C60
Journal of Organometallic Chemistry. 194 (1980) C6O-C62 0 Elsevier SequoiaS.A.,Lausanne-PrintedinTheNetherlands
Preliminary
Communication
SOME EFFECTS OF TRIFLUOROEIETHANESLJLPHONICACID ON >IERCURATION
IN TRIFLUOROACETIC
G. 5. Deacon
Chemistry
and
M. F. O'Donoghue
Department,
(Received
June
With
3rd,
suitzble
University,
Clayton,
choice
acid
of
with
conditions,
mercuration
added
2,5-dimercuration,
tetramercurated acid
Monash
alone
anisole
gives
Victoria
3168
(Australia)
1980)
in trifluoroacetic predominant
ACID
of
2,3,5_trimercuration,
in short
3-mercuration,
I-methoxybenzoic
trifluoromethanesulphonic
reaction
times,
or
acid formation
whereas
3.5~dimercuration
or,
can
use
with
of
acid give
2,3,4,5-
of trifluoroacetic
long
reaction
times,
2,3,Strimercuration.
Addition
of
fluoroacetate sulphonate proceeds
trifluoromethanesulphonic
in trifluoroacetic Cl].
Mercwation
far more
readily
though
this
compound
report
that
use
benzoic
acid
hanced
leads
1:4)
2).
(cF~sO~H:
of
By
and
of the with main
3).
The
expected
mercurating
ipso
trifluoroacetic
(scheme
when
2,5-dimercurated kinetically ions
acid.
after
favolured 5 min
Presumably,
acid
species
gave
121.
We
of
now
4-methoxy-
product,
to en-
(decarboxylation).
15 min
yielded,
of unchanged
appears
for
acid 15 min
as the
was
gave,
principal
to result
3.5~dimercurated
from
isomer,
after
(mole bromc-
anisic
of a carboxyl
group
acid, acid
added after
brorm-
product rearrangement
since
3,5-dibromo-4-methoxybenzoic
coordination
reagent
3,5-dibromo-4-methoxybenzoic
reaction
tri-
111, even
trifluoroacetate
trifluoromethanesulphonic a similar
3:5,v/v),
agent
mercuric
for
this
alone
dimercuration
a mixture
1) and
with
in mercuration
mercuration
with
acid
product,
acid
contrast,
compounds
the preferred
acid
of mercuric
trifluoromethane-
trifluoroacetate
acid
2,5-dibromo-4-methoxybenzoic
tribromide dibromo
excellent
to enhanced
the mercuration
cf3c02H=
demercuration, (scheme
an
mercuric
of 4-methoxybenzoic
3-bromo-4-methoxybenzoic (scheme
with
to a change.in
in refluxing
to a solution merEuric
of polyfluoroaromatic than
is itself
polymarcuration
demercuration
acid generates
of trifluoromethanesulphonic
Mercuration ratio
acid
cleavage acid
as the i-. 1s
to CF3.S03Hg
C61
more
thermodynamically
second
CF,SO3Eig+
Scheme
than
C02H
=OP
1.
R1,
2.
1 2 R,R,R,
3.
R1,
R2,
R3,
R3,
R4,
acid
R=,
R6=H;
R6=Br;
X=cF3C02
R4,
R6=H;
R2=HgX;
R5=Br;
X=CF3S03
R
2
15 min
gave,
benzoic
acid
some reactions
6~1,
followed
by
after
treatment
5 min.
with
acid
after
was
:CE3C02H
acid
indicative
decarboxylation not ratio
mercuration
bromodemercuration
(ipso
of major to
lrl
became
was
ratio
tribromide
acid (scheme
of 6:l
ions
v/v),
mercuration)
was
(v/v)
with
substantial
a mercuric the
2,3,4,5-tetqbromoanisole
OMe
C02H
following
(scheme after
1).
180
min.
of trifluororeaction
for
of polymercuration.
observed
However,
and
the
tri-
2,3,5-tribromo-4-methoxy-
enhancement
significance.
and
addition
a similar
predominantly of major
21,
With
3
in boiling
gave
acid
(scheme
4).
(CF3S03H:CF3C02H=3:5,
41,
mole
2 or CF3S0
3-bromo-4-methoxybenzoic
bromodemercuration,
(scheme
or CF3S03
X=CFaCO
:.nrene
trifluoroacetate
3.5-dibromo-4-methoxybenzoic
but
ipso
R4 , R6=Br;
, R5=H;
2,3,5-tribromo-4-methoxybenzoic methanesulphonic
to a
X=CF3C02
R3=HgX:
products:
15 min.
group
C02H
R5,R;
R1 , R3=HgX:
fluoroacetic
n&zboxy
4
of a mercuric
principal
of the
group.
OMe
Use
CF3S03H
coordination
OMe
4.
after
stable
in all
on
salt:
arene
predominant (scheme
the
increasing mole
foregoing the rati0
product
of
after
5).
0Me
OMe
Ggx
EL
X=CF3S03 At
this
to the
stage, methoxy
4-methoxybenzoic in mercurating
it is difficult group. acid both
to see
Certainly, (scheme
positions
the
why
4) suggests or&o
the
ready
one
vacant
formation
that
to methoxy.
there
of
position
should
be
or%
2,3,5_trimercurated
is no
intrinsic
difficulty
C62 A complicating substantial predominantly this
is in the
solution
Cur
show
in trifluoroacetic
ation
reactions
is the
polymercurated
4-methoxybenzoic
insoluble
fraction,
occurrence
acid
though
of partial
In the
arenes.
(scheme
it is also
reaction
31,
the
bulk
the main
or giving of
component
phase.
results
sulphonic
in all of the
2.5-dimercurated
product
of the
factor
precipitation
acid.
that
acid This
of mercuric
the
scope
is greatly
differing
and
of mercuration
enhanced
by
increased
trifluoromethanesulphonate
by mercuric
addition
trifluoroacetate
of trifluoromethane-
reactivity,
resulting
Cl], is to be
further
from
form-
explored.
A&nowledgement We Bristol
are
grateful
to Dr.
for
an authentic
J.F.W.
sample
of
McCXnie,
School
of Chemistry,
University
2,3,4,5-tetrabromoanisole.
References l_
G-B.
Deacon
2.
H.C.
Brown
see
also
Roberts,
and and
C.W.
D. Tunaley, R.A.
Fung,
J. Chem.
Wirkkala,
J. Organometal. J. Amer.
M. Khorramdel-Vahed,
Sot.
Perkin
Trans.
Chem.,
Chem.
Sot.,
R.J.
II, (1980)
156 88
Ranson, 267.
(1978) (1966) and
403_ 1447;
R.M.G.
of