Photochemistry of Resveratrol: Beyond the Reactivity of Metal‐Free Porphyrins Immobilized on Lignin

Resveratrol photochemistry with singlet oxygen is examined at 450 nm using blue-LED irradiation and various homogeneous and heterogeneous photosensitizers. Products of CC bond cleavage, electrocyclic ring closure, and [4 + 2] cycloaddition are identified. The selectivity of the overall transformation is controlled by the structure of the photosensitizer and by the nominal capacity of the blue-LED photon.

The photochemistry of resveratrol with singlet oxygen (¹O₂) under blue-LED irradiation is explored in the presence of three metal-free porphyrins as photosensitizers. Irradiation at 450 nm yields products of CC bond scission, 6-electron electrocyclic ring closure, and [4 + 2] cycloaddition, including benzaldehydes, 2,4,6-trihydroxyphenanthrene, and resveratrol cyclic endoperoxide. The selectivity of the process is controlled by the structure of the metal-free porphyrin and by the nominal capacity of the blue-LED photon. The scope of the reaction is extended to sustainable heterogeneous photosensitizers produced by immobilization of metal-free porphyrins on lignin, the most abundant polyphenol in nature characterized by beneficial photochemical properties.

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