Understanding the mechanism of Pd-catalyzed allylic substitution of the cyclic difluorinated carbonates

We present a mechanistic investigation of Pd-catalyzed allylic substitution of cyclic gem-difluorinated carbonates 1 and 4, previously employed in the synthesis of 3',3'-difluoro-2'-hydroxymethyl-4',5'-unsaturated carbocyclic nucleosides in 17 steps. The substitution features a reversal of regioselectivity caused by fluorine.