DECEMBER
1957
1623
ALKYLATION OF FLUORENE. I11
[CONTRIBUTION FROM THE LABORATORIES OF THE POLYTECHNIC
INSTITUTE OF
BROOKLYN]
Alkylation of Fluorene with Alcohols and Their Alkoxides. 111. Polyhydroxy Compounds ISAAC D. RUBIN1
AND
ERNEST I. BECKERZ
Received May $3, 1967 Ethylene glycol, 1,Qpropylene glycol, tetramethylene glycol, and pentamethylene glycol with catalytic quantities of their sodium derivatives react with fluorene a t 180" to 220' to give 1,2-bis(9-fluorenyl)ethane,1,2-bis(S-fluorenyl)propane, 1,4bis(9-fluoreny1)butaneand 1,5-bis(9-fluorenyl)pentane,respectively. Trimethylene glycol gave no isolable product. Glycerol gave the same product that ethylene glycol did, but in very poor yield. 2,2-Dimethylpropan-l,3-diolgave 59% of 9-isobutylfluorene.
Previous reports have shown that the pentagonal and ring in 1,2,3,4-tetraphenyl~yclopentadiene,~ in fluorene4J' can be alkylated with alcohols and their alkoxides. The first two reports showed that primary alcohols will undergo the reaction while the third showed that secondary alcohols may be used.6 Abramoff and Sprinzak' have quite recently reported a related alkylation of 2-picoline with benzyl alcohol to give 2-phenethylpyridine. The previous articles review the prior literature. The purpose of this investigation was to determine the feasibility of employing polyfunctional alcohols in this novel alkylation reaction. It has now been found that ethylene glycol, 1,2propylene glycol, tetramethylene glycol and pentamethylene glycol give the correspondingbis-fluorenyl alkanes. Equation 1 illustrates this using ethylene glycol as an example. The products were identified by their molecular weights, ultimate analysis, the presence only of hydrocarbon bands in their infra2CJ31o
+ CzHd(OH)z
HOCHsCHaONa
+
+ 2["0]
Trimethylene glycol, in contrast to its isomer, 1,2-propylene glycol, did not give an isolable product. Glycerol afforded a mixture from which only l12-bis(9-fluorenyl)ethane was isolated together with unreacted fluorene. This unexpected product was characterized by the melting point, mixture melting point, and identity of its infrared spectrum with that of the product prepared from ethylene glycol. With 2,2-dirnethylpropan-l,&diol, again the loss of one carbon atom was observed and the product, 9-isobutylfluorene, was obtained in 59% yield. I t was characterized by ultimate analysis, molecular weight, and a mixture melting point determination with a sample synthesized independently according to a known procedure.6 The loss of a carbon atom in the two preceding cases can be ascribed reasonably to degradation of the glycol prior to condensation with fl~orene.~ It is reasonable that the 1,3-glycolis oxidized to a Phydroxyaldehyde, which could then undergo a reverse aldol condensation, eliminating formaldehyde and giving an aldehyde (Equation 2). The aldehyde could then enter into the reaction scheme HOCHz-LcHzOH
I red spectra, and their insolubility in cold, concentrated sulfuric acid. I n the case of 1,2-bis(9-fluoreny1)ethane the melting point agreed with the literature value.
+ to1 H O C H e - - L H O I
+ )CHCHO (2)
CH~O
proposed for the alkylati~n.~ An alternative and possibly more feasible route is that patterned after Searles and Ives.s According to this scheme formaldehyde would be eliminated directly giving an alcohol which would then enter the alkylation. Finally, methanol might be lost directly giving an aldehyde which could enter the alkylation (Equation
(1) From the thesis submitted by Isaac D. Rubin to the Graduate Faculty of the Polytechnic Institute of Brooklyn in partial fulfillment of the requirements for the degree of Master of Science, 1957. (2) To whom inquiries should be directed. (3) S. M. Linder, E. I. Becker, and P. E. Spoerri, J . Am. 3).9 Chem. SOC.,75, 5972 (1953). (4) K. L. Schoen and E. I. Becker, J . Am. Chem. SOC., 77,6030 (1955). ( 5 ) D. N. Matthews and E. I. Becker, J . Org. Chem., 21, 1317 (1956). (6) M. F. Carroll, J . C h m . Sm., 507 (1941), also used a (8) 5. Searles, Jr., and K. E. Ives, 127th Meeting of the secondary alcohol, methyl phenyl carbinol, in the alkylation American Chemical Society, Cincinnati, Ohio, March 29 of ethyl acetoacetate in the a-position, a similar reaction. to April 7, 1955, Abstracts, p. 24N. (7) M. Abramoff and Y.Sprimak, J . Am. Clwm. Soc., 78, (9) R. W. Brown and G. Dougherty, J . 0p.g. Chem., 13, 4090 (1966), 173-(1948).
1624
RUBIN AND BECKER
VOL.
22
I n the course of the synthesis of 9-isobutylfluorene from isobutyl alcohol and fluorene it was possible to contribute to an understanding of the reaction. It is first necessary to consider the alkylation of certain amines, a related reaction. Pratt and Fraaaa,lo Rice and Kohn," Carson and Dress1er,l2 and Aimworthla have shown that the alkylation of amines is catalyzed by the use of active nickel catalysts. In particular Rice and Kohn showed that alkylation did not take place until conditions were such that the alcohol used wa.s converted to the corresponding aldehyde. The only base present was the amine beiig alkylated. Pratt and Frazza used the alkoxide along with the amine without demonstrating the effect of the alkoxide. Likewise in the alkylation of hydrocarbons in this laboratory the catalytic effect of nickel had been shown, but the necessity for a base had not been shown. In the alkylation of fluorene with isobutyl alcohol in the presence of Raney nickel no alkylation took place during 18 hours' reflux, although under the same conditions in a separate reaction, isobutyraldehyde was formed as was demonstrated by the isolation of its 2,4dinitrophenyLhydrazone.Using Raney nickel and potassium isobutylate at the same temperature, fluorene was alkylated. Thus, for the alkylation of hydrocarbons not only conditions which give the aldehyde, but also a base is required. EXPERJM%N'I"TL'4
Y
k
% n P
u
I
w"
u
tk
D
I
Fr
Starting materials. The polyhydric alcohols were commercially available materials and before use were distilled, if liquid, or recrystallized, if solid. Their constants agreed with those in the literature." Fluorene was 98% material from Reilly Tar and Chemical Co.,recrystallized from alcohol. Alkylcdion reactions. Method A. Two grama (0.087 atom) of sodium were added in small chips to 30 g. of the glycol (20g. in the case of 2,2dimethylpropan-l,3-diol)in a Carius tube temporarily fitted with a reflux condenser. With the solid 2,2-dimethylpropan-l,3-diol an oil bath was used to melt it before addition of the sodium. Heating was used in all case8 to hasten the reaction of the sodium. Fluorene (10 g., 0.060 mole) was then added, and the tube was sealed, heated to 215-220" and maintained a t this temperature for 24 hr. After cooling, the tube was opened and the contents were neutralized with 10% hydrochloric acid and transferred to a beaker. After adding 200 ml. of water, the mixture was allowed to stand in the refrigerator overnightwhereupon the pasty reaction mass became more tractable. Approximately 11-12 g. of crude product was collected. Two recrystallizations, once from ethanol and once from acetic acid, gave the yields and accompanying melting points shown in Table I. After two further crystallizations I101 E.F. Pratt and E. J. Frazza, J . Am. Chem. SOC.. . 76,. 6174 (1954). 111) R. G. Rice and E. J. Kohn. J . Am. Chem. Soc.., 77.. 4052 (1955). (12)B. B. Carson and H. Dressler, J. Org. Chem., 21, 474 (1956). (13)C.Ainsworth, J . Am. Chem. Soc., 78, 1635 (1956). (14)All melting points are corrected. Analyses were carried out bv Dr. F. Schwartzkouf, - , 56-19 37th Avenue, Woodside 77,N: Y. (15) We are grateful for a generous sample of 2,2dimethylpmpan-1,3-diolfrom Texse Eaetman Co.
DECEMBER
1957
ALKYLATION OF FLUORENE. I11
the product was stirred with cold, concentrated sulfuric acid until no further color developed. Separation of the hydrocarbon was followed by washing with water, drying and recrystallizing from ethanol and then acetic acid to give the analytical samples as indicated in Table I. Method B. The same quantities of starting materials were used as in Method A. The sodium was added to the glycol and the mixture was heated under reflux until it had all reacted. The fluorene was added and the flask was heated under reflux until it had all reacted. The fluorene was added and the flask was heated by means, of an oil bath to reflux or to 215-ZOO, whichever temperature was reached earlier. After cooling, the same procedure for isolation 88 in Method A was followed. Reaction of j€uorene with trimethylene glycol. This reaction was carried out using both Methode A and B. Upon recrystallization from acetic acid a yellow solid, m.p. 125-180', was obtained. No pure compound was isolated from this product using fractional crystallization, vacuum distillation, chromatography on alumina, and sublimation. Readion of fluorene with glycerin. Sodium (2 g., 0.087 atom) was added under nitrogen with great caution to 30 ml, (0.41 mole) of glycerine in a 1 2 5 4 . flask. The metal was added in small amounts. The flask was heated gently in an oil bath, but at no time was the temperature in the flask allowed to rise above 65'. In a few cases without these precautions the reaction mixture caught fire. Fluorene (10 g., 0.060 mole) was added, the nitrogen tube removed and the mixture was heated a t 200-210" for 24 hr. After cooling, it was extracted with successive portions of water and benzene and neutralized with 10% hydrochloric acid. The benzene layer was washed several times with water and dried over potassium carbonate. Distillation of the benzene afforded 9.6 g. of yellowish residue. By means of difference in solubility in glacial acetic acid, two substances, A and B, were isolated. Substance A (8.5 g.), the more soluble one, melted a t 113-114.5', and showed no melting point depression when mixed with a sample of pure fluorene. Substance B (0.3 g.) melted a t 227-228.4". An infrared spectrum of this compound was identical with that of 1,2-bis(%fluorenyl)ethane prepared by treating fluorene with ethylene glycol. A mixture melting point determination with 1,2-bis(9-fluorenyl)ethane showed no depression. Identical results were obtained carrying out the reaction in a Carius tube a t 220' for 24 hr. Unsuccessfulattempt to alkylate j€wenewith 6,%?-dimethylpropan-l,3diol. 2,2-Dimethylpropan-l,3-diol(10.4 g., 0.10 mole) was dissolved in 200 ml. of xylene heating to bring all the glycol into solution. Sodium (0.46 g., 0.020 mole) was then added and after the reaction was complete, 10 g. (0.05 mole) of fluorene was added together with 2 g. of Davison nickel catalyst. The mixture was refluxed under a Dean-Stark
1625
trap for 24 hr. The hot liquid was then filtered, washed repeatedly with water, and distilled, leaving 9.2 g. of a light solid, m.p. 108-112". A mixture melting point determination with fluorene showed no depression. Q-Isobutyl$uorene. The alkylation Reaction Method I1 of Matthews and Beckefi was followed. Potassium (10 g., 0.026 atom) was added in portions to a solution of 13.5 g. (0.18 mole) of isobutyl alcohol in 50 ml. of xylene. Then a slurry of 18 g. (0.11 mole) of fluorene in 200 ml. of xylene was added together with 4 g. of Davison nickel catalyst which had previously been washed with methanol and three times with isobutyl alcohol. The mixture was refluxed under a DeanStark trap for 18 hr. and then filtered hot. After washing with three loo-ml. portions of water, it was distilled leaving a residue which was recrystallized from methanol to give 14 g. of colorless product, m.p. 31-36". A number of recrystallizations alternately from ethanol and from acetic acid gave the analytical sample, m.p. 45-46". A mixture melting point with the product of the reaction between 2,2-dimethylpropan-1,3-diol was not depressed. Unsuccessful attempt to prepare ~4sobutyljluorene. I. Xylene (200 ml.) and Davison nickel catalyst (4 g.), which had been previously washed as described above, were refluxed under a Deanatark Trap for 15 min. until no more water was accumulated in the trap. Isobutyl alcohol (13.5 g., 0.18 mole) and fluorene (18 g., 0.11 mole) were added and the mixture was refluxed for 18 hr. No water layer was formed in the trap during refluxing. The mixture was filtered while hot, washed with three loo-ml. portions of water and distilled. The residue consisted of 17.5 g. of unreacted fluorene, m.p. 112-113". Unsuccessful attempt to prepare Q-kobutylfluo7ene.11. Isobutyl alcohol (100 g., 1.33 moles) was refluxed together with 30 g. of washed Davison nickel catalyst and 10 g. (0.06 mole) of fluorene for 24 hr. over a Soxhlet extractor, the thimble of which contained calcium hydride. The solution was then filtered while hot, and the alcohol-distilled.The residue consisted of 9.3 g. of unreacted fluorene, m.p. 113-115'. No alkylation product was observed. F o m t i o n of isobutyraldehyde in presence of Raney nickel. Isobutyl alcohol (20 g., 0.266 mole) was refluxed with 6 g. washed Davison nickel catalyst and the vapors formed in the reaction were collected in a test tube. The condensate was treated with 2,4-dinitrophenylhydzone reagent and gave an orange precipitate. Two recrystallizations from alcohol gave an orange product, m.p. 179-181" (reported for 2,4ainitrophenylhydrazone of isobutyraldehyde, 182'). A mixture melting point determination with the 2,4-dinitrophenylhydrazoneprepared from isobutyraldehyde showed no depression.
BROOKLYN 1, N. Y.
