Investigations on the iron-catalyzed asymmetric sulfide oxidation

The development of an enantioselective sulfide oxidation involving a chiral iron catalyst and aqueous hydrogen peroxide as oxidant is described. In the presence of a simple carboxylic acid, or a carboxylate salt, the reaction affords sulfoxides with remarkable enantioselectivities (up to 96 % ee) in moderate to good yields. The influence of the structure of the additive on the reaction outcome is reported. In the sulfoxide-to-sulfone oxidation a kinetic resolution (with s = 4.8) occurs, which, however, plays only a negligible role in the overall enantioselective process. Furthermore, a positive nonlinear relationship between the ee of the product and that of the catalyst has been found. On the basis of these observations, a possible catalyst structure is proposed.     

Highly Chemoselective Aerobic Oxidation of Amino Alcohols into Amino Carbonyl Compounds

The direct oxidation of unprotected amino alcohols to their corresponding amino carbonyl compounds has often posed serious challenges in organic synthesis and has constrained chemists to adopting an indirect route, such as a protection/deprotection strategy, to attain their goal. Described herein is a highly chemoselective aerobic oxidation of unprotected amino alcohols to their amino carbonyl compounds in which 2‐azaadamantane N‐oxyl (AZADO)/copper catalysis is used. The catalytic system developed leads to the alcohol‐selective oxidation of various unprotected amino alcohols, carrying a primary, secondary, or tertiary amino group, in good to high yield at ambient temperature with exposure to air, thus offering flexibility in the synthesis of nitrogen‐containing compounds.     

Synthesis of functional derivatives of aryl trichlorovinyl (trichloroallyl) ketones via consecutive transformations of the carbonyl group

An efficient procedure have been developed for the selective reduction of the carbonyl group in phenyl trichlorovinyl ketone and aryl trichloroallyl ketones by the action of NaBH₄ in propan-2-ol to obtain the corresponding alcohols. The hydroxy group in the latter was converted into amino by the Ritter reaction. Treatment of the alcohols and amines with 5-phenylisoxazole-3-carbonyl chloride and 4,5-dichloroisothiazole-3-carbonyl chloride gave the corresponding esters and amides, and condensation of the amines with aromatic aldehydes afforded Schiff bases.     

The Mg-oppenauer oxidation as a mild method for the synthesis of aryl and metallocenyl ketones

Magnesium alkoxides undergo a hydride-transfer oxidation with benzaldehyde as the oxidant. This magnesium variant of the Oppenauer oxidation was used for the synthesis of polyfunctional biaryl ketones. LiCl was found to promote this reaction by enhancing the solubility of magnesium alkoxides. This mild oxidation method was especially useful for preparing ketones bearing a metallocenyl unit as well as various new ferrocenyl ketones and tricarbonylchromium complexes. This last class of ketones was reduced with the CBS catalyst (CBS=Corey-Bakshi-Shibata, diphenyl oxazaborolidine) to chiral benzhydrol complexes with high enantioselectivity enabling an asymmetric synthesis of electron-rich or -poor benzhydryl alcohols (up to 94 % ee).     

Synthesis of indol-3-yl aryl ketones through visible-light-mediated carbonylation

A visible-light-catalyzed synthesis of indol-3-yl aryl ketones from aryldiazonium salts, CO and indoles at room temperature was developed. This process provides a useful method for the preparation of diverse indol-3-yl aryl ketones from readily accessible reactants under base-free, acid-free and transition-metalfree conditions.     

An improved palladium(II)-catalyzed method for the synthesis of aryl ketones from aryl carboxylic acids and organonitriles

A palladium(II)-catalyzed decarboxylative protocol for the synthesis of aryl ketones has been developed. The addition of TFA was shown to improve the reaction yield and employing THF as solvent enabled the use of solid nitriles and in only a small excess. Using this method, five different benzoic acids reacted with a wide range of nitriles to produce 29 diverse (hetero)aryl ketone derivatives in up to 94% yield.     

Baeyer-Villiger oxidation of cyclic ketones over iron-containing mesoporous MCM-48 silica materials

Fe-MCM-48 mesoporous material was found to be a highly active catalyst for the Baeyer-Villiger oxidation of several cyclic ketones. The catalyst could be reused several times without any loss of activity.     

A green oxidation protocol for the conversion of secondary alcohols into ketones using heterogeneous nanocrystalline titanium (IV) oxide in polyethylene glycol

Abstract

The oxidation of secondary alcohols into corresponding ketones has been described using heterogeneous nanocrystalline TiO₂ as catalyst at a moderate temperature with quantitative yields. Use of H₂O₂ instead of O₂ (g) is the main feature of our methodology since maintenance of P_O2 (g) at elevated temperature is not easy. Besides, this catalyst could be recovered and reused for further reactions with consistent activity. Hence, our present protocol is economical and throughout clean consisting of green reagent, solvent, and catalyst.     

Development of an Iron(II)‐Catalyzed Aerobic Catechol Cleavage and Biomimetic Synthesis of Betanidin

An aerobic iron(II)‐catalyzed cleavage of catechols was developed. This reaction allows for the preparation of 2‐methoxy‐2 H‐pyrans that can be employed as versatile building blocks for synthesis. The utility of this biomimetic oxidative cleavage is featured in the synthesis of betanidin, a natural colorant with antioxidant properties.     

Ruthenium(II) carbonyl complexes with N-[di(alkyl/aryl)carbamothioyl]benzamide derivatives and triphenylphosphine as effective catalysts for oxidation of alcohols

Ruthenium(II) complexes, [RuCl(L)(CO)(PPh₃)₂] {where L?=?N-[di(alkyl/aryl)carbamothioyl]benzamide derivatives}, are prepared from reaction between [RuHCl(CO)(PPh₃)₃] and N-[di(alkyl/aryl)carbamothioyl]benzamide derivatives in toluene and characterized by elemental analysis and spectral data (electronic, infrared, ¹H NMR, and ³¹P NMR). The combination of [RuCl(L)(CO)(PPh₃)₂] (0.01?mmol) and N-methylmorpholine-N-oxide (NMO) (3?mmol) is an active catalyst for the oxidation of primary, secondary, cyclic, allylic, aliphatic, and benzylic alcohols to their corresponding aldehydes and ketones at room temperature. The oxidation protocol is simple to operate and gives the corresponding carbonyl compounds good to excellent yields.     

First Synthesis of Bis(di(indolyl)aryl)methanes From Bis(salicylaldehydes)

In this article, a simple method for the synthesis of bis(di(indolyl)aryl)methanes is described. The iodine‐catalyzed (5 mol %) reaction of indoles with various bis(salicylaldehyde) derivatives affords the bis(di(indolyl)aryl)methanes in excellent yields. The reaction works well under mild reaction condition with shorter reaction time.     

Synthesis of fluorescent hyperbranched poly(aryl ether ketones) containing biphenyl units

Hyperbranched poly(aryl ether ketones) with M _n = (8–10) × 10³ and terminal fluorine atoms have been synthesized through the polycondensation of 3,3′,5,5′-tetramethyl-4,4′-dihydroxydiphenyl(A₂) and 1,3,5-tris[4-(4-fluorobenzoyl)phenoxy]benzene (B₃) taken at a molar ratio of (0.720–0.675): 1. The replacement of the terminal fluorine atoms by residues of m-N,N-dimethylaminophenol yields polymers demonstrating green-blue fluorescence both in solution and in the solid state. Fluorescence quenching is observed at concentrations of the said polymers in solutions above 3 g/l.     

Synthesis of functionalized fluorine-containing hyperbranched poly(aryl ether ketones) for optical applications

Hyperbranched poly(aryl ether ketones) with terminal fluorine atoms (OH: F = 0.48: 1.00) or hydroxyl groups (OH: F = 2.02: 1.00) have been obtained through the polycondensation of bis(4,4′-dihydroxydiphenyl-2,2-hexafluoropropane) with 1,3,5-tris[4-(4-fluorobenzoyl)phenoxy]benzene in tetramethylene sulfone. Both polymers have M _n = (7.1?7.3) × 10³ and M _w = (8.4?8.8) × 10³ and are transparent in the near-IR region, in particular, at 1.30 and 1.55 μm.