Hexamethylphos-phoramide

A. Indole Sodium. In a 100-ml., three-necked flask fitted with a reflux condenser, a magnetic stirring bar, and a gas inlet tube is placed 2.34 g. (0.02 mole) of indole (Note 1) and 15 ml. of hexamethylphos-phoramide (HMPA) (Note 2) under a static atmosphere of argon. The flask is cooled to 0° by means of an ice bath, and 0.53 g. (0.022 mole) of sodium hydride is added to the stirred solution over a period of 10 minutes (Note 3). The resulting slurry is then stirred for 5 hours at room temperature (Note 4). 

In the unusually effective reducing medium of sodium-hexamethylphos-phoramide (HMPA), [Mn(CO)5] underwent facile reduction to form a golden yellow to yellow brown solution. On the basis mainly of derivative chemistry and infrared spectra, the major soluble component was formulated as Na3[Mn(CO)4] (14). Once this materia] was in hand it was evident that similar binary carbonyl trianions should be possible for other rf-block transition elements of odd atomic number. Since 1976, syntheses of mononuclear binary carbonyl trianions of V, Nb, Ta, Re, Co, Rh, and Ir have also been reported from this laboratory (vide infra). Because these substances contain transition metals in their lowest known oxidation states, they have often been referred to as superreduced species (15). 

DDQ), yielding the product 126 in excellent yield (Equation 44) <1995T9531>. Trimethylsiliconide anion (Me3Si(—)), generated from hexamethyldisilane and sodium methoxide, reacts with pyridine in hexamethylphos-phoramide (HMPA) to afford 4-trimethylsilylpyridine in 92% yield <20010L1197>. 

Potassium chromate, K2Cr04, is used very rarely. It converts hydra-zomethane into azomethane [613]. In the presence of hexamethylphos-phoramide and crown ether, it transforms allylic and benzylic bromides into a,p-unsaturated aldehydes [614], and in the presence of dilute sulfuric acid, it oxidizes chlorohydroquinone to chloro-p-benzoquinone [615]. 

The conversion of ketones into a-hydroxy ketones can be achieved by the oxidation of enolates or enol ethers. A special reagent for enolates is the oxodiperoxy molybdenum complex with pyridine and hexamethylphos-phoramide. The reaction is applied to aromatic aliphatic ketones and cyclic ketones and furnishes 34-81% yields of a-hydroxy ketones with up to 26% of a-diketones (equation 401) [531]. 

There is also evidence for complexes with hexamethylphos-phoramide, 4-aminophenazone, and N-methyl and N-dimethyl acetamide. But an earlier report of a cupferron complex was not confirmed (39). 

In addition to the necessity for high-temperature SEC, each of the above solvents has its own drawbacks, such as adsorptive effects with phenol derivatives, column blocking, and carcinogenicity with hexamethylphos-phoramide and corrosion of stainless steel by the dimethylacetamide-LiCl mixture. 

REDUCTION OF ALKYL HALIDES AND TOSYLATES WITH SODIUM CYANOBOROHYDRIDE IN HEXAMETHYLPHOS-PHORAMIDE (HMPA) ... 

FeS cluster displacement experiments on Cp2 in 80% hexamethylphos-phoramide, Tris buffer + thiophenol yielded spectra very similar to those obtained by extruding clusters from C. pasteurianum ferredoxin (4Fe4S clusters) and quite dissimilar to that with bovine adrenodoxin which contains a 2Fe2S cluster (Orme-Johnson et ai, 1977). 

Mo(VI)03 in hydrogen peroxide, followed by addition of hexamethylphos-phoramide. The resulting precipitate is converted to a pyridine complex and used in that form. 

Octafluoro[2.2]paracyclophane is prepared by refluxing tetrahydrofuran (THF) and hexamethylphos-phoramide or DMSO solution from 1,4-bis (bromod-ifluoromethyl) benzene. Trimethylsilyltributyltin is used as a reducing agent [25]. Cesium fluoride as a catalyst gives superior yields (40%) in comparison to potassium fluoride. To favor the formation of rings, the reaction must be accomplished in highly diluted systems. 

Both the peroxo chromium etherate, VI, formed from reaction of H2O2 with acidic aqueous solution of chromates and ether, as well as the molybdenum complexes, VII, formed from reactions of H2O2 with M0O3 in the presence of hexamethylphos-phoramide(HMPA), selectively transfer oxygen to unsaturated organic molecules [93-95]. 

Displacement of nitro-groups by fluoride ion has been reported 2-fluoro-pyridine, 4-fluoropyridine, and 2-fluorothiazoIe (244) were prepared in 60, 60, and 20 % yield, respectively, by treating the corresponding nitro-compound with potassium fluoride in -methyl-2-pyrrolidone or hexamethylphos-phoramide. ... 

Phenylacetic acid allowed to react with Li-diisopropylamide in hexamethylphos-phoramide-tetrahydrofuran-hexane, then treated 2 hrs. at -15° with 0-methyl-hydroxylamine a-phenylglycine. Y 55.5%. - This is the first method reported for the direct conversion of carboxylic to a-aminocarboxylic acids. - Other aminating agents (s. original) gave lower yields. S. Yamada, T. Oguri, and T. Shioiri, Chem. Commun. 1972, 623. 

The next reaction to be studied was the decarboxylation reaction of 3-car-boxybenzisoxazole (Eq. [43]). The interest in this reaaion stems from the elegant and thorough investigation of the molecule and derivatives in various solvents by Kemp and co-workers.244445 Jhey discovered that the reaction rate can increase 10 -fold on going from aqueous solution to hexamethylphos-phoramide (HMPA). 

Anthrylmethyl can be readily attached, remains in place under a variety of circumstances, e. g. in acidified oxygen-containing solvents such as dioxane, and is readily removed under mild, highly specific conditions. - E 9-Anthrylmethyl mesitoate treated 30 sec. at 25° with Na-methylmercaptide in hexamethylphos-phoramide mesitoic acid. Y 93%. F. e. in dimethylformamide, also protection of phenols and mercaptans inch thiophenols, s. N. Kornblum and A. Scott, Am. Soc. 96, 590 (1974) protection of carboxyl groups as zl -oxazolines cf. A. I. Meyers et al., J. Org. Chem. 39, 2787 (1974). 

A mixture of isoquinoline and 3-5 molar equivalents NaH in hexamethylphos-phoramide warmed a few hrs. at 30-60° under Ng, then a soln. of benzoyl chloride in benzene added with ice-cooling 2-benzoyl-l,2-dihydroisoquinoline. Y 84%. F. e. s. M. Natsume et al., Tetrah. Let. 1973, 2335. 

A soln. of butyllithium in hexane injected by syringe at -78 under Ng into a stirred soln. of 7r-phenylsulfonyltricyclene in tetrahydrofuran-hexamethylphos-phoramide, allowed to warm to 0 during 0.5 hr., 3-methyl-l-chloro-2-butene added at -78 , and stirring continued 1 hr. while the temp, is allowed to rise... 

A soln. of 3,4-dimethoxybenzyl p-methoxyphenyl carbonate in hexamethylphos-phoramide heated to 140° when steady COg-evolution occurs, and kept at this temp, until conversion is complete after 1 hr. 3,4-dimethoxybenzyl p-methoxy-phenyl ether. Y 93%. F. e. s. J. M. Prokipcak and T. H. Breckles, Can. J. Chem. 49, 914 (1971). 

A mixture of 3-methyl-2-cyclohexenone, Li-diisopropylamide, hexamethylphos-phoramide, and tetrahydrofuran stirred 1 hr. at -60° under N2, then a soln. of ethyl a-phenylthiocrotonate in anhydrous tetrahydrofuran added at -75°, and stirred 1.5 hrs. at -70 to -50° ethyl l,3-dimethyl-5-oxo-2-(phenylthio)bicyclo-[2.2.2.]octane-2-carboxylate. Y 77%. F. e. s. H. Hagiwara, K. Nakayama, and H. Uda, Bull. Chem. Soc. Japan 48, 3769 (1975). 

Donating solvents such as hexamethylphos-phoramide or dimethylpropylurea give rise to upheld shifts which have been interpreted as caused by the formation of pentacoordinated complexes. The solvents shifts seem to follow Gutmann s donor number for solvents. 

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