Methylene chloride as solvent for

Methylene chloride as solvent for diazomethane etherifications, 41, 9 Methylene cyclohexane, 40, 66 Methylene iodide, reaction with zinc-copper couple and cyclohexene, 41, 73... 

The promoter of choice for direct coupling of NPGs is NIS/EtjSiOTf [13]. The reaction is usually conducted in methylene chloride as solvent at room temperature [14]. Under these conditions, the coupling reaction is very fast, often being completed within the time it takes to sample the mixture by thin-layer chromatography (TLC). The process can be rationalized by an acid-induced heterolysis of NIS, whereby a very potent source of iodonium ion is generated (Scheme 5). Usually, only a catalytic amount of EtjSiOTf is... 

Improved conditions for the oxidation of olefins with ozone to ketones (60-70%) have been described. The use of Dry Ice temperature and methylene chloride as solvent lessens the loss of volatile olefins in the... 

The results were checked by use of a common-ion procedure once again similar to that used by Sangster and Worsfold [46] in the polymerization of THF, and by workers in the field of anionic polymerizations [39]. In the case of methylene chloride as solvent, addition of a common salt depressed the overall value of fep indicating fep < fep, whereas in the case of nitrobenzene no effect was observed, so that — kp. Appropriate analysis of rate data obtained in the presence of common ion yielded values for fep and fep in both solvents, very similar to those already calculated (Table 11). 

Initially, the reduction of ester 45 proved to be problematic (Scheme 14). When THF was used as solvent, a large excess of DIBAL was required (10 equiv.) and the yield for the desired alcohol was still very low, 50%, with the remainder being unreacted 45. Use of methylene chloride as solvent led to complete reduction along with unwanted TES removal. Finally, it was found that the use of ether with 2.5 equivalents of DIBAL provided the desired alcohol in 91% yield. Oxidation gave the enal intermediate, which was converted to the diene ester 47 with allyl phosphonate 46. The selectivity was 19 1 E,Z Z,Z) and the yield was an excellent 93%. Previously, the more common methyl ester corresponding to 47 was employed. Hydrolysis to the desired acid with this substrate was... 

Molecular squares define cavities that are potential hosts for appropriate molecular guests. In methylene chloride as solvent, pyridine binds to the available Zn(II) sites of IZn with an association constant of 10 M Whether binding occurs on the square interior or exterior (or a combination of both) has not been established. Recall, however, that Zn porphyrins generally axially bind only one ligand. The free base form of the dipyridyl porphyrin used to assemble the squares binds to IZn with an equilibrium constant of 3 x 10 [7]. The stronger association is a consequence of... 

Perchloric acid has been used as a catalyst in combination with methylene chloride as solvent but has not superseded the sulfuric acid - acetic anhydride, acetic acid process. The most difficult and expensive step in the process is the isolation of the CTA in a form suitable for purification and the recovery of the acetic acid. 

The conditions used for amino acid esters with methylene chloride as solvent were found to be equally applicable to the derivatization of nucleic acid bases and hydrolysates of DNA [67]. 

As mentioned above, LiB H4 has been used very successfully for reduction of a tertiary amide to an amine. Whereas treatment in trial reactions of238 with LiBHLt in THF solution at 65 °C gave the benzyl alcohol, the outcome in methylene chloride as solvent was different. Namely, reduction of 238 with LiB H in CH2CI2 at 40 °C gave 239, the mucolytic agent bromhexine, in 43% yield with a specific activity of 54Ci/mmol . 

Dichloromethane (CH2C12, methylene chloride), trichloromethane (CHCI3, chloroform), and tetrachloromethane (CCI4, carbon tetrachloride) are often used as solvents for nonpolar and moderately polar compounds. 

When a solution is tested, both analyte and solvent absorption bands will be present in the spectrum, and identification, if that is the purpose of the experiment, is hindered. Some solvents have rather simple IR spectra and are thus considered more desirable as solvents for qualitative analysis. Examples are carbon tetrachloride (CC14, only C-Cl bonds), choloroform (CHC13), and methylene chloride (CH2C12). The infrared spectra of carbon tetrachloride and methylene chloride are shown in Figure 8.21. There is a problem with toxicity with these solvents, however. For quantitative analysis, such absorption band interference is less of a problem because one needs only to have a single absorption band of the analyte isolated from the other bands. This one band can be the source of the data for the standard curve since the peak absorption increases with increasing concentration (see Section 8.11 and Experiment 25). See Workplace Scene 8.2. 

Similar to the previous examples, the pre-selected target properties for the replacement of methylene chloride as a solvent, are listed in Table 3. 

The explanation for the fact that the obtained PSU contains only vinylbenzyl chain ends, even when the etherification is performed in methylene chloride as reaction solvent, is provided by the kinetic particularities outlined below ... 

---