Photochemical Synthesis of 4-Oxobutanal Acetals and of 2-Hydroxycyclobutanone Ketals.

Irradiation of α,β-unsaturated ketones (aliphatic, both open chain and cyclic as well as aryl substituted) in 1,3-dioxolane in the presence of a sensitizer (benzophenone or anthraquinone) led to 4-oxobutanal acetals in fair to excellent yield through a very simple procedure (workup in most cases by bulb-to-bulb distillation). The resulting acetals were irradiated to give 2-hydroxycyclobutanone ketals, again through a simple procedure that gave a good yield with open-chain aliphatic derivatives.