Isolable diboryl radicals acting as highly efficient reaction intermediates under mild conditions

Rui Feng; Wenbang Yang; Wenqing Wang; Yue Zhao; Gengwen Tan; Li Zhang; Xinping Wang

doi:10.1039/c9cc06514h

Isolable diboryl radicals acting as highly efficient reaction intermediates under mild conditions

Chem Commun (Camb). 2019 Oct 24;55(86):12908-12911. doi: 10.1039/c9cc06514h.

Authors

Rui Feng¹, Wenbang Yang¹, Wenqing Wang², Yue Zhao¹, Gengwen Tan¹, Li Zhang³, Xinping Wang¹

Affiliations

¹ State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China. gengwentan@nju.edu.cn xpwang@nju.edu.cn 544601409@qq.com.
² State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China. gengwentan@nju.edu.cn xpwang@nju.edu.cn 544601409@qq.com and College of Chemistry and Materials Science, Key Laboratory of Functional Molecular Solids, Ministry of Education, Anhui Laboratory of Molecule-Based Materials, Anhui Normal University, Wuhu, Anhui 241002, China.
³ State Key Laboratory of Coordination Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210023, China. gengwentan@nju.edu.cn xpwang@nju.edu.cn 544601409@qq.com and Center of Materials Science and Engineering, Guangxi University of Science and Technology, Liuzhou 545006, China.

PMID: 31566638
DOI: 10.1039/c9cc06514h

Abstract

Activation of the B-B bond in diborane B2(OR)4 with dimesitylpyridylboranes 1 and 2 afforded stable diboryl radicals 3 and 4 in moderate yields, respectively, which were studied by single crystal X-ray crystallography, EPR and UV/Vis spectroscopy, in conjunction with theoretical calculations. The diboryl radicals could react with the substrates p-benzoquinone, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) and its derivative to form useful boron-containing reagents. Moreover, a much higher yield was achieved in the catalytic reaction of p-benzoquinone and diborane with 1 or 2 in comparison to 4-cyanopyridine as the catalyst, in which the diboryl radicals act as reaction intermediates, highlighting the importance of the stability of the boryl radicals in improving the reaction efficiency.