Cesium with methanol, reaction

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). 

Rate studies of the reaction between cesium and water in ethylenediamine, using the stopped-flow technique, have been extended to all alkali metals. The earlier rate constant (k — 20 NT1 sec.-1) and, in some cases, a slower second-order process (k — 7 Af"1 sec.-1) have been observed. This is consistent with optical absorption data and agrees with recent results obtained in aqueous pulsed-radiolysis systems. Preliminary studies of the reaction rate of the solvated electron in ethylenediamine with other electron acceptors have been made. The rate constant for the reaction with ethylene-diammonium ions is about 105 NCl sec.-1 Reactions with methanol and with ethanol show rates similar to those with water. In addition, however, the presence of a strongly absorbing intermediate is indicated, which warrants more detailed examination. 

The reactions of all the alkali metals with water, of cesium and rubidium with methanol, of cesium with ethanol, and of cesium with HC1 and with NH4Br have been examined. Figure 1 shows a typical oscilloscope trace, and Figure 2 shows a plot of log absorbance vs. time for this trace. The reaction is pseudo-first-order in metal (since solute concentration is ten or more times greater than metal concentration), and the overall rate constants and their order in solute are obtained by varying solute concentration. 

Ethanol. Two runs with cesium and ethanol were carried out. Once again the overall reaction times were comparable with those using water. Traces giving two rate constants of 17.0 =t 3.8 and 5.4 M l sec.-1 were observed in some cases. The lower rate constant was obtained from a log k vs. log [EtOH] plot which had a slope of unity. Several traces exhibited nonreproducibility similar to that observed with methanol. 

Styrene (SM) can be synthesized in a single step via alkylation of toluene with methanol which offers significant advantages in raw material costs and energy consumption as compared to the benzene to styrene via ethylbenzene process. This single-step process is carried out at a temperature of 400°C and uses a cesium-boron type X zeolite catalyst. The reaction is [31] ... 

Vapor phase catalytic alkylation of phenols with methanol was carried out on various phosphates as catalysts. The best activity and selectivity was observed on boron, rare-earth and niobium phosphate. With boron phosphate, the reaction is very selective for O-alkylation even at high temperature. On this catalyst o-methoxy-phenol is selectively obtained from 1-2-dihydroxybenzene. With rare-earth phosphate calcinated at 400°C and with niobium phosphate, O-alkylation selectivity decreases with an increase of reaction temperature. For rare-earth phosphates it is possible to improve the selectivity by calcination at higher temperature or by a wetness impregnation of cesium hydrogenophosphate. An explanation of these results is proposed. 

Methyl terf-butyl ether (MTBE) is an important industrial product used as oxygenate additive in reformulated gasoline. Environmental concern makes its future uncertain, however. Although mainly manufactured by reaction of isobutylene with methanol, it is also produced commercially from methanol and fcrr-butyl alcohol, a by-product of propylene oxide manufacture. Numerous observations from the use of heteropoly acids have been reported. These compounds were used either as neat acids [74], or supported on oxides [75], silica or K-10 montmorillonite [76]. They were also used in silica-included form [77] and as acidic cesium salts [74,77]. Other catalysts studied were sulfated ZrOj [76], Amberlyst 15 ion-exchange resin [76], HZSM-5 [76], HF-treated montmorillonite, and commercial mineral acid-activated clays [75]. Hydrogen fluoride-treatment of montmorillonite has been shown to furnish particularly active and stable acid sites thereby ensuring high MTBE selectivity (up to 94% at 413 K) [75]. 

Addmon of cesium fluoroKysuIfate to olefins gives vicinal fluoroalky I sulfates with low regio- and stereoselectivity [162, 16J] (equations 12 and 13) Reactions of this reagent with olefins in methanol or acetic acid give vicinalfluoroalkyl methy I ethers or acetates, respectively [164, 165 166] (equation 14), with a predominance... 

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. 

Cesium p-nitrobenzoate, p-NO,C6H4COOCs (1). The salt is prepared by reaction of the acid with Cs2CO, in aqueous methanol. 

Dimethyl- and l,3-dimethyl-5-halo-substituted uracil derivatives react with cesium fluor-oxysulfate under mild reaction conditions. The reaction carried out in an acetonitrile/water mixture or in an alcohol (methanol, ethanol, propan-2-ol or /a7-butyl alcohol) results in the regioselective formation of 5-fluoro-6-hydroxy- or 6-alkoxy-5-lluoro-l, 3-dimethyl-5,6-dihydro-uracil derivatives 27, respectively, while the stereochemistry of the reaction is strongly syn predominant.29... 

The complications which result from the hydrolysis of alkali metal cyanides in aqueous media may be avoided by the use of non-aqueous solvents. The one most often employed is liquid ammonia, in which derivatives of some of the lanthanides and of titanium(III) may be obtained from the metal halides and cyanide.13 By addition of potassium as reductant, complexes of cobalt(O), nickel(O), titanium(II) and titanium(III) may be prepared and a complex of zirconium(0) has been obtained in a remarkable disproportion of zirconium(III) into zirconium(IV) and zirconium(0).14 Other solvents which have been shown to be suitable for halide-cyanide exchange reactions include ethanol, methanol, tetrahydrofuran, dimethyl sulfoxide and dimethylformamide. With their aid, species of different stoichiometry from those isolated from aqueous media can sometimes be made [Hg(CN)3], for example, is obtained as its cesium salt form CsF, KCN and Hg(CN)2 in ethanol.15... 

Methanol. Rubidium reacted with one methanol concentration, and two runs were made with cesium using several concentrations of methanol. While reaction times were comparable to those observed in the water reactions, several marked differences were apparent. In some cases two rates were observed, but the constants were not reproducible. More striking was the fact that the shapes of the traces themselves differed from picture to picture, and with dilute solutions seemed to indicate that an absorbing intermediate was formed. For these reasons we do not report any rate constants at this time. 

Electrochemical fluorination of pyridine in the presence of a source of fluoride ion gave 2-fluoropyridine in 22% yield (85M11). With xenon difluoride, pyridine formed 2-fluoropyridine (35%), 3-fluoropyridine (20%), and 2,6-difluoropyridine (11%) in a reaction unlikely to be a conventional electrophilic substitution. Xenon hexafluoride has also been used (76JFC179). With cesium fluoroxysulfate at room temperature in ether or chloroform, the major product was 2-fluoropyridine (61 and 47%, respectively). Some 2-chloropyridine was also formed in chloroform solution. In methanol the entire product was 2-methoxypyridine (90TL775). Fluorine, diluted with argon in acetic acid, gave a 42% yield of the 5-fluoro derivative of l-methyl-2-pyridone [82H( 17)429],... 

Cesium-exchanged zeolite X was used as a solid base catalyst in the Knoevenagel condensation of benzaldehyde or benzyl acetone with ethyl cyanoacetate [121]. The latter reaction is a key step in the synthesis of the fragrance molecule, citronitrile (see Fig. 2.37). However, reactivities were substantially lower than those observed with the more strongly basic hydrotalcite (see earlier). Similarly, Na-Y and Na-Beta catalyzed a variety of Michael additions [122] and K-Y and Cs-X were effective catalysts for the methylation of aniline and phenylaceto-nitrile with dimethyl carbonate or methanol, respectively (Fig. 2.37) [123]. These procedures constitute interesting green alternatives to classical alkylations using methyl halides or dimethyl sulfate in the presence of stoichiometric quantities of conventional bases such as caustic soda. 

In a similar way, 2-oxazolidinones and tetrahydro-2//-l, 3-oxazin-2-ones have been prepared by the reaction of primary allyl amines and homoallyl amines10, respectively, with carbon dioxide and iodine in methanol via an intramolecular cyclization. Prolonged reaction for a week in the presence of cesium carbonate increases the yield to 70-90%. This reaction has a large applicability and the ease of the method makes it useful in organic synthesis. 

Reaction of the monocyanoethyl-protected TTF 738 with cesium hydroxide in a mixture of methanol and DMF led to the deprotected thiolate, which was further alkylated with the bromobutyl-substituted MOM-triptycene 739 to give the MOM-TTF 740 in 89% yield (MOM = methoxymethyl). The MOM protecting group was removed quantitatively under acidic conditions and the resulting hydroquinone was oxidized to yield the TTF-quinone 741 in 54% yield (Scheme 109). The preparation of the pyrrolo-TTF derivatives 25 was accomplished in a similar way <1998JOC1198>. 

Davis and coworkers carried out a Wittig-cyclization sequence with the partially protected 2-deoxyamino sugar 191 using an amino acid based phosphonate. Reaction of 191 with the cesium enolate 192 gave a 53% yield of epimers 193 and 194 (1 1 ratio) in which epimerization of the 2-amino group had taken place. The maimo isomer 194 was then epimerized to the more stable gluco 193 derivative by simple treatment with t-BuOLi in methanol (Scheme 38) [54]. 

---