9003-19-4

The invention relates to a method for producing vinyl ether. The method comprises the following steps: (A) reacting excessive alcohol with acetaldehyde, and carrying out a continuous acetalation reaction by using immobilized superacid as a catalyst to obtain a first mixture; (B) carrying out oil-water separation and adsorption dehydration on the first mixture to obtain a second mixture; (C) carrying out acetal catalytic decomposition on the second mixture under the catalysis of a high-efficiency catalyst to obtain a third mixture; (D) rectifying the third mixture, and washing with water to obtain a vinyl ether product. According to the method, the high-temperature heating process of acetal is avoided, and the safety risk of operation is reduced; and an efficient acetal decomposition catalyst is adopted, and an acetal decomposition reaction is carried out at a low temperature, so that side reactions are few, and the selectivity of a main product is improved.

An aqueous dental glass ionomer composition comprising (a) a reactive particulate glass, (b) a linear or branched polymer comprising acidic groups, which is reactive with the particulate glass in a cement reaction, whereby the linear or branched polymer comprising acidic groups has a polymer backbone and optionally pendant groups, (c) optionally dispersed nanoparticles comprising grafted linear or branched polymer chains comprising acidic groups, and having a polymer backbone characterized in that a polymer backbone of the linear or branched polymer of component (b) and/or, if present, the grafted Sinear or branched polymer chains of component (c) are obtainable a process comprising (i) cyclopolymerizing or cyclocopolymerizing one or more compounds of the following formula (I).

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An aqueous dental glass ionomer composition comprising (a) a reactive particulate glass, (b) a linear or branched polymer comprising acidic groups, which is reactive with the particulate glass in a cement reaction, whereby the linear or branched polymer comprising acidic groups has a polymer backbone and optionally pendant groups, (c) optionally dispersed nanoparticles comprising grafted linear or branched polymer chains comprising acidic groups, and having a polymer backbone characterized in that a polymer backbone of the linear or branched polymer of component (b) and/or, if present, the grafted linear or branched polymer chains of component (c) are obtainable a process comprising (i) cyclopolymerizing or cyclocopolymerizing one or more compounds of the following formula (I):

PCT No. PCT/EP94/02294 Sec. 371 Date Jun. 28, 1996 Sec. 102(e) Date Jun. 28, 1996 PCT Filed Jul. 7, 1994 PCT Pub. No. WO95/01960 PCT Pub. Date Jan. 19, 1995The present invention relates to analogues of vitamin D, which lack the combined presence of the trans-fused six-membered C-ring and of five-membered D-ring, but still possess a central part consisting of a substituted chain of five atoms, atoms which correspond to positions 8, 14, 13, 17 and 20 of vitamin D, and at the ends of which are connected, at position 20 a structural moiety representing part of the side-chain of vitamin D or of an analogue of vitamin D, and at position 8 the DELTA (5,7)-diene moiety connected to the A-ring of the active 1-alpha-hydroxy metabolite or of an established vitamin D analogue, to their preparation process, to preparation intermediates, to pharmaceutical preparations comprising these compounds and to their use in medicine.

Transformations of 2,2′-dichlorodiethyl ether in superbasic media were studied. The optimal conditions ensuring fast reaction rate and high conversion of the ether were determined.

The C-O and G-H bonds of 18-crown-6 are activated when 18-crown-6 is complexed with the potassium salt of the benzene anion radical. Evacuated glass bulbs containing the solid anion radical salt of potassium 18-crown-6 benzene anion radical were plunged into a bath at 320 C, resulting in mini-explosions and generating a series of compounds including dioxane, 2-methyl1,3-dioxolane, divinyl ether, hydrogen, methane, and 15-crown-5. Deuterium labeling studies proved that all of these compounds originated from the 18-crown-6. Further, these labeling studies were an aid in discerning the mechanism of the decomposition. Benzene, 1,4-cyclohexadiene, and cyclohexene were also generated. The last two originated from the reaction of the anion radical of benzene with hydrogen.

The invention relates to compounds having at least one vinyl ether group which also contain in the molecule at least one further functional group selected from acrylate, methacrylate, epoxy, alkenyl, cycloalkenyl and vinylaryl groups, to compositions, especially for stereolithography, comprising those vinyl ether compounds, and to a method of producing three-dimensional objects using those compositions.

Described herein are compounds of the formula STR1 wherein R represents a hydrogen atom or a methyl radical and X stands for a --CHO, or a --CN group, are useful as perfuming ingredients for preparing perfuming compositions and a variety of perfumed articles, to which they impart sandalwood-type odor notes, together with marine, ozone type odor characters, such that said compositions and articles thus acquire a "transparent" connotation. The aldehydes of formula (I) are also useful as starting products for the preparation of the corresponding fragrant alcohols and nitriles.

A short stereo selective sequence is described for the preparation of the racemic form of the highly functionalized cyclohexene derivative 2 which comprises the upper segment of tetronolide (1), the aglycone of the antitumor tetrocarcins. A key element of this route is rapid assembly and intramolecular cycloaddition of the trienyl enol pyruvate 4, which achieves complete control over regiochemistry and good stereochemical control.

Pure dimer compounds prepared and shown to be effective photosensitizing agents are of the formula STR1 wherein one R is vinyl and the other R is hydroxyethyl or vinyl and the pharmaceutically acceptable esters and salts thereof in isolated form.

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