BITS Faculty Publications

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    Optimization of bacterial biorefineries for sustainable biodiesel production and flue gas reduction: a holistic approach to climate change mitigation and circular economy
    (RSC, 2025) Raghuvanshi, Smita; Gupta, Suresh
    The primary obstacles to addressing the current climate change problem include a rise in worldwide energy consumption, a restricted availability of fossil fuels, and the escalating carbon emissions associated with fossil fuels. Consequently, there is a pressing need to investigate sustainable alternatives to fossil fuels. Biorefineries present a potentially viable avenue for the sustainable production of fuel, as they employ a range of technologies to convert biomass into biofuels. This research aims to examine the cultivation of bacterial biomass and biodiesel production using a biorefinery approach. This process achieves a removal efficiency of 96, 93, and 98% for CO2, SO2, and NO, respectively, and a bacterial biomass of 274 g cultivated in a 20 L integrated bioreactor. The biomass entails extracting lipids (58% w/w) to generate biodiesel (91% w/w). The metabolic pathway followed by bacteria to reduce flue gas and produce lipids was analyzed to improve the production of lipids and biodiesel. A life cycle assessment was performed to assess the environmental impacts during the process. Implementing alternative and safe chemicals can potentially mitigate the adverse effects of processes and GWP100. The techno-economic analysis aimed to systematically examine the capital investment required to set up a bacterial biorefinery as compared to conventional fuel refineries. The findings indicated that the bacterial biorefinery had a net present value of $193 per litre of biodiesel produced. A bacterial biorefinery holds promise in fostering a circular economy characterized by sustainable practices and systems that aim to minimize waste, optimize resource utilization, and encourage the reuse and recycling of materials.
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    Electrochemical Oxidative Coupling Between Benzylic C(sp3)–H and N–H of Secondary Amines: Rapid Synthesis of α-Amino α-Aryl Esters
    (ACS, 2021-06) Kumar, Indresh
    An intermolecular electrochemical coupling between the benzylic C(sp3)–H bond and various secondary amines is reported. The electronic behavior of two electronically rich units viz the α-position of α-aryl acetates and amines was engineered electrochemically, thus facilitating their reactivity for the direct access of α-amino esters. A series of acyclic/cyclic secondary amines and α-aryl acetates were tested to furnish the corresponding α-amino esters with high yields (up to 92%) under mild conditions.
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    Asymmetric Synthesis of Bridged N-Heterocycles with Tertiary Carbon Center through Barbas Dienamine-Catalysis: Scope and Applications
    (ACS, 2021-11) Kumar, Indresh; Kumar, Dalip
    A direct aza-Diels–Alder reaction between 2-aryl-3H-indolin-3-ones and cyclic-enones has been developed to access chiral indolin-3-one fused polycyclic bridged compounds. This method proceeds via proline-catalyzed Barbas-dienamine intermediate formation from various cyclic-enones such as 2-cyclopenten-1-one, 2-cyclohexene-1-one, and 2-cycloheptene-1-one, followed by a reaction with 2-aryl-3H-indol-3-ones. Several indolin-3-ones fusing [2.2.2], [2.2.1], and [3.2.1] skeletons decorated with a tertiary carbon chiral center have been prepared. Computational studies (DFT) supported the observed stereoselectivity in the method. The synthesized compounds have shown exciting photophysical activities and selective sensing of Pd2+ and Fe3+ ions through the fluorescence quenching “switch-off” mode.
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    Electrochemical Oxidative Addition of Nucleophiles on 2-Arylindoles: Synthesis of C2-Heteroquaternary Indolin-3-ones
    (ACS, 2022-11) Kumar, Indresh
    An electrochemical method has been developed to synthesize 2,2-disubstituted indolin-3-ones under mild conditions. A series of nucleophiles have been added to the 2-arylindole-3-ones, generated in situ under metal-free electrochemical oxidative dearomatization of 2-arylindoles, to afford 2,2-disubstituted 3-carbonyl indoles with heteroquaternary centers in 57–79% yields.
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    Electrochemical Synthesis of 2-Aryl-3-(2-aminoaryl)quinoxalines via Oxidative Dearomatization/Ring-Opening/Cyclization Cascade Sequence of 2-Arylindoles with 1,2-Diaminoarenes
    (ACS, 2023-07) Kumar, Indresh
    A straightforward method has been developed to synthesize 2-aryl-3-(2-aminoaryl) quinoxalines from 2-arylindoles and 1,2-diaminoarenes under mild electrochemical conditions. The reaction proceeds through in situ generations of 2-arylindole-3-ones under electrochemical oxidative dearomatization of 2-arylindoles, followed by a ring opening-cyclization sequence with 1,2-diaminoarenes. A series of 2-aryl-3-(2-aminoaryl) quinoxalines have been prepared with moderate to good yields (up to 75%).
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    Direct Amine-Catalyzed Enantioselective Synthesis of Pentacyclic Dibenzo[b,f][1,4]oxazepine/Thiazepine-Fused Isoquinuclidines along with DFT Calculations
    (ACS, 2020-10) Kumar, Dalip; Kumar, Indresh
    A direct protocol for the asymmetric synthesis of dibenzoxazepine/thiazepine-fused [2.2.2] isoquinuclidines is developed. The reaction proceeds through a proline-catalyzed direct Mannich reaction followed by an intramolecular aza-Michael cascade sequence between 2-cyclohexene-1-one and various tricyclic imines, like dibenzoxazepines/thiazepines, as an overall [4 + 2] aza-Diels–Alder reaction. A series of pentacyclic isoquinuclidines have been prepared, with complete endo-selectivity, in good to high yields and excellent enantioselectivity (>99:1). Density functional theory (DFT) calculations further support the observed high stereochemical outcome of the reaction.
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    Direct Amine-Catalyzed Enantioselective Synthesis of Pentacyclic Dibenzo[b,f][1,4]oxazepine/Thiazepine-Fused Isoquinuclidines along with DFT Calculations
    (ACS, 2020) Kumar, Indresh; Kumar, Dalip
    A direct protocol for the asymmetric synthesis of dibenzoxazepine/thiazepine-fused [2.2.2] isoquinuclidines is developed. The reaction proceeds through a proline-catalyzed direct Mannich reaction followed by an intramolecular aza-Michael cascade sequence between 2-cyclohexene-1-one and various tricyclic imines, like dibenzoxazepines/thiazepines, as an overall [4 + 2] aza-Diels–Alder reaction. A series of pentacyclic isoquinuclidines have been prepared, with complete endo-selectivity, in good to high yields and excellent enantioselectivity (>99:1). Density functional theory (DFT) calculations further support the observed high stereochemical outcome of the reaction.
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    Direct Amine-Catalyzed Enantioselective Synthesis of Pentacyclic Dibenzo[b,f][1,4]oxazepine/Thiazepine-Fused Isoquinuclidines along with DFT Calculations
    (ACS, 2020-10-08) Kumar, Dalip; Kumar, Indresh
    A direct protocol for the asymmetric synthesis of dibenzoxazepine/thiazepine-fused [2.2.2] isoquinuclidines is developed. The reaction proceeds through a proline-catalyzed direct Mannich reaction followed by an intramolecular aza-Michael cascade sequence between 2-cyclohexene-1-one and various tricyclic imines, like dibenzoxazepines/thiazepines, as an overall [4 + 2] aza-Diels–Alder reaction. A series of pentacyclic isoquinuclidines have been prepared, with complete endo-selectivity, in good to high yields and excellent enantioselectivity (>99:1). Density functional theory (DFT) calculations further support the observed high stereochemical outcome of the reaction.