Boron Trifluoride Etherate Promoted Microwave-Assisted Synthesis of Antimalarial Acridones

Palladium-Catalyzed Dual C-H Carbonylation of Diarylamines Leading to Diversified Acridones under CO-Free Conditions

A Pd-catalyzed dual C-H carbonylation of commercially available diarylamines using Co2(CO)8 as a safe CO source has been developed. This methodology provides a facile approach for the synthesis of diversified acridones in moderate to good yields. The protocol features good functional group compatibility, operational safety, easy scale-up, and versatile transformations.

K2CO3-Catalyzed Dual C-C-Coupled Cyclization to 3-Amino-4-benzoylbiphenyls and In Situ I2-Catalyzed C-N Bond Forming Annulation: A Metal-Free Synthesis of Arylacridones

Unprecedented metal-free cyclization catalysis reactions are developed in a highly regioselective fashion to synthesize 3-amino-4-benzoyl biphenyls and arylacridones with high atom economy. Catalytic K2CO3 is utilized as the only reagent for the unusual rapid dual C-C-coupled cyclization between β-keto enamines and cinnamaldehydes to furnish the functionalized biphenyls. Its C(sp2)-H functionalized C-N bond-forming cyclization was performed in situ using molecular I2 as a catalyst to furnish valuable arylacridones. Plausible mechanisms for the new cyclization reactions are predicted by conducting various control experiments and ESI-MS analyses.

Base-Controlled Synthesis of Fluorescent Acridone Derivatives via Formal (4 + 2) Cycloaddition

A transition-metal-free formal (4 + 2) cycloaddition for the direct assembly of acridone derivatives has been developed from simple and easily accessible o-aminobenzamides and 2-(trimethylsilyl)aryl triflates. The base played an important role in the selective controlled synthesis of N-H and N-aryl acridones. A preliminary study on the fluorescence properties of N-aryl acridones demonstrated that they could be used as fluorescent materials with a broad emission range.

A Novel Palladium-Based Heterogeneous Catalyst for Tandem Annulation: A Strategy for Direct Synthesis of Acridones

In order to develop an efficient, rapid, and modular cascade strategy for the direct synthesis of acridones, palladium supported on sulfated alumina and microwave activation are employed. Multifunctional heterogeneous palladium catalysts were prepared in order to carry out the sequential annulation via a Buchwald–Hartwig amination followed by an intramolecular annulation in a one-pot process. This new protocol represents the first report on a catalytic tandem synthesis of acridone derivatives from commercially available starting materials, under ligand-free conditions. The scope of the present methodology is extended to the generation of a library of functionalized acridones, showing high functional group compatibility, in moderate to excellent yields. The applicability of this novel transformation was demonstrated by the concise total synthesis of the natural product arborinine.

Green synthesis of fluorescent Schiff bases: chemo-photophysical characterization, X-ray structures, and their bioimaging

Two Schiff bases have been prepared by mechano- and ultrasound-assisted synthesis and their structures were elucidated by X-ray diffraction. One of them showed good fluorescent cell staining in vitro and low cytotoxicity.

Lead Optimization of Second-Generation Acridones as Broad-Spectrum Antimalarials

The global impact of malaria remains staggering despite extensive efforts to eradicate the disease. With increasing drug resistance and the absence of a clinically available vaccine, there is an urgent need for novel, affordable, and safe drugs for prevention and treatment of malaria. Previously, we described a novel antimalarial acridone chemotype that is potent against both blood-stage and liver-stage malaria parasites. Here, we describe an optimization process that has produced a second-generation acridone series with significant improvements in efficacy, metabolic stability, pharmacokinetics, and safety profiles. These findings highlight the therapeutic potential of dual-stage targeting acridones as novel drug candidates for further preclinical development.