Browsing by Author "Anamika Prajapati"

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Formal [4+1] heteroannulative coupling of Knoevenagel adducts derived from 2-heteroaryl acetonitriles with isocyanides: subsequent Pd-catalyzed intramolecular N-arylation to 6-5-5-5-6 pentacyclic cores
(Royal Society of Chemistry, 2023) Anamika Prajapati; Manoj Kumar Saini; Shashi Kant Verma; Harshita Singh Korawat; Ashok Kumar Basak
A concise and practical approach for expedient synthesis of substituted benzoxazolpyrroles, benzothiazolpyrroles and indolizines by three-component cascade annulative coupling of an aldehyde, 2-heteroaryl acetonitrile and an isocyanide in the presence of 10 mol% 2-(hydroxymethyl)pyrrolidinium acetate has been devised in high yields for the first time. The compatibility with a wide range of functional groups makes this domino formation of one C-C and two C-N bonds interesting. In particular, the heterocycles derived from 2-bromobenzaldehydes are further converted into indole-fused novel pentacyclic (6-5-5-5-6) heteroaromatic compounds by Pd(ii)-catalyzed intramolecular N-arylation via a cross-dehydrobromination reaction. This annulative protocol not only provides an efficient method to access tricyclic heteroaromatics, but also enriches the research domain of pentacyclic scaffolds. © 2023 The Royal Society of Chemistry.
In(OTf)3 catalyzed reductive etherification of 2-aryloxybenzaldehydes and 2-(arylthio)benzaldehydes
(Elsevier Ltd, 2019) Anamika Prajapati; Mahendra Kumar; Ranjit Thakuria; Ashok K. Basak
2-Aryloxybenzaldehydes and 2-(arylthio)benzaldehydes undergo reductive etherification in presence of 5 mol% In(OTf)3 and stoichiometric amount of Et3SiH under solvent free conditions to generate novel symmetrical dibenzyl ethers and thioethers in excellent yields. In(OTf)3 is found to be superior in terms of catalytic activity over the other metal triflates tested for the reaction. Xanthenes and thioxanthenes, as anticipated, could not be obtained under these conditions. © 2019
Lewis Acid Catalyzed Reductive Cyclization of 2-Aryloxybenzaldehydes and 2-(Arylthio)benzaldehydes to Unsubstituted 9H-Xanthenes and Thioxanthenes in Diisopropyl Ether
(Wiley-VCH Verlag, 2021) Shashi Kant Verma; Anamika Prajapati; Manoj Kumar Saini; Ashok K. Basak
Readily accessible 2-aryloxybenzaldehydes and 2-(arylthio)benzaldehydes undergo a sequence of reactions leading to a wide variety of unsubstituted 9H-xanthenes and thioxanthenes in high yields when heated with a Lewis acid in diisopropyl ether. This reductive cyclization method is compatible with several important functional groups. The method is also applicable for the selective reductive cyclization of the more electron-rich aryl ring of a 2,6-bis(aryloxy)benzaldehyde. The key feature of this transformation is the chemoselective reduction of a transient xanthylium ion in the presence of aldehydic group via intermolecular hydride transfer from diisopropyl ether (solvent). (Figure presented.). © 2020 Wiley-VCH GmbH
Stereoselective synthesis of 9-vinyl substituted unsymmetrical xanthenes and thioxanthenes
(Elsevier Ltd, 2020) Anamika Prajapati; Mahendra Kumar; Ranjit Thakuria; Ashok K. Basak
Activated 2°-allylic alcohols derived from 2-aryloxybenzaldehydes and 2-(arythio)benzaldehydes undergo intramolecular Friedel-Crafts alkylation reaction when heated with catalytic amount of a Lewis acid in 1,2-dichloroethane to provide highly E-selective 9-vinyl substituted unsymmetrical novel xanthenes and thioxanthenes in good yields. © 2020 Elsevier Ltd