Divergent Chemical Synthesis of Prolines Bearing Fluorinated One-Carbon Units at the 4-Position via Nucleophilic 5-Endo-Trig Cyclizations
摘要:
N-[3-(Trifluoromethyl)homoallyl]sulfonamides, prepared via ring opening of (S)-glycidyl ethers or 2-aryloxiranes with 1-(trifluoromethyl)vinyllithium, underwent intramolecular addition or S(N)2'-type reaction in the normally disfavored 5-endo-trig fashion, leading to 2-substituted 4-(trifluoromethyl)- or 4-(difluoromethylene)pyrrolidines. Both alpha- and beta-face-selective hydrogenation of the 4-difluoromethylene group afforded syn- and anti-4-(difluoromethyl)pyrrolidines, respectively. These sequences, followed by the oxidation of a 2-hydroxymethyl or 2-aryl group, successfully provided prolines with a trifluoromethyl, difluoromethylene, or difluoromethyl group at the 4-position, including optically active prolines.
carbonylation reaction, the alkoxy- and hydroxy-carbonylation of unsaturated hydrocarbons constitutes one of the most important industrial applications of homogeneous catalysis. However, owing to the difficulties in controlling multi-selectivities for asymmetric hydrocarbonylation of alkenes, this reaction is typically limited to vinylarenes and analogues. In this work, a highly efficient asymmetric alkoxy-
1-(Trifluoromethyl)vinylation via Oxirane or Oxetane Ring-Opening: A Facile Synthesis of 4- or 5-Hydroxy-Functionalized 2-Trifluoromethyl-1-alkenes
作者:Junji Ichikawa、Ryo Nadano
DOI:10.1055/s-2005-918413
日期:——
Introduction of a 1-(trifluoromethyl)vinyl group has been accomplished by the reaction of thermally unstable 1-(trifluoromethyl)vinyllithium (1) with strained cyclic ethers. Treatment of 2-bromo-3.3.3-trifluoropropene with butyllithium generates 1. which in turn reacts with several oxiranes or an oxetane at -100 °C in the presence of BF 3 .OEt 2 to afford the corresponding 2-trifluoromethyl- -1-alkenes