Sc(OTf)3-Mediated [4 + 2] Annulations of N-Carbonyl Aryldiazenes with Cyclopentadiene to Construct Cinnoline Derivatives: Azo-Povarov Reaction

A Practical Synthetic Route to Cinnolines: Application to the Design and Synthesis of RSV NNI Inhibitor JNJ-8003 Analogues

The manuscript describes the development of an efficient synthetic route to cinnolines, facilitating faster access to JNJ-8003 related Respiratory Syncytial Virus (RSV) non-nucleoside (NNI) inhibitors. Starting from correctly functionalized aryl halides, a Sonogashira reaction followed by SNAr reaction with hydrazine 1,2-dicabroxylate reagents provided dihydrocinnolines directly via in situ 6-endo-dig cyclization. The dihydrocinnolines were conveniently transformed to corresponding cinnolines in one step. Notably, this three-step route to cinnolines is more practical and safer than traditional methods that involve hazardous diazo intermediates. The methodology demonstrated a broad substrate scope. Strategic selection of a readily available aryl halide enabled the synthesis of diverse cinnolines that served as JNJ-8003 analogues through late-stage functionalization. Furthermore, by capitalizing the inherent reactivity of aryl halides toward SNAr reactions, we explored the synthesis of various heteroaromatic cinnolines. Given the extensive biological properties exhibited by cinnolines, our approach is poised to inspire further investigations in this field.

Skeletal Reorganization Emanated via the Course of Heterocyclic N1-N2 Bond Cleavage: Electrosynthetic Approach

A unified method toward the synthesis of functionalized diazepines and quinazolines through reorganization of the molecular skeleton has been devised. The process is indulged by electrical energy via a domino N1-N2 bond cleavage followed by concomitant ring closing, initiating from cinnolines and indazoles as designed precursors. Additionally, an intermolecular ring homologation has also been established to synthesize densely functionalized dihydroquinazolines from 2,3-diaryl-indazoles and acetonitrile involving the same electrochemical strategy.

Green Oxidation of Aromatic Hydrazide Derivatives Using an Oxoammonium Salt

Aromatic diazenes are often prepared by oxidation of the corresponding hydrazides using stoichiometric quantities of nonrecyclable oxidants. We developed a convenient alternative protocol for the oxidation of aromatic hydrazides using Bobbitt's salt (1), a metal-free, recyclable, and commercially available oxoammonium reagent. A variety of aryl hydrazides were oxidized within 75 min at room temperature using the developed protocol. Computational insight suggests that this oxidation occurs by a polar hydride transfer mechanism.

Reactions of 1,3-Diphenyl Cyclopentadiene with α-Aryldiazo Ketones to Enable C-H Insertions versus [4 + 2]-Cycloadditions via Au Catalyst and P(C6F5)3 Additive, Respectively

Two distinct reaction chemoselectivities were reported for the reactions of α-aryldiazo ketone with 1,3-diphenylcyclopentadiene using gold catalyst and phosphine additives, respectively. In the presence of gold catalyst, α-aryldiazo ketone forms gold carbenes initially that are trapped with this 1,3-disubstituted cyclopentadiene to afford C-H insertion products. In the presence of P(C6F5)3 additive, α-aryldiazo ketone forms diarylketenes initially at elevated temperature, which are further stabilized by P(C6F5)3 to secure their entity before proceeding to unprecedented [4C + 2C] cycloadditions.

Design, Synthesis, and Biological Evaluation of N'-Phenylhydrazides as Potential Antifungal Agents

Fifty-two kinds of N'-phenylhydrazides were successfully designed and synthesized. Their antifungal activity in vitro against five strains of C. albicans (Candida albicans) was evaluated. All prepared compounds showed varying degrees of antifungal activity against C. albicans and their MIC80 (the concentration of tested compounds when their inhibition rate was at 80%), TAI (total activity index), and TSI (total susceptibility index) were calculated. The inhibitory activities of 27/52 compounds against fluconazole-resistant fungi C. albicans 4395 and 5272 were much better than those of fluconazole. The MIC80 values of 14/52 compounds against fluconazole-resistant fungus C. albicans 5122 were less than 4 μg/mL, so it was the most sensitive fungus (TSIB = 12.0). A11 showed the best inhibitory activity against C. albicans SC5314, 4395, and 5272 (MIC80 = 1.9, 4.0, and 3.7 μg/mL). The antifungal activities of B14 and D5 against four strains of fluconazole-resistant fungi were better than those of fluconazole. The TAI values of A11 (2.71), B14 (2.13), and D5 (2.25) are the highest. Further exploration of antifungal mechanisms revealed that the fungus treated with compound A11 produced free radicals and reactive oxygen species, and their mycelium morphology was damaged. In conclusion, the N'-phenylhydrazide scaffold showed potential in the development of antifungal lead compounds. Among them, A11, B14, and D5 demonstrated particularly promising antifungal activity and held potential as novel antifungal agents.

4-(Aryl)-Benzo[4,5]imidazo[1,2-a]pyrimidine-3-Carbonitrile-Based Fluorophores: Povarov Reaction-Based Synthesis, Photophysical Studies, and DFT Calculations

A series of novel 4-(aryl)-benzo[4,5]imidazo[1,2-a]pyrimidine-3-carbonitriles were obtained through the Povarov (aza-Diels-Alder) and oxidation reactions, starting from benzimidazole-2-arylimines. Based on the literature data and X-ray diffraction analysis, it was discovered that during the Povarov reaction, [1,3] sigmatropic rearrangement leading to dihydrobenzimidazo[1,2-a]pyrimidines took place. The structures of all the obtained compounds were confirmed based on the data from 1H- and 13C-NMR spectroscopy, IR spectroscopy, and elemental analysis. For all the obtained compounds, their photophysical properties were studied. In all the cases, a positive emission solvatochromism with Stokes shifts from 120 to 180 nm was recorded. Aggregation-Induced Emission (AIE) has been illustrated for compound 6c using different water fractions (fw) in THF. The compounds 6c and 6f demonstrated changes in emission maxima or/and intensities after mechanical stimulation.