Isobutylene acylation

The reaction of trivalent carbocations with carbon monoxide giving acyl cations is the key step in the well-known and industrially used Koch-Haaf reaction of preparing branched carboxylic acids from al-kenes or alcohols. For example, in this way, isobutylene or tert-hutyi alcohol is converted into pivalic acid. In contrast, based on the superacidic activation of electrophiles leading the superelectrophiles (see Chapter 12), we found it possible to formylate isoalkanes to aldehydes, which subsequently rearrange to their corresponding branched ketones. 

Sulfonated styrene—divinylbensene cross-linked polymers have been appHed in many of the previously mentioned reactions and also in the acylation of thiophene with acetic anhydride and acetyl chloride (209). Resins of this type (Dowex 50, Amherljte IR-112, and Permutit Q) are particularly effective catalysts in the alkylation of phenols with olefins (such as propylene, isobutylene, diisobutylene), alkyl haUdes, and alcohols (210) (see Ion exchange). Superacids. 

Another important use of BCl is as a Ftiedel-Crafts catalyst ia various polymerisation, alkylation, and acylation reactions, and ia other organic syntheses (see Friedel-Crafts reaction). Examples include conversion of cyclophosphasenes to polymers (81,82) polymerisation of olefins such as ethylene (75,83—88) graft polymerisation of vinyl chloride and isobutylene (89) stereospecific polymerisation of propylene (90) copolymerisation of isobutylene and styrene (91,92), and other unsaturated aromatics with maleic anhydride (93) polymerisation of norhornene (94), butadiene (95) preparation of electrically conducting epoxy resins (96), and polymers containing B and N (97) and selective demethylation of methoxy groups ortho to OH groups (98). 

Isobutylene, H2S04. Acyl migration has been observed using these conditions. ... 

The addition of carhon monoxide to isobutylene under high pressures and in the presence of an acid produces a carhon monoxide-olefin complex, an acyl carhocation. Hydrolysis of the complex at lower pressures yields neopentanoic acid ... 

Isobutylene, reaction with chlorosul fonyl isocyanate, 46, 52 Isobutyryl fluoride, 45, 6 Isocyanates, acyl, derivatives of, 46, 17... 

By in situ MAS NMR spectroscopy, the Koch reaction was also observed upon co-adsorption of butyl alcohols (tert-butyl, isobutyl, and -butyl) and carbon monoxide or of olefins (Ao-butylene and 1-octene), carbon monoxide, and water on HZSM-5 (Ksi/ Ai — 49) under mild conditions (87,88). Under the same conditions, but in the absence of water (89), it was shown that ethylene, isobutylene, and 1-octene undergo the Friedel-Crafts acylation (90) to form unsaturated ketones and stable cyclic five-membered ring carboxonium ions instead of carboxylic acids. Carbonylation of benzene by the direct reaction of benzene and carbon monoxide on solid catalysts was reported by Clingenpeel et al. (91,92). By C MAS NMR spectroscopy, the formation of benzoic acid (178 ppm) and benzaldehyde (206 ppm) was observed on zeolite HY (91), AlC -doped HY (91), and sulfated zirconia (SZA) (92). 

The reaction is also called hydrocarboxylation. According to a later modification, the alkene first reacts with carbon monoxide in the presence of the acid to form an acyl cation, which then is hydrolyzed with water to give the carboxylic acid.97 The advantage of this two-step synthesis is that it requires only medium pressure (100 atm). Aqueous HF (85-95%) gave good results in the carboxylation of alkenes and cycloalkenes.98 Phosphoric acid is also effective in the carboxylation of terminal alkenes and isobutylene, but it causes substantial oligomerization as well.99 100 Neocarboxylic acids are manufactured industrially with this process (see Section 7.2.4). The addition may also be performed with formic acid as the source of CO (Koch-Haaf reaction).101 102 The mechanism involves carbocation formation via protonation of the alkene97 103 [Eq. (7.10)]. It then reacts with carbon monoxide... 

An interesting example of an indirect acylation of alkenes is the reaction of small olefins (ethylene, propylene, isobutylene) over H-ZSM-5 in the presence of CO at 23°C to give unsaturated ketones.122 In this case the acylium ion is formed in situ from the alkene and CO in the pores of the zeolite at ambient temperature ... 

Acyl sulfines, a-oxo sulfines, participate readily as 2tt components of Diels-Alder reactions with a range of dienes (Chapter 5).43-45 In addition, stable acyl sulfines (Scheme 8-XI) have been shown to participate as 4v components in Diels-Alder reactions with ethyl vinyl ether43 and isobutylene.44... 

The reactions of tertiary halides are frequently different from those of the corresponding primary compounds. The former are readily converted into unsaturated hydrocarbons as the result of the elimination of hydrogen halide. Thus, tertiary butyl iodide when heated with ammonia does not form an amine as normal butyl iodide does, but is converted into isobutylene. The effect of the positive or negative nature of the group in combination with a halogen atom on its reactivity when brought into contact with other compounds, will be considered in the discussion of acyl halides (272, 275). 

A Novel Reactive Functionalization of Polyolefin Elastomers Direct Functionalization of Poly(isobutylene-co-p-methylstyrene) by a Friedel-Crafts Acylation Reaction... 

This reaction was first reported by Kriewitz in 1899. It is the condensation between formaldehyde and olefins to form unsaturated primary alcohols under conditions of high temperature (e.g., 170°C). In this reaction, water or acetic acid is usually applied as the solvent, and an acid is added as a catalyst, such as sulfuric acid. Under these conditions, formaldehyde and some ketones function as an enophile. The double bond in the new unsaturated alcohol is adjacent to its original position in the starting olefin," with the exception of camphene, which gives an allylic alcohol. For the acylic olefins in this condensation, the isobutylene-type olefins are much more reactive than the monosubstituted olefins or 1,2-disubstituted olefins. The further extension of this reaction involving an intramolecular condensation of an a-alkoxycarbenium ion with a double bond to form a hydropyran derivative is known as the Prins-Kriewitz cyclization. ... 

The direction of the addition of the hydrocarbonyl to the olefin may, within certain limitations, be influenced by varying the reaction temperature and CO partial pressure or by replacing CO ligands by other com-plexing agents. As shown by R. F. Heck and D. S. Breslow [35, 759] and by Y. Takegami et al. [58], the olefinic compound itself may exert a strong influence. Under certain conditions the hydrocarbonyl may even be forced to react in the acid form. Thus, at low temperatures isobutylene reacts with hydrocarbonyl to form trimethylacetyl cobalt carbonyl [35, 759] nearly exclusively. The acyl compound could be trapped with triphenylphosphine. It reacted with methanol to form methyl trimethylacetate. 

Taylor attempted the reaction of MA with ethylene at 25 C. An excess of aluminum chloride was needed. Interestingly, the reaction mixture absorbed two moles of ethylene before slowing down. A 15% yield of the unsaturated keto acid 165 was obtained. Isobutylene residue in the latter may reflect isomerization of a carbonium intermediate. No by-products were explored but if dimerization precedes acylation, contributions by ene reaction and polymerizations cannot be ruled out. 

Maleic anhydride grafting (cont.) poly(styrene-co-divinylbenzene), 694 poly(styrene-co-isobutylene), 675, 689 poly(styrene-co-nfialeic anhydride), 676, 679 poly(vinyl acetate), 676, 694 poly(vinyl acetate-co-vinyl fluoride), 678 poly(vinyl alkyl ethers), 675, 679, 692, 701 poly(vinyl chloride), 683, 692, 693, 695, 702 poly(vinylidene chloride), 691 poly(vinyl toluene-co-butadiene), 689 radical—initiated, 459-462, 464-466, 471, 475, 476 radiation—initiated, 459, 461, 466, 471, 474 redox-initiated, 476 rubber, 678, 686, 687, 691, 694 to saturated polymers, 459-466, 475, 476 solvents used 460-463, 465, 466, 469, 474-476 styrene block copolymers, 679 tall oil pitch, 678, 697 terpene polymers, 679, 700 thermally-initiated, 462, 464-467, 469, 476 to unsaturated polymers, 459, 466-474 vapor-phase techniques, 464, 474, 475 to wool fibers, 476 Maleic anhydride monomer acceptor for complex formation, 207-210 acetal copolymerization, 316 acetone CTC thermodynamic constants, 211 acetone photo-adduct pyrolysis, 195, 196 acetylacetone reaction, 235 acetylenic photochemical reactions, 193-196 acrylamide eutectic mixtures, 285 acylation of aromatic acids, 97 acylation of aromatics, 91, 92 acylation of fused aromatics, 92, 95, 97, 98 acylation of olefins, 99 acylation of phenols, 94-96 acylic diene Diels-Alder reactions, 104-111, 139 addition polymer condensations, 503-505 adduct with 2-cyclohexylimino-cyclopentanedi-thiocarboxylic acid, 51 adducts for epoxy resins curing, 507-510 adduct with 2-iminocyclopentanedithiocarboxylic acid, 51... 

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