The first observation of cleavage of unactivated aromatic C-N bonds on a late-transition-metal center was achieved using o-acylanilines and a ruthenium complex. Use of olefins as additives dramatically improved the rate of C-N bond cleavage. The carbon fragment remaining on the ruthenium after C-N bond cleavage was coupled with a phenylboronate to form a biphenyl framework. The present results suggest that ruthenium-catalyzed C-C bond formation from o-acylaniline and organoboronate proceeds via direct C-N bond cleavage on the ruthenium center.

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The reactivity of various o-acylaniline derivatives with ruthenium complexes was examined. The reaction of o-acylanilines with RuH2(CO)(PPh3)3 (1) or an activated ruthenium species formulated as “Ru(CO)(PPh3)3” (4) gave amido hydrido complexes 3 and aryl amido complexes 6 formed via N–H and C–N bond cleavage, respectively. Addition of olefins, such as vinylsilanes, accelerates the C–N bond cleavage. The aryl amido complexes 6 can provide the C–N arylation product upon treatment with arylboronates. The relative reactivity of o-acylanilines bearing various substituents was investigated by competition experiments, and it was found that electron-donating substituents increase the relative facileness of the C–N bond cleavage in both stoichiometric and catalytic reactions. The trend observed here is different from the one observed for the previously reported tantalum-mediated C–N bond cleavage.

Derivatives. -These two new catalytic reactions proceed via oxidative addition of the C-N-bonds, followed by a β-hydride elimination process from the ruthenium amide species. -(KOREEDA, T.; KOCHI, T.; KAKIUCHI*, F.; J. Organomet. Chem. 741-742 (2013) 148-152, http://dx.