title: Nitroxyl radical reactions with 4-pentenyl- and cyclopropylketenes: new routes to 5-hexenyl- and cyclopropylmethyl radicals.
abstract: 4-Pentenylketenes 4a and 9 and cyclopropylketenes 3a, 13, 14 (RCH=C=O) are generated by photochemical Wolff rearrangements and observed by IR as relatively long-lived species at room temperature in hydrocarbon solvents. The reactions of these ketenes with the nitroxyl radicals tetramethylpiperidinyloxyl (TEMPO, TO*) and tetramethylisoindoline-2-oxyl (TMIO, IO*) form carboxy substituted 5-hexenyl and cyclopropylmethyl radicals which are either trapped by a second nitroxyl radical or undergo rearrangements followed by trapping. The rate constant of the reaction of 4a with TEMPO was similar to that of n-BuCH=C=O (1b), while 3a was 4.3 times more reactive, indicating cyclopropyl stabilization of the incipient radical.
authors.affiliation: Department of Chemistry, University of Toronto, Toronto, Ontario, M5S 3H6 Canada.
authors.forename: A D
authors.initials: AD
authors.lastname: Allen
authors.forename: M F
authors.initials: MF
authors.lastname: Fenwick
authors.forename: H
authors.initials: H
authors.lastname: Henry-Riyad
authors.forename: T T
authors.initials: TT
authors.lastname: Tidwell