Stereoselective electrochemical carboxylation: 2-phenylsuccinates from chiral cinnamic acid derivatives

Article abstract of DOI:10.1039/b500570a

Chiral 2-phenyl succinic ester derivatives have been obtained under mild conditions, in short times and with satisfactory yields by electrochemical reduction of chiral cinnamic acid derivatives under a CO₂ atmosphere. When 4R-(diphenylmethyl)-o

Full text of DOI:10.1039/b500570a

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A R T I C L E
Stereoselective electrochemical carboxylation: 2-phenylsuccinates
from chiral cinnamic acid derivatives†
Monica Orsini,a Marta Feroci,*a Giovanni Sotgiub and Achille Inesi*c
a Dip. Ingegneria Chimica, Materiali, Materie Prime e Metallurgia, Universita` “La Sapienza”,
via Castro Laurenziano, 7, I-00161, Roma, Italy. E-mail: marta.feroci@uniroma1.it;
Fax: +39 06 49766749; Tel: +39 06 49766563; Tel: +39 06 49766780
b Dipartimento di Elettronica Applicata, Universita` di Roma Tre, Via Vasca Navale, 84,
I-00146, Roma, Italy
c Dip. Chimica, Ingegneria Chimica e Materiali, Universita` degli Studi, I-67040,
Monteluco di Roio, L’Aquila, Italy. E-mail: inesi@ing.univaq.it
Received 13th January 2005, Accepted 2nd February 2005
First published as an Advance Article on the web 23rd February 2005
Chiral 2-phenyl succinic ester derivatives have been obtained under mild conditions, in short times and with
satisfactory yields by electrochemical reduction of chiral cinnamic acid derivatives under a CO2 atmosphere. When
4R-(diphenylmethyl)-oxazolidin-2-one was used as a chiral auxiliary the two diastereoisomers could be easily
separated by flash chromatography and the R-isomer was obtained as major product.
The electrochemical activation of carbon dioxide, as well as
the electrochemical modification of the substrates via simple
procedures, has been proposed.
Introduction
Despite the efforts over previous decades to find efficient
synthetic methodologies for the production of succinates, they
remain target substances for many organic chemists. Succinates
are useful compounds as synthetic intermediates, so it is impor-
tant to study new approaches that enable them to be obtained
in easy and suitable ways.
2-Arylsuccinates are key molecules in the synthesis of indan-
1-carboxylic acids possessing anti-inflammatory activity,2 they
are precursors to anticonvulsant a-arylsuccinimides,3 and, fur-
thermore, 2-phenylsuccinic acids are antitumor agents.4
Several methods have been reported for the preparation of 2-
arylsuccinates. Theyhave been obtained byoxidative 1,2-aryl mi-
gration of 3-aroylpropionic acid,5 by catalysed conjugated addi-
tion of aryl derivatives to a,b-unsaturated carbonyl compounds6
and by palladium catalysed oxidative carbonylation of suitable
olefins.7 This latter methodology, which uses chiral palladium
complexes, allows the enantioselective synthesis of chiral 2-
arylsuccinates.8
Carbon dioxide may be activated via monoelectronic cathodic
•
−
11
reduction to CO2
. Substrates containing a carbon–halogen
bond or a double carbon–carbon bond may be activated via
bielectronic cathodic cleavage of the carbon–halogen bond
or via monoelectronic reduction of the double bond to the
corresponding radical anion. The electrochemical reduction of
the carbon–halogen bond12 and of the activated double bond,13
in the absence and in the presence of electrophilic substrates,
have been extensively studied. Finally, molecules, containing
a CH or NH group that is acidic enough, may be activated
vs. electrophilic substrates by direct cathodic reduction or by
deprotonation via electrogenerated bases.14
Recently, the diastereoselective electrochemical carboxylation
of chiral a-bromocarboxylic acid derivatives was studied by us.1
The cathodic cleavage of the carbon–halogen bond was achieved
under galvanostatic control in CO2-saturated aprotic solutions.
At the end of the electrolysis, unsymmetrical alkylmalonic ester
derivatives were isolated as main products.
Few electrochemical methods are reported for the synthe-
sis of succinates. Mattiello et al.15 obtained diethyl 2,3-bis-
arylsuccinates by electrochemical reduction and subsequent
dimerization of ethyl-a-bromoarylacetales (obtaining an excess
of the racemic products vs. the meso ones).
2-Arylsuccinates have been prepared in good yields by
electrochemical reduction of styrene in the presence of N-
carboalkoxyimidazoles,16 by electrochemical arylation of acti-
vated olefins17 and by carboxylation of suitable substrates.
In the past, the cathodic reduction of some activated olefins
(a,b-unsaturated esters, ketones, nitriles), carried out under
potentiostatic control in CO2-saturated DMF solutions, was
studied by Save´ant et al.13b The mechanism of the electrochem-
ical carboxylation of the activated double bond was extensively
discussed.
Chiral 2-phenylsuccinates have also been obtained by
asymmetric catalytic allylation and decarboxylation of malo-
nates.9
Often these methodologies need hazardous or complex
reagents, long reaction times and severe conditions.
The study of new methodologies for C–C, C–N and C–O bond
formation lies at the heart of modern synthetic organic chem-
istry. In this context, particular attention has been dedicated
to setting up ecocompatible processes, i.e., synthetic processes
carried out with high yields and selectivity, in short time, under
mild and safe conditions and avoiding the use of toxic and
dangerous chemicals as well as the formation of polluting by-
products. Electrochemistry, which deals with a clean reagent, the
electron, can fulfil these targets.
As regards the possible sources of carbon (such that these
bonds can be formed) the employment of carbon dioxide, a
cheap and abundant raw material, has been considered by several
authors.10 However, the thermodynamic stability and the relative
kinetic inertness of CO2 require its preliminary activation or,
alternatively, the activation or modification of the substrates.
To our knowledge, however, no stereoselective electrochemical
carboxylation of chiral cinnamic acid derivatives, to obtain
chiral 2-phenyl succinates, has been reported. This prompted us
to study the electrochemical behaviour of some chiral cinnamic
acid derivatives in aprotic solvents in the absence and in the
presence of carbon dioxide.
† Part 2 of a series; for part 1 see ref. 1.
1 2 0 2
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 1 2 0 2 – 1 2 0 8
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
©

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The aim of this study was the development of a possible
electrochemical route to the stereoselective carboxylation of 1a–
h to chiral 2-phenylsuccinates 2a–h (Scheme 1).
1, 2 and 5) may be rejected. In fact, no oxalates were isolated at
the end of the electrolyses (see Experimental).
A carbon dioxide-saturated DMF–(0.1 mol dm−3 Bu4NBF4)
solution, containing 1a taken as a model compound, was
electrolysed (undivided cell, Pt cathode, Al sacrificial anode)
under potentiostatic control (E = −1.6 V vs. SCE). The
reduction of the double bond and the dissolution of the Al
metal (to Al3+ anion) take place at the Pt cathode and at
the sacrificial anode, respectively, yielding (after the coupling
of the radical anion with carbon dioxide) a stable aluminium
carboxylate. Recently, the use of a sacrificial anode (Mg, Al)
and the effect of the electrogenerated ions (Mg2+, Al3+) on the
overall synthetic process have been reported and discussed by
several authors.18 At the end of the electrolysis, after treatment
with diazomethane, 2a + 2aꢀ19 were isolated in 46% yield and
with a good diastereoisomeric ratio (75 : 25) (Table 2, entry
1). Along with these two desired products, the hydrogenated
product 3a and 4R-phenyloxazolidin-2-one 4a were obtained as
by-products (Fig. 1). The formation of the free chiral auxiliary
4a can be ascribed to the decomposition of the enolate of 1a,
probably via a ketene pathway.20
Scheme 1
Results and discussion
The voltammetric analysis of DMF solutions, containing the
chiral cinnamic acid derivatives 1a–h in the presence and in
the absence of carbon dioxide, allows us to compare the
electrochemical behaviour of 1a–h with the one of the previously
studied activated olefins.
The voltammetric curves of 1a–h (DMF–(0.1 mol dm−3
Bu4NBF4), Pt cathode, m = 0.2 V s−1) show a single irreversible
and diffusion controlled reduction peak (in the range of −1.35
to −1.60 V vs. SCE), which is related to the monoelectronic
reduction of the activated double bond and to the formation of
the corresponding radical anions 1aꢀ–hꢀ (Scheme 2, reaction 1).
In the presence of carbon dioxide, i.e., in CO2-saturated DMF–
(0.1 mol dm−3 Bu4NBF4) solutions, the peak currents increase
depending on the nature of the activating groups (Table 1).
According to the Save´ant model,13b the increases can be related
to hypothesis (a), a solution electron transfer between radical
anions 1aꢀ–hꢀ and CO2, followed by a coupling reaction between
radical anions 1aꢀ–hꢀ and CO2 (Scheme 2, reactions 2 and 3) or
hypothesis (b), to a coupling reaction between CO2, as electro-
philic agent, and radical anions 1aꢀ–hꢀ (Scheme 2, reaction 4).
Fig. 1 By-products of the electrochemical reduction of 1a in the
presence of CO2.
If the electrolysis was carried out under galvanostatic control
(I = 1.6 mA cm−2), a good chemoselectivity was obtained
(Table 2, entry 2); the only products obtained were 2a + 2aꢀ
in 44% yield, but the diastereoisomeric ratio was lower (60 : 40).
To verify a possible effect of the nature of the solvent on
the yield and on the diastereometric ratio of the carboxylated
products 2a + 2aꢀ, the reduction of 1a was carried out in
CO2-saturated THF–(0.1 mol dm−3 Bu4NBF4) solutions and
in CO2-saturated CH3CN–(0.1 mol dm−3 Bu4NBF4) solutions
(Table 2, entries 3–6). Good yields in carboxylated products
were obtained in THF at −20 ◦C, with an increase of the dr (68 :
32, entry 3). An increase of the temperature (rt, entry 5) yielded
a very good dr (9 : 91), but a poor chemoselectivity. Moreover, a
new couple of products, 5a + 5aꢀ, could be isolated (Fig. 1). The
formation of all-trans cyclic hydrodimers 5a + 5aꢀ is described
by Kise,21 where the reduction is carried out in the absence of
carbon dioxide and derives from the dimerization of the radical
anion relative to 1a (formed by addition of only one electron
per molecule) with subsequent cyclization and elimination of
one molecule of oxazolidinone 4a. The formation of 4a can
be therefore due also to the formation of 5a + 5aꢀ. The same
results of entry 5 were obtained when MeCN was used as
solvent (entry 6). The chemical shifts of hydrogen atoms of the
methoxycarbonyl group of 2a + 2aꢀ showed that, in CH3CN and
in THF at rt, the diastereoisomeric ratio was the opposite of the
one obtained in DMF (Table 2, entries 5 and 6).
Scheme 2
The Ep values of chiral cinnamic acid derivatives 1a–h
(Table 1) show that the monoelectronic reduction of the activated
double bonds takes place at a potential strongly more positive
•
−
with respect to the reduction potential of CO2 to CO2 (DE >
400 mV). Therefore, as regards substrates 1a–h, according to the
Save´ant model, the mechanism via electron transfer [hypothesis
(a)] is not competitive enough vs. the coupling CO2-radical
anions [(hypothesis (b)]. In addition, in the voltammetric curves
of 1a–h. as regards the peak currents in the presence of CO2 (i1)
and in the absence of CO2 (i0), both the conditions are verified:
i1 > i0 and i1 < 2i0. Therefore, the formation of oxalate via the
During the electrolyses of 1a in THF, the current density often
dropped to zero. To reset the initial conditions, a careful cleaning
of the electrode surfaces was necessary. The same drawback
occurred also during the reduction of substrates other than 1a.
As regards substrates 1b and 1c, no detectable flow of current
•
−
catalytic reduction of CO2 to CO2 at the reduction potential
of substrates 1a–h by the electron transfer (Scheme 2, reactions
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 1 2 0 2 – 1 2 0 8
1 2 0 3

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Table 1 Voltammetric data for solutions of 1a–ha in DMF (Ep0 and i0) and in carbon dioxide saturated DMF (Ep1 and i1)b
Entry
1
Substrate
−Ep0/V
i0/lA
−Ep1/V
i1/lA
Di (%)c
1.54
9.05
1.66
15.16
67.4
2
1.59
8.75
1.58
11.45
30.8
3
4
5
1.56
1.40
1.40
8.95
8.95
8.90
1.57
1.51
1.41
10.60
8.95
18.4
—
10.30
15.7
6
7
1.39
1.42
6.30
8.10
1.45
1.40
8.50
36.0
76.5
14.30
8
1.38
6.7
1.41
9.20
37.3
a c = 5.0 × 10−3 mol dm−3
.
b Pt cathode and anode; m = 0.2 V s−1; Bu4NBF4 as supporting electrolyte. c Di(%) = (i1 − i0)100/i0
could be recorded. Replacing the platinum cathode with other
solid electrodes did not produce significant improvements.
DMF and galvanostatic conditions seemed the best choice for
the carboxylation of chiral cinnamic acid derivatives (Table 2,
entry 2), because there was no problem of passivation at the
electrodes (the current was constant during the electrolysis)
and all the reduced substrate 1a reacted with CO2 to give the
carboxylated products 2a + 2aꢀ. Furthermore, the constant
current method offers many advantages over the controlled-
potential method, that requires a references electrode and hence
a more complex cell.
(reducing in this way the reaction time to 1 h) (Table 2, entries
7–9), but with only a little improvement.
Using the experimental conditions of entry 8 (Table 2) (the
best compromise between yields, current efficiency and reaction
time), we tried to improve the diastereomeric ratio, varying the
chiral auxiliary. These results are reported in Table 3.
In all cases the desired products were obtained, but the best
yields were with the substrates 1a and 1c (Table 3, entries 1 and
3); as regards the diastereoisomeric ratio, satisfactory results
were achieved with substrate 1b and 1g (Table 3, entries 2 and
7). In fact, in these two cases, when Oppolzer’s camphor sultam
and 4R-(diphenylmethyl)-oxazolidin-2-one have been used as
chiral auxiliaries, the two carboxylated diasteomers 2 + 2ꢀ were
very easy to isolate in pure form by simple flash chromatography.
DMF was therefore chosen as solvent, and electrolyses were
carried out with the aim of consuming all the starting material,
increasing the amount of electricity and the current density
1 2 0 4
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 1 2 0 2 – 1 2 0 8

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Table 2 Distribution and yields of the products (Scheme 1 and Fig. 1) from the electrochemical reduction of 1a in carbon dioxide saturated solutionsa
Products (% yield)d
Entry Solvent T/◦C E or Ib Qc Recovered 1a 3a
5a + 5aꢀ 4a 2a + 2aꢀ (dr)e
1
2
3
4
5
6
7
8
9
DMF
DMF
THF
THF
THF
−20
−20
−20
0
E
1.3 13
2.0 46
2.0 24
2.0 24
2.0 27
10
—
—
—
—
—
—
—
—
35
15 46 (75 : 25)
I1
I1
I1
I1
I1
I1
I2
I2
—
5
44 (60 : 40)
66 (68 : 32)
25 47 (62 : 38)
21 28 (9 : 91)
26 18 (47 : 53)
Rt
MeCN −20
2.0
—
Trace 46
DMF
DMF
DMF
−20
−20
−20
6.0 24
6.0 30
8.0 28
—
—
—
—
—
—
—
—
—
57 (64 : 36)
59 (59 : 41)
60 (59 : 41)
a Undivided cell; Al anode and Pt cathode; CO2 atmosphere; Bu4NBF4 as supporting electrolyte. b Electrolysis carried out under potentiostatic control
(E = −1.6 V vs SCE) or galvanostatic control (I1 = 1.6 lA cm−2, I2 = 8.0 lA cm−2). c Faradays mol−1 of 1a. d Yields of isolated products calculated
with respect to starting 1a. e The diastereomeric ratio was determined by 1H-NMR.
Table 3 Electrochemical carboxylation of 1a–ha
diastereoisomers can be easy separated by flash chromatography.
In particular, using 4R-(diphenylmethyl)-oxazolidin-2-one, the
R-isomer has been obtained as major product.
Products (% yield)b
Entry Substrate
Recovered 1
2 + 2ꢀ(dr)c
d(Me)d
Experimental
1
2
3
4
5
6
7
8
1a
1b
1c
1d
1e
1f
30
43
31
35
47
46
41
32
59 (59 : 41)
20 (74 : 26)
3.50–3.63
3.64–3.66
Tetrahydrofuran was distilled from Na–benzophenone and
acetonitrile was distilled twice from P2O5 and CaH2. DMF was
anhydrous grade and used as received. All other reagents were
used as received.
61 (68 : 32)e 3.66–3.66
56 (69 : 31)
53 (67 : 33)
3.65–3.63
3.68–3.70
54 (64 : 36)e 3.69–3.69
Flash column chromatography was carried out using Merck
60 Kieselgel (230–400 mesh) under pressure. Optical rotations
were recorded on a Perkin-Elmer 241 polarimeter. GC-MS
measurements were carried out on a SE 54 capillary column
using a Fisons 8000 gas chromatograph coupled with a Fisons
MD 800 quadrupole mass selective detector. 1H and 13C NMR
spectra were recorded at ambient temperature using a Bruker
AC 200 spectrometer using CDCl3 as internal standard.
Where a compound has been characterised as an inseparable
mixture of diastereoisomers, the NMR data for the major and
minor isomer have been reported as far as was discernable from
the spectrum of the mixture.
1g
1h
48 (70 : 30)
30 (51 : 49)
3.70–3.64
3.64–3.52
a Solutions of 1 in DMF–Bu4NBF4, undivided cells, Pt cathode and Al
anode, CO2 atmosphere, T = −20 ◦C, galvanostatic conditions: I = 8
mA cm−2, 6 F mol−1 of 1. b Yields of isolated products, calculated with
respect to starting 1. c The diastereoisomeric ratio was determined by 1H-
NMR. The reported ratio is the one between the more abundant isomer
and the less abundant one. d Chemical shifts (ppm) of the hydrogen
atoms of the methoxycarbonyl group. e The diastereoisomeric ratio was
determined by 13C-NMR.
In order to establish the identity of major and minor
diastereoisomers 2g and 2gꢀ, the deprotection of the more abun-
dant 2g was carried out following the method of Fukuzawa22
(using mild conditions to avoid racemization), transforming
compound 2g into the corresponding methyl ester (a known
compound).
This reaction has permitted us to establish the absolute
configuration of the new chiral center of the more abundant
isomer 2g as the R-isomer (Scheme 3).
Electrochemistry
Voltammetric measurements were performed with an Amel 552
potentiostat equipped with an Amel 566 function generator and
an Amel 563 multipurpose unit in a three-electrode cell; the
curves were dispayed on an Amel 863 recorder assisted by Nico-
let 3091 digital oscilloscope. A 492/Pt/1 Amel microelectrode
was employed. The reference electrode was a modified saturated
calomel electrode. Its potential was −0.07 V vs. SCE. All the
potentials are referred to modified SCE.
Electrolyses under galvanostatic control were carried out with
an Amel 552 potentiostat equipped with an Amel 721 integrator.
A one-compartment cell was used and the cathode was a Pt spiral
(apparent area 6.25 cm2) and the counter electrode was an Al
foil (apparent area 21.00 cm2).
Scheme 3
General procedure
A solution of 3-trans-cinnamoyl-(4R)-phenyl-2-oxazolidinone
(1a, 0.5 mmol) in 25 cm3 of DMF–(0.1 mol dm−3 Bu4NBF4) was
electrolyzed (undivided cells, Pt cathode, Al anode, at −20 ◦C)
under galvanostatic conditions (I = 8.0 mA cm−2) in presence
of carbon dioxide (p = 1 atm). After the consumption of 6 F
mol−1 of 1a, the current flow was stopped and the mixture of
electrolysis was poured into 150 cm3 of water. The resulting
aqueous phase was extracted with diethyl ether (3 × 30 cm3).
The combined organic extracts were washed with water and
brine. After they were cooled at 0 ◦C and treated with ethereal
CH2N2.23 (Caution: diazomethane is toxic and prone to cause
Conclusions
Chiral 2-phenyl succinic ester derivatives have been obtained
under mild conditions, short time (1 h) and in satisfactory yields
(30–61%) by electrochemical reduction of chiral acid cinnamic
derivatives under a CO2 atmosphere.
The influence of electrolysis conditions and of the various
chiral auxiliaries on the yields and the diastereoisomeric ratio
has been studied.
When Oppolzer’s camphor sultam and 4R-(diphenylmethyl)-
oxazolidin-2-one have been used as chiral auxiliaries the two
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 1 2 0 2 – 1 2 0 8
1 2 0 5

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development of specific sensitivity; in addition, it is potentially
explosive.) The usual workup gave the mixture of 2a, 2aꢀ and
1a. The diastereomeric ratio of 2a and 2aꢀ was calculated by 1H
NMR of the crude. The mixture of two isomers was obtained
after flash column chromatography (n-hexane–ethyl acetate 8 :
2 as eluent). In no case was the presence of dimethyl oxalate
evidenced.
J 17.6 and 9.8, COCHH), 3.66 (3 H, s, OCH3), 3.85 (1 H, t, J
6.2, NCH), 4.11 (1 H, dd, J 9.8 and 4.9, COCH) and 7.24–7.27
(5 H, m, ar); dC(50 Mhz; CDCl3) 19.8, 20.7, 26.4, 32.9, 38.4,
38.9, 44.8, 46.9, 47.7, 48.6, 52.3, 52.9, 65.2, 127.6, 128.0, 128.8,
137.3, 169.6, 173.0; GC-MS m/z (M•+ absent) 373 (2%), 191
(9), 132 (11); [a]2D9 +122.2 (c 0.63 in CHCl3).). Found: C, 62.21;
H, 6.70; N, 3.46; O, 19.74. C21H27NO5S requires C, 62.20; H,
6.71; N, 3.45; O, 19.73%.
Starting materials and electrolysis products. Spectral data of
known compounds have been compared with those reported in
the literature:
3-(3-Methoxycarbonyl-3-phenylpropionyl)-(4S)-isopropyl-2-
oxazolidinone (2c + 2cꢀ, mixture of two isomers). More
abundant isomer: dH(200 MHz; CDCl3) 0.87 (3 H, d, J 6.9,
CH3), 0.89 (3 H, d, J 6.9, CH3), 2.29–2.34 (1 H, m, CH(CH3)2),
3.25 (1 H, dd, J 18.4 and 3.6, COCHH), 3.66 (3 H, s, OCH3),
3.73–3.94 (1 H, m, COCHH), 4.09–4.28 (3 H, m, OCH2 and
COCH), 4.33–4.43 (1 H, m, NCH) and 7.24–7.29 (5 H, m, ar);
dC(50 Mhz; CDCl3) 14.6, 17.9, 28.4, 39.4, 46.5, 52.3, 58.5, 63.6,
127.6, 127.8, 127.9, 128.8, 137.4, 153.9, 171.3, 173.7; GC-MS
m/z (M•+ absent) 288 (M•+ − OCH3, 3%), 260 (4), 132 (10), 104
(28).
Less abundant isomer: dH(200 MHz; CDCl3) 0.80 (3 H, d,
J 6.8, CH3), 0.87 (3 H, d, J 6.8, CH3), 2.29–2.34 (1 H, m,
CH(CH3)2), 3.19 (1 H, dd, J 20.3 and 4.2, COCHH), 3.66 (3
H, s, OCH3), 3.73–3.94 (1 H, m, COCHH), 4.09–4.28 (3 H, m,
OCH2 and COCH), 4.33–4.43 (1 H, m, NCH) and 7.24–7.29
(5 H, m, ar); dC(50 Mhz; CDCl3) 14.7, 17.8, 28.4, 39.5, 46.6,
52.3, 58.4, 63.6, 127.6, 127.8, 127.9, 128.8, 137.6, 153.9, 171.3,
173.4; GC-MS m/z (M•+ absent) 288 (M•+ − OCH3, 3%), 260
(4), 132 (10), 104 (28).
3-trans-Cinnamoyl-(4R)-phenyl-2-oxazolidinone (1a).21
3-(3-Phenylpropanoyl)-(4R)-phenyl-2-oxazolidinone (3a).24
(4R)-Phenyl-2-oxazolidinone (4a): commercial.
3-(5-Oxo-2,3-diphenyl-cyclopentancarbonyl)-4R-phenyl-2-
oxazolidinone (mixture of two diastereomers, 5a + 5aꢀ).21
N-[(5R)-10,10-Dimethyl-3,3-dioxo-3-thia-4-
azatricyclo[5.2.1.01,5]dec-4-yl]-(E)-3-phenylpropenoylamide
(1b).25
3-trans-Cinnamoyl-(4S)-isopropyl-2-oxazolidinone (1c).21
3-trans-Cinnamoyl-(4S)-tert-butyl-2-oxazolidinone (1d).25
3-trans-Cinnamoyl-(4R,5S)-indano[1,2-d]-2-oxazolidinone
(1e).25
3-trans-Cinnamoyl-(4S)-benzyl-2-oxazolidinone (1f).21
3-trans-Cinnamoyl-(4R)-diphenylmethyl-2-oxazolidinone
(1g).26
3-trans-Cinnamoyl-(4S,5R)-diphenyl-2-oxazolidinone (1h).27
(R)-(−)-Dimethyl phenyl succinate.28
3-(3-Methoxycarbonyl-3-phenylpropionyl)-(4R)-phenyl-2-oxa-
zolidinone (2a + 2aꢀ, mixture of two isomers). More abundant
isomer: dH(200 MHz; CDCl3) 3.28 (1 H, dd, J 18.1 and 4.7,
COCHH), 3.50 (3 H, s, OCH3), 3.31–3.97 (1 H, m, COCHH),
4.02–4.14 (1 H, m, COCH), 4.20–4.30 (1 H, m, OCHH),
4.60–4.74 (1 H, m, NCH), 7.25–7.43 (10 H, m, ar); dC(50 Mhz;
CDCl3) 39.4, 46.5, 52.1 57.5, 70.1, 125.7, 127.6, 127.9, 128.6,
128.8, 129.1, 137.5, 138.5, 153.6, 170.7, 173.0; GC-MS m/z
(M•+ absent) 322 (M•+ − OCH3, 2%), 162 (16), 132 (6), 104
(100).
3-(3-Methoxycarbonyl-3-phenylpropionyl)-(4S)-tert-butyl-
2-oxazolidinone (2d + 2dꢀ, mixture of two isomers). More
abundant isomer: 0.90 (3 H, s, 3 × CH3), 3.20 (1 H, dd, J 18.2
and 4.2, COCHH), 3.63 (3 H, s, OCH3), 3.85 (1 H, t, J 18.2,
COCHH), 4.09–4.28 (3 H, m, OCH2 and COCH), 4.35–4.40 (1
H, m, NCH) and 7.18–7.27 (5 H, m, ar); dC(50 Mhz; CDCl3)
25.5, 35.8, 39.6, 46.7, 52.2, 60.8, 65.4, 127.5, 127.9, 128.8, 137.5,
154.5, 171.3, 173.3; GC-MS m/z (M•+ absent) 302 (M•+
−
OCH3, 5%), 132 (7), 104 (33), 59 (12).
Less abundant isomer: dH(200 MHz; CDCl3) 3.15 (1 H, dd, J
18.0 and 2.7, COCHH), 3.63 (3 H, s, OCH3), 3.31–3.97 (1 H,
m, COCHH), 4.02–4.14 (1 H, m, COCH), 4.20–4.30 (1 H, m,
OCHH), 4.60–4.74 (1 H, m, NCH), 7.25–7.43 (10 H, m, ar);
dC(50 Mhz; CDCl3) 39.5, 46.3, 52.3, 57.5, 70.2, 125.9, 127.8,
127.9, 128.7, 128.8, 129.1, 137.3, 138.5, 153.6, 170.7, 173.7; GC-
MS m/z (M•+ absent) 322 (M•+ − OCH3, 2%), 162 (16), 132 (6),
104 (100).
Less abundant isomer: dH(200 MHz; CDCl3) 0.86 (3 H, s, 3 ×
CH3), 3.23 (1 H, dd, J 18.2 and 4.0, COCHH), 3.65 (3 H, s,
OCH3), 3.84 (1 H, dd, J 18.2 and 2.6, COCHH), 4.09–4.28 (3
H, m, OCH2 and COCH), 4.35–4.40 (1 H, m, NCH) and 7.18–
7.27 (5 H, m, ar); dC(50 Mhz; CDCl3) 25.6, 35.6, 39.6, 46.8, 52.2,
61.1, 65.5, 127.6, 127.9, 128.8, 137.5, 154.6, 171.3, 173.6; GC-
MS m/z (M•+ absent) 302 (M•+ − OCH3, 5%), 132 (7), 104 (33),
59 (12).
N -[(5R)-10,10-Dimethyl-3,3-dioxo-3-thia-4-azatricyclo-
[5.2.1.01,5]dec-4-yl]-(E)-3-methoxycarbonyl-3-phenylpropionamide
(2b or the more abundant, less polar isomer 2bꢀ). dH(200 MHz;
CDCl3) 0.95 (3 H, s, CCH3), 1.20 (3 H, s, CCH3), 1.23–1.43
(2 H, m, CHH and CHH), 1.86–1.90 (3 H, m, CHH, CHH
and CH), 2.02–2.15 (2 H, m, CHH and CHH), 2.99 (1 H, dd,
J 17.2 and 4.2, COCHH), 3.39 (1 H, d, AB, J 14.0, Dm 17.3,
CHHSO2), 3.48 (1 H, d, AB, J 14.0, Dm 17.3, CHHSO2), 3.60
(1 H, dd, J 17.3 and 10.8, COCHH), 3.64 (3 H, s, OCH3),
3.82 (1 H, dd, J 7.5 and 5.0, NCH), 4.17 (1 H, dd, J 10.8 and
4.2, COCH) and 7.23–7.33 (5 H, m, ar); dC(50 Mhz; CDCl3)
19.8, 20.8, 26.5, 32.8, 38.3, 38.9, 44.7, 46.6, 47.8, 48.7, 52.3,
52.9, 65.1, 127.6, 127.9, 128.8, 137.5, 169.7, 173.2; GC-MS
m/z (M•+ absent) 373 (2%), 191 (9), 132 (11); [a]2D9 −144.8 (c
0.58 in CHCl3). Found: C, 62.19; H, 6.73; N, 3.44; O, 19.72.
C21H27NO5S requires C, 62.20; H, 6.71; N, 3.45; O, 19.73%.
3-(3-Methoxycarbonyl-3-phenylpropionyl)-(4R,5S)-indano-
[1,2-d]-2-oxazolidinone (2e + 2eꢀ, mixture of two isomers).
More abundant isomer: dH(200 MHz; CDCl3) 3.27 (1 H, dd, J
18.4 and 4.5, COCHH), 3.36 (2 H, d, J 3.2, CH2), 3.68 (3 H, s,
OCH3), 3.80 (1 H, dd, J 18.4 and 10.3, COCHH), 4.19 (1 H,
dd, J 10.3 and J 4.5, COCH), 5.21–5.32 (1 H, m, OCH), 5.89
(1 H, d, J 6.8, NCH) and 7.19–7.59 (9 H, m, ar); dC(50 Mhz;
CDCl3) 37.9, 39.4, 46.8, 52.3, 62.8, 78.4, 125.1, 127.2, 127.9,
128.8, 129.9, 137.6, 139.3, 152.9, 171.6, 173.2.
Less abundant isomer: dH(200 MHz; CDCl3) 3.17 (1 H, dd, J
19.0 and 3.3, COCHH), 3.36 (2 H, d, J 3.2, CH2), 3.70 (3 H, s,
OCH3), 3.85 (1 H, dd, J 19.0 and 9.2, COCHH), 4.19 (1 H, dd,
J 10.3 and J 4.5, COCH), 5.21–5.32 (1 H, m, OCH), 5.89 (1 H,
d, J 6.8, NCH) and 7.19–7.59 (9 H, m, ar); dC(50 Mhz; CDCl3)
37.9, 39.5, 46.5, 52.3, 63.1, 78.4, 125.2, 127.2, 127.6, 128.8, 129.9,
137.4, 139.5, 152.9, 171.6, 173.7.
N -[(5R)-10,10-Dimethyl-3,3-dioxo-3-thia-4-azatricyclo-
[5.2.1.01,5]dec-4-yl]-(E)-3-methoxycarbonyl-3-phenylpropionamide
(2b or the less abundant, more polar isomer 2bꢀ ). dH(200 MHz;
CDCl3) 0.92 (3 H, s, CCH3), 0.99 (3 H, s, CCH3), 1.23–1.41
(2 H, m, CHH and CHH), 1.81–1.88 (3 H, m, CHH, CHH
and CH), 1.98–2.01 (2 H, m, CHH and CHH), 3.11 (1 H, dd, J
17.1 and 5.0, COCHH), 3.44 (2 H, s, CH2SO2), 3.59 (1 H, dd,
3-(3-Methoxycarbonyl-3-phenylpropionyl)-(4S)-benzyl-2-oxa-
zolidinone (2f + 2fꢀ, mixture of two isomers). More abundant
isomer: dH(200 MHz; CDCl3) 2.81 (1 H, dd, J 13.4 and 9.2,
COCHH), 3.24–3.31 (2 H, m, CH2Ph), 3.69 (3 H, s, OCH3),
3.75–3.97 (1 H, m, COCHH), 4.13–4.25 (3 H, m, COCH and
OCH2), 4.58–4.70 (1 H, m, NCH) and 7.13–7.41 (10 H, m, ar);
dC (50 MHz; CDCl3) 37.6, 39.6, 46.5, 52.3, 54.9, 66.2, 127.3,
1 2 0 6
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127.9, 128.6, 128.8, 129.1, 129.3, 135.0, 137.5, 153.3, 171.3,
173.4; GC-MS m/z (M•+ absent) 336 (M•+ − OCH3, 14%), 191
(16), 176 (5), 91 (41).
3 C. A. Miller and L. M. Long, J. Am. Chem. Soc., 1951, 73, 4895–4898.
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and C.-J. Li, SYNLETT, 2001, 9, 1470–1472.
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James and J. K. Stille, J. Am. Chem. Soc., 1976, 98, 1810–1823; (c) T.
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Saigo, Tetrahedron Lett., 1998, 39, 7529–7532; (b) S. Takeuchi, Y.
Ukaji and K. Inomata, Bull. Chem. Soc. Jpn., 2001, 74, 955–958;
(c) L. Wang, W. Kwok, J. Wu, R. Guo, T. T.-L. Au-Yeung, Z. Zhou,
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More abundant isomer: dH(200 MHz; CDCl3) 2.71 (1 H, dd,
J 13.3 and 9.6, COCHH), 3.15–3.22 (2 H, m, CH2Ph), 3.69 (3
H, s, OCH3), 3.75–3.97 (1 H, m, COCHH), 4.13–4.25 (3 H, m,
COCH and OCH2), 4.58–4.70 (1 H, m, NCH) and 7.13–7.41
(10 H, m, ar); dC (50 MHz; CDCl3) 37.7, 39.6, 46.5, 52.3, 55.1,
66.3, 127.3, 127.6, 128.6, 128.9, 129.3, 129.4, 135.1, 137.4, 153.3,
171.3, 173.6; GC-MS m/z (M•+ absent) 336 (M•+ − OCH3, 14%),
191 (16), 176 (5), 91 (41).
3-(3-Methoxycarbonyl-3-phenylpropionyl)-(4R)-diphenylmethyl-
2-oxazolidinone (2g or the more abundant, less polar isomer
2gꢀ). dH(200 MHz; CDCl3) 3.21 (1 H, dd, J 18.6 and 4.1,
COCHH), 3.70 (3 H, s, OCH3), 3.79 (1 H, dd, J 18.6 and 10.6,
COCHH), 4.13 (1 H, dd, J 10.6 and 4.1, COCH), 4.44 (2 H, d,
J 5.2, OCH2), 4.76 (1 H, d, J 4.4, CH(Ph)2), 5.23–5.31 (1 H, m,
NCH), 7.05–7.17 (5 H, m, ar) and 7.24–7.41 (10 H, m, ar); dC
(50 MHz; CDCl3) 39.6, 46.4, 49.9, 52.3, 56.1, 64.7, 127.0, 127.6,
127.9, 128.2, 128.6, 128.7, 128.8, 128.9, 129.5, 137.6, 137.8,
139.6, 153.2, 171.1, 173.4; GC-MS m/z 443 (M•+, 3%), 412
(2), 276 (2), 191 (100), 167 (50); [a]2D7 −138.6 (c 0.70 in CHCl3).
Found: C, 73.11; H, 5.69; N, 3.17. C27H25NO5 requires C, 73.12;
H, 5.68; N, 3.16%.
9 P. R. Auburn, P. B. Mackenzie and B. Bosnich, J. Am. Chem. Soc.,
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10 (a) M. Aresta and A. Dibenedetto, in Carbon Dioxide Recovery and
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2003, pp. 395–402; (c) as regards the conversion of carbon dioxide
into carbamato derivatives, see: D. B. Dell’Amico, F. Calderazzo,
L. Labella, F. Marchetti and G. Pampaloni, Chem. Rev., 2003,
103, 3857–3897; (d) as regards carbon dioxide as C1 synthon for
introducing the carbonate function, see: D. Ballivet-Tkatchenko,
S. Sorokina, in Carbon Dioxide Recovery and Utilization, ed.
M. Aresta, Kluwer Academic Publishers, Dordrecht, 2003, pp. 261–
277; (e) Proceedings of the International Conference on Carbon
Dioxide Utilization, Karlsruhe, Germany, 1999.
11 (a) J. C. Gressin, D. Michelet, L. Nadjo and J. M. Save´ant,
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Electrochem., 1997, 27, 875–889.
12 (a) L. J. Klein and D. G. Peters, in Organic Electrochemistry, ed.
M. Sainsbury, Elsevier, Amsterdam, 2002, vol. V, ch. 1; (b) D. G.
Peters, in Organic Electrochemistry, ed. H. Lund and O. Hammerich,
Marcel Dekker, New York, 2001, ch. 8; (c) J. Casanova and V. P.
Reddy, in The Chemistry of Functional Groups: the Chemistry of
Halides, Pseudohalides and Azides, ed. S. Patai and Z. Rappoport,
Wiley, New York, 1995, supplement D2, Part 2, Ch. 18.
13 (a) J. H. P. Utley and M. Folmer Nielsen, in Organic Electrochemistry,
ed. H. Lund, O. Hammerich, Marcel Dekker, New York, 2001, Ch.
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and M. Tokuda, SYNLETT, 2001, 418–420.
3-(3-Methoxycarbonyl-3-phenylpropionyl)-(4R)-diphenylmethyl-
2-oxazolidinone (2g or the less abundant, more polar isomer 2gꢀ).
dH(200 MHz; CDCl3) 3.04 (1 H, dd, J 18.4 and 3.6, COCHH),
3.64 (3 H, s, OCH3), 3.68–3.81 (1 H, m, COCHH), 4.02 (1 H,
dd, J 10.8 and 3.6, COCH), 4.34–4.49 (2 H, m, OCH2), 4.65
(1 H, d, J 5.7, CH(Ph)2), 5.25–5.32 (1 H, m, NCH), 7.01–7.08
(5 H, m, ar) and 7.24–7.37 (10 H, m, ar); dC (50 MHz; CDCl3)
39.4, 46.4, 50.9, 52.3, 56.4, 65.3, 127.1, 127.7, 127.9, 128.4,
128.6, 128.7, 128.8, 128.9, 129.2, 137.5, 137.9, 139.5, 153.3,
170.9, 173.6; GC-MS m/z 443 (M•+, 3%), 412 (2), 276 (2), 191
(100), 167 (50); [a]2D9 +68.1 (c 0.71 in CHCl3). Found: C, 73.13;
H, 5.67; N, 3.15. C27H25NO5 requires C, 73.12; H, 5.68; N,
3.16%.
3-(3-Methoxycarbonyl-3-phenylpropionyl)-(4S,5R)-diphenyl-
2-oxazolidinone (2h + 2hꢀ, mixture of two isomers). More
abundant isomer: dH(200 MHz; CDCl3) 3.30 (1 H, dd, J 17.7
and 2.9, COCHH), 3.64 (3 H, s, OCH3), 3.87–4.04 (1 H, m,
COCHH), 4.07–4.18 (1 H, m, COCH), 5.64 (1 H, d, AB, J
7.2, Dm 58.3, NCH), 5.93 (1H, d, AB, J 7.2, Dm 58.3, OCH),
6.78–7.31 (15 H, m, ar); dC (50 MHz; CDCl3) 39.7, 46.4, 52.2,
62.8, 80.5, 126.2, 126.6, 127.9, 128.1, 128.3, 128.5, 128.9, 132.7,
134.3, 137.4, 153.6, 170.6, 173.6; GC-MS m/z (M•+ absent) 398
(M•+ − OCH3, 11%), 180 (77), 132(24).
Less abundant isomer: dH(200 MHz; CDCl3) 3.36 (1 H, dd,
J 17.2 and 3.9, COCHH), 3.52 (3 H, s, OCH3), 3.87–4.04
(1 H, m, COCHH), 4.07–4.18 (1 H, m, COCH), 5.60 (1 H, d,
AB, J 7.5, Dm 45.0, NCH), 5.83 (1H, d, AB, J 7.5, Dm 45, OCH),
6.78–7.31 (15 H, m, ar); dC (50 MHz; CDCl3) 39.5, 46.6, 52.2,
62.7, 80.6, 126.1, 126.6, 127.6, 128.0, 128.2, 128.4, 128.8, 132.7,
134.0, 137.7, 153.6, 170.5, 173.0; GC-MS m/z (M•+ absent) 398
(M•+ − OCH3, 11%), 180 (77), 132(24).
14 (a) V. A. Petrosyan, Russ. Chem. Bull., 1995, 44, 1–12; (b) J. H. P. Utley
and M. Folmer Nielsen, in Organic Electrochemistry, ed. H. Lund and
O. Hammerich, Marcel Dekker, New York, 2001, pp. 1227–1257, and
references therein; (c) L. Palombi, M. Feroci, M. Orsini and A. Inesi,
Chem. Commun., 2004, 1846–1847.
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Acknowledgements
16 Y. Yamamoto, H. Maekawa, S. Goda and I. Nishiguchi, Org. Lett.,
2003, 15, 2755–2758.
The authors wish to thank Mr M. Di Pilato for his contribution
to the experimental part of this work. This work was supported
by research grants from MURST (Cofin 2004) and CNR, Roma
Italy.
17 (a) S. Condon-Gueugnot, E. Le´onel, J.-Y. Ne´de´lec and J. Pe´richon,
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