The catalyst-free [2 + 2] photocycloaddition between benzils and simple olefins is reported. The adoption of visible light proved essential for the transformation, as shorter wavelengths led to uncontrolled decomposition. When cyclic olefins were used, the reaction occurred smoothly to afford the expected oxetanes regio- and stereoselectively after 24 h of irradiation. In contrast, in the case of acyclic olefins, longer reaction times were typically required and small amounts (ca. 20%) of [4 + 2] photocycloadducts and by-products deriving from competitive hydrogen atom abstraction were observed. The selectivity of the transformation could be consistently improved by decreasing the reaction temperature, thus restoring the desired [2 + 2] reactivity. An overall mechanistic picture is also offered based on the chemical and photophysical quenching experiments and the stereochemical output is rationalized based on Griesbeck models.

Catalyst-free [2+2] photocycloadditions between benzils and olefins under visible light / Tinelli, Roberto; Ravelli, Davide; Basso, Andrea; Tarantino, Serena; Capaldo, Luca. - In: PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES. - ISSN 1474-905X. - 21:5(2022), pp. 695-703. [10.1007/s43630-021-00129-4]

Catalyst-free [2+2] photocycloadditions between benzils and olefins under visible light

Ravelli Davide;Capaldo Luca
2022-01-01

Abstract

The catalyst-free [2 + 2] photocycloaddition between benzils and simple olefins is reported. The adoption of visible light proved essential for the transformation, as shorter wavelengths led to uncontrolled decomposition. When cyclic olefins were used, the reaction occurred smoothly to afford the expected oxetanes regio- and stereoselectively after 24 h of irradiation. In contrast, in the case of acyclic olefins, longer reaction times were typically required and small amounts (ca. 20%) of [4 + 2] photocycloadducts and by-products deriving from competitive hydrogen atom abstraction were observed. The selectivity of the transformation could be consistently improved by decreasing the reaction temperature, thus restoring the desired [2 + 2] reactivity. An overall mechanistic picture is also offered based on the chemical and photophysical quenching experiments and the stereochemical output is rationalized based on Griesbeck models.
2022
Catalyst-free [2+2] photocycloadditions between benzils and olefins under visible light / Tinelli, Roberto; Ravelli, Davide; Basso, Andrea; Tarantino, Serena; Capaldo, Luca. - In: PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES. - ISSN 1474-905X. - 21:5(2022), pp. 695-703. [10.1007/s43630-021-00129-4]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11381/2961113
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