- Email: [email protected]
Stereochemistry of Migrating Carbon In Wagner-Meerwein rearrangement
Tetrahedron
LettersNo. 33, pp 3123 - 9126, 1973.
Pergwm Pros.. PrilltediaQeat%itai&
Stereochemistry of Migrating Carbon in Wagner-Meerweln rearrangement T. Shono, IC.Fujlta and S. Kumal Department of Synthetic Chemistry, Kyoto University Kyoto, Japan (Receiwdin JaPan2 JUM 1973,receivedin UK for publioatica 5 July 1973) Mechanism of Wagner-Meerweln rearrangement11
,
especially the rearrangement
of P-phenylethyl cation and norbonyl cation system, has been vastly studied on the basis of klnetlcs and stereochemistry of the migrating origin and terminus. On the other hand, the rearrangement was scarcely discussed from the standpoint of'the stereochemlcal behavior (retention or inversion) of the migrating carbon Itself.
From kinetic data, the migrating saturated carbon was suggest-
ed to attain a coordination number of five in the transition statela (The typical examples seem to be 1 or 2).
Although the configuration retention of
a substituted cyclohexyl group was observed In the rearrangement of the rigid system, 3 lf , such a stereoohemlcal result seems not to be general, since the migrating carbon was a member of a relatively rigid cyclic system.
Thus, a
direct and general study on the stereochemistry of the migrating carbon Is considered to be necessary and interesting. We wlch to report the first observatlon of the retention of configuration of the migratlrq carbon in the rearrangement of a system where the configuration of the carbon skeleton Is relatively free and the mlgratlxg site 1s asymmetric.
a
9 1 $
@ CH2
L
2 3123
3
05%
mo. 33
3124
An optically aotlve amlne,42,whlahwae prepared from d-cltronella13 (Soheme X) was deamlnated by the treatment with nitrous aold. rized In Scheme I14.
The result Is summa-
The product formation was easily explicable by the alkyl
or hydrogen migration to the P-aatlon (Scheme III).
The product,J, yielded
from the migration of the asymmetric oarbon was oxidized by chromlo acid to give a ketone,95, which showed the same optical activity as an authentic ketones whloh was prepared from d-oltronellal (optlcal purity 81.37) (Scheme IV).
The
result shows that the stereochemistry of the migrating oarbon was oompletely (10%) retained and suggests that the Wagner-Meerweln rearrangement of an alkyl group Involves neither the oomplete separation of the migrating group from both of the migrating origin and terminus nor the "pivot" type transition state,2, which would bring about the Inversion of asymmetry, but the partial bonded transltlon state such as I( the "slither" type). This seems to be the first direct and general evldenoe for the HoffmannWoodward prediction' that (~0s + r2s) (1) will be allowed whlle@Os
+ a2a] (2)
will be forbidden In the thermal reaction. Further more, this result 1s consistent with the retention of stereoohemlstry of migrating carbon In Beckman rearrangementsorin Baeyer-Vllllger OxldatlOn?
4
5 (11.8%)
6 (7.4%) Scheme II
1 (7.4%)
8 (73.4~)
3125
Rc. 33
iSt?l a
4-
H 0
CH3
a
5
b
6
A
?
Scheme III
9 Scheme IV
Beferences (1) (a) M. Stiles and B. P. Mayer, J. Amer. Chem. Sec., &.. 1497 (1957).
(b)
Y. Pocker,"Molecular Rearrangement", INTERSCIiQXE PUBLISHERS, NEW YORK, 1963 p 1.
(c) J. A. Berson,ibib_.,1963. P 111.
(a) J. B. Owen and W. H.
Saunders, Jr., J. Amer. Chem. SOC., 83 5809 (1966).
(e) J. W. Wilt, C. A.
Schneider, J. P. Berliner and H. F. Dabek, Jr., Tetrahedron Lett., 4073 (1966) (1968).
(f ) W. E. Parham and L. J. Czuba,
wAmer.,
z,
(g) J. A. Thompson and D. J. Cram, &Q&&., &1775
(1969).
4296 (1969).
(j) m.,&
429i (1969).
Harper and P. V. R. Schleyer, ibid., B, S. Winstein, Ibid., xf, 4300. 5043 (1972). *.,
&
(n) _Ibid., 2,
315 (1971).
(h)
(1) m.,
C. J. Lancelot and P. V. R. Schleyer, ibid_,9l, 4291 (1969). g
4C?C
(k) C. J. Lancelot, J. J.
4294 (1969).
(1) A. F. Dlaz and
(m) H. C. Brown and d. J. Kim, m,Xj4, 5051 (1972).
(0) C. J. Collins, Accounts Chem
(p) T. Shono, K. Fujita, K. Kumai, T. Watanabe and
I. Nlshlguchl, Tetrahedron Lett., 3249 (1972).
And Literatures cited there
In. (2) 4: bp 59-61“ (4mm) ; &(neat)
3500-3100 cm-' : nmr (CC&) T7.59
multiplet) 8.17-8.95 (9H, multiplet), 9.11 (12H, doublet). analysis agreed with the calculated value.
(2H,
The elemental
On the basis of the optical
purity of the starting material (cltronellal), the specific rotation of 4 was calculated to be 8.6 ((a];') (C=7.'L5,methanol).
3126
No. 33
(3) The startingmaterial,cltronellal,was compoundof 8.l.3$of d-enantlomer
and 38.7,~of 1-enantlomer. (4) The product,5 + 6 , p and 8, were Isolatedby the preparativevapour Phase chromatography(PEG 2oM). 2H, doublet).
7rI)uc (neat) 3600-3100cm“ ; nmr (Ccl*) 6.58 (
7.75 (IH, multlplet),8.00-8.96 (9H, multiplet),9.11 (12H,
doublet);mass spectrum (m/e) 154 (M+- H20) (The molecularpeak was not detected). B:l)~~(neat) 3600-3150om+ ; nmr (CC14)T8.17-8.97(8H, multlplet), 8.90 (6H, singlet),9.11 (9H, doublet);mass spectrum (m/e) 157 ( M+-CHs),59 &!(CHJ)pOH)(The moleoularpeak was not detected).
I and 6
could separatedby the oxidationto the oorrespondlngketones !see a footnote (5)). (5)
The ketone, 9, was separated from the ethyl ketone derived from 6 by the pre-
parativevapour phase ohromatography(PEG 20M).
9r)ho
(neat) 1715cni': nmr
(CC14)T7.58-7.87 (2H, multlplet),7.97(3H,singlet),8.03-8.94 (8H, multiplet),9.11 (9H, doublet);mass spectrum(m/e)17O(M+),43 (CHa$O), (4,":60.0" (c34.50,methanol),(a)$;
41.7O.
The ethyl ketone derived from
6 showed rlho(neat)1715cm";nmr(CCl4)27.30-7.83 (lH, multlplet),7.60 (2H, quartet),8.13-8.45(1H,multlplet),8.45-9.37(12H,superimposedabsorption), 9.06(6H,doublet) [a]t",643.8'. (a)g$b-74.5(C=1.14, methanol). (6) On the basis of the optloal purity of the startingmaterlal(citronellal), the spealficrotationof 9 was calculatedto be 66.5O ([a$!b) or 95.8°@)g%) (7) B. B. Woodwardand R. Hoffmann, "The conservationof Orbital Symmetry", Verlag Chemie, GmbH.'Welnheln/Bergstr., 1970, p 170 (8) (a) A. Campbell and J. Kenyon, and D. P. Young, m.,
J. Chem. Soo., 25 (1946).
(b) J. Kenyon
263 (1941).
(9) K. Mlslow and J. Brenner, J. Amer. Chem. Sot., 75, 2319 (1953). Y
LettersNo. 33, pp 3123 - 9126, 1973.
Pergwm Pros.. PrilltediaQeat%itai&
Stereochemistry of Migrating Carbon in Wagner-Meerweln rearrangement T. Shono, IC.Fujlta and S. Kumal Department of Synthetic Chemistry, Kyoto University Kyoto, Japan (Receiwdin JaPan2 JUM 1973,receivedin UK for publioatica 5 July 1973) Mechanism of Wagner-Meerweln rearrangement11
,
especially the rearrangement
of P-phenylethyl cation and norbonyl cation system, has been vastly studied on the basis of klnetlcs and stereochemistry of the migrating origin and terminus. On the other hand, the rearrangement was scarcely discussed from the standpoint of'the stereochemlcal behavior (retention or inversion) of the migrating carbon Itself.
From kinetic data, the migrating saturated carbon was suggest-
ed to attain a coordination number of five in the transition statela (The typical examples seem to be 1 or 2).
Although the configuration retention of
a substituted cyclohexyl group was observed In the rearrangement of the rigid system, 3 lf , such a stereoohemlcal result seems not to be general, since the migrating carbon was a member of a relatively rigid cyclic system.
Thus, a
direct and general study on the stereochemistry of the migrating carbon Is considered to be necessary and interesting. We wlch to report the first observatlon of the retention of configuration of the migratlrq carbon in the rearrangement of a system where the configuration of the carbon skeleton Is relatively free and the mlgratlxg site 1s asymmetric.
a
9 1 $
@ CH2
L
2 3123
3
05%
mo. 33
3124
An optically aotlve amlne,42,whlahwae prepared from d-cltronella13 (Soheme X) was deamlnated by the treatment with nitrous aold. rized In Scheme I14.
The result Is summa-
The product formation was easily explicable by the alkyl
or hydrogen migration to the P-aatlon (Scheme III).
The product,J, yielded
from the migration of the asymmetric oarbon was oxidized by chromlo acid to give a ketone,95, which showed the same optical activity as an authentic ketones whloh was prepared from d-oltronellal (optlcal purity 81.37) (Scheme IV).
The
result shows that the stereochemistry of the migrating oarbon was oompletely (10%) retained and suggests that the Wagner-Meerweln rearrangement of an alkyl group Involves neither the oomplete separation of the migrating group from both of the migrating origin and terminus nor the "pivot" type transition state,2, which would bring about the Inversion of asymmetry, but the partial bonded transltlon state such as I( the "slither" type). This seems to be the first direct and general evldenoe for the HoffmannWoodward prediction' that (~0s + r2s) (1) will be allowed whlle@Os
+ a2a] (2)
will be forbidden In the thermal reaction. Further more, this result 1s consistent with the retention of stereoohemlstry of migrating carbon In Beckman rearrangementsorin Baeyer-Vllllger OxldatlOn?
4
5 (11.8%)
6 (7.4%) Scheme II
1 (7.4%)
8 (73.4~)
3125
Rc. 33
iSt?l a
4-
H 0
CH3
a
5
b
6
A
?
Scheme III
9 Scheme IV
Beferences (1) (a) M. Stiles and B. P. Mayer, J. Amer. Chem. Sec., &.. 1497 (1957).
(b)
Y. Pocker,"Molecular Rearrangement", INTERSCIiQXE PUBLISHERS, NEW YORK, 1963 p 1.
(c) J. A. Berson,ibib_.,1963. P 111.
(a) J. B. Owen and W. H.
Saunders, Jr., J. Amer. Chem. SOC., 83 5809 (1966).
(e) J. W. Wilt, C. A.
Schneider, J. P. Berliner and H. F. Dabek, Jr., Tetrahedron Lett., 4073 (1966) (1968).
(f ) W. E. Parham and L. J. Czuba,
wAmer.,
z,
(g) J. A. Thompson and D. J. Cram, &Q&&., &1775
(1969).
4296 (1969).
(j) m.,&
429i (1969).
Harper and P. V. R. Schleyer, ibid., B, S. Winstein, Ibid., xf, 4300. 5043 (1972). *.,
&
(n) _Ibid., 2,
315 (1971).
(h)
(1) m.,
C. J. Lancelot and P. V. R. Schleyer, ibid_,9l, 4291 (1969). g
4C?C
(k) C. J. Lancelot, J. J.
4294 (1969).
(1) A. F. Dlaz and
(m) H. C. Brown and d. J. Kim, m,Xj4, 5051 (1972).
(0) C. J. Collins, Accounts Chem
(p) T. Shono, K. Fujita, K. Kumai, T. Watanabe and
I. Nlshlguchl, Tetrahedron Lett., 3249 (1972).
And Literatures cited there
In. (2) 4: bp 59-61“ (4mm) ; &(neat)
3500-3100 cm-' : nmr (CC&) T7.59
multiplet) 8.17-8.95 (9H, multiplet), 9.11 (12H, doublet). analysis agreed with the calculated value.
(2H,
The elemental
On the basis of the optical
purity of the starting material (cltronellal), the specific rotation of 4 was calculated to be 8.6 ((a];') (C=7.'L5,methanol).
3126
No. 33
(3) The startingmaterial,cltronellal,was compoundof 8.l.3$of d-enantlomer
and 38.7,~of 1-enantlomer. (4) The product,5 + 6 , p and 8, were Isolatedby the preparativevapour Phase chromatography(PEG 2oM). 2H, doublet).
7rI)uc (neat) 3600-3100cm“ ; nmr (Ccl*) 6.58 (
7.75 (IH, multlplet),8.00-8.96 (9H, multiplet),9.11 (12H,
doublet);mass spectrum (m/e) 154 (M+- H20) (The molecularpeak was not detected). B:l)~~(neat) 3600-3150om+ ; nmr (CC14)T8.17-8.97(8H, multlplet), 8.90 (6H, singlet),9.11 (9H, doublet);mass spectrum (m/e) 157 ( M+-CHs),59 &!(CHJ)pOH)(The moleoularpeak was not detected).
I and 6
could separatedby the oxidationto the oorrespondlngketones !see a footnote (5)). (5)
The ketone, 9, was separated from the ethyl ketone derived from 6 by the pre-
parativevapour phase ohromatography(PEG 20M).
9r)ho
(neat) 1715cni': nmr
(CC14)T7.58-7.87 (2H, multlplet),7.97(3H,singlet),8.03-8.94 (8H, multiplet),9.11 (9H, doublet);mass spectrum(m/e)17O(M+),43 (CHa$O), (4,":60.0" (c34.50,methanol),(a)$;
41.7O.
The ethyl ketone derived from
6 showed rlho(neat)1715cm";nmr(CCl4)27.30-7.83 (lH, multlplet),7.60 (2H, quartet),8.13-8.45(1H,multlplet),8.45-9.37(12H,superimposedabsorption), 9.06(6H,doublet) [a]t",643.8'. (a)g$b-74.5(C=1.14, methanol). (6) On the basis of the optloal purity of the startingmaterlal(citronellal), the spealficrotationof 9 was calculatedto be 66.5O ([a$!b) or 95.8°@)g%) (7) B. B. Woodwardand R. Hoffmann, "The conservationof Orbital Symmetry", Verlag Chemie, GmbH.'Welnheln/Bergstr., 1970, p 170 (8) (a) A. Campbell and J. Kenyon, and D. P. Young, m.,
J. Chem. Soo., 25 (1946).
(b) J. Kenyon
263 (1941).
(9) K. Mlslow and J. Brenner, J. Amer. Chem. Sot., 75, 2319 (1953). Y