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Intramolecular DielsЦAlder Reactions with Methyl 2-Trimethylsiloxy-2-vinylcyclopropanecarboxylates as Key Building Blocks.

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NEt3- 2.5 HF
e - 25°C
Intramolecular Diels-Alder Reactions with Methyl
as Key Building Blocks**
By Ruth Zschiesche, Erich L. Grimm, and
Hans- Ulrich Reissig*
Of particular interest from a preparative and mechanistic standpoint is the intramolecular Diels-Alder reactiod31
starting from 3 (Scheme I), which may be prepared in high
yield (80%) by deprotonation of 1 followed by a l k y l a t i ~ n ' ~ ]
with 5-bromo-1,3-pentadiene. Compound 3 is transformed
by desilylation and subsequent ring-opening into the trienone 4, which is ideally suited for a [4n+ 2x1 cycloaddition.
The cycloaddition is complete after four days at room temperature. The crude product consists exclusively of the cisoctalone derivatives 5a and Sb, as shown by comparison
of the NMR spectra with those of the separated isomers
and by epimerization to give the trans compounds 6 . Pure
5b (m.p. =61-62S0C) can be isolated from the crude product in 47% yield by crystallization and 5a can be obtained
in 13% yield with a purity of >go% ('H-NMR) by chromatography (silica gel).
[+I, Dip].-Chem. R. Zschiesche,
DipLChem. E. L. Grimm
lnstitut fur Organische Chemie der Universrtat
Am Hubland, D-8700 Wiirzburg (FRG)
[*] Prof. Dr. H.-U. Reissig
Present address: lnstitut fur Organische Chemie und Biochemie der
Technischen Hochschule
Petersenstrasse 22, D-6100 Darmstadt (FRG)
This work was supported by the Deutsche Forschungsgemeinschaft, the
Fonds der Chemischen Industrie, and the Universitatsbund Wiirzburg.
We thank DipLChem. H. Bader for some preliminary experiments.
H.-U. R . thanks the Karl-Winnacker-Stiftung (Hoechst AG) for a fellowship.
0 VCH Verlagsgesellschaji m b H . 0.6940 Wernheim. 1986
Methyl 2-trimethylsiloxypropanecarboxylateswith alkenyl substituents at C2 (e.g., 1 ) can readily undergo reaction
as masked vinyl ketones, resulting in C-C bond formation.
We recently described efficient one-pot procedures for the
ring-opening of 1 to give 2 and the subsequent Michael
addition reactions of 2.1r1The electron-poor C=C bond in
2 and in similar compounds should also undergo cycloaddition reactions.[*]
Scheme I . Intramolecular Diela-Alder reaction 01 4 fo gibe 5a/5b and isomerization providing 6a/6b. For clarity, only one of the enantiomers of 5 and
6 is shown. All new isolated compounds (purified by recrystallization or kugelrohr distillation) gave appropriate spectra and correct elemental analyses.
When the crude product is chromatographed on alumina, however, the epimerized trans-octalone derivative 6b is
obtained in 57% yield as colorless crystals (m.p.=9092°C). In this thermodynamically most stable isomer, all
the substituents of the cyclohexanone portion are equatorial in the chair conformation. Compound 6b is also
formed upon treatment of pure 5b with A1203, acids, or
bases. However, the equilibrium between 5a and 6a lies
on the side of 5a (5a :6a = 2 : I), since the methoxycarbonyl group in 6a is arranged axially in a chair conformation. The relative configurations given in Scheme 1 are in
accord with these equilibration experiments; moreover,
they are supported by the comparison of the I3C-NMR
data[51and are confirmed by selective proton decoupling
As expected for trienones of type 4J3,']the reaction proceeds via an endo transition state, which lead; to the cislinked bicyclic compounds 5 . The high select vity with respect to the configuration at C3, however, is not obvious,
since the folding of the chain joining the diene and the
dienophile portions is crucial for the relative configuration
of this center of chirality. Thus, the formation of the
clearly preferred 5b indicates a transition state TS with a
boatlike conformation of this part of the molecule.
This short and efficient route to octalone derivatives is
characterized by good stereocontrol and flexibility with respect to other substituents. For instance, the cyclopropane
derivative 7 can be prepared in 90% yield by alkylation of
1 with 5-bromo-3-rnethyl-1,3-pentadiene;
ring-opening of
7 results in rapid cycloaddition (compared with 4) to give
three diastereorners of 5-methyloctalone 8 in 79% yield. It
has not yet been possible to separate these diastereomers
(ratio of isomers corresponding to 5a, Sb, and 6b, 3 :6 : I).
The synthetic route described here, involving intramolecular Diels-Alder reaction via 1, should not only make
OS70-0833/86/1212-I086 $ OZ.SO/O
Angew. Chem. Inl. Ed. Engl. 25 (1986) No. 12
possible the rapid and stereoselective preparation of terpenes such as a-eudesmol 9,r81but might also be suitable
for the synthesis of more complex natural products of the
compactin o r m e v i n o h type.[']
high energy densities. So far, only Li3N has been found to
exhibit a n exceptionally high conductivity at room temperature. The use of Li3N, however, is limited by a low decomposition voltage.['] Lithium cells employing solid ionic
conductors have only been commercialized with thin-layer
electrolytes, for example, in pacemaker batteries121using a
charge-transfer complex, e.g., in the cell combination
Li/LiI/ 1-butylpyridinium polyiodide.
In an attempt to find fast solid lithium ion conductors,
we have investigated compounds of the system lithium halide-al~ohol.[~'
An indication of high ionic conductivity at
room temperature was provided by the earlier described
high ductility and the low melting points of a series of
solid phases of these system^.'^.^^ We report here on the
phase diagram of the system LiI-CH,OH and on the conductivity and crystal structure of the highest conducting
phase, LiI.4CH30H.
Received: July 21, 1986;
revised: September 16, 1986 [ Z 1866 IE]
German version: Angew. Chem. 98 (1986) 1104
1:1 2 3
CAS Registry numbers:
1, 90288-82-7: 3, 105140-87-2; Sa, 105140-88-3;Sb, 105140-89-4; 6a, 10514090-7; 6b, 105140-91-8;7, 105140-92-9;8, 105140-93-0;5-bromo-3-methyl-l,3pentadiene, 42 162-66-3.
E. L. Grimm, R. Zschiesche, H.-U. Reissig, J . Org. Chem. SO (1985) 5543.
For isolation of 2, see E. Kunkel, I. Reichelt, H.-U. Reissig, Liebigs Ann.
Chem. 1984. 802.
Thus, it is possible to prepare the plant constituent norbisabolide (4-methyI-4-(4-methyl-3-cyclo~exenyl)-y-butyro~actone;see, e.g., C. Gardrat,
Synrh. Commun. 14 (1984) 1191, and references cited therein) from 2 with
an overall yield of ca. 30%.
Recent reviews: a) E. Ciganek, Org. React. ( N Y ) 32 (1984) 4; b) A. G.
Fallis, Can. J. Chem. 62 (1984) 183; c) D. F. Taber: fntramolecular DielsAlder and Alder Ene Reactions. Springer, Berlin 1984.
I. Reichelt, H.-U. Reissig, Liebigs Ann. Chem. 1984, 531.
Especially characteristic are the chemical shifts of C2 (t), C3 (d), C4a (d)
and C8a (d): 5 a : 42.8, 39.3, 35.6,46.3; 5b: 41.2,40.2, 35.6, 48.6; 6b: 42.8,
42.8, 40.8, 5 1.2.
H.-U. Reissig, R. Zschiesche, unpublished results.
For endo cycloaddition of the trienone corresponding to 4 but without a
methoxycdrbonyl group, see W. Oppolzer, R. L. Snowden, D. P. Simmons, Helu. Chim. Acra 64 (1981) 2022; J. L. Gras, H. Bertrand, Tetrahedron Leu. 1979. 4549.
For the synthesis of (f)-a-eudesmol, see M. A. Schwartz, A. M. Willbrand, J. Ory. Chem. SO (1985) 1359, and references cited therein.
S. J. Hecker, C. H. Heathcock, J . Org. Chem. SO (1985) 5159, and references cited therein.
Fast Ionic Conduction in LiI - 4Methanol:
ILi(CH,OH),I+I By Werner Weppner, Wilfried Welzel, Rudiger Kniep, and
Albrecht Rabenau*
A detailed knowledge of ionic transport in solids is of
fundamental importance not only for a complete understanding of the properties of materials at the microscopic
level but also for the development of solid-state galvanic
cells."' Special attention is paid to solid lithium ionic conductors, because of the low atomic weight of lithium and
the high negative Gibbs free energies of formation of many
lithium compounds in view of energy storage devices with
[*] Prof. Dr. A. Rabenau, Priv.-Doz. Dr. W. Weppner,
DipLChem. W. Welzel ['I, Prof. Dr. R. Kniep ['I
Max-Planck-lnstitut fur Festkorperforschung
Heisenbergstrasse I . D-7000 Stuttgart 80 (FRG)
Permanent address:
lnstitut fur Anorganische Chemie und Strukturchemie der Universitat
Universitiitsstrasse I , D-4000 Diisseldorf (FRG)
Angew. Chem. Inr. Ed. Enyl. 25 (1986) No. I2
1 :I
80 -
40 -
- 4 O:
-80- 98
-120 -
CH30H [mot-%]
Fig. I. Phase relationships in the system LtI-CH,OH. See text and 161 for
Earlier studies had shown that lithium iodide reacts with
methanol to form adducts having the molar ratios 1 : 1,
1 :3, and 1 :4.[4.51Our determination of the phase equilibria
along the section LiI-CH30H[61(Fig. l), carried out by differential thermoanalysis (DTA) and X-ray analysis,
showed a quasi-binary section and confirmed the existence
of the 1 : I (m.p.=33"C, incongruent) and I : 4
(m.p. =49"C, congruent) compounds. A compound having
a 1 :3 c o m p ~ s i t i o n 'was
~ ~ not observed; the investigations
did, however, point to the existence of an additional (new)
2 :3 phase (m.p. = - 20°C, incongruent).
Studies of the conductivity of polycrystalline samples of
the compound LiI.4CH30H['I (Fig. 2) gave a purely ionic
conductance with the highest conductivity so far observed
at room temperature (Fig. 3). The ionic conductivity has a
value at room temperature of 2.7 x l o p 3R - ' c m - ' with an
activation enthalpy of 0.36 eV. For quenched (glasslike)
samples, conductivities were measured that were one to
two orders of magnitude less. The experimental galvanic
cells, prepared with lithium anodes and various cathodes
(TiS2, Pb12, and MnO,), gave the expected emf values. The
emf corresponds to that of a lithium concentration cell. In
contrast to methanol, LiI.4CH30H does not appear to
react with lithium.
Single crystals of the hygroscopic 1 : 4 compound were
grown from the melt in Lindemann capillaries;['' the crys-
0 VCH Verlagsgesell.schaft mbH. 0-6940 Weinheim, 1986
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methyl, trimethylsilyl, block, dielsцalder, intramolecular, reaction, vinylcyclopropanecarboxylates, key, building
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