We observed an unusual formation of four-coordinate boron(III) complexes from the reaction of 1-(2-pyridinyl)-5-pyrazolone derivatives with arylboronic acids in the basic media. The exact mechanism is not clear; however, the use of unprotected boronic acid and the presence of a bidentate ligand appeared to be the key structural requirements for the transformation. The results suggest that base-promoted disproportionation of arylboronic acid with the assistance of the [N,O]-bidentate ligation of 1-(2-pyridinyl)-5-pyrazolone should take place and facilitate the formation of pyrazole di-arylborinate. Experiments to obtain a deeper understanding of its mechanism are currently underway.
Bibliographical noteFunding Information:
Funding: This research was funded by National Research Foundation of Korea (Grant number: NRF-2017M1A2A2049100).
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- Arylboronic acid
- Four-coordinate boron(III) complex
- [N,O]-bidentate ligand