Synthesis of quinazoline-3-oxides via a Pd(ii) catalyzed azide-isocyanide coupling/cyclocondensation reaction

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.

Nitrene-transfer from azides to isocyanides: Unveiling its versatility as a promising building block for the synthesis of bioactive heterocycles

Cross-coupling azide and isocyanide have recently gained recognition as ideal methods for efficiently synthesizing asymmetric carbodiimides. This reaction exhibits high reaction rates, efficiency, and favorable atom/step/redox economy. It enables the nitrene-transfer process, facilitating the formation of C-N bonds and providing a direct and cost-effective synthetic strategy for generating diverse carbodiimides. These carbodiimides are highly reactive compounds that can undergo in-situ transformations into various functional groups and organic compounds, including heterocycles. Developing one-pot and tandem processes in this field has significantly contributed to advancements in organic chemistry. Moreover, the demonstrated utility of these architectural motifs extends to areas such as chemical biology and medicinal chemistry, further highlighting their potential in various scientific applications.

In Vitro α-Glucosidase and α-Amylase Inhibition, Cytotoxicity and Free Radical Scavenging Profiling of the 6-Halogeno and Mixed 6,8-Dihalogenated 2-Aryl-4-methyl-1,2-dihydroquinazoline 3-Oxides

Series of the 6-bromo/iodo substituted 2-aryl-4-methyl-1,2-dihydroquinazoline-3-oxides and their mixed 6,8-dihalogenated (Br/I and I/Br) derivatives were evaluated for inhibitory properties against α-glucosidase and/or α-amylase activities and for cytotoxicity against breast (MCF-7) and lung (A549) cancer cell lines. The 6-bromo-2-phenyl substituted 3a and its corresponding 6-bromo-8-iodo-2-phenyl-substituted derivative 3i exhibited dual activity against α-glucosidase (IC50 = 1.08 ± 0.02 μM and 1.01 ± 0.05 μM, respectively) and α-amylase (IC50 = 5.33 ± 0.01 μM and 1.18 ± 0.06 μM, respectively) compared to acarbose (IC50 = 4.40 ± 0.05 μM and 2.92 ± 0.02 μM, respectively). The 6-iodo-2-(4-fluorophenyl)-substituted derivative 3f, on the other hand, exhibited strong activity against α-amylase and significant inhibitory effect against α-glucosidase with IC50 values of 0.64 ± 0.01 μM and 9.27 ± 0.02 μM, respectively. Compounds 3c, 3l and 3p exhibited the highest activity against α-glucosidase with IC50 values of 1.04 ± 0.03, 0.92 ± 0.01 and 0.78 ± 0.05 μM, respectively. Moderate cytotoxicity against the MCF-7 and A549 cell lines was observed for these compounds compared to the anticancer drugs doxorubicin (IC50 = 0.25 ± 0.05 μM and 0.36 ± 0.07 μM, respectively) and gefitinib (IC50 = 0.19 ± 0.04 μM and 0.25 ± 0.03 μM, respectively), and their IC50 values are in the range of 10.38 ± 0.08-25.48 ± 0.08 μM and 11.39 ± 0.12-20.00 ± 0.05 μM, respectively. The test compounds generally exhibited moderate to strong antioxidant capabilities, as demonstrated via robust free radical scavenging activity assays, viz., DPPH and NO. The potential of selected derivatives to inhibit superoxide dismutase (SOD) was also investigated via enzymatic assay in vitro. Molecular docking revealed the N-O moiety as essential to facilitate electrostatic interactions of the test compounds with the protein residues in the active site of α-glucosidase and α-amylase. The presence of bromine and/or iodine atoms resulted in increased hydrophobic (alkyl and/or π-alkyl) interactions and therefore increased inhibitory effect against both enzymes.

Synthesis of Imidazo[1,2-a]pyridine-Fused 1,3-Benzodiazepine Derivatives with Anticancer Activity via a One-Pot Cascade GBB-3CR/Pd(II)-Catalyzed Azide-Isocyanide Coupling/Cyclization Process

A new one-pot synthesis of imidazo[1,2-a]pyridine-fused 1,3-benzodiazepine derivatives via a sequential GBB-3CR/Pd(II)-catalyzed azide-isocyanide coupling/cyclization process was developed. The Groebke-Blackburn-Bienaymé three-component reactions (GBB-3CR) of 2-aminopyridine, 2-azidobenzaldehydes, and isocyanides in the presence of a catalytic amount of p-toluenesulfonic acid gave azide intermediates without separation. The reaction was followed by using another molecule of isocyanides to produce imidazo[1,2-a]pyridine-fused 1,3-benzodiazepine derivatives in good yields by the Pd(II)-catalyzed azide-isocyanide coupling/cyclization reaction. The synthetic approach produces novel nitrogen-fused polycyclic heterocycles under mild reaction conditions. The preliminary biological evaluation demonstrated that compound 6a inhibited glioma cells efficiently, suggesting potentially broad applications of the approach for synthesis and medicinal chemistry.

A Review on the Synthesis and Chemical Transformation of Quinazoline 3-Oxides

The synthesis of quinazoline 3-oxides and their derivatives has attracted considerable attention due to their reactivity as intermediates in the synthesis of quinazoline analogues and their ring-expanded derivatives. Despite this, there is no comprehensive review dedicated to the synthesis and chemical transformation of these biologically relevant azaaromatic oxides. This review aims to provide an up-to-date record of the synthesis of quinazoline 3-oxides and their chemical transformation. It is hoped that this information will help medicinal chemistry researchers to design and synthesize new derivatives or analogues to treat various diseases.

Transition metal-catalysed carbene- and nitrene transfer to carbon monoxide and isocyanides

Transition metal-catalysed carbene- and nitrene transfer to the C1-building blocks carbon monoxide and isocyanides provides heteroallenes (i.e. ketenes, isocyanates, ketenimines and carbodiimides). These are versatile and reactive compounds allowing in situ transformation towards numerous functional groups and organic compounds, including heterocycles. Both one-pot and tandem processes have been developed providing valuable synthetic methods for the organic chemistry toolbox. This review discusses all known transition metal-catalysed carbene- and nitrene transfer reactions towards carbon monoxide and isocyanides and in situ transformation of the heteroallenes hereby obtained, with a special focus on the general mechanistic considerations.

Recent Advances in Palladium-Catalyzed Isocyanide Insertions

Isocyanides have long been known as versatile chemical reagents in organic synthesis. Their ambivalent nature also allows them to function as a CO-substitute in palladium-catalyzed cross couplings. Over the past decades, isocyanides have emerged as practical and versatile C1 building blocks, whose inherent N-substitution allows for the rapid incorporation of nitrogeneous fragments in a wide variety of products. Recent developments in palladium catalyzed isocyanide insertion reactions have significantly expanded the scope and applicability of these imidoylative cross-couplings. This review highlights the advances made in this field over the past eight years.

An Aqueous Facile Synthesis of 2,3-Dihydroquinazolin-4(1H)-One Derivatives by Reverse Zinc Oxide Micelles as Nanoreactor

A green synthetic protocol has been developed for the efficient preparation of 2,3-dihydroquinazolin−4(1H)-one derivatives with excellent yield in aqueous media. Reverse zinc oxide micelles catalyzed the reactions efficiently and selectively as the hallow nanoreactor. Moreover, the catalyst was reusable without significant loss of catalytic efficiency. The notable advantages of the procedure are high yields and mild reaction conditions, simple operation, nonchromatographic purification, environmentally friendly and good versatile substrates.

I2-Catalyzed oxidative synthesis of N,4-disubstituted quinazolines and quinazoline oxides

An easy and efficient approach to the synthesis of N,4-disubstituted quinazoline-2-amine and oxides is described. This transformation proceeds smoothly in the presence of molecular iodine. The metal-free protocol presented here is insensitive to air moisture and operationally simple. This versatile and synthetic methodology is broadly applicable to a variety of N,4-disubstituted quinazoline-2-amines and oxides, which are synthesized in good to excellent yields starting from readily available inexpensive precursors.