A selective method for the preparation of aliphatic methyl esters in the presence of aromatic carboxylic acids

2,2-Dimethoxypropane, methanol and a catalytic amount of HCl selectively esterify aliphatic carboxylic acids, in the presence of aromatic carboxylic acids, at room temperature and in high yields.     

A new method for the determination of the absolute stereochemistry of aromatic and heteroaromatic alkanols using Mosher's esters

A list of the ¹H NMR chemical shifts of the methoxy group of α-methoxy-α-(trifluoromethyl)phenylacetic acid (Mosher's) esters of α- and β-(hetero)aromatic secondary alkanols has been compiled. Methoxy groups which are orientated syn to the (hetero)aromatic group in Mosher's conformational model have lower chemical shift values than those in the anti-orientation.     

Transformation of benzonitrile into benzyl alcohol and benzoate esters in supercritical alcohols

The reactions of benzonitrile in supercritical methanol, ethanol, and 2-propanol were investigated under non-catalytic conditions. In supercritical methanol, benzonitrile was converted to methyl benzoate in high yield. The esterification reaction also occurred in supercritical ethanol to afford ethyl benzoate in moderate yield. The esterification could occur via a route analogous to the Pinner reaction. On the other hand, benzonitrile in supercritical 2-propanol yielded no ester. Benzyl alcohol was the major product in supercritical 2-propanol. We investigated the reaction of the CN bond in supercritical 2-propanol. In supercritical 2-propanol, N-benzylideneaniline was transferred to the reduction product (N-benzylaniline) and hydrolysis products (benzyl alcohol and aniline). The hydrolysis reaction was restricted when the reaction was carried out in supercritical 2-propanol with a low water content. This indicates that the water in the 2-propanol acts as a reagent for the hydrolysis of the CN bond. These results suggested the following reaction process: C₆H₅CN→C₆H₅CHNH→C₆H₅CHO→C₆H₅CH₂OH.     

A practical method for preparation of 4-hydroxyquinolinone esters

4-Hydroxyquinolinone esters are a common motif for many medicinal agents. Several methods exist for preparation of these compounds, generally involving the use of sodium hydride, which raises significant safety issues and limits their application to large-scale synthesis. In this note a practical, safe, and general method that employs a combination of diisopropylethylamine and sodium tert-butoxide is described. This allows for the synthesis of 4-hydroxyquinolinone esters and amides in good yields.     

A new method for the preparation of diphenylmethyl esters by using tri-diphenylmethyl phosphate as alkylating agent

The diphenylmethyl group is introduced for the protection of the hydroxyl group of α-hydroxy acids.     

A new and efficient one-pot synthesis of aromatic alkynyl ketones from aromatic esters

The reaction of aromatic esters with alkynyllithiums in the presence of lithium morpholinide and BF₃·OEt₂ gave aromatic alkynyl ketones in good yield (78-87%).     

A new method for the trifluoromethylation of aromatic compounds

Trifluoromethyl groups attached to aromatic compounds are usually prepared by perchlorinating a methyl group and is subsequently perfluorinated by halogen exchange using a fluorinating agent. In addition to this method, which is also used in industry, there are also a number of different synthesis methods which are however only of limited importance owing to the costly reagents required. The disadvantage of the above-mentioned two-step synthesis lies in the restricted range of application since many of the substituents attached to the aromatic compound hinder the chlorination of the methyl group or they are themselves changed (e. g. methyl, bromine …).By means of a new one-step process, the trifluoromethylation of aromatic compounds is made possible by using the reagent HF/CCl₄.

RH, alkyl, aryl, halogen, phenoxyThe anhydrous hydrofluoric acid acts as a Friedel-Crafts-catalyst, solvent and fluorinating agent. The fange of application of the reaction is discussed. Apart from indicating the influence of the concentration of the reaction components, temperature and pressure, details are also given concerning catalysts and side reactions.     

A new method for the preparation of polyfluoroalkanedithiocarboxylates

A new method for synthesis of alkyl and aryl polyfluoroalkyldithiocarboxylates by reaction of 1,1-dichloropolyfluoroalkylsulfenylchlorides with mercaptans in the presence of ZnCl₂ was developed. The sulfenylchlorides are easily obtained by chlorination of benzyl 1,1-dihydropolyfluoroalkylsulfides or benzyl dithioacetals of polyfluoroaldehydes.     

A convenient method for the preparation ofN-unsubstituted hydrazones of aromatic ketones and aldehydes

A general and useful method for the synthesis ofN-unsubstituted hydrazones of aromatic ketones and aldehydes in good yields was elaborated. The use of a large excess of hydrazine hydrate and catalytic amounts ofp-toluenesulfonic acid makes it possible to prepare the hydrazones without an admixture of the corresponding azine. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2197–2199, November, 1999.     

A new method for preparation of dihydrodinaphthopyranopyrans

The syntheses of 7a,15a-dlhydro-15a-methylnaphtho[2,l-b] naphtho [1',2':5,6] pyrano[3,2-e]pyran (II) and 7a,15a-dihydro-7a-methyl-15a-isopropyi naphtho [2,1-b] naphtho [1' ,2' : 5,6] pyrano [3,2-e] pyran (III) from 2-naphthol and corresponding dimethylol ketones in one step were described. Amberlyst-15® was used as catalyst.