As a green and sustainable alternative for producing ethyl pyruvate (EP), the selective aerobic oxidation of ethyl lactate (EL) is still facing issues such as low catalytic efficiency, harsh reaction conditions and catalyst instability. Herein, a novel crystalline vanadium-based coordination compound (VTC=VPTPYCl₂(H₂O), PTPY = 4′-phenyl-2,2′:6′,2′’-terpyridine) has been designed and synthesized. A highly efficient homogeneous catalytic system (VTC-400-O₂-CH₃CN, 400 represents the activation temperature) and a recyclable heterogeneous system (VTC-500-O₂-CH₃CN) for the liquid-phase conversion of EL to EP are developed using molecular oxygen as oxidant through activating VTC at different temperature. In VTC-400-O₂-CH₃CN system, EL can be completely converted within 4 h, and the yield of EP is 77.8 %, which outperforms the state-of-art reported catalytic system. Meanwhile, the heterogeneous VTC-500 catalyst can also promote the full conversion of EL within 4 h, and its activity remains basically unchanged after being used for 10 times. Structural characterization reveals that the soluble VTC breaks the weak coordination V-Cl bonds at a lower activation temperature of 400 ° C to expose more vanadium-based catalytic sites, but the framework of ligand remains intact. However, the organic derived carbon skeleton at higher temperature of 500 ° C can effectively confine the V-based active species and prevent the dissolution of the catalyst, which impels the transition of the homogeneous to heterogeneous catalytic system.

中文翻译：

---

受新型钒配合物调控的乳酸乙酯的均相和非均相选择性氧化


乳酸乙酯（EL）的选择性有氧氧化作为生产丙酮酸乙酯（EP）的绿色可持续替代品，仍面临催化效率低、反应条件恶劣、催化剂不稳定等问题。在此，设计并合成了一种新型结晶钒基配位化合物 （VTC=VPTPYCl₂（H₂O），PTPY = 4'-苯基-2,2'：6'，2''-三吡啶）。以分子氧为氧化剂，通过在不同温度下活化 VTC，开发了用于液相转化为 EL 的高效均相催化系统 （VTC-400-O_{2-CH 3}CN， 400 代表活化温度） 和用于液相转化为 EP 的可回收非均相系统 （VTC-500-O_{2-CH 3}CN）。在 VTC-400-O_{2-CH 3}CN 系统中，EL 可以在 4 小时内完全转化，EP 的产率为 77.8 %，优于最先进的已报道的催化系统。同时，非均相 VTC-500 催化剂也能在 4 h 内促进 EL 的完全转化，使用10 次后其活性基本保持不变。结构表征表明，可溶性 VTC 在 400 °C 的较低活化温度下打破了弱配位 V-Cl 键，暴露了更多的钒基催化位点，但配体框架保持完整。然而，有机衍生的碳骨架在 500°C 的较高温度下可以有效地限制 V 基活性物质并防止催化剂的溶解，从而推动均相催化体系向非均相催化体系的转变。