Formamide, as solvent

Synthesis The esterification of the potassium salt of flufenamic acid (see below) with 2-(2-chloroethoxy)ethanol in dimethyl formamide as solvent yields Etofenamate (Boltze and Kreisfeld, 1977 Kleemann et al., 1999). 

The use of formamide as solvent in the ammonolysis of activated aryl chlorides has been recommended when the substrate carries cyano ring substituents which can undergo hydrolysis in water.126... 

A recent improvement in the method was achieved by using formamide as solvent for the fiuorination of mesylates l.23... 

C-C double bonds are elTiciently cyclopropanated electrochemically in a one-compartment cell fitted with a sacrificial zinc anode which allowed the formation of organozinc species from geminal dihaloalkanes. Electrolysis of dibromomethane in dichloromethane/dimethyl-formamide as solvent mixture is recommended as the standard condition for electrolysis. The best chemical yields were obtained with allylic alcohols and unfunctionalized alkenes. For example electrolysis of allyl alcohol 23 gave cyclopropane 24 in 70% yield. 

Halopropionic acid derivatives are readily accessible from lactic acid via its mesylate. Thus, treatment of 156a with AICI3 affords methyl (i )-2-chloropropionate (162) with 88% ee [59]. Reaction of 156a with KF in formamide produces methyl (R)-2-fluoropropionate (163) (96% ee). The use of formamide as solvent not only increases the reaction rate but also favors Sn2 reaction due to its high polarizability. The ti ji is approximately 30 min, and reaction is complete in 3 h [57]. (R)-2-Fluoropropionic acid is prepared from 163 by transesterification with formic acid. Amberlyst A-26 (F ) can be used as an alternate fluoride source in the conversion of mesyl lactates to chiral a-fluoroesters. This polymer-supported reagent produces clean Sn2 reactions [60]. 

In Fig. 5.32b the striped texture of the lyotropic SmC phase with formamide as solvent can be seen. The stripes appear much more visible in this sample, clearly indicating the macroscopic heUcity of the lyotropic phase. The helical pitch of p = 5.2 pm is close to the value found in the mixture with water. However, there is one significant difference between the two solvents While the sample with water had to rest for several weeks before the striped texture could be detected, the sample with formamide only took seconds after the transition into the lyotropic SmC analog phase to show the texture displayed in Fig. 5.32b. This difference in the time-based evolution of the helical director configuration is quite remarkable and implies that the solvent plays a very important part in the formation of the helix, even though it has only littie impact on the absolute value of the helical pitch. Possible explanations might be the more extended solvent layer in the case of mixtures with water or a different internal structure in the solvent layer. However, these points are only speculations and the reason for the deviating behavior still has to be understood. 

Finally, in the case of formamide as solvent, the phase transition temperature of the lamellar L to lyotropic SmC analog phase transition shifts to smaller and smaller values with increasing formamide concentration cf. Sect. 5.2.1). This accounts for a loss of correlation between the partial bilayers with increasing thickness of the solvent layer. After reaching a critical formamide layer thickness of 2.7 nm all correlation is lost as the hydrogen bond network becomes less rigid. 

An acid-base reaction can be nsed to enhance separation by taking advantage of the difference in the pA values of the components to be separated (Duprat and Gau, 1991). For example, in the close-boiling 3-/4-picolines mixture, addition of trifluoroacetic acid in stoichiometric deficiency results in preferential complex-ation of 4-picoline with a selectivity of about 2 in formamide as solvent. As the pyridinium salts are nonvolatile, the vapor phase is enriched with respect to 3-picoline. A near-complete separation can be expected by repetition of this enrichment in countercurrent staging. 3-Picoline will leave the column as the distillate at the top, while 4-picoline will leave as a liquid phase complex with the... 

These debates supply a reminder that speculations about mixtures of water and other small molecules (ammonia, formamide) as solvents for extraterrestrial life are a much more subtle matter than simply looking for a low-freezing-point liquid. The interactions and partitioning of co-solvents should be expected to have a significant effect on the conformational stabilities of complex macromolecules, and in ways that are hard to predict. 

Aprotic electrolytes based upon methyl formate, propylene carbonate and dimethyl formamide as solvents and lithium chloride plus aluminum chloride, lithium hexafluoroarsenate and lithium perchlorate as solutes are discussed. The effect of additives, other aprotic solvents, other salts and trace amounts of water on species in solution and other physical properties are described. 

The 1,3 cycloaddition of NJ (from NH4N3) to nitrile compounds is a convenient method to prepare substituted tetrazoles. The reaction Is normally performed at 373 K In dimethyl-formamide as solvent see e.g. [34 to 36]. 

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