Synthesis 2024; 56(14): 2247-2258
DOI: 10.1055/a-2270-3973
paper

Friedel–Crafts Alkylation of Indoles with Aldehydes/Ketones Catalyzed by Bromodiarylethene-Based Photoacid Generators

Alexey V. Zakharov
,
Sofia M. Timofeeva
,


Abstract

Diarylethenes (DAEs) with a bromine atom at the ring-closing position catalyze C–C bonding reactions induced by UV or sunlight. Upon photo-irradiation, bromodiarylethenes undergo 6π-electrocyclization (6π-EC), followed by the release of an acid species that catalyzes the double Friedel–Crafts addition of indoles to aldehydes and isatins to form the corresponding triarylmethanes and 3,3′-diarylindolin-2-ones. This protocol is applicable to a wide spectrum of aldehydes and isatins, as well as chalcones as electrophiles. Acid or oxidant-sensitive functional groups, such as ferrocene, 4-methoxyphenyl, thiophene, pyrrole are tolerated. Mechanistic studies show that light is needed to initiate the reaction.

Supporting Information



Publikationsverlauf

Eingereicht: 16. Januar 2024

Angenommen nach Revision: 16. Februar 2024

Accepted Manuscript online:
16. Februar 2024

Artikel online veröffentlicht:
06. März 2024

© 2024. Thieme. All rights reserved

Georg Thieme Verlag KG
Rüdigerstraße 14, 70469 Stuttgart, Germany