[Show abstract][Hide abstract] ABSTRACT: For the asymmetric hydrophosphonylation of aldehydes, an efficient organocatalytic approach with a diaminomethylenemalononitrile-based hydrogen-bonding donor catalyst is presented. The catalyst induces high yields and excellent enantioselectivities (up to 98% yield, 96% ee).
No preview · Article · Dec 2015 · Advanced Synthesis & Catalysis
[Show abstract][Hide abstract] ABSTRACT: We developed an aerobic photooxidative synthesis of peroxybenzoic acids from toluenes using anthraquinone-2-carboxylic acid (AQN-2-CO2H) as a photocatalyst. We also found a one-pot epoxidation reaction of alkenes using 4-tert-butylperoxybenzoic acid produced in situ by aerobic photooxidative synthesis.
No preview · Article · Dec 2015 · Tetrahedron Letters
[Show abstract][Hide abstract] ABSTRACT: A method for the determination of ergosterol, brassicasterol, and cholesterol has been developed by ultra performance liquid chromatography with ultraviolet detection (UPLC-UV). Using an ODS column and a mobile phase of acetonitrile-water (95:5, v/v), we found that the peak area was linearly related to the amount of sterols injected, ranging from 1.5 to 100 μmol/L (r ≥0.998), except for cholesterol (2.5 to 400 μmol/L). Repeated injection showed that the relative standard deviation (RSD) at 50 μmol/L of sterols was less than 7.1% (intra-day, n=6) and 13% (inter-day, n=3). Ergosterol and brassicasterol in rat serum spiked at four concentration levels (16, 25, 100, 250 μmol/L) was determined by the internal standard (IS) method using campesterol as an IS with the recovery of more than 88.8% and the RSD (n=5) of less than 12.5%.Practical applications: This method has been applied to determine the serum ergosterol and brassicasterol concentration in spontaneously hypertensive rats stroke-prone (SHRSP rats) fed a high-ergosterol diet containing 1% ergosterol. The results indicate that no apparent peak for ergosterol was observed, whereas the serum brassicasterol concentration was increased by the ergosterol-feeding. Brassicasterol was confirmed by electrospray ionization triple quadrupole tandem mass spectrometry after derivatization to picolinyl esters. In addition, brassicasterol-d 1 was detected after oral administration of ergosterol-d 1 to SHRSP rats by ion-trap time-of-flight mass spectrometry. Because SHRSP rats are known as an experimental animal model of phytosterolemia, it has been expected that ergosterol is absorbed and converted to brassicasterol. In summary, the current method provides an experimental tool to help understand ergosterol absorption and metabolism.
No preview · Article · Sep 2015 · European Journal of Lipid Science and Technology
[Show abstract][Hide abstract] ABSTRACT: Allylic alcohols reacted with Et2Zn and CH2I2 in the presence of a catalytic amount of fluorous disulfonamide 3a to afford the corresponding cyclopropylmethanols in 69%-quantitative yields with 49-85% ee. Recovery of the fluorous ligand 3a was readily performed from the reaction mixture by the fluorous solid-phase extraction (FSPE), and the recovered 3a could be reused without a significant loss of the catalytic activity and enantioselectivity.
[Show abstract][Hide abstract] ABSTRACT: This study reports a safe, mild, and environmentally benign synthetic method toward 2-aryl-4-quinazolinones from aromatic aldehydes and aminobenzamides through a cyclization–oxidation sequence using a catalytic amount of iodine, which serves as both a Lewis acid and an oxidant, harmless visible light irradiation, and molecular oxygen as the terminal oxidant.
[Show abstract][Hide abstract] ABSTRACT: We have developed a concise oxidative coupling of primary benzylamines to yield secondary aldimines catalyzed by methylene blue by using molecular oxygen as the oxidant in the presence of visible-light irradiation from fluorescent lamps.
[Show abstract][Hide abstract] ABSTRACT: Abstract A novel diaminomethyleneindenedione (DMI) organocatalyst efficiently promotes the asymmetric conjugate addition of a ketone to a maleimide to afford the corresponding addition product in a high yield with up to 99% enantiomeric excess.
[Show abstract][Hide abstract] ABSTRACT: We report an aerobic photooxidative direct asymmetric aldol reaction using water as the solvent. In this reaction, primary benzyl alcohols are oxidized into benzaldehydes under oxygen atmosphere using anthraquinone-2-sodium sulfonate monohydrate as an organophotocatalyst. A stereoselective aldol reactions are then proceeded by proline-type organocatalyst.
[Show abstract][Hide abstract] ABSTRACT: A convenient metal-free oxidation protocol of various cyclic acetals with molecular oxygen and anthraquinone-2-carboxylic acid under visible light irradiation by a fluorescent lamp afforded their corresponding hydroxyalkyl esters.
No preview · Article · Apr 2015 · Tetrahedron Letters
[Show abstract][Hide abstract] ABSTRACT: Pyrrolidine–diaminomethylenemalononitrile (pyrrolidine–DMM) organocatalyst has been an efficient reaction medium to promote asymmetric direct aldol reactions to afford the corresponding addition products in high yields with up to 99% ee under solvent-free conditions.
No preview · Article · Jan 2015 · Tetrahedron Letters
[Show abstract][Hide abstract] ABSTRACT: We have developed a metal-free synthetic method for 3-nitroimidazo[1,2-a]pyridines from nitroalkenes and 2-aminopyridines using catalytic amounts of iodine and aqueous hydrogen peroxide as a terminal oxidant.
[Show abstract][Hide abstract] ABSTRACT: The synthesis of beta-hydroxy sulfones from alkenes and sodium sulfinates under aerobic oxidative conditions was achieved in the presence of a catalytic amount of molecular iodine. Molecular oxygen in air serves as the terminal oxidant and the catalytic amount of molecular iodine acts as the sulfonyl radical initiator and peroxide reductant.
[Show abstract][Hide abstract] ABSTRACT: Perfluorobutanesulfonamide organocatalyst 4 efficiently promotes asymmetric conjugate additions of malonates to alpha,beta-unsaturated ketones to afford the corresponding adducts with excellent enantioselectivities (up to 99% ee).
[Show abstract][Hide abstract] ABSTRACT: We report a useful method for the synthesis of phenols from arylboronic acids with hydrogen peroxide generated in situ by aerobic photooxidation. This reaction uses visible-light irradiation and easily handled 2-chloroanthraquinone as an organocatalyst under mild conditions, that is, an air atmosphere and ambient pressure and temperature. Because of this method's metal- and base-free conditions, it represents an environmentally benign approach to the synthesis of phenols from arylboronic acids.
[Show abstract][Hide abstract] ABSTRACT: This Letter proposes a safe, mild, and environmentally benign method for the synthesis of benzimidazoles from aromatic aldehydes and diamines by aerobic photooxidation using irradiation with visible light, a catalytic amount of magnesium iodide, which serves as both a Lewis acid and an oxidant, and molecular oxygen as the terminal oxidant.
No preview · Article · Oct 2014 · Tetrahedron Letters
[Show abstract][Hide abstract] ABSTRACT: In this Letter, we report the aerobic photo-oxidative synthesis of diacylamines from benzylamides in the presence of molecular oxygen and catalytic amounts of 2-chloroanthraquinones under visible light irradiation from a fluorescent lamp.
No preview · Article · Sep 2014 · Tetrahedron Letters
[Show abstract][Hide abstract] ABSTRACT: A diaminomethylenemalononitrile organocatalyst with a cinchona motif efficiently promotes the enantioselective conjugate addition of acetylacetone to various nitroalkenes to yield the corresponding addition products in high to excellent yields with up to 89% ee.
No preview · Article · Aug 2014 · Tetrahedron Letters
[Show abstract][Hide abstract] ABSTRACT: The corresponding Michael-adducts are formed with high yields and enantioselectivities (up to 99% e.e.).The excellent performance of the catalyst is probably due to the ability of the perfluoroalkyl group to function as a preferable hydrophobic reaction field in water and its strong electron-withdrawing nature.
No preview · Article · Jul 2014 · Tetrahedron Asymmetry
[Show abstract][Hide abstract] ABSTRACT: The optically active diamine title catalyst efficiently promotes the conjugate addition of malonates to enones to give the corresponding addition products in good yields with excellent enantioselectivities.
No preview · Article · Jul 2014 · Tetrahedron Letters