Study On The Cleavage Of β-O-4Lignin Model Compounds In Homogeneous Ru-catalysis

Biomaterial, compared with fossil energy, has its unique advantage, and has at-tracted more and more attention worldwide. As the second abundant component only to cellulose in all sorts of herbaceous plants, lignin, on the one hand, has restricted the full utilization of other important components such as cellulose and hemicellulose, on the other hand, the residue of which is a waste of energy and pollutant to environment. Therefore, it is a problem faced by the scientists to find a way of efficiently degrading the lignin in order to exploit it as fully as possible. Among all kinds of different link units in lignin structure, β-O-4linkage is the most important one, the efficient method of cleaving which could be a crucial factor that plays the role in lignin degradation. How-ever, there are only limited reports concerning β-O-4cleavage. Therefore, the research in mechanistic level is much more important than research in practical level. Homo-geneous catalysis, a common method used in organic chemistry, is promising in lignin research because of its high-efficiency; the lignin model compounds are also crucial in lignin research owing to its simplicity in structure, which could facilitate the analysis.The2-aryloxy-l-arylethanols with different substitution pattern are consigned to the research. This study mainly introduces the methods to synthesize model com-pounds with β-O-4linkage, and their conversions catalyzed by different kinds of ruthe-nium complex. The promotive effect of KOH in the reaction is proposed. The ex-periment includes the cleavage of β-O-4linkage in2-aryloxy-l-arylethanols catalyzed by RuHCl(CO)(PPh-3)3and KOH in toluene. Through optimization of reaction, we found that KOH is much more efficient than other organic or inorganic base such as KOtBu, NaOH, K2CO3and NEt3, and the side reactions appear at the late stage of reaction under the influence of excessive KOH. At the same time, we explored the in-fluence of different substitution pattern from2-aryloxy-l-arylethanols under optimized condition (2.5mol%RuHCl(CO)(PPh3)3and50mol%KOH). After thorough study of our data and other relevant research, a reasonable mechanism is proposed.