Recyclable Organomolybdenum
Lewis Acid Catalyst and Microwave
Assisted Pechmann Condensation
Reactions
Student : Chia-Pei Chung
Supervisor : Prof. Shuchun Joyce Yu
2006 / 07 / 20
Department of Chemistry & Biochemistry
Chung Cheng University
1
Pechmann Condensation
O
OH
+
Phenol
O
2 eq. AlCl3, PhNO2
OEt
O
O
100 ~ 130 oC
4h
Ethyl acetoacetate
80%

The Pechmann condensation is a synthesis of
coumarins, starting from a phenol and a ester or
carboxylic acid containing a β-carbonyl group.

Coumarin synthesis
Woodruff, E. H. Organic Syntheses, 1944, 24, 69.
Pechmann, H. V.; Duisberg, C. Ber. 1883, 16, 2119.
2
Coumarins
8a
O
As additives to food and cosmetics,
optical brightening agents, and
dispersed fluorescent and laser dyes

has clinical value as the precursor for
several anticoagulants, antibacterial,
anticancer

can be synthesized by one of such
methods as the Claisen
rearrangement, Perkin reaction,
Knoevenagel condensation,
Reformatsky reaction, Wittig reactions,
as well as the Pechmann
Condensation reaction
3
4a
5

O
2
6
present in seeds, root, and leaves of
many plant species
1
8
7

4
benzo-2-pyrone
3
Acidic Catalysts for Pechmann Condensation

Proton Donor Brønsted Acids
H2SO4, HCl, TFA (trifluoroacetic acid)
Pechmann V. H.; Duisberg C. Chem. Ber. 1884, 17, 929.
Woods, L. L.; Sapp, J. J. Org. Chem. 1962, 27, 3703.

Traditional Lewis Acid Catalysts
InCl3, AlCl3, BiCl3, FeCl3, TiCl4, ZrCl4, P2O5, PCl3, POCl3
Bose, D. S.; Rudradas, A. P.; Babu, M. H. Tetrahedron Lett. 2002, 43, 9195.
S. K. De, R. A. Gibbs, Synthesis, 2005, 1231.
Simmonis, H.; Remmert, P. Chem. Ber. 1914, 47, 2229.
Robertson, A.; Sandrock, W. F.; Henry, C. B. J. Chem. Soc. 1931, 2426.
4
Acidic Catalysts for
Pechmann Condensation -- continued

Lanthanide Lewis Acid Catalysts
Yb(III), Sm(III)
Fillion, E. et. al. J. Org. Chem. 2006, 71, 409.
Bahekar, S. S.; Shinde, D. B. Tetrahedron Lett. 2004, 45, 7999.

Others
graphite / montmorillonite K10
Amberlyst-15, Nafion
Heteropoly acid (H6P2W18O62．24H2O)
Fre`re, S.; Thie´ry, V.; Besson, T. Tetrahedron Lett. 2001, 42, 2791.
Sabou, R.; Hoelderich, W. F.; Ramprasad, D.; Weinand, R. J. Catal. 2005, 232, 34.
Laufer, M. C.; Hausmann, H.; Hölderich, W. F. J. Catal. 2003, 218, 315.
Autino, J. C. et. al. Tetrahedron Lett. 2004, 45, 8935.
5
TFA Catalyzed Pechmann Condensation
O
O
TFA
3.5 e.q.
OH
+
R
phenol
O
O
R
OEt
reflux
0.25 ~ 20 h
£]-carbonyl ester
30% ~100%
Phenol used: Phloroglucinol, 2-Methylresorcinol, Resorcinol, Orcinol,
4-Chlororesorcinol, Pyrogallol, 3-Hydroxydiphenyl amine
β-carbonyl esters used: Ethyl benzoyl acetate
Woods, L. L.; Sapp, J. J. Org. Chem. 1962, 27, 3703.
6
Indium(III) Chloride Catalyzed
Pechmann Condensation
O
OH
+
R
phenol
InCl3
(10 mol%)
O
OEt
ethyl acetoacetate
O
O
R
65 ~ 130 oC
30 ~ 240 min
55% ~ 98%
Phenol used: Resorcinol, Orcinol, 4-, Pyrogallol, 3-Hydroxydiphenyl amine,
3-methoxyphenol, 1,3,5-trihydroxybenzene, phenol, 1-naphthol
Bose, D. S.; Rudradas, A. P.; Babu, M. H. Tetrahedron Lett. 2002, 43, 9195.
7
POCl3 Catalyzed Pechmann Condensation
in Neutral Ionic Liquids
OH
O
+
R
phenol
POCl3
(30 mol%)
O
O
O
R
OEt
ethyl acetoacetate
[bmim]PF6
30 ~ 100 oC, 40 ~ 60 min
47% ~ 95%
Phenol used: Resorcinol, 2-Methylresorcinol, Orcinol, Pyrogallol,
1,3,5-trihydroxybenzene, 2',4'-Dihydroxyacetophenone
Potdar, M. K.; Rasalkar, M. S.; Mohile, S. S.; Salunkhe, M. M. J. Mol. Catal. A Chem. 2005, 235, 249.
8
Yb(OTf)3 Catalyzed Pechmann
Condensation
OH
R
Yb(OTf)3
(10 mol%)
OMe O
+
H
O
O
O
O
O
R
CH3NO2
100oC, 1.5h
31% ~ 88%
Phenol used: 3,5-dimethoxyphenol, 3,4-dimethoxyphenol, sesamol,
3-methoxy-2-methylphenol
Fillion, E. et. al. J. Org. Chem. 2006, 71, 409.
9
Microwave acceleration of the Pechmann
reaction on graphite/montmorillonite K10
O
H2N
OH
Experimental
conditions
+
H3CO
COOCH3
O
130oC
OCH3
H2N
O
Conventional heating
O
O
Microwave irradiation
Reaction time
(min)
Yield
(%)
Reaction time
(min)
Yield
(%)
Neat (fusion)
120
36
85
39
Support: graphite
120
44
50
44
Support:
graphite:K10 (2:1)a, b
66
64
30
66
a. No modifications were observed when a preliminary activation (2 h at 180°C) of the clay was
realized.
b. No significant results were observed in the absence of graphite (montmorillonite K10 +
phenol + b-ketoester).
10
Fre`re, S.; Thie´ry, V.; Besson, T. Tetrahedron Lett. 2001, 42, 2791.
Wells–Dawson heteropolyacid Catalyzed
Pechmann Condensation
OH
R
H6P2W18O62¡D24H2O
O
+
COOEt
H3C
X
X = H, CH3
1 mol%
toluene, reflux
or
sovent-free, 130oC
O
O
R
X
CH3
38% ~ 97%
Phenol used: resorcinol, phloroglucinol, 3-methoxyphenol, pyrogallol,
3,4-dimethylphenol, 3-methylphenol, orcinol, 1-naphthol
Romanelli,G. P.; Bennardi, D.; Ruiz, D. M.; Baronetti, G.; Thomas, H. J.; Autino, J. C.
Tetrahedron Lett. 2004, 45, 8935.
11
Synthesis of Coumarins by Grubbs’ Catalyst
O
O
5 mol% Grubbs' catalyst
O
O
CH2Cl2, reflux, 24 h
70%
Me N
N Me
Cl
Ru
Cl
Ph
PCy3
Grubbs' catalyst
Van, T. N.; Debenedetti, S.; Kimpe, N. D.
Tetrahedron Lett. 2003, 44, 4199.
12
Disadvantages of Brønsted Acids

Proton Donor Brønsted Acids
– Catalysts have to be used in excess, for example sulfuric
acid, 10–12 equiv, trifluoroacetic acid, 3–4 equiv.
– Longer reaction time and very often temperatures to be
excess 150 oC and above.
– Their corrosive nature and the formation of several side
products make them difficult to handle.
– The disposal of acidic waste leads to environmental
pollution.
13
Disadvantages of Traditional and
Lanthanide Lewis Acid

Traditional Lewis Acid Catalysts
– Many chlorinated derivatives are highly moisture sensitive and
hydrolyse rapidly under conventional storage or standard
reaction conditions.
– The disposal of acidic waste leads to environmental pollution.
– Can not control electronic and steric environments around
metal Lewis acid center.

Lanthanide Lewis Acid Catalysts
– Lanthanide metals are relatively rare.
14
Motivation

Low Oxidation State Transition Metals
– Relatively high moisture – and oxygen – stability
– Inexpensive
– Tunable electronic and steric environments around metal
center

Green Chemistry
– Greener solvents
R.T. ionic liquids, [Bmim]PF6
– Energy saving
Catalysis under microwave flash heating
replace thermal heating
– Recyclable catalyst
15
Preparation of Organomolybdenum Catalyst

Thermal conditions
CO
O
Mo
OC
P
P
CO
CO
N
N
O
CO
OC
reflux (82oC) / 18 hr
dry CH3CN
80% yield
N
OC
P
N
CO
OC
2+
P
2 eq NOBF4
Mo
OC
CO
OC
O
N
0oC / stir 1 hr
dry CH3NO2
75% yield
N
Mo
O
N
N
N
N
N
(BF4-)2
N
Mo
OC
NO
ON
16
Crotonaldehyde-Lewis Acid Adduct
L.A.
O
1
H
1
H
H3
2
H
CH3
H3
4
H
H2
O
H1
H3
CH34
H2
O
H1
H
H
L.A.
H3
CH3
4
O
2
2
CH3
L.A.
1
L.A.
O
H1
L.A.
H3
H3
CH34
4
1H
chemical shift
O
L.A.
H2
CH34
H1
H2
H3
H4
crotonaldehyde
9.41 6.08
7.01
2.03
crotonaldehyde + Cat.
9.89 6.71
8.14
2.32
Chemical shift diff.
0.48 0.63
1.13
0.29
Childs, R. F. et. al. Can. J. Chem. 1982, 60, 801.
17
Lewis acid
△δ on H3 (ppm)
BBr3
1.49
AlCl3
1.23
[OP(2-Py)3W(CO)(NO)2](SbF6)2
1.23
[OP(2-Py)3W(CO)(NO)2](BF4)2
1.22
[P(2-Py)3W(CO)(NO)2](SbF6)2
1.21
[HOC(2-Py)3W(CO)(NO)2](SbF6)2
1.19
[P(2-Py)3W(CO)(NO)2](BF4)2
1.18
BF3
1.17
AlEtCl2
1.15
[OP(2-Py)3Mo(CO)(NO)2](BF4)2
1.13
[HC(2-Py)3Mo(CO)(NO)2](SbF6)2
1.05
TiCl4
1.03
[P(2-Py)3Mo(CO)(NO)2](BF4)2
0.99
[Me3P(CO)3(NO)W]+
0.93
SnCl4
0.87
[CpMo(CO)2]+(PF6)
0.70
Et3Al
0.63
[CpFe(CO)2]+BF4
0.54
18
Spectral Data of CO Coordinated Catalysts
Organometallic
compound
chemical shift
(13C NMR)
[OP(2-py)3W(CO)(NO)2](BF4)2
190.5 ppm
2156 cm-1/ nujol
[P(2-py)3W(CO)(NO)2](SbF6)2
192.0 ppm
2143 cm-1/ nujol
[P(2-py)3W(CO)(NO)2](BF4)2
192.2 ppm
2148 cm-1/KBr
Vapor CO
IR
absorption band
2143 cm-1
Mo(CO)6
202.3 ppm
2115,1983 cm-1/nujol
W(CO)6
192.1 ppm
2110,1980 cm-1/KBr
[OP(2-py)3Mo(CO)(NO)2](BF4)2
223.0 ppm
2060 cm-1/KBr
[P(2-py)3Mo(CO)(NO)2](BF4)2
222.0 ppm
2046cm-1/KBr
OP(2-py)3Mo(CO)3
227.5 ppm
1910,1806 cm-1/nujol
P(2-py)3Mo(CO)3
227.3 ppm
1908,1797cm-1/CD3Cl
OP(2-py)3W(CO)3
222.1 ppm
1890 cm-1/ nujol
P(2-py)3W(CO)3
222.9 ppm
1880,1762 cm-1/KBr
19
Organomolybdenum Lewis Acid Catalyzed
Pechmann Condensation

Thermal conditions
OH
O
[O=P(2-py)3Mo(CO)(NO)2](BF4)2
1 mol%
O
+
R
OEt
phenol
O
O
R
120 oC, neat or 0.5 ml solvent
ethyl acetoacetate
Solvent system: [bmim]PF6 or CH3CN or DMF or CH3NO2 or THF
OH
OH
HO
OH
HO
HO
OH
HO
O
O
3-methoxyphenol
OH
2-methylresorcinol
HO
OH
3,5-dimethoxyphenol
OH
Orcinol
OH
O
OH
HO
OH
1,3,5-trihydroxybenzene
Pyrogallol
Resorcinol
OH
H2N
O
OH
O
3-aminophenol
sesamol
NO2
1-naphthol
OH
OH
O2N
Phenol
2-nitrophenol
4-nitrophenol
20
Ionic Liquids
Seddon, K. R. et. al. Pure Appl. Chem. 2000, 72, 2275.
21
Coordinative Characteristics of Various
Anions
basic/ strongly
coordinating
AcONO3SO42Cl-
neutral/
weakly
coordinating
SbF6BF4PF6-
acidic/
coordination
acidic/noncoordinating
Al2Cl7AlCl4-
Al3Cl10-
CuCl2-
Cu2Cl3Cu3Cl4-
Wasserscheid, P., et. al. Angew. Chem. Int. Ed. 2000, 39, 3772.
22
Room temperature ionic liquids exhibit many
properties which make them potentially attractive
media for homogeneous catalysis:

They have essentially no vapour pressure.

They generally have reasonable thermal stability.

They are able to dissolve a wide range of organic,
inorganic and organometallic compounds.

The solubility of gases.

They are immiscible with some organic solvents.

Ionic liquids have been referred to as ‘designer
solvents’ by a suitable choice of cation / anion.
23
OH
O
+
R
Entry
OH
11
n. d.
O
7
Yield
(%)
Phenol
OH
n. d.
O
n. d.
Entry
OH
6
OH
OH
Yield
(%)
Phenol
O
n. d.
HO
R
OEt
Yield
(%)
1
2
O
ethyl acetoacetate
Phenol
HO
O
no catalyst
120 oC, 48 h, neat
phenol
Entry
O
NO2
n. d.
OH
12
n. d.
OH
OH
HO
3
4
5
n. d.
HO
OH
HO
OH
HO
OH
8
O
OH
n. d.
O
n. d.
9
H2N
OH
13
n. d.
O2N
n. d.
OH
n. d.
10
n. d.
24
OH
O
+
R
phenol
OEt
[O=P(2-py)3Mo(CO)(NO)2](BF4)2
1 mol%
Phenol
HO
OH
O
O
R
120 oC, neat
ethyl acetoacetate
Entry
1
O
Time
Yield
(%)
Entry
1h
98
8
Phenol
HO
O
Time
(h)
Yield
(%)
10 h
82
4h
84
24 h
81
24 h
n. d.
24 h
n. d.
24 h
n. d.
O
OH
2
HO
OH
OH
3
HO
4
OH
HO
OH
HO
OH
5
6
25
min
15
min
15
min
OH
O
O
9
OH
OH
75
10
OH
69
11
NO2
4h
O
80
H2N
10 h
69
93
12
OH
OH
13
O2N
7
5h
OH
91
25
OH
O
+
R
O
OEt
[O=P(2-py)3Mo(CO)(NO)2](BF4)2
1 mol%
O
O
R
o
phenol
120 C, 0.5 ml solvent
ethyl acetoacetate
Yield (%)
Entry
1
Phenol
HO
Time
OH
2
3
OH
HO
OH
4
OH
5
6
HO
OH
[Bmim]PF6
CH3NO2
THF
CH3CN
DMF
1h
91
64
32
9
n. d.
24 h
--
86
54
24
3
25
min
84
(20 min)
12
5
4
n. d.
7h
--
82
42
(68)*
40
(69)*
n. d.
(5)*
15
min
82
(10 min)
19
12
13
n. d.
2h
--
83
81
82
*After reacting 24 h, the products’ yield
12
(79)*
26
OH
O
+
R
O
OEt
[O=P(2-py)3Mo(CO)(NO)2](BF4)2
1 mol%
O
O
R
o
phenol
120 C, 0.5 ml solvent
ethyl acetoacetate
Yield (%)
Entry
Phenol
Time
[Bmim]PF6
CH3NO2
THF
CH3CN
DMF
15
min
84
21
18
16
n. d.
8
2h
--
82
80
80
9
4h
22
10
n. d.
n. d.
60
26
5
n. d.
7
HO
10
HO
OH
OH
24 h
82
(20 min)
--
*After reacting 24 h, the products’ yield
n. d.
(5)*
27
OH
O
+
R
O
OEt
[O=P(2-py)3Mo(CO)(NO)2](BF4)2
1 mol%
O
O
R
o
phenol
120 C, 0.5 ml solvent
ethyl acetoacetate
Yield (%)
Entry
Phenol
Time
[Bmim]PF6
11
O
OH
12
13
24 h
O
14
15
16
10 h
O
24 h
OH
HO
5h
O
O
10 h
24 h
92
(6 h)
-93
(1 h)
--
88
(5 h)
--
CH3NO2
THF
CH3CN
DMF
31
21
6
n. d.
54
40
12
n. d.
43
14
11
n. d.
82
68
52
15
18
10
11
n. d.
34
24
28
n. d.
28
OH
O
+
R
O
[O=P(2-py)3Mo(CO)(NO)2](BF4)2
1 mol%
OEt
O
O
R
o
phenol
120 C, 0.5 ml solvent
ethyl acetoacetate
Yield (%)
Entry
Phenol
Time
[Bmim]PF6
17
4h
H2N
92
(2 h)
CH3NO2
THF
CH3CN
DMF
75
64
65
61
OH
18
6h
--
92
88
90
77
19
8h
--
--
--
--
82
10 h
88
16
10
5
n. d.
24 h
--
38
23
14
n. d.
20
21
OH
29
OH
O
+
R
O
OEt
[O=P(2-py)3Mo(CO)(NO)2](BF4)2
1 mol%
O
O
R
o
phenol
120 C, 0.5 ml solvent
ethyl acetoacetate
Yield (%)
Entry
Phenol
Time
[Bmim]PF6
CH3NO2
THF
CH3CN
DMF
24 h
n. d.
n. d.
n. d.
n. d.
n. d.
24 h
n. d.
n. d.
n. d.
n. d.
n. d.
24 h
n. d.
n. d.
n. d.
n. d.
n. d.
OH
22
NO2
23
OH
OH
24
O2N
30
OH
O
O
+
R
[O=P(2-py)3Mo(CO)(NO)2](BF4)2
1 mol%
OEt
O
O
R
o
phenol
Entry
1
Yield (%)
Phenol
HO
120 C
ethyl acetoacetate
OH
neat
[Bmim]PF6
98
(1 h)
91 (1 h)
69 (20 min)
80
(25 min)
84
(20 min)
Entry
8
2
OH
HO
9
H2N
OH
3
HO
4
OH
HO
OH
HO
OH
5
6
O
OH
O
75
(15 min)
82
(10 min)
69
(15 min)
84
(15 min)
69
(4 h)
82
(20 min)
93
(10 h)
92
(6 h)
91
(5 h)
93 (1 h)
O
7
OH
71 (20 min)
O
O
OH
HO
Yield (%)
Phenol
OH
OH
10
OH
11
NO2
12
OH
OH
13
O2N
neat
[Bmim]PF6
82
(10 h)
88
(5 h)
92
84
(4 h)
(2 h)
81
(24h)
88
(10 h)
n. d.
(24 h)
n. d.
(24 h)
n. d.
(24 h)
n. d.
(24 h)
n. d.
(24 h)
n. d.
(24 h)
31
Thermal Heating
Liquid boiling
temperature is always
lower than surface
temperature of
container
Convection
transition
32
Mechanism of Microwave Heating
Dipole Rotation
33
Ionic Conduction
34
Interactive Characteristic between
Materials and Microwave
Conductor
(Metal Material)
Insulator
(Telflon)
Dielectric Materials
(Water)
Reflective
Transparent
Absorptive
35
Microwave Flash Heating
Digestion bottle
Microwave energy
Liquid raises temperature quickly
36
Preparation of Organomolybdenum Catalyst

Microwave Flash Heating Conditions
CO
OC
O
P
Mo
P
OC
N
N
O
CO
CO
CO
N
OC
CO
OC
O
P
N
2 eq NOBF4
N
CO
dry CH3NO2
75 % yield
N
N
0oC / stir 1 hr
Mo
OC
2+
O
P
OC
N
Mo
uw(300W/100%)/ 120 oC/ 5 min
dry CH3CN
90 % yield
N
N
N
(BF4-)2
N
Mo
OC
NO
ON
37
Organomolybdenum Lewis Acid Catalyzed
Pechmann Condensation

Microwave Flash Heating Conditions
OH
O
O
+
R
[O=P(2-py)3Mo(CO)(NO)2](BF4)2
1 mol%
OEt
phenol
ethyl acetoacetate
OH
HO
HO
OH
OH
2-methylresorcinol
HO
OH
3,5-dimethoxyphenol
HO
OH
Orcinol
OH
O
OH
3-methoxyphenol
OH
OH
1,3,5-trihydroxybenzene
Pyrogallol
O
O
R
OH
HO
Resorcinol
O
mw, 120 oC
neat or 0.5 ml [bmim]PF6
OH
HO
O
H2N
O
OH
O
3-aminophenol
sesamol
NO2
1-naphthol
OH
OH
O2N
Phenol
2-nitrophenol
4-nitrophenol
38
OH
O
+
R
phenol
Entry
1
O
OEt
Yield (%)
OH
neat
[Bmim]PF6
93
(7 min)
86
(7 min)
92
(5 min)
83
(3 min)
89
(3 min)
91
(1 min)
86
(6 min)
90
(2 min)
73
(15 min)
84
(3 min)
93
(17 min)
51
(17 min)
91
(15 min)
68
Entry
8
2
OH
HO
HO
4
OH
HO
OH
HO
OH
5
6
O
OH
O
O
7
OH
(17 min)
O
9
H2N
OH
3
O
R
Yield (%)
Phenol
O
OH
HO
O
mw, 120 oC
neat or 0.5 ml [bmim]PF6
ethyl acetoacetate
Phenol
HO
[O=P(2-py)3Mo(CO)(NO)2](BF4)2
1 mol%
OH
OH
10
OH
11
NO2
12
OH
OH
13
O2N
neat
[Bmim]PF6
80
(15 min)
46
(17 min)
69
86
(10 min)
(10 min)
66
(17 min)
17
(17 min)
n. d.
(17 min)
n. d.
(17 min)
n. d.
(17 min)
n. d.
(17 min)
n. d.
(17 min)
n. d.
(17 min)
39
Microwave Flash Heating and
Power Supply Curve
Microwave Flash Heating Curve
140
Temp. (degree celsius)
Mo
H
O
O
OEt
R
O
120
100
80
60
40
20
Microwave Power Supply Curve
120
0
4
6
8
10
12
14
16
Time (min)
100
Power (%)
2
IL
IL + phenol + Et-acetate
phenol + Et-acetate
80
IL + 3-OH-phenol + Et-acetate
3-OH-phenol + Et-acetate
60
40
20
0
0
2
4
6
8
10
12
14
16
18
Time (min)
IL
IL + phenol + Et-acetate
phenol + Et-acetate
IL + 3-OH-phenol + Et-acetate
3-OH-phenol + Et-acetate
40
18
OH
+
R
phenol
O
[O=P(2-py)3Mo(CO)(NO)2](BF4)2
1 mol%
OEt
ethyl acetoacetate
Entry
1
O
HO
OH
O
R
120 oC
neat or 0.5 ml [bmim]PF6
Thermal / Yield (%)
Phenol
O
MW / Yield (%)
neat
[Bmim]PF6
neat
[Bmim]PF6
98
(1 h)
91 (1 h)
86 (7 min)
69 (20 min)
93
(7 min)
80
(25 min)
84
(20 min)
92
(5 min)
83
(3 min)
75
(15 min)
82
(10 min)
89
(3 min)
91
(1 min)
69
(15 min)
84
(15 min)
86
(4 min)
90
(2 min)
69
(4 h)
82
(20 min)
73
(15 min)
84
(3 min)
94 (8 min)
OH
2
HO
OH
OH
3
4
5
HO
OH
HO
OH
HO
OH
41
OH
O
+
R
phenol
O
OEt
[O=P(2-py)3Mo(CO)(NO)2](BF4)2
1 mol%
ethyl acetoacetate
Entry
O
OH
6
O
O
R
120 oC
neat or 0.5 ml [bmim]PF6
Thermal / Yield (%)
Phenol
O
MW / Yield (%)
neat
[Bmim]PF6
neat
[Bmim]PF6
93
(10 h)
92 (6 h)
93
(17 min)
51
(17 min)
91
(15 min)
68
O
91
(5 h)
7
93 (1 h)
71 (20 min)
(17 min)
OH
HO
8
O
O
9
H2N
OH
82
(10 h)
84
(4 h)
81
(24 h)
88
(5 h)
92
80
(15 min)
46
(17 min)
69
(2 h)
86
(10 min)
(10 min)
88
(10 h)
66
(17 min)
17
(17 min)
OH
10
42
Recyclability of Organomolybdenum Lewis
Acid Catalyst
Substrate
Adduct
Added
Extraction
CHCl3
Ionic Liquid
[Bmim]PF6
Catalyst
Solution
43
Recyclability of Organomolybdenum
Lewis Acid Catalyst in [bmim]PF6
OH
O
O
[O=P(2-py)3Mo(CO)(NO)2](BF4)2
5 mol%
O
+
OEt
O
O
120 oC
[bmim]PF6
Catalyst 1 Recycling in [Bmim]PF 6
analytic yield (%)
O
100
90
80
70
60
50
40
30
20
10
0
0
1
2
3
4
5
6
7
number of experiment
44
Proposed Mechanism
O
O
P
N NN
Mo
NO
NO
2+
P
N NN
Mo
OC
NO
NO
( BF4- )2
- CO
O
2+
( BF4- )2
O
OEt
Mo
O
O
P
N NN
Mo
NO
O NO
£_
+
HO
2+
O
O
R
OEt
( BF4- )2
nucliphilic attack
HO
R
OEt
45
Proposed Mechanism
Mo
Mo
H
O
O
OEt
R
O
Mo
O
O
-EtOH
O
OH
O
O
R
R
Mo
O
O
R
£_
+
Mo
Michael
addition
O
R
OH
O
Mo
+H+
H
OH
O
O
R
O
+
O
-H+
P
N NN
Mo
NO
NO
R
O
O H
H
2+
( BF4- )2
46
Catalytic Reactivity of [A(2-py)3M(CO)(NO)2]2+
on Pechmann Condensation
HO
OH
O
+
[A(2-py)3M(CO)(NO)2](BF4)2
1 mol%
O
HO
O
O
120 oC
neat, 1h
OEt
Catalysts
Yield (%)
A(2-py)3
M
O=P(2-py)3
Mo
98
P(2-py)3
Mo
82
O=P(2-py)3
W
74
P(2-py)3
W
71
47
Catalytic Reactivity of [A(2-py)3M(CO)(NO)2]2+
on Mukaiyama Aldol Reaction
[A(2-py)3M(CO)(NO)2](BF4)2
O
Si(CH3)3
Cl3C
OH
10 mol%
Cl3C
DMF, 40oC, 5h
Catalysts
Yield (%)
A(2-py)3
M
O=P(2-py)3
Mo
93
P(2-py)3
Mo
85
O=P(2-py)3
W
56
P(2-py)3
W
45
48
李婉甄碩士論文 ‘有機鉬金屬路易士酸在微波中對於Mukaiyama Aldol反應催化活性之探討’ 中正大學化學研究所, 2005.
Catalytic Reactivity of [A(2-py)3M(CO)(NO)2]2+
on Diels Alder Reaction
O
[A(2-py)3M(CO)(NO)2](BF4)2
3 mol%
bmimPF6
Catalysts
O
Concentration (M)
/Time (min)
Yield (%) (endo: exo)
A(2-py)3
M
O=P(2-py)3a
W
0.67 / 45
97 (90:10)
O=P(2-py)3b
Mo
0.67 / 45
85 (90:10)
P(2-py)3c
W
0.022 / 30
87 (94:6)
a:陳宜宏碩士論文 “水溶性有機鎢金屬路易士酸在綠色溶劑及微波中對於Diels-Alde 反應的影響”中正大學化學研究所, 2003.
b:李婉甄碩士論文 ‘有機鉬金屬路易士酸在微波中對於Mukaiyama Aldol反應催化活性之探討’ 中正大學化學研究所, 2005.
c: 傅耀賢博士論文 “過渡金屬錯合物觸媒的合成、催化活性以及動力學研究 中正大學化學研究所, 2001
49
Conclusions

We have successfully demonstrated the catalytic activity
of [O=P(2-py)3Mo(CO)(NO)2](BF4)2 for the synthesis of a
variety of coumarins under solvent-free and ionic liquid
system ([Bmim]PF6) conditions. This practical and simple
method led to good yields of the coumarin derivatives
under mild conditions and within short times.

The time economy, along with the conservation of the
organomolybdenum Lewis acid catalyst activity and the
high recovery of the Lewis acid catalyst, play for both low
environmental impact and low cost. Other green
advantages of the procedure are the low formation of
wastes, easy purification; and principally, the replacement
of corrosive and environmental unfriendly acids.
50
Conclusions

The successful use of microwave irradiation in
providing this rapid and direct route to coumarins in
comparison to classical procedures contributes to
confirming the participation of specific effects in
some microwave-assisted organic synthesis.

Because the [O=P(2-py)3Mo(CO)(NO)2](BF4)2 catalyst
is relatively high moisture – and oxygen – stability,
we use neutral ionic liquids, [Bmim]PF6, for
Pechmann condensation as a recyclable media, and
still have good yield for several times.
51
OH
O
+
R
phenol
Entry
O
OEt
[O=P(2-py)3Mo(CO)(NO)2](BF4)2
1 mol%
ethyl acetoacetate
O
R
120 oC
neat or 0.5 ml [bmim]PF6
Thermal / Yield (%)
Phenol
O
MW / Yield (%)
neat
[Bmim]PF6
neat
[Bmim]PF6
n. d.
(24 h)
n. d.
(24 h)
n. d.
(17 min)
n. d.
(17 min)
n. d.
(24 h)
n. d.
(24 h)
n. d.
(17 min)
n. d.
(24 h)
n. d.
(24 h)
n. d.
(17 min)
OH
11
NO2
OH
12
OH
13
n. d.
(17 min)
n. d.
(17 min)
O2N
52