The intermolecular or intramolecular asymmetric benzoin reaction was catalyzed by a small amount of N-heterocyclic carbene (NHC) (0.2–1 mol %) under solvent-free conditions. The solvent-free intramolecular asymmetric Stetterreaction also proceeded efficiently with NHC (0.2–1 mol %). In some cases, even solid-to-solid or solid-to-liquid conversions took place with low catalyst loading (0.2–1 mol %)
An efficient enantioselective oxidative reaction catalyzed by a chiral cobalt complex has been developed by using molecularoxygen as the stoichiometric oxidant (see scheme). The very mild reaction conditions of the catalytic system provide access to a wide range of benzoins (α‐hydroxyketones) in high yield and excellent enantioselectivity (s (kf/ks) up to 47). This method is very versatile because
通过使用分子氧作为化学计量的氧化剂,已经开发了一种有效的由手性钴配合物催化的对映选择性氧化反应(参见方案)。催化系统的反应条件非常温和,可以高产率获得各种安息香(α-羟基酮),并具有出色的对映选择性(s(k f / k s)至47)。该方法用途广泛,因为氧化过程的唯一副产品是水,这使我们的系统更加环保,绿色。
N-Heterocyclic Carbene-Catalyzed Asymmetric Benzoin Reaction in Water
A chiral N-heterocyclic carbene-catalyzed benzoin condensation reaction in water has been developed, affording α-hydroxy ketones in good to high yields and high enantioselectivities. Water was proposed as a proton shuttle in the aqueous asymmetric condensation reaction.
Chiral Zn-catalyzed aerobic oxidative kinetic resolution of α-hydroxy ketones
作者:Pandi Muthupandi、Govindasamy Sekar
DOI:10.1016/j.tetasy.2011.02.025
日期:2011.3
The aerobic oxidative kinetic resolution of racemic alpha-hydroxy ketones was accomplished using a chiral Zn-quinine complex as the catalyst in the presence of molecular oxygen. The resulting optimized reaction conditions were applied to resolute different types of racemic alpha-hydroxy ketones and a maximum of 9.2 selectivity (s) was obtained with 88% ee for the recovered alpha-hydroxy ketone. (C) 2011 Elsevier Ltd. All rights reserved.