Hajar Hosseini

A simple and highly chemoselective heteroannulation protocol for the synthesis of polysubstituted heterocycles is reported. In this work, various oxa-aza[3.3.3]propellanes were synthesized via a sequential one-pot reaction of ninhydrin, malononitrile and nitroketene acetal or nitroketene aminals in water at ambient temperature. This successive Knoevenagel condensation/Michael addition/cyclization sequence features high atom economy, excellent efficiency, and the use of water as a solvent without the need for metal catalysts or external activators. This method can be presented as a good example of group-assisted purification (GAP), in which traditional purification techniques such as recrystallization and column chromatography are avoided and pure products are obtained simply by washing the crude products.

A very convenient one-pot method for the synthesis of new biologically active compounds, spiro-4H-pyran derivatives, has been developed. This approach, enables the incorporation of three pharmacophoric cores: pyran, pyridine and triazine scaffolds, within a single molecular skeleton using an efficient sequential multicomponent reaction. The starting materials include ninhydrin, cyanoacetohydrazide, ethyl cyanoacetate, aromatic aldehydes, pyrazolone and malononitrile. In this process, spiropyran derivatives were produced with high efficiency through three consecutive reactions. The first step involves the synthesis of 1,6-diaminopyridinone via a three-component approach using readily available starting materials. The second step, the synthesis of pyridotriazine, occurs in a domino way without the need to separate the intermediate product of the first step. Finally, the third step involves the synthesis of new spiro-4H-pyran derivatives through a one-pot three-component reaction. This method offers several advantages, including fast and simple purification of products, the use of safe solvents, no need for metallic and toxic catalysts, high atomic economy and excellent chemoselectivity of the reactions.

A one-pot three-component synthesis of indenoquinoxalines and various exocyclic enaminones, imidazolidin-2-ylidene-indenedione, pyrimidine-2-ylidene-indenedione, in water.

A highly efficient and straightforward synthesis of N-fused heterocyclic compounds including 5-amino-7-(aryl)-8-nitro-N'-(1-(aryl)ethylidene)-3,7-dihydro-2H-thiazolo[3,2-a]pyridine-6-carbohydrazide derivatives is successfully achieved via a five-component cascade reaction utilizing cyanoacetohydrazide, various acetophenones, aromatic aldehydes, 1,1-bis(methylthio)-2-nitroethylene and cysteamine hydrochloride in ethanol at reflux conditions. The new approach involves domino N,S-acetal formation, Knoevenagel condensation, Michael reaction, imine–enamine tautomerization and N-cyclization sequences. The prominent advantages of this protocol include: facility of operation, available and economical starting materials, no need for toxic solvents, high yields and tolerance of a wide variety of functional groups.

Here, we have described the synthesis of novel spiropyridineoxindole derivatives containing a pyridone ring via a four-component reaction between various diamines, 1,1-bis(methylthio)-2-nitroethylene, isatin derivatives and Meldrum's acid in the presence of p-toluenesulfonic acid. This protocol has some advantages such as the availability of starting materials, good yields, facile separation of products, the use of ethanol as an environmentally benign solvent and easy formation of three new bonds in one operation.

A highly efficient and straightforward synthesis of N-fused heterocyclic compounds including N′-(1-(4-nitrophenyl)ethylidene)imidazo[1,2-a]pyridine-6-carbohydrazide and N′-(1-(4-nitrophenyl)ethylidene)pyrido[1,2-a]pyrimidine-7-carbohydrazide derivatives is successfully achieved via a five-component cascade reaction utilizing cyanoacetohydrazide, 4-nitroacetophenone, 1,1-bis(methylthio)-2-nitroethylene and various diamines in a mixture of water and ethanol. The new efficient domino protocol involving a sequence of N,N-acetal formation, Knoevenagel condensation, Michael reaction, imine–enamine tautomerization and N-cyclization as key steps. The merit of this catalyst free approach is highlighted by its easily available starting materials, operational simplicity, clean reaction profile, the use of environmentally benign solvents and tolerance of a wide variety of functional groups.

A new class of tetrahydroimidazo[1,2-a]pyridine derivatives has been successfully prepared via a five-component domino reaction using cyanoacetohydrazide, 9-fluorenone, aromatic aldehydes, 1,1-bis(methylthio)-2-nitroethene and ethylenediamine in ethanol at reflux. The new efficient cascade approach involves a sequence of N,N-acetal formation, Knoevenagel condensation, Michael addition, imine–enamine tautomerization and N-cyclization as key steps. The merit of this protocol is highlighted by its available and economical starting compounds, operational simplicity, clean reaction profile and tolerance of a wide diversity of functional groups.

A simple and convenient protocol has been developed for the synthesis of N-amino-3-cyano-2-pyridone derivatives by a one-pot reaction of cyanoacetohydrazide, activated nitrile substrates (malononitrile, ethyl cyanoacetate, cyanoacetamide) and aromatic aldehydes in the presence of piperidine in water or a mixture of water and ethanol. The sequence of cascade reactions includes Knoevenagel condensation, Michael addition, intramolecular cyclization, imine-enamine tautomerization and oxidative aromatization. The main advantages of this procedure are availability of starting compounds, simple procedure, mild conditions, easy purification of products and the use of water or water/ethanol as green solvents.

A convenient one-pot protocol was developed for the synthesis of spiro[indeno[2,1-c]pyridazine-9,4′-pyran]-3′,4-dicarbonitrile derivatives by the reaction of cyanoacetohydrazide, ninhydrin, malononitrile and various cyclic CH-acids under reflux condition in ethanol. No hazardous solvent or catalyst was used in this method. The main advantages of this procedure are the availability of starting materials, very high yields and easy purification.