Calcium epoxides

Typically, soHd stabilizers utilize natural saturated fatty acid ligands with chain lengths of Cg—C g. Ziac stearate [557-05-1/, ziac neodecanoate [27253-29-8] calcium stearate [1592-23-0] barium stearate [6865-35-6] and cadmium laurate [2605-44-9] are some examples. To complete the package, the soHd products also contain other soHd additives such as polyols, antioxidants, and lubricants. Liquid stabilizers can make use of metal soaps of oleic acid, tall oil acids, 2-ethyl-hexanoic acid, octylphenol, and nonylphenol. Barium bis(nonylphenate) [41157-58-8] ziac 2-ethyIhexanoate [136-53-8], cadmium 2-ethyIhexanoate [2420-98-6], and overbased barium tallate [68855-79-8] are normally used ia the Hquid formulations along with solubilizers such as plasticizers, phosphites, and/or epoxidized oils. The majority of the Hquid barium—cadmium formulations rely on barium nonylphenate as the source of that metal. There are even some mixed metal stabilizers suppHed as pastes. The U.S. FDA approved calcium—zinc stabilizers are good examples because they contain a mixture of calcium stearate and ziac stearate suspended ia epoxidized soya oil. Table 4 shows examples of typical mixed metal stabilizers. 

Propylene Oxide. Propylene oxide is produced from propylene by two main processes. The first is chi orohydrin a tion of propylene at ca 310 K, followed by epoxidation of the chi orohydrin by calcium hydroxide. 

Epoxid tion. Epoxidation, also referred to as saponification or dehydrochlorination, of propylene chlorohydrin (both isomers) to propylene oxide is accompHshed using a base, usually aqueous sodium hydroxide or calcium hydroxide. 

Dichlorides and e2thers are the main by-products in this reaction. Treatment with base produces propylene oxide. Specialty epoxides, eg, butylene oxide, are also produced on an industrial scale by means of HOCl generated from calcium hypochlorite and acetic acid followed by dehydrohalogenation with base. 

Vulcanisation may also be brought about by zinc and calcium peroxides, p-quinone dioxime, epoxide resins, phenolic resins and di-isocyanates. 

Reactant for /-butyl phenolic resins. Magnesium oxide reacts in solution with /-butyl phenolic resin to produce an infusible resinate (Fig. 36) which provides improved heat resistance. The resinate has no melting point and decomposes above 200°C. Although oxides of calcium, lead and lithium can also be used, they are not as efficient as magnesium oxide and also tend to separate from solution. Where clear adhesive solutions are required epoxide resins, zinc-calcium resinates or zinc carbonate can be used. 

Vitamin K is the cofactor for the carboxylation of glutamate residues in the post-synthetic modification of proteins to form the unusual amino acid y-carboxygluta-mate (Gla), which chelates the calcium ion. Initially, vitamin K hydroquinone is oxidized to the epoxide (Figure 45-8), which activates a glutamate residue in the protein substrate to a carbanion, that reacts non-enzymically with carbon dioxide to form y-carboxyglut-amate. Vitamin K epoxide is reduced to the quinone by a warfarin-sensitive reductase, and the quinone is reduced to the active hydroquinone by either the same warfarin-sensitive reductase or a warfarin-insensitive... 

The CaH2/Si02 System. Almost by chance, Zhou and colleagues found that the reaction time in Sharpless epoxidation could be reduced dramatically by adding a catalytic amount of calcium hydride and silica gel to the reaction system, although the mechanism is not yet clarified (Table 4 1).12... 

Conditions Method A Epoxidation using Sharpless reagent method B addition of 0.05-0.1 equivalent of calcium hydride and 0.1-0.15 equivalent of silica gel to the Sharpless reagent, ee = Enantiomeric excess. 

Reduction of benzyl ethers. Benzyl ethers are cleaved in high yield by calcium (2 equiv.) in liquid ammonia. By proper control of the amount of metal, selective reduction of benzyl ethers is possible in the presence of a triple bond or a t-butyldimethylsilyl ether group. However, there is little selectivity between benzyl ethers and thiophenyl, epoxide, or keto groups in this reduction. 

Addition of l,3-bis(methylthio)allyllithium to aldehydes, ketones, and epoxides followed by mercuric ion-promoted hydrolysis furnishes hydroxyalkyl derivatives of acrolein5 that are otherwise available in lower yield by multistep procedures. For example, addition of 1,3-bis-(methylthio)allyllithium to acetone proceeds in 97% yield to give a tertiary alcohol that is hydrolyzed with mercuric chloride and calcium carbonate to saturated aldehyde.8 Similarly, addition of l,3-bis(methylthio)allyl-lithium to an epoxide, acetylation of the hydroxyl group, and hydrolysis with mercuric chloride and calcium carbonate provides a 5-acetoxy-a,/ -unsaturatcd aldehyde,6 as indicated in Table I. Cyclic cis-epoxides give aldehydes in which the acetoxy group is trans to the 3-oxopropenyl group. 

Yamaguchi I, Matsumura F, KadousAA. 1980. Heptachlor epoxide Effects on calcium-mediated transmitter release from brain synaptosomes in rat. Biochem Pharmacol 29(12) 1815-1823. 

Domb, A. J., Manor, N., Elmalak, O. (1996). Biodegradable bone cement compositions based on acrylate and epoxide terminated poly(propylene fumarate) oligomers and calcium salt compositions. Biomaterials, 77,411-417. 

The dihydrofuran derivative 35 was also employed for the synthesis of ethyl 3-amino-3-deoxy-/3-DL-arafiino-pentofuranoside (40b). The synthesis was accomplished27 in three stages. By the action of calcium hypochlorite on 35, a chlorohydrin intennediate was formed which, on treatment with a base, afforded a mixture of the epoxides 37, 38,... 

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