Arylideneisoxazole-5(4H)-One Synthesis by Organocatalytic Three-Component Hetero-Cyclization

Abstract

An expedient, green, practical, and vastly efficient three-component cyclo-condensation is catalyzed by triphenylphosphine. The 4-arylideneisoxazol-5(4H)-one heterocycles are generated in good to excellent isolated reaction yields. Experiments show that the best results were obtained using 15 mol% of the catalyst under aqueous conditions at room temperature. The sonochemical synthesis of 4-arylideneisoxazol-5(4H)-one derivatives were also performed by using 10 mol% of triphenylphosphine in water as an eco-friendly reaction medium. In the comparative method, ultrasonication showed shorter reaction times and also requires smaller amounts of catalyst. While aryl/heteroaryl aldehydes were used, the variation of β-keto-ester was also explored. The β-keto-esters (ethyl acetoacetate/ethyl 4-chloro-3-oxobutanoate/ethyl 3-oxohexanoate) under optimized reaction conditions reacted well and afforded the corresponding 4-arylideneisoxazol-5(4H)-ones in shorter reaction times. The approach is simple, approximately compatible with the pot-, atom-, and step-economy.

Keywords:

• Aryl/hetero aryl aldehyde
• green synthesis
• isoxazole-5(4H)-one
• triphenylphosphine
• ultrasonication
• water

Acknowledgements

We would to express our thankfulness to the Damghan University Research Council. The corresponding author would also like to thank Shahrekord University.

Disclosure statement

No potential conflict of interest was reported by the author(s).