SCHEDULED MAINTENANCE
Convenient synthesis of substituted cyclopentenones via [3 + 2] annulation of allylidenetriphenylphosphorane with 1,2-diacylethylenes: application to synthesis of (±)-methyl dehydrojasmonate
Abstract
(3-Alkoxycarbonyl-2-ethoxyprop-2-enylidene)triphenylphosphoranes 1 and 2 undergo [3 + 2] annulation with 1,2-diacylethylenes 3 to give 2-ethoxycyclopentadienes 6 as mixtures of the 1,3- and 1,4-diene. The mixtures are conveniently converted upon mild acid treatment into cyclopentenones 7 in a single form. Annulation of phosphorane 1 with acylmethylenemalonates 10 affords cyclopenta-1,3-dienes 11 in a highly regioselective fashion, which are readily converted into substituted cyclopentenones 12 in excellent yields. Phosphorane 1 also undergoes annulation with 1,2-acylacetylene 14 to give the fulvene 15, which is transformed into the exomethylenecyclopentenone 16. Furthermore, an application of the annulation to the synthesis of (±)-methyl dehydrojasmonate is described.
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