title: Interceptive [4 + 1] annulation of in situ generated 1,2-diaza-1,3-dienes with diazo esters: direct access to substituted mono-, bi-, and tricyclic 4,5-dihydropyrazoles.
abstract: In situ derived acyclic and cyclic 1,2-diaza-1,3-dienes (DDs) were engaged in interceptive [4 + 1] annulation strategy with diazo esters (DEs). The catalytic activity of inexpensive copper(II) chloride allows the direct synthesis of mono-, bi-, and tricyclic 4,5-dihydropyrazole-5-carboxylic acid derivatives in a process that circumvents the use of an anhydrous and inert atmosphere.
authors.affiliation: Department of Biomolecular Sciences, Section of Organic Chemistry and Organic Natural Compounds, University of Urbino "Carlo Bo" , Via I Maggetti 24, 61029 Urbino, Italy.
authors.forename: Orazio A
authors.initials: OA
authors.lastname: Attanasi
authors.forename: Lucia
authors.initials: L
authors.lastname: De Crescentini
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Favi
authors.forename: Fabio
authors.initials: F
authors.lastname: Mantellini
authors.forename: Serena
authors.initials: S
authors.lastname: Mantenuto
authors.forename: Simona
authors.initials: S
authors.lastname: Nicolini