Diastereoselective α-alkylation of 2-acyl-3-phenyl-l-menthopyrazoles

Article abstract of DOI:10.1021/jo00104a045

N-Acylpyrazoles were α-alkylated in good yields by the treatment with alkyl halides after metalation with LDA or LiHMDS. In the case of chiral N-acylpyrazoles, e.g., 2-acyl-3-phenyl-l-menthopyrazoles (4), the α-alkylation was highly diastereoselective. The subsequent α-alkylation products could be converted into esters in good yield in the presence of BF₃·OEt₂ without the loss of the optical purity.