alkali metal ions for templating the assembly of [2]catenanesfrom di-, tri-, and tetra(ethylene glycol)-containing guest diamines and isophthalaldehyde has indicated that Na+, K+, and Rb+ ions are optimal for preparing [2]catenanes containing at least one di(ethylene glycol) unit, two tri(ethylene glycol) units, and at least one tetra(ethylene glycol) unit [in the absence of a di(ethylene glycol) unit]
Self‐Assembly, Adaptive Response, and
<i>in</i>
,
<i>out‐</i>
Stereoisomerism of Large Orthoformate Cryptands
作者:Henrik Löw、Elena Mena‐Osteritz、Kathleen M. Mullen、Christof M. Jäger、Max von Delius
DOI:10.1002/cplu.202000254
日期:2020.5
We report on triethylene glycol-based orthoformate cryptands, which adapt their bridgehead configurations in response to metal templates and intramolecular hydrogen bonding in a complex manner. In contrast to smaller 1.1.1-orthoformate cryptands, the inversion from out,out-2.2.2 to in,in-2.2.2 occurs spontaneously by thermal homeomorphic isomerization, i. e., without bond breakage. The global thermodynamic
作者:Oleksandr Shyshov、René‐Chris Brachvogel、Tobias Bachmann、Rubitha Srikantharajah、Doris Segets、Frank Hampel、Ralph Puchta、Max von Delius
DOI:10.1002/anie.201609855
日期:2017.1.16
dynamic chemistry of cryptands remains unexplored. Reported here is that cryptands based on orthoester bridgeheads offer an elegant entry to experiments in which a metal ion selects its preferred host from a dynamic mixture of competing subcomponents. In such dynamic mixtures, the alkali metal ions Li+, Na+, K+, Rb+, and Cs+ exhibit pronounced preferences for the formation of cryptands of certain sizes
Tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (TFPB) anion was highly lipophilic, practically insoluble in water, and durable against acid and oxidants. Partition equilibria of alkali TFPB between water and organic solvents and the stability in acid media are described and compared with the properties of the parent tetraphenylborate and of some fluorine-containing homologues.
N‐(1‐(naphthalene‐1‐yl)vinyl)acetamide, 78 % ee). The ligand design enabled the regulation of enantioselectivity by generation of an array of catalysts that simultaneously preserve the advantages of a privileged structure in asymmetric catalysis and offer geometrically close catalytic sites. The highest enantioselectivities in the hydroformylation of vinyl acetate with ligand 4 b were achieved by using the Rb[B(3
本文中,我们报道了使用聚醚粘合剂作为调节剂(RA)来增强铑催化的转化的对映选择性。对于通过α的铑络合物介导的不同底物的反应中,ω -二亚磷酸盐-聚醚配体1 - 5,一- d,对映体过量(EE加氢甲酰基化的)增加了高达82%(底物:苯甲酸乙烯酯,96% ee),加氢的ee值提高了5%(底物:N-(1-(萘-1-基)乙烯基)乙酰胺,ee达78% )。配体设计通过生成一系列催化剂来调节对映选择性,这些催化剂同时保留了不对称催化中优先结构的优势,并提供了几何上紧密的催化位点。通过使用Rb [B(3,5-(CF 3)2 C 6 H 3)4 ](RbBArF)作为RA ,可以实现乙酸乙烯酯与配体4b加氢甲酰化的最高对映选择性。基板的对映选择性氢化10需要从双亚磷酸酯得到的铑催化剂3或4,单独或与不同的RA(钠,铯或它们的组合(R,R)-双(1-苯乙基)铵盐)。这种设计方法得到了计算研究结果的支持。