Isopropylnaphthalene oxidation

Another method of manufacture involves the oxidation of 2-isopropylnaphthalene ia the presence of a few percent of 2-isopropylnaphthalene hydroperoxide/i)ti< 2-22-(y as the initiator, some alkaU, and perhaps a transition-metal catalyst, with oxygen or air at ca 90—100°C, to ca 20—40% conversion to the hydroperoxide the oxidation product is cleaved, using a small amount of ca 50 wt % sulfuric acid as the catalyst at ca 60°C to give 2-naphthalenol and acetone in high yield (70). The yields of both 2-naphthalenol and acetone from the hydroperoxide are 90% or better. 

A process variation of the extraction of 2-isopropylnaphthalene hydroperoxide from the cmde oxidation product with an alkylene glycol has been patented (71). The 2-naphthalenol plant of American Cyanamid, which was using the hydroperoxidation process and had a 14 x 10 t /yr capacity (72), ceased production in 1982, leaving the United States without a domestic producer of 2-naphthol. The 2-naphthol capacity in the Western world is approximately 50 x 10 t/yr, with ACNA, Italy and Hoechst AG, Germany operating the largest plants. China produces about 7 x 10 t/yr. Other important producing countries are Poland, Romania, the former Czechoslovakia, and India (35,52). 

Several biocatalytic processes for the production of (5)-(+)-naproxen (5) have also been developed (see Chapter 19). Direct isomerization of racemic naproxen (4) by a microorganism catalyst, Exophialia wilhansil, was reported to give the (S)-isomer 5 (92%, 100% ee) (Scheme 6.5).2X A 1-step synthesis of (5)-(+)-naproxen (5) by microbial oxidation of 6-methoxy-2-isopropylnaphthalene (12) was developed by IBIS (Scheme 6.6).29 In both cases, typical bioprocess-related issues such as productivity, product isolation, and biocatalyst production have apparently prevented them from rapid commercialization. 

An analogous process has been used industrially for the synthesis of 2,6-di-isopropylnaphthalene from naphthalene and propylene in the presence of H-mordenite, another shape-selective zeolite (Equation 7). Oxidation of... 

Enzymatic reduction, oxidation, ligase, or lyase reactions, especially, provide us with numerous examples in which prochiral precursor molecules are stereo-selectively functionalized. Ajinomoto s S-tyrosinase-catalyzed L-dopa process [112], the formation of L-camitine from butyro- or crotonobetaine invented by Lonza [113], and the IBIS naproxen route oxidizing an isopropylnaphthalene to an (S)-2-arylpropionic acid are representative, classic examples for many successful applications of enzymatic asymmetric synthesis on an industrial scale. A selection of recent industrial contributions in this field are summarized below. 

Two routes have gained industrial prominence to produce 2-naphthol, namely alkali fusion of sodium naphthalene-2-sulfonate and the oxidative cleavage of 2-isopropylnaphthalene. 

American Cyanamid operated a plant with a capacity of 14,000 tpa 2-naphthol, for some years prior to 1982 for the oxidation of 2-isopropylnaphthalene. 2-Iso-propylnaphthalene can be obtained from propylene and naphthalene at 150 to 240 °C and 10 bar with a phosphoric acid catalyst using a large excess of naphthalene, followed by isomerization to a mixture of 1- and 2-isopropylnaphthalenes (5 95). The introduction of air (oxygen) at 110 °C produces the a-hydroperoxide of the 2-isomer. The hydroperoxide is cleaved with sulfuric acid, in a manner analogous to the Hock synthesis of phenol the 2-naphthol yield is around 95%. 

Zawadiak et al. [620] studied the retention of three oxidation products of 2-isopropylnaphthalene (IPN), l-(2-naphthyl)ethanone, 2-(2-naphthyI)-2-propanol,... 

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