Isopropenylation

Isopropenyl acetate gives spinnable fibres on copolymerization with vinyl chloride. 

Apparatue 500-ml three-necked round-bottomed flask, with a dropping funnel, a mechanical stirrer and a thermometer, combined with a vent, for the addition to the isopropenyl ether for the further reaction the dropping funnel was replaced with a thermometer and the combination of thermometer and vent with a reflux condenser. 

In the flask were placed 1.50 mol of the isopropenyl ether (conmercially available) and 0.10 mol of the (dry) acetylenic alcohol (also commercially available), and in the dropping funnel 0.4 mol of the latter compound. The mixture was cooled to 0°C and 100 mg of anhydrous p-toluenesulfonic acid were added with stirring. 

We noted m Section 2 13 that the common names of certain frequently encoun tered alkyl groups such as isopropyl and tert butyl are acceptable m the lUPAC sys tern Three alkenyl groups—vinyl, allyl, and isopropenyl—are treated the same way... 

Isopropenyl acetate [108-22-5] which forms upon reaction of acetone [67-64-1] with anhydride, rearranges to acetylacetone [123-54-6] in the presence of BF3 (19) ... 

With aldehydes, primary alcohols readily form acetals, RCH(OR )2. Acetone also forms acetals (often called ketals), (CH2)2C(OR)2, in an exothermic reaction, but the equiUbrium concentration is small at ambient temperature. However, the methyl acetal of acetone, 2,2-dimethoxypropane [77-76-9] was once made commercially by reaction with methanol at low temperature for use as a gasoline additive (5). Isopropenyl methyl ether [116-11-OJ, useful as a hydroxyl blocking agent in urethane and epoxy polymer chemistry (6), is obtained in good yield by thermal pyrolysis of 2,2-dimethoxypropane. With other primary, secondary, and tertiary alcohols, the equiUbrium is progressively less favorable to the formation of ketals, in that order. However, acetals of acetone with other primary and secondary alcohols, and of other ketones, can be made from 2,2-dimethoxypropane by transacetalation procedures (7,8). Because they hydroly2e extensively, ketals of primary and especially secondary alcohols are effective water scavengers. 

The aggregation pheromone of the boU weevil, Jinthonomusgrandis is a mixture of the alcohols D-i7j -2-isopropenyl-l-methylcyclobutaneethanol [30820-22-5] (168) and OT-3,3-dimethyl-A, p-cyclohexaneethanol [26532-23-0] (169) and of the cis- and trans-isomers of the aldehyde of the latter (170). The pheromone is marketed as grandlure [11104-05-5] for monitoring and removal trapping of boU weevil populations. 

Ketones with labile hydrogen atoms undergo enol acetylation on reaction with ketene. Strong acid catalysis is required. If acetone is used, isoptopenyl acetate [108-22-5] (10) is formed (82—85). Isopropenyl acetate is the starting material for the production of 2,4-pentanedione (acetylacetone) [123-54-6] (11). 

Other uses include use as a reaction and extraction solvent in pharmaceutical production as an intermediate for the preparation of catalysts, antioxidants (qv), and perfumes and as a feedstock in the production of methyl isopropenyl ketone, 2,3-butanedione, and methyl ethyl ketone peroxide. Concern has also arisen at the large volume of exported MEK which has been covertly diverted and used to process cocaine in Latin American countries... 

Methyl Isopropenyl Ketone. Methyl isopropenyl ketone [814-78-8] (3-methyl-3-buten-2-one) is a colorless, lachrymatory Hquid, which like methyl vinyl ketone readily polymerizes on exposure to heat and light. Methyl isopropenyl ketone is produced by the condensation of methyl ethyl ketone and formaldehyde over an acid cation-exchange resin at 130°C and 1.5 MPa (218 psi) (274). Other methods are possible (275—280). Methyl isopropenyl ketone can be used as a comonomer which promotes photochemical degradation in polymeric materials. It is commercially available in North America (281). 

The industrial precursor to 2,4-pentanedione is isopropenyl acetate, produced from acetone and ketene (307,308). The diketone is formed by the high temperature isomerization of isopropenyl acetate over a metal catalyst (309—311). 

Reaction conditions depend on the reactants and usually involve acid or base catalysis. Examples of X include sulfate, acid sulfate, alkane- or arenesulfonate, chloride, bromide, hydroxyl, alkoxide, perchlorate, etc. RX can also be an alkyl orthoformate or alkyl carboxylate. The reaction of cycHc alkylating agents, eg, epoxides and a2iridines, with sodium or potassium salts of alkyl hydroperoxides also promotes formation of dialkyl peroxides (44,66). Olefinic alkylating agents include acycHc and cycHc olefinic hydrocarbons, vinyl and isopropenyl ethers, enamines, A[-vinylamides, vinyl sulfonates, divinyl sulfone, and a, P-unsaturated compounds, eg, methyl acrylate, mesityl oxide, acrylamide, and acrylonitrile (44,66). 

Hydration and Dehydration. Succinic anhydride reacts slowly with cold water and rapidly with hot water to give the acid. For this reason it must be carefully stored in anhydrous conditions. Succinic acid can be dehydrated to the anhydride by heating at 200°C, optionally in the presence of a solvent (31). Dehydration can also be performed with clay catalysis in the presence of isopropenyl acetate under microwave irradiation (32) or with his (trichi oromethyl) carbonate at room temperature (33). 

Acetylsucrose [63648-81-7] has been prepared in 40% yield by direct acetylation of sucrose using acetic anhydride in pyridine at 40° C (36). The 6-ester has subsequently been obtained in greater than 90% yield, by way of 4,6-cycHc orthoacetate. Other selective methods for the 6-acylated derivatives include the use of alkyl tin reagents such as dibutyl tin oxide (37) and of dibutyl stannolane derivatives (38). Selective acetylation of sucrose by an enzymic process has also been described. Treatment of sucrose with isopropenyl acetate in pyridine in the presence of Lipase P Amano gave, after chromatography, 6-0-acetylsucrose (33%) and 4/6-di-O-acetylsucrose (8%). The latter compound has been obtained in 47% yield by the prolonged treatment (39). 

Linalool can be converted to geranyl acetone (63) by the CarroU reaction (34). By transesterification with ethyl acetoacetate, the intermediate ester thermally rearranges with loss of carbon dioxide. Linalool can also be converted to geranyl acetone by reaction with methyl isopropenyl ether. The linalyl isopropenyl ether rearranges to give the geranyl acetone. 

HMD was originally produced by Du Pont as a coproduct in the manufacture of Qiana fiber. Du Pont subsequently sold the product to Bayer. In the 1990s MDA is hydrogenated by Air Products for Bayer (see Amines, aromatic-methylenedianiline). Commercial HMDI is a mixture of three stereoisomers. Semicommercial aUphatic diisocyanates include /n j -cyclohexane-l,4-diisocyanate (CHDI) and y -tetramethylxylylene diisocyanate (TMXDI). A coproduct in the production of TMXDI is y -isopropenyl-a,a-dimethylben2yl isocyanate (TMI), which can be copolymerized with other olefins to give aUphatic polyisocyanates. 

Benzo[6]furan, 5-acetyl-6-hydroxy-2-isopropenyl-UV, 4, 589 (71AJ093)... 

Benzo[b]furan, 2,3-dihydro-2-hydroxymethyl-4//-chromene synthesis from, 3, 764 Benzo[b]furan, 2,3-dihydro-2-isopropenyl-synthesis, 4, 678, 680... 

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