Cyclopropanation of alkenes, N-H and S-H insertion of ethyl diazoacetate catalysed by ruthenium porphyrin complexes

Article abstract of DOI:10.1016/S0040-4020(99)01050-9

Product yields, stereoselectivities and regioselectivities for cyclopropanation reactions of ethyl diazoacetate with styrene derivatives and α-heteroatom alkenes, catalysed by ruthenium porphyrins, are reported and compared with observed stereoselectivities for cyclopropanation reactions catalysed with other metalloporphyrin catalysts. Linear correlations are observed when the rates for competitive cyclopropanation or product stereoisomer ratio are plotted against Hammet constants of various ring- substituted groups on styrenes. Isomeric distribution for the cyclopropanation of isoprene and 1,3-pentadiene with ethyl diazoacetate and competition studies of the cyclopropanation and diazo insertion into heteroatom-hydrogen bonds are also reported. All these results agree with a major electronic and steric influence on both the regiochemical and stereochemical control in the catalytic cyclopropanation and diazo insertion reactions. (C) 2000 Elsevier Science Ltd.

Full text of DOI:10.1016/S0040-4020(99)01050-9

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 615–621
Cyclopropanation of Alkenes, N–H and S–H Insertion of Ethyl
Diazoacetate Catalysed by Ruthenium Porphyrin Complexes
*
´
Erwan Galardon, Paul Le Maux and Gerard Simonneaux
´
´
Laboratoire de Chimie Organometallique et Biologique, UMR 6509, Universite de Rennes 1, 35042 Rennes Cedex, France
Received 20 April 1999; accepted 6 December 1999
Abstract—Product yields, stereoselectivities and regioselectivities for cyclopropanation reactions of ethyl diazoacetate with styrene
derivatives and a-heteroatom alkenes, catalysed by ruthenium porphyrins, are reported and compared with observed stereoselectivities
for cyclopropanation reactions catalysed with other metalloporphyrin catalysts. Linear correlations are observed when the rates for com-
petitive cyclopropanation or product stereoisomer ratio are plotted against Hammet constants of various ring-substituted groups on styrenes.
Isomeric distribution for the cyclopropanation of isoprene and 1,3-pentadiene with ethyl diazoacetate and competition studies of the
cyclopropanation and diazo insertion into heteroatom–hydrogen bonds are also reported. All these results agree with a major electronic
and steric influence on both the regiochemical and stereochemical control in the catalytic cyclopropanation and diazo insertion reactions.
᭧ 2000 Elsevier Science Ltd. All rights reserved.
Introduction
porphyrin bearing electron-withdrawing pentafluorophenyl
groups can be employed as precatalyst.7 As a consequence,
our attention turned to the use of ruthenium analogues,
which were anticipated to be more stable.
Catalytic cyclopropanation reactions have become one of
the most general and efficient methods available to the
synthetic organic chemist.1 There is also considerable
interest in the development of effective catalytic systems
for the enantioselective cyclopropanation of prochiral
olefins.2,3 The major advances have recently been achieved
with various chiral rhodium derivatives4 and with chiral
ruthenium bis(oxazolinyl)pyridine catalysts, the latter
developed by Nishiyama.5 Although the accomplishments
achieved thus far are quite impressive, exploration of new
effective catalysts is still essential to extend the scope of
these reactions.
Ruthenium porphyrins have been used frequently for oxida-
tion reactions,8,9 based on the greater stability of ruthenium
compounds in various oxidation states, ranging from Ru(II)
to Ru(VI). In contrast to these extensive investigations, only
a few examples of catalytic reactions that proceed through
ruthenium carbene complexes have been reported using
Ru(II) porphyrins as catalysts.10,11 This is quite unexpected
since all the synthetic methods for the insertion of ruthenium
into porphyrins yield ruthenium carbonyl complexes,12 which
are good precursors of carbene derivatives.13 Other methods
for the preparation of (porphyrin) ruthenium (carbene)
complexes were also previously reported.14 Our interest in
the chemistry of ruthenium porphyrins prompted us to inves-
tigate the cyclopropanation reaction. We previously reported
the preparation and the first X-ray structure of a (porphyrin)
ruthenium (carbene) compound.13 We now wish to report
herein the details of the catalytic reaction of diazoesters
with simple olefins catalysed with ruthenium porphyrins.
Comparison with other rhodium,15 osmium16 and iron
porphyrin catalytic systems7 will also be discussed.
The discovery that carbene complexes of hepatic cyto-
chrome P450 iron(II) are important intermediates during
the reductive metabolisation of polyhalogenated com-
pounds6a has stimulated intense interest in the chemistry
of carbene derivatives such as carbene ferrous porphyrin
complexes.6 Also of interest are precursor metalloporphyrins
that can serve to catalyse carbene addition to unsaturated
organic substrates. One strategy would be to employ ferrous
porphyrins or ferric porphyrins under reducing conditions.
Actually, such a system has been recently reported for the
cyclopropanation of styrene.7 However, the ferrous
porphyrin precursors are too reactive towards dioxygen to be
very promising for practical application in organic synthesis. It
must also be underlined that a nice system with iron(III)
Results
Cyclopropanation of styrene derivatives
Keywords: catalysis; cyclopropanation; porphyrins; ruthenium.
* Corresponding author. Tel.: ϩ33-02-99-28-62-85; fax: ϩ33-02-99-28-
16-46; e-mail: simonnea@univ-rennes1.fr
meso-Tetraphenylporphyrin carbonyl ruthenium (TPP)Ru-
(CO) (Fig. 1) catalysed decomposition of ethyl diazoacetate
0040–4020/00/$ - see front matter ᭧ 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(99)01050-9

616
E. Galardon et al. / Tetrahedron 56 (2000) 615–621
Figure 1. Catalysts used in this study.
(EDA) in the presence of styrene resulted in the formation of
the corresponding cyclopropane in 93% yield with more
than 500 turnover (Eq. 1).11a
To examine the scope of this cyclopropanation, the reaction
of a number of styrene derivatives and conjugated alkenes
with EDA in the presence of (TPP)Ru(CO) at 25ЊC in
toluene was studied (Tables 1–3). First, cyclopropanation
competition experiments were conducted with a large
excess of each substrate and limiting quantities of ethyl
diazoacetate (substrate/EDAˆ10/1) (Table 1). The relative
reactivities were measured by the molar ratio in GC/MS of
cyclopropyl esters derived from styrene and from the other
substrates. In all these experiments, cyclopropanes are the
major products, usually obtained with diethyl maleate and
fumarate as by-products. Electron-rich styrenes (4-XˆOMe
and Me; a-methyl styrene; 2,4-dimethyl styrene) are
cyclopropanated more efficiently than alkenes bearing
electron-withdrawing groups (4-XˆCl and CF3).
Proton NMR and GC analysis of the crude reaction mixture
indicated a trans/cis stereoselectivity of 13/1.
Table 1. Competition studies of the cyclopropanation of various substituted
styrenes (substrate A) and styrene (substrate B) with EDA catalysed by
(TPP)Ru(CO) (catalyst: 0.0027 mmol; styrenes: 2.70 mmol; EDA:
0.270 mmol; 4 h; RT)
Substrate A
Ratio of products
derived from A/B
4-Methoxystyrene
4-Methylstyrene
3.2
2.8
The data were fit to a Hammett plot (Fig. 2), with a good
correlation ꢀr2ˆ0:991† which allowed us to calculate a r
value of Ϫ1:29^0:08: Analogous preferences for electron
rich alkenes were observed in the corresponding cyclo-
propanation reactions catalysed by iron porphyrins.7
4-Chlorostyrene
0.9
4-Trifluoromethylstyrene
a-Methylstyrene
2,4-Dimethylstyrene
0.3
10.1
2.9
Table 2. Isomeric distribution (%) for the cyclopropanation of isoprene with EDA catalysed by (TPP)Ru(CO) (catalyst: 0.0027 mmol; olefin: 2.70 mmol;
EDA: 0.270 mmol; 4 h; RT)
Isomeric distribution
34.1
40.1
2.6
23.2
Table 3. Isomeric distribution (%) for the cyclopropanation of trans-1-3-pentadiene with EDA (catalyst: 0.0027 mmol; olefin: 2.70 mmol; EDA: 0.270 mmol;
4 h; RT)
Isomeric distribution
5.7
6.4
40.8
47.1

E. Galardon et al. / Tetrahedron 56 (2000) 615–621
617
Figure 2. Hammet plot for the competitive cyclopropanation of styrene derivatives with EDA.
Table 4. Diastereoselectivity in the cyclopropanation of 4-substituted
styrene derivatives catalysed by (MPIXDME)Ru(CO) (catalyst:
0.0027 mmol; styrene: 0.540 mmol; EDA: 0.270 mmol; 4 h; RT)
cyclopropanation of trans-1-3-pentadiene, the selectivity
being close to one (Table 3). However, increasing the steric
bulk of the olefinic substituents results in an enhancement of
the relative percentage of the less encumbered cyclopropane
product with isoprene, and changes the trans/cis ratios from
1.1 to 8.9 for the two different regioisomers (Table 2).
X
trans/cis Ratio
OMe
Me
H
4.3
5.4
9.3
We then investigated the relation between the diastereo-
selectivity of the reaction and the electronic effect of the
para-substituent of styrenes. We used the mesoporphyrin
dimethyl ester carbonyl ruthenium complex17 (MPIXD-
ME)Ru(CO) (Fig. 1) as catalyst to avoid steric interactions
between the meso-substituents of the porphyrin ring and the
olefin. Data are shown in Table 4.
Cl
12.0
To complete these data, we also studied the cyclopropan-
ation of isoprene and trans-1,3-pentadiene. Isomeric distri-
butions reported in Tables 2 and 3, respectively, emphasise
the pronounced electronic and shape preference of the
catalyst previously reported.11a Thus the results indicate
that the cycloaddition of isoprene preferentially occurred
(Ͼ74%) at the electron-rich double bond and confirm the
results obtained with substituted styrenes. The regioisomer
distribution is also influenced by steric effects. Terminal
linear olefins were cyclopropanated with high yields.
Accordingly the cycloaddition preferentially occurred at
the terminal double bond with trans-1-3-pentadiene
(Ͼ87%).
The plot of the log(trans/cis) against the Hammet constant is
displayed in Fig. 3 and gives rˆϩ0:93^0:07 ꢀr2ˆ0:957†:
The trans/cis ratio is strongly affected by the electronic
effect of the alkene substituents; the reaction with
4-chlorostyrene is almost three times more selective than
the reaction with 4-methoxystyrene.
To get more information about the alkenes that are elec-
tronically tolerated by the ruthenium catalyst, we investi-
gated the cyclopropanation of some vinyl compounds
having an a-heteroatom. The results are summarised in
The influence of olefin structure on observed stereo-
selectivity (trans/cis ratio) is surprisingly weak for
Figure 3. trans/cis Ratio against Hammet parameters for the cyclopropanation of styrene derivatives with EDA.

618
E. Galardon et al. / Tetrahedron 56 (2000) 615–621
Table 5. Cyclopropanation of vinyl compounds with a-Heteroatoms cata-
lysed by (TPP)Ru(CO) (catalyst: 0.0027 mmol; olefin: 0.270 mmol; EDA:
0.270 mmol; 6 h; RT)
Table 6. Competition studies of the cyclopropanation and diazo insertion
into heteroatom–hydrogen bond (catalyst: 0.0027 mmol; substrates A and
B: 2.70 mmol; EDA: 0.270 mmol; 4 h; RT)
Vinyl compound
Yield (%)
74
trans/cis Ratio
Substrate A
Substrate B
% of Insertion
11.5
Ͼ99
Ͼ99
Ͼ99
61
2.1
0
–
–
67
3.6
61
0
1.8
–
rhodium-catalysed reaction of diazoesters with unsaturated
alcohols.18
Discussion
The data in Tables 1–6 clearly show that the chemical
reactivity of alkenes in the cyclopropanation catalysed by
ruthenium–porphyrin complexes is strongly dependent
upon the electronic nature of the substrate. These results
are in agreement with our precedent studies13 showing
that a porphyrin ruthenium carbene complex can be an inter-
mediate of the cyclopropanation reaction, the limiting step
being the attack of the double bond on the electrophilic
carbene. When the rate of the carbene transfer from the
ruthenium complex to the olefin is too low, the competitive
formation of diethyl maleate and fumarate by attack of EDA
on the electrophilic carbon becomes the major process.
Electron-releasing groups increase the nucleophilic
behaviour of the alkene, and so increase the rate of cyclo-
propanation, whereas the presence of electron-withdrawing
groups decreases this rate. The same trend has already been
reported by Kodadeck7 and Woo16 using iron and osmium
porphyrins, respectively. In contrast, no electronic influence
was detected for rhodium porphyrin catalysed cyclo-
propanation.15c
0
–
Table 5. Alkenes bearing electron-donating groups (S–R;
O–R) are efficiently cyclopropanated with a weak stereo-
selectivity (an equimolar ratio of alkene to EDA was used
for these reactions). In contrast, alkenes bearing electron-
withdrawing groups (O–CyO; Br; SO2) show a dramatic
loss of reactivity, only the dimeric by-products, diethyl
maleate and fumarate, being observed. Simple olefins such
as 4-vinyl-1-cyclohexene or allylbenzene are also very poor
substrates.11a Thus heteroatom substituents such as oxygen
in vinyl ether and sulphur in vinyl thioether offer advantages
in reactivity but not in selectivity. However, increasing the
steric bulk of the olefinic substituent such as in 1-vinyl-2-
pyrrolidinone, does result in enhancement of the relative
percentage of the less encumbered cyclopropane product
with a ratio of trans=cisˆ11:5: These data confirm the
very strong sensitivity of the catalyst to both electronic
and steric effects of the alkene substituents.
When there are no (or weak) steric interactions between the
substrate and the meso-substituents of the macrocycle, the
diastereoselectivity (trans/cis ratio) is also influenced by
electronic effects. As shown by data in Table 4, the trans
isomer is very predominant when electron-withdrawing
groups are in the para-position of the styrene. Thus decreas-
ing the reactivity of the double bond results in an enhance-
ment of the trans/cis ratio. In contrast, it must be noted that
we have recently shown that the enantioselectivity of the
cyclopropanation with chiral ruthenium porphyrin
complexes is not affected by such electronic effects.11b
The selectivity is also strongly dependent upon the metallo-
porphyrin used as catalyst. Osmium and iron,7,16 as well as
ruthenium derivatives, provide the trans cyclopropyl ester
as the major product. In contrast rhodium usually leads to a
trans/cis ratio close to 1, and sometimes to the cis isomer as
main product.15
Competition between cyclopropanation and insertion
into N–H or S–H bonds
To fully characterise the catalytic property of the ruthenium
porphyrin compound, an investigation of the competition
between the cyclopropanation of alkenes with EDA and
the insertion of the diazo compound into heteroatom–
hydrogen bond was also undertaken. In a typical experi-
ment, 1 equiv. of EDA was added to a mixture of
10 equiv. of styrene and 10 equiv. of a thiol or an amine
in toluene (see Section 4). Results are displayed in Table 6.
All the data show that the major reaction is the insertion of
EDA into a heteroatom bond to give either an a-thio ethyl
ester or an N-substituted glycine ester. For example, only
the insertion compound is observed by GC/MS and 1H NMR
when 4-aminostyrene is the substrate. It should be noted that
a preference for insertion has already been observed in the
The second main characteristic of ruthenium porphyrin
catalyst is its strong shape selectivity. Only alk-1-enes and
1,1-disubstituted alkenes react efficiently with EDA. This is

E. Galardon et al. / Tetrahedron 56 (2000) 615–621
619
Scheme 1. Catalytic cycle for the cyclopropanation of alkenes with (TPP)Ru(CO).
shown by data in Table 3, the more activated double bond
analyses were performed on a CE GC8000 coupled with
being cyclopropanated more slowly than the less hindered.
Thus the ruthenium is still similar to iron and osmium
based catalysts, and contrasts with the broader substrate
compatibility of rhodium porphyrins.15
a
Finnigan Mat AutomassII. High-Resolution Mass
Spectrometry (EI) was performed at the Centre de Mesures
Physiques de l’Ouest, Rennes on a Varian MAT311 spectro-
meter (2980 V, 30Њ) coupled with a GC. Toluene was
distilled under sodium/benzophenone. The porphyrins
Based on our previous results13 and on other work,7 we
were synthesised by literature methods: TPPH2 and
20
propose
a
catalytic cycle to rationalise these data
MPIXDME-H2.21 The corresponding ruthenium carbonyl
complexes were obtained by refluxing the porphyrins in
o-dichlorobenzene22 with Ru3CO12.23 Ethyl diazoacetate,
styrenes and vinyl derivatives were purchased from Aldrich,
Acros Organics or Lancaster.
(Scheme 1). The first step of this cycle is the formation of
a ruthenium carbene complex. After the liberation of the
cyclopropane, a highly reactive bare ruthenium(II) complex
[(TPP)Ru] (possibly coordinated by nitrogen19) is released
in solution, and can react with a new molecule of EDA. A
tri-centre late transition state with a small cationic charge
dϩ on the double bond,7 which is consistent with the fact
that porphyrin ruthenium(II) carbene complexes are isolable
and with the moderate negative r value obtained from the
Hammet plot, is probably involved in the formation of the
cyclopropane. This scheme is supported by the strong shape
selectivity observed with tri- or tetra-substituted alkenes.
This is explained by severe steric interactions between the
porphyrin ring and the olefin substituents in the transition
state. Such interactions would be reduced in the early
transition state proposed for rhodium-catalysed cyclo-
propanation.7
1
Stereochemistry of cyclopropyl esters was assigned by H
NMR spectroscopy by comparison with published data
when previously described.24,25 The stereochemical assign-
ments for the new cyclopropyl esters were based on a
combination of NOE enhancement studies and determina-
tion of coupling constants on the cyclopropane ring. Once
the major isomer was assigned by NMR, product ratios were
then determined by GC/MS.
Cyclopropanation of styrene derivatives using (MPIXD-
ME)Ru(CO). In a typical experiment 2.7 mmol of catalyst,
0.54 mmol of olefin were placed in a schlenk tube under
argon, and dissolved in 300 ml of toluene. Ethyl diazoace-
This model and the data in Table 4 showing that the trans/
cis ratio is inversely proportional to the reactivity of the
olefin also support the proposal of Kodadek and co-workers7
that the diastereoselectivity of the cyclopropanation is the
result of a late transition state.
tate (28 ml, 0.27 mmol) was then slowly added (16 ml hϪ1
)
at room temperature. After 3 h of stirring, GC/MS analysis
was performed to determine yields.
Cyclopropanation of vinyl compounds using (TPP)Ru-
(CO). In a typical experiment 2.7 mmol of catalyst and
0.27 mmol of olefin were placed in a schlenk tube under
argon and dissolved in 300 ml of toluene. Ethyl diazoacetate
(28 ml, 0.27 mmol, in 92 ml of toluene) was then slowly
added (9 ml hϪ1) at room temperature. After 3 h of stirring,
GC/MS analysis was performed to determine yields.
Products were purified by silica gel chromatography
(pentane/ether, 5:1).
In summary, highly efficient cyclopropanations have been
developed by reaction of ethyl diazoacetate with alkenes
using a commercially available ruthenium porphyrin
catalyst. The success of this methodology rests on the
excellent stereoselectivity and high turnovers that are
observed in the cyclopropanation and also the easy
extension to chiral ruthenium porphyrins.
Competition studies. In a typical experiment 2.7 mmol of
catalyst, 2.70 mmol of thiol (or styrene derivative) and
2.70 mmol of styrene were placed in a schlenk tube under
argon, and dissolved in 300 ml of toluene. Ethyl diazo-
acetate (28 ml, 0.27 mmol) was then slowly added
(20 ml hϪ1) at room temperature. After 3 h of stirring,
GC/MS analysis was performed to determine yields.
Experimental
General procedures
NMR spectra were recorded in CDCl3 on a Bruker 200 DPX
and chemical shifts are referenced to internal TMS. GC/MS

620
E. Galardon et al. / Tetrahedron 56 (2000) 615–621
with Organometallic Compounds; Cornhils, B., Herrmann, W. A.,
Eds.; VCH: Weinheim, 1996; p 733.
When an amine was used as substrate, the amine was added
together with EDA to avoid catalyst poisoning.11e
3. Doyle, M. P.; Peterson, C. S.; Zhou, Q. L.; Nishiyama, H.
J. Chem. Soc., Chem. Commun. 1997, 211.
1
Ethyl 2-butoxycyclopropanecarboxylate (E isomer). H
4. (a) Doyle, M. P.; Pieters, R. J. J. Am. Chem. Soc. 1991, 113,
1423. (b) Doyle, M. P.; Eismont, M. Y.; Protopova, M. N.; Kwan,
M. M. Y. Tetrahedron 1994, 50, 4519. (c) Doyle, M. P.; Austin,
R. E.; Bailey, A. S.; Dwyer, M. P.; Dyatkin, A. B.; Kalinin, A. V.;
Kwan, M. M. Y.; Liras, S.; Oalmann, C. J.; Pieters, R. J.;
Protopopova, M. N.; Raab, C. E.; Roos, G. H. P.; Zhou, Q. L.;
Martin, S. F. J. Am. Chem. Soc. 1995, 117, 5763.
5. (a) Nishiyama, H.; Itoh, Y.; Matsumoto, H.; Park, S.-B.; Itoh, K.
J. Am. Chem. Soc. 1994, 116, 2223. (b) Nishiyama, H.; Itoh, Y.;
Sugawara, Y.; Matsumoto, H.; Aoki, K.; Kenji, I. Bull. Chem. Soc.
Jpn. 1995, 68, 1247.
NMR (CDCl3, d): 4.11 (q, 2H, Jˆ7.1 Hz, CH2); 3.57 (d of d
of d, 1H, Jˆ1.9 Hz, 4.3 Hz, 6.1 Hz, OCH); 3.52 (m, 2H,
CH2O); 1.72 (d of d of d, 1H, Jˆ2.1 Hz, 6.2 Hz, 9.4 Hz,
CHCO2); 1.28 (m, 2H, CH2); 1.55–0.82 (10H,
CH3ϩCH3CH2CH2). IR (cmϪ1): 1725 (nCO). Mass (m/z)
(relative intensity): 186 (3), 129 (8), 101 (22), 85 (17), 57
(69), 41 (46), 19 (100); HR-MS (m/z): calcd for C10H18O3
(Mϩ): 186.1256, found: 186.1263.
Ethyl 2-pyrrolidinonecyclopropanecarboxylate (E isomer).
1H NMR (CDCl3, d): 4.19 (q, 2H, Jˆ7.2 Hz, CH2); 3.35 (t,
2H, 7.0 Hz, CH2CO); 3.21 (m, 1H, NCH); 2.43 (t, 2H,
Jˆ8.0 Hz, CH2N); 2.06 (m, 2H, CH2); 1.89 (d of d of d,
1H, Jˆ3.0 Hz, 5.9 Hz, 9.1 Hz, CHCO2); 1.50 (m, 2H, CH2);
1.29 (t, 3H, Jˆ7.2 Hz, CH3). IR (cmϪ1): 1713 (nCOO), 1704
(nCO). Mass (m/z) (relative intensity): 197 (8), 168 (10), 151
(16), 140 (8), 124 (100), 112 (64), 96 (21), 84 (27), 69 (35),
56 (31), 41 (79), 28 (34), 18 (39); HR-MS (m/z): calcd for
C10H15NO3 (Mϩ): 197.1052, found: 197.1046.
´
6. (a) Mansuy, D.; Lange, M.; Chottard, J. C.; Guerin, P.;
`
Morliere, P.; Brault, D. J. Chem. Soc., Chem. Commun. 1977,
648. (b) Mansuy, D.; Lange, M.; Chottard, J. C.; Bartoli, J. F.;
Chevrier, B.; Weiss, R. Angew. Chem., Int. Ed. Engl. 1978, 781.
(c) Mansuy, D.; Battioni, J. P. J. Chem. Soc., Chem. Commun.
1982, 638.
7. Wolf, J. R.; Hamaker, C. G.; Djukic, J. P.; Kodadek, T.; Woo,
L. K. J. Am. Chem. Soc. 1995, 117, 9194.
8. (a) Groves, J. T.; Quinn, R. Inorg. Chem. 1984, 23, 3844. (b)
Groves, J. T.; Quinn, R. J. Am. Chem. Soc. 1985, 107, 5790. (c)
Groves, J. T.; Ahn, K. H. Inorg. Chem. 1987, 26, 3831. (d) Groves,
J. T.; Roman, J. S. J. Am. Chem. Soc. 1995, 117, 5594. (e) Groves,
J. T.; Bonchio, M.; Carofiglio, T.; Shalyaev, K. J. Am. Chem. Soc.
1996, 118, 8961.
9. (a) Higuchi, T.; Satake, C.; Hirobe, M. J. Am. Chem. Soc. 1995,
117, 8879. (b) Higushi, T.; Ohtake, H.; Hirobe, M. Tetrahedron
Lett. 1989, 30, 6545. (c) Higushi, T.; Ohtake, H.; Hirobe, M.
Tetrahedron Lett. 1991, 32, 7435. (d) Ohtake, H.; Higushi, T.;
Hirobe, M. J. Am. Chem. Soc. 1992, 114, 10660.
Ethyl 2-ethylmercaptocyclopropanecarboxylate (E isomer).
1H NMR (CDCl3, d): 4.15 (q, 2H, Jˆ7.1 Hz, CH2); 2.63 (q,
2H, Jˆ7.4 Hz, CH2S); 2.45 (d of d of d; 1H, Jˆ3.6 Hz,
5.7 Hz, 8.3 Hz; SCH); 1.77 (d of d of d; 1H; Jˆ3.6 Hz,
5.2 Hz, 8.7 Hz; CHCO2); 1.48 (d of d of d; 1H; Jˆ4.6 Hz,
5.3 Hz, 8.3 Hz; CH); 1.29 (m; 6H; CH3); 1.12 (d of d of d;
1H; Jˆ4.6 Hz, 5.7 Hz, 8.6 Hz; CH). IR (cmϪ1): 1716
(nCOO). Mass (m/z) (relative intensity): 174 (25), 145 (12),
128 (30), 101 (48), 73 (12), 45 (30), 29 (23), 18 (100);
HR-MS (m/z): calcd for C8H14O2S (Mϩ): 174.0714, found:
174.0712.
10. As underlined by a referee, these complexes do not react
with cyclohexene, see: Collman, J. P.; Rose, E.; Venburg, G. D.
J. Chem. Soc., Chem. Commun. 1993, 11, 934.
1
Ethyl 2-(4-vinylphenylamino)acetate. H NMR (CDCl3,
d): 7.33 (d, 2H, Jˆ8.4 Hz, Ph); 6.68 (m, 1H, CHyCH2);
6.63 (d, 2H, Jˆ8.4 Hz, Ph); 5.61 (d, 1H, Jˆ17.0 Hz,
CHyCH2); 5.10 (d, 1H, Jˆ10.8 Hz, CHyCH2); 4.41 (q,
2H, Jˆ7.2 Hz, CH2); 3.97 (d, 2H, Jˆ5.0 Hz, NCH2); 1.37
(t, 3H, 7.1 Hz, CH3). IR (cmϪ1): 1739 (nCOO), 1611 (nCyC).
Mass (m/z) (relative intensity): 205 (25), 132 (100), 103
(12), 119 (31), 91 (9), 77 (15), 65 (3), 39(2), 29 (7), 18
(9); HR-MS (m/z): calcd for C12H15NO2 (Mϩ): 205.1103,
found: 205.1099.
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´
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Acknowledgements
We are grateful to S. Sinbandhit for recording and inter-
preting the NMR spectra. We also gratefully acknowledge
the financial support of the MESR for a grant to E. G.
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