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The Taft's substituent constant of the pentafluorophenyl group is reestimated to be 1.50 by correlation between IR spectral data and sigma constants for a series of esters of 3-phenylpropanic acid and butanoic acid. The pentafluorophenyl group is found to possess the moderate electron-withdrawing ability between 3,5-dinitrophenyl and difluoromethyl groups.

Research has been conducted on zinc porphyrin and 5-[4-(1-hydroxyethyl)phenyl]-10,15,20-triphenylporphyrin. The validity of the transition-state model proposed for the lipase-catalyzed secondary alcohol kinetic resolution has been investigated via the synthesis of these porphyrin compounds and the results are reported.

The synthesis of optically pure and active 1,2-bis(pentafluorophenyl)ethane-1,2-diols (1R,2R) and (1S,2S) using lipase-catalyzed transesterification derived cyanohydrin intermediates (R)- and (S)- is described. X-ray structural data of the naproxen ester of the intermediates indicate that they exhibit well-ordered packing structure with pentafluorophenyl and the 6-methoxynaphthyl groups exhibiting face-to-face stacking interactions and end-to-end parallel contacts.

An NADPH-dependent reductase that exhibit reducing activity for 1-chloro-2-hexanone was isolated from bakers' yeast. Gel filtration and sodium dodecyl sulphate-polyacrylamide gel electrophoresis indicated that the reductase is a monomeric enzyme with a 37-kilodalton molecular weight. Moreover, the reductase exhibited low Michaelis values and high specificity constants for all the substrates investigated.

The acyl moiety of acylating agents enhances the enantioselectivity of Pseudomonas cepacia lipase-promoted acylations of racemic alcohols. This stereochemical controlling function, which arises from the transient attachment of the acyl group at the active site of the lipase, was evident in the kinetic resolution of 2-((N,N-dimethylcarbamoyl)-methyl)-3-cyclopenten-1-ol and 2-(2-(tert-butyldimethylsilyloxy)ethyl)-3-cyclopenten-1-ol using enol esters as acyl donors.

Research has been conducted on the enantioselectivity and substrate specificity of the chiral catalysts. The potential capabilities of the carbonyl reductase, a monomeric NADPH-dependent enzyme, as a chiral biocatalyst have been investigated and the results are reported.

Chiral macrocycles with the hydrogen bond donor/acceptor sites in the cavity are prepared and covalently bonded to silica gel to provide chiral stationary phases (CSPs), which has displayed excellent abilities to solve chiral compounds including ketones, esters, carboxylic acids, sulfoxides, amines amino acid derivatives and metal complexes. The MM calculations have shown that the chiral recognition of Co[(acac).sub.2] is obtained by a combination of steric interactions and hydrogen bonds between the carbonyl O atom coordinated to the Co atom and the macrocyclic amide NH groups.

The size and shape of the chiral cavity of a macrocyclic receptor are tuned by the alteration of the binaphthyl moiety in order to improve the chiral recognition/discrimination ability. The host with the 3,5-bis(trifluoromethyl)phenyl group at the 3,3'-positions has an excellent ability as an NMR chiral solvating agent.

Optically active aziridine derivatives have attracted considerable attention because of their versatile synthetic utilities, and a variety of methods for asymmetric syntheses are reported. Methods for the regio-and stereoselective ring cleavage of the aziridines are well studied, and are still under active investigation for the syntheses of chiral amines, amino alcohols, and amino acids.

The temperature effect on enantioselectvity (E) in lipase-catalyzed kinetic resolutions of 34-phenyl-2H-azirine-2-methanol was evaluated through the utilization of a lipase from Pseudomonas cepacia (PS) in a reaction with vinyl acetate in ether under -40 degrees Celsius. Lowering the temperature even as to as low as -40 degrees Celsius enhances the E value, favoring the (R)-enantiomer.

Tetrabutylammonium acetate (TBAA) and Cu(OAc) 2 worked as a binary catalytic system for the solvent-free N -formylation of amines with CO 2 and PhSiH 3 . This catalysis making C-H and C-N bonds with CO 2 was coupled with the C-C bond-forming reactions to achieve the one-pot synthesis of enamines, aldehydes, and nitriles. The X-ray crystal structure of a Cu(OAc) 2 -TBAA complex was also revealed.

Bifunctional Al III porphyrins with quaternary ammonium halides, 2-Cl and 2-Br , worked as excellent catalysts for the copolymerization of cyclohexene oxide (CHO) and CO 2 at 120 °C. Turnover frequency (TOF) and turnover number (TON) reached 10 000 h -1 and 55 000, respectively, and poly(cyclohexene carbonate) (PCHC) with molecular weight of up to 281 000 was obtained with a catalyst loading of 0.001 mol%. In contrast, bifunctional Mg II and Zn II counterparts, 3-Cl and 4-Cl , as well as a binary catalyst system, 1-Cl with bis(triphenylphosphine)iminium chloride (PPNCl), showed poor catalytic performances. Kinetic studies revealed that the reaction rate was first-order in [CHO] and [ 2-Br ] and zero-order in [CO 2 ], and the activation parameters were determined: Δ H ‡ = 12.4 kcal mol -1 , Δ S ‡ = -26.1 cal mol -1 K -1 , and Δ G ‡ = 21.6 kcal mol -1 at 80 °C. Comparative DFT calculations on two model catalysts, Al III complex 2' and Mg II complex 3' , allowed us to extract key factors in the catalytic behavior of the bifunctional Al III catalyst. The high polymerization activity and carbonate-linkage selectivity originate from the cooperative actions of the metal center and the quaternary ammonium cation, both of which facilitate the epoxide-ring opening by the carbonate anion to form the carbonate linkage in the key transition state such as TS3b (Δ H ‡ = 13.3 kcal mol -1 , Δ S ‡ = -3.1 cal mol -1 K -1 , and Δ G ‡ = 14.4 kcal mol -1 at 80 °C)., (This journal is © The Royal Society of Chemistry 2020.)