62921-46-4Relevant academic research and scientific papers
Kinetic resolution of trans-2-acetoxycycloalkan-1-ols by lipase-catalysed enantiomerically selective acylation
Bodai, Viktoria,Orovecz, Oliver,Szakacs, Gyoergy,Novak, Lajos,Poppe, Laszlo
, p. 2605 - 2612 (2003)
Kinetic resolution of a series of racemic trans-cycloalkane-1,2-diol monoacetates rac-2a-d was performed by enantiomerically selective transesterification with vinyl acetate catalysed by commercial and our own-prepared fungal lipases to yield diacetates (
Regioselective lithiation of benzyl imidazole: Synthesis and evaluation of new organocatalysts for trans-diol functionalization.
El-Mansy, Mohamed,Ghosh, Ankan,Cheong, Paul Ha-Yeon,Carter, Rich
supporting information, p. 3131 - 3139 (2019/09/03)
Benzyl imidazole was successfully lithiated using n-BuLi at ?78 °C and verified by deuterium incorporation. The chemical reaction of the lithiated benzimidazole was explored with a series of different electrophiles. This approach was utilized to synthesiz
Chemoselective Oxidation of Equatorial Alcohols with N-Ligated λ3-Iodanes
Mikhael, Myriam,Adler, Sophia A.,Wengryniuk, Sarah E.
supporting information, p. 5889 - 5893 (2019/08/26)
The site-selective and chemoselective functionalization of alcohols in complex polyols remains a formidable synthetic challenge. Whereas significant advancements have been made in selective derivatization at the oxygen center, chemoselective oxidation to the corresponding carbonyls is less developed. In cyclic systems, whereas the selective oxidation of axial alcohols is well known, a complementary equatorial selective process has not yet been reported. Herein we report the utility of nitrogen-ligated (bis)cationic λ3-iodanes (N-HVIs) for alcohol oxidation and their unprecedented levels of selectivity for the oxidation of equatorial over axial alcohols. The conditions are mild, and the simple pyridine-ligated reagent (Py-HVI) is readily synthesized from commercial PhI(OAc)2 and can be either isolated or generated in situ. Conformational selectivity is demonstrated in both flexible 1,2-substituted cyclohexanols and rigid polyol scaffolds, providing chemists with a novel tool for chemoselective oxidation.
A highly efficient protocol for regioselective ring-opening of epoxides with alcohols, water, acetic acid, and acetic anhydride catalyzed by SbF3
Zeynizadeh, Behzad,Gilanizadeh, Masumeh,Aminzadeh, Farkhondeh Mohammad
, p. 1051 - 1056 (2016/07/06)
SbF3as an efficient catalyst has been used for regioselective alcoholysis, acetolysis and hydrolysis of epoxides to the corresponding β-alkoxy, β-acetoxy alcohols, and 1,2-diols in high to excellent yields. This study also represents a convenient synthesis of vic-diacetates from ring-opening of epoxides with acetic anhydride.
Uncovering Key Structural Features of an Enantioselective Peptide-Catalyzed Acylation Utilizing Advanced NMR Techniques
Procházková, Eli?ka,Kolmer, Andreas,Ilgen, Julian,Schwab, Mira,Kaltschnee, Lukas,Fredersdorf, Maic,Schmidts, Volker,Wende, Raffael C.,Schreiner, Peter R.,Thiele, Christina M.
, p. 15754 - 15759 (2016/12/16)
We report on a detailed NMR spectroscopic study of the catalyst-substrate interaction of a highly enantioselective oligopeptide catalyst that is used for the kinetic resolution of trans-cycloalkane-1,2-diols via monoacylation. The extraordinary selectivity has been rationalized by molecular dynamics as well as density functional theory (DFT) computations. Herein we describe the conformational analysis of the organocatalyst studied by a combination of nuclear Overhauser effect (NOE) and residual dipolar coupling (RDC)-based methods that resulted in an ensemble of four final conformers. To corroborate the proposed mechanism, we also investigated the catalyst in mixtures with both trans-cyclohexane-1,2-diol enantiomers separately, using advanced NMR methods such as T1relaxation time and diffusion-ordered spectroscopy (DOSY) measurements to probe molecular aggregation. We determined intramolecular distance changes within the catalyst after diol addition from quantitative NOE data. Finally, we developed a pure shift EASY ROESY experiment using PSYCHE homodecoupling to directly observe intermolecular NOE contacts between the trans-1,2-diol and the cyclohexyl moiety of the catalyst hidden by spectral overlap in conventional spectra. All experimental NMR data support the results proposed by earlier computations including the proposed key role of dispersion interaction.
A photoinduced cyclization cascade - Total synthesis of (-)-leuconoxine
Pfaffenbach, Magnus,Gaich, Tanja
, p. 6355 - 6357 (2015/04/22)
A protecting-group-free and enantioselective total synthesis of the monoterpenoid indole alkaloid (-)-leuconoxine was accomplished. The key step comprises a novel photoinduced domino macrocyclization/transannular cyclization involving the Witkop cyclization, for which additional mechanistic evidence is provided. This process furnishes a diaza[5.5.6.6]fenestrane skeleton, which is a hitherto unprecedented structure element.
Synthesis and characterization of a novel Fe3O4@SiO2/bipyridinium dichloride nanocomposite and its application as a magnetic and recyclable phase-transfer catalyst in the preparation of β-azidoalcohols, β-cyanohydrins, and
Kiasat, Ali Reza,Chadorian, Fatemeh,Saghanezhad, Seyyed Jafar
, p. 1297 - 1306 (2015/12/11)
β-Azidoalcohols, β-cyanohydrins, and β-acetoxy alcohols have been synthesized in the presence of a Fe3O4@SiO2/bipyridinium nanocomposite (Fe3O4@SiO2/BNC) as a novel magnetic and recyclable
Alcohol cross-coupling for the kinetic resolution of diols via oxidative esterification
Hofmann, Christine,Schümann, Jan M.,Schreiner, Peter R.
, p. 1972 - 1978 (2015/02/19)
We present an organocatalytic C-O-bond cross-coupling strategy to kinetically resolve racemic diols with aromatic and aliphatic alcohols, yielding enantioenriched esters. This one-pot protocol utilizes an oligopeptide multicatalyst, m-CPBA as the oxidant, and N,N-diisopropylcarbodiimide as the activating agent. Racemic acyclic diols as well as trans-cycloalkane-1,2-diols were kinetically resolved, achieving high selectivities and good yields for the products and recovered diols.
Functionality, Effectiveness, and Mechanistic Evaluation of a Multicatalyst-Promoted Reaction Sequence by Electrospray Ionization Mass Spectrometry
Alachraf, M. Wasim,Wende, Raffael C.,Schuler, S?ren M. M.,Schreiner, Peter R.,Schrader, Wolfgang
, p. 16203 - 16208 (2015/11/03)
A multicatalytic three-step reaction consisting of epoxidation, hydrolysis, and enantioselective monoacylation of cyclohexene was studied by using mass spectrometry (MS). The reaction sequence was carried out in a one-pot reaction using a multicatalyst. All reaction steps were thoroughly analyzed by electrospray ionization (ESI) MS (and MS/MS), as well as high-resolution MS for structure elucidation. These studies allow us to shed light on the individual mode of action of each catalytic moiety. Thus, we find that under the epoxidation conditions, the catalytically active N-methyl imidazole for the terminal acylation step is partially deactivated through oxidation. This observation helps to explain the lower efficiency of the catalyst in the last step compared to the monoacylation performed separately. All reactive intermediates and products of the reaction sequence, as well as of the side-reactions, were monitored, and we present a working mechanism of the reaction.
Highly enantioselective organocatalytic oxidative kinetic resolution of secondary alcohols using chiral alkoxyamines as precatalysts: Catalyst structure, active species, and substrate scope
Murakami, Keiichi,Sasano, Yusuke,Tomizawa, Masaki,Shibuya, Masatoshi,Kwon, Eunsang,Iwabuchi, Yoshiharu
supporting information, p. 17591 - 17600 (2015/02/19)
The development and characterization of enantioselective organocatalytic oxidative kinetic resolution (OKR) of racemic secondary alcohols using chiral alkoxyamines as precatalysts are described. A number of chiral alkoxyamines have been synthesized, and their structure-enantioselectivity correlation study in OKR has led us to identify a promising precatalyst, namely, 7-benzyl-3-n-butyl-4-oxa-5-azahomoadamantane, which affords various chiral aliphatic secondary alcohols (ee up to >99%, krel up to 296). In a mechanistic study, chlorine-containing oxoammonium species were identified as the active species generated in situ from the alkoxyamine precatalyst, and it was revealed that the chlorine atom is crucial for high reactivity and enantioselectivity. The present OKR is the first successful example applicable to various unactivated aliphatic secondary alcohols, including heterocyclic alcohols with high enantioselectivity, the synthetic application of which is demonstrated by the synthesis of a bioactive compound.
