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

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

Journal Name: Current Organocatalysis

Volume 8 , Issue 2 , 2021


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Abstract:

Background: For the green synthesis of furocoumarins in water, PEG-OSO3H was used as a recyclable catalyst for the one-pot synthesis in water. To avoid the use of toxic lachrymators and unstable phenacyl bromides, we prepared them in-situ and directly condensed with 4-hydroxycoumarins.

Objective: PEG-OSO3H was 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 was found to be rapid, simple, eco-friendly and obtained relatively higher yield than other reported methods.

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

Results: It was observed that electrons withdrawing groups (-NO2,-F etc.) on the benzene ring of aromatic ketones increased the rate of reactions as well as the 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 at 3.94 ppm. The above spectral data confirmed the structure of the compound. The 13C NMR spectrum of 4b also showed the peaks of CH3, at 23.25 ppm.

Conclusion: PEG-OSO3H has been 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, eco-friendly and obtained relatively higher yield than other reported methods.

Keywords: PEG-OSO3H, ultrasound, one-pot, green catalyst, Furo[3, 2-c]coumarins, Cascade Synthesis.

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Article Details

VOLUME: 8
ISSUE: 2
Year: 2021
Published on: 05 July, 2020
Page: [217 - 222]
Pages: 6
DOI: 10.2174/2213337207999200706001142
Price: $25

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