A novel photorearrangement of (coumarin-4-yl)methyl phenyl ethers
In the present study, we describe synthesis and photochemical behaviour of the coumarinylmethyl phenyl ethers 1 and 6–10. Irradiation of the compounds in polar solvents leads to o-, p- and m-hydroxybenzyl substituted coumarins as main products. A side reaction is the photosolvolysis of the ethers that gives the (coumarin-4-yl)methyl alcohol and the corresponding phenol. Detailed studies of the quantum yields and product distributions upon irradiation of 6 as a function of the solvents are indicative of a dominant role of an ionic pathway in photochemical conversions. The found photochemical rearrangement is a useful tool for the preparation of hydroxylated 4-benzylcoumarins. A series of such compounds have been synthesised.
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 208, Issues 2–3, 15 December 2009, Pages 171–179