[CONTRIBUTION FROM THE
DEPARTMENT OF CHEMISTRY OF
THE OHIO STATE UNIVERSITY]
NEW SYNTHESES OF PICENE MELVIN S. NEWMAN Received June 29,
is&
In this paper the synthesis of picene by two closely related new methods and of 5-methylpicene, 13-methylpicene, and 13-piceno11is reported. The synthesis of picene and its derivatives is of interest in connection with attempts to determine the structure of hydropicene triterpenoids by dehydrogenation (1). Most of the previously reported syntheses (2) of picene involve an intramolecular cyclization requiring prolonged treatment with aluminum chloride. Yields are very poor and the structure of any methylated picenes thus prepared must be regarded as not absolutely certain in view of the known lability of alkyl groups in Friedel-Crafts condensations (3). Indeed, one synthesis of picene definitely involves the loss of a methyl group (2 e). For these reasons it was decided to study the synthesis of picene by new methods which would be generally applicable to the preparation of any mono- or poly-substituted picene, and which would use only reactions leading undeniably to expected products. The two syntheses reported herein are closely related to the chrysene syntheses previously developed in this laboratory (4, 6). 2-Naphthylacetonitrile, I, was produced from 2-naphthylmethyl ketone via the thiomorpholide (5), hydrolysis to 2-naphthylacetic acid, conversion to the amide, and dehydration. In the modified Willgerodt reaction ( 5 ) , it was found that more than one equivalent of sulfur and of morpholine was required to secure highest yields. The alkylation of I to I1 went well as in similar cases (6). Hydrolysis and ring closure to 111, followed by Reformatsky reaction, dehydration and hydrolysis to IV went without trouble. The position of the double bond in IV is assumed. The reduction of IV to V was difficult of accomplishmentbut was finally carried out with sodium amalgam in dilute aqueous alcoholic solution. The remaining steps require no comment except that it was easier to secure the final hydrocarbons, VI1 and VI11 when sulfur rather than palladium-on-charcoal was used as dehydrogenating agent. 13-Picenol was easily obtained by dehydrogenation of the methyl ester of IV, followed by hydrolysis to IX, cyclization to the acetate (7) of X, and hydrolysis to x. The alkylation of benzyl cyanide with I proceeded well as in other cases (6). Hydrolysis of IIa and ring closure of the resulting acid yielded the ketone IIIa which, after Reformatsky reaction dehydration, and hydrolysis, yielded IVa. As a check on the structure of IIIa, it was reduced to the corresponding alcohol which was dehydrated and dehydrogenated to 2-phenylphenanthrene, XI, a new hydrocarbon which was characterized by oxidation to 2-phenylphenanthraquinone, XII. The position of the double bond in IVa is assumed. The acid, IXa, was obtained by dehydrogenation of the methyl ester of IVa, followed by hydrolysis. The cyclization of acids IVa and IXa by procedures similar to those 1
Chemical Abstracts numbering.
518
1. NaNHs 2. CEHKCH~CHZBL
I1
I
I11
1. Reformataky 2. -H*O 3. H20
1. AczO, ZnCk 2. Ha0
X
-Hi
IV
IX
IV
HZ
1. PClr ____f
2. AlCL
Synthesis of 13-Substituted Picenes 519
520
MELVIN 6. NEWMAN
used in a previous case t o prepare dihydrochrysenol (4) and chrysenol yielded mixtures of compounds which undoubtedly contained the nucleus of XI11 in addition to the picene nucleus. For this reason, and also because of the difficulty of reducing IVa to Va without simultaneously getting more highly hydrogenated acids, this synthesis was abandoned.2 Later, however, when it was found
CHlBr
/ CH?
CH,
Ia
IIa
IIIa 1. Reformatsky 2. -HpO
VIa
I
CHaMgBr
OH
o\/ I
II
I
VIb
CHa
1. -Ha0 2. -2Ha
VIIIa
IXa
Synthesis of 5-Methylpicene2 2 All of the reactions through the preparation of IVa and Xa were completed during 1939 and 1940 before the synthesis of 13-methylpicene was started. Part of this time the author was working a t Yale University on a grant from the Jane Coffin Childs Memorial Fund for Medical &search (1939) and later (1940) as the Elizabeth Clay Howald Scholar at The Ohio State University.
52 1
NEW SYNTHESES OF PICENE
IIIa
1. Ha
ox.
+
___)
-Ha0 3. -Ha
2.
0 XI
XI1
XI11
practical to reduce IT to V by sodium amalgam, tu, synt-esis was resumed, and IVa was reduced to Va in the same way. The remaining steps occasioned no trouble. The picene obtained in both syntheses melted at 366.0-366.5' corr. in a Pyrex sealed-tube and proved identical to a sample of picene previously synthesized (2a) by M. Orchin. EXPERIMENTAL3
Thiomorpholide of 2-naphthylacetic acid. A mixture of 373 g. (2.2 moles) of 2-naphthyl methyl ketone, 105 g. (3.3 moles) of sulfur, and 290 g. (3.3 moles) of morpholine was heated in a good hood a t gentle reflux for 14 hours and at brisk reflux for 2 hours and was poured while still hot into 1.2 1. of warm alcohol. On cooling, a yield of 534 g. (89.6%) of pale buff crystals, m.p. 100-106" was obtained. When only theoretical amounts of sulfur and morpholine were used (5) the yield varied from 53% to 65%. For hydrolysis t o the acid there was no advantage in purification of the crude crystals. $&j.R-NaphthyZaceticacid. In the best of several experiments a mixture of 388 g. of thiomorpholide, 800 cc. of acetic acid, 120 cc. of concentrated sulfuric acid, and 180 cc. of water was refluxed for 5 hours and poured into 6 1. of water. Considerable tar remained in the reaction flask. After standing overnight, the solid was collected, washed with water, and 8 All melting points corrected. Melting points above 250' were taken in an apparatus described by Bergstrom, Ind. Eng. Chem. Anal. Ed., 9, 340 (1937) with the calibrated thermometer described by Newman, J. Am. Chem. Soc., 82,1686 (1940). The pressure recorded for all vacuum distillations is not accurate to greater than f 0 . 5 mm. All microanalyses markeda by J. E. Varner;b by J. A. Curtiss;n by D. Lester;d by G. Beatty;" by Arlington Laboratories;f by J. Walker.
522
MELVIN S. NEWMAN
digested with a solution of 150 g. of sodium hydroxide in 3 1. of water. A dark insoluble substance was removed by filtration and crude 2-naphthylacetic acid precipitated as a cream colored solid by acidification. After washing with water, drying, and digesting with several portions of benzene-petroleum ether, the acid was obtained as a purplish tinged solid, m.p. 138-141", in 89.5% yield. On one crystallization from benzene i t melted a t 142.2-143.0", but yields of amide were just as good when crude acid was used. 2-Naphthylacetamide. I n a typical experiment, 50 g. of acid was converted into the acid chloride by heating with 57 g. of phosphorus pentachloride in 150 cc. of benzene. The solvent and phosphorus oxychloride were removed under reduced pressure, the acid chloride was dissolved in 100 cc. of dry acetone, and this solution was added slowly with efficient stirring to 300 cc. of concentrated ammonia. After diluting with one liter of water, the amide was collected, washed with water, and oven-dried to yield 4 7 4 8 g. of purplish amide, m.p. 198-202". On recrystallization from alcohol the amide melted at 202-204.6' but darkened on melting. This preparation worked as well on a large scale (361 g.). 2-iVaphth~ZacetonitriZe,I. I n the best of several experiments 20 g. of crude amide was added t o 20 g. of phosphorus pentoxide under benzene. The pasty mass was heated to reflux in a glycerine bath for 36 hours with stirring. After decanting the clear benzene layer, the residue was cautiously treated with water and the ether-soluble organic matter added to the benzene solution. After washing with alkali, the nitrile, I, b.p. 145-150' a t 2 mm., was obtained in 76.5% yield as a crystalline solid. Recrystallization from dilute alcohol with almost no loss gave a white nitrile, m.p. 85.6-86.2" (8). In larger runs the yield was often less, mainly because of mechanical difficulties. cu-(2-NaphthyZ)-r-phenyZ~~~yron~~riZe, 11. To a slowly stirred suspension of 19.5 g. of sodium amide4 in 400 cc. of dry sulfur-free benzene was added during one hour 79 g. of I. The evolution of ammonia was brisk and the solution turned blood-red. After refluxing for two hours and cooling somewhat, a large amount of crystalline orange-brown solid was suspended in a dark solution. Upon the slow addition of 90 g. of 8-phenethyl bromide much heat was generated. After the vigorous reaction had subsided the mixture was refluxed for 6 hours. The reaction mixture was washed with water and the solvent removed. Fractionation a t 2 mm. yielded 86 g. (67%) of I1 as a viscous orange-yellow oil, b.p. 210-230". From the forerun 5 g. of I was recovered, The nitrile I1 crystallized from dilute alcohol to give colorless small crystals, m.p. 62.W4.0' but for further work the crude nitrile was used. Anal. Calc'd for CmHIJV: C, 88.5; H, 6.3; N, 5.2. Found*: C, 89.1, 88.8; H, 6.5, 6.4; N, 5.3, 5.1. cu-(~-NaphthyZ)-r-phenylbulZlricacid. I n the best of several experiments a mixture of 86 g. of 11,350 cc. of acetic acid, 20 cc. of water, and 30 cc. of concentrated sulfuric acid was refluxed for 46 hours in an all glass system. After cooling, the mixture was diluted with water and extracted with ether. After thorough washing with water, the ether layer was extracted many times with dilute potassium carbonate solution. The crude acid obtained on acidification was dried and crystallized from benzene-petroleum ether. I n all, 81.3 g. (88.5%) of crystalline acid was obtained. A portion recrystallized for analysis melted at 122.6-124.0'. Anal. Calc'd for C20H1802:C, 82.7, H, 6.3. Found*: C, 82.6, 82.8; H, 6.1, 6.3. From the neutral fraction of the above hydrolysis mixture was isolated a small amount of colorless crystals, m.p. 147.8-149.0'. This compound was proved by analysis t o be di-8-
' The author is indebted to Drs. A. L. Henne and K. Greenlee for directions for the preparation of sodium amide in liquid ammonia. These directions, shortly t o be published in "Inorganic Synthesis", John Wiley and Sons, Inc., New York, made possible the conversion of a pound or more of sodium into finely granulated sodium amide in a few hours working time.
NEW SYKTHESES OF PICENE
523
phenethyl-2-naphthylacetamide,arising from incomplete hydrolysis of a small amount of dialkylation product in the preceding step. Anal. Calc'd for C ~ S H Z T NC, O :85.5;H, 6.9;N,3.6. Founda: C,85.4,85.2;H, 7.0,6.8;N, 3.5, 3.4. $?-($-Naphthyl)-l-keto-l,2,S,Q-tetrahydronaphthalene, ZZI. I n the best of several experiments, 58 g. of acid was converted into the acid chloride with 42 g. of phosphorus pentachloride in 300 cc. of benzene. After removal of the solvent and phosphorus oxychloride under reduced pressure, the acid chloride was dissolved in 400 cc. of S-free benzene and treated with 27.5g. of aluminum chloride during hour with no attempt a t cooling. When all of the aluminum chloride had been added, the mixture was heated rapidly to reflux and refluxed 5 hour. After pouring on ice, the solvent was removed by steaming and the solid ketone collected and dissolved in acetone. All solids were removed by filtration and the acetone displaced by alcohol from which the ketone largely crystallized as pale buff plates. The ketone remaining in the mother liquor was distilled, coming over a t about 250"a t 3 mm. In all, 47.5 g. (87.5%) of good ketone was obtained, m.p. 142.8-144.2'. T o get colorless ketone i t was necessary to vacuum distil, but if the crude reaction product was distilled without a previous crystallization, losses were greater. A sample recrystallized for analysis from alcohol formed fern-like white crystals, m.p. 143.8-144.6'. Anal. Calc'd for C~OH~BO: C, 88.2;H , 5.9. Foundb: C, 87.8,88.0; H,6.0,6.1. The oxime, m.p. 158.6-159.4",was prepared by heating with hydroxylamine hydrochloride in pyridine. Anal. Calc'd for CzoHlrNO: C, 83.6;H, 6.0; N, 4.9. Foundb: C, 83.2,83.1;H, 6.0,5.8;N,4.8,4.8. 2-(2-Naphthyl)-S,4-dihydro-l-naphthaleneacetic acid, ZV. The Reformatsky reaction between 54.4 g. of 111,35g. of methyl bromoacetate, 16 g. of zinc, and 400 cc. of dry S-free benzene proceeded slowly and was completed by refluxing for two hours. The organic reaction product was dehydrated by heating a t 190-240" for one hour with a crystal of iodine. After saponification with alcoholic potassium hydroxide, the acid and neutral reaction products were separated to yield 17.1 g. (31.5%) of starting ketone and 37.4 g. (60%, or 8770 if allowance is made for recovered ketone) of acid. The acid fraction yielded 24 g. of crystalline acid, IV, m.p. 177.0-178.6'. A sample regenerated from the methyl ester and recrystallized from benzene for analysis melted at 178.0-178.6'. Anal. Calc'd for C22Hl802: C, 84.1;H, 5.8. Foundb: C, 83.9,83.8;H , 5.9,5.8. By converting the non-crystalline acid fraction into methyl esters, distilling (b.p. about 250" a t 4.5mm.), and saponifying, additional crystalline acid, m.p. 177.0-178.6",was obtained. 9 similar isomerization has been reported previously (9) and has been noticed frequently in other cases I have encountered. The methyl ester of IV crystallized as colorless needles, m.p. 99-101",from benzene-methanol. Anal. Calc'd for C23HZ0O2: C, 84.1;H , 6.1. Foundb: C, 83.7,83.8; €1, 6.4,6.2. 2-(2-Naphthyl)-1-naphthaleneaceticacid, I X . A mixture of 5.80 g. of the methyl ester of IV and 0.566 g. of sulfur was heated a t 220" for one hour and then a t 250' for one-half hour. The product was crystallized from hot propyl alcohol using decolorizing charcoal (Darco G-60)to give 4.70g. (85.5y0)of the methyl ester of IX. A sample recrystallized twice from benzene-methanol for analysis melted a t 107.2-108.6'. On saponification the free acid, IX, was obtained in quantitative yield as colorless needles, m.p. 191.0-192.6'. Anal. Calc'd for C13H1802: C, 84.6;H, 5.6. Foundb: C, 84.5, 84.3;H, 5.4,5.5. Calc'd for CL~HIBO~: C, 84.6;H, 5.2. Foundb: C, 84.1, 84.0;H, 5.0, 5.2. IS-P'icenolacetate and id-picenol,X . A mixture of 2.14g. of IX, 5 cc. of acetic acid, 5 cc.
524
MELVIN S. NEWMAN
of acetic anhydride, and a few small crystals of anhydrous zinc chloride was refluxed for one hour and was then diluted with a few drops of water. On cooling, 1.49 g. (65%) of white crystals, m.p. 207-208" was obtained. The purest sample of 13-picenol acetate melted a t 208.5-209.2". Anal. Calc'd for Ce4H1sOz:C, 85.7; H, 4.8. Foundb: C, 86.1, 85.9; H, 4.8, 4.7. On hydrolysis with dilute aqueous-alcoholic potassium hydroxide by refluxing for 30 minutes, this acetate was converted in high but undetermined yield to 13-picenol, X. Because of decomposition on melting, the melting point of X was not sharp, the material sintering near 275" and melting near 286". I n spite of several attempts, X was not obtained colorless, a pale buff color being present. Anal. Calc'd for CzzHlaO:C, 89.8; H, 4.8. Foundb: C, 89.9, 89.8; H, 5.0, 4.9. d-(%Naphthyl)-i,I,b,4-tetrahydronaphthaleneaceticacid, V . The reduction of IV to V proved difficult and has not really been efficiently done t o date. Catalytic hydrogenation over Adams platinic oxide catalyst a t low hydrogen pressure or over catalyst 37KAF (IO) in dioxane at 200" and 1800 lbs. initial pressure proved unsatisfactory. Reduction was successfully accomplished by stirring an alkaline solution of the sodium salt of IV in aqueous alcohol over an excess of 1.5-2y0 sodium amalgam for a period of from 4 days to 18 days. Frequent additions of dilute acid were made to neutrality. This caused precipitation of acid but this slowly redissolved on reaction of the sodium amalgam and was replaced by a nacreous precipitate of the sodium salt. When the reduction mixture was worked up the precipitate and the iiltrate were worked up separately but later combined as there was no great difference. The acid mixture proved difficult to separate into any homogeneous fractions and for further work crude mixtures were used. There was isolated a small amount of unsaturated acid, IV, m.p. 176.4-177.2'; and of a pure isomer of V, m.p. 160.4162.4'. Anal. Calc'd for C n H z 0 0 ~C, : 83.5; H, 6.4. Foundb: C, 83.8, 83.8; H, 6.1, 6.0. Picene, VII. The acid chloride was made from 3.3 g. of crude acid mixture, V, in the usual way using phosphorus pentachloride, and this was cyclized in chlorobenzene solution a t 40" for one hour using 1.5 g. of aluminum chloride. After hydrolysis, the benzene solution of the products deposited 1.00 g. (32%) of a mixture of ketones, VI. A small amount of a pure isomer of iS-keto-6,6,6a71S,i4,14a-hezahydropicene, m.p. 194.6-195.6", was isolated as pale orange prisms. Anal. Calc'd for CPZH~aO: C, 88.6; H, 6.1. Foundb: C, 88.4, 88.4; H, 5.8, 5.6. The material remaining in the mother liquors after the original crystallization was vacuum distilled to yield 1.58 g. (51y0)of ketone as a clear darkstraw colored viscousliquid. This was dissolved in toluene and reduced with aluminum isopropoxide (11) for six hours. A benzene solution of the dehydrated (simple heating) reaction products deposited a small amount (0.113 g . ) of almost colorless needles which on recrystallization melted at 297-307". This compound gave fair analyses for a tetrahydropicene. Anal. Calc'd for CZ2H18:C, 93.6; H, 6.4. Foundb: C, 93.3, 93.2; H, 5.5, 5.6. The remaining product was heated up t o 350' over 23% palladium-charcoal (12) for 4 hours and was then vacuum distilled to yield 1.05 g. (71%) of crude picene, VII. After decolorization with charcoal (Darco G-60) in xylene followed by vacuum sublimation a t 300" and 2 nim. and crystallization from xylene there was obtained pure white glistening leaflets of picene, m.p. 366-366.5", with a n intense blue-violet fluorescence in ultraviolet light and even in indirect daylight. A mixed melting point with other synthetic picene (2a) showed no depression. IS-Methylpicene, V I I I . A somewhat different fraction of crude acid, V, (4.90 9.) was cyclized as above and the crude ketone vacuum distilled to yield 3.2 g. (69%) of a mixture of
NEW SYNTHESES OF PICENE
525
crystals and oil. The crystals, separated from a benzene solution, amounted t o 0.53 g. and were saved for attempted isolation of pure ketone isomers. Of the remaining oil 1.71 g. was treated in ether solution with a n excess of methylmagnesium bromide. The carbinol fraction thus obtained was heated at 240" with 0.37 g. of sulfur for 2 hours and was then vacuum distilled t o yield 1.35 g. of a yellow crystalline solid. Crystallization from benzene yielded 0.98 g. (58%) of crude 13-methylpicene, VIII, m.p. 187-199". Decolorization with charcoal (Darco G-60) followed by recrystallization from benzene-alcohol yielded pure VIII, m.p. 203.6-204.4', as fine colorless needles having a blue-violet fluorescence in ultraviolet light. Anal. Calc'd for CZaHIG: C, 94.5; H, 5.5. Foundb: C, 94.4, 94.5; H, 5.4, 5.2. The addition compound with two molecules of s-trinitrobenzene formed orange-red needles, m.p. 178.4-179.0". Anal. Calc'd for CssHazNaOlt: C, 68.9; H, 3.8; N, 8.3. Foundb: C, 69.0, 68.8; H, 3.7, 3.7; N, 8.2, 8.3. 5-MethylpiceneSynthesis p-(l-NaphthyZ)ethyZbromide,la. 8-(1-Naphthy1)ethanol was prepared in 76% yield from 1-naphthylmagnesium bromide and ethylene oxide (13). Only material boiling constantly at 148" a t 1.5 mm. was taken. A mixture of 150 g. of p-(1-naphthy1)ethanol and 220 cc. of 48% hydrobromic acid was refluxed for 1 hour and then concentrated until 190 cc. of distillate had been collected. The organic layer of the distillate was returned t o the residue together with 60 cc. of 48% hydrobromic acid. After refluxing 1 hour, 60 cc. of liquid was distilled. The bromide layer was then separated, washed with water and 80% sulfuric acid, and finally vacuum distilled t o yield 185.5. g. (90.5%) of Ia (14), b.p. 135-137' at 1-1.5 mm. a-PhenyZ-y-(l-naphthyZ)butyronitrile, IIa. I n the best of several experiments 63 g. of pure benzyl cyanide in 100 cc. of benzene was added to a stirred suspension of 22 g. of sodium amide4 in 300 cc. of benzene. A brownish-red color was produced, some heat was evolved, and a little ammonia was given off. After 5 minutes 119 g. of Ia was added i n several portions. Much heat and ammonia were evolved and a solid began to precipitate. After about half of the bromide had been added the color lightened to light brown. After refluxing for 4 hours and standing a t room temperature overnight, the product was worked up as for compound I1t o yield 99 g. (73%) of IIa, a yellow viscous oil, b.p. 218-219'at 2 mm. This compound was not analyzed but hydrolyzed directly to the acid. a-Phenyl-y-(1-naphthyZ)butyric acid. I n the best of several experiments 103 g. of nitrile, IIa, 700 cc. of acetic acid, and 130 cc. of 50% sulfuric acid were refluxed for 63 hours, during the last hour of which 300 cc. of acetic acid was distilled. The remainder was diluted with water and the organic product taken into warm benzene and well washed with water. The acid was then extracted with aqueous potassium hydroxide. From the benzene solution a small amount of the amide was obtained as rosettes of fine white needles, m.p. 124.6-125.4". On acidification of the alkaline extract, the free acid was taken into benzene and crystallized t o yield 100.0 g. (91%) of d i t e needles, m.p. 106-107". A sample purified for analysis melted at 107.2-108.2". Anal. Calc'd for C10H1802. C, 82.7; H, 6.3. Foundo: C, 82.7; H, 6.3. Calc'd for CzoHlsNO. N, 4.8. Foundd: K, 4.8, 4.9. i-Keto-d-phenyZ-l,2,3,4-tetrahydrophenanthtene, IIIa. In the best of several experiments the acid chloride, prepared from 100 g. of acid in benzene using 73 g. of phosphorus pentachloride, in 200 cc. of benzene was treated with 49 g. of aluminum chloride added slowly with cooling and stirring. At first the color became deep red-brown and hydrogen chloride was evolved. After stirring at room temperature for one hour a n orange complex suddenly separated, the color became much lighter and the mixture went solid. This mixture was then scraped into ice and hydrochloric acid and the benzene was removed b y
526
MELVIN S. NEWMAN
steaming. The solid was collected, dried, and crystallized from benzene. These crystals were vacuum distilled, boiling at 259" a t 4.5 mm., and the distillate was crystallized from toluene-alcohol to yield 85.3 g. (91%) of IIIa, m.p. 176-177". A sample recrystallized for analysis formed colorless plates, m.p. 177.4-177.8'. Anal. Calc'd for C~OHIOO: C, 88.2; H, 5.9. Foundc: C, 88.2; H, 5.9. %Phenylphenanthrene,XI, and related compounds. A solution of 8.2 g. of IIa in 100 CC. of isopropyl alcohol containing 1 g. of dissolved aluminum (15) was refluxed for 10 hours during which acetone and alcohol were allowed t o distil slowly and also 100 cc. of isopropyl alcohol was added to the reaction. The reaction mixture was hydrolyzed with dilute hydrochloric acid and the solution of secondary alcohol in dry benzene was treated with dry hydrogen chloride. The solution became milky. After all reaction with hydrogen chloride ceased and the solution had been dried with calcium chloride a n attempt was made to alkylate malonic ester according t o the procedure of Bachmann (11). However, no acid fraction was obtained on hydrolysis. From the crystalline neutral fraction, 1.6 g. (2170) m.p. 150.6-151.0" was removed for the purification of 2-phenyl-3,4-dihydrophenanthrene, and its characterization as dipicrate, deep red needles, m.p. 144.5-145.6'. Anal. Calc'd for CPOHW.: C, 93.7; H, 6.3. Founde: C, 93.7; H, 6.3. Calc'd for C32H2201,Ne: C, 53.8; H, 3.1. Founde: C, 53.9; H, 2.9. The remaining 5.4 g. (70%) of dihydrophenylphenanthrene was heated with 0.65 g. of sulfur a t 235-240" for 1 hour. After removal of unreacted sulfur by refluxing a benzene solution with mercury, 4.72 g. (88%) of 2-phenylphenanthrene, XI m.p. 195-197", was isolated by crystallization from benzene. A sample purified for analysis melted at 196.6197.2'. The molecular compound with 2 molecules of s-trinitrobenzene formed bright yellow small needles, m.p. 156.4-157.4'. Anal. Calc'd for C20H14: C, 94.5; H , 5.5. Found": C, 94.7; H, 5.5. Calc'd for CtzH2OOlzN6: C, 56.5; H, 3.0; N, 12.4. Foundo: C, 55.9; H, 2.9; N, 12.4, 12.3. On oxidation with chromic oxide in acetic acid 2-phenylphenanthrene was converted in good yield into 2-phenyl-9,lO-phenanthrenequinone, X I 1 deep red needles, m.p. 220-221O with previous sintering and decomposition. The phenazine derivative, yellow needles, m.p. 285-287", uncorr., was prepared with o-phenylenediamine. Anal. Calc'd for CzoHllO2: C, 84.5; H, 4.3. Foundc: C , 83.9; H, 4.2. Calc'd for C26Hla2: C, 87.6; H, 4.5; N, 7.9. Found': C, 87.6; H, 4.4; N, 7.6. 2-Phenyl-S,Q-dihydro-l-phenanthreneacetic acid, IVa. In the best of several experiments, 13 g. of sandpapered zinc foil (16) was added t o a hot solution of 36.8 g. of ketone, IIIa, and 33.4 g. of ethyl bromoacetate in 350 cc. of toluene and 150 cc. of benzene. The reaction proceeded immediately but sluggishly so that external heating was required to maintain reflux. After four hours, the mixture was cooled and treated in the usual fashion. On concentration of the toluene-benzene solution of the products, 14.0 g. of unreacted ketone crystallized. The remaining product was dehydrated by heating near 220" with a small amount of iodine and the resulting mixture was vacuum distilled at 230-250' and 1 mm. After saponification with alcoholic potassium hydroxide, the products were separated into acidic and neutral fractions. From the neutral fraction there was isolated a further 2.3 g. of starting ketone, IIIa, making a total of 16.3 g. (44.3%) of recovered ketone. From the acid fraction was isolated 13.5 g. (31.8% or 57y0 on ketone consumed) of crude acid. Crystallization from toluene-alcohol yielded 11.5 g. of colorless acid, IVa, m.p. 226-228" (decomp.). The melt bubbled copiously just at and above its melting point. Evidently decarboxylation was occurring for the fact that this acid gave good analytical figures rules out solvation.
NEW SYNTHESES OF PICENE
527
Anal. Calc'd for C22Hle02: C, 84.1; H, 5.8. Found': C, 84.3; H, 5.6. 8-Phenyl-1,X,S,4-tetrahydro-l-phenanthreneaceticacid, Vu. A hot suspension of 8.08 g. of pulverized acid, IVa, in 30 cc. of alcohol was diluted t o 450 cc. with water, a milky solution being formed. This solution was stirred continuously for 32 days with a n amalgam prepared from 12 g. of sodium and 100 cc. of mercury. After the first day, a nacreous white precipitate of sodium salts was formed. Each day dilute hydrochloric acid was added until the solution was about neutral. Frequently considerable amounts of organic acid were precipitated by these additions of acid. By the next day, however, the precipitated acids had redissolved in the alkali produced by the action of the sodium amalgam. The quantity of nacreous precipitate seemed t o increase with time. At the end of 32 days there still remained considerable sodium i n the amalgam. The suspension was decanted from the amalgam and filtered. The acids liberated from the precipitate and filtrate were treated separately but were found to be essentially the same and were united. A total of 7.48 g. (92%) of colorless crystalline acid, a mixture of stereoisomeric acids, m.p. 170-215", was obtained. The separation of pure compounds from this mixture proved exceedingly difficult and absolutely pure isomers were not obtained. However, a low-melting racemate, m.p. 173-176", and a higher-melting one, m.p. 205-226', were separated. Anal. Calc'd for CZZH~OOZ: C, 83.5; H, 6.4. Found": (low-melting isomer) C, 83.4; H, 6.4 (high-melting isomer). C, 83.1, 83.0; H, 6.5, 6.4. Picene. The acid chloride from 1.48 g. of acid, Va, in 10 cc. of chlorobenzene was treated with 0.63 g. of anhydrous aluminum chloride. There was immediate darkening and evolution of hydrogen chloride. After five minutes a dark yellow crystalline complex separated. The mixture was heated to 55" during five minutes and then cooled and treated with water and acid. Benzene was added and the organic layer was well washed with acid and alkali and the solvents removed under reduced pressure. The resulting ketone was not isolated but reduced to the secondary alcohol using aluminum isopropoxide in toluene (11). The product thus obtained was heated for 2 hours from 240" to 340" with 0.281 g. of sulfur. The crystalline residue was sublimed at 300" under reduced pressure and the sublimate was crystallized from xylene, yielding 0.72 g. (55%) of picene, m.p. 355-360" uncorr. in a sealed Pyrex tube. By decolorization using carbon (Darco G-60) i n boiling xylene, followed b y sublimation and recrystallization pure picene (see above) was obtained. 6-Methylpicene. T o a benzene solution of the ketone prepared as above from 2.73 g. of acid, Va, was added a n excess of methylmagnesium bromide. After the initial vigorous reaction the mixture was left a t room temperature for one hour and was then decomposed with dilute acid. After standing for twelve hours in benzene, 0.54g. (20%) of the expected carbinol, VIb, crystallized and was collected. After crystallization from benzene-alcohol i t separated as stout colorless prisms, m.p. 169-170". Anal. Calc'd for Cz~H220:C, 87.9; H, 7.1. Foundb: C, 87.9; 87.8; H, 7.2, 7.4. No attempt mas made to secure more of this carbinol but the filtrate from the crystals was treated a second time with methylmagnesium bromide. The entire mixture thus obtained, but omitting the crystalline carbinol, was heated with 0.43 g. of sulfur at 240-280" for 1 hour and was then vacuum distilled. The crystalline distillate, 1.33 g., was crystallized t o yield 0.995 g. (40%) of crude 5-methylpicene, m.p. 243-251'. After decolorization with charcoal, sublimation, and crystallization from toluene, 5-methylpicene was obtained as almost colorless stout needles, m.p. 251.6-252.2", having strong blue-violet fluorescence in ultraviolet light. Anal. Calc'd for C23H1,: C, 94.5;H, 5.5. Foundb: C, 93.8, 93.9; H, 5.6, 5.8. The di-s-trinitrobenzene derivative, m.p. 215.4-216.2', crystallized in orange red fine needles. Anal. Calc'd for C ~ S H ~ Z N GC, O ~68.9; ~ : H, 3.8; N, 8.3. Foundb: C, 68.8, 68.9; H, 3.8, 3.9; N, 8.3, 8.2.
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MELVIN S. N E W N
SUMMARY
The synthesis of picene, 5-methylpicene, 13-methylpicene, and 13-picenol and the necessary intermediates is described. COLUMBUS, OHIO. REFERENCES (1) For example, (a) RUZICKA et al., Helv. Chim. Acta, 16, 431, 1496 (1932). (b) Helv. Chim. Acta, 17, 200,442 (1943). (c) Helv. Chim. Acta, 20, 791 (1937). (d) NOLLER,J . Am. Chem. SOC.,66, 1582 (1934). (e) DRAKEet al., J. Am. Chem. SOC., 68, 1684, 1687 (1936). (f) WIELANDet al., Ann., 622, 191 (1936). (9) JACOBS
ISLER, J . Biol. Chem., 119, 155 (1937). (h) HEYWOOD, KON,AND WARE,J. Chem. SOC.,1124 (1939). (i) SIMPSON AND WILLIAMS, J. C h m . SOC.,686 (1938). (j) HEILBRON et al., J. Chem. Soc., 344 (1941). (2) RUZICKA AND HBSLI, Helv. Chim. Acta, 17, 470 (1934). (b) RUZICKA AND MORGELI, Helv. Chim. Acta, 19, 377 (1936). (c) RUZICKAAND HOFFMANN, Helv. Chim. Acta, 20, 1155 (1937). (d) Helv. Chim. Acta, 22, 126 (1939). (e) DRAKEAND MCVEY,J. Org. Chem., 4, 464 (1939). (f) WEIDLICH, Ber., 71, 1203 (1938). (3) THOMAS, “Anhydrous Aluminum Chloride in Organic Chemistry”, A. C. S. Monograph No. 87, Reinhold Publishing Corp., New York, 1941, p. 77-94. (4) NEWMAN, J. Am. Chem. SOC.,80,2947 (1938). AND BLOCK, J. Am. Chem. SOC.,64,3051 (1942). (5) SCHWENK J. Am. Chem. SOC.,62, 870, 2295 (1940). (6) NEWMAN, AND HERSHBERG, J. Am. Chem. Soc., 69,1028 (1937). (7) FIESER ( 8 ) KIKKOJI,Biochem. Z., 36, 77 (1911). (9) SCHROETER, Ber., 68, 713 (1925). (IO) CONNOR, FOLKERS, AND ADKINS, J . Am. Chem. SOC.,64,1138 (1932). (11) BACHMANN AND STRUVE, J. Org. Chem., 4,456 (1939). Ber., 68, 1295 (1925). (12) ZELINSKYAND TUROWA-POLLAK, (13) COOKAND HEWETT,J. Chem. Soc., 1098 (1933). (14) Compare HAWORTH AND MAVIN,J. Chem. Xoc., 1012 (1933). (15) LUND,Ber., 70, 1520 (1937). (16) NATELSON AND GOTTFRIED, J. Am. Chem. SOC.,61,970 (1939). AND
