for the synthesis of highly functionalized molecular targets. 2 Therefore, the catalytic and enantioselective construction of these motifs is a valuable challenge for synthetic chemists. 3 AsymmetricMichaeladdition followed by intramolecular nucleophilic substitution is a representative process for this purpose. There have been several reports on the metal-free, organocatalyzed asymmetric synthesis
diameter of about 70 A is observed on the Pd(nano)/HT surface by transmission electron microscopy analysis. These hydrotalcite-supported metal catalysts can effectively promote alpha-alkylation reactions of various nitriles with primary alcohols or carbonylcompounds through tandem reactions consisting of metal-catalyzed oxidation and reduction, and an aldol reaction promoted by the base sites of the
An enantioselective one-pot catalytic strategy to dihydroquinoxalinones, featuring novel 1-phenylsulfonyl-1-cyano enantioenriched epoxides as masked α-halo acylhalidesynthons, followed by a domino ring-opening cyclization (DROC), is documented. A popular quinine-derived urea served as the catalyst in two out of the three steps performed in the same solvent using commercially available aldehydes,
lariat ethers have been synthesized. These macrocycles and their derivatives proved to be efficient catalysts in the cyclopropanation of (E)-3-phenyl-2-(phenylsulfonyl)acrylonitrile performed with diethyl bromomalonate under mild phase transfer conditions. Among the catalysts tested, the macrocycle having methylα-d-galactopyranoside unit generated the highest asymmetric induction (80% ee). In the
Abstract New recyclable monoaza-15-crown ethers have been synthesized starting from ( R , R )-(+)- and ( S , S )-(−)-hydrobenzoin. These macrocycles proved to be efficient and reusable phase transfer catalysts in a few asymmetric reactions under mild conditions. The asymmetric epoxidation of trans -chalcone took place with up to 81% ee, while using other chalcone derivatives, the products were formed
摘要 以 ( R , R )-(+)- 和 ( S , S )-(-)- 氢安息香为原料合成了新的可回收单氮杂-15-冠醚。在温和条件下的一些不对称反应中,这些大环被证明是有效且可重复使用的相转移催化剂。反式查耳酮的不对称环氧化反应的 ee 高达 81%,而使用其他查耳酮衍生物时,生成的产物 ee 高达 68-88%。还使用溴丙二酸二乙酯在一些缺电子烯烃的环丙烷化中测试了基于氢安息香的套索醚,以提供具有良好对映选择性(54-75% ee)的产物。催化剂通过成盐回收,然后萃取,并在不损失活性和对映选择性影响的情况下重复使用。