132654-10-5Relevant articles and documents
Kinetic resolution of secondary carbinols by a chiral N,N-4-dimethylaminopyridine derivative containing a 1,1′-binaphthyl unit: Hydrogen bonding affects catalytic activity and enantioselectivity
Fujii, Kazuki,Mitsudo, Koichi,Mandai, Hiroki,Suga, Seiji
, p. 1081 - 1092 (2016/10/11)
We developed an acylative kinetic resolution of secondary carbinols using a binaphthyl-based N,N-4-dimethylaminopyridine (DMAP) derivative 1d with tert-Alcohol substituents. The reaction proceeded with a wide range of carbinols with moderate to high selectivity (s) (up to s = 79.5). Kinetic studies revealed that catalyst 1d was more catalytically active than the corresponding bis-methyl ether 1d′ or DMAP. Hydrogen bonding between tert-Alcohols of the catalyst and secondary carbinols was responsible for the enhanced reaction rate and high enantioselectivity.
Methodology for in situ protection of aldehydes and ketones using trimethylsilyl trifluoromethanesulfonate and phosphines: Selective alkylation and reduction of ketones, esters, amides, and nitriles
Yahata, Kenzo,Minami, Masaki,Yoshikawa, Yuki,Watanabe, Kei,Fujioka, Hiromichi
, p. 1298 - 1307 (2014/01/06)
A methodology for selective transformations of ketones, esters, Weinreb amides, and nitriles in the presence of aldehydes has been developed. The use of a combination of PPh3-trimethylsilyl trifluoromethanesulfonate (TMSOTf) promotes selective transformation of aldehydes to their corresponding, temporarily protected, O,P-acetal type phosphonium salts. Because, hydrolytic work-up following ensuing reactions of other carbonyl moieties in the substrates liberates the aldehyde moiety, a sequence involving aldehyde protection, transformation of other carbonyl groups, and deprotection can be accomplished in a one-pot manner. Furthermore, the use of PEt3 instead of PPh 3 enables ketones to be converted in situ to their corresponding O,P-ketal type phosphonium salts and, consequently, selective transformations of esters, Weinreb amides, and nitriles in the presence of ketones can be performed. This methodology is applicable to various dicarbonyl compounds, including substrates that possess heteroaromatic skeletons and hydroxyl protecting groups.
5-[4-(1-Hydroxyethyl)phenyl]-10,15,20-triphenylporphyrin as a probe of the transition-state conformation in hydrolase-catalyzed enantioselective transesterifications
Ema, Tadashi,Jittani, Masahito,Furuie, Kenji,Utaka, Masanori,Sakai, Takashi
, p. 2144 - 2151 (2007/10/03)
5-[4-(1-Hydroxyethyl)phenyl]-10,15,20-triphenylporphyrin (1a) and zinc porphyrin 1b were designed and synthesized to experimentally examine the validity of the transition-state model previously proposed for the lipase-catalyzed kinetic resolution of secondary alcohols. The lipases from Pseudomonas cepacia (lipase PS), Candida antarctica (CHIRAZYME L-2), Rhizomucor miehei (CHIRAZYME L-9), and Pseudomonas aeruginosa (lipase LIP) exhibited excellent enantioselectivity (E > 100 at 30 °C). Subtilisin Carlsberg from Bacillus licheniformis (ChiroCLEC-BL) also showed high enantioselectivity for 1a (E = 140 at 30 °C), and the thermodynamic parameters were determined: ΔΔH? = -6.8 ± 0.8 kcal mol-1, ΔΔS? = -13 ± 3 cal mol-1 K-1. Lipases and subtilisin showed R- and S-preference for 1, respectively. The mechanisms underlying the experimental observations are explained in terms of the transition-state models. The large secondary alcohol 1 is a powerful tool for investigating the conformation of the transition state of the enzyme-catalyzed reactions. The fact that 1 was resolved with high enantioselectivity strongly suggests that the gauche conformation, but not the anti conformation, is taken in the transition state, in agreement with the transition-state models involving the stereoelectronic effect.
Highly Enantioselective Synthesis of Optically Active Hydroxyaldehydes Using a Chiral Catalyst
Soai, Kenso,Hori, Hiroshi,Kawahara, Masato
, p. 769 - 770 (2007/10/02)
Optically active hydroxyaldehydes are synthesized in 88-94percent e.e. by the catalytic enantioselective addition of dialkylzinc using N,N-dibutylnorephedrine.
