The Sensitized Photooxygenation of 2-Vinylbenzofurans

Abstract
The sensitized photooxygenation of benzofuran, 2-methylbenzofuran, and six 2-vinylbenzofurans was investigated. Benzofuran and 2-methylbenzofuran were stable toward singlet oxygen. On the other hand, the vinylbenzofurans were easily photooxygenated to give the 1,4-endoperoxides. The 1,4-cycloaddition of singlet oxygen to the 2-benzofurans was confirmed to proceed with stereospecificity.