A New Class of Chiral P,N-Ligands and Their Application in Palladium-Catalyzed Asymmetric Allylic Substitution Reactions

Tetrahydroquinolinone derivatives exert antiproliferative effect on lung cancer cells through apoptosis induction

The anticancer properties of quinolones is a topic of interest among researchers in the scientific world. Because these compounds do not cause side effects, unlike the commonly used cytostatics, they are considered a promising source of new anticancer drugs. In this work, we designed a brief synthetic pathway and obtained a series of novel 8-phenyltetrahydroquinolinone derivatives functionalized with benzyl-type moieties at position 3. The compounds were synthesized via classical reactions such as nucleophilic substitution, solvent lysis, and condensation. Biological evaluation revealed that 3-(1-naphthylmethyl)-4-phenyl-5,6,7,8-tetrahydro-1H-quinolin-2-one (4a) exhibited potent cytotoxicity toward colon (HTC-116) and lung (A549) cancer cell lines. Analysis of the mechanism of action of compounds showed that compound 4a induced cell cycle arrest at the G₂/M phase, leading to apoptotic cell death via intrinsic and extrinsic pathways. Taken together, the findings of the study suggest that tetrahydroquinolinone derivatives bearing a carbonyl group at position 2 could be potential lead compounds to develop anticancer agents for the treatment of lung cancers.

Design, synthesis, and biological evaluation of tetrahydroquinolinones and tetrahydroquinolines with anticancer activity

Colorectal cancer (CRC) is the most commonly diagnosed cancer in Europe and the United States and the second leading cause of cancer related mortality. A therapeutic strategy used for the treatment of CRC involves targeting the intracellular levels of reactive oxygen species (ROS). In this study, we synthesized a series of novel tetrahydroquinolinones and assessed their ability to inhibit CRC growth and proliferation by evoking cellular stress through ROS. Our results revealed that (2-oxo-4-phenyl-5,6,7,8-tetrahydroquinolin-8-yl) N-(3-fluorophenyl)carbamate (20d) exhibited in vitro antiproliferative activity at micromolar concentrations. The compound also suppressed colony formation and the migration of HCT-116 cells, as well as deregulated the expression of several proteins involved in cell proliferation and metastasis. Furthermore, 20d induced massive oxidative stress by disrupting the balance of cells survival resulting in autophagy via the PI3K/AKT/mTOR signaling pathway. These findings suggest that this tetrahydroquinolinone can be an ideal lead compound for drug discovery based on quinone derivatives.

Are bis(pyridine)iodine(I) complexes applicable for asymmetric halogenation?

Enantiopure halogenated molecules are of tremendous importance as synthetic intermediates in the construction of pharmaceuticals, fragrances, flavours, natural products, pesticides, and functional materials. Enantioselective halofunctionalizations remain poorly understood and generally applicable procedures are lacking. The applicability of chiral trans-chelating bis(pyridine)iodine(i) complexes in the development of substrate independent, catalytic enantioselective halofunctionalization has been explored herein. Six novel chiral bidentate pyridine donor ligands have been designed, routes for their synthesis developed and their [N–I–N]⁺-type halogen bond complexes studied by ¹⁵N NMR and DFT. The chiral complexes encompassing a halogen bond stabilized iodenium ion are shown to be capable of efficient iodenium transfer to alkenes; however, without enantioselectivity. The lack of stereoselectivity is shown to originate from the availability of multiple ligand conformations of comparable energies and an insufficient steric influence by the chiral ligand. Substrate preorganization by the chiral catalyst appears a necessity for enantioselective halofunctionalization.

The enantioselectivity of the iodine(i) transfer process from chiral bis(pyridine)iodine(i) complexes to alkenes is explored.

Architecture and synthesis of P,N-heterocyclic phosphine ligands

Diverse P,N-phosphine ligands reported to date have performed exceptionally well as auxiliary ligands in organometallic catalysis. Phosphines bearing 2-pyridyl moieties prominently feature in literature as compared to phosphines with five-membered N-heterocycles. This discussion seeks to paint a broad picture and consolidate different synthetic protocols and techniques for N-heterocyclic phosphine motifs. The introduction provides an account of P,N-phosphine ligands, and their structural and coordination benefits from combining heteroatoms with different basicity in one ligand. The body discusses the synthetic protocols which focus on P–C, P–N-bond formation, substrate and nucleophile types and different N-heterocycle construction strategies. Selected references are given in relation to the applications of the ligands.

The cooperative effect of Lewis pairs in the Friedel–Crafts hydroxyalkylation reaction: a simple and effective route for the synthesis of (±)-carbinoxamine

Lewis acid (with or without a Lewis base) enhances the electrophilicity of aldehydes to react with aromatic π-nucleophiles and generate carbinols.

Enantiopure synthesis of 7-(1-pyrindanyl)propargyl ethers as rasagiline analogues via chemical or enzymatic resolution of 1-pyrindan-7-ol

Enantiopure 7-(1-pyrindanyl)propargyl ethers – rasagiline analogues – were efficiently obtainedviachemical and/or enzymatic resolution of the racemic precursor 1-pyrindan-7-ol.

Chichibabin-type direct alkylation of pyridyl alcohols with alkyl lithium reagents

Direct C(6) alkylation of pyridyl alcohols can be achieved following an initial deprotonation of the hydroxy group. This transformation, which is believed to occur by a Chichibabin-type alkylation, avoids lateral deprotonation prior to pyridine ring alkylation and gives increased regioselectivity for C(6) over C(4) alkylation.

Synthesis and evaluation of new chiral nonracemic C2-symmetric and unsymmetric 2,2′-bipyridyl ligands

The synthesis of a series of chiral nonracemic and C2-symmetric 2,2'-bipyridyl ligands (R = Me, i-Pr and Ph) as well as the syntheses of the corresponding unsymmetric 2,2'-bipyridyl ligands (R = Me and Ph) is described. These bipyridyl ligands were prepared, in a notably direct and modular fashion, from the readily available and corresponding 2-chloropyridine acetals (R = Me, i-Pr and Ph). The bipyridyl ligands were evaluated in copper(I)-catalyzed cyclopropanation reactions of styrene with the ethyl and t-butyl esters of diazoacetic acid. The stereoselectivities, as well as the yields of the cyclopropanation reactions, were dependant on the ratio of the bipyridyl ligands and copper triflate that was employed. The best result was obtained in the asymmetric cyclopropanation reaction of styrene and tert-butyl diazoacetate with the C2-symmetric bipyridyl ligand (R = i-Pr). This afforded the corresponding trans-cyclopropane in good diastereoselectivity (4 : 1) and in moderate enantioselectivity (44% ee). The X-ray structure determination of a complex formed between the C2-symmetric 2,2'-bipyridyl ligand (R = Ph) and copper(I) chloride showed that two bipyridyl ligands had coordinated to the copper(I) ion. This information, along with the results of a series of cyclopropanation reactions and NMR data, led to the conclusion that the 2,2'-bipyridyl ligands had the propensity to form catalytically inactive bis-ligated copper(I) species in solution that were in equilibrium with catalytically active copper(i) triflate and the desired mono-ligated copper(I) species. Moreover, it was observed that the complex of the bipyridyl ligand (R = Ph) and copper(I) chloride had a particularly large optical rotation (sodium D-line). The maximum positive optical rotation was subsequently found to be +1.1 x 10(4) at 304 nm and the maximum negative optical rotation was -1.3 x 10(4) at 329 nm.

Synthesis and evaluation of 7-hydroxyindan-1-one-derived chiral auxiliaries

A series of novel chiral acetals were prepared from 7-hydroxyindan-1-one and a variety of substituted chiral nonracemic C2-symmetric 1,2-ethanediols (R = Me, Ph, CH2OMe, CH2OBn, CH2O(1-Np), and i-Pr). These acetals were evaluated as chiral auxiliaries for use in asymmetric synthesis. A high degree of stereochemical induction was observed in the diethylaluminum chloride-promoted Diels–Alder reaction of an acrylate derivative (R = i-Pr) with cyclopentadiene (91:9 dr). This demonstrated that these acetals could serve as effective chiral directors in asymmetric substrate-directed reactions.Key words: 7-hydroxyindan-1-one, chiral nonracemic C2-symmetric 1,2-diols, acetals, chiral auxiliaries, Diels–Alder reaction.

Alkenylation of allylic alcohols using alkenylboron dihalides: a formal transition-metal free Suzuki reaction

Carbon-carbon bond formation via substitution of an allylic hydroxide with stereodefined alkenyl groups using alkenylboron dihalides in the absence of transition metals.