Synthesis of Quinazolines and Tetrahydroquinazolines: Copper-Catalyzed Tandem Reactions of 2-Bromobenzyl Bromides with Aldehydes and Aqueous Ammonia or Amines

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.

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.

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.

Possible competitive modes of decarboxylation in the annulation reactions of ortho-substituted anilines and arylglyoxylates

Annulation reactions of ortho-substituted anilines and arylglyoxylates to the tandem synthesis of nitrogen heterocycles in the presence of K₂S₂O₈ have been investigated, which occur via decarboxylation before or after the reaction with anilines.

Inverse-electron-demand [4+2] cycloaddition of photogenerated aza-ortho-quinone methides with 1,3,5-triazinanes: access to perfluoroalkylated tetrahydroquinazolines

A [4+2] cycloaddition of photogenerated aza-ortho-quinone methides with formaldimines derived from 1,3,5-triazinanes is described.

One-pot regioselective C-H activation iodination-cyanation of 2,4-diarylquinazolines using malononitrile as a cyano source

A one-pot cyanation of 2,4-arylquinazoline with NIS and malononitrile has been developed. The one-pot reaction includes two steps. The Rh-catalyzed selective C-H activation/iodization of 2,4-diarylquinazoline with NIS, and then Cu-catalyzed cyanation of the corresponding iodinated intermediate with malononitrile to selectively give 2-(2-cyanoaryl)-4-arylquinazolines or 2-(2,6-dicyanoaryl)-4-arylquinazolines in good to excellent yields.

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.

One-pot three-component selective synthesis of isoindolo[2,1-a]quinazoline derivatives via a palladium-catalyzed cascade cyclocondensation/cyclocarbonylation sequence

A practical and highly efficient procedure for the selective preparation of 6,6a-dihydroisoindolo[2,1-a]quinazoline-5,11-diones through a palladium-catalyzed one-pot three-component cascade reaction of 2-aminobenzamides with 2-bromobenzaldehydes and carbon monoxide under atmospheric pressure has been developed. This cascade reaction, in which four new C-C/C-N bonds and two new rings are simultaneously constructed, is triggered by a cyclocondensation of 2-aminobenzamides with 2-bromobenzaldehydes, followed by a Pd-catalyzed cyclocarbonylation of the in situ formed 2,3-dihydroquinazolin-4(1H)-ones with CO (1 atm). Compared with the existing methods, the present protocol has the advantages of readily available starting materials, broad substrate scope, structural diversity of products, and free of high-pressure equipment.

Experimental and theoretical investigations into the stability of cyclic aminals

Background: Cyclic aminals are core features of natural products, drug molecules and important synthetic intermediates. Despite their relevance, systematic investigations into their stability towards hydrolysis depending on the pH value are lacking. Results: A set of cyclic aminals was synthesized and their stability quantified by kinetic measurements. Steric and electronic effects were investigated by choosing appropriate groups. Both molecular mechanics (MM) and density functional theory (DFT) based studies were applied to support and explain the results obtained. Rapid decomposition is observed in acidic aqueous media for all cyclic aminals which occurs as a reversible reaction. Electronic effects do not seem relevant with regard to stability, but the magnitude of the conformational energy of the ring system and pKa values of the N-3 nitrogen atom. Conclusion: Cyclic aminals are stable compounds when not exposed to acidic media and their stability is mainly dependent on the conformational energy of the ring system. Therefore, for the preparation and work-up of these valuable synthetic intermediates and natural products, appropriate conditions have to be chosen and for application as drug molecules their sensitivity towards hydrolysis has to be taken into account.

One-pot three-component synthesis of quinazolines via a copper-catalysed oxidative amination reaction

A copper-catalysed three-component reaction for constructing a series of quinazoline derivatives has been developed.

Tandem copper (Cu) catalysed N-arylation–vinylogous nitroaldol condensation of 3,5-disubstituted 4-nitropyrazoles

A tandem process involving copper catalysed N-arylation and vinylogous nitroaldol condensation is described.

Palladium-catalyzed one pot 2-arylquinazoline formation via hydrogen-transfer strategy

The palladium catalytic system was first applied to 2-arylquinazoline synthesis via hydrogen transfer methodology. Various (E)-2-nitrobenzaldehyde O-methyl oximes reacted easily with alcohols or benzyl amines to provide N-heterocyclic compounds in good to high yields. Similarly, the heterocyclic products could be prepared by the reaction of 1-(2-nitrophenyl)ethanone, urea and benzyl alcohols. In these reactions, the nitro group was reduced in situ by hydrogen generated from the alcohol dehydrogenation step.

A convenient palladium-catalyzed carbonylative synthesis of quinazolines from 2-aminobenzylamine and aryl bromides

An interesting approach for the synthesis of 2-functionalized quinazolines has been developed. Various quinazolines have been produced in moderate to excellent yields.

Rapid assembly of quinazolinone scaffold via copper-catalyzed tandem reaction of 2-bromobenzamides with aldehydes and aqueous ammonia: application to the synthesis of the alkaloid tryptanthrin

An efficient synthesis of quinazolinones via copper-catalyzed tandem reaction of 2-bromobenzamides with aldehydes and aqueous ammonia has been developed.