MARCH,1964
OZONOLYSIS OF NAPHTHALENES
703
Ozonolysis of Naphthalenes. The Aliphatic Products and Mechanism C. D. JOHNSON AND PHILIP S. BAILEY Department of Chemistry, The University of Texas, Austin 18, Texas Received August 16, 1963 Further evidence for the course of ozonolysis in methanol of naphthalene and certain substituted naphthalenes has been obtained by V.P.C. examination of the decomposition products of the hydroperoxides formed from carbons 2 and 3 of the naphthalene ring system. These products are compared with the decomposition products of certain olefinic compounds which should give the same hydroperoxides upon ozonolysis in methanol. In two cases the products from ozonolysis of only one bond of the naphthalene nucleus have been studied. Evidence is presented for the stage a t which ozonolvsis of 2-alkoxynaphthalenes differs from that of 6-naphthol and the other naphthalenes studied.
SCHEME 1 The preceding paper' discusses the aromatic peroxidic and nonperoxidic ozonolysis products of naphthalene 1 (Ia), 2,3-dimethylnaphthalene (Ib), 2-naphthol (IC), 2-methoxy- (Id), and 2-ethoxynaphthalene (Ie). From R' ozonolyses of Ia, Ib, and ICin methanol the major peroxidic product was 4-methoxy-2,3-benzodioxan-l-o1 (IV), whereas from Id and Ie under the same conditions / J (Xb). Evidence it was 1,4-dimethoxy-2,3-benzodioxan J OH was presented that IV arose from cyclization of 11, H / produced along with peroxides I11 which were not isolated, and that the precursor to X b was IX, produced along with methyl or ethyl glyoxalate (VIIId or e) VI1 which were isolated. IV + Since the yields of IV from I b and ICwere not high, and since the possibility was not entirely eliminated R'-C-OCHs II that X b could have arisen from IV, and VIIId or e from 0 the corresponding peroxides I11 (e.g. VIIId from IIId or IIIj), it was important to check the validity of the OR H. proposed reaction courses by seeking evidence for or against peroxides I11 in the ozonolysis reaction mixtures. Thus, the present paper reports a study of the aliphatic ozonolysis products (involving carbons 2 and 3) of 'CH3 1A Ia, Ib, IC,Id, Ie, 2-methylnaphthalene (If), I-methylX naphthalene, and 1,4-dimethylnaphthalene. The latter 0 3 R-C-CH=CH--C-R VI11 + 111 three compounds were included because, although some II 1 I CHnOH 0 0 of the nonperoxidic ozonolysis products are known, the XI route to these substances was not fully e l ~ c i d a t e d , " ~ os c6;iy30 + I11 and it was of interest to compare the reaction courses in CsHs-CH=C H- C- R CH,OH methanol of these three with those of the other naphI1 C6H5CH/ooH 0 thalene compounds studied. The paper also discusses 'OCHa XI1 XIV partial ozonolysis products (from cleavage of the 1,2 + bond of ICand Id) and the mechanism of ozonolysis of VI11 the naphthalene ring system. a,R=R'=H f, R = CHs; R ' = H b, R = R' = CHs Peroxides I11 proved to be too unstable to isolate, g, R = H ; R' = CHa C, R = OH; R' = H h, R = phenyl; R' = H although their presence was indicated by iodide reducd, R = OCHa; R' = H i, R = R' = E t tion of the dilute ozonolysis mixtures of I a and Ib, e, R = OEt; R' = H H ; R' = OCHj 1, R k, R = CHI; R ' = E t which showed 1 mole equiv. of active oxygen; peroxide IV under these conditions undergoes rearrangeoxyacophenones (e.g. IIIh). These peroxides decomment rather than reduction.' pose in methanol to an acid and an ester, presumably Compounds 111were studied by means of quantitative via a concerted rearrangement (e.g. IIIh --.+ VIIh + v.p. c. determinations of the vola tile aliphatic ozonolVh VIh). ysis decomposition products of the various naphthalene The compounds studied for comparison with the compounds. The results, shown in Table I, were comnaphthalenes were fumaric acid (XIc), methyl fumarate pared with the results of similar studies with several (XId), and ethyl fumarate (XIe), which should give olefinic compounds which should give identical perthe corresponding 111 and VI11 compounds, and transoxides 111 upon ozonolysis, and with the results of cinnamaldehyde (XIIa), which should give a t least Bailey and Chang4 with several a-alkoxy-a-hydropersome IIIa. It had been desired to study maleic dialdehyde (XIa) which should give only I I I a and VIIIa, (1) P. S.Bailey, S.S. Bath, F. Dobinson, F. J . Garcia-Sharp, and C. D. Johnson, J . Or& Chem.. 19, 697 (1964). whereas XIIa, according to the Criegee mechanism,66 (2) R. H. Callighan and M. H. Wilt, i b i d . , 16, 5212 (1961).
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