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Heptalenebis(tricarbonyliron).

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Heptalenebis( tricarbonyliron)
By Emanuel Vogel, Dimitrios Kerimis, Neil T. Allison, Robert
Zellerhofl, and Jiirgen Wassen['l
Dedicated to Professor Tetsuo Nozoe on the occasion of his
77th birthday
In accord with expectation, the 12n-electron system heptalene (1) previously characterized by spectroscopic['"] and
structural'' h' investigations as being an olefin, readily reacts
with electrophilic agents, but the heptalenium salts formed
thereby in some cases have hitherto defied all attempts at
transforming them into substituted heptalenes. However. after independently synthesized disubstituted heptalenes had
been shown to be stable compounds"l, renewed attempts at
the derivatization of ( I ) seemed warranted. We have now
found that ( I ) can be substituted in the 1,6 position by way
of heptalenebis(tricarbony1iron) (2).
plexed 1,6-heptalenedicarbaldehyde (3). Like the known
heptalenes bearing two electronegative substituents. (3) is
also air-stable.
It could be concluded from the changes observed in the
'H-NMR spectrum of (3) below -40 "C that a rapid n-bond
shift takes place in the molecule and that the two nonequivalent double bond isomers existing in equilibrium with each
other are present in a ratio of 1 : 1. From the coalescence
(Tc= -70°C; Su=38 Hz) of the aldehyde proton signals it
follows that the activation enthalpy ACS of the n-bond shift
is 9.9 kcal/mol.
1,6-Heptalenedicarbaldehyde (3) is a suitable starting
compound for the synthesis of dimethyl I ,6-heptalenedicarboxylate (4) and other 1,6-disubstituted heptalenes. The diester (4),readily accessible by Curej!'s method1" [red prisms
(from hexane); yield 41%]. is likewise a dynamic system containing almost equal proportions of the two double-bond
isomers, as was deduced from the temperature dependence
of the 'H-NMR spectrum (Table 1 ) (changes in the methyl
proton signals: T, = - 17 "C; 6 u = 2.8 Hz). I t seems remarkable that the replacement of the aldehyde groups in /.3) by the
carbomethoxy groups increases the free enthalpy of activation of the n-bond shift from 9.9 to 14 kcal/mol. This is undoubtedly due to steric effects.
R
(3), R
= CHO
( 4 ) , R = COOCH3
Heptalenebis(tricarbony1iron) (21, which in contrast to the
free ligand is completely air-stable, is formed as the major
product when (1) is heated with benzylideneacetone(tricarbonyliron) (molar ratio 1 :2.5) in toluene for 15 h at 50 "C.
After chromatographic separation on silica gel (ether/pentane), (2) crystallizes from tetrachloromethane as deep-red
rhombs; yield 35-40%.
The structure of the new heptalene-transition metal complex (2) (excluding the stereochemistry) follows from the 'HNMR spectrum (Table 1). This shows an ABCDE spin system which, considering both decoupling experiments and the
fact that the protons of diene-Fe(CO), moieties absorb at
higher field strength than the protons of uncomplexed double bonds, is compatible only with the structure (2). The
number and positions of the "C-NMR signals also lend support to structure (2). The stereochemistry of the complex (2)
has recently been elucidated by an X-ray structure analysis
surprisingly, it is found that both
by H . J. Lindner et a/.[31:
Fe(CO), groups are located o n the same side of the heptalene
ligand.
From experience gained with other olefin-tricarbonyliron
complexes141it appeared that formylation by the Vilsmeier
method would be the most favorable approach for electrophilic substitution of (2). Indeed, it was found that reaction
of (2) with phosphorus oxide chloride (molar ratio 1 :20) in
dimethylformamide (initially at 0 ° C and then 12 h at 5 0 ° C )
afforded a formylation product, which was isolated as redbrown crystals after chromatography on silica gel (ether/
pentane) and recrystallization from ether/pentane; yield
20%. Interestingly, this product proved to be the uncom[ * ] Prol: I>r 1. V ~ g d Dipl.-Chrm.
.
1). Krrimi?. Dr N. T. Alliwn
Zellerhoff. Dr. J . Wassen
lnstitur lur Organische Chemie der Universitdt
Greinstrase 4. D-5000 Koln 41 (Germany)
[**I
Alexander-von-Humholdt Fellow.
AnKen,. Chem. In!. Ed. Engl. I X / l Y 7 Y / N o . 7
0
[**I.
Dr.
R.
The complex (2) promises to open up new perspectives in
heptalene chemistry provided that better routes to the hydrocarbon become available. A practical novel synthesis of heptalene, based on the observation that the tetrasubstituted
double bond of isotetralin (5) can be protected by a reversible epoxidation, has now been developed.
1 1-Oxatricyclo[4.4.1 .O]undeca-3,8-diene, which can be obtained selectively from isotetralin (S), reacts with bromoform
(fivefold excess) and 50% sodium hydroxide in the presence
of benzyltriethylammonium chloride (TEBA) to give the bisadduct (6)l6]having cyclopropane rings trans to the oxirane
ring [m. p. 100 "C (decomp.); yield 60-70%]. Treatment of
(6) with lithium and fert-butanol in tetrahydrofuran (24
hours' heating under reflux after the initially vigorous reaction has subsided) leads both to the reductive elimination of
the four bromine atoms as well as to deoxygenation of the
epoxide ring. i. e. the hydrocarbon (7) is formed in one step
(yield 50-5596; see Table 1). Since the bromine atoms are
removed more rapidly than the epoxide oxygen, it is possible
to isolate the epoxide of (7). frans,trans-l3-oxapentacycl0[5.5.1.O'~~.O~~'.O'~'']tridecane
(m.p. 71--72 " C ; yield 60 6 5 % ) if the duration of reaction is kept short. In order to
transform (7) into (8). (7) was heated with N-bromosuccinimide (NBS) (molar ratio 1 :6) in the presence of azobisisobutyronitrile in tetrachloromethane (60 min), and the resulting semicrystalline mixture, consisting mainly of the expected tetrabromo-substitution product (stereoisomers), was
then dehalogenated in the crude state with zinc in tetrahydrofuran (30 min reflux). Subsequent distillation in a high
Verlug Chemie. GmhH. 694U Wemheim. I Y T Y
0 5 70-081.~/79/07f17-054.5 $ f P 3 0 / 0
545
vacuum afforded the previously unknown 33-dihydroheptalene (b.p. 44--45"C/ca. 10 torr) having a purity of 95%
(yield 35-40%). At this stage (8) is sufficiently pure for use
in further reactions. but if necessary it can be purified by
crystallization from pentane at low temperature, albeit at the
expense of loss in yieldl'l. Conversion of (8) into ( I )could be
accomplished, as already described for the isomeric dihydroheptalenesl"'), by dehydrogenation-hydride abstraction with
triphenylmethyl hexafluoroantimonate in dichloromethane
and deprotonation with trimethylamine (yield 88-93% and
55 -60'4, respectively). The hitherto unknown intermediary
heptalenium salt was isolated, m. p. 155 "C (decomp).
Another practical heptalene synthesis, also starting from isotetralin, has been developed independently by Paquette and
co-workersfhl.
An Expeditious Synthesis of Heptalene from Naphthalene uiu a Bis(bicyclo[l.l.O]butane) Intermediate'**'
By Leo A . Paquette, Alan R. Browne, and Ernest Charnot"'
T o the present time, two syntheses of heptalene ( I ) have
been
and access has been gained to a few derivatives. While both routes to (1) are elegant in their conception,
they are lengthy, and the hydrocarbon has therefore remained difficultly accessible. As a result, theoretical predictions often have preceded the execution of experimental
work in this field.
Br. .Br
Table I . Physical data of compounds (2). (3). 14). (7). and (8)
/I).m. p. 1x5 C (decomp.). U V (cyclohexane): A,,,.,, = 2 X h nm ( b = 17200). 329
(21 100).443 (XX00): 1K (CCI,): 2058. 2040. 1988. 1975 cni ' ( C 0). 'H-NMK
(C<D,,):6 = 2 . 4 4 It. H-4, 9). 2.9X (d. H - I . 6 ) . 4.60 (in.H-2. 7). 4 79 (m. H-3. 8).
5.46 (d. H-5. 10) [a]
/ 3 j . m . p 105'C. U V (ethanol): A,,,.,,=290nm ( t = 15x00). 362 (5100).4X5 (XhO):
I K (Cslt- I670 cm ' (C 0): 'H-NMR [CDCI,: room temperature (region of
rapid exchange)]. 6= 6.1 I (d. H-5. 10). 6.65 (m. H-3.4. X. 9). 7.0X (d. H-2. 7). 9.X0
(5.
2 CHO)
(41. m p. 90- 91 C: U V (ethanol): A,,,,,=271 nm ( > = 1700). 334 (4300). 420
(790. jh). I K ( G I ) . 1720 cm ' I C 0): ' H- NM R r[D,]-tetrachloroethane:
-t 110°C (region of rapid exchange)): S = 3 70 ( 5 . 2 CH,). 6.13 (m. H-5. 10). 6.50
(m. H-3.4. X. 9). 7.15 (d. H-2. 7)
(7). h p 52 -53 C /O 4 torr: 'H- NM R (CDCI,). 6=0.22 (m. H-4. 4. 10. 10). 0.95
( i n . H-3. 5. 9 1 1 ) . 2.1 (m.H-2. 2.6.6. 8. 8. 12. 12)
(8). m.p. 3 3 - 34 C: U V (cyclohexane). A ,,,,,. = 2 3 0 nm ( t = 4 0 9 0 0 . sh). 234
(43 100). 299 (7700). 'H -N M K (CCI,). 8 = 2 . l h (1. J z 6 . X H7. H-3. 3. X. X). 5.50
6.X H r . H-2. 4. 7. 9).h.25 (d. J = 10.2 H r . H-I. 5. 6 . 10)
[a] A closer study of the ' H - and "C-NMR spectra of this complex has shown
that the douhle honds which are localized at room temperature. iis in structure
(I). migrate at higher temperature with siniultaneotis 1.2-shift of the Fe(CO),
groups. the reactant and product being in the relationship ofenantiomers: cf. the
dynamic hehabior of cyclooctatetraene(tricarhony1iron):F. A . ('orron. D L.
Hinwr, J Am Chem. Soc. YX 1413 (197h).
[Z 237h It;]
I'iihlication delayed at authors' requeht
German ver\ion' Angew. Chem. 01. 579 (1979)
Keceived. February 22. 1979
CAS Registry nunihrrr( l ) . 257-24-9, 1-71. 70629-73-1. ( 3 ) . 70576-00-0. ( 4 ) . 70576-01-1. (7). 70576-02-2:
((57, 70576-03-3: hen7~lideneacet~ine(triciirbon~lir~in).
61216-69-1: IF). 493-04-9:
(6).
70576-04-4:
rt-un\.rruns-I 3-oxapenti1cyclolS.5. I 0' '.I)'' 0" "Itridecane.
70592-72-2
[I]a ) H J Dunhen. Jr.. D.J . Berrelli. _I.
Am Chem. Soc. 83. 4659 (1961): E. Vop e / . H. Kunigsho/en. J. Wu.%.wn.K . Mullen. J F. M. Orh. Angew. Chem. 8 6 .
777 (1974): Angrw. Chem. Int. Ed Engl. li. 732 (1974): h ) I f . J. Lindner, 8.
K i r ~ h k ehid.
.
A??. 123 (1976) arid IF, I06 ( I976): J Srcgwnunn. H. J. Lindner.
Tetrahedron Lett. lY77. 25 15.
121 E. V&.
J Ippen. Angew. Chcm. 86. 77X (1974): Angew. Chem. Int. Ed.
I!ngl /I. 734 (1974): L' V o g d . F. Hogrefe. !hid. 86, 779 (1974) and 13. 735
(1974). K. Hujuer. f/. Diehl. H . U . S i r r . ihid XX. I21 (1976) and /.i104
.
(1976)
(31 J Srqemunw. H. J. Luidner. J . Organomet. Chem 166, 223 (1979).
141 Review: A. J Birch. 1. 11. Jenkins in H . Alpcr. Transition Metal Organometallic\ in Organic Synthe\is. Academic Pre\s. New York 1976. V o l . 1. p. I
[ 51 E. J . ( ' w e ) . . N W. Gi/mun. B. E. Gunmi. J . Am. Chem. Soc. UO1. 5616
(IYOX)
[ b ]J lppm. Dissertation. Univerbitat K o l n 1915. It has meanwhile been found
that the tetrachloro analog of / 6 j , obtained hy reaction of- the 4a.Xa-epoxide
ol.irotetraliii IS/ with chloroform and \odium hydroxide under phase-transfer
conditions In1.p. 125 "C (decomp.): yield 75- XO%l. can he advantageously
he w e d instead of ( 6 ) .
171 T h e conbersion of (7) into (8) is similar to the final step i n the synthesi? ofoctalene. \ee E. Vogc/. H: V. Runzheimer. F. Ifogreffr. B. Rnower. J . Lei. Angew. Chem. 89.909 (1977): Angew. Chem. In1 Ed. Fngl. 16. 871 (1977).
[XI I-. A. Pugue/re. A. R. Bruicnr. E C'bomor. Angrw Chem. 91. 5x1 (1979): Angew. Chem Int. Ed. tngl. l X 546 (1979)
546
0 Verlrrg Chemie. CmbH. 6940 Weinheim. /Y7Y
In this communication we describe an efficient six-step
conversion of naphthalene to (f). The new methodology capitalizes on the regiospecificity of two-fold intramolecular carbene insertion to give (4)13)and the ability of silver([) ions to
promote the isomerization of bicyclo[ 1.1.O]butanes to ringopened conjugated dienes141.
Addition of dibromocarbene to tetrahydronaphthalene
(isotetralin) (Z)lsl using a modification1"I of Vogers procedure''] afforded bisadduct (3) (38%) admixed with the corresponding mono- (12%) and tris-adducts (0.8%). These products could be efficiently separated by recrystallization: resubmission of the monoadduct to the same reaction conditions
returned additional (3) in 72% yield. When the tetrabromide
(3) was treated with 2 M ethereal methyllithium at 0-25 "C
for 3 h, the colorless bis(bicyclo[ 1.1.O]bu tane) (4) was obr
tained in 59% yield ufrer molecular distillation (80-100 "C/
0.3 torr). The 'H-NMR spectrum of (4) (C,D,) contains two
series of multiplets at 6=6.03-5.06 (2H) and 2.46--1.11
(10H) while its I3C-NMR exhibits 12 lines, thus demonstrating the isomeric homogeneity of the hydrocarbon. The definitive structural assignment follows from the Ag +-catalyzed
isomerization of (4) exclusively to 1,6-dihydroheptalene (S)
and catalytic hydrogenation of this pentaene to cis-bicycl0[5.5.0]dodecane~~~.
Whereas (5) belongs to the CZhpoint
group, the 1.10 isomer (6) has C2- symmetry; a clear distinction between them becomes apparent upon "C-NMR analysis (in CDCI,) which reveals the six lines ( F = 132.8, 131.0,
125.6, 123.6. 123.0, and 33.6) demanded uniquely by (5).
[*I
Prof. Dr. L A Paquette. D r A K . Browne. L)r E Charnot
Evanr Chemical Laboratories. 7 he Ohio State University
Columhus. Ohio 43210 ( U S A )
[**I
We acknowledge the financial support of the donors to the Petroleum Kcsearch Fund. administered hy the American Chemical Society. the National
Cancer Institute. and an Ohio Stale University tiraduate School postdocturiil
fellow\hip award tu A R H.
(15 70- OX</ 7Y /(I 70 7-0546 $ 0_7,50/0
A n g e u Chem. I n [ . Ed. €fig/. 18 l l Y 7 Y j No. 7
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