62566-68-1Relevant articles and documents
Synthesis of new chiral Mn(iii)-salen complexes as recoverable and reusable homogeneous catalysts for the asymmetric epoxidation of styrenes and chromenes
Chaudhary, Pooja,Damodaran, Krishna K.,Singh, Surendra,Yadav, Geeta Devi
, p. 1308 - 1318 (2022/02/07)
New chiral Mn(iii)-salen complexes 1a-e and 2a-e were synthesized from the reaction of C2-symmetric chiral salen ligands and Mn(CH3COO)2·4H2O under an inert atmosphere followed by aerobic oxidation. These complexes were obtained in 91-96% yields and characterized by HRMS, FT-IR, UV-visible spectroscopy, TGA, and elemental analysis. The chiral Mn(iii)-salen complexes 1a-e and 2a-e were evaluated in the asymmetric epoxidation of styrene using NaOCl as an oxidant in ethyl acetate as a green solvent. The chiral Mn(iii)-salen complexes 1b and 2b (2 mol%) catalyzed the asymmetric epoxidation of substituted styrenes and chromenes to afford the corresponding epoxides in 95-98% yields with 29-88% ee's. The catalysts 1b and 2b were recovered and reused for up to 2 and 3 runs, respectively, in the asymmetric epoxidation of styrene, and the yield of styrene oxide gradually decreased but the ee was consistent.
The Stereoselective Oxidation of para-Substituted Benzenes by a Cytochrome P450 Biocatalyst
Chao, Rebecca R.,Lau, Ian C.-K.,Coleman, Tom,Churchman, Luke R.,Child, Stella A.,Lee, Joel H. Z.,Bruning, John B.,De Voss, James J.,Bell, Stephen G.
, p. 14765 - 14777 (2021/09/14)
The serine 244 to aspartate (S244D) variant of the cytochrome P450 enzyme CYP199A4 was used to expand its substrate range beyond benzoic acids. Substrates, in which the carboxylate group of the benzoic acid moiety is replaced were oxidised with high activity by the S244D mutant (product formation rates >60 nmol.(nmol-CYP)?1.min?1) and with total turnover numbers of up to 20,000. Ethyl α-hydroxylation was more rapid than methyl oxidation, styrene epoxidation and S-oxidation. The S244D mutant catalysed the ethyl hydroxylation, epoxidation and sulfoxidation reactions with an excess of one stereoisomer (in some instances up to >98 %). The crystal structure of 4-methoxybenzoic acid-bound CYP199A4 S244D showed that the active site architecture and the substrate orientation were similar to that of the WT enzyme. Overall, this work demonstrates that CYP199A4 can catalyse the stereoselective hydroxylation, epoxidation or sulfoxidation of substituted benzene substrates under mild conditions resulting in more sustainable transformations using this heme monooxygenase enzyme.
Peroxygenase-Catalysed Epoxidation of Styrene Derivatives in Neat Reaction Media
Alcalde, Miguel,Arends, Isabel W. C. E.,Hollmann, Frank,Paul, Caroline E.,Rauch, Marine C. R.,Tieves, Florian
, (2019/08/30)
Biocatalytic oxyfunctionalisation reactions are traditionally conducted in aqueous media limiting their production yield. Here we report the application of a peroxygenase in neat reaction conditions reaching product concentrations of up to 360 mM.
Asymmetric synthesis of α-bromohydrins by carrot root as biocatalyst and conversion to enantiopure β-hydroxytriazoles and styrene oxides using click chemistry and SN2 ring-closure
Hosseinzadeh, Rahman,Mohadjerani, Maryam,Mesgar, Sakineh
, p. 583 - 591 (2019/02/17)
In this study we have combined the bioreduction of α-bromoketones using carrot root as biocatalyst and click chemistry for the preparation of enantiopure β-hydroxytriazoles in excellent enantiomeric excesses and yields. Moreover, we have utilized chiral α-halohydrins for the synthesis of enantiopure styrene oxides in very good yields and enantiomeric excesses. Structural assignments of the products were based on their 1H and 13C NMR data and their optical rotations. The enantiomeric excess of the chiral products was obtained by HPLC analysis.
Highly Enantioselective Hydrosilylation of Ketones Catalyzed by a Chiral Oxazaborolidinium Ion
Kang, Byung Chul,Shin, Sung Ho,Yun, Jaesook,Ryu, Do Hyun
supporting information, p. 6316 - 6319 (2017/12/08)
A highly enantioselective hydrosilylation of ketones was developed for the synthesis of a variety of chiral secondary alcohols. In the presence of a chiral oxazaborolidinium ion (COBI) catalyst, the reaction proceeded with good yields (up to 99%) with excellent enantioselectivities (up to 99% ee).
Multistep Organic Transformations over Base-Rhodium/Diamine-Bifunctionalized Mesostructured Silica Nanoparticles
Liao, Hang,Chou, Yajie,Wang, Yu,Zhang, Han,Cheng, Tanyu,Liu, Guohua
, p. 3197 - 3202 (2017/08/29)
The assembly of multiple catalytic functionalities within a single mesoporous silica as a catalyst for multistep enantioselective organic transformations in an environmentally friendly medium is a significant challenge in heterogeneous asymmetric catalysis. Herein, we took advantage of a BF4 ? anion hydrogen bonding strategy to anchor a chiral cationic rhodium/diamine complex within base-functionalized mesostructured silica nanoparticles conveniently to construct a bifunctional heterogeneous catalyst. The solid-state 13C NMR spectrum discloses the well-defined chiral Rh/diamine active species, and we used XRD, N2 adsorption–desorption, and electron microscopy to reveal the ordered mesostructure. The combination of bifunctionality in the silica nanoparticles enables two kinds of efficient enantioselective organic transformations with high yields and enantioselectivities, in which the asymmetric transfer hydrogenation of α-haloketones followed by epoxidation provides various chiral aryloxiranes, and the amination of α-haloketones with anilines followed by asymmetric transfer hydrogenation produces various β-amino alcohols. Furthermore, the catalyst can be recovered and recycled for seven times without a loss of catalytic activity, which is an attractive feature for multistep organic transformations in a sustainable benign process.
Catalytic Enantioselective Conversion of Epoxides to Thiiranes
Liao, Saihu,Leutzsch, Markus,Monaco, Mattia Riccardo,List, Benjamin
supporting information, p. 5230 - 5233 (2016/05/19)
A highly efficient and enantioselective Br?nsted acid catalyzed conversion of epoxides to thiiranes has been developed. The reaction proceeds in a kinetic resolution, furnishing both epoxide and thiirane in high yields and enantiomeric purity. Heterodimer formation between the catalyst and sulfur donor affords an effective way to prevent catalyst decomposition and enables catalyst loadings as low as 0.01 mol %.
The Activation of Carboxylic Acids via Self-Assembly Asymmetric Organocatalysis: A Combined Experimental and Computational Investigation
Monaco, Mattia Riccardo,Fazzi, Daniele,Tsuji, Nobuya,Leutzsch, Markus,Liao, Saihu,Thiel, Walter,List, Benjamin
supporting information, p. 14740 - 14749 (2016/11/18)
The heterodimerizing self-assembly between a phosphoric acid catalyst and a carboxylic acid has recently been established as a new activation mode in Br?nsted acid catalysis. In this article, we present a comprehensive mechanistic investigation on this activation principle, which eventually led to its elucidation. Detailed studies are reported, including computational investigations on the supramolecular heterodimer, kinetic studies on the catalytic cycle, and a thorough analysis of transition states by DFT calculations for the rationalization of the catalyst structure-selectivity relationship. On the basis of these investigations, we developed a kinetic resolution of racemic epoxides, which proceeds with high selectivity (up to s = 93), giving the unreacted epoxides and the corresponding protected 1,2-diols in high enantiopurity. Moreover, this approach could be advanced to an unprecedented stereodivergent resolution of racemic α-chiral carboxylic acids, thus providing access to a variety of enantiopure nonsteroidal anti-inflammatory drugs and to α-amino acid derivatives.
Azidolysis of epoxides catalysed by the halohydrin dehalogenase from Arthrobacter sp. AD2 and a mutant with enhanced enantioselectivity: an (S)-selective HHDH
Mikleu?evi?, Ana,Primo?i?, Ines,Hrenar, Tomica,Salopek-Sondi, Branka,Tang, Lixia,Elenkov, Maja Majeri?
, p. 930 - 935 (2016/09/13)
Halohydrin dehalogenase from Arthrobacter sp. AD2 catalysed azidolysis of epoxides with high regioselectivity and low to moderate (S)-enantioselectivity (E?=?1–16). Mutation of the asparagine 178 to alanine (N178A) showed increased enantioselectivity towards styrene oxide derivatives and glycidyl ethers. Conversion of aromatic epoxides was catalysed by HheA-N178A with complete enantioselectivity, however the regioselectivity was reduced. As a result of the enzyme-catalysed reaction, enantiomerically pure (S)-β-azido alcohols and (R)-α-azido alcohols (ee???99%) were obtained.
Self-supported chiral polymeric MnIII salen complexes as highly active and recyclable catalysts for epoxidation of nonfunctionalized olefins
Roy, Tamal,Kureshy, Rukhsana I.,Khan, Noor-Ul H.,Abdi, Sayed H. R.,Bajaj, Hari C.
, p. 1038 - 1044 (2015/06/08)
Abstract A series of self-supported chiral polymeric MnIII N,N′-ethylenebis(salicylimine) (salen) complexes were synthesized through metalation of the corresponding salen ligands obtained by condensation of several bis/tris-aldehydes with (1R,2
