Cesium carbonate

Other Peroxohydrates. Potassium, mbidium, and cesium carbonates all form peroxohydrates having the general formula M2CO2 3H20. Crystal stmctures have not been estabflshed Raman spectra (31) confirm the presence of molecular hydrogen peroxide in the crystal. These compounds are unstable and have no commercial appHcation. 

Decomposition with Bases. Alkaline decomposition of poUucite can be carried out by roasting poUucite with either a calcium carbonate—calcium chloride mix at 800—900°C or a sodium carbonate—sodium chloride mix at 600—800°C foUowed by a water leach of the roasted mass, to give an impure cesium chloride solution that is separated from the gangue by filtration (22). The solution can then be converted to cesium alum [7784-17-OJ, CS2SO4 Al2(S0 2 24H20. Extraction of cesium from the poUucite is almost complete. Solvent extraction of cesium carbonate from the cesium chloride solution using a phenol in kerosene has also been developed (23). 

Magnesium is used to obtain cesium metal from cesium hydroxide [21351 -79-17, Cs(OH), cesium carbonate [534-17-8J, or cesium... 

Under anhydrous conditions, cesium carbonate or bicarbonate quantitatively cleaves an aryl dibenzoate or diacetate to the monoester yields are considerably lower with potassium carbonate. ... 

Cesium carbonate [534-17-8] M 325.8, m 792°(at red heat). Crystd from ethanol (lOmL/g) by partial evaporation. 

Using cesium carbonate in methanol, Kellogg and coworkers were able to convert catechol and pentaethylene glycol into benzo-18-crown-6 in 74% yield. They found that the cesium salts in these reactions were usually equal or superior to the potassium salts. 

The most demanding test of cesium carbonate as base was with 2,3-dihydroxypyridine (3-hydroxypyridone). The cesium salt was found to be fairly unstable, apparently oxidizing quite rapidly. Model reactions suggested that alkylation would occur 1,3 (N, 0) to give the substituted pyridone. Nevertheless, on the basis of UV and H-nmr analysis, the product of reaction between 2,3-dihydroxypyridine and tetraethylene glycol dibromide was assigned as the pyridocrown (23% yield, mp 77—78.5°) as shown in Eq. (3.60). 

Modification of the burning rates, pressure exponents, and temp coefficients of burning rate of the fluorocarbon composites has been accomplished with copper, lead, tin, sodium, ammonium and potassium fluoborates sodium, potassium, lithium, lead, copper and calcium fluorides potassium and ammonium dichromate lead and zinc stearate cesium carbonate potassium and ammonium sulfate copper chromite oxides of magnesium, copper and manganese boron zinc dust and carbon black (Ref 75)... 

This reaction is similar to 13-1 and, like that one, generally requires activated substrates. With unactivated substrates, side reactions predominate, though aryl methyl ethers have been prepared from unactivated chlorides by treatment with MeO in HMPA. This reaction gives better yields than 13-1 and is used more often. A good solvent is liquid ammonia. The compound NaOMe reacted with o- and p-fluoronitrobenzenes 10 times faster in NH3 at — 70°C than in MeOH. Phase-transfer catalysis has also been used. The reaction of 4-iodotoluene and 3,4-dimethylphenol, in the presence of a copper catalyst and cesium carbonate, gave the diaryl ether (Ar—O—Ar ). Alcohols were coupled with aryl halides in the presence of palladium catalysts to give the Ar—O—R ether. Nickel catalysts have also been used. ... 

Synthesis of 5,10,15,20-Tetrakis(4-(polyethyleneoxy)phenyl)) porphyrin. A slurry of polyethylene methylsulfonic ester (PEvoo-OMs) (20.0 g, 69% functionalized, Mn -780 Daltons) and anhydrous cesium carbonate (CS2CO3) (9.05 g, 27 mmol) in dry toluene (75 ttiL) was prepared and to this mixture a purple solution of 5,10,15,20-tetrakis(4-hydroxyphenyl)-21H,23H-porphine (2.9 g, 4.27 mmol) in 75 mL A. A-DMF was added. The reaction mixture was warmed to 95°C with stirring for 18 hours, then the temperature increased to 130°C for a further 5 hours before coohng. The purple-brown solid was collected by filtration, washed thoroughly with methanol and dried under vacuum to yield 21.0 g of the crude ligand, h NMR (toluene-dg, 80°C) 5 8.96 (s), 8.10 (d), 7.22 (d), 4.05 (t), 1.88 (quia), 1.58 (quin.), 1.31 (br. s), 0.88 (t). 

For the installation of the pyrrolidinylethanol moiety 10 on the aryl group, we first tested Buchwald s Cu-catalyzed conditions with 10, aryl iodide 12, Cs2C03, Cul and 1,10-phenanthroline at 110°C in toluene to prepare the penultimate 49 [14a], The reaction was very slow, giving only 5-10% conversion even after 2 days. The reaction was faster at higher temperatures but two impurities 50 and 51 were observed (Scheme 5.14). To find the optimal conditions, xylene and diglyme were tested as solvents, lithium, potassium and cesium carbonates were screened as bases and 2,2 -bipyridy], TMEDA and l-(2-dimethylaminoethyl)-4-methylpiperazine were examined as ligands. The optimized protocol was identified as 10mol% of... 

With the nitro group successfully introduced, the aromatic fluoride substituent in 11 was ready to undergo the nucleophilic aromatic substitution with the hydrox-ypyridine 9. The reaction proceeded smoothly in DMF at 55 °C using an equimolar amount of cesium carbonate as the base and provided a 90% isolated yield of 23 after crystallization. With compound 23 in hand, only the reduction of the nitro... 

A cobalt-catalyzed method for arylation of heteroarenes including thiazole and benzothiazole was reported in 2003 <030L3607>. According to this report, the direct C-5 arylation of thiazole with iodobenzene was carried out in the presence of cobalt catalyst [Co(OAc)2/IMes] and cesium carbonate, and a complete reversal of arylation from C-5 to C-2 was observed with the bimetallic Co/Cu/IMes system. This report has been retracted as the laboratory of the senior author has not been able to reproduce the key results disclosed in the communication <06OL2899>. 

Another example where PEG played the role of polymeric support, solvent, and PTC was presented by the group of Lamaty [72]. In this study, a Schiff base-proteded glycine was reacted with various electrophiles (RX) under microwave irradiation. No additional solvent was necessary to perform these reactions and the best results were obtained using cesium carbonate as an inorganic base (Scheme 7.64). After alkylation, the corresponding aminoesters were released from the polymer support by transesterification employing methanol in the presence of triethylamine. 

Dithiocarbamates have been prepared by the reaction of carbon disulfide with primary or secondary amines. The addition of DMF, cesium carbonate and a sulfonamide to the crude dithiocarbamate, give di-, tri- and tetra-substituted thioureas in 65-76% yields (Scheme 41).121... 

Intramolecular Michael addition.1 Cesium carbonate catalyzes the intramolecular Michael addition of a cyclic (3-keto ester to an a,(3-ynone to form a cyclic enone after protonation. This reaction proceeds readily when a five- or six-mem-bered ring is formed higher rings can be formed, but in low yield.1... 

The polymerization catalysts that are preferred because of their selectivity are the alkali metal (especially cesium) carbonates, tetraalkylammonium and bis(triphenylphosphoranylidene)ammonium (PPN) chlorides and bicarbonates (Table 4.2). Undesired side reactions are minimized by using relatively low (< 5% by weight) catalyst levels. Under these conditions, the fraction of cyclic oligomer was usually 5% or less and was easily removed from the desired polymer by Kugelrohr distillation. Conversions of 5 were essentially quantitative as judged by product weights and lack of detectable amounts of unreacted monomer by GPC. 

Cesium carbonate was found to be a far more efficient additive for purely alkyl-derived substrates 57r-w. Very useful enantioselectivities were obtained for all entries with the exception of a tertiary isobutyl-derived alkene 57u, which was converted with a respectable 90% ee. The yields were slightly lower for purely alkyl-derived substrates, but full conversions were reported by the authors. 

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