协同亲核取代,称为 S N 2 反应,是合成中用于引入新官能团并构建碳-碳和碳-杂原子键1 的基本有机转化。 S N 2 反应通常涉及亲核试剂对C( sp 3 )−X 键(X=卤素或其他离去基团)的σ* 轨道的背面攻击,导致立体中心2的完全反转。相比之下,电子无偏sp 2乙烯基亲电子试剂上相应的立体反转亲核取代,即协同 S N V(σ) 反应,要罕见得多,并且到目前为止,仅限于精心设计的底物,主要发生在成环过程中3,4 。在这里,我们表明,金属化配合物中提出的应变释放机制可以加速协同的 S N V 反应,从而导致多种有机硼酸酯的通用和立体特异性亚烯基同系物的发展。该方法能够迭代并入多个亚烯基单元,从而产生以其他方式难以制备的交叉共轭多烯。还证明了其在含有多取代烯烃的生物活性化合物的合成中的进一步应用。计算研究表明,方形平面过渡态中空间应变的减少促进了一种不寻常的 S N 2 样协同途径,这解释了这种金属化物
Photocatalytic Isomerization of Styrenyl Halides: Stereodivergent Synthesis of Functionalized Alkenes
作者:Hao Zhang、Qing Xu、Lei Yu、Shouyun Yu
DOI:10.1002/ejoc.201901119
日期:2020.3.15
An efficient and general method for the isomerization of styrenyl halides under photocatalytic conditions is reported. A series of stereospecific transformations constitute preliminary validation of this strategy in the synthesis of functionalized alkenes, including two diaryl alkenes, a styrenyl boronic ester, and an enyne.
bromine/lithium and bromine/zinc exchangereactions take place preferentially at the sterically more hindered bromine atom of the starting gem-dibromo compounds. The observation is rationalized by an exchange mechanism involving a linear transition state of either an ate complex formation or an SN2 reaction at the more hindered bromine atom where strain relief due to the elongation of the carbon-bromine bond is
通过宝石的溴/金属交换反应生成锂和锌酸类胡萝卜素的立体化学已经研究了分别与BuLi和三有机锌酸锂形成的二溴化合物。已证明,衍生自1,1-二溴烯烃的锂和锌酸酯类化合物在低温下是构型稳定的,而在未反应的起始二溴烯烃的存在下,锂类化合物而不是锌酸酯类化合物在类胡萝卜素碳上容易进行异构化。在起始二溴环丙烷存在下,衍生自1,1-二溴环丙烷的Zincate类胡萝卜素在类胡萝卜素碳上缓慢进行异构化。事实证明,锂和锌酸盐类胡萝卜素的异构化反应是通过涉及类胡萝卜素与起始二溴化合物之间的溴/金属交换的机理进行的。在1,1-二溴烯烃在热力学条件下的反应中观察到锂类胡萝卜素的高度立体选择性形成。在动力学控制的条件下,溴/锂和溴/锌的交换反应均优先发生在起始位点的空间受阻溴原子上宝石-二溴化合物。通过交换机制合理化该观察,该交换机制涉及在受阻溴原子处的盐配合物形成或S N 2反应的线性过渡态,在这种情况下,由于碳-溴键的延长,应力会减轻。
MICROREACTOR AND LIQUID PHASE CHEMICAL REACTION METHOD USING MICROREACTOR
申请人:Ryu Ilhyong
公开号:US20100210876A1
公开(公告)日:2010-08-19
This invention provides a microreactor comprising a microchamber provided with a raw material introduction port and a product discharge port; wherein solid catalysts are aligned in a line in the longitudinal direction of the microchamber to fill the microchamber.
An electrorheological fluid composition comprising a dispersion of disperse-phase particles formed of a sulfonated polymer possessing aromatic rings substituted with sulfonic acid groups in an electrically non-conducting oil which electrorheological fluid is characterized by the fact that the number of sulfonic acid groups in said sulfonated polymer forming said disperse-phase particles exceeds the number of aromatic rings present in said sulfonated polymer.
MICROREACTOR AND LIQUID PHASE CHEMICAL REACTION METHOD USING THE MICROREACTOR
申请人:Nippon Soda Co., Ltd.
公开号:EP2206550A1
公开(公告)日:2010-07-14
MICROREACTOR AND LIQUID PHASE CHEMICAL REACTION METHOD USING MICROREACTOR
This invention provides a microreactor comprising a microchamber provided with a raw material introduction port and a product discharge port; wherein solid catalysts are aligned in a line in the longitudinal direction of the microchamber to fill the microchamber.