title: Air-persistent monomeric (amino)(carboxy) radicals derived from cyclic (alkyl)(amino) carbenes.
abstract: A series of monomeric (amino)(carboxy) radicals featuring carbonyl substituents with increasing electron-withdrawing properties (3a, phenyl; 3b, 3,5-bis(trifluoromethyl)phenyl; 3c, perfluorophenyl; 3d, heptafluoropropyl; 3e, 2H-pyrroliumyl) were synthesized in two or three steps from stable cyclic (alky)(amino)carbenes (CAACs). Although (amino)(carboxy) radicals had been previously considered as highly air-sensitive, some of these compounds feature half-lives of hours (3d), and even days (3c and 3e) in well-aerated solutions. DFT calculations show that (amino)(carboxy) radicals evolve from C-centered radical to ambidentate C,O-radicals when increasing the electron-withdrawing properties of the carbonyl substituent. This is paralleled with a destabilization of the peroxide resulting from the addition of dioxygen to the radical. This latter reaction is even predicted to be endothermic for substituents with Hammett constant σp > 0.2.
authors.affiliation: †UCSD-CNRS Joint Research Laboratory (UMI 3555), Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0343, United States.
authors.forename: Janell K
authors.initials: JK
authors.lastname: Mahoney
authors.affiliation: †UCSD-CNRS Joint Research Laboratory (UMI 3555), Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0343, United States.|‡UMR CNRS 5250, Département de Chimie Moléculaire, Université Joseph Fourier B. P. 53, 38041 Cedex 9 Grenoble, France.
authors.forename: David
authors.initials: D
authors.lastname: Martin
authors.affiliation: ‡UMR CNRS 5250, Département de Chimie Moléculaire, Université Joseph Fourier B. P. 53, 38041 Cedex 9 Grenoble, France.
authors.forename: Fabrice
authors.initials: F
authors.lastname: Thomas
authors.affiliation: §UCSD Crystallography Facility, San Diego, La Jolla, California 92093-0343, United States.
authors.forename: Curtis E
authors.initials: CE
authors.lastname: Moore
authors.affiliation: §UCSD Crystallography Facility, San Diego, La Jolla, California 92093-0343, United States.
authors.forename: Arnold L
authors.initials: AL
authors.lastname: Rheingold
authors.affiliation: †UCSD-CNRS Joint Research Laboratory (UMI 3555), Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0343, United States.
authors.forename: Guy
authors.initials: G
authors.lastname: Bertrand