Publications
All Publications
2024
11) HFIP-Mediated Intramolecular Cyclization of Allenamides to Access C1-Vinyl Tetrahydro-β-carbolines
Dhananjay Chaudhary and Malleswara Rao Kuram
10) Facile Access to C-Substituted Piperazin-2-ones and Mianserin Derivative Enabled by Chemoselective Carbene Insertion and Cyclization Cascade
Dharmendra Kumar, Urmila Unnikrishnan and Malleswara Rao Kuram
Abstract
The chemoselective N-H insertion of unsymmetrical diamines into carbene is a longstanding challenge. A simple copper-catalyzed strategy for synthesizing C-substituted piperazinones is described, employing easily accessible diazo compounds and 1,2-diamines. The reaction proceeded via chemo-selective carbene insertion at the comparatively less nucleophilic amine, followed by instantaneous cyclization. The protocol was further extended to access NH-free piperazinone, and the synthesis of a Mianserin derivative.
9) Regio- and Stereoselective Hexafluoroisopropoxylation and Trifluoroethoxylation of Allenamides
Dhananjay Chaudhary and Malleswara Rao Kuram
J. Org. Chem. 2024 (10.1021/acs.joc.3c02457)
Abstract
Incorporating fluorinated moieties into organic molecules is an attractive strategy to enhance drug-like properties. Herein, we have developed a simple and self-promoted protocol for hexafluoroisopropoxylation and trifluoroethoxylation of allenamides with fluorinated alcohols such as HFIP and TFE. The reaction provided the fluoroalkoxylated products in a regio and stereoselective manner in good to moderate yields under mild conditions.
2023
8) Copper-Catalyzed Chemoselective Divergent Carbene Insertion into the N-H bonds of Tryptamines Dharmendra Kumar and Malleswara Rao Kuram
Abstract
Easy access to divergent products with chemoselectivity is of great importance in organic synthesis. Herein, we have developed a chemoselective copper-catalyzed carbene insertion protocol onto N-H bonds of tryptamine derivatives. Divergent insertion products are obtained by varying the nucleophilicity of the aliphatic NH of tryptamine with electron-donating or electron-withdrawing groups. The reaction provided N-H insertion products with broad substrate scope in good yields.
7) Metal-Free Transfer Hydrogenation/Cycloaddition Cascade of Activated Quinolines and Isoquinolines with Tosyl Azides
Suman Yadav, Ruchir Kant and Malleswara Rao Kuram
Chem. Commun. 2023, 59, 7088-7091
Abstract
The difficulty in isolating cyclic enamines emanating from their intrinsic instability has impeded their exploration in cycloaddition reactions. Here, we achieved a metal-free domino reaction providing quinoline and isoquinoline-derived cyclic amidines by the cycloaddition of azides with in situ generated enamines via dearomatization.
6) Ir-Catalyzed Transfer Hydrogenation and Alkylation of Aldehydes and Ketones Using Ethanol as a Hydrogen Source
Suman Yadav and Malleswara Rao Kuram
Eur. J. Org. Chem. 2023, 26, e202201344
Abstract
Bio-derived ethanol is a promising green and sustainable hydrogen-donor solvent. Herein, we have developed Ir-catalyzed transfer hydrogenation of ketones and aldehydes using ethanol as a hydrogen source with amides as simple ligands. Furthermore, the alkylation of ketones and tandem alkylation/transfer hydrogenation of acetophenones is reported with ethanol.
2022
5) Copper-Catalyzed Cascade Reaction of Tryptamines with Diazo Compounds to Access Hexahydropyrroloindoline Derivatives
Dharmendra Kumar, Dhananjay Chaudhary, Km Ishu, Suman Yadav, Naveen Kumar Maurya, Ruchir kant and Malleswara Rao Kuram
Abstract
A domino reaction sequence of cyclopropanation/ring-opening/iminium cyclization of tryptamine derivatives with donor-acceptor diazo compounds is developed to furnish pyrroloindolines creating three consecutive stereogenic centers in a single step. The copper-catalyzed reaction provided pyrroloindolines at room-temperature with good substrate scope.
4) Palladium-Catalyzed C(sp3)-H Biarylation of 8-Methyl Quinolines with Cyclic Diaryliodonium Salts to Access Functionalized Biaryls and Fluorene Derivatives
Naveen Kumar Maurya, Suman Yadav, Dhananjay Chaudhary, Dharmendra Kumar, Km Ishu and Malleswara Rao Kuram
Abstract
Herein, we have developed the cyclic diaryliodonium salts as biarylating agents in the C(sp3)-H functionalization using 8-methyl quinoline as the intrinsic directing group. The oxidant-free reaction produces a vast array of the biarylated products with iodo-functionality which can be further functionalized. Additionally, intramolecular C(sp3)-H functionalization in a step-wise manner under palladium-catalyzed conditions produced the fluorene derivatives in excellent yields.
3) Regiodivergent Cascade Cyclization/Alkoxylation of Allenamides via N-Protecting Group Driven Rearrangement to Access Indole and Indoline Derivatives
Dhananjay Chaudhary, Suman Yadav, Naveen Kumar Maurya, Dharmendra Kumar, Km Ishu and Malleswara Rao Kuram
Abstract
A mild, palladium-catalyzed domino Heck-cyclization/alkoxylation sequence of aryl halide tethered allenamides is described, providing regiodivergent indole and indoline derivatives controlled by the N-protecting group. This room temperature reaction provided functionalizable olefinic moiety with broad substrate scope. Preliminary mechanistic studies support the rearrangement of indoline derived intermediate to indoles with the N-acetyl allenamides forming free (NH) indoles.
2) Transfer hydrogenation of pyridinium and quinolinium species using ethanol as a hydrogen source to access saturated N-heterocycles
Suman Yadav, Dhananjay Chaudhary, Naveen Kumar Maurya, Dharmendra Kumar, Km Ishu and Malleswara Rao Kuram
Abstract
Catalytic transfer hydrogenation (TH) for the reduction of heterocycles is an emerging strategy for accessing biologically active saturated N-heterocycles. Herein, we report a TH protocol that utilizes ethanol as a renewable hydrogen source and an Ir catalyst for the reduction of quinolines and pyridines. The reaction is promoted by simple amides as ligands.
2021
1) Dicarbofunctionalization of Unactivated Alkenes by Palladium-Catalyzed Domino Heck/Intermolecular Direct Hetero Arylation with Heteroarenes
Km Ishu, Dharmendra Kumar, Naveen Kumar Maurya, Suman Yadav, Dhananjay Chaudhary and Malleswara Rao Kuram
Abstract
A palladium-catalyzed domino Heck/intermolecular direct hetero arylation sequence of unactivated alkenes was developed, providing 1,2,3-triazole containing bisheterocycles bearing all-carbon quaternary centers with yields of 25–90%. The protocol was extended to 1,3,4-oxadiazoles as well. The installed triazole was further exploited for late-stage functionalizations, and the mechanistic studies indicate the involvement of C–H activation.
Publications from PhD and PostDoc Research
8) Emerging C–H functionalization strategies for constructing fused polycyclic aromatic hydrocarbons and nanographenes (Invited Review)
Bijoy P. Mathew, Malleswara Rao Kuram
Abstract
Extended π-conjugated small polycyclic aromatic hydrocarbons (PAHs), nanographenes and graphene nanoribbon (GNR) molecules find wide applications in materials chemistry owing to their exceptional physical and optical properties. Apparently, extensive research interest has been focused on the efficient synthesis of these molecules. In this review, recent developments by C-H functionalization strategies that can efficiently control the crucial size and edge configurations have been discussed.
7) Copper‐Catalyzed Direct Synthesis of 1, 2, 4‐Oxadiazoles from Amides and Organic Nitriles by Oxidative N–O Bond Formation
M. R. Kuram, W. G. Kim, K. Myung, S. Y. Hong
Abstract
Herein, we report the first Cu‐catalyzed one‐step method for the synthesis of 1,2,4‐oxadiazoles from stable, less toxic, and readily available amides and organic nitriles by a rare oxidative N–O bond formation using O2 as sole oxidant. This method has a broad substrate scope and a good tolerance for diverse functional groups. Moreover, the synthetic utility of this method is highlighted by the synthesis of biologically active 3,5‐disubstituted derivatives.
6) A palladium and gold catalytic system enables direct access to O-and S-linked non-natural glyco-conjugates
M. H. Jeon, B. P. Mathew, M. R. Kuram, K. Myung, S. Y. Hong.
5) Direct Access to Benzo [b] furans through Palladium‐Catalyzed Oxidative Annulation of Phenols and Unactivated Internal Alkynes
M. R. Kuram, M. Bhanuchandra, A. K. Sahoo.
4) Ru(II)-Catalyzed Intermolecular ortho-C–H Amidation of Aromatic Ketones with Sulfonyl Azides.
M. Bhanuchandra, M. R. Yadav, R. K. Rit, M. R. Kuram, A. K. Sahoo
3) Silver (I)-Catalyzed Reaction between Pyrazole and Propargyl Acetates: Stereoselective Synthesis of the Scorpionate Ligands (E)-Allyl-gem-dipyrazoles (ADPs)
M Bhanuchandra, M. R. Kuram, A. K. Sahoo
2) A convenient approach to β-heteroarylated (C–N bond) ketones from Cs2CO3 promoted reaction between propargyl alcohols and nitrogen-heterocycles
M. Bhanuchandra, M. R. Kuram, A. K. Sahoo
1) Gold-catalyzed intermolecular hydrophenoxylation of unactivated Internal alkynes
M. R. Kuram, M. Bhanuchandra, A. K. Sahoo