A General Method for the Preparation of 5-Trifluoromethylated Oxazoles from .ALPHA.-Amino Acids.
作者:Masami KAWASE、Hiroshi MIYAMAE、Teruo KURIHARA
DOI:10.1248/cpb.46.749
日期:——
The reactions of N-acyl-N-benzyl-α-amino acids (1) or N-acylprolines (5) with trifluoroacetic anhydride in the presence of pyridine afford 5-trifluoromethyloxazoles (2 or 7) in good yields. The reaction could proceed through the transient formation of mesoionic 1, 3-oxazolium-5-olates, followed by oxazolium salts.
Unusual reactions of secondary amino acids with trifluoroacetic anhydride: A novel access to α-trifluoromethylated acyloins
作者:Masami Kawase
DOI:10.1016/0040-4039(94)88187-1
日期:1994.1
A new fragmentation reaction of secondary α-amino acids with trifluoroaceticanhydride under Dakin-West reaction conditions proceeds through oxazolium salt intermediates followed by ring cleavage to form α-trifluoromethylated acyloins in good yields.
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。
Convenient Synthesis of .ALPHA.-Trifluoromethylated Acyloins from .ALPHA.-Hydroxy or .ALPHA.-Amino Acids.
作者:Masami KAWASE、Setsuo SAITO、Teruo KURIHARA
DOI:10.1248/cpb.48.1338
日期:——
acyloins (2 and 6) have been prepared from alpha-hydroxy acids (1), N-acylprolines (5) or N-acyl-N-alkyl alpha-amino acids (8) by novel transformation reactions with trifluoroacetic anhydride (TFAA) in the presence of pyridine. The former reaction of 1 could proceed through mesoionic 1,3-dioxolium-4-olates, whereas the latter two reactions of alpha-amino acids (5 and 8) could involve mesoionic 1,3-oxazolium-5-olates