AbstractAlcohol groups and β‐O‐4 (C−C) linkages are widespread in biomass feedstock that are abundant renewable resource for value‐added chemicals. The development of sustainable protocols for direct oxidation or oxidative cleavage of feedstock materials in a controlled fashion, using open air as an oxidant is an intellectually stimulating task to produce industrially important value‐added carbonyls. Further, the oxidative depolymerization of lignin into fine chemicals has evoked interest in recent times. Herein, we report the first example of a catalyst system that could activate molecular oxygen from atmospheric air for controlled oxidation and oxidative cleavage/depolymerization of feedstock materials such as alcohols, β‐O‐4 (C−C) linkages and real lignin in water under open air conditions. The selectivity of carbonyl products is controlled by altering the pH between ~7.0 and ~12.0. The current strategy highlights the non‐involvement of any external co‐catalyst, oxidant, radical additives, and/or destructive organic solvents. The catalyst shows a wide substrate scope and eminent functional group tolerance. The upscaled multigram synthesis using an inexpensive catalyst and easily available oxidant evidences the practical utility of the developed protocol. A plausible mechanism has been proposed with the help of a few controlled experiments, and kinetic and computational studies.
摘要 醇基和 β-O-4 (C-C) 链广泛存在于生物质原料中,它们是丰富的可再生增值化学品资源。利用露天空气作为氧化剂,以可控方式开发原料材料的直接氧化或氧化裂解的可持续方案,是生产具有重要工业价值的羰基化合物的一项具有启发性的任务。此外,将木质素氧化解聚成精细化学品近来也引起了人们的兴趣。在此,我们报告了首个催化剂系统实例,该催化剂系统可激活大气中的分子氧,在露天条件下对醇类、β-O-4(C-C)连接和水中真正的木质素等原料进行受控氧化和氧化裂解/解聚。羰基产物的选择性可通过在 ~7.0 和 ~12.0 之间改变 pH 值来控制。目前的策略突出了不使用任何外部助催化剂、氧化剂、自由基添加剂和/或破坏性有机溶剂的特点。该催化剂具有广泛的底物范围和出色的官能团耐受性。使用廉价的催化剂和易于获得的氧化剂进行多克级合成,证明了所开发方案的实用性。在一些对照实验、动力学和计算研究的帮助下,我们提出了一种合理的机制。