<i>N</i>-Heterocyclic Carbene Catalyzed Highly Chemoselective Intermolecular Crossed Acyloin Condensation of Aromatic Aldehydes with Trifluoroacetaldehyde Ethyl Hemiacetal
作者:Bandaru T. Ramanjaneyulu、Sriram Mahesh、Ramasamy Vijaya Anand
DOI:10.1021/ol502581b
日期:2015.1.2
A highlychemoselectiveintermolecularcrossed acyloin condensation between aromaticaldehydes and trifluoroacetaldehyde ethyl hemiacetal has been developed under mild reaction conditions using N-heterocyclic carbene as a catalyst. A wide range of aromaticaldehydes bearing electron-withdrawing and -donating substituents underwent a smooth transformation to their corresponding trifluoromethyl containing
Facile synthesis of aromatic unsymmetrical fluorine-containing acyloins through the reductive trifluoroacetylation of benzaldehyde and transposition of the carbonyl group
The reductive coupling reaction between benzaldehyde and ethyl trifluoroacetate in the presence of magnesium and chlorotrimethylsilane in N-methyl-2-pyrrolidinone gave the acetal of the corresponding coupling compound in good yields. The yield of the coupling product largely depended on the benzaldehyde concentration in the solution and it was essential to avoid the formation of pinacol type compounds
Hydrogen-Bonding Ability of Noyori–Ikariya Catalysts Enables Stereoselective Access to CF<sub>3</sub>-Substituted <i>syn</i>-1,2-Diols via Dynamic Kinetic Resolution
vinyl, and alkylketones are tolerated, delivering products with ≥95% ee and ≥87:13 syn/anti. This methodology offers rapid access to stereopure bioactive molecules. Furthermore, DFT calculations for three types of Noyori–Ikariya ruthenium catalysts were performed to show their general ability of directing stereoselectivity via the hydrogen bond acceptor SO2 region and CH/π interactions.
立体纯CF 3取代的顺式-1,2-二醇通过HCO 2 H/Et 3 N中相应外消旋α-羟基酮的还原动态动力学拆分来制备。 (Het)芳基、苄基、乙烯基和烷基酮是可耐受的,提供 ≥95% ee 和 ≥87:13 syn / anti的产品。这种方法可以快速获得立体纯的生物活性分子。此外,对三种类型的Noyori-Ikariya钌催化剂进行了DFT计算,以显示它们通过氢键受体SO 2区域和CH/π相互作用引导立体选择性的一般能力。