Type II photoreactions of α-alkyl β-oxoesters. Neighboring group effect on 1,4-biradical reactions and effective internal filter effect by the type II photoproduct
The α-alkyl β-oxoesters 1 undergo typeIIphotoreactions. The process of back hydrogen transfer in the 1,4-biradical intermediate to revert to the starting ester is suppressed because of the intramolecular hydrogen bonding between the hydroxyl and carboalkoxyl groups in the biradical intermediate. The hydrogen bonding determines the stereochemistry of 1,4-biradical cyclization. The cyclobutanols having