Dioxane nickel

Raney nickel catalyst evaporated with small amounts of methanol, ethanol, isopropanol, pentanol, acetone, benzene, cyclohexane or p-dioxane and then heated towards 200°C eventually explodes See 1,4-Dioxane Nickel... 

C8H1iCdCl2N03, Dichloro(pyridoxine)cadmium(II), 44B, 964 C8H1gBr2Hg04, 1,4-Dioxane mercury II) bromide, 37B, 562 C8H1gBr2Ni04, Dibromobis(1,4-dioxan)nickel(II), 43B, 1353 C8H,6CI2CUO4, 1,4,7,10-Tetraoxacyclododecanecopper(II) chloride,... 

Nickel Aluminum, aluminum(III) chloride, ethylene, 1,4-dioxan, hydrogen, methanol, nonmetals, oxidants, sulfur compounds... 

Displacement of aromatic halogen in 2,4-diiodo-estradiol with tritiated Raney nickel yields 2,4-ditritiated estradiol. Aromatic halogen can also be replaced by heating the substrate with zinc in acetic acid-OD or by deuteration with palladium-on-charcoal in a mixture of dioxane-deuterium oxide-triethylamine, but examples are lacking for the application of these reactions in the steroid field. Deuteration of the bridge-head position in norbornane is readily accomplished in high isotopic purity by treatment of the... 

Polymerization of alkynes by Ni" complexes produces a variety of products which depend on conditions and especially on the particular nickel complex used. If, for instance, O-donor ligands such as acetylacetone or salicaldehyde are employed in a solvent such as tetrahydrofuran or dioxan, 4 coordination sites are available and cyclotetramerization occurs to give mainly cyclo-octatetraene (cot). If a less-labile ligand such as PPhj is incorporated, the coordination sites required for tetramerization are not available and cyclic trimerization to benzene predominates (Fig. A). These syntheses are amenable to extensive variation and adaptation. Substituted ring systems can be obtained from the appropriately substituted alkynes while linear polymers can also be produced. 

The perhydroisoindole system can be prepared by high-pressure hydrogenation of the isoindole over nickel on alumina at elevated temperatures. The use of Raney nickel with dioxane in the reduction of l,3-diphenyl-2-methylisoindole (47) gives the perhydro product (96), accompanied by the isoindoline (97). An alternative route to partially hydrogenated isoindoles has been described in Section III, D. 

The benzodiazepine 4-oxide 5 (15 g, 50 mmol) in warm dioxane (200 mL) was cooled to 20 C and hydrogenated at atmospheric pressure in the presence of Raney nickel (20 g). The theoretical volume of hydrogen had been absorbed after 2 h. The precipitated product was dissolved by heating tile mixture and the catalyst was removed by filtration. The product separated yield 14.1 g (99.5%) yellowish plates mp 240-241 C (acetone). 

Transformation of the amino nitriles to the corresponding amino acids, with removal of the dioxane ring, is carried out in two steps. Treatment with concentrated hydrochloric acid results in the hydrolysis of both the nitrile and the acetal group, and in cyclization to the corresponding 3-substituted 5-hydroxyniethyl-3-methyl-2-oxo-6-phenylmorpholinc hydrochlorides. Oxidative cleavage with 2 N sodium hydroxide solution, air and Raney nickel at 120 CC (ca. 30 h) delivers the hydrochlorides of the free a-methylamino acids in high yield. 

In the case of the hexacarbonyls, the rate-expression contains not only the same type of first-order term but in addition one second-order overall. For good entering groups (but not CO, for example) the rate expression contains a term strictly first-order in both the complex and the entering nucleophile. The first-order rates of CO exchange are practically identical with the rates of substitution in hydrocarbon solvents, but there is nevertheless some acceleration in ether (THF, dioxan) solutions. This solvent-dependence is not so well-marked ° as in the case of nickel tetracarbonyl. The second-order rate of substitution very strongly depends upon the basicity of the entering nucleophile... 

Isopropyl (/ )-( —)-methylphosphinate (134) has been prepared" in > 90% optical purity by Raney nickel desulphurization of optically pure O-isopropyl (5)-(-f-)-methyIphosphonothioate (135). The phosphonate (134) is rapidly racemized by base, but not by acid, unlike secondary phosphine oxides"" [although whether these have been prepared optically active now seems doubtful (see Chapter 4)]. The phosphinate (134) can be reconverted into 89% optically pure (5)-( + )-(135) by addition of sulphur in dioxan. As shown in the Scheme, a series of interconversions has been used to establish the configurations. 

Besides palladium catalysts, nickel was also found to be an effective catalyst for the Sonogashira reaction in aqueous media. Recently, Beletskaya et al. reported a Ni(PPh3)2Cl2/CuI-catalyzed Sonogashira coupling reaction of terminal acetylenes with aryl iodides in aqueous dioxane in high yields (Eq. 4.19).39... 

Dioxane reacts with Raney nickel catalyst almost explosively above 210°C. 

Nickel used nitromethane and acetonitrile for the titration of primaquine and other basic pharmaceuticals in various solvents with 0.05 N perchloric acid in dioxane [9]. Half-neutralizaton potentials were determined in acetonitrile, methyl nitrite, and acetic acid anhydride with respect to pyramidon, arbitrarily taken as 500 mV and were shown in a table. 

The choice of solvent can also be beneficial in another respect. This possibility was highlighted by the findings of Cioffi on the Raney Nickel catalyzed hydrogen-deuterium exchange of a model carbohydrate [l-0-methyl-/l-D-galactopyranoside] but under ultrasonic irradiation (Tab. 13.2) [43], Extensive deuteration at C-4 position occurred for a series of ethereal solvents, the C-3 position was deuterated by seven solvent systems and the C-2 position deuterated less extensively, also by seven solvent systems. For l,4-dioxane-D20 no labeling at the C-2 position occurred and for l,2-dimethoxyethane-D20 no C-3 labeling was observed. 

Desymmetrization of cyclic allyl acetals such as 2-substituted 4,7-hydrodioxepins or 5-methylene-1,3-dioxanes was investigated using ruthenium or nickel catalysts. The isomerization of the dioxanes was accomplished using Ru2Cl4(DIOP)/LiBHEt3 in high yield with up to 38% ee (Equation (22)).81... 

Reductive desulfurizations with Raney nickel have been conducted in absolute alcohol, aqueous alcohol, dioxane, and ether, the first two solvents being most frequently used. Presumably any neutral solvent, containing neither halogen nor sulfur and not readily reduced, could be employed. 

Mesylation of alcohol 14 and hydrolysis of the acetal with oxalic acid leads to the key decalone 16 which cyclises in the presence of NaH in dioxane to afford twistanone 17 in quantitative yields. The elimination of the carbonyl group was carried out by an alternative method to the Wolff-Kishner reduction, which involves the thioacetalisation of the twistanone (18) with ethane-1,2-dithiol and removal of the resulting thioacetal by Raney nickel in boiling ethanol (62% yield). 

A. 2,4,6-Tnphenylaniline. To a filtered solution of 70 g. (0.20 mole) of 2,4,6-triphenylnitrobenzene (Note 1) in 500 ml. of dioxane (total volume ca. 540 ml.) in a 1-1. pressure vessel equipped with a magnetic stirrer is added 10 g. of Raney nickel catalyst (Note 2) that has been previously rinsed with absolute ethanol. The head and fittings are attached, and the vessel is connected to a hydrogen cylinder. The system is alternately... 

With palladium catalysts aromatic chlorides are rather unreactive, however, nickel is able to catalyze the reactions of these substrates, too. The water-soluble catalyst was generated in situ from the easily available [NiCl2(DPPE)] and an excess of TPPTS by reduction with Zn in mixtures of 1,4-dioxane and water. Although it had to be used in relatively large quantities (10 mol %), the resulting compound catalysed the cross-coupling... 

Schrauzer, Mayweg and Heinrich have reported the preparation of the complex 5 from the reaction of aqueous nickel(ll) chloride with a reaction mixture of benzoin in dioxane and phosphorus(V) sulfide. The parent acid and its salts have not been characterized. The only other closed ring complex, 6, was isolated in low yield (3%) subsequent to the reaction of nickel (II) acetate with the mixture resulting from the reaction of 1,3-propanediol with phosphorus(V) sulfide. As for 5, the parent acid and its salts were not... 

Stereoselective) additions of nucleophiles to 5-alkylidene Meldmm s acid as displayed in Scheme 17 (Section 8.11.6.1.3) <2006TA2957, 2007AGE4964> and to the carbonyl group of 2,2-dimethyl-l,3-dioxan-5-one (Scheme 47, Section 8.11.6.3.3) either in a three component transformation <2006OL3689> or in a nickel-catalyzed reaction... 

An N-heterocyclic carbene ligand, formed from l,3-bis-(2,4,6-trimethylphenyl)-3//-imidazol-l-ium chloride and cesium carbonate, with dipalladium tris(dibenzylideneacetone) gave excellent yields (93-96% yields) in the Suzuki coupling of 2-chloropurines and arylboronic acids in anhydrous dioxane <2001TL8751>. The combination of an imidazolium-carbene and nickel(O) bis(cyclooctadiene) formed a catalyst capable of insertion into the C-F bond of 6-fluoropurine nucleosides (Scheme 35) <20050L1149>. 

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