Novel Synthesis of 2-thienylcarbonyl-cyclohexane-1,3-dione as Building Block for Indazolones and Isoxazolones

Abstract

A new synthetic methodology using ultrasonic treatment was applied to the C-acylation of 1,3-cyclohexanedione with thiophene-2-carbonyl chloride to afford 3-hydroxy-2-(2-thienylcarbonyl)cyclohex-2-en-1-one (5). This compound was used as a building block to prepare different bicyclic systems: tetrahydro-4H-indazol-4-ones (7a–c and 9a,b,d), and 6,7-dihydrobenzisoxazole (11) by reaction with different hydrazines and hydroxylamine, respectively. Structural elucidation of all compounds was thoroughly achieved by NMR spectroscopy.