1,1 - ether formation

Silyl enol ether formation with RsSiCl-p EtsN gives thermodyanamic silyl enol ether... 

Addition of a hydroxy group to alkynes to form enol ethers is possible with Pd(II). Enol ether formation and its hydrolysis mean the hydration of alkynes to ketones. The 5-hydroxyalkyne 249 was converted into the cyclic enol ether 250[124], Stereoselective enol ether formation was applied to the synthesis of prostacyclin[131]. Treatment of the 4-alkynol 251 with a stoichiometric amount of PdCl2, followed by hydrogenolysis with formic acid, gives the cyclic enol ether 253. Alkoxypalladation to give 252 is trans addition, because the Z E ratio of the alkene 253 was 33 1. 

Condensation reaction (Section 15 7) Reaction m which two molecules combine to give a product accompanied by the expulsion of some small stable molecule (such as water) An example is acid catalyzed ether formation... 

Ether alcohols Ether formation Ether hydroperoxides Etherification... 

Mobil MTG and MTO Process. Methanol from any source can be converted to gasoline range hydrocarbons using the Mobil MTG process. This process takes advantage of the shape selective activity of ZSM-5 zeoHte catalyst to limit the size of hydrocarbons in the product. The pore size and cavity dimensions favor the production of C-5—C-10 hydrocarbons. The first step in the conversion is the acid-catalyzed dehydration of methanol to form dimethyl ether. The ether subsequendy is converted to light olefins, then heavier olefins, paraffins, and aromatics. In practice the ether formation and hydrocarbon formation reactions may be performed in separate stages to faciHtate heat removal. 

Trifluoromethanesulfonic acid is miscible in all proportions with water and is soluble in many polar organic solvents such as dimethylformamide, dimethyl sulfoxide, and acetonitrile. In addition, it is soluble in alcohols, ketones, ethers, and esters, but these generally are not suitably inert solvents. The acid reacts with ethyl ether to give a colorless, Hquid oxonium complex, which on further heating gives the ethyl ester and ethylene. Reaction with ethanol gives the ester, but in addition dehydration and ether formation occurs. 

Liquid Fuels via Methanol Synthesis and Conversion. Methanol is produced catalyticaHy from synthesis gas. By-products such as ethers, formates, and higher hydrocarbons are formed in side reactions and are found in the cmde methanol product. Whereas for many years methanol was produced from coal, after World War II low cost natural gas and light petroleum fractions replaced coal as the feedstock. 

Transesterification of methyl methacrylate with the appropriate alcohol is often the preferred method of preparing higher alkyl and functional methacrylates. The reaction is driven to completion by the use of excess methyl methacrylate and by removal of the methyl methacrylate—methanol a2eotrope. A variety of catalysts have been used, including acids and bases and transition-metal compounds such as dialkjitin oxides (57), titanium(IV) alkoxides (58), and zirconium acetoacetate (59). The use of the transition-metal catalysts allows reaction under nearly neutral conditions and is therefore more tolerant of sensitive functionality in the ester alcohol moiety. In addition, transition-metal catalysts often exhibit higher selectivities than acidic catalysts, particularly with respect to by-product ether formation. 

Etherification. Carbohydrates are involved in ether formation, both intramoleculady and intermoleculady (1,13). The cycHc ether, 1,4-sorbitan, an 1,4-anhydroalditol, has already been mentioned. 3,6-Anhydro-a-D-galactopyranosyl units are principal monomer units of the carrageenans. Methyl, ethyl, carboxymethyl, hydroxyethyl, and hydroxypropyl ethers of cellulose (qv) are all commercial materials. The principal starch ethers are the hydroxyethyl and hydroxypropylethers (see Cellulose ethers Starch). 

The stmcturaUy similar starch amylose polymer is linked through the a anomeric configuration. The three hydroxyl functions pet anhydroglucose unit ate noteworthy these hydroxyls ate the active sites for ether formation. 

Reactions of the Side Chain. Benzyl chloride is hydrolyzed slowly by boiling water and more rapidly at elevated temperature and pressure in the presence of alkaHes (11). Reaction with aqueous sodium cyanide, preferably in the presence of a quaternary ammonium chloride, produces phenylacetonitrile [140-29-4] in high yield (12). The presence of a lower molecular-weight alcohol gives faster rates and higher yields. In the presence of suitable catalysts benzyl chloride reacts with carbon monoxide to produce phenylacetic acid [103-82-2] (13—15). With different catalyst systems in the presence of calcium hydroxide, double carbonylation to phenylpymvic acid [156-06-9] occurs (16). Benzyl esters are formed by heating benzyl chloride with the sodium salts of acids benzyl ethers by reaction with sodium alkoxides. The ease of ether formation is improved by the use of phase-transfer catalysts (17) (see Catalysis, phase-thansfer). 

The piincipal by-pioducts aie the result of direct chlorine addition to give 1,2-dichlotoptopane [78-87-5] and ether formation. The ether product is dichloropropyl ether [108-60-1] or 2,2 -oxybis(l-chloropropane). 

Diethyl ether is the principal by-product of the reaction of ethyl alcohol with diethyl sulfate. Various methods have been proposed to diminish its formation (70—72), including separation of diethyl sulfate from the reaction product. Diethyl sulfate not only causes an increase in ether formation but is also more difficult to hydroly2e to alcohol than is ethyl hydrogen sulfate. The equiUbrium constant for the hydrolysis of ethyl hydrogen sulfate is independent of temperature, and the reaction rate is proportional to the hydrogen ion concentration (73—75). 

MILLER - SNYDER Aiyl Cyanide Synthesis Synthesis of benzonitnies from aldehydes via oxime ethers Formation of p-cyanophenol from p nrtrobenzaldoxime and p-nitiobenzonitnle (used as a sometimes recyclable chain carrier)... 

PEDERSEN Crown Ethers Crown ether formation and its use in substitutions, oxidations,etc... 

Coclaurine is of special interest since worcoclaurine (I MeO HO) can be regarded as the parent substance from which by ether formation the series of bisbenzylisoquinoline alkaloids can arise. Thus, the dauricine type of alkaloid may be formed by a single ether linkage between the 4 -hydroxyl of one woreoclaurine molecule and a hydrogen atom ortho to the 4 -hydroxyl of a second molecule. 

Steroidal 17-cyanohydrins are relatively stable towards chromium trioxide in acetic acid (thus permitting oxidation of a 3-hydroxyl group ) and towards ethyl orthoformate in ethanolic hydrogen chloride (thus permitting enol ether formation of a 3-keto-A system ). Sodium and K-propanol reduction produces the 17j -hydroxy steroid, presumably by formation of the 17-ketone prior to reduction. ... 

With 11/3-hydroxy steroids, 11/3, 19-ether formation competes with hemi-acetal formation.This is a consequence of steric hindrance of the 11/5-oxygen by the C-18 and C-19 iodomethyl groups which reduces the rate of hypoiodite formation [(3) (5)] even though the conformation of the... 

Because of the increased acidity and reduced steric requirement of the carbohydrate hydroxyl, t-BuOK can be used as a base to achieve ether formation. 

A study of the reductive cleavage of a series of alkoxymethyl ethers using the glucose backbone shows that, depending on the reagent, excellent selectivity can be obtained for deprotection vs. methyl ether formation for most of the common protective groups. ... 

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