Iridium-catalysed primary alcohol oxidation and hydrogen shuttling for the depolymerisation of lignin,Green Chemistry

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Iridium-catalysed primary alcohol oxidation and hydrogen shuttling for the depolymerisation of lignin
Green Chemistry ( IF 9.3 ) Pub Date : 2018-06-18 , DOI: 10.1039/c8gc01366g
Christopher S. Lancefield _{1,

2,

3,

4,

5} , Lucas W. Teunissen _{1,

2,

3,

4,

5} , Bert M. Weckhuysen _{1,

2,

3,

4,

5} , Pieter C. A. Bruijnincx _{1,

2,

3,

4,

5}

Affiliation

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 (C_α–C_β) 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.

中文翻译：

铱催化的伯醇氧化和氢穿梭用于木质素解聚

木质素是用于生产芳香族化学品的潜在丰富的可再生资源，但是其选择性解聚具有挑战性。在这里，我们报告了一种在基本条件下，基于Cp * Ir-联吡啶鎓催化剂配合物的选择性β-O-4伯醇脱氢，将木质素解聚为新型，非酚类单芳族化合物的新型催化体系。我们表明，这种系统能够促进模型化合物和分离的木质素的解聚的经由选择性伯醇脱氢，复古羟醛（C的序列_α -C _β）键断裂和原位通过将（脱）氢转移为醇和羧酸来稳定醛产品。发现该方法对于醚化和游离酚木质素模型化合物均具有优异的裂解产物收率，并且可以应用于真正的木质素以产生包括二醇和二酸在内的一系列新型非酚类单体。我们还显示，通过在收敛的一锅法中使用相同的催化剂，这些产物可以选择性地引导至单一的二酸产物，从而得到更简单的产物混合物。

更新日期：2018-07-16

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