The SN2' displacement of allylic trichloroacetimidates mediated by the palladium(II) complex [COP-OAc]2 is a useful method for the asymmetric synthesis of chiral branched allylic esters. A wide range of (Z)-allylic trichloroacetimidates can be converted to allylic esters in high enantiomeric excess (86�99%) and yield (60�98%). Evaluation of isotopically labeled substrates identified that the reaction takes place with antarafacial SN2' geometry. The trichloroacetimidate functional group is proposed to serve as a chelating template for enantioinduction. DFT studies (B3-LYP/def2-TZVP) provide evidence for bidentate substrate-bound intermediates that react via anti-oxypalladation/syn-deoxypalladation as the preferred pathway. On the basis of these calculations, a model for enantioinduction has been developed.

Investigation of the scope and mechanism of the palladium-catalyzed synthesis of enantioenriched allylic esters from prochiral (<i>Z</i>)-allylic alcohols

240th National Meeting (2010)

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Investigation of the scope and mechanism of the palladium-catalyzed synthesis of enantioenriched allylic esters from prochiral (Z)-allylic alcohols