title: Unusual chemoselective Rh(II)-catalysed transformations of α-diazocarbonyl piperidine cores.
abstract: The reactivity of various α-diazocarbonyl piperidine scaffolds, characterised by an increased molecular complexity, was tested with various Rh(II) catalysts. The structure of the starting reagent is of relevance to the synthetic results. An unexpected dimerisation took place, starting from the simple piperidine scaffold, to give the hexahydrotetrazine ring system. Products derived from a nitrogen ylide intermediate or aromatic substitution (1,3,4,5-tetrahydro-2,5-methanobenzo[c]azepine and 1,2,3,3a-tetrahydrocyclopenta[de]isoquinolin-4(5 H)-one rings, respectively) were obtained from tetrahydroisoquinoline derivatives. The chemoselectivity of the reaction could be controlled by the choice of starting reagent, Rh(II) catalyst and the reaction conditions. Finally, it was found that the azepino heterocycle could coordinate to the catalyst to give new Rh(II) complexes.
authors.affiliation: DISFARM, Sezione di Chimica Generale e Organica "A. Marchesini", Università degli Studi Milano, Via Venezian 21, 20133 Milano (Italy), Fax: (+39) 02-50314481.
authors.forename: Andrea
authors.initials: A
authors.lastname: Bonetti
authors.forename: Egle
authors.initials: E
authors.lastname: Beccalli
authors.forename: Alessandro
authors.initials: A
authors.lastname: Caselli
authors.forename: Francesca
authors.initials: F
authors.lastname: Clerici
authors.forename: Sara
authors.initials: S
authors.lastname: Pellegrino
authors.forename: Maria Luisa
authors.initials: ML
authors.lastname: Gelmi
keywords: catalysis; chemoselective reactions; hexahydrotetrazines; rhodium; α-diazocarbonyl piperidines