Sulfoxides from Substituted Allylic Systems

Another type of substitution reaction is increasing in popularity—the use of an allylic substrate, such as an allyl acetate where the nucleophile is introduced with stereochemical control in the presence of a palladium catalyst and a chiral ligand. Reactions where a chiral anion, be it derived from a chiral heteroatom group, such as a sulfoxide, or an auxiliary, such as Evans s oxazolidinones, are not included in this chapter because the alkyl halide is usually relatively simple and the stereochemical selectivity is derived from the system itself. 

Induction in the chirality transfer from C-l to C-3 overrides that of the chirality transfer from the sulfur atom to C-3. Therefore, the chirality at the heteroatom only has an impact on systems lacking a stereogenic center at C-l. The two diastereomeric transition states for the rearrangement of such chiral sulfoxides are designated as exo and endo"1. These lead to the different enantiomers of the allylic alcohol. Their energy difference, which depends mainly on the substitution of the double bond, determines the enantioselectivity of the process. 

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