ASYMMETRIC CYCLIZATION OF 3,4-DIHYDRO-2-VINYL-2H-1,4-BENZOXAZINE CATALYZED BY PALLADIUM-BHMP CATALYST

The reaction of 1,4-diacetoxy-cis-2-butene 20 with 2-(benzylamino)phen ol 3 in THF in the presence of Et(3)N and a catalytic amount of Pd(0)- BHMP-beta-Ala Ic gave optically active 4-benzyl-2-vinylbenzoxazine of up to 56.2%ee. The reaction of (Z)-2-butene-1,4-diylbis(methylcarbonat e) 2b instead of 20 with 2-(benzylamino)phenol 3, 4 was obtained with e.e. up to 71.4%. We could improve the enantioselectivity of (R)-4 by introducing a carboxyl group at the terminal position of the pendant s ide chain on the bisphosphine ligand and by using a methyl carbonate e ster 2b instead of diacetate 2a.