Planar-Chiral 1,1′-Diboryl Metallocenes: Diastereoselective Synthesis from Boryl Cyclopentadienides and Spin Density Analysis of a Diborylcobaltocene
作者:Emmanuel Lerayer、Patrice Renaut、Stéphane Brandès、Hélène Cattey、Paul Fleurat-Lessard、Ghenwa Bouhadir、Didier Bourissou、Jean-Cyrille Hierso
DOI:10.1021/acs.inorgchem.6b02510
日期:2017.2.20
congestion. The new boryl dienes are obtained as mixtures of isomers, and subsequent deprotonation with MeLi or LiHMDS affords the lithium 1,3-disubstituted cyclopentadienides 5a,b in yields over 95%. Direct assembling of tert-butylated boryl cyclopentadienides with MCl2 (M = Fe, Co) selectively leads to 1,1′-planar chiral ferrocenes 6a,b and cobaltocene 7. To shed light into the diastereoselective formation
未取代的碱金属环戊二烯与卤代烷的反应生成约90:10的异构二烯产物混合物,可以将其去质子化,得到简单的硼基环戊二烯。我们使用FBMes 2(Mes = 2,4,6-三甲基苯基)和ClBCy 2作为亲电子试剂将这种转化扩展到空间受阻的叔丁基环戊二烯化锂1。硼烷基被选择性地引入远端位置以使空间拥塞最小化。以异构体的混合物形式获得新的硼基二烯,随后用MeLi或LiHMDS进行去质子化,可得到1,3,2-二取代的环戊二烯酸锂5a,b,产率超过95%。直接装配叔具有MCl 2(M = Fe,Co)的丁基丁基硼基环戊二烯选择性地生成1,1'-平面手性二茂铁6a,b和钴并茂7。为了阐明6a的非对映选择性结构,进行了DFT计算。仔细检查势能表面,以鉴定和比较其非对映异构体和构象异构体。该立体选择性归因于外消旋非对映异构体的Eclipse构象中叔丁基和BMes 2基团之间的空间排斥最小。报道了硼基二烯2a和