High throughput one pot synthesis of 2-methylquinolines

Five new quinoline alkaloids from Sauropus hirsutus Beille and their cytotoxicity

Chemical investigation of the whole plant of Sauropus hirsutus Beille led to the isolation of eight quinolines and two known flavonoids. Furthermore, five quinolines were new, two were reported in plant for the first time and one was known. Cytotoxicity evaluation against cholangiocarcinoma, KKU-M156, showed that the most active compound was 4-hydroxy-6-methoxy-7,8-methylenedioxyquinaldine (IC₅₀ 20.54 ± 6.82 µM) which was a little more active than the cisplatin standard (IC₅₀ 24.39 ± 1.14 µM).

Structure-Activity Relationships of Styrylquinoline and Styrylquinoxaline Derivatives as α-Synuclein Imaging Probes

Synucleinopathies are characterized by the deposition of α-synuclein (α-syn) aggregates before the onset of clinical symptoms. Therefore, in vivo imaging of α-syn may contribute to early diagnosis of these diseases and has attracted much attention in recent years. However, no clinically useful probes have been reported. In the present study, 16 quinoline/quinoxaline derivatives with different styryl and fluorine groups were evaluated in order to develop α-syn imaging probes. Among them, SQ3, which is a quinoline analogue with a p-(dimethylamino)styryl group and fluoroethoxy group at the 2- and 7- positions of the skeleton, displayed moderate selectivity for α-syn aggregates over β-amyloid (Aβ) aggregates (K i = 230 nM), while maintaining high binding affinity for α-syn aggregates (K i = 39.3 nM). In a biodistribution study, [18F]SQ3 exhibited high uptake (2.08% ID/g at 2 min after intravenous injection) into a normal mouse brain. Taken together, we demonstrate that [18F]SQ3 has basic properties as a lead compound for the development of a useful α-syn imaging probe.

Green Approach for Visible-Light-Induced Direct Functionalization of 2-Methylquinolines

A transition metal- and oxidant-free visible light-photoinduced protocol for direct functionalization of 2-methylquinolines has been developed. This protocol enabled the C-H functionalization of substituted 2-methylquinolines with diacetyl or ethyl pyruvate, under environmentally friendly conditions. A mechanistic investigation based on density functional theory (DFT) calculations provided details about the origins of reactivity and selectivity.

Synthesis of substituted 2-alkylquinolines by visible-light photoredox catalysis

A simple and efficient protocol for the synthesis of substituted 2-alkylquinoline scaffolds was developed by employing visible-light photoredox catalysis.

Recent synthetic efforts in the preparation of 2-(3,4)-alkenyl (aryl) quinoline molecules towards anti-kinetoplastid agents

Leishmaniasis, Chagas disease and African sleeping sickness have been considered some of the most important tropical protozoan afflictions. As the number of drugs currently available to treat these human illnesses is severely limited and the majority has poor safety profiles and complicated administration schedules, actually there is an urgent need to develop new effective, safe and cost-effective drugs. Because quinoline alkaloids with antiprotozoal activity (quinine, chimanine, cryptolepine or huperzine groups) were historically and are still essential models for drug research to combat these parasitic infections, synthetic or semi-synthetic quinoline-based molecules are important for anti-kinetoplastid drug design approaches and synthetic methods of their preparation become a key task that is the central subject of this review. Its goal is to highlight the advances in the conventional and current syntheses of new 2-(3,4)-alkenyl (aryl) quinoline derivatives, which kill the most important kinetoplastid protozoa, – Leishmania and Trypanosoma and could be useful models for antileishmanial and antitrypanosomal research. An attempt has been made to present and discuss the more recent contributions in this field over the period 2015–2019, paying special attention to molecular design, synthetic efforts to new green reaction conditions for classical methods such as Skraup synthesis, Friedländer synthesis, Conrad–Limpach, Doebner–Miller, as well as contemporary methods like Gould–Jacobs, Meth–Cohn and Povarov reactions. This review includes brief general information on these neglected tropical diseases, their current chemotherapies, and primary natural models (quinoline alkaloids), suitable for development of anti-kinetoplastid quinoline-based agents. The main part of the review comprises critical discussion on the synthesis and chemistry of new quinolines diversely substituted by alkyl (alkenyl, aryl) fragments on the pyridine part of the quinoline skeleton, which could be considered interesting analogues of chimanine alkaloids. The methods described in this review were developed with the aim of overcoming the drawbacks of the traditional protocols using revolutionary precursors and strategies.

Leishmaniasis, Chagas disease and African sleeping sickness have been considered some of the most important tropical protozoan afflictions.

Assembly of Diversely Substituted Quinolines via Aerobic Oxidative Aromatization from Simple Alcohols and Anilines

An aerobic oxidative aromatization of simple aliphatic alcohols and anilines under the Pd(OAc)₂/2,4,6-Collidine/Brønsted acid catalytic system has been established, providing a direct approach for the preparation of diverse substituted quinoline derivatives in high yields with wide functional group tolerance. Practically, the protocol can be easily scaled up to gram-scale and was utilized in the concise formal synthesis of a promising herbicide candidate.

Oxidant-free synthesis of benzimidazoles from alcohols and aromatic diamines catalysed by new Ru(ii)-PNS(O) pincer complexes

A greener method for synthesizing 2-substituted benzimidazole through the acceptorless dehydrogenative condensation of alcohols and ortho-arylenediamine is developed.

A dual removable activating group enabled the Povarov reaction of N-arylalanine esters: synthesis of quinoline-4-carboxylate esters

A dual removable activating group enabled Povarov reaction of N-arylalanine esters was reported.

Palladium-catalyzed synthesis of polysubstituted quinolines from 2-amino aromatic ketones and alkynes

A palladium-catalyzed one-pot method for the synthesis of quinolines from commercial or readily available 2-amino aromatic ketones and alkynes is reported for the first time.