[CONTRIBUTION FROM
THE
SCHOOL OF CHEMISTRY OF MINNESOTA]
THE
UNIVERSITY OF
THE ACTION OF BENZENE AND ALUMINUM CHLORIDE ON 2 ,&DIPHENYLINDONE C. F. KOELSCH Received September SO, 1858
When diphenylindone (I) is boiled with two moles of aluminum chloride in an excess of benzene, the emerald green color of the original complex rapidly changes to a greenish-brown, and from the resulting solution there can be isolated a colorless compound whose weight corresponds to about 109% of that of the diphenylindone used. Although this product has finally been shown to be the expected 2,3,3triphenylhydrindone (11), this formula could not be assumed without proof because (1) the action of benzene and aluminum chloride on quinone stops with the formation of 2,fi-diphenylquinone;l (2) the action of benzene and aluminum chloride on p ,8-diphenylacrylophenone is one of re’duction, leading to 0 ,fldiphenylpropiophenone;2(3) the properties of the product itself, stability towards fused alkali and towards chromic acid, resistance to phenylation by phenylmagnesium bromide, solubility in Claisen’s solution and easy formation of o-esters and ethers are not those of the analogous acyclic ketone diphenylacetophenone. The proof of the structure of the product, reported in this paper, is complicated somewhat by the occurrence of an unusual rearrangement, the generality and mechanism of which will be the subject of future investigations. Although I1 itself is not attacked by cold permanganate or chromic acid and on more vigorous treatment with these reagents is completely destroyed, its benzoate can be oxidized by chromic acid to IV. On careful treatment of IV with sodium hydroxide it yields sodium benzoate and V, and this, treated more vigorously with the same reagent, is converted into the sodium salt of the acid VI. Dehydration of VI by warming with acetic acid containing a trace of sulfuric acid gives a new acid VII, which can be oxidized with chromic acid to a neutral substance, VIII. When VI11 is reduced with potassium iodide in acetic acid, it yields 9,lOdiphenylanthracene (IX), the only previously known compound in the series of degradation products. The presence of the phenyl groups on the meso carbon atoms of the final 1
PUMMERER AND PRELL,Ber., 66,3105 (19%).
* ALEXANDER, JACOBY, AND FUSON, J . Am. Chem. SOC.,67, 2208 456
(1935).
457
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2,3-DIPHElNYLINDONE AND BENZENE
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XI degradation product (IX) points incorrectly to the structure X for the substance (11) obtained from diphenylindone, benzene, and aluminum chloride. The non-occurrence of rearrangements during the two dehydrations by acid is made certain by the fact that acid VI may be oxidized to o-benzoyltriphenylmethane, (XI), a known compound. Compound V, the precursor of VI, on account of its reactions and composition must be a triphenylhydroxy ketone with the indene nucleus intact, but it gives on reduction a substance isomeric with but different from 11. Thus in the reactions involved in the conversion of I1 into IX migration of a phenyl
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group must have taken place, and accordingly structure I1 correctly represents the Friedel-Crafts product. A consideration of the following facts serves to locate the reaction during which the migration takes place. Benzoate I11 is reconverted into benzoic acid and I1 on treatment with alcoholic alkali, and benzoate IV may be reduced to benzoic acid and 11. If it is assumed that reduction is accompanied by rearrangement of a phenyl group, the improbable conclusion is reached that oxidation involves the migration of both a phenyl and the benzoyloxy groups. If, however, reduction involves no rearrangement, the rearrangement must occur during the hydrolysis of IV to V. EXPERIMENTAL
The Friedel-Crafts reaction.-A mixture of 20 g. of diphenylindone, 30 g. of aluminum chloride, and 200 ml. of benzene is boiled for ten minutes, the green color of the mixture changing to greenish brown. The addition of dilute hydrochloric acid and removal of the benzene by steam distillation leaves a crystalline residue. This, crystallized once from acetic acid, is white, weighs 21.8 g., and melts at 191-193'. As evidence of the reversibility of the reaction, 2,3,3-triphenylhydrindonemay also be obtained from Z-phenyl-3-p-tolylindone, benzene and aluminum chloride in a similar yield. C, 90.0; H, 5.6. Anal. Calc'd for CZIH~OO: Found: C, 89.8; H, 5.6. The ketone is recovered unchanged after treatment with phenylmagneaium bromide, with sodium in butyl alcohol, or with chromic acid in acetic acid a t 50'. On fusion with potassium hydroxide at 250" it is converted into a yellow solid which gives back the original hydrindone on treatment with water. The ketone is difficultly soluble in hot alcohol, but readily forms a yellow solution in alcohol containing a little sodium hydroxide. Acylation and etherification.-A solution of 2,3,3-triphenylhydrindone(5 g.), benzoyl chloride (5ml.) and pyridine (5ml.) in chloroform (15 ml.) is warmed for a few minutes, cooled and washed with dilute acid and dilute base. From acetic acid the product, 1,1,2-triphenyl-3-benzoyloxyindene,separates in the form of colorless prisms that melt a t 152-154"; yield, 5.3 g. C, 87.9; H, 5.2. Anal. Calc'd for CUHMO~: Found: C, 87.5;H, 5.1 A similar procedure using p-chlorobenzoyl chloride gives a mixture of p-chlorobenzoic anhydride and the p-chloro-benzoate, which forms white prisms from acetic acid that melt a t 203-204'. Anal. Calc'd for CaaHmOsC1: C, 81.8;H, 4.62. Found: C, 81.6; H, 5.13. On boiling the hydrindone with an excess of acetic anhydride containing potassium acetate i t is converted into 1, l,Z-tripheny1-3-acetoxyindene,white plates from acetic acid that melt a t 147-148'. Anal. Calc'd for CZSHIIOZ:C, 86.5; H, 5.5 Found: C, 86.0;H, 5.5 1 ,1,2-Triphenyl-3-benzyloxyindeneis obtained in a 70% yield when benzyl chloride (3 ml.) is added to a solution of sodium (0.6 g.) and the hydrindone (1 g.)
2,3-DIPHENYLINDONE AND BENZENE
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in absolute alcohol (20 ml.) and the mixture is boiled until neutral. The ethoxytoluene and alcohol are removed by steam distillation, and the residue is crystallized from acetic acid. I t forms white plates that melt a t 149-151". Anal. Calc'd for CIL;H~~O: C, 90.6; H, 5.8. Found: C, 90.0;H, 5.8. 1,1 ,2-Triphenyl-3-methoxyindeneis obtained by adding 40% aqueous sodium hydroxide and methyl sulfate alternately to a suspension of the hydrindone in alcohol until the addition of the base no longer causes the development of a yellow color. From acetic acid the product forms white plates that melt a t 117-119". Anal. Calc'd for CzsHzgO: C, 89.8;H, 5.9. Found: C, 89.4;H, 5.9. The acyl derivatives are rapidly hydrolyzed on boiling with alcoholic alkali, giving the original hydrindone, while the ethers are completely hydrolyzed to the hydrindone on boiling with a mixture of 40% aqueous hydrobromic acid (1 vol.) and acetic acid (2 vols.) for two hours. Ozidation of the benzoate.-A suspension of the finely divided benzoate (111) (209 . ) in acetic acid (100 ml.) is treated with a solution of 7 g. of chromic anhydride in 5 ml. of water and 20 ml. of acetic acid. The mixture is kept a t 60" for three hours, then cooled and poured into water and ether. The ether solution is washed with aqueous sodium carbonate and evaporated. The residue is crystallized from acetic acid, when there is obtained 16.5 g. of 1,1,2-triphenyl-3-benzoyloxy-2,3epoxyhydrindene (IV), white prisms that melt a t 193-195". Anal. Calc'd for Ca,H*dOa: C, 85.0;H, 5.0. Found: C, 84.7;H, 5.2. Reduction of the oxide (ZV).-A solution of the oxide (0.5 9.) and 50% aqueous hydriodic acid (0.5ml.) in 10 ml. of acetic acid is boiled for one hour. After working up the mixture there is obtained 0.35 g. of 2,3,3-triphenylhydrindoneand 0.1 g. of benzoic acid. Hydrolysis of the ozide (IV).-The oxide (16.3 g.) is added to a solution of 2.5 g. of sodium in 100 ml. of 95% methanol, and the mixture is boiled until complete solution takes place (about ten minutes). The products are transferred to ether, from which sodium carbonate removes benzoic acid (3.0 g. after crystallization from water). The neutral hydroxyketone (V) is purified by crystallization from tolueneligroin. There is obtained 11.85 g. of 1,1,3-triphenyl-3-hydroxyhydrindone-2, fine white needles that melt a t 157-159'. Anal. Calc'd for Cz,HnoOr: C, 86.1;H, 5.3. Found: C, 85.5;H, 5.4. Reduction of the hydrozyketone (V).-A solution of 1 g. of the hydroxyketone and 4 ml. of 47% hydriodic acid in 15 ml. of acetic acid is boiled for one minute. The solution is decolorized with aqueous bisulfite, and the product is crystallized from ether. There is obtained 0.8 g. of 1,3,3-triphenylhydrindone-2,white prisms that melt a t 106-109". Anal. Calc'd for Ct,H2oO: C, 90.0; H, 5.6. Found: C, 90.1; H, 5.7. Cleavage of the hydrozyketone (V).-The hydroxyketone (5 g.) is boiled for two hours with a solution of 2 g. of sodium hydroxide in 50 ml. of 90% ethanol. The solution is poured into 100 ml. of water, warmed to dissolve the sodium salt, and acidified. The precipitated acid becomes solid on boiling ita aqueous suspension; i t is filtered and crystallized from dilute acetic acid. There is obtained 4.9 g. of o-beneohydrylbenzilic acid (VI), fine white plates that melt a t 188-189" with gas evolution.
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F. KOELSCH
A n d . Calc'd for CtrHnO,: C, 82.2; E, 5.6. Found: C, 82.3; H, 6.0. Shaking a suspension of the sodium salt of the acid in warm 6% sodium hydroxide with an excess of methyl sulfate gives the methyl ester, white needles from methanol that melt a t 121-123". Anal. Calc'd for CISHZ~OS: C, 82.3; H, 5.9. Found: C, 82.1; H, 5.9. Dehydration of the acid (VI).-A solution of 1 g. of o-benzohydrylbenzilic acid in 10 ml. of acetic acid containing 0.1 ml. of concentrated sulfuric acid is boiled for five minutes and then poured into water and ether. Washing the ether solution with sodium carbonate removes the acidic products in the form of their difficultly soluble sodium salts. These are separated by crystallization into a small amount of the sodium salt of the acid (VI) (more eesily soluble) and that of the acid (VII). 9,lODiphenyl-9,10-dihydroanthracene-9-carboxylic acid crystallizes from acetic acid in white prisms that have a violet fluorescence and melt a t 236-238'. Anal. Calc'd for C~~HIOOS: C, 86.1; H, 5.3. Found: C, 86.2; H, 5.7. The methyl ester, obtained from the sodium salt and methyl sulfate in warm alkali, forms a white powder with a violet fluorescence; crystallized from acetic acid it melts a t 195-197'. Anal. Calc'd for CSSH~ZO~: C, 86.1; H, 5.7. Found: C, 85.5; H, 5.8. Oxidation of the acid (VII).-A solution of 0.9 g. of 9,lO-diphenyl-9,lO-dihydroanthracene-9-carboxylic acid and 0.5 g. of chromic anhydride in 10 ml. of acetic acid is kept a t 80" for ten minutes. The mixture is poured into water and ether, and the unchanged acid (SO mg.) is removed by washing the ether solution with carbonate. From the ether is obtained 0.5 g. of 9,10-dipheny1-9,10-dihydroxy-9,10-dihydroanthracene (VIII) which melts a t 183-185" after crystallization from benzene and drying at 100". Anal. Calc'd for C&&: C, 85.7; H, 5.5. Found: C, 85.6; H, 5.6. This glycol is distinctly different from the previously known 9,1O-diphenyl-9,10dihydroxy-9,lOdihydroanthrscenea of m.p. 247'. Since, however, like the latter compound i t gives a blue color with sulfuric acid, and on reduction is converted into 9,lO-diphenylanthracene,i t must be a stereoisomer of the 247" glycol. Reduction of the glycol is carried out by warming it in acetic acid with an excess of sodium iodide. The resulting 9, lodiphenylanthracene melts a t 246-246' alone or mixed with a sample prepared by reduction' of the 247" glycol. Ozidation of the acid (VI).-To a solution of 1 g. of o-benzohydrylbenzilic acid warmed to 85" is added a small excess chromic acid in acetic acid. Crystallized from ethanol the neutral oxidation product (0.55 g.) forms white prisms that melt a t 84-86' (literature,6 88"). On treatment with phenylmagnesium bromide i t gives o-benzohydryltriphenylcarbinol that melts a t 213-215' (literature,' 218"). Dehy8
HILLER AND GUYOT,Bull. soc. chirn., [3], 31, 798 (1904). SIMONIS AND REMMERT, Ber., 48, 208 (1915). SEIDBLAND BEZNER,ibid., 66, 1566 (1932). COOK,AND NIXON,J. Chem. Soc., 1927, 504. BARNETT,
2,3-DIPHENYLINDONE AND BENZENE
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dration of the carbinol so obtained gives 9,9,lO-triphenyl-9,10-dihydroanthracene that melts a t 223-225' (literature,' 223'). SUMMARY
The action of benzene and aluminum chloride on 2,3-diphenylindone or on 2-phenyl-3-p-tolylindone leads to 2,3,3-triphenylhydrindone.The structure of the product is prbved by conversion through a series of degradation products into known compounds. The degradation involves a rearrangement, whose mechanism and generality will be investigated. KOVACHE, Ann. chim. phys., [9], 10, 227 (1918).
