Preparation of NH-Pyrazoleacetic Acid Anilides from Trilithiated Acetoacetanilide, Select Aromatic Esters, and Hydrazine

摘要

Acetoacetanilide was trilithiated with excess lithium diisopropylamide to form a reactive trianion-type intermediate. This was followed by a regioselective Claisen-type condensation of the trilithiated intermediate with a variety of aromatic esters to afford new C-acylated intermediates, 3,5-diketopentane-carboxanilides, that were not isolated but immediately condensed-cyclized with hydrazine to afford the NH-pyrazoleacetanilides, 5-aryl-1H-pyrazole-3-acetanilides, before these C-acylated intermediates had an opportunity to rearrange to anilino-pyranones, 4-anilino-6-aryl-2H-pyran-2-ones.