Studies with 2-(Arylhydrazono)aldehydes: Synthesis and Chemical Reactivity of Mesoxalaldehyde 2-Arylhydrazones and of Ethyl 2-Arylhydrazono-3-oxopropionates

Abstract

The coupling reaction of 3-(dimethylamino)acrolein (2a) and ethyl 3-(dimethylamino)acrylate (2b) with arenediazonium chlorides afforded the 2-(arylhydrazono)aldehydes 1a -e. Compounds 1a, b reacted with hydroxylamine hydrochloride to yield the oximes 4a, b. The dioxime 5 was obtained from reaction of 1a with an excess of hydroxylamine hydrochloride. This dioxime afforded the 1,2,3-triazole carbonitrile 6 when treated with acetic anhydride, while α-hydrazono propionitrile 8 was obtained when 5 was treated with acetic acid. Compounds 1a -e could be utilized for the synthesis of a variety of pyrazoles and arylazolopyrimidines via reaction with hydrazines, haloketones and aminoazoles, respectively.

Regio-orientation in condensation of aminopyrazoles with 1,3-difunctional reagents: synthesis of new pyrazolo[1,5-a]pyrimidines; pyrazolo[3,4-d]pyridazines and 2,4-dihydropyrano[2,3-c]pyrazoles

“…4-Phenyldiazenyl-1H-pyrazole-3,5-diamine 1, was prepared utilizing the procedure originally reported by Elnagdi et al 12 This was condensed with 3-piperidino-2-propenenitrile 2, prepared following our recently reported procedure, 13 to yield a product of addition and piperidine elimination, followed by cyclization and hydrolysis under the reaction conditions. This product could thus be formulated as 4,7-dihydropyrazolo[1,5-a]pyrimidin-7-one 5 or isomeric 4,5-dihydropyrazolo[1,5-a]pyrimidin-5-one 6.…”

Chemistry of 2-Arylhydrazonals

“…Almost forty years later, Elnagdi and co-workers [6][7][8][9][10][11][12][13][14][15][16][17] de-scribed several examples of this type of coupling process involving enamines 5a-j, which react to yield the respective arylhydrazonals 1a-j (Scheme 2, Table 1). Subsequently, enamines 5k-m were shown to produce 1k-m. [14][15][16][17][18][19][20][21][22] The mechanistic pathway followed in these reactions is thought to involve addition of the enamine 5 to the diazonium ion to furnish the zwitterionic intermediate 6 that then undergoes hydrolysis to produce the arylhydrazonal 1 (Scheme 2).…”

“…As mentioned above (Scheme 15), the reaction of arylhydrazonal 1 with hydroxylamine hydrochloride in the presence of sodium carbonate, under microwave irradiation and conventional heating conditions, affords oxime 46, which can be converted into triazole 48 6,39 in refluxing pyridine. On the other hand, reaction of 1 with hydroxylamine hydrochloride in the presence of ammonium acetate, under microwave irradiation conditions, results in the formation of 3-oxoalkanonitrile 47 (Scheme 17 and Table 6).…”

Green methodologies in organic synthesis: recent developments in our laboratories

“…Subsequently Makhseed et al [80] extended this approach to the synthesis of benzene-1,3,5-trials 104 (R0H) and triethylbenzene-1,3,5-tricarboxylates 104 (R0OH). Recently Al-Zaydi et al were able to affect the conversion of 103d to 104d more efficiently using pyridine hydrochloride as an ionic liquid and MW as the energy source (Scheme 24) [81] refluxing acetic acid reacts to generate 105 only, when the process is carried out in the presence of pyridinium hydrochloride 104e is formed [81].…”