The Diels-Alder reaction, which is a traditional [4 + 2] cycloaddition with two carbon-carbon bond formations, is one of the most powerful tools to synthesize versatile and unique six-membered rings. We show that chiral supramolecular U-shaped boron Lewisacid catalysts promote the unprecedented multiselective Diels-Alder reaction of propargyl aldehyde with cyclic dienes. Independent from the substrate
Diels-Alder 反应是一种传统的 [4 + 2] 环加成反应,具有两个碳-碳键形成,是合成通用且独特的六元环的最强大工具之一。我们表明手性超分子 U 形硼路易斯酸催化剂促进了炔丙醛与环二烯前所未有的多选择性 Diels-Alder 反应。独立于底物控制,对映-、内/外-、π-面-、区域-、位点和底物选择性可以通过本 U 形催化剂进行控制。所得反应产物可用于手性二烯配体和(+)-沙霉素关键中间体的简明合成。这里介绍的结果可能部分有助于开发用于多选择性反应的人工酶样超分子催化剂,
An enantioselective ambimodal cross-Diels–Alder reaction and applications in synthesis
作者:Meng-Meng Xu、Limin Yang、Kui Tan、Xiangyang Chen、Qi-Tao Lu、K. N. Houk、Quan Cai
DOI:10.1038/s41929-021-00687-x
日期:——
d adducts with high enantioselectivity under mild reaction conditions. Computational studies showed that this reaction proceeds through an ambimodal transition state: post-transition-state bifurcation leads to [2+4] and [4+2] adducts with the same enantioselectivity, followed by a facile Cope rearrangement to provide a single observed thermodynamic [2+4] product. This reaction occurs with a wide variety
CH-Aktivierungsreaktionen an substituierten Zirconocenkomplexen und deren Verwendung in der katalytischen Ethylenpolymerisation
作者:Andrea I Licht、Helmut G Alt
DOI:10.1016/s0022-328x(03)00508-4
日期:2003.11
Zirconocene dichloride complexes with substituents containing aliphatic end groups at the aromatic ligands react with two equivalents of n-butyllithium to give metallacyclic zirconocene complexes via aliphatic CH-activation reactions. As well as ω-alkenyl substituted zirconocene dichloride complexes with terminal aliphatic groups as zirconocene dichloride complexes with purely aliphatic substituents
在芳族配体上具有包含脂族端基的取代基的二茂锆二茂合物与二当量的正丁基锂反应,通过脂族CH活化反应生成金属环茂锆茂配合物。具有末端脂族基团的ω-烯基取代的二氧化锆茂金属配合物以及具有纯脂族取代基的二氯化锆茂金属配合物也适用于此类金属环的合成。与甲基铝氧烷(MAO)结合使用时,这些金属环对于乙烯聚合而言是极好的催化剂。它们的活性可以是相应的二茂锆二氯化物离析物的活性的三倍半。催化剂25 / MAO能够生产2640 kg PE g -1 Zr h(60°C,戊烷溶液,10 bar乙烯压力)。
Synthesis of bis (alkyl cyclopentadienyl) metallocenes
申请人:Boulder Scientific Company
公开号:US06175027B1
公开(公告)日:2001-01-16
A method for producing an alkyl cyclopentadiene by reacting cyclopentadienyl Grignard with an alkyl halide and for converting the alkyl cyclopentadiene to a bis(n-alkyl cyclopentadienyl) Group IV metal dihalide is described.
TANTALUM COMPOUND, METHOD FOR PRODUCING SAME, TANTALUM-CONTAINING THIN FILM AND METHOD FOR FORMING SAME
申请人:Sekimoto Kenichi
公开号:US20090043119A1
公开(公告)日:2009-02-12
Objects of the present invention are to provide a novel tantalum compound which enables to selectively form a tantalum-containing thin film free of halogen and the like, and various tantalum-containing thin films which contain the desired element, and a method for producing the same, and further provide a method for stably forming a tantalum-containing thin film which contains the desired element.
The present invention relates to a tantalum compound represented by the following formula (1)
(In the formula, R
1
represents a straight-chain alkyl group having from 2 to 6 carbon atoms),
or a tantalum compound represented by the general formula (2)
(In the formula, R
2
represents a straight-chain alkyl group having from 2 to 6 carbon atoms), and a method for producing the same.
The present invention further relates to form a tantalum-containing thin film by using a tantalum compound represented by the following general formula (6)
(In the formula, j, k, m and n is an integer of from 1 to satisfying j+k=5 and m+n=5, and R
3
to R
6
represent a hydrogen atom, an alkyl group having from 1 to 6 carbon atoms, and the like) as a raw material.