Zhang Zhenlei, Guo Ge, Yang Huaizhou, Csechala Lina, Wang Zhiwen, Cziegler Clemens, Zijlstra Douwe S, Lahive Ciaran W, Zhang Xiangping, Bornscheuer Uwe T, Deuss Peter J
State Key Laboratory of Heavy Oil Processing, College of Chemical Engineering and Environment, China University of Petroleum (Beijing), 102249, Beijing, China.
Department of Chemical Engineering (ENTEG), University of Groningen, Nijenborgh 4, 9747 AG, Groningen, The Netherlands.
Angew Chem Int Ed Engl. 2024 Dec 2;63(49):e202410382. doi: 10.1002/anie.202410382. Epub 2024 Nov 2.
Aromatic monomers obtained by selective depolymerization of the lignin β-O-4 motif are typically phenolic and contain (oxygenated) alkyl substitutions. This work reveals the potential of a one-pot catalytic lignin β-O-4 depolymerization cascade strategy that yields a uniform set of methoxylated aromatics without alkyl side-chains. This cascade consists of the selective acceptorless dehydrogenation of the γ-hydroxy group, a subsequent retro-aldol reaction that cleaves the C-C bond, followed by in situ acceptorless decarbonylation of the formed aldehydes. This three-step cascade reaction, catalyzed by an iridium(I)-BINAP complex, resulted in 75 % selectivity for 1,2-dimethoxybenzene from G-type lignin dimers, alongside syngas (CO : H≈1.4 : 1). Applying this method to a synthetic G-type polymer, 11 wt % 1,2-dimethoxybenzene was obtained. This versatile compound can be easily transformed into 3,4-dimethoxyphenol, a valuable precursor for pharmaceutical synthesis, through an enzymatic catalytic approach. Moreover, the hydrodeoxygenation potential of 1,2-dimethoxybenzene offers a pathway to produce valuable cyclohexane or benzene derivatives, presenting enticing opportunities for sustainable chemical transformations without the necessity for phenolic mixture upgrading via dealkylation.
通过木质素β-O-4基序的选择性解聚获得的芳香族单体通常为酚类且含有（氧化的）烷基取代基。这项工作揭示了一锅法催化木质素β-O-4解聚级联策略的潜力，该策略可产生一组不含烷基侧链的均匀甲氧基化芳烃。该级联反应包括γ-羟基的选择性无受体脱氢、随后切断C-C键的逆羟醛反应，接着是所形成醛的原位无受体脱羰反应。由铱（I）-联萘酚（BINAP）配合物催化的这三步级联反应，从G型木质素二聚体中得到了75%的1,2-二甲氧基苯选择性，同时还生成了合成气（CO∶H≈1.4∶1）。将该方法应用于合成的G型聚合物，得到了11 wt%的1,2-二甲氧基苯。这种多功能化合物可以通过酶催化方法轻松转化为3,4-二甲氧基苯酚，这是药物合成中有价值的前体。此外，1,2-二甲氧基苯的加氢脱氧潜力为生产有价值的环己烷或苯衍生物提供了一条途径，为可持续化学转化提供了诱人的机会，而无需通过脱烷基对酚类混合物进行升级。
