Acetals, acid catalyzed

Chevron Chemical Co. began commercial production of isophthahc acid in 1956. The sulfur-based oxidation of / -xylene in aqueous ammonia at about 320°C and 7,000—14,000 kPa produced the amide. This amide was then hydrolyzed with sulfuric acid to produce isophthahc acid at about 98% purity. Arco Chemical Co. began production in 1970 using air oxidation in acetic acid catalyzed by a cobalt salt and promoted by acetaldehyde at 100—150°C and 1400—2800 kPa (14—28 atm). The cmde isophthahc acid was dissolved and recrystallized to yield a product exceeding 99% purity. The Arco technology was not competitive and the plant was shut down in 1974. 

These are initial rates of acetohydroxamic acid formation from acetic acid, catalyzed by nickel chloride. 

Scheme 2.34 Acetic acid-catalyzed ring-opening.

Yuen et al. [24] first demonstrated the nature of the information that can be obtained regarding chemical mapping within a fixed-bed reactor, using the liquid phase esterification of methanol and acetic acid catalyzed within a fixed bed of H+ ion-exchange resin (Amberlyst 15, particle size 600-850-pm) catalyst as the model... 

The concept of zeolite action was tested in a particular reaction where the enzyme is exposed from the beginning to an acidic environment the esterification of geraniol with acetic acid catalyzed by Candida antarctica lipase B immobilized on zeolite NaA [219]. Lipases have been used for the hydrolysis of triglycerides and due to their ambivalent hydrophobic/hydrophilic properties they are effective biocatalysts for the hydrolysis of hydrophobic substrates [220]. When water-soluble lipases are used in organic media they have to be immobilized on solid supports in order to exhibit significant catalytic activity. 

With a-hydroxy ketones and their related tosyloxy derivatives. The imidazo [2,T ]thiazole 364 was prepared by acetic acid-catalyzed cyclocondensation of 2-hydroxy-l,2-diphenyl-ethanone with thiophenyl-substituted 2-aminothiazole 363 (Equation 163) <2002MI110>. Under MW irradiation and in the presence of montmorillonite K-10 clay, a mixture of a-tosyloxyketones 365 and 2-imidazolidinethione led to the substituted 5,6-dihydro-imidazo[2,l- ]thiazoles 366 (Equation 164) <1998J(P1)4093>. When using a-tosyloxyacetophenone, prepared by reaction of acetophenone with [hydroxyl(tosyloxy)iodo]benzene (HTIB), 5-aminopyrazole 367 could be converted to imidazo[l,2- ]pyrazole 368 in basic medium (Equation 165) <2005JHC209>. 

Three methods have thus emerged for the cyclization of dipeptide esters base-catalyzed cyclization (Fischer) cyclization without any added catalyst, under essentially neutral conditions (autoaminolysis Nitecki) and acetic acid-catalyzed cyclization (Suzuki). 

The acetic acid-catalyzed cyclization procedure was adopted in a synthesis of the antifungal antibiotic piperazinomycin (86TL4481). The for-... 

In one case, however, the carbonyl group did migrate in the acetic acid catalyzed rearrangement of cyclobutanone 5 in refluxing toluene.141 This is probably due to a different mechanism involving the second carbonyl and the methoxy group present in 5. 

The broken line in Figure 2 shows that the steady rate of oxidation of 4.07M ethylbenzene in acetic acid, catalyzed by cobalt acetate, reaches a limiting rate of 2.2 X 10 r> mole liter"1 sec. 1 (after correcting for the dielectric effect (5,9), 1.8 X 10 5), which is in excellent agreement with the theoretical limiting rate of 1.85 X 10"r> mole liter 1 sec. 1 as calculated by 32(RH)2/2 6. 

Industrial Applications. Several large scale industrial processes are based on some of the reactions listed above, and more are under development. Most notable among those currently in use is the already mentioned Wacker process for acetaldehyde production. Similarly, the production of vinyl acetate from ethylene and acetic acid has been commercialized. Major processes nearing commercialization are hydroformylations catalyzed by phosphine-cobalt or phosphine-rhodium complexes and the carbonylation of methanol to acetic acid catalyzed by (< 3P) 2RhCOCl. 

Figure 8. Overall description of the acetic acid catalyzed reconstruction of a defect containing indium oxide overlayer on indium (20)...

Another interesting and different type of catalysis is involved in the catalyzed reconstruction of an indium oxide overlayer on indium. This study was alluded to earlier in the discussion of acetate ion species formed on indium oxide by chemisorption from several torr of acetic acid gas. At low partial pressures of acetic acid (<< 0.1 torr) the reversible adsorption of acetic acid catalyzes the reconstruction of a thin ( 10-15A), porous indium oxide overlayer to a defect-free (no pin holes) film as judged by pinhole sensitive tunnel junction measurements. Some clues as to the mechanism were obtained from IR plus Auger and electron loss spectroscopy as well as ellipsometry measurements. The overall process is shown in Fig. 8. This is an example where processes in the substrate themselves can be usefully catalyzed. 

Imamura S, Hirano A, Kawabata N. Wet oxidation of acetic acid catalyzed by Co-Bi complex oxides. Ind Eng Chem Prod Dev 1982 21(suppl 4) 570-575 Imamura S, Fukuda I, Ishida S. Wet oxidation catalyzed by ruthenium supported on cerium(IY) oxides. Ind Ing Chem Res 1988 27(suppl 4) 718-721. 

Clemmensen-type reduction.1 Aromatic ketones can be reduced to the corresponding methylene compounds with ammonium formate on transfer hydrogenation in acetic acid catalyzed by 10% Pd/C. The reduction is usually complete in 10-30 minutes at 110°. Halo and nitro substituents can be reduced under these conditions, and a,p-unsaturated carbonyl groups are reduced to saturated carbonyl groups. 

Al.2.6 Analysis of a Model System the Monsanto Carbonylation of Methanol to Acetic Acid Catalyzed by Rh/I ... 

The Monsanto carbonylation of methanol to acetic acid catalyzed by Rh/H is a well-understood example of an organometallic catalytic cycle and can act as a good model with well defined steps (shown schematically in Chapter 4, Section 4.2.4). The starting material is the square planar Rh(I) complex, [Rh(CO)2l2] which is easily accessible by reaction of rhodium trichloride in solution with CO in the presence of iodide. This undergoes oxidative addition with Mel very readily to give the methyl-Rh(III) complex [Rh(Me)(CO)2l3] as an unstable... 

Later, an alternative synthesis of similar symmetrical calix [3]indoles was reported.In this work, also from Black s group, it was disclosed that macrocycles such as 2.386-2.391 could be prepared in ca. 60% yield via the acetic acid-catalyzed trimerization of the corresponding 7-hydroxymethyl indole derivatives 2.380-2.385 (Scheme 2.3.25). Calix [3]indole 2.390 can also be obtained by treatment of the 2-hydroxymethyl indole compound 2.392 with p-TsOH in dichloromethane. In 1996, Black and coworkers reported yet a third, but related, means of synthesizing... 

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