Although natural sunlight-mediated photocatalysis is
a clean, efficient,
and green approach to access organic products, its application in
the synthesis of covalent organic frameworks (COFs), however, is still
unprecedented. Herein, we first report the sunlight photocatalytic
synthesis of COF under ambient conditions. Furthermore, this “window
ledge” reaction generated benzoxazole-linked COF is stable
and can be applied as a reusable photocatalyst to highly promote visible-light-driven
aerobic oxidation of sulfides to sulfoxides. These results not only
enrich the COF synthetic methodology but also open a new route to
access COFs in a green and sustainable way.
By using a catalytic amount of a porphyrin-based covalent organic framework (Por-Ad-COF) as the efficient recyclable photocatalyst, the photocatalytic oxidative [3 + 2] cycloaddition reaction between tetrahydroisoquinolines and N-substituted maleimides was developed under aerobic conditions at room temperature. Various substituted pyrrolo[2,1-a]isoquinolines were obtained in moderate to good yields via the dipolar [3 + 2] cycloaddition and oxidative aromatization cascade process under visible light irradiation. This was the first example to employ the covalent organic framework as the heterogeneous photocatalyst to perform the photocatalytic dipolar [3 + 2] cycloaddition reaction for the synthesis of pyrrolo[2,1a]isoquinolines.
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