Issue 15, 2021

Radical addition reaction between chromenols and toluene derivatives initiated by Brønsted acid catalyst under light irradiation

Abstract

A Brønsted acid-catalyzed benzylic C(sp3)–H functionalization of toluene and its derivatives was accomplished through the photo-excitation of benzopyrylium cation intermediates. Light irradiation promoted the reaction of chromenols with toluene and its derivatives in the presence of a Brønsted acid catalyst, affording the corresponding benzylated chromene derivatives having tetrasubstituted carbon centers. Experimental and theoretical studies elucidated that the reaction proceeds through a radical addition pathway in which the benzopyrylium cation intermediate acts as both an electrophile and a photo-redox catalyst. The use of a chiral phosphoric acid catalyst enables the enantioselective radical addition reaction through a chiral anion-controlled asymmetric induction via an ion-pairing interaction to provide an addition product in an enantioenriched form.

Graphical abstract: Radical addition reaction between chromenols and toluene derivatives initiated by Brønsted acid catalyst under light irradiation

Supplementary files

Article information

Article type
Research Article
Submitted
27 apr 2021
Accepted
15 mei 2021
First published
19 mei 2021

Org. Chem. Front., 2021,8, 4153-4159

Radical addition reaction between chromenols and toluene derivatives initiated by Brønsted acid catalyst under light irradiation

J. Kikuchi, S. Kodama and M. Terada, Org. Chem. Front., 2021, 8, 4153 DOI: 10.1039/D1QO00657F

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