Halogenated meso-phenyl Mn(III) porphyrins as highly efficient catalysts for the synthesis of polycarbonates and cyclic carbonates using carbon dioxide and epoxides

Article abstract of DOI:10.1016/j.molcata.2015.10.025

Introduction of halogen electron withdrawing atoms (chloro and fluoro) in the ortho position of the aryl groups of meso-tetraphenylporphyrin manganese(III) complexes increased their activity as catalysts in the reaction of carbon dioxide with epoxides, wh

Full text of DOI:10.1016/j.molcata.2015.10.025

Accepted Manuscript
Title: Halogenated meso-phenyl Mn(III) porphyrins as highly
efficient catalysts for the synthesis of polycarbonates and
cyclic carbonates using carbon dioxide and epoxides
Author: Laia Cuesta-Aluja Javier Castilla Anna M.
Masdeu-Bult o´ C e´ sar A. Henriques M a´ rio J.F. Calvete Mariette
M. Pereira
PII:
S1381-1169(15)30129-1
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.molcata.2015.10.025
MOLCAA 9668
To appear in:
Journal of Molecular Catalysis A: Chemical
Received date:
Revised date:
Accepted date:
4-9-2015
26-10-2015
27-10-2015
Please cite this article as: Laia Cuesta-Aluja, Javier Castilla, Anna M.Masdeu-Bult o´ ,
C e´ sar A.Henriques, M a´ rio J.F.Calvete, Mariette M.Pereira, Halogenated meso-phenyl
Mn(III) porphyrins as highly efficient catalysts for the synthesis of polycarbonates and
cyclic carbonates using carbon dioxide and epoxides, Journal of Molecular Catalysis
A: Chemical http://dx.doi.org/10.1016/j.molcata.2015.10.025
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Halogenated meso-phenyl Mn(III) porphyrins as highly efficient catalysts for the
synthesis of polycarbonates and cyclic carbonates using carbon dioxide and
epoxides
a
a
a*
Laia Cuesta-Aluja , Javier Castilla , Anna M. Masdeu-Bultó
b
b
annamaria.masdeu@urv.cat, César A. Henriques , Mário J. F. Calvete , Mariette M.
b*
Pereira mmpereira@qi.uc.pt
a
Department of Physical and Inorganic Chemistry. University Rovira i Virgili. Marcel·lí
Domingo, s/n. 43007 Tarragona (Spain).
b
CQC, Department of Chemistry, University of Coimbra, Rua Larga, 3004-535
Coimbra (Portugal).

Graphical Abstract

Highlights
•
New halogenated Mn(III)-porphyrin catalysts for CO fixation into
2
polycarbonates and cyclic carbonates.
•
This catalyst produces poly(cyclohexene carbonate) increasing by ten-fold the
TOF respect to the non-halogenated analog. Cyclic carbonates are obtained from
linear epoxides.
•
This system uses very low catalyst loading, does not require a co-catalyst and,
when soluble, it can be used in net substrate.

Abstract
Introduction of halogen electron withdrawing atoms (chloro and fluoro) in the
ortho position of the aryl groups of meso-tetraphenylporphyrin manganese(III)
complexes increased their activity as catalysts in the reaction of carbon dioxide with
epoxides, when compared with the meso-tetraphenylporphyrin manganese(III)
counterpart, even in the absence of co-catalysts. In the polymerization reaction of
carbon dioxide and cyclohexene oxide, almost ten-fold increase of the TOF was
observed when 5,10,15,20-tetra(2,6-dichlorophenyl)porphyrinatomanganese(III) acetate
or 5,10,15,20-tetra(2,6-difluorophenyl)porphyrinatomanganese(III) acetate complexes
were used as catalysts.
Under similar conditions, when terminal epoxides were used as substrates, the
selective cycloaddition of CO with styrene oxide, epichlorohydrin, propylene oxide,
2
and 1,2-epoxytetradecane yielded exclusively the corresponding cyclic carbonates
(conversion 54-98 %).
Keywords: polycarbonates, cyclic carbonates, metalloporphyrins, manganese(III),
carbon dioxide.

1
. Introduction
Carbon dioxide is a renewable C -building block for the synthesis of monomeric or
1
polymeric organic carbonates [1]. Cyclic carbonates have wide applications such as
polar aprotic solvents, antifoam additives, plasticizers [2,3,4] and also as raw materials
for the synthesis of polyurethane and urea derivatives [5]. In addition, aliphatic
polycarbonates are materials possessing extreme toughness, high impact strength, high
transparency and biodegradability [
2, 6, 7, 8], which explains its broad use as anti foam
.
additives, as binders and plastic substitute derivatives [
2,
6,
7
, ]. However, the chemical
8
transformation of carbon dioxide, an almost inert compound, requires the use of
appropriate catalysts and highly reactive substrates, such as epoxides, to obtain cyclic
carbonates or polycarbonates (Scheme 1) [9,10,11,12].
A variety of catalysts have been developed for carbon dioxide and epoxide
coupling, which include halide, quaternary alkyl ammonium or phosphonium salts,
ionic liquids and metal complexes [9]. Halides, quaternary salts and ionic liquids are
known to produce preferentially cyclic carbonates, which are the most stable
thermodynamic products [9], while metal complexes can catalyze the formation of
polymers and/or cyclic carbonate products, depending from the co-catalyst, substrate
and reaction conditions [9]. It should be mentioned that most of the metal based
complexes, of which tetrapyrrolic macrocycles are privileged compounds for many
applications [13,14,15,16,17,18,19,20,21], require the presence of a co-catalyst, acting
as nucleophile, whether added to the reaction (binary catalytic systems) [22,23,24,25] or
already included in the structure of the complex (bifunctional catalytic systems) [26].

On the other hand Inoue et al. [27] reported that 5,10,15,20-tetraphenylporphyrinato
Mn(III) acetate (Mn-TPP, Figure 1), in the absence of any additional co-catalyst, was
able to promote the copolymerization of CO and cyclohexene oxide (CHO) with a
2
-
1
moderate TOF of 16.3 h when compared with that reported for Cr(III)-salen based
-1
systems (1200 h ) [28]. Darensbourg and Frantz proposed the low ability of the five-
coordinate Mn(III) complexes to bind the epoxide as a plausible explanation for their
low activity [29]. So, the introduction of electron-withdrawing groups at the periphery
of the porphyrin ligand would strengthen their Lewis acidity, favoring the coordination
of the epoxide to the metal center as observed for other catalytic systems [30].
Therefore, herein we describe the synthesis of the 5,10,15,20-tetra(2,6-dichlorophenyl)-
and 5,10,15,20-tetra(2,6-difluorophenyl)porphyrinato manganese(III) complexes having
acetate or chloride as axial coordination ligands (1, 2 and 3, Figure 1) and their
evaluation as selective catalysts either for the copolymerization of cyclic epoxides with
CO or the cycloaddition of terminal epoxides with CO , without the addition of co-
2
2
catalysts.
2
2
. Experimental
.1. General Comments
Reagents for the synthesis of catalysts were acquired from Aldrich, and used as
received. Epoxides were dried over CaH , distilled and stored under inert atmosphere
2
except 1,2-epoxyhexane and 1,2-epoxydodecane and epichlorohydrin, which were
purchased at Sigma-Aldrich and used as received. Solvents were purified by the system
Braun MB SPS-800 and stored under nitrogen atmosphere. Carbon dioxide (SCF Grade,
9
9.999 %, Air Products) was used introducing an oxygen/moisture trap in the line
(Agilent). UV-visible spectra were recorded on a UV-3100PC spectrophotometer. NMR
1
13
spectra were recorded at 400 MHz Varian, with tetramethylsilane ( H NMR and C

NMR) as internal standards. MALDI-TOF measurements were performed on a
Voyager-DE-STR (Applied Biosystems, Franingham, MA) instrument equipped with a
3
37 nm nitrogen laser. All spectra were acquired in the positive ion reflector mode.
Dithranol was used as matrix, which was dissolved in MeOH at a concentration of 10
-1
mg·mL . The polymer (5 mg) was dissolved in 1 mL of CHCl . 1µL of sample, 1µL of
3
matrix and 1µL of potassium trifluoroacetate (KTFA) solution in the case of polymers
(1 mg of KTFA in 1mL of THF) were deposited consecutively on the stainless steel
sample holder and allowed to dry before introduction into the mass spectrometer. Three
independent measurements were made for each sample. For each spectrum 100 laser
shots were accumulated. The molecular weights (Mn) of copolymers and the molecular
weight distributions (Mw/Mn) were determined by gel permeation chromatography
versus polystyrene standards. Measurements were made in THF on a Millipore-Waters
5
1
10 HPLC Pump device using three-serial column system (MZ-Gel 100Å, MZ-Gel
000 Å, MZ-Gel 10000 Å linear columns) with UV-Detector (ERC-7215) and IR-
Detector (ERC-7515a). The software used to get the data was NTeqGPC 5.1. Samples
were prepared as follow: 10 mg of the copolymer was dissolved with 2 mL of
tetrahydrofuran (HPLC grade) stabilized with 2,6-di-tert-4-methylphenol.
2
.2. Synthesis of Mn(III) porphyrin catalysts
5
,10,15,20-tetra(phenyl)porphyrin (TPP), [36] 5,10,15,20-tetra(2,6-
dichlorophenyl)porphyrin (TDCPP) [36] and 5,10,15,20-tetra(2,6-
difluorophenyl)porphyrin (TDFPP) [36] were prepared according to our previously
reported method [35] and their characterization data is in agreement with the literature.
2
.3. General method of metallation of TDCPP and TDFPP

The corresponding porphyrin was dissolved in DMF and 10 equivalents of the
corresponding metal salt were added. The reaction mixture was kept at reflux
temperature (~150ºC) for 24 hours. After cooling to room temperature, chloroform (50
mL) was added and the mixture was washed with distilled water (3 times x 100 mL).
The organic phase was dried with anhydrous sodium sulfate and the solution was
concentrated. Column chromatography was performed on silica gel with ethyl
acetate:dichloromethane (3:1) as eluent to obtain the title porphyrins.
2
.4. 5,10,15,20-tetrakis(phenyl)porphyrinatomanganese(III) acetate (Mn-TPP)
Following the general method, 500 mg (0.8 mmol) of TPP, 31.96 g (8.0 mmol) of
manganese (II) acetate tetrahydrate were used, mixed in 50mL of DMF. We obtained
Mn-TPP in 80% yield (473 mg). Characterization data was in agreement with the
literature [27].
2
.5. 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrinatomanganese(III) acetate (1)
Following the general method, 800 mg (0.9 mmol) of TDCPP, 2.20 g (9.0 mmol) of
manganese (II) acetate tetrahydrate were used, mixed in 75 mL of DMF. We obtained
metalloporphyrin 1 in 84 % yield (757 mg). Characterization data was in agreement
with the literature [31].
2
.6. 5,10,15,20-tetrakis(2,6-difluorophenyl)porphyrinatomanganese(III) acetate (2)
Following the general method, 300 mg (0.4 mmol) of TDFPP, 0.96 g (4.0 mmol) of
manganese (II) acetate tetrahydrate were used, mixed in 25 mL of DMF. We obtained
metalloporphyrin 2 in 40 % yield (138 mg). Characterization data was in agreement
with the literature [32].

2
.7. 5,10,15,20-tetrakis(2,6-dichlorophenyl)porphyrinatomanganese(III) chloride
(3) Following general method, 500 mg (0.6 mmol) of TDCPP, 1.19 g (6.0 mmol) of
manganese (II) chloride tetrahydrate were used, mixed in 50mL of DMF. We obtained
metalloporphyrin 3 in 88% yield (370 mg). Characterization data was in agreement with
the literature [33].
2
.8. General procedure for the catalytic reactions of epoxides with CO2
The catalytic tests were carried out in a 100 mL Berghof reactor, which was previously
kept for 4 hours, under vacuum, at 100 ºC. After cooling down, a solution under inert
atmosphere containing the catalyst dissolved in net distilled substrate or with solvent
(when indicated) and the co-catalyst, when indicated, was injected into the reactor. The
autoclave was pressurized with CO , and then heated to the specific temperature to
2
reach the desired pressure. After the reaction time, the reactor was cooled with an ice
bath and slowly depressurized through a dichloromethane trap. The % conversion was
1
determined by H NMR of the crude mixture by integral ratio between alkene oxide and
cyclic carbonate. The work-up was as follow depending on the substrate.
2
.9. Work-up for cyclohexene oxide: the final mixture was dissolved in
dichloromethane, the solvent was evaporated and the residue dried in vacuum at 100 ° C
for 3 hours to remove excess of cyclohexene oxide. The final residue was washed
several times with hexane to purify the poly(cyclohexene carbonate) and was analyzed
1
by H NMR spectroscopy. The productivity in polymer was calculated from the mass of
the isolated product-weight of the catalyst and co-catalyst [34]. The % of CO content
2

1
was calculated from H NMR data by the integral ratio between copolymer carbonate
linkages (δ = 4.65 ppm) respect to ether linkage signals (δ = 3.45 ppm).
2
.10. Work-up for styrene oxide, propylene oxide, 1,2-epoxyhexane, 1,2-
epoxydodecane, epichlorohydrin and cyclooctene
Purification in the case of the styrene carbonate was performed by extraction with
hexane to remove the styrene oxide. The remaining solid was evaporated and diluted in
CH Cl and passed through a silica pad to remove the catalyst. The purification of
2
2
propylene carbonate was performed removing the propylene epoxide by vacuum
evaporation and the remaining oily residue was diluted in dichloromethane and passed
through a silica pad to remove the catalyst.
3
3
. Results and discussion
.1. Catalysts synthesis
The meso-substituted porphyrins 5,10,15,20-tetra(2,6-dichlorophenyl)porphyrin
TDCPP) and 5,10,15,20-tetra(2,6-difluorophenyl)porphyrin (TDFPP) were prepared
(
according to our previously reported methods by mixing equimolar amounts of pyrrol
with the desired aldehydes in acetic acid/nitrobenzene using zeolite NaY as solid
catalyst [35,36], while their Mn(III) complexes 1, 2 and 3 were prepared by metal
insertion with the appropriate metal salts (Mn(OAc) in the case of 1 and 2 and MnCl
2
2
for 3), using DMF as solvent [37] (Scheme 1).
3
.2. Catalytic polymerization studies
The effect of the halogen atoms at the 2,6-positions of the phenyl ring in meso-
substituted porphyrin manganese(III) complexes was evaluated on the copolymerization

of CO and cyclohexene oxide, in the absence of any co-catalyst, and the results are
2
presented in Table 1. First, the catalytic activity of complex 1 on the copolymerization
of CO with cyclohexene oxide, at the same reaction conditions reported by Inoue et al.
2
(
0.2 molar % respect to epoxide, 50 bar of CO and 80 ºC) [27] was tested.
2
Complex 1, bearing chlorine atoms in its structure, in absence of co-catalyst selectively
1
afforded the poly(cyclohexene carbonate) (no cyclic carbonate was detected by H
NMR) with 84 % epoxide conversion and 72 % of polymer isolated yield (entry 1,
Table 1). Additionally, very high alternate incorporation of CO into the polymer
2
linkages was obtained (98 %), with 4700 g/mol molecular weight.
Then, catalyst loading optimization was performed (from 0.07 mol% to 0.01 mol%;
-1
entries 2-4, Table 1) leading to a maximum TOF of 154 h at very low catalyst loading
(0.01 mol %, entry 4, Table 1), which is nearly tenfold higher than the result previously
described using the non-halogenated Mn(III)TPP-OAc catalyst [27]. Furthermore, the
molecular weight of the copolymer obtained using catalyst 1 increased up to 5300-8800
g/mol, concomitantly with very narrow polydispersity (M /M =1.09, 1.20; entries 2-3,
w
n
Table 1). Next, decreasing the temperature to 60 ºC, using catalyst 1 at 0.07 mol %,
only 56 % of epoxide conversion and 47% isolated yield were obtained, but achieving
the highest molecular weight polycarbonate (8800 g/mol ;entry 5, Table 1).
Catalyst 1 was still active using 1 bar of CO , although the reaction proceeded slower
2
than under 50 bar of CO , since 43 % conversion and 39 % isolated yield of
2
polycarbonate were obtained only after 90 h (entry 6, Table 1). Moreover, the use of
catalyst 1 and dimethylaminopyridine (DMAP) as co-catalyst induced a decrease in the
epoxide conversion towards the polycarbonate, and a mixture of polymer and cyclic
monomeric carbonate was obtained (entry 7, Table 1). These results are in good
agreement with the ones reported by Inoue and coworkers using [Mn(OAc)(TPP)]

catalyst [27]. An attempt to run the reaction at supercritical conditions (120 bar, 80 ºC)
produced only 10 % conversion toward polycarbonate, showing low incorporation of
carbonate linkages (74 %) and low molecular weight (700 g/mol, entry 8, Table 1),
which may be attributed to the low solubility of the catalyst in the supercritical media.
In addition, catalyst 2 (0.2 mol %; PCO =50 bar; T=80ºC), possessing fluorine atoms in
2
its structure, was also evaluated under the same reaction conditions, and 92 % epoxide
conversion with 77 % polymer isolated yield was obtained (entry 9, Table 1) presenting
higher conversion than 1 (entry 1, Table 1). In this case, the average molecular weight
of the polycarbonate obtained was 6000 g/mol, displaying a narrow polydispersity
(
M /M = 1.11).
w n
To corroborate the relevance of the presence of halogens on the catalyst structure a
comparative experiment using Mn-TPP as catalyst (0.01 mol %) at 50 bar and 80ºC
was carried out and only 3% conversion was obtained (entry 10 vs 4, Table 1).
In sum, it can be clearly seen that the presence of halogens at the meso-phenyl groups of
the Mn(III) porphyrins plays a key role on the efficiency of the catalysts on the reaction
of cyclohexene oxide with CO (entries 1, 9 and 10, Table 1), being the halogenated
2
ones the best performing catalysts. Moreover, the addition of co-catalyst (DMAP) also
caused a significant decrease of the conversion of cyclohexene oxide (entries 7, Table
1
), which demonstrates the considerable effect of the fifth axial ligand. As proposed by
Rao et al., the competitive effect of free DMAP decreased conversion and selectivity
38].
[
3
.3. Catalytic monomeric carbonate synthesis

Using the best reaction conditions previously determined, the scope of catalyst 1 was
analyzed in the reaction of CO with different epoxides, at 0.07 mol % catalyst loading,
2
5
0 bar of CO pressure and temperature of 80 ºC (Scheme 2).
2
When terminal epoxides such as styrene oxide, propylene oxide and tetradecylene oxide
were used as substrates, the corresponding cyclic carbonates were exclusively formed in
5
6, 54 and 6% isolated yields, respectively (entry 1-3, Table 2). In the case of hexylene
1
oxide, the presence of the corresponding polycarbonate was detected by H NMR
-
spectroscopy by comparison with reported data [39]. The presence of acetate (AcO ) as
Mn(III)porphyrin axial ligand enhances the efficiency of the catalyst, when compared
-
with the corresponding Mn(III)porphyrin bearing chloride (Cl ) as axial ligand (entries 1
and 2, Table 2).
In the case of propylene oxide and 1,2-epoxyhexane, a co-solvent (CH Cl ) was
2
2
required due to the low solubility of the porphyrin complex in the epoxide. It is worth
mentioning the excellent conversion (> 98%) and selectivity (> 98%) obtained in the
cycloaddition reaction of epichlorohydrin with CO (entry 6, Table 2). Conversely,
2
reaction of cyclic cyclooctene oxide with CO did not occur, neither in the presence of 1
2
nor using a combination of catalyst 1 and DMAP as co-catalyst (entries 7-8, Table 2).
In sum, when terminal epoxides were used, the selectivity for the production of cyclic
carbonates was very high, while when cyclohexene oxide was used it was found that the
reaction selectivity shifted toward the production of polycarbonates
3
.4. MALDI-TOF determination of poly(cyclohexene carbonate) chain end groups

The polycarbonate chain end groups obtained in the experiments described in Table 1,
at entry 5 (using catalyst 1 at 50 bar, 60ºC), at entry 6 (using catalyst 1 at 1 bar, 80 ºC)
and entry 7 (using catalyst 1/DMAP), were analyzed by matrix assisted laser desorption
ionization time-of-flight mass spectrometry (MALDI-TOF) (Supplementary
Information). They all presented repeating peaks at differences of 142 m/z
corresponding to a cyclohexylcarbonate -C H C(O)O- repeating unit. A common main
6
10
peak distribution was observed in all three cases, attributed to fragments at m/z 1149.50,
that may correspond to a chain with two –OH terminal groups (a + K in Scheme 3,
expected for n = 7 HO(C H O ) C H OH; m/z 1149.52). Using catalyst 1/DMAP a
7
10 3 7
6
10
different mass spectrum peak distribution was observed, which fitted with the presence
+
of DMAP as end group (b + H) as well as –OH (observed m/z 1215.66; expected for
+
n= 7 [(DMAP)(C H O ) C H OH] ; m/z 1215.60).
7
10 3 7
6
10
The formation of poly(cyclohexene carbonate) using catalyst 1 alone (a, Scheme 4)
suggests that the initiation step involves the epoxide opening by a nucleophilic attack,
with -OH arising from water traces present in the reactor (Scheme 5). On the other
hand, when DMAP is present, the formation of polymer b (Scheme 6) may be explained
by an initiation step involving nucleophilic attack of DMAP to the coordinated epoxide
and a termination step produced by hydrolysis (Scheme 7). The role of DMAP as
initiator in the CO /propylene oxide polymerization using salen- and salan-
2
Cr(III)/DMAP catalytic systems was studied by Rao et al. [38]. They proposed that
coordination of DMAP took place before the opening of the epoxide, and
simultaneously, the axial ligand anion produced the initiation. Contrary, Darensbourg
and co-workers proposed that DMAP coordinates to Mn center and subsequently
activate the CO to afford a weak zwitterionic carbamic complex, followed by a reaction
2
with CHO to provide a stabilized zwitterion [22] We did not find any chain end

containing a carbamate or acetate group; therefore, the role of DMAP should be the ring
opening of the epoxide although we do not have evidences whether it coordinates prior
to nucleophilic attack.
5
. Conclusions
We demonstrated the significantly beneficial presence of halogen atoms at the
meso-phenyl groups of the Mn(III) porphyrins, which act as catalysts for the
copolymerisation of cyclohexene oxide with CO , without the presence of any co-
2
-1
catalyst, yielding poly(cyclohexene carbonate), with TOF up to 154 h . Moreover, we
also observed a strong influence of the Mn(III)porphyrin fifth axial ligand, where
-
-
acetate (AcO ) enhanced the efficiency of the catalyst, while chloride (Cl ) and DMAP
axial ligands almost inhibited the reaction.
In addition, a direct correlation between the nature of the epoxide structure and
the catalyst used was observed, using the same reaction conditions. Thus, while terminal
epoxides form cyclic carbonates with high selectivity by cycloaddition with CO2,
cyclohexene oxide selectively react in the copolymerization with CO , forming
2
exclusively poly(cyclohexene carbonate).
Acknowledgements
We gratefully acknowledge the Ministerio de Economia y Competitividad (CTQ2013-
4
2
3438-R), Departament d'Economia i Coneixement (Generalitat de Catalunya,
014SGR 670) for financial support. We also thank FCT-Portugal (Portuguese
Foundation for Science and Technology) and FEDER –European Regional
Development Fund through the COMPETE Programme (Operational Programme for
Competitiveness) for funding (UID/QUI/00313/2013). C.A.H.is grateful for their PhD
grant SFRH/BD/84146/2012. M.J.F.C. is grateful to Ciencia2008 Programme
QREN/FEDER.

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Figure Caption
Scheme Error! Main Document Only.. a) Cycloaddition and b) copolymerization of
CO with epoxides
2
Scheme 1. Synthesis of complexes 1-3
Scheme Error! Main Document Only.. Cycloaddition of CO with different epoxides.
2
Scheme 3. General mechanism proposed for the formation of polycarbonate chains a
and b
Figure Error! Main Document Only.. Manganese(III) meso-substituted porphyrin
based complexes.

Tables
Table Error! Main Document Only. Copolymerization of cyclohexene oxide (CHO)
a
and CO using catalysts 1, 2, and Mn-TPP.
2
b
d
3
e
Entry Cat
Cat
P
T
Conv
(%)
(
% CO2 Yield M ·10
ccontent (%)
M /Mn
n
w
(mol %) (bar) (º C)
TOF)
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
2
0.2
50
50
50
50
50
1
80
80
80
80
60
80
80
84
17)
75
19)
76
86)
37
154)
56
33)
43
25)
33
19)
10
98
96
96
96
98
91
89
74
98
51
72
52
71
29
47
39
23
10
77
4.7
8.8
5.3
3.3
8.8
1.7
1.4
0.7
6.0
1.50
1.20
1.09
1.09
1.22
1.12
1.14
1.11
1.11
n.d.
(
(
(
f
0.07
0.036
0.01
0.07
0.07
0.07
0.07
0.2
(
f
(
g
(
h,i
50
(
120 80
(6)
50
50
80
80
92
19)
3
(
1
0
MnTPP 0.01
n.d.
n.d.
(
13)
a
b
1
c
Reaction conditions: t = 24h, n.d. = not determined. % Based on H NMR.
Determined by H NMR integral ratio of carbonate linkages/(carbonate linkages+ether
linkages). Isolated yield. Determined by GPC using polystyrene as standard.
bimodal 90h using DMAP/1 = 1/1. 78 % selectivity, 22 % cyclic carbonate
1
d
e
f
g
h
i

Table Error! Main Document Only.. Cycloaddition of CO to different epoxides using
2
catalyst 1.
b
b
Entry
1
Epoxide Cat.
Solvent (mL) Co-cat (mmol) Conv. (%)
Select. (%)
1
-
-
-
-
-
56
6
> 98
2
3
4
3
1
1
-
>98
CH Cl (1.2)
54
74
> 98
2
2
c
CH Cl (1.8)
77
2
2
5
6
1
1
CH Cl (1.8)
6
> 98
> 98
2
2
-
-
-
> 98
7
1
1
CH Cl (3)
< 2
< 2
< 2
2
2
8
CH Cl (3)
DMAP (0.025) < 2
2
2
a
Reaction conditions: 35 mmol of epoxide and 0.025 mmol of catalyst (epoxide/catalyst
1400 /1), P = 50 bar, T = 80 ºC, t = 24 h. Estimated by H NMR. 23 % polycarbonate
b
1
c
=