The Influence of Boronate Groups on the Selectivity of the Br-Li Exchange in Model Dibromoaryl Boronates
作者:Krzysztof Durka、Sergiusz Luliński、Jaromir Smętek、Marek Dąbrowski、Janusz Serwatowski、Krzysztof Woźniak
DOI:10.1002/ejoc.201300145
日期:2013.5
lithiation of ortho- and meta-brominated phenyl boronates revealed that ortho-lithiated aryl boronates are thermodynamically more stable, but that the Br/Li exchange is generally dictated by kinetics, which accounts for the variation of selectivity depending on the type of boronate group. In addition, the successful generation of the 2,5-dilithiophenyl boronate species 2,5-Li2C6H3B(OCH2CH2)2NBu by a double
6-丁基-2-(2,5-二溴苯基)-1,3,6,2-二氧杂硼烷 (2,5-Br2C6H3B(OCH2CH2)2NBu) 和类似阴离子衍生物的 Br/Li 交换反应的选择性,使用 nBuLi 作为锂化试剂研究了 2,5-Br2C6H3B(OiPr)3Li 和 2,5-Br2C6H3BF3K。在前一种化合物的情况下,在 5 位有轻微的锂化倾向。对于 2,5-Br2C6H3B(OiPr)3Li,锂化仅发生在 C5,但对于 2,5-Br2C6H3BF3K,2-锂化是首选。对邻位和间位溴化苯基硼酸酯的锂化计算表明,邻位锂化芳基硼酸酯在热力学上更稳定,但 Br/Li 交换通常由动力学决定,这解释了选择性取决于类型的变化硼酸组。另外,2的成功生成,5-二硫代苯基硼酸酯物质 2,5-Li2C6H3B(OCH2CH2)2NBu 通过双 Br/Li 互变被报道。相关的6-丁基-2-[3-(2,5-二溴噻吩基)]-1