Synthesis of novel urushiol-like compounds from tung oil using silica-supported phosphotungstic heteropoly acid catalyst

Tung oil, a kind of natural plant oil, has recently received increasing attention due to its high value of research and application. In this study, we report a facile approach to synthesize novel urushiollike compounds (CAT-ME) starting from tung oil using silica-supported phosphotungstic heteropoly acid (PW/SiO2) as an effective and recyclable catalyst. To be specific, firstly, eleostearic acid glyceride, the main component of tung oil, is reacted with methanol by trans-esterification to obtain methyl eleostearate. And then Friedel-Crafts alkylation reaction of methyl eleostearate with catechol is carried out in the presence of a solid acid catalyst PW/SiO2 And the CAT-ME productive rate is about 69.3%. Furthermore, the chemical structures of the target compound CAT-ME are characterized by Fourier transform infrared spectroscopy (FTIR), ultraviolet and visible spectrophotometer (UV-vis), proton nuclear magnetic resonance spectra (1H NMR), carbon nuclear magnetic resonance spectra (13C NMR) and mass spectra. The characterization results show the designed alkylation products similar to urushiol have been synthesized successfully. Noting that urushiol (the major component of raw lacquer) can be cured by UV irradiation under air atmosphere without any photoinitiator. Thus, this present study develops a promising approach to guide the further modifications of tung oil and other unsaturated natural oils, which can improve the functional properties and expand the application fields of unsaturated natural plant oils by introducing new UV curing system. (C) 2016 Elsevier B.V. All rights reserved.