Mar. 20, 1964
STRUCTURE OF
1653
LONGIFOLENE
[CONTRIBUTION No. 1193 FROM STERLING CHEMISTRY LABORATORY, YALEUNIVERSITY ]
The Structure of Longifolene. The Longifolic Acids' BY HAROLD H. ZEISS AND MORIMASA ARAKAWA RECEIVED SEPTEMBER 26, 1953 The longifolic acids are shown to be CljH~~02 and not C&202 monobasic acids as previously reported by other workers. This result together with other data proves the unsaturation in longifolene to be of a methylenecyclopentano form and not of a vinyl type. The acid isomerization of longifolene to 8-longifolene is also described.
The simultaneous appearance of three commu- isolated which proved to be longifolene on the basis nications relating to the structure of l~ngifolene*-~ of optical rotation and infrared spectrum. Clearly, prompts us to place on record work which we have isolongifolic acid cannot be a C14-acid. Similar completed and presented recently in verbal f0rm.l treatment of the longifolol obtained above gave a While one portion of our work is coincidental with hydrocarbon mixture which appeared to contain that reported by Naffa and Ourisson3both in design longifolene. These results suggest that longifolic and result, another is not only novel but is also of con- and a-longifolic acids are a t least in part epimeric siderable significance in the reactions of longifolene. mixtures. Neutralization equivalent determinaIt has been reported by Simonsen5that oxidation tions of all three acids in our hands gave correct of the tricyclic sesquiterpene, longifolene, C15H24, values for C15H2402 monobasic acids. This concluin acetic acid with chromium trioxide and in sulfu- sion has been reached also by Naffa and Ourisson.* Examination of the neutral fractions from the ric-acetic acid with potassium dichromate leads in the first case to longifolic acid and in the second to ozonization and acidic oxidations of longifolene isolongifolic acid. These acids were considered to revealed the presence of large quantities of a monobe isomeric and of the formula C14H2202 on the basis ketone whose infrared spectrum characterized it as of neutralization equivalent determinations, analy- a 5-membered ring ketone (5.73 p). This ketone is sis of the silver salt of longifolic acid, combustion undoubtedly the same as the Cld-ketone isolated by analyses and the isomerization of longifolic acid to Naf€a and Ourisson from the same sources. After isolongifolic acid in mineral acid. In addition to cleavage of this ketone with peracid, an uncharacthe acids a yellow a-diketone, C15H2202, was iso- terized crystalline hydroxy acid was obtained uia a lated from the neutral fractions of both oxidations. 6-membered lactone ( 5 . i 6 p). All these data, toLater, Bradfield, Francis and Simonsens obtained gether with the infrared absorption bands of longiformaldehyde and a third acid, a-longifolic acid, folene a t 3.25, fi.01 and 11.46 p, prove that the doualso considered to be of the C14 variety, from the ble bond in longifolene is methylenic and exocyclic ozonization of longifolene. The isolation of these to a .i-niembered ring. The C15-acids must arise, three acids was used as proof of a vinyl forniulation therefore, by terminal oxidation in the same way as the camphenilanic acids are formed from camphene. of the monounsaturation in longifolene. The uncertain relationships between these acids Longifolene is isomerized slowly in sulfuric-acetic and the apparently anomalous formation of the acid a t 80" over a period of 14 days. The course of Clb-diketone, longifdione, led us to repeat these the isomerization is followed easily by the change in oxidations. The three acids and the diketone were rotation from + 3 3 " to a value of - 16" and by thc obtained identical in n1.p. to those previously de- gradual and complete disappearance of the infrared scribed. Lithium aluminum hydride reduction of absorption bands due to methylenic unsaturation. iriethyl isolongifolate or of isolongifolic acid yielded The olefin, b-longifolene, which is recovered, arises as sole product, isolongifolol, m p . 112', [ a ] ~from the migration of the exocyclic double bond - 4fi.9". Oxidation of isolongifolol with dichro- with rearrangement, since its infrared spectrum inmate in sulfuric-acetic acid regenerated isolongifolic dicates completely different olefinic unsaturation acid. However, similar reduction of longifolic (12.26 p, possibly R1CH=CR2R8). acid gave isolongifolol in predominant yield and a Dehydration of isolongifolol or longifolol with second alcohol, longifolol, m.p. 78.5-80.5", [a]D potassium bisulfate a t 220" produces hydrocarbons +23.5". Furthermore, reduction of a-longifohc whose infrared spectra are similar to one another in acid also led to isolongifolol and a series of impure that they have absorption bands a t 6.10 and 11.28 p alcohol fractions rich in isolongifolol. It is appar- as compared to 6.01 and 11.46 p in the spectrum of ent, therefore, that 1ongiEolic and a-longifolic longifolene itself. This shift of absorption indicates acids are not homogeneous acids but are mixtures new unsaturation of the RlR2C=CH2 type. predominating in isolongifolic acid. From the Inasmuch as Naffa and Ourisson are continuing treatment of isolongifolol with phosphorus penta- their study of longifolene and its derivatives, we chloride in ether a t room temperature an olefin was propose to limit our work to the investigation of plongifolene and the dehydration products obtained (1) Presented a t Chicago, Ill., September 10, 1953, Abst. 1 2 4 t h in this Laboratory. Meeting, Amer. Chem. SOC., p. 69-0. (2) R. H. M o f f e t t a n d D. Roger, Chem. and Znd.,916 (1953). (3) P . N a f f a a n d G. Ourisson, ibid., 917 (1953). ( 4 ) G. Ourisson, i b i d . , 916 (1953). ( 5 ) J. L. Simonsen, J . Chem. Sac., 123, 2642 (1923). See also J. L. Simonsen a n d D. H. R. Barton, "The Terpenes," Vol. 111, C a m bridge Univ. Press, 14.52. ( 6 ) A . E. Bradfield, E , Ll. l r d n c i s atld J . L . Sinioiiscti, J . C'iiciii. S u c . , 168 (l!l34),
Experimental? Longifolene .-The longifolene used in the following experiments was isolated from the oleoresin of the Japanese (7) All melting points are corrected.
Rotations were measured in
9.5% ethanol unless otherwise specified. Xficroanalysis were performed Iry the Schwnrzkopf Xlirroanalytical Laboratories aud ncu-
Lralizdtiun equivalents tiy h l r . N . 'I'sutsui.
1654
G. E. MCCASL.AND AND E. CLYDEHORSWILL
Vol. 76
pine, Pinus densifEora, Sieb. and Zucc., and supplied to us ether proved to be slightly impure isolongifolol (0.3 g.) by the Arakawa Forest Products Company of Osaka, Japan. which further cryztallization failed t o improve: m.p. 107The sesquiterpene was distilled from sodium before use and log", [ a ]-45.0 ~ . fraction 2 (0.2 g.), m . p . 63-66", [ a ] ~ had the following constants: b.p. 144-146' (30 mm.), -23.5", and fraction 3 (0.3 g.), tr1.p. 63-70", [ a ] D--29.2', n Z 5 ~1.5000, a Z 5 +38.14'; ~ hydrochloride, m.p. 5X.k also were not improved by recrystallization. The infrared 59.5', [CY]"D +9.S0 (in CHCla); hydrobromide, m.p 69 . spectra of the three first fraction isolongifolols were identical, Simonsens reports these constants for longifolene obtained and those of fractions 2 and 3 from the reduction of cu-longifrom Indian terpentine oil: b.p. 150-151° (36 mm.), Z30D folic acid were very similar to t h a t spectrum of isolongifolol. 1.495, CYD +42.73'; hydrochloride, m.p. 59-60', [ a ] D Longifolene from Isolongifolo1.-Pure isolongifolol (2.0 +7.1" (in CHC13); hydrobromide, m.p. 69-70'. g.) was dissolved in 50 ml. of anhydrous ether and 2.0 g. Longifolene hydrobromide was dehydrobrominated in of phosphorus pentachloride was added. \\:bile the mixture 10% alcoholic potassium hydroxide a t reflux for 11 hr. to stood for 36 hours a t room temperature the solid peritachlolongifolene. The hydrochloride was considerably more reride lying initially at the bottom of the flask slowly dissistant to this treatment. solved. The clear solution was poured into water, and the Annl. Calcd. for C15Hz4: C, 88.16; H, 11.84. Found: ether layer was removed. This ether layer was washed with \vater, then with dilute sodium hydroxide solution, again C, 88.12; H, 11.51. \T ith water and finally dried over sodium sulfate. EvaporaThe Longifolic Acids.-Longifolene was oxidized and ozontive distillation of the residue, remaining after evaporation ized according t o the procedures of S i i n ~ n s e n . ~ ~Discrepant B values are given: longifolic acid, [a111+5.6" (opt. i n a ~ t . ~ ) ;of ether, at 100" (1 mm.) gave 0.2 g. of longifolene, [ a ] D +36.2", whose infrared spectrum was superimposable upon neut. equiv., 233, 234 (Cl6Hz4O2requires 236) ; isolongifolic t h a t of the sesquiterpene described above. If the ether acid, neut. equiv., 236, 236; a-longifolic acid, neut. equiv., solution of the reaction product is concentrated, a white 239, 239.5. The Longifolo1s.-Methyl isolongifolate (3.2 g . ) , m . p . crystalline substance is deposited, m.p. 121-123', as major product, and this material, which gave a positive phosphate 54-53' (54-55°),g was reduced in ether with excess lithium test, is believed to be the phosphate ester of isolongifolol. aluminum hydride. After working up in the usual manner, Isomerization of Longifo1ene.-Longifolene (10 9.) , [ a ] ~ the crude alcohol was crystallized from petroleum ether, was added to 20 ml. of sulfuric acid, 50 ml. of aceyielding 2 . 8 g. of pure isolongifolol, m.p. 111-112°, [ c Y ] ~ ~ +33.7", D - 46.9". Similar reduction of isolongifolic acid gave the tic acid and 70 ml. of water. This mixture was maintained a t ca. 80" on the steam-bath for 14 days, during which time same product. aliouots were withdrawn for rotation and infrared measureA n n l . Calccl. for C15EIzcO:C, 81.02; €1, 11.79. Found: ments. Specific rotation changes were: +33.7' (0 days), C, 80.98; H,11.38. t 2 1 . 1 ' ( l ) , f10.1" (2), +1.8' (3), -3.9" (4), -7.2' Reduction of longifolic acid (3.0 9.) yielded 1.6 g. of crudc (j),-9.6" (6), -15.4' ( 8 ) , -15.7' (9), -15.0' ( l l ) , alcohol, m.p. 50-90'. Crystallization of this material from -16.5" 114). petroleum ether gave as fraction 1, isolongifolol (0.46 g.), The isomerized product, p-longifolene, decolorized perm.p. 111-112', [ a ]-46.4'; ~ as fraction 2, crude longifolol, manganate solution and bromine in carbon tetrachloride. m.p. 75-80 , whose m.p. became constant a t $8.5-80.5' Anal. Calcd. for C15H84: C, 88.16; H , 11.84. Found: after two recrystallizations from the same solvent: 0.21 g., C, 87.72; H , 11.80. [ a ]+23.5". ~ Dehydration of Isolongifolo1.-Isolongifolol (1.3 9.) was A n a l . Calcd. for C I ~ H ~ ~C,O81.02; : H, 11.79. Found: heated with 0.9 g. of freshly fused potassium bisulfate beC , 81.03; H, 11.52. tween 220-230' for 1.5 hours. The product was extracted The reduction of a-longifolic acid (1.49.) gave 1.1 g. of with ether, washed and dried. Evaporative distillation a t crude alcohol, m.p. 57-90". Fraction 1 from petroleum 100' (1 mm.) yielded 0.5 g. of colorless, liquid hydrocarbon, -~ [ a ] D -62.6'. (8) J. I.. Simonsen. J , Citein. S o r . , 117, 570 (1920). ( 0 ) Value reported b y J. I.. Simonsen.
[ COXTRIBLTIOS FROM
Cyclitols. VI.
XEWHAVEN. CONNECTICUT
THE DEPARTMENT O F CHEMISTRY, UNIVERSITY O F TORONTO]
A New Tetrol and Enediol from Cyclohexadiene-1,4 by the Prevost Reaction1 BY G. E. ~ICC.ISL.AND AND E. CLYDSHORSWILL~ RECEIVED XOVEMBER 5, 1953
Cyclohexadicne-l,3 i n excess reacts with silver iodine dibenzoate t o give trans-cyclohexenediol-3,~dibenzoate, which can be saponified to tra~ts-cyclohexenediol-4,5. The diene in deficiency reacts to give cyclohexanetetrol-l,2,4,5tetrabenzoate (m.p. 1 8 l 0 ) , which on arnmotiolysis gives a new cyclohexanetetrol-l,2,4,5of m.p. 208". Acetylation of the tetrol gives a tetraacetate of m.p. 148" The benzoylation of cyclohexeticdiol-3,4 is described. New Prevost reaction products of cyclohexene are reported.
Continuing our investigations 011 cyclitol cheniistry,' we wish to report the synthesis of a new cvclohexanetetrol 111 and a new cyclohexenediol V. The cyclohexanetetrols are of interest because of their close relationship to the naturallv occurring betit01,~quercitols and inositols. CyclohexenediolI I ) For previous (iinnumhered) papers in thi? series, see G. R . IlcCaslanrl and I?. Clvtle Horswill, T i r r s J O I J R X I I . . 75, -1020 (10JR). and references there r i t e i l . f 2 ) Fellow of t h r N:rtion:il Research Criiuicil, l!i>2 - 1 9 5 3 ( 3 ) n e t i t n l , :L de=tromtntnry crcl~,hexanetetri,l. was isolxte
