485809-21-0Relevant academic research and scientific papers
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.
Catalytic asymmetric epoxidation of α,β-unsaturated carboxylic acid imidazolides and amides by lanthanide-BINOL complexes
Ohshima, Takashi,Nemoto, Tetsuhiro,Tosaki, Shin-Ya,Kakei, Hiroyuki,Gnanadesikan, Vijay,Shibasaki, Masakatsu
, p. 10485 - 10497 (2007/10/03)
Highly enantioselective catalytic asymmetric epoxidation of α,β-unsaturated carboxylic acid imidazolides and simple amides was developed. In the presence of 5-10mol% of lanthanide-BINOL complexes, the reaction proceeded smoothly with high substrate generality. In particular, in the cases of α,β-unsaturated amides, there was nearly perfect enantioselectivity (>99% ee). The corresponding epoxides were successfully transformed into many types of useful chiral compounds such as α,β-epoxy esters, α,β-epoxy amides, α,β-epoxy aldehydes, α,β-epoxy β-keto ester, and α- and β-hydroxy carbonyl compounds. B3LYP density functional studies were performed to predict substrate reactivity.
Catalytic asymmetric epoxidation of α,β-unsaturated amides: Efficient synthesis of β-aryl α-hydroxy amides using a one-pot tandem catalytic asymmetric epoxidation - Pd-catalyzed epoxide opening process
Nemoto, Tetsuhiro,Kakei, Hiroyuki,Gnanadesikan, Vijay,Tosaki, Shin-Ya,Ohshima, Takashi,Shibasaki, Masakatsu
, p. 14544 - 14545 (2007/10/03)
The catalytic asymmetric epoxidation of α,β-unsaturated amides using Sm-BINOL-Ph3As=O complex was succeeded. Using 5-10 mol % of the asymmetric catalyst, a variety of amides were epoxidized efficiently, yielding the corresponding α,β-epoxy amides in up to 99% yield and in more than 99% ee. Moreover, the novel one-pot tandem process, one-pot tandem catalytic asymmetric epoxidation-Pd-catalyzed epoxide opening process, was developed. This method was successfully utilized for the efficient synthesis of β-aryl α-hydroxy amides, including β-aryllactyl-leucine methyl esters. Interestingly, it was found that beneficial modifications on the Pd catalyst were achieved by the constituents of the first epoxidation, producing a more suitable catalyst for the Pd-catalyzed epoxide opening reaction in terms of chemoselectivity. Copyright
