title: Anhydrous TEMPO-H: reactions of a good hydrogen atom donor with low-valent carbon centres.
abstract: In this paper, we report a novel synthesis of anhydrous 1-hydroxy-2,2,6,6-tetramethyl-piperidine (TEMPO-H). An X-ray crystal structure and full characterization of the compound are included. Compared to hydrated TEMPO-H, its anhydrous form exhibits improved stability and a differing chemical reactivity. The reactions of anhydrous TEMPO-H with a variety of low-valent carbon centres are described. For example, anhydrous TEMPO-H was reacted with 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), an unsaturated NHC. Crystals of [CHNC(6)H(2)(CH(3))(3)](2)C···HO(NC(5)H(6)(CH(3))(4)), IMes···TEMPO-H, were isolated and a crystal structure determined. The experimental structure is compared to the results of theoretical calculations on the hydrogen-bonded dimer. Anhydrous TEMPO-H was also reacted with the saturated NHC, 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene (SIPr), giving the product [CH(2)Ni-Pr(2)C(6)H(3)](2)CH···O(NC(5)H(6)(CH(3))(4)). In contrast, the reaction of hydrated TEMPO-H with 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene gave small amounts of the hydrolysis product, N-(2,6-diisopropylphenyl)-N-[2-(2,6-diisopropylphenylamino)ethyl]formamide. Finally, anhydrous TEMPO-H was reacted with (triphenylphosphoranylidene)ketene to generate Ph(3)PC(H)C(=O)O(NC(5)H(6)(CH(3))(4)). A full characterization of the product, including an X-ray crystal structure, is described.
authors.affiliation: The Maritimes Centre for Green Chemistry, Department of Chemistry, Saint Mary's University, Halifax, NS, Canada. jason.masuda@smu.ca
authors.forename: Nick A
authors.initials: NA
authors.lastname: Giffin
authors.forename: Miller
authors.initials: M
authors.lastname: Makramalla
authors.forename: Arthur D
authors.initials: AD
authors.lastname: Hendsbee
authors.forename: Katherine N
authors.initials: KN
authors.lastname: Robertson
authors.forename: Cody
authors.initials: C
authors.lastname: Sherren
authors.forename: Cory C
authors.initials: CC
authors.lastname: Pye
authors.forename: Jason D
authors.initials: JD
authors.lastname: Masuda
authors.forename: Jason A C
authors.initials: JA
authors.lastname: Clyburne