title: 6-(Aryldiazenyl)pyrazolo[1,5-a]pyrimidines as Strategic Intermediates for the Synthesis of Pyrazolo[5,1-b]purines.
abstract: 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.
authors.affiliation: Bioorganic Compounds Research Group, Department of Chemistry, Universidad de los Andes , Carrera 1 No. 18A-10, Bogotá 111711, Colombia.
authors.forename: Juan-Carlos
authors.initials: JC
authors.lastname: Castillo
authors.affiliation: Bioorganic Compounds Research Group, Department of Chemistry, Universidad de los Andes , Carrera 1 No. 18A-10, Bogotá 111711, Colombia.
authors.forename: Diego
authors.initials: D
authors.lastname: Estupiñan
authors.affiliation: Departamento de Química Inorgánica y Orgánica, Universidad de Jaén , Jaén 23071, Spain.
authors.forename: Manuel
authors.initials: M
authors.lastname: Nogueras
authors.affiliation: Departamento de Química Inorgánica y Orgánica, Universidad de Jaén , Jaén 23071, Spain.
authors.forename: Justo
authors.initials: J
authors.lastname: Cobo
authors.affiliation: Bioorganic Compounds Research Group, Department of Chemistry, Universidad de los Andes , Carrera 1 No. 18A-10, Bogotá 111711, Colombia.
authors.forename: Jaime
authors.identifier: 0000-0002-8206-7481
authors.initials: J
authors.lastname: Portilla