C 2对称的路易斯酸/路易斯碱塞伦配体的金属配合物提供双功能激活,从而使二乙基锌对醛的对映选择性加成速率加快(最高ee为92%)。进一步的实验探查了催化剂中各个路易斯酸和路易斯碱组分的反应性,并确定这两个部分对于不对称催化都是必不可少的。这些催化剂在将二乙基锌不对称加成到α-酮酸酯中也是有效的。这一发现意义重大,因为单独的α-酮酸酯充当其自身的配体,以加速Et 2的外消旋1,2-羰基加成反应锌与外消旋羰基还原。后者通过金属茂途径进行,并且通常占主要产物。奇异的路易斯酸催化剂不能在这两个竞争路径上加速对映选择性的1,2-加成。然而,双官能氨基塞伦催化剂以优异的收率,完全的化学选择性和良好的对映选择性(高达88%ee)快速提供对映体富集的1,2-加成产物。合成了双功能氨基塞隆的文库,并在该反应中进行了评估。已经在鸦片拮抗剂的合成中证明了α-酮酸酯方法的实用性。
Phosphorus-containing podands 7. Complexing properties of ortho-diphenylphosphinyl-substituted diphenyl ethers of oligoethylene glycols with respect to alkali-metal cations
摘要:
Stability constants of complexes of alkali-metal cations with oligoethylene glycol diethers RO(CH2CH2O)n(R) (n = 1-5), where R = 2-Ph2P(O)C6H4 and 2-Ph2(O)-4-t-BuC6H3P, have been determined conductometrically in a tetrahydrofuran-chloroform mixture (4:1 by volume). The dependence of complexing ability on a number of monopodand donor centers for Li+ and Na+ has multiple extrema. For K+, Rb+, and Cs+ the complexing abilities steadily increase with the length of the ligand polyether chain. Monopodands based on triethylene glycol and its pyrocatechol analog are highly effective (log K = 6.7-7.0) with respect to Li+. The synthesis of ligands with a lipophilic tert-butyl substituent in the terminal group is described.
Functionalization of 2-Phosphoryl-Substituted Phenols
作者:Yu. I. Rogacheva、D. V. Baulin、V. E. Baulin、A. Yu. Tsivadze
DOI:10.1134/s1070363219080097
日期:2019.8
The nitration, bromination, diazocoupling, sulfonation, and alkylation of the aromatic ring of a series of 2-phosphoryl-substituted phenols have been studied for the first time. 2,6-Diphosphorylphenols have been obtained for the first time via 1,3-phosphorotropic phosphate-phosphonate rearrangement. The alkylation of 2-(diphenylphosphoryl)phenol at the hydroxy group with 2-bromo- and 2-chloroethanols