Synthesis and photophysical properties of 2-aryl-6,8-bis(arylethenyl)-4-methoxyquinolines

Aerobic Dehydrogenative Aromatization in the Preparation of 4-Aminoquinoline Derivatives by Synergistic Pd/Cu Catalysis

The 4-aminoquinoline moiety is widely present in various bioactive compounds and marketed drugs, while the preparation of this target structure relies heavily on the amination of 4-chloroquinolines. Herein, an atom and step economic procedure was developed based on an aerobic dehydrogenative aromatization strategy. Unlike the well-known palladium-catalyzed dehydrogenative aromatization of cyclohexanones with amines, synergistic Pd/Cu catalysis is crucial for 2,3-dihydroquinolin-4(1H)-one type of substrates. Under the optimized conditions, a range of aromatic/aliphatic amines and 2,3-dihydroquinolin-4(1H)-ones were coupled to give the corresponding 4-aminoquinoline products in moderate to high yields, and the application of the current methodology for the preparation and late-stage diversification of marketed drugs was also demonstrated.

Elucidation of the Structure of the 2-amino-3,5-Dibromochalcone Epoxides in Solution and Solid State

The conformation of the title compounds was determined in solution by 1H-NMR spectroscopy and in solid state by single-crystal X-ray diffraction (XRD) complemented with density functional theory. The compounds were found to exist exclusively in solution and solid state as trans-2-aminochalcone epoxides with strong intramolecular hydrogen bonding interaction between the amino and carbonyl groups. These 2-aminochalcone epoxides experienced a solvent effect in DMSO-d6, which resulted in an anomalous chemical shift for the α-hydrogen signal, presumably due to complexation of solute molecules with DMSO. The solute–solvent interaction would probably fix the trans conformation of epoxyketone such that α-H is more accessible to both aryl rings, and in turn, experience their combined anisotropic effect. Intermolecular interactions in the crystal structures were confirmed and quantified using the Hirshfeld surface analysis. Moreover, the trans stereochemistry of the α-epoxyketones facilitated direct one-pot sequential sulfuric acid-mediated ring opening and aryl migration to afford the corresponding 3-arylquinolin-4(1H)-ones (azaisoflavones).

Novel polycarbo-substituted alkyl (thieno[3,2-c]quinoline)-2-carboxylates: synthesis and cytotoxicity studies

Direct one-pot base-promoted conjugate addition–elimination of 6,8-dibromo-4-chloroquinoline-3-carbaldehyde with methyl mercaptoacetate and subsequent cyclization afforded methyl [(6,8-dibromothieno[3,2-c]quinoline)]-2-carboxylate. The latter undergoes Suzuki-Miyaura cross-coupling with arylboronic acids to yield exclusively the corresponding alkyl [(6,8-diarylthieno[3,2-c]quinoline)]-2-carboxylates,. The cytotoxicity of the prepared compounds was evaluated against the human breast cancer cell line MCF-7 using the MTT assay. The effects of compounds 2, 3c and 4d on cell kinetics were further determined using the xCELLigence Real Time Cell Analysis (RTCA) system. In both the MTT assay and Real Time Cell Analysis, the compounds inhibited cancer cell growth in a dose- and time-dependent manner. Furthermore, on the basis of the calculated LC₅₀ values, the compounds compared favourably with nocodazole, a well-established anticancer drug.

Advances in metal-catalyzed cross-coupling reactions of halogenated quinazolinones and their quinazoline derivatives

Halogenated quinazolinones and quinazolines are versatile synthetic intermediates for the metal-catalyzed carbon–carbon bond formation reactions such as the Kumada, Stille, Negishi, Sonogashira, Suzuki-Miyaura and Heck cross-coupling reactions or carbon-heteroatom bond formation via the Buchwald-Hartwig cross-coupling to yield novel polysubstituted derivatives. This review presents an overview of the application of these methods on halogenated quinazolin-4-ones and their quinazolines to generate novel polysubstituted derivatives.

One-Pot Site-Selective Sonogashira Cross-Coupling–Heteroannulation of the 2-Aryl-6,8-Dibromoquinolin-4(1H)-Ones: Synthesis of Novel 6-H-Pyrrolo[3,2,1-ij]Quinolin-6-Ones

The 2-aryl-6,8-dibromoquinolin-4(1 H)-ones were subjected to site-selective Sonogashira cross-coupling with terminal acetylenes as models for C sp2-C sp bond formation in the presence of Pd/C–PPh3 and CuI as catalysts and K2CO3 as a base in dioxane to afford the 2-substituted 4-aryl-8-bromo-4 H-pyrrolo[3,2,1- ij]quinolin-6-ones. These were, in turn, subjected to Suzuki–Miyaura cross-coupling with 4-fluorophenylboronic acid as coupling partner to afford the 2-substituted 4,8-diaryl-4 H-pyrrolo[3,2,1- ij]quinolin-6-ones.

Synthesis and photophysical property studies of the 2,6,8-triaryl-4-(phenylethynyl)quinazolines

The 2-aryl-6,8-dibromo-4-chloroquinazolines derived from the 2-aryl-6,8-dibromoquinazolin-4(3H)-ones were subjected to the Sonogashira cross-coupling with terminal acetylenes at room temperature to afford novel 2-aryl-6,8-dibromo-4-(alkynyl)quinazoline derivatives. Further transformation of the 2-aryl-6,8-dibromo-4-(phenylethynyl)quinazolines via Suzuki-Miyaura cross-coupling with arylboronic acids occurred without selectivity to afford the corresponding 2,6,8-triaryl-4-(phenylethynyl)quinazolines. The absorption and emission properties of these polysubstituted quinazolines were also determined.

4,6,8-Triarylquinoline-3-carbaldehyde derivatives: synthesis and photophysical properties

Palladium catalyzed Suzuki-Miyaura cross-coupling of 6,8-dibromo-4-chloroquinoline-3-carbaldehyde with arylboronic and arylvinylboronic acid derivatives in the presence of potassium carbonate in aqueous dioxane afforded the corresponding 4,6,8-triarylquinoline-3-carbaldehydes, exclusively. These products were transformed into 4,6,8-triaryl-3-(4-fluorophenyl)amino)-N-(quinolin-3-yl)methylenes and their 4,6,8-triaryl-quinoline-3-methanol derivatives. The absorption and emission spectra were measured for the 4,6,8-triarylquinoline-3-carbaldehydes and their derivatives in selected solvents of different polarity.