23159-87-7Relevant articles and documents
Improved Synthesis of MediPhos Ligands and Their Use in the Pd-Catalyzed Enantioselective N-Allylation of Glycine Esters
Albat, Dominik,Neud?rfl, J?rg-Martin,Reiher, Martin,Schmalz, Hans-Günther
supporting information, p. 4237 - 4242 (2021/08/24)
A new class of chiral C2-symmetric diphosphines (MediPhos) was recently shown to give superior results in the Pd-catalyzed asymmetric N-allylation of amino acid esters. We here describe a new, improved protocol for the preparation of such ligands through bidirectional SN2-coupling of a tartrate-derived ditosylate with 6-alkyl-2-bromophenols followed by double lithiation/phosphanylation. This method gave access to a series of nine ligands with branched alkyl substituents, which were benchmarked in the enantioselective Pd-catalyzed N-allylation of tert-butyl glycinate with racemic (E)-2,8-dimethylnona-5-en-4-yl methyl carbonate (up to 95 % ee). In addition, the analogous transformation of tert-butyl glycinate with methyl (E)-nona-5-en-4-yl carbonate was optimized. The obtained allylic amines were then used in the stereoselective synthesis of the conformationally restricted proline-derived dipeptide analogs ProM-17 and ProM-21.
Regioselective Halogenation of Arenes and Heterocycles in Hexafluoroisopropanol
Tang, Ren-Jin,Milcent, Thierry,Crousse, Benoit
, p. 930 - 938 (2018/01/28)
Regioselective halogenation of arenes and heterocycles with N-halosuccinimides in fluorinated alcohols is disclosed. Under mild condition reactions, a wide diversity of halogenated arenes are obtained in good yields with high regioselectivity. Additionally, the versatility of the method is demonstrated by the development of one-pot sequential halogenation and halogenation-Suzuki cross-coupling reactions.
Chiral Phosphine–Phosphite Ligands in Asymmetric Gold Catalysis: Highly Enantioselective Synthesis of Furo[3,4-d]-Tetrahydropyridazine Derivatives through [3+3]-Cycloaddition
Du, Qingwei,Neud?rfl, J?rg-Martin,Schmalz, Hans-Günther
supporting information, p. 2379 - 2383 (2018/01/27)
The AuI-catalyzed reaction of 2-(1-alkynyl)-2-alken-1-ones with azomethine imines regio- and diastereoselectively affords furo[3,4-d]tetrahydropyridazines in a tandem cyclization/intermolecular [3+3]-cycloaddition process under mild conditions.
Vanadate-dependent bromoperoxidases from Ascophyllum nodosum in the synthesis of brominated phenols and pyrroles
Wischang, Diana,Radlow, Madlen,Hartung, Jens
, p. 11926 - 11940 (2013/09/02)
Bromoperoxidases from the brown alga Ascophyllum nodosum, abbreviated as VBrPO(AnI) and VBrPO(AnII), show 41% sequence homology and differ by a factor of two in the percentage of α-helical secondary structures. Protein monomers organize into homodimers for VBrPO(AnI) and hexamers for VBrPO(AnII). Bromoperoxidase II binds hydrogen peroxide and bromide by approximately one order of magnitude stronger than VBrPO(AnI). In oxidation catalysis, bromoperoxidases I and II turn over hydrogen peroxide and bromide similarly fast, yielding in morpholine-4-ethanesulfonic acid (MES)-buffered aqueous tert-butanol (pH 6.2) molecular bromine as reagent for electrophilic hydrocarbon bromination. Alternative compounds, such as tribromide and hypobromous acid are not sufficiently electrophilic for being directly involved in carbon-bromine bond formation. A decrease in electrophilicity from bromine via hypobromous acid to tribromide correlates in a frontier molecular orbital (FMO) analysis with larger energy gaps between the π-type HOMO of, for example, an alkene and the σ*Br,X-type LUMO of the bromination reagent. By using this approach, the reactivity of substrates and selectivity for carbon-bromine bond formation in reactions mediated by vanadate-dependent bromoperoxidases become predictable, as exemplified by the synthesis of bromopyrroles occurring naturally in marine sponges of the genera Agelas, Acanthella, and Axinella. The Royal Society of Chemistry.
Substrate-Based fragment identification for the development of selective, nonpeptidic inhibitors of striatal-enriched protein tyrosine phosphatase
Baguley, Tyler D.,Xu, Hai-Chao,Chatterjee, Manavi,Nairn, Angus C.,Lombroso, Paul J.,Ellman, Jonathan A.
, p. 7636 - 7650 (2013/11/06)
High levels of striatal-enriched protein tyrosine phosphatase (STEP) activity are observed in a number of neuropsychiatric disorders such as Alzheimer's disease. Overexpression of STEP results in the dephosphorylation and inactivation of many key neuronal
TARTROL-derived chiral phosphine-phosphite ligands and their performance in enantioselective Cu-catalyzed 1,4-addition reactions
Dindaroglu, Mehmet,Akyol, Sema,Simsir, Hamza,Neudoerfl, Joerg-Martin,Burke, Anthony,Schmalz, Hans-Guenther
, p. 657 - 662 (2013/07/11)
By using (R,R,R,R)-2,3-dimethoxy-2,3-dimethyl-1,4-dioxane-5,6-bis- diphenylmethanol (TARTROL) as a chiral building block, a set of six modular phosphine-phosphite ligands (with a 1,2-phenylene backbone) were synthesized and evaluated in the Cu-catalyzed a
Multi-faceted reactivity of alkyltellurophenols towards peroxyl radicals: Catalytic antioxidant versus thiol-depletion effect
Amorati, Riccardo,Valgimigli, Luca,Diner, Peter,Bakhtiari, Khadijeh,Saeedi, Mina,Engman, Lars
, p. 7510 - 7522 (2013/07/19)
Hydroxyaryl alkyl tellurides are effective antioxidants both in organic solution and aqueous biphasic systems. They react by an unconventional mechanism with ROO. radicals with rate constants as high as 107 M-1 s-1 at 303 K, outperforming common phenols. The reactions proceed by oxygen atom transfer to tellurium followed by hydrogen atom transfer to the resulting RO. radical from the phenolic OH. The reaction rates do not reflect the electronic properties of the ring substituents and, because the reactions occur in a solvent cage, quenching is more efficient when the OH and TeR groups have an ortho arrangement. In the presence of thiols, hydroxyaryl alkyl tellurides act as catalytic antioxidants towards both hydroperoxides (mimicking the glutathione peroxidases) and peroxyl radicals. The high efficiency of the quenching of the peroxyl radicals and hydroperoxides could be advantageous under normal cellular conditions, but pro-oxidative (thiol depletion) when thiol concentrations are low. Anti- and pro-oxidants: Hydroxyaryl alkyl tellurides are unconventional antioxidants able to quench chain-carrying peroxyl radicals with rate constants as high as 107 M-1 s-1 by a mechanism involving oxygen atom transfer to tellurium followed by reaction of the RO. radical with the phenol (see figure). They can also catalytically decompose both the ROO. radical and H2O2 in the presence of excess thiols. Copyright
Bromination of phenols in bromoperoxidase-catalyzed oxidations
Wischang, Diana,Hartung, Jens
supporting information, p. 9456 - 9463 (2012/11/07)
Phenol and ortho-substituted derivatives furnish products of selective para-bromination, if treated with sodium bromide, hydrogen peroxide, and the vanadate(V)-dependent bromoperoxidase I from the brown alga Ascophyllum nodosum. Relative rates of bromination in morpholine-4-ethane sulfonic acid (MES)-buffered aqueous tert-butanol (pH 6.2) increase by a factor 32, as the ortho-substituent in a phenol changes from F via Cl, OCH3, C(CH 3)3, and H to CH3. The polar effect in phenol bromination by the enzymatic method, according to a Hammett-correlation (ρ=-3), compares to reactivity of molecular bromine under identical conditions (ρ=-2). Hypobromous acid is not able to electrophilically substitute bromine for hydrogen at pH 6.2 in aqueous tert-butanol. The tribromide anion behaves in MES-buffered aqueous tert-butanol as electrophile (ρ～-3), showing a similar polar effect in phenol bromination as molecular bromine.
Steric effects compete with aryne distortion to control regioselectivities of nucleophilic additions to 3-silylarynes
Bronner, Sarah M.,MacKey, Joel L.,Houk,Garg, Neil K.
supporting information, p. 13966 - 13969 (2012/10/29)
We report an experimental and computational study of 3-silylarynes. The addition of nucleophiles yield ortho-substituted products as a result of aryne distortion, but meta-substituted products form predominately when the nucleophile is large. Computations correctly predict the preferred site of attack observed in both nucleophilic addition and cycloaddition experiments. Nucleophilic additions to 3-tert-butylbenzyne, which is not significantly distorted, give meta-substituted products.
Asymmetrie hydroformylation using Taddol-based chiral phosphine - Phosphite ligands
Robert, Tobias,Abiri, Zohar,Wassenaar, Jeroen,Sandee, Albertus J.,Romanski, Steffen,Neudoerfl, Joerg-Martin,Schmalz, Hans-Guenther,Reek, Joost N. H.
scheme or table, p. 478 - 483 (2010/04/01)
A small library of 17 modular and easily accessible phenol-derived chiral phosphine - phosphite ligands was evaluated in the asymmetric Rh-catalyzed hydroformylation of styrene. It was found that the stereochemical outcome of the reaction is highly dependent on the chiral phosphite moiety and the substituents on the phenolic backbone. Among the ligands studied, Taddol-based ligands of type 10 bearing bulky substituents in ortho-position to the phosphite performed best, with enantioselectivities of up to 85% ee and regioselectivities of ≥98:2. High-pressure NMR of the active catalyst [HRh(P-P)(CO)2] (P-P = 10h) revealed an equatorial-apical coordination of the ligand at rhodium. Temperature dependency of the coupling constants observed during the experiment indicates equilibrium between the two equatorial-apical isomers, with the isomer in which the phosphite occupies the equatorial position being the dominant species.
