20730-75-0Relevant academic research and scientific papers
Iridium-catalysed primary alcohol oxidation and hydrogen shuttling for the depolymerisation of lignin
Lancefield, Christopher S.,Teunissen, Lucas W.,Weckhuysen, Bert M.,Bruijnincx, Pieter C. A.
, p. 3214 - 3221 (2018/07/31)
Lignin is a potentially abundant renewable resource for the production of aromatic chemicals, however its selective depolymerisation is challenging. Here, we report a new catalytic system for the depolymerisation of lignin to novel, non-phenolic monoaromatic products based on the selective β-O-4 primary alcohol dehydrogenation with a Cp?Ir-bipyridonate catalyst complex under basic conditions. We show that this system is capable of promoting the depolymerisation of model compounds and isolated lignins via a sequence of selective primary alcohol dehydrogenation, retro-aldol (Cα-Cβ) bond cleavage and in situ stabilisation of the aldehyde products by transfer (de)hydrogenation to alcohols and carboxylic acids. This method was found to give good to excellent yields of cleavage products with both etherified and free-phenolic lignin model compounds and could be applied to real lignin to generate a range of novel non-phenolic monomers including diols and di-acids. We additionally show, by using the same catalyst in a convergent, one-pot procedure, that these products can be selectively channelled towards a single di-acid product, giving much simpler product mixtures as a result.
The incorporation of 3,4-dichloroaniline, a pesticide metabolite, into dehydrogenation polymers of coniferyl alcohol (DHPs)
Brunow, Goesta,Raiskila, Sanni,Sipilae, Jussi
, p. 1338 - 1342 (2007/10/03)
A mechanism by which pesticide metabolites may become incorporated into plant lignins has been studied with the aid of 3,4-dichloroaniline (DCA) and lignin model compounds. DCA was found to react rapidly with a quinone methide representing an intermediate in lignin biosynthesis. The resulting benzylamine group was stable to mild acidolysis under simulated stomach conditions. Addition of DCA to dehydrogenative polymerizations of coniferyl alcohol yielded DHPs containing covalently bonded DCA. NMR spectroscopy showed that the DCA had become bonded to the benzylic position in arylglycerol-β-guaiacyl ether structures. The majority of these structures were phenolic. This observation and the fact that the DCA accumulates in the low molecular weight fraction of the DHP indicates that the DCA functions as a trap for quinone methides and stops the further growth of the polymer. Acta Chemica Scandinavica 1998.
