Oxanes

Pyranoid examples have been prepared in all possible configurations altro,396,397 ido39 399 manno39S,40° and talo.185 396 From the furanose group, 2,6-anhydro-D-mannofuranose and its derivatives are known.366,401,402 

The first compound of this group, methyl 2,6-anhydro-a-D-altropyrano-side (124), was prepared by the action of sodium methoxide on the corresponding 6-tosylate 123.397 This method was later applied to the preparation of other 2,6-anhydrohexoses having a cw-oriented hydroxymethyl group and a free hydroxyl group at C-2. 

An alternative synthesis is based on the replacement of the mesyloxy group at C-2 by the hydroxymethyl group with inversion of configuration.400 

A derivative (130) of 2,6-anhydrohept-l-en-3-ulose, prepared as an unstable intermediate by a three-step synthesis from D-g/nco-hept-l-enitol (128) via 1-iodo derivative 129, undergoes spontaneous cyclodimerization.415 

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On the basis of the mechanism for the acid catalyzed formation of diethyl ether from ethanol in Figure 15 3 write a stepwise mechanism for the formation of oxane from 1 5 pentanediol (see the equation on page 637)... 

In each case the ring is numbered starting at the oxygen The lUPAC rules also permit oxirane (without substituents) to be called ethylene oxide Tetrahydrofuran and tetrahy dropyran are acceptable synonyms for oxolane and oxane respectively... 

Oxane bonds, M—O—Si, are hydroly2ed during prolonged exposure to water but reform when dried. Adhesion in composites is maintained by controlling conditions favorable for equiUbrium oxane formation, ie, maximum initial oxane bonding, minimum penetration of water to the interface, and optimum morphology for retention of silanols at the interface. The inclusion of a hydrophobic silane, such as phenyltrimethoxysilane [2996-92-17, with the organofunctional silane increases thermal stabiUty of the silane and make the bond more water resistant (42). 

Reaction of pyroc techol with epichlorohydrin in the presence of base affords the benzodioxan derivative, 136, (The reaction may well involve initial displacement of halogen by phenoxide followed by opening of the oxirane by the anion from the second phenolic group.) Treatment of the alcohol with thio-nyl chloride gives the corresponding chloro compound (137). Displacement of halogen by means of diethylamine affords piper-oxan (138), a compound with a-sympathetic blocking activity. 

Finally, a Mannich reaction of with formaldehyde and 4-acet-yl-p-benzodi oxane ( ) leads to pyrroxan (48). 

Sol in dimethyl formamide si sol in acet, di-oxane and tetrahydrofuran v si sol in chlf. 

Paraformaldehyde. (CH20)g, mw (30.03)n white, cryst powder mp 64, bp sublimes, range of polymerization n=8 to 100. Note Paraformaldehyde is not the same as sym-tri-oxane, which melts at 150—60°. Slowly sol in cold, more readily in hot w, with evolution of formaldehyde insol in ale eth sol in fixed alkali hydroxide solns. Obtained by concentrating formaldehyde soln. At ordinary temps, it gradually vaporizes, yielding formaldehyde gas... 

Properties, Its Qf was calcd to be -105kcal/ mole (Ref 4). It forms a complex Be(C104)2.-4H20,4(dioxane) colorl crysts which lose di-oxane on slow heating, but expld on rapid heating (Ref 3)... 

During the sulfation of alcohol ethoxylates the undesired byproduct 1,4-di-oxane may be formed. Although the formation of 1,4-dioxane is predominantly governed by the sulfation and neutralization conditions and by the chemical composition of the organic feedstock, other factors, such as the quality of the raw material, also contribute. This prompted a reappraisal of the required quality standards for this feedstock. In Table 11 guideline specifications are presented. 

As was pointed out, refinement of ethoxysulfated alcohols is sometimes required to satisfy current standards for product quality, in particular 1,4-di-oxane content. Due to the particular characteristics and outstanding suitability of FAES for application in personal care detergent products, the commercially accepted content of 1,4-dioxane in FAES has been progressively reduced to meet the demand of higher safety margins for the end-users, without requiring any change in product formulation and choice of surfactant. 

Die Reduktion von 9-Brom-ll/3-hydroxy-steroiden mit Chrom(II)-Salzen, insbeson-dere mit Chrom(II)-acetat fiihrt zu 11/3-Hydroxy-steroiden (s. S.515), A9 (11)-Ste-roiden (s. S.518) und 5,9-Cyclo-steroiden. Die Cyclopropan-Bildung wird durch Chrom(II)-acetat in Dimethylsulfoxid bzw. Dimethylformamid begiinstigt. So laufen beim 9a-Brom-l l/3-hydroxy-3-oxo-l 7/ -acetyl-ostren-(510) in waBr. Aceton, THF, 1,4-Di-oxan oder N-Methyl-pyrrolidon Substitution, Eliminierung und Cyclisierung nebeneinan-der ab, in Dimethylsulfoxid oder Dimethylformamid erhalt man fast ausschlieBlich ///3-Hydroxy-3-oxo-17 3-acetyl-5,9-cyclo-dstran5 ... 

N,N-Dichlor-amine werden iiber die Nitrene zu Aminen, in Gegenwart von 1,4-Di-oxan zu 2-Amino-l,4-dioxanen umgesetzt2 ... 

C4 H35C1N 0 120568-18-5) see Losartan potassium tert-butyl (4R,6S)-2-(6-cyanomethyl-2,2-dimcthyl-13-di-oxan-4-yl)acetale... 

S)-2-(6-methoxy-2-naphthalenyl)-a,5,5-trimethyl-l,3-di-oxane-2-methanal methanesulfonate... 

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