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Four Linearly Annelated Cyclobutane Rings The Tetracyclo[4.4.0.02 5

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The fact that ( 1 ) and (2) both give the same product
(7) shows the first step of thermolysis of (1) to be rupture
ofthecentral strained bond (path A in ref. ['I). A bicyclo[6.2.0]decatetraene (6) which is unstable under the reaction conditions has been proposed as the first intermediate en route
from ( 1 ) to (7). Its tetrahydro derivative (9), which is no
longer accessible to electrocyclicring opening to form a cyclodecapentaene, should be isolable. The behavior of compound
(3), from which (9) could be formed thermally, therefore
attracted our interest.
Thermolysis of pterodactylane (3), m. p. 57-60°C, prepared from (1) by hydrogenation (Pd/C in CH,OH), in boiling
CCI4 gives not only (9) but also surprisingly compound (10)
(ratio 1 : 1).
The structures (9) and (10) are based on spectral data,
on the oxidative degradation of (9) with ozone or
KMnO,/KIO,, which leads to succinic acid, and on the dehydrogenation of (10) with dichlorodicyanoquinone (DDQ) to
dimethyl 1,5-naphthalenedicarboxylate.
[6] J . H . Brewsster, J. Am. Chem. Soc. 81, 5475, 5483,5493 (1959); Tetrahedron
13, 106 (1961).
[7] The absolute configurations of compounds ( 1 ) and ( 2 ) are unknown;
an X-ray structural study of ( 1 c ) is in progress.
[8] J . H . Brewsrer, Top. Curr. Chem. 47, 29 (1974).
[9] E. Ruch, Acc. Chem. Res. 5, 49 (1972).
Four Linearly Annelated Cyclobutane Rings :
The Tetracyclo[4.4.0.02~
5.079'Oldecane System[**]
By Hans-Dieter Martin and Mirko Hekman"]
We recently reported the synthesis['] of pterodactyladiene
( I ) , a highly strained representative of the (CH),, isomers.
In the present communication we now report:
a) The preparation and an unexpected thermal isomerization
of pterodactylane ( 3 ) , the course of which has been established
by isotopic labeling.
b) The elucidation of the mechanism of thermolysis of (1 ).
c) The synthesis and thermolysis of the azo compounds
( 2 ) and ( 4 ) . Compound ( 2 ) provides an entry to the (CH),,
energy surface which is distinct from (1) and permits a decision
between the various reaction pathways proposed for (1 ).
R
131
I
R = COzCH3
60-80 "C
A
R
R = COzCH3
Reaction of cyclobutadienetricarbonylironand ammonium
cerium(1v) nitrate with the 3,6-disubstituted s-tetrazine ( 5 )
at 0°C affords ( 2 ) , m.p. 103--105°C. Heating of ( 2 ) in per-
The transformation of (9) to (10) only at temperatures
of about 190°C shows that (10) cannot be regarded as a
product of (9) under the given reaction conditions (60-80°C).
Rather both (9) and (10) are formed directly from (3).
The thermolysis of tetradeuteriated (3) furnishes evidence
for the reorganization of the molecule and for the formation
pathway of (9) and (10). In [D4]-(9) the deuterium occupies
the positions 4a,5a,9a, and 10a, and in [D4]-(10) positions
4, 5, 9, and 10. The site of deuteriation in (3) follows from
the NMR spectra of (3) and [D4]-(3) in the presence of
a shift reagent.
R
'N A
ce4+
I
R
(5J
[OI
-
R = C02CH3
+
R
12)
chlorobutadiene (2h, 140°C)gives the naphthalene (8) almost
quantitatively. Transient formation of 4a,8a-dihydronaphthalene (7)"' can be detected by NMR spectroscopy.
rD4]-
I I ) Rupture 1.6
(31
2) Rupture2.517.10
to form bisallyl
radical [2]
3 ) Head-to-tall
linkage 2.1
1
R = COzCH3
D
R = C02CH3
[*I
Prof. Dr. H.-D. Martin and
Dipl.-Ing. M. Hekman
Institut fur Organische Chemie der Universitat
Am Hubland, 8700 Wurzhurg (Germany)
[**I This work was supported by the Deutsche Forschungsgemeinschaft
and the Fonds der Chemischen Industrie. We are indebted to Prof. Dr.
H . Schmid. Zurich, and Dr. D . Belfuf, Basel, for discussions, and to Prof.
Dr. J . Sauer, Regensburg, for communication of unpublished results. A
generous gift of COT from the Badische Anilin- und Sodafabrik AG is
gratefully acknowledged. Small Rings, Part 18.-Part 17: H.-D. Martin, S.
Kagabu, and H . - J . Schiwek, Tetrahedron Lett. 1975, 331 1.
A I I ~ L WCIIPI~.
.
l i l t . Ed. EIIL]~.
! Vol. 15 11976) N o . 7
~
R
[D41-
(101D
D
The azo compound ( 4 ) , m.p. 160--162"C, prepared by
diimide reduction of (2) (potassium azodicarboxylate and
acetic acid at 0°C) affords (9) as major product accompanied
by only about 5 % of (10) on thermolysis. This product
distribution is in accord with results obtained for other azo
The kinetic parameters of ( l ) , (3), ( l l ) , ( 1 2 ) , and (13)
(Table 1) confirm the uniform mechanism, which is initiated
43 1
by cleavage of the central o-bond; comparison with ( 1 2 )
and ( 1 3 ) rules out a primary cyclobutene ring opening as
(proposed['') alternative mechanism in the case of (I). Annelated cyclobutane or cyclobutene rings such as those in (3)
and (1) therefore have practically no influence on the Arrhenius parameters of (11).
flli
113,
/I21
Table 1. Kinetic data. G=gas phase, L=liquid phase.
Compound
(1)
L
(3)
L
(11)
(12)
(13)
L
L
G
E, [kcal/mol]
log.4
24.5
24.1
25.5
31.7
32.6
32.4
12.0
11.9
12.1
13.6
14.0
14.2
Ref
[I1
this communication
this communication, [4]
this communication
PI
[61
Received: March 23, 1976;
in abridged form: April 1, 1976 [Z 452 IE]
German version: Angew. Chem. 88,447 (1976)
CAS Registry numbers:
( I ) , 49542-83-8;( 2 ) , 59247-30-2;( 3 ) , 59247-31-3;( 4 ) , 59247-32-4;
( S ) , 2166-14-5;(?), 59247-33-5;(81, 840-65-3;( 9 ) , 59247-34-6;
(101, 59247-35-7;(If), 31947-22-5;( 1 2 ) , 3097-63-0;
cyclobutadienetricarbonyliron, 12078-17-0
H.-D. Martin and M. Hekman, Angew. Chem. 85, 615 (1973);Angew.
Chem. Int. Ed. Engl. 22,572 (1973).
The fragmentation of a 1,4-cyclohexanediyl into two ally1 radicals is
endothermic to the extent of about 25 kcal/mol; however, annelation
of two four-membered rings (strain energy 52 kcal/mol) can lead to
exothermic cleavage. The formation of an intermediate transpans-diene
from (3) as a precursor of ( 1 0 ) has been suggested as an interesting
alternative by H . Schmid.
L. A. Paquette, M . R. Short, and 1. F. Kelly, J. Am. Chem. SOC.93,
7179 (1971);W R. Roth cited in J . K . Kochi: Free Radicals. Vol. I,
Wiley-Interscience 1973,p. 229; W R . Roth and M. Martin, Tetrahedron
Lett. 1967, 3865. The equilibration of intermediate nitrogen-free fragments, as observed in the case of diazabicyclo[2.2.2]octenes, possibly
does not occur here.
The kinetics of thermolysis of ( 1 1 ) was investigated in collaboration
with Dr. Daniel B e h f , Basel.
H. M. Frey, H.-D. Martin, and M. Hekman, J. Chem. SOC.Chem. Commun.
1975, 204.
R. S. Case, M . J . S . Dewar, S . Kirscltner, R. Pettit, and W Sleyier,
J. Am. Chem. SOC.96, 7581 (1974).
[l]
[2]
[3]
[4]
[5]
[6]
spite of the considerable difference in electronic character
of the substituents attached to the azo group both regioisomers
(3) and ( 4 ) should be formed. In contrast, the comparable
reactions of a r y l a z ~ n i t r i l e sand
~ ~ ~ethyl benzeneazocarboxylate[2.4l with (1) were found to give only one 1,2-diazetidinone
of type (3) in each case.
The exothermic reaction of ( I ) with (2) is complete within
ca. 1 h; the 'H-NMR spectrum of the crude solution shows
it to proceed quantitatively. Compounds (3) and ( 4 ) are
isolated by fractional crystallization from ,methanol. Pure ( 5 )
and (6) can be obtained by rearrangement of (3)['1 and
( 4 ) , respectively, under the influence of trifluoroacetic acid.
Crystalline (5) and (6) are also obtained on seeding the
reaction solution after extensive removal of (3) and ( 4 ) .
The structures of ( 3 ) and (5) have been proved by independent
syntheses[*r61,and the structures of ( 4 ) and (6) by IR, 'HNMR, and I3C-NMR spectra (Table I).
Table 1. Cycloadducts from diphenylketene (1) and acetylazobenzene (2).
All compounds gave correct CHN analyses. The product composition was
determined from theintegrals of the methyl signals in the 'H-NMR spectrum
of the crude solution.
Cpd.
131
(4)
(5)
(6)
Competing Cycloadditionsin the Reaction of Acetylazobenzene with Diphenylketene
By Sven Sommer"]
Among the few cycloadditions undergone by aryl azo compounds of the type Ar-N=N-X
[X=Ar, CH(CH&,
N(CH3)2, C 0 2 C 2 H 5 , C=N] are to be found the reactions
with diphenylketene (1 )['- 3 1 . Only [2+2] cycloadducts (1,2diazetidinones) have so far been isolated as reaction products.
In contrast, the reaction of acetylazobenzene (2) with (I)
(1 : 1 in benzene at room temperature) leads to the two [ 2 21
cycloadducts (3) and ( 4 ) , to a [4+2] cycloadduct ( 5 ) , and
to a product (6) formally arising by [4+2] cycloaddition
and subsequent 1,3-H shift.
No mutual interconversion of the products under the reaction conditions could be detected. It is remarkable that in
+
[*] Dr. S. Sommer
Organisch-chemisches Institut der Technischen Universitat
Arcisstrasse 21, 8000 Miinchen 2 (Germany)
432
'H-NMR
M.p.
["CI
171 [bl
169-170
167-168
136-137
136f61
182-183
SCH3
IR [cm-']
W r l
vC=O (Ring)
vC=O
[%I
I.[
Proportion
1.65
1792
1709
60
[2]
[b]
[b]
2.50
2.08
1796
1678
1725
(C=N
26
10
[c]
2.67
1680
(SNH
(sNH
= 8.43)
= 3280)
= 1660)
1715
4
[a] &values [ppm], in CDCI3 with TMS as internal standard.
[h] From methanol.
[c] Dissolved in ethyl acetate and precipitated with methanol.
Received: March 26, 1976 [Z 453 IE]
German version: Angew. Chem. 88,449 (1976)
CAS Registry numbers:
( I ) , 525-06-4;(2), 13443-97-5;( 3 ) , 59231-00-4;(41, 59231-01-5;
( S ) , 59231-02-6;( 6 ) , 59231-03-7
[l] R. C. Kerbrr, 7: J . Ryan, and S . D.Hsu, J. Org. Chem. 39, 1215 (1974).
C.W Bird, J. Chem. SOC.1963, 674.
131 C . W Bird, J. Chem. SOC.1964, 5285.
[4] On the basis of a shoulder at ca. 1820cm-' in the 1R spectrum of
the crude solution, Kerber et al. [l] suspect the formation of small
amounts of the regioisomer of type ( 4 ) ; confirmatory evidence and
an isolation have yet to be reported.
[5] The rearrangement ( 3 ) + ( 5 ) has already been performed with the aid
of concentrated HCI. Under these conditions ( 5 ) is formed together
with two other products in only 23 % yield [2]. In trifluoroacetic acid
the rearrangements ( 3 ) + ( 5 ) and ( 4 ) + ( 6 ) are quantitative.
161 J. van Alphen, Rec. Trav. Chim. Pays-Bas 48, 163 (1929).
121
Angrw. Chem. Int. Ed. Enyl. J Vol. 15 (1976) No. 7
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