Enantioselective Halo-oxy- and Halo-azacyclizations Induced by Chiral Amidophosphate Catalysts and Halo-Lewis Acids

Catalytic enantioselective halocyclization
of 2-alkenylphenols
and enamides have been achieved through the use of chiral amidophosphate
catalysts and halo-Lewis acids. Density functional theory calculations
suggested that the Lewis basicity of the catalyst played an important
role in the reactivity and enantioselectivity. The resulting chiral
halogenated chromans can be transformed to α-Tocopherol, α-Tocotrienol,
Daedalin A and Englitazone in short steps. Furthermore, a halogenated
product with an unsaturated side chain may provide polycyclic adducts
under radical cyclization conditions.