A New and Efficient Method for the Preparation of 2,4,6,8-Tetraazabicyclo[3.3.0]octane-3,7-diones (Glycolurils) Catalyzed by Keggin, Wells-Dawson, and Preyssler Heteropolyoxometalates, Effect of Structure on the Reactivity

Some important cis- and trans-alkyl substituted glycolurils were prepared via condensation of vicinal dicarbonyl compounds with urea and/or methylurea catalyzed by 0.95 mol% of Keggin- type H3PW12O40 under environmentally benign and simple condition. Proficiency of structurally different heteropolyoxometalates, including Keggin, Wells-Dawson, and Preyssler, was investigated in the reaction of urea with 2, 3-butanedione. A common method was introduced for the isolation of cis- and trans-isomers, role of different solvents was studied, and effect of catalyst mol% was also investigated in this reported. Keywords: Condensation, diketone, glycoluril, heteropolyoxometalate, urea, molecular capsules, dimethylglycoluril, commodities, polyoxometalates, isomers