β‐Isocupreidine‐Catalyzed Asymmetric Baylis—Hillman Reaction of Imines.

Abstract

Enantioselective syntheses Enantioselective syntheses O 0031β-Isocupreidine-Catalyzed Asymmetric Baylis-Hillman Reaction of Imines. -The title reaction of imines (I) as well as N-benzoyl, N-mesyl, and N-tosyl analogues of (Ia), with activated alkene (II) gives (S)-enriched N-protected-α-methylene-β-amino acid esters. The highest enantioselectivities are obtained with (I). In contrast to the corresponding aldehydes which afford (R)-selectivity as was previously reported, the imines show opposite enantioselectivity. The synthetic utility of this method is demonstrated by conversion of product (IIIa) into β-lactam (V). -(KAWAHARA, S.; NAKANO, A.; ESUMI, T.; IWABUCHI, Y.; HATAKEYAMA*, S.; Org. Lett. 5 (2003) 17, 3103-3105; Grad. Sch. Biomed. Sci., Nagasaki Univ., Nagasaki 852, Japan; Eng.) -Klein 52-035

Privileged chiral catalysts in asymmetric Morita-Baylis-Hillman/aza-Morita-Baylis-Hillman reaction

“…Remarkably, the aza-MBH adducts in all cases have the opposite absolute configuration of the adducts derived from aldehydes. Hatakeyama and co-workers [28] explained this reversal by assuming that the steric hindrance around the imine nitrogen center governs the rate of elimination that leads to the preferential formation of one enantiomer.…”

“…The catalyst 4 was also adopted by Hatakeyama and co-workers [28] in an enantioselective aza-MBH reaction of HFIPA with N-phosphinoyl imines. In this case, enantioselectivities were less impressive (54% 73% ee, Scheme 7); nevertheless, nearly enantiopure products were obtained in satisfactory yields after one recrystallization.…”