849831-77-2Relevant articles and documents
Substituent effect on the asymmetric induction with (1R,2S,5R)-and (1S,2R,5S)-menthol auxiliaries
Er, Mustafa,Coskun, Necdet
experimental part, p. 198 - 208 (2011/10/04)
Substituted benzaldehydes reacts in cis-diastcrcoselective manner with mentliyl haloacetates in the presence of phase transfer catalyst and a base in THF at room temperature to give the corresponding 3-arvloxirane-2-carboxvlates (2/3a-h) in moderate to high yields The magnitude of asymmetric induction in the latter reaction was quantified by a Hammett type equation log(2/3)x = ρσr - log(2/3)X-H The stereochemistry of compounds 2 and 3 was elucidated b correlation with (4S. 5R)-2.4-diphenyll-4,5- dihydrooxazole-5-carboxylic acid (+)-8 as well as its enantiomer (-)-8.
Dynamic ligand exchange of the lanthanide complex leading to structural and functional transformation: One-pot sequential catalytic asymmetric epoxidation-regioselective epoxide-opening process
Tosaki, Shin-Ya,Tsuji, Riichiro,Ohshima, Takashi,Shibasaki, Masakatsu
, p. 2147 - 2155 (2007/10/03)
The characteristic property of the lanthanide complex, which easily undergoes a dynamic ligand exchange and alters its structure and function in situ, is described. After the completion of the catalytic asymmetric epoxidation of various α,β-unsaturated amides 2 in the presence of the Sm-(S)-BINOL-Ph3-As=O (1:1:1) complex 1 (2-10 mol %), the addition of Me3SiN3 directly to the reaction mixture led to smooth epoxide-opening at room temperature, affording the corresponding anti-β-azido-α-hydroxyamide 4 in excellent overall yield (up to 99%) with complete regioselectivity and excellent enantiomeric excess (up to >99%). The key to the success of the sequential process was the in situ generation of the highly reactive samarium azide complex through dynamic ligand exchange. In situ IR spectroscopy and other experiments provided strong evidence that the samarium azide complex was generated. In addition, the relatively high Lewis basicity of the amide moiety had a key role in the high reactivity of both the epoxidation and the epoxide-opening reactions. Examinations of other nucleophiles such as sulfur or carbon nucleophiles as well as transformations of epoxide-opened products are also described.