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Submitted by C. R. H. I. De Jonge, H. J. Haqeman,
G. Hoentjen and W. J. Mijs1
Checked by Ê. Â alasttbramania*, Robert K. Boeckman, and Caul R. Johnson
In a 200-ml,, three-necked flask equipped with a mechanical stirrer, a thermometer, and a gas-inlet tube are placed 41.2 g. (0.2 mole) of 2,6-di-<erf-butylphenol (Note 1) in 75 ml. of dimethylformamide (Note 2) and 2.5 g. (0.0075 mole) of salcomine (Note 3). With stirring, oxygen is introduced at such a rate that the temperature does not exceed 50°. This is continued for 4 hours. At the end of the reaction the temperature drops to about 25°. The reaction mixture is then poured onto 500 g. of crushed ice and 15 ml. of Ø hydrochloric acid. A yellow-brown precipitate is formed. The solid material is collected by suction filtration and washed on the filter three times with 50-ml. portions of IN hydrochloric
acid, three times with 100-ml. portions of water, and twice with 25-ml. portions of cold ethanol. Drying under reduced pressure at 50° for
3 hours gives 43 g. of crude 2,6-di-ter<-butyl p-benzoquinone as a dark-yellow crystalline solid. Recrystallization from ethanol gives 36.5 g. (83%) of pure 2,6-di-teri-butyl-p-benzoquinone, m.p. 65-66° (Notes, 4, 5).
1. 2,6-Di-<eri-butylphenol purchased from Aldrich Chemical Company, Inc., was used.
2. When chloroform or methanol is used as the solvent for thanxida-tion of phenols, other products, originating from coupling of aryloxy radicals, e.g., polyphenylene ethers and/or diphenoquinones, are also formed.2
3. Bis(salicylidene)ethylenediiminocobalt (II) can be prepared according to the procedure described by H. Diehl and Ñ. C. Hack, Inorg. Syn., 3, 196 (1950).
4. 2,6-Di-tert-butyl-jp-benzoquinone should be stored in a brown bottle.
5. The product has the following spectral properties; infrared (chloroform) cm.-1: 1652, 1597; proton magnetic resonance (chloroform-d) 8 1.33, 6.56.
Various 2,6-disubstituted p-benzoquinones have been prepared by oxidation of the corresponding 2,6-disubstituted phenols with potassium nitrosodisulfonate 3•4 or lead dioxide in formic acid.5 Oxidative coupling of 2,6-disubstituted phenols to poly-2,6-disubstituted phenylene ethers followed by treatment of the polymers in acetic acid with lead dioxide is reported6 to give low yields of the corresponding 2,6-disubstituted j)-benzoquinones.
Salcomine is a useful catalyst for the selective oxygenation of 2,6-disubstituted phenols to the corresponding ;p-benzoquinones when dimethylformamide is used as the solvent; laborious procedures are avoided and high yields of pure 2)-benzoquinones are obtained. Following the procedure described above, the authors have prepared 2,6-diphenyl-p-benzoquinone (m.p. 134-135°, yield 86%) and 2,6-dimethoxy-p-benzoquinone (m.p. 252°, yield 91%) from the appropriate phenols.
1. Organic and Polymer Chemistry Department, Akzo Corporate Research Laboratories, Arnhem, The Netherlands.
2. H. M. van Dort and H. J. Geursen, Bec. Travl. Ghim. Pays-Bas, 86, 520 (1967).
3. H. J. Teuber and W. Rau, Ber. 86, 1036 (1953).
4. H. J. Teuber and O. Glosauer, Ber. 98, 2643 (1965).
5. C. R. H. I. de Jonge, H. M. van Dort, and L. VoIIbracht, Tetrahedron Lett1881, 1970.
6. H. Finkbeiner and A. T. Toothaker, J. Org. Chem., 33, 4347 (1968).
(PENTAFLUOR0PHENYL) ACETONITRILE [Benzeneacetonitrile, 2,3,4,5,6-pentafluoro-]
CeFe + NCCH2C02C2H5 „ KaC°3-------------------> CeF 5CH(CN)C02C2H5 + KF + H20 + COa
CeF5CH(CN)C02C2H5 Íç8°4'ÑÍçÑÎÎÍ > CeF5CH2CN + C2H50H + C02
Submitted by Robert Filler1 and Sarah M. Woods2 Cheeked by Andrew E. Fexring and William A. Sheppard
A. Ethyl Cyano(pentafluorophenyl)acetate. A 2-1., four-necked flask equipped with mechanical stirrer, addition funnel, thermometer, and condenser is charged with 650 ml. of dimethylformamide (Note 1) and 140 g. (1.0 mole) of anhydrous potassium carbonate. The rapidly stirred mixture is heated to 152-154° and 113 g. (1.0 mole) of ethyl cyano-acetate is added dropwise during 10-15 minutes without further heating.
The temperature of the mixture is allowed to drop to 110-120° and maintained within this range while 186 g. (1.0 mole) of hexafluoro-benzene (Note 2) is added dropwise over 1 hour. The dark mixture is stirred for 3 hours after the addition is complete, then poured into 31. of ice water contained in a 5-1. Erlenmeyer flask, and acidified (Caution! Foaming) with 20% sulfuric acid. After cooling overnight in the refrigerator, the top aqueous layer is decanted from a lower, viscous organic layer. The organic layer is dissolved in 600 ml. of ether, washed with water, and 10% aqueous sodium hydrogen carbonate, and dried over anhydrous magnesium sulfate. The ether is removed on a rotary evaporator to afford 217 g. (78%) of dark oil which crystallizes on standing (Note 3). An analytical sample is prepared by dissolving 2 g.