Primary, secondary, and tertiary alkyl radicals formed by the photocatalyzed oxidation of organosilicates underwent efficient carbonylation with carbon monoxide (CO) to give a variety of unsymmetrical ketones. This study introduces the possibility of radical carbonylation under a photooxidative regime.
of alkyl and acyl radicals onto electron-poor olefins or diisopropyl azodicarboxylate has been carried out on a multi-gram scale under continuous flow conditions. The process is based on the use of the inorganic photocatalyst tetrabutylammonium decatungstate (TBADT), which is capable to activate selectively a variety of CH bonds in different substrates, including aldehydes, amides, ethers and alkanes
已经在连续流动条件下以克为单位进行了一组烷基和酰基自由基在贫电子烯烃或偶氮二羧酸二异丙酯上的原子经济自由基共轭加成反应。该方法基于使用无机光催化剂四丁基癸二酸铵(TBADT),它能够选择性地活化不同底物(包括醛,酰胺,醚和烷烃)中的多种CH键。根据该程序已经合成了广泛的合成靶,包括1,4-双官能化的衍生物(例如1,4-二酮或酮酯)。所有反应均在中观条件下进行规模的流量光反应器,包括缠绕在水冷500 W中压汞蒸气灯周围的紫外线透明FEP管(氟化乙烯丙烯)的盘管。这种光化学设备的使用导致了停留时间的减少,相对于相应的批处理过程所测得的停留时间而言,STY(时空产率)和生产率值显着提高,通常会导致整体效率的提高。过程的可持续性(过程质量强度– PMI –值低至10 kg kg -1)。
Solar light-driven photocatalyzed alkylations. Chemistry on the window ledge
Tetrabutylammonium decatungstate photocatalysis is effective for the C–H activation of alkanes, aldehydes, ethers and amides and the alkylation of alkenes occurs effectively by merely exposing the solution to the sun in a glass vessel on a window ledge (up to 10 g per dm2 in a few days).
system has been exploited upon irradiation to catalyze C–H to C–Cbond conversion via the addition of hydrogen donors (ethers and aldehydes) onto Michael acceptors in a redox-neutral fashion without the need of any external oxidant. Laser flash photolysis experiments confirmed that the triplet excited state of the photocatalyst triggers the desired C–H cleavage.
Acylation of dimethyl maleate photocatalyzed by decatungstate anion: insights into the hydrogen atom transfer reaction mechanism
作者:Juan Pablo Martínez、Ernesto Rivera-Avalos、Sarai Vega-Rodríguez、Denisse de Loera
DOI:10.1007/s11164-017-3214-y
日期:2018.3
efficiently achieved when it is catalyzed by this polyoxometalate. Two reaction mechanisms have been formulated to account for the role of W10O324− in organic chemical reactions: the single electron transfer and the hydrogen atom transfer (HAT) mechanisms. In this contribution, the HAT pathway for the acylation of dimethylmaleate is experimentally and quantum-chemically explored in detail. Results based
多金属氧酸盐由于其多种性质和功能而成为有机化学领域的重要催化剂。基于实验证据和密度泛函理论(DFT)计算的最新进展提供了有价值的信息,可以使去离子重金属阴离子W 10 O 32 4−的化学脱神秘。特别是,当醛被该多金属氧酸盐催化时,可以通过均一的C–H键断裂来有效地实现醛的官能化。制定了两种反应机理来解释W 10 O 32 4−的作用在有机化学反应中:单电子转移和氢原子转移(HAT)机理。在这一贡献中,对马来酸二甲酯的酰化作用的HAT途径进行了实验和量子化学的详细研究。根据无限制形式主义下的DFT计算得出的结果表明,在W 10 O 32 4−的能量最低的三重态激发态形成后,酰化反应会在无障碍过程中发生。。这些结果与实验证据非常吻合,因为酰化的加合物的收率为90%。在这方面,诸如自由基偶联和脱羰基的副反应导致竞争力降低。因此,当前的工作可能有助于理解机械细节,即使在太阳辐射下,也可以合成由多金属氧酸盐光催化的有机化合物。