Chemicals hexamethylphosphoramide

Mixtures of products are frequentiy observed. Oxidation by peroxycarboxylic acids usually give similar products (22). Several chemical oxidants give good yields of specific oxidation products. Dimethyl sulfoxide in aqueous acid gives oxindoles (23). In methanol, MoO HMPA (hexamethylphosphoramide) gives 3-hydroxy-2-methoxyindolines (24). 

Hexamethylphosphoramide was purchased from the Fisher Scientific Company and the Aldrich Chemical Company, Inc. It was distilled from calcium hydride prior to use. 

U(III) species and a second three-electron reduction to give U(0) metal. The first reduction, U(IV)/U(III) couple, is elec-trochemically and chemically irreversible except in hexamethylphosphoramide at 298 K where the authors report full chemical reversibility on the voltammetric timescale. The second reduction process is electrochemically irreversible in all solvents and only in dimethylsulfone at 400 K was an anodic return wave associated with uranium metal stripping noted. Electrodeposition of uranium metal as small dendrites from CS2UCI6 starting material was achieved from molten dimethylsulfone at 400 K with 0.1 M LiCl as supporting electrolyte at a platinum cathode. The deposits of uranium and the absence of U CI3, UCI4, UO2, and UO3 were determined by X-ray diffraction. Faradaic yield was low at 17.8%, but the yield can be increased (55.7%) through use of a mercury pool cathode. 

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. 

Chemicals AIBN CAN DIBAL DMAP DMSO HMPA LAH LDA mCPBA NBS NCS or PCC PDC Py TBAF TEMPO a.a -azobislisobutyronitrile) cerium(IV) ammonium nitrate diisobutylaluminium hydride 4-(dimethylamino)pyridine dimethyl sulfoxide hexamethylphosphoramide lithium aluminum hydride lithium diisopropylamide m-chloroperoxybenzoic acid A-bromosuccinimide A-chlorosuccinimide superoxide anion radical pyridinium chlorochromate pyridinium dichromate pyridine tetrabutylammonium fluoride 2,2,6,6-tetramethyl-l-piperidinyloxy free radical... 

HMPA, hexamethylphosphoramide, is toxic and a cancer-suspect agent. It was purchased from Tokyo Kasei Kogyo Co. or Aldrich Chemical Company, Inc. and distilled from calcium hydride under reduced pressure before use. When dimethylpropyleneurea (DMPU) was used in place of HMPA, none of the desired bis(trimethy silyl)benzene was obtained. 

Ashby J, Lefevre P. 1983. Genetic toxicology studies with formaldehyde and closely related chemicals including hexamethylphosphoramide (HMPA). In Gibson JE, ed. Formaldehyde toxicity. Washington, DC Hemisphere Publishing Corporation, 85-97. 

Cyclopentane-1,2,3,4-tetracarboxy lie 1,2 3,4-dianhydride (CpDA) was prepared from cis,cis,cis,cis-1,2,3,4-cyclopentanetetracarboxylie acid by thermal dehydration reaction then sublimation at 170-190 °C. Bicyclo[2.2.1]heptane-2,3,5,6-tetracarboxylic 2,3 5,6-dianhydride (BHDA) was synthesized according to the previous paper.[5] Bis(aminomethyl)bicyclo[2.2.1]heptane (BBH) was donated by Mitsui Chemical Co. Ltd, and used without further purification. BBH consists of four isomers 2-exo,5-exo- (30 wt %), 2-endo,5-exo- (35 wt %), 2-exo,6-exo- (20 wt %), 2-endofi-exo- (15 wt %). 4,4 -Methylenebis(2-methylcyclohexylamine) (MCHM) and hexamethylphosphoramide (HMPA) were purchased from Aldrich Chemical Co Inc and Tokyo Kasei Kogyo Co. Ltd, respectively, and used as received. 

When conditions of slow exchange are approached the chemical shift between the signals corresponding to the free and coordinated states becomes a function of the mean life-time of the complex. Thus the kinetics can be evaluated from shift measurements at different temperatures provided the temperature dependence of 4b, the shift in the absence of chemical exchange is known. This approach has been used by Bidzilya et al. (1975) to study the kinetics of exchange of the Pr(fod)3 and Eu(fod)3 adducts with hexamethylphosphoramide chloroform. For the analysis of the results a T temperature dependence was assumed for 4b of the praseodymium complex and a T dependence for the europium one. The enthalpies of activation thus obtained are much lower than those reported by Evans and Wyatt (1974) for the same adducts. It is not clear whether this discrepancy is due to a solvent effect or stems from some of the approximations involved in the data treatment. 

Note XI.2 Warning—toxic. Precaution—See the product safety bulletins from the supplier of the chemicals used in preparing these columns or before Benzyl Cyanide-Silver Nitrate Column X1.1.3 Hexamethylphosphoramide (HMPA) column, and XI. 1.4 Dimethylsufolane (DMS) Benzyl Cyanide-Silver Nitrate Column. 

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