Abstract
Microwave induced synthesis of new class of pyrano isoxazoline and isoxazole annulated chromones - an intramolecular nitrile oxide cycloaddition with tethered olefins and alkynes
Highlights
Chromone heterocyclic frameworks are privileged scaffolds widely occur in the natural products especially in plant kingdom.[1,2] Chromone derivatives extensively showed diverse biological activities[3,4,5,6,7,8] such as antiinflammatory, anti-viral, antioxidant, anti-tumor, anti-hypertensive and proved as Tyrosine kinase protein inhibitors
With a view to increase the yields of products 3a-h and to reduce reaction time compare to conventional method, we have performed intramolecular cycloaddition using ceric ammonium nitrate (CAN) (0.002 mol) as an oxidizing agent under microwave irradiation by taking substrate 2a as model compound and screened with various solvents
We obtained higher yields of products 3a-h and 5a-f in eco-friendly microwave irradiation compared to conventional heating
Summary
Chromone heterocyclic frameworks are privileged scaffolds widely occur in the natural products especially in plant kingdom.[1,2] Chromone derivatives extensively showed diverse biological activities[3,4,5,6,7,8] such as antiinflammatory, anti-viral, antioxidant, anti-tumor, anti-hypertensive and proved as Tyrosine kinase protein inhibitors. We report the synthesis of tetracyclic 6-6-6-5-membered pyrano isoxazoline/isoxazole annulated chromones by tandem intramolecular 1,3-dipolar cycloaddition of in situ generated nitrile oxides from alkene/alkyne tethered chromone aldoximes using conventional as well as microwave induced methods.
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