1,3-Dioxanes oxidation

The hydroperoxides are the primary products of oxidation of phthalane and isochromane [202,203,284,293]. Hydroperoxide is the main product of dioxan oxidation. The decomposition occurs according to... 

Since this reaction is acid catalyzed, it can be minimized by adding a buffer such as sodium acetate or by adding water [30]. Lithium acetate catalyst also produces less ethers than since acetate. Some other side reactions are the formation of aldehyde, cyclic trimer of ET, and dioxane. Oxidation of glycol ends produce aldehydes that lead to colored compounds. Traces of dioxane can form from the cyclization of glycol. 

Separate C15 isomers by preparative TLC and recycyie the (3-isomer by Mn02/CH2Ci2 or DDQ-dioxane oxidation, foiiowed... 

Fit a 1-litre three-necked flask with two double surface condensers and a glycerine-scaled stirrer (Fig. II, 7, 10). Place 25 g. (29 ml.) of mesityl oxide (Section 111,79), 50 ml. of dioxan and a cold (10°) solution... 

Oxidation of acetophenone with selenium dioxide iu the i)reseiice of dioxan or ethyl alcohol as solvent affords j.henylglyoxal ... 

Hydrogenations with coppcr-chromium oxide catalyst are usually carried out in the liquid phase in stainless steel autoclaves at pressures up to 5000-6000 lb. per square inch. A solvent is not usually necessary for hydrogenation of an ester at 250° since the original ester and the alcohol or glycol produced serve as the reaction medium. However, when dealing with small quantities and also at temperatures below 200° a solvent is desirable this may be methyl alcohol, ethyi alcohol, dioxan or methylcyc/ohexane. 

In order to prepare an acid, a dioxan solution of the diazo ketone is added slowly to a suspension of silver oxide in a dilute solution of sodium thiosulphate Iftheco)iversion to the acid yields unsatisfactory results, it is usually advisable to prepare the ester or amide, which are generally obtained in good yields hydrolysis of the derivative gives the free acid. 

Introduce a solution of 15 g. of the diazo ketone in 100 ml. of dioxan dropwise and with stirring into a mixture of 2 g. of silver oxide (1), 3 g. of sodium thiosulphate and 5 g. of anhydrous sodium carbonate in 200 ml. of water at 50-60°. When the addition is complete, continue the stirring for 1 hour and raise the temperature of the mixture gradually to 90-100°. Cool the reaction mixture, dilute with water and acidify with dilute nitric acid. Filter off the a-naphthylacetic acid which separates and recrys-talhse it from water. The yield is 12 g., m.p. 130°. 

Add, with stirring, a solution of 6 8 g. of the fiis-diazo ketone in 100 ml. of warm dioxan to a suspension of 7 0 g. of freshly precipitated silver oxide in 250 ml. of water containing 11 g. of sodium thiosulphate at 75°. A brisk evolution of nitrogen occurs after 1 5 hours at 75°, filter the liquid from the black silver residue. Acidify the almost colourless filtrate with nitric acid and extract the gelatinous precipitate with ether. Evaporate the dried ethereal extract the residue of crude decane-1 10-dicarboxylic acid weighs 4 -5 g. and melts at 116-117°. RecrystaUisation from 20 per cent, aqueous acetic acid raises the m.p. to 127-128°. 

Retrosynthetic path e in Scheme 2.2 requires a regioselective oxidation of an o-nitrostyrene to the corresponding phenylacetaldehyde. This transformation has been accomplished hy Wacker oxidation carried out in such a way as to ensure the desired regioselectivity. The required o-nitrostyrenes can be prepared by Heck vinylation. One procedure for oxidation uses 1,3-propaiiediol to trap the product as a l,3-dioxane[15]. These can then be hydrogenated over Rh/C and cyclized by treatment with dilute HCl,... 

A reaction carried out by Haruki et al. is the energic oxidation of 5-(l-hydroxyethyl)2-phenylthiazole (5) in dioxane by aqueous Kl-iodine to give 2-phenyl-5-thiazolecarboxylic acid (6) (Scheme 2) (28). 

Thiazolecarboxaldehydes are very easily oxidized to carboxylic acids by most oxidizing agents, the most common being KMn04 in cold pyridine or boiling acetone. Thiazolecarboxylic acids are obtained in 50% yield (29). Other oxidizing agents such as Ag 0 in dioxane and water (29, 103), chromic acid, and so forth are also used. 

Nickel Aluminum, aluminum(III) chloride, ethylene, 1,4-dioxan, hydrogen, methanol, nonmetals, oxidants, sulfur compounds... 

Organophosphorus Derivatives. Neopentyl glycol treated with pyridine and phosphorus trichloride in anhydrous dioxane yields the cycHc hydrogen phosphite, 5,5-dimethyl-l,3-dioxaphosphorinane 2-oxide (2) (32,33). Compounds of this type maybe useful as flameproofing plasticizers, stabilizers, synthetic lubricants, oil additives, pesticides, or intermediates for the preparation of other organophosphoms compounds (see Flame retardants Phosphorus compounds). 

Because lactic acid has both hydroxyl and carboxyl functional groups, it undergoes iatramolecular or self-esterificatioa and forms linear polyesters, lactoyUactic acid (4) and higher poly(lactic acid)s, or the cycUc dimer 3,6-dimethyl-/)-dioxane-2,5-dione [95-96-5] (dilactide) (5). Whereas the linear polyesters, lactoyUactic acid and poly(lactic acid)s, are produced under typical condensation conditions such as by removal of water ia the preseace of acidic catalysts, the formation of dilactide with high yield and selectivity requires the use of special catalysts which are primarily weakly basic. The use of tin and ziac oxides and organostaimates and -titanates has been reported (6,21,22). 

Virtually all of the organo derivatives of CA are produced by reactions characteristic of a cycHc imide, wherein isocyanurate nitrogen (frequendy as the anion) nucleophilically attacks a positively polarized carbon of the second reactant. Cyanuric acid and ethylene oxide react neady quantitatively at 100°C to form tris(2-hydroxyethyl)isocyanurate [839-90-7] (THEIC) (48—52). Substitution of propylene oxide yields the hydroxypropyl analogue (48,49). At elevated temperatures (- 200° C). CA and alkylene oxides react in inert solvent to give A/-hydroxyalkyloxazohdones in approximately 70% yield (53). Alternatively, THEIC can be prepared by reaction of CA and 2-chloroethanol in aqueous caustic (52). THEIC can react further via its hydroxyl fiinctionahty to form esters, ethers, urethanes, phosphites, etc (54). Reaction of CA with epichlorohydrin in alkaline dioxane solution gives... 

The selective epoxidation of ethylene by hydrogen peroxide ia a 1,4-dioxane solvent ia the presence of an arsenic catalyst is claimed. No solvent degradation is observed. Ethylene oxide is the only significant product detected. The catalyst used may be either elemental arsenic, an arsenic compound, or both. 

Appropriate pyrido[2,3-d]pyrimidin-5-ones with formyl groups in the 6-position have been oxiized to piromidic (68) and pipemidic (69) acids, or to intermediates for these, using moist silver oxide, chromium trioxide (potassium dichromate), potassium permanganate or, alternatively, sodium chlorite/hydroxylamine-O-sulfonic acid. 6-Acetyl groups have been similarly oxidized using sodium hypobromite in aqueous dioxane, whilst 2-acetyl groups give dimethylaminomethylene derivatives en route to 2-pyrazolylpyrido[2,3-d]pyrimidines. 

A novel Af-oxide (595) was prepared by the solvolysis at room temperature of (594) in 1 1 water-dioxane. A kinetic and mechanistic study of this reaction was carried out. 

Perchloric acid (79% HCIO4/CH2CI2, 0°, 1 h 25°, 3 h, 87% yield) and periodic acid (aq. dioxane, 3 h, quant, yield) cleave 1,3-dioxolanes the latter drives the reaction to completion by oxidation of the ethylene glycol that forms. Yields are substantially higher from cleavage with perchloric acid (3 AHCIO4/THF, 25°, 3 h, 80% yield) than with hydrochloric acid (HCl/HOAc, 65% yield)... 

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. 

The solubility parameter is about 19.2MPa and being amorphous they dissolve in such solvents as tetrahydrofuran, mesityl oxide, diacetone alcohol and dioxane. Since the main chain is composed of stable C—C and C—O—C linkages the polymer is relatively stable to chemical attack, particularly from acids and alkalis. As already mentioned, the pendant hydroxyl groups are reactive and provide a site for cross-linking. 

Chemical Designations - Synonyms Di (Ethylene Oxide) Dioxan p-Dioxane Chemical Formula CH2CH2OCH2CH2O... 

The cyclooligomerization of ethylene oxide to yield dioxane as well as compounds we now call crowns predates Pedersen s discovery by more than a decade ". The full utility of these cyclic oligomers was not recognized, however, and the patent reporting these early efforts remains an interesting historical footnote. The promise of utilizing cyclo-oligomerization commercially is so important, however, that attention is called to the method and the existence of the patent. 

Dale and co-workers examined this reaction in considerable detail some years later and utilized a mixture of HF and BFj in dioxane as catalyst. They noted that this catalyst mixture was stable for months at room temperature and did not etch glass. It was useful for initiating the cyclooligomerization reaction which led to a product mixture. The composition of the mixture was apparently independent of the ethylene oxide concentration and the reaction was apparently not kinetically controlled. 

In a typical case, ethylamine is allowed to react with ethylene oxide to produce N-ethyldiethanolamine (5). The latter is then treated with additional ethylene oxide to afford N,N-di(polyoxyethylene)ethylamine (6) where the sum a -t b is 3. This material is then stirred at room temperature for 3 h with toluenesulfonyl chloride and powdered sodium hydroxide in dioxane solution. After filtration and Kugelrohr distillation, N-eth-ylmonoaza-15-crown-5 is isolated in 75% yield as illustrated below in Eq. (4.7). 

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