Photogenerated chlorine radicals activate C(sp3)-H bonds of alkylbenzenes to access quinazolinones

An Fe-catalyzed visible-light induced condensation of alkylbenzenes with anthranilamides has been developed. Upon irradiation, the trivalent iron complex could generate chlorine radicals, which successfully abstracted the hydrogen of benzylic C-H bonds to form benzyl radicals. And these benzyl radicals were converted into oxygenated products under air conditions, which subsequently reacted with anthranilamides for the synthesis of quinazolinones.

Chemodivergent Photocatalyzed Heterocyclization of Hydrazones and Isothiocyanates for the Selectivity Synthesis of 2-Amino-1,3,4-thiadiazoles and 1,2,4-Triazole-3-thiones

A photocatalytic chemodivergent reaction for the selectivity formation of C-S and C-N bonds in a controlled manner was proposed. The reaction medium, either neutral or acidic, is critical to dictate the formation of 2-amino-1,3,4-thiadiazoles and 1,2,4-triazole-3-thiones from isothiocyanates and hydrazones. This is a practical protocol to achieve the chemoselectivity under mild and metal-free conditions.

Synthesis, antitumor activity, 3D-QSAR and molecular docking studies of new iodinated 4-(3H)-quinazolinones 3N-substituted

A novel series of 6-iodo-2-methylquinazolin-4-(3H)-one derivatives, 3a–n, were synthesized and evaluated for their in vitro cytotoxic activity. Compounds 3a, 3b, 3d, 3e, and 3h showed remarkable cytotoxic activity on specific human cancer cell lines when compared to the anti-cancer drug, paclitaxel. Compound 3a was found to be particularly effective on promyelocytic leukaemia HL60 and non-Hodgkin lymphoma U937, with IC₅₀ values of 21 and 30 μM, respectively. Compound 3d showed significant activity against cervical cancer HeLa (IC₅₀ = 10 μM). The compounds 3e and 3h were strongly active against glioblastoma multiform tumour T98G, with IC₅₀ values of 12 and 22 μM, respectively. These five compounds showed an interesting cytotoxic activity on four human cancer cell types of high incidence. The molecular docking results reveal a good correlation between experimental activity and calculated binding affinity on dihydrofolate reductase (DHFR). Docking studies proved 3d as the most potent compound. In addition, the three-dimensional quantitative structure–activity relationship (3D-QSAR) analysis exhibited activities that may indicate the existence of electron-withdrawing and lipophilic groups at the para-position of the phenyl ring and hydrophobic interactions of the quinazolinic ring in the DHFR active site.

New iodinated 4-(3H)-quinazolinones 3N-substituted with antitumor activity and 3D-QSAR and molecular docking studies as dihydrofolate reductase (DHFR) inhibitors.

Electro-organic synthesis: an environmentally benign alternative for heterocycle synthesis

Heterocyclic compounds are considered to be one of the most established structural classes due to their extensive application in agrochemicals, pharmaceuticals and organic materials. Over the past few years, the development of heterocyclic compounds has gone through a considerable renaissance from conventional traditional methodologies to non-conventional electro-organic synthesis. Replacing metal catalysts, strong oxidants and multi-step methodologies with metal and strong oxidant-free single-step protocols has revolutionized the field of sustainable organic synthesis. Electro-organic synthesis has evolved as a scalable and sustainable approach in different synthetic protocols in an environment-benign manner. The current review outlines the recent developments in C-C, C-N, C-S and C-O/Se bond formation for heterocycle synthesis using electrochemical methods. Different synthetic strategies and their detailed mechanistic description are presented to enlighten the future applications of electrochemistry in heterocycle synthesis.

Synthesis of quinazolinone and quinazoline derivatives using green chemistry approach

Green chemistry has been most compelling area of research. Green chemistry is vital to long-term sustainability, not only because of its fundamental notion of reducing the use and manufacture of hazardous materials, but also because of its broad applicability as one of the most efficient and problem-solving pathways for the synthesis of new materials. Various chemists have studied a plethora of strategies to lessen the release of hazardous chemical waste, waste material recyclization and reuse. New techniques have been created based on a green chemistry strategy that includes the utilization of catalysts, nanosized materials and composites, such as metal and non-metal nanoparticles, their oxides and salts, and different heterocyclic rings. Quinazolines and quinazolinones are biologically significant heterocyclic rings with a wide range of characteristics. In a summary, this chapter focuses on recent novel synthesis methods for quinazoline and quinazolinone derivatives, which are vital to humanity.

Electro-oxidative cyclization: access to quinazolinones via K2S2O8 without transition metal catalyst and base

A K₂S₂O₈-promoted oxidative tandem cyclization of primary alcohols with 2-aminobenzamides to synthesize quinazolinones was successfully achieved under undivided electrolytic conditions without a transition metal and base. The key feature of this protocol is the utilization of K₂S₂O₈ as an inexpensive and easy-to-handle radical surrogate that can effectively promote the reaction via a simple procedure, leading to the formation of nitrogen heterocycles via direct oxidative cyclization at room temperature in a one-pot procedure under constant current. Owing to the use of continuous-flow electrochemical setups, this green, mild and practical electrosynthesis features high efficiency and excellent functional group tolerance and is easy to scale up.

A K₂S₂O₈-promoted oxidative tandem cyclization of primary alcohols with 2-aminobenzamides to synthesize quinazolinones was successfully achieved under undivided electrolytic conditions without a transition metal and base.

Advances in Electrochemical Decarboxylative Transformation Reactions

Owing to their non-toxic, stable, inexpensive properties, carboxylic acids are considered as environmentally benign alternatives as coupling partners in various organic transformations. Electrochemical mediated decarboxylation of carboxylic acid has emerged as a new and efficient methodology for the construction of carbon-carbon or carbon-heteroatom bonds. Compared with transition-metal catalysis and photoredox catalysis, electro-organic decarboxylative transformations are considered as a green and sustainable protocol due to the absence of chemical oxidants and strong bases. Further, it exhibits good tolerance with various functional groups. In this Minireview, we summarize the recent advances and discoveries on the electrochemical decarboxylative transformations on C-C and C-heteroatoms bond formations.

Probing the catalytic activity of highly efficient sulfonic acid fabricated cobalt ferrite magnetic nanoparticles for the clean and scalable synthesis of dihydro, spiro and bis quinazolinones

An exceptionally productive, rapid, simple, and eco-friendly approach for the synthesis of 2,3-dihydroquinazolin-4(1H)-one has been developed utilizing acidic magnetically retrievable cobalt ferrite nanoparticles (CFNP@SO3H).

Electrochemical Synthesis of Quinazolinones by the Metal-Free and Acceptor-Free Dehydrogenation of 2-Aminobenzamides

An efficient approach has been developed for the construction of quinazolin-4(3H)-ones by the selective anodic dehydrogenative oxidation/cyclization of benzylic chlorides and 2-aminobenzamides. The method features acceptor-free and metal-free dehydrogenation of amines to imines; a subsequent intermolecular addition provides the products in moderate to good yields.

Anodic Oxidation for the Stereoselective Synthesis of Heterocycles

Stereodefined aliphatic heterocycles are one of the fundamental structural motifs observed in natural products and biologically active compounds. Various strategies for the synthesis of these building blocks based on transition metal catalysis, organocatalysis, and noncatalytic conditions have been developed. Although electrosynthesis has also been utilized for the functionalization of aliphatic heterocycles, stereoselective transformations under electrochemical conditions are still a challenging field in electroorganic chemistry. This Account consists of four main topics related to our recent efforts on the diastereo- and/or enantioselective synthesis of aliphatic heterocycles, especially N-heterocycles, using anodic oxidations as key steps. The first topic is the development of stereoselective synthetic methods for multisubstituted piperidines and pyrrolidines from anodically prepared α-methoxy cyclic amines. Our strategies were based primarily on N-acyliminium ion chemistry, and the key electrochemical transformations were diastereoselective anodic methoxylation, diastereoselective arylation, and anodic deallylative methoxylation. Furthermore, we found a unique property of the N-cyano protecting group that enabled the electrochemical α-methoxylation of α-substituted cyclic amines. The second topic of investigation is memory of chirality in electrochemical decarboxylative methoxylation. We observed that the electrochemical decarboxylative methoxylation of oxazolidine and thiazolidine derivatives with the appropriate N-protecting group occurred in a stereospecific manner even though the reaction proceeded through an sp² planar carbon center. Our findings demonstrated the first example of memory of chirality in N-acyliminium ion chemistry. The third topic is the synthesis of chiral azabicyclo-N-oxyls and their application to chiral organocatalysis in the electrochemical oxidative kinetic resolution of secondary alcohols. The final topic is stereoselective transformations utilizing anodically generated halogen cations. We investigated the oxidative kinetic resolution of amino alcohol derivatives using anodically generated bromo cations. We also developed an intramolecular C-C bond formation of keto amides, a diastereoselective bromoiminolactonization of α-allyl malonamides, and an oxidative ring expansion reaction of allyl alcohols. It is noteworthy that most of the electrochemical reactions were performed in undivided cells under constant-current conditions, which avoided a complicated reaction setup and was beneficial for a large-scale reaction. In addition, we developed some enantioselective electrochemical transformations that are still challenges in electroorganic chemistry. We hope that our research will contribute to the further development of diastereo- and/or enantioselective transformations and the construction of valuable heterocyclic compounds using an electrochemical approach.

α-Hydroxy acid as an aldehyde surrogate: metal-free synthesis of pyrrolo[1,2-a]quinoxalines, quinazolinones, and other N-heterocycles via decarboxylative oxidative annulation reaction

A metal-free and efficient procedure for the synthesis of pyrrolo[1,2-a]quinoxalines, quinazolinones, and indolo[1,2-a]quinoxaline has been developed. The key features of our method include the in situ generation of aldehyde from α-hydroxy acid in the presence of TBHP (tert-butyl hydrogen peroxide), and further condensation with various amines, followed by intramolecular cyclization and subsequent oxidation to afford the corresponding quinoxalines, quinazolinones derivatives in moderate to high yields.

A TBHP mediated, metal-free approach for the synthesis of quinoxalines, quinazolinones, and indolo quinoxaline was developed from alpha hydroxy acids via decarboxylation followed by condensation.

Iron-Catalyzed Nitrene Transfer Reaction of 4-Hydroxystilbenes with Aryl Azides: Synthesis of Imines via C═C Bond Cleavage

C═C bond breaking to access the C═N bond remains an underdeveloped area. A new protocol for C═C bond cleavage of alkenes under nonoxidative conditions to produce imines via an iron-catalyzed nitrene transfer reaction of 4-hydroxystilbenes with aryl azides is reported. The success of various sequential one-pot reactions reveals that the good compatibility of this method makes it very attractive for synthetic applications. On the basis of experimental observations, a plausible reaction mechanism is also proposed.