With dimethyl

The reactions of aqueous solutions of nickel(II) salts with hydroxide ions, with excess ammonia, with sulphide ion and with dimethyl-glyoxime (see above) all provide useful tests for nickel(II) ions. 

Methyl and ethyl ethers of phenols are most conveniently prepared by alkylation with dimethyl sulphate and diethyl sulphate respectively in weakly alkaline solution, for example ... 

This substance may be conveniently methylated with dimethyl sulphate to 3deld 1-phenyl-2 3-dimethyl-5-pyrazolone or antipyrin (III) ... 

The most stable protected alcohol derivatives are the methyl ethers. These are often employed in carbohydrate chemistry and can be made with dimethyl sulfate in the presence of aqueous sodium or barium hydroxides in DMF or DMSO. Simple ethers may be cleaved by treatment with BCI3 or BBr, but generally methyl ethers are too stable to be used for routine protection of alcohols. They are more useful as volatile derivatives in gas-chromatographic and mass-spectrometric analyses. So the most labile (trimethylsilyl ether) and the most stable (methyl ether) alcohol derivatives are useful in analysis, but in synthesis they can be used only in exceptional cases. In synthesis, easily accessible intermediates of medium stability are most helpful. 

Thioglycosides can be activated for gfycosylation reactions with sulfur electrophiles, e.g., with dimethyl(methylthio)sulfonium triflate or with methanesulfenyi bromide and silver(l +) to form reactive sulfonium intermediates (F. Dasgupta, 1988). 

J. Rebek, Jr., (1987) first developed a new synthesis of Kemp s acid and then extensively explored its application in model studies. The synthesis involves the straightforward hydrogenation (A. Steitz, 1968), esterification and methylation of inexpensive 1,3,5-benzenetricar-boxylic acid (trimesic acid 30/100 g). The methylation of the trimethyl ester with dimethyl sulfate, mediated by lithium diisopropylamide (V. J. Shiner, 1981), produced mainly the desired aff-cis-1,3,5-trimethyl isomer, which was saponified to give Kemp s acid. 

As illustrated in Scheme 8.1, both 2-vinylpyrroles and 3-vinylpyiroles are potential precursors of 4,5,6,7-tetrahydroindolcs via Diels-Alder cyclizations. Vinylpyrroles are relatively reactive dienes. However, they are also rather sensitive compounds and this has tended to restrict their synthetic application. While l-methyl-2-vinylpyrrole gives a good yield of an indole with dimethyl acetylenedicarboxylate, ot-substitiients on the vinyl group result in direct electrophilic attack at C5 of the pyrrole ring. This has been attributed to the stenc restriction on access to the necessary cisoid conformation of the 2-vinyl substituent[l]. 

Alkylation of bis(4-methyl-2-thiazolyl)urea (257) with dimethyl sulfate gives product 258 dimethylated on the ring nitrogens (Scheme 154) (488). Alkylation of l-alkyl-3-(2-thiazolyl)urea from its derived anion formed by NaH gives 259 (Scheme 155). 

The reactivity of sulfathiazoles has been reviewed (65). Methylation in alkaline solution with dimethyl sulfate gives only the ring methylated derivative (85). Mixtures of products are obtained with diazomethane as alkylating agent (see p. 37). Other alkyl halides in aqueous alkali lead also to ring-alkylated products (85. 251, 650. 669-671). 

Treatment of 192 with dimethyl acetylenedicarboxylate yields a thiophene derivative (195) when R = Ph and a 2-p3Tidone (1S>6) derivative when R = H (Scheme 100). The proposed mechanism involves the formation of a mesoionic derivative (193) initially further dipolar addition yields adduct 194, the decomposition of which is dependent on the R substituent as described for related compounds (435). ... 

Like pyridines (334), thiazoles undergo addition reactions with dimethyl acetylenedicarboxylate leading to 2 1 molar adducts, the structure of which has been a matter of controversy (335-339). 

Under appropriate conditions 2-amino-4-alkylthiazoles are alkylated in the 5-position 2-acetylamino-4-methylthiazole reacts with dimethyl-amine and formaldehyde to afford the corresponding Mannich base (113) (372). 2-Amino-4-methyl-thiazole is alkylated in the 5-position by heat-... 

Allene can be converted to a tnmer (compound A) of molecular formula C9H12 Compound A reacts with dimethyl acetylenedicarboxylate to give compound B Deduce the structure of compound A... 

Poly(7-benzyl-L-glutamate) is known to possess a helical structure in certain solvents. As part of an investigationf of this molecule, a fractionated sample was examined in chloroform (CHCI3) and chloroform saturated ( 0.5%) with dimethyl formamide (DMF). The following results were obtained ... 

Ethylene glycol esterification of BHET is driven to completion by heating and removal of the water formed. PET is also formed using the same chemistry starting with dimethyl terephthalate [120-61-6] and ethylene glycol to form BHET also using an antimony oxide catalyst. 

The products are Hquids, soluble in various solvents and stable over prolonged periods. Monochloroborane is an equiUbtium mixture containing small amounts of borane and dichloroborane complexes with dimethyl sulfide (81). Monobromoborane—dimethyl sulfide complex shows high purity (82,83). Solutions of monochloroborane in tetrahydrofuran and diethyl ether can also be prepared. Strong complexation renders hydroboration with monochloroborane in tetrahydrofuran sluggish and inconvenient. Monochloroborane solutions in less complexing diethyl ether, an equiUbtium with small amounts of borane and dichloroborane, show excellent reactivity (88,89). Monochloroborane—diethyl etherate [36594-41-9] (10) may be represented as H2BCI O... 

Other approaches have explored the reaction of amines with dimethyl carbonate or its precursors (28). A reaction scheme for the production of polymeric MDI is as follows ... 

Subsequent studies (63,64) suggested that the nature of the chemical activation process was a one-electron oxidation of the fluorescer by (27) followed by decomposition of the dioxetanedione radical anion to a carbon dioxide radical anion. Back electron transfer to the radical cation of the fluorescer produced the excited state which emitted the luminescence characteristic of the fluorescent state of the emitter. The chemical activation mechanism was patterned after the CIEEL mechanism proposed for dioxetanones and dioxetanes discussed earher (65). Additional support for the CIEEL mechanism, was furnished by demonstration (66) that a linear correlation existed between the singlet excitation energy of the fluorescer and the chemiluminescence intensity which had been shown earher with dimethyl dioxetanone (67). 

Bromination. 1-Bromoalkanes are produced commercially by the anti-Markovnikow free-radical addition of HBr to a-olefins. These are further reacted with dimethyl amine to produce alkyldimethyl amines, which ultimately are converted to amine products for household cleaning and personal care. 

An analogue of the transesterification process has also been demonstrated, in which the diacetate of BPA is transesterified with dimethyl carbonate, producing polycarbonate and methyl acetate (33). Removal of the methyl acetate from the equihbrium drives the reaction to completion. Methanol carbonylation, transesterification using phenol to diphenyl carbonate, and polymerization using BPA is commercially viable. The GE plant is the first to produce polycarbonate via a solventiess and phosgene-free process. 

Some time earlier, Eastman-Kodak has been working on a novel polyester as an entry into the important polyester fiber market and had devised a new ahcychc diol, 1,4-cydohexanedimethanol [105-08-5] effectively made by exhaustive hydrogenation of dimethyl terephthalate. Reaction of the new diol with dimethyl terephthalate gave a crystalline polyester with a higher melting point than PET and it was introduced in the United States in 1954 as a new polyester fiber under the trade name Kodel (5). Much later the same polyester, now called PCT, and a cyclohexanedimethanol—terephthalate/isophthalate copolymer were introduced as mol ding resins and thermoforming materials (6). More recentiy stiU, copolymers of PET with CHDM units have been introduced for blow molded bottie resins (7). 

Wetting times of /V,/V-dimethy1-/ -alkyl amine oxides as a function of the alkyl chain length show a minimum with dimethyl dodecyl amine oxide (Table 3). Foam generation of dimethyl-/ -alkylamine oxides solutions show a maximum when the alkyl group contains 14 carbons. 

V,/V-dimethy1amino)pheno1 (177). In addition, 3-aminophenol may be methylated with dimethyl sulfate under neutral conditions, or its hydrochloride salt heated with methanol at 170°C under pressure for 8 h to give the desired product (178). The compound is used primarily as an intermediate in the production of basic (Red 3 and Red 11) and mordant (Red 77) dyes. 

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