Air-Persistent Monomeric (Amino)(carboxy) Radicals Derived from Cyclic (Alkyl)(Amino) Carbenes

作者：Mahoney Janell K; Martin David^*; Thomas Fabrice; Moore Curtis E; Rheingold Arnold L; Bertrand Guy

来源：Journal of the American Chemical Society, 2015, 137(23): 7519-7525.

DOI：10.1021/jacs.5b04414

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 (allcy)(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 CO-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 sigma(p) > 0.2.

• 出版日期2015-6-17