and control reactions. In the design of Nheterocycliccarbene catalysts both electronic and steric nature of the nitrogen substituents play a crucial role. While hydrocarbon-based systems and especially aryl residues have considerably contributed to surmount multifaceted catalytic challenges, the unique properties of carborane moieties such as delocalized charge, potential planar chirality and their
Aerobic α-hydroxylation of β-keto esters and amides by co-catalysis of SmI3 and I2 under mild base-free conditions
作者:Shun-Ming Yu、Kai Cui、Fei Lv、Zhen-Yu Yang、Zhu-Jun Yao
DOI:10.1016/j.tetlet.2016.05.052
日期:2016.6
A clean base-free α-hydroxylation of β-keto esters and amides has been developed, in which air was used as the oxygen source and SmI3 and I2 were applied as the catalysts, affording the corresponding α-hydroxylated 1,3-dicarbonyl products in good to excellent yields undermildconditions. Mechanism discussion shows that both oxygen atoms of dioxygen are utilized and incorporated into the product through
Cerium-catalyzed α-Oxidation of β-Dicarbonyl Compounds with Molecular Oxygen
作者:Jens Christoffers、Thomas Werner
DOI:10.1055/s-2002-19331
日期:——
β-Ketoesters and β-diketones are α-hydroxylated by molecularoxygen in the presence of 5 mol% CeCl 3 .7 H 2 O in i-PrOH as solvent. The method is limited to substrates with an α-alkyl substituent. Optimal yields are achieved with cyclic starting materials.
β-酮酯和β-二酮在作为溶剂的 i-PrOH 中,在 5 mol% CeCl 3 .7 H 2 O 存在下被分子氧α-羟基化。该方法仅限于具有 α-烷基取代基的底物。使用环状起始材料可实现最佳产率。
Preparation of Acyloins by Cerium-Catalyzed, Direct Hydroxylation ofβ-Dicarbonyl Compounds with Molecular Oxygen
We report the metal-catalyzed α-hydroxylation of a variety of cyclic and acyclic β-dicarbonylcompounds by molecularoxygen. The decisive advantage of this new method is the use of catalytic amounts of the nontoxic cerium salt CeCl3·7H2O in 2-propanol at ambient temperature. Most of the cyclic substrates 4a−4i give high yields of analytically pure products 5a−5i, and the workup procedure is simple