Dealkylation Of Alkyl Aryl Ethers And Its Application To Degradation Of Lignin Model Compounds

Non-food based lignocellulosic biomass is an important renewable feedstock for the production of chemicals, fuels and energy. Although it is considered an intractable useless by-product of the paper and pulp industries. Lignin, a key component (15-30%by weight,40%by energy) of lignocellulose, is an complex biopolymer composed of mainly methoxy substituted phenolic subunits. Because of its highly functionalised and bulky structure, lignin has been considered a key difficulty to its use as renewable feedstock. Some heterogeneous catalysis methods were developed in the recent past. However these usually require higher reaction temperatures. There are also several reported homogeneous promising catalytic processes for both reductive or oxidative lignin depolymerizations by Ru, V, Co, Cu, Fe, Ni, Re, two-step redox-neutral method. Their studies focus on the cleavage of P-aryl ethers, foremost of lignin’s β-O-4linkage, which is comprising around50-60%of native lignin.Recently, we have developed an efficient method for the dealkylation of aryl alkyl ethers under mild reaction conditions. The reaction is highly selective, dealkylating only one of the methyl groups in polymethylated aryl ether system. This highly selective dealkylative method is applied to the synthesis of a few advanced intermediates for drug synthesis. On the other hand, it can be used as an effective method to cleavage the β-O-4-ether bond of lignin model compounds. Detailed mechanistic studies have shown that this reaction probably proceeded via a single-electron transfer process.