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.

Crystal structure of chlorido-(4-chloro-6-(p-tolyl)pyrimidine-κ2 C,N)-(triphenylphosphane-κP)palladium(II), C29H23Cl2N2PPd

C29H23Cl2N2PPd, monoclinic, P21/c (no. 14), a = 9.4028(16) Å, b = 30.928(5) Å, c = 9.3071(16) Å, β = 103.222(2)°, V = 2634.8(8) Å3, Z = 4, R gt(F) = 0.0423, wR ref(F 2) = 0.1047, T = 296(2) K.

Crystal structure of chlorido-(5-acetyl-2-(5-methylpyridin-2-yl)benzen-1-ido-κ2C,N)-pyridine-κN-palladium(II), C19H17ClN2OPd

C19H17ClN2OPd, monoclinic, P21/c (no. 14), a = 9.0720(8) Å, b = 10.9390(10) Å, c = 17.9604(7) Å, β = 97.054(6)°, V = 1768.9(2) Å3, Z = 4, Rgt(F) = 0.0389, wRref(F2) = 0.0816, T = 293(2) K.

Visible-Light-Initiated One-Pot, Three-Component Synthesis of 2-Amino-4H-pyran-3,5-dicarbonitrile Derivatives

A novel approach for the visible-light-initiated synthesis of 2-amino-4H-pyran-3,5-dicarbonitrile derivatives via a one-pot, three-component reaction of aldehydes or isatins, malononitrile, and α-cyano ketones has been developed. The reaction was carried out at room temperature in ethanol/water to give the corresponding products with a wide range of functional groups in high yields. This process did not require any additives or chromatographic separation and could be applied for gram-scale synthesis.

Crystal structure of 5-bromo-2-(naphthalen-6-yl)pyridine, C15H10BrN

C15H10BrN, monoclinic, P21/c (no. 14), a = 14.6998(9) Å, b = 5.9337(4) Å, c = 14.6275(11) Å, β = 113.542(8)°, V = 1169.67(15) Å3, Z = 4, R gt(F) = 0.0396, wR ref(F 2) = 0.1103, T = 293(2) K.

Palladium-Catalyzed Allylic C-H Oxidative Annulation for Assembly of Functionalized 2-Substituted Quinoline Derivatives

An efficient and practical palladium-catalyzed aerobic oxidative approach to afford functionalized 2-substituted quinolines in moderate to good yields from readily available allylbenzenes with aniline is developed. The present annulation process has high functional-group tolerance and high atom economy, making it a valuable and practical method in synthetic and medicinal chemistry. Moreover, this transformation is supposed to proceed through oxidation of allylic C-H functionalization to form C-C and C-N bonds in one pot.

Crystal structure of 4-(1H-imidazol-1-yl)-6-pyrimidinylferrocene, C17H14FeN4

C17H14FeN4, monoclinic, P21/c, a = 11.8213(11) Å, b = 10.3610(10) Å, c = 11.8552(11) Å, α = γ = 90°, β = 101.1540(10)°, V = 1424.6(2) Å3, Z = 4, R gt (F) = 0.0233, wR ref (F 2 ) = 0.0653, T = 296(2) K.

Crystal structure of [2-(4-methoxyphenyl)pyrazine-κ2 C,N) chlorido[N,N′-bis-(2,6-diisopropyl-phenyl)imidazol-2-ylidene-κC)] palladium(II), C38H45ClN4OPd

C38H45ClN4OPd, trigonal, R3m, a = 30.1968(8) Å, b = 30.1968(8) Å, c = 11.4611(3) Å, α = β = 90°, γ = 120.00°, V = 9050.7(4) Å3, Z = 9, R gt (F) = 0.0397, wR ref (F 2 ) = 0.1053, T = 291.15 K.

Cyclometalated Pd(ii) and Ir(iii) 2-(4-bromophenyl)pyridine complexes with N-heterocyclic carbenes (NHCs) and acetylacetonate (acac): synthesis, structures, luminescent properties and application in one-pot oxidation/Suzuki coupling of aryl chlorides containing hydroxymethyl

A series of cyclometalated 2-(4-bromophenyl)pyridine complexes have been synthesized and characterized.