Hexamethyl phosphoric triamid

Hydroxymethylene formation proceeded in the standard fashion (7 ) to give a 93% yield of 22. Carcinogenic hexamethyl-phosphoric triamide was replaced by N-methylpyrrolidone as the solvent for the condensation reaction of 22 with the bromo-butenolide 23 in the presence of excess K.CO. and gave a mixture of racemic strigol (1) (35%) and 4 -epistrigol (25) (39%), which were readily separated by chromatography on silica gel. 

Intensive studies concerning the photoreductive cyclization of distinct ketones and aldehydes are made by Cossy et al. [170], They describe how bicyclic tertiary cycloalkanols 173 and 174 can be prepared from, s-un-saturated ketones 172 in good yields, initiated by photoinduced electron transfer from triethylamine in acetonitrile or by photoionization in pure hexamethyl-phosphoric triamide (HMPA) [171, 172], The reaction is stereo-, chemo- and... 

Synonyms HMPA HMPT HPT hexamethyl phosphoric triamide... 

Figure 2.3 Variable-temperature H NMR spectra recorded in a hexamethyl phosphoric triamide solution of 2,6-dihydroxybenzoic acid at 135, 163, 177, and 240 K. (Reproduced with permission from ref. 26.)...

For the alkylation of tnetallated acetylenes, diethyl ether and tetrahydrofuran are unsuitable solvents, unless a certain amount of dimethyl sulfoxide (DMSO) or hexamethyl-phosphoric triamide (HMPT) is added. Alkylations in liquid ammonia with higher alkyl bromides are also slow, though addition of DMSO or HMPT followed by evaporation of (pan of) the ammonia in most cases gives rise to a smooth conversion. For methods of purifying, solvents, one should consult our previous book [ I, Chapter I). 

Selective chlorination or bromination of the 5 -hydroxyl group in unprotected D-ribonucleosides has been achieved75 by treatment with thionyl chloride or thionyl bromide, respectively, in hexamethyl-phosphoric triamide at room temperature for 10-15 hours the 5 -deoxy-5 -halogeno derivatives of cytidine and adenosine have been prepared in this way. The reactions presumably occur by way of alkoxyphosphonium salts as intermediates.78... 

BICYCLOANNELATION Hexamethyl-phosphoric triamide. Isopropenyl-tri-phcnylphosphonium bromide. Phenyl vinyl sulfone. 

Further improvements in dehalogenation selectivity and yields can be achieved by using dipolar aprotic solvents. Dimethylformamide has mostly been used for this purpose,18,56,84 97 although dimethyl sulfoxide,98,99 especially when combined with sonication at room temperature (vide infra), deserves attention in particular cases.100,101 Other polar and dipolar aprotic solvents have also been used, namely, acetone,4 butan-2-one,4 acetonitrile,102 acetic anhydride,103104 ethyl acetate,61 tetrahydrothiophene 1,1-dioxide (sulfolane)105 and hexamethyl-phosphoric triamide,106 but no details were reported on their advantages over dimelhylform-amide or dimethyl sulfoxide. Better performance of dipolar aprotic solvents, such as dimethyl-formamide, over other solvents has been demonstrated in the recent comparison of the dehalogenation of 4,5-dichloro-4,5,5-trifluoropentan-l-ol (4) with zinc in various solvents.90... 

Multiple, but not complete, substitution of fluorine by sulfur nucleophiles proceeds under conditions rather similar to those for single elimination, i.e. generally in diethylene glycol/ pyridine mixture with sodium hydroxide as base, but with an increased molar ratio of the respective thiol, corresponding to the number of fluorines to be eliminated. On reaction in ethylene glycol/ pyridine, rather than in dimethylformamide or, particularly, in hexamethyl-phosphoric triamide, at least two fluorine atoms remain in the molecule, even under drastic... 

Potassium r-butoxide-Hexamethyl-phosphoric triamide, 252 Potassium r-butoxide-Xonotlite, 254 Potassium hydroxide, 258 Potassium hydroxide-18-Crown-6, 258 Potassium hydroxide-Tricaprylyl-methylammonium chloride, 258 Sodium hydroxide-Methyltrioctyl-ammonium chloride, 192 Sodium hydroxide-Triethyl(2-methyl-butyl)ammonium bromide, 239 Sodium hydroxide-N-(p-Trifluoro-methylbenzyl)cinchoninium bromide, 325... 

Trimethylsilyllithium-Hexamethyl-phosphoric triamide, 328 Trimethylstannylmethyllithium, 331 Trityllithium, 338 Magnesium Compounds Allylmagnesium bromide, 73 1,5-Bis(bromomagnesio)hexane, 138 1,4-Bis(bromomagnesio)pentane, 138 t-Butyllithium-Magnesium bromide, 58 Butylmagnesium bromide, 203... 

Oxaziridines, 276, 277 2-Oxazolidones, chiral, 379-381 2-Oxazoline-5-ones, 151 Oxazolines, 147, 265, 588 Oxime sulfonates, 245-246 jx-Oxobis(chlorotriphenylbismuth), 381-382 Oxodiperoxymolybdenum(pyridine)(hexamethyl phosphoric triamide), 382-383 p,3-Oxohexakis( x-triinethylacetato)trimethanol-triiron(ffl), 382-383 a-Oxoketene dithioacetals, 185 Oxomethoxymolybdenum(V) 5,10,15,20-totraphcnylpoiphyrin, 383 Oxone, 442 Oxosulfenylation, 205... 

Hexamethyl phosphoric triamide l-Chloro-4-acetoxy-2-methyl-2-butene Sodium amide... 

Alkyl Chlorides. 3-Chloropentane was prepared by the reaction of thionyl chloride with 3-pentanol. Hexamethyl-phosphoric triamide, HMPT, was used as a complexing agent to ensure substitution at the 3 position (17). The organic layer was dried with magnesium sulfate and distilled. The middle fraction, b.p. 104°C, was collected for use. 1-Chloropentane was purified by repeated distillations. The above preparation procedures ensure maximum purity of the compounds for ESR study. 

Cyclopentanols 214 and 217 are synthesized by intramolecular ketyl radical addition to tethered olefin by a photochemically induced electron-transfer activation of 8,co-unsaturated ketones 213 and 216, respectively, using either hexamethyl-phosphoric triamide (HMPA) or triethylamine in CH3CN [98] as solvent (see Scheme 8.59). 

The first reaction of this type was reported by Lippard et al. in 1988 the reaction of 2-cyclo-hexenone (3) with Grignard reagents in the presence of the chiral aminotroponeimine copper complex 5 as catalyst gave the 1,4-adducts 4 with 4- 14 % ee [3a]. The selectivity was increased to 74 % ee by addition of hexamethyl-phosphoric triamide (HMPA) and silyl halides [3b]. 

Unfortunately, donor numbers have been defined in the non-SI unit kcal mol b Marcus has presented a scale of dimensionless, normalized donor numbers DN, which are defined according to DN = DNl i%.% kcal mol ) [200]. The non-donor solvent 1,2-dichloroethane [DN = DN = 0.0) and the strong donor solvent hexamethyl-phosphoric triamide (EiMPT DN = 38.8 kcal mol DN = 1.0) have been used to define the scale. Although solvents with higher donicity than EiMPT are known [cf. Table 2-3), it is expedient to choose the solvent with the highest directly [i.e. calori-metrically) determined DN value so far as the second reference solvent [200] f The DN values are included in Table 2-3. 

Although the solvent effects are small, the alkene formation diminishes as predicted with increasing water content (corresponding to increased solvent polarity). The Sn2/E2 reaction of 2-phenylpropyl tosylate with sodium cyanide (in hexamethyl-phosphoric triamide and in A,A-dimethylformamide as solvents at 100 °C) gives a-methylstyrene (elimination product) and l-cyano-2-phenylpropane (substitution product) [75]. It has been found, in accordance with the predictions of the Hughes-Ingold rules, that the elimination/substitution ratio decreases as the polarity of the solvents (measured by the relative permittivity) increases [75]. Theoretical investigations of the... 

For electrolysis with the hydrogen anode we use a mixture of THF and HMPA (hexamethyl-phosphoric triamide) with 0.02 M Et4NBF4 as solvent/electrolyte system. Trying to find a substitute for HMPA, we tested several rotic solvents, known to replace HMPA very effectively in organic synthesis (see Table 1). 

SYNS EASTMAN INHIBITOR HPT ENT 50,882 HEMPA HEXAMETAPOL HEXAMETHYLPHOS-PHORIC ACID TRIAMIDE (MAK) HEXAMETHYL-PHOSPHORIC TRIAMIDE N,N,N,N -HEXA-... 

In the presence of phosphorus(III) reagents such as triphenylphosphine or hexamethyl-phosphorous triamide the trihaloethyl esters are reduced in situ yielding activated acyloxy-phosphonium intermediates that undergo trapping by amine and alcohol nucleophiles.h l... 

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