1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 z Catalysis An Efficient Phosphotungstic Acid Catalysed Synthesis of 4,5-Dioxopyrrolidines and Study of the Mechanistic Effect of the Solvent on the Reaction Soumyadip Basu, [a] Tanushree Ghosh, [a] Suvendu Maity, [b] Prasanta Ghosh, [b] and Chhanda Mukhopadhyay* [a] An efficient protocol for the synthesis of dioxopyrrolidine scaffolds has been established using phosphotungstic acid as an effective catalyst in a multicomponent reaction of aromatic primary amines, dialkyl acetylene dicarboxylates and formaldehyde at room temperature in alcohol as a green solvent. In this methodology, the reactant solvent has an important part and is involved in the reaction mechanism to increase the versatility of the product. This protocol involves environment friendly, cost effective methodology with a comparatively simple reaction mechanism. Introduction Pyrrolidines, being biologically important heterocycles, exhibit antifungal, [1] antibacterial, [2] and most importantly anticancer [3] properties. Previous work that were reported [4] for the synthesis of dioxopyrrolidines, generally involved higher reaction tem- perature, longer time period or hazardous catalysts. In one of those examples, Das and his group synthesised dioxopyrroli- dines using HCl as catalyst. [4c] In addition, in another report, they synthesized the same products using I 2 . [4d] Again, in few reports, the exchange of the functional groups of the alkynoates with the solvents was observed whereas, in some cases, the solvent did not attach to the product. In both the reports of Das and his group, the solvent did not take part in the mechanism (Scheme 1). Although some previous work was done on the synthesis of this moiety, but the difference in the product formation concluded that detailed investigation of the mechanism of the reaction is yet to be disclosed. We studied the reaction in both possible ways, i. e. one in which chance of exchange of group and the other one where no exchange is observed. We have also tried various solvents and detected the effect of the solvent on the reaction. This study also increases the diversity of the synthesis of dioxopyrrolidines. In addition, we also explained the reaction mechanism in much simpler path than the previous reports. Generally, heteropoly acids are oxygen acids where oxygen atom connects heteroatomic and multiatomic molecules through bridging ligand. [5] These acids normally dissolve in small polar solvents like water, methanol, ethanol and acetone, [6] but remain undissolved in non polar or macro- molecular polar solvents. These acids have a very distinctive acidic property, and the acidity can be adapted according to the situation by altering the composition of the elements. [7] It has strong acidic and redox properties. It also offers advantages of stable structure, high-speed regeneration, easy loading, noncorrosive nature, high activity, easy modification and low pollution [8] and hence emerges as a type of enviro-friendly green catalyst. [9] Heteropoly acid exhibits high catalytic activity in various reactions in both liquid-solid and gas-solid systems. One of the most widely studied heteropoly acid is phospho- tungstic acid which has metal oxide as well as complex structures. [10] Phosphotungstic acid (PTA) also, has a distinctive “pseudo-liquid phase” nature, which allows reactions to be taken place in both on the surface as well as inside the catalyst. Phosphotungstic acid is strongly acidic in solids and in solutions too, and retains a firmed Keggin structure [11] in both the phases. Phosphotungstic acid has been used widely in both homogeneous and heterogeneous reactions [12] because of its strong catalytic activity, superior selectivity, low reducibility, thermal stability and usability in mild conditions. [13] For all these [a] S. Basu, T. Ghosh, Prof. C. Mukhopadhyay Department of Chemistry, University of Calcutta, 92 APC Road, Kolkata- 700009, India E-mail: cmukhop@yahoo.co.in [b] Dr. S. Maity, Dr. P. Ghosh Department of Chemistry, R. K. Mission Residential College, Narendrapur, Kolkata 700103, India Supporting information for this article is available on the WWW under https://doi.org/10.1002/slct.201901011 Scheme 1. Synthesis of 4,5-Dioxopyrrolidines. Full Papers DOI: 10.1002/slct.201901011 5763 ChemistrySelect 2019, 4, 5763 – 5767 © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim