Preparation of Quinazolines via a 2+2+2 Annulation from Aryldiazonium Salts and Nitriles

A Systematic Review of Synthetic and Anticancer and Antimicrobial Activity of Quinazoline/Quinazolin-4-one Analogues

Quinazolines/quinazolin-4-ones are significant nitrogen-containing heterocycles that exist in various natural products and synthetic scaffolds with diverse medicinal and pharmacological applications. Researchers across the globe have explored numerous synthetic strategies to develop safer and more potent quinazoline/quinazolinone analogues, particularly for combating cancer and microbial infections. This review systematically examines scholarly efforts toward understanding this scaffold's synthetic pathways and medicinal relevance, emphasizing the role of metal and non-metal catalysts and other reagents in their synthesis. Additionally, the article discusses selected compounds' anticancer and antimicrobial properties, with a brief look into their structure-activity relationships.

One-Pot Three-Component Reaction for the Synthesis of 3,4-Dihydroquinazolines and Quinazolin-4(3H)-ones

A highly efficient and straightforward one-pot synthesis of diversely substituted 3,4-dihydroquinazolines and quinazolin-4(3H)-ones has been achieved through a domino three-component assembly reaction of arenediazonium salts, nitriles, and bifunctional aniline derivatives. This new protocol involves three C-N bond formations through the initial formation of N-arylnitrilium intermediates from arenediazonium salts and nitriles, followed by the sequential nucleophilic addition and cyclization reactions with bifunctional anilines, leading to such N-heterocyclic compounds of biological and pharmacological importance. This method offers a simple, expedient, and robust approach with the use of amenable and easily accessible reactants/reagents under metal-free mild conditions, good functional group tolerance, and high efficiency. The synthetic applications were also demonstrated by derivatization of the products obtained from these processes and syntheses of a diverse range of valuable polycyclic N-heterocycles.

Recent Advances in the Transition-Metal-Free Synthesis of Quinazolines

Quinazolines are a privileged class of nitrogen-containing heterocycles, widely present in a variety of natural products and synthetic chemicals with a broad spectrum of biological and medicinal activities. Owing to their pharmaceutical applications and promising biological value, a variety of synthetic methodologies have been reported for these scaffolds. From the perspective of green and sustainable chemistry, transition-metal-free synthesis provides an alternative method for accessing several biologically active heterocycles. In this review, we summarize the recent progress achieved in the transition-metal-free synthesis of quinazolines and we cover the literature from 2015 to 2022. This aspect is present alongside the advantages, limitations, mechanistic rationalization, and future perspectives associated with the synthetic methodologies.

One-Pot Synthesis of α-Amino Bisphosphonates from Nitriles via Tf2O/HC(OR)3-Mediated Interrupted Ritter-Type Reaction

A versatile synthesis of α-amino bisphosphonates has been achieved through one-pot interrupted Ritter-type reaction under mild conditions. The reactive Ritter intermediate nitrilium is in situ generated by treatment of nitrile with readily accessible Tf₂O/HC(OR¹)₃, which is trapped by phosphite ester to deliver the desired product. This protocol is efficient, scalable, and well compatible with a broad scope of substrates. In addition, plentiful characteristic J_P-C couplings including unusual five-bond long-range ⁵J_P-C and ³J_P-C across quaternary carbon and hetero (N) atoms were observed in ¹³C NMR spectra.

Microwave-Assisted Synthesis of Quinazolines and Quinazolinones: An Overview

Microwave irradiation (MWI), as a unique, effective, sustainable, more economic, and greener source of energy compared to conventional heating, is applied in different organic transformations to result in the rapid formation of desired compounds due to thermal/kinetic effects. In this review, we try to underscore the applications of microwave irradiation (MWI) in the synthesis of quinazoline and quinazolinone derivatives that have been achieved and reported on in the last two decades.

Synthesis of 2-arylamino-3-cyanoquinolines via a cascade reaction through a nitrilium intermediate

A new method for the preparation of 2-amino-3-cyanoquinolines from readily available aryldiazonium salts, 2-aminoarylketones, and malononitrile via a cascade reaction is reported. This one-pot approach involves the in situ generation of an N-arylnitrilium intermediate from the direct reaction of aryldiazonium salts and malononitrile, which undergoes intermolecular amination, Knoevenagel condensation, and then aromatization to yield the desired compound in moderate to good yields. This methodology features a quick assembly of C2 and C3 functionalized quinolines.

Graphene oxide: a green oxidant-acid bifunctional carbon material for the synthesis of functionalized isoindolin-1-ones via formal amide insertion and substitution

A formal amide insertion and substitution reaction using graphene oxide as an oxidant-acid bifunctional carbon material

TMSOTf-catalyzed synthesis of substituted quinazolines using hexamethyldisilazane as a nitrogen source under neat and microwave irradiation conditions

An efficient synthetic route for the synthesis of substituted quinazolines under neat, metal-free and microwave irradiation conditions has been developed by using TMSOTf as an acid catalyst and HMDS as a nitrogen source.

Assembly of 1H-isoindole derivatives by selective carbon-nitrogen triple bond activation: access to aggregation-induced emission fluorophores for lipid droplet imaging

A method of selectively activating carbon–nitrogen triple bonds has been developed to access 1H-isoindole AIE fluorophores for lipid droplet imaging.

A novel strategy has been established to assemble a series of single (Z)- or (E)-1H-isoindole derivatives through selectively and sequentially activating carbon–nitrogen triple bonds in a multicomponent system containing various nucleophilic and electrophilic sites. The reaction provides efficient access to structurally unique fluorophores with aggregation-induced emission characteristics. These new fluorophores show fluorescence wavelengths and efficiencies that can be modulated and have excellent potential to specifically light up lipid droplets (LDs) in living cells with bright fluorescence, low cytotoxicity and better photostability than commercially available LD-specific dyes.

Preparation of N-Arylquinazolinium Salts via a Cascade Approach

An easy manipulation method for the preparation of N-arylquinazolinium salts is described from readily available aryldiazonium salts, nitriles, and 2-aminoarylketones in a one-pot operation. This method relies on the in situ generation of the N-arylnitrilium intermediate from the reaction of aryldiazonium salt with nitrile, which undergoes amination/cascade cyclization/aromatization, leading to N-arylquinazolinium salts in excellent yields. Nucleophilic addition of alkoxide to these N-arylquinazolinium salts provides functionalized dihydro- N-arylquinazoline.

Efficient Tandem Addition/Cyclization for Access to 2,4-Diarylquinazolines via Catalytic Carbopalladation of Nitriles

The first example of the palladium-catalyzed tandem addition/cyclization of 2-(benzylidenamino)benzonitriles with arylboronic acids has been developed. This transformation features good functional group tolerance and provides an alternative synthetic pathway to access 2,4-diarylquinazolines in moderate to good yields. A plausible mechanism for the formation of 2,4-diarylquinazolines involving sequential nucleophilic addition followed by an intramolecular cyclization is proposed.

Copper-catalyzed oxidative amination of methanol to access quinazolines

A novel method for the copper-catalyzed oxidative amination of 2′-aminoarylketones with methanol as a C1 carbon source and ammonium acetate as an amine source to construct quinazolines was established in a one-pot manner.

Biaryl synthesis with arenediazonium salts: cross-coupling, CH-arylation and annulation reactions

The rich legacy of arenediazonium salts in the synthesis of unsymmetrical biaryls, built around the seminal works of Pschorr, Gomberg and Bachmann more than a century ago, continues to make important contributions at various evolutionary stages of modern biaryl synthesis. Based on in-depth mechanistic analysis and design of novel pathways and reaction conditions, the scope of biaryl synthesis with arenediazonium salts has enormously expanded in recent years through applications of transition metal/photoredox-catalysed cross-coupling, thermal/photosensitized radical chain CH-arylation of (hetero)arenes and arylative radical annulation reactions with alkynes. These recent developments have provided facile synthetic access to a wide variety of unsymmetrical biaryls of pharmaceutical, agrochemical and optoelectronic importance with green scale-up options and created opportunities for late-stage modification of peptides, nucleosides, carbon nanotubes and electrodes, the details of which are captured in this review.

Preparation of Ketimines from Aryldiazonium Salts, Arenes, and Nitriles via Intermolecular Arylation of N-Arylnitrilium Ions

A transition-metal-free approach for the preparation of N-arylketimines has been developed from the direct reaction of aryldiazonium salts, arenes, and nitriles in a one-pot fashion with the consecutive formation of N-C and C-C bonds. This approach proceeds via an in situ generation of N-arylnitrilium intermediate, which then undergoes intermolecular arylation. This three-component strategy offers a step- and atom-efficient way to N-arylketimines from easily accessible reagents under mild reaction conditions. The characterization of stereochemistry of ketimine was achieved by X-ray crystallographic structure and theoretical calculation. Operational simplicity, shorter reaction time, excellent functional group compatibility, and scalability are the key features of this report.

Pd-Catalyzed tandem reaction of N-(2-cyanoaryl)benzamides with arylboronic acids: synthesis of quinazolines

A Pd-catalyzed tandem reaction of N-(2-cyanoaryl)benzamides with arylboronic acids for the synthesis of quinazolines has been reported.

Preparation of 3-hydroxyquinolines from direct oxidation of dihydroquinolinium salts

A series of functionalized 3,4-dihydroquinolinium salts were prepared from the reaction of aryldiazonium salt with alkene in a nitrile solution. Further oxidation yielding either 3-hydroxyquinoline or quinoline products was investigated. A one-pot process from aryldiazonium salts, alkenes and nitriles leading to 3-hydroxyquinolines was also developed. Furthermore, an intramolecular trapping of an N-arylnitrilium ion with a vinyl group at the ortho position leading to 2-substituted quinolines was revealed.

3-Hydroxyquinoline derivatives can be prepared by a cascade cyclization of aryldiazonium salts with nitriles and alkenes followed by oxygenation.