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The komppa synthesis of camphoric acid
TetrahedronLetters No.12, pp. 1415-1417,1968. Pergmon Press. Printed in Gre8tBritain.
THE KOMPPA SYNTHESIS OF CAMPHORIC ACID K. Aghoramurthy
and (Miss) P. M. Lewis
("Shell" Research Limited, Egham, Surrey) (Receivedin IX 8
1967)
December
During the period 1909-1912 certain aspects of Komppa's synthesis of camphoric
acid were discussed, with the implication that the work was not
above criticism
(l-5).
The bone of contention was a crystalline
melting at 85-88' which is the' all-important
intermediate
It was obtained from methyl diketo=camphorate iodide in the presence of sodium methoxide structure of a C-methyl
derivative
Thorpe and Blanc
derivative
that cold aqueous alkali slowly hydrolysed in an amount corresponding
(I) by methylation with methyl
and Komppa assigned to it the
(II) (1).
asserted that it must be the g-methyl
substance
in the synthesis.
(2), however,
(III) since they observed
it to the extent of 90%, to give
to 50"/.and @8-dimethylglutaric
(I)
acid corresponding
to a further 40%, without yielding any aS8-trimethylglutaric
acid.
Since
Komppa prepared camphoric acid from the substance melting at 85-88O, the yields claimed for the synthesis were considered to be open to doubt.
P co/c-yy&
e*/c-Y2;e
cq
co,
/“Me
CH-C02Me
CH-C0214e II
I In reply
,cxMe
III
(3) Komppa pointed out that his critics had not attempted to
reduce the ester melting at 85-88O according to his directions. controversy experimental camphorate,
ended with an admission by Thorpe and Blanc
The
(4) that "under the
conditions used by Komppa for the reduction of methyl diketothe methyl group remains attached to the carbon.
his synthetical
Our criticism of
formation of camphoric acid is therefore baseless".
more was said about the supposed O-methyl compound
Nothing
(III) and no explanation
was given for the results of their hydrolysis experiments. In view of this unsatisfactory
state of affairs and since it cannot be
1415
1416
No.12
ruled out that the 0-methylation
had indeed occurred in the first instance,
but that the methyl group had migrated influence of hydriodic
from oxygen to carbon under the
acid used in the subsequent reduction,as
suggested by 0
Pickles
(5), it was considered desirable to re-examine the ester, m-p. 85-88 ,
with the aid of NMR. Methyl diketoscamphorate prepared
(I) and methyl diketocamphorate According
as described by Komppa.
has the structure assigned to it by Komppa. entirely
Both compounds
of methyl diketozcamphorate
methyl S-methoxy-4-ketodehydrocamphorate obtain a good analysis
(II)
(I and II) are
Komppa also isolated a neutral compound from
in the enolic form,
the methylation
(II) were
to the NMR spectrum, compound
(IV).
and this he considered to be Though he was unable to
(c, H) of this compound, his structural assignment has
now also been shown by NMR to be correct. H C COOCH3 3 0 H3C H3C
OCH 3 ;c1 COOCH3 IV
The chemical shifts
(r)
in the NNR spectra of compounds
(I), (II) and
(IV) taken in Ccl4 as solvent with TN8 as the internal standard are presented in the Table below.
The chemical shifts are accurate to .02 ppm. TABLE Protons
Compound
Compound
I
II
enol H
2
.05
6
6.13
CH3
6
8.65
enol H
CH3 IV
7
CH3 (Ester)
CH3 (Ester) w
Compound
Total NO. of Protons
0.59 3
6.09
3
6.38
6
8.76
CH3 Ester CH3
3
8.72
3
6.03
0 CH3
3
6.22
Ester CH3
3
6.37
3
8.76
3
8.78
3
8.83
CH3 ,,
No.12
1417
In an attempt to find out how Thorpe and Blanc obtained the hydrolysis product with aqueous alkali, their experiment was repeated. insufficient dissolved
experimental
Owing to
details, viz. "the substance melting at 85-88O was
in cold aqueous potassium hydroxide
and a large excess of strong
alkali was added, etc.", it could not be duplicated exactly. treatment
of methyl diketocamphorate
solution of potassium hydroxide deposition
of a crystalline
of methyl diketocamphorate could not be detected
However,
with a twentyfold excess of a 40%
at room temperature
for 1 hour,caused
the
solid which was found to be the potassium
salt
(recovery 84%), and methyl diketowcsmphorate
in the mother liquor.
The authors thank Sir Robert Robinson for drawing their attention to this problem. References 1.
G. Komppa, Annalen, 368, 126 (1909);
2.
J. F. Thorpe and G. L. Blanc, 2. e.
3.
G. Komppa, 2. w.
4.
J. F. Thorpe and G. L. Blanc, w.,
5.
S. Pickles, Discussion
e.,
E,
370, 209 (1909) B.,
97,
836 (1910)
29 (1912) 2010
in Proc. Chem. Sot., 2&,
84 (1910)
THE KOMPPA SYNTHESIS OF CAMPHORIC ACID K. Aghoramurthy
and (Miss) P. M. Lewis
("Shell" Research Limited, Egham, Surrey) (Receivedin IX 8
1967)
December
During the period 1909-1912 certain aspects of Komppa's synthesis of camphoric
acid were discussed, with the implication that the work was not
above criticism
(l-5).
The bone of contention was a crystalline
melting at 85-88' which is the' all-important
intermediate
It was obtained from methyl diketo=camphorate iodide in the presence of sodium methoxide structure of a C-methyl
derivative
Thorpe and Blanc
derivative
that cold aqueous alkali slowly hydrolysed in an amount corresponding
(I) by methylation with methyl
and Komppa assigned to it the
(II) (1).
asserted that it must be the g-methyl
substance
in the synthesis.
(2), however,
(III) since they observed
it to the extent of 90%, to give
to 50"/.and @8-dimethylglutaric
(I)
acid corresponding
to a further 40%, without yielding any aS8-trimethylglutaric
acid.
Since
Komppa prepared camphoric acid from the substance melting at 85-88O, the yields claimed for the synthesis were considered to be open to doubt.
P co/c-yy&
e*/c-Y2;e
cq
co,
/“Me
CH-C02Me
CH-C0214e II
I In reply
,cxMe
III
(3) Komppa pointed out that his critics had not attempted to
reduce the ester melting at 85-88O according to his directions. controversy experimental camphorate,
ended with an admission by Thorpe and Blanc
The
(4) that "under the
conditions used by Komppa for the reduction of methyl diketothe methyl group remains attached to the carbon.
his synthetical
Our criticism of
formation of camphoric acid is therefore baseless".
more was said about the supposed O-methyl compound
Nothing
(III) and no explanation
was given for the results of their hydrolysis experiments. In view of this unsatisfactory
state of affairs and since it cannot be
1415
1416
No.12
ruled out that the 0-methylation
had indeed occurred in the first instance,
but that the methyl group had migrated influence of hydriodic
from oxygen to carbon under the
acid used in the subsequent reduction,as
suggested by 0
Pickles
(5), it was considered desirable to re-examine the ester, m-p. 85-88 ,
with the aid of NMR. Methyl diketoscamphorate prepared
(I) and methyl diketocamphorate According
as described by Komppa.
has the structure assigned to it by Komppa. entirely
Both compounds
of methyl diketozcamphorate
methyl S-methoxy-4-ketodehydrocamphorate obtain a good analysis
(II)
(I and II) are
Komppa also isolated a neutral compound from
in the enolic form,
the methylation
(II) were
to the NMR spectrum, compound
(IV).
and this he considered to be Though he was unable to
(c, H) of this compound, his structural assignment has
now also been shown by NMR to be correct. H C COOCH3 3 0 H3C H3C
OCH 3 ;c1 COOCH3 IV
The chemical shifts
(r)
in the NNR spectra of compounds
(I), (II) and
(IV) taken in Ccl4 as solvent with TN8 as the internal standard are presented in the Table below.
The chemical shifts are accurate to .02 ppm. TABLE Protons
Compound
Compound
I
II
enol H
2
.05
6
6.13
CH3
6
8.65
enol H
CH3 IV
7
CH3 (Ester)
CH3 (Ester) w
Compound
Total NO. of Protons
0.59 3
6.09
3
6.38
6
8.76
CH3 Ester CH3
3
8.72
3
6.03
0 CH3
3
6.22
Ester CH3
3
6.37
3
8.76
3
8.78
3
8.83
CH3 ,,
No.12
1417
In an attempt to find out how Thorpe and Blanc obtained the hydrolysis product with aqueous alkali, their experiment was repeated. insufficient dissolved
experimental
Owing to
details, viz. "the substance melting at 85-88O was
in cold aqueous potassium hydroxide
and a large excess of strong
alkali was added, etc.", it could not be duplicated exactly. treatment
of methyl diketocamphorate
solution of potassium hydroxide deposition
of a crystalline
of methyl diketocamphorate could not be detected
However,
with a twentyfold excess of a 40%
at room temperature
for 1 hour,caused
the
solid which was found to be the potassium
salt
(recovery 84%), and methyl diketowcsmphorate
in the mother liquor.
The authors thank Sir Robert Robinson for drawing their attention to this problem. References 1.
G. Komppa, Annalen, 368, 126 (1909);
2.
J. F. Thorpe and G. L. Blanc, 2. e.
3.
G. Komppa, 2. w.
4.
J. F. Thorpe and G. L. Blanc, w.,
5.
S. Pickles, Discussion
e.,
E,
370, 209 (1909) B.,
97,
836 (1910)
29 (1912) 2010
in Proc. Chem. Sot., 2&,
84 (1910)