Vinyl ether production from acetylene

POLYVINYL ALKYL ETHERS. These products have properties which range from sticky resins to elastic solids. They are obtained by the low-temperature cationic polymerization of alkyl vinyl ethers having the general formula ROCH=CH-. These monomers are prepared by the addition of die selected alkanol to acetylene in the presence of sodium alkoxide or mercury(ll) catalyst, As shown by the following equations, the latter yields an acetal which must be thermally decomposed to produce the alkyl vinyl ether. 

A new approach to /3-alkyl substituted a-methoxy vinyllithiums 540 with Z-configuration involved the stereoselective metallation of a-bromo vinyl ethers 539, prepared from acetylenes 538, with f-BuLi at — 78 °C (Scheme 145)821. These anions react with different electrophiles to give the corresponding vinyl ethers in good yields. The /3-isobutyl substituted derivative as cuprate has been added to an enone in the total synthesis of the anticancer natural product OSW-1822. 

Several groups have completed computational studies on the relative stabilities of osmium carbyne, carbene, and vinylidene species. DFT calculations on the relative thermodynamic stability of the possible products from the reaction of OsH3Cl(PTr3)2 with a vinyl ether CH2=CH(OR) showed that the carbyne was favored. Ab initio calculations indicate that the vinylidene complex [CpOs(=C=CHR)L]+ is more stable than the acetylide, CpOs(-C=CR)L, or acetylene, [CpOs() -HC=CR)L]+, complexes but it doesn t form from these complexes spontaneously. The unsaturated osmium center in [CpOsL]+ oxidatively adds terminal alkynes to give [CpOsH(-C=CR)L]+. Deprotonation of the metal followed by protonation of the acetylide ligand gives the vinylidene product. 

Three important processes have evolved from Reppe s work. Vinylation, the formation of vinyl derivatives by reaction of such compounds as acids, glycols, and alcohols with acetylene, produces the important vinyl esters and vinyl ethers. Ethinylation is defined as the reaction of acetylene with the carbon atom of a reactant without loss of the triple bond. A major application of the ethinylation reaction is to aldehydes and ketones to give alkynols and alkyndiols—e.g., the reaction of acetylene with formaldehyde to give propargyl alcohol and butyn-2-diol-l,4. Carboxylation (also referred to as carbonylation), the reaction of acetylene with carbon monoxide in the presence of metal carbonyls, has been applied to the production of acrylic acid, acrylates, and hydroquinone. 

The preparation, properties, and reactions, especially polymerization, of products from the acetylene-carbon monoxide reaction, such as acrylic acid and its esters, are given by Blout and Mark (8) and by Schildknecht (98). Similarly treated therein are the vinyl esters from acetylene and carboxylic acids, and other vinylation products such as vinyl ethers. The esterification of organic acids with olefins is reviewed by Morin and Bearse (76). 

As can be seen from equations 2-5, the formation of A -acylenamines proceeds from derivatives of carboxylic acids (having an oxidation level equal to three ), namely anhydrides or add halides RCOX or amides RCONH2, on the one hand, and from carbonyl compounds or their derivatives (oxidation level equal to two ), namely enamines 3, acetylenes 5, or vinyl ethers 6, on the other. Indeed, the acetylenes 5, being the dehydration products of enols, may be regarded as having a masked carbonyl functionwhile the enamines 3 rank with vinyl ethers, vinyl esters and enols, as the heteroanalogs of these carbonyl derivatives (see Section IV). 

Among the hazardous products are the vinyl ethers (flammable) formed from reactions with alcohols in the presence of caustic potash at 150°C (302°F), acetaldehyde (flammable) formed by catalytic addition of water, andtrinitromethane (melts at 15°C/59°F and explodes in the hquid state) formed when acetylene reacts with concentrated nitric acid. 

Butadiene byu-to- dI- en, - dI-K [ISV butane - - dir -h -ene] (1900) N. Buta-1,3-diene, 1,3-butadiene, erythrene, vinylethylene, bivinyl, divinyl. CH2=CHCH=CH2. A gas, insoluble in water but soluble in alcohol and ether, obtained from cracking of petroleum, from coal-tar benzene, or from acetylene. It is widely used in the formation of copolymers with styrene, acrylonitrile, vinyl chloride and other monomers, imparting flexibility to the products made from them. Its homopolymer is a synthetic rubber. As noted it is a synthetic chemical compound, used principally in the... 

Cationic platinum(II) acetylene complexes react with a variety of nucleophiles. Chisholm and Clark showed that the reaction of methanol with coordinated disubsti-tuted acetylenes (generated in situ) affords trans u-bonded vinyl ether complexes (Equation 11.35). The trans stereochemistry of the cr-vinyl group of the product suggests that the nucleophilic attack occurs external to the metal and does not involve prior coordination of methanol, Reger has shown that stable cationic iron-alkyne complexes undergo reaction with a wide variety of nucleophiles to give stable cr-alkenyl complexes resulting from trans attack of the nucleophile on the coordinated acetylene (Equation 11.36). A variety... 

Lithium alkoxides play an important role in the oligomeric cyclization of dinitriles in the synthesis of phthalocyanines. The combination of potassium alkoxide-crown ether complex in a hydrocarbon solvent gives a very powerful catalyst for production of vinyl ethers from alcohols and acetylene (Eq. 7.9). ... 

The cyclization did not work well with 4- or 6-carbon terminal aUcynols or with compounds containing nonterminal alkynes. The proposed mechanism involved initial oxidative addition of the OH group to the rhodium center with loss of CO and coordination of the pendant acetylene. Migratory insertion in a 5-exo-dig mode produces the coordinated cyclic vinyl ether, which could add an alcohol to the vinyl group and reductive elimination of the organic product regenerates the reactive metal complex. Alternatively, reductive elimination from the metal vinyl ether would produce a vinyl ether, which would be trapped by the alcoholic solvent (Scheme 14). 

In the first route, methylbutenol is made from acetone and acetylene followed by hydrogenation. Reaction with methyl isopro-penyl ether yields methylheptenone (6). The second route involves the reaction of isobutylene, formaldehyde and acetone (7 ). Methyl vinyl ketone is an intermediate. Finally, methylheptenone is made by alkylation of acetone with prenyl chloride which is derived from isoprene (8). The initial product is the terminal olefin which is isomerized to the desired isopropylidene compound. 

You will see on the walls the well-known acetylene tree diagram. This shows the wide range of products that can be made from calcium carbide and are made elsewhere - alas, not here - alcohol, acetaldehyde, acetic acid, ether, acetone, ethylene, the vinyl products, solvents, plastics, artificial silk, resins, rubbers. .. Calcium carbide is the only substance which provides these indispensable commodities without requiring one ton of shipping. It is the only route by which they can be made without adding a penny to our already unfavourable balance of trade. It is the only material which costs neither blood nor treasure in war time. .. Our imports of calcium carbide were last year about 70,000 tons. They are increasing. ... 

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