14. Visible Light Uncaging of Proline

Abstract

Caged organic molecules provide an opportunity to selectively switch certain reaction pathways on and off. These compounds have a photochemical protecting group that renders the compound inactive. By exposing these compounds to light, one can uncage the compound by removing the protecting group and thus “turn on” these pathways. Proline is an organocatalyst, which has many uses in C-C/C-X bond formation and C-H bond activation. Caged proline was previously synthesized with 4-carboxy-5,7-dinitroindolinyl (CDNI), a photocleavable protecting group, which was shown to work well at short wavelengths. By using a functionalized coumarin system, one can shift the absorbance to the visible light region, increasing the synthetic usefulness of these caged organocatalysts.