Advances in the reduction of quinolines to 1,2,3,4‐tetrahydroquinolines

Abstract

The pursuit of modern sustainable chemistry has stimulated the development of innovative catalytic processes that enable chemical transformations to be performed under mild and clean conditions with high efficiency. Herein, we report that the hydrogenation of heteroaromatic compounds is one of the most efficient methods for the construction of heterocyclic skeletons, and only a few promising progress has been achieved. Transition metal‐catalyzed, a countless number of transition metals include have been used toward the development of homo/heterogeneous hydrogenation of quinolines via the most convenient route (Direct Hydrogenation) to obtain the corresponding tetrahydroquinoline derivatives.

Chemoselective Quinoline and Isoquinoline Reduction by Energy Transfer Catalysis Enabled Hydrogen Atom Transfer

“…In 2019, Baran and co‐workers demonstrated an elegant electrochemical Birch reduction protocol with high efficiency and broad scope, but only one quinoline example was shown with 40 % yield [4b] . In contrast, mild quinoline and isoquinoline reduction protocols with borane, silane or Hantzsch ester exhibit high generality and good functional‐group compatibility, although the dearomative reduction typically takes place on the pyridine ring [17a–c] . Regioselective reduction of the benzenoid ring in (iso)quinolines has remained challenging and elusive, and to access it to provide new Birch‐type products would be of great interest to the synthetic community.…”

Electrostatically tuned phenols: a scalable organocatalyst for transfer hydrogenation and tandem reductive alkylation of N-heteroarenes

“…[27][28][29][30] Nevertheless, signicant effort has been devoted to improve the reactivity prole of N-arenes such as quinoline for its selective partial hydrogenation to access 1,2,3,4-tetrahydroquinoline (THQ) derivatives. [31][32][33][34][35][36][37][38][39] In pioneering work, Rueping and co-workers reported the organocatalytic reduction of N-arenes with a biomimetic reductant, HE, and also successfully extended the strategy to an asymmetric version using a chiral phosphoric acid catalyst. [40][41][42] Subsequently, diverse catalytic systems have been explored for the transfer hydrogenation reaction of quinolines.…”

Designing New Magnesium Pincer Complexes for Catalytic Hydrogenation of Imines and N-Heteroarenes: H2 and N–H Activation by Metal–Ligand Cooperation as Key Steps

“…In the specific area of hydrogenation, the reduction of imines by H 2 offers an atom-economic approach to access amines (linear and cyclic) . Although various catalysts based on FLPs and sustainable metals ,,,,,,,, have been developed to avoid using expensive and toxic metals, examples of using early main-group metals are scarce. ,, In 2018, Harder’s group reported the first successful example of hydrogenation of imines catalyzed by alkaline earth and alkali metal amides via a metal hydride mechanism .…”