Environmentally Benign PEG-OSO3H-Catalysed Ultrasound Promoted Cascade Synthesis of Furocoumarins in Water

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Author(s): Devendra S. Wagare*, Mujahed Shaikh, Dinesh Lingampalle, Ayesha Durrani

Journal Name: Current Organocatalysis

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Abstract:

Background: Green synthesis of furocoumarins in water, PEG-OSO3H used as a recyclable catalyst for the one-pot syntheis in water. avoid used of toxic, lachrymatric and unstablephenacyl bromides instead of that we prepared it in-situ and directly condence with 4-hydroxycoumarins.

Objective: PEG-OSO3H found to be an efficient and reusable catalyst for the microwave irradiated one-pot synthesis of 3- Aryl-furo[3,2-c]coumarins in PEG-water as a greener reaction medium. This method found to be rapid, simple, ecofriendly and yield obtained relatively higher than other reported methods.

Methods: Aromatic ketones (5 mmol), NBS (5mmol) was added in solution of PEG-OSO3H (10 mol%) in 10 ml water and irradiated under ultrasound at 80-85°C. then solution of 4-hydroxycoumarin (5 mmol) and solution of acetic acid and ammonium acetate (1 ml) were added into it. Reaction mass was further irradiated for 3 min. The reaction mixture was extracted with ethyl acetate (3 x 10ml) and the combined ethyl acetate phase was concentrated under reduced pressure to obtain corresponding 3-Aryl-furo[3,2-c]coumarins. Aqueous layer was reused for the next reactions.

Results: It was observed that electrons withdrawing groups (-NO2,-F etc.) on benzene ring of aromatic ketones increases the rate of reactions as well as yield of the products. The IR spectrum of compound 4a showed prominent peaks at 1737cm-1C=O stretching for lactone, 1H NMR of compound 4c showed characteristic singlets for –CH3 of methoxy group of at 3.94 ppm, The above spectral data confirmed the structure of compound. The 13C NMR spectrum of 4b also shows the peaks of CH3, at 23.25 ppm.

Conclusion: PEG-OSO3H found to be an efficient and reusable catalyst for the microwave irradiated one-pot synthesis of 3-Aryl-furo[3,2-c]coumarins in PEG-water as a greener reaction medium. This method found to be rapid, simple, ecofriendly and yield obtained relatively higher than other reported methods.

Keywords: PEG-OSO3H, Ultrasound, one-pot, Green catalyst, Furo[3, 2-c]coumarins.

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(E-pub Ahead of Print)
DOI: 10.2174/2213337207999200706001142
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