Hydrogen bond formation between aliphatic alcohols and tertiary amines

Hydrogen bond formation between tertiary amines and long chain and branched chain alcohols has been studied in order to understand the influence of chain length and the steric effect on the complex formation between tertiary amines and alcohols. On the addition of the amine to the alcohol the intensity of the monomeric OH band decreases and the new band appears corresponding to the alcohol—amine complex. The equilibrium constants of the complex formation are correlated by a two parameter equation. The three correlation equations obtained for three tertiary amines are: log K = 3.41 + 10.01σ* + 0.02χ (for triethylamine-alcohol) log K = 0.97 + 2.54σ* + 0.21χ (for tributylamine-alcohol) log K = 1.01 + 1.81σ* + 0.26χ (for trioctylamine-alcohol), where σ* is Taft's polar constant and χ the molecular connectivity index of the R skeleton of the alcohol.     

Recent studies of internal hydrogen bonding of alcohols,amines and thiols

Some selected results of recent studies of alcohols, amines and thiols are reviewed and discussed.     

Manganese-mediated acetylation of alcohols,phenols, thiols,and amines utilizing acetic anhydride

Manganese(II) chloride-catalyzed acetylation of alcohols, phenols thiols and amines with acetic anhydride is reported. This method is environment-friendly and economically viable as it involves inexpensive, relatively benign catalyst, mild reaction condition, and simple workup. Acetylation is performed under the solvent-free condition at ambient temperature and acetylated products obtained in good to excellent yields. Primary, secondary heterocyclic amines, and phenols with various functional groups are smoothly acetylated in good yields. This method exhibits exquisite chemoselectivity, the amino group is preferentially acetylated in the presence of a hydroxyl/thiol group.     

Vanadium 8-hydroxyquinolate as a reagent for the detection of alcohols,thiols and amines

The 8-hydroxyquinolate of pentavalent vanadium (“vanadium 8-hydroxyquinolate”, (C₉H₆ON)₂. VO.OH) dissolves in a number of chlorohydrocarbons to give deep blue-black solutions. These solutions undergo distinctive colour changes upon addition of acids (blue), alcohols (red via purple), thiols (yellow via green) and amines (yellow via green), provided that these reagents are soluble in the chlorohydrocarbon. These sensitive and specific qualitative tests are extended to the semiquantitative determination of alcohols. For comparable compounds the rate of reaction with vanadium 8-hydroxyquinolate is as follows: [—NH₂, NH,  N] > [—CH₂OH,—CH₂SH] > [CHOH, CHSH] > [COH,  CSH].     

Fluoroboric acid adsorbed on silica gel as a new and efficient catalyst for acylation of phenols, thiols, alcohols, and amines

Fluoroboric acid supported on silica gel efficiently catalyzes acylation of structurally diverse phenols, alcohols, thiols, and amines under solvent free conditions. Acid-sensitive alcohols are smoothly acylated without competitive side reactions.     

Ruthenium(III) chloride catalyzed acylation of alcohols, phenols, thiols, and amines

Ruthenium(III) chloride catalyzes the acylation of a variety of phenols, alcohols, thiols, and amines under mild conditions. Some of the major advantages of this method are high yields, short reaction times, ease of operation, and compatibility with other protecting groups.     

Deallyloxy- and debenzyloxycarbonylation of protected alcohols, amines and thiols via a naphthalene-catalysed lithiation reaction

The naphthalene-catalysed lithiation of Alloc- and Cbz-protected alcohols, amines and thiols in THF at 0 °C led, after quenching with methanol, to the recovery of the free alcohols, amines and thiols in short reaction times and with very good yields. The selectivity for the removal of the Alloc- or the Cbz- group in a polyfunctionalised substrate has been studied. The selective reductive cleavage of a benzylic carbon-oxygen bond was achieved in the presence of an allylic carbon-oxygen or carbon-nitrogen bond. This method represents a great improvement in comparison with the previously reported deprotection procedures by dissolving metals, since it avoids the use of the toxic liquid ammonia and, therefore, the need to perform the reaction at low temperatures.     

Organocatalytic enantioselective acyl transfer onto racemic as well as meso alcohols, amines, and thiols

Acyl transfer is at the heart of functional-group transfers utilized both in nature and in the chemical laboratory. Acylations are part of the natural assembly machinery for the generation of complex molecules and for energy transport in biological systems. The recognition of covalent acyl-enzyme intermediates led to both mechanistic studies as well as the development of biomimetic approaches. Consequently, chemists first used the tools of nature in the form of enzymes and naturally occurring alkaloids as catalysts, before eventually developing a large variety of synthetic small molecules for selective acyl transfer. In contrast to nature, chemists utilize acylation reactions as a practical way for stereoselection and functional-group protection. Indeed, the number of studies concerning acyl transfer has significantly increased over the last 15 years. This Review examines and highlights these recent developments with the focus as given in the title.     

Transition-metal-free O-, S-, and N-arylation of alcohols, thiols, amides, amines, and related heterocycles

A new protocol for the Ullmann-type arylation process of different aromatic heterocycles without any transition-metal catalyst, implying the use of a combination of an excess of potassium hydroxide and dimethyl sulfoxide, is described. The reaction can be performed between a broad range of starting nucleophiles including phenol, alcohols, amines, nitrogen-containing five-membered systems such as pyrazoles, imidazoles, and indoles, and amides with haloarenes, iodide and bromide derivatives giving the best results, the possible pathway involving the in situ generation of the corresponding benzyne intermediate. When the reaction was performed with 2-iodoaniline and either carboxamides or isothiocyanato derivatives, the corresponding benzoazole derivatives were obtained.     

Perchloric acid adsorbed on silica gel as a new,highly efficient,and versatile catalyst for acetylation of phenols,thiols, alcohols,and amines

Perchloric acid adsorbed on silica gel efficiently catalyses acetylation of structurally diverse phenols, alcohols, thiols, and amines under solvent free conditions.     

Efficient and regioselective ring-opening of arylaziridines with alcohols,thiols, amines and N-heteroaromatic compounds using sulphated zirconia

Sulphated zirconia is an efficient catalyst for the regioselective ring-opening of aryl-substituted aziridines. This heterogeneous catalyst can be used several times without loss of activity and is compatible with a variety of acid sensitive and slightly basic nucleophiles.     

A one-pot synthesis of alkyl acylcarbamodithioates from acid chlorides, thiols, and ammonium thiocyanate

Abstract  

An efficient synthesis of alkyl acylcarbamodithioates by reaction of acid chlorides with ammonium thiocyanate in the presence of thiols is described. The unusually large values of ⁵ J _FH = 12–15 Hz, observed for alkyl (2-fluorobenzoyl)carbamodithioates provide information about Ar–C–N–H torsion in these compounds.     

Mild and efficient methods for the conversion of benzylic bromides to benzylic thiols

Very mild and efficient methods are established for the conversion of the benzylic bromides at room temperature to their corresponding benzylic thiols with high yields (94-99%) in 1 h under N₂.     

Mild and general methods for the palladium-catalyzed cyanation of aryl and heteroaryl chlorides

[reaction: see text] New methods for the palladium-catalyzed cyanation of aryl and heteroaryl chlorides have been developed, featuring sterically demanding, electron-rich phosphines. Highly challenging electron-rich aryl chlorides, in addition to electron-neutral and electron-deficient substrates, as well as nitrogen- and sulfur-containing heteroaryl chlorides can all undergo efficient cyanation under relatively mild conditions using readily available materials. In terms of substrate scope and temperature, these methods compare very favorably with the state-of-the-art cyanations of aryl chlorides.     

Synthesis of phosphonomethylated acid chlorides,alcohols, and aldehydes of the furan series

Diethoxyphosphorylmethyl derivatives of furancarboxylic acids react with thionyl chloride in the presence of DMF to form the corresponding acid chlorides. Compounds synthesized were reduced with sodium borohydride in the DMF-dioxane medium to give hydroxymethyl compounds. Obtained phosphorylated alcohols were oxidized to aldehydes by chromium trioxide-pyridine complex in methylene chloride. The diethoxyphosphorylmethyl group remains untouched in all these transformations. A series of phosphorylated acid chlorides, alcohols, and aldehydes including all six versions of mutual location of phosphorus-containing substituent and another functional group in the furan ring was synthesized. It is established that 2,3- and 3,2-(diethoxyphosphorylmethyl)(chlorocarbonyl)furans in the course of vacuum distillation undergo cyclization to 4,5(2,3-furo)- and 4,5(3,2-furo)-1,2-oxaphosphorines.     

Saccharin sulfonic acid catalyzed N-Boc protection of amines and formation of tert-butyl ethers from alcohols

Saccharin sulfonic acid (SaSA), as a stable reagent is easily prepared by the reaction of saccharin with neat chlorosulfonic acid at room temperature. This compound is able to catalyze conversion of amines to their corresponding N-Boc protected amines with (Boc)₂O. Alcohols were also converted to their corresponding tert-butyl ethers. All reactions took place under mild conditions giving the desired products in good to high yields.     

Rice husk: Introduction of a green,cheap and reusable catalyst for the protection of alcohols,phenols, amines and thiols

A mild, efficient and eco-friendly protocol for the chemoselective protection of benzylic and primary and less hindered secondary aliphatic alcohols and phenols as trimethylsilyl ethers and different types of amines as N-tert-butylcarbamates is developed using rice husk (RiH) as the catalyst. This reagent is also able to catalyze the acetylation of alcohols, phenols, thiols and amines with acetic anhydride. Easy work-up, relatively short reaction times, excellent yields and low cost, availability and reusability of the catalyst are the striking features of this methodology, which can be considered to be one of the best and general methods for the protection of alcohols, phenols, thiols and amines. In addition, the use of a green reagent in the above-mentioned reactions results in a reduction of environmental pollution and of the cost of the applied methods.     

Amidation and esterification of carboxylic acids with amines and phenols by N,N′-diisopropylcarbodiimide: A new approach for amide and ester bond formation in water

The present study reports the successful synthesis of two important and abundant functional groups "ester and amide" by N,N′-diisopropylcarbodiimide (DIC) in water as a green solvent. A wide range of substrates could be employed with high functional group tolerance. The products were obtained in high yields after short reaction times. This method provides an efficient, economic, simple and very mild protocol for ester and amide bond formation in aqueous media. In addition, this work not only may lead to environmentally benign systems but also will provide a new aspect of organic chemistry in water.     

Mild and tunable benzoic acid catalysts for rearrangement reactions of allylic alcohols

An efficient and simple catalytic method for the isomerization of readily prepared allylic alcohols is described. We focus particularly on cyclic examples and the synthesis of unusual enyne and dienols. The benzoic acid catalysts employed are commercially available and very inexpensive and can be tuned for reactivity and substrate sensitivity.