Barium oxide/dimethylformamid

Cuprous iodide s. under CgH Li Barium oxide dimethylformamide N-Methylation of indigo compounds... 

Industrial grade dimethylformamide is purified by distillation, first at atmospheric pressure to remove most of the water in the initial small fraction, and then by distillation at reduced pressure from barium oxide, b.p. 63° (30 mm.). 

The structure of compounds 45, 47, and 49 was ascertained42 by methylation with methyl iodide in N.N-dimethylformamide in the presence of barium oxide.48 In each experiment, the corresponding l,l-bis(acetamido)-l-deoxy-octa-0-methylaldobiitol was obtained on acid hydrolysis, this afforded two methylated monosaccharides, whose structures confirmed the acyclic formulas proposed. 

One seminal example has been reported by Butterworth and associates, who described the methylation of a 2-deoxy 3-ketosugar with methyl iodide and barium oxide in dimethylformamide (DMF) [153]. 

Dimethylformamide is a versatile reaction solvent that is polar, fairly high-boiling (153°), and miscible with water. It is purified by distillation from barium oxide. 

Dimethyl sulfate-Barium oxide, see also Methyl iodide. Dimethyl sulfate in combination with barium oxide or barium hydroxide, Ba(0H)j-8H20, provides an effective method for the perraethylation of carbohydrates. Dimethyl sulfate is cheaper and sometimes superior to methyl iodide. Dimethylformamide is the usual solvent, but for carbohydrates only slightly soluble in this solvent dimethyl sulfoxide or a mixture of dimethyl sulfoxide and dimethylformamide is used. 

Kuhn found that carbohydrates can be completely methylated in a single step by silver oxide and methyl iodide if dimethylformamide is used as solvent. The carbohydrate is dissolved in 10-25 times its weight of DMF and treated at room temperature with methyl iodide (3 equiv. per OH group) and silver oxide (2 equiv. per OH group). Barium oxide can also be used." 1,2-Diketones are converted by this procedure into monoketals. Thus benzil is converted into (1), phenanthrenequinone into (2), and ninhydrin into (3). ... 

Alkylation with alkyl halides and barium oxide in N,N-dimethylformamide... 

An excess of alkyl halide is added to a solution of the substrate in N,N-dimethylformamide (1 1 to 1 20 w/v) followed by finely divided barium oxide, and the mixture is stirred vigorously in a flask equipped with an efficient condenser (not necessary for high boiling halides, in... 

Methylation of the hydroxyl groups of carbohydrates and other alcohok has usually been effected [la] with dimethyl sulphate and concentrated aqueous sodium hydroxide or with methyl iodide and silver oxide. More recently [lb, 2], the use of dimethyl sulphate in combination with barium oxide jind barium hydroxide in dimethylformamide or dimethyl sulphoxide solution has been recommended. 

Triethylamine is now employed extensively as a base. Recently, it has been used for an improved prepn. of hydrazones and their conversion into em-diiodides and a,/ -ethyleneiodides A number of condensations, e.g. the prepn. of 4-hydroxycoumarins from phenols, can be performed under mild conditions with a mixture of zinc chloride and phosphorus oxide chloride One of the most frequently used media, dimethylformamide, is still extending its range of applications. Recently, it has been used successfully for ring closures, e.g. to purine derivatives and for various kinds of reactions with methyl iodide in the presence of silver or barium oxides... 

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