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
Polymers obtained by heating allybicyclo[2.2.1]hept-5-ene-2-carboxylic
申请人:Ciba-Geigy Corporation
公开号:US04992518A1
公开(公告)日:1991-02-12
The present invention relates to amides of formula I ##STR1## wherein R.sup.1, R.sup.2 and R.sup.3 are each independently hydrogen or methyl, m is 1 to 5 and n is 1 to 5 and R.sup.4 is --NH.sub.2 or is derived from a mono- to pentavalent amine. Intermediates of formula VIII ##STR2## wherein R.sup.1, R.sup.2, R.sup.3 and m are as defined above and X is a carboxylic acid or acid ester group, --COCl, --COBr, --CHO or --CN, are also described. The compounds of formula I can be polymerized thermally. They are suitable for the preparation of adhesives, matrix resins or electrical insulating materials.
The present invention relates to amides of formula I ##STR1## wherein R.sup.1, R.sup.2 and R.sup.3 are independently hydrogen or methyl, m is 1 to 5 and n is 1 to 5 and R.sup.4 is --NH.sub.2 or is derived from a mono- to pentavalent amine. Intermediates of formula VIII ##STR2## wherein R.sup.1, R.sup.2, R.sup.3 and m are as defined above and X is a carboxylic acid or acid ester group, --COCl, --COBr, --CHO or --CN, are also described. The compounds of formula I can be polymerized thermally. They are suitable for the preparation of adhesives, matrix resins or electrical insulating materials.