Synthesis of Arylated Quinolines by Chemo- and Site-selective Suzuki-Miyaura Reactions of 5,7-Dibromo-8-(trifluoromethanesulfonyloxy)quinoline

Regioselective 1,4-Addition of P(O)-H Species to In Situ-Formed 1-Benzopyrylium Ion from C3-Substituted 2H-Chromene Hemiketals to Construct C3-Functionalized C4-Phosphorylated 4H-Chromenes

Herein, we report the first example that P(O)-H species including H-phosphonates and H-phosphine oxides could participate in a highly regioselective 1,4-addition to in situ generated 1-benzopyrylium ion from C3-substituted 2H-chromene hemiketals, which provides a brand-new and effective approach for the synthesis of C4-phosphorylated 4H-chromenes with diverse C3-functionality (ketone, ester, sulfonyl, aryl, and alkyl groups). In total, the reaction features the use of inexpensive Zn(ClO4)2·6H2O as a catalyst, low catalyst loading (only 5 mol %), mild reaction conditions (60 °C, 10 min to 24 h), and broad substrate scope (46 examples) as well as good to high yields (>90% yield on average). More importantly, mechanistic experiments demonstrated the essential role of the C3-substituent on 2H-chromene hemiketals in stabilizing the in situ generated 1-benzopyrylium ion and the regioselective 1,4-addition control.

Pd-, Cu-, and Ni-Catalyzed Reactions: A Comprehensive Review of the Efficient Approaches towards the Synthesis of Antibacterial Molecules

A strong synthetic tool for many naturally occurring chemicals, polymers, and pharmaceutical substances is transition metal-catalyzed synthesis. A serious concern to human health is the emergence of bacterial resistance to a broad spectrum of antibacterial medications. The synthesis of chemical molecules that are potential antibacterial candidates is underway. The main contributions to medicine are found to be effective in transition metal catalysis and heterocyclic chemistry. This review underlines the use of heterocycles and certain effective transition metals (Pd, Cu, and Ni) as catalysts in chemical methods for the synthesis of antibacterial compounds. Pharmaceutical chemists might opt for clinical exploration of these techniques due to their potential.

Cross-Coupling Reactions of Polyhalogenated Heterocycles

Palladium-catalyzed cross-coupling reactions of polyhalogenated heterocycles provide a convenient access to multifold arylated and alkynylated ring systems with a broad spectrum of physical and medicinal properties. Products include thiophenes, selenophenes, pyrroles, indoles, furans, benzofurans, pyrazoles, pyridines, quinolines, pyrimidines, pyrazines, naphthyridines, quinoxalines, and others. The regioselectivity of the coupling reactions is controlled by a combination of electronic and steric parameters. While a number of couplings can be carried out essentially under standard conditions, others require the use of more sophisticated ligands and a thorough optimization of the conditions, such as solvent, temperature, or reaction time. The present Account provides a personalized overview of coupling reactions of polyhalogenated heterocycles.

1 Introduction

2 Thiophenes

3 Selenophenes

4 Pyrroles and Indoles

5 Furans and Benzofurans

6 Pyrazoles

7 Pyridines

8 Quinolines

9 Pyrimidines and Pyrazines

10 Naphthyridines and Quinoxalines

11 Miscellaneous

12 Conclusions

Synthesis of aryl-substituted quinolines and tetrahydroquinolines through Suzuki–Miyaura coupling reactions

The synthesis and characterization of substituted (trifluoromethoxy, thiomethyl, and methoxy) phenyl quinolines is described. Dichlorobis(triphenylphosphine)palladium(II)-catalyzed Suzuki–Miyaura cross-coupling of 6-bromo- and 6,8-dibromo-1,2,3,4-tetrahydroquinolines, 5-bromo-8-methoxyquinoline, and 5,7-dibromo-8-methoxyquinoline with substituted phenylboronic acids affords the corresponding 6-aryl- (13a–d), 6,8-diaryl- (14a–c), 5-aryl- (15), and 5,7-diaryl- (16b, c) tetrahydroquinolines and quinolines in high yields (68%–82%). The structures of all the products are characterized by 1H NMR, 13C NMR,19F NMR, and Fourier transform infrared spectroscopy and by elemental analysis.

Hydroxy group-enabled highly regio- and stereo-selective hydrocarboxylation of alkynes

Hydrogen bonding-enabled highly regio- and stereo-selective hydrocarboxylation of alkynes has been successfully developed to afford 3-hydroxy-2(E)-alkenoates with up to 97% yield.

Here we present an example of utilizing hydroxy groups for regioselectivity control in the addition reaction of alkynes—a highly efficient Pd-catalyzed syn-hydrocarboxylation of readily available 2-alkynylic alcohols with CO in the presence of alcohols with an unprecedented regioselectivity affording 3-hydroxy-2(E)-alkenoates. The role of the hydroxy group has been carefully studied. The synthetic potential of the products has also been demonstrated.

C-H 18F-fluorination of 8-methylquinolines with Ag[18F]F

This report describes a Pd-mediated C-H radiofluorination of 8-methylquinoline derivatives with no-carrier-added Ag[18F]F. To achieve this transformation, a new method was developed for the generation of Ag[18F]F using a sep-pak cartridge. The C-H radiofluorination was then optimized and applied to a series of substituted 8-methylquinoline derivatives. Finally, this method was fully automated using a radiochemistry synthesis module.

Synthesis of Highly Substituted Quinolines via a Tandem Ynamide Benzannulation/Iodocyclization Strategy

A two-stage "tandem strategy" for the regiocontrolled synthesis of very highly substituted quinolines is described. Benzannulation based on the reaction of cyclobutenones or diazo ketones with N-propargyl-substituted ynamides proceeds via a cascade of several pericyclic reactions to generate multiply substituted aniline derivatives. In the second stage of the tandem strategy, triflate derivatives of the phenolic benzannulation products undergo Larock cyclization upon exposure to iodine to form products that are further elaborated by methods such as palladium-catalyzed coupling to generate quinolines that can be substituted at every position of the bicyclic system.