Pt-Catalyzed selective oxidation of alcohols to aldehydes with hydrogen peroxide using continuous flow reactors
Pt-Catalyzed selective oxidation of alcohols to aldehydes with hydrogen peroxide using continuous flow reactors
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DOI：
10.1039/d0ob02213f
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发表时间：
2021-02-07
影响因子：
3.2
通讯作者：
Sato, Kazuhiko
中科院分区：
文献类型：
--
作者：
Kon, Yoshihiro;Nakashima, Takuya;Sato, Kazuhiko
醇氧化成醛是获得用于药物和生物活性化合物的有价值的精细化学品的强有力的反应途径。虽然许多氧化剂可以氧化醇，但只有少数过氧化氢氧化可以用于使用液-液两相流反应器以高产率连续合成醛，尽管有可能应用于安全和快速的多步合成。本文报道了由（E）-肉桂醇连续流合成（E）-肉桂醛的方法，采用Pt分散在SiO_2中的催化剂柱，通过过氧化氢的选择性氧化，反应5天以上，产率95%-98%，选择性99%。从氧化前后Pt表面的X射线光电子能谱测量发现，用于开发的选择性氧化的活性物种是零价Pt（0）。采用SiO2稀释的Pt黑作为催化剂，在最佳底物和H2 O2引入速率下保留Pt（0）物种，不仅提高了催化活性，而且在流动反应过程中保持了活性。使用流动反应器优化衬底与Pt和H2 O2的接触时间对于进行选择性氧化以防止催化H2 O2分解是重要的。
The oxidation of alcohols to aldehydes is a powerful reaction pathway for obtaining valuable fine chemicals used in pharmaceuticals and biologically active compounds. Although many oxidants can oxidize alcohols, only a few hydrogen peroxide oxidations can be employed to continuously synthesize aldehydes in high yields using a liquid-liquid two-phase flow reactor, despite the possibility of the application toward a safe and rapid multi-step synthesis. We herein report the continuous flow synthesis of (E)-cinnamaldehyde from (E)-cinnamyl alcohol in 95%-98% yields with 99% selectivity for over 5 days by the selective oxidation of hydrogen peroxide using a catalyst column in which Pt is dispersed in SiO2. The active species for the developed selective oxidation is found to be zero-valent Pt(0) from the X-ray photoelectron spectroscopy measurements of the Pt surface before and after the oxidation. Using Pt black diluted with SiO2 as a catalyst to retain the Pt(0) species with the optimal substrate and H2O2 introduction rate not only enhances the catalytic activity but also maintains the activity during the flow reaction. Optimizing the contact time of the substrate with Pt and H2O2 using a flow reactor is important to proceed with the selective oxidation to prevent the catalytic H2O2 decomposition.