amidophosphine ligand 5 bearing two bulky substituents, 2,4,6-trimethylphenylmethyl or 2,4,6-triisopropylphenylmethyl groups, on the pyrrolidine ring was improved by employing the borane-THF reduction of the lactam-alcohol intermediate 8. The resulting amino alcohol was selectively acylated to give an amide-alcohol 11, which was then converted to the chloride 12 in 55-73% yields by the treatment with
Two types of external, chiral amidophosphine ligands, 1–5, were prepared. Examination of their behavior in an asymmetric conjugateaddition reaction of organocuprate revealed the possibility for steric tuning to realize high selectivity.
prolines (1a–h) has been developed and tested as organocatalysts in the direct catalytic asymmetric aldolreaction of several aliphatic ketones with aldehydes. Catalyst 1g affords the best enantioselectivities for this transformation. The reaction was carried out in DMF using a catalyst loading of 10 mol % at −10 °C to give the aldol products in up to 97 % ee for acetone. In the cases of cyclohexanone