Kinetics and Mechanisms of Homogeneous Catalytic Reactions. Part 11. Regioselective Hydrogenation of Quinoline Catalyzed by Rhodium Systems Containing 1,2-Bis(diphenylphosphino)ethane

Abstract

The system prepared in situ by addition of two equivalents of 1,2-bis(diphenylphosphino)ethane (dppe) to Rh 2 Cl 2 (COE) 4 (COE = cyclooctene) showed to be an efficient and regioselective precatalyst for the hydrogenation of quinoline (Q). This reaction showed to be independent of the Q concentration and of fractional order on H 2 and catalyst concentrations (1.5 and 0.6, respectively). The fractional order on catalyst concentration indicates that several catalytic species with different activities are present in the reaction medium; however, the cationic species [Rh (dppe) 2 ] ? was the only phosphorous-containing compound detected by 31 P{ 1 H} NMR. For the acac salt of this cationic bis(dppe) complex, a kinetic study led to the rate law r = {K 1 k 2 /(1 ? K 1 [H 2 ])}[M][H 2 ] 2 ; [M(Q)(j 2 -dppe) (j 1 -dppe)] ? was proposed as the catalytically active species (CAS) of the cycle. The general mechanism involves a reversible oxidative addition of H 2 to generate a dihydrido complex, which transfers the hydride ligands to the coordinated Q to yield species containing a 1,2-dihydroquinoline (DHQ) ligand, followed by a second oxidative addition of H 2 , considered as the rate-determining step of the cycle; hydrogen transfer toward the DHQ ligand yields THQ, regenerates the CAS and restarts the catalytic cycle.

Nanolayered Cobalt–Molybdenum Sulfides as Highly Chemo- and Regioselective Catalysts for the Hydrogenation of Quinoline Derivatives

“…Catalytic hydrogenation of N -heteroarenes is a fundamentally important reaction in the petrochemical industry and represents a promising method for organic synthesis. , In particular, the hydrogenation of quinoline derivatives has drawn the attention of the synthetic chemists because of its practical simplicity and high atom efficiency for the production of 1,2,3,4-tetrahydroquinolines, a core structural motif present in many alkaloids and bioactive molecules used as drugs and agrochemicals . However, hydrogenation of these N -heteroarenes involves the challenging tasks of breaking aromaticity as well as overcoming catalyst poisoning by strong interaction with starting materials and their hydrogenated products. , Nonetheless, different homogeneous systems based on transition metals, such as Ir, Ru, , Rh, , Mo, Os, , Fe, and Co, have been applied for the hydrogenation of quinolines. Particularly worth mentioning, since it represents a suitable route to valuable N -heterocyclic compounds, is a well-defined homogeneous cobalt catalyst that allows the chemoselective hydrogenation of N -heteroarenes functionalized with other sensitive reducible groups (Scheme a). , However, despite the good reactivity and selectivity exhibited by some of these homogeneous catalysts, the use of air-sensitive and/or expensive ligands and additives as well as the inherent recyclability issues hinder their industrial-scale application.…”

Study on the Selective Hydrogenation of Quinoline Catalyzed by Composites of Metal-Organic Framework and Pt Nanoparticles※

“…在这些合成方 法中, 喹啉选择性加氢被认为是合成 THQ 最方便和最 有前途的方法. 喹啉的催化加氢反应通常使用均相贵金 属催化剂, 如 Rh [7] , Ir [8] , Os [9] 和 Ru [10] 等金属配合物分子. 这些均相贵金属催化剂在催化反应过程中表现出较高 的活性和选择性, 但是反应后均相催化剂的分离回收比 较困难 [11] .…”

Cobalt Encapsulated in N-Doped Graphene Layers: An Efficient and Stable Catalyst for Hydrogenation of Quinoline Compounds

“…Achieving the chemoselective hydrogenation of the pyridine ring without byproducts remains a challenging task. Many homogeneous metal catalysts, such as Rh, , Ir, , and Ru, have been applied in the transformation. Despite the high activity and selectivity, the difficulties in recovering the catalysts, ligand, and additives from the reaction mixtures limit the catalysts on an industrial scale.…”