Synthesis and application of P,olefin type axially chiral ligands with <i>sec</i>-alkyl groups

Abstract

We synthesized N-trans-cinnamyl-N-cyclohexylaniline type aminophosphine 2 and a series of N-2-adamantyl-N-trans-cinnamylaniline type aminophosphines 3. Although aminophosphine 2 failed to find the existence of axial chirality, aminophosphines 3, which exist in the axial chirality in a C(aryl)-N(amine) bond by chiral HPLC analysis as 1-adamantyl type chiral ligands 1. Enantiomeric isomers of 3b, 3c, and 3d were obtained in an enantiomerically pure form. We also identified the palladium-catalyzed asymmetric allylic substitution of 1,3-diphenyl-2-propenyl acetate with indoles using aminophosphines 3b-d as effective chiral ligands in high enantioselectivities (up to 96% ee).