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Item Organocatalytic [4+2] Benzannulation between 1,4-dithiane-based enal and nitroolefins to access 2-nitrobiaryls(Wiley, 2025-01) Kumar, IndreshA simple method for constructing unsymmetrical 2-nitrobiaryls has been developed between substituted 1,4-dithiine-2-carbaldehyde and nitroolefins under metal-free conditions. To gain the advantage of the HOMO-raising effect of temporary substitutions on in situ generated dienamine intermediate, the present protocol established [4+2] benzannulation of 1,4-dithiane-tethered enals with nitroolefin. Further, easy unmasking of 1,4-dithiine units results in a benzannulation product like that of unsubstituted enals, which are difficult to access. Several 2-nitrobiaryls have been accessed with moderate to good yields and with promising synthetic applications.Item Organo-catalyzed enantioselective [4+2] Annulation of glutaraldehyde and c3-indolyl-imines to access indol-3-yl-piperidines(Wiley, 2023-10) Kumar, IndreshA simple and straightforward method is developed for the enantioselective synthesis of indol-3-yl-piperidine. The reaction proceeds through a proline-catalyzed direct Mannich reaction between glutaraldehyde and C3-indolyl-imines, followed by intramolecular reductive cyclization as an overall [4+2] annulation in one-pot fashion. A series of indol-3-yl-piperidine have been accessed with good yields up to 71 % and high enantioselectivity up to >99 % ee.Item Organocatalytic asymmetric construction of 2,6-diazabicyclo-[2.2.2]Octanes by harnessing the potential of an 3-oxindolium ion intermediate(Wiley, 2024-10) Kumar, IndreshDue to its structural complexity and intrinsic sensitivity of bridged aminal junction, 2,6-diazabicyclo[2.2.2]octane (2,6-DABCO) has remained a highly desirable target in synthetic chemistry. However, the asymmetric access to this unit is still insufficient and hampered by the need for meticulously created functionalities for intricate double aza-cyclizations. Herein, we have developed a novel enantio- and diastereoselective protocol to access polycyclic chiral 2,6-DABCOs under metal-free conditions. This domino process involves the amine-catalyzed [4+2] annulation between glutaraldehyde and 2-arylindol-3-ones, followed by an acid-mediated Pictet–Spengler reaction/intramolecular aza-cyclization cascade sequence with tryptamine by trapping of in situ generated 3-oxindolium ion intermediate for the first time. Overall, 2,6-DABCOs fused with medicinally relevant scaffolds were isolated with good yield and excellent stereoselectivity by constructing five new bonds and four stereocenters in a one-pot operation.Item Direct multicomponent synthesis of C3-arylated pyrroles under catalyst-free conditions(Thieme, 2025) Kumar, IndreshAn operationally simple catalyst-free protocol for the direct regiospecific synthesis of C3-arylated/alkenylated pyrroles has been developed. The enamine-intermediate, in situ generated from succinaldehyde and a primary amine, was trapped with activated carbonyls before the Paal–Knorr reaction in a direct multicomponent ‘just-mix’ protocol to furnish pyrroles in good yields. Several C3-substituted N-alkylpyrroles have been prepared under open-flask conditions, avoiding protection-deprotection chemistry.Item Enantioselective synthesis of α-(3-pyrrolyl)methanamines with an aza-tetrasubstituted center under metal-free conditions(RSC, 2025) Kumar, IndreshConstruction of a chiral methanamine unit at the C3 position of pyrrole is highly desirable; nevertheless, it remains challenging due to its intrinsic electronic properties. Herein, we present an operationally straightforward and direct asymmetric approach for accessing α-(3-pyrrolyl)methanamines under benign organocatalytic conditions for the first time. The one-pot transformation proceeds smoothly through an amine-catalyzed direct Mannich reaction of succinaldehyde with various endo-cyclic imines, followed by a Paal–Knorr cyclization with a primary amine. Several N–H/alkyl/Ar α-(3-pyrrolyl)methanamines with an aza-tetrasubstituted center have been synthesized with good yields and excellent enantioselectivity.Item Organocatalytic [4+2] Benzannulation between 1,4-dithiane-based enal and nitroolefins to access 2-nitrobiaryls(Wiley, 2025-01) Kumar, IndreshA simple method for constructing unsymmetrical 2-nitrobiaryls has been developed between substituted 1,4-dithiine-2-carbaldehyde and nitroolefins under metal-free conditions. To gain the advantage of the HOMO-raising effect of temporary substitutions on in situ generated dienamine intermediate, the present protocol established [4+2] benzannulation of 1,4-dithiane-tethered enals with nitroolefin. Further, easy unmasking of 1,4-dithiine units results in a benzannulation product like that of unsubstituted enals, which are difficult to access. Several 2-nitrobiaryls have been accessed with moderate to good yields and with promising synthetic applications.Item Recent developments in the catalytic asymmetric synthesis of indolin-3-one derivatives(RSC, 2025) Kumar, Indresh2,2-Disubstituted indolin-3-ones, which are essential components in many manufactured chemicals, dyes, and naturally occurring bioactive alkaloids, have emerged as exciting synthetic targets. Much attention has been paid to accessing these units, particularly in an asymmetric fashion, during the last decade. In this review article, we discuss the current state of available methods with existing mechanistic pathways for accessing chiral indolin-3-one derivatives under various catalytic systems. This overall presentation of asymmetric catalytic protocols to access 2,2-disubstituted or fused indolin-3-ones with an aza-quaternary centre is categorized based on the reaction modes of 2-substituted-3H-indole-3-one derivatives or other similar protocols.Item Two-pot synthesis of indolizinoindole derivatives via lewis acid-mediated intramolecular regioselective cyclization of 3-acylpyrroles(Wiley, 2025-02) Khungar, Bharti; Kumar, IndreshA two-pot method has been developed to access indolizino[8,7-b]indole derivatives through Lewis acid-mediated regioselective C5-cyclization of 3-acylpyrrole prepared from the feedstock materials. The overall reaction proceeds through amine-catalyzed direct aldol reaction/Paal-Knorr reaction/oxidation between succinaldehyde, aromatic aldehyde, and tryptamine in a sequential multicomponent fashion for N-alkyl pyrrole followed by dearomative cyclization. A series of substituted indolizino[8,7-b]indoles have been prepared with good yields and excellent regioselectivity.Item Direct catalytic synthesis of β-(C3)-substituted pyrroles: a complementary addition to the Paal–Knorr reaction(RSC, 2021) Kumar, IndreshThe synthesis of β-(C3)-functionalized pyrroles is a challenging task and requires a multistep protocol. An operationally simple direct catalytic synthesis of β-substituted pyrroles has been developed. This one-pot multicomponent method combined aqueous succinaldehyde as 1,4-dicarbonyl, primary amines, and isatins to access hydroxyl-oxindole β-tethered pyrroles. Direct synthesis of the β-substituted free NH-pyrrole is the central intensity of this work. DFT-calculations and preliminary mechanism investigation support the possible reaction pathway.Item 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, IndreshAn 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.