Synthesis of CF3-Isoquinolinones and Imidazole-Fused CF3-Isoquinolinones Based on C-H Activation-Initiated Cascade Reactions of 2-Aryloxazolines

Presented herein are novel syntheses of CF3-isoquinolinones and imidazole fused CF3-isoquinolinones based on the cascade reactions of 2-aryloxazolines with trifluoromethyl imidoyl sulfoxonium ylides. The formation of CF3-isoquinolinone involves an intriguing cascade process including oxazolinyl group-assisted aryl alkylation through C(sp2)-H bond metalation, carbene formation, migratory insertion, and proto-demetalation followed by intramolecular condensation and water-promoted oxazolinyl ring-scission. With this method, the isoquinolinone scaffold tethered with valuable functional groups was effectively constructed. By taking advantage of the functional groups embedded therein, the products thus obtained could be readily transformed into imidazole-fused CF3-isoquinolinones or coupled with some clinical drugs to furnish hybrid compounds with potential applications in drug development. In general, the developed protocols feature expeditious and convenient formation of valuable CF3-heterocyclic skeletons, broad substrate scope, and ready scalability. In addition, studies on the activity of selected products against some human cancer cell lines demonstrated their potential as lead compounds for the development of novel anticancer drugs.

Copper-Catalyzed Domino-Double Annulation of o-Aminobenzamides with 2-Iodoisothiocyanates for the Synthesis of 12H-Benzo[4,5]thiazolo[2,3-b]quinazolin-12-ones

A facile and efficient copper-catalyzed domino-double annulation strategy was developed from easily accessible o-aminobenzamides and 2-iodoisothiocyanates, which affords a direct pathway for the synthesis of tetracyclic fused 12H-benzo[4,5]thiazolo[2,3-b]quinazolin-12-ones in moderate to good yields without the addition of ligands, bases, and external oxidants. The reaction involves a C-N bond cleavage and the formation of a C-N/C-S bond in one step with the advantages of using an inexpensive copper catalyst and easy operation. Mechanistic studies suggest that this transformation proceeds via intermolecular condensation of o-aminobenzamides with 2-iodoisothiocyanates, followed by an intramolecular Ullmann-type cross-coupling cyclization reaction.

Persulfate-Promoted Carbamoylation/Cyclization of Alkenes: Synthesis of Amide-Containing Quinazolinones

The incorporation of amide groups into biologically active molecules has been proven to be an efficient strategy for drug design and discovery. In this study, we present a simple and practical method for the synthesis of amide-containing quinazolin-4(3H)-ones under transition-metal-free conditions. This is achieved through a carbamoyl-radical-triggered cascade cyclization of N3-alkenyl-tethered quinazolinones. Notably, the carbamoyl radical is generated in situ from the oxidative decarboxylative process of oxamic acids in the presence of (NH4)2S2O8.

Synthesis of fused quinazolinones via visible light induced cyclization of 2-aminobenzaldehydes with tetrahydroisoquinolines

This study reports a novel method for the synthesis of fused quinazolinones by visible-light-induced cyclization of 2-aminobenzaldehydes and tetrahydroisoquinolines. The reaction is easily carried out by irradiation with a blue LED in the presence of 9-fluorenone and air. A broad substrate scope with good tolerance of functionalities was observed under the optimized reaction conditions. Moreover, using 2-aminophenone as the substrate and under similar reaction conditions, the same product was obtained when a carbon was removed. The bio-active naturally occurring alkaloid rutaecarpine could be obtained by this strategy. The success of the reaction on the gram-scale and the further transformation of the substrate demonstrated the synthetic practicability of this reaction.

Radical-mediated photoredox hydroarylation with thiosulfonate

Herein, we report a novel visible light-induced photocatalytic system that enables intramolecular hydroarylation of unactivated alkenes. Thiosulfonate compounds were found to be the key radical precursor that mediates the Minisci-type intramolecular cyclization reaction. Under the optimal reaction conditions, a wide range of pyridyquinazolinone and pyrroloquinazolinone products were obtained in moderate to good yields.

Synthesis of Quinazolinone-Fused Tetrahydroisoquinolines and Related Polycyclic Scaffolds by Iodine-Mediated sp3 C-H Amination

An iodine-mediated intramolecular sp³ C-H amination reaction producing quinazolinone-fused polycyclic skeletons from 2-aminobenzamide precursors is reported. This reaction does not use transition metals, has a broad substrate scope, and can be used on a gram scale. Under the optimal reaction conditions, a variety of quinazolinone-fused tetrahydroisoquinolines and derivatives of Rutaecarpine were synthesized from readily accessible compounds. The reaction proceeds well with crude 2-aminobenzamide derivatives, allowing for the synthesis of the products from simple 2-aminobenzoic acids and tetrahydroisoquinolines without purification of the 2-aminobenzamide intermediates. Preliminary biological experiments have identified Cereblon (CRBN) inhibitory activity and relevant anti-myeloma medicinal properties in some of these polycyclic products.

t-BuOK-Catalyzed Regio- and Stereoselective Intramolecular Hydroamination Reaction Leading to Phthalazinoquinazolinone Derivatives

We report herein an efficient and practical strategy for the preparation of 5H-phthalazino[1,2-b]quinazolin-8(6H)-one derivatives through a t-BuOK-catalyzed intramolecular hydroamination reaction of functionalized quinazolinones under extremely mild reaction conditions. A variety of quinazolinone substrates are well tolerated to furnish the corresponding products in good to high yields via an exclusive 6-exo-dig cyclization process. The present protocol has the advantages of readily obtainable starting materials, broad substrate scope, and high regio- and stereoselectivity.

Recent Advances on the Synthesis of 2,3-Fused Quinazolinones

As one of the most important structural units in pharmaceuticals and medicinal chemistry, quinazolinone and its derivatives exhibit a wide range of biological and pharmacological activities, including anti-inflammatory, antitubercular, antiviral,...

Tryptanthrin derivatives as efficient singlet oxygen sensitizers

Halogenated tryptanthrin and aminotryptanthrin were synthesized from indigo or isatin precursors. Dibromo- and tetrabromo-tryptanthrin were obtained from indigo dyes following green chemistry procedures, through microwave-assisted synthesis in mild oxidation conditions. Spectral and photophysical properties of the compounds, including quantitative determination of all the different deactivation pathways of S₁ and T₁, were obtained in different solvents and temperatures. The triplet state (T₁) has a dominant role on the photophysical properties of these compounds, which is further enhanced by the halogens at the fused-phenyl rings. Substitution with an amino group, 2-aminotryptanthrin (TRYP-NH₂), leads a dominance of the radiative decay channel. Moreover, with the sole exception of TRYP-NH₂, S₁ ~  ~  > T₁ intersystem crossing constitutes the dominant route, with internal conversion playing a minor role in the deactivation of S₁ in all the studied derivatives. In agreement with tryptanthrin, emission of the triplet state of tryptanthrin derivatives (with exception of TRYP-NH₂), was observed together with an enhancement of the singlet oxygen sensitization quantum yield: from 70% in tryptanthrin to 92% in the iodine derivative. This strongly contrasts with indigo and its derivatives, where singlet oxygen sensitization is found inefficient.