6
190 Sun et al.
Asian J. Chem.
FeCl
acid and alcohol as a dispersing agent, the solution was heated
to boiling and the FeCl was hydrolyzed, then nano-iron
3
was dissolved in water as the precursor, by adding tartaric
TABLE-2
EFFECTS OF THE DIFFERENT BASES TO THE REACTION
a
OH
O
COOMe
3
5
mol % Fe(OH)3
hydroxide sol was obtained.Aging ferric hydroxide sol at 50 ºC
for 72 h, the iron hydroxide turned into dry gel. The dry gel
was used as a catalyst directly.
+
Cl
COOMe
0 oC, 6h, DMF
8
b
Entry
Base
NaOH
Na PO
Na PO /K CO (10 mol %)
GC Yield (%)
Typical procedure for the catalytic reactions: 0.47 g
phenol (5 mmol, 1 eq.), 0.48 mL methyl chloroacetate (5.5
mmol, 1.1 eq.), 26.7 mg nanosized ferric hydroxide (0.25
1
2
3
4
5
6
0
35
46
80
98
90
3
4
3
4
2
3
K CO3
2
2 3 2 3
mmol, 5 mol %), 82.7 mg K CO and 572 mg Na CO (1.2 eq.
Na CO /K CO (10 mol%)
2
3
2
3
base) and 2 mL DMF were added to a sealed tube. The reaction
mixture was then heated at 80 ºC for 6 h under magnetic stirring.
After cooling, the mixture was diluted to 50.0 mL by adding
Na CO3
2
a
A mixture of 5 mmol phenol, methyl chloroacetate 5.5 mmol, 1.2 eq.
K CO (10 mol %)/Na CO and 2 mL DMF was heated at 80 ºC for 6 h.
The yield was determined by gas chromatography.
2
3
2
3
b
2 2
CH Cl . The resulting solution was separated in two parts: 5 mL
was added 100 mg n-bromo dodecane as internal standard for
GC analysis and others was washed with water and dried over
anhydrate sodium sulphate. After the solvent was evaporated,
the residue was purified by flash chromatography then
phenoxyacetic methyl ester was obtained as colourless oil. The
TABLE-3
EFFECTS OF THE DIFFERENT
TEMPERATURE AND REACTION TIME
OH
O
COOMe
1
product was identified by H NMR and then was used as stan-
5 mol % Fe(OH)3
+
Cl
COOMe
1
dard material to correct GC peak area. The calculated GC yield
was 98 %.
0% K CO -Na CO ,
2
3
DMF
2
3
Entry
Temperature (ºC)
Time (h)
GC Yield (%)
RESULTS AND DISCUSSION
1
2
3
4
5
6
7
60
80
6
6
48
98
84
38
56
98
75
First, we examine the impact of different iron compounds
as catalysts on the reaction. The results are listed in Table-1.
Various iron compounds have catalytic activity. Without cata-
lyst the production of phenoxy acetic acid methyl ester was
only 25 %, while the use of ferric chloride, ferric sulphate as a
catalyst, high yield of 80-90 % were obtained, respectively.
The catalytic activity of ferric oxide, ferrous sulphate, ferric
acetylacetonate is poor to give the moderate yield. Among the
ferric catalyst, nanosized ferric hydroxide gave the best results
of the reaction. It catalyzed the cross-coupling reaction of
phenol and methyl chloroacetate to give methyl phenoxy
acetate in almost quantitative yield.
100
80
6
1
80
3
80
6
80
12
equal molar producing of hydrogen halide generated in the
reaction. We find that the effect of alkali type is also evident,
especially to the yield and selectivity. Strong base such as
NaOH, Na
, entry 1, 2). With the alkaline reducing, the production yield
is better.
3 4
PO are unfavorable factors for the reactions (Table-
2
TABLE-1
CROSS-COUPLING OF PHENOL WITH METHYL
CHLOROACETATE CATALYZED BY FERRIC
Both of the pure potassium carbonate and sodium carbo-
nate is acceptable base, but the highest yield was obtained
when a mixture base was used. The alkaline of pure sodium
carbonate is a little weak and that of pure potassium carbonate
is a little strong. So they are not the best choice. While, the
mixed base containing 10 mol % of potassium carbonate gave
the best results. Contrastively, the sodium phosphate is a strong
base, when the mixture of sodium phosphate and potassium
carbonate was used, lower yield of 46 % was obtained. It is
better than pure sodium phosphate but worse than potassium
carbonate. It is conformed that the alkaline of adding base is a
key factor for the C-O cross-coupling, especially when an
alkali sensible substrate is employed.
a
OH
O
COOMe
5
mol % [Fe] cat.
0 oC, 6h, DMF
+
Cl
COOMe
8
b
Entry
Catalyst
Fe O
Yield (%)
1
2
3
4
5
6
7
40
90
80
98
54
35
25
2
3
FeCl3
Fe (SO )
4 3
2
Fe(OH)3
FeSO4
Fe(acac)3
No Cat.
a
In addition, we also explored the optimal reaction tempe-
rature and reaction time (Table-3). Low reaction temperature
caused the incomplete conversion of starting material and the
side reactions occur while the temperature is too high. To
determine the best reaction time is similar to that of the tempe-
rature, the reaction should be stopped at a suitable time in
order to get best selectivity of target product. The results show
that the reaction gives the best result at 80 ºC for 6 h with
A mixture of 5 mmol phenol, methyl chloroacetate 5.5 mmol, 1.2 eq.
K CO (10 mol %)/Na CO and 2 mL DMF was heated at 80 ºC for 6 h.
The yield was determined by gas chromatography.
2
3
2
3
b
In order to exert nanosized ferric hydroxide's best
catalytic activity, the reaction conditions were then optimized.
Specifically, we investigated the influence of reaction tempe-
rature, reaction time, the addition of alkali and other various
factors on the catalytic reaction. The results are summarized
in Tables 2 and 3. The addition of alkali is necessary for the
98 % yield.