5-Methylene-1,3-dioxane

Dioxanes, 308 5-Methylene-1,3-dioxane, 310 5,5-Dibromo-1,3-dioxane, 310 5-(2 -Pyridyl)-1,3-dioxane, 311 5-Trimethylsilyl-1,3-dioxane, 311... 

Desymmetrization of cyclic allyl acetals such as 2-substituted 4,7-hydrodioxepins or 5-methylene-1,3-dioxanes was investigated using ruthenium or nickel catalysts. The isomerization of the dioxanes was accomplished using Ru2Cl4(DIOP)/LiBHEt3 in high yield with up to 38% ee (Equation (22)).81... 

The stability of the cation, in this case trialkoxycarbenium cation versus allyl one, decides which of these two mechanisms predominates.The selective ROP of 5-methylene-1,3-dioxan-2-one to the linear PC can be explained by assuming that the competitive vinyl polymerization is suppressed by neighboring electron-withdrawing carbonate group. 

Acetic anhydride adds to acetaldehyde in the presence of dilute acid to form ethyUdene diacetate [542-10-9], boron fluoride also catalyzes the reaction (78). Ethyfldene diacetate decomposes to the anhydride and aldehyde at temperatures of 220—268°C and initial pressures of 14.6—21.3 kPa (110—160 mm Hg) (79), or upon heating to 150°C in the presence of a zinc chloride catalyst (80). Acetone (qv) [67-64-1] has been prepared in 90% yield by heating an aqueous solution of acetaldehyde to 410°C in the presence of a catalyst (81). Active methylene groups condense acetaldehyde. The reaction of isobutfyene/715-11-7] and aqueous solutions of acetaldehyde in the presence of 1—2% sulfuric acid yields alkyl-y -dioxanes 2,4,4,6-tetramethyl-y -dioxane [5182-37-6] is produced in yields up to 90% (82). 

Norethindrone may be recrystakhed from ethyl acetate (111). It is soluble in acetone, chloroform, dioxane, ethanol, and pyridine slightly soluble in ether, and insoluble in water (112,113). Its crystal stmcture has been reported (114), and extensive analytical and spectral data have been compiled (115). Norethindrone acetate can be recrystakhed from methylene chloride/hexane (111). It is soluble in acetone, chloroform, dioxane, ethanol, and ether, and insoluble in water (112). Data for identification have been reported (113). The preparation of norethindrone (28) has been described (see Fig. 5). Norethindrone acetate (80) is prepared by the acylation of norethindrone. Norethindrone esters have been described ie, norethindrone, an appropriate acid, and trifiuoroacetic anhydride have been shown to provide a wide variety of norethindrone esters including the acetate (80) and enanthate (81) (116). 

Solubility and Solvent Resistance. The majority of polycarbonates are prepared in methylene chloride solution. Chloroform, i7j -l,2-dichloroethylene, yy -tetrachloroethane, and methylene chloride are the preferred solvents for polycarbonates. The polymer is soluble in chlorobenzene or o-dichlorobenzene when warm, but crystallization may occur at lower temperatures. Methylene chloride is most commonly used because of the high solubiUty of the polymer (350 g/L at 25°C), and because this solvent has low flammabiUty and toxicity. Nonhalogenated solvents include tetrahydrofuran, dioxane, pyridine, and cresols. Hydrocarbons (qv) and aUphatic alcohols, esters (see Esters, organic), or ketones (qv) do not dissolve polycarbonates. Acetone (qv) promotes rapid crystallization of the normally amorphous polymer, and causes catastrophic failure of stressed polycarbonate parts. 

Methylene chloride is one of the more stable of the chlorinated hydrocarbon solvents. Its initial thermal degradation temperature is 120°C in dry air (1). This temperature decreases as the moisture content increases. The reaction produces mainly HCl with trace amounts of phosgene. Decomposition under these conditions can be inhibited by the addition of small quantities (0.0001—1.0%) of phenoHc compounds, eg, phenol, hydroquinone, -cresol, resorcinol, thymol, and 1-naphthol (2). Stabilization may also be effected by the addition of small amounts of amines (3) or a mixture of nitromethane and 1,4-dioxane. The latter diminishes attack on aluminum and inhibits kon-catalyzed reactions of methylene chloride (4). The addition of small amounts of epoxides can also inhibit aluminum reactions catalyzed by iron (5). On prolonged contact with water, methylene chloride hydrolyzes very slowly, forming HCl as the primary product. On prolonged heating with water in a sealed vessel at 140—170°C, methylene chloride yields formaldehyde and hydrochloric acid as shown by the following equation (6). 

P-o 3-ketal in 130 ml of glacial acetic acid and 130 ml of water is maintained at 80° for 30 min, poured onto ice, made alkaline with sodium hydroxide and extracted with methylene dichlofide. The extracts are washed once with water, dried over magnesium sulfate, filtered, and evaporated to a residue. A solution of this residue in 240 ml of pyridine and 120 ml of acetic anhydride is kept at room temperature for 1.25 hr and then poured into hydrochloric acid-ice water. The mixture is extracted with methylene dichloride and the methylene dichloride solution is washed until neutral, dried over magnesium sulfate and filtered. The filtrate is evaporated to dryness to yield 13 g. Crystallization from aqueous acetone yields 11.8 g (92%) mp 251-255° [ ]d —1° (dioxane). 

A solution of 16jS-methyl-l la,17a,21-trihydroxy-5j5-pregnane-3,20-dione 21-acetate (52), 45 g, in dioxane (297 ml) is cooled to 15° and treated over a 5 min period with a solution of bromine (34.2 g) in dioxane (594 ml) precooled to 18°. After 2 min a solution of sodium acetate (60 g) in water (600 ml) is added and the mixture poured into ice water (8 liters). The precipitate is filtered off, washed to neutrality with water, and dried to give the crude dibromide (53), 55.7 g mp 125-126° (dec.) [aJu 58°. A mixture of dibromide (53), 55.5 g, lithium bromide (27.8 g), lithium carbonate (27.8 g) and DMF (1.11 liters) is refluxed under rapid stirring for 6 hr. The mixture is concentrated under vacuum to about 250 ml, poured into ice water (8 liters) containing hydrochloric acid (250 ml), and extracted with methylene dichloride. The extracts are washed to neutrality with water and evaporated to dryness. The residue is dissolved in acetone, evaporated to dryness under reduced pressure, redissolved in acetone and crystallized by the additon of hexane. This gives the dienone (54) 24.4 g, mp 236-239°. 

Photolysis of a dioxane solution of (2) using a 250 watt quartz lamp also provides 16a,17a-methylene-20-ketones (4). ... 

A solution of 500 mg 3 -acetoxypregn-5-en-20-one-[17a,16a-c]-A -pyrazoline in 100 ml of anhydrous dioxane is stirred with a magnetic stirrer and irradiated in a water-cooled quartz reactor with a high pressure Biosol Philips 250 W quartz lamp for 1 hr. The solvent is removed at reduced pressure and the residue is chromatographed on alumina (activity III). Elution with petroleum ether-benzene (3 1) gives 0.2 g (42%) of 3 -acetoxy-16a,17a-methylene-pregn-5-en-20-one mp 193-193.5° after two recrystallizations from methylene dichloride-ethyl acetate. 

During the next fifty years the interest in derivatives of divalent carbon was mainly confined to methylene (CHg) and substituted methylenes obtained by decomposition of the corresponding diazo compounds this phase has been fully reviewed by Huisgen. The first convincing evidence for the formation of dichlorocarbene from chloroform was presented by Hine in 1950. Kinetic studies of the basic hydrolysis of chloroform in aqueous dioxane led to the suggestion that the rate-determining step was loss of chloride ion from the tri-chloromethyl anion which is formed in a rapid pre-equilibrium with hydroxide ions ... 

The cycloaddition of methyleneketene 180 with 5-methylene-l,3-dioxane-4,6-dione 181 in principle allows all three double bonds of 180 to react with 181 (Scheme 120) [99JST187]. 

A solution of 3.4 grams of N-bromosuccinimide in 60 cc of absolute dioxane is added drop wise in the dark, during the course of 5 minutes, to a stirred solution, heated to 60°C, of 9.2 grams of ergocryptine in 180 cc of absolute dioxane. The reaction mixture is stirred at this temperature for 70 minutes and is concentrated to a syrup-like consistency in a rotary evaporator at a bath temperature of 50°C. The reaction mixture is subsequently diluted with 300 cc of methylene chloride, is covered with a layer of about 200 cc of a 2N sodium carbonate solution in a separating funnel and is shaken thoroughly. The aqueous phase is extracted thrice with 100 cc amounts of methylene chloride. The combined... 

The 4-(2,3-apoxypropoxy)carbazole used as starting material is prepared as follows. A solution of 16.3 g 4-hydroxycarbazole in a mixture of 190 ml dioxan and 98 ml 1 N sodium hydroxide is, after the addition of 66 ml epichlorohydrin, stirred for 2 hours at 40°C to 45°C. The reaction mixture is then diluted with water and shaken out with methylene chloride. The methylene chloride phase is washed with water, dried over anhydrous sodium sulfate and evaporated. There are obtained 16.8 g 4-(2,3-epoxypropoxy)carbazole. 

A suspension of 37.3 g (0.1 mol) of 7/3-amino-3-methoxy-3-cephem-4-carboxylic acid hydrochloride dioxanate in 500 ml methylene chloride is stirred for 15 minutes at room temperature under an argon atmosphere and treated with 57.2 ml (0.23 mol) of bis-(trimethylsilyl)-acetamide. After 45 minutes the faintly yellow slightly turbid solution is cooled to 0°C and treated within 10 minutes with 31.2 g (0.15 mol) of D-Ct-amino-Ct-d, 4-cyclohexadienyl (acetyl chloride hydrochloride. Thirty minutes thereafter 15 ml (about 0.21 mol) of propylene oxide is added and the mixture is further stirred for 1 hour at 0°C. A cooled mixture of 20 ml of absolute methanol in 200 ml of methylene chloride is added within 30 minutes, after another 30 minutes the precipitate is filtered off under exclusion of moisture, washed with methylene chloride and dried under reduced pressure at room temperature. The obtained hygroscopic crystals of the hydrochloride of 7j3-[D-a-(1,4-cyclohexadienyl)acetylamino] -... 

A mixture of 1.38 grams of the above compound and 15 cc of dioxane was treated with 1.9 cc of a 0.5 N aqueous solution of perchloric acid and 600 mg of N-bromoacetamide, adding the latter in the dark, in three portions, in the course of half an hour and under continuous stirring. It was then stirred for a further 1% hours in the dark, then the excess of reagent was decomposed by the addition of aqueous sodium bisulfite solution and ice water was added the product was extracted with methylene chloride, washed with water, dried over anhydrous sodium sulfate and the solvent was evaporated under reduced pressure, thus giving a yellow oil consisting of the 16,21-diacetate of 6a-fluoro-9a-bromo-16o-hydroxy-hydrocortisone which was used for the next step without further purification. 

Isopropyl-4(or 5-nitroimidazole) (31 g = 0.2 mol), dioxane (70 g) and dimethylsulfate (28 g = 0.22 mol) were heated on a steam bath under reflux for 45 minutes. The solvent was removed in vacuo on a steam bath, the residue dissolved in 20 ml of water and the product precipitated by the gradual addition of 80 g of 25% sodium hydroxide solution at 0°C. A small additional amount was obtained by extraction of the mother liquor with methylene chloride. The product melted at 60°C. 

Normal /, /i -Oxydipropionitrile Carbowax (400, 600, 750, etc.) Glycols (ethylene, diethylene) Cyanoethylsilicone Saturated hydrocarbons, e.g. hexane, heptane aromatic solvents, e.g. benzene, xylene saturated hydrocarbons mixed with up to 10 per cent dioxan, methanol, ethanol, chloroform, methylene chloride (dichloromethane)... 

Table 4.6 Extent of Ring-Opening During Polymerizations of 4-Methylene-1,3-dioxolane and 2-Methylene-1,4-dioxane Derivatives...

The polymer is then diluted with acet and pptd in w. Post polymerization nitration is accomplished by adding 40Gml of 100% nitric acid at 0° to 25g of the dried polymer. When the polymer is completely dissolved, the excess acid is removed by distn at reduced press. The anhyd dioxane-acet soln is then pptd in methylene chloride and dried. 1... 

Methylene chloride was the solvent most compatible with the reagents and resin. Tetrahydrofuran or a 1 1 mixture of dimethylformamide (DMF) and methylene chloride could also be employed, but longer reaction times were necessary. 1,4-Dioxane, toluene, N-methylpyrrolidinone, and DMF alone were not suitable as solvents. 

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