Metal-Free Frustrated Lewis Pair Catalyzed 1,4-Hydrogenation of Conjugated Metallocene Dienamines
摘要:
Frustrated Lewis pairs, highly active in heterolytic dihydrogen splitting, were used as active and very selective hydrogenation catalysts for organometallic substrates. Conjugated dienamines fixed at the ferrocene framework and at the zirconocene nucleus were selectively 1,4-hydrogenated under catalytic conditions at ambient temperature.
to form a (13·n-BuLi) dimer that was also characterized by X-ray diffraction. Directed lithiation of the nonbridged ferrocenederivative 1-(dimethylaminobenzyl)ferrocene (16) with tert-butyllithium resulted in an opposite stereoselectivity to yield (R*,p-R*)-17, which forms a chiral dimeric structure in the solid state, as was revealed by its X-ray crystal structure analysis.
用正丁基锂处理α-二甲基氨基[3]二茂铁oph烷衍生物3导致在二茂铁单元的相邻Cp环上进行定向o-金属化反应,以选择性地产生(R *,R *,p - S *)非对映异构体4。类似地,rac - 12的锂化得到(R *,p - S *)- 13。这两种化合物均在晶体中形成以中心C 2 Li 2四元环部分为特征的内消旋型二聚体。化合物13用过量的正丁基锂结晶,形成(13 · n -BuLi)二聚体,该二聚体也通过X射线衍射表征。非桥二茂铁衍生物1-(二甲基氨基苄基)二茂铁(16)与叔丁基锂的直接锂化反应产生相反的立体选择性,生成(R *,p - R *)- 17,形成固态的手性二聚体结构,如通过X射线晶体结构分析所揭示的那样。
Development of a convenient new synthetic route to [3]ferrocenophanones
[3]Ferrocenophanone rac-8 was prepared by several non-Friedel–Crafts pathways starting from a Mannich-type coupling of 1,1′-diacetylferrocene followed by catalytic hydrogenation. Hydride abstraction from the resulting α-dimethylamino[3]ferrocenophane rac-14 with B(C6F5)3 followed by hydrolysis gave the ketone rac-8. Several variants of the Sommelet reaction, using ethylglyoxylate, formaldehyde or hexamethylenetetramine (urotropine) as the “oxidizing” reagent gave the α-[3]ferrocenophanone 8 in good to excellent yield. Some variants of these reactions were also used for the preparation of the pure enantiomer (R)-8. The electrochemical behaviour of 8 has been investigated and compared with related derivatives.
Frustrated Lewis Pairs: Metal-free Hydrogen Activation and More
作者:Douglas W. Stephan、Gerhard Erker
DOI:10.1002/anie.200903708
日期:2010.1.4
Sterically encumbered Lewis acid and Lewis base combinations do not undergo the ubiquitous neutralization reaction to form “classical” Lewis acid/Lewis base adducts. Rather, both the unquenched Lewisacidity and basicity of such sterically “frustrated Lewis pairs (FLPs)” is available to carry out unusual reactions. Typical examples of frustrated Lewis pairs are inter‐ or intramolecular combinations
立体阻碍的路易斯酸和路易斯碱组合不会进行普遍存在的中和反应,以形成“经典的”路易斯酸/路易斯碱加合物。而是,这种空间“受阻的路易斯对(FLP)”的未淬灭的路易斯酸度和碱度均可用于进行异常反应。沮丧的路易斯对的典型例子是大分子膦或胺与强亲电性RB(C 6 F 5)2组分的分子间或分子内组合。这种沮丧的路易斯对的许多例子能够杂合地裂解二氢。将所得ħ + / H -对(例如以相应的phospho阳离子/氢硼酸盐阴离子盐的形式稳定化)可作为无活性金属的催化剂,用于例如大块亚胺,烯胺或烯醇醚的氢化反应。沮丧的路易斯对还可以通过三组分协同反应与烯烃,醛和其他各种小分子(包括二氧化碳)发生反应,从而为合成化学提供了新的策略。