Palladium-Catalyzed tert-Butoxycarbonylation of Trifluoroacetimidoyl Iodides
摘要:
A modification and details of the palladium-catalyzed tert-butoxycarbonylation of 2,2,2-trifluoroacetimidoyl iodides 1, which gave the iminocarboxylates 2, one of the promising precursors to fluorinated ol-amino acids, are described. The Pd-catalyzed carbonylation reaction was remarkably promoted by the use of DMF or DMI as an additive, enough to achieve the selective formation of tert-butyl iminoesters. Nucleophilic alkylation of the imine moiety of 2 and subsequent removal of N- and O-protecting groups gave a variety of 2-substituted 2-amino-3,3,3-trifluoropropanoic acid derivatives 3 in high yields.
Pd-Catalyzed Asymmetric Hydrogenation of α-Fluorinated Iminoesters in Fluorinated Alcohol: A New and Catalytic Enantioselective Synthesis of Fluoro α-Amino Acid Derivatives
作者:Hajime Abe、Hideki Amii、Kenji Uneyama
DOI:10.1021/ol0002471
日期:2001.2.1
[figure: see text] Under hydrogen pressure, a catalytic amount of palladium(II) trifluoroacetate and 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (BINAP) promoted asymmetric hydrogenation of alpha-fluorinated iminoesters to afford highly enantioenriched beta-fluorinated alpha-amino esters. The yield and ee were much improved by employing fluorinated alcohols such as 2,2,2-trifluoroethanol (up to 91%
A modification and details of the palladium-catalyzed tert-butoxycarbonylation of 2,2,2-trifluoroacetimidoyl iodides 1, which gave the iminocarboxylates 2, one of the promising precursors to fluorinated ol-amino acids, are described. The Pd-catalyzed carbonylation reaction was remarkably promoted by the use of DMF or DMI as an additive, enough to achieve the selective formation of tert-butyl iminoesters. Nucleophilic alkylation of the imine moiety of 2 and subsequent removal of N- and O-protecting groups gave a variety of 2-substituted 2-amino-3,3,3-trifluoropropanoic acid derivatives 3 in high yields.
Preparation, Structure, and Reactions of Trifluoroacetimidoyl Palladium(II) Complexes
with Pd2(dba)3 provided the phosphine-free imidoyl palladiumcomplex in high yields. The X-raycrystalstructure analysis of the phosphine-free complex [Pd(μ-I)μ-C(CF3)═N(PMP)}]4 revealed a cyclic tetranuclear structure containing the imidoyl and iodo bridges. The generation of aminotrifluoromethylcarbene equivalents by protonation or electrophilic alkylation of imidoyl palladium(II) complexes is discussed