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Catalytic Transformations of Sesquiterpene Hydrocarbons on Alkali MetalAluminum Oxide.

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the formal addition of H-I, Ph-I, and F-I to olefins is
possible. The resulting 1,2-iodofunctionalized compounds
can be converted into other synthetically useful compounds by transformation of the iodo functionality. The
yields of compounds 4 and the reaction conditions have
not yet been optimized.
Received: November 12, 1984;
revised: January 30, 1985 [ Z 1066 IE]
German version: Angew. Chem. 97(1985) 341
CAS Registry numbers:
1, 15656-28-7; 2a, 74-85-1: 2b, 110-83-8; Zc, 100-42-5; 3A, 16984-48-8; 38,
16887-00-6; 3C, 24959-67-9; 3D, 14797-65-0; 3E, 71000-82-3; 3F, 7732-185; 3G, 67-56-1; 3H, 64-19-7; 31, 75-05-8: 35, 71-43-2; 3K, 617-86-7: 4Ab,
6906-08-7; 4Bb, 33427-17-7; 4Cb, 34701-03-6; 4Db, 95617-18-8; 4Eb,
89877-27-0: 4Fb, 10039-14-2; 4Fc, 54766-50-6: 4Cc, 13684-98-5; 4Ha, 62710- I : 41b, 7707-58-6; 4Jb, 95617-19-9: 4Kb, 626-62-0; HgO. HBF,, 9564677-8: I?, 7553-56-2; pyridine, 110-86-1.
[ I ] Selected examples: H. 0. House: Modern Synthetic Reactions. W. A. Benjamin, Menlo Park, CA, 1972. A. Hassner, M. E. Lorber, C. Heathcock, J.
Org. Chem. 32 (1967) S40: E. J. Corey, N. M. Weinshenker, T. K. Schaaf,
J. A m . Chem. Sot. 51 (1969) 5675; G. L'abbe, A. Hassner, Anqew. Chem.
83 (1971) 103: Angew. Chem. I n / . Ed. Eng/. I 0 (1971) 98; K. Dehnicke,
ihid. 51 (1979) 527 and 16 (1979) 507, respectively.
121 U. E. Diner, J . W. Lown, Chem, Commun. 1970. 333: Can. J. Chem. 4 9
(1971) 403.
[3] J. Barluenga, P. J. Campos, J. M. Gonrilez, G. Asensio, J. Chem. SOC.
Perkin Trans. I 1984, 2623.
[4] M.p.= 149-151 "C (decomp.) (recrystallized from dichloromethane), IR
(Nujol): v=690, 760, 1610 c m - ' (pyridine) and 1040 c m - ' (BE).' H NMR (CDCI,-CH2C12, 80 MHz): 6=7.63 (In, 2H), 8.33 (br. t , IH), 5.87
(br. d, 2H). "C-NMR (CH2CI2,20 MHz): 6 = 127.76, 141.97, 149.27.
[ 5 ] A single stereoisomer, tentatively assigned the trans configuration, is
formed.
[6] Only the regioisomer PhCHNu-CH21 is formed.
The hydrocarbon ( - ) - 4 , unreported up to now, is obtained quantitatively from 3 with K/A1203 at room temperature; 4 can be transformed thermally to (+)-y-gurjunene 5.'s1When the isomerization of 3 with K/A1203 is carried out at I O O T , 42% (+)-ledene 6 is obtained along
with 4 and other isomers.
i
4, 100%
5. 80%
3
6 , 42%
Upon treatment of 7 with Na/AI20,, the isomerization
is followed by a dehydrogenation with formation of (+)cis-calamenene 8, ( - ))-trans-calamenene9, and the hydrocarbon (+)- 10.
7
Catalytic Transformations of Sesquiterpene
Hydrocarbons on Alkali Metal/Aluminum Oxide
By Roland Rieniicker* and Jiirgen Graefe
Dedicated to Professor Giinther Wilke on the occasion
of his 60th birthday
1
Of the variety of media used for the base-catalyzed
isomerization of olefins,"] alkali metaValuminum oxide
catalysts are especially noteworthy; according to our studies, they are able to effect new, selective transformations of
cyclic sesquiterpene hydrocarbons. C=C bond shifts, dehydrogenations, and skeletal rearrangements can take
place, depending on the structure of the substrate, the type
of catalyst, and the reaction conditions. In some cases,
compounds that were unknown up to now are formed.
Of the numerous sesquiterpene hydrocarbons studied by
us, (+)-calarene 1, (+)-aromadendrene 3, (+)-6-cadinene
7, and (+)-longifolene 11 are presented here as examples
of the possibilities of such catalytic transformations.
For instance, in the presence of K/A1203, 1 undergoes
an extensive isomerization already at 20°C to (-)-arktolene 2, which is thus easily accessible for the first time.
[*] Dr. R. Rienacker, Dr. J. Grdefe
['I
8 , 20%
9 , 30%
1 0 , 50%
When 11 is heated with Na/AI2O3, an equilibrium is established below 140°C with (+)-longicyclene 12. At
higher temperatures, a skeletal rearrangement to ( - )-isoand other
longifolene 13,12]( -)-alloisolongifolene 14,[3.41
['I
Max-Planck-Institut fur Kohlenforschung
Postfach 01 1325, D-4330 Miilheim a. d. Ruhr 1 (FRG)
N e w Address: Schering A G
Po5tfach 1540, D-4709 Rergkamen (FRG)
320
I
0 VCH Verlagsgesellsrha/r mhH. 0-6940 Weinheim. 1985
13, 62%
1)570-(1833/85/0404-~320S 02.501'0
A ~ i y e w .Chem
1 4 , 28%
Int Ed. h g l . 24 1198.51 No. 4
hydrocarbons takes place. Thus, e.g., a mixture containing
62% 13 and 28941 14 is obtained from 11 at 180°C.
The products were obtained in a purity of over 99% by
vacuum fractional distillation on lm-SpaltrohP columns
and identified on the basis of 'H-NMR, l3C-NMR, and
mass spectroscopy, as well as on the basis of the physical
data given in Table 1 .
Table 1. Physical data of 1
~
14
n ;,"
n I;
1
2
3
4
5
6
7
8
9
10
11
12
13
14
1.5050
1.5028
1.4965
1.4939
1.5012
1.5050
1.5096
1.5228
1.5230
1.5285
1.5049
1.493 I
1.4992
1.5009
Measured values [c]
Reported values
+
+
70.9
+
- 91.7
-
+
10.9
69.1
90.0
10.7
[6]
[6]
[7]
-
- 51.2
+ 133.8 [XI
+ 48.4 [a] [9]
+ 86.2 [lo]
+ 142.0
+
64.1
99.2
3.7
- 65.1
39.2
44.2
27.7
- 124.7
- 34.4
+
+
+
-
+
41.3 [a] [I I]
96.0 [a] [12)
-
+
+
+43.1
[I31
31.3
[I41
- 125.0 [b] [I51
- 40.6 [a] [3]
+
[a] Specific rotation [a]$. [b] Calculated for optically pure 13. [c] Neat
Experimental Procedure
All work was carried out under argon with oxygen- and water-free solvents
and with mbstrdtes that had been distilled from NaAIEtl.
In order to prepare the catalysts, basic AllOi (Alumina W o e h e B-Super I) is
dried in w c u u m ( I tom) at 200°C and then vigorously stirred with 2 to 10
wt.-% sodium o r potassium until the mixture cools. Uniformly colored, freeflowing powders are obtained which are not pyrophoric, but which, o n exposure to air o r water, immediately discolor and lose their activity. Na/AI20, is
bright to dark grey, K/AI,03 is bright to deep blue; the color intensity
markedly increases with increasing alkali-metal content.
For isomerization or dehydrogenation, 5 to 10 wt.-% catalyst is added to the
sesquiterpene hydrocarbons and the suspension is vigorously stirred for several hours under the conditions given. The course of the reaction is followed
to completion by gas chromatography. Subsequently, the reaction products
are distilled from the catalyst in an oil-pump vacuum.
Alternatively, in the conversion of 3 to 4, 200 mL n-hexane and 400 g K/
A1203(I0"a K) are added per mole of 3 ; at the end of the reaction, the catalyst is filtered off and the residue washed twice with n-hexane.
Received: November 14, 1984;
revised: February 20, 1985 [Z 1069 IE]
German version: Anqew. Chem. 97 (1985) 348
Review cf. H. Pines, W. M. Stalick: Base-Catalyzed Reactions oJHydrocarhuris and Related Compounds, Academic Press, New York 1977.
In contrast to the acid-catalyzed isomerization of 11 (for a review see S.
Dev, Forfschr. Chem. Org. Naturst. 40 (1981) 49), 13 ([a),?,''
- 134.3), prepared in the presence of Na/AI2OI, exhibits a significantly higher enantiomeric purity. As we were able t o show, enantiomerically pure 13 has
- 159.9.
a specific rotation of
H. R. Shitole, P. Vyas, U. R. Nayak, Tetrahedron Lett. 1983, 2411.
H. R. Shitole, V. S. Dalavoy, V. B. Deodhar, U. R. Nayak, K. R. Acharya, S. S. Tavale, T. N. Guru Row, V. P. Kamat, S. K. Paknikar, Tetrahedroti LPII.1983, 4739.
R. Rienscker, unpublished.
P. Tesnelle. P. Teisseire, Recherche 17 (1969) 121.
G . Buchi, S. W. Chow, T. MatsUUrd, T. L. Popper, H. H. Rennhard, M.
Schach von Wittenau, Tetrahedron Lett. 1959. 14.
C . Ehret, G. Ourisson, Tetrahedron 28 (1969) 1795.
N. P. Kirgalow, Zh Ohshch. Khim. 19 (1949) 2127.
V. Herrout, V . Sykova, Tetrahedron 4 (1958) 246.
K . D. Croft, E. L. Ghisalberti, C. H. Hocart, P. H. Jefferies, C. L. Raston,
A. H. White, J . Chem. SOC.Perkin Trans. I 1977, 1267.
N. H. Andersen, I). D. Syrdal, C . Graham, Tetrahedron Lett. 1972,
903.
U. R. Nayak, S. Dev, Tetrahedron 8 (1960) 42.
U. R. Nayak, S. Dev, Tetrahedron Lett. 1963, 243.
R. Ranganathan. S. Dev, Tefrahedron 26 (1970) 621.
Anyew. Cheni. Int. Ed. Engl. 24 (1985) No. 4
Torsional Isomerism in Metailocenes:
Hindered Cp-Rotation in (s-cis-q-Butadiene)bis(q-fert-butylcyclopentadienyI)zirconium* *
By Gerhard Erker,* Thomas Miihlenbernd, Reinhard Benn.
Anna RuJiriska, Yi-Hung Tsay, and Carl Kriiger
Dedicated to Professor Giinther Wilke on the occasion
of his 60th birthday
The cyclopentadienyl(Cp)-metal torsional barrier in metallocenes is often very small. The activation energy for rotation about the Cp-M bond, e.g. in ferrocene, has been
determined reliably by various methods to be 0.9 to
1.8& 0.3 kcal/mol.~'l Consequently, rotation about the
Cp(centroid)-metal vector in (ycyclopentadieny1)transition-metal complexes has been regarded as unhindered in
solution. This assumption, however, does not generally
hold in the case of metallocenes when bulky substituents
are present on the C p ligands.[*I Substituted bent metallocenes are finding increasing application in organometallic
chemistry."] We present here to the best of our knowledge
the first evidence for hindered Cp-M rotation in solution
in such molecules together with the estimated activation
energy for this process.
At high temperature, the NMR spectra of (sqis-q-butadiene)bis(q-tert-buty1cyclopentadienyl)zirconium 1["] appear consistent with the molecule having C2" molecular
symmetry. Lineshape analysis of the low-temperature 'Hand I3C-NMR spectra reveals that this apparent simplicity
of the high-temperature spectra results from two separate
dynamic processes. In the 100.6-MHz "C-NMR spectrum
of 1 at 188 K all the diene- and Cp-carbon atoms are nonequivalent (cf. Fig. 1, Spectrum A). On raising the temperature, pairwise coalescence of signals is observed (Spectrum
B). We interpret this as resulting from equilibration of two
enantiomeric Cp-rotational isomers 1 $1 ' (for a schematic
representation, cf. Fig. I). All these coalescences are consistent
with
a
Gibbs
activation
energy
of
AG'(233 K)=9.8+0.2 kcal/mol. On increasing the temperature further, only two signals are observed for the Cpmethine carbon atoms (Spectrum C). In addition to the
equilibration of the fert-butyl signals, the 'H-NMR spectrum indicates that the terminal diene protons undergo exchange. This second dynamic process is a typical ring inversion in a metallacyclic oz,n skeleton (1 '*1"),L'lfor
which a barrier AG'(265K)= 13.5k0.2 kcal/mol was estimated from the coalescences of signals in the NMR spectra. The transformation from apparent C2,- via C,-molecular symmetry to a chiral complex geometry can also be
monitored in the temperature dependence of the 400-MHz
'H-NMR spectra of I.[']
The X-ray structure analysis of 1 shows a molecular
geometry in the solid state that exhibits the characteristics
of the most stable conformation found in solution at low
temperature. The (s-cis-q4-butadiene)zirconium moiety in
1 has a pronounced o-character. The Zr-CI/C4 bond
lengths are short. The substantially greater Zr-C2/C3 distances indicate n-interaction of the metal with the internal
[*I Priv.-Doz. Dr. G. Erker, DipLChem. T. Mhhlenbernd, Dr. R. Benn ['I,
Dr.A. Rufinska[+], Dr.Y.-H.Tsay(++], Pr0f.Dr.C. Kriiger[+*]
Max-Planck-lnstitut fur Kohlenforschung
Kaiser-Wilhelm-PIatz 1, D-4330 Miilheim a. d. Ruhr (FRG)
['I
[+ 1'
N M R analysis.
X-ray structure analysis.
I**] This work was supported by the Minister fur Wissenschaft und Forschung des Landes Nordrhein-Westfalen and the Fonds der Chemischen Industrie.
0 VCH Verlagsgesellschafi mbH,
0-6940 Weinheiin. 1985
0570-0833/85/0404-0321 $ 02.50/0
32 I
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transformation, oxide, hydrocarbonic, catalytic, sesquiterpene, alkali, metalaluminum
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