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Mercury in organic chemistry. 19. Rhodium promoted methylation of organomercurials
0040-40~9/01/26244~-04~02.00/0
Tetrahedron Letters, V01.22, N0.26, pp 2443 - 2446, 1981 Printed in Great Britain
RHODIUM
MERCURY IN ORGANIC CHEMISTRY. 19. PROMOTED METHYLATION OF ORGANOMERCURIALS R. C. Larock*
Department
631981 Pergamon Press Ltd.
of Chemistry,
and S. S. Hershberger
Iowa State University,
Ames,
Iowa 50011
Summary: Alkenyl-, alkynyl- and arylmercurials are methylated in excellent yield upon treatment with stoichiometric amounts of CHaRhI2(PPha)z (1). Catalytic methylation of these organomercurials is possible using 1 and methyl iodide, but side reactions interfere.
Organomercurials availability, A number nately,
are attractive
stability,
of important
synthetic
and ability
synthetic
organic
to accommodate
applications
intermediates
substantial
due to their ready
organic
of these compounds
functionality. 1 are now known. Unfortu-
methods
often proceed dimerization'
for the alkylation of organomercurials have proven quite limited and 2-8 in low yield. Our previous success using rhodium catalysts in the 10 of alkenyl- and arylmercurials encouraged us to look at and carbonylation
the cross-coupling of organomercurials and alkyl halides using rhodium reagents. Semmelhackl 12 and Schwartz have previously reported that methylorganorhodium(II1) complexes undergo reductive
elimination
to afford
(eq. 11.
We reasoned
that similar mixed diorganorhodium(II1)
CH3Rh(R)XLn
by transmetallation reductive
methyl
-
should
of this approach
arenes
R-CH
of organorhodium(II1)
elimination
the success
cross-coupled
halides
afford cross-coupled to the alkylation
Our initial cross-coupling
efforts
+
R'HgX
A>
were devoted
+
olefins
species might
respectively
be generated
XRhLn
(1)
and organomercurials products.
(eq. 2).
Subsequent
We wish at this time to report
of organomercurials.
-HgX? RRhX2Ln
3
and methyl
RRh(R')XLn
to studying
-XRhL " d>
the optimal
R-R'
conditions
(2)
necessary
for
alkenylmercuric chlorides and readily available bis(triphenylphosphine)methyl13 Using thoroughly dried hexamethylphosphoramide (1) (eqs. 3,4).
di-iodorhodium(II1)
2443
2444
CH31
+
ClRh(PPh3)3
_____,
CH3RhI2(PPh3)2
(3)
1
RCH=CHHgCl
+
1
--up>
RCH=CHCH3
(HMPA) as a solvent
(1 ml per 0.1 mm01 of 1 and organomercurial),
chloride
and heating
(10 equiv)
excellent included
yields
also be methylated arylmercurials
to 7O'C for -24 hours under nitrogen,
of the corresponding
in the Table
in excellent
as well as the desired
+
yield
arene
and replacing
this side product
arene can be obtained electron
However,
donating
amounts
and HMPA.
the lithium
(entries 4-7). and electron
Unfortunately,
chloride
by methyl
withdrawing
to methylate product
to small amounts
(5)
drying the HMPA prior
iodide
(0.2 ml per 0.1 mm01
and excellent
appears general
groups,
can
Ar-H
eliminated
This reaction
alkylmercurials
+
By scrupulously
can be essentially
are
substitution
was traced
3
yields
dialkynylmercurials
in attempting
Ar-CH
lithium
one is able to obtain
of hydrogen
This difficulty
>
to each experiment
containing
(eq. 5).
excess
Some representative
these conditions,
significant
in the lithium chloride
organomercurials.
Using
1
of arylmercurial), methyl
olefin.
(entry 3).
afforded
methyl
ArHgCl
of water present
methyl
(entries 1 and 2).
this procedure
adding
(4)
yields
of
for arylmercurials
as well as heterocyclic
cannot be successfully
methylated
using
either of the above procedures. With the successful we turned
our attention
organomercurials
using
stoichiometric
methylation
to the catalytic 1 as a catalyst
of alkenyl-,
cross-coupling
of methyl
In theory
(eq. 6).
alkynyliodide
this approach
and arylmercurials, and these same should prove
cat. 1 RHgX
catalytic
in rhodium
+
CH3X
h>
(Scheme).
R-CH3
However,
(III) salts are known to catalyze
problems
the dimerization
+
Hg-X2
were envisioned
(6)
since rhodium(I)
of these same organomercurials.'
SCHEME HgX2
RHg,3;"cH3Rh'R'xL2~RCH3
cH3vx*L2 ‘CH3X
and In
2445
practice
alkenyl-
of cross-coupled
and arylmercurials products
turnovers
of 2-10).
(eq. 7).
Excellent
gave predominantly
(-20% yields).
However,
Using a dialkynylmercurial, results
have also recently
dimerization
the reactions
substantially been obtained
and only low yields
were catalytic
better
results
(catalyst
were obtained
in the catalyticcross-coupling
2% L [(CH3)3CC'C-12Hg
+
xs CH31 e
2(CH3)3CCfCCH3 70°C
of arylmercurials choice of organic of cross-coupled
and alkenyl
halides
(eq. 8).
organomercurial
halide, products
and rhodium
Table
1.
Methylation
catalyst
synthetically
is presently
useful yields
under examination.
>
Ar-CH=CH
(8)
2
of Organomercurials 70°C RHgCl
+
24 h >
1 HMPA
entry
likely that with the appropriate
I
H2C=CHBr
+
(7)
58-65%
It appears
This possibility
are feasible.
cat. Rh ArHgCl
24 h
organomercurial
added reagent
3
% yielda
product
1
C6H$H=CHHgCl
2
(CH3)3CCH=CHHgC1
KH3)3CCH=CHCH3
92
3
[(CH3j3CC:C-12Hg
(CH3)3CC:CCH3
9gb
4
C6H5HgCl
C6H5CH3
97
5
p-CH30C6H4HgC1
p-CH30C6H4CH3
97
6
m-CH302CC6H4HgC1
m-CH 0 CC H CH _ 32 64 3
91
7
a
LiCl
R-CH
CH31
C6H5CH=CHCH3
nCH S
97
99
3
2446
Acknowledgment:
The authors
of rhodium
trichloride
Department
of Health,
Professional
gratefully
essential Education
Opportunities
acknowledge
for this work. and Welfare
Johnson
Mathey
S. S. Hershberger
Inc. for a generous would
and Iowa State University
loan
like to thank the
for a Graduate
and
Fellowship.
REFERENCES
1.
Larock,
R. C. Angew.
2.
Kekulg,
A.; Franchimont,
3.
Whitmore,
4.
Schroeder,
5.
Gilman,
6.
Beletskaya,
I. P.; Vol'eva,
Proc. Acad.
Sci. USSR, Chem. Sec. 1972, 204,
Chem.,
Bergbreiter,
8.
Russell,
9.
Larock,
R. C.; Bernhardt,
10.
Larock,
R. C.; Hershberger,
11.
Semmelhack,
12.
Schwartz,
13.
Lawson,
V. B.; Reutov,
D. E.; Whitesides,
G. A.; Hershberger,
M. F.; Ryono,
3302-14.
0. A. Dokl. Akad. Nauk SSSR 1972, 204, 93-5; 383-5.
G. M. J. Am. Chem. Sot. 1974, 96, 4937-44.
J.; Owens, K. J. Am. Chem. SOC. 1979, 101,
1312-3.
J. C. J. Org. Chem. 1977, 42, 1680-4. S. S. J. Org. Chem. 1980, 45, 3840-6. L. Tetrahedron
J.; Hart, D. W.; Holden,
in USA
1491-1503.
R. Q. J. Am. Chem. Sot. 1938, 60, 751-3.
G. F. J. Am. Chem. Sot. 1933, 2,
D. N.; Osborn,
27-37.
E. N. J. Am. Chem. Sot. 1929, 2,
W. D.; Brewster,
7.
(Received
1978, z,
A. Chem. Ber. 1872, 2, 906-8.
F. C.; Thurman,
H.; Wright,
Int. Ed. Engl.
J. L. J. Am. Chem. Sot. 1972, 94, 9269-71.
J. A.; Wilkinson,
5 March 1981)
Lett. 1973, 2967-70.
G, J. Chem. Sot., A, 1966, 1733-6.
Tetrahedron Letters, V01.22, N0.26, pp 2443 - 2446, 1981 Printed in Great Britain
RHODIUM
MERCURY IN ORGANIC CHEMISTRY. 19. PROMOTED METHYLATION OF ORGANOMERCURIALS R. C. Larock*
Department
631981 Pergamon Press Ltd.
of Chemistry,
and S. S. Hershberger
Iowa State University,
Ames,
Iowa 50011
Summary: Alkenyl-, alkynyl- and arylmercurials are methylated in excellent yield upon treatment with stoichiometric amounts of CHaRhI2(PPha)z (1). Catalytic methylation of these organomercurials is possible using 1 and methyl iodide, but side reactions interfere.
Organomercurials availability, A number nately,
are attractive
stability,
of important
synthetic
and ability
synthetic
organic
to accommodate
applications
intermediates
substantial
due to their ready
organic
of these compounds
functionality. 1 are now known. Unfortu-
methods
often proceed dimerization'
for the alkylation of organomercurials have proven quite limited and 2-8 in low yield. Our previous success using rhodium catalysts in the 10 of alkenyl- and arylmercurials encouraged us to look at and carbonylation
the cross-coupling of organomercurials and alkyl halides using rhodium reagents. Semmelhackl 12 and Schwartz have previously reported that methylorganorhodium(II1) complexes undergo reductive
elimination
to afford
(eq. 11.
We reasoned
that similar mixed diorganorhodium(II1)
CH3Rh(R)XLn
by transmetallation reductive
methyl
-
should
of this approach
arenes
R-CH
of organorhodium(II1)
elimination
the success
cross-coupled
halides
afford cross-coupled to the alkylation
Our initial cross-coupling
efforts
+
R'HgX
A>
were devoted
+
olefins
species might
respectively
be generated
XRhLn
(1)
and organomercurials products.
(eq. 2).
Subsequent
We wish at this time to report
of organomercurials.
-HgX? RRhX2Ln
3
and methyl
RRh(R')XLn
to studying
-XRhL " d>
the optimal
R-R'
conditions
(2)
necessary
for
alkenylmercuric chlorides and readily available bis(triphenylphosphine)methyl13 Using thoroughly dried hexamethylphosphoramide (1) (eqs. 3,4).
di-iodorhodium(II1)
2443
2444
CH31
+
ClRh(PPh3)3
_____,
CH3RhI2(PPh3)2
(3)
1
RCH=CHHgCl
+
1
--up>
RCH=CHCH3
(HMPA) as a solvent
(1 ml per 0.1 mm01 of 1 and organomercurial),
chloride
and heating
(10 equiv)
excellent included
yields
also be methylated arylmercurials
to 7O'C for -24 hours under nitrogen,
of the corresponding
in the Table
in excellent
as well as the desired
+
yield
arene
and replacing
this side product
arene can be obtained electron
However,
donating
amounts
and HMPA.
the lithium
(entries 4-7). and electron
Unfortunately,
chloride
by methyl
withdrawing
to methylate product
to small amounts
(5)
drying the HMPA prior
iodide
(0.2 ml per 0.1 mm01
and excellent
appears general
groups,
can
Ar-H
eliminated
This reaction
alkylmercurials
+
By scrupulously
can be essentially
are
substitution
was traced
3
yields
dialkynylmercurials
in attempting
Ar-CH
lithium
one is able to obtain
of hydrogen
This difficulty
>
to each experiment
containing
(eq. 5).
excess
Some representative
these conditions,
significant
in the lithium chloride
organomercurials.
Using
1
of arylmercurial), methyl
olefin.
(entry 3).
afforded
methyl
ArHgCl
of water present
methyl
(entries 1 and 2).
this procedure
adding
(4)
yields
of
for arylmercurials
as well as heterocyclic
cannot be successfully
methylated
using
either of the above procedures. With the successful we turned
our attention
organomercurials
using
stoichiometric
methylation
to the catalytic 1 as a catalyst
of alkenyl-,
cross-coupling
of methyl
In theory
(eq. 6).
alkynyliodide
this approach
and arylmercurials, and these same should prove
cat. 1 RHgX
catalytic
in rhodium
+
CH3X
h>
(Scheme).
R-CH3
However,
(III) salts are known to catalyze
problems
the dimerization
+
Hg-X2
were envisioned
(6)
since rhodium(I)
of these same organomercurials.'
SCHEME HgX2
RHg,3;"cH3Rh'R'xL2~RCH3
cH3vx*L2 ‘CH3X
and In
2445
practice
alkenyl-
of cross-coupled
and arylmercurials products
turnovers
of 2-10).
(eq. 7).
Excellent
gave predominantly
(-20% yields).
However,
Using a dialkynylmercurial, results
have also recently
dimerization
the reactions
substantially been obtained
and only low yields
were catalytic
better
results
(catalyst
were obtained
in the catalyticcross-coupling
2% L [(CH3)3CC'C-12Hg
+
xs CH31 e
2(CH3)3CCfCCH3 70°C
of arylmercurials choice of organic of cross-coupled
and alkenyl
halides
(eq. 8).
organomercurial
halide, products
and rhodium
Table
1.
Methylation
catalyst
synthetically
is presently
useful yields
under examination.
>
Ar-CH=CH
(8)
2
of Organomercurials 70°C RHgCl
+
24 h >
1 HMPA
entry
likely that with the appropriate
I
H2C=CHBr
+
(7)
58-65%
It appears
This possibility
are feasible.
cat. Rh ArHgCl
24 h
organomercurial
added reagent
3
% yielda
product
1
C6H$H=CHHgCl
2
(CH3)3CCH=CHHgC1
KH3)3CCH=CHCH3
92
3
[(CH3j3CC:C-12Hg
(CH3)3CC:CCH3
9gb
4
C6H5HgCl
C6H5CH3
97
5
p-CH30C6H4HgC1
p-CH30C6H4CH3
97
6
m-CH302CC6H4HgC1
m-CH 0 CC H CH _ 32 64 3
91
7
a
LiCl
R-CH
CH31
C6H5CH=CHCH3
nCH S
97
99
3
2446
Acknowledgment:
The authors
of rhodium
trichloride
Department
of Health,
Professional
gratefully
essential Education
Opportunities
acknowledge
for this work. and Welfare
Johnson
Mathey
S. S. Hershberger
Inc. for a generous would
and Iowa State University
loan
like to thank the
for a Graduate
and
Fellowship.
REFERENCES
1.
Larock,
R. C. Angew.
2.
Kekulg,
A.; Franchimont,
3.
Whitmore,
4.
Schroeder,
5.
Gilman,
6.
Beletskaya,
I. P.; Vol'eva,
Proc. Acad.
Sci. USSR, Chem. Sec. 1972, 204,
Chem.,
Bergbreiter,
8.
Russell,
9.
Larock,
R. C.; Bernhardt,
10.
Larock,
R. C.; Hershberger,
11.
Semmelhack,
12.
Schwartz,
13.
Lawson,
V. B.; Reutov,
D. E.; Whitesides,
G. A.; Hershberger,
M. F.; Ryono,
3302-14.
0. A. Dokl. Akad. Nauk SSSR 1972, 204, 93-5; 383-5.
G. M. J. Am. Chem. Sot. 1974, 96, 4937-44.
J.; Owens, K. J. Am. Chem. SOC. 1979, 101,
1312-3.
J. C. J. Org. Chem. 1977, 42, 1680-4. S. S. J. Org. Chem. 1980, 45, 3840-6. L. Tetrahedron
J.; Hart, D. W.; Holden,
in USA
1491-1503.
R. Q. J. Am. Chem. Sot. 1938, 60, 751-3.
G. F. J. Am. Chem. Sot. 1933, 2,
D. N.; Osborn,
27-37.
E. N. J. Am. Chem. Sot. 1929, 2,
W. D.; Brewster,
7.
(Received
1978, z,
A. Chem. Ber. 1872, 2, 906-8.
F. C.; Thurman,
H.; Wright,
Int. Ed. Engl.
J. L. J. Am. Chem. Sot. 1972, 94, 9269-71.
J. A.; Wilkinson,
5 March 1981)
Lett. 1973, 2967-70.
G, J. Chem. Sot., A, 1966, 1733-6.