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The transition metal complex induced rearrangement of bicyclo[2.1.0]pentane to cyclopentene
TetrahedronLetters No. 20, pp. 1643-1646,1971. PergamonPress. Printed in Great Britain.
THE TRANSITIONMETAL CMPJXX INLUCEDBEARFMGEMENTOF BICYCLO[2.l.C]PENTANE TO CYCMPEETEEE Paul G. Gasmnm, Thomas J. Atkins,* audJ. pevor Lmb Departmnt of Chemistry,Ihe Ohio State University,Columbus,Ohio 43210 (Receivedin USA 1 March 1971; receivedin UK for publication5 April 1971) Cyclobutaneto diolefintrausfcmations prauotedby transition-metal compounds,such as 1-s the isomerisationof quadricyclauesto norbornadienes and of cube type moleculestoring 495 cleaved products, have recently attractedcmsiderable attention. Lately,we' and others have exploredthe related iscmsrizationsof derivativesof bicyclo[l.l.O]bu+ae, such as that exemplifiedby the stereospecificconversionof &to 2 on addition of rhodium dicsrbonylchloride dimer or dichlaotricarbonylruthenium dinr?r.eWe now wish to report
CH3
H
-
I
the first example of the transition-a&alpranoted ismerization of a simple bicyclo[2.1.0]pentane. Bicyclo[2.1.0]peutaneneY (I) possessessurprisingthermal stability. It can be pepared pyrolyticallyfrm 2,J-diazabicyclo[2.2.l]hept-2-ene (k, at 200' with no detectable 9 therm& isomerisaticn. Criegee reported'that rwas isomerizedto cyclopentene(2) in the vicinity of 33Oo. We have now found that bicyclo[2.l.O]pentaue is extremelylabile in
it NationalScience Foundatim Trainee,1968-1971 1643
No.20
1644
3oo” I
c \
2ooe l
t N
d
5
a
cl 5
5
[RhNDj$l]2 t
I 250 10
When zwas treatedwith 5 mol $ of
the presence of rhodium dicarbonylchloridedimer.
rhodium dicarbanylchloridedimer in either acetonitiileor chloroformat 25" (roan temperature), ismrization to 2 occurredwith a half-lifeof ca. 8 hr. At 65O, no trace of 1 could be detectedafter 48 hr in the presence of 2 mol$ of transitionmotel compound. Vpc analysis indicatedthat the isomerizatianof rto swas quantitative. In order to study some of the mechanisticaspectsof this facile rearrengementwe Synthesisof gaccording to litera-
desired certain isotopicallylabelledversions of > 11
12
ture procedures followedby pyrolysisat 200' gave a 2.9:1 mixture of land 5
& 0
17 -
D
N
HA
Ir-
O&q+ H@ HH 7
6
& 12
radiation of 6 in an n-butanolglass at ca. -70" gave a 1.3:lmixture of x&d
g.
Syn-
thesis of 5,5-dideuteriobicyclo[2.l.O]pentane (2) was accomplishedthrough the reaction of
+
ICD2ZnCt$I
D
b !x!
9
3
D
13
cyclobutene(l-0) with &&.
This proceduregave materialwhich was 84% dideuterated.
1645
No.20
When we subjectedeither the 2.9:1 mixture of Iand 5
the l.3:1
mixture of 2. and 5
or
zto rhodium dicarbonylchloridedimer, we found that the same mixture of deuteratedcyclopenteneswas found. and s
For instance,it was shown by nmr spectroscopythat both mixtures,
gave cyclopsntenein which the ratio of vinylic hydrogensto hydrcgenson saturated
carbon was ~3.21
+ o.G9.
A purely random distributionof the two deuteriumswould have
given a ratio of 1:3, assuming no deuteriumisotope effect on the ratio. It was demonstrated that the observedratio was not due to rearrangementfollowedby scramblingof the free 12
deuteratedcyclopentenes,through the subjectionof l-deuteriocyclopentene (12)
to the
reacticm conditions. After four half-lives,no isomerizationof 12 could be detected. This indicatedthat the deuteriumscramblingmust have occurredat an intermediatestage, when the transitim metal complexwas associatedwith the C&
moiety, and before the
cyclopentenewas freed from the transitionmetal complex. Our studies indicatethat ring systemswith ccmsiderahlyless strain energy than quadricyclanes,cubanes,and bicyclo[l.l.O]butenes are susceptibleto reerrangermntsprcrmoted by transitionmetal complexes. Furthermore,our isotope studies indicatethat extensive rearrangementlnayrapidly follow the initial cleavageof the strainedring system.
A_.
We are indebtedto the NationalScience Foundationand to the Alfred
P. Sloan Foundationfor support of this investigation.
REFERENCES 1. H. Hogeveen and H. C. Volger, J. Amer. Chem. Sot., 83 2486 (1967);F. D. Mango and J. H. Schachtschneider, ibid., _, 89 2484 (1967);F. D. Mango, Advan. Catsl., l& 291 (1%9), and referencescontainedtherein. 2. P. G. Gassnmn and D. S. Patton, J. Amer. Chem. Sot., a D. H. Aue, and D. S. Patton, m, 93 7271 (1968). 3.
L. Cassar and J. Halpern, Chem. Corns., E,
7276 (1968)+P. G. Gassman,
1082, and referencescontainedtherein.
4. L. Cassar, P. E. Eaton, and J. Hslpern, J. Amer. Chem. Sot., & referencescontainedtherein. 5.
J. Wristers, L. Rrener, and R. Pettit, ibid., & therein.
6.
P. G. Gassman and F. J. Williams,s,
_, 92
6366 (19’70),
and
7499 (1970),and referencescontained
7631 (m’o).
1646
7.
L. A. Paquette,G. R. Allen, Jr., and R. P. Henzel, a
92 7002 (1970).
8.
R. Criegee and A. Rimmelin,Chem. Ber., 93 414 (1954).
9.
P. G. Gassman and K. T. Mansfield,Org. Syn., 2, 1 (1969).
10.
This work was presentedin part before the 13th Conferenceon ReactionMechanisms, Santa Cruz, Calif., June 23-26, 1970.
IL
W. Roth and M. Martin, Ann;, m
12.
The details of the preparationof this materialwill.be presentedin the full paper on this subject.
13.
The Focedure used was a modificationof that of G. Wittig and F. Wingler, Chem..Ber., ?& 2146 (1964), describedfor the preparationof 2
1 (1967).
THE TRANSITIONMETAL CMPJXX INLUCEDBEARFMGEMENTOF BICYCLO[2.l.C]PENTANE TO CYCMPEETEEE Paul G. Gasmnm, Thomas J. Atkins,* audJ. pevor Lmb Departmnt of Chemistry,Ihe Ohio State University,Columbus,Ohio 43210 (Receivedin USA 1 March 1971; receivedin UK for publication5 April 1971) Cyclobutaneto diolefintrausfcmations prauotedby transition-metal compounds,such as 1-s the isomerisationof quadricyclauesto norbornadienes and of cube type moleculestoring 495 cleaved products, have recently attractedcmsiderable attention. Lately,we' and others have exploredthe related iscmsrizationsof derivativesof bicyclo[l.l.O]bu+ae, such as that exemplifiedby the stereospecificconversionof &to 2 on addition of rhodium dicsrbonylchloride dimer or dichlaotricarbonylruthenium dinr?r.eWe now wish to report
CH3
H
-
I
the first example of the transition-a&alpranoted ismerization of a simple bicyclo[2.1.0]pentane. Bicyclo[2.1.0]peutaneneY (I) possessessurprisingthermal stability. It can be pepared pyrolyticallyfrm 2,J-diazabicyclo[2.2.l]hept-2-ene (k, at 200' with no detectable 9 therm& isomerisaticn. Criegee reported'that rwas isomerizedto cyclopentene(2) in the vicinity of 33Oo. We have now found that bicyclo[2.l.O]pentaue is extremelylabile in
it NationalScience Foundatim Trainee,1968-1971 1643
No.20
1644
3oo” I
c \
2ooe l
t N
d
5
a
cl 5
5
[RhNDj$l]2 t
I 250 10
When zwas treatedwith 5 mol $ of
the presence of rhodium dicarbonylchloridedimer.
rhodium dicarbanylchloridedimer in either acetonitiileor chloroformat 25" (roan temperature), ismrization to 2 occurredwith a half-lifeof ca. 8 hr. At 65O, no trace of 1 could be detectedafter 48 hr in the presence of 2 mol$ of transitionmotel compound. Vpc analysis indicatedthat the isomerizatianof rto swas quantitative. In order to study some of the mechanisticaspectsof this facile rearrengementwe Synthesisof gaccording to litera-
desired certain isotopicallylabelledversions of > 11
12
ture procedures followedby pyrolysisat 200' gave a 2.9:1 mixture of land 5
& 0
17 -
D
N
HA
Ir-
O&q+ H@ HH 7
6
& 12
radiation of 6 in an n-butanolglass at ca. -70" gave a 1.3:lmixture of x&d
g.
Syn-
thesis of 5,5-dideuteriobicyclo[2.l.O]pentane (2) was accomplishedthrough the reaction of
+
ICD2ZnCt$I
D
b !x!
9
3
D
13
cyclobutene(l-0) with &&.
This proceduregave materialwhich was 84% dideuterated.
1645
No.20
When we subjectedeither the 2.9:1 mixture of Iand 5
the l.3:1
mixture of 2. and 5
or
zto rhodium dicarbonylchloridedimer, we found that the same mixture of deuteratedcyclopenteneswas found. and s
For instance,it was shown by nmr spectroscopythat both mixtures,
gave cyclopsntenein which the ratio of vinylic hydrogensto hydrcgenson saturated
carbon was ~3.21
+ o.G9.
A purely random distributionof the two deuteriumswould have
given a ratio of 1:3, assuming no deuteriumisotope effect on the ratio. It was demonstrated that the observedratio was not due to rearrangementfollowedby scramblingof the free 12
deuteratedcyclopentenes,through the subjectionof l-deuteriocyclopentene (12)
to the
reacticm conditions. After four half-lives,no isomerizationof 12 could be detected. This indicatedthat the deuteriumscramblingmust have occurredat an intermediatestage, when the transitim metal complexwas associatedwith the C&
moiety, and before the
cyclopentenewas freed from the transitionmetal complex. Our studies indicatethat ring systemswith ccmsiderahlyless strain energy than quadricyclanes,cubanes,and bicyclo[l.l.O]butenes are susceptibleto reerrangermntsprcrmoted by transitionmetal complexes. Furthermore,our isotope studies indicatethat extensive rearrangementlnayrapidly follow the initial cleavageof the strainedring system.
A_.
We are indebtedto the NationalScience Foundationand to the Alfred
P. Sloan Foundationfor support of this investigation.
REFERENCES 1. H. Hogeveen and H. C. Volger, J. Amer. Chem. Sot., 83 2486 (1967);F. D. Mango and J. H. Schachtschneider, ibid., _, 89 2484 (1967);F. D. Mango, Advan. Catsl., l& 291 (1%9), and referencescontainedtherein. 2. P. G. Gassnmn and D. S. Patton, J. Amer. Chem. Sot., a D. H. Aue, and D. S. Patton, m, 93 7271 (1968). 3.
L. Cassar and J. Halpern, Chem. Corns., E,
7276 (1968)+P. G. Gassman,
1082, and referencescontainedtherein.
4. L. Cassar, P. E. Eaton, and J. Hslpern, J. Amer. Chem. Sot., & referencescontainedtherein. 5.
J. Wristers, L. Rrener, and R. Pettit, ibid., & therein.
6.
P. G. Gassman and F. J. Williams,s,
_, 92
6366 (19’70),
and
7499 (1970),and referencescontained
7631 (m’o).
1646
7.
L. A. Paquette,G. R. Allen, Jr., and R. P. Henzel, a
92 7002 (1970).
8.
R. Criegee and A. Rimmelin,Chem. Ber., 93 414 (1954).
9.
P. G. Gassman and K. T. Mansfield,Org. Syn., 2, 1 (1969).
10.
This work was presentedin part before the 13th Conferenceon ReactionMechanisms, Santa Cruz, Calif., June 23-26, 1970.
IL
W. Roth and M. Martin, Ann;, m
12.
The details of the preparationof this materialwill.be presentedin the full paper on this subject.
13.
The Focedure used was a modificationof that of G. Wittig and F. Wingler, Chem..Ber., ?& 2146 (1964), describedfor the preparationof 2
1 (1967).