Unique features of chiral palladium enolates derived from β-ketoamide: structure and catalytic asymmetric Michael and fluorination reactions

Abstract

We have previously reported enantioselective reactions of 1,3-diketones and β-ketoesters with various electrophiles catalyzed by chiral Pd complex, in which chiral Pd enolates play a key role. Here, we present a detailed examination of Pd-catalyzed enantioselective Michael addition and fluorination reactions of β-ketoamides. β-Ketoamide showed higher reactivity than 1,3-diketone and β-ketoester, though its α-proton is likely to be least acidic. Pd enolate formation of β-ketoamide was much faster than that of β-ketoester. The crystal structures of (R)-BINAP-Pd-diketone and ketoamide complexes were found to be quite distinct. Pd-diketone complex has bidentate square-planar geometry as have been predicted before, whereas Pd-ketoamide complex was greatly distorted, probably due to steric constraints of the amide bond.