Regiospecific generation and application of 3-lithiomethyl-2-methyl-1-phenylpyrazolin-5-one as 1,3-binucloephile in aromatic annelation: A novel approach for synthesis of 1,2-disubstituted indazolones and their condensed analogs

Article abstract of DOI:10.1016/0040-4020(95)00650-W

The enolate anion 5A generated by deprotonation of 2,3-dimethyl-1-phenylpyrazolin-5-one is shown to undergo highly regioselective γ-1,4-addition to α-oxoketene dithioacetals followed by cycloaromatization in the presence of boron trifluoride etherate to afford wide range of novel substituted and condensed indazolones in good yields.