[CONTRIBUTION FROM
THE
CHENICAL LABORATORY O F HARVARD UNIVERSITY]
THE ADDITION OF TRIPHENYLMETHYLSODIUM AND PHEXYLLITHIUM TO CINNAMIC ESTER AND BENZALACETOPHENONE ARTHUR MICHAEL
AND
CHARLES M. SAFFER, J R . ~
Received September 30, 1942
Although the addition of diphenylmethylsodiuni to methyl cinnamate and to benzalacetophenone was carried out by Bergmann (l), no mention appears in the literature of the reaction of triphenylmethylsodium with these conjugated systems. Such addition was found to occur, leading to the formation of compounds hitherto unreported in the literature. The yields, however, are not rery high, varying from 25% to 35%, as considerable polymerization with the formation of tars seems to occur. The reactions must be carried out a t low temperatures in complete absence of any moisture or enolizable hydrogen, to obtain the addition product. These conditions account for the non-mention of our products by Hauser and Abramovitch (2), who carried out experiments with triphenylmethylsodium in the presence of both methyl cinnamate and benzalacetophenone. In their studies, however, either ethyl acetate or ethyl isobutyrate was invariably present to compete for the triphenylmethylsodium, and was invariably successful. Our experiment with methyl crotonate, a molecule containing both an enolizable hydrogen and a conjugated system, shows clearly that there is very little, if any, addition in such a case. The addition of phenyllithium t o conjugated systems has been widely studied. Gilman and Kirby (3) have carried out its addition to benzalacetophenone, obtaining 13% l14-addition and 69% 1,2-addition. In our experiments, by using excess phenyllithium, the 1,2-addition product, diphenylstyryl carbinol, was obtained in good yield, as well as 5 more complicated addition compound, 1, I ,2,3,3-pentaphenylpropanol. The reaction between phenyllithium and methyl cinnamate was found to yield this interesting product also. Neither the propanol nor the 1,1,2,3,3-pentaphenylpropylene, its dehydration product, were found to have been reported in the literature. EXPERIMEXTAL PART I. CONDENSATIONS WITH TRIPHENYLMETHYLSODIUM
A. With methyl cinnamate. TriphenyImethyIsodium was prepared by shaking 6.3 g. (0 .023 mole) of triphenylchloromethane in a Schlenk tube with 210 g. of 1%sodium amalgam in 150 cc. of anhydrous ether for three hours according to the method of Schlenk (4). The red triphenylmethylsodium solution so obtained was forced by pressure of dry nitrogen t o drip into 5 g. (0.032 mole) of methyl cinnamate in 30 cc. of anhydrous ether under dry 1 A t present, Lieutenant (junior grade) United States Naval Reserve, at the Bureau of Ordnance, Navy Department, Washington, D. C. Any errors t h a t may occur herein are the sole responsibility of the junior author. 60
REACTIOKS OF TI11PHEKYLJIETEIYLSODIU1\I
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nitrogen a t -20". The red solution immediately decolorized on mixing with the ester t o give a pale yellow solution out of which, on standing, a yellow solid separated. After 12 hours the solid was separated by filtration, washed with light petroleum and dried; yield 5 g. I t was shown to contain sodium. It was suspended in ether and hydrolyzed a t h dilute hydrochloric acid. The ether layer was washed with bicarbonate solution and water and dried over calcium chloride. The ether was removed on the steam-bath and crystallization occurred. The product, 3,4,4,4-tetraphenylbutyricacid methyl ester, was recrystallized from dry methanol in small white prisms, m.p. 170.5-171': yield 3 g. Anal. Calc'd for C29HZ602: C, 85.7;H, 6.5. Found: C, 86.0;H, 7.0. A 0.2-g. sample of this 3,4,4,4-tetraphenylbutyricacid methyl ester was hydrolyzed by refluving for one hour with 0.05 g. of potassium hydroxide in 10 cc. of alcohol. Acidification and recrystallization from ether gave an acid, 3,4,4,4-tetraphenylbutyricacid, m.p. 227228";yield 0.15 g. Anal. Calc'd for CpaHZaOz:C, 85.7;H, 6.2. Found: C, 85.3;H, 6.5. By heating some of this acid in methanol with a trace of hydrochloric acid, a white crystalline product was obtained, m.p. 170.5-171",the original methyl ester. One gram of the methyl ester was destructively distilled a t atmospheric pressure. A t about 280-310" material began t o sublime over; this was crystallized from methanol, m.p. 92". A mixed melting point with a known sample of triphenylmethane, m.p. 93",gave no depression, z.e., m.p. 92". Another portion of the pyrolyzed ester was hydrolyzed by refluxing with alcoholic potash for an hour. On dilution with Prater solid material separated and was removed by filtration. The filtrate was acidified with dilute hydrochloric acid and the resulting crystalline compound recrystallized from ether-petroleum ether mixture. I t melted a t 133" and gave no depression in a mixed melting point with a known sample of cinnamic acid, m.p. 133". B. W i t h ethyl cinnamate. Triphenylmethylsodium prepared as described above from 6.3g. (0.023mole) of triphenylchloromethane was added slowly to 6 g. (0.034mole) of ethyl cinnamate in 25 cc. of anhydrous ether under dry nitrogen. Reaction occurred and the solution became yellow. On addition of 50 cc. of dry petroleum ether considerable solid separated. The mixture was allowed to stand overnight before filtering. The yellow salt obtained was washed with petroleum ether and dried. It was found to contain sodium; yield 2.7 g. I t was suspended in ether and hydrolyzed with dilute hydrochloric acid. The ether layer was aashed with water and bicarbonate solution and dried over calcium chloride. On removal of the ether, crystalline 3,4,4,4-tetraphenylbutyricacid ethyl ester was obtained and was recrystallized from methanol, m.p. 127-127.5'; yield 2 g. Anal. Calc'd for C30H2802:C, 85.7;H, 6.7. Found: C, 85.4;H, 7.0. By refluxing for an hour with 0.05 g. of potassium hydroxide in 10 cc. of alcohol, 0.1 g. of this ethyl ester was hydrolyzed. On acidification a n acid was obtained which melted a t 228" after recrystallization from ether. A mixed melting point with the acid obtained from the methyl ester in (il) m.p. 228" gave no depression. The ether filtrate from the solid sodium salt described above was examined, and 0.5 g. of triphenylmethane, m.p. 93", was isolated, as well as 0.3 g. of cinnamic acid, m.p. 133". A considerable amount of non-crystalline material was also found, similar in appearance t o t h e material described by Michael (5) in his investigation of the action of sodium on cinnamic ester. C. W i t h methyl crotonate. Tritylsodium prepared from 6.3g. (0.023mole) of triphenylchloromethane was slowly added t o 4 g. (0.04 mole) of methyl crotonate in 30 cc. of anhydrous ether under dry nitrogen at -20". Reaction was instantaneous, giving a yellow solution containing some yellow solid which was separated by filtration (2g.). I t s hydrolysis with dilute hydrochloric acid yielded only tarry material which could not be crystallized. On removal of the ether from the filtrate, however, crystalline material was obtained which
62
ARTHUR MICHAEL AXD C. &I. SAFFER, JR.
was recrystallized from methanol to give white needles, m.p., 93". This was s h o w to be triphenylmethane by a mixed melting point with a known sample, which gave no depression; yield 4.8 g. (0.021 mole). D. With benzalacetophenone. Triphenylmethylsodium prepared from 6.3 g. (0.023 mole) of triphenylchloromethane was added t o 4.8 g. (0.023 mole) of benealacetophenone in anhydrous ether under dry nitrogen. The red solution became yellow but very little solid appeared. After two hours the whole mixture was hydrolyzed with dilute hydrochloric acid. The ether layer was washed with bicarbonate and water, then dried over calcium chloride. It yielded a sticky material on removal of the ether, which was crystallized by scratching with methanol. The 2,3,3,3-tetraphenylpropyl phenyl ketone was recrystallized from hot ligroin in the form of fine white needles, m.p. 169.5-170"; yield 4 g. Anal. Calc'd for C34H280: C, 90.3; H, 6.2. Found: C, 90.2; H, 6.7. 11. CONDENSATIONS WITH PHESYLLITHIUM
A. With methyl cinnamate. Using the method of Evans and Allen (6), phenyllithium was prepared from 3.5 g. (0.5 mole) of lithium and 40 g. (0.25 mole) of bromobenzene in 150 cc. of anhydrous ether. To i t at -20" was added slowly 40 g. (0.25 mole) of methylcinnamate i n 100 cc. of anhydrous ether. The mixture was allowed t o stand overnight. It was then hydrolyzed with dilute acetic acid and the ether layer washed with bicarbonate solution and water, then dried over calcium chloride. On removal of the ether on the steam-bath a n oil resulted which crystallized on scratching with ligroin. The 1,1,2,3,3-~entaphenylpropanol was recrystallized from ligroin in the form of white prisms, m.p. 160.5-161'. Anal. Calc'd for CalHlsO: C, 90.0; H, 6.4; Mol. wt., 440. Found: C, 90.5; H, 6.6; Mol. wt. (camphor), 439. Some of the crude product was placed in a distilling flask and heated a t 180-200" for 4 hours at 4 mm. pressure. The resulting decomposition product waa extracted with hot benzene, from which i t separated on cooling as white crystals. This material, 1,1,2,3,3pentaphenylpropylene was recrystallized from benzene, and melted a t 214-215". Anal. Calc'd for C33H28: Mol. Wt. 422; C, 93.8; H, 6.2. Found: Mol. Wt. (camphor) 410; C, 93.8; H, 6.1. Lithium cinnamate. This salt, a conceivable by-product of the above reaction between phenyllithium and methylcinnamate, was prepared by refluxing 0.5 g. of lithium in a mixture of 25 cc. of water and 25 cc. of alcohol until i t had completely reacted. Fifteen grams of ethylcinnamate was then added and the mixture refluxed for two hours. On cooling, lithium cinnamate separated in the form of white plates, and was recrystallized from alcohol. It melted at 303-305" with decomposition; yield, 10 g. Anal. Calc'd for CsH?LiO3: C, 70.1; H, 4.6. Found: C, 70.0; H, 4.8. B. With benzalacetophenone. Ten grams (0.05 mole) of benzalacetophenone was added t o a solution of phenyllithium prepared from 2.1 g. (0.3 mole) of lithium and 22.8 g. of bromobenzene in 125 cc. of anhydrous ether, giving a wine red solution which was refluxed an hour and allowed t o stand overnight. It was decomposed with dilute acetic acid. The ether layer was washed with bicarbonate solution and water and then dried over calcium chloride. On evaporation of the ether, crystallization occurred. The material was recrystallized from ligroin t o give 11.5 g. of diphenylstyrylcarbinol, melting at 110-11lo as described by Luttringhaus, Jr. (7). From the ligroin filtrate a small amount of material was obtained which melted a t 159" and gave no depression in a mixed melting point with a known sample of 1,1,2,3,3-pentaphenylpropanol. Repetition of the above experiment using varying proportions of materials failed t o increase the yield of this by-product. All melting points are corrected.
REACTiOSS O F TRIPRENYLMETHYLSODIUM
63
SUMMARY
1. Triphenylmethylsodium has been found to add to ethyl cinnamate, methyl cinnamate, and benzalacetophenone, resulting in the formation of three compounds hitherto unreported in the literature. The two esters were hydrolyzed to the same acid. 2. Phenyllithium was added to methyl cinnamate and benzalacetophenone, giving, besides the expected products, 1,1,2,3,3-pentaphenylpropanol. This was dehydrated to the corresponding propylene derivative. 3. Lithium cinnamate was prepared. CAMBRIDGE, MASS.
REFERENCES (1) BERGMANN, J . Chem. Xoc., 412 (1936). ( 2 ) & U S E R . ~ N D ABRAMOVITCH, J . Am. Chem. Soc., 62, 1764 (1940). (3) GILMANA N D KIRBY,J . Am. Chem. Soc., 63, 2046 (1941). (4) SCHLENK . ~ N DQCHS, Ber., 49, 608 (1916). (5) MICHAEL, Ber., 33, 3765 (1900). (6) Evaxr ASD ALLEN, “Organic Syntheses,” John Wiley, New York City, 1937,Vol. YVIII, p. 71. (7) LTTTRISCHAUS, JR.,Ber., 67,1602 (1934).
