Palladium-catalyzed asymmetric allylic substitution with indoles using a chiral ligand 3b, which have fewer hindered substituents such as secondary alkyl groups than 1-adamantyl group, gave desired products (R)-9 with high enantioselectivities (up to 96% ee).
We synthesized a series of phosphine–olefin-type chiral aminophosphines, and we confirmed that these each exists as two rotamers at the C(aryl)–N(amine) bond. We also investigated the ability of these aminophosphines to act as chiral ligands for Pd-catalyzed asymmetric allylic substitution reactions, such as the alkylation of allylic acetates with malonates or indoles, and we found they gave high enantioselectivities (up to 98% ee).
We designed and synthesized a series of N,N-disubstituted allylic amine type aminophosphines 2, 3 and 4, which are derivatives of chiral ligands 1. Aminophosphines 2-4 (except 2a) exist in C(aryl)-N(amine) bond axial chirality by chiral HPLC analysis. Both enantiomeric isomers of 4b were successfully obtained in an enantiomerically pure form. We demonstrated that 1a, 1b, and 4b can be used as effective chiral ligands for the palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate with malonates in high enantioselectivities (up to 90% ee).
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