1,8-Diazabicyclo [5.4.0] undec-7-ene functionalized cellulose nanofibers as an efficient and reusable nanocatalyst for the synthesis of tetraketones in aqueous medium

1,8-Diazabicyclo [5.4.0] undec-7-ene functionalized cellulose nanofibers (CNF@DBU[Cl]) were simply prepared and characterized by analytical techniques. Scanning electron microscope confirmed that CNF@DBU[Cl] was formed with average size of 30-60 nm. X-ray diffraction of CNF@DBU[Cl] showed that the crystalline structure of the cellulose nanofibers was remained unchanged after functionalization. According to elemental analyses and thermal gravimetric analysis, the loading amount of organic group on cellulose nanofibers was found to be 1.46 mmol/g. The catalytic activity of DBU functionalized cellulose nanofibers was studied for the synthesis of biologically important tetraketone derivatives in the reaction of aldehydes with 1,3-dicarbonyl compounds. In the presence of CNF@DBU[Cl], the corresponding tetraketones were obtained in 80-96% yields under very mild reaction conditions. The catalyst was recovered and reused four successive runs without significant loss of catalytic activity. This method showed several significant advantages including short reaction times, high yields of products, use of various substrates, convenient work-up, no necessity of extraction or chromatographic purification steps, environmentally friendly conditions and lack of use of any harmful solvent. [GRAPHICS] .