Allyl sulfones as precursors to allylzincs in the palladium-catalyzed zinc-ene cyclization: Highly efficient synthesis of enantiopure (-)-erythrodiene

[GRAPHICS] Easily prepared allyl phenyl sulfones, capable of introduction of the alkene by electrophilic alpha-substitution, are superior to allyl acetates as substrates for Pd-catalyzed Zn-ene cyclizations, providing C5 or C4N rings with cis-1,2-vinyl and -CH2Zn substituents. Several examples, with different methods of substrate preparation, are presented.