Diethyl-1,3-dioxanes

Physical properties of glycerol are shown in Table 1. Glycerol is completely soluble in water and alcohol, slightly soluble in diethyl ether, ethyl acetate, and dioxane, and insoluble in hydrocarbons (1). Glycerol is seldom seen in the crystallised state because of its tendency to supercool and its pronounced freesing point depression when mixed with water. A mixture of 66.7% glycerol, 33.3% water forms a eutectic mixture with a freesing point of —46.5°C. 

The dihydrate is very soluble ia polar solvents, such as methanol, ethanol, acetone, dioxane, and tetrahydrofuran, but insoluble ia benzene, chloroform, and petroleum ether. SolubiUty of the dihydrate ia diethyl ether (1.47 g/100 g solvent) is different from that of the anhydrous form (23.6 g/100 g solvent). 

AlkoxyaLkyl hydroperoxides are more commonly called ether hydroperoxides. They form readily by the autoxidation of most ethers containing a-hydrogens, eg, dioxane, tetrahydrofuran, diethyl ether, diisopropyl ether, di- -butyl ether, and diisoamyl ether (10,44). From certain ethers, eg, diethyl ether (in the following, R = H R = 35 — CH2CH2), the initially formed ether hydroperoxide can yield alcohol on standing, or with acid treatment... 

Peroxides. These are formed by aerial oxidation or by autoxidation of a wide range of organic compounds, including diethyl ether, allyl ethyl ether, allyl phenyl ether, dibenzyl ether, benzyl butyl ether, n-butyl ether, iso-butyl ether, r-butyl ether, dioxane, tetrahydrofuran, olefins, and aromatic and saturated aliphatic hydrocarbons. They accumulate during distillation and can detonate violently on evaporation or distillation when their concentration becomes high. If peroxides are likely to be present materials should be tested for peroxides before distillation (for tests see entry under "Ethers", in Chapter 2). Also, distillation should be discontinued when at least one quarter of the residue is left in the distilling flask. 

Dioxane with benzene, carbon tetrachloride, chloroform, ethanol, diethyl ether, petroleum ether, pyridine or water. 

The alkynylation of estrone methyl ether with the lithium, sodium and potassium derivatives of propargyl alcohol, 3-butyn-l-ol, and propargyl aldehyde diethyl acetal in pyridine and dioxane has been studied by Miller. Every combination of alkali metal and alkyne tried, but one, gives the 17a-alkylated products (65a), (65c) and (65d). The exception is alkynylation with the potassium derivative of propargyl aldehyde diethyl acetal in pyridine at room temperature, which produces a mixture of epimeric 17-(3, 3 -diethoxy-T-propynyl) derivatives. The rate of alkynylation of estrone methyl ether depends on the structure of the alkyne and proceeds in the order propar-gylaldehyde diethyl acetal > 3-butyn-l-ol > propargyl alcohol. The reactivity of the alkali metal salts is in the order potassium > sodium > lithium. 

By reaction of an a-halo ester 1 with zinc metal in an inert solvent such as diethyl ether, tetrahydrofuran or dioxane, an organozinc compound 2 is formed (a Grignard reagent-like species). Some of these organozinc compounds are quite stable even a structure elucidation by x-ray analysis is possible in certain cases ... 

Bonhote and co-workers [10] reported that ILs containing triflate, perfluorocar-boxylate, and bistrifylimide anions were miscible with liquids of medium to high dielectric constant (e), including short-chain alcohols, ketones, dichloromethane, and THF, while being immiscible with low dielectric constant materials such as alkanes, dioxane, toluene, and diethyl ether. It was noted that ethyl acetate (e = 6.04) is miscible with the less-polar bistrifylimide and triflate ILs, and only partially miscible with more polar ILs containing carboxylate anions. Brennecke [15] has described miscibility measurements for a series of organic solvents with ILs with complementary results based on bulk properties. 

Early efforts to effect the photoinduced ring expansion of aryl azides to 3H-azepines in the presence of other nucleophiles met with only limited success. For example, irradiation of phenyl azide in hydrogen sulfide-diethyl ether, or in methanol, gave 17/-azepine-2(3//)-thione35 (5% mp 106—107 " O and 2-methoxy-3//-azepine (11 %),2 3 respectively. Later workers194 failed to reproduce this latter result, but found that in strongly basic media (3 M potassium hydroxide in methanol/dioxane) and in the presence of 18-crown-6, 17/-azepin-2(3//)-one was produced in 48% yield. In the absence of the crown ether the yield of azepinone falls to 35%. 

A solution of 1-phenyl-1//-pyrazolo[3,4-rf]pyridazinc-7-carbonitrilc (150 mg. 0.68 mmol) and A,A-diethyl-prop-l-ynamine(151 mg, 1.36 mmol) in l,4-dioxane(2 mL) was refluxed for 5 h. After cooling, the reaction mixture was poured onto excess ice, and extracted with CHC13. The extract was washed with H20, dried (Na2S04) and concentrated under reduced pressure. Purification by chromatography (silica gel, benzene then bcnzene/EtOAc 20 1) gave, from the benzene eluate, 6-diethylamino-1 -phenyl-1 //-indazole-7-carbo-nitrile [yield 81 mg (39 %) mp 104-105 C (benzene/petroleum ether)] as slightly yellow prisms and, from the second eluate, the diazocine 5 as yellow needles yield 90 mg (40 %) mp 121-122 C (benzene/ petroleum ether). 

To a stirred solution of 4 mmol of the diamide in 40 mL of dioxane (distilled from LiAlH4) and 13 mL of water is added 1 mg of osmium tetroxide. When the solution turns brownish (after about 10 min) 2.06 g (9.2 mmol) of sodium metaperiodale are added at 25 26 "C. The progress of the reaction is monitored by TLC on silica gel coated plastic sheets with CHCI,/diethyl ether/methanol (3.3 0.1) as eluent. When the reaction is complete, the precipitated solid is filtered and the filtrate concentrated in vacuo at 1 Torr. The residue is dissolved in 50 mL of CHC13, dried over MgSO,. and evaporated in vacuo to leave a residue, which is crystallized from a suitable solvent. 

List B contains all compounds that form peroxides which become dangerous when they reach a critical concentration. The danger will often become apparent during distillation operations. For hydrocarbons, this is the case for deca- and tetrahydronaphthalene, cyclohexene, dicyclopentadiene, propyne and butadiene. S ondary alcohols such as 2-butanol also form part of this list. Finally, for ethers there are diethyl ethers, ethyl and vinyl ethers, tetrahydrofuran, 1,4-dioxan, ethylene glycol diethers and monoethers. 

In reversed-phase thin-layer chromatography (RP-TLC), the choice of solvents for the mobile phase is carried out in a reversed order of strength, comparing with the classical TLC, which determines a reversed order of values of compounds. The reversed order of separation assumes that water is the main component of the mobile phase. Aqueous mixmres of some organic solvents (diethyl ether, methanol, acetone, acetonitrile, dioxane, i-propanol, etc.) are used with good results. 

There are a reasonable number of structurally characterized zinc compounds with bound THF molecules. For example, a six-coordinate zinc porphyrin complex with axial THF donors and a four-coordinate zinc center with two THF ligands and two phenolate ligands.341,357 Although less common there are other structural examples of ether solvents, such as diethyl ether, coordinated.358 The X-ray structure of zinc chloride with 1,4-dioxane ligands shows a monomeric four-coordinate zinc center with two 1,4-dioxane ligands.359... 

Many ethers, either of open chain (diethyl or diisopropyl ether) or cyclic type (tetrahydrofuran, dioxane), are readily autoxidised on exposure to air or oxygen in presence of light. The hydroperoxides formed are less volatile than the parent ether and may be concentrated to a dangerous extent if distillation of peroxidised material is attempted. 

Diphosphitylation of 2,4-0-methylene-D-glucitol (8) with phosphorus trichloride in dioxane gave 1,3 5,6-bis- 0-(chlorophosphitc) 9 (99.5%). Its amination with diethyla-mine in benzene-diethyl ether afforded the corresponding bis-amidophosphites 10. Their reaction with sulfur afforded three P-diastereomers of cyclic thiophosphate 11 in 24.8, 4.8, and 19.5% yields (Scheme 4) [19],... 

Reagent and conditions i, diethyl chloromalonate, DMF ii, DBN, MeOH iii, AcOH, H2O iv, AcONa, diethyl aminomalonate HCI, MeOH/H20 v, MeONa, MeOH vi, 2,5-dimethoxyTHF, 4-chloropyridine hydrochloride, dioxane vii, pyrrolidine viii, (a)POCI3, (b) 10%NaOH... 

An unexpected reaction occurs when 2-alkyl-4(5)-nitroimidazoles (27 R = alkyl) are reduced in protic solvents [92JCS(P1)2779]. Catalytic hydrogenation of 2-methyl-4(5)-nitroimidazole (27 R = Me) in a solution of acetic anhydride and acetic acid gave 4,4 -diacetamido-2,2 -dimethyl-5,5 -diimidazole (32 yield 10%) in addition to the expected 4-acetamido-l-acetyl-2-methylimidazole (28%). Similarly, reduction of the 2-alkyl-4(5)-nitroimidazoles (27 R = Me, Et, iPr) in ethanol solution in the presence of diethyl ethoxymethylenemalonate [EMME (135)] gives predominantly the 5,5 -diimidazole adducts (33). The formation of these products (33) is believed to involve an electrophilic addition of the starting material (27) to the electron-rich aminoimidazoles (25) [92JCS(P1)2779]. Interestingly, replacement of ethanol by dioxane suppressed diimidazole formation. 

With ethoxymethylenemalononitrile (136), C-addition appears to be the only mode of reaction with simple 5-aminoimidazole derivatives. Typically, reaction of 5-amino-1,2-dimethylimidazole (96 R = R2 = Me) with the reagent (136) in dioxane solution gave an 84% yield of the product (144 R = R2 = Me). In contrast, reaction of the same amine with diethyl ethoxymethylenemalonate (135) in dioxane solution gave exclusively an... 

Peroxidizable hazard on concentration Diethyl ether Tetrahydrofuran Dioxane Acetal... 

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