Synthesis of pyrimido[2,1-a]isoindolone and isoindolo[2,1-a]quinazolinone via intramolecular aza-Prins type reaction

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.

Cascade Alkynyl Prins Cyclization and Aza-Michael Reaction: En Route to Regioselective Pyrano- and Isochromenoquinoline Scaffolds

A metal-free, Lewis acid approach for the regioselective synthesis of dihydropyranoquinoline scaffolds has been unveiled. The methodology employs a cascade alkynyl Prins-aza-Michael reaction sequence to deliver the products in good to excellent yields. The strategy features mild reaction conditions, broad substrate scope, and high functional group tolerance. The protocol has been further extended to include isochromenoquinoline derivatives. The utility of the reaction lies in the synthesis of highly fused polycyclic N,O-heterocycles via intramolecular Heck coupling. Additionally, a Rh(III)-catalyzed annulation results in the formation of highly fluorescent pentacyclic ammonium salts in excellent yields. Photophysical studies reveal that these pentacyclic ammonium salts exhibit strong emission in the green region (500-550 nm).

A Lewis Acid-Catalyzed Cascade Synthesis of Fused N-Heterocycles from 2-Alkynylanilines and 2-Formylbenzonitriles: Unveiling Iminoisoindoloindolone and Its Derivatives

We herein reveal a streamlined synthesis of structurally fused 6-iminoisoindoloindolones via a meticulously orchestrated cascade reaction. This process seamlessly intertwines 2-alkynylaniline and 2-formylbenzonitrile under the catalytic influence of TMSOTf, giving rise to these compounds in remarkable yields that stand as a testament to the efficiency of our approach. Moreover, the versatility of this synthetic strategy extends far beyond mere synthesis, offering a gateway to the creation of both isoindoloindolone and unprecedented diphenylbenzopyrrolizinoisoquinolinone derivatives, thereby opening new horizons in the realm of chemical innovation. Furthermore, the strategic elegance of this synthetic methodology is underscored by its potential for scale-up production and applicability across diverse chemical contexts.

Synthesis of Highly π-Extended Dihydrobenzo[a]indenocarbazole Scaffolds via Tandem Benzannulation and Friedel-Crafts Reaction of 2-Alkynylanilines and 2-Alkynylbenzaldehydes Promoted by Lewis Acid

A novel and efficient tandem protocol for the swift synthesis of dihydrobenzo[a]indenocarbazole frameworks from 2-alkynylanilines and 2-alkynylbenzaldehydes via BF3·OEt2-facilitated benzannulation and Friedel-Crafts reaction has been described. This innovative approach accommodates a wide array of functional groups, offering a myriad of diversified carbazole products. Later, postsynthetic modification leads to its C(sp3)-H hydroxylation. Furthermore, the photophysical properties of some selected synthesized moieties have been meticulously investigated, promising exciting avenues for further exploration.

Stereoselective synthesis of gem-dihalopiperidines via the halo-aza-Prins cyclization reaction: access to piperidin-4-ones and pyridines

An efficient methodology for the synthesis of 4,4-dihalopiperidine derivatives in excellent yields has been developed using N-(3-halobut-3-en-1-yl)-4-methylbenzenesulfonamide and an aldehyde catalyzed by In(OTf)3. The reaction involves an initial formation of a six-membered carbocation via the aza-Prins cyclization reaction followed by a nucleophilic attack by a halide ion to give 4,4-dihalopiperidine. The dihalopiperidine is converted to tetrahydropiperidinone using Ac2O/Et3N in DCM/H2O (1 : 1). It is also utilized for the synthesis of pyridine scaffolds by treatment with DBU. Furthermore, the dihalopiperidine is transformed to its enol ether derivatives using KOH in alcohol.

Nitrile stabilized synthesis of pyrrolidine and piperidine derivatives via tandem alkynyl aza-Prins-Ritter reactions

An efficient methodology for the synthesis of N-(pyrrolidine-3-ylidenemethyl)acetamides mediated by triflic acid in good yields with separable Z/E isomers within a short reaction time has been demonstrated. The reaction involves the initial formation of the pyrrolidin-3-ylidenemethylium carbocation via the Prins cyclization reaction followed by the Ritter reaction to produce N-(pyrrolidine-3-ylidenemethyl)acetamides. This methodology is also used for the synthesis of their piperidine derivatives.

Leveraging cascade alkynyl Prins cyclization towards the stereoselective synthesis of spiro-furan quinazolinone scaffolds

A TfOH-promoted, metal-free protocol has been unveiled for the synthesis of spiro-furan quinazolinones employing alkynol urea derivatives utilizing alkynyl Prins cyclization reaction. This methodology produces highly functionalized spiro-heterocycles in excellent yields with exclusive E-selectivity under ambient conditions. Furthermore, late-stage modifications incorporate bromide and acetyl functionalities into the synthesized spiro-heterocycles.

Synthesis of 1,2,3-triazole-fused N-heterocycles from N-alkynyl hydroxyisoindolinones and sodium azide via the Huisgen reaction

An efficient methodology for the synthesis of dihydro[1,2,3]triazolo-pyrimidoisoindolones and dihydro[1,2,3]triazolo-diazepinoisoindolones has been developed using the Huisgen reaction from sodium azide and alkyne substituted amido alcohols in moderate to good yields. The reaction involves the in situ generation of the N-acyliminium ion intermediate, which undergoes a nucleophilic attack by the azide ion, followed by a [3 + 2]-intramolecular azide-alkyne cycloaddition reaction. Importantly, the reaction proceeds without the involvement of any transition metal catalyst. This methodology can be further utilized for the synthesis of dihydro[1,2,3]triazolo-pyrimidoisoindolthiones via thionation of amides.

Stereoselective synthesis of 1,6-diazecanes by a tandem aza-Prins type dimerization and cyclization process

We report the stereocontrolled synthesis of 1,6-diazecanes via a tandem aza-Prins type reaction of N-acyliminium ions with allylsilanes. It involves an aza-Prins type dimerization and cyclization in a single-step operation. This reaction represents the first example of 10-membered N-heterocycle synthesis using an aza-Prins reaction. Also, the interesting formation of an unusual tetracyclic compound through further cyclization of 1,6-diazecane and bicyclic compounds by the intramolecular cyclization of linear allylsilane are described. This tandem aza-Prins protocol provides a new synthetic strategy for the direct synthesis of medium-sized nitrogen heterocycles.

AgNTf2 catalyzed cycloaddition of N-acyliminium ions with alkynes for the synthesis of the 3,4-dihydro-1,3-oxazin-2-one skeleton

A catalyzed process for the synthesis of the 4,6-substituted 3,4-dihydro-1,3-oxazin-2-one skeleton has been developed through cycloaddition of in situ generated acyliminium intermediates with alkynes. A range of chain N,O-acetals and terminal alkynes were amenable for this mild transformation. As a result, a series of desired cycloaddition products were obtained in moderate to good yields.

Synthesis of Polycyclic Aminal Heterocycles via Decarboxylative Cyclisation of Dipeptide Derivatives

An oxidative-decarboxylative intramolecular cyclisation of dipeptide derivatives is reported. This transformation is promoted by phenyl iodine (III) diacetate (PIDA) in combination with BF3·OEt2. The reaction gives access to a variety...

Synthesis of 3C-alkylated active methylene substituted 2H-indazole derivatives via sequential ring opening of donor–acceptor cyclopropanes and reductive cyclization reaction

A facile synthesis of 3C-alkylated active methylene substituted 2H-indazoles from o-nitrocyclopropanes and primary arylamines catalyzed by Ni(ClO4)2.6H2O/SnCl2.2H2O is reported.