Cp*rhodium and iridium complexes with bisoxazolines: synthesis, fluxionality and applications as asymmetric catalysts for Diels–Alder reactions
摘要:
Reaction of the dimers [MCl2CP*](2) (M = Rh, It) with bis-oxazolines [N-N = bis(2-oxazoline) (box), 2,2-bis(2-oxazolinyl)propane (bop), 1,2-bis(2-oxazolinyl)benzene (benbox)] in the presence of NaSbF6 (or KPF6) gives complexes [MCl(N-N)Cp*] [EF6] (E = P or Sb) which have been fully characterised. Treatment of some of these with AgSbF6 generates dications [Rh(OH2)(N-N)Cp*]2(+), some of which are fluxional at room temperature. One of these is an enantioselective catalyst for the Diels-Alder reaction of methacrolein and cyclopentadiene. Three complexes, [RhCl(Pr-i-box)Cp*][SbF6], [RhCl(Pr-i-bop)Cp*][SbF6] and [RhCl(Et-benbox)Cp*][SbF6] have been characterised by X-ray crystallography. (C) 2002 Elsevier Science B.V. All rights reserved.
Expeditious preparation of β-<i>sec</i>-alkyl vicinal amino alcohols used for chiral ligand synthesis
作者:Guoqi Huang、Yu Wu、Hegui Gong、Yunrong Chen
DOI:10.1039/d3ob00803g
日期:——
quick access to chiralβ-aminoalcohols bearing one β-sec-alkyl group was developed. This protocol starts with commercially available and cheap chiral sources such as derivatives of L-serine and L-threonine. A series of vicinal amino alcohols with high optical purity were prepared in good yields through 4 or 6 operationally simple steps. Two different strategies (three routes) were designed for the synthesis