946411-09-2Relevant articles and documents
Asymmetric Carbon-Carbon Bond Forming Reactions Catalyzed by Chiral Schiff Base-Titanium Alkoxide Complexes
Hayashi, Masahiko,Inoue, Tetsuya,Miyamoto, Yasunori,Oguni, Nobuki
, p. 4385 - 4398 (1994)
The enantioselective addition of trimethylsilyl cyanide to a variety of aldehydes proceeded by the aid of a catalyst prepared in situ from titanium tetraisopropoxide and chiral Schiff bases and gave the corresponding cyanohydrins in high optical yield (up to 96percent e.e.).A remarkable rate enhancement was brought about by the addition of the Schiff base to the titanium alkoxide mediated silylcyanation of aldehydes.This catalyst system also promoted the highly enantioselective reaction of diketene with aldehydes, which led to the formation of optically active 5-hydroxy-3-oxoesters.
Synthesis, characterization, and structures of oxovanadium(v) complexes of Schiff bases of β-amino alcohols as tunable catalysts for the asymmetric oxidation of organic sulfides and asymmetric alkynylation of aldehydes
Hsieh, Sheng-Hsiung,Kuo, Ya-Pei,Gau, Han-Mou
, p. 97 - 106 (2007/10/03)
Oxovanadium(v) complexes 3a-3k and 4a-4d with general formula VO(L 3*)(OR5) were prepared in quantitative yields in alcohol (R5OH) from reactions of VO(O-i-Pr)3 and tridentate Schiff bases of β-amino alcohols having one or two stereogenic centers, (HO)C*(R1)(R2)C*H(R 3)NCH(2-OH-3,5-R42-C6H2) (H2L3*). The alkoxy OR5 ligand exchanges readily with the alcoholic molecule in the solvent. Crystal structures of 3b, 3f, 3i, and 4a were determined to be five-coordinate square pyramidal monomers. However, 1H NMR spectra of the complexes reveal two sets of signals, indicating the presence of two isomers in solution. The two isomers are suggested to be the endo/exo pair or the monomer/dimer pair. Asymmetric oxidations of methyl phenyl sulfide catalyzed by catalyst precursors 3 were demonstrated to afford the chiral sulfoxide in yields and ee values similar to those obtained from the in situ-formed catalytic systems of VO(acac)2 and corresponding Schiff base ligands. Complexes 3 and 4 are also good catalysts for asymmetric alkynyl additions to aldehydes. Structural differences between the oxovanadium complexes, for inducing high stereoselectivities in the asymmetric oxidation of organic sulfides and the asymmetric alkynyl addition to aldehydes, are rationalized. This journal is The Royal Society of Chemistry.
A highly enantioselective Strecker reaction catalyzed by titanium-N-salicyl-β-aminoalcohol complexes
Banphavichit, Vorawit,Mansawat, Woraluk,Bhanthumnavin, Worawan,Vilaivan, Tirayut
, p. 10559 - 10568 (2007/10/03)
N-salicyl-β-amino alcohols 1 were synthesized and evaluated as ligands for catalytic asymmetric Strecker reactions. N-Benzhydrylaldimines derived from aromatic and aliphatic aldehydes reacted with TMSCN in the presence of 10 mol% of Ti-1 complex to give t
Enantioselective Trimethylsilylcyanation of Some Aldehydes Catalyzed by Chiral Schiff Base-Titanium Alkoxide Complexes
Hayashi, Masahiko,Miyamoto, Yasunori,Inoue, Tetsuya,Oguni, Nobuki
, p. 1515 - 1522 (2007/10/02)
A variety of aldehydes (aromatic, heteroaromatic, α,β-unsaturated, and nonconjugate aliphatic aldehydes) has been trimethylsilylcyanated in highly enantiomeric excess (ee) with a catalyst prepared in situ from titanium tetraisopropoxide and chiral Schiff bases.A remarkable rate enhancement was brought about by the addition of the Schiff base into the titanium alkoxide mediated silylcyanation of aldehydes.The chemical structure of chiral Schiff base-titanium alkoxide complexes is discussed based on their 13C NMR spectra, field desorption (FD) mass spectra, and molecular weights.
COPPER(II) IN ORGANIC SYNTHESIS. X. THE IMPORTANCE OF STERIC HINDRANCE IN THE DESIGN OF CHIRAL TRIDENTATE LIGAND COPPER(II) CATALYSTS FOR ENANTIOSELECTIVE MICHAEL REACTIONS
Desimoni, Giovanni,Faita, Giuseppe,Mellerio, Giorgio,Righetti, Pier Paolo,Zanelli, Claudio
, p. 269 - 273 (2007/10/02)
Several copper(II) complexes with tridentate chiral ligands derived from 2-substituted 2-aminoethanols have been tested as catalysts for enantioselective Michael reactions.The degree of enantioselection increases with the increase of the steric hindrance of the substituents and the best result (65percent e.e.) was obtained with the benzyl-substituted catalyst.A comparison of these results with those obtained with complexes derived from 2-amino-1-indanols gives useful information about the requirements for the optimization of the catalyst design.
