Recent Developments in the MCRs Synthesis of Pyridopyrimidines and Spiro‐Pyridopyrimidines

Recent advances in microwave-assisted multicomponent synthesis of spiro heterocycles

Spiro heterocycle frameworks are a class of organic compounds that possesses unique structural features making them highly sought-after targets in drug discovery due to their diverse biological and pharmacological activities. Microwave-assisted organic synthesis has emerged as a powerful tool for assembling complex molecular architectures. The use of microwave irradiation in synthetic chemistry is a promising method for accelerating reaction rates and improving yields. This review provides insights into the current state of the art and highlights the potential of microwave-assisted multicomponent reactions in the synthesis of novel spiro heterocyclic compounds that were reported between 2017 and 2023.

Ionic Liquid Modified SPION@Chitosan as a Novel and Reusable Superparamagnetic Catalyst for Green One-Pot Synthesis of Pyrido[2,3-d]pyrimidine-dione Derivatives in Water

In this paper, the chitosan-functionalized ionic liquid is modified with superparamagnetic iron oxide nanoparticles to form a novel and reusable catalyst (SPION@CS-IL), which was carried out using an ultrasonic promoted approach. Transmission electron microscopy (TEM), vibrating-sample magnetometer (VSM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and thermogravimetric analysis (TGA) are some of the techniques that are used to fully characterize SPION@CS-IL. The created nanoparticles were discovered to be a reusable heterogeneous superparamagnetic catalyst for the environmentally friendly one-pot synthesis of pyrido[2,3-d]pyrimidine derivatives using a simple three-component reaction approach involving thiobarbituric acid, 4-hydroxy coumarin, and various aromatic aldehydes. The method is studied by performing the reaction under ultrasonic irradiation, while the approach is a “green” method, it uses water as the solvent. The isolated yields of the synthesized products are very advantageous. The catalyst has outstanding reusability and is easily removed from the products via filtration (5 runs). Short reaction times, low catalyst loadings, the nanocatalyst’s capacity to be recycled five times, and the absence of harmful chemical reagents are all significant benefits of this environmentally benign process.

Ag-Catalyzed Multicomponent Synthesis of Heterocyclic Compounds: A Review

The investigation of the procedures for the multi-component synthesis of heterocycles has attracted the interest of organic and medicinal chemists. The use of heterogeneous catalysts, especially transition metal catalysts in organic synthesis, can provide a new, improved alternative to traditional methods in modern synthetic chemistry. The main focus is on the utilization of silver as a catalyst for the multi-component synthesis of heterocyclic compounds. The present review describes some important reported studies for the period of 2010 to 2020. Conclusion: The present review addresses some of the important reported studies on multi-component synthesis of heterocycles in the period of 2010-2020. These approaches were performed under classical and nonclassical conditions, using Ag salts, Ag NPs, Ag on the support, Ag as co-catalysts with other transition metals, ionic liquids, acidic or basic materials. Most of the reported reactions were performed under solvent-free conditions or in green solvents and the utilized catalysts were mostly recyclable. The main aim of the present review is to provide the organic chemists with the most appropriate procedures in the multi-component synthesis of desired heterocycles using silver catalysts.

An expeditious one-pot synthesis of pyrido[2,3-d]pyrimidines using Fe3O4–ZnO–NH2–PW12O40 nanocatalyst

An efficient protocol for the facile synthesis of a series of pyrido[2,3- d]pyrimidine derivatives has been developed applying Fe3O4–ZnO–NH2–PW12O40 nanocatalyst in water. This novel method has the benefits of operational simplicity, green aspects by avoiding toxic solvents and high to excellent yields of products. Fe3O4–ZnO–NH2–PW12O40 was synthesized and characterized by Fourier transform infrared, X-ray diffraction, vibrating sample magnetometer, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy analyses. The nanocatalyst is readily isolated and recovered from the reaction mixture by an external magnet.

Merging catalyst-free synthesis and iodine catalysis: one-pot synthesis of dihydrofuropyrimidines and spirodihydrofuropyrimidine pyrazolones

A new and efficient one-pot strategy combining catalyst-free synthesis and iodine catalysis has been developed for the synthesis of dihydrofuropyrimidines and spirodihydrofuropyrimidine pyrazolones. This approach affords products in moderate to high yields (up to 96%) with excellent diastereoselectivities (up to >25 : 1 dr). The reaction is simple to carry out and is metal-free.

A new and efficient one-pot strategy combining catalyst-free synthesis and iodine catalysis has been developed for the synthesis of dihydrofuropyrimidines and spirodihydrofuropyrimidine pyrazolones.

Simple synthesis of new imidazopyridinone, pyridopyrimidinone, and thiazolopyridinone derivatives and optimization of reaction parameters using response surface methodology

The reaction between ketene animal/ketene N,S-acetals (derived from diamines/cysteamine hydrochloride and 1,1-bis(methylthio)-2-nitroethene) with aromatic aldehydes, and Meldrum's acid led to the title compounds. The reaction conditions were optimized using response surface methodology (RSM). The two independent variables (temperature and water content of aqueous ethanol), and the responses (yield of product and reaction time) were studied. The range of each parameter selected was: T = 25–100 °C and water = 0–100%. The optimal values were: T = 72 °C and water = 33%. This work offers significant advantages including use of a green solvent, experimental simplicity, absence of catalyst, a simple work-up and purification process, moderate to good yields, and preparation of potentially bioactive compounds.

The one-pot reaction of various diamines with cysteamine hydrochloride or 1,1-bis(methylthio)-2-nitroethene, aromatic aldehydes, and Meldrum's acid led to pyridone compounds in good yields. The reaction conditions were optimized using response surface method.

Chemodivergent, multicomponent-tandem facile synthesis of novel 1H-pyrazolo[1,2-b]phthalazine-5,10-dione using acetic acid functionalized imidazolium salt {[cmdmim]I} as a recyclable catalyst

A novel one-pot four-component, highly efficient and environmentally benign approach for the synthesis of a wide range of 1H-pyrazolo[1,2-b]phthalazine-5,10-dione derivatives in the presence of acetic acid functionalized imidazolium salt as a newly synthesized Brønsted acid catalyst is described.

Facile synthesis and efficient electrochemiluminescence of a readily accessible pyridopyrimidine

Through a facile one-pot three-component reaction and a subsequent acetylation strategy, a novel greenish-blue fluorescent 4-imino-4H-pyrido[1,2-a]pyrimidine-3-carbonitrile (IPPC) was synthesized.

Organo-Catalyzed Asymmetric Michael-Hemiketalization-Oxa-Pictet-Spengler Cyclization for Bridged and Spiro Heterocyclic Skeletons: Oxocarbenium Ion as a Key Intermediate

A Michael-hemiketalization-oxa-Pictet-Spengler cyclization has been developed for the construction of chiral bridged and spiro heterocyclic skeletons with one spiro stereogenic carbon center and two bridgehead carbon centers, utilizing cooperative catalysts of a Takemoto thiourea catalyst and a triflimide. In particular, an oxocarbenium ion acts as a key intermediate for this cyclization reaction. Additionally, biological evaluation of this type of novel structure has revealed obvious antiproliferative activity against some cancer cell lines.

The Beneficial Sinergy of MW Irradiation and Ionic Liquids in Catalysis of Organic Reactions

The quest for sustainable processes is becoming more and more important, with catalysis playing a major role in improving atom economy and reducing waste. Organic syntheses with less need of protecting/de-protecting steps are highly desirable. The combination of microwave irradiation, as energy source, with ionic liquids, as both solvents and catalysts, offered interesting solutions in recent years. The literature data of the last 15 years concerning selected reactions are presented, highlighting the importance of microwave (MW) technology coupled with ionic liquids.