Palladium meditated CPhenyl–H bond activation of 2-furylimines versus tert-2-furylbenzylamines

The reactions of 2-furylimines 2a–f and Na2PdCl4 in the presence of NaOAc at 8–10 °C result in nitrogen–palladium coordinated complexes 3a–f. Reduction of 2d–f with NaBH4 followed by N-methylation leads to the corresponding tert-2-furylbenzylamines 5a–c. Treatment of 5a–c with Na2PdCl4 at the same reaction condition as mentioned above affords palladacycles 6a–c where the Pd atoms connect to the phenyl ring rather than the furyl ring. The fact that 5a–c are more active than 2d–f in CPhenyl–H bond activation implies that the electron density of C10 or C8 atom in former is higher than those in latter. Compounds 3a–f, 5a–c, 6a–c were identified by elemental analysis, IR and NMR. In addition, the structures of 3b, 3f and 6c were also confirmed by their single crystal X-ray diffractions.

The reactions of N-(2-furylmethylene)imines 2 and tert-N-(2-furylmethyl)benzylamines 5 with Na2PdCl4 in the presence of NaOAc at 8–10 °C afforded palladium coordinated complexes 3 and palladacycles 6 derived from the CPhenyl–H bond activation, respectively. It is clearly demonstrated that ligands 5 are more active than 2 in regioselective CPhenyl–H bond activation.Figure optionsDownload as PowerPoint slide