American Chemical Society
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Regioisomerism in Symmetric Dimethyl Dialdehydes Dictates their Photochemical Reactivity

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posted on 2022-06-24, 19:08 authored by Florian Feist, Leona L. Rodrigues, Sarah L. Walden, Christopher Barner-Kowollik
We herein report the first light-driven selective monoderivatization (desymmetrization) of two chemically equivalent carbonyl groups in a single chromophore. By comparing of four symmetric regioisomers, featuring two equivalent ortho-methylbenzaldehyde units, we identify dimethyl­therephtalaldehydes (DMTAs) which can be activated in a dual wavelength-selective fashion. Under visible light and UV-light irradiation, DMTAs undergo two consecutive Diels–Alder reactions exhibiting near-quantitative endo-selectivity (>99%) and provide excellent yields (96–98%). The influence of the regioisomerism of the dialdehydes on their photochemical behavior is profound, evidenced by an in-depth investigation of their photochemical performance. We exemplify the capability of the photosystems via the synthesis of complex Diels–Alder adducts with various dienophiles, including alkynes.