Metal-Free a Simple and Versatile N B Dative Bond Stabilized Boron-Based Catalysts for Transfer Hydrogenation of Aromatic Ketones

In this study, novel boron-containing salen ligands (1 and 2) and their tetra-coordinated boron-based polymers (1a-b and 2a-b) containing N -> B coordination bonds were synthesized under suitable conditions. In the first step, the synthesis of boron-containing salen ligands (1 and 2) was carried out as a result of the reaction of 4-formyl phenylboronic acid with different primary amines. Then, the obtained boron-containing salen ligands (1 and 2) were reacted with pentaerythritol and different N-donor ligands, respectively, to synthesize tetra-coordinated polymers (1a-b and 2a-b) containing N -> B coordination bonds. Synthesized boron-containing salen ligands and corresponding tetra-coordinated polymers containing (N -> B) coordination bonds were characterized by melting point, elemental analysis, LC-MS/MS spectrometer, FT-IR, UV-Vis and NMR (H-1, C-13, and B-11) spectroscopy for illuminate of their structures. The use of synthesized boron-containing salen ligands (1 and 2) and their polymers (1a-b and 2a-b) containing N -> B coordination bonds as novel organocatalysts were tested for the transfer hydrogenation of various aromatic ketones under suitable conditions. Considering all the catalytic results, it was seen that salen ligands (1 and 2) and tetra-coordinated boron-based polymers (1a-b and 2a-b) containing N -> B coordination bonds to be suitable organocatalysts in the future for transfer hydrogenation with other boron compounds. [GRAPHICS]