Preparation and catalytic applications of partially fluorinated binaphthol ligands

New partially fluorinated binaphthols were obtained using a copper-catalyzed oxidative coupling. The corresponding enantiomerically pure compounds were prepared by fractional crystallization of the corresponding bis(menthyl)carbamates. Nucleophilic aromatic substitution using oxygen- and carbon-based nucleophiles resulted in functionalized derivatives without concomitant racemization. The titanium(IV) complexes of these ligands are catalytically active in the asymmetric oxidation of sulfides.     

Nitrite increases the enantioselectivity of sulfoxidation catalyzed by myoglobin derivatives in the presence of hydrogen peroxide

The effect of nitrite in the sulfoxidation of organic sulfides catalyzed by myoglobin (Mb) in the presence of hydrogen peroxide has been investigated. A general improvement in enantioselectivity was found for the reaction catalyzed by horse heart metMb and a series of sperm whale metMb derivatives including the wild type protein, the active site mutants T67K Mb, T67R Mb, T67R/S92D Mb, and the T67K Mb derivative reconstituted with the modified prosthetic group protohemin-l- histidine methyl ester.     

HbA/H2O2: an efficient biomimetic catalytic system for the oxidation of sulfides to sulfoxides

Human hemoglobin (HbA) catalyzed chemo-selective oxidation of sulfides to sulfoxides has been reported using hydrogen peroxide as an oxidant in a phosphate buffer. This biomimetic catalytic procedure was found to be simple, environmentally friendly, selective, and high yielding. Purified human oxyhemoglobin (HbA₀), crude human oxyhemoglobin, and ferryl oxyhemoglobin were used for sulfoxidation. HbA₀ and ferryl oxyhemoglobin (Fe⁺⁴O) efficiently catalyze the sulfoxidation reaction without over oxidation to the sulfone.     

Synthesis of a new estradiol-iron metalloporphyrin conjugate used to build up a new hybrid biocatalyst for selective oxidations by the ‘Trojan horse’ strategy

The synthesis of a new cationic iron metalloporphyrin-estradiol conjugate is reported. After a study of its association with the anti-estradiol antibody 7A3 by UV-visible spectroscopy, the influence of the antibody on the sulfoxidation of thioanisole by H₂O₂ catalyzed by the iron-metalloporphyrin has been investigated.     

An efficient solvent free catalytic oxidation of sulfides to sulfoxides with hydrogen peroxide catalyzed by a binaphthyl-bridged Schiff base titanium complex

A titanium binaphthyl-bridged Schiff base complex proved to be an efficient catalyst for the hydrogen peroxide oxidation of aromatic and aliphatic sulfides to the corresponding sulfoxides in satisfactory yields under solvent-free conditions.     

Catalytic asymmetric S-oxidation of N-benzoyl-1,5-benzothiazepines

An efficient catalytic asymmetric oxidation reaction of N-benzoyl-1,5-benzothiazepines using a chiral titanium complex formed in situ from Ti(O-iPr)₄, (R, R)-diethyl tartrate was developed. This reaction is helpful for the synthesis of the active form of (E, aS, 1S)-sulfoxide of N-benzoyl-1,5-benzothiazepines which should be recognized by vasopressin receptors. Furthermore, a prospective dynamic kinetic resolution utilizing this system was achieved.     

Oxomolybdenum(VI) complexes with glycine bisphenol [O,N,O,O′] ligand: synthesis and catalytic studies

The oxomolybdenum(VI) complex [MoOCl(L)] with a tetradentate glycine bisphenol ligand (H₃L) was prepared by reaction of [MoO₂Cl₂(DMSO)₂] with a ligand precursor in hot toluene. The product was isolated in moderate yield as separable cis and trans isomers along with the third minor component, [MoO₂(HL)]. The solid-state structure of trans-[MoOCl(L)] was determined by X-ray diffraction. The ligand has tetradentate coordination through three oxygens and one nitrogen, which is located trans to the terminal oxo whereas the sixth coordination site is occupied by a chloride. Both cis and trans isomers of [MoOCl(L)] are active catalysts for epoxidation of cis-cyclooctene and sulfoxidation of tolyl methyl sulfide. The cis isomer gave higher activity in epoxidation and sulfoxidation reactions at room temperature than the trans isomer but they performed identically at 50?°C.     

Bis-phosphine monoxide platinum(II) and palladium(II) cationic complexes as Lewis acid catalysts in Diels-Alder and sulfoxidation reactions

A series of bis-phosphine monoxide (BPMO) palladium(II) and platinum(II) cationic complexes of the type [M(BPMO-κ²-P,O)₂][X]₂ (M = Pd, Pt; BPMO = Ph₂P-(CH₂)_n-P(O)Ph₂ with n = 1 (dppmO), 2 (dppeO), 3 (dpppO); X = BF₄, TfO) were prepared from the corresponding chlorides [MCl₂(BPMO-κ¹-P)₂] upon treatment with 2 equiv. of AgX in wet acetone/CH₂Cl₂ or MeOH solutions. They were characterized by ¹H and ³¹P{¹H} NMR spectroscopies and, in the case of the complex [Pt(dppeO-κ²-P,O)₂][BF₄]₂, also by X-ray crystallography. These complexes were tested as catalysts in some Diels-Alder and oxidation reactions with different substrates. In the latter reaction Pt(II) complexes showed moderate activity, while for the former one, both classes of complexes were active in the C-C coupling, in particular the Pt(II) species showed interesting high endo/exo diasteroselectivity depending on the counteranion.     

Syntheses,crystal structures,and catalytic properties of dioxomolybdenum(VI) complexes with hydrazone ligands

Two new dioxomolybdenum(VI) complexes, [MoO₂L¹(CH₃OH)] (1) and [MoO₂L²(H₂O)] (2), where L¹ and L² are dianionic form of N′-(2-hydroxy-3-methoxybenzylidene)-4methoxybenzohydrazide and N′-(2-hydroxy-3methoxybenzylidene)-2-hydroxybenzohydrazide, respectively, have been synthesized and structurally characterized by spectroscopic methods and single-crystal X-ray determination. The complexes are mononuclear molybdenum(VI) compounds. Mo in each complex is octahedral. The difference in the substituent groups in the benzohydrazides leads to coordination of different solvent molecules. Crystals of the complexes are stabilized by hydrogen bonds. The complexes are effective catalysts for sulfoxidation.     

Non-covalent modification of the active site of cytochrome P450 for inverting the stereoselectivity of monooxygenation

The enantioselectivity in the sulfoxidation of thioanisole catalyzed by cytochrome P450_BSβ with a decoy molecule, a dummy molecule of the natural substrate, can be inverted by changing the structure of the decoy molecule. The methodology demonstrated herein shows the potential for controlling the stereoselectivity of biocatalysts without any mutagenesis.