Regioselective Synthesis of 3-Bromoquinoline Derivatives and Diastereoselective Synthesis of Tetrahydroquinolines via Acid-Promoted Rearrangement of Arylmethyl Azides

Unveiling Route for the Synthesis of Tröger's Bases Through Azide Rearrangement

This study introduces a novel method for producing Tröger's bases by utilizing the rearrangement chemistry of benzyl azide. This method offers a convenient and adaptable pathway for synthesizing these important molecular structures with potential for further advancements. By reacting benzyl azide derivatives with TfOH under the presence of water, this process generates iminium ion, formaldehyde, and aniline intermediates in situ. Notably, this conversion is reversible under acidic conditions, allowing for the regeneration of the iminium ion and ultimately leading to the formation of the desired Tröger's base product. Additionally, this method could decrease the risk of exposure to an excess amount of formaldehyde.

Fluorine-Assisted Rearrangement of Geminal Azidofluorides to Imidoyl Fluorides

Organoazide rearrangement constitutes versatile synthetic strategies but typically requires an extremely strong acid and/or a high reaction temperature. Our group recently discovered the remarkable accelerating effect of the geminal fluorine substituent that enables the facile rearrangement of azides into imidoyl fluorides without the aid of acid under much milder reaction conditions. The role of geminal fluorine was elucidated by both experimental and computational investigations. This new reactivity led to the development of a practical one-step tandem preparative method for potentially useful and bench-stable imidoyl fluorides from a wide range of structurally diverse geminal chlorofluorides. Our additional efforts to expand the reaction scope regarding the migrating group, halogen, and carbonyl function are described, and the synthetic utility of the imidoyl fluoride products was demonstrated in hopes of promoting the use of this under-appreciated functional group in the synthetic organic community.

HFIP-Empowered One-Pot Synthesis of C4-Aryl-Substituted Tetrahydroquinolines with Propargylic Chlorides and Anilines

Transition-metal-free, practical one-pot synthesis of C4-aryl-substituted tetrahydroquinolines from simple anilines and readily accessible propargylic chlorides has been developed. Activation of the C-Cl bond by 1,1,1,3,3,3-hexafluoroisopropanol turned out to be the key interaction, which allowed C-N bond formation under an acidic medium. Propargylated aniline is formed as an intermediate via propargylation, and subsequential cyclization and reduction gave 4-arylated tetrahydroquinolines. To demonstrate the synthetic utility, total syntheses of aflaquinolone F and I have been accomplished.

Synthesis of α-Ketoimidoyl Fluorides via Geminal Fluorine-Promoted Azide Rearrangement

Despite the promising synthetic potential, the utilization of imidoyl fluorides has been hampered by the lack of broadly applicable preparative methods. Herein, bench-stable α-ketoimidoyl fluorides were synthesized from geminal chlorofluorides through tandem azidation/rearrangement under mild conditions. The efficiency was consistently high, regardless of the steric and electronic environments. The synthetic utility of the α-ketoimidoyl fluoride was also demonstrated. Furthermore, the remarkable accelerating effect of the geminal fluorine substituent was identified and rationalized by density functional theory calculation.

Synthesis of Benzoazepine Derivatives via Azide Rearrangement and Evaluation of Their Antianxiety Activities

A new synthetic method for the construction of benzoazepine analogues has been developed employing ortho-arylmethylbenzyl azide derivatives as precursors using an azide rearrangement reaction. In this work, 14 benzoazepine compounds were successfully synthesized in moderate to excellent yields. All synthetic benzoazepines were evaluated for their cytotoxicity against normal human kidney cell line (HEK cell). The results showed that compound 18c had the lowest cytotoxicity (IC₅₀ = 65.68 μM) among tested compounds, which was comparable with the antianxiety drug diazepam (IC₅₀ = 87.90 μM). Based on the cytotoxicity results, five benzoazepine analogues (compounds 18c, 18h, 18j, 18n, and 18p) were selected to determine the antianxiety effect on stressed rats using elevated plus maze (EPM) and open field test (OFT) methods. Interestingly, compound 18c showed better anxiolytic activity than diazepam without a sedative effect by showing superior hyperlocomotor activity. Therefore, this discovery could pave the way for drug development to treat patients with anxiety disorder.

Visible-Light-Induced Synthesis of 1,2,3,4-Tetrahydroquinolines through Formal [4+2] Cycloaddition of Acyclic α,β-Unsaturated Amides and Imides with N,N-Dialkylanilines

1,2,3,4-Tetrahydroquinolines should be applicable to the development of new pharmaceutical agents. A facile synthesis of 1,2,3,4-tetrahydroquinolines that is achieved by a photoinduced formal [4+2] cycloaddition reaction of acyclic α,β-unsaturated amides and imides with N,N-dialkylanilines under visible-light irradiation, in which a new Ir^III complex photosensitizer, a thiourea, and an oxidant act cooperatively in promoting the reaction, is reported. The photoreaction enables the synthesis of a wide variety of 1,2,3,4-tetrahydroquinolines, while controlling the trans/cis diastereoselectivity (>99:1) and constructing contiguous stereogenic centers. A chemoselective cleavage of an acyclic imide auxiliary is demonstrated.

Au-Catalyzed intermolecular (3 + 2 + 1) and (5 + 2) cycloaddition for the synthesis of 1,4-dioxenes and 4,7-dihydrooxepines

1,4-Dioxenes and 4,7-dihydrooxepines present interesting potential as motifs for the incorporation of biologically relevant molecules, agrochemicals and materials. In this study, two efficient intermolecular (3 + 2 + 1) and (5 + 2) cycloadditions for the synthesis of 1,4-dioxenes and 4,7-dihydrooxepines are achieved with gold catalysis.

Decision making for promising quinoline-based anticancer agents through combined methodology

During the development of effective drugs for the treatment of cancer, one of the most important tasks is to identify effective drug candidates having maximum antiproliferation and minimum side effects. This paper considers the problem of selecting the most promising anticancer agents, showing inhibition at low IC50 concentration and low releasing lactate dehydrogenase percentage (cytotoxicity). Recently, we prepared quinoline analogs bearing different functional groups and determined their anticancer potential against the HeLa, C6, and HT29 cancer cell lines using different anticancer assays. Experimentally, seven quinoline derivatives consisting of different substituents were determined as promising anticancer agents. We propose a multicriteria recommendation method to identify the most promising anticancer agents against all tested cell lines with an accurate prediction algorithm according to the available input data. A multicriteria decision-making methodology (MCDM) was used for the solution of the relevant problem in this study. Both the experimental results and MCDM method indicated that 5,7-dibromo-8-hydroxyquinoline (2) and 6,8-dibromo-1,2,3,4-tetrahydroquinoline (6) are the most promising anticancer agents against the HeLa, HT29, and C6 cell lines.

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.

Recent advances and prospects in the metal-free synthesis of quinolines

Metal-free synthesis of quinolines has recently gained attention, and this review focuses on the recent advances in the metal-free synthesis of quinolines.

Progress in the Chemistry of Tetrahydroquinolines

Tetrahydroquinoline is one of the most important simple nitrogen heterocycles, being widespread in nature and present in a broad variety of pharmacologically active compounds. This Review summarizes the progress achieved in the chemistry of tetrahydroquinolines, with emphasis on their synthesis, during the period from mid-2010 to early 2018.

A convergent formal [4 + 2] cycloaddition of 1,6-diynes and benzyl azides: construction of spiro-polyheterocycles

A convergent formal [4 + 2] cycloaddition reaction for the construction of structurally appealing spiro-tetrahydroquinolines has been developed, in which, a one-pot reaction is established for the in situ generation of two reagents, a cyclic alkyne and an N-aryliminium ion, from the corresponding precursors in the presence of an Au-catalyst and Brønsted acid, respectively.

Synthesis of quinolines via copper-catalyzed domino reactions of enaminones

Enaminones showcase synthetic utility for the synthesis of quinoline derivatives via copper-catalyzed domino reactions involving C–N bond formation, aldol reaction and dehydration.

Crystal structure of (Z)-2-((2-bromo-1-phenylvinyl)oxy)benzonitrile, C15H10BrNO

C15H10BrNO, monoclinic, P21/n, a = 12.567(3) Å, b = 8.7170(17) Å, c = 12.773(3) Å, β = 111.41(3)°, V = 1302.7(4) Å3, Z = 4, R gt (F) = 0.0510, wR ref (F 2 ) = 0.1265, T = 293 K.

Synthesis of quinolines through copper-catalyzed intermolecular cyclization reaction from anilines and terminal acetylene esters

A simple and convenient copper-catalyzed intermolecular cyclization reaction for the synthesis of quinolines from anilines and terminal acetylene esters has been developed.

A concise synthesis of quinolinium, and biquinolinium salts and biquinolines from benzylic azides and alkenes promoted by copper(ii) species

​A copper promoted multiple aza-[4 + 2] cycloaddition reactions between benzylic azides and alkenes to form four different products including quinolinium and biquinolinium cations, biquinolines and quinolines are described.

Copper promoted synthesis of substituted quinolines from benzylic azides and alkynes

A novel method for the synthesis of substituted quinolines from benzylic azides and internal alkynes using Cu(OTf)₂is described. The reaction features a broad substrate scope, high product yields and excellent regioselectivity.