Cycloruthenation of aryl imines and N-heteroaryl benzenes via C–H bond activation with Ru(II) and acetate partners

• Room temperature (N–Ru–C)-cycloruthenation of arylimines.
• Key role of acetate for C–H bond activation/deprotonation.
• Ru–Cl remaining bond is crucial for cycloruthenate isolation.

The reaction of arylimines with [RuCl2(p-cymene)]2 and 4 equiv. of KOAc at room temperature in methanol leads to the formation of N–Ru–C cycloruthenates RuCl(arylimine-kC,N)(p-cymene) 3a-3d via ortho C–H activation/deprotonation by acetate. The presence of the stable Ru–Cl bond rather than a labile Ru–OAc bond is crucial for the isolation of the complexes. This preparative method of cyclometallates was applied to 2-phenyloxazoline, and benzo[h]quinoline and to the improved synthesis of 2-phenylpyridine and 1-phenylpyrazole derivatives. The molecular structures of three cycloruthenates are reported.

(N–Ru–C)-cycloruthenates are easily prepared at room temperature on reaction of arylimines with [RuCl2(p-cymene)]2 and KOAc in methanol, via ortho arene C–H activation/deprotonation by acetate. The presence of a Ru–Cl remaining bond, instead of a Ru–OAc bond, is crucial for compound isolation. This preparative method was applied to 2-phenyloxazoline, benzo[h]quinoline, 2-phenylpyridine and 1-phenylpyrazole derivatives.Figure optionsDownload as PowerPoint slide