Selenocyanation using a combined reagent of triphenylphosphine and selenocyanogen. A new and simple synthesis of alkyl selenocyanates and symmetrical alkyl diselenides from alcohols

A novel reagent Ph₃SeCN)₂, easily prepared by adding an equimolar amount of tri-phenylphosphine to selenocyanogen solution in methylene chloride and tetrahydrofuran reacts below ?60° with primary alcohols to produce directly the corresponding alkyl selenocyanates and alkyl diselenides in good yields. With secondary alcohols mixtures of selenocyanates and isoselenocyanates are obtained, while tertiary alcohols fail to react with the reagent.     

Solvent-Free Esterification of Carboxylic Acids and Alcohols in the Presence of Silphos [PCl3-n(SiO2)n] as a Heterogeneous Phosphine Reagent

An efficient solvent-free method for the preparation of esters from various aromatic and aliphatic acids with primary, secondary, and tertiary alcohols using a heterogeneous phosphine reagent, silphos [PCl_3-n(SiO₂)_n], in good yields is reported.     

An efficient one-pot synthesis of carbazates and dithiocarbazates through the corresponding alcohols using Mitsunobu��s reagent

A novel Mitsunobu-based protocol has been developed for the synthesis of carbazates and dithiocarbazates through the variety of corresponding primary, secondary and tertiary alcohols and various kinds of substituted hydrazines using Mitsunobu??s reagent and CO₂/CS₂ system, in good to excellent yields.     

Oxidation of alcohols by TBHP in the presence of sub-stoichiometric amounts of MnO2

Commercially available activated MnO₂ has been investigated as a catalyst for the oxidation of alcohols (phenylethanol, 4-methyl- and 4-methoxybenzyl alcohol, trans-cinnamyl alcohol, cyclohexanol, menthol, perillyl alcohol and myrtenol) by TBHP/decane or TBHP/water in MeCN. The activity is highest for benzylic and allylic alcohols. Secondary alcohols yield ketones with good selectivities, while the aldehydes generated from primary alcohols are further oxidized. The process competes with the TBHP catalyzed decomposition. It thus requires the use of excess TBHP and high catalyst loadings to achieve high conversions. However, the low cost of the reagents makes this new protocol convenient for the oxidation of reactive secondary alcohols. The study also suggests that MnO₂ should be proscribed as a reagent to quench excess TBHP in oxidative processes when the synthetic target contains easily oxidizable alcohol functions and when carrying our detailed kinetic monitoring of oxidation processes.     

Triphenylphosphine-free approach for one-pot N-alkylation of purine,pyrimidine, and azole derivatives with alcohols using P2O5/KI: A facile and selective route to access carboacyclic nucleosides

A facile, selective, and mild synthetic approach for one-pot N-alkylation of nucleobases and other related N-heterocycles via alcohols, using a mixture of P₂O₅ and KI is described. The reaction of structurally diverse purines, pyrimidines, and/or azoles with primary alcohols with the use of P₂O₅/KI and basic mixture of Et₃N/K₂CO₃ in refluxing DMF affords the corresponding N-alkyl derivatives (carboacyclic nucleosides) in good to reasonable yields. The influence of different parameters comprising solvent, base, temperature, and substrate/reagent ratios was assessed on the reaction progress. The secondary and tertiary alcohols were failed to react with nucleobases. The main advantageous of current protocol is formation of water soluble side products in which provides simple work-up and purification processes.     

3,4-dihydro-6,7-dimethoxy-4-methyl-3-oxoquinoxaline-2-carbonyl chloride as a sensitive fluorescence derivatization reagent for amines in liquid chromatography

A rapid and sensitive method for the fluorescence derivatization of primary and secondary amines is described, based on the reaction of the amines with 3,4-dihydro-6,7-dimethoxy-4-methyl- 3-oxoquinoxaline-2-carbonyl chloride. Cyclohexylamine, n-hexylamine and di-n-butylamine were used as model compounds to optimize the derivatization conditions. The reagent reacts with the amines in acetonitrile in the presence of potassium carbonate very rapidly to give the corresponding fluorescent amides, which can be separated on a reversed-phase column, TSKgel ODS-80TM, with aqueous acetonitrile as eluent. Alcohols and amino acids did not give any fluorescent products under the derivatization conditions. The detection limits are in the range 5–50 fmol per 20-μl injection. Reactions with other amines are also discussed.     

A novel B(C(6)F(5))(3)-catalyzed reduction of alcohols and cleavage of aryl and alkyl ethers with hydrosilanes

The primary alcohols 1a-e and ethers 4a-d were effectively reduced to the corresponding hydrocarbons 2 by HSiEt(3) in the presence of catalytic amounts of B(C(6)F(5))(3). To the best of our knowledge, this is the first example of catalytic use of Lewis acid in the reduction of alcohols and ethers with hydrosilanes. The secondary alkyl ethers 4j,k enabled cleavage and/or reduction under similar reaction conditions to produce either the silyl ethers 3m-n or the corresponding alcohol 5a upon subsequent deprotection with TBAF. It was found that the secondary alcohols 1g-i and tertiary alcohol 1j, as well as the tertiary alkyl ether 4l, did not react with HSiEt(3)/(B(C(6)F(5))(3) reducing reagent at all. The following relative reactivity order of substrates was found: primary > secondary > tertiary. A plausible mechanism for this nontraditional Lewis acid catalyzed reaction is proposed.     

12-Tungstophosphoric acid supported on inorganic oxides as heterogeneous and reusable catalysts for the selective preparation of alkoxymethyl ethers and their deprotections under different reaction conditions

A wide variety of primary and secondary alcohols were efficiently converted to their corresponding methoxymethyl (MOM) and ethoxymethyl (EOM) ethers in the presence of catalytic amounts of supported H₃PW₁₂O₄₀ on silica gel and zirconia at room temperature and under microwave irradiation at solvent-free conditions, whereas, phenols and tertiary alcohols remained intact under the same reaction conditions. Deprotection of these ethers to their parent alcohols was also achieved using these heterogeneous catalysts in ethanol, as a green solvent, under reflux conditions and microwave irradiation. Selective deprotection of primary and secondary MOM- and EOM-ethers in the presence of phenolic and tertiary ones, methyl and benzyl ethers, esters and trimethylsilyl ethers was achieved by these reagent systems. The present methodology offers several advantages such as short reaction times, high yields, simple procedure, heterogeneous reaction conditions, selectivity, non-toxicity and reusability of the catalysts.     

Efficient chemoselective alcohol oxidation using oxygen as oxidant. Superior performance of gold over palladium catalysts

Gold nanoparticles supported on nanocrystalline ceria (Au/CeO₂) is a general, air- and moisture-stable, commercial catalyst for the atmospheric pressure, solventless oxidation of aromatic, primary and secondary alcohols to the corresponding benzaldehyde or ketone compound. Aliphatic primary alcohols are oxidized to the corresponding alkyl ester and aliphatic secondary alcohols are oxidized to ketones. Conversions and product yields are in most of the cases excellent. The oxidizing reagent and the experimental conditions are almost ideal from the environmental point of view. Comparison with analogous ceria supported and hydroxyapatite-supported palladium catalysts, Au/CeO₂ clearly shows the superior performance of Au/CeO₂ in terms of higher chemoselectivity. In contrast to palladium catalysts that promote CC double isomerization, Au/CeO₂ oxidizes selectively allylic alcohols to conjugated ketones.     

Selective reagents in chemical ionization mass spectrometry: Tetramethylsilane with aliphatic alcohols

Mixtures of tetramethylsilane and helium have been found to form [M + 73]⁺ adducts, hydrated trimethylsilyl ions and alkyl ions with aliphatic alcohols. The adduct ions were found to be formed by displacement of water from the hydrated trimethylsilyl ion. Ratios of the abundances of the adduct ions to the hydrated trimethylsilyl ion can be used to differentiate among primary, secondary and tertiary alcohols. Sensitivities for a number of alcohols with the tetramethylsilane/helium chemical ionization reagent system are approximately equal.     

Site‐Selective Tertiary Alkyl–Fluorine Bond Formation from α‐Bromoamides Using a Copper/CsF Catalyst System

A copper‐catalyzed site‐selective fluorination of α‐bromoamides possessing multiple reaction sites, such as primary and secondary alkyl?Br bonds, using inexpensive CsF is reported. Tertiary alkyl?F bonds, which are very difficult to synthesize, can be formed by this fluorination reaction with the aid of an amide group. Control experiments revealed that in situ generated CuF₂ is a key fluorinating reagent that reacts with the tertiary alkyl radicals generated by the reaction between an α‐bromocarbonyl compound and a copper(I) salt.     

Highly efficient tetrahydropyranylation of alcohols and phenols catalyzed by a new and reusable high-valent vanadium(IV) porphyrin

In the present work, the catalytic activity of high-valent tetraphenylporphyrinatovanadium(IV) trifluoromethanesulfonate, [V^IV(TPP)(OTf)₂], in the tetrahydropyranylation of alcohols and phenols with 3,4-dihydro-2H-pyran (DHP) is reported. This new electron-deficient V(IV) compound was used as a highly efficient catalyst for pyranylation of primary (aliphatic and benzylic), sterically-hindered secondary and tertiary alcohols with DHP. Tetrahydropyranylation of phenols with DHP was also performed to afford the desired THP-ethers. The chemoselectivity of this method was also investigated. The results indicated that primary alcohols are more reactive in the presence of secondary and tertiary alcohols and phenols. This catalyst was reused several times without loss of its activity.     

Highly efficient and chemoselective trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) catalyzed by reusable electron-deficient [Ti(salophen)(OTf)2]

In the present work, highly efficient trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) catalyzed by high-valent [Ti^IV(salophen)(OTf)₂] is reported. Under these conditions, primary, secondary and tertiary alcohols as well as phenols were silylated in short reaction times and high yields. It is noteworthy that this method can be used for chemoselective silylation of primary alcohols in the presence of secondary and tertiary alcohols and phenols. The catalyst was reused several times without loss of its catalytic activity.     

Ruthenium-catalysed synthesis of tertiary amines from alcohols

Secondary amines have been converted into tertiary amines by reactions with primary alcohols. A catalytic system of [Ru(cymene)Cl₂]₂ with dppf has been shown to be effective for this transformation for a range of primary alcohols and secondary amines. The methodology has been applied to the one pot synthesis of Piribedil and other piperazine and morpholine-containing products.     

Selective tetrahydropyranylation of alcohols and phenols using titanium(IV) salophen trifluoromethanesulfonate as an efficient catalyst

Titanium(IV) salophen trifluoromethanesulfonate, [Ti^IV(salophen)(OSO₂CF₃)₂], as a catalyst enables selective tetrahydropyranylation of alcohols and phenols with 3,4‐dihydro‐2H‐pyran. Using this catalytic system, primary, secondary and tertiary alcohols, as well as phenols, were converted to their corresponding tetrahydropyranyl ethers in high yields and short reaction times at room temperature. Investigation of the chemoselectivity of this method showed discrimination between the activity of primary alcohols in the presence of secondary and tertiary alcohols and phenols. This heterogenized catalyst could be reused several times without loss of its catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

[Sn(TPP)(BF4)2]: An efficient and reusable catalyst for chemoselective trimethylsilylation of alcohols and phenols with hexamethyldisilazane

Tin(IV)tetraphenylporphyrinato tetrafluoroborate, [Sn^IV(TPP)(BF₄)₂], was used as an efficient catalyst for trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS). High-valent [Sn^IV(TPP)(BF₄)₂] catalyzes trimethylsilylation of primary, secondary and tertiary alcohols as well as phenols, and the corresponding TMS-ethers were obtained in high yields and short reaction times at room temperature. While, under the same reaction conditions [Sn^IV(TPP)Cl₂] is less efficient to catalyze these reactions. One important feature of this catalyst is its ability in the chemoselective silylation of primary alcohols in the presence of secondary and tertiary alcohols and phenols. The catalyst was reused several times without loss of its catalytic activity.     

Rapid,highly efficient and chemoselective trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) catalyzed by reusable electron‐deficient tin(IV)porphyrin

In this paper, rapid and highly efficient trimethylsilylation of alcohols and phenols with hexamethyldisilazane (HMDS) in the presence of catalytic amounts of high‐valent [Sn^IV(TPP)(OTf)₂] is reported. This catalytic system catalyzes trimethylsilylation of primary, secondary and tertiary alcohols as well as phenols, and the corresponding TMS‐ethers were obtained in high yields and short reaction times at room temperature. It is noteworthy that this method can be used for chemoselective silylation of primary alcohols in the presence of secondary and tertiary alcohols and phenols. The catalyst was reused several times without loss of its catalytic activity. Copyright © 2009 John Wiley & Sons, Ltd.     

Efficient and Selective Halogenation of Allylic and Benzylic Alcohols under Mild Conditions

Summary. A simple, mild, and high yielding procedure for the halogenation of allylic and benzylic alcohols using a combination of SOCl₂, benzotriazole, and potassium halides in DMF is described. The effectiveness of the protocol is manifested in its selectivity towards allylic and benzylic alcohols whereas other simple alcohols such as primary, secondary, and tertiary are found to be unreactive.     

Reaction of 2,7-dialkyl- and 1,2.7-trialkyldecahydro-4-quinolones with triethylaluminum

The reaction of triethylaluminum with stereoisomeric 2,7-dimethyl- and 1,2,7-trimethyldecahydro-4-quinolones and their 7-tert-butyl-substituted analogs was studied. The reaction of triethylaluminum with ketones that have an equatorial 2-CH₃ group proceeds in two directions — reduction of the carbonyl group to an alcohol group and alkylation to give tertiary 4-ethyl-substituted alcohols — in benzene. depending on the reagent ratio. The stereochemistry of the reduction of the carbonyl group depends on the temperature. Only an alkylation product is formed in tetrahydrofuran (THF) and diethyl ether. The reaction of triethylaluminum with ketones that have an axial 2-CH₃ group depends on the nature of the solvent. Epimeric secondary alcohols are formed in toluene at various ratios of the reacting substances, whereas tertiary ethyl-substituted alcohols are formed in THF and diethyl ether.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 946–952, July, 1976.     

NMR spectral studies—XII : Trichloroacetyl isocyanate as an in situ derivatizing reagent for C NMR spectroscopy of alcohols, phenols and amines

Trichloroacetyl isocyanate (TAI) has been found to be a useful in situ derivatizing reagent for the ¹³C NMR studies on alcohols, phenols and amines. The carbinol carbon of aliphatic alcohols shows downfield shifts the size of which permits distinction between primary, secondary and tertiary saturated alcohols. In allylic and propargylic alcohols the γ-carbon undergoes large downfield shifts while the β-carbon is shifted upfield. In the case of phenols, the OH-bearing carbon is shifted upfield, the o - and p-carbons are shifted downfield but m-carbons are virtually unaffected. Addition of TAI to amines and anilines produces various size shifts for the - and β-carbons. The use of TAI is thus a valuable aid in the assignment of the resonance signal of a carbon carrying an OH or NH-group as well as some neighboring carbons in ¹³C NMR spectra for structural and biosynthetic studies.