Methyl tert-butyl ether catalysis

Abstract This chapter explores the role of abiotic reactions such as acid catalysis (hydrolysis) as well as the adsorption of methyl tert-butyl ether (MTBE) and other fuel oxygenates in environmental issues as the remediation of these substances is notoriously difficult. First of all, these methods are briefly classified with other abiotic technologies. The suitability of hydrolysis and adsorption for the remediation of water contaminated by fuel oxygenates is then discussed in detail, with information being provided about the principle of the reactions, potential catalysts and sorbents, limitations of the reactions, and practical implications. To conclude, the possible application of hydrolysis and adsorption in combination with other remediation techniques is also examined. 

Shikata, S., Nakata, S., Okuhara, T., Misono, M. 1997. Catalysis by heteropoly compounds. 32. Synthesis of methyl tert-butyl ether catalyzed by heteropolyacids supported on silica. Journal of Catalysis 166(2) 263-271. 

Catalytic Distillation Catalytic or reactive distillation is another example of the use of a hybrid reactor and combines catalysis and distillation in one column/reactor. Usually, we have a two-phase process with gas and liquid flowing in countercurrent mode. This requires special catalysts and packings, for example, monoliths, as in case of a fixed-bed flooding of the reactor would occur at high flow rates. In industry, catalytic distillation is already used for the production of MTBE (methyl tert-butyl ether), an important octane booster (Figure 4.10.77 DeGarmo, Parulekar, and Pinjala, 1992), cumene (DeGarmo, Parulekar, and Pinjala, 1992), and ethylbenzene (Podrebarac, Ng, and Rempel, 1997). 

An alternative method for dialkyl peroxide synthesis is the nucleophilic addition of an alkyl hydroperoxide to an alkene under acid catalysis reported by Davies and coworkers (Scheme 31, path B)113. A similar reaction is the nucleophilic addition of alkylhy-droperoxides to vinyl ethers under acid catalysis, producing perketals. Perketals can be deprotected under mild conditions (THF/water/acetic acid) and this hydroperoxide protection-deprotection sequence has been used by Dussault and Porter as a means for the resolution of racemic hydroperoxides (see also Section II.A.2)67. In this respect more detailed studies were carried out with the perketals 75, which were prepared via reaction of alkyl hydroperoxides with vinyl ethers (Scheme 33). Weissermel and Lederer reported that in the presence of tert-butyl hypochlorite, a-chlorodialkyl peroxides can be formed in yields between 12% and 45% (Scheme 31, path C)114. a-Alkoxydialkyl peroxides and diperoxyacetals were prepared by Rieche and coworkers via acid catalyzed reaction of one or two equivalents of alkyl hydroperoxides with acetals, ketals or aldehydes (Scheme 31, path D)115 or by methylation of the corresponding a-alkoxy hydroperoxides with diazomethane (yields 11%, 27%)"6. The diperoxyacetals 76 were isolated in yields ranging from 39 to 77%. 

Allyl methyl ether292 (ethyl diazoacetate, rhodium catalysis) and allyl tert-butyl ether124 (dimethyl diazomalonate, copper catalysis) yield cyclopropanes exclusively. With y-substituted allyl methyl ethers, C-0 insertion is generally strongly favored over cyclopropanation, even with tetraacetatodirhodium as catalyst.293 In view of these findings, the cyclopropanation of ( )- ,4-dibenzyloxybut-2-ene in moderate yield, only, to give (la,2a,3/ )-31 is notable.294... 

An illustrative example is the resolution of the carbon-14-labeled hydroxyindane derivative 11, an intermediate in the synthesis of the serotonin uptake inhibitor MDL 21111 A. Under catalysis by lipase from Pseudomonas flourescens, vinyl acetate reacted with the alcohol 11 in tert-butyl methyl ether solvent. After flash-chromatography on silica gel the acylated (12, 43% yield 97% e.e.) and nonacylated (13. 47% yield, 98% e.e.) compounds were obtained in excellent optical pmities. ... 

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