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as distillate. The distillation residue of triphenylphosphine
oxide solidities (m.p. 150 "C, 97%, 6.75 g).
Received: April 17, 1968
[Z 776 IE]
German version: Angew. Chem. 80, 535 (1968)
[*] Dr. J. Buddrus
Lehrstuhl fur Theoretische Organische Chemie
der Technischen Universitat
1000 Berlin 12,Strasse des 17. Juni, No. 135 (Germany)
[I J J. Buddrus and F. Nerdel, German Pat. 1198355 (Jan. 7,
1963); Chem. Zbl. 137, 18-2333(1966).
121 F. Nerdel and J . Buddrus, Tetrahedron Letters 1965, 3585.
[3]Nachr. Chem. Techn. IS, 79 (1967).
[4]D . Klamann, M . Fligge, P. Weyerstahl, K . Ulm, and F. Nerdel,
Chemie-1ng.-Techn. 39, 1024 (1967).
[5]For a summary, see A. Maerker, Org. Reactions 14, 270
By R . Criegee and R . Askani[*l
When any of the valence-isomeric hydrocarbons ( I ) , (21, and
( 3 ) is heated in 1% N a ethoxide solution in ethanol at 240 "C
a hydrocarbon C16H24 of m.p. 23 OC is formed to which the
constitution (4)of a n octarnethylbicyclo[4.2.0]octatriene was
previously provisionally assigned [I]. This constitution is incorrect and is to be replaced by that of octamethylsemibullvalene (octamethyltricyclo[]octa-3,6-diene)( 5 ) .
The change of formula (4)to ( 5 ) for the hydrocarbon requires that the structures of the products derived from it also
be changed. Thus the peroxide (m.p. 7S°C), which is also
formed in the dark, is now to be formulated as ( 8 ) , and the
hydrocarbon of m.p. 55 OC obtained by way of the diol ( 9 )
or directly from ( 5 ) with silver nitrate is to be formulated as
( l o ) . In accord with their different symmetries the H atoms
of the bridgehead methyl groups in (8) show in the N M R
spectrum two singlets lying close together (T = 9.03 and 9.10),
whereas (10) shows only one singlet (T = 8.90). Following
the unsubstituted parent [*I and a bis(trifluoromethy1) derivativer41, compound ( 5 ) is the third semibullvalene. In contrast to the other two it is not formed by a photoreaction and
it is relatively easily accessible in gram quantities. The fourth
semibullvalene (with eight methoxycarbonyl groups) was
prepared by J . C. Kauer and H. E. Sirnrnons[51. Recently
L. A . Paquette obtained a n azasemibullvalene [61.
Received: April 11, 1968
[Z 775a IE]
German version: Angew. Chem. 80, 531 (1968)
[*1 Prof. Dr. R. Criegee and Dr. R. Askani
Institut fur Organische Chemie der Universitat
75 Karlsruhe, Richard-Willstatter-Allee (Germany)
[l] R. Criegee, W. D. Wirth, W. Engel, and H.-A. Brune, Chem.
Ber. 96, 2230 (1963).
[2] H . E. Zimmermann and G. L. Grunewald, J. Amer. chern. SOC.
88, 183 (1966).
131 We thank H. Korber for carrying out this experiment.
[4]R . S.H. Liu, J. Arner. chem. SOC.90, 215 (1968).
[5] J . C.Kauer, private communication.
[6]L. A. Paquette, Tetrahedron Letters 1968, 2133.
Photolysis of Tetramethylcyclobutenedicarboxylic
Anhydride, a Possible Route to
By G . Maier and U.Mender*]
As a result of the extremely rapid valence isomerization of
this system[21 the N M R spectrum is independent of temperature down to -100 OC; in pyridine/CC14 (9: 1) it shows 3
singlets at7 =, and 9.10 in the intensity ratio 1:2:1.
The U V spectrum shows no maximum, only a shoulder a t
240 nm, which requires additional assumptions on the basis
of structure (4)but is at once intelligible on the basis of ( 5 ) .
With tetracyanoethylene and azodicarboxylic ester the new
hydrocarbon gives adducts that are different from those obtained from (3). whereas those from (3) and ( 4 ) must be
identical. The new hydrocarbon gives the crystalline diozonide
(6)[31, whose N M R spectrum shows that, apart from the
four CH3 groups o n the ozonide ring [T = 8.41 (s), 8.43 (s)],
all the methyl groups are attached to saturated C atoms
[T = 8.87 (s), and 8.90 (s)].
In connection with attempts to synthesize a compound with
the ring skeleton of tetrahedrane we illuminated the anhydride
( I ) (Hanovia 450W high-pressure mercury tamp, Vycor
filter, ether, 20 "C, 40 min). The following products were isolated by chromatography o n silica gel:
Thus, the hydrocarbon can contain only two double bonds,
i.e. it must be tricyclic. The two double bonds present in ( 5 )
can add to each other photochemically (1 % ethereal solution,
100 W low-pressure lamp, O O C , 12 h), affording the saturated hydrocarbon, octamethylpentacyclo[]octane (7) in 10-20% yield. M.p. 92OC. N M R (CC14): T =
8.92 (s), 9.13 (s), and 9.15(s) in the proportions 1:2: 1.
Angew. Chem. internat. Edit. J Vol. 7 (1968) No. 7
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