Effect of rhodium carbenoid structure on cyclopropanation chemoselectivity

Article abstract of DOI:10.1016/S0040-4020(00)00202-7

Rhodium-stabilized carbenoids derived from aryldiazoacetates and vinyldiazoacetates undergo highly chemoselective intermolecular cyclopropanations, and this selectivity has been quantified by a Hammett study. These donor/acceptor substituted carbenoids are much more chemoselective than the traditional carbenoids derived from alkyl diazoacetates. (C) 2000 Published by Elsevier science Ltd.

Full text of DOI:10.1016/S0040-4020(00)00202-7

TETRAHEDRON
Pergamon
Tetrahedron 56 (2000) 4871±4880
Effect of Rhodium Carbenoid Structure on
Cyclopropanation Chemoselectivity
*
Huw M. L. Davies and Stephen A. Panaro
Department of Chemistry, State University of New York at Buffalo, Buffalo, NY 14260-3000 USA
Received 10 December 1999; accepted 6 February 2000
AbstractÐRhodium-stabilized carbenoids derived from aryldiazoacetates and vinyldiazoacetates undergo highly chemoselective inter-
molecular cyclopropanations, and this selectivity has been quanti®ed by a Hammett study. These donor/acceptor substituted carbenoids are
much more chemoselective than the traditional carbenoids derived from alkyl diazoacetates. q 2000 Published by Elsevier Science Ltd.
Introduction
functionalized with both an electron withdrawing group and
an electron-donating group (vinyl or aryl).12,13 In contrast to
the traditional diazoacetate system, cyclopropanations with
vinyldiazoacetates and phenyldiazoacetates are routinely
highly diastereoselective.14±17 Furthermore, rhodium(II)
prolinates such as Rh2(S-DOSP)4 (3) are exceptional chiral
catalysts in vinyldiazoacetate and phenyldiazoacetate cyclo-
propanations,15,17±20 even though these catalysts result in
low enantioselectivity in ethyl diazoacetate cyclopropana-
tions.15
The metal catalyzed decomposition of diazo compounds in
the presence of alkenes is a powerful method for the
construction of densely functionalized cyclopropanes. The
most extensively utilized carbenoids (1) are those derived
from diazoacetates.1±4 Even though a wide range of alkenes
can be used in this chemistry, in general, intermolecular
cyclopropanations by these carbenoids are not particularly
diastereoselective.5,6 Furthermore, with most catalysts only
moderate chemoselectivity occurs in competition reactions
between different alkenes.7 Highly asymmetric cyclo-
propanations, however, are possible with diazoacetates
using a variety of chiral catalysts.8±11
During our extensive studies of aryl- and vinyldiazo-
acetates, it appeared to us that these carbenoids were
much more chemoselective than those derived from diazo-
acetates. In this paper, we quantify the chemoselectivity
differences between the various classes of carbenoids and
demonstrate that vinyl and aryldiazoacetates are indeed
considerably more chemoselective than unsubstituted
diazoacetates. The ®rst section will give a brief summary
on the cyclopropanation chemistry of the traditional car-
benoids derived from diazoacetates with emphasis on the
chemoselectivity of this chemistry. This will be followed by
a description of the cyclopropanation chemistry of car-
benoids derived from vinyl- and phenyldiazoacetates,
which will illustrate the synthetic utility of this chemistry
and contrast the differences to diazoacetate cyclopropana-
tions. In the results section a systematic study on the chemo-
selectivity of the various carbenoids will be described.
Finally, the implications of these results on the future
outlook of vinyl- and aryldiazoacetate chemistry will be
considered.
Over the last 15 years we have explored the cyclopropana-
tion chemistry of a different class of carbenoid (2), which is
Background on Diazoacetate Cyclopropanations
Keywords: cyclopropanation; carbenes and carbenoids; diazo compounds;
rhodium catalysis.
* Corresponding author. Tel.: 11-716-6456800, ext. 2186; fax: 11-716-
645-6963; e-mail: hdavies@acsu.buffalo.edu
The decomposition of alkyl diazoacetates in the presence of
alkenes is an excellent method for the synthesis of cyclo-
propanes.1±4 The reaction is extremely general, with
0040±4020/00/$ - see front matter q 2000 Published by Elsevier Science Ltd.
PII: S0040-4020(00)00202-7

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H. M. L. Davies, S. A. Panaro / Tetrahedron 56 (2000) 4871±4880
Table 1. Relative rates of cyclopropanation of various alkenes by ethyl
diazoacetate
Alkene
Rh2(OAc)4
Rh2(acetamide)4
1-Hexene
Styrene
n-Butyl vinyl ether
Vinyl acetate
Cyclohexene
1.0
3.5
8.6
1.1
2.5
2.1
1.5
1.0
10
15
±
1.0
2.0
±
2,5-Dimethyl-2,4-hexadiene
2-Methyl-2-butene
Several studies have been carried out to explore the relative
reactivity of different alkenes towards cyclopropanation by
diazoacetates,1±4 and some selective examples are shown in
Table 1.5±7 The most commonly used catalyst for the
decomposition of diazo compounds is dirhodium tetra-
acetate. With this catalyst the chemoselectivity is moderate,
with only a 3.5 fold difference between 1-hexene and
styrene. Slightly improved chemoselectivity was observed
when dirhodium tetraacetamide was used as catalyst.6 The
most impressive chemoselectivity to date has been observed
with an iron porphyrin catalyst, which resulted in a 74 fold
difference between 1-decene and styrene.38 This porphyrin
catalyst, however, has not been broadly used in metal
catalyzed transformations of diazo compounds.
electron rich, electron neutral, and even slightly electron
de®cient alkenes subject to cyclopropanation. A range of
substitution patterns, from monosubstituted to tetrasubsti-
tuted can be tolerated. The major limitation of cyclopropa-
nations by diazoacetates is that, in general, the
cyclopropanations are not particularly stereoselective.3,5 In
the standard reaction of styrene with ethyl diazoacetate (4)
catalyzed by dirhodium tetraacetate the diastereoselectivity
is less than 2:1 favoring the trans isomer of cyclopropane 5
(Eq. (1)), although considerable enhancement in the dia-
stereoselectivity can be achieved by using bulky ester
derivatives.6 The majority of catalysts have only a moderate
effect on the diastereoselectivity of diazoacetate cyclopro-
panations but there are some notable exceptions.1,2,21
Certain rhodium amide6 and ruthenium22±24 catalysts favor
the formation of trans cyclopropanes while very bulky cata-
lysts25±28 can lead to a slight preference of cis cyclopro-
panes. Over a hundred types of chiral catalysts have been
developed for asymmetric cyclopropanations by diazoace-
tates, and asymmetric induction of greater than 90% ee can
be achieved with many of these catalysts.8,9,11 The most
notable are the copper catalysts 629,30 and 7,31±33 the ruthe-
nium catalysts 8,22±24 and the C2-symmetric rhodium amide
catalysts 934 all of which contain chiral C2-symmetric
ligands. Rhodium(II) carboxylates have been generally inef-
fective at asymmetric cyclopropanations with diazoace-
Background on Vinyldiazoacetate and
Phenyldiazoacetate Cyclopropanations
In recent years, it has become clear that carbenoids derived
from vinyldiazoacetates have a very different reactivity
pro®le to carbenoids derived from diazoacetates. Inter-
molecular cyclopropanations will only occur with mono-
substituted alkenes, 1,1-disubstituted alkenes, and cis 1,2-
disubstituted alkenes.18 Furthermore, many of these
reactions are highly diastereoselective as shown in Eq. (2)
for the reaction of 11 with styrene,14,18 again differing from
the typical results obtained with the diazoacetate system.
The highest diastereoselectivity is obtained with electron
rich alkenes, such as styrene and vinyl ethers, and with
vinylcarbenoids lacking an electron-withdrawing group
on the vinyl portion. In many of the ideal systems, the
second diastereomer cannot be observed in the NMR of
the crude reaction mixtures. Similar highly diastereo-
selective cyclopropanations have been reported for the
phenyldiazoacetate system 13 (Eq. (3)).15±17 A comparison
study of a range of carbenoid systems concludes that these
highly diastereoselective cyclopropanations occur only in
the case of carbenoids that are ¯anked with both an electron
withdrawing group and an electron releasing group such as
vinyl or phenyl.15
tates.35,36
A recent exception has been the
biphenylcarboxylate derivative 10 that resulted in intermo-
lecular cyclopropanation in high enantioselectivity.37
ꢀ1†
ꢀ2†

H. M. L. Davies, S. A. Panaro / Tetrahedron 56 (2000) 4871±4880
4873
variety of dienes, including pyrroles, furans and benzenes
can be used.
ꢀ3†
Rhodium(II) prolinates are extremely effective for asym-
metric cyclopropanations with vinyldiazoacetates and
phenyldiazoacetates even though they are poor chiral
catalysts for diazoacetate cyclopropanations.20,39 The high-
est asymmetric inductions are obtained when the reaction is
carried out in non-polar solvents at low temperatures.
Consequently, the most effective catalyst to date is
Rh2(S-DOSP)4 (3), which is soluble in pentane even at
2788C. Rh2(S-DOSP)4 catalyzed decomposition of the
vinyldiazoacetate 11 in the presence of styrene at 2788C
results in cyclopropane 12 in 98% ee.18
ꢀ5†
Spectacular chemoselectivity and diastereoselectivity in
this chemistry has been demonstrated on numerous
occasions.12,13 The key cyclopropanation step that was
used in the synthesis of the ether analog of acetomycin 17
is a good illustrative example (Eq. (4)).40 Decomposition of
the vinyldiazoacetate 15 in the presence of an E/Z mixture
of ethyl 1-propenyl ether results in the formation of 16,
containing three stereogenic centers, as a single dia-
stereomer. Only the Z vinyl ether is capable of reacting
with the carbenoid, and the high diastereoselectivity is
typical of the vinyldiazoacetate system.
During the course of the cyclopropanation studies of vinyl-
diazoacetates and phenyldiazoacetates we became aware
that there was a qualitative difference in the chemo-
selectivity of these carbenoids compared to the carbenoids
derived from diazoacetates. This was readily seen in the
reaction of vinyldiazoacetates with dienes.12,41 In most
instances, a single regioisomer of the cycloheptadienes
(19) was formed which would mean that the initial cyclo-
propanation was highly regioselective. In contrast, the
cyclopropanation reactions of ethyl diazoacetates with
dienes often gave a mixture of regioisomers even when
the diene was electronically biased to favor formation of
one of the possible cyclopropanes.43 A good example of
the vinylcarbenoid regioselectivity is the key step in the
synthesis of tremulenolide (23) in which the reaction of
vinyldiazoacetate 20 with E,Z diene 21 gave a single
cycloheptadiene derivative 22 that is formed by initial
cyclopropanation of the cis double bond in 21.44
ꢀ4†
ꢀ6†
Vinyldiazoacetate cyclopropanations can be effectively
used for the stereoselective synthesis of various ring
systems because the resulting vinylcyclopropanes are
prone to ring expansion in a stereoselective manner. The
most exciting application of this chemistry is the formal
[314] cycloadditions between vinyldiazoacetates and
dienes.12,41 The initially formed cis-divinylcyclopropanes
18 undergo a Cope rearrangement through a boat transition
state to form cycloheptadienes with full control of relative
stereochemistry at three stereogenic centers. Combined with
the use of chiral catalyst 3, this reaction results in the asym-
metric synthesis of highly functionalized cycloheptadienes
19 (Eq. (5)).42 The reaction is of very broad scope as a wide
In this paper we describe a study to quantify the chemo-
selectivity of the rhodium-carbenoids derived from vinyl-
and phenyldiazoacetates and unsubstituted diazoacetates.

4874
H. M. L. Davies, S. A. Panaro / Tetrahedron 56 (2000) 4871±4880
The results con®rm that the carbenoids derived from aryl-
and vinyldiazoacetates are much more chemoselective than
the traditional carbenoids derived from diazoacetates.
was less pronounced in the Rh2(S-DOSP)4 catalyzed reac-
tions. Very little difference in reactivity was seen for the
series of styrene derivatives consistent with virtually no
build-up of positive charge at the benzylic carbon in the
transition state of these diazoacetate cyclopropanations.
Results
At the onset of this study, a hypothesis was made that the
combination of an electron withdrawing and electron donat-
ing group on the carbenoid considerably enhances the
chemoselectivity of carbenoid cyclopropanations. We had
seen some dramatic examples of how these types of car-
benoids are sensitive to the steric environment of the
trapping agent. We also suspected, however, that the car-
benoid was sensitive to the electronic nature of that trapping
agent. Consequently, reactions between a series of car-
benoid systems and various monosubstituted alkenes were
examined, as this would be a de®nitive test on how the
carbenoid selectivity depends on carbenoid structure.
Ethyl diazoacetate (4) was taken as the prototypical car-
benoid precursor. This was then compared to the phenyl-
vinyldiazoacetate 11, which has been extensively used by
us. In order to compare the effect of the electronic nature of
the second group, diazoglutaconate 24,14 containing an elec-
tron withdrawing group on the vinyl group, and diazomalo-
nate 2545 were examined. To complete the study two aryl
diazoacetates 13 and 2646 were explored. If the original
hypothesis is correct, both of these substrates would be
expected to be highly chemoselective, with the methoxy
substituted derivative being the most chemoselective.
ꢀ7†
Relative rate versus styrene
R
Rh2(S-DOSP)4
Rh2(OAc)4
0.90
p-MeOC6H4
p-CH3C6H4
p-ClC6H4
p-CF3C6H4
n-Bu
0.90
1.0
1.0
0.70
0.31
1.3
0.293
2.53
n-BuO
The next series of experiments was carried out with vinyl-
diazoacetate 11 so that the in¯uence of the electron
donating phenylvinyl functionality on the chemoselectivity
could be determined. These reactions were carried out in
CH2Cl2 at room temperature using Rh2(S-DOSP)4 as
catalyst. In contrast to the ethyl diazoacetate cyclopropana-
tions, the reactions with vinyldiazoacetate 11 were highly
chemoselective (Eq. (8)). The selectivity between styrene
and 1-hexene was around 50, compared to 3.3 for the ethyl
diazoacetate system. Considerable differences in the relative
rate of reaction of 11 with the various substituted styrenes
were also observed. The Hammett analysis of the reactions
of 11 is shown in Fig. 1. A much closer ®t was observed for
the graph in which the relative reactivity was plotted against
s1(Rˆ0.99) rather than s (Rˆ0.83). This result indicates
that charge build up at the benzylic position does occur for
cyclopropanations of styrenes with 11. Even though the r
value of 21.0 indicates that the extent of the charge build up
is only moderate, resonance effects stabilize this charge
build-up.
ꢀ8†
The ®rst series of experiments was carried out to determine
if there was any major difference between Rh2(S-DOSP)4
and rhodium(II) acetate in controlling the chemoselectivity
of cyclopropanations by ethyl diazoacetate (Eq. (7)). Each
substrate was compared to styrene. The reactivity trends for
cyclopropanations of ethyl diazoacetate catalyzed by Rh2(S-
DOSP)4 were similar to the published results of rhodium(II)
acetate catalyzed reactions,7 although the chemoselectivity
Relative rate versus styrene
R
Rh2(S-DOSP)4
p-MeOC6H4
p-CH3C6H4
p-ClC6H4
p-CF3C6H4
n-Bu
8.3
3.9
1.3
0.39
0.02
4.0
n-BuO

H. M. L. Davies, S. A. Panaro / Tetrahedron 56 (2000) 4871±4880
4875
The effect of solvent and catalyst was then further explored
by comparing the selectivity of reactions between ethyl
diazoacetate (4) and the vinyldiazoacetate 11 with styrene
and 4-methoxystyrene (Eq. (9)). In the case of ethyl diazo-
acetate, virtually no chemoselectivity between styrene and
4-methoxystyrene was observed under all the reaction
conditions that were examined. With vinyldiazoacetate 11,
the chemoselectivity was considerably greater. The highest
chemoselectivity was obtained when electron de®cient
catalysts such as Rh2(S-DOSP)4 or Rh2(TFA)4 were used.
Even though solvent can play a critical role in the outcome
of many vinylcarbenoid reactions,47±49 the chemoselectivity
was virtually independent of solvent.
carbenoid. However, neither is as selective as the vinyl-
diazoacetate 11. In the Hammett studies, the best correlation
was found when the rate selectivity was plotted against s1.
With the diazoglutaconate 24, r was 20.7, while with
diazomalonate 25, r was 20.2. Thus, cyclopropanation
with a carbenoid from a diazoacetate with a vinylogous
ester as the second functionality (24) results in considerably
greater charge build-up in the transition-state than that of a
carbenoid derived from diazomalonate (25).
ꢀ10†
ꢀ9†
Relative rate versus styrene
R
Relative rate versus styrene
Catalyst
Solvent
Diazo 4
Diazo 11
p-MeOC6H4
p-CH3C6H4
p-ClC6H4
p-CF3C6H4
n-Bu
3.4
1.5
1.1
0.38
0.03
1.5
0.85
1.1
0.65
0.08
Rh2(OAc)4
Rh2(TFA)4
Rh2(S-DOSP)4
Rh2(S-DOSP)4
CH2Cl2
CH2Cl2
CH2Cl2
Hexane
0.90
1.1
0.90
0.80
5.2
8.1
8.3
8.1
In order to further test the hypothesis that an electron-
donating group was required on the diazoacetate in order
to have high chemoselectivity, the next series of experi-
ments were carried out on diazoglutaconate 24 and diazo-
malonate 25 (Eq. (10)). Diazoglutaconate 24 displays many
of the characteristics of vinyldiazoacetate 11 but the result-
ing carbenoid behaves as an extremely electrophilic species
that will even cyclopropanate benzene.50 The carbenoid
derived from diazomalonate is also very reactive as it is
functionalized by two electron-withdrawing groups.
Remarkably, even though both systems might be expected
to generate a more reactive carbenoid than that derived from
ethyl diazoacetate, both are considerably more chemo-
selective in the competition reactions than the diazoacetate
The ®nal series of experiments were carried out on the
aryldiazoacetates 13 and 26. On the basis of the original
hypothesis the presence of the aryl group would be expected
to lead to a carbenoid that would be highly chemoselective.
This proved to be the case as shown in the competition
studies summarized in Eq. (11). In the competition studies
between styrene and 1-hexene only a trace of the product
derived from cyclopropanation of 1-hexene was observed.
In the Hammett study (s1) with a series of styrenes, r of
21.0 was obtained for the phenyldiazoacetate 13, while r of
21.3 was obtained for the 4-methoxyphenyldiazoacetate
26. Once again, the highest chemoselectivity was observed
for the diazoacetate functionalized with the most electron-
donating group.
Figure 1. Hammet plot of relative rates of cyclopropanation by 11.

4876
H. M. L. Davies, S. A. Panaro / Tetrahedron 56 (2000) 4871±4880
An even more interesting possibility would be that the
added stability of the donor/acceptor-substituted carbenoids
could enable transformations to be achieved that simply
were not feasible with carbenoids derived from diazo-
acetates. An especially promising development is the
discovery that aryldiazoacetates are capable of very effec-
tive asymmetric intermolecular C±H insertions.51 In the
case of diazoacetates, only the intramolecular C±H
insertions are considered to be synthetically viable. The
carbenoids derived from diazoacetates are poorly selective
in intermolecular C±H insertions, and are prone to
dimerization.3,4,52
ꢀ11†
Relative rate versus styrene
Due to the added stabilization of the aryldiazoacetate car-
benoids dimerization of the carbenoid is considerably less
prevalent such that effective C±H insertions into alkanes
can be achieved.53 An illustrative example is the reaction
of methyl phenyldiazoacetate with cyclohexane catalyzed
by Rh2(S-DOSP)4 at 108C, which results in the formation
of 27 in 95% ee (Eq. (12)).54 Selectivity is also possible
between different C±H bonds as seen in the reaction with
2-methybutane where clean insertion into the tertiary C±H
bond is observed to form 28 (Eq. (13)).54 This result should
be contrasted with the reaction of ethyl diazoacetate and
2-methylbutane, where C±H insertion at every possible
position is observed.55 Further demonstration of the
synthetic utility of the intermolecular C±H insertion was
recently described in a direct synthesis of ritalin in the reac-
tion between phenyldiazoacetate and N-BOC-piperidine56,57
and the asymmetric synthesis of syn-aldol products by the
reaction between aryldiazoacetates and allyl silyl ethers.58 A
notable feature of the second transformation is that excellent
control of diastereoselectvity is also possible in this
chemistry.
R
Diazo 13
R1vH
Diazo 26
R1vOMe
p-MeOC6H4
p-CH3C6H4
p-CIC6H4
p-CF3C6H4
n-Bu
8.4
1.9
18
3.2
1.1
1.3
0.43
0.02
5.7
0.40
0.03
n-BuO
The Hammett studies demonstrate that the structure of the
carbenoid has a major effect on the chemoselectivity of the
cyclopropanation, and that this effect dominates over
rhodium catalyst structure and solvent used. The least
selective carbenoid was that derived from ethyl diazo-
acetate. Even carbenoids derived from diazoglutaconate or
diazomalonate are more selective than diazoacetate. Func-
tionalization of the diazoacetate with an electron-donating
group results in a much more chemoselective carbenoid.
Presumably, the electron donating group would stabilize
the highly electron de®cient carbenoid. Consequently,
cyclopropanation with this carbenoid proceeds through a
later transition state than the carbenoid derived from diazo-
acetate, and during the formation of a late transition state,
there is more opportunity for charge build up to occur.
ꢀ12†
Future Outlook for Vinyldiazoacetate and
Aryldiazoacetate Chemistry
The observation that the carbenoids derived from vinyl-
diazoacetates and phenyldiazoacetates are much more
stabilized and chemoselective than the traditional car-
benoids derived from diazoacetates offers exciting new
opportunities for the utilization of metal-stabilized car-
benoids in organic synthesis. One of the most challenging
problems in diazoacetate cyclopropanations is the control of
diastereoselectivity, while with the donor/acceptor-substi-
tuted carbenoids, high diastereoselectivity is the routine
outcome.12,13 Similarly, Rh2(S-DOSP)4, which is ineffective
at asymmetric diazoacetate cyclopropanations, is excep-
tional for cyclopropanations by donor/acceptor substituted
carbenoids.20 Both of these effects have been proposed to be
caused by the more demanding requirement for the trajec-
tory of approach of the alkene to the donor/acceptor-
substituted carbenoids compared to the carbenoid derived
from diazoacetate.20 A more demanding approach would be
consistent with a reaction that proceeds through a later
transition state.
ꢀ13†
In summary, the reactions of rhodium-stabilized carbenoids
derived from aryl- and vinyldiazoacetates display consider-
able versatility in organic synthesis. These donor/acceptor
substituted carbenoids often undergo highly stereoselective
transformations. In the study described herein, quantitative
data has been obtained that demonstrates that these car-
benoids are much more chemoselective than the traditional

H. M. L. Davies, S. A. Panaro / Tetrahedron 56 (2000) 4871±4880
4877
carbenoid derived from ethyl diazoacetate. Presumably,
these donor/acceptor substituted carbenoids are consider-
ably more stabilized compared to the diazoacetate car-
benoid, and this in turn, explains why they are capable of
such selective transformations.
2.25 (s, 3H), 2.00 (dd, 1H, Jˆ9.2, 4.8 Hz), 1.78 (dd, 1H,
Jˆ7.6, 4.8 Hz); 13C NMR (CDCl3) d 174.2, 137.1, 136.3,
132.9, 132.3, 128.9, 128.7, 128.3, 127.3, 126.2, 124.2, 52.3,
34.8, 33.2, 20.9, 18.6. Anal. Calcd for C20H20O2: C, 82.16;
H, 6.89. Found: C, 82.22; H, 7.01.
Methyl 2b-butoxy-1b-(2-(E)-styryl)cyclopropane-1a-car-
boxylate. (9:1) 60% yield. IR (neat) 2962, 2930, 2871,
Experimental
1
1721 cm21; H NMR (500 MHz, CDCl3) d 7.39 (d, 2H,
Methyl 2-diazo-4-phenyl-3-butenoate (11),18 diethyl 4-diazo-
2-pentenedioate (24),59 dimethyl diazomalonate (25),59
methyl phenyldiazoacetate (13),51 methyl 4-methoxyphenyl-
diazoacetate (26),46 [dimethyl 2-phenylcyclopropane-1,1-
dicarboxylate,18 methyl 2b-butyl-1b-(2-(E)-styryl) cyclo-
propane-1a-carboxylate,18 methyl 2b-(4-methoxyphenyl)-
1b-(2-(E)-styryl)cyclopropane-1a-carboxylate,18 methyl 2b-
(4-chlorophenyl)-1b-(2-(E)-styryl)cyclopropane-1a-carboxy-
late,18 were prepared by literature procedures.
Jˆ7.0 Hz), 7.30 (t, 2H, Jˆ7.5 Hz),7.20(t, 1H, Jˆ7.5 Hz),
6.74 (d, 1H, Jˆ16.0 Hz), 6.42 (d, 1H, Jˆ16.0 Hz), 3.77 (m,
1H), 3.73 (s, 3H), 3.47 (dt, 1H, Jˆ6.5, 6.0 Hz), 3.33 (dt, 1H,
Jˆ7.0, 6.5 Hz), 1.87 (t, 1H, Jˆ7.0 Hz), 1.64 (t, 1H,
Jˆ6.0 Hz), 1.43 (m, 2H), 1.26 (m, 2H), 0.79 (t, 3H,
Jˆ7.5 Hz); 13CNMR (CDCl3) d 172.9, 137.5, 129.7,
128.4, 127.0, 126.1, 121.5, 71.6, 68.2, 52.1, 31.7, 31.4,
21.6, 19.2, 13.7. Anal. Calcd for C17H22O3: C, 74.42; H,
8.08. Found: C, 74.56; H, 8.05.
Ethyl 2b-butyl-1b-((E)-2-ethoxycarbonylvinyl)cyclopro-
pane-1a-carboxylate. (3:1) 68% yield. IR (neat) 2990,
2963, 2936, 2865, 2869, 1729, 1654, 1273, 1181,
General Procedure for Rhodium(II)-Catalyzed
Decompositions of Diazomethanes in the Presence of
Alkenes
1
1037 cm21; H NMR (CDCl3, 300 MHz) d 7.31 (d, 1H,
Jˆ16.0 Hz), 5.70 (d, 1H, Jˆ16.0 Hz), 4.12 (dq, 4H,
Jˆ7.1, 3.8 Hz), 1.77±1.70 (m, 1H), 1.63 (dd, 1H, Jˆ4.7,
4.4 Hz), 1.40±1.10 (m, 12H), 1.00 (dd, 1H, Jˆ7.1, 4.4 Hz),
0.90±0.70 (m, 3H); 13C NMR (CDCl3) d 172.7, 166.3,
143.6, 121.2, 61.1, 60.2, 33.8, 31.3, 30.0, 27.3, 22.1, 21.1,
14.1, 14.0, 13.8. Anal. Calcd for C15H24O4: C, 67.14; H,
9.01. Found: C, 66.88; H, 8.98.
A mixture of alkene (5.0 equiv.) and Rh(II) catalyst
(0.01 equiv.) in solvent was stirred at room temperature
under an argon atmosphere. To this solution was added
the diazoacetate (1 equiv., 0.09 M) in solvent over 10 min,
and the mixture was then stirred for 3±4 h. The mixture was
then concentrated in vacuo, and the residue was puri®ed on
silica using petroleum ether/ether as the eluent in the ratio
speci®ed in parentheses.
Ethyl 1b-((E)-2-ethoxycarbonylvinyl)-2b-(4-tri¯uoro-
methylphenyl)cyclopropane-1a-carboxylate. (4:1) 81%
1
yield. IR (neat) 2990, 2946, 2908, 2882, 1730 cm21; H
Methyl 2b-(4-tri¯uoromethylphenyl)-1b-(2-(E)-styryl)-
cyclopropane-1a-carboxylate. (9:1) 63% yield. IR (neat)
NMR (500 MHz, CDCl3) d 7.53 (d, 2H, Jˆ8.5 Hz), 7.25
(d, 2H, Jˆ8.0 Hz), 6.89 (d, 1H, Jˆ16.0 Hz), 5.68 (d, 1H,
Jˆ16.0 Hz), 4.26 (q, 2H, Jˆ7.0 Hz), 4.08 (q, 2H,
Jˆ7.0 Hz), 3.22 (dd, 1H, Jˆ9.0, 7.5 Hz), 2.12 (dd, 1H,
Jˆ9.0, 5.5 Hz), 1.80 (dd, 1H, Jˆ7.5, 5.5 Hz), 1.32 (t, 3H,
Jˆ7.0 Hz), 1.18 (t, 3H, Jˆ7.0 Hz); 13C NMR (CDCl3) d
171.5, 165.7, 141.5, 138.7 (q, Jˆ1.4 Hz), 129.7, 129.4 (q,
Jˆ32.3 Hz), 125.1 (q, Jˆ4.1 Hz), 124.0 (q, Jˆ270.5 Hz),
122.4, 61.7, 60.2, 36.3, 32.5, 19.7, 14.1, 14.0. Anal. Calcd
for C18H19F3O4: C, 60.67; H, 5.37. Found: C, 60.71; H, 5.36.
1
3031, 3295, 1730, 1327, 1119 cm21; H NMR (500 MHz,
CDCl3) d 7.47 (d, 2H, Jˆ8.5 Hz), 7.30±7.60 (m, 5H), 7.15
(d, 2H, Jˆ8.5 Hz), 6.38 (d, 1H, Jˆ16.0 Hz), 6.10 (d, 1H,
Jˆ16.0 Hz), 3.76 (s, 3H), 3.02 (dd, 1H, Jˆ9.0, 5.0 Hz), 2.06
(dd, 1H, Jˆ9.0, 5.0 Hz), 1.85 (dd, 1H, Jˆ5.0, 2.0 Hz); 13C
NMR (CDCl3) d 173.6, 139.8 (q, Jˆ1.4 Hz), 136.5, 133.8,
129.2, 128.8 (q, Jˆ32.4 Hz), 128.4, 127.6, 126.2, 124.8 (q,
Jˆ4.1 Hz), 124.1 (q, Jˆ270.1 Hz), 123.2, 52.5, 34.0, 33.7,
18.5. Anal. Calcd for C20H17F3O2: C, 69.36; H, 4.95. Found:
C, 69.25; H, 4.99.
Ethyl 1b-((E)-2-ethoxycarbonylvinyl)-2b-(4-chlorophenyl)-
cyclopropane-1a-carboxylate. (4:1) 78% yield. IR (neat)
2990, 2935, 2903, 1721 cm21; 1H NMR (500 MHz, CDCl3)
d 7.24 (d, 2H, Jˆ9.0 Hz), 7.06 (d, 2H, Jˆ9.0 Hz), 6.90 (d,
1H, Jˆ16.0 Hz), 5.64 (d, 1H, Jˆ16.0 Hz), 4.24 (q, 2H,
Jˆ7.0 Hz), 4.09 (q, 2H, Jˆ7.0 Hz), 3.15 (dd, 1H, Jˆ9.0,
7.5 Hz), 2.08 (dd, 1H, Jˆ9.0, 5.5 Hz), 1.72 (dd, 1H, Jˆ7.5,
5.5 Hz), 1.31 (t, 3H, Jˆ7.0 Hz), 1.21 (t, 3H, Jˆ7.0 Hz); 13C
NMR (CDCl3) d 171.6, 165.8, 141.8, 133.0, 132.9, 130.6,
128.4, 121.9, 61.6, 60.2, 36.4, 32.3, 19.9, 14.1, 14.1. Anal.
Calcd for C17H19ClO4: C, 63.26; H, 5.93. Found: C, 63.19;
H, 5.92.
Methyl 2b-phenyl-1b-(2-(E)-styryl)cyclopropane-1a-car-
boxylate. (9:1) 98% yield. IR (neat) 3084, 3062, 3030,
2950, 1736, 1490, 1454, 1241, 1132, 969, 708; H NMR
(500 MHz, CDCl3) d 7.50±7.35 (m, 3H), 7.30±7.08 (m,
12H), 6.46 (d, 1H, Jˆ27 Hz), 6.18 (d, 1H, Jˆ27 Hz), 3.40
(s, 3H), 2.62 (d, 1H, Jˆ9 Hz), 2.05 (d, 1H, Jˆ9 Hz); 13C
NMR (CDCl3) d 171.2, 142.2, 140.8, 137.3, 130.9, 129.9,
128.8, 128.3, 128.3, 128.3, 127.2, 126.8, 126.8, 126.7,
126.1, 51.8, 47.1, 38.8, 22.5. HRMS (EI) calcd for
C25H22O2, 354.1620, found 354.1665.
1
Methyl 2b-(4-methylphenyl)-1b-(2-(E)-styryl)cyclopro-
pane-1a-carboxylate. (9:1) 82% yield. Mp 64±668C; IR
(neat) 3089, 3031, 2956, 2924, 1721, 1438, 1252, 1151;
1H NMR (400 MHz, CDCl3) d 7.30±7.10 (m, 5H), 7.01
(s, 4H), 6.35 (d, 1H, Jˆ16.2 Hz), 6.15 (d, 1H,
Jˆ16.2 Hz), 3.74 (s, 3H), 2.96 (dd, 1H, Jˆ9.2, 7.6 Hz),
Ethyl 1b-((E)-2-ethoxycarbonylvinyl)-2b-phenylcyclo-
propane-1a-carboxylate. (7:3) 95% yield. IR (neat)
1
1725, 1655 cm21; H NMR (500 MHz, CDCl3) d 7.3±7.1
(m, 5H), 6.90 (d, 1H, Jˆ15.9 Hz), 5.92 (d, 1H, Jˆ15.9 Hz),
4.24 (q, 1H, Jˆ7.1 Hz), 4.06 (q, 1H, Jˆ7.1 Hz), 3.20 (dd,

4878
H. M. L. Davies, S. A. Panaro / Tetrahedron 56 (2000) 4871±4880
1H, Jˆ9.3, 8.0 Hz), 2.09 (dd, 1H, Jˆ9.3, 5.1 Hz), 1.75 (dd,
1H, Jˆ8.0, 5.1 Hz), 1.32 (t, 3H, Jˆ7.1 Hz), 1.18 (t, 3H,
Jˆ7.1 Hz); 13C NMR (CDCl3) d 172.0, 166.0, 142.4,
134.4, 129.4, 128.3, 127.3, 121.7, 61.5, 60.1, 37.4, 32.3,
20.1, 14.2, 14.1. Anal. Calcd for C17H20O4: C, 70.81; H,
6.99. Found: C, 70.80; H, 7.03.
Dimethyl 2-(4-methylphenyl)cyclopropane-1,1-dicarboxyl-
ate. (4:1) 84% yield. IR (neat) 3021, 2957, 1745,
1
1443 cm21; H NMR (500 MHz, CDCl3) d 7.06 (s, 3H),
3.76 (s, 3H), 3.37 (s, 3H), 3.19 (dd, 1H, Jˆ9.0, 7.5 Hz),
2.29 (s, 3H), 2.16 (dd, 1H, Jˆ7.5, 5.0 Hz), 1.71 (dd, 1H,
Jˆ9.0, 5.0 Hz); 13C NMR (CDCl3) d 170.1, 166.9, 136.8,
131.3, 128.7, 128.1, 52.6, 52.0, 37.0, 32.2, 20.9, 19.0. Anal.
Calcd for C14H16O4: C, 67.73; H, 6.50. Found: C, 67.98; H,
6.51.
Ethyl 1b-((E)-2-ethoxycarbonylvinyl)-2b-(4-methylphen-
yl)cyclopropane-1a-carboxylate. (4:1) 84% yield. IR
1
(neat) 2983, 1726, 1252, 1183 cm21; H NMR (300 MHz,
CDCl3) d 7.07 (d, 2H, Jˆ7.8 Hz), 7.01 (d, 2H, Jˆ8.4 Hz),
6.91 (d, 1H Jˆ15.9 Hz), 5.66 (d, 1H, Jˆ15.9 Hz), 4.23 (q,
2H, Jˆ7.2 Hz), 4.07 (q, 2H, Jˆ7.2 Hz), 3.17 (dd, 1H,
Jˆ9.0, 7.8 Hz), 2.29 (s, 3H), 2.07 (dd, 1H, Jˆ9.0,
5.0 Hz), 1.73 (dd, 1H, Jˆ7.8, 5.0 Hz), 1.31 (t, 3H,
Jˆ7.2 Hz), 1.19 (t, 3H, Jˆ7.2 Hz); 13C NMR (CDCl3)
Dimethyl 2-(4-methoxyphenyl)cyclopropane-1,1-dicar-
boxylate. (3:1) 69% Yield. IR (neat) 3009, 2962, 2839,
1731, 1620, 1514, 1444, 1344, 1289, 1252, 1141, 1039,
1
850 cm21; H NMR (300 MHz, CDCl3) d 7.08 (d, 2H,
Jˆ8.4 Hz), 6.77 (d, 2H, Jˆ8.4 Hz), 3.75 (s, 3H), 3.74 (s,
3H), 3.35 (s, 3H), 3.15 (dd, 1H, Jˆ9.2, 8.6 Hz), 2.12 (dd,
1H, Jˆ8.6, 5.1 Hz), 1.69 (dd, Jˆ9.2, 5.1 Hz); 13C NMR
(CDCl3) d 170.3, 167.1, 158.9, 129.6, 126.4, 113.5, 55.1,
52.7, 52.2, 37.0, 32.1, 19.2. Anal. Calcd for C14H16O5: C,
63.63; H, 6.10. Found: C, 63.72; H, 6.14.
d
172.0, 166.0, 142.5, 136.8, 131.2, 129.2, 128.9,
121.5, 61.3, 60.0, 37.3, 32.2, 20.9, 20.1, 14.1, 14.0. Anal.
Calcd for C18H22O4: C, 71.50; H, 7.33. Found: C, 71.44; H,
7.28.
Ethyl 1b-((E)-2-ethoxycarbonylvinyl)-2b-(4-methoxy-
phenyl)cyclopropane-1a-carboxylate. (7:3) 88% yield.
Methyl 2b-butyl-1b-phenylcyclopropane-1a-carboxyl-
ate. (99:1) 82% yield. IR (neat) 2955, 2867, 1719 cm21
;
IR (neat) 1725, 1655 cm21; H NMR (500 MHz, CDCl3)
1H NMR (400 MHz, CDCl3) d 7.33±7.25 (m, 5H), 3.60
(s, 3H), 1.83±1.78 (m, 1H), 1.69 (dd, 1H, Jˆ8.5, 3.7 Hz),
1.38±1.34 (m, 3H), 1.27±1.20 (m, 2H), 1.08 (dd, 1H, Jˆ6.1,
3.7 Hz), 0.80 (t, 3H, Jˆ7.3 Hz), 0.53±0.45 (m, 1H);
13C NMR (CDCl3) d 175.2, 136.4, 131.4, 127.9, 127.0,
52.0, 33.4, 31.2, 29.8, 28.5, 22.2, 21.5, 13.8. Anal.
Calcd for C15H20O2: C, 77.55; H, 8.68. Found: C, 77.61;
H, 8.74.
1
d 7.04 (d, 2H, Jˆ8.6 Hz), 6.86 (d, 1H, Jˆ15.9 Hz), 6.79
(d, 2H, Jˆ8.6 Hz), 5.61 (d, 1H, Jˆ15.9 Hz), 4.23 (q, 2H,
Jˆ7.0 Hz), 4.07 (q, 2H, Jˆ7.1 Hz), 3.77 (s, 3H), 3.15 (dd,
1H, Jˆ9.1, 7.6 Hz), 2.07 (dd, 1H, Jˆ9.1, 5.0 Hz), 1.70 (dd,
1H, Jˆ7.6, 5.0 Hz), 1.31 (t, 3H, Jˆ7.1 Hz), 1.20 (t, 3H,
Jˆ73.1 Hz); 13C NMR (CDCl3) d 172.0, 166.1, 158.7,
142.6, 130.5, 126.3, 121.4, 113.7, 61.5, 60.2, 55.2, 37.3,
20.5, 14.3, 14.2. Anal. Calcd for C18H22O4: C, 67.91; H,
6.96. Found: C, 67.99; H, 7.01.
Methyl 2b-butoxy-1b-phenylcyclopropane-1a-carboxy-
late. (1:99±2.5:97.5) 84% yield. IR (neat) 2955, 2867,
1
Dimethyl 2-butylcyclopropane-1,1-dicarboxylate. (3:1)
41% yield. IR (neat) 2956, 2930, 2871, 1742, 1438, 1332,
1284, 1215, 1135 cm21; 1H NMR (500 MHz, CDCl3) d 3.72
(s, 3H), 3.68 (s, 3H), 1.87 (m), 1.50±1.21 (m, 7H), 1.20±
1.07 (m, 1H), 0.84 (t, 3H, Jˆ7.3 Hz); 13C NMR (CDCl3) d
170.9, 168.7, 52.5, 52.4, 33.9, 31.0, 28.8, 28.3, 22.3, 21.4,
13.9. Anal. Calcd for C11H18O4: C, 61.66; H, 8.47. Found: C,
61.91; H, 8.46.
1719 cm21; H NMR (300 MHz, CDCl3) d 7.31 (m, 5H),
3.93 (dd, 1H, Jˆ6.9, 4.5 Hz), 3.63 (s, 3H), 3.60 (q, 2H,
Jˆ6.0 Hz), 1.79 (dd, 1H, Jˆ7.2, 5.7 Hz), 1.61 (dd, 1H,
Jˆ10.5, 4.8 Hz), 1.87±1.80 (m, 2H), 1.10 (sextet, 2H,
Jˆ6.7 Hz), 0.76 (t, 3H, Jˆ7.2 Hz); 13C NMR (CDCl3) d
173.4, 134.1, 131.3, 127.6, 126.7, 70.5, 64.7, 51.9, 34.8,
31.1, 20.6, 18.6, 13.4. Anal. Calcd for C15H20O3: C, 72.55;
H, 8.12. Found: C, 72.55; H, 8.07.
Dimethyl 2-(4-tri¯uoromethylphenyl)cyclopropane-1,1-
dicarboxylate. (4:1) 56% yield. IR (neat) 3010, 2962,
Methyl 2b-(4-tri¯uoromethylphenyl)-1b-phenylcyclo-
propane-1a-carboxylate. (9:1) 60% yield. IR (neat)
1
1
1745, 1452 cm21; H NMR (300 MHz, CDCl3) d 7.54 (d,
3025, 2951, 2850, 2253, 1923, 1721, 1620, 1438 cm21; H
2H, Jˆ8.4 Hz), 7.32 (d, 2H, Jˆ8.4 Hz), 3.80 (s, 3H), 3.39
(s, 3H), 3.26 (dd, 1H, Jˆ9.6, 8.1 Hz), 2.22 (dd, 1H, Jˆ8.1,
5.4 Hz), 1.79 (dd, 1H, Jˆ9.6, 5.4 Hz); 13C NMR (CDCl3) d
169.7, 166.6, 138.8, 129.5 (q, Jˆ32.4 Hz), 128.7, 125.0 (q,
Jˆ3.6 Hz), 124.0 (q, Jˆ270.1 Hz), 52.8, 52.3, 37.3, 31.7,
19.0. Anal. Calcd for C14H13F3O4: C, 55.63; H, 4.34. Found:
C, 55.78; H, 4.47.
NMR (300 MHz, CDCl3) d 7.29 (d, 2H, Jˆ8.1 Hz), 7.20±
7.10 (m, 3H), 7.10±6.80 (m, 2H), 6.84 (d, 2H, Jˆ8.1 Hz),
3.66 (s, 3H), 3.15 (dd, 1H, Jˆ9.0, 6.8 Hz), 2.18 (dd, 1H,
Jˆ9.0, 5.1 Hz), 1.89 (dd, 1H, Jˆ6.8, 5.1 Hz); 13C NMR
(CDCl3) d 173.8, 140.8 (q, Jˆ1.4 Hz), 134.0, 131.7,
131.7, 128.3 (q, Jˆ32.4 Hz), 128.1, 127.3, 124.5 (q,
Jˆ4.1 Hz), 124.1 (q, Jˆ270.1 Hz), 52.7, 37.9, 32.4, 20.8.
Anal. Calcd for C18H15F3O2: C, 67.50; H, 4.72. Found: C,
67.23; H, 4.80.
Dimethyl 2-(4-chlorophenyl)cyclopropane-1,1-dicarboxyl-
ate. (4:1) 65% yield. IR (neat) 3009, 2956, 2850,
1
1737 cm21; H NMR (500 MHz, CDCl3) d 7.24 (d, 2H,
Methyl 2b-(4-chlorophenyl)-1b-phenylcyclopropane-1a-
carboxylate. (5:95) 95% yield. Mp 68±708C; IR (neat)
Jˆ8.5 Hz), 7.13 (d, 2H, Jˆ8.5 Hz), 3.79 (s, 3H), 3.40 (s,
3H), 3.18 (dd, 1H, Jˆ9.0, 8.0 Hz), 2.15 (dd, 1H, Jˆ8.0,
5.0 Hz), 1.74 (dd, 1H, Jˆ9.0, 5.0 Hz); 13C NMR (CDCl3)
d 169.8, 166.7, 133.2, 133.0, 129.7, 128.2, 52.8, 52.3, 37.1,
31.6, 19.0. Anal. Calcd for C13H13ClO4: C, 58.11; H, 4.88.
Found: C, 58.40; H, 4.96.
;
3031, 2954, 1713, 1336 cm21 1H NMR (300 MHz,
CDCl3) d 7.16±6.99 (m, 7H), 6.73 (m, 2H), 3.65 (s, 3H),
3.11 (dd, 1H, Jˆ9.4. 7.3 Hz), 2.15 (dd, 1H, Jˆ9.4, 4.9 Hz),
1.82 (dd, 1H, Jˆ7.3, 4.9 Hz); 13C NMR (CDCl3) d 174.1,
134.9, 134.2, 131.9, 131.7, 129.1, 127.7, 127.7, 127.1, 52.5,

H. M. L. Davies, S. A. Panaro / Tetrahedron 56 (2000) 4871±4880
4879
37.3, 32.2, 20.5. Anal. Calcd for C17H15ClO2: C, 71.21; H,
5.27. Found: C, 71.25; H, 5.26.
Jˆ9.0, 7.0 Hz), 2.12 (dd, 1H, Jˆ9.0, 5.0 Hz), 1.76 (dd,
1H, Jˆ7.0, 5.0 Hz); 13C NMR (CDCl3) d 174.3, 158.4,
135.1, 132.8, 131.9, 129.2, 127.8, 126.2, 113.2, 55.0, 52.6,
36.7, 32.4, 20.9. HRMS (EI) calcd for C18H17ClO3,
316.0872, found 316.0866.
Methyl 1b,2b-diphenylcyclopropane-1a-carboxylate.
(5:95) 95% yield. Mp 68±708C; IR (neat) 3031, 2954,
1
1713, 1336 cm21; H NMR (300 MHz, CDCl3) d 7.16±
6.99 (m, 10H), 6.73 (m, 2H), 3.65 (s, 3H), 3.11 (dd, 1H,
Jˆ9.4, 7.3 Hz), 2.15 (dd, 1H, Jˆ9.4, 4.9 Hz), 1.87 (dd, 1H,
Jˆ7.3, 4.9 Hz); 13C NMR (CDCl3) d 174.3, 136.3, 134.7,
131.9, 128.0, 127.7 (2C), 127.0, 126.3, 52.6, 37.4, 33.1,
20.5. Anal. Calcd for C17H16O2: C, 80.93; H, 6.39. Found:
C, 80.71; H, 6.52.
Methyl 2b-phenyl-1b-(4-methoxyphenyl)cyclopropane-
1a-carboxylate. (4:1) 46% yield. IR (neat) 3041, 2999,
2956, 2839, 1721, 1518 cm21
;
1H NMR (500 MHz,
CDCl3) d 7.80±7.20 (m, 3H), 6.92 (d, 2H, Jˆ9.0 Hz),
6.79±6.74 (m, 2H), 6.65 (d, 2H, Jˆ9.0 Hz), 3.69 (s, 3H),
3.64 (s, 3H), 3.07 (dd, 1H, Jˆ9.0, 7.0 Hz), 2.11 (dd, 1H,
Jˆ9.0, 5.0 Hz), 1.81 (dd, 1H, Jˆ7.0, 5.0 Hz); 13C NMR
(CDCl3) d 175.0, 158.8, 136.8, 133.3, 128.4, 128.1, 127.1,
126.6, 113.5, 55.4, 53.0, 37.0, 33.6, 21.2. Anal. Calcd for
C18H18O3: C, 76.57; H, 6.43. Found: C, 76.56; H, 6.41.
Methyl 2b-(4-methylphenyl)-1b-phenylcyclopropane-
1a-carboxylate. (9:1) 60% yield. IR (neat) 3036, 2951,
1
1721, 1257 cm21; H NMR (400 MHz, CDCl3) d 7.11 (m,
3H), 7.02 (dd, 2H, Jˆ6.8, 3.6 Hz), 6.84 (d, 2H, Jˆ8.0 Hz),
6.63 (d, 2H, Jˆ8.0 Hz), 3.62 (s, 3H), 3.06 (dd, 1H, Jˆ9.6,
6.8 Hz), 2.18 (s, 3H), 2.11 (dd, 1H, Jˆ9.6, 4.8 Hz), 1.82 (dd,
1H, Jˆ6.8, 4.8 Hz); 13C NMR (CDCl3) d 174.4, 135.7,
134.8, 133.2, 131.9, 128.4, 127.8, 127.6, 126.9, 52.5, 37.1,
32.9, 20.8, 20.5. Anal. Calcd for C18H18O2: C, 81.17; H,
6.81. Found: C, 80.93; H, 6.87.
Methyl 2b-(4-methylphenyl)-1b-(4-methoxyphenyl)cyclo-
propane-1a-carboxylate. (4:1) 58% yield. IR (neat) 3020,
2957, 2836, 1730 cm21; 1H NMR (500 MHz, CDCl3) d 6.93
(d, 2H, Jˆ8.5 Hz), 6.87 (d, 2H, Jˆ8.0 Hz), 6.66 (dd, 4H,
Jˆ8.5, 8.0 Hz), 3.71 (s, 3H), 3.64 (s, 3H), 3.02 (dd, 1H,
Jˆ9.0, 7.0 Hz), 2.20 (s, 3H), 2.09 (dd, 1H, Jˆ9.0,
5.0 Hz), 1.77 (dd, 1H, Jˆ7.0, 5.0 Hz); 13C NMR (CDCl3)
d 174.6, 158.3, 135.7, 133.3, 132.8, 128.4, 127.9, 126.9,
113.1, 55.0, 52.5, 36.4, 33.0, 20.9, 20.8. HRMS (EI) calcd
for C19H20O3, 296.1418, found 296.1412.
Methyl 2b-butoxy-1b-phenylcyclopropane-1a-carboxy-
late. (9:1) 84% yield. IR (neat) 2955, 2867, 1719 cm21; 1H
NMR (300 MHz, CDCl3) d 7.31 (m, 5H), 3.93 (dd, 1H,
Jˆ6.9, 4.5 Hz), 3.63 (s, 3H), 3.60 (q, 2H, Jˆ6.0 Hz), 1.79
(dd, 1H, Jˆ7.2, 5.7 Hz), 1.61 (dd, 1H, Jˆ10.5, 4.8 Hz),
1.87±1.80 (m, 2H), 1.10 (sextet, 2H, Jˆ6.7 Hz), 0.76 (t,
3H, Jˆ7.2 Hz); 13C NMR (CDCl3) d 173.4, 134.1, 131.3,
127.6, 126.7, 70.5, 64.7, 51.9, 34.8, 31.1, 20.6, 18.6, 13.4.
Anal. Calcd for C15H20O3: C, 72.55; H, 8.12. Found: C,
72.55; H, 8.07.
Methyl 1b, 2b-(di-4-methoxyphenyl)cyclopropane-1a-
carboxylate. (4:1) 60% yield. IR (neat) 3009, 2951, 2839,
1721, 1520, 1255 cm21; 1H NMR (500 MHz, CDCl3) d 6.93
(d, 2H, Jˆ9.0 Hz), 6.68 (d, 2H, Jˆ9.0 Hz), 6.66 (d, 2H,
Jˆ9.0 Hz), 6.60 (d, 2H, Jˆ9.0 Hz), 3.70 (s, 3H), 3.67 (s,
3H), 3.63 (s, 3H), 3.01 (dd, 1H, Jˆ9.5, 7.5 Hz), 2.09 (dd,
1H, Jˆ9.5, 4.5 Hz), 1.74 (dd, 1H, Jˆ7.5, 4.5 Hz); 13C NMR
(CDCl3) d 174.6, 158.2, 157.9, 132.8, 128.9, 128.3, 126.8,
113.1, 113.0, 55.0, 54.9, 52.4, 36.2, 32.7, 20.7. HRMS (EI)
calcd for C19H20O4, 312.1389, found 312.1362.
Methyl 2b-(4-methoxyphenyl)-1b-phenylcyclopropane-
1a-carboxylate. (9:1) 95% yield. Mp 68±708C; IR (neat)
3031, 2954, 1713, 1336 cm21; 1H NMR (300 MHz, CDCl3)
d 7.26±6.96 (m, 9H), 3.68 (s, 3H), 3.62 (s, 3H), 3.03 (dd,
1H, Jˆ10.7, 9.3 Hz), 2.10 (dd, 1H, Jˆ9.3, 4.8 Hz), 1.79 (dd,
1H, Jˆ10.7, 4.5 Hz); 13C NMR (CDCl3) d 174.3, 158.0,
134.8, 131.9, 128.9, 128.2, 127.6, 126.9, 113.1, 54.9, 52.5,
36.9, 32.6, 20.4. Anal. Calcd for C18H18O3: C, 76.57; H,
6.43. Found: C, 76.54; H, 6.49.
General procedures for competition studies
An equimolar (5.0 equiv.: 5.0 equiv.) solution of styrene
and alkene in solvent was stirred with Rh(II) catalyst
(0.01 equiv.) at room temperature under an argon
atmosphere. To this solution was added diazo (1 equiv.,
0.09 M) in solvent over 5 min and the reaction mixture
was then stirred for a further 3±4 h. The solvent was
removed by reduced pressure. The ratio of the products
Methyl 2b-(4-tri¯uoromethylphenyl)-1b-(4-methoxy-
phenyl)cyclopropane-1a-carboxylate. (4:1) 41% yield.
1
IR (neat) 3025, 2957, 2842, 1724, 1615, 1518 cm21; H
NMR (500 MHz, CDCl3) d 7.31 (d, 2H, Jˆ8.0 Hz), 6.92
(d, 2H, Jˆ8.5 Hz), 6.85 (d, 2H, Jˆ8.0 Hz), 6.68 (d, 2H,
Jˆ8.5 Hz), 3.72 (s, 3H), 3.66 (s, 3H), 3.10 (dd, 1H,
Jˆ9.0, 7.0 Hz), 2.17 (dd, 1H, Jˆ9.0, 5.0 Hz), 1.84 (dd,
1H, Jˆ7.0, 5.0 Hz); 13C NMR (CDCl3) d 174.2, 158.6,
140.9 (q, Jˆ1.4 Hz), 132.8, 128.3 (q, Jˆ32.4 Hz), 128.2,
126.0, 124.5 (q, Jˆ4.0 Hz), 124.1 (q, Jˆ270.1 Hz), 113.3,
55.0, 52.7, 37.2, 32.5, 21.2. HRMS (EI) calcd for
C19H17F3O3, 350.1100, found 350.1130.
1
was determined from H NMR (500 MHz) of the crude
reaction residue.
Acknowledgements
Financial support of this work by the National Science
Foundation (CHE 9726124) is gratefully acknowledged.
Methyl 2b-(4-chlorophenyl)-1b-(4-methoxyphenyl)cyclo-
propane-1a-carboxylate. (4:1) 88% yield. IR (neat) 3014,
2957, 2842, 1718 cm21; 1H NMR (500 MHz, CDCl3) d 7.03
(d, 2H, Jˆ8.5 Hz), 6.92 (d, 2H, Jˆ8.5 Hz), 6.68 (d, 4H,
Jˆ8.5 Hz), 3.72 (s, 3H), 3.65 (s, 3H), 3.03 (dd, 1H,
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