Dimethyl hydration

Acetyl-3-mercaptopropanol reacts with acetaldehyde in the presence of hydrazine hydrate to yield 2,4-dimethyl-5-(/3-hydroxyethyl)thiazole (10), R, = Rj = Me, R3 = CH2CH2OH (556). 

Vinyl chloride reacts with sulfides, thiols, alcohols, and oximes in basic media. Reaction with hydrated sodium sulfide [1313-82-2] in a mixture of dimethyl sulfoxide [67-68-5] (DMSO) and potassium hydroxide [1310-58-3], KOH, yields divinyl sulfide [627-51-0] and sulfur-containing heterocycles (27). Various vinyl sulfides can be obtained by reacting vinyl chloride with thiols in the presence of base (28). Vinyl ethers are produced in similar fashion, from the reaction of vinyl chloride with alcohols in the presence of a strong base (29,30). A variety of pyrroles and indoles have also been prepared by reacting vinyl chloride with different ketoximes or oximes in a mixture of DMSO and KOH (31). 

Trifluoromethylpteridine and its 7-methyl and 6,7-dimethyl derivatives (69JCS(C)l75l) are, as expected, even more subject to hydration. The first two are essentially completely hydrated across the 3,4-double bond at equilibrium in neutral solution and the last is partly hydrated. On dissolution of 4-trifluoromethylpteridine in aqueous acid the 5,6,7,8-dihy-drated cation is the main product initially, rearranging more slowly to the thermodynamically more stable 3,4-hydrate. 

There is also evidence for stable 3,4-adducts from the X-ray analysis of 2-amino-4-ethoxy-3,4-dihydropteridinium bromide, the nucleophilic addition product of 2-aminopteridine hydrobromide and ethanol (69JCS(B)489). The pH values obtained by potentiometric titration of (16) with acid and back-titration with alkali produces a hysteresis loop, indicating an equilibrium between various molecular species such as the anhydrous neutral form and the predominantly hydrated cation. Table 1 illustrates more aspects of this anomaly. 2-Aminop-teridine, paradoxically, is a stronger base than any of its methyl derivatives each dimethyl derivative is a weaker base than either of its parent monomethyl derivatives. Thus the base strengths decrease in the order in which they are expected to increase, with only the 2-amino-4,6,7-trimethylpteridine out of order, being more basic than the 4,7-dimethyl derivative. 

X-ray, 4, 160 (79AX(B)2228> lH-Pyrrole-2,4-diamine, 1-t-butyl-JV, JV -dimethyl-3-phenyl-JV -phenylsulfonyl-X-ray, 4, 160 (78BSB893) lH-Pyrrole-3-methanol, 4-acetyl-X-ray, 4, 160 (78AX(B)1248> lH-Pyrrole-3-methanol, 4-acetyl-, hydrate X-ray, 4, 160 (78AX(B)1248> lH-Pyrrole-3-propanoic acid, ester C NMR, 4, 172 (74JCS(P2)1004>... 

The equilibrium constants for addition of alcohols to carbonyl compounds to give hemiacetals or hemiketals show the same response to structural features as the hydration reaction. Equilibrium constants for addition of metiianoHb acetaldehyde in both water and chloroform solution are near 0.8 A/ . The comparable value for addition of water is about 0.02 The overall equilibrium constant for formation of the dimethyl acetal of... 

Manske has isolated from several papaveraceous plants an alkaloid aurotensine (items 9, 19, 23, 44, 47, 48 list, pp. 170-3) which occius in rhombic plates, m.p. 128° [a]n — 69-9° and appears to be an addition compound of I- and di-scoulerine (Manske ). Its dimethyl ether caseanine item 10 list, p. 170), m.p. 115-6° (hydrated) or 142° (ex benzene) must be tetrahydropalmatine (p. 292) and casealutine, found with caseanine, was shown later by Manske to be i-isocorypalmine. 

The cation of 4,4 -biquinazolinyl and its 2,2 -dimethyl derivative readily add water across the 3,4- and 3, 4 -double bonds, but the cation of 2,2 -biquinazolinyl is not hydrated. Hydration in the 4,4 -isomers has been attributed to restricted rotation about the 4,4 -bond, a steric effect which is relieved by hydration. The ultraviolet spectrum of 2,2 -biquinazolinyl (neutral species and cation) shows that there is considerable conjugation between the quinazoline groups. Covalent hydration is absent from the latter compound because it would otherwise destroy the extended conjugation present. 

The ratio, at equilibrium, of the hydrated to anhydrous forms (for both neutral species and anions) has been measured for the following 2-hydroxjrpteridine and its 4-, 6-, and 7-methyl and 6,7-dimethyl derivatives 6-hydroxypteridine and its 2-, 4-, and 7-methyl derivatives 2,6-dihydroxypteridine and 2-amino-4,6-dihydroxypteridine. The following showed no evidence of hydration 4- and 7-hydroxy-pteridine 2,4-, 2,7-, 4,7-, and 6,7-dihydroxypteridine and 2-amino-4-hydroxypteridine. The kinetics of the reversible hydration of 2-hydroxypteridine and its C-methyl derivatives (also 2-mercapto-pteridine) have been measured in the pH region 4-12, and all these reactions were found to be acid-base cataljrzed. The amount of the hydrated form in the anions is always smaller than in the neutral species, but it is not always negligible. Thus, the percentages in 2-hydroxy-, 2-hydroxy-6-methyl-, 2-mercapto-, and 2,6-dihydroxypteridine are 12, 9, 19, and 36%, respectively (see also Table VI in ref. 10). 

Similar analyses of 2-methyl-, 2,3-dimethyl-, 2,3,6-trimethyl-, and 2,3,6,7-tetramethyl-l,4,5,8-tetraazanaphthalene showed that all the neutral species were anhydrous. Whereas the cations (in aqueous solution) of the 2-methyl and 2,3-dimethyl derivatives were predominantly ( > 95%) hydrated, the 2,3,6-trimethyl cation had only a trace of hydrated species and that of the 2,3,6,7-tetramethyl derivative was anhydrous. ... 

The classical procedure for the Wolff-Kishner reduction—i.e. the decomposition of the hydrazone in an autoclave at 200 °C—has been replaced almost completely by the modified procedure after Huang-Minlon The isolation of the intermediate is not necessary with this variant instead the aldehyde or ketone is heated with excess hydrazine hydrate in diethyleneglycol as solvent and in the presence of alkali hydroxide for several hours under reflux. A further improvement of the reaction conditions is the use of potassium tcrt-butoxide as base and dimethyl sulfoxide (DMSO) as solvent the reaction can then proceed already at room temperature. ... 

A third method of converting citronellol into rhodinol is by hydrating citronellol by means of 30 per cent, sulphuric acid. This yields the glycol 3-7-dimethyl octanediol-1-7, of the formula—... 

The reaction occurs in the liquid phase at relatively low temperatures (about 50°C) in the presence of a solid acid catalyst. Few side reactions occur such as the hydration of isohutene to tertiary hutyl alcohol, and methanol dehydration and formation of dimethyl ether and water. However, only small amounts of these compounds are produced. Figure 5-8 is a simplified flow diagram of the BP Etherol process. 

Trimethylamine oxide is normally available as a hydrate, and for the present preparation it is necessary to convert it to its anhydrous form. A convenient way of doing this is as follows. A solution of 45.0 g. of trimethylamine oxide dihydrate (supplied by Beacon Chemicals) is dissolved in 300 ml. of warm dimethyl-formamide and placed in a three-necked flask set up for distillation. At atmospheric pressure the flask is heated and solvent distilled off until the boiling point reaches 152-153°. Then the pressure is reduced using a water aspirator, and the remainder of the solvent is distilled. At the end of the distillation the temperature of the bath is slowly raised to 120°. The residual anhydrous trimethylamine oxide (30 g.) can be dissolved in 100 ml. of chloroform and may remain in the same flask for use in the present preparation. 

The rate-acidity profile for pyrimidin-2-one indicated reaction on the free base but since the derived second-order rate coefficient is 104 times greater than that for 2-pyridone, and the acidity dependence in the H0 region was also greater, the slope of log kt versus —H0 plot being 0.45, cf. 0.15 for 2-pyridone reaction was, therefore, postulated as occurring via a covalent hydrate, hydration taking place at the 4 position. Methyl substitution increased the rate as expected and N-methyl substitution produced a larger effect than 4,6-dimethyl substitution and this may be due to alteration of the amount of covalent hydration at equilibrium. The data... 

Cobalt, dichlorobis(AvY -dimethyl-1,2-ethanediamine)-chloride hydrate isomerization, 1, 468 Cobalt, dich orobis(l,2-ethanediamine)-base hydrolysis, 1, 304 chloride anation, 1, 469 halogen exchange, 1, 468 chloride hydrate isomerization, 1, 468 isomers, 1,191 nitrate... 

Ytterbium, trinitratotris(dimethyl sulfoxide)-structure, 1, 97 Ytterbium, tris(acetylacetone)(4-ammo-3-penten-stereochemistry, 1,81 Ytterbium complexes acetylacetone, 2,373 dipositive oxidation state hydrated ions, 3,1109 polypyrazolylborates, 2,255 Ytterbium(III) complexes ethyl glycinate, diacetate... 

Meissner and coworkers36 studied the pulse radiolysis of aqueous solutions of dimethyl sulfoxide. It was found that hydrated electrons react with DMSO with a rate constant of... 

Dimethyl-I,l -biphenyl has been prepared by a wide variety of procedures, but few of these are of any practical synthetic utility Classical radical biarjl syntheses such as the Gomberg reaction or the thermal decomposition of diaroyl peroxides give complex mixtures of products m which 4,4 dimethyl-l.l -biphenyl is a minor constituent A radical process maj also be involved in the formation of 4,4 dimethyl-1, l -biphenyl (13%) by treatment of 4-bromotoluene with hydrazine hydrate 5 4,4 -Dimethyl-l,l -biphenyl has been obtained in moderate to good yield (68-89%) by treatment of either dichlorobis(4-methyl phenyl)tellurium or l,l -tellurobis(4-methylbenzene) with degassed Raney nickel in 2 methoxyethyl ether 6... 

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