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  • Nitrogen-boron coordination...
    Steciuk, I; Durka, K; Gontarczyk, K; Dąbrowski, M; Luliński, S; Woźniak, K

    Dalton transactions : an international journal of inorganic chemistry, 2015-Oct-07, Letnik: 44, Številka: 37
    Journal Article

    Pyridoxaboroles - fused heterocyclic systems composed of pyridine and five-membered oxaborole rings - have been obtained for the first time from simple halopyridines. Thus, 6-butyl-2-(3'-bromo-4'-pyridyl)-(N-B)-1,3,6,2-dioxazaborocan obtained from 3-bromopyridine was converted into a lithio derivative by Br/Li exchange using nBuLi/THF at -85 °C. This intermediate was trapped with benzaldehydes to give the corresponding pyridoxaboroles after hydrolysis. The use of chlorodiphenylsilane as an electrophile gave rise to a related pyridosiloxaborole. The fluorinated pyridoxaborole was obtained by deprotonation of α-(2-methoxyphenyl)-2-fluoro-4-iodopyridylmethanol with NaH and consecutive iodine-lithium exchange/boronation followed by hydrolysis. Single-crystal X-ray analysis of pyridino4,3-c-1,3-dihydro-1-hydroxy-3-mesityl2,1oxaborole revealed the formation of a unique 1D coordination polymer based on N-B dative bonds between monomeric molecules. In contrast, the crystal structure of 2-fluoropyridino4,3-c-1,3-dihydro-1-hydroxy-3-(2'-methoxyphenyl)2,1oxaborole features an infinite H-bonded chain as the main structural motif. The presented considerations are quantified in terms of various computational methods (single molecule and dimer energy calculations, electron density topology, NBO analyses) providing a comprehensive picture of the structural properties of pyridoxaboroles.