Cross-condensation of derivatives of cyanoacetic acid and carbonyl compounds. Part 1: Single-stage synthesis of 1′-substituted 6-amino-spiro-4-(piperidine-4′)-2 H ,4 H -pyrano[2,3- c ]pyrazole-5-carbonitriles

Facile One Pot Microwave Assisted Solvent-Free Synthesis of Novel Spiro-Fused Pyran Derivatives via the Three-Component Condensation of Ninhydrin with Malononitrile and Active Methylene Compounds

“…In the literature, there is no consensus of opinion regarding the structures of pyranopyrazoles derived from pyrazol-5-ones. [30][31][32][33][34][35][36] The efficiency of the above reactions prompted us to extend this procedure to the synthesis of different fused spiropyran derivatives. Thus, ninhyrin (1) reacted with 2 and 1-methylhydantoin (10), tetrahydrofuran-2,4-dione (11), 2indolinone (12), and barbituric acid derivatives 13a-c to give the corresponding spiropyrans 14-17, respectively (Scheme III).…”

An efficient and simple approach for the synthesis of pyranopyrazoles using imidazole (catalytic) in aqueous medium, and the vibrational spectroscopic studies on 6-amino-4-(4′-methoxyphenyl)-5-cyano-3-methyl-1-phenyl-1,4-dihydropyrano[2,3-c]pyrazole using density functional theory

“…Nadia et al reported a method using a mixture of 5-methyl-2,4-dihydro-3H-pyrazol-3-one, malononitrile and different aromatic aldehydes in the presence of ammonium acetate in ethanol [4]. A four component reaction of aldehydes, ethyl acetoacetate, malononitrile and hydrazine hydrate in water and catalytic ␤-cyclodextrin was reported by Vasuki and Kandhasamy [8] and the same reaction is carried out by Shestopalov et al using catalytic amounts of triethyl amine in ethanol [13]. However, all the reported methods are associated with disadvantages such as: use of expensive and environmentally hazardous reagents, low yields of products, drastic reaction conditions and tedious work-up procedures.…”

Ring transformation of spirocyclopropanepyrazoles into pyrano[2,3‐c]pyrazoles

“…Some heterocyclic compounds containing condensed pyrazoles such as pyrano[2,3‐ c ]pyrazoles possess a wide spectrum of pharmacological action, including analgesic, anti‐inflammatory, vasodilating and antihypertensive activities [19–21]. Hence, the preparation and biological properties of new substituted pyrano[2,3‐ c ]pyrazoles are of interest [22–36]. For these reasons, we focused our attention on the development of a new method for the preparation of pyrano[2,3‐ c ]pyrazoles starting from spirocyclopropanepyrazoles and now report the results of our investigation, a ring‐opening/cyanomethylation and intramolecular cyclization of them in the presence of a base such as sodium hydride.…”