Cyclic ketones are oxidized to lactones or hydroxy acids with peracids in the Baeyer-Villiger reaction. Such peracids include persulfuric, perbenzoic, perphthalic, peracetic and trifluoroperacetic acid. In some instances peracids can be substituted by concentrated (90%) H.sub.2 O.sub.2 and carboxylic acid anhydride.
S. Kamimura et al. in Japan Patent Publication No. 10243-1969 issued May 13, 1969 disclose a method for making esters including cyclic esters, i.e. lactones, by oxidation of ketones including substituted saturated and unsaturated cyclic ketones and alkyl aryl ketones, with hydrogen peroxide in the presence of arsenic, and in general, organic and inorganic arsenic compounds as catalysts. Desirably the ketone contains the structure --CH.sub.2 CO--; and the arsenical catalyst is an arsenate, arsenite or arsenic oxide soluble in the reaction solvent.
S. Kamimura et al. in Japan Patent Publication No. 2728/1970 dated Jan. 29, 1970 discloses a method for making 6-hydroxycaproic acid or its cyclohexylester by decomposition of cyclohexanone peroxides in the presence of arsenic or an arsenic compound as catalyst. A variety of arsenic compounds is proposed, such as oxides, halides and sulfides; and simple organic compounds of arsenic. Use of a solvent stable under the reaction conditions is said to be desirable; a number of specific solvents are named.
In generally similar manner, it is known to oxidize olefins to epoxides by use of arsenic or an arsenic compound as catalyst (U.S. Pat. No. 3,993,673 of Nov. 23, 1976 to McMullen).
To us it seemed possibly desirable to substitute, for the arsenic compounds proposed by Kamimura et al., and by McMullen, polymeric compounds substituted by arsenic groups in porous solid form such as porous granules or beads. Thereby an easy and complete separation of the product mixture in liquid form from such solid granules or beads of arsenical catalyst might be obtainable e.g. by filtration; provided that the polymer, substituted by arsenic groups, is highly stable to the oxidizing reaction conditions employed and sufficiently adsorptive toward the oxidation reaction mixture to achieve good contact of the reaction mixture with the catalytic sites. Accordingly, the polymer must be sufficiently inert and rugged, when in contact with the oxidation reaction mixture, to be resistant to the reaction mixture and easily separated therefrom and not be abraded, or dissolved, or decomposed, or converted into a soft, pulpy gel difficult to separate from the liquid reaction mixture; and at the same time, the polymer must allow ready access of the reaction mixture within the polymer.
Certain macroporous bead polymers substituted by arsenic groups have been studied for purposes of concentration and separation of trace metals from aqueous solutions such as sea water. One of these, polystyrene crosslinked with divinylbenzene ("DVB") and substituted in some of the phenyl rings by arsono (--As(O)(OH).sub.2) groups, appeared to us to be of possible interest for our purpose if it could be prepared with improved stability, toward oxidation by H.sub.2 O.sub.2, over the product of the prior art. The prior art product from crosslinked polystyrene contained substantial amounts of nitrogenous and oxygen-containing substituents on the aromatic ring, such as azo and amino groups and also phenolate, which would be reactive with hydrogen peroxide. Such prior art is represented by the literature article of R. F. Hirsch et al. (Talanta vol. 17 of 1970, pages 483-489; polymer analysis at 486); and article of J. S. Fritz et al. (Talanta vol. 23 of 1976; pages 590-593) wherein use of three macroporous polystyrene DVB resins of differing average pore diameters and surface areas is described, each substituted by arsono groups by the general method of Hirsch, above noted (involving diazotization followed by coupling with sodium arsenite).
A possible alternative preparation might be by bromination and lithiation along the lines proposed in U.S. Pat. No. 3,998,864 of Dec. 21, 1976 to A. E. Trevillyan and divisional U.S. Pat. No. 4,045,493 (preparation of polyphenylene substituted by diphenylphosphine). In our case lithiation might allow introduction of arsenic groups; however we are not aware of any such disclosure in the prior art.