Ruthenium-catalyzed mild C-H oxyfunctionalization of cyclic steroidal ethers

Ruthenium-catalyzed site-specific C-H oxyfunctionalization of steroidal ethers with periodate or bromate as terminal oxidants in phosphate buffer provided the acid-sensitive C-16 hydroxy compounds in high yields. Phosphate buffer (pH 7.5) significantly inhibits formation of unwanted side products generated under more acidic reaction conditions. A key example is demonstrated at the 100 g scale.     

Hazard evaluation for oxidation of cyclic ethers

Ethers are widely used as a solvent for synthesis reactions, however, they are known as hazardous chemicals as they have low flash points and form peroxides under oxidative conditions. In this study, the oxidative reactivity of cyclic ethers was evaluated by thermal analysis. The accelerated test was performed in a pressure vessel under a high oxygen pressure (2 MPa), and DSC was used to detect the products of the reaction. Tetrahydrofuran (THF) and 1,3-dioxolane were used as a sample. The result of the DSC measurement of THF without any antioxidant showed that the DSC curve depended on the exposure time. It was found that this method can be used for the oxidation evaluation. The DSC measurement was also used for the detection of ether peroxides, and this method was faster and simpler than the potassium iodine titration.     

An unexpected oxidation of unactivated methylene C-H using DIB/TBHP protocol

An in situ generated hypervalent iodine species, bis(tert-butylperoxy)iodobenzene, was used as a peroxy radical source for the oxidation of unreactive, remote, and isolated alkyl (cyclic or aliphatic) esters and amides to the corresponding keto compounds under very mild conditions.     

New efficient catalysts for the aerobic oxidation of ethers

Some nickel, copper, and silver salts or complexes are efficient catalysts for the oxidation of benzylic ethers with oxygen in 1,2-dimethoxyethane. Salts of the weakly coordinating anion trifluoroacetate are particularly efficient, approaching (and, in some cases, improving) the yields obtained with cobalt(II) chloride, the best catalyst so far reported.     

An efficient and sustainable protocol for oxidation of alcohols to carbonyl compounds

A simple and extremely efficient protocol is developed for oxidation of alcohols to carbonyl compounds at room temperature by using green solvent lactic acid and green oxidant H₂O₂. This protocol provides high conversion under catalyst free conditions. The easy work up procedure allows high selectivity and good to excellent yields of carbonyl compounds with purity. We have performed wide range of substrates in present study with primary focus on reusability of lactic acid.     

An efficient protocol for synthesizing dibenzodithiapentalenes

Two new scalable methods for the synthesis of dibenzo[bc,fg]dithiapentalene (2) (DPP) are reported starting from either 1-bromo-3-fluoro-2-iodobenzene over four steps in 57% yield or from THP-protected 3-fluorothiophenol over three steps in 43% yield. Attempts to prepare dibenzodioxapentalene (15) using similar conditions were unsuccessful. Instead, we observed the formation of a macrocyclic dimeric product 16. Fluorine-hydrogen bond interactions were observed by NMR in the F/SH- and F/OH-substituted dibenzothiophene and dibenzofuran intermediates.     

An efficient method for demethylation of aryl methyl ethers

A new efficient method for demethylation of aryl methyl ethers using iodocyclohexane in DMF under reflux condition is described.     

An efficient protocol for the preparation of MOM ethers and their deprotection using zirconium(IV) chloride

An efficient protocol for the preparation of MOM ethers from alcohols and formaldehyde dimethyl acetal (DMFA) using ZrCl₄ (10 mol %) at room temperature under solvent free conditions has been developed. Similarly, the same Lewis acid, ZrCl₄ (50 mol %), in isopropanol at reflux was utilised for the deprotection of MOM ethers.     

A one-pot tandem oxidation-reduction protocol for the synthesis of cyclic ethers from their diols

A novel and an efficient one-pot cyclization method for the preparation of cyclic ethers from their diols via a tandem oxidation-reduction protocol using a cocktail of MnO₂/Et₃SiH/CF₃COOH is reported.     

A convenient protocol for C-H oxidation mediated by an azido radical culminating in Ritter-type amidation

Cerium(IV) ammonium nitrate in combination with sodium azide reacts with unactivated hydrocarbons in acetonitrile to furnish acetamides in one pot. The strategy can be used to introduce nitrogen functionality into a variety of compounds; a carboxylic ester directly afforded the corresponding α-amino acid.     

An efficient protocol for solid phase aminothiazole synthesis

An efficient synthesis of 2,4-diamino-5-ketothiazoles under solid phase conditions has been achieved by the reaction of polymer supported amidinothioureas with α-haloketones. This novel synthetic approach involving traceless cleavage from the support is suited for automation, and allows solid phase combinatorial synthesis of 2,4-diamino-5-ketothiazoles in good yields and purities.     

An efficient catalytic protocol for the Pauson-Khand reaction

New experimental conditions have been developed for an efficient catalytic Pauson-Khand reaction. These are based on the use of a mixture of molecular sieves and tert-butanol as inducers of the process. This mixture, with the appearance of a paste, is able to adsorb CO, thus improving the conversion and making it possible to effect the reactions in the absence of a CO atmosphere. The protocol is applied to known and unknown substrates and compared to previously described conditions, showing good results with intra- and intermolecular examples.     

A highly efficient catalyst-free protocol for C-H bond activation: sulfamidation of alkyl aromatics and aldehydes

A catalyst-free protocol has been developed for amidation of alkyl aromatics and aldehydes using TsNBr(2)via a nitrene transfer process in the presence of a base in excellent yield within a short time. The reaction was found to be selective for secondary and tertiary benzylic C-H bonds and C-H bonds of aldehydic groups.     

An efficient protocol for the solid-phase synthesis of malondiamides

A novel and straightforward solid-phase synthesis of malondiamides containing a free nitrogen has been developed. These intermediates, which can be directly obtained in good yield and purity, can be further derivatised. This approach can be used for the synthesis of large split-and-mix-libraries.     

A mild and efficient amidation of cyclic ethers catalyzed by rhodium caprylate

A small quantity of Rh₂(O₂CC₇H₁₅)₄ (2.5 mol % to 0.6 mol %) catalyzed the α-amidation of cyclic ethers under mild conditions, 35 °C, in the presence of electron-withdrawing p-chlorobenzenesulfonamide/PhI(OAc)₂ as the nitrene source, in CH₂Cl₂ for 4 h. The corresponding N-substituted amino cyclic ethers were successfully obtained in good yields (up to 87% based on 99% conversion) and compatibility with other oxidant sensitive structures in one-pot reaction.     

A mild and efficient protocol for oxidation of thiols to disulfides in water

A novel vanadium polyoxometalate [(C₇H₇)(CH₃)₃N]₃[H₃V₁₀O₂₈].3H₂O works as a useful oxidant for the oxidation of thiols to disulfldes in water under mild reaction conditions in an excellent yield. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 23:231–234, 2012; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20760     

An efficient three-component protocol for the synthesis of novel spiro-oxazinobarbiturates

Some novel spiro-oxazinobarbiturate derivatives have been successfully synthesized in a one-pot, three-component cascade reaction from various azines (pyridine, isoquinoline, quinoline and phenanthridine), 1,3-dimethylalloxan, and several activated acetylenes (alkyl propiolates, dialkyl acetylenedicarboxylates, and butyne-2-one). The high bond forming efficiency (formation of new C-N, C-C, and C-O bonds) of this reaction makes it attractive for the synthesis of spiro-oxazinobarbiturates in a single operation.