N-Acylpyrazoles were alpha-alkylated in good yields by the treatment w
ith alkyl halides after metalation with LDA or LiHMDS, In the case of
chiral N-acylpyrazoles, e.g., 2-acyl-3-phenyl-l-menthopyrazoles (4), t
he alpha-alkylation was highly diastereoselective. The subsequent alph
a-alkylation products could be converted into esters in good yield in
the presence of BF3.OEt(2) without the loss of the optical purity.