Base catalysed rearrangements of 4-hydroxyphenyl allyl ethers: syntheses of alliodorin and alliodorol

Abstract

The 4-hydroxyphenyl allyl ethers 1a–e in refluxing aqueous methanol in the presence of KOH and oxygen furnish 2-substituted 1,4-dihydroxybenzene derivatives; products 2a,b and 3c are derived via base catalysed Claisen rearrangement, whereas presence of 3′-substitution on the allylic moiety disfavours this pathway, leading to formation of products 4b–c, consistent with the operation of base catalysed tandem [2,3]- and Cope rearrangements; this latter process has been applied to the total synthesis of alliodorin and alliodorol, constituents of the heartwood of Cordia alliodora.