480427-57-4Relevant academic research and scientific papers
Phase-transfer catalyzed asymmetric arylacetate alkylation
Andrus, Merritt B.,Harper, Kaid C.,Christiansen, Michael A.,Binkley, Meisha A.
supporting information; experimental part, p. 4541 - 4544 (2009/12/03)
Phenethyl arylacetates are alkylated under phase-transfer conditions with cinchona catalysts with alkyl halides in high yield with excellent enantioselectivity (84-99% ee) following recrystallization. Cinchonidine (CD) derived catalyst gave the (R)-product and cinchonine (CN) catalyst produced the (S)-product. The phenethyl (PE) ester group is removed, using ammonium formate and catalytic Pd/C, to give alkylated carboxylic acid products in high selectivity. The utility of the approach is demonstrated by a direct synthesis of (S)-naproxen.
Synthesis of kurasoin B using phase-transfer-catalyzed acylimidazole alkylation
Christiansen, Michael A.,Butler, Aaron W.,Hill, Amanda R.,Andrus, Merritt B.
body text, p. 653 - 657 (2009/08/07)
The hydroxy ketone natural product kurasoin B is synthesized using a phase-transfer-catalyzed alkylation reaction with benzyloxyacetyl imidazole. A biscinchonidinium dimethylnaphthalene catalyst allowed for high yield and near complete selectivity (99% ee
Polymeric chiral phase-transfer catalysts derived from cinchona alkaloids for enantioselective synthesis of α-amino acids
Lee, Jeong-Hee,Yoo, Mi-Sook,Jung, Ji-Hee,Jew, Sang-sup,Park, Hyeung-geun,Jeong, Byeong-Seon
, p. 7906 - 7915 (2008/02/09)
A series of dimeric/trimeric chiral quaternary ammonium salts derived from cinchona alkaloids were designed as efficient and practical chiral phase-transfer catalysts (PTCs). Presented are the details on the development of the dimeric PTCs for the synthesis of optically active α-amino acid derivatives and the optimization of the reaction variables suitable for the dimeric PTCs. The 1,3-phenyl- and the 2,7-naphthyl-linked dimeric PTCs showed excellent catalytic capability on the reactivity and enantioselectivity in the catalytic phase-transfer alkylation of N-(diphenylmethylene)glycine tert-butyl ester (1). A variety of α-amino acid derivatives were obtained with high enantiopurities using the dimeric PTCs, especially the 2,7-naphthyl-dimer 41, in a very practical manner.
Phase-transfer-catalyzed asymmetric acylimidazole alkylation
Andrus, Merritt B.,Christiansen, Michael A.,Hicken, Erik J.,Gainer, Morgan J.,Bedke, D. Karl,Harper, Kaid C.,Mikkelson, Shawn R.,Dodson, Daniel S.,Harris, David T.
, p. 4865 - 4868 (2008/03/14)
(Chemical Equation Presented) 2-Acylimidazoles are alkylated under phase-transfer conditions with cinchonidinium catalysts at -40°C with allyl and benzyl electrophiles in high yield with excellent enantioselectivity (79 to >99% ee). The acylimidazole substrates are made in three steps from bromoacetic acid via the N-acylmorpholine adduct. The catalyst is made in high purity allowing for S-product formation (6-20 h) under mild conditions, consistent with an ion-pair mechanism. The products are readily converted to useful ester products using methyltriflate and sodium methoxide, via a dimethylacylimidazolium intermediate without racemization. The process is efficient, direct, and amenable to other electrophiles and transformations that proceed through an enolate intermediate.
