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The Berson-Willcott Rearrangement of 11 11-Dimethyltricyclo[4.4.1

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Intramolecular asymmetric aldol reactions: A . Fischli, Chimia 30, 4
(1976); N . Cohen, Acc. Chem. Res. 9, 412 (1976); aldol-type asymmetric
reactions; J . D. Morrison, H . S . Mosher: Asymmetric Organic Reactions.
Prentice-Hall, Englewood Cliffs 1971; C . Mioskowski, G . SolladiP, J.
Chem. SOC.Chem. Commun. 1977, 162; I . Ojima, K . Yoshida, S . Inaba,
Chem. Lett. 1977, 429.
D. Enders, H . Eichenauer, Angew. Chem. 88, 579 (1976); Angew. Chem.
Int. Ed. Engl. 15, 549 (1976); Tetrahedron Lett. 1977, 191.
For the cleavage of dimethylhydrazones with singlet oxygen, see E.
Friedrich, W Lutz, H . Eichenauer, D . Enders, Synthesis 1977, 893.
All new compounds gave correct elemental analyses. IR, NMR, and
mass spectra are in agreement with the structures given.
the hyperfine data of ( I ) . e (Table 2) and those of the radical
anion of the reference compound (4)L8I indicates that ( I )se,
like (4).e, contains
separate butadiene rr-systems[9'.
0
q
"
~
s<
~
f
f 4
-
(4)
~
l
7
Upon warming of the solution of ( I ) * e above -llO"C,
the spectrum of the primary radical anion was gradually re-
Table 1. Activation parameters for the valence isornerizations ( 1 ) + ( 3 ) and ( 1 ) * % ( 3 ) * ' ,
~~
k (25°C)
(11-(3)
(1).R+(3)*0
~~
-
*
E,
[kJ/mol]
A H (25 T)
[kJ/mol]
A S * (25°C)
[J/mol K]
134f03
1 3 f 2 [a]
150+2
4 6 + 8 [a]
147f2
43 f 8 [a]
4+4
20+20 [a]
-
-10-'2
103
~
log A
___
-
[a] Large range of error is due to the very rapid course of the reactlon
The Berson-Willcott Rearrangement of 11,ll-Dimethyltricyclo[4.4.1.01~6]undeca-2,4,7,9-tetraene and Its
Radical Anion[*']
By Fabian Gerson, Walter Huber, and Klaus Miillen"]
The nature of the frontier orbitals of a molecule is of prime
importance for the discussion of its valence isomerizations[l].
It is therefore of interest to investigate the way in which
the formation of the corresponding radical anion affects such
a conversion. While mechanistic studies of this kind have
thus far been mainly restricted to pericyclic reactions of the
nrr + o + (n+ 1)n type['], the present work on 11 ,I 1-dimethyltricycl0[4.4.1.0~*~]undeca-2,4,7,9-tetraene
(1)l3l permits the
first comparison between the B e r s o n - W i l l ~ o t trearrangement
[~~
of a norcaradiene derivative and the analogous valence isomerization of its radical anion.
As has been observed by Vogel et ~ 1 . [ ~ ]thermolysis
,
of
( I ) leads to 5,5-dimethylbenzocycloheptene(3). This reaction.
which proceeds via the transient valence isomer ( 2 ) , mimics
the rearrangement described by Berson and Willcott for the
parent cycloheptatriene-norcaradiene system.
We investigated the kinetics of the thermolysis of ( 1 ) by
monitoring the intensities of the 'H-NMR signals of ( 1 )
and (3) in the range of 150 to 190°C. The resulting activation
parameters are listed in Table
Reduction of ( I ) with potassium in 2-methyltetrahydrofuran below - 110°C enabled us to record the ESR spectrum
of the primary radical anion (1 )*' c7l. The similarity between
[*] Prof. Dr. F. Gerson, Dipl.-Chem. W. Huber
Physikalisch-chemisches Institut der Universitat
Klingelbergstrasse 80, CH-4056 Basel (Switzerland)
Priv.-Doz. Dr. K. Mullen
Laboratorium fur Organische Chemie der Eidgenossischen Technischen
Hochschule
Universitatsstrasse 16, CH-8092 Zurich (Switzerland)
[**I This work was supported by the Swiss National Foundation (project
2.523.76).
208
Table 2. 'H- and 39Kcoupling constants [GI, a H and a K , respectively, for
the radical anions
( 4 ) * e , and ( 3 ) ' e .
'
aHu
p=
(4Ye
p = 6
(3)'"
aK
2, 5, 7 , 10
3, 4, 8, 9
11 (12)
4.16
3.80
1.I5
1.51
0.25 [a]
0.45 [b]
7
7.34 2.68
8
9
4
3
4.93 4.55 0.21 4.05
[a] Six methyl protons.
2
1
1.40 3.16
0.22
0.20
5
0.86 [a]
0.17
[b] Four methylene protons.
placed by that of a secondary paramagnetic species. This spectrum, which also appears on direct reduction of (3), has
been analyzed by the ENDOR
its hyperfine data
(Table 2) are fully consistent with the structure of the radical
anion (3).' [''I.
Starting from ( I ) , the ESR signals of both radical anions
were readily observed in the range of -100 to -70°C and
thus the kinetics of the valence isomerization ( I ) * e + ( 3 ) - 0
could be deduced from the changes in the signal intensities.
The pertinent activation parameters (Table 1) differ strikingly
from corresponding values for the rearrangement (1)- (3).
In the case of the radical anion, the rate constant k (25°C)
is higher by a factor of
and the activation enthalpy
AH* (25°C) lower by ca. 100 kJ/mol, than for the neutral
compound.
It has been concluded from the stereospecificity of the thermolysis of structurally related compounds of lower symmetry
that the isomerization ( I )+(3) proceeds concertedly["! On
the other hand, the considerable enhancement of the rate
constant for the radical anion can be easily rationalized if
one assumes the biradical ( 5 ) - and its reduced form ( 5 ) ~ ~
to be intermediates in (1)-(3) and (1)*0+(3)*e, respectively" ' I .
H35
(5)..
Beyond the mechanistic aspects, such an enhancement has
potential preparative applications. Reduction and subsequent
reoxidation would yield a valence isomer of the neutral compound under relatively mild conditions.
Angew. Chem. Int. Ed. Engl. 17 (1978) No. 3
Received: December 27, 1977;
revised: January 20, 1978 [Z 908 IE]
German version: Angew. Chem. 90,216 (1978)
CAS Registry numbers:
( I J, 38963-97-2; ( 1 J , radical anion, 65636-00-2; ( 3 J , 65635-99-6; (3J, radical
anion, 65701-69-1 ; (4J, radical anion, 65701-70-4
See, e.g., R . B. Woodward, R . Hoffmann, Angew. Chem. 81, 797 (1969);
Angew. Chem. Int. Ed. Engl. 8, 781 (1969).
S. F . Nelsen, J . P . Gillespie, J. Org. Chem. 38, 3592 (1973); J. Am.
Chem. SOC.95, 2940 (1973); N. L. Bauld, J . Cessac, C . S . Chang, F .
R . Farr, R . Holloway, ibid. 98, 4561 (1976).
E. Vogel, Pure Appl. Chem. 20, 237 (1969). E. de Cleur, Ph. D. thesis,
Universitat Koln 1969.
J . A. Berson, M . R . Willcott I l l , J. Am. Chem. SOC.87, 2752 (1965); 88,
2494 (1 966).
a) E. Vogel, personal communication; b) G . Jabs, Ph. D. thesis, Universitat Koln 1971.
These parameters agree within the limits of error with the corresponding
values in ref. [Sb].
Experimental details, in particular those concerning the ESR and
ENDOR spectra, will be published in a forthcoming paper.
F. Gerson, E. Heilbronner, W A . Boll, E. Vogel, Helv. Chim. Acta
48, 1494 (1965).
This finding also permits unequivocal assignment of the coupling constants to the two sets of four equivalent ring protons in
The assignment of the coupling constants to the eight single ring protons
in ( 3 p e is largely based on correlation with n-spin populations calculated according to the McLachlan procedure [ A . D. McLachlan, Mol.
Phys. 3 , 233 (1960)l.
F . G . Kliirner, unpublished work, quoted in ref. [Sb].
In contrast to ( 1 )-e where the additional electron occupies the lowest
antibonding orbital of one butadiene n-moiety, in ( 5 p e such an electron
enters the nonbonding orbital of the nonatetraenyl n-system. The difference in rr-energies (0.62p in the HMO model) would facilitate the
opening ofthe three-memberedring in the radical anion [ ( I J.e+(5)*e]
relative to the neutral compound [ ( l J + ( 5 Y ] and thus lower the
activation energy.
Regioselective Synthesis of Isomeric Bicyclic
Peroxides[**]
By Waldemar Adam, A . John Bloodworth, Henny J . Eggelte,
and Mark E . Loueittr]
Monocyclic peroxides ( 1 ) have recently been shown to
serve as useful synthons for the preparation of unusual organic
molecules1']. Equally importantly they constitute valuable precursors of the mechanistically interesting diradicals[']. The
geometrical contraint in bicyclic peroxides (2) is expected
to impart new synthetic and mechanistic behavior, but unfortunately no general and convenient methods are presently
available for the preparation of such compounds.
n
In this communication we describe potentially general
routes to isomeric bicyclic peroxides involving: a) reaction
[*] Prof. Dr. W. Adam [+I, Dr. H. J. Eggelte
Department of Chemistry, University of Puerto Rico
Rio Piedras, Puerto Rico 00931 (USA)
Prof. Dr. A. J. Bloodworth, Dr. M. E. Loveitt
Christopher Ingold Laboratories
University College, London WCIH OAJ (England)
['I Author to whom correspondence should be addressed.
[**I We acknowledge the financial support of the National Institute of
Health to W. A., the Science Research Council to M. E. L., and a FulbrightHays travel grant and a visiting professorship from the University of Puerto
Rico to A. J . 8 .
Angew. Chem. Int. Ed. Engl. 17 (1978J No. 3
of non-conjugated cyclic dienes with hydrogen peroxide and
mercury bis(trifluor0acetate) (peroxymercuration)followed by
reduction with NaBH4I3],and b) photooxygenation of conjugated cyclic dienes followed by reduction with azodicarboxylateC41.
These complementary and regioselective peroxybicyclizations are illustrated for the saturated compounds 9,lO-dioxabicyclo[3.3.2]decane (1,5-epidioxycyclooctane)( 6 a ) and 7,8dioxabicyclo[4.2.2]decane (1,4-epidioxycyclooctane)(6 b), respectively.
n
n-0
When the diene (3a) was added to a mixture of hydrogen
peroxide (85-95 %) and mercuric trifluoroacetate in CHZC12
at room temperature, equal amounts of the bicyclic peroxide
( 4 ) and the corresponding bicyclic ether were formed [use
of Hg(N03)2.H20[31
in this particular case affords only the
ether]. The products were separated by dissolving the mixture
in benzene, whereupon crystals of the pure (solvated) peroxide
were precipitatedc5].Reduction of ( 4 ) in CH2Clzwith NaBH4
in aqueous NaOH gave the previously unknown cyclic peroxide (6 a)[61, together with an approximately equal amount
of 4-cycloocten-1-01. Catalytic hydrogenation of ( 6 a ) over
Pd/C led quantitatively to the known cis-1,5-cyclooctanediolr7],m.p. 73-75°C.
On the other hand, photooxygenation of the diene ( 3 b )
in CH2C12 with tetraphenylporphyrin as sensitizer gave the
known['] unsaturated peroxide ( 5 ) , which on reduction with
azodicarb~xylate[~]
in methanol afforded the previously
unknown saturated peroxide (6 bjC9].Catalytic hydrogenation
of ( 6 b ) over PdjC gave quantitatively the known cis-1,4-cyclooctanediol["], m.p. 81-83 "C.
For the first time saturated bicyclic peroxides with mediumsized rings have become conveniently available from readily
accessible starting materials. Furthermore, ( 6 a ) is the first
bicyclic peroxide to be prepared that does not contain a
1,2-dioxane ring.
Received: December 27, 1977 [Z 91 1 IE]
German version: Angew. Chem. 90, 216 (1978)
[l] W Adam, Angew. Chem. 86, 683 (1974); Angew. Chem. Int. Ed. Engl.
13, 619 (1974).
[2] W Adam, J . Sanabia, Angew. Chem. 85, 914 (1973); Angew. Chem.
Int. Ed. Engl. 12, 843 (1973); L. Salem, C . Rowland, ibid. 84, 86 (1972)
and J I , 92 (1972), respectively.
131 A. J . Bloodworth, M . E. Loveitt, J. Chem. SOC.Chem. Commun. 1976,
94; 3. Chem. SOC.Perkin I 1978, in press.
141 W Adam, H . J . Eggelte, Angew. Chem. 89, 762 (1977); Angew. Chem.
Int. Ed. Engl. 16, 713 (1977).
[S] Solvated ( 4 J was isolated in 42 % yield, m.p. 118-1 19°C (dec.); elemental analysis indicated the presence of 0.81 equivalents of benzene.
NMR (CDCls, TMS): 6=128.6 (CeH,), 85.3, 48.4, 34.1, 29.1.
[6] ( 6 a J was isolated in 25 % yield by chromatography on SiO2/CH2CI2,
and purification by fractional sublimation (45"C/15 torr); m.p. 116118°C; 'H-NMR (CCI.,, TMS): 6=1.50-2.30 (m, 12H) 4.35-4.65
(m, 2H); "C-NMR (CDCls,TMS):6=83.96,31.38,23.82; MS: m/e= 142
(7 %), 55 (100).
209
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