Unexpected Copper-Catalyzed Cascade Synthesis of Quinazoline Derivatives

Base-Promoted [4 + 1 + 1] Multicomponent Tandem Cycloaddition of Ortho-Substituted Nitroarenes, Aldehydes, and Ammonium Salts To Access 2,4-Substituted Quinazoline Frameworks

We report a base-promoted, metal-free multicomponent tandem reaction, involving a [4 + 1 + 1] cycloaddition process between ortho-substituted nitroarenes, aldehydes, and ammonium salts. Modifying the substituents on the nitroaromatic compounds effectively provides structurally diverse 2-substituted and 4-alkenylquinazolines with good to excellent yields (77%-90% and quinazoline 51 examples) and high tolerance for various inorganic ammonium salts (13 examples, such as NH3·H2O, NH4Cl, and NH4HF2). A new method for constructing 2,4-substituted quinazoline compounds with high selectivity from simple nitrogen source compounds was developed, and the reaction can be scaled up to a gram scale. Additionally, this method also facilitates the preparation of organic molecules with photophysical properties, offering new insights into the further transformation of quinazolines.

Sustainable Synthesis of Substituted 1,3,5-Triazines by [ONO]-Pincer-Supported Nickel(II) Complexes via an Acceptorless Dehydrogenative Coupling Strategy

A facile, cost-effective, and sustainable synthesis of substituted triazines from primary alcohols by newly synthesized nickel pincer-type complexes (1-3) has been described. Herein, we report the synthesis of a set of three well-defined Ni(II) O^N^O pincer-type complexes, structurally characterized by analytical, spectral, and X-ray diffraction techniques. Further, the nickel complexes are explored as efficient catalysts (4 mol %) for the construction of 2,4,6-substituted 1,3,5-triazines from readily available alcohols via an acceptorless dehydrogenative coupling (ADC) strategy. A wide range of substituted triazine derivatives (33 examples) has been synthesized from the coupling of alcohols and benzamidine/guanidine hydrochloride with a maximum isolated yield of 92% under mild conditions, with eco-friendly H2O and H2 gas as the only byproducts. A plausible mechanism has been proposed based on a sequence of control experiments. Interestingly, the short synthesis of the antiulcer drug irsogladine and the large-scale synthesis of 2,4-diphenyl-6-(p-tolyl)-1,3,5-triazine highlight the convenience of the current methodology.

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.

Recent Advances in Metal-Catalyzed Approaches for the Synthesis of Quinazoline Derivatives

Quinazolines are an important class of heterocyclic compounds that have proven their significance, especially in the field of organic synthesis and medicinal chemistry because of their wide range of biological and pharmacological properties. Thus, numerous synthetic methods have been developed for the synthesis of quinazolines and their derivatives. This review article briefly outlines the new synthetic methods for compounds containing the quinazoline scaffold employing transition metal-catalyzed reactions.

Arene Ruthenium(II)-Catalyzed Sustainable Synthesis of 2,4-Disubstituted Quinazolines via Acceptorless Dual Dehydrogenative Coupling of Alcohols

We demonstrate an efficient and sustainable strategy for the direct synthesis of 2,4-disubstituted quinazolines by arene Ru(II)benzhydrazone complex via the eco-friendly sequential acceptorless dehydrogenative coupling of 2-aminobenzhydrol derivatives and benzyl alcohols for the first time. The new ruthenium(II) complex of the general formula [(η6-p-cymene)Ru(L1)Cl] (L1-acenaphthenequinone hydrazone) has been synthesized and characterized by analytical, spectroscopic, and single-crystal X-ray diffraction techniques. A broad spectrum of 2,4-disubstituted quinazolines have been successfully derived (25 examples) from 2-aminobenzhydrol derivatives with various benzyl alcohols using 1 mol % of catalyst loading in the presence of NH4OAc. The present protocol is highly selective and produces a maximum yield of 95% under mild reaction conditions. The different reaction intermediates detected through control experiments such as aldehyde, 2-aminobenzophenone, benzylidene(amino)phenylmethanone, and 1,2-dihydroquinazoline are isolated and authenticated by the NMR study. Gratifyingly, the coupling reaction is a simple and atom economic with the release of water and hydrogen gas as the only byproducts. A gram-scale synthesis of 2-(4-methoxyphenyl)-4-phenylquinazoline illustrates the synthetic utility of the present protocol.

Transition-metal-catalyzed synthesis of quinazolines: A review

Quinazolines are a class of nitrogen-containing heterocyclic compounds with broad-spectrum of pharmacological activities. Transition-metal-catalyzed reactions have emerged as reliable and indispensable tools for the synthesis of pharmaceuticals. These reactions provide new entries into pharmaceutical ingredients of continuously increasing complexity, and catalysis with these metals has streamlined the synthesis of several marketed drugs. The last few decades have witnessed a tremendous outburst of transition-metal-catalyzed reactions for the construction of quinazoline scaffolds. In this review, the progress achieved in the synthesis of quinazolines under transition metal-catalyzed conditions are summarized and reports from 2010 to date are covered. This is presented along with the mechanistic insights of each representative methodology. The advantages, limitations, and future perspectives of synthesis of quinazolines through such reactions are also discussed.

Metal-Free Synthesis of 2-Substituted Quinazolines via Green Oxidation of o-Aminobenzylamines: Practical Construction of N-Containing Heterocycles Based on a Salicylic Acid-Catalyzed Oxidation System

Conventional quinazoline synthesis methods involve a highly multistep reaction, and often require excess amounts of substrate to control the product selectivity, leading to significant resource wastage. Hence, in this study, from the viewpoint of green chemistry, we developed a novel metal-free synthetic method for 2-substituted quinazoline derivatives by the 4,6-dihydroxysalicylic acid-catalyzed oxidative condensation of o-aminobenzylamines and benzylamines using atmospheric oxygen. In this system, the use of a catalytic amount of BF₃‧Et₂O (10 mol%) as a Lewis acid successfully led to the efficient oxidative condensation and intramolecular cyclization of these amines, followed by aromatization to afford the corresponding 2-arylquinazolines in up to 81% yield with excellent atom economy and environmental factor. Furthermore, to expand this green oxidation method to gram-scale synthesis, we investigated the development of an oxidation process using salicylic acid itself as an organocatalyst, and established a method for the practical green synthesis of a series of nitrogen-containing heterocycles. We expect that the findings will contribute to the development of practical synthesis methods for pharmaceutical manufacturing and industrial applications, along with further advancements in green chemistry.

Fe–FeOx nanoparticles encapsulated in N-doped carbon material: a facile catalyst for selective synthesis of quinazolines from alcohols in water

A Fe–FeOx@NC catalyst with N-doped carbon encapsulated Fe–FeOx nanoparticles has excellent performance in the synthesis of quinazolines.

Ruthenium pincer complex catalyzed efficient synthesis of quinoline, 2-styrylquinoline and quinazoline derivatives via acceptorless dehydrogenative coupling reactions

The synthesis of N-heterocycles has been considered an emerging area of chemical research due to their extensive utilization in pharmaceuticals, materials science, and natural product synthesis.

Unexpected Annulation between 2-Aminobenzyl Alcohols and Benzaldehydes in the Presence of DMSO: Regioselective Synthesis of Substituted Quinolines

An unexpected annulation among 2-aminobenzyl alcohols, benzaldehydes, and DMSO to quinolines has been disclosed. For the reported annulation between 2-aminobenzyl alcohols and benzaldehydes, the change of the solvent from toluene to DMSO led to the change of the product from the diheteroatomic cyclic benzoxazines to monoheteroatomic cyclic quinolines. This annulation can be used to synthesize regioselectively different substituted quinolines by the choice of different 2-amino alcohols, aldehydes, and sulfoxides as substrates. Interestingly, introducing substituent groups to the α-position of sulfoxides resulted in the interchange of the positions between benzaldehydes and sulfoxides in the product quinolines. On the basis of the control experiments and literatures, a plausible mechanism for this annulation was proposed.

Access to 2-arylquinazolines via catabolism/reconstruction of amino acids with the insertion of dimethyl sulfoxide

Quinazoline skeletons are synthesized by amino acid catabolism/reconstruction combined with the insertion/cyclization of dimethyl sulfoxide for the first time. The amino acid acts as a carbon and nitrogen source through HI-mediated catabolism and is then reconstructed using aromatic amines and dimethyl sulfoxide (DMSO) as a one-carbon synthon. This protocol is of great significance for the further study of the conversion of amino acids.

Chemical Insights Into the Synthetic Chemistry of Quinazolines: Recent Advances

In medicinal chemistry, one of the most significant heterocyclic compounds are quinazolines, possessing broad range of biological properties such as anti-bacterial, anti-fungal, anti-HIV, anti-cancer, anti-inflammatory, and analgesic potencies. Owing to its numerous potential applications, in the past two decades, there is an increase in the importance of designing novel quinazolines, exploring promising routes to synthesize quinazolines, investigating different properties of quinazolines, and seeking for potential applications of quinazolines. The present review article describes synthesis of quinazolines via eco-friendly, mild, atom-efficient, multi-component synthetic strategies reported in the literature. The discussion is divided into different parts as per the key methods involved in the formation of quinazoline skeletons, aiming to provide readers an effective methodology to a better understanding. Consideration has been taken to cover the most recent references. Expectedly, the review will be advantageous in future research for synthesizing quinazolines and developing more promising synthetic approaches.

Mn(iii)-mediated cascade cyclization of 1-(azidomethyl)-2-isocyanoarenes with organoboronic acids: construction of quinazoline derivatives

A novel and efficient Mn(iii)-mediated oxidative radical cascade reaction of 1-(azidomethyl)-2-isocyanoarenes with organoboronic acids is reported.

Palladium(ii) N,N,O-pincer type complex-mediated dehydrogenative coupling of alcohols to quinazolines

A diverse range of quinazolines were synthesized in moderate to high yields using 0.5 mol% Pd(ii) catalyst loading under aerobic conditions.

Recent advances in multi-component reactions and their mechanistic insights: a triennium review

This review summarizes the recent developments in MCRs, incorporating different strategies along with their mechanistic aspects.

Recent advances in sustainable synthesis of N-heterocycles following acceptorless dehydrogenative coupling protocol using alcohols

In this review, we have summarized various aspects of homogeneous and heterogeneously catalyzed recent advancements in the synthesis of heterocycles following the ADC approach.

Hypervalent iodine promoted ortho diversification: 2-aryl benzimidazole, quinazoline and imidazopyridine as directing templates

The mild and efficient palladium-catalyzed ortho C(sp²)-H diversification of (NH)-free 2-substituted benzimidazole, quinazoline, and imidazopyridine is reported using hypervalent iodine as the key reagent. Acetoxy, aryl, iodide and nitro functional groups were introduced on the same substrate by simply shifting the reaction conditions in the presence of inorganic additives (Cs₂CO₃, I₂, NaNO₂) and the hypervalent iodine reagent (diacetoxyiodo)benzene (PIDA) under aerobic conditions. The combination of NaNO₂ with PIDA was successfully employed in Pd-catalyzed C-H bond nitration to achieve a library of nitrated 1,3 N-heterocycles. This versatile ortho C(sp²)-H activation strategy features operational simplicity, short reaction times, and ample substrate possibilities, it requires no ligands or silver salts as additives, and it shows good tolerance of oxidation prone functional groups.

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.

I2-Promoted Multicomponent Dicyclization and Ring-Opening Sequences: Direct Synthesis of Benzo[e][1,4]diazepin-3-ones via Dual C-O Bond Cleavage

A novel and efficient formal [4 + 2+1] annulation of aryl methyl ketones and 2-aminobenzyl alcohols for the synthesis of benzo[e][1,4]diazepin-3-ones is reported. This reaction successfully affords diverse seven-membered ring lactams via dual C-O bond cleavage. A preliminary mechanistic study showed that a multicomponent dicyclization and ring-opening sequence might occur, with the introduction of methyl sulfide proposed as the last step. This efficient strategy with mild reaction conditions and a broad substrate scope has potential applications in chemistry and medicine.

Bio-based Catalysts from Biomass Issued after Decontamination of Effluents Rich in Copper—an Innovative Approach towards Greener Copper-based Catalysis

The abundance of Cu-contaminated effluents and the serious risk of contamination of the aquatic systems combine to provide strong motivating factors to tackle this environmental problem. The treatment of polluted effluents by rhizofiltration and biosorption is an interesting ecological alternative. Taking advantage of the remarkable ability of the selected plants to bioconcentrate copper into roots, these methods have been exploited for the decontamination of copperrich effluents. Herein, we present an overview on the utility of the resulted copper-rich biomass for the preparation of novel bio-sourced copper-based catalysts for copper-mediated reactions: from the bioaccumulation of copper in plant, to the preparation and full analysis of the new Eco-Cu catalysts, and their application in selected key reactions. The hydrolysis of a thiophosphate, an Ullmanntype coupling leading to N- and O-arylated compounds, and a CuAAC “click” reaction, all performed under green and environmentally friendly conditions, will be described.

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.

Copper-Catalyzed Synthesis of Substituted Quinazolines from Benzonitriles and 2-Ethynylanilines via Carbon-Carbon Bond Cleavage Using Molecular Oxygen

A copper-catalyzed process for the synthesis of substituted quinazolines from benzonitriles and 2-ethynylanilines using molecular oxygen (O₂) as sole oxidant is described. The mild catalytic system enabled the effective cleavage of the C-C triple bond and construction of new C-N and C-C bonds in one operation. Furthermore, the compound N, N-dimethyl-4-(2-(4-(trifluoromethyl)phenyl)quinazolin-4-yl)aniline (3dj) exhibited obvious aggregation-induced emission phenomenon, and the fluorescence quantum yield (Φ_F,film) and lifetime (τ_film) were measured to be 45.5% and 5.8 ns in thin films state, respectively.

Base-Promoted Synthesis of 2-Aryl Quinazolines from 2-Aminobenzylamines in Water

A transition-metal-free procedure for the synthesis of a highly valuable class of heteroaromatics, quinazolines, was developed by using easily available 2-aminobenzylamines and α,α,α-trihalotoluenes. The transformation proceeded smoothly in the presence of only sodium hydroxide and molecular oxygen in water at 100 °C, furnishing a variety of 2-aryl quinazolines. The crystallization process of the crude reaction mixture for the purification of the solid products circumvents huge solvent-consuming workup and column chromatographic techniques, which make the overall process more sustainable and economical.