Synthesis of Diverse Azolo[c]quinazolines by Palladium(II)- Catalyzed Aerobic Oxidative Insertion of Isocyanides

Palladium-catalyzed cascade cyclization of isocyanides with di-(o-iodophenyl)sulfonylguanidines: access to heterocyclic fused quinazolines

A palladium-catalyzed cascade cyclization reaction of di-o-iodophenyl sulfonylguanidines with isocyanides for the efficient and selective synthesis of 5- or 6-membered heterocyclic fused quinazolines has been developed. Diverse functional groups are well tolerated, and this method has been successfully applied to a larger scale synthesis.

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.

Nucleophile-nucleofuge duality of azide and arylthiolate groups in the synthesis of quinazoline and tetrazoloquinazoline derivatives

5-Arylthio-tetrazolo[1,5-c]quinazolines (tautomers of 2-arylthio-4-azido-quinazolines) undergo facile nucleophilic aromatic substitution reactions with amines, alcohols and alkylthiols. This, combined with the recently reported arylsulfanyl group dance, provides straightforward access to 4-azido-2-N-, O-, S-substituted quinazolines and/or their tetrazolo tautomers from commercially available 2,4-dichloroquinazoline. The azidoazomethine-tetrazole tautomeric equilibrium and the electron-withdrawing character of the fused tetrazolo system plays a central role in the developed transformations. 5-Amino-substituted tetrazolo[1,5-c]quinazolines undergo media-controlled tautomeric equilibrium, which permits them to demonstrate the reactivity traditionally associated with the azido substituent. Furthermore, a method for 5-O-substitited tetrazolo[1,5-a]quinazolines from 2,4-diazidoquinazoline was developed during the structural elucidation of the substitution products. The developed methodology will facilitate medicinal chemistry investigations into quinazoline derivatives and the discovered fluorescent properties of some of the products (e.g., 4-(4-phenyl-1H-1,2,3-triazol-1-yl)-2-(4-methylpiperazin-1-yl)quinazoline: λ_em. = 461 nm, Φ_DCM = 0.89) could serve as a starting point for their further applications in analytical and materials science.

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.

Transition-metal and oxidant-free approach for the synthesis of diverse N-heterocycles by TMSCl activation of isocyanides

A highly efficient TMSCl-mediated addition of N-nucleophiles to isocyanides has been achieved. This transition-metal and oxidant-free strategy has been applied to the construction of various N-heterocyles such as quinazolinone, benzimidazole and benzothiazole derivatives by the use of distinct amino-based binucleophiles. The notable feature of this protocol includes its mild reaction condition, broad functional group tolerance and excellent yield.

A highly efficient TMSCl-mediated addition of N-nucleophiles to isocyanides has been achieved.

Bimetallic Cu/Pd-catalyzed three-component azide-alkyne cycloaddition/isocyanide insertion: synthesis of fully decorated tricyclic triazoles

The construction of fully decorated 1,2,3-triazole-fused 5-, 6- and 7-membered rings has been disclosed via a bimetallic relay-catalyzed cascade process combining azide-alkyne cycloaddition, C(sp2)-H functionalization of intermediary 1,2,3-triazoles and isocyanide insertion. The salient features of this methodology include simple starting materials, reduced synthetic steps, good substrate scope and high efficiency.

I2/CHP mediated [1 + 1 + 1 + 1] cyclization of aromatic isocyanides with amines to construct 1,3-diazetidine-2,4-diimine derivatives

An I₂/CHP (cumene hydroperoxide) mediated [1 + 1 + 1 + 1] cyclization of aromatic isocyanides with readily accessible amines via the formation of 4 new C–N bonds has been developed to construct unsymmetric 1,3-diazetidine-2,4-diimine derivatives under mild conditions.

Co(acac)2/O2-catalyzed oxidative isocyanide insertion with 2-vinylanilines: efficient synthesis of 2-aminoquinolines

A series of 2-aminoquinolines were afforded by Co(acac)₂ catalyzed isocyanide insertion with 2-vinylanilines under an O₂ atmosphere.

Synthesis of benzoimidazoquinazolines by cobalt-catalyzed isocyanide insertion–cyclization

The synthesis of benzoimidazoquinazoline amines by the reaction of isocyanides and benzo[d]imidazol-anilines via a cobalt-catalyzed isocyanide insertion reaction into the two N–H active bonds is reported.

The Conversion of 4-Anilinoquinazoline- and 3-Aryl-4-imino-3,4-dihydro-quinazoline-2-carbonitriles into Benzo[4,5]imidazo[1,2-c]quinazoline-6-carbonitriles via Oxidative and Nonoxidative C-N Couplings

Benzo[4,5]imidazo[1,2-c]quinazoline-6-carbonitriles are prepared in high yields via three new routes: (1) a Cu(OTf)2 (0-5 mol %) catalyzed hypervalent iodine [PhI(OTf)2] mediated oxidative coupling of 4-anilinoquinazoline-2-carbonitriles in neat trifluoroacetic acid (TFA); (2) a Pd(OAc)2 (10 mol %) or CuI (10 mol %) mediated nonoxidative coupling of 4-(2-bromoanilino)quinazoline-2-carbonitrile; and (3) a nonoxidative Pd(Ar3P)3 [Ar = 3,5-(F3C)2C6H3] [aka Superstable Pd(0) Catalyst] (10 mol %) mediated intramolecular C-N cyclization of 3-(2-bromophenyl)-4-imino-3,4-dihydroquinazoline-2-carbonitriles. All new compounds are fully characterized.

Palladium-catalyzed direct coupling of 2-vinylanilines and isocyanides: an efficient synthesis of 2-aminoquinolines

A variety of 2-aminoquinolines were prepared in good to excellent yields.

Palladium(0)-catalyzed single and double isonitrile insertion: a facile synthesis of benzofurans, indoles, and isatins

A palladium(0)-catalyzed cascade process consisting of isonitrile insertion and α-Csp(3)-H cross-coupling can be achieved for the synthesis of benzofurans and indoles. The construction of isatins by a Pd-catalyzed cascade reaction incorporating double isonitrile insertion, amination, and hydrolysis has also been achieved. The key features of this work include diverse heterocycle synthesis, phosphine-ligand-free reaction conditions, a one-pot procedure, simple and commercially available starting materials, broad functional-group compatibility, and moderate to good reaction yields.

Synthetic approaches, functionalization and therapeutic potential of quinazoline and quinazolinone skeletons: the advances continue

The presence of N-heterocycles as an essential structural motif in a variety of biologically active substances has stimulated the development of new strategies and technologies for their synthesis. Among the various N-heterocyclic scaffolds, quinazolines and quinazolinones form a privileged class of compounds with their diverse spectrum of therapeutic potential. The easy generation of complex molecular diversity through broadly applicable, cost-effective, practical and sustainable synthetic methods in a straightforward fashion along with the importance of these motifs in medicinal chemistry, received significant attention from researchers engaged in drug design and heterocyclic methodology development. In this perspective, the current review article is an effort to recapitulate recent developments in the eco-friendly and green procedures for the construction of highly challenging and potentially bioactive quinazoline and quinazolinone compounds in order to help medicinal chemists in designing and synthesizing novel and potent compounds for the treatment of different disorders. The key mechanistic insights for the synthesis of these heterocycles along with potential applications and manipulations of the products have also been conferred. This article also aims to highlight the promising future directions for the easy access to these frameworks in addition to the identification of more potent and specific products for numerous biological targets.