A Carbometallation-Intramolecular Cycloaddition Strategy for the AB-Taxane Ring and an Enone Accelerated Cope Rearrangement to Bicyclo[2.2.2]octanones

All articles of this category The one pot transformation of the magnesium chelates, derived from alkynyl alcohols, into tetraene-diols for the construction of substituted bicyclo[5.3.1]undecenes is described. This sequence affords a direct route to the AB-taxane ring system via a Lewis acid catalyzed intramolecular Diels-Alder reaction. The cycloaddition gives a single diastereomer due to the preferential formation of the Et 2 AlCl chelate. This adduct undergoes a facile enone accelerated Cope rearrangement to generate a substituted bicyclo[2.2.2]octanone. This isomerization fails below 110 °C when the ketone is absent. Cope - synthesis - Diels-Alder - taxoid - magnesium - propargyl