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. 2023 Jan 20;3(3):130-135.
doi: 10.1021/acsorginorgau.2c00064. eCollection 2023 Jun 7.

Organophotoredox 1,6-Addition of 3,4-Dihydroquinoxalin-2-ones to para-Quinone Methides Using Visible Light

Jaume Rostoll-Berenguer  1 , Víctor García-García  1 , Gonzalo Blay  1 , José R Pedro  1 , Carlos Vila  1
Affiliations

Organophotoredox 1,6-Addition of 3,4-Dihydroquinoxalin-2-ones to para-Quinone Methides Using Visible Light

Jaume Rostoll-Berenguer et al. ACS Org Inorg Au. .

Abstract

An organophotoredox 1,6-radical addition of 3,4-dihidroquinoxalin-2-ones to para-quinone methides catalyzed by Fukuzumi's photocatalyst is described under the irradiation of a HP Single LED (455 nm). The corresponding 1,1-diaryl compounds bearing a dihydroquinoxalin-2-one moiety (20 examples) are obtained with good to excellent yields under mild reaction conditions. Several experiments have been carried out in order to propose a reaction mechanism.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Scheme 1
Scheme 1
(A) 1,6-Radical addition with para-quinone methides. (B) 1,6-Addition of α-amino radicals to para-quinone methides. (C) 1,6-Radical addition of dihydroquinoxalin-2-ones.
Scheme 2
Scheme 2. Scope of the 1,6-Radical Addition Reaction Regarding the Dihydroquinoxalin-2-one Derivatives 1
Reaction conditions: 1 (0.15 mmol), 2a (0.1 mmol), [Mes-Acr-Me][BF4] (5 mol %), DCM (1 mL), under argon atmosphere and under HP Single LED (455 nm) irradiation for 6–16 h. Diastereomeric ratio was determined by 1H NMR of the crude reaction mixture. Yield determined after purification by column chromatography using Et3N-deactivated silica gel.
Scheme 3
Scheme 3. Scope of the 1,6-Radical Addition Reaction Regarding the para-Quinone Methides Derivatives 2
Reaction conditions: 1a (0.15 mmol), 2 (0.1 mmol), [Mes-Acr-Me][BF4] (5 mol %), DCM (1 mL), under argon atmosphere and under HP Single LED (455 nm) irradiation for 6–16 h. Diastereomeric ratio was determined by 1H NMR of the crude reaction mixture. Yield determined after purification by column chromatography using Et3N-deactivated silica gel.
Figure 1
Figure 1
(A) Emission spectra of different DCM solutions containing 0.02 mM of [Mes-Acr-Me][BF4] and varying amounts of 3,4-dihydroquinoxalin-2-one 1a. (B) Stern–Volmer plot of I0/I vs [1a]. Determination of KSV through linear regression.
Scheme 4
Scheme 4. Mechanistic Hypothesis for the Photochemical 1,6-Radical Addition for the Synthesis of 3
See this image and copyright information in PMC

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