No abstract

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. J. Heterocyclic Chem., 2010.

A variety of substituted spiro(benzoisothiazole-pyrazoles) have been prepared by the condensation of dilithiated C(a),N-carboalkoxyhydrazones with lithiated methyl 2-(aminosulfonyl)benzoate followed by the cyclization of intermediates with acetic anhydride, which also resulted in spiro N-acetylated products when carbomethoxyhydrazones or carboethoxyhydrazones were used, and spiro NH products when carbo-tert-butoxyhydrazones were used.

Deprotonation of 1-benzoylacetone with excess lithium hexamethyldisilazide (LHMDS) or lithium diisopropylamide (LDA) resulted in a dilithium dianion-type intermediate, which underwent a Claisen-type condensation with substituted aromatic esters or an isatoic anhydride to afford unsymmetrical 1,3,5-pentanetriones or a cyclized heterocyclic product when the C-acylated intermediates contained a select ortho-substituted phenacyl pendant group. Spectral data indicated that a particular tautomer, a (1Z,4Z)-1-(4-aryl)-1,5-dihydroxy-5-phenylpenta-1,4-dien-3-one, resulted upon recrystallization of the linear products. Condensation−cyclization of the dianion-type intermediate with methyl thiosalicylate resulted in a phenacyl benzoheterocyclic thiopyranone and with 5-chloroisatoic anhydride in a phenacyl quinolinone. X-ray crystal analysis of several products afforded additional proof of structure, especially regarding which tautomer was isolated.

No abstract