Methanolic sulphuric acid

Work by Ono et al. [66] has been specifically directed at ultrasonic control of product-selectivity in electroreductions. Using a lead cathode, in dilute methanolic sulphuric acid, at a constant current of 20 mA cm , Ono electroreduced benzaldehyde under stirred, unstirred and ultrasonic conditions (Fig. 6.17). In an unstirred system, benzyl alcohol (two-electron process) was the major product, while mechanical stirring reversed the position in favour of the hydrodimer (one-electron product). Ultrasonic irradiation from a cleaning bath (100 W, 36 kHz) so strongly favoured the hydrodimer that the alcohol was barely evident (Tab. 6.16). 

Vanillin and 4-dimethylaminobenzaldehyde (DMABA) react with hydroxyl groups in the Ko-marowsky reaction. These postcolumn reagents, prepared in methanolic sulphuric acid, react with the carboxylic acid PETs at elevated temperatures. The PETs decompose in a poorly understood reaction, to form colored products detected at ca. 520 nm. Typically, the extraction step consists of either LLE or SPE (98). 

The diol (86) cyclises in the presence of acid and molecular sieve to give products the nature of which are dependent upon the nature of the acid. In methanolic sulphuric acid the mixed acetal (87) is produced, but with TFA a mixture of the bisdioxepane (88) and the novel... 

In the case of selective extraction of compounds from steam distillate after pH adjustment, about 1.5 L distillate were collected by co-distilling 200 g of powdered nuts with 2.5 L of water. The basic, neutral and acidic compounds were extracted using either methylene chloride or ether and the solvent was removed by distillation. In the case of the acidic fraction, the ether extract was methylated by refluxing with methanol-sulphuric acid (50 1) reagent for 2 hours. The methylated samples were washed free of acid and extracted with redistilled hexane, dried and stored frozen. 

Many reactions of ketones were performed with methanolic DIB in either an acidic or alkaline environment. When DIB is dissolved in methanol (or other alcohols) an exchange with acetate takes place, so that the reacting species may be PhI(OMe)OAc or PhI(OMe)2 the latter is actually an isolable compound [12]. Oxidation of methanol at room temperature is negligible. Acetophenones react with DIB in methanol-sulphuric acid affording mixtures of a-methoxyacetophenones (minor products) and rearranged esters. A solvent change from methanol to... 

Analysis of the CLA content and profile of animal tissues or biological fluids containing a mixture of lipid classes is more difficult. In order for all of the fatty acids to be methylated, a two-stage methylation procedure is recommended. Kramer et al. (1997) evaluated many different combinations of acid/base catalysts and concluded that the best compromise was the use of sodium methoxide followed by a mild acidic methylation, which resulted in the methylation of the majority of the fatty acids with minimal isomerization of the CLA isomers. However, mild boron triflouride or 1% methanolic sulphuric acid with a minimal temperature and reaction time are often used with good success. 

A neat way of preparing96 the system (215) (useful in bufadienolide synthesis) from (214) is illustrated for compound (216). Bromination to (217) followed by dehydrobromination with lithium bromide in DMF gave the dienone (218), which on triethylsilane reduction produced (219) and thence, by condensation with diethyl oxalate, (220). Methylthiotoluene-p-sulphonate in ethanol-potassium acetate now produced (221) whose oxidation with N-chlorosuccinimide in 2% methanolic sulphuric acid gave (223). A previous route to such compounds was by way of the a-acetoxy-ketones (219) but suffers from a low yield at the acetoxylation step, (219) —> (222). 

To the purified residue obtained from the urine sample (5 ml) after extraction with 25 ml ethanol-chloroform (1 5), is added 0.6 ml of the methanolic sulphuric acid, the mixture is vortexed to ensure complete dissolution, and kept at 85°C for ten minutes. After cooling, the reaction product (cocaine) is extracted with diethyl ether. The diethyl ether is evaporized,... 

Reactions of more complex methylenedioxybenzene derivatives have been examined. The bicyclic compound shown, upon treatment with methyl vinyl ketone in dichloromethane afforded a regiospecific Diels-Alder adduct which, in the same refluxing solvent containing a catalytic quantity of methanolic sulphuric acid, produced a 95% yield of 1-carbonylmethoxy-3-(3-oxobutyl)-... 

The pyrrolo-indole (712) forms the tryptophan derivative (713) by the action of methanolic sulphuric acid/ ... 

Ring-expansion reactions have been carried out in a dienone-phenol rearrangement of (7) to the oxygen-containing heterocycle (8) with 30% methanolic sulphuric acid," and in a stereospecific synthesis of a 4-thiacyclo-octene via a [2,3] sigmatropic shift (see last year s Report, p. 412). 

The inclusion of phosphoric acid in the mobile phase increases the potential for error in subsequent quantitation by lipid phosphorus determinations and has been replaced with a mobile phase containing acetonitrile-methanol-sulphuric acid (100 3 0.05) to provide resolution of phosphatidylinositol, phosphatidylserine, phosphatidyl-ethanolamine, phosphatidylcholine, lysophosphatidylcholine and sphingomyelin (Kaduce et al., 1983). The authors reported that a reduction in the sulphuric acid content of the mobile phase caused a broadening of the eluted peaks and an increase in the retention of phosphatidylserine, phosphatidylethanolamine and phosphatidylcholine, while if omitted, these components did not elute. It was also noted that if the methanol content of the mobile phase was increased then the retention times of all the phospholipids were decreased. Samples were therefore injected in chloroform-diethyl ether (1 1) to avoid altering the concentration of methanol in the mobile phase. 

The hydroxy-nitrone (8a) gave the isomeric hydroxy-nitrone (9) on treatment with acid. The latter hydroxy-nitrone underwent base-catalysed deuteriation at C-21, presumably via the dihydroxy-enamine tautomer. Treatment of either hydroxy-nitrone with methanolic sulphuric acid gave the unstable methoxy-nitrone (10), which yielded the dimeric compound (11) on attempted crystallization. The reaction of nitrone (8b) with dialkyl phosphite derivatives was reported earlier details of this study have now been published. ... 

The dehydration of hexose, heptose, and octose phenylosazones in methanolic sulphuric acid has been studied. Each osazone gave rise to two 3,6-anhydrides epimeric at C-3 except 7-deoxy-D-wa no-heptulose phenylosazone which afforded only the 3,6-anhydro-7-deoxy-L- M/o-heptulose phenylosazone with... 

Pistoia has used electrochemically generated nitrate radicals to effect the bulk polymerization of acrylonitrile the system shows a remarkable postpolymerization effect which is affected by such factors as the anode material, current, temperature, stirring, electrolysis time, and HNO, concentration. Radical occlusion phenoma and the formation of oligomers limit the monomer to >oly-mer conversion. Pistoia has also reported the polymerization of acrylonitrile by the oxidation of sulphuric acid at the anode and has extended the work to the anodic polymerization of methyl methacrylate in methanol-sulphuric acid... 

From both embryos and seeds the lipids were extracted using a Bligh Dyer type extraction and the fatty acid composition of the triacylglycerol (TAG) fraction was determined after transmethylation for three hours in 5% methanolic sulphuric acid using capillary GC. The GC was equipped with a Chrompack CPwax-52CB column (25 m x 0.32 mm) and an FID for detection. 

Electrochemical Reactions.— The electrochemical oxidation of 2- and 3-methylthiophens with methanolic ammonium bromide as electrolyte on a carbon or platinum anode gives 5-bromo-2-methylthiophen and 2-bromo-3-methylthiophen as main products. Electrochemical oxidation of methyl thiophen-2-carboxylate on a graphite anode in methanolic sulphuric acid gives the cis and trans forms of (133). Methyl thiophen-3-carboxylate yields (134). On the other hand, electrolysis of thiophen-2-carboxylic acid in DMF on platinum electrodes gives (135). ... 

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