Photolysis of cyclobutanones in the presence of acetic acid produced 2-acetoxy-5-alkoxytetrahydrofurans regiospecifically and with retention of configuration at the migrating α-position. The acetoxy group was replaced by nucleophiles such as allylsilane, trimethylsilyl azide, diethylaluminum cyanide, and silylated thymine in the presence of Lewis acids.

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Photochemical Ring Expansion of α-Alkoxycyclobutanones to 2-Acetoxy-5-alkoxytetrahydrofurans: Nucleophilic Reactions at the 2-Position.-Irradiation of cyclobutanones in the presence of nucleophiles results in efficient ring expansion to tetrahydrofurans, with retention of configuration of all resident stereocenters, but with no stereoselectivity at the newly formed stereogenic center. The tetrahydrofurans smoothly undergo substitution with a variety of nucleophiles at the 2-position. -(UMBRICHT, G.; HELLMAN, M. D.; HEGEDUS, L. S.; J. Org. Chem. 63 (1998) 15, 5173-5178; Dep. Chem., Colo. State Univ., Fort Collins, CO 80523, USA; EN)