Hexa-methylphosphoric triamide

The pyrolysis of sodium chlorodinuoroacetate is still a widely used, classical method for generating difluorocarbene, especially with enol and allyl acetates [48, 49, 50, 51] (equation 21) A convenient alternative that avoids the hygroscopic salt uses methyl chlorodifluoroacetate with 2 equivalents of a lithium chlonde-hexa-methylphosphoric triamide complex at 75-80 °C in triglyme [52], Yields are excellent with electron-rich olefins but are less satisfactory with moderately nucleophilic alkenes (4-5% yields for 2-bulenes)... 

As expected, similar treatment of 3-nitroarenes furnishes mixtures of 4- and 6-substituted 3H-azepines, 54 and 55, respectively.176 Comparable yields of mixed azepines were also obtained by deoxygenation of 3-nitroarenes with alkylphophorous triamides, formed in situ from hexa-methylphosphorous triamide and excess of a secondary amine.66 In a few cases the 3//-azepines were separated by fractional crystallization of their oxalate salts66 but, in general, pure isomers were not isolated and the yields cited in the table were determined by HNMR spectroscopy. 

Ultraviolet irradiation43 of a methanolic solution of compound 3 in the presence of alkali led to its rapid, almost quantitative, conversion into l,2 3,4-di-0-isopropylidene-a-D-fucopyranose (5) an excellent yield of 5 was also obtained44 by irradiation of a solution of 6-O-acetyl-l,2 3,4-di-0-isopropylidene-a-D-galactopyranose (6) in aqueous hexa-methylphosphoric triamide. 

Potassium hydroxide, 258 Trimethylsilyl chlorochromate, 327 of carbon-carbon double bonds substituted by heteroatoms m-Chloroperbenzoic acid, 76 of oximes to carbonyl compounds Lithium aluminum hydride-Hexa-methylphosphoric triamide, 159 Titanium(III) chloride-Diisobutylalu-minum hydride, 303 Trimethylsilyl chlorochromate, 327 of protected alcohols Chlorodimethylthexylsilane, 74 Formic acid, 137 p-Methoxyphenol, 181 of thioacetals and -ketals Methoxy(phenylthio)trimethyl-silylmethane, 182... 

Lithium aluminum hydride-Hexa-methylphosphoric triamide, 159 Methoxyamine, 177 Titanium(III) chloride-Diisobutyl-aluminum hydride, 303 Trimethylsilyl chlorochromate, 327 From vinylsilanes m-Chloroperbenzoic acid, 76 Miscellaneous methods to prepare ketones... 

Ethylenediamine, 157 Hexamethyldisilazane, 175, 331 Isopropylamine, 164 N-Lithioethylenediamine, 157, 200 Lithium amides, chiral, 159 Lithium 3-aminopropylamide, 157, 160 Lithium 3-aminopropylamide-Potas-sium /-butoxide, 160 Lithium dicyclohexylamide, 110 Lithium diisopropylamide, 106, 143, 148, 163, 188, 256, 257, 326 Lithium diisopropylamide-Hexa-methylphosphoric triamide, 143, 172 Lithium diisopropylamide-Potassium t-butoxide, 164... 

Lithium aluminum hydride, 61, 62, 282 Lithium aluminum hydride-Bis-(cyclopentadienyl)nickel, 158 Lithium aluminum hydride-Cerium(III) chloride, 159 Lithium aluminum hydride-Hexa-methylphosphoric triamide, 159 Lithium aluminum hydride-Potassium methoxide, 159... 

Of the homoleptic carbonylmetallates(l -) we have attempted to reduce, [Co(CO)4] appears to be the most difficult. Although the sodium salts of [M(CO)6] (M = V, Nb, and Ta) were quickly reduced in liquid ammonia by sodium metal to provide the corresponding trianions, [M(CO)5]3 (vide supra), it seems unlikely that we have ever effected complete reduction of Na[Co(CO)4] to Na3[Co(CO)3]. Even after 2 days of refluxing (at — 33°C) anhydrous ammonia solutions of Na[Co(CO)4] with excess Na, considerable amounts of the tetracarbonylcobaltate(l —) remained. Low yields of a heterogeneous-appearing brown to olive-brown insoluble solid were isolated this solid has been shown to contain Na3[Co(CO)3] (vide infra). As in the case of [Re(CO)s], we found that solutions of potassium in liquid ammonia were far more effective at reducing [Co(CO)4]-. However, unlike [Re(CO)s], [Rh(CO)4], or [Ir(CO)4] (vide infra), there was no evidence that [Co(CO)4] was reduced by sodium or potassium metal in hexa-methylphosphoric triamide. We observed that excess sodium naphthalenide slowly (over a period of 40-50 hr at room temperature) converted Na[Co(CO)4] in THF to an impure and insoluble brown powder that contained Na3[Co(CO)3], but this synthesis appeared to be of little or no utility. 

Although phosphoric acid has three hydroxy groups that can be used to form derivatives, the various reactions involved are again similar to those of carboxylic acids. For example, the reaction of phosphorus oxychloride, which can be viewed as a tri(acid chloride) of phosphoric acid, with excess dimethyl amine produces a triamide, hexa-methylphosphoric triamide ... 

Accelerated rates of substitution often result when reactions are carried out in polar aprotic rather than in hydroxylic solvents. This largely is a consequence of poor solvation of centers of negative charge in the aprotic media. By contrast, in hydroxylic media solvation of such centers by hydrogen-bonding is important.27 Commonly employed aprotic solvents include DMSO, N,N-dimethylformamide (DMF) and hexa-methylphosphoric triamide (HMPA). Thus, the reaction of 2-bromopyridine with methoxide ion at 110 °C to give 2-methoxypyridine is 3590 times faster in HMPA than in methanol.28 ... 

The steric course of the reaction is strongly dependent on the polarity of the solvent and the base. This was demonstrated for methyl 5-fe/-t-butylthio-4-mesyloxypentanoate which gave the trans-prodnct only on treatment with sodium methoxide in tetrahydrofuran when hexa-methylphosphoric triamide was used, the cw-product was formed predominantly (cisllrans 85 15). ... 

MoOPH [pronounced moof and more correctly oxidoperoxymolybdenum(aqua)-(hexa-methylphosphoric triamide)] is a molybdenum peroxide complex 245 that hydroxylates lithium enolates.39... 

In some instances Downie et al.1 found difficulty in separating the alkyl chloride from triphenylphosphine oxide. In such cases, triphenylphosphine can be replaced by hexamethylphosphorous triamide, [(CH3)2N]3P, which is converted into hexa-methylphosphoric triamide, [(CH3)2N ]3PO. 

Peptide synthesis. Based on analogy with use of onium salts derived from DMSO, Kenner and co-workers9 developed a useful new method of peptide synthesis. Tosic anhydride10 is allowed to react for 15 min. with excess hexa-methylphosphoric triamide to form the ditosylate (1). The solution is then cooled... 

Hexamethylphosphorio triamide, supplied by Eisher Scientific Company, was purified by distillation from sodium (approximately 6 g. per 500 ml.). The boiling point was 69° (1 mm.). In place of hexa-methylphosphoric triamide, tetrahydrofuran can be used, and 120 ml. of this solvent was slowly added over 30 minutes through a stainless steel cannula. Mallinckrodt analytical-reagent tetrahydrofuran was purified by distillation from a dark purple solution of disodium benzo-phenone dianion under nitrogen before use. The checkers used only hexamethylphosphorio triamide (see p. 103 for warning). 

CYCLOPROPANF.S Benzyltriethylammonium chloride. Dicobalt octacarbonyl. Lithium diethylamide-Hexamethylphosphoric triamide. Lithium diisoptopylamido-Hexa-methylphosphoric triamide. 

Examination of Solvent Effect on Nucleophilic Fluorination with KF/ dicvclohexano-18 crown-6. Using 1-bromodocosane (12) as substrate and KF/DC-18-C-6 as reagent system, solvent effect was examined. Solvents were chosen from common dipolar aprotic solvent [acetonitrile, hexa-methylphosphoric triamide (HMPT), dimethylsulfoxide (DMSO), diglyme], from weakly basic dipolar aprot c solvents (sulfolane, ethylene carbonate, propylene carbonate) " and from acid amide solvents [N,N-dimethylformamide (DMF), N,N-diethylacetamide (DEA), N-methyl-pyrrolidone (NMP), tetramethylurea]. ... 

When the reaction was carried out with ordinary magnesium in hexa-methylphosphoric triamide heating was required for several days. 

Aryloxysulfonylalkyllithiums can be converted to ketones in one pot by reaction with oxodiperoxymolybdenum(pyridine)(hexa-methylphosphoric triamide), his(trimethylsilyl) peroxide, or chlorodimethoxyborane/m-chloroperbenzoic acid. ... 

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