[CONTRIBUTION FROM THE N O Y E S CHEMICAL
LABORATORY, UNIVERSITY
OF ILLINOIS]
CONJUGATE BIMOLECULAR REDUCTION OF HINDERED KETONES INVOLVING REPLACEMENT OF METHOXYL GROUPS. SECOND PAPER REYNOLD C. FUSON
AND
RALPH 0 . KERR
Received July SO, 1969
I n the first paper (1) it was reported that, when treated with the binary mixMgIz ( 2 ) , mesityl o-methoxyphenyl ketone undergoes reductive ture, Mg coupling with the loss of methoxyl groups to give the hydrocarbon, 9,10-dimesitylphenanthrene. An analogous hydrocarbon (V) has now been obtained from duryl o-methoxyphenyl ketone (I) and evidence has been accumulated which indicates that a diketone (11) and a pinacol are probable intermediates.
+
OH OH DurCO
DurCO
(y.. \
~
I
T
or
Dur C 0
OCDur
6-4 DG-I () /
I-Dur
\
/
\
/
+
I1
I11
I
\
IV
V
0
0
0
/\
DurC
MgI
VI
(pj M&6 VI1
OH O H
0
Mes
Ix
VI11 373
I1
374
R. C. FUSON -4ND R. 0. KERR
The starting material in the duryl series was o-bromophenyl duryl ketone (IV), prepared by the Friedel-Crafts procedure from durene and o-bromobenzoyl chloride. The acid chloride was made by the method of Shotten (3). It may be pointed out that the order of mixing the reactants is important in the FriedelCrafts condensation. If the durene is allowed to remain in contact with the aluminum chloride while the acid chloride is being added, a mixture of products is obtained, presumably because of migration of methyl groups in the durene ring. The o-bromoketone (IV) yields the corresponding methoxy ketone (I) when heated under reflux with 5 N methanolic sodium methoxide, benzene being added to achieve complete solution and a higher reaction temperature. Conversion of the bromo ketone to the diketone (11) affords a high yield under the usual Ullmann conditions. It is interesting that the methoxy ketone (I) does not undergo coupling under these conditions or when heated with zinc or magnesium. As the blue color of the reaction mixtures suggests, the coupling reaction effected with the binary mixture corresponds to dimerization of a ketyl, which on theoretical grounds might be expected to behave as though it had structure VI. The postulated dimer (VII) could restore the aromatic character of the benzene rings by losing magnesium iodide and magnesium methoxide. The pinacol (111) was oxidized by chromic acid to the diketone (11). Conversion of the piiiacol to the hydrocarbon (V) was achieved by treatment with a mixture of phosphorus, iodine, propionic acid, and water. In the light of these results the earlier work with mesityl o-methoxyphenyl ketone has been reexamined; the hydroxy derivative, formerly thought to be 9,10-dihydro-lO-hydroxy-l-methoxy-9 ,10-dimesitylphenanthrene (1), has been shown to be instead the pinacol (VIII). This pinacol has also been made by reduction of 2,2'-dimesitoylbiphenyl. EXPERIMENTAL
Duryl o-methoxyphenyl ketone. The method differs from that described earlier (4) in that sodium methoxide is used. With this reagent it was necessary to add benzene in order t o achieve satisfactory results. A solution of 200 g. of o-bromophenyl duryl ketone in 1200 ml. of benzene was added to a 5 N sodium methoxide solution previously prepared by the gradual introduction of 301 ml. of dry methanol into a vessel containing 29 g. of metallic sodium. The mixture was heated under reflux, with stirring, for 48 hours, cooled, and poured on cracked ice. The methoxy ketone was recrystallized from ethanol; m.p. 123.5-124.5" (corr.) ; yield 142 g. (85%). d,d'-DiduroyEbiphenyZ.The coupling of o-bromophenyl duryl ketone was effected by the Ullmann method. A mixture of 100 g. of the bromo ketone with 150 g. of sand was heated t o 220" in a round-bottomed flask and 110 g. of purified copper bronze was added over a period of 30 minutes. The temperature was raised t o 230-250" and heating was continued for an additional hour. Throughout the reaction the mixture was stirred continuously with a Hershberg stirrer ( 5 ) . The cooled solid mass was broken up and extracted with toluene. The diketone, after recrystallization from toluene and from benzene, was a powdery solid with a very faintly yellow tinge; m.p. 255-256" (corr.) ;yield 46 g. (67%). AnaZ.1 Calc'd for C3aHa40s: C, 86.04; H , 7.22. Found: C, 86.19; H, 7.09. d,d'-Dimesitoylbiphenyl. A mixture of 200 g. of o-bromophenyl mesityl ketone, 300 g. of 1 The microanalyses were carried out by Mr. J. Nemeth, Mrs. K. Pih, Mrs. J. Fortney, Mrs. L. M. Chang, and Miss E. Davis.
CONJUGATE BIMOLECULAR REDUCTION
375
copper, and 400 g. of sand was stirred a t 230-250" for 1.5 hours. The diketone was recrystallized from benzene and from ethyl acetate; m.p. 228" (corr.); yield 139 g. (95%). A n a l . Calc'd for C ~ ~ H S OC,O86.06; ~: H , 6.77. Found: C, 86.03; H, 6.68. Reduction of duryl o-methoxyphenyl ketone. Iodine (47.5 g.) was added slowly to a mixture of 45.3 g. of magnesium turnings, 289 ml. of toluene, and 300 ml. of n-butyl ether. The entire operation was carried out with stirring and in a nitrogen atmosphere. Heat was applied initially and the reaction proceeded exothermally thereafter. After 20 minutes the solution became colorless and excess magnesium remained. A solution of 25 g. of the ketone in 200 ml. of toluene was added over a period of 30 minutes. A white solid formed on the walls of the reaction vessel a t the start of the addition. When half of the ketone had been added the reaction mixture assumed a bright blue color. At the end of 3 hours of heating under reflux the solution was still blue and all the precipitate had dissolved. At the end of 5 hours heating was discontinued and the solution was cooled, the color meanwhile changing to green and finally to brown. The solution was poured into a mixture of ice, concentrated hydrochloric acid, and ether. The ether solution passed from brown to colorless then became red. The red color was not discharged by sodium sulfite. The ether layer was washed with water, with sodium bicarbonate solution, and again with water. The solution was dried and concentrated by distillation of solvents, under diminished pressure, until crystals began to form. Crystallization was allowed to proceed a t 0' and the crystals were then collected. Concentration of the filtrate was again carried t o the point a t which crystals appeared and these in turn were collected. This process was repeated four times. The higher-melting fractions were treated with ethyl acetate, in which the hydrocarbon is more soluble than the diol. The lower-melting fractions were crystallized from benzene and from toluene, in which solvents the diol is the more soluble component. The total yield was 14.7 g. The hydrocarbon, 9,lO-didurylphenanthrene(V), was recrystallized from ethyl acetate; m p. 290-296", yield 5.4 g. (26%). After repeated recrystallieation the hydrocarbon formed colorless, rectangular crystals melting a t 289.5-291.5' (corr.). A n a l . Calc'd for C34Ha4:C, 92.26; H, 7.74. Found: C, 92.30; H , 7.81. The pinacol, 9,lO-diduryl-O, 10-dihydro-9, IO-dihydroxyphenanthrene (III),recrystallized from benzene and then from xylene, formed colorless, rectangular crystals; m.p. 232" (corr.); yield 5.2 g. (23%). A n a l . Calc'd for CatHasOz:C, 85.67; H, 7.61. Found: C , 85.76; H, 7.69. The infrared spectrum2 has a band a t 3534 cm.-* attributable t o a hydroxyl group. Conversion of the diduryl pinacol (111) lo the corresponding hydrocarbon (V). A mixture of 2.5 g. of the pinacol, 4.5 g. of red phosphorus, 2.0 g. of potassium iodide, 1 g. of iodine, 80 ml. of propionic acid, and 5 ml. of water was heated under reflux, with stirring, for 12 hours and cooled. Water was added and the product was extracted with a mixture of benzene and toluene. The final solution was filtered to remove phosphorus. After removal of the solvents the product was recrystallized from toluene, from ethyl acetate, and from benzene; m.p. 291.5-292.5' (corr.); yield 1.5 g. (66%). A n a l . Calc'd for Cs4HS4:C, 92.26; H , 7.74. Found: C, 92.09; H, 8.15. Comparison of infrared spectra showed the compound to be 9,10-didurylphenanthrene, identical with the product obtained from duryl o-methoxyphenyl ketone. A mixture of the two samples showed no lowering of melting point. Reduction of 2,8'-diduroylbiphenyl. The procedure was similar to that described for the reduction of duryl o-methoxyphenyl ketone. A solution of 25 g. of the diketone in 200 ml. of toluene was added, with stirring, to a colorless reducing mixture made from 22 g. of a The infrared spectra were measured and interpreted by Miss Helen Miklas and Mrs. H. P. Leighly.
376
R . C. FUSON AND R . 0 . XERR
iodine, 22.4 g. of magnesium, 200 ml. of n-butyl ether, and 250 ml. of toluene. The reaction mixture developed a brilliant, deep blue color after ten drops of the diketone solution had been added. The addition was completed in 30 minutes and the mixture was heated under reflux, with stirring, for 12 hours, at v-hich time the color had become a greenish-gray. The reaction mixture was poured into a mixture of 2 1. of cracked ice and 50 ml. of concentrated hydrochloric acid. The glycol (111) was recrystallized from benzene and ethyl acetate; m.p. 231-232" (corr.); yield 17 g. (68%). Anal. Calc'd for C31H3602:C, 85.67; H , 7.61. Found: C, 85.59; H, 7.84. The infrared spectrum is identical to that of the glycol from the methoxy ketone. The melting point of a mixture of the two samples was not depressed. Oxidation of the pinacol (111). A mixture of 1 g. of the pinacol, 0.5 g. of chromium oxide, and 20 ml. of glacial acetic acid was heated on a steam cone for one hour and poured on ice. The product, after recrystallization from benzene and from acetone, melted a t 258259.5", yield 30%. A mixture with a sample of 2,2'-diduroylbiphenyI made by the Ullmann procedure melted a t 259-260'. The two samples had identical infrared spectra. Reduction of 2,2'-dinzesitoylbiphenyE. Reduction with the binary mixture, Mg-MgI?:, converted the diketone to the corresponding pinacol (VIII). The yield of crude product, obtained from 60 g. of the diketone, was 46 g. (77%) ; m.p. 199-202". The colorless crystals were recrystallized from benzene, from high-boiling petroleum ether, and from a mixture of benzene and low-boiling petroleum ether; m.p. 200.5-201.5° (corr.). Anal. Calc'd for C3?:Ha202: C, 85.67; H, 7.19. Found: C, 85.91; H, 7.21. This compound was shown to he the same as that obtained earlier (1) by the reduction of mesityl o-methoxyphenyl ketone. The two samples have identical infrared spectra. The melting points differ by 3" but a mixture of the two samples melts a t a point between the two values. Dehydration of the dinzesityl pinacol (VIII). -4solution of 0.7 g. of the pinacol, 20 ml. of pyridine, and 8 ml. of acetic anhydride was heated under reflux for 15 minutes, cooled, and poured on ice. The product, recrystallized from ethanol and from ethyl acetate, formed colorless rhombohedra; m.p. 243-244' (corr.). Anal. Calc'd for C32H&: C , 89.26; H , 7.02. Found: C, 89.30; H, 7.14. The dehydration product cannot be 9,lO-dimesityl-1-methoxyphenanthreneas previously suggested (1) ; its infrared spectrum, which is identical with that of the sample obtained earlier, has no band corresponding to a ketone group and is consistent with the structure of the a-pinacolone (IX). However, because of the resistance of the compound t o chemical reagents, the epoxide structure could not be confirmed. Conversion of the dimesityl pinacol (VIII) to the corresponding hydrocarbon. By a procedure similar t o that described for the diduryl analog Q,lO-dihydro-9,10-dihydroxy-9,10dimesitylphenanthrene (17111) was converted to 9,lO-dimesitylphenanthrene;m.p. 244" (corr.), yield 40%. Anal. Calc'd for C32H30:6, 92.70; H , 7.29. Found: C, 92.51; H, 7.15. The ultraviolet spectrum3 is very similar to that of the diduryl analog; the log of the molar extinction of the diduryl compound is 4.86 a t 2580 A and that of the dimesityl compound is 4.79 a t 2580 d. Log e for 9-phenylphenanthrene was found to be 4.78 at 2550 &. (6). SUMMARY
Duryl o-methoxyphenyl ketone undergoes conjugate bimolecular reduction when treated with the binary mixture, Mg-MgIn; the products are 9,lO-didurylphenanthrene and 9,10-didury1-9,10-dihydro8,10-dihydroxyphenanthrene. 8
The ultraviolet spectra were measured and interpreted by Mrs. B. Burnett.
CONJUGATE BIXOLECULAR REDUCTION
377
'The pinacol, formed also by reduction of 2,2'-diduroylbiphenyl, has been reduced to the hydrocarbon and has been reconverted to the diketone by chromic acid oxidation. Analogous results have been obtained with mesityl o-methoxyphenyl ketone and 2,2'-dimesitoylbiphenyl. URBANA, ILLINOIS
REFERENCES (1) FUSON AND HORNBERGER, J . Org. Chem., 16, 637 (1951). (2) GOMBERG AND BACHMANN, J. Am. Chem. SOC.,62,2455 (1930). (3) SHOTTEN, Ber., 21,2235 (1888). (4) FUBON AND HAMMANN, J . Am. Chem. SOC.,73, 1851 (1951). (5) Org. Syntheses, Coll. Vol. 11, p. 117 (1943). (8) FRIEDEL AND ORCHIN, Ultraviolet Spectra of Aromatic Compounds, John Wiley and Sons, Inc., New York, 1951,plate No.383.
