Facile Synthesis of π-Conjugated Quinazoline-Substituted Ethenes from 2-Ethynylanilines and Benzonitriles under Transition-Metal-Free Conditions

Visible-light-mediated photocatalytic aerobic oxidative synthesis of pyrazolo[4,3-d]pyrimidin-7(6H)-ones and sildenafil

A novel, efficient and sustainable methodology involving visible-light-mediated construction of pyrazolo[4,3-d]pyrimidin-7(6H)-ones from easily available 4-amino-1-methyl-3-propyl-1H-pyrazole-5-carboxamide and aldehydes in the presence of 4CzIPN under an oxygen atmosphere has been developed. This photocatalytic system worked under mild conditions and avoided the use of any excess amount of toxic oxidants and transition metals. A variety of functionalized products were obtained in good to excellent yields. Notably, the marketed drug sildenafil was successfully synthesized. In addition, a plausible reaction mechanism involving a radical process has been proposed and further applications of this protocol are under way in our laboratory.

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.

Synthesis of C-N or C-C Spiroindolines via Rearrangement Coupling Reaction

Herein, we report a general approach to effectively construct C-N or C-C spiroindolines using tetrahydro-β-carbolines as starting materials via a rearrangement coupling reaction. This method is characterized by its operational simplicity and mild conditions. Notably, a wide range of anilines and indoles are suitable for this intermolecular coupling, yielding the corresponding C-N or C-C spiroindolines in good to excellent yields.

RuII-Catalyzed C-H Activated Diverse Cyclization with Transformation of Substrate-DG to Functional Groups: Synthesis of Functionalized Indoles and Indenones

We present an elegant and efficient method for Ru(II)-catalyzed C-H activation, followed by a diverse range of intermolecular cross-dehydrogenative coupling reactions. This process is facilitated by an intrinsic directing group (DG) and includes the in situ transformation of the DG into common and useful functional groups. Notably, this method avoids the installation and deinstallation of the directing group. Our approach enables the selective functionalization of benzimidate, coupled with the cyclization of o-alkynyl-aniline, resulting in the high-yield synthesis of diverse compounds such as indoles, and indenones. The sequential formation of C-N, C-C, and C-O bonds, followed by hydrolysis, underscores the versatile in situ transformation of the directing group. This work not only broadens the synthetic toolbox for constructing complex heterocyclic structures but also highlights the potential for sustainable and selective synthesis of valuable compounds.

Hybrid Heterocycles: Ag(I)-Catalyzed C-C/C-N/C-O Coupled Cascade Dual Cyclization to Valuable Indolo-4H-indolones and Indolo-4H-chromenes

Herein, we report a highly efficient Ag(I)-catalyzed indolyzation with Friedel-Crafts alkylation through a cascade cyclization strategy for accessing valuable hybrid heterocycles for the first time. This general strategy consists of forming four C-C/C-N/C-O bonds toward dual annulation reactions of 2-alkynylanilines with methyl benzoate-2-carboxaldehydes and aromatic amines, as well as with salicylaldehydes and malononitrile. Variably substituted new indolo-4H-phthalimidines and indolo-4H-chromenes were synthesized with excellent yields (85-93%) under mild reaction conditions.

Recent Advances in the Transition-Metal-Free Synthesis of Quinazolines

Quinazolines are a privileged class of nitrogen-containing heterocycles, widely present in a variety of natural products and synthetic chemicals with a broad spectrum of biological and medicinal activities. Owing to their pharmaceutical applications and promising biological value, a variety of synthetic methodologies have been reported for these scaffolds. From the perspective of green and sustainable chemistry, transition-metal-free synthesis provides an alternative method for accessing several biologically active heterocycles. In this review, we summarize the recent progress achieved in the transition-metal-free synthesis of quinazolines and we cover the literature from 2015 to 2022. This aspect is present alongside the advantages, limitations, mechanistic rationalization, and future perspectives associated with the synthetic methodologies.

Palladium(II)-Catalyzed Three-Component Tandem Cyclization Reaction for the One-Pot Assembly of 4-Arylquinazolines

A one-pot method for joining three separate components leading to an assortment of 4-arylquinazolines (27 examples) in good to excellent yields is described. The method consists of a palladium(II)-catalyzed­ cascade reaction involving C(sp)–C(sp2) coupling followed by intramolecular C–N bond formation. The reaction was readily scaled up to gram quantity and successfully applied to the synthesis of a translocator­ protein (TSPO) ligand.

Innovative Synthetic Procedures for Luminogens Showing Aggregation-Induced Emission

As a consequence of their intrinsic advantageous properties, luminogens that show aggregation-induced emission (AIEgens) have received increasing global interest for a wide range of applications. Whereas general synthetic methods towards AIEgens largely rely on tedious procedures and limited reaction types, various innovative synthetic methods have now emerged as complementary, and even alternative, strategies. In this Review, we systematically highlight advancements made in metal-catalyzed functionalization and metal-free-promoted pathways for the construction of AIEgens over the past five years, and briefly illustrate new perspectives in this area. The development of innovative synthetic procedures will enable the facile synthesis of AIEgens with great structural diversity for multifunctional applications.

Assembly of 1H-isoindole derivatives by selective carbon-nitrogen triple bond activation: access to aggregation-induced emission fluorophores for lipid droplet imaging

A method of selectively activating carbon–nitrogen triple bonds has been developed to access 1H-isoindole AIE fluorophores for lipid droplet imaging.

A novel strategy has been established to assemble a series of single (Z)- or (E)-1H-isoindole derivatives through selectively and sequentially activating carbon–nitrogen triple bonds in a multicomponent system containing various nucleophilic and electrophilic sites. The reaction provides efficient access to structurally unique fluorophores with aggregation-induced emission characteristics. These new fluorophores show fluorescence wavelengths and efficiencies that can be modulated and have excellent potential to specifically light up lipid droplets (LDs) in living cells with bright fluorescence, low cytotoxicity and better photostability than commercially available LD-specific dyes.

On water: iodine-mediated direct construction of 1,3-benzothiazines from ortho-alkynylanilines by regioselective 6-exo-dig cyclization

Herein, we report the 6-exo-dig ring closure of ortho-alkynylanilines with readily available aroyl isothiocyanate. An environmentally benign, metal- and base-free, iodine promoted cascade synthesis of highly functionalized (benzo[1,3]thiazin-2-yl)benzimidic acids has been accomplished via in situ generated ortho-alkynylthiourea. The established methodology employs the abundant chemical feedstock of ortho-alkynylanilines and aroyl isothiocyanates and could be applied in the late-stage synthesis of pharmaceutically active 1,3-benzothiazine containing molecules. Furthermore, the discovered protocol exclusively delivers bis (benzo[1,3]thiazin-2-yl)dibenzimidic acid products and preserves the iodo-olefin substitution pattern which can be exploited by further derivatization.