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some double bond migrations were observed; the yields of the major products are shown in Fig. 1. a-Guaiene (VIII) and IX, which we now name pguaiene, have been described previously12; y30 guaiene (X,: A 256, E 8900) and 10-epiguaiol (XI) are new compounds. All three guaienes from this reaction probably are mixtures of epimers a t carbon -6 20 10. .e Thus bulnesol (I) can be converted in the labora31 tory directly into guaiol (111) and “6-guaiene” (V), and, since VI1 has been converted into 11,13 indi10 rectly into patchouli alcohol (11). A reaction similar to that shown in Fig. 1 was run in AcOD to gain information about double bond migrations during the reaction. The major components of samples withdrawn occasionally were 0 10 20 30 40 50 60 70 80 90 100 analyzed by combustion (to give % deuterium inTime, hours. corporated) and by n.m.r. (to give information Fig. 1.” about the location of the deuterium). The guaiol (proposed to be (IV)) and a-chigadmarene6 (pro- (111) and 10-epiguaiol (XI) isolated after 14 hours posed to have the constitution of (V)), bulnesol (I) contained slightly more than one deuterium each, is an attractive biogenetic precursor for these located (as expected) almost exclusively a t Clo, structurally related sesquiterpenoids. Of partic- since in place of a doublet centered a t 9.0 r for the ular interest is the transannular reaction to yield CK, methyl group in each undeuterated alcohol, a patchouli alcohol (11), for which there is a labora- single peak a t 9.0 T was observed in each deuterated alcohol. Clearly, the configurations a t C4 and C, tory precedent? We have tried to duplicate these proposed bio- are largely unchanged in these conversions of I to synthetic conversions of bulnesol (I) in the labora- I11 and XI. The P-patchoulene (VII) isolated after 14 hours contained 1.4 deuteriums, all but 0.3 tory, without enzymes. To get two bulnesenes by an unambigous route, of which were in methyl groups; undoubtedly most bulnesyl acetate was pyrolyzed a t 275”, giving a- of the deuterium in this sample is in the gem-dibulnesene (V, 84%) and 0-bulnesene (VI, 7%). methyl group, and under these conditions the asyma-Bulnesene (V, [ a I z 50”) ~ was not identical with metry a t C4 and C7 is largely preserved in the I + a-chigadmarenes ( [CX]~*D- E O ” ) , but proved to be VI1 reaction. These experiments, coupled with the the same (infrared spectrum, refractive index, demonstration that VI1 has the same configurations optical rotation) as the compound from patchouly as I1 a t C4 and C7,13 confirm that bulnesol (I), oil called “6-guaiene”s~s ( [ a l Z 0 ~ 0.3’). The patchouli alcohol (11) and guaiol (111) possess the finding that V occurs in the same plant as I1 lends same configurations a t C4 and C7.I4 (11) Yields were calculated from areas under vapor phase chromasome credence to the hypothesis that I1 is formed in tography peaks; each component which was identified was characternature from bulnesyl carbonium ion. ized by n.m.r. and infrared. 111 and XI were not well resolved by Bulnesol (I) was treated under a variety of condi- vapor phase chromatography, and thus are included together; careful tions which should favor carbonium ion formation : vapor phase chromatography of a sample of the mixture isolated after of I11 and X I . When bulnesol (I) was refluxed with p-toluenesul- 14 hours indicated it to contain nearly equal amounts (12) K . Takeda, H . Minato and S. Nosaka, Tefrahedron. 13, 308 fonyl chloride in 2,6-lutidine, a mixture of a- and (1961). p-bulnesenes (V, 31% and VI, 13%) was obtained. (13) Private communication with Dr. G. Biichi and Mr. W. hlacBulnesol (I) was heated with alumina and ~ y r i d i n e , ~Lead. (14) We gratefully acknowledge the financial support of the Public yielding p-bulnesene (VI, 10%) and P-patchoulene3 Service (RG-7689). (VII, 6070), the latter identical (infrared, n.m.r., Health DEPARTMENT OF CHEMISTRY AND optical rotation, refractive index, vapor phase CHEMICAL ENGINEERING chromatographic retention time) with an authentic UNIVERSITY OF ILLINOIS R. B. BATES ILLINOIS R. C. SLAGEL sample from the degradation of patchouli alcohol URBANA, 1, 1962 RECEIVED FEBRUARY (II).l0 When bulnesol (I) in acetic acid was treated with a drop of sulfuric acid a t room temperature,
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(4) E . J. Eisenbraun, T. George, B. Riniker and C. Djerassi. ibid., 82, 3648 (1960); K . Takeda and H. Minato, Tetrahedron Letters. 22,
33 (1960). ( 5 ) F. Sorm, L. Dole& 0 . Knessl and J. Plfva, Coll. Czech. Chem. Comm., 16, 82 (1950). (6) A. S. Rao, K . B. Dutt, S. D e v and P . C. Guha, J. Indian Chem. Soc., 29, 604, 620 (1952); the structure of a-chigadmarene is being reinvestigated (private communication with Dr. s. Dev). (7) G. Le N y , Comfit. rend., 2 6 1 , 1526 (1960). (8) It is possible that “8-guaiene” is the enantiomorph of V, but since an overwhelming majority of sesquiterpenoids have the configuration shown in V at their carbon corresponding to C7 in I , this is quite unlikely. (9) E. von Rudloff, Canadian J. Chem., 89, 1860 (1961). (10) We are grateful to Dr. G . Buchi for authentic samples of I1 and VII.
MAGNETIC ANISOTROPY OF FERROCENE
sir : The anisotropy measurements were made by the method of maximum torque originally developed by Krishnan, in which a number of modifications, including those suggested by Gordon,‘ were inincluded. The torsion fibers used in the measurements on the ferrocene crystals were calibrated by means of the known principal susceptibilities and crystal structure of naphthalene and acenaphthene. The field strength of the electromagnet ranged from about 4,000 to 9,000 oersteds. (1) D. A. Gordon, Reo. Sci. Instruments, 29, 929 (1958).
COMMUNICATIONS TO THE EDITOR
April 5, 1962
Fig. 2.-Molecular
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axes for the magnetic anisotropy of ferrocene.
The results clearly show that the contribution to susceptibility a t right angles to the plane of the cyclopentadienyl ring (along the K3 direction) is b-3 Fig. 1.-Relationship of the crystal axes a, b, c, to the priiici- quite large and may be attributed to the circulation of n electrons in this ring; the anisotropy AK = pal magnetic axes: 1, 2, 3. 49.5 X lo+. The situation is reminiscent of the Single crystals of ferrocene were grown by slow large susceptibility a t right angles to the plane evaporation from appropriate solvents. The crys- of the benzene ring, for which AK = 54 X While ferrocene would involve a total of eight tals were extremely well formed and the mountings were made by sight based on the morphology and a electrons in two different rings,6 nevertheless the X-ray data of the crystal^.^ The size of the crys- radius of their circulation in each ring probably is tals used for the measurement varied from about reduced. The distance from the K3 axis to the 25 to 165 mg. Measurements were made on carbon atoms of ferrocene is approximately 1.2 A. fourteen ferrocene crystals using four different while in benzene i t is 1.39 A. quartz fibers. The anisotropies obtained for According to preliminary calculations the theoferrocene in terms of molar susceptibilities times retical susceptibility arising from the n electrons c.g.s. units are: x1 - x2 = 37.0 f 0.4, in the cyclopentadienyl ring shows the same order X I - x3 = 40.9 0.3, x2 - x 3 = 3.9 f 0.3, of magnitude as the experimental value. How$ = 24.0’ f lo, where J. is the angle between the ever, i t appears that the ‘IT-electron current” c-crystal axis and the direction of x1 (Fig. 1). approach708in benzene cannot be simply applied to Using the average susceptibility as reported by the cyclopentadienyl ring in spite of its aromaWilkinson, et al. ,4 the principal susceptibilities are ticity in the ferrocene molecule. It may be noted x1 = -99.0, x2 = that in the ferrocene molecule K1 is not equal to found to be in units of -136.0, x3 = -139.9. K2. While this is generally found to be the case of The uncertainties in the anisotropies are average aromatic systems, the situation is given little deviations and reflect the internal consistency of attention. However, several factors suggest themthe results. Any systematic errors in the cali- selves as possible reasons for this anisotropy : bration of the magnet and of the torsion fibers (1) The symmetry of the molecule about the Kz will add to the absolute error in the final values. axis is much greater than about the K1 axis. (2) The diamagnetic susceptibility of ferrocene is The only condition under which K1 is identical under further investigation in our laboratories. with K2 is that the ferrocene molecule can be treated A preliminary calculation of the principal molec- as a spherically symmetrical system of atoms toular susceptibilities has been made on the basis of gether with a non-interacting system of mobile these susceptibility values and crystal structure a electrons, which are constrained in orbits of according to the method worked out by Lonsdale cylindrical symmetry defined roughly by the and Krishnad for monoclinic crystals. The molec- contour of the rings. This does not seem likely; ular axes have been chosen as shown in Fig. 2. i t is more probable that there is some distortiong All the values are expressed in c.g.s. units: of the localized electron distribution, which accounts for the anisotropy in the KI-KS plane. It Ki = -105 K1 - Kz = 7 may be noted that in ferrocene the C-C distances Kt = -112 Kz - Kt = 46 $ 22” are not equal,3 which is also true of the C-Fe Ka = -158 K I - Ka 53 distances. The agreement in the fi values may be regarded The experimental values of anisotropy have as a check on the determined values of the molecular been used to explain the observed n.m.r. chemical direction cosines and the crystal susceptibilities. shifts for protons in some derivatives of ferrocene. lo J
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(2) Sr. ?V E. Fox I. and L. N. Mulay, Rev. Sci. Znslrumcnls, 88, 119 (1962). (3) J. D. Dunitz, L. E. Orgel and A. Rich, Acfa Crysf., 9 , 373 (1956). (4) G. Wilkinson, M. Rosenblum, M . C. Whiting and R. B. Woodward, J . A m . Chem. Soc., 1 4 , 2125 (1952). ( 5 ) K . Lonsdale and K. S. Krishnan, Proc. Roy. SOC.(Londoii), 166A, 597 (1936).
(6) W. Moffitt, J Ani. Chem. Soc., 76, 3386 (1954). (7) Linus Pauling, J . Chem. P h y s . , 4, 673 (1936). (8) J. A. Pople, W. G. Schneider and H. J. Bernstein, “High Resolution Nuclear Magnetic Resonance,” McGraw-Hill Book C o . , Inc., New York, N. Y., 1959. (9) Cj’.L. Singh. Trans. Farad. SOC.,64, 1117 (1958). (IO) This will be published separately.
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COMXUNICATIONS TO THE E ' DITOK
The details of the experimental method, calculations and a complete discussion of their bearing on the concepts of chemical bonding in ferrocene proposed and discussed by various workers6j11-13 will be published elsewhere.
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The author wishes to thank the Research Corporation and the Monsanto Chemical Co. for supporting this work. (11) E. 0. Fischer, Rec. Tmu. Chim. PUYS-BQS, 7 6 , 829 (195b); I n t . Conf. Coord. Chem. Publicationof Chem. SOC.,London, 1959, p . 73. (12) A. Cotton and G. Wilkinson, Z. 3-atuvfousch.,96, 453 (1934). (13) J. D. Dunita and L. E. Orgel, J . Chem. Phys., 23, 924 (1955).
DEPARTMEST OF CHEMISTRY UNIVERSITYOF CINCINNATI L. N.MULAY 21, OHIO CINCINSATI Fox, S.N.D. SR. MARYELEANOR RECEIVED FEBRUARY 5 , 1962
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expulsion of the propene, followed by the addition of the Fe-H across the olefinic double bond. This latter reaction has been shown separate1y.j The reaction may proceed by hydride ion attack either HYDRIDE ADDITION TO SOME T-BONDED on the metal, as suggested for the reduction of the OLEFIN-IRON COMPLEXES related cobalticinium cation,' or on the cyclopentaSir: dienyl group, with transfer from the intermediate \Ye have noted previously the abstraction of a cyclopentadiene complex to the ethylenic group,6 hydride ion from some a-bonded iron-alkyl com- or directly on the ethylenic group. Since the propene cation (111) may be prepared p1exes.l We now report that this reaction is wversible and that reduction with sodium boro- readily from the n-propyl complex, a-CsHsFehydride of tetrahydrofuran solutions of the cation (CO)zn-propyl,l and its reduction gives high yields complex (IV),the isomerization of perchlorates, [ T - C ~ H ~ F ~ ( C O ) ~ C H ~ C H R ] +ofCthe ~ Oisopropyl ~where R = H,Me,lnZm3 forms a-alkyl complexes. the n-propyl to isopropyl may be understood The cation (I), R = H, gives the ethyl complex as a simple, two-step hydride removal and addition process. This mechanism is very similar to that put forward recently for the isomerization of olefins r l+ on metal surfaces.8 Also this reversible conversion of alkyl to olefin complexes very clearly bears a strong relationship to the intermediate steps postulated to occur in the hydroformylation, Fe Fischer-Tropsch and related reactions.8 'CH;-CH3 Acknowledgments.---\iTe thank the Interriatioiial Nickel Company (llond) Ltd. for a gift of iron 1. carbonyl, the Ethyl Corporation for a gift of manganese carbonyl and the Hungarian Relief Fund I I1 for financial support to P.L.I.N. (11) in good yields. The product was identified (7) hI. L. H. Green, L. P r a t t and G . Wilkinson, i b i d . , 8753 (105'3). by comparison of the infrared and proton magnetic (8) H. W. Sternberg and I. \Vender. I n t . Conf. Co-ordination Chem resonance spectra with those of a sample of the London, 1959. Chem. Soc. Special Publ., S o . 13, p. 35, and references therein. ethyl compound prepared as previously reported. CHEMICAL LABORATORY 11.L. €I. GREEN Reduction of the cation (111),R = Me, gives the UNIVERSITY P. L. I. ?;AGX ENGLAXD isopropyl complex (IV) in high yield. The iso- CAMBRIDGE, RECEIVED FESKUAICY 1 , lOtL2 1)ropj-l complex was identified by the comparison o f the spectra with those of characterized sainplcs A N E W SYNTHESIS OF BARBITURIC ACIDS of the isopropyl and n-propyl complexes prepared by the reaction of the sodiuni salt, Na+[n-CSHs- Sir: Fe(C0)2]- with the propyl ha1ides.j KO n\iTe wish to report that the reaction of carbodipropyl isomer was found in the reaction products. imides with substituted malonic acids leads to barThe major product of the reduction of the cation biturates in many instances. Thus, when malonic [Mn(CO)~.propene] +,j under similar conditions, acid and two moles of N, N'-dicyclohexylcarbodiwas manganese carbonyl. \\Then the reduction of imide were brought together in tetrahydrofuran the cation (111) was carried out in the presence of a solution, an exothermic reaction ensued with the large excess of 1-hexene and also of butadiene only separation of crystalline N,N'-clicyclohexylurea. the isopropyl complex (IV) was formed. It there- .On filtering off the urea and evaporating the tetrafore seciiis reasonablc that the reaction proceeds hydrofuran solution, a colorless crystalline cor11 by a11 iiitcrual Iiieclianisni rather than by the prior pound I, imp. 200-201°, was obtained in 65% yield formation of the hydride n--CbH6Fe(C0)2H6and (based on the malonic acid). Anal. Calcd. for C16H24N203: C, 65.72; H, 8.27; N , 9.38. Found: (1) M. L. H . Green and P . L. I. Nagy, Proc. Chem. Soc., in press. C, 66.00; H, 8.19; N , 9.39. (2) E. 0. Fischer and K. Fichtel, Chem. Ber., 1200 (1961). ( 3 ) A I . T.. H. Green and P. T, I Xagy, PYOC.Chem. S o r . , 37X (1961). Partly on the basis of n.m.r. and infrared spectra. ( 4 ) 1'.S. Piper and G. Wilkinson, J . Inorg. a u i i . Y i d ~ l ,( ' I I C , I L . ,3, I O i the barbituric acid structure I was assigned to this (19:jti). compound. The correctness of this assignment was ( 2 ) AI. 1,. H. Green and P I,. I. Sag>-, l o he uublishcd. later proved bv the synthesis of I by the action of (6) A. Davison, hI. T,, H . Green and G Wilkinson, .I. Ch,o, .\oc , : i l i Z (1961). malonyl chloride on N,N'-dicyclohexylurea.
