3194
J. Org. Chem. 1997, 62, 3194-3199
Catalytic Activities of CuSO4/Al2O3 in Dehydrogenation of Arenes by Dioxygen Takaaki Sakamoto,* Hisatomo Yonehara, and Chyongjin Pac* Kawamura Institute of Chemical Research, 631 Sakado, Sakura, Chiba 285, Japan Received July 22, 1996X
The oxidation reactions of hydroquinones, 2-naphthols, or 2,6-di-tert-butylphenol efficiently occurred by catalysis with alumina-supported copper(II) sulfate to give the corresponding benzoquinones, 1,1′-bi-2-naphthols, and 4,4′-diphenoquinone, respectively, in good yields. The synthetic potentiality of the catalytic reactions was demonstrated by easy isolation of the final products using only filtration and solvent evaporation as well as by application to large-scale syntheses of the benzoquinones and binaphthols. The catalysis with alumina-supported copper(II) sulfate was also applied to the oxidative intramolecular coupling of 5,5′-diacenaphthene to the corresponding perylene compound. Introduction Oxidative dehydrogenation reactions of arenes have been providing an important class of synthetic methods, particularly for the oxidation reactions of hydroxyarenes. For instance, the preparation of 1,1′-bi-2-naphthols has been conveniently achieved by the oxidative coupling of 2-naphthols using a variety of oxidants, e.g., FeCl3,1,2 K3[Fe(CN)6],3 Mn(acac)3,4,5 and Cu(II)-amine complexes,6-8 as stoichiometric reagents as well as by such catalyst systems as CuCl2-amine-AgCl combinations,9 CuCl(OH)‚tetramethylethylenediamine complex under O2,10 and solid FeCl3.1 Similarly, the preparative conversion of hydroquinones to quinones has been carried out with a wide variety of stoichiometric oxidants in homogeneous solution11 and also with some catalysts.12-16 While the oxidation of phenols very often gives complex mixtures, hindered phenols are readily oxidized to give discrete oxidation products depending upon the oxidants used as well as upon reaction conditions. A typical example is the oxidation of 2,6-di-tert-butylphenol under O2 that gives usually mixtures of the 1,4-benzoquinone and diphenoquinone, whereas the selective formation of the Abstract published in Advance ACS Abstracts, April 15, 1997. (1) Toda, F.; Tanaka, K.; Iwata, S. J. Org. Chem. 1989, 54, 3007. (2) Pummerer, R.; Rieche, A.; Prell, E. Ber. 1926, 59, 2159. (3) Feringa, B.; Wynberg, H. J. Org. Chem. 1981, 46, 2547. (4) Yamamoto, K.; Fukushima, H.; Okamoto, Y.; Hatada, K.; Nakazaki, M. J. Chem. Soc., Chem. Commun. 1984, 1111. (5) Dewar, M. J. S.; Nakaya, T. J. Am. Chem. Soc. 1968, 90, 7134. (6) Feringa, B.; Wynberg, H. Tetrahedron Lett. 1977, 4447. (7) Feringa, B.; Wynberg, H. Bioorg. Chem. 1978, 7, 397. (8) Brussee, J.; Groenendijk, J. L. G.; te Koppele, J. M.; Jansen, A. C. A. Tetrahedron 1985, 41, 3313. (9) Smrcina, M.; Polakova, J.; Vyskocil, S.; Kocovsky, P. J. Org. Chem. 1993, 58, 4534. (10) Noji, M.; Nakajima, M.; Koga, K. Tetrahedron Lett. 1994, 35, 7983. (11) (a) Fisher, G. N. H. Synthesis 1985, 641. (b) McKillop, A.; Perry, D. H.; Edwards, M.; Antus, S.; Farkas, L.; Nogradi, M.; Taylor, E. C. J. Org. Chem. 1976, 41, 282. (c) Ansell, M. F.; Nash, B. W.; Wilson, D. A. J. Chem. Soc. 1963, 3028. (d) Vliet, E. B. Organic Synthesis; Wiley: New York, 1941; Coll. Vol. I, p 482. (e) Fieser, L. F. J. Am. Chem. Soc. 1939, 61, 3467. (12) (a) Bosch, E.; Rathmore, R.; Kochi, J. K. J. Org. Chem. 1994, 59, 2529. (b) Rathmore, R.; Bosch, E.; Kochi, J. K. Tetrahedron Lett. 1994, 35, 1335. (13) Sain, B.; Murthy, P. S.; Venkateshwar Rao, T.; Prasada Rao, T. S. R.; Joshi, G. C. Tetrahedron Lett. 1994, 35, 5083. (14) Fujibayashi, S.; Nakayama, K.; Nishiyama, Y.; Ishii, Y. Chem. Lett. 1994, 1345. (15) Radel, R. J.; Sullivan, J. M.; Hatfield, J. D. Ind. Eng. Chem. Prod. Res. Dev. 1982, 21, 566. (16) McKillop, A.; Ray, S. J. Synthesis 1977, 847. X
S0022-3263(96)01377-1 CCC: $14.00
latter has been achieved by using particular catalysts.13,14,17,18 In the oxidation reactions of hydroxyarenes, the use of homogeneous oxidants often results in low-yield formation of desired products accompanied by side reactions, thus bringing about difficulties in controlling the reactions as well as in separation of the products from reaction mixtures. In those cases, therefore, heterogeneous catalyst of the oxidation reactions should be advantageous, if suitable heterogeneous catalysts are available. A useful way for preparation of effective heterogeneous catalysts might be the insolubilized deposition of reagents on inorganic solid surfaces19,20 that can be achieved without significant losses of activities of the reagents or even with activation of the reagents. From practical and environmental viewpoints, moreover, it is desirable that dioxygen can be used as the net oxidant to promote efficient catalytic cycles of the oxidation reactions without participation of oxygenation reactions. In a previous paper,21 we preliminarily reported that copper(II) sulfate supported on alumina efficiently catalyzes the oxidative coupling of 2-naphthols to the corresponding 1,1′-bi-2-naphthols under dioxygen. In the present paper, we wish to report details of the oxidative coupling reactions of 2-naphthols and also successful applications of this catalyst to the high-yield oxidation of hydroquinones, the selective oxidative coupling of 2,5di-tert-butylphenol to the diphenoquinone, and the intramolecular oxidative cyclization of 5,5′-diacenaphthene to the corresponding perylene compound under dioxygen. Results 1. Preparation of Supported Catalyst CuSO4/ Al2O3 (SCAT). The supported catalyst (SCAT) was easily obtained as sky blue powder as follows; commercially available neutral alumina was dispersed in an aqueous solution of CuSO4, and then the mixture was evaporated to dryness at 150 °C under vacuum (eq 1). Unless otherwise noted, SCAT contains 10% (w/w) CuSO4 supported on neutral alumina. (17) Lissel, M.; in de Wal, H. J.; Neumann, R. Tetrahedron Lett. 1992, 33,. 1795. (18) Frostin-Rio, M.; Pujol, D.; Bied-Charreton, C.; Perree-Fauvet, M.; Gaudemar, A. J. Chem. Soc., Perkin Trans. 1 1984, 1971. (19) McKillop, A.; Young, D. W. Synthesis 1979, 401. (20) Posner, G. H. Angew. Chem., Int. Ed. Engl. 1978, 17, 487. (21) Sakamoto, T.; Yonehara, H.; Pac, C. J. Org. Chem. 1994, 59, 6859.
© 1997 American Chemical Society
Catalytic Dehydrogenation of Arenes by Dioxygen
CuSO4 aq + Al2O3 F CuSO4/Al2O3 (SCAT)
J. Org. Chem., Vol. 62, No. 10, 1997 3195
(1)
Other similar catalysts were also prepared by using such solid supports as acidic and basic alumina, Florisil, Celite, silica gel, and molecular sieves and by supporting Cu(OAc)2 and CuF2 on neutral alumina. Although these catalysts were extensively investigated in all the oxidative dehydrogenation reactions shown below, their catalytic activities were significantly or much lower, in most cases, than those of SCAT. Therefore, details of the reactions using SCAT are described in this paper. 2. Oxidation of Hydroquinones to Quinones. Hydroquinone (1a) was efficiently oxidized to 1,4-benzoquinone (2a) under air with a catalytic amount of SCAT. As a typical run, a slurry of 1a (1 mmol) and SCAT (0.2 mmol in Cu(II)) in propyl acetate (10 mL) was heated at 100 °C for 8 h under bubbling air through the mixture. Analyses of the reaction by TLC (silica gel) and GLC showed the complete consumption of 1a accompanied by the quantitative formation of 2a. After conventional workup procedures, 2a was obtained in g95% yield as the sole product. With a smaller amount of SCAT (0.05 mmol of Cu(II)), this reaction was comparably effected under similar conditions to give 2a in 94% yield. On the other hand, the use of still smaller amounts of SCAT (e0.03 mmol of Cu(II)) led to incomplete conversions of 1a and lower-yield formation of 2a (e65%), though the turnover numbers were higher (g22 mol of 2a formed/ mol of Cu(II) used). It was found that such other solvents as hexanol, butyl ether, chlorobenzene, and nonane are much less favorable for the oxidation reaction than propyl acetate; yields of 2a were
