KOVEMBER
1959
METHOXYTETRALOXES
1759
hr. After renioval of the thionyl chloride, the residue was showed the presence of orange-yellow and pale yellow dissolved in nitrobenzene (30 ml.) and aluminum chloride crystals. (12 g.) was added gradually at 20-25'. The mass turned dark A m / . Calcd. for C2aH9XO5:C, 70.0; H, 2.6; N, 4.1. then violet. Sfter overnight stirring a t room temperature, Found: C, 70.1; H, 2.7; ii,4.0. the reaction product was drowned in ice and hydrochloric The above mixture of nitro isomers X and I X ( 5 g.) was acid and the nitrobenzene was steam distilled. The residue stirred with concentrated sulfuric acid in the manner dewas removed by filtration and slurried with an excess of scribed for the mixture of nitro isomers I11 and IV. The dilute sodium hydroxide solution to separate unreacted insoluble material crystallized from o-dichlorobenzene starting material. The alkali insoluble product was purified yielded 2.6 g. of I X as bright orange cryst>als;m.p. 344by vatting to yield 1.1 g. of crude material, m.p. 325-328", 346 " . which on crystallization from toluene (Darco) gave 1.0 g. Anal. Calcd. for C20H9N05:C, 70.0; H, 2.6; 5 , 4.1. of VI11 as orange crystals; m.D. 330-332". Found: C, 70.0; H, 2.7; K,4.0. Anal. Calcd. for CpoHgBrOj: C, 63.6; H, 2.4. Found: The sulfuric acid filtrate, drovined slowly on ice, gave 2.1 C, 63.4; H, 2.4. g. of X as a red-brown precipitate; m.p. 314-322". CrystalThe alkaline filtrate upon acidification with concentrated lization from o-dichlorobenzene yielded yellow crystals (m.p. hydrochloric acid gave 1.9 g. of unreacted a-(o-bromoben- 320-324") with little loss. Anal. Calcd. for CzoH9?;05:C, 70.0; H, 2.6; S , 4.1. Found: zoy1)naphthn [2,1-b]furan-l-carboxylic acid (VII); m.p. 174C, 70.2; H, 2.7; N, 4.0. 176". 8-Aminodinaphtho[1,2-2',Y]furan-?,ld-dione (SII). The Ak mixture of VI11 with the bromo compound obtained from T' (m.p. 330-332") melted a t 330-332'. The identity amine XII, obtained from the nitro isomer S as described of the two bromo derivatives was further substantiated by for the amine V, crystallized from nitrobenzene as redbrown crystals of m.p. 362-364". comparison of the infrared spectra. 9-( p-Tolylsu1fonamido)dinaphtho [b,i-b',S']fu~an-8,iS- Anal. Calcd. for C20Hl1NO3: C, 76.6; Hj 3.5; X, 4.4. dione. A mixture of VI11 (0.2 g.), p-toluenesulfonamide Found: C, 76.8; H, 3.3; K, 4.6. The benaamide of XI1 crystallized from chlorobenzene as (0.14 g.), sodium carbonate (0.08 g.), cuprous chloride (0.01 g.) and nitrobenzene (15 ml.) was heated at 200" for 6 hr. orange needles, m.p. 310-312'. Anal. Calcd. for C&1&04: C, 77.7; H, 3.6; S , 3.35. The crude product was removed by filtration, washed and crystallized from acetic acid to yield bright yellow crystals Found: C, 77.5; H, 3.3; X, 3.4. ll-Aminodinaphtho[1,R-2',S']furan-7,l~-clione (XI). The (90% yield) of n1.p. 286-288". Anal. Caliid. for C P ~ H ~ & O ~C,S :60.0; H, 3.6. Found: amine XI, obtained from the nitro isomer IX, crystallized from nitrobenzene as violet-red cryst,als, m . p 302-30-1". C, 69.3; H, 3.8. Anal. Calcd. for C20HllN03:C, 76.6; H, 3 . 5 ; N, 4.4. The identity of this derivative of VI11 with the p-toluene- Found: C, 76.6; H, 3.3; N, 4.5. sulfonamide obtained from V was established by mixed The benzamide of X I crystallized from chlorobenzene as m.p. determinations and infrared spectra. On the ot,her orange needles, m.p. 292-204'. hand, the mixed m.p. of the p-toluenesulfonsmides of VI11 Anal. Calcd. for C2,H15SOa:X, 3.35. Found: 5 , 3.4. and VI (m.11. 282-284") showed a significant depression Chrowiatographic separation of the 8- and 1I-amino isomers (mixed m.p. 253-260"). ( X I 1 and X I ) . The mixture of the isomeric amines XI1 and Condensatton of 1-naphthol with 2,S-dichloro-5-nitro-i,4- X I (m.p. 2(34-298'), obtained from t'he mixture of the nitro naphthoquinone. 8- and 1I-.Vitrodinaphtho [i,S-S',S'] furan- isomers S and I X by reduction with alkaline sodium hydro7,ld-diones ( X and IX). 2,3-Dichloro-5-nitro-1,4-naphtho- sulfite, was chromatographed as described for the isomeric quinone of n1.p. 175' (13.5 g.), prepared by the method of amines V and VI. The brownish-orange band gave XI1 Fries,8 was r;acted with 1-naphthol (8.0 g.) in the manner (4074 of the mixture) as dark red crystals, m.p. 362-364", described for the nitro isomers I11 and 11'. The precipitate, and the bright violet band gave X I (60%) iis red crystals, after filtration and repeated extraction with boiling water, m.p. 302-304". gave 11.5 g. of an orange product of m.p. 306-308", which WILhIINGTON, 1)EL. was a inixt,iire o f S and IX. Microscopic examination I
"
[CONTRIBUTION FROM
THE
SCHOOL O F CIIEXISTRY, GEORGIA INSTITUTE OB TEcimor,oou]
-4 New Synthetic Route to Methoxytetralones
Received M a y 26, 1%:) 5-ll.lethoq -1-tetralone has been prepared from 8-chloro-5-methoxy-1-tetralone by preferential hydrogenolysis of the halogen atom. The chlorotetralone has also been converted to 5-chloro-8-methoxy-1-tetralone in lorn yield. The infrared and ultraviolet spectra of these compounds are discussed.
Although 5-methoxy-1-tetralone has been previously prepared, it, 8-methoxy-1-tetralone and their derivatives are relatively inaccessible, compared with the well known 6- and 7-methoxytetralones. 5-Methoxytetralone has been prepared from coumarin' in low yield by a six-step synthesis, -
(1) J. Lotkett and W , F. Short, J . Chem. Soc., 787 (1939).
and also by hydrogenation of substituted naphthalene derivatives,2 followed by appropriate conversions. The preparation of 7-methoxytetralone from anisole via ~-(4-rnethoxybensoyl)propionic (2) (a) E. Hardegger, D. Redlich, and A. Gal, H d r . Chim. Acta, 27, 628 (1944). ( b ) D. Papa and E. Schwenk, J. Org. Chem., 14, 366 (1949).
1760
HUFFMAN
acid is well know,3 and the preparation of 6methoxy-l-tetralone in moderate yield has been r e p ~ r t e dUnfortunately .~ all attempts a t preparing 5- and 8-methoxytetralone by the direct succinoylation of an unsubstituted anisole ring afford as the final product, only 7-methoxy-l-tetralone. 5-Methoxy-8-methyl-l-tetralone has, however, been prepared from p-cresyl methyl ether,5 and 5methoxy-4, 8-dimet hyl- 1-tetralone has been syn thesized from the same starting material.6 The parent 5-methoxytetralone would appear to be readily available from some appropriately para substituted anisole derivative, containing an easily removable blocking group. Although the facile hydrogenolysis of halogen bound to an aromatic ring is well known,7 and has been used in the preparation of tetracycline from aureomycin, without disturbing the sensitive ring system of these antibiotics,s this potentially useful blocking group has fouiid little use in organic synthesis until this time. Haworth and Perkin attempted to use a bromine atom as a blocking group in order to accomplish the synthesis of a berberine alkaloid of the natural series rather than the pseudo alkaloid; however, this attempt led only to the extrusion of the bromine and cyclization to the pseudo berberine d e r i ~ a t i v e .An ~ aromatic bromine has been reported to have been successfully employed in the I'schorr synthesis of a phenanthrene derivative,la while one failure of this blocking group in a similar synthesis has been observed. * l The present investigation is concerned with the use of chlorine as a blocking group in the synthesis of 5-methoxy-l-tetralone. Succinoylation of p chloroanisole (I) with aluminum chloride in tetrachloroethane-nitrobenzene afforded 0-(2-methoxy5-chlorobenzoy1)propionic acid (11) in 51% yield. l 2 I n an effort to characterize this compound it was
VOL.
24
oxidized with alkaline permanganate to yield the known 2-methoxy-5-chlorobenzoic acidI3 (111) ; however, unexpected difficulties were encountered in identifying this material. Earlier workers had found the compound to melt a t 79'; our substance had m.p. 97-98', and the infrared spectrum in chloroform solution showed carbonyl absorption a t 5.75 p, and a sharp O-H stretching band a t 3.00 p. The expected spectrum for 2-methoxyd-chlorobenzoic acid in chloroform solution would have a broad -OH band at 3.5 to 4.0 p and a carbonyl band at 5.88 to 5.95 p.I4 I n spite of the anomalous spectrum, the compound was a strong acid, as evidenced by its solubility in aqueous bicarbonate solution, and analysis showed the correct empirical formula, CsH,CIOa, for a chloromethoxybenzoic acid, Since 2-chloro-5-methoxybcnzoic acid has m.p. 170';13 our oxidation product must be 2methoxy-5-chlorobenzoic acid. It seems probable that the acid obtained by the Italian workers was a hydrate or polymorph, because recrystallization of the acid, m.p. 98', from water gave material, m.p. 74-75', which could in turn bc recrystallized from cyclohexane to give the original melting point. Final confirmation of the structure of the
c1
c1
I
H Q
___-
(3) E. D. Haworth arid G. Sheldrick, J . Chem. S O ~ .1951 , (1934). (4) (a: 1'. C. E. Burnop, G. H. Elliott, and R. P. Linstead, J . Chent. Soc., 731 (1940). (b) G. Stork, J . A m . Chem. SOC.,69, 576 (1947). (5) It. B. Woodward and T. Singh, J . Am. Chem. SOC.,72, 494 (1950). ( 6 ) S. AI. Bloom, J . Am. C k e m . Soc., 80, 6280 (1958). Baltzly and A. P. Phillips, J . Am. Chmn. SOC., 68, (7) 1%. 261 (1946). (8) (a) J. 11. Bootlie, J. hlorton, J. P. Petisi, and 11. C. \Vilhinsoii, J . Ani. Clxm. Soc., 75, 4621 (1953). ( b ) C. R. Stephens, L. H. Conover, It. Pasternak, I?. A. Hochstein, P. P. Regna, F. J. Pilgrim, I
