Photosensitized tetrahydropyran transfer

THP ethers were formed cleanly during photolysis of 3,4dihydro-2H-pyran, an alcohol, and catalytic 1,5-dichloro-9, 10-anthraqui none with use of visible light. The reaction could be conducted under ambient fluorescent lighting or with sunlight as well as in a Rayonet reactor. The scope and mechanism are discussed.