52695-39-3Relevant academic research and scientific papers
Effect of the Ligand Backbone on the Reactivity and Mechanistic Paradigm of Non-Heme Iron(IV)-Oxo during Olefin Epoxidation
Biswas, Jyoti Prasad,Ansari, Mursaleem,Paik, Aniruddha,Sasmal, Sheuli,Paul, Sabarni,Rana, Sujoy,Rajaraman, Gopalan,Maiti, Debabrata
supporting information, p. 14030 - 14039 (2021/05/11)
The oxygen atom transfer (OAT) reactivity of the non-heme [FeIV(2PyN2Q)(O)]2+ (2) containing the sterically bulky quinoline-pyridine pentadentate ligand (2PyN2Q) has been thoroughly studied with different olefins. The ferryl-oxo complex 2 shows excellent OAT reactivity during epoxidations. The steric encumbrance and electronic effect of the ligand influence the mechanistic shuttle between OAT pathway I and isomerization pathway II (during the reaction stereo pure olefins), resulting in a mixture of cis-trans epoxide products. In contrast, the sterically less hindered and electronically different [FeIV(N4Py)(O)]2+ (1) provides only cis-stilbene epoxide. A Hammett study suggests the role of dominant inductive electronic along with minor resonance effect during electron transfer from olefin to 2 in the rate-limiting step. Additionally, a computational study supports the involvement of stepwise pathways during olefin epoxidation. The ferryl bend due to the bulkier ligand incorporation leads to destabilization of both (Formula presented.) and (Formula presented.) orbitals, leading to a very small quintet–triplet gap and enhanced reactivity for 2 compared to 1. Thus, the present study unveils the role of steric and electronic effects of the ligand towards mechanistic modification during olefin epoxidation.
Organomagnesium Based Flash Chemistry: Continuous Flow Generation and Utilization of Halomethylmagnesium Intermediates
Von Keutz, Timo,Cantillo, David,Kappe, C. Oliver
supporting information, p. 7537 - 7541 (2020/10/12)
The generation of highly unstable chloromethylmagnesium chloride in a continuous flow reactor and its reaction with aldehydes and ketones is reported. With this strategy, chlorohydrins and epoxides were synthesized within a total residence time of only 2.6 s. The outcome of the reaction can be tuned by simply using either a basic or an acidic quench. Very good to excellent isolated yields, up to 97%, have been obtained for most cases (30 examples).
Reprogramming Epoxide Hydrolase to Improve Enantioconvergence in Hydrolysis of Styrene Oxide Scaffolds
Li, Fu-Long,Qiu, Yan-Yan,Zheng, Yu-Cong,Chen, Fei-Fei,Kong, Xu–Dong,Xu, Jian-He,Yu, Hui-Lei
supporting information, p. 4699 - 4706 (2020/09/21)
Enantioconvergent hydrolysis by epoxide hydrolase is a promising method for the synthesis of important vicinal diols. However, the poor regioselectivity of the naturally occurring enzymes results in low enantioconvergence in the enzymatic hydrolysis of styrene oxides. Herein, modulated residue No. 263 was redesigned based on structural information and a smart variant library was constructed by site-directed modification using an “optimized amino acid alphabet” to improve the regioselectivity of epoxide hydrolase from Vigna radiata (VrEH2). The regioselectivity coefficient (r) of variant M263Q for the R-isomer of meta-substituted styrene oxides was improved 40–63-fold, and variant M263V also exhibited higher regioselectivity towards the R-isomer of para-substituted styrene oxides compared with the wild type, which resulted in improved enantioconvergence in hydrolysis of styrene oxide scaffolds. Structural insight showed the crucial role of residue No. 263 in modulating the substrate binding conformation by altering the binding surroundings. Furthermore, increased differences in the attacking distance between nucleophilic residue Asp101 and the two carbon atoms of the epoxide ring provided evidence for improved regioselectivity. Several high-value vicinal diols were readily synthesized (>88% yield, 90%–98% ee) by enantioconvergent hydrolysis using the reprogrammed variants. These findings provide a successful strategy for enhancing the enantioconvergence of native epoxide hydrolases through key single-site mutation and more powerful enzyme tools for the enantioconvergent hydrolysis of styrene oxide scaffolds into single (R)-enantiomers of chiral vicinal diols. (Figure presented.).
Discovery of carboxyl-containing biaryl ureas as potent RORγt inverse agonists
Sun, Nannan,Huang, Yafei,Yu, Mingcheng,Zhao, Yunpeng,Chen, Ji-An,Zhu, Chenyu,Song, Meiqi,Guo, Huimin,Xie, Qiong,Wang, Yonghui
supporting information, (2020/07/21)
GSK805 (1) is a potent RORγt inverse agonist, but a drawback of 1 is its low solubility, leading to a limited absorption in high doses. We have explored detailed structure-activity relationship on the amide linker, biaryl and arylsulfonyl moieties of 1 trying to improve solubility while maintaining RORγt activity. As a result, a novel series of carboxyl-containing biaryl urea derivatives was discovered as potent RORγt inverse agonists with improved drug-like properties. Compound 3i showed potent RORγt inhibitory activity and subtype selectivity with an IC50 of 63.8 nM in RORγ FRET assay and 85 nM in cell-based RORγ-GAL4 promotor reporter assay. Reasonable inhibitory activity of 3i was also achieved in mouse Th17 cell differentiation assay (76percent inhibition at 0.3 μM). Moreover, 3i had greatly improved aqueous solubility at pH 7.4 compared to 1, exhibited decent mouse PK profile and demonstrated some in vivo efficacy in an imiquimod-induced psoriasis mice model.
Nucleophilic Organic Base DABCO-Mediated Chemospecific Meinwald Rearrangement of Terminal Epoxides into Methyl Ketones
Li, Siqi,Shi, Yi,Li, Pingfan,Xu, Jiaxi
, p. 4443 - 4450 (2019/04/30)
Nucleophilic organic base DABCO (1,4-diazabicyclo[2.2.2]octane)-mediated Meinwald rearrangement of various epoxides was investigated. 2-Aryl-, alkenyl-, and alkynylepoxides generate the corresponding methyl ketones chemospecifically in good to excellent yields. The current DABCO-mediated Meinwald rearrangement of epoxides features readily accessible starting materials, a wide substrate scope, a transition-metal- and acid-free environment, and chemospecificity in the isomerization of epoxides.
Remarkable increase in the rate of the catalytic epoxidation of electron deficient styrenes through the addition of Sc(OTf)3 to the MnTMTACN catalyst
Nodzewska, Aneta,Watkinson, Michael
supporting information, p. 1461 - 1464 (2018/02/19)
The effect of Lewis acids on the catalytic activity of [Mn2(μ-O)3(TMTACN)2](PF6)2 in the epoxidation of styrenes using hydrogen peroxide as the oxidant has shown that the addition of Sc(OTf)3 at low catalytic loading results in a very significant increase in the efficiency of the catalyst and a reduction of the reaction time to only 3 minutes in most cases.
Dirhodium(II)-Mediated Alkene Epoxidation with Iodine(III) Oxidants
Nasrallah, Ali,Grelier, Gwendal,Lapuh, Maria Ivana,Duran, Fernando J.,Darses, Benjamin,Dauban, Philippe
supporting information, p. 5836 - 5842 (2018/11/24)
Dirhodium(II) complexes and iodine(III) oxidants have found useful applications in synthetic nitrene chemistry. In this study, the combination of the dirhodium(II) complex Rh2(tpa)4 (tpa = triphenylacetate) with the iodine(III) oxidant PhI(OPiv)2 is shown to promote the epoxidation of alkenes in the presence of 2 equivalents of water. The reaction can be applied to diversely substituted alkenes and the corresponding epoxides are isolated with yields of up to 90 %. A possible mechanism involves the dirhodium(II) complex as a Lewis acid species that would tune the oxidizing character of the iodine(III) reagent.
Regioselective Epoxide Ring Opening for the Stereospecific Scale-Up Synthesis of BMS-960, A Potent and Selective Isoxazole-Containing S1P1 Receptor Agonist
Hou, Xiaoping,Zhang, Huiping,Chen, Bang-Chi,Guo, Zhiwei,Singh, Amarjit,Goswami, Animesh,Gilmore, John L.,Sheppeck, James E.,Dyckman, Alaric J.,Carter, Percy H.,Mathur, Arvind
, p. 200 - 207 (2017/02/26)
This article presents a stereospecific scale-up synthesis of (S)-1-((S)-2-hydroxy-2-(4-(5-(3-phenyl-4-(trifluoromethyl)isoxazol-5-yl)-1,2,4-oxadiazol-3-yl)phenyl)ethyl)piperidine-3-carboxylic acid (BMS-960), a potent and selective isoxazole-containing S1P
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.
Catalyst structure and substituent effects on epoxidation of styrenics with immobilized Mn(tmtacn) complexes
Ignacio-De Leon, Patricia Anne A.,Contreras, Christian A.,Thornburg, Nicholas E.,Thompson, Anthony B.,Notestein, Justin M.
, p. 78 - 86 (2015/12/11)
Monomeric and dimeric complexes of Mn 1,4,7-trimethyl-1,4,7-triazacyclononane (tmtacn) were immobilized under reaction conditions onto solid supports to create heterogeneous catalysts for epoxidation with H2O2. These solid supports consist of activated carbon or silica grafted or co-condensed with benzoic or C3/C4 acids that function both as tethering points and as required co-catalysts. Immobilized catalysts were as much as 50-fold faster than the analogous soluble system, and an immobilized, dimeric Mn(tmtacn) complex with a solid benzoic acid co-catalyst gave the highest yields to epoxide. A Hammett study on the catalytic epoxidation of a series of styrenes showed weak increases in yield for more electron-withdrawing p-substituents reactants for both immobilized complexes, which runs counter to previous observations with analogous homogeneous catalysts, and which appears to reflect a previously unappreciated tradeoff between the intrinsic epoxidation reactivity and strong catalyst inhibition by styrene oxides and glycols. Finally, these catalysts were tested with a variety of solid-co-catalysts, and were successfully utilized in the challenging epoxidation of divinylbenzene to industrially-useful divinylbenzene dioxide using a cascade of two catalyst charges.
