Shyam Kumar Banjare

National Institute of Science Education and Research

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Ponneri C. Ravikumar

National Institute of Science Education and Research

Tanmayee Nanda

National Institute of Science Education and Research

Bedadyuti Vedvyas Pati

National Institute of Science Education and Research

Pragati Biswal

National Institute of Science Education and Research

Smruti Ranjan Mohanty

Deutsches Elektronen-Synchrotron DESY

Namrata Prusty

National Institute of Science Education and Research

Gopal Krushna Das Adhikari

National Institute of Science Education and Research

Rajesh Chebolu

National Institute of Science Education and Research

Komal Yadav

University of Hawaiʻi at Mānoa

Adinarayana Doddi

Indian Institute of Science Education and Research Berhampur

Cooperative Institutions

National Institute of Science Education and Research

Homi Bhabha National Institute

University of Münster

Indian Institute of Science Education and Research Berhampur

University of California, Davis

Industrial Technology Institute

Institute of Medical Sciences

National Institute Of Technology Silchar

National Renewable Energy Laboratory

University of Colorado Boulder

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Breaking the Trend: Insight into Unforeseen Reactivity of Alkynes in Cobalt-Catalyzed Weak Chelation-Assisted Regioselective C(4)–H Functionalization of 3-Pivaloyl Indole

ACS Catalysis (2021)

Shyam Kumar Banjare Tanmayee Nanda Bedadyuti Vedvyas Pati Gopal Krushna Das Adhikari Juhi Dutta

Unique reactivity of diphenylacetylene has been uncovered through weak chelation-assisted cobalt-catalyzed regioselective C(4)–H activation of 3-pivolyl indole. α-Hydroxy ketone and α,β-unsaturated ketone derivatives have been synthesized in good yields from indole and alkynes. Notably, the indole C(4)–H-functionalized α,β-unsaturated ketone product was obtained with high stereo- and regioselectivity simply by changing the coupling partner from symmetrical alkynes to unsymmetrical aromatic-aliphatic alkynes. Most importantly, trifluoroethanol acts as a sole source of water for this conversion. Quantitative detection of bis(2,2,2-trifluoroethyl) ether from dry trifluoroethanol through 19F NMR and LCMS studies indirectly confirms the in situ formation of water. A six-membered cobaltacycle intermediate was detected in HRMS, and also, this was further confirmed by the quantum mechanical calculations, which accounts for the highly regioselective C(4)–H functionalization.

Reactivity

Surface Modification

10.1021/acscatal.1c02689

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Citations (22)

Uncovering the Reactivity of Cobalt‐Catalyst Towards Regioselective Hydroarylation of 1,6‐Diyne via Weak‐Chelation Assisted C−H Bond Activation

Advanced Synthesis & Catalysis (2023)

Shyam Kumar Banjare Saista Afreen Pranav Shridhar Mahulkar Annapurna Saxena Ponneri C. Ravikumar

Abstract Herein, we report the reactivity of cobalt(III)‐catalyst towards hydroarylative functionalization of 1,6‐diyne, which has never been explored before. The N ‐aryl lactam is the prime substrate that undergoes sp 2 C−H bond activation. C−Co(III) bond formation occurs through weakly coordinating lactam group. The reaction mechanism reveals the in‐situ formation of a six‐membered cobaltacycle which undergoes further functionalization with 1,6‐diyne. Also, radical quenching experiments suggest the involvement of the ionic pathway for this conversion. In addition, hydrogen scrambling and kinetic isotope experiments support the proposed mechanism. A wide range of electronically biased substrates and reacting partners work well with this method in a highly atom‐economical fashion.

Reactivity

Surface Modification

10.1002/adsc.202300515

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Palladium-Catalyzed C–C Bond Activation of Cyclopropenone: Modular Access to Trisubstituted α,β-Unsaturated Esters and Amides

The Journal of Organic Chemistry (2021)

Tanmayee Nanda Pragati Biswal Bedadyuti Vedvyas Pati Shyam Kumar Banjare Ponneri C. Ravikumar

Strain-driven palladium/N-heterocyclic carbene-catalyzed C–C bond activation of diphenylcyclopropenone (DPC) has been explored for one-step access to trisubstituted α,β-unsaturated esters and amides. The designed transformation works under mild conditions providing exclusively a single stereoisomer. Mechanistic studies support the oxidative addition of the C–C bond of cyclopropenone to in-situ-generated Pd(0) intermediate. We have proved that vinylic hydrogen in the product is coming from phenol/aniline through deuterium-labeling studies. Late-stage functionalization of bioactive molecules such as procaine, estrone, and hymecromone demonstrates the robustness of this protocol.

10.1021/acs.joc.0c02700

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N-Allylbenzimidazole as a strategic surrogate in Rh-catalyzed stereoselective trans-propenylation of aryl C(sp²)–H bond

Chemical Communications (2022)

Pragati Biswal Tanmayee Nanda Shyam Kumar Banjare S. R. Mohanty Ranjit Mishra

A Rh-catalyzed C(sp2)-H propenylation has been reported by taking N-allyl benzimidazole as an allylamine congener. This transformation has been observed for the first time, where a tandem process of C-H allylation followed by alkene isomerization delivers a highly stereoselective trans-propenylated product. Detailed mechanistic studies including the characterization of rhodacycle-intermediates have been conducted to understand the mechanism.

Alkene

Tandem

10.1039/d2cc06048e

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Weak‐Chelation Assisted Regioselective Indole C(4)‐Alkynylation via Six‐Membered Cobaltacycle Intermediate

Advanced Synthesis & Catalysis (2024)

Sofaya Joshi Riya Dutta Shyam Kumar Banjare Annapurna Saxena Ponneri C. Ravikumar

Abstract Herein a regioselective indole C4‐alkynylation has been uncovered utilizing an earth‐abundant cobalt(III)‐catalyst. For this process, (bromoethynyl)benzene was used as an alkynylating agent. Also, after screening various amide‐protected chelating groups we found dimethyl‐amide is optimal for the in‐situ generation of cobaltacycle intermediate. The six‐membered cobaltacycle intermediate has been detected through high‐resolution mass spectrometry HRMS, which is a key intermediate for this conversion. Further, mechanistic studies were performed such as KIE experiments, and reactions with radical scavengers, and based on the results a plausible mechanism has been proposed. Moreover, to show the application of this methodology, the product has been oxidized to diketone, monoketone, alkene, alkane and further derivatized to a tricycle indole derivative, which is a core structure of many natural products.

Amide

Alkene

Derivative (finance)

10.1002/adsc.202301194

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Recent Advancement in Palladium Catalysed C-C bond Activation of Strained Ring Systems: Three and four-membered carbocycles as prominent C3/C4 building blocks

Tanmayee Nanda Muhammed Fastheem Astha Linda Bedadyuti Vedvyas Pati Shyam Kumar Banjare

In recent years, transition metal catalysed strong C-C bond activation has significantly attracted the attention of synthetic chemists. This enables simultaneous and direct functionalization of two different M-C bonds. Among different types of C-C bond activation strategies, strain-driven C-C bond activation has resulted in a variety of transformations, which is otherwise impossible. In this context, palladium catalyst has been extensively used and studied due to its robust nature in terms of its reactivity and selectivity. Herein, we have provided a brief discussion about palladium catalysed C-C bond activation of three and four-membered cycloalkane derivatives.

Ring strain

Reactivity

Cycloalkane

10.26434/chemrxiv-2022-p8l62

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CCDC 2091676: Experimental Crystal Structure Determination

The Cambridge Structural Database (2021)

Namrata Prusty Shyam Kumar Banjare Smruti Ranjan Mohanty Tanmayee Nanda Komal Yadav

10.5517/ccdc.csd.cc286kfh

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CCDC 1960668: Experimental Crystal Structure Determination

The Cambridge Structural Database (2020)

Shyam Kumar Banjare Pragati Biswal Ponneri C. Ravikumar

10.5517/ccdc.csd.cc23t7ck

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Transition Metal-catalyzed C-H /C-C Activation and Coupling with 1, 3-diyne

Bedadyuti Vedvyas Pati Nitha Nahan Puthalath Shyam Kumar Banjare Tanmayee Nanda Ponneri C. Ravikumar

This review focuses on providing a broad overview of the recent developments in the field of transition metal-catalyzed C-H bond activation and coupling with 1,3-diyne for assembling alkynylated heterocycles and bis-heterocycles. In recent years the use of 2π-unsaturated units as coupling partners for the synthesis of heterocycles through C-H bond activation and an-nulation sequence has received immense attention. Among the unsaturated units employed for assembling heterocycles, the use of 1,3-diynes has garnered significant attention due to its ability in rendering the straightforward bis-heterocycles. Earlier methods employed to assemble bis-heterocycle include the use of preformed and pre-functionalized heterocycles via transi-tion metal-catalyzed coupling reactions. The expensive pre-functionalized halo-heterocycles and sensitive & expensive heterocyclic metal reagents limit its use. However, the transition metal-catalyzed C-H activation obviates the need for expensive heterocyclic metal reagents and pre-functionalized halo-heterocycles. The C-H bond activation strategy makes use of C-H bonds as functional groups for effecting the transformation. This renders the overall synthetic sequence both step and costs economic. Hence, this strategy of C-H activation and subsequent reaction with 1,3-diyne is useful for the larger-scale synthesis of chemicals in the pharmaceutical industry. Despite these advances, there is still the possibility of exploration of earth-abundant, and cost-effective first-row transition metals (Ni, Cu, Mn. Fe, etc.) for the synthesis of bis-heterocycles. Moreover, the Cp* ligand free, simple metal salt mediated synthesis of bis-heterocycles is also less explored. Thus, more exploration of reaction conditions for the Cp* free synthesis of bis-heterocycles is called for. We hope this review will inspire scientists to explore the unexplored domains.

Coupling reaction

Organic Synthesis

10.26434/chemrxiv-2022-lqjqr

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Citations (1)

Weak-Chelation Assisted Cobalt-Catalyzed C–H Bond Activation: An Approach Toward Regioselective Ethynylation of N-Aryl γ-Lactam

Organic Letters (2022)

Shyam Kumar Banjare Annapurna Saxena Tanmayee Nanda Namrata Prusty Sofaya Joshi

The sustainable C-H bond ethynylation of N-aryl γ-lactam has been achieved in a highly regioselective manner. In this protocol, earth-abundant cobalt(III)-catalyst was found to be effective, triggering the C-H metalation using a weakly coordinating lactam group. Herein, the ortho-(sp2)-H ethynylation has been obtained regioselectively. The mechanistic studies reveal the non-involvement of the radical pathway for this conversion. However, the parallel kinetic isotope experiment suggests that the C-H bond activation is involved in the rate-determining step. In addition, the synthetic utility of ethynylated N-aryl γ-lactam has been demonstrated for many useful transformations.

Lactam

Metalation

10.1021/acs.orglett.2c04098

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Citations (4)