Dimethylformamide special

The bromination of 4,5-j -dihydrocortisone acetate in buffered acetic acid does not proceed very cleanly (<70%) and, in an attempt to improve this step in the cortisone synthesis, Holysz ° investigated the use of dimethylformamide (DMF) as a solvent for bromination. Improved yields were obtained (although in retrospect the homogeneity and structural assignments of some products seem questionable.) It was also observed that the combination of certain metal halides, particularly lithium chloride and bromide in hot DMF was specially effective in dehydrobromination of 4-bromodihydrocortisone acetate. Other amide solvents such as dimethylacetamide (DMA) and A-formylpiperidine can be used in place of DMF. It became apparent later that this method of dehydrobromination is also prone to produce isomeric unsaturated ketones. When applied to 2,4-dibromo-3-ketones, a substantial amount of the A -isomer is formed. 

The bromo substituent in l-bromo-19-meLhyl-l,l9-dideoxybiladienes- c is not essential for porphyrin formation. When 1-methylbiladiene-ac dihydrobromide or the 1,19-dimethyl-biladienc-ac are heated in refluxing methanol or dimethylformamide in the presence of cop-per(II) salts, the porphyrin copper complexes 13 are formed by oxidative cyclization. The free porphyrins can then be obtained by removal of the copper with acid. A wide range of porphyrins 13 can be prepared by this method. However, a restriction is the accessibility of the starting material with special substitution patterns. 

Alkaline hydrolysis in a solvent (dimethylformamide, dimethylsulphoxide or dimethyl-acetamide) containing sodium hydroxide has been investigated [164]- Fabric geometry [165] and the degree of heat setting of the polyester also influence the results. As the temperature of heat setting was increased, the accelerating effect of dodecylbenzyldimethylammonium chloride decreased [166]. Basic-dyeable polyester is particularly sensitive to alkaline hydrolysis [167]. In some cases, saponification has been used to produce special effects such as a leather-like finish [168]. 

In solution, the drug may hydrolyze to yield diethylaminoethanol and 4-aminobenzoic acid. For the analysis, the sample solution is treated with 0.2 M (NH4>2Zn(SCN)4, heated to the onset of boiling, and cooled with slow rotational mixing for 4 minutes. This process yields clear solution and an oily precipitate, which is filtered through cotton wool. The filter is washed with 10% NH4SCN solution, and cooled to IT C. The precipitate is dissolved in acetone or dimethylformamide. Water, ammonia buffer solution (pH unspecified), and acid chrome black special indicator are added, and the mixture titrated with 10 mM EDTA to determine Zn(II), and hence procaine. 

Dimethylformamide initiation is a special case. Polythiocarbonyl fluoride prepared with this initiator, as has been stated, also has all three possible ends with —SCF=0 being present in smallest amount. Also, the polymer as isolated is free of the formamide. It is here proposed that dimethylformamide initiation may proceed as follows ... 

Among the solvents suggested for azo coupling reactions, aside from aqueous and specialized nonaqueous systems as mentioned above, are mixtures of water with water-soluble alcohols (e.g., methanol, ethanol, propanol), other water-soluble solvents such as tetrahydrofuran, N, A-dimethylacetamide, iV,iV-dimethylformamide, and organic acids such as formic, acetic, and propionic acids [11 ]. 

Dimethylformamide — Fire Hazards Flash Point (deg. F) 153 OC 136 CC Flammable Limits in Air (%) 2.2 -15.2 Fire Extinguishing Agents Water, foam carbon dioxide, or dry chemical Fire Extinguishing Agents Not to be Used Not pertinent Special Hazards of Combustion Products ... 

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... 

A special process for the production of coppered l,5-bis(2-hydroxyphenyl)-formazans 32 is based on the demethylative copperization of 1,5-bis(2-methoxy-phenyl)formazans [63], The method involves heating for a short time in pyridine, formamide, or dimethylformamide. 

The Vilsmeier-Haack reaction (herein, Vilsmeier reaction ) provides an effective method for the formylation of aromatic systems. The combination of phosphoryl chloride with V-methylaniline or dimethylformamide generates an iminium phosphorus derivative or chloro-iminium cation that is the active electrophile in an electrophilic substitution reaction. The resulting substitution product is an iminium salt 1, which is hydrolyzed on workup with alkali to give the carbaldehyde product 2 (Scheme l).1,2 The method is particularly useful with activated arenes or electron-rich heterocycles, such as pyrroles, furans, thiophenes, and indoles. We had a special interest in the preparation of indole-7-carbal-dehydes, namely, their properties as isosteres of salicylaldehyde. Thus, we became involved in a wide-ranging investigation of 4,6-dimethoxy-... 

Boltom H40 dendritic molecules were covalently linked in this work to make a network with aliphatic 1,6-hexamethylene diisocyanate (HDI). The molar NCO/OH ratio was varied for the reactants from 10 to 50% to prepare networks with different degrees of connectivity of dendritic units. The network samples are designated as H40/Z where Z stands for NCO/OH ratio expressed as a percentage. The network formation reaction of H40 with HDI was carried out in N,N-dimethylformamide (DMF) of 99.8% purity at 90 C. No catalyst was added. Isocyanates react readily with moisture to form urea linkages, therefore special precautionary measures were implemented to prevent moisture uptake either by HDI or DMF. Observation of the reaction vessel was maintained over the course of the reaction to monitor the viscosity of the solution. As viscosity of the solution increased to the desired level, suggesting that the gelation point was near, the solution was cast onto a glass plate which was immediately placed... 

Special solvent. Newman - recommends N-methyl-2-pyrrolidone as solvent for the reaction of an aryl halide with cuprous cyanide to produce the corresponding nitrile. Dimethylformamide (b.p. 153°) has been suggested as a better solvent than originally used pyridine (b.p. 115°), but l-methyl-2-pyrrolidone has an even higher boiling point and seems still more satisfactory. An example is the synthesis of... 

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