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

Rui FengWenbang YangWenqing WangYue ZhaoGengwen TanLi ZhangXinping Wang
Published in: Chemical communications (Cambridge, England) (2019)
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.
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