Palladium-catalyzed asymmetric arylation of 2,3-dihydrofuran: 1,8-Bis(dimethylamino)naphthalene as an efficient base

Reaction of 2,3-dihydrofuran with aryl triflate (1) in the presence of a base and a palladium catalyst, generated in situ from Pd(OAc)2 and (R)-BINAP, gave (R)-2-aryl-2,3-dihydrofuran (2) and a small amount of (S)-2-aryl-2,5-dihydrofuran (3). The enantiomeric purity of major product 2 was strongly affected by the base. 1,8-Bis(dimethylamino)naphthalene (proton sponge) as a highly basic and sterically demanding amine gave (R)-2 in high enantioselectivities ( > 96-87% ee) for a variety of aryl triflates.