C,N-chelated organotin(IV) compounds as catalysts for transesterification and derivatization of dialkyl carbonates

Article abstract of DOI:10.1002/aoc.2858

The potential catalytic activity of selected C,N-chelated organotin(IV) compounds (e.g. halides and trifluoroacetates) for derivatization of both dimethyl carbonate (DMC) and diethyl carbonate (DEC) was investigated. Some tri-, di- and monoorganotin(IV) species (L^CN(n-Bu)₂SnCl (1), L^CN(n-Bu)₂SnCl.HCl (1a), L^CN(n-Bu) ₂SnI (2), L^CNPh₂SnCl (3), L^CNPh ₂SnI (4), L^CN(n-Bu)SnCl₂ (5), L ^CNSnBr₃ (6) and [L^CNSn(OC(O)CF ₃)]₂(μ-O)(μ-OC(O)CF₃)₂ (7)) bearing the L^CN moiety (L^CN = 2-(N,N-dimethylaminomethyl) phenyl-) were assessed as catalysts for reactions of both DMC and DEC with various substituted anilines. The catalytic activities of 4 and 7 for derivatization of DMC with p-substituted phenols were studied for comparison with the standard base K₂CO₃/Silcarbon K835 catalyst (catalyst 8). The composition of resulting reaction mixtures was monitored by multinuclear NMR spectroscopy, GC and GC-MS techniques. In general, catalysts 1, 3 and 7 exhibited the highest catalytic activity for all reactions studied, while some of them yielded selectively carbonates, carbamates, lactam or substituted urea. Copyright

Full text of DOI:10.1002/aoc.2858

Full Paper
Received: 18 January 2012
Revised: 12 March 2012
Accepted: 12 March 2012
Published online in Wiley Online Library
(wileyonlinelibrary.com) DOI 10.1002/aoc.2858
C,N-chelated organotin(IV) compounds as
catalysts for transesterification and
derivatization of dialkyl carbonates
Tomáš Weidlicha, Libor Dušeka, Barbora Vystrčilováa, Aleš Eisnerb,
Petr Švecc and Aleš Růžičkac*
The potential catalytic activity of selected C,N-chelated organotin(IV) compounds (e.g. halides and trifluoroacetates) for derivati-
zation of both dimethyl carbonate (DMC) and diethyl carbonate (DEC) was investigated. Some tri-, di- and monoorganotin(IV)
species (LCN(n-Bu)2SnCl (1), LCN(n-Bu)2SnCl.HCl (1a), LCN(n-Bu)2SnI (2), LCNPh2SnCl (3), LCNPh2SnI (4), LCN(n-Bu)SnCl2 (5), LCNSnBr3
(6) and [LCNSn(OC(O)CF3)]2(m-O)(m-OC(O)CF3)2 (7)) bearing the LCN moiety (LCN = 2-(N,N-dimethylaminomethyl)phenyl-) were
assessed as catalysts for reactions of both DMC and DEC with various substituted anilines. The catalytic activities of 4 and 7 for
derivatization of DMC with p-substituted phenols were studied for comparison with the standard base K2CO3/Silcarbon K835
catalyst (catalyst 8). The composition of resulting reaction mixtures was monitored by multinuclear NMR spectroscopy, GC and
GC-MS techniques. In general, catalysts 1, 3 and 7 exhibited the highest catalytic activity for all reactions studied, while some
of them yielded selectively carbonates, carbamates, lactam or substituted urea. Copyright © 2012 John Wiley & Sons, Ltd.
Keywords: organotin(IV) compounds; C,N-chelating ligand; dialkyl carbonates; catalysis
carbamate (MPC) from aniline and dimethyl carbonate) has been
investigated thoroughly. Thus Gurgiolo prepared MPC over zinc
Introduction
Dialkyl carbonates are attractive compounds for the preparation
of carbamates since they offer genuine green advantages over
classical alkylating reagents:[1] (i) they are non-toxic; (ii) their
alkylation mediated reactions are always catalytic processes, with
no by-products except for alcohols recyclable to the synthesis of
dialkyl carbonates, and CO2 which does not involve disposal
problems; (iii) very often, (light) organic carbonates can be used
not only as reactants, but also as reaction solvents. Moreover, their
alkylation reactivity can be tuned for a variety of nucleophiles. This
behavior has been extensively investigated by Selva’s research
group in the past 15 years.[2]
Organic carbamates represent an important class of compounds,
largely employed in pharmacology (medical drugs), agriculture
(pesticides, fungicides, herbicides), and chemical industry
(intermediates of synthesis).[3] Aryl-alkyl carbamates are important
intermediates for the preparation of pharmaceuticals (e.g.
kinase inhibitors)[4] and can be also used as raw materials for
synthesizing polyurethanes using a phosgene-free route: carbamate
! isocyanate ! polyurethane.[5] Cyclic carbamates are useful as
chemical technology intermediates for the production of
remedies for treating of pain and inflammation,[6] novel inhibitors
of S-nitroisoglutathione reductase,[7] and for the preparation of
azepino[1,2-b]isoquinolines.[8]
acetate catalyst, the selectivity of MPC to aniline being 99.8% under
the conditions of 140ꢀC and 0.88 MPa.[12] Fu and Ono have
obtained high aniline conversion and MPC yield over Pb(OAc)2
catalyst, too. At a temperature of 400 K for 1 h, the conversion of
aniline was 96.7%, yielding 95.1% of MPC.[13] It can be inferred from
the above that metal acetates possess excellent catalytic activity.
However, they bring about troublesome problems such as product
separation and recovery of the homogeneous metal acetate
catalyst.
We have published recently a study of the zwitterionic tri- and
diorganostannates containing the protonated 2-(dimethylamino-
methyl)phenyl- moiety prepared by reactions of C,N-chelated
organotin(IV) chlorides with various protic acids (both inorganic
and organic).[14] Results concerning the reaction of LCN(n-Bu)2SnCl
with CF3COOH were also described there. Latter results led
us to prepare and structurally characterize some novel C,N-
chelated organotin(IV) trifluoroacetates bearing the LCN ligand(s)
*
Correspondence to: Aleš Růžička, Department of General and Inorganic
Chemistry, Faculty of Chemical Technology, University of Pardubice,
Studentská 573, CZ-532 10 Pardubice, Czech Republic. E-mail: ales.ruzicka@
upce.cz
Aryl-alkyl carbamates are generally prepared from phosgene,[9]
phosgene derivatives[10] or isocyanates[11] by reactions with
alcohols, in the case of carbamates, and amines in the case of ureas.
Nevertheless, none of these methods are environmentally benign
because of the necessary use of toxic reagents and the generation
of by-products.
a Institute of Environmental and Chemical Engineering, Faculty of Chemical
Technology, University of Pardubice, CZ-532 10 Pardubice, Czech Republic
b Department of Analytical Chemistry, Faculty of Chemical Technology, University
of Pardubice, CZ-532 10 Pardubice, Czech Republic
The synthesis of aryl-alkyl carbamates from diethyl carbonate
(DEC) or dimethyl carbonate (DMC) (e.g. synthesis of methyl phenyl
c
Department of General and Inorganic Chemistry, Faculty of Chemical Technology,
University of Pardubice, CZ-532 10 Pardubice, Czech Republic
Appl. Organometal. Chem. 2012, 26, 293–300
Copyright © 2012 John Wiley & Sons, Ltd.

T. Weidlich et al.
subsequently employed as catalysts in the direct synthesis of DMC
from carbon dioxide and methanol as discussed elsewhere.[15]
As a contribution to this field of chemistry, we report on the
use of selected C,N-chelated organotin(IV) species (e.g. halides
and trifluoroacetates) as catalysts for the derivatization of DMC
and DEC. In addition, a new and easy procedure for the synthesis
of LCN(n-Bu)2SnI (2) and LCNPh2SnI (4) is described (for general 1H
NMR numbering see Scheme 1).
Catalysis
Transesterification of 2-N-phenylaminoethanol with DMC
N-Phenylaminoethanol A was chosen as the bidentate nucleophile.
The transesterification of dialkyl carbonates with N-phenylami-
noethanol A represents a safe approach to the simple preparation
of 3-phenyl-1,3-oxazolidin-2-one C. Lactam C, a product of the
acylation of N-phenylaminoethanol A with phosgene, serves as a
useful synthetic intermediate and mimics 2-phenylaziridine in the
decarboxylative ring opening reaction under the action of nucleo-
philes. The reaction of 3-phenyl-1,3-oxazolidin-2-one C with cya-
nide produces 3-N-phenylaminopropanenitrile,[24] with amines
produces N-phenylethylenediamine derivatives,[25] and with mer-
captoethanol produces N-phenylamino-substituted thioethers.[26] In
addition, 3-phenyl-1,3-oxazolidin-2-one works as an alkylamination
reagent of aromatics under Friedel–Crafts alkylation.[27] Action of
dialkyl carbonate on 2-N-benzylaminoethanol using a base was de-
scribed earlier[28]; this reaction gives 3-benzyl-1,3-oxazolidin-2-one in
good yield.
The reaction of the 2-N-aminoethanol A with an excess of boiling
DMC gave linear aminocarbonate B and/or the lactam C (Scheme 2
and Table 2). When the reaction is conducted without a catalyst, no
conversion of the starting 2-N-aminoethanol is observed. On the
other hand, the specific formation of carbonate B is observed when
catalysts 1, 3, 5 and 7 are used under boiling DMC reflux for 17 h.
The lowest catalytic activity among all catalysts used was observed
for catalyst 1a because only traces of aminocarbonate B were
formed. The highest yield is found for triorganotin(IV) species 1
and 3 with lower Lewis acidity (Table 2, entries 2 and 4) of the tin
atom. Within these two catalysts, the n-butyl-substituted one (1)
seems to be slightly more efficient, probably because of the higher
tendency of n-butyl-substituted triorganotin compounds to form
stannylium cations.[29] Catalysts 5 and 7 reveal much lower activity,
but the selectivity towards the carbonate B is again satisfactory. To
complete the reaction catalyzed by 3 (entry 5) a much longer
reaction time is necessary, but the reaction is no more selective,
Results and Discussion
General Remarks
All of the C,N-chelated organotin(IV) compounds used as catalysts
(for numbering see Table 1) have been already prepared and
structurally characterized by us and/or other authors (for details
see the Experimental section).
In addition, compounds 2 and 4 were prepared by a very quick
alternative procedure compared to that reported in the litera-
ture.[17,19] It is based on a modification of the Finkelstein
reaction,[18] in which the corresponding triorganotin(IV) chloride
reacts with an equimolar amount of sodium iodide in acetone.
The insoluble sodium chloride is then simply filtered off.
Evaporation of the filtrate to dryness gave desired triorganotin(IV)
iodide with a very high isolated yield (96% and 85%, respectively).
Owing to the excellent purity of the triorganotin(IV) iodides formed,
no necessity for recrystallization of the products is another advan-
tage of this alternative synthetic route. The 1H and 119Sn NMR spec-
tral patterns of 2 and 4 prepared by this procedure are in excellent
agreement with data found in the literature.[17,19]
Table 2. Results of transesterification of 2-N-phenylaminoethanol
(A) with DMC (reflux), reaction time 17 h
Scheme 1. General 1H NMR numbering of prepared compounds
Table 1. Compounds (catalysts) studied
Entry
Catalyst
(% mol.)
Conversion
Conversion
Conversion
of A (% mol.) to B (mol. %) to C (mol. %)
1
—
0
100
0
0
100
0
0
0
Catalyst
Compound
LCN(n-Bu)2SnCl
LCN(n-Bu)2SnCl.HCl
LCN(n-Bu)2SnI
LCNPh2SnCl
Ref.
2
1 (10%)
1a (10%)
3 (10%)
3 (10%)
3 (10%)
5 (10%)
7 (5%)
3
0
1
[16]
4
56
56
78
0
0
1a
2
[14]
5a
6b
7
95
17
100
0
[17]
100
20
3
[18]
4
L
CNPh2SnI
[19]
20
34
9
5
LCN(n-Bu)SnCl2
[16,20]
[16,21]
[15]
8
9b
34
0
6
LCNSnBr3
7 (5%)
100
91
7
[LCNSn(OC(O)CF3)]2(m-O)(m-OC(O)CF3)2
K2CO3/Silcarbon K835
aReaction time 72 h.
bRemoval of methanol by azeotropic distillation.
8
[22]
Scheme 2. Transesterification of 2-N-phenylaminoethanol (A) with DMC catalyzed by 1, 1a, 3, 5 and 7
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Appl. Organometal. Chem. 2012, 26, 293–300

Dialkyl carbonate use catalyzed by organotin species
and lactam C is observed with about 17% yield. However, the
lactam C is the only product obtained under prolonged heating
of an excess of DMC and 2-N-aminoethanol A in the presence of
3 as a catalyst with subsequent removal of methanol (entry 6).
Under the same conditions, the lactam is also formed in the
case of catalyst 7, but the selectivity is lower. The identity of the
Table 3. Results of reaction of 4-t-butylaniline (D) with DEC (reflux),
reaction time 17 h
Entry
Catalyst
(% mol)
Conversion of
D (% mol)
Conversion to
E (% mol)
1
2
3
4
5
6
—
0
99
0
0
95
0
1
lactam C was confirmed by H and 13C NMR spectroscopy and
1 (10%)
1a (10%)
2 (10%)
3 (10%)
7 (10%)
the single crystals obtained from the chloroform solution gave
essentially the same unit cell parameters as published
elsewhere.[30] The main advantage of catalyst 3 over catalysts 7
and 1 is the possibility of simple recycling of non-destroyed
catalyst 3 by filtration of the precipitated 3 obtained by cooling
of the reaction mixture.
0
0
38
91
38
91
Reaction of 4-t-butylaniline with DEC
Reactions of p-substituted phenols with DMC
The carbamate E produced by the acylation of 4-tert-butylaniline
D with dialkyl carbonates is the starting material for a new
synthetic route for heterocycles, e.g. tryptamines.[31]
Different phenols are chosen as the model nucleophilic
substrates for the testing the above-mentioned C,N-chelated
organotin(IV) catalysts. Both anisoles and aryl methyl carbonates
as the possible products of the reaction of phenols with DMC are
industrially important solvents and/or synthetic building blocks
for the preparation of polycarbonates,[36] plasticizing agents for
epoxide resins,[37] pharmaceuticals and dyestuffs.[38]
The carbamate E is the major product of the reaction of 4-t-
butylaniline (D) with an excess of boiling DEC when catalyzed by
1, 3, and 7 (Scheme 3 and Table 3). When the catalyst 1 protonated
by HCl, 1a and triorganotin(IV) iodide 2 is used, only traces of
desired products were obtained. The catalytic activity of di-n-butyl-
substituted chloride 1 is slightly higher than of monoorganotin(IV)
trifluoroacetate 7, but a major decrease in yield is observed upon
switching from di-n-butyl to diphenyl chloride 3. On the other
hand, a non-identified by-product is formed in the reaction
catalyzed by 1 (entry 2) in 4% yield (as determined by 1H NMR).
Reactions of p-substituted phenols (I) with an excess of DMC
catalyzed by 4, 7 and 8 (Scheme 5) provided corresponding
anisoles (J, method I) and mixed alkyl-aryl carbonates (K, method II)
(together with other by-products, analyzed by GC-MS; see
Tables 5–7). Despite the amounts of catalysts 4 and 7 involved in
the reactions studied being 120 times lower when compared to
the amount of base catalyst 8 used, the yields of corresponding
products were still satisfactory and, in some cases, even higher.
Formation of the corresponding diaryl carbonates was not
observed. In general, higher temperature (200ꢀC) and short
reaction times (6h) promoted the formation of anisoles J, which
is a consequence of the thermodynamic driving of the reaction
(Table 6). On the other hand, the kinetic driving of the reaction at
lower temperatures (100ꢀC) and prolonged reaction times (15 h)
provided slightly higher yields of the respective alkyl-aryl
carbonates K (Table 5) when compared with yields of K by
thermodynamically driven reactions. When catalyst 4 was used in
kinetically driven reactions (Table 5) the overall yields of by-
products were distinctly higher when compared to yields observed
for the same reactions catalyzed by 8, but this trend vanished
when higher temperatures and long reaction times were applied
(Table 6).
Reaction of 4-bromoaniline (F) with excess DEC
The products prepared by the acylation of 4-bromoaniline F using
DEC (carbamate G or urea H) are versatile synthetic intermediates.
Bis(4-bromophenyl)urea H forms 4-bromophenylisocyanate under
acylation with acetanhydride[32]; 1,3,5-triphenylimidazolidine-2,4-
diones and 1,3,5-triphenyl-2-thioxoimidazolidin-4-ones (new CB1
cannabinoid receptor inverse agonists/antagonists) are simply
available by the reaction of bis(4-bromophenyl)urea with
phenylglyoxal.[33]
Ethyl N-bromophenylcarbamate G serves as bromoaromatic
compound for C-C or C-heteroatom cross-coupling reactions[34]
or on the other hand as a weak N-nucleophile.[35]
The catalyzed reaction of 4-bromoaniline (F) with boiling
DEC yields carbamate G and urea H (Scheme 4 and Table 4). The
conversion of starting 4-bromoaniline is nearly quantitative in the
cases of reactions catalyzed by 1, 2 and 7. While the reactions
catalyzed by 1 and 7 gave essentially quantitatively urea H, the
reaction catalyzed by iodide 2 is non-specific, yielding a mixture
of carbamate G and urea H. The specific formation of only
carbamate G in about 17% yield is observed in the case of the
reaction catalyzed by monoorganotin(IV) tribromide 6.
The nature of the X substituent attached to the phenols
influenced the transesterification of DMC independently of
temperature. Phenols bearing electron-donating substituents
reacted with DMC more readily while electron-withdrawing
substituents clearly decreased their reactivity towards the DMC,
as demonstrated in Tables 5–7.
Scheme 3. Reaction of 4-t-butylaniline (D) with excess of DEC catalyzed by 1, 1a, 2, 3 and 7
Appl. Organometal. Chem. 2012, 26, 293–300
Copyright © 2012 John Wiley & Sons, Ltd.
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T. Weidlich et al.
Scheme 4. Reaction of 4-bromoaniline (F) with excess of boiling DEC catalyzed by 1, 1a, 2, 5, 6 and 7
1
inverse gated-decoupling mode. H NMR spectroscopy in CDCl3
was also used for evaluation of some reaction products as
well as to monitor the conversion of some of the reactants.
Multinuclear NMR spectra of 2 and 4 were recorded only in
CDCl3. The identity of the catalysts was assessed by 119Sn NMR
after completion of the reactions.
Table 4. Results of reaction of 4-bromoaniline (F) with DEC (reflux),
reaction time 17 h
Entry
Catalyst
(% mol)
Conversion of Conversion to Conversion to
F (% mol)
G (% mol)
H (% mol)
1
2
3
4
5
6
7
—
0
94
0
0
0
0
94
0
1 (10%)
1a (10%)
2 (10%)
5 (10%)
6 (10%)
7 (10%)
0
GC and GC-MS Techniques
100
0
32
0
68
0
All the standard solutions were prepared and analyzed using GC
and GC-MS techniques. The first gas chromatograph used, model
GC-72FT (Labio, Czech Republic), equipped with flame ionization
detector (FID) and thermal conductivity detector with a double-
channel arrangement integrator (CSW Data Apex), was employed
for all quantitative analyses of major products of reaction
mixtures. Commercially available p-substituted phenols, anisole
and phenyl carbonates were used as internal standards (Sigma-
Aldrich). The GC-72FT system was equipped with a capillary
column SUPELCO EquityW-5 L, length 30 m, 0.32 mm internal
diameter, 0.25 mm film (Supelco, Bellefonte, PA, USA). Nitrogen
5.0 (Linde Gas, a.s., Pardubice, Czech Republic) was used as a
carrier gas at a constant flow of 20 ml minꢁ1 at an excess pressure
of 100 kPa. The injection volume was 1 ml in split mode 1:100. The
column temperature was programmed as follows: the initial
temperature was 40ꢀC (3 min), Δ10ꢀC minꢁ1 to 180ꢀC (20 min).
FID temperature was 280ꢀC.
17
100
17
0
0
100
The second gas chromatograph used, model GC-2010, coupled
with a mass selective detector (QP 2010plus, Shimadzu, Tokyo,
Japan) with quadrupole mass analyzer and AOC-20i auto-sampler
(Shimadzu), was employed for all analyses of by-products. The
GC-MS system was equipped with a capillary column MDN-5,
length 30 m, 0.25 mm internal diameter, 0.25 mm film (Supelco).
Helium 5.3 (Linde Werk. Tech. Gase, Düsseldorf, Germany) was
Scheme 5. Derivatization of DMC with p-substituted phenols catalyzed
by 4 (0.1 mmol), 7 (0.1 mmol) and 8 (12.0 mmol) leading to formation
of p-substituted anisoles (J, method I) and mixed alkyl-aryl carbonates
(K, method II)
used as a carrier gas at a constant linear velocity of 30 cm sꢁ1
.
The composition of reaction mixtures was determined using the
following conditions: the injector temperature was maintained
at 220ꢀC, and the injection volume was 1 ml in split mode 1:100.
Interface and ion source temperatures were maintained at 200
and 220ꢀC, respectively. The column temperature was
programmed as follows: the initial temperature was 40ꢀC
(3 min) Δ20ꢀC minꢁ1 to 280ꢀC (3 min). Electron energy was set
at 70 eV. Initially, mass spectra were obtained in full-scan mode
(m/z 10–600) to obtain a set of masses of the corresponding
compounds. To improve the sensitivity of the measurement,
selected ion monitoring (SIM) mode was employed for the
masses acquired from full-scan mode. The identity of each
compound was confirmed using the NIST 27 and NIST 147 mass
spectra libraries.
Experimental
NMR Spectroscopy
The multinuclear NMR spectra were recorded from solutions of
reaction mixture residues in DMSO-d6 or in CDCl3 on a Bruker
Avance 500 spectrometer (equipped with Z-gradient 5 mm
1
probe) at frequencies H (500.13 MHz), 13C{1H} (125.76 MHz) and
119Sn{1H} (186.50 MHz) at 295 K. The solutions were obtained by
dissolving approximately 20 mg of each reaction mixture residue
in 0.6 ml deuterated solvent. The values of the 1H chemical shifts
were calibrated to the residual signal of CDCl3 (d(1H) = 7.27 ppm)
and DMSO-d6 (d(1H) = 2.50 ppm). 13C chemical shift values were
calibrated to the signal of DMSO-d6 (d(13C) = 39.5 ppm). 119Sn
chemical shift values are referred to external neat tetramethyltin
(d(119Sn) = 0.0 ppm). 119Sn NMR spectra were measured using the
X-Ray Crystallography
Data for colorless crystal of lactam C were collected on a Nonius
KappaCCD diffractometer using MoKa radiation (l = 0.71073 Å)
and a graphite monochromator at 150 K.
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Appl. Organometal. Chem. 2012, 26, 293–300

Dialkyl carbonate use catalyzed by organotin species
Table 5. Results of reactions of 4-X-phenols (I) with DMC in the presence of catalyst 4 (0.1 mmol) and 8 (12.0 mmol), reaction time 15 h,
temperature 100ꢀC
Entry
1
Cat.
I X
Conversion of
I (% mol.)
Conversion to
J (% mol.)
Conversion to
K (% mol.)
By-products
(% mol.)
Specification of by-products
4
H
H
20
75
1
24
1-Methoxy-4-methylbenzene
4-Methylphenol
1,2-Dimethoxybenzene
1-Methoxy-4-phenoxybenzene
1-Methoxy-4-methylbenzene
Methoxybenzene
2
3
8
4
19
5
69
45
27
19
4
CH3
36
1-Methoxy-4-methoxybenzene
4-Methoxybenzene
Not identified
4
5
6
7
8
4
8
4
CH3
7
8
43
34
21
10
55
28
74
—
2
38
5
OCH3
OCH3
NH2
14
27
4-Methoxyphenol
90
4-Hydroxybenzonitrile
4-Methoxyaniline
4-Methoxybenzonitrile
4-Methoxy-n-methylaniline
4-Hydroxybenzonitrile
4-Methoxyaniline
8
8
NH2
23
9
6
67
4-Methoxybenzonitrile
4-Methoxy-n-methylaniline
Phenol
9
4
8
Cl
Cl
18
29
11
97
11
78
3
4-Methylphenol
4-Methoxyphenol
10
—
Phenol
4-Methylphenol
4-Methoxyphenol
11
12
13
14
15
4
8
4
8
4
CN
84
77
10
7
87
99
83
92
11
—
—
—
—
—
13
1
Methoxybenzene
1-Methoxy-4-methylbenzene
Methoxybenzene
CN
1-Methoxy-4-methylbenzene
Methoxybenzene
NO2
NO2
COOH
17
8
4-Methoxybenzonitrile
4-Methoxyaniline
4-Methoxybenzonitrile
Phenol
1
89
Methyl-4-hydroxybenzoate
Methyl-4-methoxybenzoate
Phenol
16
8
COOH
2
17
—
83
Methyl-4-hydroxybenzoate
Methyl-4-methoxybenzoate
Synthesis
dryness, giving 1178 mg of pure oily 2. Yield 96%. 1H NMR
(CDCl3, 295 K, ppm): 8.35 (d, 1H, H(6′), 3J(1H(5′), 1H(6′))= 7.9Hz,
3J(119Sn, 1H)=64.8Hz); 7.36 (m, 2H, H(4′, 5′)); 7.15 (d, 1H, H(3′), 3J(1H
L
CN(n-Bu)2SnCl (1),[16] LCN(n-Bu)2SnCl.HCl (1a),[14] LCN(n-Bu)2SnI
(2),[17] LCNPh2SnCl (3),[18] LCNPh2SnI (4),[19] LCN(n-Bu)SnCl2
(5),[16,20] LCNSnBr3 (6)[16,21] as well as [LCNSn(OC(O)CF3)]2(m-O)
(m-OC(O)CF3)2 (7),[15] were prepared according to published
procedures. Acetone and sodium iodide for alternative preparation
of 2 and 4, as well as K2CO3, were purchased from Sigma-Aldrich
and used as received. Silcarbon K835 was obtaining from Silcarbon
Aktivkohle GmbH, Kirchhundem, Germany.
1
(4′), H(3’))= 6.6Hz); 3.67 (s, 2H, NCH2); 2.42 (s, 6H, N(CH3)2); 1.71
(m, 4H, H(1)); 1.50 (m, 4H, H(2)); 1.41 (m, 4H, H(3)); 0.93 (t, 6H,
H(4)). 119Sn NMR (CDCl3, 295 K, ppm): ꢁ34.0.
Alternative preparation of 4
The same procedure was used as for 2, using 3 (1000 mg,
2.26 mmol) and sodium iodide (339 mg, 2.26 mmol). Pure 4 was
1
isolated as a yellowish crystalline solid. Yield 1023 mg (85%). H
Alternative preparation of 2
NMR (CDCl3, 295 K, ppm): 8.56 (d, 1H, H(6’), 3J(1H(5′), 1H
1
3
To begin, compound 1 (1000 mg, 2.48 mmol) was dissolved in
acetone (40 ml) and a solution of sodium iodide (372 mg,
2.48 mmol) in acetone (10 ml) was added. The reaction mixture
was stirred for 1 h while sodium chloride precipitated. The
precipitate was filtered off and the filtrate was evaporated to
(6′)) = 6.6Hz, 3J(119Sn, H) = 71.2 Hz); 7.68 (d, 4H, H(200), J(1H(300),
1H(200)) = 7.0 Hz, 3J(119Sn, 1H) = 70.2 Hz); 7.49 (m, 1H, LCN
)
7.41–7.31 (m, 7H, LCN and Ph groups); 7.14 (d, 1H, H(3′), J(1H(4′),
1H(3′)) = 7.4 Hz); 3.53 (s, 2H, NCH2); 1.87 (s, 6H, N(CH3)2). 119Sn
NMR (CDCl3, 295 K, ppm): ꢁ199.0.
3
Appl. Organometal. Chem. 2012, 26, 293–300
Copyright © 2012 John Wiley & Sons, Ltd.
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T. Weidlich et al.
Table 6. Results of reactions of 4-X-phenols (I) with DMC in the presence of catalyst 4 (0.1 mmol) and 8 (12.0 mmol), reaction time 6 h,
temperature 200ꢀC
Entry
1
Cat.
I X
Conversion of
I (% mol.)
Conversion to
J (% mol.)
Conversion to
K (% mol.)
By-products
(% mol.)
Specification of by-products
4
H
H
94
71
3
26
1-Methoxy-4-methylbenzene
4-Methylphenol
1,4-Dimethoxylbenzene
1-Methoxy-4-phenoxybenzene
1-Methoxy-4-methylbenzene
4-Methoxy benzoic acid methyl ester
Methoxybenzene
2
3
8
4
97
95
72
59
2
3
26
38
CH3
1-Methoxy-4-methoxybenzene
1-Methyl-2-(phenylmethoxy)benzene
Methoxybenzene
4
5
6
7
8
4
8
4
CH3
99
100
93
69
89
72
2
2
2
29
9
OCH3
OCH3
NH2
Not identified
4
24
96a
Not identified
98
—
4-Hydroxybenzonitrile
4-Methoxyaniline
4-Methoxybenzonitrile
4-Methoxy-N-methylaniline
4-Hydroxybenzonitrile
4-Methoxyaniline
8
8
NH2
97
73
—
27
4-Methoxybenzonitrile
4-Methoxy-N-methylaniline
Phenol
9
4
8
Cl
Cl
100
99
64
65
—
36
34
4-Methylphenol
4-Methoxyphenol
10
1
Phenol
4-Methylphenol
4-Methoxyphenol
11
12
13
4
8
4
CN
100
100
99
69
91
95
<1
—
—
30
9
Methoxybenzene
1-Methoxy-4-methylbenzene
Methoxybenzene
CN
1-Methoxy-4-methylbenzene
Methoxybenzene
NO2
3
4-Methoxybenzonitrile
1-Nitro-4-(phenylmethoxy)benzene
Methoxybenzene
14
15
8
4
NO2
100
100
74
—
—
26
8
4-Methoxybenzamine
4-Methoxybenzonitrile
Phenol
COOH
92b
2-Methylphenol
4-Methylphenol
Methyl-4-hydroxybenzoate
Methyl-4-methoxybenzoate
Phenol
16
8
COOH
98
68b
—
32
2-Methylphenol
4-Methylphenol
Methyl-4-hydroxybenzoate
Methyl-4-methoxybenzoate
ap-Hydroxybenzonitrile as the major product.
bMethyl ester of p-methoxybenzoic acid as the major product.
The standard base K2CO3/Silcarbon K835 catalyst (8) was
prepared by a similar procedure to that reported in the
literature[22]: solid K2CO3 (7.5g, 0,05 mol) was dissolved in distilled
water (200ml). Subsequently, well-dried activated carbon Silcarbon
K835 (42.5g) was added and the resulting dark mixture was stirred
overnight at ambient temperature. After evaporation of the water
under reduced pressure the residue was dried for 6 h at 150ꢀC to
give solid granules of the catalyst. Total content of the potassium
carbonate was 15% by weight based on the weight of the carrier:
Silcarbon K835.
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Copyright © 2012 John Wiley & Sons, Ltd.
Appl. Organometal. Chem. 2012, 26, 293–300

Dialkyl carbonate use catalyzed by organotin species
Table 7. Results of reactions of 4-X-phenols (I) with DMC in the presence of catalyst 7 (0.1 mmol) and 8 (12.0 mmol), reaction time 6 h,
temperature 200ꢀC
Entry
1
Cat.
I X
Conversion of
I (% mol.)
Conversion to
J (% mol.)
Conversion to
K (% mol.)
Byproducts
(% mol.)
Specification of byproducts
7
H
H
99
71
72
77
1
2
3
28
26
20
1-Methoxy-4-methylbenzene
4-Methylphenol
1,2-Dimethoxylbenzene
1-Methoxy-4-phenoxybenzene
1-Methoxy-2-methylbenzene
1-Methoxy-4-methylbenzene
2-Methoxy benzoic acid methyl ester
4-Methoxy benzoic acid methyl ester
Methoxybenzene
2
3
8
7
97
CH3
100
1-Methyl-2-(phenylmethoxy)benzene
Methoxybenzene
4
5
6
7
8
7
8
7
CH3
99
95
93
99
69
88
72
81
2
5
29
7
OCH3
OCH3
NH2
Not identified
4
24
29
4-Methoxyphenol
—
4-Methoxyaniline
4-Methoxybenzonitrile
4-Methoxy-N-methylaniline
4-Methoxyaniline
8
8
7
8
7
NH2
Cl
97
100
99
73
87
65
96
—
—
1
27
13
34
4
4-Methoxybenzonitrile
4-Methoxy-N-methylaniline
Phenol
9
4-Methylphenol
4-Methoxyphenol
10
11
Cl
Phenol
4-Methylphenol
4-Methoxyphenol
CN
100
—
Methoxybenzene
1-Methoxy-4-methylbenzene
Methoxybenzene
12
13
8
7
CN
100
100
91
82
—
—
9
NO2
18
Methoxybenzene
1-Nitro-4-(phenylmethoxy)benzene
Methoxybenzene
14
15
8
7
NO2
100
99
74
68
—
—
26
32
4-Methoxyaniline
4-Methoxybenzonitrile
Phenol
COOH
2-Methylphenol
4-Methylphenol
Methyl-4-hydroxybenzoate
Methyl-4-methoxybenzoate
Phenol
16
8
COOH
98
68
—
32
2-Methylphenole
4-Methylphenole
Methyl-4-hydroxybenzoate
Methyl-4-methoxybenzoate
Catalytic Experiments
carbonate solution (50 ml) of the appropriate organic substrate
(5mmol). The resulting reaction mixture was heated to reflux for
17 h under vigorous stirring and evaporated to dryness in the next
step. The final composition of the residue of the reaction mixture
was monitored by 1H and 13C NMR and GC-MS techniques.
DMC, DEC and all other reactants used were obtained from
commercial sources (Acros Organics) and used as received.
General procedure for experiments run in boiling DMC or DEC
General procedure for experiments performed in the Berghof
BTC-3000 autoclave
The experiments were carried out in a 250 ml round-bottomed flask
equipped with a condenser using a magnetic stirrer equipped with
a StarFishW attachment. The outlet of the condenser was fitted to a
glass tube filled with granulated charcoal. The flask was charged
with the selected catalyst (0.50 or 0.25 mmol) and a dialkyl
Starting organic substrate (10.0 mmol, various p-substituted
phenols) and DMC (36 ml, 400 mmol) was charged into the
autoclave. The appropriate catalyst (0.1 mmol of 4 or 7 and
Appl. Organometal. Chem. 2012, 26, 293–300
Copyright © 2012 John Wiley & Sons, Ltd.
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T. Weidlich et al.
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Conclusion
First, some well-known organotin(IV) halides and one dinuclear
monoorganotin(IV) trifluoroacetate bearing the C,N-chelating
ligand(s) were employed as catalysts for the derivatization of
DEC and DMC with 2-N-phenylaminoethanol, 4-t-butylaniline and
4-bromoaniline. These reactions, catalyzed by 1, 3 and 7 (which
exhibited the best catalytic activity in almost all reactions studied),
provided corresponding substituted carbonates, carbamates,
lactam or substituted urea as depicted in Schemes 2–4 in
reasonable yields. When these reactions were carried out under
the same conditions without the presence of the catalyst, no
formation of desired products was observed, as expected. In the
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4 and 7 with the reactions of DMC with p-substituted phenols.
Studied reactions gave corresponding anisoles and mixed alkyl-aryl
carbonates in varying yields depending on the substrate, reaction
time and temperature used. It was found that compounds 4 and
7 reveal promising catalytic activity when compared to the
standard base K2CO3 catalyst, which was used at 120 times higher
amounts relative to 4 and 7 in all cases. In addition, an alternative
procedure for the quick preparation of 2 and 4 with excellent yields
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Acknowledgements
The authors would like to thank the Grant Agency of the
Czech Republic (grant no. 104/09/0829) for the financial support
of this work.
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