59119-50-5Relevant academic research and scientific papers
6-(Aryldiazenyl)pyrazolo[1,5-a]pyrimidines as Strategic Intermediates for the Synthesis of Pyrazolo[5,1-b]purines
Castillo, Juan-Carlos,Estupi?an, Diego,Nogueras, Manuel,Cobo, Justo,Portilla, Jaime
, p. 12364 - 12373 (2016)
A microwave-assisted approach for the regioselective synthesis of functionalized 6-(aryldiazenyl)pyrazolo[1,5-a]pyrimidin-7-amines from the cyclization of 3-oxo-2-(2-arylhydrazinylidene)butanenitriles with 5-amino-1H-pyrazoles under solvent-free conditions has been developed. This methodology was distinguished by its broad substrate scope, operational simplicity, high atom economy, and high-yielding without requiring chromatographic purification. In addition, an efficient and versatile palladium-catalyzed reductive azo cleavage is disclosed for the synthesis of diverse heteroaromatic 1,2-diamines, a valuable synthetic building block to develop new fused heteroaromatic systems. As synthetic example, several substituted pyrazolo[5,1-b]purines were synthesized in yields up to 96% by using microwave irradiation in the cyclocondensation of these 1,2-diamines with orthoesters.
The effect of ortho and para substituents on the formation of the E and Z isomers of the arylhydrazones obtained from diazonium coupling with methyl 3-aminocrotonate and 3-aminocrotononitrile
Jollimore, Jason V.,Vacheresse, Marc,Vaughan, Keith,Hooper, Donald L.
, p. 254 - 262 (2007/10/03)
Reaction of arene diazonium salts with 3-aminocrotononitrile or methyl 3-aminocrotonate affords the 2-arylhydrazono-3-oxobutanenitrile (1 or 3 and 3′) or the methyl 2-arylhydrazono-3-oxobutanoate (2 and 2′ or 4 and 4′). A series of these hydrazones has been prepared with a range of electron-withdrawing and -donating substituents in the ortho or para position of the aryl moiety. The hydrazones have been characterized by spectroscopic methods, with emphasis on the 1 H NMR spectra, which have been used to determine the configuration of the hydrazones as E or Z or a mixture of the two. The para-substituted hydrazononitriles (1) are formed as a single species, namely the Z isomer, whereas the ortho isomers are formed as a mixture of E and Z configurations (3 and 3′). The hydrazonobutanoates (2 and 2′ or 4 and 4′) are formed as E/Z mixtures regardless of the position of the substituent in the aryl moiety. Complete assignments of all signals in the 1 H NMR spectra have been made on the basis of the ability of the various substituents to participate in intramolecular hydrogen bonding and a mechanism is proposed to account for the variations in the proportions of E and Z isomers and the effect of the nature of the substituent on this ratio. 13C NMR spectra of selected hydrazones have been recorded as an aid to structure assignment.
