Chiral π-Cu(II) Catalysts for the Enantioselective α-Amination of N-Acyl-3,5-dimethylpyrazoles

We report the highly enantioselective alpha-amination of N- acyl-3,5-dimethylpyrazoles with dialkyl azodicarboxylates, catalyzed by in situ generated pi-Cu(II) complexes that consist of Cu(OTf)2 and N- (5H-dibenzo[a,d][7]annulen-5-yl)-L-alanine-derived amides, to give the corresponding products as D-alpha-amino acid derivatives (up to >99% yield and 99% ee). The site-selectivity and enantioselectivity can be satisfactorily explained by the coordination of dialkyl azodicarboxylate with pi-Cu(II) complex. The synthetic potential of this one-pot transformation to the alpha-amino ester is also described.

Automated summary

A highly enantioselective alpha-amination reaction is reported, where N-acyl-3,5-dimethylpyrazoles react with dialkyl azodicarboxylates catalyzed by in situ generated pi-Cu(II) complexes. The corresponding D-alpha-amino acid derivatives are obtained with high yield and enantiopurity.