Nickel-catalyzed C-F bond activation and alkylation of polyfluoroaryl imines

In this paper we show the C-F bond activation and alkylation in polyfluoroaryl imines. An active trimethylphosphine supported nickel-catalyzed cross-coupling reaction of polyfluoroaryl imines with ZnMe2 under mild conditions is described. According to the in situ F-19 NMR spectroscopic data, the substrates are quantitatively converted into di-methylation products, while mono-methylation can also be realized under the controlled conditions in moderate yields. Apart from ZnMe2, other organozinc regents were tried in this system. However, due to the nucleophilicity and steric hindrance, they show much lower reactivity than ZnMe2. Only in the case of benzylic zinc chloride, the dibenzylation product can be obtained quantitatively by raising temperature to 90 degrees C. The results reported here will benefit the development of C-F bond activation as well as the diversity of Schiff bases. (C) 2012 Elsevier B. V. All rights reserved.