Hexamethylphosphoramide preparation

Other Reactions. Primary amyl alcohols can be halogenated to the corresponding chlorides by reaction with hydrogen chloride in hexamethylphosphoramide (87). Neopentyl chloride [753-89-9] is formed without contamination by rearrangement products. A convenient method for preparing / f/-amyl bromide and iodide involves reaction of / f/-amyl alcohol with hydrobromic or hydroiodic acid in the presence of Li or Ca haUde (88). The metal haUdes increase the yields (85 —95%) and product purity. 

Using hexamethylphosphoramide as the solvent, only the second reaction occurs. Disilane also reacts with potassium in 1,2-dimethoxyethane to form KS1H3, although S1H4 and nonvolatile polysHanes are also produced (28,31). Pure crystalline KSiH prepared from SiH and potassium in 1,2-dimethoxyethane has been obtained by slow evaporation of the solvent. WhenHquid ammonia is used as the solvent, only a small fraction of SiH is converted into metal salt most of the SiH undergoes ammonolysis (32). 

Dibromo-3-ketones may also be used as substrates for the preparation of A -3-ketones by Joly s method. " Hexamethylphosphoramide has been recommended as a medium suitable for the dehydrobromination of a-bromo ketones to give a, -unsaturated ketones in high yield without rearrange-... 

A well dried sample of this complex exploded violently when pushed through a funnel with a steel spatula. The pyridine adduct, which was being prepared, is claimed to be a useful, safe, oxidant, replacing the hexamethylphosphoramide complex of M0O5 (ibid.). 

Miconazole nitrate was prepared by Godefori and co-workers [5-7]. Imidazole 1 was coupled with brominated 2,4-dichloroacetophenone 2 and the resulting ke-tonic product 3 was reduced with sodium borohydride to its corresponding alcohol 4. The latter compound 4 was then coupled with 2,4-dichlorotoluene by sodium borohydride in hexamethylphosphoramide (an aprotic solvent), which was then extracted with nitric acid to give miconazole nitrate. 

Ficini and Barbara [14, 15] prepared lithium aminoacetylides and allowed them to react with alkyl bromides or tosylates in hexamethylphosphoramide to give good yields of substituted ynamines (Eq. 16). This method shows promise of being a general route to ynamine derivatives. 

The hexamethylphosphorus triamide is obtained from the Eastman Kodak Company. It is distilled under reduced pressure (water aspirator) to yield a clear, colorless oil, b.p. 46-48° (7 mm.). It is then stored under nitrogen (rubber septums should be avoided as they tend to deteriorate on prolonged contact with phosphine vapors). Hexamethylphosphorus triamide that has not been freshly distilled often requires much longer reaction times. Since this chemical is an irritant, all operations with it should be performed in a well-ventilated hood. Hexamethylphosphoramide is a classified carcinogen see Org. Syn., 55, 103 (1976). It should not be confused with hexamethylphosphorus triamide used in this preparation. 

Solvated electrons are readily prepared in hexamethylphosphoramide (HMPA), ammonia, and methylamine [19]. Lithium chloride is the preferred electrolyte for this application. 

These preparations that illustrate the use of sodium cyanoborohydride in hexamethylphosphoramide as an effective, selective, and convenient procedure for the reduction of alkyl halides and tosylates is essentially the same as previously described.8 The very mild reducing ability of sodium cyanoborohydride makes the method particularly valuable when other functional groups are present in the molecule... 

In the original discovery route by Sugimoto,19,46 aldol condensation of 5,6-dimethoxy-l-indanone (25) and l-benzyl-4-piperidine-carboxaldehyde (26) in the presence of freshly prepared LDA and hexamethylphosphoramide (HMPA) in THF provided exocyclic enone 27 in 62% yield (Scheme 2). Hydrogenation with 10% Pd/C followed by salt formation with hydrochloric acid afforded donepezil hydrochloride (3) in 86% yield. 

In attempts to prepare 3-acyl-substituted BIPS (113), various salicylaldehydes were condensed with l,3,3-trimethyl-2-formylmethyleneindoline (Fischer s aldehyde). In alcohol, dimethylformamide, tetrahydrofuran, Y-mcthylpyrrolidonc. and hexamethylphosphoramide as the sole solvents, decarbonylation occurred and the only products were the BIPS compounds. However, in dimethyl sulfoxide, 5-nitro-and 3-bromo-5-nitrosalicylaldehydes gave 11 and 5.6% of the desired 3-formyl-BIPS, respectively. The structures were assigned from their IR and NMR spectra. 

Preparative Methods prepared by lithiation of (l/ ,25)-l-phenylsulfonyl-2- [(terf-butyldiphenyl)silyl]oxymethyl oxir-ane (1, [a]o -1-55.9°, c 1.0, CHCI3) (1.0 equiv) in THF (0.15 M solution) with -BuLi (1 equiv, 1.6 M solution in hexane) in the presence of DMPU or hexamethylphosphoramide (HMPA) (3.0 equiv) at —100 °C under argon. Deprotonation is completed within a few minutes (eq 1 ). ... 

An unexpected displacement of a diazonium group in diazotized aminonaphthalenes by hydrogen was discovered when diazonium mercury(II) bromides, prepared by treatment of diazonium bromides with mercury(II) bromide, were stirred at room temperature for 10-20 min in hexamethylphosphoramide (HMPA) (equation 99). ... 

The Chemistry of Ring A.—Two methods have been described for smoothly hydrolysing the highly-hindered axial C-4 methyl esters such as methyl 0-methyl podocarpate. The first uses boron trichloride in methylene chloride, and the otherlithium n-propyl mercaptide in hexamethylphosphoramide. The oxidative decarboxylation of dehydroabietic acid and 0-methyl podocarpic acid affords a mixture of C-4 olefins which are separable over 10 % silver nitrate by t.l.c. Thus in a partial synthesis of callitrisic acid, the 4(19)-epoxide prepared... 

The reduction of UCI4 to prepare these compounds can also be effected by sodium in hexamethylphosphoramide solution (43). 

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