Enhancing Metalating Efficiency of the Sodium Amide NaTMP in Arene Borylation Applications.

Though LiTMP (TMP=2,2',6,6'-tetramethylpiperidide) is a commonly used amide, surprisingly the heavier NaTMP has hardly been utilised. Here, by mixing NaTMP with tridentate donor PMDETA (N,N,N',N'',N''-pentamethyldiethylenetriamine), we provide structural, and mechanistic insights into the sodiation of non-activated arenes (e.g. anisole and benzene). While these reactions are low yielding, adding B(OiPr) 3 has a profound effect, not only by intercepting the C Ar -Na bond, but also by driving the metalation reaction towards quantitative formation of more stabilized sodium aryl boronates. Demonstrating its metalating power, regioselective C2-metalation/borylation of naphthalene has been accomplished contrasting with single-metal based protocols which are unselective and low yielding. Extension to other arenes allows for in situ generation of aryl boronates which can then directly engage in Suzuki-Miyaura couplings, furnishing a range of biaryls in a selective and efficient manner.