An acetate anion bearing an imidazolium cation as its charge tag was reacted with M(OAc)(2) complexes (where M = Ni, Cu, and Pd; in situ reaction) to form members of a new class of charge-tagged metal complexes. The formation of these unprecedented precatalysts with potential for cross-coupling reactions was confirmed by electrospray ionization (and tandem) mass spectrometry. The catalytic performance of the palladium complex was tested in Heck and Suzuki cross-coupling reactions, often with superior activity and yields as compared with Pd(OAc)(2).
The /3-carbon of ,/3-unsaturated ketones, esters, lactones, and nitriles can be oxidatively functionalized in a regiospecific manner in a simple sequence of reactions. Michael addition of thiophenol followed by oxidation with jV-chlorosuccinimide gives chloro sulfides that readily lose HC1 to give 3-phenylthio enones, acrylates, and other vinyl derivatives.
The 7-norbornenyl radical is generated in solution by photolysis of syn-and anti-tert-butylperoxy 7-norbornenecarboxylates. Geminate combination of the 7-norbornenyl and tert-butoxy radicals favors antirelative to syn-7-tert-butoxynorbornene from both isomeric peresters. Deuterium labeling at the 7 position indicates that hydrogen abstraction from the solvent also occurs preferentially from the anti side of the norbornenyl radical. The 7-norbornenyl radicals generated from the photolysis of syn or anti perester are, thus, chemically indistinguishable. The esr spectra of the 7-norbornenyl radical and of some deuterium substituted 7-norbornenyl radicals are also reported. The hyperfine isotropic coupling constant for the proton in the 7 position is unusually small (10.8 G) and has a temperature coefficient of opposite sign to those hitherto reported for a protons in alkyl radicals (e.g., methyl). The unusual temperature dependence together with an anomalous isotope shift in the magnitude of the corresponding coupling constant for the deuterium labeled species in the 7 position is consistent with a positice sign for the a-proton coupling constant. INDO-MO calculations support this interpretation and are used in conjunction with the esr data to probe the vibrational behavior and the equilibrium structure in this radical.he 7-norbornenyl system offers a structural frame-
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