CuCl catalyzed selective oxidation of primary alcohols to carboxylic acids with tert-butyl hydroperoxide at room temperature

Direct oxidation of primary alcohols to the corresponding carboxylic acids is performed highly efficiently at room temperature with anhydrous tert-butyl hydroperoxide in the presence of a catalytic amount of easily available CuCl under ligand free conditions in acetonitrile. Benzylic alcohols are more reactive than aliphatic alcohols, and these benzylic alcohols are selectively oxidized to the corresponding acids in the presence of aliphatic alcohols such as 1-octanol and 1-decanol.     

Glucosidation shifts of allylic and benzylic alcohols in 13C NMR spectroscopy

The ¹³C FT NMR spectra of β-D -glucopyranosides (including their tetraacetates) of several secondary allylic and benzylic alcohols were compared with those of methyl β-D -glucopyranoside and the corresponding parent alcohols. The characeristic glucosidation shifts observed for these alcohols may be applicable to the determination of the absolute configuration of the hydroxy group in these alcohols.     

New chiral amino alcohol ligands derived from 1-phenylethylamine for efficient Ru-catalyzed asymmetric transfer hydrogenation

A series of chiral amino alcohols have been prepared from cheap and readily available (S)-1-phenylethylamine through a one-step transformation. The ability of these newly developed amino alcohols as chiral ligands was evaluated in the Ru-catalyzed asymmetric transfer hydrogenation of aromatic alkyl ketones, providing chiral secondary alcohols with good to excellent conversions (71-100%) and moderate to good enantioselectivities (67-95% ee). The results also showed that the structure of these amino alcohols has a significant influence on the conversion and enantioselectivity.     

Mixed disproportionation versus radical trapping in titanocene(III)-promoted epoxide openings

The formation of either deoxygenation products or allylic alcohols from epoxides is observed when these substrates are treated with Cp₂TiCl under anhydrous conditions. It seems that processes via trisubstituted radicals give allylic alcohols whereas processes via disubstituted radicals may give deoxygenation products or allylic alcohols depending on the structure of the original epoxide. This method allows a controlled access to these functional groups, providing a useful tool in organic synthesis. A mechanistic discussion for these transformations is reported.     

Reaction of allylic and benzylic alcohols and esters with PPh3/I2: one-pot synthesis of β,γ-unsaturated compounds

The treatment of tertiary and secondary allylic alcohols containing a terminal double bond, and their acetyl derivatives, with triphenylphosphine and iodine under mild conditions leads regiospecifically and in high stereoselectivity to the corresponding primary allylic iodides, which can react ‘in situ’ with diverse nucleophiles. Primary allylic alcohols and benzyl alcohols and acetates are also transformed into the corresponding iodides under these conditions.     

Copper-catalyzed arylation of beta-amino alcohols

[reaction: see text] Methods for synthesizing N-aryl beta-amino alcohols and O-aryl beta-amino alcohols are described. The presence of a neighboring hydroxyl or amino group, respectively, is thought to activate beta-amino alcohols toward these transformations. These protocols significantly increase access to a variety of arylated beta-amino alcohols.     

Extension of the exp-6 model to the simulation of vapor-liquid equilibria of primary alcohols and their mixtures

Configurational-biased Gibbs ensemble Monte Carlo simulations were performed to obtain the phase behavior of the homologous series of primary alcohols from ethanol to 1-heptanol. Molecular interactions in these systems are modeled by a newly developed exp-6 potential in combination with a Coulombic intermolecular potential. Some of exp-6 potential parameters required to describe these alcohols were taken from the previous literature data reported for methanol and n-alkanes. The oxygen's potential parameters were optimized to fit the coexistence curve of these alcohols to the experimental data. Simulated values of saturated liquid and vapor densities, vapor pressures and critical constants of the alcohols are in good agreement with experimental data. The efficiency of the new model in the prediction of binary phase diagram of water/ethanol and n-hexane/1-propanol mixtures is also evaluated. The calculated mole fractions in the vapor and liquid phases of these binary mixtures also show satisfactory agreement with the experimental data.     

A facile and efficient [bmim]N3 catalyzed direct oxidative esterification of arylaldehydes with alcohols

Task-specific ionic liquid, [bmim]N₃ was used as an effective catalyst and reaction medium for the direct oxidative esterification of arylaldehydes with alcohols. The oxidative esterification reaction of a variety of arylaldehydes took place smoothly with some primary and secondary alcohols in [bmim]N₃. Satisfactory results were obtained with arylaldehydes containing electron withdrawing groups. Tertiary alcohols did not react under these conditions.     

On the adsorption of aliphatic alcohols on gold Part II

The adsorption of a wide selection of aliphatic alcohols on a polycrystalline gold electrode from 0.02 M NaF solution was studied using the tensammetric method. The thermodynamic data presented for the primary and secondary alcohols show close correlations between structure and Gibbs energy of adsorption. The standard Gibbs energy of adsorption increases with the chain length of primary alcohols by 3.5 kJ/mol for every additional C atom and by 2.7 kJ/mol in the case of secondary alcohols. The discussion of the data includes results presented previously and shows new aspects for the interpretation of the kinetic data of the anodic oxidation of these alcohols in alkaline solutions. This is supported by the tensammetric data obtained for some typical alcohols and the gold electrode in an electrolyte solution of 0.04 M KOH.     

Ice nucleation by monolayers of aliphatic alcohols

Monolayers of aliphatic long chain alcohols (C_nH_2n+1OH) were found to induce nucleation of ice at temperatures approaching O°C in contrast to water-soluble alcohols which are efficient antifreeze agents. The corresponding fatty acids and alcohols with bulky hydrophobic groups, induce ice nucleation at temperatures lower by as much as 12°C. The freezing point induced by the amphiphilic alcohols was found to be sensitive not only to area per molecule but also to chain length and parity, reaching higher temperatures for monolayers with n odd. Grazing incidence X-ray diffraction studies performed on some of these alcohols at the air/water interface (at 5°C and at zero pressure), demonstrated the formation of crystalline two-dimensional clusters with a distorted hexagonal cell whose dimensions resemble those of hexagonal ice. The catalysis of ice nucleation by these alcohol monolayers may be rationalized in terms of the structural match between the monolayer domains and the ab layer of hexagonal ice.     

Highly powerful and practical acylation of alcohols with acid anhydride catalyzed by Bi(OTf)(3).

Bi(OTf)(3)-catalyzed acylation of alcohols with acid anhydride was evaluated in comparison with other acylation methods. The Bi(OTf)(3)/acid anhydride protocol was so powerful that sterically demanding or tertiary alcohols could be acylated smoothly. Less reactive acylation reagents such as benzoic and pivalic anhydride are also activated by this catalysis. In these cases, a new technology was developed in order to overcome difficulty in separation of the acylated product from the remaining acylating reagent: methanolysis of the unreacted anhydride into easily separable methyl ester realized quite easy separation of the desired acylation product. The Bi(OTf)(3)/acid anhydride protocol was applicable to a wide spectrum of alcohols bearing various functionalities. Acid-labile THP- or TBS-protected alcohol, furfuryl alcohol, and geraniol could be acylated as well as base-labile alcohols. Even acylation of functionalized tertiary alcohols was effected at room temperature.     

Stereo- and regioselectivity in iodo diol formation from acyclic allylic alcohols

Reaction of electrophiles with a variety of acyclic allylic alcohols was investigated. Both aqueous iodine and acetylhypoiodite convert certain alkenols into iodo diols and acetoxy iodo alcohols, respectively, with regio- and stereoselectivities as high as 99%. Protection of the alcohol group lowers the selectivity only slightly. Structural factors that control the regioselectivity ofiodohydrin formation in these substrates have been delineated. Some of the iodo diols have been deiodinated, illustrating a simple two step procedure for converting allylic alcohols into threo-1,3-diols.     

Reactivity of β-amino alcohols against dialkyl oxalate: synthesis and mechanism study in the formation of substituted oxalamide and/or morpholine-2,3-dione derivatives

The reactivity of various β-amino alcohols with dialkyl oxalates, in several reaction conditions, has been investigated. Linear disubstituted oxalamides were obtained with primary β-amino alcohols and linear tetrasubstituted oxalamides, or a mixture of linear tetrasubstituted oxalamides and cyclic morpholine-2,3-diones were obtained with N-substituted β-amino alcohols. A DFT study of the possible mechanism has been made. The theoretical results indicate that these reactions are not kinetically controlled, there is an equilibrium between all species and therefore follow a thermodynamic control. The different behavior between the primary β-amino alcohols and N-methyl β-amino alcohols is due to the greater stability of linear disubstituted oxalamides with respect to linear tetrasubstituted oxalamides. The energy of tetrasubstituted oxalamides is closer to the energy of the corresponding morpholine-2,3-diones.     

Magtrieve™: a convenient catalyst for the oxidation of alcohols

We find that Magtrieve™ (CrO₂) catalyzes the oxidation of a wide variety of alcohols with periodic acid as the terminal oxidant. Mild conditions, short reaction times, and facile aqueous work-up make this a most attractive method. Olefins are not oxidized under these conditions; thus alcohols react selectively in the presence of alkenes. Conditions have been optimized with respect to catalyst loading, solvent, and co-oxidant; and the scope of the reaction includes primary and secondary benzylic, allylic, and aliphatic alcohols.     

Catalytic asymmetric generation of (Z)-disubstituted allylic alcohols

A one-pot method for the direct preparation of enantioenriched (Z)-disubstituted allylic alcohols is introduced. Hydroboration of 1-halo-1-alkynes with dicyclohexylborane, reaction with t-BuLi, and transmetalation with dialkylzinc reagents generate (Z)-disubstituted vinylzinc intermediates. In situ reaction of these reagents with aldehydes in the presence of a catalyst derived from (-)-MIB generates (Z)-disubstituted allylic alcohols. It was found that the resulting allylic alcohols were racemic, most likely due to a rapid addition reaction promoted by LiX (X = Br and Cl). To suppress the LiX-promoted reaction, a series of inhibitors were screened. It was found that 20-30 mol % tetraethylethylenediamine inhibited LiCl without inhibiting the chiral zinc-based Lewis acid. In this fashion, (Z)-disubstituted allylic alcohols were obtained with up to 98% ee. The asymmetric (Z)-vinylation could be coupled with tandem diastereoselective epoxidation reactions to provide epoxy alcohols and allylic epoxy alcohols with up to three contiguous stereogenic centers, enabling the rapid construction of complex building blocks with high levels of enantio- and diastereoselectivity.     

A mild and efficient method for the oxidation of benzylic alcohols by two-phase electrolysis

Electrochemical oxidation of benzylic and substituted benzylic alcohols by two-phase electrolysis yields the corresponding aldehydes as products. The reaction was carried out in a single compartment cell with platinum electrodes at room temperature in chloroform using an aqueous sodium bromide solution (25%) containing a catalytic amount of HBr. The two-phase electrolysis resulted in high yields (74-96%) of benzaldehyde from primary alcohols and secondary alcohols were oxidized to the corresponding ketone but only in low yields under these conditions.     

An Efficient and Highly Chemoselective Method to Desilylate Silyl Ethers

An efficient and highly chemoselective desilylating method is described. Trimethylsilyl ethers (0.25 M) in a CH₃OH/CCl₄ (1:1) solvent mixture are deprotected to their corresponding alcohols with ultrasound in a commercial ultrasonic cleaning bath. Selective deprotection of tert-butyldimethylsilyl ethers of benzyl alcohols and phenols is achieved under ultrasonic conditions. We deprotected also tert-butyldimethylsilyl ethers of primary alcohols, whereas tert-butyldimethylsilyl ethers of secondary and tertiary alcohols are stable under these conditions.     

Water-in-crude oil emulsions from the Norwegian continental shelf

A destabilization study of water-in-crude oil emulsions based on crude oils from the Norwegian Continental Shelf is reported. It is found that medium-chain alcohols (1-butanol and benzyl alcohol) and amines are speeding up the separation of water. The destabilization mechanisms in these two cases seem to be fundamentally different. The alcohols seem to modify the rigidity of the interfacial film by a diffusion/partitioning process while the amines show a strong and specific interaction with interfacial groups, hence hydrophilizing the whole film. Observed trends in the time-dependence of the interfacial tension upon addition of alcohols and amines support these suggestions to destabilization mechanisms. Data for a commercial demulsifier Dissolvan 4455 are also given.     

Combined epimerisation and acylation: Meerwein-Ponndorf-Verley-Oppenauer catalysts in action

A practical racemisation-epimerisation method for chiral secondary alcohols has been developed. Meerwein-Ponndorf-Verley-Oppenauer catalysts such as neodymium(III) isopropoxide are able to racemise these alcohols with retention of other stereocentres in the molecule. This is particularly useful for the recycling of the undesired products of kinetic resolutions of alcohols. By combination of such a racemisation with an acylation using isopropenyl or ethoxyvinyl esters as acyl donors, a fast straightforward recycling of starting materials may be achieved. The combined epimerisation and acylation process is demonstrated for the steroid estradiol methyl ether.     

Addition of organochromium reagents to heteroaryl aldehydes. Synthesis of heteroaryl substituted bis-allyl ethers and homoallyl ethers

Heteroaryl substituted allyl and homoallyl alcohols were synthesised with two different method. Synthesis of bis-allyl ethers and homoallyl ethers were carried out via reaction of allyl bromide with allyl alcohols and homoallyl alcohols, respectively. [2.3]-Wittig Rearrangement reactions of heteroaryl substituted bis-allyl ethers were investigated using GC/MS techniques. In these reactions two unexpected products were isolated in high yield.