Copper-Catalyzed Cascade Cyclization of Arylsulfonylhydrazones Derived from ortho-Alkynyl Arylketones: Regioselective Synthesis of Functionalized Cinnolines

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.

Cu(II)-catalyzed synthesis of N-sulfonated quinolin-2(1H)-one-3-carboxamides

Herein, N-N bond cleavage of sulfonylhydrazides was observed and applied in the synthesis of N-sulfonated quinolin-2-(1H)-one-3-carboxamides. More than 30 examples were forged in 52%-97% yields. Further transformation delivered a 3,4-dihydro-quinolin-2(1H)-one derivative.

Divergent Synthesis of 3-(Indol-2-yl)quinoxalin-2-ones and 4-(Benzimidazol-2-yl)-3-methyl(aryl)cinnolines via Polyphosphoric Acid (PPA)-Mediated Intramolecular Rearrangements of 3-(Methyl/aryl(2-phenylhydrazono)methyl)quinoxalin-2-ones

Herein, we report a polyphosphoric acid (PPA)-mediated divergent metal-free operation to access a diverse collection of 3-(indol-2-yl)quinoxalin-2-ones and 4-(benzimidazol-2-yl)-3-methylcinnolines in moderate to excellent overall yields. The described process involves two distinct, and competing rearrangements of 3-(methyl(2-phenylhydrazono)methyl)quinoxalin-2-ones, namely [3,3]-sigmatropic Fischer rearrangement with the formation of an indole ring to produce 3-(indol-2-yl)-quinoxalin-2-ones, and Mamedov rearrangement with simultaneous construction of benzimidazole and cinnoline rings to form the new biheterocyclic system─4-(benzimidazol-2-yl)-3-methylcinnolines. The reaction mechanism of both rearrangement channels is explored by extensive dispersion-corrected DFT calculations. It is partcularly remarkable that when 3-(aryl(2-phenylhydrazono)methyl)quinoxalin-2-ones is used, instead of 3-(methyl(2-phenylhydrazono)methyl)quinoxalin-2-ones, reactions proceed regioselectively with the formation of only rearrangement products─4-(benzimidazol-2-yl)-3-arylcinnolines with high yields. This operationally simple protocol enables a rapid access to these scaffolds and is compatible with a wide scope of starting materials. In addition, the new rearrangement found features a promising approach for the design of unique compound libraries for drug design and discovery programs.

Diphenhydramine Hydrochloride-CuCl as a New Catalyst for the Synthesis of Tetrahydrocinnolin-5(1H)-ones

The current study deals with the synthesis and characterization of a novel catalyst made from diphenhydramine hydrochloride and CuCl ([HDPH]Cl-CuCl). The prepared catalyst was thoroughly characterized using various techniques, such as ¹H NMR, Fourier transform-infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis and derivative thermogravimetry. More importantly, the observed hydrogen bond between the components was proven experimentally. The activity of this catalyst was checked in the preparation of some new derivatives of tetrahydrocinnolin-5(1H)-ones via a multicomponent reaction between dimedone, aromatic aldehydes, and aryl/alkyl hydrazines in ethanol as a green solvent. Also, for the first time, this new homogeneous catalytic system was effectively used for the preparation of unsymmetric tetrahydrocinnolin-5(1H)-one derivatives as well as mono- and bis-tetrahydrocinnolin-5(1H)-ones from two different aryl aldehydes and dialdehydes, respectively. The effectiveness of this catalyst was further confirmed by the preparation of compounds containing both tetrahydrocinnolin-5(1H)-one and benzimidazole moieties from dialdehydes. The one-pot operation, mild conditions, rapid reaction, and high atom economy, along with the recyclability and reusability of the catalyst, are other notable features of this approach.

Catalyst-Free Cascade Annulation of Enaminones and Aryl Diazonium Tetrafluoroboronates for Cinnoline Synthesis and the Anti-Inflammatory Activity Study

A simple and concise method for the synthesis of cinnolines has been developed by the reactions of readily available enaminones and aryl diazonium tetrafluoroboronates. The reactions run efficiently to provide cinnolines with broad diversity in the substructure by heating in dimethyl sulfoxide without using any catalyst or additive. In addition, the primary investigation of the anti-inflammatory activity of these products leads to the observation of p-chlorobenzoyl (3f) and p-nitrobenzoyl (3j) cinnolines as attractive anti-inflammatory compounds in vitro.

Efficient method for the synthesis of novel methyl 4-cinnolinecarboxylate

A new method is designed for the synthesis of some novel methyl 3-aryl/alkyl-4-cinnolinecarboxylate with developed a general Richter cyclization through diazotization strategy of commercially available 2-aryl/alkyl ethynyl aniline and methyl acetate. Most substrates were achieved in moderate to excellent yields in one-pot procedures under mild reaction conditions.

Recent developments in the green synthesis of biologically relevant cinnolines and phthalazines

Both cinnolines and phthalazines are heterocyclic compounds which have a wide range of biological activities and pharmacological profiles. This work represents the recent advances in the green synthesis of cinnolines and phthalazines as 1,2 and 2,3-diazanaphalenes were cited. The docking studies and mode of action for key scaffolds were also reported.

Intramolecular redox cyclization reaction access to cinnolines from 2-nitrobenzyl alcohol and benzylamine via intermediate 2-nitrosobenzaldehyde

An efficient base-promoted synthesis of cinnolines from 2-nitrobenzyl alcohol and benzylamine via an intramolecular redox cyclization reaction. The formation of intermediate 2-nitrosobenzaldehyde plays an important role in this transformation.

Desulfonylation via Radical Process: Recent Developments in Organic Synthesis

As the "chemical chameleon", sulfonyl-containing compounds and their variants have been merged with various types of reactions for the efficient construction of diverse molecular architectures by taking advantage of their incredible reactive flexibility. Currently, their involvement in radical transformations, in which the sulfonyl group typically acts as a leaving group via selective C-S, N-S, O-S, S-S, and Se-S bond cleavage/functionalization, has facilitated new bond formation strategies which are complementary to classical two-electron cross-couplings via organometallic or ionic intermediates. Considering the great influence and synthetic potential of these novel avenues, we summarize recent advances in this rapidly expanding area by discussing the reaction designs, substrate scopes, mechanistic studies, and their limitations, outlining the state-of-the-art processes involved in radical-mediated desulfonylation and related transformations. With a specific emphasis on their synthetic applications, we believe this review will be useful for medicinal and synthetic organic chemists who are interested in radical chemistry and radical-mediated desulfonylation in particular.

Pd-Catalyzed Sequential Formation of C-C Bonds: A New Strategy for the Synthesis of (E)-α,β-Unsaturated Carbonyl Compounds from Sulfoxonium Ylides and 1-Iodo-2-((2-methylallyl)oxy)benzene Compounds

α,β-Unsaturated carbonyl compounds are significant moieties in many biological molecules and have attracted considerable attention in organic synthetic chemistry. A Pd-catalyzed cascade cyclization for the synthesis of (E)-α,β-unsaturated carbonyl compounds with the sequential formation of C-C bonds was developed. This method offers high efficiency, good functional group tolerance, and moderate to excellent yields and generally displays high stereoselectivity.

Desymmetrization of meso-Dicarbonatecyclohexene with β-Hydrazino Carboxylic Esters via a Pd-Catalyzed Allylic Substitution Cascade

The desymmetrization of meso-dicarbonatecyclohexene with β-hydrazino carboxylic esters has been achieved via a RuPHOX/Pd-catalyzed allylic substitution cascade for the construction of chiral hexahydrocinnoline derivatives with high performance. Mechanistic studies reveal that the reaction exploits a pathway different from that of our previous work and that the first nitrogen nucleophilic process is the rate-determining step. The protocol could be conducted on a gram scale without any loss of catalytic behavior, and the corresponding chiral hexahydrocinnolines can undergo diverse transformations.