An eco‐friendly and facile three‐component reaction for the synthesis of 2‐amino‐4H‐pyran and tetrahydrobenzo[b]pyran derivatives is established using agro‐waste based Water Extract of Muskmelon Fruit Shell Ash (WEMFSA) as a catalyst. The present method offers several advantages such as efficient, mild reaction condition, simple product isolation and economic approach at room temperature in the absence of an external base or ligand/catalyst/additives. Thus, this approach is a very good alternative to existing protocols, because of non‐hazardous catalyst and mild condition use. Muskmelon fruit dried shells underwent thermal treatment followed by deionised water soak gave WEMFSA catalytic media. It is notable that, this method is found to be clean and high yielding target product isolation using simple filtration after reaction mixture dilution with water and analytical pure form was obtained after recrystallization with absolute ethanol. The synthesized products are characterized using various spectroscopic methods such as FT‐IR, 1H‐, 13C‐NMR and mass spectrometry techniques.

Development of alternative method that use environmentally benign solvents and biodegradable, non-toxic chemical alternative to pollution and toxic chemicals for the organic reaction are emerging in recent years as a green protocol in organic synthesis [1]. Recently, use of agro waste stuff [2] as chemical surrogates has become one of the most emerging in research endeavours for organic chemists. Researchers also reported several agro waste stuff extracted were employed for many organic syntheses and observed successful alternative replacement of many toxic and environmentally causing solvent. Some of the recent reported extracts are water extract of papaya bark ash (WEPBA) [3], water extract of banana peel ash (WEBPA) [4], water extract of rice straw ash (WERSA) [5], etc. These sustainable technologies protect environment and human health by an economically safer approach. It focuses pollution free, environmentally friendly design on production and use of alternative chemical solvent in economical feasibility. However, use of solvent remain a constant source of concern in organic synthesis as it gives toxic and hazardous in storing and waste solvent disposal issues. Solvents are still preferred on account of their easy separation and evaporation, which helps in extraction and separation of many compound which are thermally sensitive reactants. Therefore, in recent years the chemical synthesis based solvent free or neat condition [6] is the best alternative for these issues, as the replace of toxic solvent to simple water extract makes a protocol green.

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Background: Present chemists are more interested to develop eco-friendly, simple, efficient and economic approach methods as an important tool for many synthetic transformations, which employ various natural feedstock extracts, which are well known for their non-hazardousness, no usage of any external base and replace many organic and inorganic based catalysts. At present literature reported so many homogenous catalytic approaches, which follow green chemistry principle established for various organic transformations catalyzed by WERSA, BFE, WEPPA, WEMFSA, WEMPA, Eichhorniacrassipes. 2-aryl benzimidazole derivatives represents as prominent molecules with wide variety of applications showed in biological activities and in material science. In the present study, an agro-waste sourced catalytic media Banana Peel Ash Extract (BPAE) established for the green method synthesis of 2-aryl benzimidazole derivatives at chromatographically pure form promoted by ultrasound at room temperature condition is described. BPAE stands as a low cost, abundantly available, natural feedstock extract. Selected derivatives were screened for the antimicrobial studies and showed comparable activity to the reference drug used. Methods: The agro-waste sourced from banana peel is utilized for the preparation of BPAE catalyst, which is employed for the synthesis of 2-aryl benzimidazole derivatives under ultrasound waves at room temperature. Results: 2-aryl benzimidazoles obtained through reaction of substituted o-phenylene diamine with substituted benzoyl choride catalyzed by BPAE under ultrasound waves at room temperature. BPAE catalyst is characterized by flame emission spectrometry, SEM-EDX and XRD techniques. Conclusion: An eco-friendly, sustainable and novel approach for the synthesis of 2-aryl benzimidazoles using natural feedstock BPAE. The major merits of using BPAE are agro-waste derived catalyst, abundant availability, faster reaction, simple work-up and no usage of column chromatography.

Background: Amide bond plays a key role in medicinal chemistry, and the analysis of bioactive molecular database revealed that the carboxamide group appears in more than 25% of the existing database drugs. Typically amide bonds are formed from the union of carboxylic acid and amine; however, the product formation does not occur spontaneously. Several synthetic methods have been reported for amide bond formation in literature. Present work demonstrated simple and eco-friendly amide bond formation using carboxylic acid and primary amines through in situ generation of O-acylurea. The reaction was found to be more efficient, faster reaction rate; simple work-up gave pure compound isolation in moderate to excellent yield using microwave irradiation as compared to conventional heating. Methods: Developed one-pot synthesis of amide compounds using agro-waste derived greener catalyst under microwave irradiation. Results: Twenty amide bond containing organic compounds are synthesized from carboxylic acid with primary amine catalyzed by agro-waste derived medium under microwave irradiation. First, the reaction involved carboxylic acid activation using EDC.HCl, which is the required base for the neutralization and coupling. The method employed natural agro-waste derived from banana peel ash (WEB) for the coupling gave target amide product without the use of an external organic or inorganic base. Conclusion: In the present work, we demonstrated that agro-waste extract is an alternative greener catalytic medium for the condensation of organic carboxylic acid and primary amine under microwave irradiation. The method found several advantages compared to reported methods like solventfree, non-toxic, cheaper catalyst, and simple reaction condition. The final isolated product achieved chromatographically pure by simple recrystallization and did not require further purification.