Due to its potential as a method for late-stage functionalization of complex organic molecules, catalytic CHA is considered as a “holy grail” in chemistry. The objective of this study is to evaluate catalytic CHA of biorefinery lignin by using transition metal complexes to produce high value molecules and to contribute to the expansion of lignocellulosic biorefinery industry for the production of both fuels and chemicals. We have examined both Ru and Pd catalysts under a range of conditions to understand the influence of different factors on the functionalization of several lignin models. The effect of different lignin model’s substituents and ligation sites (i.e. methoxy groups, phenolic oxygens), on the yield and selectivity of the functionalized products has been analyzed. Direct CHA of aromatic ketones with the Murai catalyst [RuH2(CO)(PPh3)3] introduces new functional groups at the ortho-C-H bond via Ru-coordination to the directing group at the ortho-position. The stabilizing interaction of the arene π-system with the transition metal and the formation of a strong aryl-metal bond facilitates the activation of such bonds, which usually have low reactivity. As a result, high yield is achieved when acetophenone is functionalized with triethoxyvinylsilane. We have found that free-OH groups appear to interfere with the reaction—4′-hydroxyacetophenone fails to react. Methoxy groups, by contrast, do not interfere with the conversion of p-anisaldehyde to the olefinated product (74% yield). Similar results were found when methyl substitituents were present. The expansion of a sustainable fuel and chemical industry based on lignocellulosic biomass will not be possible without the development of biorefineries that make an efficient use of all the biomass constituents including lignin. This work will show that CHA has the potential to contribute to the production of high value chemicals by using the lignin stream from the biorefinery industry.

Biorefinery lignin valorization through carbon-hydrogen activation (CHA) using transition-metal catalysts

256th National Meeting (2018)

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