Catalytic asymmetric arylation of olefins

Abstract

Catalytic asymmetric arylation of 2,3-dihydrofuran with aryl triflate (1) in benzene at 40 °C in the presence of a base and a palladium catalyst, generated in situ from Pd(OAc)2 and (R)-BINAP gave optically active (R )-2-aryl-2,3-dihydrofuran (2) and a small amount of (S)-2-aryl-2,5-dihydrofuran (3). The relative ratio of 2 to 3 and the enantiomeric purities of the products were dependent upon the base employed. l,8-Bis(dimethylamino)naphthalene (proton sponge) as a highly basic and sterically demanding amine gave major product (R)-2 in extremely high enantioselectivity (>96-87% ee) for a variety of aryl trifiates. The mechanism of this novel catalytic asymmetric reaction is discussed in detail. © 1992 IUPAC