Acid catalysed rearrangements of 1-hydroxy-2,3,4,4a-tetrahydro-9H-xanthen-9-ones: synthesis and cycloaddition reactions of 3,4-dihydro-9H-xanthen-9-ones
Abstract
The acid catalysed rearrangement of 1-hydroxy-2,3,4,4a-tetrahydro-9H-xanthen-9-ones can give 1-alkoxy- or 1-alkylidene-1,2,3,4-tetrahydro-9H-xanthen-9-ones and/or 3,4-dihydro-9H-xanthen-9-ones depending on the conditions employed. The last compounds undergo facile Diels–Alder cycloaddition reactions.