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Synthesis Reference(s)

Chemical and Pharmaceutical Bulletin, 20, p. 876, 1972 DOI: 10.1248/cpb.20.876

Upstream product

• 607-34-1 5-nitroquinoline 
• 611-34-7 5-Aminoquinoline 
• 77738-77-3 5-(2-oxocyclopentacarboxamido)-1,2,3,4-tetrahydroquinoline 

Relevant academic research and scientific papers

Continuous and Selective Hydrogenation of Heterocyclic Nitroaromatics in a Micropacked Bed Reactor

The hydrogenation of heterocyclic nitroaromatics is of great importance in the pharmaceutical industry for the synthesis of key intermediates. However, high selectivity is difficult to achieve in conventional batch reactors owing to severe back mixing and poor mass transfer performance, resulting in the high requirement for subsequent separation processes. In this work, a continuous flow system based on a micropacked bed reactor is developed for the selective hydrogenation of heterocyclic nitroaromatics and the reductions of 5-nitroisoquinoline to 5-aminoisoquinoline and 5-amino-1,2,3,4-tetrahydroisoquinoline are selected as the model reactions. With the optimal reaction conditions, maximal yields of 99.9% (5-aminoisoquinoline) and 99.3% (5-amino-1,2,3,4-tetrahydroisoquinoline) are obtained successfully. Moreover, this system exhibits remarkable performance for the selective hydrogenation of relevant heterocyclic nitroaromatics with all yields beyond the level of 97.5%. The continuous flow system enables efficient hydrogenation of heterocyclic nitroaromatics and remarkable selectivity of target products with shorter reaction time and safer operation compared with batch reactors.

Design, synthesis, and biological evaluation of 5-aminotetrahydroquinoline-based LSD1 inhibitors acting on Asp375

The abnormal expression of lysine-specific histone demethylase 1 (LSD1) is associated with different cancer types, and LSD1?inhibitory activity seems to have high therapeutic potential in cancer treatment. Here, we report the design, synthesis, and biochemical evaluation of novel 5-aminotetrahydroquinoline-based LSD1 inhibitors. Among them, compounds A6, A8, B1–B5, and C4 showed preferable inhibitory effects on LSD1, with IC50 = 0.19–0.82 μM. Several potent compounds were selected to evaluate their antiproliferative activity on A549 cells and MCF-7 cells with a high expression of LSD1. The potential binding modes of the compounds were revealed through molecular docking to rationalize the potency of compounds toward LSD1. Our data recognized that the 5-aminotetrahydroquinoline scaffold may serve as a starting point for developing potent LSD1 inhibitors for cancer therapy.

Cu-Catalyzed Chemoselective Reduction of N-Heteroaromatics with NH3·BH3 in Aqueous Solution

An efficient catalytic system was successfully developed on reduction of N-heteroaromatics with H3N?BH3 as hydrogen source in CuSO4 solution, featuring excellent chemoselectivity as well as very broad functional group tolerance. Various challenging substrates, such as OH-, NH2-, Cl-, Br-, etc., contained quinolines, quinoxalines, 1,5-naphthyridines and quinazolines were all reduced smoothly. Mechanistic studies suggested that [Cu-H] intermediate might be generated from NH3?BH3, which was believed to form with H3N?BH3 in CuSO4 solution.

Boric acid catalyzed chemoselective reduction of quinolines

Boric acid promoted transfer hydrogenation of substituted quinolines to synthetically versatile 1,2,3,4-tetrahydroquinolines (1,2,3,4-THQs) was described under mild reaction conditions using a Hantzsch ester as a mild organic hydrogen source. This methodology is practical and efficient, where isolated yields are excellent and reducible functional groups are well tolerated in the N-heteroarene moiety. The reaction parameters and tentative mechanistic pathways are demonstrated by various control experiments and NMR studies. The present work can also be scaled up to obtain gram quantities and the utility of the developed process is illustrated by the transformation of 1,2,3,4-THQs into a series of biologically important molecules including the antiarrhythmic drug nicainoprol.

Metal-free Reduction of Nitro Aromatics to Amines with B 2 (OH) 4 /H 2 O

A metal-free reduction of nitro aromatics mediated by diboronic acid with water as both the hydrogen donor and solvent under mild conditions has been developed. A series of aromatic amines were obtained with good functional group tolerance and in good yields.

Boron-Catalyzed Hydrogenative Reduction of Substituted Quinolines to Tetrahydroquinolines with Hydrosilanes

A metal-free procedure for the hydrogenative reduction of substituted N-heteroaromatics has been developed by using hydrosilanes as reducing agents. The optimized conditions were successfully applied to the reactions of quinolines, quinoxalines, and quinoline N -oxides. They were also effective for the reduction of quinolines bearing amino or hydroxy groups, where H 2 was evolved through dehydrogenative silylation of the amine or hydroxy moieties. Preliminary mechanistic studies revealed that the initial step in the catalytic cycle involves 1,4-addition of the hydrosilane to the quinoline to give a 1,4-dihydroquinoline; this is followed by (transfer) hydrogenation to deliver the tetrahydroquinoline as the final product.

Rhodium catalyzed hydrogenation of quinolines and isoquinolines under water-gas shift conditions

Wide variety of quinolines and isoquinolines can be hydrogenated selectively in the nitrogen-containing ring by means of carbon monoxide and water in the presence of catalytic amount of rhodium carbonyl cluster. These reactions provide a useful method for the preparation of 1,2,3,4-tetrahydroquinolines and 1,2,3,4-tetrahydroisoquinolines which are key intermediates for the synthesis of isoquinoline alkaloids and other biologically active nitrogen compounds.

RHODIUM CATALYZED HYDROGENATION OF NITROGEN HETEROAROMATICS UNDER WATER GAS SHIFT CONDITIONS. SELECTIVE SYNTHESIS OF 1,2,3,4-TETRAHYDROQUINOLINES AND N-FORMYL-1,2,3,4-TETRAHYDROISOQUINOLINES

Quinolines and isoquinolines are hydrogenated selectively in the nitrogen-containing ring by means of carbon monoxide and water in the presence of catalytic amount of rhodium carbonyl cluster.