Synthesis of nitro and amino N‐heterocycles via ring transformation of 2‐methyl‐3‐nitrochromone

Abstract

2‐Methyl‐3‐nitrochromone (1) reacted with acid hydrazides, S‐methylisothiourea, hydroxylamine and ethyl aminoethanoate to give the nitro derivatives of pyrazole 2, pyrimidine 6, isoxazole 11 and pyrrole 13, respectively. These nitro compounds were reduced by catalytic hydrogenation to the corresponding amino derivatives. In the case of 2, a rearrangement of the acyl group took place during the reduction. Substitution reactions of the 2‐methylthio group in 6 were also described.

Synthesis of Novel Azo-Linked 5-Amino-Pyrazole-4-Carbonitrile Derivatives Using Tannic Acid–Functionalized Silica-Coated Fe3O4 Nanoparticles as a Novel, Green, and Magnetically Separable Catalyst

“…Recently, different methods have been proposed to synthesize diverse pyrazole derivatives (Salaheldin et al, 2007). These include the synthesis of 4-substituted pyrazoles during the 1,3dipolar ring-forming reaction between diazo compounds with triple bonds (Martin et al, 2006); the three-component reaction between aromatic aldehydes, malononitrile, and phenylhydrazine (Bhale et al, 2014); the Michael addition reaction using 2-methyl-3-nitrochrome as a starting material (Takagi et al, 1987); the preparation of oxoalkanenitrile or aminonitrile derivatives (Al-Qalaf et al, 2009), from a four-component reaction with aryl aldehydes, hydrazines, ethylacetoacetate, and malononitrile (Kiyani et al, 2013), and the reaction of enamines with hydroxylamine hydrochloride (Tominaga et al, 1990). Some methods have also been reported for the synthesis of pyrazoles with azo bridges, such as the preparation of azo dyes from pyrazoles with a nitro group, such as 1-aryl-5-amino-4cyano-pyrazole as the starting material (Towne et al, 1968), and the coupling reaction between pyrazolo[3,4-d]-pyrazine with phenol and 1-naphthol (Kasimogullari et al, 2010).…”

Synthetic Approaches to Nitro-Substituted Isoxazoles

“…Thus, 5-aryl-4-nitroisoxazole was obtained starting from 2-methyl-3-nitro-4H-chromen-4-one, treatment of which by hydroxylamine led to dihydropyran ring cleavage followed by the formation of the isoxazole moiety (Scheme 14). 80,81 Scheme 14 Heterocyclization of 2-methyl-3-nitro-4H-chromen-4-one by treatment with hydroxylamine 80,81…”

Green synthesis of novel 5-amino-bispyrazole-4-carbonitriles using a recyclable Fe3O4@SiO2@vanillin@thioglycolic acid nano-catalyst

“…8 Recently, assorted methods have been proposed for the synthesis of diverse pyrazole derivatives. 9 These include the synthesis of 4-substituted pyrazoles via the reaction of 1,3dipolar ring-forming of diazo compounds with triple bonds, 10 the three-component reaction among aromatic aldehydes, malononitrile and phenyl hydrazine, 11 the 2-methyl-3nitrochrome starting material during the Michael addition reaction, 12 and the preparation of the oxoalkanenitrile or an aminonitrile derivatives, from a four-component reaction involving aryl aldehydes, hydrazines, ethylacetoacetate, malononitrile, 13 and the reaction of enamines with hydroxylamine hydrochloride. 14 The newer synthetic endeavours focus on the environmental aspects and the use greener techniques such as nonharmful solvents (such as water), solvent-free syntheses, inexpensive and abundant catalysts, one-step multicomponent reactions, among others where nanocatalysts play an important role in such green synthesis.…”