Metal-free oxidative cyclization of 2-amino-benzamides, 2-aminobenzenesulfonamide or 2-(aminomethyl)anilines with primary alcohols for the synthesis of quinazolinones and their analogues

Cooperation between the Cu+ and Cu2+ species in CuCoAl layered double hydroxide and the substrate promoting effect afford a really simple protocol for the efficient synthesis of quinazolines

In this study, a really simple and efficient catalytic protocol for the construction of quinazolines from alcohol and diamine has been developed based on CuCoAl layered double hydroxide (CuCoAl-LDH). The developed CuCoAl-LDH catalyst could accelerate the cascade reactions without any additives and tolerate various alcohols with satisfactory yields. Cooperation between the Cu+ and Cu2+ species in CuCoAl-LDH was observed in the cascade reaction, and they are believed to be responsible for the oxidation of alcohol and dehydrogenation of the intermediate, respectively. The promoting effect of the substrate diamine was observed in the oxidation of alcohol, which simplifies the reaction system by eliminating the requirement for a base additive. The catalytic system exhibited highly practical potential for the synthesis of quinazolines, as demonstrated through recyclability investigations and scale-up experiments. A possible catalytic mechanism has been proposed based on a series of control experiments and EPR analysis.

Visible light-mediated synthesis of quinazolinones and benzothiadiazine-1,1-dioxides utilizing aliphatic alcohols

The activation and utilization of challenging aliphatic alcohols like methanol and ethanol is a very appealing approach to synthesize valuable organic molecules. Utilization of methanol and ethanol as a coupling partner has emerged as a valuable alternative to synthesize industrially relevant N-heterocycles because they can be easily procured from renewable sources unlike other activated coupling partners which are expensive and also unstable. Herein, a mild and metal-free photocatalytic protocol to synthesize quinazolinones and more challenging benzothiadiazine-1,1-dioxides, which is unprecedented at room temperature, is demonstrated. This methodology showcased broad substrate scope and provided important N-heterocycles more efficiently than the transition metal-based high temperature protocols. An unexplored reactivity with allyl alcohol is observed following the developed protocol. A series of control experiments were carried out to understand the mechanism.

Molecular modelling, synthesis and in vitro evaluation of quinazolinone hybrid analogues as potential pancreatic lipase inhibitors

Obesity is a multifactorial metabolic disorder, growing in an alarming rate across the world. Amongst the numerous targets explored for obesity management, inhibition of pancreatic lipase (PL) is considered as one of the promising approaches. Orlistat is the only PL inhibitory drug approved for long term treatment of obesity. However, it is reported to possess hepatotoxicity and nephrotoxicity. Thus, novel drug candidates that act through PL inhibition are considered the hour's need. Based on this aim, a series of quinazolinone hybrid analogues have been synthesized, characterized and evaluated for their PL inhibitory potential. The physicochemical properties and toxicity parameters suggested that these parameters are in an acceptable range for the screened analogues. Amongst the synthesised analogues, QH-25 exerted potential PL inhibition (IC50 = 16.99 ± 0.54 µM). Further, enzyme inhibition studies suggested a reversible competitive inhibition. Molecular docking of these analogues was in line with in vitro results, wherein the obtained MolDock scores exhibited a significant correlation with their inhibitory activity (Pearson's r = 0.6629). To further confirm the stability of the QH-25-PL complex in a dynamic environment, a molecular dynamics study (100 ns) was carried out and the results suggested that this complex is stable at dynamic conditions. Overall, these results shed light on the quinazolinone hybrids as potential PL inhibitors. Further structural modification may result in the development of potent anti-obesity agents which acts through PL inhibition.Communicated by Ramaswamy H. Sarma.

Microwave-assisted commercial copper-catalyzed aerobic oxidative synthesis of AChE quinazolinone inhibitors under solvent free conditions

A facile and green one-pot synthesis of AChE quinazolinone inhibitors was developed using microwave irradiation under solvent free conditions. Quinazolinones were synthesized from 2-aminobenzamide derivatives and various alcohols such as benzyl alcohol derivatives and butanol using economical commercially available copper as a catalyst in the presence of base, Cs2CO3. The desired products were achieved in moderate to high yields with up to 92% isolated yield. These quinazolinone products were then evaluated for acetylcholinesterase inhibition so that they can be developed as promising anti-acetylcholinesterase agents.

Cobalt Homeostatic Catalysis for Coupling of Enaminones and Oxadiazolones to Quinazolinones

Transition metal catalysis has revolutionized modern synthetic chemistry for its diverse modes of coordination reactivity. However, this versatility in reactivity is also the predominant cause of catalyst deactivation, a persisting issue that can significantly compromise its synthetic value. Homeostatic catalysis, a catalytic process that can sustain its productive catalytic cycle even when chemically disturbed, is proposed herein as an effective tactic to address the challenge. In particular, a cobalt homeostatic catalysis process has been developed for the water-tolerant coupling of enaminones and oxadiazolones to quinazolinones. Dynamic covalent bonding serves as a mechanistic handle for the preferred buffering of water onto enaminone and reverse exchange by a released secondary amine, thus securing reversible entry into cobalt's dormant and active states for productive catalysis. Through this homeostatic catalysis mode, a broad structural scope has been achieved for quinazolinones, enabling further elaboration into distinct pharmaceutically active agents.

Ru Doped Hydrotalcite Catalyzed Borrowing Hydrogen-Mediated N-Alkylation of Benzamides, Sulfonamides, and Dehydrogenative Synthesis of Quinazolinones

An efficient Ru doped hydrotalcite catalyzed N-alkylation of benzamides and sulfonamides with alcohols via borrowing hydrogen catalysis is illustrated. Various primary alcohols, including benzyl, heteroaryl, and aliphatic alcohols, were alkylated in good to excellent yields. To shed light on the mechanistic details, several control studies and deuterium labeling experiments were performed. Mechanistic studies underpin that the reaction is going via a borrowing hydrogen pathway rather than an S_N1 type mechanism. The reaction can be easily scaled up without any detrimental effect on the yield. The catalyst is also capable of synthesizing quinazolinone directly from 2-aminobenzamide and alcohols. Successful recyclability and high reactivity highlight the practical applicability of the catalyst.

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.

Photoinduced Enhanced Decomposition of TBHP: A Convenient and Greener Pathway for Aqueous Domino Synthesis of Quinazolinones and Quinoxalines

Catalyst-free photoinduced processes in aqueous medium represent significant advancement toward development of green and sustainable pathways in organic synthesis. tert-Butyl hydroperoxide (TBHP) is a widely used oxidant in organic reactions, where the decomposition of TBHP into its radicals by metal catalysts or other reagents is a key factor for efficient catalytic outcome. Herein, we report a simple and environmentally friendly visible light-promoted synthetic pathway for the synthesis of N-heterocyclic moieties, such as quinazolinones and quinoxalines, in the presence of TBHP as an oxidizing agent in aqueous medium that requires no catalysts/photocatalysts. The enhanced rate of decomposition to generate free radicals from TBHP upon visible light irradiation is the driving force for the domino reaction.

An efficient transition-metal-free route to quinazolin-4(3H)-ones via 2-aminobenzamides and thiols

An efficient approach to quinazolin-4(3H)-ones was developed by a one-pot intermolecular annulation reaction of o-amino benzamides and thiols.

Visible-light induced copper(i)-catalyzed oxidative cyclization of o-aminobenzamides with methanol and ethanol via HAT

The use of the in situ generated ligand-copper superoxo complex absorbing light energy to activate the alpha C(sp³)-H of MeOH and EtOH via the hydrogen atom transfer (HAT) process for the synthesis of quinazolinones by oxidative cyclization of alcohols with o-aminobenzamide has been investigated. The synthetic utility of this protocol offers an efficient synthesis of a quinazolinone intermediate for erlotinb (anti-cancer agent) and 30 examples were reported.

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.

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.

Efficient Synthesis of Quinazolinones by Transition-Metal-Free Direct Aerobic Oxidative Cascade Annulation of Alcohols with o-Aminoarylnitriles

A mild and atom-economic method was developed for direct and efficient synthesis of quinazolinones through a transition-metal-free aerobic oxidative cascade annulation reaction of widely available o-aminoarylnitriles and alcohols. Air could be employed as an effective oxidant under mild conditions, generating water as the only byproduct. Possibly owing to the "cesium effect", the water-soluble base CsOH was found to be crucial in all key steps of the reaction mechanism. Because a wide range of substrates can be used to prepare substituted quinazolinones without contamination by transition-metal residues, this method may be of interest for application in pharmaceutical synthesis. Possible reaction paths were also proposed according to control reactions.

Quinazolin-4(3H)-ones and 5,6-Dihydropyrimidin-4(3H)-ones from β-Aminoamides and Orthoesters

Quinazolin-4(3H)-ones have been prepared in one step from 2-aminobenzamides and orthoesters in the presence of acetic acid. Simple 2-aminobenzamides were easily converted to the heterocycles by refluxing in absolute ethanol with 1.5 equivalents of the orthoester and 2 equivalents of acetic acid for 12–24 h. Ring-substituted and hindered 2-aminobenzamides as well as cases incorporating an additional basic nitrogen required pressure tube conditions with 3 equivalents each of the orthoester and acetic acid in ethanol at 110 °C for 12–72 h. The reaction was tolerant towards functionality on the benzamide and a range of structures was accessible. Workup involved removal of the solvent under vacuum and either recrystallization from ethanol or trituration with ether-pentane. Several 5,6-dihydropyrimidin-4(3H)-ones were also prepared from 3-amino-2,2-dimethylpropionamide. All products were characterized by melting point, FT-IR, ¹H-NMR, ¹³C-NMR, and HRMS.

Bismuth-Catalyzed Synthesis of 2-Substituted Quinazolinones

The bismuth-catalyzed oxidative condensation of aldehydes with 2-aminobenzamide under aerobic conditions is reported using ethanol as the solvent. Good to excellent isolated yields (68-95%) of the corresponding 2-substituted quinazolinones were obtained under mild reaction conditions with excellent functional group tolerance. The quinazolinones were further functionalized to afford N-allylated quinazolinones, 2-aminopyridine derivatives, and annulated polyheterocyclic compounds via transition-metal catalyzed reactions.