Quinazoline Synthesis via Rh(III)-Catalyzed Intermolecular C–H Functionalization of Benzimidates with Dioxazolones

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.

Tunable Rh(III)-Catalyzed C(sp2)-H Bond Functionalization of Aryl Imidates with Cyclic 1,3-Diones: Strategic Use of Directing Groups

A tunable Rh(III)-catalyzed C(sp2)-H bond functionalization of aryl imidates with cyclic 1,3-diones was developed. With suitable and straightforward reaction condition adjustments, the C-H bond functionalization of diverse aryl imidates with cyclic 1,3-diones occurred smoothly and precisely at room temperature. Accompanied by different directing group transformations, a series of corresponding aryl nitriles, hydrophenanthridin-1(2H)-ones, spiro isoindoles, or hydrophenanthridine-1,6(2H,5H)-diones were synthesized in good yields to provide a rational directing group utilization strategy for the Rh(III)-catalyzed C(sp2)-H bond activation. Control experiments and primary mechanistic studies revealed that solvent effects and functional group electronic effects might influence the reaction's selectivity.

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.

2-Substituted quinazolines: Partial agonistic and antagonistic ligands of the constitutive androstane receptor (CAR)

Following the discovery of 2-(3-methoxyphenyl)-3,4-dihydroquinazoline-4-one and 2-(3-methoxyphenyl)quinazoline-4-thione as potent, but non-specific activators of the human Constitutive Androstane Receptor (CAR, NR1I3), a series of quinazolinones substituted at the C2 phenyl ring was prepared to examine their ability to selectively modulate human CAR activity. Employing cellular and in vitro TR-FRET assays with wild-type CAR or its variant 3 (CAR3) ligand binding domains (LBD), several novel partial human CAR agonists and antagonists were identified. 2-(3-Methylphenyl) quinazolinone derivatives 7d and 8d acted as partial agonists with the recombinant CAR LBD, the former in nanomolar units (EC50 = 0.055 μM and 10.6 μM, respectively). Moreover, 7d did not activate PXR, and did not show any signs of cytotoxicity. On the other hand, 2-(4-bromophenyl)quinazoline-4-thione 7l possessed significant CAR antagonistic activity, although the compound displayed no agonistic or inverse agonistic activities. A compound possessing purely antagonistic effect was thus identified for the first time. These and related compounds may serve as a remedy in xenobiotic intoxication or, conversely, in suppression of undesirable hepatic CAR activation.

Evaluation of Antimicrobial, Anticholinesterase Potential of Indole Derivatives and Unexpectedly Synthesized Novel Benzodiazine: Characterization, DFT and Hirshfeld Charge Analysis

The pharmacological effectiveness of indoles, benzoxazepines and benzodiazepines initiated our synthesis of indole fused benoxazepine/benzodiazepine heterocycles, along with enhanced biological usefulness of the fused rings. Activated indoles 5, 6 and 7 were synthesized using modified Bischler indole synthesis rearrangement. Indole 5 was substituted with the trichloroacetyl group at the C⁷ position, yielding 8, exclusively due to the increased nucleophilic character of C⁷. When trichloroacylated indole 8 was treated with basified ethanol or excess amminia, indole acid 9 and amide 10 were yielded, respectively. Indole amide 10 was expected to give indole fused benoxazepine/benzodiazepine 11a/11b on treatment with alpha halo ester followed by a coupling agent, but when the reaction was tried, an unexpectedly rearranged novel product, 1,3-bezodiazine 12, was obtained. The synthetic compounds were screened for anticholinesterase and antibacterial potential; results showed all products to be very important candidates for both activities, and their potential can be explored further. In addition, 1,3-bezodiazine 12 was explored by DFT studies, Hirshfeld surface charge analysis and structural insight to obrain a good picture of the structure and reactivity of the products for the design of derivatised drugs from the novel compound.

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.

Cobalt Homeostatic Catalysis for Coupling of Enaminones and Oxadiazolones to Quinazolinones

Transition metal catalysis has revolutionized modern synthetic chemistry for its diverse modes of coordination reactivity. However, this versatility in reactivity is also the predominant cause of catalyst deactivation, a persisting issue that can significantly compromise its synthetic value. Homeostatic catalysis, a catalytic process that can sustain its productive catalytic cycle even when chemically disturbed, is proposed herein as an effective tactic to address the challenge. In particular, a cobalt homeostatic catalysis process has been developed for the water-tolerant coupling of enaminones and oxadiazolones to quinazolinones. Dynamic covalent bonding serves as a mechanistic handle for the preferred buffering of water onto enaminone and reverse exchange by a released secondary amine, thus securing reversible entry into cobalt's dormant and active states for productive catalysis. Through this homeostatic catalysis mode, a broad structural scope has been achieved for quinazolinones, enabling further elaboration into distinct pharmaceutically active agents.

Direct Synthesis of Biphenyl-2-carbonitriles by Rh(III)-Catalyzed C-H Hiyama Cross-Coupling in Water

This method represents an efficient rhodium(III)-catalyzed o-C-H arylation of readily available benzimidate derivatives with diverse arylsilanes in water as a sustainable solvent, enabling the straightforward synthesis of potentially useful biphenyl-2-carbonitrile derivatives. This silicon-based protocol employs benzimidates as both an efficacious directing group and the source of a nitrile group.

Cp*CoIII-catalyzed formal [4 + 2] cycloaddition of 2-phenyl-1H-imidazoles to afford imidazo[1,2-c]quinazoline derivatives

A synthetic protocol based on Cp*Co^III-catalyzed C-H amidation/annulation of 2-aryl-1H-imidazoles with 1,4,2-dioxazol-5-ones was developed to give imidazo[1,2-c]quinazoline derivatives with broad substrate scope in moderate to good yields. The method has good prospects of application in the synthesis of imidazo[1,2-c]quinazoline drugs.

1,4,2-Dioxazol-5-ones as Isocyanate Equivalents: An Efficient Synthesis of 2-Quinolinones via β-Keto Amides

Under thermal conditions, 1,4,2-dioxazol-5-ones are known to undergo decarboxylation followed by Lossen’s rearrangement to yield isocyanates. Described herein is the in situ trapping of the resulting isocyanates with carbon nucleophiles to synthesize β-keto amides. Furthermore, a general and mild method for the conversion of the resulting β-keto amides into quinolin-2-ones is reported.

Mechanism-Guided Development of Transition-Metal-Catalyzed C-N Bond-Forming Reactions Using Dioxazolones as the Versatile Amidating Source

Catalytic reactions that construct carbon-nitrogen bonds are one of central themes in both synthetic and medicinal chemistry since the obtainable nitrogen-containing motifs are commonly encountered in natural products and have also seen a growing prominence as key structural features in marketed drugs and preclinical candidates. Pd-catalyzed cross-couplings, such as Buchwald-Hartwig amination, are at the forefront of such synthetic methods in practical settings. However, they require prefunctionalized substrates such as (hetero)aryl halides that must be prepared independently, often by multiple operations. One emerging way to circumvent these preparatory steps and directly convert ubiquitous C-H bonds into valuable C-N bonds is catalytic C-H amination, which allows synthetic chemists to devise shorter and more efficient retrosynthetic schemes. The past two decades have witnessed considerable progress in expanding the repertoire of this strategy, especially by identifying effective amino group precursors. In this context, dioxazolones have experienced a dramatic resurgence in recent years as a versatile nitrogen source in combination with transition-metal catalyst systems that facilitate decarboxylation to access key metal-acylnitrenoid intermediates. In addition to their high robustness and easy accessibility from abundant carboxylic acids, the unique reactivity of the transient intermediates in the amido group transfer has led to a fruitful journey for mild and efficient C-H amidation reactions.This Account summarizes our recent contributions to the development of C-N bond-forming reactions using dioxazolones as effective nitrenoid precursors, which are categorized into two subsets according to their mechanistic differences: inner- versus outer-sphere pathways. The first section describes how we could unveil the synthetic potential of dioxazolones in the realm of the inner-sphere C-H amidation, where we demonstrated that dioxazolones serve not only as manageable alternatives to acyl azides but also as highly efficient reagents to significantly reduce the catalyst loading and temperature. Taking advantage of the mild conditions in combination with group 9 Cp*M complexes (M = Rh, Ir, Co) or isoelectronic Ru species, we have dramatically expanded the accessible synthetic scope. Mechanistic investigations revealed that the putative metal-nitrenoid species is involved as a key intermediate during catalysis, which leads to facile C-N bond formation. On the basis of the mechanistic underpinning, we have succeeded in developing novel catalytic platforms that harness the intermediacy of metal-nitrenoids to explore C-H insertion chemistry via an outer-sphere pathway. Indeed, the tailored catalysts were capable of suppressing the competitive Curtius-type decomposition, thus granting access to versatile lactam products. We have further repurposed the catalytic systems upon modification of chelating ligands and also the identity of the transition metal to achieve three goals: (i) addressing selectivity issues to control the regio-, chemo-, and enantioselectivities, (ii) developing sustainable catalysis by first-low metals, and (iii) navigating chemical space for (di)functionalization of alkenes/alkynes. Together with our own research efforts, highlighted herein are some important relevant advances by other groups. We finally conclude with a brief overview with an eye toward further developments.

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.

Synthesis of N-acylbenzimidazoles through [4 + 1] annulation of N-arylpivalimidamides with dioxazolones

Presented herein is a novel and efficient synthesis of N-acylbenzimidazoles through an unprecedented [4 + 1] annulation of N-arylpivalimidamides with dioxazolones.

Recent advances in quinazolinones as an emerging molecular platform for luminescent materials and bioimaging

This review summarized recent advances relating to the luminescence properties of quinazolinones and their applications in fluorescent probes, biological imaging and luminescent materials. Their future outlook is also included.

Rh(iii)-Catalyzed acylation of heteroarenes with cyclobutenones via C-H/C-C bond activation

Rhodium(iii)-catalyzed C-H acylation of heteroarenes has been realized using cyclobutenones as an acylating reagent. This coupling proceeded via integration of C-H activation of heteroarenes and C-C cleavage of cyclobutenones. The reaction features excellent regio/chemoselectivity leading to versatile chalcones with exclusive E-selectivity.

Recent advances in the synthesis of Quinazoline analogues as Anti-TB agents

Quinazoline analogues are one of the important nitrogen containing heterocycles that have significant bioactivity as well as found in a plethora of natural products. Tuberculosis is one of the serious universal health threats caused by Mycobacteriumtuberculosis (MTB) and primarily affects the lungs. Due to their significant bioactivity and natural occurrences of quinazolines, researchers are trying to synthesize new quinazoline analogues which may have significant potency against tuberculosis. This particular review summarizes recent development of different types of quinazoline bearing analogues as anti-tubercular (anti-TB) agents and their synthesis with structure-activity relationship.

Iron Complexes Anchored onto Magnetically Separable Graphene Oxide Sheets: An Excellent Catalyst for the Synthesis of Dihydroquinazoline-Based Compounds

In this work, a green, sustainable, and efficient protocol for the syntheses of dihydroquinazoline derivatives is proposed. Initially, three Schiff base complexes of iron containing the ligand (2,2-dimethylpropane-1,3-diyl)bis(azanylylidene)bis(methanylylidene)bis(2,4-Xphenol), where X = Cl (complex 1)/Br (complex 2)/I (complex 3), were synthesized, fully characterized, and used in the desired syntheses. Complex 1 excelled as a catalyst, closely followed by complexes 2 and 3. DFT calculations helped in rationalizing the role of the halide substituent in the ligand backbone as a relevant factor in the catalytic superiority of complex 1 over complexes 2 and 3 for the synthesis of the dihydroquinazoline derivatives. Finally, to facilitate catalyst recoverability and reusability, complex 1 was immobilized on GO@Fe₃O₄@APTES (GO, graphene oxide; APTES, 3-aminopropyltriethoxysilane) to generate GO@Fe₃O₄@APTES@FeL¹ (GOTESFe). GOTESFe was thoroughly characterized through scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy and efficiently used for the synthesis of dihydroquinazoline derivatives. GOTESFe could be magnetically recovered and reused up to five cycles without compromising its catalytic efficiency. Therefore, immobilization of the chosen iron complex onto magnetic GO sheets offers an extremely competent route in providing a blueprint of a readily recoverable, reusable, robust, and potent catalyst for the synthesis of dihydroquinazoline-based compounds.

Preparation of 4-arylquinazolines with o-(N-alkyl,N-p-tosyl)aminobenzonitriles, aryllithiums, and NIS

The treatment of o-(N-alkyl,N-p-tosyl)aminobenzonitriles with aryllithiums, followed by the reaction with water, NIS under irradiation with a fluorescent lamp, and then ^tBuOK gave 2-alkyl-4-arylquinazolines or 4-arylquinazolines in good to moderate yields. The present reaction proceeds through the formation of N-iodoimines from imines with NIS, the generation of iminyl radicals, the 1,6-H shift by iminyl radicals, the cyclization via 6-exo-tet mode, and finally the elimination of p-toluenesulfinate to generate 2-alkyl-4-arylquinazolines or 4-arylquinazolines.

Synthesis of quinazoin-4-ones through an acid ion exchange resin mediated cascade reaction

An interesting cascade reaction of N-(2-(4,5-dihydrooxazol-2-yl)phenyl)benzamide in the presence of an acid ion exchange resin is described. In this reaction, a range of substrates bearing various substituent groups are well compatible. This work provides a green and atom-economical alternative approach for the synthesis of quinazolin-4-ones in good yields.

Synthesis of 8-Alkoxy-5H-isochromeno[3,4-c]isoquinolines and 1-Alkoxy-4-arylisoquinolin-3-ols through Rh(III)-Catalyzed C-H Functionalization of Benzimidates with 4-Diazoisochroman-3-imines and 4-Diazoisoquinolin-3-ones

Rh(III)-catalyzed C-H activation/annulation of benzimidates with 4-diazoisochroman-3-imines furnished 8-alkoxy-5H-isochromeno[3,4-c]isoquinolines in moderate to excellent yields with a broad range of substrate scope. The reaction was carried out under mild reaction conditions and could be scaled up with practical usage. Similar reaction between benzimidates and 4-diazoisoquinolin-3-ones provided 1-alkoxy-4-arylisoquinolin-3-ols in excellent yields. Moreover, the synthesized products could be conveniently transformed to the corresponding heterocycles with a 1,8-naphthyridinone or isochromenopyridinone core, which are privileged structures in medicinal chemistry.

RhIII-Catalyzed one-pot cascade synthesis of quinazolines with N-alkoxyamide as an amidating reagent

Novel and efficient rhodium(iii)-catalyzed C–H bond activation and tandem annulation for the synthesis of structurally complex quinazolines have been successfully developed.

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.