Mechanochemical Conversion of (5-5')-(β-O-4) Type of Lignin Model Compound

As a lignin model compound having a biphenyl structure, (5-5')-(β-O-4) type of Compound [I] was synthesized and treated mechanically to find out the reaction mechanisms. Mechanical treatments of Compound [I] with a CBM (ceramic ball mill) in air furnished four products, but those of VBM (vibration ball mill) in air or nitrogen afforded six products, respectively, as shown in Table 1 and Fig. 2. Among the products, the corresponding p-carbonyl phenol _??_ was obtained in the highest yields. Differently from the cases of syringylglycerol-β-guaiacyl ether shown in the previous report, treatments of Compound [I] with both CBM and VBM resulted in much lower yields of the products. The reason for this was ascribed to the presence of a large hydrophobic trityl ether group bound to the sterically hindered biphenyl group via the methylene bridge.