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exhaustive methylation reactions2 must differ from the stable czs-cis-l,5cyclooctadieneby the geometric configuration of one or both of the double bonds. The trans-trans-configuration was con sidered most probable for the labile diene because of the smaller amount of steric strain indicated by molecular models.4 We have obtained unequivocal evidence that the compound is cis-frans-1,5-cyclooctadiene.The product of the first Hofmann exhaustive methylation of N-methylgranatanine proved to be cis4-cycloocten-1-yl dimethylamine, identical with a sample prepared from cis-4-cycloocten-l-y1 brosylate6 and dimethylamine. This amine (I) has an asymmetric carbon atom, and has been resolved
4
N(CH3)z
I
by fractional crystallization of the d-10-camphorsulfonic acid salts from diisobutyl ketone. The less atoms. All spurious peaks decreased and practi- soluble form had m.p. 144.0-145.5", [ c ~ ] ~ ' D- 1.88" cally disappeared in both p2 and pa. (c 13.0, water), and the more soluble form had m. . The two peaks ignored in p1 as being too close to 142.5-143.5", [ar12BD +30.71° (c 13.0, water7. a %fold axis (- 1.2 8.)persisted and increased in (Anal. Calcd. for C20H~SN04S: C, 62.29; H, 9.15; height in p2 and pa. It now became apparent that N, 3.63. Found for the (-) isomer: C, 62.42; the benzene molecules were on 2-fold axes (multi- H, 9.17; N, 3.83. Found for the (+) isomer: plicity two in C2) thus accounting for a half of a C, 62.43; H, 9.20; N, 3.61.) The salts were conmole of solvent. verted to the tertiary amines I, [ C Y ] ~ D-59.5' Refinement continued through conventional elec- (c 7.0, acetone) (obtained from levorotatory salt) tron and difference density considerations employ- and [ C X ] ~ +61.5' ~D (c 2.4, acetone) (obtained from ing individual isotropic thermal parameters. The the dextrorotatory salt). The amines were charsixth and final structure factor computation gave R acterized by conversion to picrates and methiodides. = 0.146. The density based on these phases is The methiodide obtained from the (-) amine shown in Fig. 3; that of the benzene is shown in had map. 258' (dec.), [ a r I z 5 ~ -14.92' (c 6.0, Fig. 4. water), while that obtained from the (+) amine I n addition to confirming the structure deduced had m.p. 262' (dec.), [ L X ] ~ ~+14.30 D (c 2.7, water). by chemical means, this determination revealed the (Anal. Calcd. for C I I H ~ ~ N IC, : 44.75; H, 7.51; stereochemistry of the molecule; the bridgehead N, 4.75. Found for the (-) isomer: C, 43.58; H, methoxy is trans to the carbamoyloxpethyl group 7.19; N, 4.86. Found for the (+) isomer: and the aziridine. Moreover, the methyl and 44.44; H, 7.64; N, 4.80.) methoxy functions on the quinone are established The optically active methiodides were converted with certainty. The pyrrolizine nitrogen in this separately to the corresponding methohydroxides molecule was known to be non-basic3; in the solid, with suspensions of silver hydroxide in water. The this nitrogen is planar within the accuracy of its solutions were concentrated, and then distilled determination (f0.03 A.). And finally, the nitro- under reduced pressure under the usual conditions gen and oxygen atoms of neighboring carbamate of the Hofmann elimination. The (-) methiodide groups are intermolecularly hydrogen bonded along yielded (+)-cis-trans-l,5-~ycloOctadiene, n 2 6 ~ the b axis. 1.4893, [ C ~ ] ~$121.3" ~ D (c 2.0, pentane), while the A more detailed account of this determination will (+) methiodide formed the enantiomer, n% appear elsewhere. 1.4885, [ a I 2 6~ 120.5' (c 2.0, pentane). This demonstration of optical activity confirmed (3) Ledede Laboratories, private communication. the fact that the labile diene must be different from STERLING CHEMISTRY LABORATORY A. TULINSKYthe symmetrical cis-cis-1,5-cyclooctadiene. The YALEUNIWRSITY NEWHAVEN,CONNECTICUT trans-trans structure for the labile diene is ruled RECEIVED JUNE 28, 1962 out by the cis geometry of the double bond in amine I. This double bond would not change to trans geometry during the second Hofmann elimiOPTICALLY ACTIVE C~S-~~~S-~,S-CYCLO~CTADIENE FROM AN ASYMMETRIC HOFMANN ELIMINATION' nation since the cis double bond is highly favored Fig. 4.-Electron
density in the plane of the benzene ring.
c,
Sir: The labile 1,5-cyclooctadiene obtained from Nmethylgranatanine by two successive Hofmann (1) Presented at the Carl S.Marvel Honorary Symposium, Tucson, Arizona, December 28, 1961.
(2) R. Willstatter and H. Veraguth, Ber., 88, 1975 (1905). (3) K.Ziegler and H. Wilms, Ann., 681, 1 (1950). (4) K. Ziegler, H. Sauer, L. Burns, H. Froitzheim-Rfihlhorn and J. Schneider, i b i d . , 689, 122 (1964). (5) A. C. Cope and P. E. Peterson, J . Am. Chcm. SoC., 81, 1643
(1959).
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3.99; N, 3.27; Pt, 45.74. Found: C, 30.54; H , 4.00; N, 3.31; Pt, 46.74.) Reaction of trans-cyclooctene5 with I in methylene chloridee gave the expected complex CsH14PtC12dex, 11. Fractional crystallization from hexane a t -20" gave as the least soluble material IIa, a viscous oil a t room temperature (crystalline a t -no"), [ a I z 8f3 ~4' (c 2.5, methylene chloride); and as the most soluble material IIb, a viscous oil also crystalhe a t lower temperatures, [aIz8D +4" (c 2.5, methylene chloride). (Anal. Calcd. for C1,H27NPtCl2: C, 39.91; H I 5.32; N, 2.75; Pt, 38.17. Found for I I a : C, 39.90; H, 5.26; N, 2.82; Pt, 38.04. Found for IIb: C, 40.28: (6) R. B. Turner and \V. R. Meador, J. Am. Chcm. Soc., 79, 4133 (1957). H, 5.41; N, 3.03; Pt, 37.95.) ARTHURC. COPE DEPARTMENT OF CHEMISTRY The olefin and amine were liberated by shaking MASSACHUSETTS INSTITUTEO F TECIINOLOGY a solution of each complex (IIa and IIb) in methylCHARLE5 Ii.I1OIVELL CAMBRlDGE 39, MASSACHUSElTS AUBREYKSOWLES ene chloride with 10% aqueous potassium cyanide solution. The methylene chloride solutions RECEIVED J U N E 25, 1%f? were washed with water, 5% hydrochloric acid (to remove the amine), 5% sodium bicarbonate and RESOLUTION OF trans-CYCLOOCTENE ; water. After drying over sodium sulfate, the CONFIRMATION OF THE.ASYMMETRY OF c i s - l r ~ ~ s - solvent was evaporated a t room temperature and 1,S-CY CLOOCTADLENE' the residues were distilled, yielding trans-cycloSir: octene, identified by comparison of infrared spectra Optically active stereoisomers of tram-cyclo- with the spectrum of an authentic sample. From ~ (c 2, alkenes should be capable of existence provided IIa the trans-cycloiictene had [ a l Z 8-21" the ring is sufficiently small to preclude rotation of pentane); from I I b [a]"D +18.S" (c 2 , pentane).' the -CR=CRunit relative to the rest of the Each sample was hydrogenated over prereduced molecule. This expectation has been realized by platinum oxide in acetic acid to optically inactive cyclooctane (1n.p. 11') with the uptake of 95% partial resolution of trczns-cyclooctene, Complexes with square planar geometry (formula of the theoretical amount of hydrogen. I ) can be prepared from "ethylene p1atii:ous Application of the same method to cis-tram-1,5chloride" [ 1,3-diethylene-2,4-dichtoro-p-dichloro-cyclooctadiene also resulted in partial resolution, diplatinum(l1) or Zeise's acid [H(PtC&C13) 1 confirming the asymmetry of the molecule (cf. derived from it, and an amine such as p-toluidine.2 the preceding communication). Reaction of cistrans-1,5-cyclooctadiene with I gave a coniplex CTT~==CII2 (111), CBH12Pt&X4dex2,which was fractionally crystallized from benzene-cyclohexane yielding as the most soluble material IIIa, m.p. 106-108" I (after further recrystallization from carbon tetrachloride), l ~ r ] ? ~ D4-55.2" ( 6 2.5, methylene chloride); and as the least soluble material IIIb, m.p. 155-157', [a]"D -18.3" (c 2.5, methylene chloride). ( A n d . Calcd. for CzaHasNzPt2CI4: C, 34.28; Displacenient of ethylene by other olefins in H, 4.20; N, 3.08; Pt, 42.87. Found for I I I a : platinum(T1) complexes is well known,3 and one case C, 34.42; H, 4.05; N, 2.75; Pt, 43.22. Found involving an olefin amine platinum(I1) complex for I I I b : C, 34.10; H, 4.33; N,3.06; Pt, 42.46.) has been reported. Treatment of I I I a and I I I b in the manner deThe method of resolution was to prepare a scribed for I I a and IIb gave samples of cis-transcomplex using optically active ( + ) - I -phenyl-3- 1,5-cyclooctadiene, identified by comparison of aminopropane ("Dexedrine," dex) (I, where R is infrared spectra with the spectrum of an authentic CaH6CH2*CH(CH&-) and then to displace the sample. The diene from I I I a had [ C Y ] ~ ~-26" D ethylene by trans-cyclooctene, forming trans- (c 1.3, pentane); the diene from I I I b had [ C Y ] ~ ~ D dichloro-trans-cyclooctene ''Dexedrine" platinum- f 3 4 " (i 1.2, pentane). (11) (11). If trans-cycloiictene is capable of This method of resolution should be general for existence in optically active forms, this complex olefins forming sufficiently stable pi complexes I1 would constitute a mixture of diastereomers. The reaction of H(PtCzH4Cla)with "Dexedrine" with platinum. I t is being extended to other led to the complex I, CzH4PtCl?dex, m.p. 120- cyclic olefins with molecular asymmetry, and rates 121", [cx]"D +20.5O (c 2.6, methylene chloride), (.5) A. C. Cope, R. A. Pike and C. F . Spencer, J . Am. Chcm. Soc., (Anal. Calcd. for C11H1,NPtC12: C, 30.76; H, 71, 3212 (1953). in the eight-membered ring.8 This leaves cis-trans1,5-cycloOctadiene as the only possible structure for the labile diene. The fact that the enantiomeric methohydroxides lead to enantiomeric cis-trans1,5-cyclooctadienes shows that the asymmetry characteristic of the bases is preserved in the transition states leading to the olefins. This is the first case in which a cyclic trans olefin has been shown to be asymmetric. The rigid structure of the ring and the non-bonded hydrogen interactions prevent rotation of the trans-CH=CH-unit with respect to the rest of the ring, which would result in racemization.
(1) Presented at the Carl S . Marvel Honorary Symposium, Tucson, Arizona, December 28, 1961. ( 2 ) J . Chatt, J. Chpm. S o c . , 3310 (InLQ). ( 3 ) J. S. Anderson, i b i L , 971 (1931). (4) A. H. Gelman, Coirtpl. rend. A c o d . Sci. U H S S , S a , 347 (1941).
(6) For one of many similar examples see J. R. Joy and M. Orchin, i b i d . , 81, 305,310 (1959). (7) NOTEADDRD IN PROOF.-()-trow.Cyclo6ctene completely resolved through the tomplex CaHl~PtCi,CIHrCII(NHI)CH*has [ a l ~ ~ o -411' ( c 0.27, methylene chloride) (A. C. Cope and T. V. Van Auken, unpublished results).
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