Activated ethers

This reaction is the reverse of the initial ketyl radical formation by the benzophenone triplet and is therm Q4ynamically favorable. The experiments using optically active alcohols as source of hydrogen atoms show, however, that under normal conditions this reaction is unimportant. This is probably due to other, more efficient pathways for reaction of the ketyl radicals or perhaps to diffusion rates which separate the radicals before reverse transfer can occur. That this reaction can be important in some cases even without the presence of sulfur compounds was shown by studying the photoreduction of benzophenone in optically active ethers.<68) Although the reaction of benzophenone in methyl 2-octyl ether is only 0.17 times as fast as that in isopropanol, ethers can be used as sources of hydrogen atoms for photoreduction ... 

Because the reduction potential of ether is usually more negative than that of halides, examples that belong to this category are rather rare. Generally, cathodic reduction of ethers is similar to that of alcohols, and nonactivated ethers are not reducible under the conditions of electroreduction. Activated ethers such as benzylic and allylic ethers are elec-trochemically reduced to a limited extent (Scheme 7) [1, 15, 16]. Reduction of epoxides is usually difficult however, electroreductive cleavage of activated epoxides to the corresponding alcohols is reported [17, 18]. The cleavage of the C—O bond of ethers is more easily accomplished in anodic oxidation than in cathodic reduction, which is stated in Chapter 6. 

DNA synthesis inhibition. Ethanol (90%) extract of the dried entire plant at a concentration of 0.25 mg/mL, was active " " ". Fibrinolytic activity. Ether extracts of the dried gum and gum resin, administered orally to 10 healthy subjects fed 100 g of butter to produce alimentary hyperlipemia, were active " "". ... 

Antioxidant activity. Ether extract of the dried fruit, administered externally to adults as an ingredient in cosmetic, was active. The biological activity has been patented . 

Rate Information from an Optically Active Ether... 

A bisallylically activated ether bridge 94 has been opened by ZrCU (Eq. 42) [44], OSMea... 

Of these reactions, the [2,3]-Wittig rearrangement in particular has often been used as a means of transferring chirality. The product of this reaction has potential stereogenic centers at C-3 and C-4 (if R ), and if the starting ether is optically active because of a stereogenic center at C-1, the product may be optically active as well. Many examples are known in which an optically active ether was converted to a product that was optically active because of chirality at C-3, C-4, or both. If a... 

The barbiturates have little effect on pituitary adrenal activity. Ether, however, is a potent adrenocortical stimulus. This effect of ether can be overcome by giving large amounts of barbiturates. 

Aplysin and (—) debromoaplysin were prepared analogously via lithiation (t-BuLi) of the following optically active ether. 

The previous results discussed here were put in question by a stereochemical study for the optically active ether (+)-50-2-g (68). In this case a one-center... 

Biologically Active Ether Lipids" by P. Braquet et aL, Eds. (Karger, Basel, 1988),... 

Many of the reagents that are used to activate alcohols toward nucleophilic substitution (e.g., SOCI2, PCI3) cannot be used to activate ethers. When an alcohol reacts with an activating agent such as a sulfonyl chloride, a proton dissociates from the intermediate in the second step of the reaction and a stable sulfonate ester results. 

Ionescu et al. exhibited that T. vulgare showed antihelmintic activity. Ether extract, essential oils and (3-thujone isolated from T. vulgare were found as active principles and toxic doses were recorded [183]. 

The only other known work along these lines was reported by Scott and Walker (10). The reaction described therein involves the reduction of metal halides with the highly colored addition compounds (9) which are formed when sodium metal is added to polynuclear hydrocarbons in certain active ether media such as 1,2-dimethoxyethane and dimethyl ether. For example, sodium reacts with a solution of naphthalene in 1,2-dimethoxyethane to produce a dark green solution which contains the sodium addition compound of naphthalene, having the empirical formula CioHsNao. If nickel chloride is added to the colored solution, the metal is reduced to the elemental state as a finely divided nickel powder with an average particle size of less than 20 microns. Similarly, iron, cobalt, and other metal powders can be produced by this method. 

Preliminary studies indicated that extracts from various species of the genus Amomum possessed different activities. Aqueous ethanolic extracts of the rhizomes of A. aromaticum and A. subulatum showed hypoglycemic activity [80]. Water extract of the fruits of A. compactum [81] and 4. xanthiodes [82] possessed anti-tumor activity. Ether extract of the fhiits of A. medium had anti-inflammatory action [83]. Fresh leaf essential oil of A. subulatum showed anti-fungal activity [84]. Methanolic extract of the... 

Alkylation of aromatic compounds, including polystyrene, by halogen alkyls, a-halogen-activated ethers, or acetals represents the reaction of electrophilic substitution on the aromatic ring, which occurs in the presence of Lewis acids (Friedel-Crafts reaction) ... 

Lit. Braquet, Mangold Vargaftig (eds.). Biologically Active Ether Lipids, p. 48-57, Basel Karger 1988. - [HS290949 CAS 10567-22-3 (B.) 506-03-6 (chimyl alcohol) 34043-91-9 (selachyl alcohol)]... 

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