title: In search of a new class of stable nitroxide: synthesis and reactivity of a peri-substituted N,N-bissulfonylhydroxylamine.
abstract: Acyclic bissulfonylnitroxides have never been isolated, and degrade through fragmentation. In an approach to stabilising a bissulfonylnitroxide radical, the cyclic, peri-substituted N,N-bissulfonylhydroxylamine, 2-hydroxynaphtho[1,8-de][1,3,2]dithiazine 1,1,3,3-tetraoxide (1), has been prepared by formal nitrogen insertion into the sulfur-sulfur bond of a sulfinylsulfone, naphtho[1,8-cd][1,2]dithiole 1,1,2-trioxide. The heterocyclic ring of 1 is shown to adopt a sofa conformation by X-ray crystallography, with a pseudo-axial hydroxyl group. N,N-Bissulfonylhydroxylamine 1 displays high thermal, photochemical and hydrolytic stability compared to acyclic systems. EPR analysis reveals formation of the corresponding bissulfonylnitroxide 2 upon oxidation of 1 with the Ce(IV) salts CAN and CTAN. Although 2 does not undergo fragmentation, it cannot be isolated, since hydrogen atom abstraction to reform 1 occurs in situ. The stability and reactivity of 1 and 2 are compared with the known cyclic benzo-fused N,N-bissulfonylhydroxylamine, N-hydroxy-O-benzenedisulfonimide (6), for which the X-ray data, and EPR of the corresponding nitroxide 10, are also reported for the first time.
authors.affiliation: School of Chemistry, University of Birmingham, Edgbaston, Birmingham, UK B15 2TT.
authors.forename: Bhaven
authors.initials: B
authors.lastname: Patel
authors.forename: Julie
authors.initials: J
authors.lastname: Carlisle
authors.forename: Steven E
authors.initials: SE
authors.lastname: Bottle
authors.forename: Graeme R
authors.initials: GR
authors.lastname: Hanson
authors.forename: Benson M
authors.initials: BM
authors.lastname: Kariuki
authors.forename: Louise
authors.initials: L
authors.lastname: Male
authors.forename: John C
authors.initials: JC
authors.lastname: McMurtrie
authors.forename: Neil
authors.initials: N
authors.lastname: Spencer
authors.forename: Richard S
authors.initials: RS
authors.lastname: Grainger