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Bicyclo[2.2

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Bicycle[2.2.2]0cta-5,7-dien-Zone ("Barrelenone")[**]
By Rudolf Gompper and Karl-Heinz Etzbach"]
Polar substituents influence the reactive behavior of ambifunctional anions and cations by inducing an alteration in
charge distribution (allopolarization principle"]). The aroma.ticity of a ring system can also alter the polarity and reactivity
of an ambifunctional system. The same would appear to apply
for bicycloaromaticity : reaction of the anion of bicyclo[4.2.2]decatrienone with dimethyl sulfate['] gives a remarkably high
yield of enol ether (0-methylation).
In continuation of our investigations on the alkylation of
the dibenzobarrelenone anion (predominantly C-methylation,
cf. [ I ] ) , we have therefore synthesized bicyclo[2.2.2]octa-5,7dien-2-one (6) in order to study the alkylation of its anion
bicyclo[2.2.2]octa-2,5,7-trien-2-olate.
On heating dihydrophthalic anhydride (1) (prepared from
dihydrophthalic acid and acetic anhydride) with the acrylonitriles ( 2 a ) and ( 2 b ) (for the use of (2) as ketone equivalent
cf. [31), 7-acetoxy-7-cyanobicyclo[2.2.2]octa-5-ene-2,3-dicarboxylic anhydride ( 3 a ) (45%, yellow, amorphous powder)
and the 7-chloro analog (3 b ) (50 %, colorless powder, m.p.
159-161 "C (from chloroform) are obtained, respectively.
1615, 1580cm- ; 2,4-dinitrophenylhydrazone: red needles
m. p. 183-1 84 "C (from ethanol)).
A second route to ( 6 ) starts from bicyclo[2.2.2]oct-7-ene2,5-dione (7)[51. Reaction of (7) with Na-bis(trimethylsily1)amide in ether at -78°C affords the Na-salt. which reacts
1. 2 NaN(SlMes)?
E120,- 78 "C
2.2 Me3SiCl
with trimethylchlorosilane to give the barrelenone derivative
5-trimethylsiloxybicyclo[2.2.2]octa-5,7-dien-2-one ( 8 ) (7580 %; colorless oil, b.p. 119"C/17 mbar). Reaction of the
disodium salt of (7) with trimethylchlorosilane yields 2,5-bis(trimetbylsiloxy)bicyclo[2.2.2]triene ( 1 0 ) , a new barrelene derivative (70 %, colorless oil). Reaction of (8) with LiBH4 and
acid hydrolysis of the reaction mixture affords S-hydroxybicyclo[2.2.2]oct-5-en-2-one ( 9 ) (68 %, colorless needles (from
ether/hexane), m.p. 150-155°C). ( 9 ) can be converted by
known methods[5]into the thiocarbonate (1 1 ) (99 % ; yellowred oil) whose subsequent thermolysis ( 180°C/17 mbar)
likewise affords barrelenone ( 6 ) in 70% yield.
1. KOH
R = OAc
2. HCI
R = O A c KOH
$-
Table 1. Methylation of the Na-salts [a] of bicyclic ketones with methyl
fluorosulfate in the presence of [18]-crown-6 at 78°C in ether.
c
Barrelenone (6)
Benzobarrelenone ( 1 2 j
Dibenzobarrelenone (13)
Dihydroharrelenone ( 1 4 )
Dihydrobenzobarrelenone ( 1 5 )
Tetrahydroharrelenone ( 1 6 )
1.63
2.02
2.33
2.06
2.39
2.78 [d]
0.05
0.10
0.35
0.53
0.87
I.90
(a), R = OAc; ( b ) , R = C1
Electrolysis of (3 a ) and of ( 3 b ) (pyridine/triethylamine/
water, 90 V, 0.6-0.4 A, room temperature 7 h; cfJ4]) leads
to 7-acetoxy-7-cyanobicyclo[2.2.2]octa-2,5-diene ( 4 a ) (ca.
20 %; colorless oil, b.p. 100°C/O.Ol mbar (bulb-to-bulb dist.)
and the 7-chloro analog ( 4 b ) (25-30 % ; colorless needles
(from ether) m. p. 62-64"C), respectively.
Alkaline hydrolysis of (3 a ) yields the dicarboxylic acid
(5) (70 %, colorless, amorphous powder). Both electrolysis
of ( 5 ) (22% yield) as well as alkaline hydrolysis of ( 4 a )
(70 % yield) then afford the barrelenone ( 6 ) (colorless oil,
b. p. 90°C/17 mbar (bulb-to-bulb dist.); 'H-NMR (CDC13):
6=1.86 (d, J = 3 H z ; 2H, CHI), 3.76-4.32 (m; 2H, CH),
6.60 (mc; 4H, -CH=);
IR (film): 3065, 2990, 2923, 1725,
[a] Prepared with NaN[Si(CH3),I2 in E t 2 0 at -78°C.
[b] I = HMO charge, calculated with ho = 1 .O,kcc = kco = 1.O, homoconjugation kcc= +0.5.
[c] Yield ratio % 0-methylation to % C-methylation.
[d] Calculated for the anion of 2-butanone.
The course of methylation of Na-salt of (6) and other
bicyclic ketones proceeds according to predictions based on
the allopolarization principle: As can be seen from Table
1 the tendency towards 0-methylation also increases with
increasing polarity index POic in the seriesf6J
Received: April 27, 1978 [ Z 8 IE]
revised: May 22, 1978
German version: Augew. Chem. 90,630 (1978)
[*] Prof. Dr. R. Gompper, Dip].-Chem. K. H. Etzbach
Institut fur Organische Chemie der Universitat
Karlstrasse 23, D-8000 Munchen 2 (Germany)
[**I This work was supported by the Deutsche Forschungsgemeinschaft
and the Fonds der Chemischen lndustrie. We thank BASF for supplying
the dihydrophthalic acid.
Angew. Chem. Int. Ed. Engl. 1 7 (1978) N o . 8
CAS Registry numbers:
( I ) , 85-44-9; (2a), 3061-65-2; ( 2 b ) , 920-37-6; (3a). 67209-47-6; (3 b ) ,
67209-48-7; ( 4 a ) , 67209-49-8; ( 4 b ) , 67209-50-1 ; IS), 67209-51-2; (6),
67209-52-3; ( 6 ) , 2.4-DNPH, 67209-53-4; (6), Na salt, 67209-54-5; ( 6 ) ,
0-methylation, 67209-55-6; ( 6 ) , C-methylation, 67209-56-7; (7), 17660-74-1;
603
(71, di-Na salt, 67209-57-8; (a),
67209-58-9; (9), 67209-59-0; ( l o ) ,
67209-60-3; ( l l ) , 67209-61-4; ( 1 2 ) Na salt, 67209-62-5; ( 1 2 ) 0-methylation,
67209-63-6; ( I Z ) , C-methylation, 67209-64-7; ( 1 3 1 , Na salt, 67209-65-8;
( 1 3 ) . 0-methylation, 67209-66-9; ( 1 3 ) , C-methylation, 67209-67-0; ( 1 4 ) ,
Na salt, 67209-68-1 ; (141, Omethylation, 67209-69-2; ( 1 4 ) , C-methylation,
67209-70-5; ( 1 5 ) . Na salt, 67209-71-6; ( 1 5 ) , 0-methylation, 67209-72-7;
( I S ) , C-methylation, 67209-73-8; (16), Na salt, 67209-74-9; (16), O-methylation, 67209-75-0; ( 1 6 ) , C-methylation, 67209-76-1 ; Na-bis(trimethylsily1)amide, 1070-89-9; trimethylchlorosilane, 75-77-4
R. Gompper, H : U . Wagner, Angew. Chem. 88,389 (1976); Angew. Chem.
Int. Ed. Engl. 15, 321 (1976).
J . B. Press, H . Shechter, J. Org. Chem. 40, 2446 (1975).
S . Ranyanathan, D. Ranganathan, A . K . Mehrotra, Synthesis 1977, 289.
H . H. Westberg, H. J . Dauben, Tetrahedron Lett. 1968, 5123.
C. Weitemeyer, A . de Meijere, Angew. Chem. 88, 721 (1976); Angew.
Chem. Int. Ed. Engl. 15, 686 (1976).
Note added in proof(July I I, 1978): Presented in part at the "Third International Symposium on Novel Aromatic Compounds" at San Francisco,
August 22-26, 1977 (cf. Abstr. of Papers).-Meanwhile, H. Prinzbach,
H.-P. Schai, and D. Hunkler (Tetrahedron Lett. 1978, 2195) have
mentioned a further mode of formation of (6).
Synthesis and Properties of
Tris(trirnethylgerrnyl)alurninurn[**]
By Lutz Rosch and Wolfgang Erb"]
Organoaluminum compounds are well known and are of
considerable preparative interest. In contrast, very few analogs
with germanium replacing carbon have so far been described.
R 3 G e A I R 2 has been postulated as an intermediate in the
reaction of germanium halides with alkylaluminum derivatives"], and Calm and co-workers recently isolated the salt
Li+[(CbH5)3GeA1H3]-[ 2 ] in the reaction of hexaphenyldigermane with lithium aluminum hydride.
We have now synthesized the first alkylgermylaluminum
compound by reaction of bis(trimethylgermy1)mercury with
aluminum:
3Hg[Ge(CH3),I2 + 2A1
-
Sl"C,lO
' torr
+{A1[Ge(?H3)&) + THF
CH3AI[Ge(CH3)3]2+ (Ge(CH3M
Isolation of the intermediary solvent-free tris(trimethy1germy1)aluminum is not possible under these conditions.
Attempts to prepare the likewise unknown tin compound
(2) in an analogous way showed that ( 2 ) already decomposes
below room temperature.
AI[Sn(CH3),-THF
(2)
On reaction of bis(trimethylstanny1)mercury with aluminum
the solution instantaneously decolorizes. During workup a
colorless solid is obtained which contains tin as well as aluminum, but no mercury, and which ignites spontaneously
in air. Hydrolysis leads to formation of trimethylstannane
and methane. The 'H-NMR spectrum shows a broad multiply
split signal in the TMS region, thus indicating spontaneous
decomposition of the initially formed tris(trimethylstanny1)aluminum with loss of dimethylstannanediyl under such reaction
conditions. This instability in comparison to the germanium
compound is consistent with the properties of the corresponding mercury compounds. Bis(trimethylgermy1)mercury is
stable up to 120"C[41,bis(trimethylstanny1)mercury decomposes at - 1 0 ~ c [ ~ l .
Procedure
5g (Me3Ge)2Hg is dissolved in 50ml pentane and 2ml
T H F and stirred together with 8 g aluminum powder under
argon until disappearance of the green color (ca. 24 h). The
solution is filtered through a glass frit and the readily volatile
components removed in an oil-pump vacuum at room temperature. The residue is recrystallized twice from a little pentane
at - 78°C. 3.86 g (80 %) A1[Ge(CH3)3]3. THF is obtained
as a white crystalline powder.
Received: May 26, 1978 [Z 9 IE]
German version: Angew. Chem. 90, 631 (1978)
THFlPenfane
2A1[Ge(CH3),], .THF + 3Hg
The colorless, crystalline tetrahydrofuran adduct (1 ) ignites
spontaneously in air; its decomposition in water or D 2 0
leads to formation of trimethylgermane or trimethyldeuteriogermane, respectively.
The new compound (I) is readily soluble in organic solvents
such as ether, benzene, or pentane. The 'H-NMR spectrum
(benzene) shows only one additional sharp signal in the TMS
region besides the coordinated tetrahydrofuran, as well as
the I3C-NMR spectrum which shows only one signal for
the trimethylgermyl group at 6=1.18. The structure of (1)
is confirmed by elemental analysis and the mass spectrum
(molecular ion with expected isotopic satellites). (1) has an
astonishingly high thermal stability; it melts without decomposition at 81"C, but at lo-' torr it loses part of the coordinated solvent at this temperature. The 'H-NMR spectrum
of the residue shows a broad signal in the TMS region. Hydrolysis affords trimethylgermane together with methane, which
can be detected by IR spectroscopy. This would indicate
decomposition with formation of dimethylgermanediyl, corresponding to the mode of decomposition already observed in
the case of the homologous silicon compound[3].
[*] Dr. L. Rosch, DipLChem. W. Erb
Institut fir Anorganische und Analytische Cbemie
der Technischen Universitat
Strasse des 17. Juni 135, D-1000 Berlin 12 (Germany)
[**I This work was supported by the Deutsche Forschungsgemeinschaft
604
Al[Ge(CH,),], .THF
[I] F. Glockiing, J . R . C. Light, J. Chem. SOC.A1967, 623.
123 N . Duffaut, J . Dunogues, R. Calas, P. Reviere, J . Satge, A . Cazes, J .
Organomet. Chem. 149, 57 (1978).
[3] L. Rosch, Angew. Chem. 89, 497 (1977); Angew. Chem. Int. Ed. Engl.
16, 480 (1977).
[4] C. Eaborn, W A . Dutton, F. Glockling, K . A . Hooton. J. Organomet.
Chem. 9, 175 (1967).
[S] U . Blaukat, W P . Neumann, J. Organomet. Chem. 63, 27 (1973).
Evidence for a Dialkoxyalkene Radical Cation in
Aqueous Solution
By Giinter Behrens, Eberhard Bothe, Johann Eibenberger,
Giinther Koltzenburg, and Dietrich Schulte-Frohlindepl
In connection with our investigations on the radiation
damage of DNA['] we were interested in the elimination of
phosphoric acid from P-phosphatoalkyl radicalsr2].As model
species for our studies we used the I-methoxy-2-phosphatoethyl radical, which rapidly loses phosphate in aqueous solution ( k = 3 x 106s-') and is converted into CH30-eHCHzOH and CH30-CH(OH)-kH,[21.
An analogous reaction in which chloride instead of phosphate is eliminated
[*] Prof. Dr. D. Schulte-Frohlinde, Dr. G. Behrens, Dr. E. Bothe, J. Eibenberger, Dr. G. Koltzenburg
Institut fur Strahlenchemie im Max-Planck-Institut f i r Kohlenforschung
Stiftstrasse 34-36, D-4330 Mulheim-Ruhr 1 (Germany)
Angew. Chem. lnt. Ed. Engl. 1 7 (1978) No. 8
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