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Issue 3, 2020
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Switching of regioselectivity in base-mediated diastereoselective annulation of 2,3-epoxy tosylates and their N-tosylaziridine analogs with 2-mercaptobenzimidazole

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Abstract

A base-mediated dinucleophilic cyclization of readily accessible 2,3-epoxy tosylates with 2-mercaptobenzimidazole has been developed for the one-pot diastereoselective synthesis of benzimidazole-based tricyclic compounds equipped with two stereogenic centres. With trans-substrates bearing an aryl or alkyl substituent at the C3 position, the reaction involves an initial S–C1 bond-forming intermolecular alkylation followed by an N–C3 bond-forming, endo-selective intramolecular epoxide ring-opening cyclization reaction. A spectacular regioselectivity switching (tandem S–C3 and N–C1 bond formation reactions) was observed with related trans-N-tosylaziridine substrates. Wide substrate scope, complete diastereoselectivity, high to complete regioselectivity and mild transition metal-free conditions render this protocol particularly efficient and practical.

Graphical abstract: Switching of regioselectivity in base-mediated diastereoselective annulation of 2,3-epoxy tosylates and their N-tosylaziridine analogs with 2-mercaptobenzimidazole

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Article information


Submitted
13 Nov 2019
Accepted
12 Dec 2019
First published
12 Dec 2019

Org. Biomol. Chem., 2020,18, 441-449
Article type
Paper

Switching of regioselectivity in base-mediated diastereoselective annulation of 2,3-epoxy tosylates and their N-tosylaziridine analogs with 2-mercaptobenzimidazole

A. J. Das, H. Borgohain, B. Sarma and S. K. Das, Org. Biomol. Chem., 2020, 18, 441
DOI: 10.1039/C9OB02454A

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