Boron halide catalysed regioselective ortho-Claisen rearrangements of 4′-allyloxycoumaric acid derivatives: total synthesis of demethylsuberosin
Abstract
6-Allyl-7-hydroxycoumarin 3 and the naturally occurring linear coumarin, demethylsuberosin (7-hydroxy-6-prenylcoumarin)7 have been prepared in goods yields via regioselective boron halide catalysed ortho-Claisen rearrangements. This procedure provides an efficient alternative approach to linear substituted coumarins without using a halogen to block the 8-(angular) position.