Sigmatropic rearrangement of 3-(aryloxymethyl)coumarins: a simple synthesis of hydroxylated 3-benzylcoumarins

Abstract

3-Aryloxymethyl[1]benzopyran-2-ones 3a–e, when heated in diphenyl ether for 4 h, gave high yields of hydroxylated 3-benzyl[1]benzopyran-2-ones 4a–e, whereas 3-[(ortho-substituted)aryloxymethyl][1] benzopyran -2- ones 3a, e in refluxing quinoline furnished 4-(hydroxyphenyl)-3-methyl[1]benzopyran-2-ones 7a, e in 60–62% yield, these products being expected from [3,3]sigmatropic rearrangement, together with compounds 4a, e in 35% yield. Compounds 3b–d on refluxing in quinoline furnished exclusively the hydroxylated 3-benzylcoumarins 4b–d.