title: Thermal reactions of tributyltin hydride with alpha-azido esters: unexpected intervention of tin triazene adducts under both nonradical and radical conditions.
abstract: Thermal reaction of various alpha-azido esters with Bu(3)SnH in refluxing benzene results in smooth production of 3-(tributylstannyl)-1-triazene adducts affording cyclized 1,2,3-triazol-4-ones in preference to reduced amines and thence provides a new useful method for the preparation of these triazole derivatives. In the presence of AIBN the occurrence of triazene products still remains important or even exclusive and, consequently, generation of the expected stannylaminyl radicals is seriously limited. With 2-azidomalonates and alpha-azido-beta-keto esters stannyltriazenes can similarly occur in the absence of the radical initiator, but in the latter cases the ensuing triazenes undergo preferential cyclization onto the ketone moiety to give reactive hydroxytriazolines. Contrary to alpha-azido esters, in the presence of AIBN alpha-azido-beta-keto esters as well as azidomalonates give rise only to the usual stannylaminyl radicals. A possible explanation for the different behavior of the mono- and dicarbonyl azides in the presence of AIBN is put forward.
authors.affiliation: Dipartimento di Chimica Organica A. Mangini, Università di Bologna, Viale Risorgimento 4, I-40136 Bologna, Italy.
authors.forename: Luisa
authors.initials: L
authors.lastname: Benati
authors.forename: Giorgio
authors.initials: G
authors.lastname: Bencivenni
authors.forename: Rino
authors.initials: R
authors.lastname: Leardini
authors.forename: Matteo
authors.initials: M
authors.lastname: Minozzi
authors.forename: Daniele
authors.initials: D
authors.lastname: Nanni
authors.forename: Rosanna
authors.initials: R
authors.lastname: Scialpi
authors.forename: Piero
authors.initials: P
authors.lastname: Spagnolo
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Zanardi