Triazoloquinazoline: Synthetic Strategies and Medicinal Importance

Abstract

Triazoloquinazoline is a fused heterocyclic nucleus, formed by the fusion of two fundamental heterocyclic moieties; triazole and quinazoline. This class of compound is known for its potential as a therapeutic agent and is endowed with several pharmacological applications. Triazoloquinazoline and its derivatives have shown a variety of biological applications such as anticancer, anti-inflammatory, antimicrobial, antiviral, antihypertensive, anticonvulsant, antidiabetic, antioxidant, adenosine receptor antagonist, and significant cytotoxic activities. Hence, this privileged scaffold could act as an important candidate in the field of drug development. Many synthetic protocols have been developed to efficiently synthesize this fused heterocycle and its derivatives. Triazole and quinazoline rings fused at different positions which occurs in various isomeric forms such as, 1,2,4-triazolo[1,5-c]quinazoline, 1,2,4-triazolo[1,5-a]quinazoline, 1,2,4-triazolo[4,3-c]quinazoline, 1,2,4-triazolo[4,3-a]quinazoline, etc. This book chapter covers the synthesis of various isomeric forms of triazoloquinazoline as well as their biological activities.

Design, Synthesis and Photophysical Properties of 5-Aminobiphenyl Substituted [1,2,4]triazolo[4,3-c]- and [1,2,4]triazolo[1,5-c]quinazolines

“…Triazoloquinazoline represents polyazaheterocycle, which consists of triazolo moiety fused to a quinazoline ring. Its derivatives are widely known as an important class of heterocyclic aromatic compounds for various pharmaceutical applications [1,2]. Moreover, triazoloquinazolines provide a promising molecular platform for materials sciences.…”

“…The quinazoline component has been explored in the context of fundamental research [3][4][5], with some quinazoline derivatives revealed to have potential application in optoelectronics [6][7][8][9], detection of analytes [10,11], bioimaging [12], etc. [1,2,4]Triazole derivatives, in turn, are considered as blue phosphorescent, TADF emitters or host materials for OLED devices [13][14][15]. Other D-π-A-π-D structures with a triazole ring as an acceptor part show strong emission in solution and potential for optoelectronic purposes [16,17].…”

“…The advantages of fused triazoles, such as the extended π-conjugation system, rigid planar stricture, tuning of the molecular energy levels, and good thermal and morphological stabilities were taken into account when creating the [1,2,4]triazolo [4,3-a]pyridine and [1,2,4]triazolo [1,5-a]pyridine luminophores [19][20][21]. Moreover, [1,2,4]triazolopyridine derivatives are suitable scaffolds for the designing of highly twisted π-conjugation structures, maintaining high triplet energies.…”

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Two series of novel [1,2,4]triazolo [4,3-c]-and [1,2,4]triazolo [1,5-c]quinazoline fluorophores with 4′-amino[1,1′]-biphenyl residue at position 5 have been prepared via Pd-catalyzed cross-coupling Suzuki-Miyaura reactions. The treatment of 2-(4-bromophenyl)-4-hydrazinoquinazoline with orthoesters in solvent-free conditions or in absolute ethanol leads to the formation of [4,3-c]-annulated triazoloquinazolines, whereas [1,5-c] isomers are formed in acidic media as a result of Dimroth rearrangement.

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“…A 1D-NMR and 2D-NMR spectroscopy, as well as a single-crystal X-ray diffraction analysis, unambiguously confirmed the annelation type and determined the molecular structure of p-bromophenyl intermediates and target products. Photophysical properties of the target compounds were investigated in two solvents and in the solid state and compared with those of related 3-aryl-substituted [1,2,4]triazolo [4,3-c]quinazolines. The exclusion of the aryl fragment from the triazole ring has been revealed to improve fluorescence quantum yield in solution.…”