Formation of 4-hydroxy-3-(oxan-3-yl)coumarin from photochemical reaction between 4-hydroxycoumarin and 3,4-dihydro-2H-pyran and MO analysis

摘要

Photochemical reaction of 4-hydroxycoumarin with 3,4-dihydro-2H-pyran gave 4-hydroxy-3-(oxan-3-yl)coumarin whose formation was explained by considering a hydrogen shift and Successive keto-enol isomerization from a head-tail biradical intermediate (A). The reaction mechanism was confirmed by molecular orbital analysis to he induced by intermolecular hydrogen bonding between the 4-OH and pyran oxygen at the transition state.