Remote functionalisation by ferrous ion-cupric ion induced decomposition of alkyl hydroperoxides

By decomposition of alkyl hydroperoxides 1-8 with ferrous sulfate-cupric acetate reagent, intramolecular functionalisation of remote non-activated C atom takes place and unsaturated alcohols with double bond mainly at δ-position are obtained. The reaction proceeds involving the corresponding alkoxy radical 9 and δ-carbon radical 10 as intermediates. One-electron oxidative interception of δ-carbon radical by cupric acetate does not involve the corresponding carbonium ion; instead, the alkyl-copper intermediate 11 is formed and by elimination affords olefinic alcohols. The isotope effect for this elimination process was found to be k_h/k_d=6.1.     

The hydroxylation of alkanes and alkyl chains

A solution of 30% aqueous H₂O₂ in trifluoroacetic acid converts linear alkanes and cycloalkanes to an equilibrium mixture of secondary alcohols and their trifluoroacetates. There is no trace of further oxidation to ketones. Yields and conversions can be 70–90%, but are limited by elimination and epoxidation to form vicinal glycols. Linear alkyl chains are also hydroxylated in good yields with selectivity for introducing the alcohol group remote from electronegative substituents. The active reagent is trifluoroperoxyacetic acid, and it is effective in the presence of 4–10% water. When tertiary hydrogens are present, the oxidations are more complex.     

New procedure for synthesis alkyl esters of 5-acetyl-2-furan-carboxylic acid alkyl ester

The possibility to synthesize alkyl esters of 5-acetyl-2-furan-carboxylic acid by the reaction of 5-acetyl-2-furan with CCl₄ and aliphatic alcohols under the action of iron-containing catalysts was studied.

     

Repeller-Induced dissociation of alkyl alcohols in thermospray mass spectrometry

Six alkyl alcohols were studied using thermospray mass Spectrometry. Whereas the dominant ion in the spectrum up to a repeller potential of 120 V was [M + NH₄]⁺, above that potential [M + H]⁺ and fragment ions appeared. The fragments observed were largely due to hydrogen release from alkyl ions ([C_nH_2n+1]⁺ – H2 → [C_nH_2n-1]⁺) and loss of water or some other stable molecule from the same species. The results are compared with those from ionization of the same alcohols under electron impact and photoionization conditions and with results obtained for methanol under thermospray conditions.     

Gram scale,metal-free and selective aerobic oxidation of alcohol and alkyl benzenes using homogeneous recyclable TAIm[MnO4] oxidative ionic liquid under mild conditions: Microwave/ ultrasonic-assisted to carboxylic acid

A homogeneous catalyst-free system has been developed for the selective oxidation of alcohols and alkyl benzenes to the corresponding carbonyl compounds using a recyclable TAIm[MnO₄] oxidative ionic liquid. The reactions were performed in the presence of previously reported TAIm[MnO₄]/ TAIm[OH] ionic liquids and KMnO₄ at ambient temperature under solvent-free conditions. Benzyl alcohols were selectively transferred to benzaldehydes, while under ultrasonic or microwave irradiation, they oxidized to benzoic acid selectively and directly. Scalability of the process also studied at high scale. Also, the ionic liquid could be readily recycled from the aqueous mixture and reused for several consecutive times without any pre-treatment and loss of catalytic activity. In this work, the highly active and toxic KMnO₄ salt has been transformed into a mild recyclable oxidant reagent with high selectivity towards alcohol oxidation.     

Conversion of tertiary alcohols to tert-alkyl azides by way of quinone-mediated oxidation-reduction condensation using alkyl diphenylphosphinites

A novel method for the preparation of alkyl azides from alcohols by way of oxidation-reduction condensation is described. In this reaction, the sterically-hindered tert-alkyl phosphinites that are prepared from the corresponding alcohols are converted into tert-alkyl azides with almost complete inversion of their stereochemistry: the obtained alkyl azides are then successfully reduced to afford the corresponding amines on treatment with LiAlH₄, thus, a versatile method for the preparation of chiral amines from the corresponding chiral alcohols is established.     

Stereoselective cyclization of alkyl N-phthaloyl-4-bromoglutamates to cyclopropane derivatives

The kinetics of the reactions of alkyl N-phthaloyl-4-bromoglutamates with Et₃N and KOH was investigated. The reactions proceed stereospecifically to form alkyl 1-phthalimidocyclopropane-r-1,t-2-dicarboxylates. In alcohols, the reactions are accompanied by transesterification. The concerted mechanism accounting for the stereospecificity of these reactions is proposed.     

Percolation in alkyl polyglycoside microemulsions

Mixtures of oil, water, alkyl polyglycosides and long-chain alcohols form almost-temperature-invariant microemulsions. The phase behaviour depends on the content of cosurfactant, usually long-chain alcohols. We show that the system C_8/10G_1.5/octane/water/octanol exhibits cosurfactant-induced percolation phenomena. The percolation transition from an electrically conducting oil-in-water microemulsion to an electrically non-conducting water-in-oil microemulsion with increasing cosurfactant content is observed by measurements of electrical conductivity and time-resolved electric birefringence. The field-off relaxation time yields information on the internal length scale. The scaling behaviour of field-off relaxation times and Kerr constants with respect to the percolation point leads to insight into the influence of cosurfactant on phase behaviour. Received: 27 July 1999/Accepted: 8 February 2000     

Generation of alkyl hypochlorites in oxidation of alcohols with carbon tetrachloride catalyzed by vanadium and manganese compounds

Primary alcohols and diols with various structures were subjected to transformations into esters, aldehydes, ketones, and lactones under the action of carbon tetrachloride in the presence of manganese compounds (MnCl₂, MnO₂, Mn(OAc)₂, Mn(acac)₃) and vanadium compounds (VCl₅, V₂O₅, VO(acac)₂) as catalysts. These transformation proceeded with the involvement of alkyl hypochlorites, which were generated in the course of oxidation of alcohols with carbon tetrachloride catalyzed by manganese or vanadium compounds. The optimum molar ratios between the catalyst and reagents were determined, and the reaction conditions for the highly selective synthesis of esters, aldehydes, ketones, and lactones from alcohols were found.     

A new diphenylphosphinite ionic liquid (IL-OPPh2) as reagent and solvent for highly selective bromination, thiocyanation or isothiocyanation of alcohols and trimethylsilyl and tetrahydropyranyl ethers

A new diphenylphosphinite ionic liquid (IL-OPPh₂) is introduced. This ionic liquid is used as both a reagent and a solvent to convert alcohols and trimethylsilyl and tetrahydropyranyl (THP) ethers into their corresponding alkyl bromides, thiocyanates or isothiocyanates in the presence of Br₂ and SCN⁻ at 80 °C. In this ionic liquid, bromination and thiocyanation of alcohols occurs highly selectively in the presence of trimethylsilyl and THP-ethers and also between different classes of alcohols. The use of this ionic liquid allows easy separation of the desired products from the phosphinate by-product.     

Middle-phase microemulsions of green surfactant alkyl polyglucosides

Microemulsions are important organized molecular assembles in surfactant solutions and are used in various fields such as tertiary oil recovery, pharmaceutics, cosmetics, nanoparticle synthe-sis and chemical engineering. The more commonly used nonionic surfactants to produce micro- emulsions are the ethylene oxide-based compounds (CiEj). In recent years alkyl polyglucosides have been received considerable attention in producing microemulsions[17]. Alkyl polyglucosides (APG), which are widely…     

A new reagent for the efficient synthesis of disulfides from alkyl halides

Benzyltriethylammonium tetracosathioheptamolybdate [(C₆H₅CH₂N(Et)₃)₆Mo₇S₂₄] has been found to be a superior sulfur transfer reagent for the conversion of alkyl halides to the corresponding disulfides in excellent yields under very mild reaction conditions.     

Silicaphosphine (Silphos): a filterable reagent for the conversion of alcohols and thiols to alkyl bromides and iodides

Silicaphosphine (Silphos), [P(Cl)_3−n(SiO₂)_n], as a new heterogeneous reagent is introduced. This reagent converts alcohols and thiols to their corresponding bromides and iodides in the presence of X₂ (X=Br, I) in refluxing CH₃CN in high to quantitative yields. Use of Silphos provides a highly practical method for the easy separation of the Silphos oxide byproduct by a simple filtration.     

Enzymatic synthesis of alkyl α-2-deoxyglucosides by alkyl alcohol resistant α-glucosidase from Aspergillus niger

Aspergillus niger α-glucosidase (ANGase) was used for an efficient syntheses of alkyl α-d-2-deoxyglucosides (A2DGs) and for regioselectivity studies of alkoxy-hydro additions of d-glucal in the presence of alkyl alcohols. ANGase showed a high stability with respect to the high concentration of alkyl alcohols. The reaction conditions were optimized for pH, temperature, alkyl alcohol concentration, and d-glucal concentration. On the basis of MS and NMR analyses, A2DGs were confirmed to have only an α-2-deoxyglucosidic bond and the two-dimensional NMR (HMBC) spectra showed to be made up of 2-deoxyglucosyl and alkyl moieties.     

Gold-catalyzed substitution reaction with ortho-alkynylbenzoic acid alkyl ester as an efficient alkylating agent

ortho-Alkynylbenzoic acid alkyl esters behave as alkylating agents in combination with gold catalysts. The reaction with alcohols occurs smoothly in the presence of catalytic amounts of Ph₃PAuCl and AgOTf under mild conditions to produce the corresponding ether products in high yields. The protocol is also useful for Friedel-Crafts alkylation and N-alkylation of sulfonamides. The reaction likely proceeds through the gold-induced in situ construction of leaving groups and subsequent nucleophilic attack of nucleophiles, such as alcohols, aromatic compounds, and sulfonamides.     

Striking differences between alkyl sulfate and alkyl sulfonate when mixed with cationic surfactants

The properties of alkyl sulfate and alkyl sulfonate are similar except for their Krafft points. However, alkyl sulfate and alkyl sulfonate behave quite differently when they are mixed with cationic surfactants and show some totally unexpected results. In this work sodium alkyl sulfate (C_nH_2n+1SO₄Na,C_nSO₄)–alkyl quaternary ammonium bromide [C_nH_2n+1N(C_mH_2m+1)₃Br, C_nN, m=1–4] mixtures and sodium alkyl sulfonate (C_nH_2n+1SO₃Na, C_nSO₃)–C_nN mixtures were studied. It was found that, in contrast to the single surfactants, C_nSO₃–C_nN mixtures were much more soluble than C_nSO₄–C_nN mixtures. Besides, the two kinds of catanionic surfactant mixtures were quite different in their phase behavior and aggregate properties. The results were interpreted in terms of the interactions between surfactant molecules, which were very different in the two kinds of mixed systems owing to the distinction between alkyl sulfate and alkyl sulfonate in the molecular charge distribution.     

Role of the Polymer Backbone in the Oxidative Properties of Polymer-Supported Dichromate

Crosslinked co/poly(styrene-4-vinylpyridine)/ (1) was converted with hydrogen bromide or alkyl bromide to a pyridinium salt (2) which was further converted in water medium to various immobilized dichromates (3) with CrO₃. The insoluble reagent containing 0.6–1.0 mmol of dichromate on a gram of resin (depending on the structure of the polymer backbone) oxidized several secondary alcohols to ketones. The rate of conversion of alcohols to ketones depended on the structure of the polymer backbone, the structure of the alcohol, and the amount of water (5% or 20%) occluded in the reagent 3.     

Completely stereospecific 1,2-migration of alkyl groups in Et2AlCl promoted pinacol-type rearrangement

Completely stereospecific 1,2-migration of alkyl groups was achieved in Et₂AlCl promoted pinacol-type rearrangement of chiral β-mesyloxy alcohols to give optically pure α-alkyl ketones including both enantiomers of 4-methyl-3-hexanone, an alarm pheromone of ant.     

Direct Olefination of Alcohols with Sulfones by Using Heterogeneous Platinum Catalysts

Carbon‐supported Pt nanoparticles (Pt/C) were found to be effective heterogeneous catalysts for the direct Julia olefination of alcohols in the presence of sulfones and KOtBu under oxidant‐free conditions. Primary alcohols, including aryl, aliphatic, allyl, and heterocyclic alcohols, underwent olefination with dimethyl sulfone and aryl alkyl sulfones to give terminal and internal olefins, respectively. Secondary alcohols underwent methylenation with dimethyl sulfone. Under 2.5 bar H_2, the same reaction system was effective for the transformation of alcohol OH groups to alkyl groups. Structural and mechanistic studies of the terminal olefination system suggested that Pt⁰ sites on the Pt metal particles are responsible for the rate‐limiting dehydrogenation of alcohols and that KOtBu may deprotonate the sulfone reagent. The Pt/C catalyst was reusable after the olefination, and this method showed a higher turnover number (TON) and a wider substrate scope than previously reported methods, which demonstrates the high catalytic efficiency of the present method.     

Organoboron compounds,synthesis of allyl(dialkyl)boranes and diallyl(alkyl)boranes

Highly reactive allyl(dialkyl)-, crotyl(dialkyl)-, 3,3-dimethylallyl(dialkyl)-(= prenyl(dialkyl), and diallyl(alkyl)-boranes were prepared by allylation of esters R₂BOR′, RB(OR′)₂ or thioesters R₂BSR′ (R = alkyl) using allylic derivatives of aluminium, magnesium or boron in exchange reactions.The titled compounds are stable up to 100°C and do not symmetrize even on heating at 100°C for a long time. PMR spectroscopy data show that the characteristic feature of these compounds is a permanent allyl rearrangement, the rate of which increases with an increase in temperature. For allyl(diethyl)-borane at 100°C and 125°C the rates are equal to 2500 and 5000 sec^?1 respectively; activation energy of the rearrangement amounts to 11.8±0.2 kcal mol^?1.The boronallyl bonds in unsymmetrical allyl(alkyl)boranes readily split under the action of water and alcohols, protonolysis being accompanied by allyl rearrangement, crotyl and prenyl compounds are converted into 1-butene or 3-methyl-1-butene, respectively.