Regio- and Enantioselective Pd-Catalyzed Allylic Amination of Monosubsti­tuted Allylic Substrates with BocNHOMe

Abstract

A new type of N-nucleophile has been developed in Pd-catalyzed asymmetric allylic amination with monosubstituted allyl substrates, affording corresponding branched allyl amines in high regio- and enantioselectivities. Either OMe or Boc group in products can be removed easily to provide primary amine derivatives with the optical purity unchanged.

Key words

palladium - allylic amination - catalysis - regioselectivity - enantioselectivity

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12

General Procedure for the Allylic Amination
To a flame-dried Schlenk tube were added [Pd(C₃H₅)Cl]₂ (1.8 mg, 0.005 mmol), ligand (R,R)-L1 (6.4 mg, 0.010 mmol), and CH₂Cl₂ (2.0 mL) under Ar at r.t. The solution was allowed to stir for 5 min before ester 1 (0.2 mmol), MeONHBoc (44 mg, 0.3 mmol), and K₃PO₄ (63 mg, 0.3 mmol) were added. The reaction was allowed to stir at r.t. and monitored by TLC until the disappearance of the ester 1. The reaction mixture was passed through a short plug of kieselgur eluted with CH₂Cl₂. The solvent was removed under reduced pressure. The crude residue [after ^¹H NMR analysis to check the regioisomeric ratio (3/4)] was purified by flash chromatography (FC) with EtOAc-PE as the eluent (generally, the two regioisomers could be separated by FC) to afford the compound 3.