Methanol as cosolvent

Bicyclic Tf-butyrolactones. Cyclohexanols and cyclopentanols fused to a cyclopropane ring at the 2,3-position and substituted at the 4-position by an acetic acid group rearrange when treated with 7% aqeuous perchloric acid (methanol as cosolvent) at room temperature to bicyclic 7-butyrolactones. Examples ... 

An equimolar soln. of glycine isopropyl ester hydrochloride and D-alanine methyl ester in methanoll 3 M tris(hydroxymethyl)aminomethane containing a little 2-mer-captoethanol adjusted to pH 9.5 with 10 MNaOH, 0.5 eqs. of N-benzyloxycarbonyl-phenylalanine methyl ester and a little (crude) papain added successively, the mixture shaken for 1 min, methyl isobutyl ketone added, and stirred vigorously at room temp, for 12 h - Z-Phe-Gly-D-Ala-OMe. Y 57%. A 2-fold increase in yield was observed with methanol as cosolvent compared with dioxane. The method appears to be quite... 

In the enzymatic polymerization of phenol derivatives, a mixture of hy-drophihc organic solvent and buffer is often used as a medium for the efficient production of polymers [45-47]. The HRP-catalyzed polymerization of catechin was carried out in an equivolume mixture of 1,4-dioxane and buffer (pH 7) to give a polymer with a molecular weight of 3.0 x 10 in 30% yield [48]. Using methanol as cosolvent improved the polymer yield and molecular weight [49]. 

The PEE technique has so far been used almost exclusively as a first step in methods for analyzing several polyphenols from fresh grapes. Thus, Pineiro et al. [204] determined frani-resveratrol in grapes by using a method involving a triple-discrete PEE step with methanol as cosolvent. Also, Ju and Howard [205,206] examined the effect of various solvents and temperature conditions on the PLE of... 

H2NOH-HC1, Pyr, 60°. This is the standard method for the preparation of oximes. Ethanol or methanol can be used as cosolvents. 

Whereas stoichiometric versions of this strategy were initially reported [43, 44], a catalytic process involving a Ni(COD)2/PBu3 catalyst system, Et3B as reducing agent, and a methanol/THF cosolvent system was recently developed. The process proceeds both inter- and intramolecularly to provide access to a variety of cyclopentenol derivatives (Scheme 22). 

Use of cosolvent. Various cosolvents, such as acetone, ethanol, methanol, hexane, dichloromethane, and water, have been used for the removal of carotenoids using SC-CO2 extraction (Ollanketo and others 2001). All these cosolvents except water (only 2% of recovery) increased the carotenoid recovery. The use of vegetable oils such as hazelnut and canola oil as a cosolvent for the recovery of carotenoids from carrots and tomatoes have been reported (Sun and Temelli, 2006 Shi, 2001 Vasapollo and others 2004). For the extraction without cosolvent addition, the lycopene yield was below 10% for 2- to 5-hr extraction time, whereas in the presence of hazelnut oil, the lycopene yield increased to about 20% and 30% in 5 and 8 hr, respectively. The advantages of using vegetable oils as cosolvents are the higher extraction yield the elimination of organic solvent addition, which needs to be removed later and the enrichment of the oil with carotenoids that can be potentially used in a variety of product applications. 

The electrolysis in aqueous sulfuric acid with methanol as a cosolvent was perfomed in a filterpress membrane cell stack developed at Reilly and Tar Chemicals. Because of the low current density of the process, a cathode based on a bed of lead shot was used. A planar PbOa anode was used. The organic yield was 93% with approximately 1% of a dimer. The costs of the electrochemical conversion were estimated as one-half of the catalytic hydrogenation on a similar scale. 

Sodium methoxide in methanol, often with chloroform as cosolvent, has customarily been the basic reagent employed. Less frequently, particularly with water-soluble esters, sodium or potassium hydroxide in aqueous solution has been used. Generally, an excess of the basic reagent is taken, except where the possibility of epoxide migration arises (see p. 127). In the latter situation, only a limited excess of reagent is used, at low temperature, or, alternatively, the... 

Alternatively, a 100 mL sample portion pH adjusted to 5.0 chloroacetic acid separated on an anion exchange column and eluted with small aliquots of acidic methanol a small volume of MTBE then added as cosolvent, resulting in esterification of the analyte methyl ester partitions into the MTBE phase the ester analyzed by GC-ECD (U.S. EPA Method 552.1, 1992). 

Various organic solvents were tested for the PLE-catalyzed asymmetric hydrolysis of diester (12) in a biphasic system. The results (Table 5) indicate that the reaction yields and e.e. of monoester (13) were dependent on the solvent used in the asymmetric hydrolysis. Tetrahydrofuran (THF), methyl isobutyl ketone (MIBK), hexane, and dichloromethane inhibited PLE. Lower reaction yields (28-56 M%) and lower e.e. (59-72%) were obtained using f-butyl methyl ether, dimethylformamide (DMF), and dimethylsulfoxide (DMSO) as cosolvent. Higher e.e. (>91%) was obtained using methanol, ethanol, and toluene as cosolvent. Ethanol gave highest reaction yield (96.7%) and e.e. (96%) for monoester (13). 

The peracid must be used in excess, as in another example (Scheme 31). When methanol was used as cosolvent to the methylene chloride the reaction took a different course, giving a product in which a regiospecific incorporation of methanol had occurred46 (Scheme 31). 

The mode of asymmetric induction can be rationalized from the mechanism of the photopinacolization in the presence of aliphatic amines. The electron transfer from the amine to the excited triplet ketone furnishes charge transfer complex 5, from which a radical pair is formed by protoirtransfer. The weakly coordinated chiral amine seems to favor the dimerization of radical 6 from the si face leading to the (/ , ft)-enantiomer 3. The much lower selectivities observed with methanol as the cosolvent (3% ee at 27°C) indicate dipolar or hydrogen bonding interactions between the chiral diamine and the prochiral radical (Scheme 4). 

Reduction of aromatic hydrocarbons. Anthracene is reduced quantitatively to 9,10-dihydroanthraccncby sodium in HMPT with THF as cosolvent. The reaction has been extended to benzanthracene, tetracene, and 9-alkyl- and 9,10-dialkylanthraocnes to give the corresponding mejo-dihydro derivatives. Water or methanol diluted in THF is used as the proton source. ... 

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