N, V-Dimethylformamide

When D-fructose and L-sorbose are refluxed with aqueous HC1, dihexulose dianhydrides are formed.91 If the water is replaced by N./V-dimethylformamide, substantially increased yields are obtained and 1,2-linked disaccharides are detected. Higher yields of dianhydrides were obtained from fructose, rather than sorbose, under comparable conditions. Treatment of levan with dilute H2S04 at 60°C yielded92 a-D-Fru/-l,2 2,1 -fi-D-Fru/(5). Presumably, any products that contain 2,6-linkages with large central rings would rapidly isomerize to the more stable 1,2-linked product. 

N, /V-dimethylformamide.60 The sugars were isolated on a column of Dowex-50 X8 in the calcium form.6 Both d-(1-i3C)- and D-(2-l3C)-ribose are now commercially available. These sugars allowed the preparation of samples of AIRs labeled with 13C either on C-T or on C-2 In conclusion, four ribonucleosides are now available practically fully labeled at a single position.58... 

AW, Acid-washed Choi, Cholesterol DMAP, 4-(Dimethylamino)pyridine DMF, N,/V-Dimethylformamide DMTr, Di(p-niethoxyphenyl)phenyl methyl GalNAc, N-Acetylgalactosamine, 2-acetamido-2-deoxy-D-galactose HMF, 5-Hydroxymethylfur-fural, 5-(hydroxymethyl)-2-furaldehyde INOC, Intramolecular nitrile oxide-alkene cycloaddition Lea, Lewisa Lex, Lewisx MOM, Methoxymethyl MP, p-Methoxyphe-nyl MS, Molecular sieves NIS, N-Iodosuccinimide PCC, Pyridinium chlorochromate PDC, Pyridinium dichromate PMA, Phosphomolybdic acid PMB, p-Methoxybenzyl ... 

Cunico and Motta reported (202) on the very interesting one-pot synthesis of SENAs, such as 3-nitrocarboxylic acid /V./V-dimethylamides derivatives, from silylated N./V-dimethylformamides 57a,b and conjugated nitroalkenes (Scheme 3.57). 

In the first DNMR studies of push-pull ethylenes, a strong effect of solvent polarity on the C=C barriers was noted. Thus Kende et al. (64) found AG = 18.0 kcal/mol for 46a in N,/V-dimethylformamide (dielectric constant e = 38) and 19.4 kcal/mol in Ph20 ( = 4). Similar observations have been made by many other workers, and they have been seen as a strong support for a zwitterionic transition state. Kessler et al. (140) observed reasonably linear correlations between AG for two ketene aminals and the solvent polarity parameter T (141) with variations in AG of ca. 2.5 kcal/mol over T values between 25 and 46. Similarly, Shvo et al. (78) found linear correlations between log km and the polarity parameter Z (141) for three compounds from Table 12. 

Phenanthrenequinone (8) 9,10-Phenanthrenedione (9) (84-11-7) Lithium aluminum hydride Aluminate (1-), tetrahydro, lithium (8), Aluminate (1-), tetrahydro-, lithium, (T-4)- (9) (16853-85-3) N,/V-Dimethylformamide dimethyl acetal Trimethylamine, 1,1-dimethoxy- (8) Methanamine, 1,1-dimethoxy-(V,N-dimethyl- (9) (4637-24-5)... 

The following procedure is an operatively simple route for the synthesis of bromotrimethylsilane on a preparative laboratory scale from reagents that are readily accessible and inexpensive. This could be a method of choice in some laboratories despite the fact that bromotrimethylsilane is now commercially available (Petrach Systems, Aldrich, or Alpha). Moreover, the procedure also serves as a suitable method for the synthesis of azidotrimethylsilane and isocyanatotrimethylsilane, and is specially useful for the preparation of cyanotrimethylsilane. Thus a mixture of triphenylphosphine dibromide, hexamethyldisiloxane, and a catalytic amount of powdered metal zinc in 1,2-dichlorobenzene is heated under reflux to produce bromotrimethylsilane in nearly quantitative yield, which is simultaneously distilled over a suspension of the corresponding pseudohalogenoacid salt in N, /V-dimethylformamide as solvent.6... 

Halogen atoms have been placed at C-6 of substituted 6-deoxy-hexoses by a variety of interesting ways, and the products provide potential routes to 6-deoxyhexoses. Helferich and coworkers 4 reported a low yield of methyl 6-chloro-6-deoxy-a-D-glucoside which they prepared by reaction of the (suitably protected) corresponding 6-trityl ether with phosphorus pentachloride. Sinclair 44 has provided a convenient procedure for the preparation of the 6-chloro derivative in yields of 30-35% by allowing methyl a-D-glucopyranoside to react with sulfur monochloride, SjClj, in N,/V-dimethylformamide. A much better yield (73%) of the 6-bromo derivative was reported1 in the reaction of methyl 2,3,4-tri-O-benzoyl-6-O-trityl-a-D-altroside with phosphorus tribromide and bromine. 

Me O, acetone Me2SO, dimethyl sulfoxide MeOH, methanol HCONMe2, N, /V-dimethylformamide AcOH, acetic acid CDC13, deuterated chloroform. 

Similar to crotylsilicates, crotyltrichlorosilanes react regioselectively with aldehydes in N,/V -dimethylformamide (DMF) without a catalyst to afford the corresponding homoallylic alcohols in high yields (Scheme 3.2c).7 New carbon-carbon bond formation takes place only at the y-positions of the crotyltrichlorosilanes. In addition, syn -isomers are obtained from Z-crotyltrichlorosilanes, while... 

The best known application of N V-dimethylformamide in sucro-chemistry is as a solvent for a transesterification reaction leading to sucrose mono- and poly-esters of fatty acids. This reaction has been extensively studied and reviewed,73,259-269 and will not be further... 

However, there are many molecules where rotation around a particular single bond is restricted, that is, prevented from rotating freely. If rotation is much slower than the NMR time scale, the molecule is essentially locked in one conformation. One example of such a compound is N./V-dimethylformamide (DMF, 10-1), whose NMR data are given in Table 8.1 ... 

An example of such a third competing step is the reaction of the intermediate aryl radical with H-atom donors present in the reaction medium, possibly the solvent itself. Indeed, aryl radicals are good H-atom scavengers and reduction of aryl halides is often carried out in organic solvents such as acetonitrile (ACN), N./V-dimethylformamide (DMF), dimethyl sulphoxide (DMSO), and ethers, that are good H-atom donors... 

Chain length dependence on the solvent used and concurrently on reaction temperature was demonstrated in an experiment involving the same components as given in Equation 16, but using m-cresol in place of N,]V-dimethylformamide. 

Hasegawa and Fletcher25,37 studied the reaction of some aldoses, mainly 2-acetamido-2-deoxyaldohexoses, with 2,2-dimethoxypro-pane-N V-dimethylformamide-p-toluenesulfonic acid at 25 and 80°. The products obtained at the two temperatures differed markedly, and, again, lack of activity at the anomeric hydroxyl group in the presence of N,N-dimethylformamide was noted. To account for this phenomenon, it was postulated that the dimethyl acetal ofA/JV-dimethyl-formamide, presumably formed in situ, reacts to afford highly labile (dimethylamino)methylene acetals which may thereby permit insertion of isopropylidene groups in abnormal positions. 

Fig. 17. —Mutarotation of D-Fructose in N V-Dimethylformamide-Water Mixtures at 24°. [(1) Change following addition of an equal volume of water to a previously equilibrated solution of D-fructose in N,N-dimethylformamide (2) change following addition of an equal volume of water to a freshly prepared solution of crystalline D-fructose in N V-dimethylformamide.1,7]...

N V-Dimethylformamide has been particularly useful as a solvent for nucleophilic displacements in carbohydrate chemistry for... 

The 2 -0-p-tolylsulfonyl derivative of 8-hydroxyadenosine underwent intramolecular sulfonate displacement when heated at 100-105° with sodium benzoate in N V-dimethylformamide, and the 2, 8-anhydro structure (170) was indicated.434 A derivative of2, 8-anhydro-guanosine (171) was obtained by a similar method.435... 

A lactone and a free sugar of this series have been obtained during investigations of nucleophilic displacements at C-5 of a hexonic acid derivative, in reactions (similar to those previously reported1) by which related enamines were formed. Treatment of 2,3,4,6-tetra-O-benzyl-N,N-dimethyl-5-0-(methylsulfonyl)-D-gluconamide with potassium acetate in N V-dimethylformamide gave 2,4,6-tri-0-benzyl-3-deoxy - L - threo - hex - 2 - enono -1,5 - lactone (53, R = O) which, with... 

The solubilities of these complexes in common organic solvents are rather limited, being somewhat soluble in N,]V -dimethylformamide, methylene chloride, and chloroform, sparingly soluble in benzene, and insoluble in acetonitrile, acetone, hexane, etc. The limited solubility precludes measurements such as molecular weight determinations. Nevertheless, the products generally precipitate out of solvents such as benzene as microcrystalline solids and can be recrystallized with mixed solvents (1,3,4). 

Vapor-liquid equilibrium data of polysulfone in N, V-dimethylformamide and 2-propanone... 

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