as photoprotective agents, and their effect on UVA-induced senescence in human dermal fibroblast cells (FB) and the associated mechanism are delineated. 11d plus UVA can induce a decrease in reactive oxygen species (ROS) production and senescence-associated β-galactosidase (SA-β-gal) activity but an increase in adenosine triphosphate (ATP) synthesis and mitochondrial membrane potential (ΔΨmt). The mRNA levels of six senescence-associated genes, matrix metalloproteinase-1 (MMP-1), was decreased, while elastin, procollagen I type I, fibronectin, COL1α1, and tissue inhibitor of metalloproteinase-1 (TIMP-1) were increased. 11d plus UVA also decreased MMP-1 and increased TIMP-1 protein levels. Additionally, the thickness of the murine dorsal skin and epidermis, by UVA, was decreased by topical 11d treatment. Our results indicate that bicyclic[1,2,3]triazoles protect UVA-induced senescence-like characteristics in FB cells, which may provide potential prevention against photoaging.

Iodine-promoted cyclization of N-propynyl amides and N-allyl amides via sulfonylation and sulfenylation

An iodine-promoted regioselective cyclization of N-propynyl/allyl amides with sulfonyl hydrazides has been developed for the synthesis of 5-methyl-arylsulfonyloxazoles and 5-methyl-arylthiooxazolines via sulfonylation and sulfenylation reactions. The notable features of this reaction are the formation of new C-S and C-O bonds, the broad functional group tolerance, and its applicability to alkyl sulfonyl hydrazides as well as internal alkynes.

BF3-Etherate-Promoted Cascade Reaction of 2-Alkynylanilines with Nitriles: One-Pot Assembly of 4-Amido-Cinnolines

A BF3-etherate-promoted cascade reaction of nitriles with 2-alkynylanilines is described. This method achieves the formation of two new C-N bonds through a reaction sequence of diazotization with t-BuONO, nucleophilic addition of the alkyne to the BF3-coordinated diazonium ion, followed by nitrile addition to the intermediary vinyl cation and hydrolysis. The method provides efficient and general access to a variety of 4-amido-cinnolines. Notable features of the method include its broad functional group tolerance and avoidance of transition metals.

A New Approach to 1,4-Oxazines and 1,4-Oxazepines via Base-Promoted Exo Mode Cyclization of Alkynyl Alcohols: Mechanism and DFT Studies

A new approach was developed to synthesize 1,4-oxazine and 1,4-oxazepine derivatives without solvent and metal. Regioselective cyclization occurred to afford exclusively the exo-dig product, and stereochemistry was studied by circular dichroism and specific optical rotation techniques. The Grignard reaction is a key synthetic step to produce high diastereomeric compounds via Crams rule and was well supported by DFT calculations. A hydroalkoxylation mechanism was proposed and supported by DFT calculations.

Palladium-Catalyzed Double-Isocyanide Insertion via Oxidative N–O Cleavage of Acetyl Oximes: Syntheses of 2H-Pyrrol-2-imines

The palladium-catalyzed reaction of acetyl oximes with isocyanides was developed for the synthesis of 2H-pyrrol-2-imines. The key steps were (i) generation of an enamido-palladium(II) species, (ii) migratory double-isocyanide insertion, and (iii) cyclization. The scope of the synthesis of some 2H-pyrrol-2-imines was extended to the synthesis 1H-pyrrole-2,3-dione/1H-benzo[g]indole-2,3-dione derivatives via acid hydrolysis in a sequential one-pot manner.

An Iron‐Catalyzed Cascade Approach to Benzo[b]carbazole Synthesis Followed by 1,4‐Sulfonyl Migration

A simple and straightforward approach was developed to construct 5H-benzo[b]carbazole derivatives by iron catalysis in a cascade sequence. The notable features of this work include an atom-economical cascade sequence, unprecedented 1,4-sulfonyl migration, tolerance of a variety of functional groups, good yields, and an economical catalytic system.