Characterization and Reactivity of the [N,N-Dimethyl(thioformamidyl)]-9-fluorenyl Cation(1).
The 9-[N,N-dimethyl(thioformamidyl)]-9-fluorenyl cation was generated under stable ion conditions and characterized by UV/visible and NMR spectroscopy and methanol trapping reactions. The same cation was generated by laser excitation of the appropriate chloride precursor in 2,2,2-trifluoroethanol, and rate constants for nucleophilic quenching by alcohols and several anions were measured. The quenching data for this and other 9-fluorenyl cations demonstrate that the reactivity decreases for 9-substituents in the order H > carbomethoxy > N,N-dimethyl(thioformamidyl), demonstrating that the thioamidyl group imparts substantial kinetic stabilization to an adjacent cationic center. Both steric and electronic factors are suggested to be important in determining this reactivity order.
Lew
Calvin S. Q.
CS
Steacie Institute for Molecular Sciences, National Research Council Canada, Ottawa, Ontario, Canada K1A 0R6, and Department of Chemistry, York University, North York, Ontario, Canada M3J 1P3.
Wong
David F.
DF
Johnston
Linda J.
LJ
Bertone
Michael
M
Hopkinson
Alan C.
AC
Lee-Ruff
Edward
E