Synthesis of Optically Active Spirocycles by a Sequence of Decarboxylative Asymmetric Allylic Alkylation and Heck Reaction

Optically active spirocycles were prepared in a sequence of two palladium-catalyzed reactions. In the first step, racemic α-(<i>ortho</i>-iodophenyl)-β-oxo allyl esters were submitted to the palladium-catalyzed decarboxylative asymmetric allylic alkylation reaction, furnishing the α-allylated products with a quaternary stereocenter with good yields and enantioselectivities. Subsequently, these intermediate products were converted in a Heck reaction yielding the spirocyclic structures as a mixture of <i>exo</i>- and <i>endo</i>-cyclic regioisomers. These mixtures could be isomerized with an acidic ion-exchange resin to give the <i>endo</i>-products with quantitative yield and selectivity. The target structure of this study could be further submitted to Friedel-Crafts reactions with electron-rich aromatic compounds.