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Professor Sharma received his MSc degree from Guru Nanak Dev University and his Ph.D. from CSIR-Institute of Himalayan Bioresource Technology (IHBT), Palampur, India. He followed this with a lecturer position at the National Institute of Technology, Jalandhar, India. He was a postdoctoral fellow at KU Leuven, the University of Cambridge, the University of Eindhoven, and the Shanghai Institute of Organic Chemistry. He has also worked as a visiting research scientist at the Massachusetts Institute of Technology (MIT). In 2020, he joined KU Leuven as a research expert (Jr. group leader) starting his independent research career before joining the UMSL faculty in the fall of 2024.. |
Research Interests
The revival of radical chemistry in organic synthesis over the past decade has initiated a resurgence in the interest towards photoredox catalysis and synthetic organic electrochemistry. Much of this renewed attention has transpired due to the reactivity that can be accessed via the intermediacy of open shell reactive species that is otherwise difficult or nearly impossible by other means of chemical catalysis. However, understanding reactivity and selectivity patterns in radical chemistry is crucial to fully exploit the potential of open-shell species in synthetic settings.
Dr Sharma’s research has been focused on the challenging chemical transformations that require extreme oxidation or reduction potential e.g., SET oxidations of boronic acid derivatives (> +2.0 V vs SCE), and SET reduction of aryl/alkyl halides (> -2.0 V vs SCE) (Figure 1a). One of the major research areas is ‘Boron-Based Radical Chemistry for the Sustainable Synthesis of (Bio)molecules’ with an aim of developing continuous-flow friendly chemical processes. Boron enjoys unique chemical bonding that could expand its photo- or electro-chemical applications including modes of Lewis acidity not available to typical elements of life.
Work carried out by Dr. Sharma’s research group has shown that hydrogen-bonding interactions with free boronic acids (BA) and amide based solvents (DMF, DMA, DMSO etc.) can photoactivate them towards alkyl radicals generation which then participate in various Giese-type addition, E1cB type elimination chemistry, Petasis multicomponent reaction, and a flow compatible Minisci alkylation chemistry (Figure 1b and 1c). The Lewis acidity of the sp2-hybridized boron atom was exploited along with its interaction with different amide-based solvents, substrates, and reaction intermediates.
Even though the benefits of flow over batch for visible-light-driven transformations are nowadays well-established, yet its potential has not been fully exploited in combination with other enabling technologies. The group has demonstrated the scalability of both Giese-type addition and Minisci reaction in flow with a throughput of up to 615 mg/h. In addition, the potential of microwave-microfluidics for ultrafast organic synthesis, including modular flow cells with low-power, variable-MW frequency heating reactor with CSRR as a resonator has recently been revealed.
Dr Sharma’s research group aims to design and realize a wide pool of reaction pathways employing organoboranes as radical precursors as well as radical mediators under the photo- and electrochemical conditions. Additionally, improving the efficiency, scalability and sustainability of the chemical synthesis is the ultimate goal. The subsequent line of research in this field is to study such free radical SET events (open shell) with closed shell fundamental organometallic steps (Pd, Ni, Co) under mild conditions. Most importantly, the approach towards scalability is more from a Chemist’s perspective - to develop new chemical methodologies more suitable towards flow chemistry.
Selected Publications:
“Lab-scale flow chemistry? Just do it yourself!” L. Y. Vázquez-Amaya, G. A. Coppola, E. V. Van der Eycken, and U. K. Sharma, J. Flow Chem. 2024, 14, 257.
“Highly modular PDMS microwave-microfluidic chip reactor for MAOS applications” L. Y. Vázquez-Amaya, M. Martinic, B. Nauwelaers, E. V. Van der Eycken, T. Markovic, and U. K. Sharma, : React. Chem. Eng. 2024, 9, 2098.
“Hydroalkylation of styrenes enabled by boryl radical mediated halogen atom transfer” S. Pillitteri, R. Walia, E. V. Van der Eycken, and U. K. Sharma, Chem. Sci. 2024, 15, 8813.
“Light-driven four-component reaction with boronic acid derivatives as alkylating agents: an amine/imine mediated activation approach” L. Y. Vázquez-Amaya, B. Dootselaere, G. M. Ojeda-Carralero, S. Pillitteri, E. V. Van der Eycken, and U. K. Sharma. Org. Lett. 2023, 25, 4010.
“Boronic acids and their derivatives as continuous-flow friendly alkyl radical precursors” M. Oliva, V. V Chernobrovkina, E. V. Van Der Eycken, and U. K Sharma. Synlett 2023, 34, 1662.
“Going with the µFlow: Reinterpreting energy input in organic synthesis” L. Y. Vázquez-Amaya, G. A. Coppola, E. V. Van der Eycken, and U. K. Sharma. Chimia 2023, 77, 327.
“Visible-light-induced cascade difunctionalization of indoles enabled by the synergy of photoredox and photoexcited ketones: direct access to alkylated pyrrolophenanthridones” S. Chen, S. Pillitteri, E. Fron, L. Van Meervelt, E. V. Van der Eycken, and U. K. Sharma. Org. Lett. 2022, 24, 9386.
“Merging dual photoredox/cobalt catalysis and boronic acid (derivatives) activation for the Minisci reaction” S. Pillitteri, P. Ranjan, G. M. Ojeda-Carralero, L. Y. Vázquez Amaya, J. E. Alfonso-Ramos, E. V. Van der Eycken, and U. K. Sharma. Org. Chem. Front. 2022, 9, 6958.
“Multicomponent reactions and photo/electrochemistry join forces: atom economy meets energy efficiency” G. A. Coppola, S. Pillitteri, E. V. Van der Eycken, S. -L. You, and U. K. Sharma. Chem. Soc. Rev. 2022, 51, 2313.
“Visible-light-driven palladium-catalyzed radical tandem dearomatization of indoles with unactivated alkenes” S. Chen, L. Van Meervelt, E. V. Van der Eycken, and U. K. Sharma. Org. Lett. 2022, 24, 1213.
“Photoredox-catalyzed multicomponent Petasis reaction in batch and continuous flow with alkyl boronic acids” M. Oliva, P. Ranjan, S. Pillitteri, G. Coppola, M. Messina, E. V. Van der Eycken, and U. K. Sharma. iScience, 2021, 24, 103134
“Unlocking the accessibility of alkyl radicals from boronic acids through hydrogen-bond assisted organophotoredox activation” P. Ranjan, S. Pillitteri, G. Coppola, M. Oliva, E. V. Van der Eycken, and U. K. Sharma. ACS Catal. 2021, 11, 10862.
“Palladium-catalyzed domino synthesis of 2,3-difunctionalized indoles via migratory insertion of isocyanides in batch and continuous flow” S. Chen, M. Oliva, L. Van Meervelt, E. V. Van der Eycken, and U. K. Sharma. Adv. Synth. Catal. 2021, 363, 3220.
“Photochemical and electrochemical strategies towards benzylic C‐H functionalization: a recent update” M. Oliva, G. Coppola, E. V. Van der Eycken, and U. K. Sharma. Adv. Synth. Catal. 2021, 363, 1810.
“Photochemical methods for deuterium labelling of organic molecules” P. Ranjan, S. Pillitteri, E. V. Van der Eycken and U. K. Sharma. Green Chem. 2020, 22, 7725.
