Issue 28, 2025

UV-assisted rearrangement of substituted 3-arylaminopyrazoles with an allomaltol fragment into tricyclic cyclopenta[4,5]pyrrolo[2,3-c]pyrazole derivatives

Abstract

In the present study, we report a novel photochemical rearrangement of substituted 3-arylaminopyrazoles incorporating an allomaltol fragment. Under UV-irradiation, these compounds undergo ESIPT-induced contraction of the pyran-4-one ring, leading to an unstable α-hydroxy-1,2-diketone intermediate. For the first time, this transient intermediate was successfully trapped via intramolecular cyclization involving the nitrogen atom of the aniline moiety. Using this UV-induced cascade transformation, a facile method for the synthesis of tricyclic cyclopenta[4,5]pyrrolo[2,3-c]pyrazole derivatives was elaborated. The applicability of the designed approach was demonstrated by the preparation of 14 photoproducts with yields up to 78%. The structures of the representative starting pyrazole and one of the target photoproducts were unambiguously confirmed by X-ray analysis.

Graphical abstract: UV-assisted rearrangement of substituted 3-arylaminopyrazoles with an allomaltol fragment into tricyclic cyclopenta[4,5]pyrrolo[2,3-c]pyrazole derivatives

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Article information

Article type
Paper
Submitted
14 May 2025
Accepted
24 Jun 2025
First published
01 Jul 2025

Org. Biomol. Chem., 2025,23, 6738-6744

UV-assisted rearrangement of substituted 3-arylaminopyrazoles with an allomaltol fragment into tricyclic cyclopenta[4,5]pyrrolo[2,3-c]pyrazole derivatives

A. N. Komogortsev, C. V. Milyutin, B. V. Lichitsky and V. A. Migulin, Org. Biomol. Chem., 2025, 23, 6738 DOI: 10.1039/D5OB00796H

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