The Friedländer reaction: A powerful strategy for the synthesis of heterocycles

Synthesis of continuously substituted quinolines from o-alkenyl aromatic isocyanides by palladium-catalyzed intramolecular imidoylative 6-endo cyclization

An efficient synthesis of continuously substituted quinoline derivatives via palladium-catalyzed intramolecular 6-endo imidoylative cyclization of o-alkenyl aryl isocyanides with (hetero)aryl halides or vinylic triflates has been developed. The reaction proceeds through the concerted metalation-deprotonation (CMD) mechanism by activation of a vinyl C-H bond with imidoylpalladium assisted by the carboxylate.

Enhanced Method for the Synthesis and Comprehensive Characterization of 1-(4-Phenylquinolin-2-yl)propan-1-one

We present an enhanced method for synthesizing a novel compound, 1-(4-phenylquinolin-2-yl)propan-1-one (3), through the solvent-free Friedländer quinoline synthesis using poly(phosphoric acid) as an assisting agent. The crystal structure of compound 3 is analyzed using FT-IR, and the chemical shifts of its 1H- and 13C NMR spectra are measured and calculated using B3LYP/6-311G(d,p), CAM-B3LYP/6-311G(d,p), and M06-2X/6-311G(d,p) basis sets in the gas phase. Additionally, the optimized geometry of quinoline 3 is compared with experimental X-ray diffraction values. Through density functional theory calculations, we explore various aspects of the compound's properties, including noncovalent interactions, Hirshfeld surface analysis, nonlinear optical properties, thermodynamic properties, molecular electrostatic potential, and frontier molecular orbitals. These investigations reveal chemically active sites within this quinoline derivative that contribute to its chemical reactivity.

Divergent synthesis of two types of indolizines from pyridine-2-acetonitrile, (hetero)arylglyoxal, and TMSCN

Herein we describe the divergent synthesis of two types of indolizines via construction of the pyrrole moiety from pyridine-2-acetonitriles, arylglyoxals, and TMSCN. While one-pot three-component coupling provided 2-aryl-3-aminoindolizines via an unusual fragmentation process, a sequential two-step assembly protocol with these starting materials allowed efficient access to a wide range of new 2-acyl-3-aminoindolizines through an aldol condensation-Michael addition-cycloisomerization process. The subsequent manipulation of 2-acyl-3-aminoindolizines enabled direct access to novel polycyclic N-fused heteroaromatic skeletons.

Synthesis of Novel Benzo[b][1,6]naphthyridine Derivatives and Investigation of Their Potential as Scaffolds of MAO Inhibitors

In this work, 2-alkyl-10-chloro-1,2,3,4-tetrahydrobenzo[b][1,6]naphthyridines were obtained and their reactivity was studied. Novel derivatives of the tricyclic scaffold, including 1-phenylethynyl (5), 1-indol-3-yl (8), and azocino[4,5-b]quinoline (10) derivatives, were synthesized and characterized herein for the first time. Among the newly synthesized derivatives, 5c-h proved to be MAO B inhibitors with potency in the low micromolar range. In particular, the 1-(2-(4-fluorophenyl)ethynyl) analog 5g achieved an IC₅₀ of 1.35 μM, a value close to that of the well-known MAO B inhibitor pargyline.

Friedlӓnder's synthesis of quinolines as a pivotal step in the development of bioactive heterocyclic derivatives in the current era of medicinal chemistry

In the current scenario of medicinal chemistry, quinoline plays a pivotal role in the design of new heterocyclic compounds with several pharmacological properties, so the search for new synthetic methodologies and their application in drug discovery has been widely studied. So far, many procedures have been performed for the preparation of quinoline scaffolds, among which Friedländer quinoline synthesis plays an important role in obtaining these heterocycles. The Friedländer reaction involves condensation between 2-aminobenzaldehydes and keto-compounds. The quinoline nucleus, once obtained through the Friedländer synthesis, has been extensively modified so that these derivatives can exhibit a large number of biological activities such as anticancer, antimalarial, antimicrobial, antifungal, antituberculosis, and antileishmanial properties. In this work, the focus is on the applicability of the Friedländer reaction in the synthesis of various types of bioactive heterocyclic quinoline compounds, which to date has not been reported in the context of medicinal chemistry. The main part of this review selectively focuses on research from 2010 to date and will present highlights of the Friedländer quinoline synthesis procedures and findings to address biological and pharmacological activities.

Copper-Catalyzed Reactions of Alkenyl Boronic Esters via Chan-Evans-Lam Coupling/Annulation Cascades: Substrate Selective Synthesis of Dihydroquinazolin-4-ones and Polysubstituted Quinolines

Copper-catalyzed cascade cyclization reactions between alkenyl boronic esters and N-H-based nucleophiles have been established, providing new approaches for one-pot assembly of azacycles. Following the Chan-Evans-Lam C-N couplings, the cyclization processes occur via divergent pathways based on the utilized substrates, affording hydroamination product dihydroquinazolin-4-ones or aromatization product quinolines. Via this one-pot C-N coupling/annulation cascade, the target substituted azacycles can be obtained in moderate to good yields in each case.

S16020 pyridocarbazole derivatives display high activity to lung cancer cells

BACKGROUND

Despite the dynamic development of medicine, globally cancer diseases remain the second leading cause of death. Therefore, there is a strong necessity to improve chemotherapy regimens and search for new anticancer agents. Pyridocarbazoles are compounds with confirmed antitumor properties based on multimodal mechanisms, i.a. DNA intercalation and topoisomerase II-DNA complex inhibition. One of them, S16020, displayed a wide spectrum of activity.

OBJECTIVE

The aim of the study was to investigate the antitumor potency of six S16020 derivatives, synthesized according to the SAR (structure-activity relationship) method.

METHODS

The biological evaluation included influence on cancer cell viability, proliferation, and migration, as well as P-glycoprotein activity. NHDF, A549, MCF-7, LoVo, and LoVo/DX cell lines were used in the study.

RESULTS

All derivatives displayed low toxicity to normal (NHDF) cells at 1 and 2 µM (≤ 20% of cell growth inhibition). The highest reduction in cell viability was noted in A549 cells which was accompanied by significant disruption of cells proliferation and motility. Compound 1 exhibited the strongest cytotoxic, antiproliferative, and antimigratory effects, higher than the reference olivacine. A significant reduction in P-glycoprotein activity was found for derivatives 6 and 1.

CONCLUSION

S16020 derivatives could be considered as potential candidates for new anticancer drugs.

Augmenting Adaptive Machine Learning with Kinetic Modeling for Reaction Optimization

We combine random sampling and active machine learning (ML) to optimize the synthesis of isomacroin, executing only 3% of all possible Friedländer reactions. Employing kinetic modeling, we augment machine intuition by extracting mechanistic knowledge and verify that a global optimum was obtained with ML. Our study contributes evidence on the potential of multiscale approaches to expedite the access to chemical matter, further democratizing organic chemistry in a data-motivated fashion.

The synthesis, biological evaluation and fluorescence study of chromeno[4,3-b]pyridin/quinolin-one derivatives, the backbone of natural product polyneomarline C scaffolds: a brief review

This review presents the synthesis, biological and fluorescence study of chromeno[4,3-b]pyridin/quinolin-ones via classical reactions including metal-catalyzed and green reaction protocols.