Ruthenium-catalyzed transformations of cyclopropylethynes

Article abstract of DOI:10.1055/s-2007-990874

The addition of various carboxylic acids to (trans-2-ethoxycyclopropyl) ethyne (1) by catalysis with [Ru(O₂CH)(CO)₂(PPh ₃)]₂ proceeds regioselectively in the Markovnikov sense with ring opening of the cyclopropy

Full text of DOI:10.1055/s-2007-990874

3574
SPECIAL TOPIC
Ruthenium-Catalyzed Transformations of Cyclopropylethynes1
R
utheniu
n
m-Catalyzed
g
T
ransforma
o
tions of Cycloprop
E
ylethynes mme,a Christian Bruneau,b Pierre H. Dixneuf,*b Hans-Christian Militzer,a Armin de Meijere*a
a
Institut für Organische und Biomolekulare Chemie, Georg-August-Universität Göttingen, Tammannstraße 2, 37077 Göttingen, Germany
Catalyse et Organométalliques UMR 6226, CNRS-Université de Rennes 1, Institut Sciences Chimiques de Rennes, Campus de Beaulieu,
35042 Rennes Cedex, France
b
Fax +49(551)399475; E-mail: Armin.deMeijere@chemie.uni-goettingen.de
Received 19 July 2007
Dedicated to the late Professor Yoshihiko Ito for his outstanding contribution to synthetic organic chemistry and catalysis
Among the various ruthenium complexes that were found
Abstract: The addition of various carboxylic acids to (trans-2-
to catalyze additions of carboxylic acids to alkynes,12
[Ru(O2CH)(CO)2(PPh3)]2 (A) promotes the regioselective
ethoxycyclopropyl)ethyne
[Ru(O2CH)(CO)2(PPh3)]2 proceeds regioselectively in the Mar-
kovnikov sense with ring opening of the cyclopropyl group to fur-
(1)
by
catalysis
with
addition of carboxylic acids to terminal alkynes according
nish allenylacetaldehyde acyl ethyl acetals 3 in high yields (44– to the Markovnikov rule.12a–e Treatment of the readily
available (5 steps, up to 52% overall yield)13 racemic
96%, 11 examples). The allenylacetaldehyde derivatives undergo
palladium-catalyzed Heck-type cross coupling with iodobenzene
(trans-2-ethoxycyclopropyl)ethyne (1) with an equimolar
and subsequent trapping of the p-allylpalladium intermediate with
amount of acetic acid (2b) in the presence of 0.4 mol% of
primary and secondary amines to yield labile [b-(1-aminometh-
the ruthenium catalyst A gave, after three hours at 75 °C,
yl)styryl]acetaldehyde acyl ethyl acetals 12 (24–83%, 4 examples).
1-ethoxypenta-3,4-dienyl acetate (3b) in 96% isolated
Anti-Markovnikov addition of carboxylic acids to the triple bond in
(trans-2-ethoxycyclopropyl)ethyne (1) without ring opening can be
brought about under [Ru(CH2CMeCH2)2(dppb)] catalysis to give 2-
(trans-2-ethoxycyclopropyl)ethenyl esters 13 (69–92%, 3 exam-
ples). (1-Hydroxycyclopropyl)ethyne (14), under catalysis by
[Ru(O2CH)(CO)2(PPh3)]2, reacts with carboxylic acids to yield 1-
acetylcyclopropyl esters 15 (49–74%, 4 examples) by Markov-
yield as the sole product (Table 1).14
Under similar conditions, the reactions of pentanoic acid
(2c), undec-10-enoic acid (2d), and cyclopropanecarbox-
ylic acid (2e) gave the corresponding allenylacetaldehyde
acyl ethyl acetals 3c–e in 84%, 92%, and 93% yields, re-
nikov-sense addition and intramolecular transesterification. Anti- spectively. The treatment of 1 with formic acid (2a) in
Markovnikov- and Markovnikov-sense addition of carboxylic acids
to unsubstituted cyclopropylethyne can both be achieved regiose-
benzene-d6 (70 °C, 2 h) also led exclusively to the allene
3a, as identified by its 1H and 13C NMR spectra, however,
lectively under catalysis with [Ru(CH2CMeCH2)2(dppb)] and
isolation of 3a failed, mainly because of its low boiling
[Ru(O2CH)(CO)2(PPh3)]2 to furnish 2-cyclopropylethenyl esters 23
point. The addition of succinic acid (2f) to 1 gave the bis-
(68–98%, 6 examples) and 1-cyclopropylethenyl esters 24 (66–
allenyl bisacetal 3f in moderate yield (44%), when carried
out in dichloromethane.
97%, 5 examples), respectively.
Key words: acetylenes, cyclopropanes, allenes, ruthenium cataly-
sis, palladium catalysis
Carboxylic acids with more sterically demanding groups
such as pivalic acid (2g), benzoic acid (2h), 5-methyl-
thiophene-2-carboxylic acid (2i), 2-iodobenzoic acid (2j),
and 2-acetylbenzoic acid (2k) also reacted quantitatively
with 1, however, they each gave two products 3 and 4. The
main products were the allenes 3g–k (50–68%, Table 1),
which could be separated by chromatography on silica gel
from the 1-(trans-2-ethoxycyclopropyl)ethenyl esters 4g–
k (10–29%) formed as side products.
Modern ‘acetylene chemistry’ has much to do with transi-
tion-metal-mediated and -catalyzed transformations.2
Among the various catalysts employed, relatively simple
ruthenium complexes3 play a pivotal role. Some of their
reactions proceed via vinylideneruthenium intermediates4
with oxidative coupling or cycloisomerization.5 Particu-
larly interesting reactions are those that take place with
skeletal rearrangements accompanied by C–C bond
breaking and forming, such as additions to disubstituted
alkynes,6 enyne metatheses,7 or reorganizations.8 Ethy-
nylcyclopropane and its derivatives constitute versatile
oligofunctional building blocks that have both enhanced
reactivity across their triple bond as well as their three-
membered ring.9–11 In fact, activation of their triple bond
and, as a result, their cyclopropyl group, with electrophilic
metals has been found to be a versatile reaction princi-
ple.11
As is evident from these examples, the conditions are
compatible with the presence of aryl halide, alkenyl dou-
ble bond, carbonyl, and thiophene moieties in the carbox-
ylic acid. With cyanoacetic acid, however, decomposition
occurred,15 and with hydroxyacetic acid no reaction was
observed.
The choice of solvent and concentration was critical. Gen-
erally, the reactions were performed in benzene in a 0.7 M
solution. Under these conditions, acetic acid (2b) gave the
allene 3b in 96% isolated yield. When run at a concentra-
tion of 6.1 M, the same reaction gave the enol ester 4b in
8% yield along with 3b in 84% yield. When toluene was
employed instead of benzene, the yields were slightly
lower (4% and 11%, respectively), yet the product ratios,
SYNTHESIS 2007, No. 22, pp 3574–3588
Advanced online publication: 31.10.2007
DOI: 10.1055/s-2007-990874; Art ID: C04207SS
x
x.
x
x
.
2
0
0
7
© Georg Thieme Verlag Stuttgart · New York

SPECIAL TOPIC
Ruthenium-Catalyzed Transformations of Cyclopropylethynes
3575
e.g. for 3h/4h, remained virtually the same. For the reac- by 1H NMR. No reaction was observed when a solution of
tion of succinic acid, the use of dichloromethane instead 1 and 2b was treated with pyridinium p-toluenesulfonate
of benzene increased the yield from 10% to 44% due to (PPTS), or when the alkyne 1 was treated with the ruthe-
better solubility.
nium complex without an added carboxylic acid. Silver(I)
and mercury(II) salts are also known to catalyze the addi-
tion of nucleophilic reagents to triple bonds.16 Indeed, ad-
dition of silver tetrafluoroborate to a solution of 1 and 2b
in benzene-d6 resulted in complete conversion of the
alkyne within 15 hours at 70 °C. However, only 30% of
the allene 3b was observed along with a complex mixture
In order to learn something about the mechanism of this
reaction, some control experiments were performed. To
rule out a simple acid catalysis, (trans-2-ethoxycyclopro-
pyl)ethyne (1) was heated with pentanoic acid (2c) in the
absence of the ruthenium complex. After 17 hours at 75
°C, only a trace of the product 3c (<2%) could be observed
Table 1 Ruthenium-Catalyzed Reaction of (trans-2-Ethoxycyclopropyl)ethyne (1) with Carboxylic Acids 2 To Yield 5-Acyloxy-5-ethoxy-
penta-1,2-dienes 3 and 1-(trans-2-Ethoxycyclopropyl)ethenyl Esters 414
RCO2H 2
[Ru] cat.
OEt
•
O
OEt
+
O
O
R
O
OEt
R
1
3
4
Carboxylic acid
Solvent
[Ru] cat.a (mol%) Temp. (°C)
Time (h)
Yieldb (%)
2
a
b
RCO2H
3
4
–
–
8
–
–
–
HCO2H
C6D6
0.3
0.4
1.0
0.2
1.4
––
70
75
70
70
80
80
2
3
>95c
96
d
MeCO2H
C6H6
e
C6H6
12
6
84
c
BuCO2H
C6H6
84
toluene
14
24
80
f
C6D6
<2
CO2H
d
e
f
C6H6
C6H6
C6H6
0.4
0.4
0.4
70
70
70
6
4
92
93
10
–
–
–
8
cPrCO2H
15
HO2C
CO2H
CH2Cl2
C6H6
0.4
0.4
0.4
1.0
70
70
70
80
15
6
44
62
58
50
–
g
t-BuCO2H
29
27
24
h
PhCO2H
C6H6
6
toluene
18
S
CO2H
i
C6H6
C6H6
0.4
0.4
70
70
6
6
64
68
25
18
CO2H
j
I
CO2H
k
C6H6
0.4
70
6
58
10
O
a [Ru] cat. = [Ru(O2CH)(CO)2(PPh3)]2 (A).12a
b Isolated yield unless otherwise indicated.
c Yield according to 1H NMR of the crude product.
d Concentration 0.73 molar.
e Concentration 6.1 molar.
f Control experiment without catalyst.
Synthesis 2007, No. 22, 3574–3588 © Thieme Stuttgart · New York

3576
I. Emme et al.
SPECIAL TOPIC
of decomposed material. Complete decomposition oc- ployed in a Heck-type coupling with iodobenzene
curred under the influence of mercury(II) acetate.
(Table 2). Since allenes usually undergo carbopallada-
tions regioselectively to yield p-allylpalladium intermedi-
ates that are trapped by added nucleophiles,18 the
palladium-catalyzed coupling of 3b with iodobenzene
was carried out in the presence of a primary or a secondary
amine 11. The employed catalyst system [Pd(OAc)2, TFP,
amine 11] performed well with bulky tert-butylamine
(11a) and dibenzylamine (11d) to furnish the 2-phenyl-
allylamines 12ba and 12bd in 82% and 83% yield, res-
pectively, but with cyclohexylamine (11b), and
isobutylamine (11c) the yields of 12bb and 12bc were
only 46% and 24%, respectively. Whereas all three prima-
ry amines selectively gave the Z-isomers of the highly
functionalized styrene derivatives 12, N,N-dibenzyl-
allylamine 12bd was a 1:1 mixture of the E- and Z-iso-
mers. These allylamines cannot be stored for long periods,
but must be rapidly transformed to more stable products.
The sequence of events that eventually leads to the allenes
3, apparently starts with electrophilic attack of the ruthe-
nium complex on the triple bond of 1 (Scheme 1). As a re-
sult of the complexation, the electron-withdrawing ability
of the ethynyl group in the h2-complex 5 is increased, and
this may initiate ring opening of the donor-substituted cy-
clopropyl group leading to the zwitterionic s-allenylruth-
enate intermediate 7, the positive end of which is
stabilized by the ethoxy group. Nucleophilic attack of a
carboxylate ion on the electrophilic carbon furnishes the
s-allenylruthenium complex 9, from which the allene 3 is
formed by protiodemetalation. Alternatively, the rutheni-
um center in 5 can be protonated first to give the cationic
h2-alkyneruthenium complex 6. Subsequent ring opening,
followed by nucleophilic attack and reductive elimination
would also form the allene 3. The enol esters 4b,g–k must
be formed by direct nucleophilic attack of the respective As earlier work of Dixneuf et al. has shown,12f–h
carboxylate ion on the activated triple bond in 5 or 6. Al- [Ru(CH2CMeCH2)2(dppe)] (B) and
ternatively, the coordination of the triple bond is expected [Ru(CH2CMeCH2)2(dppb)] (C) catalyze the regioselec-
to increase the electrophilicity of the ethoxy-substituted tive addition of carboxylic acids to terminal alkynes in the
cyclopropyl carbon atom in 5 and 6 and favor direct nu- anti-Markovnikov sense to yield Z-configured alkenyl es-
cleophilic addition of the carboxylate to give 9 and 3.
ters with high efficiency. Indeed, under similar conditions
as used for the transformation to the allenes 3, (trans-2-
ethoxycyclopropyl)ethyne (1), in the presence of
[Ru(CH2CMeCH2)2(dppb)] (C) in benzene at 60 °C for 15
hours, reacted with pentanoic acid (2c) and benzoic acid
(2h) to furnish (Z)-2-(trans-2-ethoxycyclopropyl)ethenyl
esters 13c and 13h in 85% and 92% yield, respectively
(Table 3). Thus, this ruthenium-catalyzed addition of the
two acids occurred regio- as well as diastereoselectively
Allenes are known to be versatile starting materials for a
wide range of applications.17 The particular allenes 3 ob-
tained by transformation of 1 with carboxylic acids con-
tain a protected aldehyde functionality and thus have
additional reactivity that should make them valuable
building blocks for organic synthesis. To demonstrate just
one type of further transformation, the allene 3b was em-
[Ru–H]
[Ru]
H+
+
[Ru]
OEt
OEt
OEt
1
5
6
3
H
H
–
[H–Ru]
[Ru]
•
•
OEt
OEt
7
8
H+–O2CR
–
RCO2
–
[Ru]
•
OEt
H
•
OEt
O
O
O
O
R
R
3
9
Scheme 1 Mechanistic rationalization of the formation 5-acyloxy-5-ethoxypenta-1,2-dienes 3a–k from (trans-2-ethoxycyclopropyl)ethyne
(1)
Synthesis 2007, No. 22, 3574–3588 © Thieme Stuttgart · New York

SPECIAL TOPIC
Ruthenium-Catalyzed Transformations of Cyclopropylethynes
3577
Table 2 Heck-Type Couplings of 3b with Iodobenzene and Immediate Trapping of the Formed p-Allylpalladium Species by Primary and
Secondary Amines 11
Ph
Ph
R1R2N
•
OEt
11
Pd cat.
OEt
O
O
Pd
O
O
O
OEt
10
O
3b
12
Amine
11a
NR1R2
NHt-Bu
NHCy
NHi-Bu
NBn2
Conditionsa
55 °C, 45 min
70 °C, 2 h
Product
12ba
Yield (%)
Ratio E/Z
>98:2
>98:2
>98:2
1:1
82
46
24
83
11b
12bb
12bc
11c
60 °C, 1 h
11d
50 °C, 2 h then 75 °C, 1 h
12bd
a Pd(OAc)2 (5 mol%), tri(2-furyl)phosphine (10 mol%), PhI (1 equiv), R1R2NH 11 (6–8 equiv), DMF.
Table 3 Anti-Markovnikov Addition of Carboxylic Acids 2 to
(trans-2-Ethoxycyclopropyl)ethyne (1)
Just like the addition of carboxylic acids to 1 catalyzed by
A, that of 14 occurs regioselectively according to Mar-
kovnikov’s rule to yield an intermediate enol ester 17,
which experiences an intramolecular transesterification to
give the cyclopropyl ester 18.22 The latter finally tau-
tomerizes to the corresponding ketone 15 after reductive
elimination.
RCO2H 2
[Ru] cat. (2.5 mol%)
benzene, 60 °C
O
O
R
EtO
EtO
1
13
Product
13c
This new access to 1-acetylcyclopropyl esters 15 is supe-
rior to the previously published synthesis by Conia et al.23
A preparation of tetrahydropyranyl ethers of 1-acylcyclo-
propanols has been reported by Salaün et al.24
Carboxylic acid R
Time (h)
Yield (%)
2c
2h
2l
Bu
15
15
85
92
69
Since the dppe ligand in the ruthenium complex
[Ru(CH2CMeCH2)2(dppe)] (B) has a smaller bite angle
than the dppb ligand in complex C used above, it also usu-
ally shows different catalytic properties.12f–i When a mix-
ture of (1-hydroxycyclopropyl)ethyne (14) and benzoic
acid (2h) was treated with the ruthenium complex
[Ru(CH2CMeCH2)2(dppe)] (B) (1.5 mol%), a mixture of
two products 15h and 19h (ratio 1:2.6) was isolated in
36% yield. The main product 19h, in this case, apparently
is the result of the addition of benzoic acid to the triple
bond of 14 in the anti-Markovnikov sense with subse-
quent or concomitant opening of the cyclopropyloxy to an
ethyl ketone moiety. Such ring openings are known to oc-
cur easily under acid or base catalysis. The ring opening
in this case might actually occur at the stage of the ruthe-
nium-activated alkyne as depicted in 20 or 21 before the
carboxylate ion attacks (Scheme 2).
Ph
13h
CH2=CH
4.5
13l
a [Ru] cat. = [Ru(CH2CMeCH2)2(dppb)] (C).
without ring opening. Apparently, the activation of the
ethynyl group by this ruthenium complex is such that the
nucleophilic carboxylate can only attack at the alkyne ter-
minus. The adduct 13l of acrylic acid (2l) could also be
obtained in 69% yield, but it decomposed within a few
days even when stored at –15 °C.
The alkenyl esters 13 with their masked acetaldehyde
functionality attached to a cyclopropyl ether moiety, rep-
resent multifunctional building blocks, which are poten-
tially valuable for organic synthesis.19 In view of these
results it appeared to be worthwhile also to evaluate addi-
tions of carboxylic acids to 1-ethynylcyclopropanol (14),
a differently substituted ethynylcyclopropane, which is
also easily available in four steps from ethyl 3-chloropro-
panoate via cyclopropanone ethyl hemiacetal20 and 1-(tri-
methylsilylethynyl)cyclopropanol in 54% overall yield.21
Regioselective addition of carboxylic acids 2 to unsubsti-
tuted cyclopropylethyne (22)25 in both the Markovnikov
as well as the anti-Markovnikov sense without ring open-
ing could be achieved by ruthenium catalysis. Thus treat-
ment of 22 with pentanoic acid (2c) in the presence of
[Ru(O2CH)(CO)2(PPh3)]2 (A) at 80 °C for seven hours
gave the 1-cyclopropylethenyl ester 24c in 66% yield. Cy-
clopropanecarboxylic acid (2e) and bulky pivalic acid
(2g), after 15 hours at 80 °C, yielded the corresponding
enol esters 24e and 24g (82% and 76%, respectively,
Upon reaction with several carboxylic acids (pentanoic,
cyclopropanecarboxylic, benzoic, methoxyacetic, and sal-
icylic acid) in the presence of [Ru(O2CH)(CO)2(PPh3)]2
(A), 1-ethynylcyclopropanol (14) gave 1-acetoxycyclo-
propyl esters 15c,e,h,m,n in 28–74% yield (Table 4).
Synthesis 2007, No. 22, 3574–3588 © Thieme Stuttgart · New York

3578
I. Emme et al.
SPECIAL TOPIC
Table 4 Ruthenium-Catalyzed Additions of Various Carboxylic Acids 2 to 1-Ethynylcyclopropanol (14)a
O
[Ru] cat. (0.5 mol%)
O
R
toluene, 60 °C, 1 d
OH
+
RCO2H
O
14
[Ru]
2
15
O
O
R
RCO2H
OH
2
H
OH
H
O
R
OH
[Ru]
O
[H–Ru]
[H–Ru]
16
17
18
Carboxylic acid
R
Time (h)
18.5
18
Product
15c
Yield (%)
2c
Bu
68
49
74
55
28
2e
cyclopropyl
Ph
15e
2h
2m
2n
16.5
17.5
20
15h
MeOCH2
2-HOC6H4
15m
15n
a [Ru] cat. = [Ru(O2CH)(CO)2(PPh3)]2 (A).
Table 5, entries 2 and 3). For the addition of benzoic acid ed benzoic acids 2o,p,q were carried out in toluene solu-
(2h) to occur quantitatively, the reaction mixture had to be tions and provided the corresponding cis-2-substituted
heated to 80 °C for 40 hours (entries 4 and 5).
ethenyl esters in good to excellent yields (98%, 97%, and
68% respectively, entries 12–14).
The addition of benzoic acid (2h) to 22 in the presence of
the [1,4-bis(diphenylphosphino)butane]ruthenium com- Surprisingly, methoxyacetic acid (2m) reacted with 22 at
plex C occurred in the anti-Markovnikov sense and gave 80 °C to yield a 2:1 mixture of 23m and 24m. At 55 °C,
the enol ester 23h in 98% yield, when an equimolar solu- however, only 23m was formed in 92% yield in four hours
tion of both substrates was heated at 70 °C for six hours; (entries 10 and 11). In contrast, acetic acid (2b) upon ad-
no reaction was observed at 20 °C for 15 hours (Table 5, dition to 22 in the presence of the same catalyst C yielded
entries 8 and 9). When both substrates are liquid, the reac- exclusively the 1-cyclopropylethenyl acetate 24b even at
tion may be performed without solvent. Thus, treatment of 50 °C (entry 6).26
22 with pentanoic acid (2c) at 65 °C in the presence of C
(1 mol%) for 15 hours gave the enol ester 23c in almost
quantitative yield (entry 7). The additions of the substitut-
With the (p-cymene)ruthenium complex D, which is
known to favor the Markovnikov-sense addition,12a–c,27
O
O
2h, [Ru] cat. (1.5 mol%)
toluene, 75 °C, 17 h
OH
O
Ph
+
O
36%
O
O
Ph
14
15h
1:2.6
19h
[Ru] cat. = [Ru(CH2CMeCH2)2(dppe)] (B)
O–
H
[Ru]
[Ru]
H
O
........
H
H
20
21
Scheme 2
Synthesis 2007, No. 22, 3574–3588 © Thieme Stuttgart · New York

SPECIAL TOPIC
Ruthenium-Catalyzed Transformations of Cyclopropylethynes
3579
Table 5 Ruthenium-Catalyzed Additions of Carboxylic Acids 2 to Cyclopropylethyne 22
[Ru] cat.
O
R
+
RCO2H
+
O
O
O
R
22
2
23
24
Entry
2
R
[Ru] cat.a (mol%) Temp. (°C)
Time (h)
Solvent
Yield (%)
23
24
66
82
76
61
97
94
–
1
2
c
Bu
A (0.5)
A (0.5)
A (0.5)
A (0.5)
A (0.5)
C (0.3)
C (1.0)
C (1.0)
C (1.0)
C (1.0)
C (1.0)
C (1.0)
C (1.0)
C (2.0)
D (10)
D (10)
80
80
80
80
80
50
65
20
70
80
55
80
80
80
50
80
7
15
15
7
toluene
toluene
toluene
toluene
toluene
neat
–
e
cyclopropyl
–
3
g
t-Bu
–
4
h
h
b
c
Ph
–
5
Ph
44
12
15
15
6
–
6
Me
–
7
Bu
neat
97
8
h
h
m
m
o
Ph
toluene
toluene
neat
–
–
9
Ph
98
–
10
11
12
13
14
15
16
CH2OMe
CH2OMe
2,6-F2C6H3
2,6-(MeO)2C6H3
4-H2NC6H4
Ph
15
4
(2)b
92
(1)b
–
neat
21
18
21
42
39
toluene
toluene
toluene
toluene
toluene
98
–
p
q
h
h
97
–
68
–
65 (1:7)
59 (1:6)
Ph
a [Ru] cat: A: [Ru(O2CH)(CO)2(PPh3)]2. C: [Ru(CH2CMeCH2)2(dppb)]. D: [RuCl2(p-cymene)(PPh3)].
b The yield was not determined, as the 1H NMR spectrum indicated the formation of a mixture of the two products in the ratio of 2:1.
Transfer) techniques and are quoted as (+) for CH3 and CH groups,
(–) for CH2 groups and (Cq) for quaternary carbon atoms. IR: Bruker
IFS 66. LR-MS (EI): Finnigan MAT 95, ionizing voltage 70 eV.
HRMS: Finnigan MAT 95; employing preselected ion peak match-
ing, all HRMS results were satisfactory in comparison to the calcu-
lated accurate mass of the molecular ion (+/-2 ppm, R ~10000); for
this reason, only calculated values are stated. Elemental analyses:
Mikroanalytisches Labor des Instituts für Organische und Biomole-
kulare Chemie der Universität Göttingen, Germany. Melting points
are uncorrected. Solvents for extraction and chromatography were
of technical grade and distilled before use. Flash chromatography
(FC) was performed using Merck Kieselgel 60 (200–400 mesh).
Alumina (ICN Alumina N, Super I) was obtained from ICN Bio-
medicals. Unless otherwise specified, alumina was deactivated with
5% H2O. TLC analyses were performed using Machery–Nagel pre-
coated plates, 0.25 mm, Alugram Sil G/UV254 (I) and Merck pre-
coated silica gel 60 F254 aluminum sheets (II). All reactions were
carried out under an atmosphere of dry N2 or argon in oven- and/or
flame-dried glassware. Unless otherwise specified, solns of NH4Cl,
NaCl, Na2SO3, and NaHCO3 were sat. aq solns. Benzene, decalin,
toluene, THF, and Et2O were distilled from Na/benzophenone.
CH2Cl2 was distilled from CaH2.
benzoic acid (2h) reacted with 22 to give inseparable mix-
tures of both regioisomers 23h and 24h in ratios ranging
from 1:6 to 1:7 at 80 and 50 °C, respectively (entries 16
and 15).
Ruthenium-complex-catalyzed additions of carboxylic
acids to cyclopropylethynes can be brought about in the
Markovnikov as well as the anti-Markovnikov sense to
give 1- and 2-cyclopropylethenyl esters, respectively, in
high yields. (trans-2-Ethoxycyclopropyl)ethyne, in the
presence of [Ru(O2CH)(CO)2(PPh3)]2 regioselectively
adds carboxylic acids with ring opening to furnish allenyl-
acetaldehyde acyl ethyl acetals.
1H NMR: Varian VXR-300 (300 MHz), Bruker AM 250
(250 MHz). Chemical shifts in CDCl3 are reported as d values rela-
tive to CHCl3 (d = 7.26) or benzene (d = 7.20) as internal referenc-
es. 13C NMR Varian VXR-300 (75.5 MHz), Bruker AW 250
(62.9 MHz). Chemical shifts in CDCl3 are reported as d values rel-
ative to CHCl3 (d = 77.0) or benzene (d = 128); the multiplicities of
the signals were determined by APT (Varian, Attached Proton Test)
and DEPT (Bruker, Distortionless Enhancement of Polarization
Synthesis 2007, No. 22, 3574–3588 © Thieme Stuttgart · New York

3580
I. Emme et al.
SPECIAL TOPIC
Carboxylic Acid 1-Ethoxypenta-3,4-dienyl Esters 3a–k and 1-
(2-Ethoxycyclopropyl)ethenyl Esters 4b,g–k; General Proce-
dure
A small screw-capped Pyrex bottle was charged with (trans-2-
ethoxycyclopropyl)ethyne (1, 1 equiv), carboxylic acid 2 (1 equiv),
and [Ru(O2CH)(CO)2(PPh3)]2 (A, 0.2–0.4 mol%, based on 1) in de-
gassed anhyd benzene (ca. 1 mL/mmol), and the sealed vessel was
heated at 70–75 °C (3–15 h). After cooling to r.t., the solvent was
evaporated under reduced pressure, and the products were separated
by column chromatography (silica gel).
CH3COO), 3.28 (mc, 1 H, H2¢), 3.44 (mc, 2 H, OCH2CH3), 4.73–
4.74 (m, 2 H, H2).
13C NMR (62.9 MHz, CDCl3): d = 11.26 (–, C3¢), 14.78 (+,
OCH2CH3), 20.13 (+, CH3COO), 20.82 (+, C–1¢), 57.12 (+, C2¢),
66.11 (–, OCH2CH3), 101.72 (–, C2), 152.07 (Cq, C1), 168.84 (Cq,
C=O).
MS (70 eV): m/z (%) = 170 (2) [M+], 128 (33) [M+ – CH3CO], 81
(42), 43 (100) [CH3CO+].
MS (DCI, NH3, 70 eV): m/z (%) = 171 (28) [M + H+], 188 (100) [M
+
+ NH4 ].
1-Ethoxypenta-3,4-dienyl Formate (3a)
A mixture of 1 (80.0 mg, 726 mmol), formic acid (2a, 33.4 mg, 726
mmol), and ruthenium catalyst A (2.0 mg, 0.3 mol%) in benzene-d6
(0.5 mL) in an NMR tube was heated at 70 °C for 2 h. The 1H NMR
spectrum indicated quantitative conversion of 1 into 3a with traces
of impurities only. An attempted separation of 3a from the benzene
solvent failed due to the similar boiling points.
1H NMR (250 MHz, C6D6): d = 0.95 (t, 3J = 7.0 Hz, 3 H,
OCH2CH3), 2.34 (mc, 2 H, H2), 3.19–3.31 (A part of an AB system,
m, 1 H, OCH2CH3), 3.44–3.54 (B part of an AB system, m, 1 H,
OCH2CH3), 4.54 (mc, 2 H, H5), 5.02 (mc, 1 H, H3), 5.88 (t, 3J = 5.4
Hz, 1 H, H1), 7.68 (s, 1 H, HCOO).
1-Ethoxypenta-3,4-dienyl Pentanoate (3c)
Using 1 (80.0 mg, 726 mmol), pentanoic acid (2c, 74.2 mg, 726
mmol), and A (1.3 mg, 0.2 mol%) in benzene (0.5 mL) and heating
at 70 °C for 6 h; chromatography (silica gel, PE–Et2O, 20:1) gave
3c (130 mg, 84%) as a colorless oil; Rf = 0.48 (PE–Et2O, 9:1).
IR (neat): 1959 (C=C=C), 1738 cm–1 (C=O).
1H NMR (250 MHz, C6D6): d = 0.75 (t, 3J = 7.3 Hz, 3 H, H5), 1.02
(t, 3J = 7.1 Hz, 3 H, OCH2CH3), 1.16 (quint, 3J = 7.3 Hz, 2 H, H4),
3
3
1.50 (quint, J = 7.3 Hz, 2 H, H3), 2.12 (t, J = 7.3 Hz, 2 H, H2),
2.45 (mc, 2 H, H2¢), 3.33–3.45 (A part of an AB system, m, 1 H,
OCH2CH3), 3.59–3.71 (B part of an AB system, m, 1 H, OCH2CH3),
4.56 (mc, 2 H, H5¢), 5.12 (mc, 1 H, H3¢), 6.02 (t, 3J = 5.4 Hz, 1 H,
H1¢).
13C NMR (62.9 MHz, C6D6): d = 14.94 (+, OCH2CH3), 34.26 (–,
C2), 65.12 (–, OCH2CH3), 75.12 (–, C5), 84.28 (+, C3), 97.30 (+,
C1), 160.37 (+, C=O), 209.98 (Cq, C4).
13C NMR (62.9 MHz, C6D6): d = 13.79 (+, C5), 15.17 (+,
OCH2CH3), 22.44 (–, C4), 27.19 (–, C3), 34.25, 34.59 (–, C2, C2¢),
65.00 (–, OCH2CH3), 74.97 (–, C5¢), 84.71 (+, C3¢), 97.32 (+, C1¢),
172.92 (Cq, C1), 210.02 (Cq, C4¢).
1-Ethoxypenta-3,4-dienyl Acetate (3b) and 1-(2-Ethoxycyclo-
propyl)ethenyl Acetate (4b)
Experiment I: Using 1 (80.0 mg, 726 mmol), AcOH (2b, 43.6 mg,
726 mmol), and A (2.6 mg, 0.4 mol%) in benzene (1 mL) and heat-
ing at 75 °C for 3 h; chromatography (silica gel, PE–Et2O, 20:1)
gave 3b (119 mg, 96%) as a colorless oil; Rf = 0.42 (PE–Et2O, 9:1).
Compound 4b was not observed.
MS (70 eV): m/z (%) = 212 (1) [M+], 183 (5) [M+ – C2H5], 159 (6)
[M+ – CH2=C=CHCH2], 111 (53) [M+ – C4H9COO], 85 (100)
+
[C4H9CO+], 57 (43) [C4H9 ].
HRMS: calcd for C12H20O3: 212.1412.
Experiment II: Using 1 (4.00 g, 36.3 mmol), AcOH (2b, 2.18 g, 36.3
mmol), and A (326 mg, 1 mol%) in benzene (6 mL) and heating at
70 °C for 12 h; chromatography (silica gel, PE–Et2O, 20:1 to 5:1)
gave 3b (5.22 g, 84%) and 4b (512 mg, 8%) as colorless oils.
Anal. Calcd for C12H20O3 (212.3): C, 67.89; H, 9.50. Found: C,
68.11; H, 9.64.
1-Ethoxypenta-3,4-dienyl Undec-10-enoate (3d)
Using 1 (80.0 mg, 726 mmol), undec-10-enoic acid (2d, 134 mg, 726
mmol), and A (2.6 mg, 0.4 mol%) in benzene (2 mL) and heating at
70 °C for 6 h; chromatography (silica gel, PE–Et2O, 20:1) gave 3d
(197 mg, 92%) as a colorless oil; Rf = 0.56 (PE–Et2O, 9:1).
3b
Rf = 0.65 (PE–Et2O, 9:1).
IR (neat): 1959 (C=C=C), 1742 cm–1 (C=O).
IR (neat): 1958 (C=C=C), 1735 (C=O), 995 (C=C), 911 cm–1
(C=C).
1H NMR (250 MHz, C6D6): d = 0.99 (t, 3J = 7.0 Hz, 3 H,
OCH2CH3), 1.69 (s, 3 H, CH3COO), 2.38 (mc, 2 H, H2), 3.31–3.38
(A part of an AB system, m, 1 H, OCH2CH3), 3.53–3.62 (B part of
an AB system, m, 1 H, OCH2CH3), 4.55 (mc, 2 H, H5), 5.06 (mc, 1
H, H3), 5.92 (t, 3J = 5.4 Hz, 1 H, H1).
13C NMR (62.9 MHz, C6D6): d = 15.13 (+, OCH2CH3), 20.66 (+,
CH3COO), 34.43 (–, C2), 64.99 (–, OCH2CH3), 74.96 (–, C5), 84.63
(+, C3), 97.45 (+, C1), 170.08 (Cq, C=O), 209.98 (Cq, C4).
1H NMR (250 MHz, C6D6): d = 1.03 (t, 3J = 7.0 Hz, 3 H,
OCH2CH3), 1.05–1.40 (m, 10 H, H4, H5, H6, H7, H8), 1.55 (mc, 2
H, H3), 1.96 (mc, 2 H, H9), 2.15 (t, 3J = 7.1 Hz, 2 H, H2), 2.44 (mc,
2 H, H2¢), 3.40–3.48 (A part of an AB system, m, 1 H, OCH2CH3),
3.62–3.70 (B part of an AB system, m, 1 H, OCH2CH3), 4.58 (mc, 2
H, H5¢), 5.06 (mc, 3 H, 2 H11, H3¢), 5.77 (mc, 1 H, H10), 6.00 (t,
3J = 5.4 Hz, 1 H, H1¢).
13C NMR (62.9 MHz, C6D6): d = 15.02 (+, OCH2CH3), 25.18,
29.23, 29.37 (2 C), 29.54, 29.63 (–, C3, C4, C5, C6, C7, C8), 34.15,
34.56, 34.59 (–, C2, C2¢, C9), 65.00 (–, OCH2CH3), 74.98 (–, C5¢),
84.71 (+, C3¢), 97.33 (+, C1¢), 114.50 (–, C11), 139.16 (+, C10),
172.93 (Cq, C1), 210.03 (Cq, C4¢).
MS (70 eV): m/z (%) = 170 (2) [M+], 141 (23) [M+ – C2H5], 117 (30)
[M+ – CH2=C=CHCH2], 111 (29) [M+ – CH3COO], 83 (26), 81
+
(28), 53 (15) [CH2=C=CHCH2 ], 43 (100) [CH3CO+].
HRMS: calcd for C9H14O3: 170.0942.
Anal. Calcd for C9H14O3 (170.2): C, 63.51; H, 8.29. Found: C,
63.55; H, 8.15.
MS (70 eV): m/z (%) = 294 (1) [M+], 265 (3) [M+ – C2H5], 251 (2)
[M+ – C2H5 – CH2], 167 (23) [C10H19CO+], 149 (39), 128 (30), 111
4b
(100) [M+
[CH2=CHCH2CH2 ], 41 (34) [CH2=CHCH2 ].
– C10H19COO], 81 (44), 67 (31), 55 (69)
(Rf = 0.20 in PE–Et2O, 9:1).
IR (neat): 1759 (C=O), 1662 cm–1 (C=C).
+
+
HRMS: calcd for C18H30O3: 294.2194.
1H NMR (250 MHz, CDCl3): d = 0.81–0.91 (m, 2 H, H3¢), 1.09 (t,
Anal. Calcd for C18H30O3 (294.4): C, 73.43; H, 10.27. Found: C,
73.60; H, 10.39.
3J = 7.0 Hz, 3 H, OCH2CH3), 1.45 (mc, 1 H, H1¢), 2.07 (s, 3 H,
Synthesis 2007, No. 22, 3574–3588 © Thieme Stuttgart · New York

SPECIAL TOPIC
Ruthenium-Catalyzed Transformations of Cyclopropylethynes
HRMS: calcd for C12H20O3: 212.1412.
3581
1-Ethoxypenta-3,4-dienyl Cyclopropanecarboxylate (3e)
Using 1 (80.0 mg, 726 mmol), cyclopropanecarboxylic acid (2e,
62.5 mg, 726 mmol), and A (2.6 mg, 0.4 mol%) in benzene (0.5 mL)
and heating at 70 °C for 4 h; chromatography (silica gel, PE–Et2O,
20:1) gave 3e (132 mg, 93%) as a colorless oil; Rf = 0.46 (PE–Et2O,
9:1).
Anal. Calcd for C12H20O3 (212.3): C, 67.89; H, 9.50. Found: C,
67.96; H, 9.55.
4g
Rf = 0.20 (PE–Et2O, 9:1).
IR (neat): 1748 cm–1 (C=O).
IR (neat): 1959 (C=C=C), 1728 cm–1 (C=O).
1H NMR (250 MHz, C6D6): d = 0.39–0.47 (m, 2 H, cPr-H), 0.84–
1.05 (m, 5 H, cPr-H, OCH2CH3), 1.40 (mc, 1 H, cPr-H), 2.41 (mc, 2
H, H2), 3.32–3.42 (A part of an AB system, m, 1 H, OCH2CH3),
3.56–3.66 (B part of an AB system, m, 1 H, OCH2CH3), 4.55 (mc, 2
H, H5), 5.08 (mc, 1 H, H3), 5.97 (t, 3J = 5.4 Hz, 1 H, H1).
13C NMR (62.9 MHz, C6D6): d = 8.38 (–, 2 C, cPr-C), 13.11 (+, cPr-
C), 15.16 (+, OCH2CH3), 34.53 (–, C2), 64.99 (–, OCH2CH3), 74.96
(–, C5), 84.65 (+, C3), 97.45 (+, C1), 174.19 (Cq, C=O), 210.01 (Cq,
C4).
1H NMR (250 MHz, C6D6): d = 0.72 (dt, 2J = 3J = 6.3 Hz, 1 H, H3¢),
0.96 (mc, 1 H, H3¢), 1.03 (t, 3J = 7.0 Hz, 3 H, OCH2CH3), 1.12 [s, 9
H, C(CH3)3], 1.68 (mc, 1 H, H1¢), 3.29 (mc, 1 H, H2¢), 3.37 (q,
3J = 7.0 Hz, 2 H, OCH2CH3), 4.44 (dd, 2J = 1.5 Hz, 4J = 0.8 Hz, 1
H, H2A), 4.66 (d, 2J = 1.5 Hz, 1 H, H2B).
13C NMR (62.9 MHz, C6D6): d = 13.18 (–, C3¢), 15.21 (+,
OCH2CH3), 22.26 (+, C1¢), 27.10 [+, 3 C, C(CH3)3], 33.96 [Cq,
C(CH3)3], 59.49 (+, C2¢), 66.06 (–, OCH2CH3), 99.44 (–, C2),
155.53 (Cq, C1), 175.73 (Cq, C=O).
MS (70 eV): m/z (%) = 196 (1) [M+], 167 (3) [M+ – C2H5], 111 (53)
MS (70 eV): m/z (%) = 212 (1) [M+], 167 (1) [M+ – OC2H5], 111 (2)
[M+ – C3H5COO], 83 (51), 81 (43), 69 (100) [C3H5CO+].
+
[M+ – C4H9COO], 85 (13) [C4H9CO+], 57 (100) [C4H9 ].
HRMS: calcd for C11H16O3: 196.1099.
HRMS: calcd for C12H20O3: 212.1412.
Anal. Calcd for C11H16O3 (196.3): C, 67.32; H, 8.22. Found: C,
67.50; H, 8.48.
Anal. Calcd for C12H20O3 (212.3): C, 67.89; H, 9.50. Found: C,
68.00; H, 9.50.
Bis(1-ethoxypenta-3,4-dienyl) Succinate (3f)
1-Ethoxypenta-3,4-dienyl Benzoate (3h) and 1-(2-Ethoxycyclo-
propyl)ethenyl Benzoate (4h)
Using 1 (80.0 mg, 726 mmol), benzoic acid (2h, 88.7 mg, 726 mmol),
and A (2.6 mg, 0.4 mol%) in benzene (1 mL) and heating at 70 °C
for 6 h; chromatography (silica gel, PE–Et2O, 20:1) gave 3h (98.1
mg, 58%) and 4h (45.7 mg, 27%) as colorless oils.
Using 1 (120 mg, 1.09 mmol), succinic acid (2f, 129 mg, 1.09
mmol), and A (3.9 mg, 0.4 mol%) in CH2Cl2 (20 mL) and heating
at 70 °C for 15 h; chromatography (silica gel, PE–Et2O, 4:1) gave
3f (82 mg, 44%) as a colorless oil; Rf = 0.55 (PE–Et2O, 4:1).
IR (neat): 1958 (C=C=C), 1735 cm–1 (C=O).
1H NMR (250 MHz, C6D6): d = 1.02 (t, 3J = 7.1 Hz, 6 H,
OCH2CH3), 2.12–2.44 (m, 8 H, CH2CH2, H2), 3.56 (AB system, mc,
4 H, OCH2CH3), 4.57 (dt, 4J = 7.0 Hz, 5J = 2.8 Hz, 4 H, H5), 5.11
(tt, 3J = 4J = 7.0 Hz, 2 H, H3), 6.00 (t, 3J = 5.4 Hz, 2 H, H1).
3h
Rf = 0.52 (PE–Et2O, 9:1).
IR (neat): 1958 (C=C=C), 1718 cm–1 (C=O).
13C NMR (62.9 MHz, C6D6): d = 15.11 (+, 2 C, OCH2CH3), 29.08
(–, 2 C, CH2CH2), 34.46 (–, 2 C, C2), 65.06, 65.09 (–, OCH2CH3),
75.06 (–, 2 C, C5), 84.56 (+, 2 C, C3), 97.84, 97.87 (+, C1), 171.95
(Cq, 2 C, COO), 210.00 (Cq, 2 C, C4).
1H NMR (250 MHz, C6D6): d = 0.99 (t, 3J = 7.0 Hz, 3 H,
OCH2CH3), 2.53 (mc, 2 H, H2), 3.37–3.44 (A part of an AB system,
m, 1 H, OCH2CH3), 3.61–3.68 (B part of an AB system, m, 1 H,
OCH2CH3), 4.53 (mc, 2 H, H5), 5.15 (mc, 1 H, H3), 6.24 (t, 3J = 5.3
Hz, 1 H, H1), 7.36–7.61 (m, 3 H, Ar-H), 7.96–8.11 (m, 2 H, Ar-H).
13C NMR (62.9 MHz, C6D6): d = 15.14 (+, OCH2CH3), 34.64 (–,
C2), 65.18 (–, OCH2CH3), 75.04 (–, C5), 84.55 (+, C3), 98.39 (+,
C1), 128.59 (+, 2 C, Ar-C), 130.05 (+, 2 C, Ar-C), 130.71 (Cq, Ar-
C), 133.11 (+, Ar-C), 166.04 (Cq, C=O), 210.10 (Cq, C4).
MS (70 eV): m/z (%) = 211 (1), 111 (100), 83 (42).
+
MS (DCI, NH3, 70 eV): m/z (%) = 694 (18) [2 M + NH4 ], 356 [M
+
+ NH4 ].
1-Ethoxypenta-3,4-dienyl Pivalate (3g) and 1-(2-Ethoxycyclo-
propyl)ethenyl Pivalate (4g)
Using 1 (160 mg, 1.45 mmol), pivalic acid (2g, 148 mg, 1.45
mmol), and A (5.2 mg, 0.4 mol%) in benzene (1 mL) and heating at
70 °C for 6 h; chromatography (silica gel, PE–Et2O, 20:1) gave 3g
(192 mg, 62%) and 4g (88.2 mg, 29%) as colorless oils.
MS (70 eV): m/z (%) = 232 (1) [M+], 203 (1) [M+ – C2H5], 111 (6)
[M+ – PhCOO], 105 (100) [PhCO+], 77 (17) [Ph+].
HRMS: calcd for C14H16O3: 232.1099.
Anal. Calcd for C14H16O3 (232.3): C, 72.39; H, 6.94. Found: C,
72.35; H, 6.96.
3g
4h
Rf = 0.48 (PE–Et2O, 9:1).
Rf = 0.24 (PE–Et2O, 9:1).
IR (neat): 1732 (C=O), 1660 (C=C), 1270 (C–O), 1232 cm–1 (C–O).
IR (neat): 1959 (C=C=C), 1730 cm–1 (C=O).
1H NMR (250 MHz, C6D6): d = 1.00 (t, 3J = 7.0 Hz, 3 H,
OCH2CH3), 1.14 [s, 9 H, C(CH3)3], 2.40 (mc, 2 H, H2), 3.29–3.39
(A part of an AB system, m, 1 H, OCH2CH3), 3.54–3.64 (B part of
an AB system, m, 1 H, OCH2CH3), 4.55 (mc, 2 H, H5), 5.08 (mc, 1
H, H3), 5.95 (t, 3J = 5.3 Hz, 1 H, H1).
13C NMR (62.9 MHz, C6D6): d = 15.19 (+, OCH2CH3), 27.11 [+, 3
C, C(CH3)3], 34.61 (–, C2), 38.95 [Cq, C(CH3)3], 64.84 (–,
OCH2CH3), 74.89 (–, C5), 84.61 (+, C3), 97.40 (+, C1), 177.47 (Cq,
C=O), 210.05 (Cq, C4).
1H NMR (250 MHz, C6D6): d = 0.77 (dt, 2J = 3J = 6.4 Hz, 1 H, H3¢),
0.96–1.03 (m, 4 H, H3¢, OCH2CH3), 1.77–1.81 (m, 1 H, H1¢), 3.31–
3.40 (m, 3 H, H2¢, OCH2CH3), 4.51 (d, 2J = 1.8 Hz, 1 H, H2A), 4.77
(d, 2J = 1.8 Hz, 1 H, H2B), 6.97–7.10 (m, 3 H, Ar-H), 8.07–8.11 (m,
2 H, Ar-H).
13C NMR (62.9 MHz, C6D6): d = 13.44 (–, C3¢), 15.16 (+,
OCH2CH3), 22.39 (+, C1¢), 59.71 (+, C2¢), 66.08 (–, OCH2CH3),
100.14 (–, C2), 128.65 (+, 2 C, Ar-C), 130.14 (+, 2 C, Ar-C), 130.35
(Cq, Ar-C), 133.24 (+, Ar-C), 155.62 (Cq, C1), 164.42 (Cq, C=O).
MS (70 eV): m/z (%) = 212 (1) [M+], 111 (35) [M+ – C4H9COO], 85
+
(28) [C4H9CO+], 57 (100) [C4H9 ].
Synthesis 2007, No. 22, 3574–3588 © Thieme Stuttgart · New York

3582
I. Emme et al.
SPECIAL TOPIC
4
5
MS (70 eV): m/z (%) = 233 (4) [M+ + H], 232 (2) [M+], 187 (1) [M+
– OEt], 128 (28) [M+ – PhCO], 105 (100) [PhCO+], 85 (5)
[C3H4OEt+], 77 (23) [Ph+].
OCH2CH3), 4.56 (dt, J = 6.9 Hz, J = 2.8 Hz, 2 H, H5), 5.13 (tt,
3J = 4J = 6.9 Hz, 1 H, H3), 6.15 (t, 3J = 5.3 Hz, 1 H, H1), 6.59 (dt,
3J = 3J = 7.7 Hz, 4J = 1.7 Hz, 1 H, Ar-H), 6.90 (dt, 3J = 3J = 7.7 Hz,
4J = 1.1 Hz, 1 H, Ar-H), 7.69 (mc, 2 H, Ar-H).
HRMS: calcd for C14H16O3: 232.1099.
13C NMR (62.9 MHz, C6D6): d = 15.22 (+, OCH2CH3), 34.44 (–,
C2), 65.48 (–, OCH2CH3), 75.35 (–, C5), 84.57 (+, C3), 94.64 (Cq,
CI), 99.06 (+, C1), 127.91 (+, Ar-C), 131.13 (+, Ar-C), 132.70 (+,
Ar-C), 135.42 (Cq, Ar-C), 141.63 (+, Ar-C), 165.84 (Cq, COO),
209.97 (Cq, C4¢).
Anal. Calcd for C14H16O3 (232.3): C, 72.39; H, 6.94. Found: C,
72.55; H, 7.18.
1-Ethoxypenta-3,4-dienyl 5-Methylthiophene-2-carboxylate
(3i) and 1-(2-Ethoxycyclopropyl)ethenyl 5-Methylthiophene-2-
carboxylate (4i)
Using 1 (80.0 mg, 0.726 mmol), 5-methylthiophene-2-carboxylic
acid (2i, 71.2 mg, 501 mmol), and A (2.6 mg, 0.4 mol%) in benzene
(2 mL) and heating at 70 °C for 6 h; chromatography (silica gel, PE–
Et2O, 8:1) gave 3i (80.8 mg, 64%) and 4i (31.5 mg, 25%) as color-
less oils.
MS (70 eV): m/z (%) = 358 (1) [M+], 231 (100) [M+ – I], 203 (7)
[C6H4I+], 127 (1) [I+], 111 (15) [M+ – C6H4ICOO].
HRMS: calcd for C14H15IO3: 358.0065.
Anal. Calcd for C14H15IO3 (358.2): C, 46.95; H, 4.22. Found: C,
46.96; H, 4.12.
4j
3i
Rf = 0.25 (PE–Et2O, 7:1).
Rf = 0.60 (PE–Et2O, 4:1).
IR (neat): 1741 (C=O), 1660 (C=C), 1287 (C–O), 1246 cm–1 (C–O).
IR (neat): 1958 (C=C=C), 1706 cm–1 (C=O).
1H NMR (250 MHz, C6D6): d = 0.65 (mc, 1 H, H3¢), 0.86 (mc, 1 H,
1H NMR (250 MHz, C6D6): d = 0.99 (t, 3J = 7.0 Hz, 3 H,
OCH2CH3), 1.91 (s, 3 H, H6), 2.51 (mc, 2 H, H2¢), 3.55 (AB system,
3
3
H3¢), 1.04 (t, J = 7.0 Hz, 3 H, OCH2CH3), 1.47 (dt, J = 6.5 Hz,
3J = 9.6 Hz, 1 H, H1¢), 3.02 (mc, 1 H, H2¢), 3.42 (mc, 2 H,
OCH2CH3), 4.83 (s, 1 H, H2), 4.99 (s, 1 H, H2), 6.57 (dt,
3J = 3J = 7.6 Hz, 4J = 1.6 Hz, 1 H, Ar-H), 6.88 (dt, 3J = 3J = 7.6 Hz,
4J = 1.1 Hz, 1 H, Ar-H), 7.72 (mc, 2 H, Ar-H).
4
mc, 2 H, OCH2CH3), 4.54 (dt, J = 7.0 Hz, 5J = 2.9 Hz, 2 H, H5¢),
5.14 (tt, 3J = 4J = 7.0 Hz, 1 H, H3¢), 6.19 (t, 3J = 5.3 Hz, 1 H, H1¢),
6.30 (d, 3J = 3.7 Hz, 1 H, H4), 7.65 (d, 3J = 3.7 Hz, 1 H, H3).
13C NMR (62.9 MHz, C6D6): d = 15.14, 15.19 (+, C6, OCH2CH3),
34.66 (–, C2¢), 65.20 (–, OCH2CH3), 75.03 (–, C5¢), 84.54 (+, C3¢),
98.31 (+, C1¢), 126.68 (+, C4), 131.82 (Cq, C2), 134.34 (+, C3),
148.33 (Cq, C5), 161.81 (Cq, C1), 210.10 (Cq, C4¢).
13C NMR (62.9 MHz, C6D6): d = 12.14 (–, C3¢), 15.35 (+,
OCH2CH3), 20.79 (+, C1¢), 57.84 (+, C2¢), 66.43 (–, OCH2CH3),
94.72 (Cq, CI), 102.08 (–, C2), 127.95 (+, Ar-C), 131.36 (+, Ar-C),
132.77 (+, Ar-C), 135.31 (Cq, Ar-C), 141.60 (+, Ar-C), 153.19 (Cq,
C1), 164.17 (Cq, COO).
MS (70 eV): m/z (%) = 252 (1) [M+], 125 (100) [C5H5SCO+].
Anal. Calcd for C13H16O3S (252.3): C, 61.88; H, 6.39. Found: C,
62.08; H, 6.30.
MS (70 eV): m/z (%) = 358 (1) [M+], 231 (100) [M+ – I], 203 (11)
[C6H4I+].
Anal. Calcd for C14H15IO3 (358.2): C, 46.95; H, 4.22. Found: C,
46.94; H, 4.16.
4i
Rf = 0.45 (PE–Et2O, 4:1).
IR (neat): 1724 (C=O), 1661 (C=C), 1255 (C–O), 1233 cm–1 (C–O).
1-Ethoxypenta-3,4-dienyl 2-Acetylbenzoate (3k) and 1-(2-
Ethoxycyclopropyl)ethenyl 2-Acetylbenzoate (4k)
Using 1 (80.0 mg, 726 mmol), 2-acetylbenzoic acid (2k, 119 mg,
726 mmol), and A (2.6 mg, 0.4 mol%) in benzene (2 mL) and heat-
ing at 70 °C for 6 h; chromatography (silica gel, PE–Et2O, 4:1) gave
3k (115 mg, 58%) and 4k (20 mg, 10%) as colorless oils.
1H NMR (250 MHz, C6D6): d = 0.80 (q, 3J = 6.4 Hz, 1 H, H3¢¢), 0.98
(mc, 2 H, H1¢, H3¢¢), 1.01 (t, 3J = 7.0 Hz, 3 H, OCH2CH3), 1.80 (mc,
1 H, H2¢¢), 1.86 (s, 3 H, H6), 3.34–3.42 (m, 2 H, OCH2CH3), 4.49
(d, 2J = 2.1 Hz, 1 H, H2¢), 4.82 (d, 2J = 2.1 Hz, 1 H, H2¢), 6.24 (d,
3J = 3.7 Hz, 1 H, H4), 7.62 (d, 3J = 3.7 Hz, 1 H, H3).
13C NMR (62.9 MHz, C6D6): d = 13.38 (–, C3¢¢), 15.14, 15.19 (+,
C6, OCH2CH3), 22.45 (+, C1¢¢), 59.61 (+, C2¢¢), 66.10 (–,
OCH2CH3), 100.21 (–, C2¢), 126.79 (+, C4), 131.17 (Cq, C2),
134.83 (+, C3), 148.64 (Cq, C5), 155.19, (Cq, C1¢), 159.69 (Cq, C1).
MS (70 eV): m/z (%) = 252 (1) [M+], 125 (100) [C5H5SCO+], 81
(19).
3k
Rf = 0.40 (PE–Et2O, 4:1).
IR (neat): 1957 (C=C=C), 1773 (C=O), 1705 (C=O), 1266 cm–1 (C–
O).
1H NMR (250 MHz, C6D6): d = 1.02 (t, 3J = 7.1 Hz, 3 H,
OCH2CH3), 2.23 (s, 3 H, COCH3), 2.54 (mc, 2 H, H2), 3.60 (AB
system, mc, 2 H, OCH2CH3), 4.55 (dt, 4J = 7.0 Hz, 5J = 2.9 Hz, 2 H,
HRMS: calcd for C13H16O3S: 252.0820.
H5), 5.16 (tt, 3J = 4J = 7.0 Hz, 1 H, H3), 6.18 (t, J = 5.3 Hz, 1 H,
3
Anal. Calcd for C13H16O3S (252.3): C, 61.88; H, 6.39. Found: C,
61.95; H, 6.18.
H1), 6.94–6.99 (m, 3 H, Ar-H), 7.74 (mc, 1 H, Ar-H).
13C NMR (62.9 MHz, C6D6): d = 15.12 (+, OCH2CH3), 29.49 (+,
COCH3), 34.40 (–, C2), 65.49 (–, OCH2CH3), 75.11 (–, C5), 84.52
(+, C3), 99.15 (+, C1), 126.79 (+, Ar-C), 129.79 (+, Ar-C), 129.83
(+, Ar-C), 129.85 (Cq, Ar-C), 131.77 (+, Ar-C), 143.28 (Cq, Ar-C),
166.84 (Cq, COO), 200.97 (Cq, COCH3), 210.04 (Cq, C4).
1-Ethoxypenta-3,4-dienyl 2-Iodobenzoate (3j) and 1-(2-Ethoxy-
cyclopropyl)ethenyl 2-Iodobenzoate (4j)
Using 1 (400 mg, 3.63 mmol), 2-iodobenzoic acid (2j, 901 mg, 3.63
mmol), and A (13 mg, 0.4 mol%) in benzene (6 mL) and heating at
70 °C for 6 h; chromatography (silica gel, PE–Et2O, 8:1) gave 3j
(881 mg, 68%) and 4j (238 mg, 18%) as colorless oils.
MS (70 eV): m/z (%) = 177 (1), 147 (100) [C8H7OCO+], 111 (11)
[M+ – C8H7OCO2].
3j
+
MS (DCI, NH3, 70 eV): m/z (%) = 292 [M + NH4 ] (58), 566 [2 M
+ NH4 ] (100).
Rf = 0.65 (PE–Et2O, 7:1).
IR (neat): 1958 (C=C=C), 1728 cm–1 (C=O).
1H NMR (250 MHz, C6D6): d = 1.01 (t, 3J = 7.0 Hz, 3 H,
OCH2CH3), 2.51 (mc, 2 H, H2), 3.55 (AB system, mc, 2 H,
+
Anal. Calcd for C16H18O4 (274.3): C, 70.06; H, 6.61. Found: C,
69.93; H, 6.36.
Synthesis 2007, No. 22, 3574–3588 © Thieme Stuttgart · New York

SPECIAL TOPIC
Ruthenium-Catalyzed Transformations of Cyclopropylethynes
3583
4k
70 °C for 2 h; chromatography (PE–Et2O, 1:1) gave 12bb (160 mg,
46%) as a colorless oil; Rf = 0.25 (PE–Et2O, 1:1).
Rf = 0.25 (PE–Et2O, 4:1).
IR (neat): 1738 (C=O), 1703 (C=O), 1661 (C=C), 1266 (C–O),
1232 cm–1 (C–O).
IR (neat): 1738 cm–1 (C=O).
1H NMR (250 MHz, CDCl3): d = 0.98–1.26 (m, 5 H, Cy-H), 1.21 (t,
3J = 7.1 Hz, 3 H, OCH2CH3), 1.57–1.82 (m, 5 H, Cy-H), 2.09 (s, 3
H, CH3COO), 2.41 (mc, 1 H, Cy-H), 2.66 (dd, 3J = 7.5 Hz, 3J = 5.4
Hz, 2 H, H2), 3.65 (mc, 2 H, OCH2CH3), 3.65 (d, 3J = 5.9 Hz, 2 H,
1H NMR (250 MHz, C6D6): d = 0.81 (q, 2J = 3J = 6.3 Hz, 1 H, H3¢),
0.99–1.03 (m, 2 H, H1¢, H3¢), 1.05 (t, 3J = 7.0 Hz, 3 H, OCH2CH3),
1.83 (mc, 1 H, H2¢), 2.16 (s, 3 H, COCH3), 3.42 (mc, 2 H,
OCH2CH3), 4.49 (d, 2J = 1.8 Hz, 1 H, H2), 4.86 (d, 2J = 1.8 Hz, 1 H,
H2); 6.89–6.92 (m, 3 H, Ar-H), 7.65 (mc, 1 H, Ar-H).
H5), 5.75 (t, 3J = 7.5 Hz, 1 H, H1), 5.89 (t, J = 5.4 Hz, 1 H, H3),
3
7.21–7.43 (m, 5 H, Ar-H).
13C NMR (62.9 MHz, C6D6): d = 13.51 (–, C3¢), 15.22 (+,
OCH2CH3), 22.09 (+, C1¢), 29.18 (+, COCH3), 59.88 (+, C2¢), 66.13
(–, OCH2CH3), 100.00 (–, C2), 126.96 (+, Ar-C), 127.87 (+, Ar-C),
129.87 (+, Ar-C), 129.96 (Cq, Ar-C), 131.73 (+, Ar-C), 142.96 (Cq,
Ar-C), 155.72 (Cq, C1), 164.11 (Cq, COO), 200.38 (Cq, COCH3).
13C NMR (62.9 MHz, CDCl3): d = 14.96 (+, OCH2CH3), 21.17 (+,
CH3COO), 24.90 (–, 2 C, Cy-C), 26.06 (–, 2 C, Cy-C), 33.35 (–, Cy-
C), 34.03 (–, C2), 45.14 (–, C5), 56.42 (+, Cy-C), 65.11 (–,
OCH2CH3), 97.73 (+, C1), 123.23 (+, C3), 126.27 (+, 2 C, Ar-C),
127.04 (+, Ar-C), 128.31 (+, 2 C, Ar-C), 141.63, 141.74 (Cq, Ar-C,
C4), 170.75 (Cq, COO).
MS (70 eV): m/z (%) = 147 (100) [C8H7OCO+], 91 (12), 81 (17).
MS (70 eV): m/z (%) = 345 (6) [M+], 316 (23) [M+ – C2H5], 285
+
MS (DCI, NH3, 70 eV): m/z (%) = 292 (100) [M + NH4 ], 566 [2 M
(100) [M+ – CH3COOH], 256 (39), 240 (82), 211 (53), 187 (67), 155
+
+ NH4 ] (42).
+
(37), 138 (82), 112 (35), 99 (82) [C6H11NH2 ], 84 (22), 56 (31).
Anal. Calcd for C16H18O4 (274.3): C, 70.06; H, 6.61. Found: C,
69.77; H, 6.39.
HRMS: calcd for C21H31NO3: 345.2303.
(Z)-1-Ethoxy-5-(isobutylamino)-4-phenylpent-4-enyl Acetate
(12bc)
(Z)-5-(Alkylamino)-1-ethoxy-4-phenylpent-3-enyl Acetates 12;
General Procedure
A mixture of 3b (201 mg, 1.18 mmol), i-BuNH2 (585 mg, 8.00
mmol), PhI (204 mg, 1.00 mmol), Pd(OAc)2 (11 mg, 5 mol%), and
tri(2-furyl)phosphine (23 mg, 10 mol%) in DMF (0.75 mL) was
heated at 60 °C for 1 h. After cooling to r.t. the mixture was diluted
with CH2Cl2 (70 mL), washed with H2O (5 × 5 mL), and the organic
phase dried (MgSO4). After evaporation of the solvent under re-
duced pressure and chromatography of the residue (silica gel, PE–
Et2O, 1:1) 12bc (76 mg, 24%) was isolated as a colorless oil;
Rf = 0.25 (PE–Et2O, 1:1).
A screw-cap Pyrex bottle was charged with 1-ethoxypenta-3,4-di-
enyl acetate (3b, 1.18 mmol), amine (6–8 mmol), PhI (1.0 mmol),
Pd(OAc)2 (5 mol% based on PhI), tri(2-furyl)phosphine (TFP, 10
mol%, based on PhI) and degassed anhyd DMF (0.75 mL) under an
inert atmosphere (N2 or argon). The sealed bottle was heated for the
stated time. After cooling to r.t., Et2O (10 mL) was added, and the
mixture was filtered through a short column [Celite (1 cm), activat-
ed carbon (1 cm), and silica gel (1 cm), Et2O, 350 mL]. After evap-
oration of the solvent under reduced pressure the residue was
subjected to column chromatography (silica gel).
IR (neat): 1739 (C=O), 1676 cm–1 (C=C).
1H NMR (250 MHz, CDCl3): d = 0.81 [d, 3J = 6.7 Hz, 6 H,
(Z)-5-(tert-Butylamino)-1-ethoxy-4-phenylpent-3-enyl Acetate
(12ba)
Using 3b (201 mg, 1.18 mmol), t-BuNH2 (439 mg, 6.00 mmol), PhI
(204 mg, 1.00 mmol), Pd(OAc)2 (11 mg, 5 mol%), and tri(2-fur-
yl)phosphine (23 mg, 10 mol%) in DMF (0.75 mL) and heating at
55 °C for 45 min; chromatography (PE–Et2O, 1:1) gave 12ba (263
mg, 82%) as a colorless oil; Rf = 0.20 (PE–Et2O, 1:1).
3
CH(CH3)2], 1.20 (t, J = 7.1 Hz, 3 H, OCH2CH3), 1.64 [mc, 1 H,
3
CH(CH3)2], 2.08 (s, 3 H, CH3COO), 2.32 [d, J = 6.8 Hz, 2 H,
CH2CH(CH3)2], 2.66 (dd, 3J = 7.5 Hz, 3J = 5.4 Hz, 2 H, H2), 3.45–
3.77 (mc, 2 H, OCH2CH3), 3.62 (s, 2 H, H5), 5.75 (t, 3J = 7.5 Hz, 1
H, H1), 5.89 (t, 3J = 5.4 Hz, 1 H, H3), 7.23–7.41 (m, 5 H, Ar-H).
13C NMR (62.9 MHz, CDCl3): d = 14.95 (+, OCH2CH3), 20.57 [+,
2 C, CH(CH3)2], 21.15 (+, CH3COO), 28.06 [+, CH(CH3)2], 33.95
(–, C2), 47.85 [–, CH2CH(CH3)2], 57.23 (–, C5), 65.08 (–,
OCH2CH3), 97.73 (+, C1), 123.36 (+, C3), 126.37 (+, 2 C, Ar-C),
127.06 (+, 2 C, Ar-C), 128.23 (+, Ar-C), 141.61 (Cq, 2 C, Ar-C, C4),
170.76 (Cq, COO).
MS (70 eV): m/z (%) = 319 (4) [M+], 290 (10) [M+ – C2H5], 259
(29) [M+ – CH3COOH], 216 (49), 187 (100), 170 (35), 159 (22), 141
(45), 86 (27), 57 (20) [CH2CH(CH3)2], 43 (34) [CH(CH3)2].
IR (neat): 1739 (C=O), 1239 cm–1 (C–O).
1H NMR (250 MHz, CDCl3): d = 1.13 [s, 9 H, C(CH3)3], 1.21 (t,
3J = 7.1 Hz, 3 H, OCH2CH3), 2.09 (s, 3 H, CH3COO), 2.67 (dd,
3J = 5.4 Hz, 3J = 7.5 Hz, 2 H, H2), 3.59 (s, 2 H, H5), 3.64 (mc, 2 H,
OCH2CH3), 5.76 (t, 3J = 7.5 Hz, 1 H, H1), 5.90 (t, 3J = 5.4 Hz, 1 H,
H3), 7.23–7.47 (m, 5 H, Ar-H).
13C NMR (62.9 MHz, CDCl3): d = 14.97 (+, OCH2CH3), 21.17 (+,
CH3COO), 28.80 [+, 3 C, C(CH3)3], 34.05 (–, C2), 41.20 (–, C5),
50.46 [Cq, C(CH3)3], 65.11 (–, OCH2CH3), 97.84 (+, C1), 123.11 (+,
C3), 126.19 (+, 2 C, Ar-C), 127.01 (+, Ar-C), 128.26 (+, 2 C, Ar-
C), 141.75 (Cq, 2 C, Ar-C, C4), 170.75 (Cq, COO).
MS (70 eV): m/z (%) = 319 (6) [M+], 304 (5) [M+ – CH3], 290 (6)
[M+ – C2H5], 259 (41) [M+ – CH3COOH], 244 (24), 214 (32), 187
(100), 159 (23), 77 (6) [Ph+], 59 (14) [CH3COO+], 43 (23)
[CH3CO+].
HRMS: calcd for C19H29NO3: 319.2147.
(E)-5-(Dibenzylamino)-1-ethoxy-4-phenylpent-3-enyl Acetate
[(E)-12bd] and (Z)-5-(Dibenzylamino)-1-ethoxy-4-phenylpent-
3-enyl Acetate [(Z)-12bd]
Using 3b (201 mg, 1.18 mmol), Bn2NH (1.18 g, 6.00 mmol), PhI
(204 mg, 1.00 mmol), Pd(OAc)2 (11 mg, 5 mol%), and tri(2-fur-
yl)phosphine (23 mg, 10 mol%) in DMF (0.75 mL) and heating at
50 °C for 2 h then at 75 °C for1 h; chromatography (PE–Et2O, 5:1),
gave a mixture of (E)-12bd and (Z)-12bd (368 mg, 83%) as a col-
orless oil; ratio E/Z, 1:1; Rf = 0.40 (PE–Et2O, 2:1).
HRMS: calcd for C19H29NO3: 319.2147.
(Z)-5-(Cyclohexylamino)-1-ethoxy-4-phenylpent-3-enylAcetate
(12bb)
IR (neat): 1737 cm–1 (C=O).
Using 3b (200 mg, 1.18 mmol), CyNH2 (793 mg, 8.00 mmol), PhI
(204 mg, 1.00 mmol), Pd(OAc)2 (11 mg, 5 mol%), and tri(2-fur-
yl)phosphine (23 mg, 10 mol%) in DMF (0.75 mL) and heating at
1H NMR (250 MHz, CDCl3): d = 1.25 (t, 3J = 7.1 Hz, 3 H,
3
OCH2CH3), 1.27 (t, J = 7.1 Hz, 3 H, OCH2CH3), 2.07 (s, 3 H,
CH3COO), 2.13 (s, 3 H, CH3COO), 2.56 (t, 3J = 6.4 Hz, 2 H, H2),
Synthesis 2007, No. 22, 3574–3588 © Thieme Stuttgart · New York

3584
I. Emme et al.
SPECIAL TOPIC
2.81 (t, 3J = 6.4 Hz, 2 H, H2), 3.41–3.82 (m, 16 H, OCH2CH3, H5,
CH2C6H5), 5.84–6.02 (m, 4 H, H3, H1), 7.16–7.45 (m, 30 H, Ar-H).
Anal. Calcd for C14H16O3 (232.3): C, 72.39; H, 6.94. Found: C,
72.31; H, 7.07.
13C NMR (62.9 MHz, CDCl3): d = 14.88 (+, OCH2CH3), 14.95 (+,
OCH2CH3), 21.00 (+, CH3COO), 21.09 (+, CH3COO), 33.89 (–,
C4), 34.13 (–, C2), 52.09 (–, C5), 57.46 (–, 2 C, CH2C6H5), 57.90 (–,
2 C, CH2C6H5), 61.11 (–, C5), 64.82 (–, OCH2CH3), 65.01 (–,
OCH2CH3), 97.73 (+, C1), 97.54 (+, C1), 122.46 (+, C3), 124.87 (+,
C3), 139.34, 139.46 (3 C), 139.51 (3 C), 141.17, 142.04 (Cq, 6 Ar-
C, 2 C4), 170.60 (Cq, COO), 170.66 (Cq, COO).
(Z)-(2-trans-2-Ethoxycyclopropyl)ethenyl Acrylate (13l)
Using 1 (80.0 mg, 0.726 mmol), acrylic acid (2l, 52.3 mg, 0.726
mmol), and C (11.6 mg, 2.5 mol%) in benzene (0.5 mL) and heating
for 4.5 h; Kugelrohr distillation gave 13l (91.0 mg, 69%) as a color-
less oil; bp 50 °C/0.1 mbar.
IR (neat): 1739 (C=O), 1635 cm–1 (C=C).
MS (70 eV): m/z (%) = 443 (9) [M+], 383 (21) [M+ – CH3COOH],
1H NMR (250 MHz, C6D6): d = 0.38 (q, 2J = 3J = 3J = 6.0 Hz, 1 H,
H3¢¢), 1.04 (t, 3J = 3J = 7.0 Hz, 3 H, OCH2CH3), 0.94–1.05 (m, 1 H,
H3¢¢), 2.01 (mc, 1 H, H1¢¢), 2.96 (mc, 1 H, H2¢¢), 3.34 (mc, AB sys-
tem, 2 H, OCH2CH3), 4.00 (dd, 3Jcis = 6.4 Hz, 3Jallyl = 9.8 Hz, 1 H,
355 (15) [M+ – CH3COOEt], 210 (100) [Bzl2NCH2 ], 91 (81)
+
+
[C7H7 ].
2
3
2-(trans-2-Ethoxycyclopropyl)ethenyl Esters 13; General Pro-
cedure
A screw-cap Pyrex bottle was charged with (trans-2-ethoxycyclo-
H2¢), 5.20 (dd, Jgem = 1.4 Hz, Jcis = 10.4 Hz, 1 H, HB), 5.83 (dd,
3
3Jcis = 10.4 Hz, Jtrans = 17.3 Hz, 1 H, CH=CH2), 6.23 (dd,
2Jgem = 1.4 Hz, 3Jtrans = 17.3 Hz, 1 H, HA), 7.28 (d, 3Jcis = 6.4 Hz, 1
H, H1¢).
propyl)ethyne (1,
1
equiv), carboxylic acid (1 equiv),
[Ru(CH2CCH3CH2)2(dppb)] (C, 2.5 mol%), and anhyd benzene,
and the degassed mixture was heated in the sealed bottle at 60 °C
for 4.5–15 h. After evaporation of the solvent under reduced pres-
sure the residue was subjected to column chromatography (silica
gel) or distilled in a Kugelrohr apparatus.
13C NMR (62.9 MHz, C6D6): d = 15.09 (–, C3¢¢), 15.27, 16.16 (+,
C1¢¢, OCH2CH3), 60.26 (+, C2¢¢), 65.92 (–, OCH2CH3), 115.03 (+,
C2¢), 127.52 (+, CH=CH2), 131.73 (–, CH=CH2), 133.99 (+, C1¢),
162.70 (Cq, COO).
MS (70 eV): m/z (%) = 182 (3) [M+], 127 (25) [M+ – CH2=CHCO],
+
111 (4) [M+ – CH2=CHCO2], 84 (29), 71 (7) [CH2=CHCO2 ], 55
(Z)-(2-trans-2-Ethoxycyclopropyl)ethenyl Pentanoate (13c)
Using 1 (80.0 mg, 726 mmol), pentanoic acid (2c, 74 mg, 726 mmol),
and C, (11.5 mg, 2.5 mol%) in benzene (1.5 mL) and heating for 15
h; chromatography (silica gel, PE–Et2O, 20:1) gave 13c (131 mg,
85%) as a colorless oil; Rf = 0.18 (PE–Et2O, 9:1).
(100) [CH2=CHCO+].
HRMS: calcd for C10H14O3: 182.0942.
1-Ethynylcyclopropanol (14)28
A previously published protocol of Salaün29 was adjusted for the
preparation of 14 in its terminally trimethylsilyl-protected form.
IR (neat): 1752 (C=O), 1669 cm–1 (C=C).
1H NMR (250 MHz, CDCl3): d = 0.63 (q, 2J = 3J = 3J = 6.1 Hz, 1 H,
3
To a soln of 3 M MeMgCl in THF (160 mL, 0.480 mol) in anhyd
THF (450 mL) was added dropwise with stirring at 0 °C a soln of
cyclopropanone ethyl hemiacetal20 in THF (200 mL), and the mix-
ture was stirred at the same temperature for an additional 1 h.
H3¢¢), 0.92 (t, J = 7.3 Hz, 3 H, H4), 1.08 (mc, 1 H, H3¢¢), 1.18 (t,
3J = 7.0 Hz, 3 H, OCH2CH3), 1.37 (mc, 2 H, H3), 1.64 (mc, 2 H, H2),
1.88 (mc, 1 H, H1¢¢), 2.41 (t, 3J = 7.5 Hz, 2 H, H1), 3.20 (mc, 1 H,
H2¢¢), 3.54 (q, 3J = 7.0 Hz, 2 H, OCH2CH3), 4.30 (dd, 3J = 6.4 Hz,
3J = 9.8 Hz, 1 H, H2¢), 7.03 (dd, 3J = 6.4 Hz, 4J = 0.7 Hz, 1 H, H1¢).
To a soln of (trimethylsilyl)ethyne (51.86 g, 0.528 mol) in anhyd
Et2O (450 mL) was added at –78 °C 2.36 M BuLi in hexane
(220 mL, 0.518 mol). The resulting soln of [(trimethylsilyl)ethy-
nyl]lithium was added at 0 °C within 30 min to the soln of chloro-
magnesium 1-ethoxycyclopropanolate described above, and the
mixture was stirred at 40 °C for 17 h. Then sat. NH4Cl (600 mL)
was added, the aqueous phase was extracted with Et2O (2 ×
100 mL), the combined organic phases were washed with H2O (4 ×
100 mL) and dried (MgSO4). The solvents were distilled in vacuo to
yield 1-[(trimethylsilyl)ethynyl]cyclopropanol (64.42 g, 87%); bp
81 °C/12 mbar.
13C NMR (62.9 MHz, CDCl3): d = 13.64 (+, C4), 14.80 (–, C3¢¢),
15.04, 15.71 (+, OCH2CH3, C1¢¢), 22.16 (–, C3), 26.74 (–, C2),
33.72 (–, C1), 59.90 (+, C2¢¢), 65.98 (–, OCH2CH3), 114.22 (+, C2¢),
133.93 (+, C1¢), 170.74 (Cq, COO).
MS (70 eV): m/z (%) = 212 (2) [M+], 127 (49) [M+ – C4H9CO], 99
+
+
(37), 85 (93) [C4H9CO+], 57 (100) [C4H9 ], 43 (15) [C3H7 ].
Anal. Calcd for C12H20O3 (212.3): C, 67.89; H, 9.50. Found: C,
68.05; H, 9.52.
(Z)-(2-trans-2-Ethoxycyclopropyl)ethenyl Benzoate (13h)
Using 1 (73.4 mg, 666 mmol), benzoic acid (2h, 81.3 mg, 666 mmol),
and C, (10.6 mg, 2.5 mol%) in benzene (1.5 mL) and heating for 15
h; chromatography (silica gel, PE–Et2O, 20:1) gave 13h (142 mg,
92%) as a colorless oil; Rf = 0.25 (PE–Et2O, 9:1).
To a soln of NH4F (2.2 g, 60 mmol) in MeOH (30 mL) and H2O (10
mL) was added 1-[(trimethylsilyl)ethynyl]cyclopropanol (4.0 g,
26 mmol) and the mixture was stirred at r.t. for 1.5 d, then poured
into H2O (50 mL). The mixture was carefully extracted with Et2O
(7 × 30 mL), the combined organic extracts were dried (MgSO4)
and concentrated by distilling the ether at ambient pressure. The
residue was bulb-to-bulb distilled under reduced pressure to yield
14 (1.70 g, 80%); bp 48–50 °C/25 mbar.
IR (neat): 1732 (C=O), 1672 (C=C), 1111 cm–1 (C–O).
1H NMR (250 MHz, CDCl3): d = 0.72 (q, 2J = 3J = 3J = 6.1 Hz, 1 H,
3
H3¢¢), 1.17 (mc, 1 H, H3¢¢), 1.20 (t, J = 7.1 Hz, 3 H, OCH2CH3),
2.04 (mc, 1 H, H1¢¢), 3.28 (mc, 1 H, H2¢¢), 3.59 (q, 3J = 7.1 Hz, 2 H,
OCH2CH3), 4.46 (dd, 3J = 6.3 Hz, 3J = 9.8 Hz, 1 H, H2¢), 7.28 (dd,
3J = 6.3 Hz, 4J = 0.8 Hz, 1 H, H1¢), 7.43–7.49 (m, 2 H, Ar–H), 7.55–
7.62 (m, 1 H, Ar-H), 8.10–8.14 (m, 2 H, Ar-H).
1H NMR (270 MHz, CDCl3): d = 1.05 [AA¢BB¢ system, 4 H,
H2(3)], 2.43 (s, 1 H, H2¢), 2.69 (br s, 1 H, OH).
1-Acetylcyclopropyl Esters 15; General Procedure
In a sealed Schlenk tube were placed 1-ethynylcyclopropanol (14),
the carboxylic acid, and the catalyst [Ru(O2CH)(CO)2(PPh3)]2 (A)
in toluene, and the mixture was heated at 60 °C for the stated time.
After cooling to r.t., the mixture was diluted with CH2Cl2 (50 mL),
washed with 1 M NaOH (15 mL), dried (MgSO4), and the solvent
was evaporated under reduced pressure. The products were purified
by Kugelrohr distillation in vacuo.
13C NMR (62.9 MHz, CDCl3): d = 14.93 (–, C3¢¢), 15.01, 15.92 (+,
C1¢¢, OCH2CH3), 59.97 (+, C2¢¢), 66.00 (–, OCH2CH3), 114.97 (+,
C2¢), 128.43 (+, 2 C, C–Ar), 129.13 (Cq, Ar-C), 129.82 (+, 2 C, Ar-
C), 133.39, 134.03 (+, C1¢, Ar-C), 163.33 (Cq, COO).
MS (70 eV): m/z (%) = 232.2 (1) [M+], 127 (18) [M+ – PhCO], 105
(100) [PhCO+], 89 (10) [PhC+], 77 (22) [Ph+].
Synthesis 2007, No. 22, 3574–3588 © Thieme Stuttgart · New York

SPECIAL TOPIC
Ruthenium-Catalyzed Transformations of Cyclopropylethynes
3585
1-Acetylcyclopropyl Pentanoate (15c)
1H NMR (200 MHz, CDCl3): d = 1.12 (AA¢ part of an AA¢BB¢ sys-
tem, mc, 2 H, cPr-H), 1.44 (BB¢ part of an AA¢BB¢ system, mc, 2 H,
cPr-H), 1.99 [s, 3 H, (C=O)CH3], 3.32 (s, 3 H, OCH3), 3.96 (s, 2 H,
OCH2).
13C NMR (50.3 MHz, CDCl3): d = 17.08 (–, 2 C, cPr-C), 24.99 [+,
(C=O)CH3], 59.32 (+, OCH3), 64.20 (Cq, cPr-C), 69.42 (–, OCH2),
170.31 (Cq, COO), 203.72 (Cq, COMe).
Using 14 (246 mg, 3.00 mmol), pentanoic acid (2c, 308 mg, 3.02
mmol), and A (14 mg, 0.5 mol%) in degassed toluene (3 mL) and
heating for 18.5 h; distillation gave 15c (375 mg, 68%) as a color-
less oil; bp 140 °C/0.2 mbar.
IR (neat): 1752 (C=O), 1709 cm–1 (C=O).
1H NMR (200 MHz, CDCl3): d = 0.74 (t, 3J = 7.2 Hz, 3 H, H4), 0.99
(AA¢ part of an AA¢BB¢ system, mc, 2 H, cPr-H), 1.35 (BB¢ part of
an AA¢BB¢ system, mc, 2 H, cPr-H), 1.14–1.49 (m, 4 H, H3, H2),
1.95 (s, 3 H, COCH3), 2.19 (t, 3J = 7.2 Hz, 2 H, H1).
13C NMR (50.3 MHz, CDCl3): d = 13.55 (+, C4), 17.25 (–, 2 C, cPr-
C), 22.10 (–, C3), 25.16 (+, COCH3), 26.68 (–, C2), 33.59 (–, C1),
63.65 (Cq, cPr-C), 173.70 (Cq, COO), 204.53 (Cq, COCH3).
MS (70 eV): m/z (%) = 69 (8) [C4H5O+], 45 (100) [CH2OMe+], 43
(79) [CH3CO+].
+
MS (DCI, NH3, 70 eV): m/z (%) = 362 (2) [2 M + NH4 ], 207 (27)
+
+
[M + NH3 + NH4 ], 190 (100) [M + NH4 ].
1-Acetylcyclopropyl Salicylate (15n)
Using 14 (239 mg, 2.91 mmol), salicylic acid (2n, 414 mg, 3.00
mmol), and A (13 mg, 0.5 mol%) in toluene (3 mL) and heating for
20 h; distillation gave 15n (180 mg, 28%) as a colorless oil; bp 250
°C/0.2 mbar.
MS (70 eV): m/z (%) = 141 (56) [M+ – CH3CO], 85 (100)
+
[C4H9CO+], 57 (63) [C4H9 ], 43 (12) [CH3CO+].
+
MS (DCI, NH3, 70 eV): m/z (%) = 386 (5) [2 M + NH4 ], 219 (58)
[M + NH3 + NH4 ], 202 (100) [M + NH4 ], 185 (3) [MH+].
+
+
IR (neat): 3224 (O–H), 1711 (C=O), 1686 (C=O), 1615 (C=C),
1584 cm–1 (C=C).
1H NMR (200 MHz, CDCl3): d = 1.33 (AA¢ part of an AA¢BB¢ sys-
tem, mc, 2 H, cPr-H), 1.64 (BB¢ part of an AA¢BB¢ system, mc, 2 H,
cPr-H), 2.18 (s, 3 H, CH3), 6.84–7.06 (m, 2 H, Ar-H), 7.43–7.52 (m,
1 H, Ar-H), 7.81–7.86 (m, 1 H, Ar-H), 10.46 (s, 1 H, OH).
1-Acetylcyclopropyl Cyclopropanecarboxylate (15e)
Using 14 (241 mg, 2.94 mmol), cyclopropanecarboxylic acid (2e,
258 mg, 3.00 mmol), and A (14 mg, 0.5 mol%) in toluene (3 mL)
and heating for 18 h; distillation gave 15e (243 mg, 49%) as a col-
orless oil; bp 130 °C/0.2 mbar.
IR (neat): 1744 (C=O), 1708 cm–1 (C=O).
13C NMR (50.3 MHz, CDCl3): d = 17.59 (–, 2 C, cPr-C), 25.48 (+,
CH3), 64.90 (Cq, cPr-C), 116.72 (Cq, Ar-C), 117.87 (+, Ar-C),
119.47 (+, Ar-C), 130.05 (+, Ar-C), 136.60 (+, Ar-C), 162.04 (Cq,
COH), 170.54 (Cq, COO), 204.18 (Cq, COCH3).
1H NMR (200 MHz, CDCl3): d = 0.77–0.92 (m, 4 H, cPr-H), 1.06
(AA¢ part of an AA¢BB¢ system, mc, 2 H, cPr-H), 1.35 (BB¢ part of
an AA¢BB¢ system, mc, 2 H, cPr-H), 1.50–1.62 (m, 1 H, cPr-H), 2.01
(s, 3 H, CH3).
13C NMR (50.3 MHz, CDCl3): d = 8.80 (–, 2 C, cPr-C), 12.64 (+,
cPr-C), 17.49 (–, 2 C, cPr-C), 25.37 (+, CH3), 63.84 (Cq, cPr-C),
174.96 (Cq, COO), 205.09 (Cq, COCH3).
+
MS (DCI, NH3, 70 eV): m/z (%) = 255 (100) [M + NH3 + NH4 ],
+
238 (62) [M + NH4 ].
1-Cyclopropylethenylcarboxylates 24; General Procedure
In a sealed Schlenk tube were placed cyclopropylethyne (22), the
carboxylic acid, and the catalyst [Ru(O2CH)(CO)2(PPh3)]2 (A) in
degassed toluene under an inert atmosphere and the mixture was
heated at 50–80 °C for 7–44 h. After cooling to r.t., the mixture was
diluted with Et2O or CH2Cl2 (100 mL), washed with 1 M NaOH (15
mL), and dried (MgSO4) and the solvent was evaporated under re-
duced pressure. The products were purified by Kugelrohr distilla-
tion in vacuo or by column chromatography (silica gel).
MS (70 eV): m/z (%) = 125 (18) [M+ – CH3CO], 69 (100)
+
[C3H5CO+], 41 (41) [C3H5 ].
+
MS (DCI, NH3, 70 eV): m/z (%) = 354 (2) [2 M + NH4 ], 203 (29)
+
+
[M + NH3 + NH4 ], 186 (100) [M + NH4 ].
1-Acetylcyclopropyl Benzoate (15h)
Using 14 (281 mg, 3.42 mmol), benzoic acid (2h, 489 mg, 4.00
mmol), and A (16 mg, 0.5 mol%) in toluene (3.5 mL) and heating
for 16.5 h; distillation gave 15h (514 mg, 74%) as a colorless oil; bp
160 °C/0.2 mbar.
1-Cyclopropylethenyl Pentanoate (24c)
Using 22 (331 mg, 5.00 mmol), pentanoic acid (2c, 511 mg, 5.00
mmol), and A (23 mg, 0.5 mol%) in toluene (2.5 mL) and heating
at 80 °C for 7 h; chromatography (silica gel, PE–Et2O, 20:1) gave
24c (553 mg, 66%) as a colorless oil; Rf = 0.50 (PE–Et2O, 10:1).
IR (neat): 1730 (C=O), 1707 (C=O), 1601 cm–1 (C=C).
1H NMR (200 MHz, CDCl3): d = 1.21 (AA¢ part of an AA¢BB¢ sys-
tem, mc, 2 H, cPr-H), 1.56 (BB¢ part of an AA¢BB¢ system, mc, 2 H,
cPr-H), 2.11 (s, 3 H, CH3), 7.33–7.51 (m, 3 H, Ar-H), 7.96–8.00 (m,
2 H, Ar-H).
13C NMR (50.3 MHz, CDCl3): d = 17.64 (–, 2 C, cPr-C), 25.50 (+,
CH3), 64.46 (Cq, cPr-C), 128.59 (+, 2 C, Ar-C), 129.17 (Cq, Ar-C),
129.82 (+, 2 C, Ar-C), 133.69 (+, Ar-C), 166.68 (Cq, COO), 204.76
(Cq, COCH3).
IR (neat): 1757 (C=O), 1653 (C=C), 1150 (C–O), 1091 cm–1 (C–O).
1H NMR (200 MHz, CDCl3): d = 0.51–0.72 (m, 4 H, cPr-H), 0.91
(t, 3J = 7.3 Hz, 3 H, H5), 1.26–1.70 (m, 5 H, H3, H4, cPr-H), 2.35
3
2
(t, J = 7.1 Hz, 2 H, H2), 4.63 (d, J = 1.7 Hz, 1 H, HA), 4.75 (d,
2J = 1.7 Hz, 1 H, HB).
13C NMR (50.3 MHz, CDCl3): d = 5.39 (–, 2 C, cPr-C), 13.65, 13.74
(+, cPr-C, C5), 22.16 (–, C4), 26.96 (–, C3), 34.00 (–, C2), 99.55
(–, C2¢), 156.60 (Cq, C1¢), 171.95 (Cq, COO).
MS (70 eV): m/z (%) = 161 (16) [M+ – CH3CO], 105 (100) [Ph-
CO+], 77 (28) [Ph+].
MS (70 eV): m/z (%) = 168 (3) [M+], 153 (2) [M+ – CH3], 140 (4)
+
MS (DCI, NH3, 70 eV): m/z (%) = 426 (4) [2 M + NH4 ], 239 (100)
[M+ – C2H4], 126 (2) [M+ – C3H6], 112 (1) [M+ – C4H8], 85 (100)
+
+
[M + NH3 + NH4 ], 222 (72) [M + NH4 ], 205 (4) [MH+].
+
+
[C4H9CO+], 69 (15) [C4H9C+], 57 (62) [C4H9 ], 41 (18) [C3H5 ].
HRMS: calcd for C10H16O2: 168.1150.
1-Acetylcyclopropyl Methoxyacetate (15m)
Using 14 (222 mg, 2.70 mmol), methoxyacetic acid (2m, 270 mg,
3.00 mmol), and A (28 mg, 1.1 mol%) in toluene (3 mL) and heating
for 17.5 h; distillation gave 15m (254 mg, 55%) as a colorless oil;
bp 140 °C/0.2 mbar.
1-Cyclopropylethenyl Cyclopropanecarboxylate (24e)
Using 22 (291 mg, 4.40 mmol), cyclopropanecarboxylic acid (2e,
344 mg, 4.00 mmol), and A (19 mg, 0.5 mol%) in toluene (2 mL)
and heating at 80 °C for 15 h; distillation gave 24e (497 mg, 82%)
as a colorless oil; bp 90 °C/0.2 mbar.
IR (neat): 1772 (C=O), 1706 (C=O), 1184 (C–O), 1126 cm–1 (C–O).
Synthesis 2007, No. 22, 3574–3588 © Thieme Stuttgart · New York

3586
I. Emme et al.
SPECIAL TOPIC
IR (neat): 1746 (C=O), 1657 (C=C), 1263 (C–O), 1230 (C–O), 1148
cm–1 (C–O).
residue, 24b (3.56 g, 94%) was obtained as a colorless oil; bp 87–
89 °C.
1H NMR (200 MHz, CDCl3): d = 0.50–0.64 (m, 4 H, cPr-H), 0.82–
1.00 (m, 4 H, cPr-H), 1.46–1.75 (m, 2 H, cPr-H), 4.58 (s, 1 H, HA),
4.69 (s, 1 H, HB).
13C NMR (50.3 MHz, CDCl3): d = 5.44 (–, 2 C, cPr-C), 8.84 (–, 2
C, cPr-C), 12.87 (+, cPr-C), 13.83 (+, cPr-C), 99.53 (–, C2¢), 156.61
(Cq, C1¢), 173.03 (Cq, COO).
IR (neat): 1761 (C=O), 1658 (C=C), 1230 (C–O), 1196 cm–1 (C–O).
1H NMR (200 MHz, CDCl3): d = 0.51–0.76 (m, 4 H, cPr-H), 1.52
(mc, 1 H, cPr-H), 2.11 (s, 3 H, CH3), 4.63 (d, 2J = 1.6 Hz, 1 H, C2¢),
4.74 (d, 2J = 1.6 Hz, 1 H, C2¢).
13C NMR (50.3 MHz, CDCl3): d = 5.34 (–, 2 C, cPr-C), 13.65 (+,
cPr-C), 20.75 (+, CH3), 99.55 (–, C2¢), 156.63 (Cq, C1¢), 168.88 (Cq,
C=O).
MS (70 eV): m/z (%) = 152 (3) [M+], 69 (100) [C3H5CO+], 41 (24)
+
[C3H5 ].
MS (70 eV): m/z (%) = 126 (8) [M+], 98 (10) [M+ – C2H4], 84 (100),
+
HRMS: calcd for C9H12O2: 152.0837.
69 (71), 43 (98) [CH3CO+], 41 (19) [C3H5 ].
Anal. Calcd for C9H12O2 (152.2): C, 71.03; H, 7.95. Found: C,
71.24; H, 7.75.
HRMS: calcd for C7H10O2: 126.0680.
(Z)-2-Cyclopropylethenyl Carboxylates 23; General Procedure
In a sealed Schlenk tube cyclopropylethyne (22), the carboxylic ac-
id, and the catalyst [Ru(CH2C(CH3)CH2)2(dppb)] (C) were dis-
solved in degassed toluene under an inert atmosphere and the
mixture was heated at 55–80 °C for 4–21 h. After cooling to r.t. the
mixture was diluted with Et2O or CH2Cl2 (100 mL), the soln was
washed with 1 M NaOH (15 mL) and dried (MgSO4), and the sol-
vent was evaporated under reduced pressure. The products were pu-
rified by Kugelrohr distillation in vacuo or by column
chromatography (silica gel).
1-Cyclopropylethenyl Pivalate (24g)
Using 22 (291 mg, 4.40 mmol), pivalic acid (2g, 409 mg, 4.00
mmol), and A (19 mg, 0.5 mol%) in toluene (2 mL) and heating at
80 °C for 15 h; distillation gave 24g (512 mg, 76%) as a colorless
oil; bp 100 °C/0.2 mbar.
IR (neat): 1749 (C=O), 1657 (C=C), 1285 (C–O), 1256 (C–O), 1131
cm–1 (C–O).
1H NMR (200 MHz, CDCl3): d = 0.47–0.60 (m, 4 H, cPr-H), 1.15
[s, 9 H, C(CH3)3], 1.45 (mc, 1 H, cPr-H), 4.51 (d, 3J = 1.6 Hz, 1 H,
HA), 4.65 (dd, 2J = 1.6 Hz, 4J = 0.47 Hz, 1 H, HB).
(Z)-2-Cyclopropylethenyl Pentanoate (23c)
13C NMR (50.3 MHz, CDCl3): d = 5.19 (–, 2 C, cPr-C), 13.81 (+,
cPr-C), 27.03 [+, 3 C, C(CH3)3], 39.01 [Cq, C(CH3)3], 99.26 (–,
C2¢), 156.47 (Cq, C1¢), 176.40 (Cq, COO).
Using 22 (331 mg, 5.00 mmol), pentanoic acid (2c, 511 mg, 5.00
mmol), and C (32 mg, 1.0 mol%) and heating without solvent at 65
°C for 15 h; chromatography (silica gel, PE–Et2O, 30:1) gave 23c
(814 mg, 97%) as a colorless oil; Rf = 0.50 (PE–Et2O, 5:1).
MS (70 eV): m/z (%) = 168 (10) [M+], 125 (10) [M+ – C3H7], 85
IR (neat): 1744 (C=O), 1654 cm–1 (C=C).
+
(40) [C4H9CO+], 69 (35) [C4H9C+], 57 (100) [C4H9 ], 41 (20)
+
1H NMR (200 MHz, CDCl3): d = 0.36 (mc, 2 H, cPr-H), 0.75 (mc, 2
H, cPr-H), 0.90 (t, 3J = 7.3 Hz, 3 H, H4), 1.27–1.47 (m, 2 H, H3),
1.54–1.82 (m, 3 H, H2, cPr-H), 2.40 (t, 3J = 7.3 Hz, 2 H, H1), 4.28
[C3H5 ].
HRMS: calcd for C10H16O2: 168.1150.
3
(dd, 3J = 6.4 Hz, J = 9.8 Hz, 1 H, H2¢), 7.02 (d, 3J = 6.4 Hz, 1 H,
1-Cyclopropylethenyl Benzoate (24h)
H1¢).
Using 22 (331 mg, 5.00 mmol), benzoic acid (2h, 611 mg, 5.00
mmol), and A (45 mg, 1.0 mol%) in toluene (2.5 mL) and heating
at 80 °C for 44 h; and chromatography (silica gel, PE–Et2O, 20:1)
gave 24h (911 mg, 97%) as a colorless oil; Rf = 0.55 (PE–Et2O,
10:1).
13C NMR (50.3 MHz, CDCl3): d = 6.79 (–, 2 C, cPr-C), 7.35 (+, cPr-
C), 13.68 (+, C4), 22.20 (–, C3), 26.79 (–, C2), 33.79 (–, C1),
118.21 (+, C2¢), 133.59 (+, C1¢), 170.95 (Cq, COO).
IR (neat): 1736 (C=O), 1658 (C=C), 1272 (C–O), 1235 cm–1 (C–O).
(Z)-2-Cyclopropylethenyl Benzoate (23h)
Using 22 (331 mg, 5.00 mmol), benzoic acid (2h, 611 mg, 5.00
mmol), and C (32 mg, 1.0 mol%) in toluene (5 mL) with heating at
70 °C for 6 h; chromatography (silica gel, PE–Et2O, 10:1) gave 23h
(921 mg, 98%) as a colorless oil; Rf = 0.50 (PE–Et2O, 5:1).
1H NMR (200 MHz, CDCl3): d = 0.60–0.77 (m, 4 H, cPr-H), 1.64
(mc, 1 H, cPr-H), 4.79 (d, 2J = 1.6 Hz, 1 H, HA), 4.87 (dd, 2J = 1.6
Hz, 4J = 0.54 Hz, 1 H, HB), 7.38–7.63 (m, 3 H, Ar-H), 7.95–8.11 (m,
2 H, Ar-H).
13C NMR (50.3 MHz, CDCl3): d = 5.47 (–, 2 C, cPr-C), 13.88 (+,
cPr-C), 99.87 (–, C2¢), 128.35 (+, 2 C, Ar-C), 129.56 (Cq, Ar-C),
129.79 (+, 2 C, Ar-C), 133.21 (+, Ar-C), 156.63 (Cq, C1¢), 164.61
(Cq, COO).
IR (neat): 1729 (C=O), 1669 (C=C), 1268 cm–1 (C–O).
1H NMR (200 MHz, CDCl3): d = 0.45 (mc, 2 H, cPr-H), 0.81 (mc, 2
H, cPr-H), 1.90 (mc, 1 H, cPr-H), 4.43 (dd, 3J = 6.4 Hz, 3J = 9.9 Hz,
1 H, H2¢), 7.38 (d, 3J = 6.4 Hz, 1 H, H1¢), 7.42–7.59 (m, 3 H, Ar-H),
8.08–8.15 (m, 2 H, Ar-H).
13C NMR (50.3 MHz, CDCl3): d = 6.96 (–, 2 C, cPr-C), 7.63 (+, cPr-
C), 119.00 (+, C2¢), 128.44 (+, 2 C, Ar-C), 129.32 (Cq, Ar-C),
129.84 (+, 2 C, Ar-C), 133.34, 133.66 (+, Ar-C, C1¢), 163.55 (Cq,
COO).
MS (70 eV): m/z (%) = 188 (1) [M+], 160 (4) [M+ – C2H4], 105 (100)
+
[PhCO+], 77 (36) [Ph+], 41 (2) [C3H5 ].
HRMS: calcd for C12H12O2: 188.0837.
Anal. Calcd for C12H12O2 (188.2): C, 76.57; H, 6.43. Found: C,
76.75; H, 6.56.
MS (70 eV): m/z (%) = 188 (5) [M+], 105 (100) [PhCO+], 77 [Ph+],
83 (2) [M+ – PhCO].
1-Cyclopropylethenyl Acetate (24b)
HRMS: calcd for C12H12O2: 188.0837.
A mixture of 22 (2.64 g, 40.0 mmol), AcOH (2b, 1.80 g, 30.0
mmol), and [Ru(CH2C(CH3)CH2)2(dppb)] (C) (50 mg, 0.33 mol%)
without solvent was heated at 50 °C for 12 h. After cooling to r.t.,
the crude product was taken up in Et2O (100 mL), the soln was then
washed with 1 M NaOH (15 mL) and dried (MgSO4). After evapo-
ration of the solvent under reduced pressure and distillation of the
Anal. Calcd for C12H12O2 (188.2): C, 76.57; H, 6.43. Found: C,
76.88; H, 6.69.
(Z)-2-Cyclopropylethenyl Methoxyacetate (23m)
Using 22 (291 mg, 4.40 mmol), methoxyacetic acid (2m, 360 mg,
4.00 mmol), and C (26 mg, 1.0 mol%) and heating without solvent
Synthesis 2007, No. 22, 3574–3588 © Thieme Stuttgart · New York

SPECIAL TOPIC
Ruthenium-Catalyzed Transformations of Cyclopropylethynes
3587
at 55 °C for 4 h; Kugelrohr distillation gave 23m (573 mg, 92%) as
a colorless oil; bp 80 °C/0.2 mbar.
3-Oxopent-1-enyl Benzoate (19h) and 1-Acetylcyclopropyl Ben-
zoate (15h)
In a sealed Schlenk tube 1-ethynylcyclopropanol (14, 411 mg,
5.00 mmol), benzoic acid (2h, 611 mg, 5.00 mmol), and
[Ru(CH2C(CH3)CH2)2(dppe)] B (46 mg, 1.5 mol%) were dissolved
in toluene (5 mL) and the mixture was heated at 75 °C for 17 h. Af-
ter cooling to r.t., the mixture was diluted with CH2Cl2 (100 mL),
washed with 1 M NaOH (15 mL), and dried (MgSO4) and the sol-
vent was evaporated under reduced pressure. Column chromatogra-
phy of the crude product (silica gel, PE–Et2O, 4:1) gave a mixture
of 19h and 15h (374 mg, 36%) as a colorless oil; ratio 19h/15h
2.6:1; Rf = 0.30 (PE–Et2O, 4:1).
1H NMR (200 MHz, CDCl3): d = 0.35 (mc, 2 H, cPr-H), 0.74 (mc, 2
H, cPr-H), 1.69 (mc, 1 H, cPr-H), 3.44 (s, 3 H, OCH3), 4.11 (s, 2 H,
3
CH2OMe), 4.33 (dd, J = 10.0 Hz, 3J = 6.3 Hz, 1 H, H2¢), 7.03 (d,
3J = 6.3 Hz, 1 H, H1¢).
13C NMR (50.3 MHz, CDCl3): d = 6.91 (–, 2 C, cPr-C), 7.41 (+, cPr-
C), 59.50 (+, OCH3), 69.45 (–, CH2OMe), 119.35 (+, C2¢), 132.98
(+, C1¢), 167.58 (Cq, COO).
MS (70 eV): m/z (%) = 156 (10) [M+], 83 (8) [M+ – MeOCH2CO],
67 (5) [M+ – MeOCH2COO], 45 (100) [CH2OMe].
HRMS: calcd for C8H12O3: 156.0786.
19h
1H NMR (200 MHz, CDCl3): d = 1.05 (t, 3J = 7.3 Hz, 3 H, H5), 2.54
(q, 3J = 7.3 Hz, 2 H, H4), 6.12 (d, 3J = 12.8 Hz, 1 H, H2), 7.34–7.96
(m, 5 H, Ar-H), 8.42 (d, 3J = 12.8 Hz, 1 H, H1).
13C NMR (50.3 MHz, CDCl3): d = 8.00 (+, C5), 34.01 (–, C4),
124.23 (+, C2), 128.76 (+, Ar-C), 128.86 (Cq, Ar-C), 130.26 (+, Ar-
C), 134.40 (+, Ar-C), 148.56 (+, C1), 162.70 (Cq, COO), 199.93
(Cq, CO).
(Z)-2-Cyclopropylethenyl 2,6-Difluorobenzoate (23o)
Using 22 (291 mg, 4.40 mmol), 2,6-difluorobenzoic acid (2o, 632
mg, 4.00 mmol), and C (26 mg, 1.0 mol%) in toluene (4 mL) and
heating at 80 °C for 21 h, Kugelrohr distillation gave 23o (875 mg,
98%) as a colorless oil; bp 220 °C/0.2 mbar.
IR (neat): 1740 (C=O), 1625 (C=C), 1289 (C–O), 1260 cm–1 (C–O).
1H NMR (200 MHz, CDCl3): d = 0.38 (mc, 2 H, cPr-H), 0.76 (mc, 2
3
3
H, cPr-H), 1.82 (mc, 1 H, cPr-H), 4.44 (dd, J = 10.0 Hz, J = 6.2
Hz, 1 H, H2¢), 6.90–7.42 (m, 4 H, H1¢, H3, H4, H5).
Acknowledgment
MS (70 eV): m/z (%) = 224 (3) [M+], 141 (100) [C6H3F2CO+], 113
This work was supported by the State of Niedersachsen as well as
the companies BASF AG and Chemetall GmbH (chemicals). The
authors are grateful to Stefan Beußhausen (Göttingen) for his tech-
nical support in preparing the final manuscript.
(11) [C6H3F2 ], 83 (4) [M+ – C6H3F2CO], 67 (2) [M+ – C6H3F2CO2].
+
HRMS: calcd for C12H10F2O2: 224.0648.
(Z)-2-Cyclopropylethenyl 2,6-Dimethoxybenzoate (23p)
Using 22 (291 mg, 4.40 mmol), 2,6-dimethoxybenzoic acid (2p,
729 mg, 4.00 mmol), and B (26 mg, 1.0 mol%) in toluene (4 mL)
and heating at 80 °C for 18 h; chromatography (silica gel, PE–Et2O,
3:1) followed by Kugelrohr distillation gave 23p (964 mg, (97%) as
a colorless oil; bp 230 °C/0.2 mbar; Rf = 0.40 (PE–Et2O, 3:1).
References
(1) For AdM, this is to count as Part 145 in the series
‘Cyclopropyl Building Blocks for Organic Synthesis’.
(a) For Part 144, see: Nakamura, I.; Nagata, R.; Nemoto, T.;
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Org. Chem. 2007, 4479. (b) For Part 143, see: Yucel, B.;
Valentić, N.; Noltemeyer, M.; de Meijere, A. Eur. J. Org.
Chem. 2007, 4081.
1H NMR (200 MHz, CDCl3): d = 0.37 (mc, 2 H, cPr-H), 0.72 (mc, 2
H, cPr-H), 1.83 (mc, 1 H, cPr-H), 3.80 (s, 6 H, OCH3), 4.41 (dd,
3
3J = 9.8 Hz, 3J = 6.3 Hz, 1 H, H2¢), 6.55 (d, J = 8.5 Hz, 2 H, H3,
H5), 7.16–7.33 (m, 2 H, H1¢, H4).
(2) Acetylene Chemistry; Diederich, F.; Stang, P. J.; Tikwinski,
13C NMR (50.3 MHz, CDCl3): d = 6.92 (–, 2 C, cPr-C), 7.58 (+, cPr-
C), 56.02 (+, 2 C, OCH3), 103.97 (+, 2 C, C3, C5), 112.19 (Cq, C1),
119.35 (+, C2¢), 131.62, 134.15 (+, C4, C1¢), 157.76 (Cq, 2 C, C2,
C5), 163.79 (Cq, COO).
MS (70 eV): m/z (%) = 248 (1) [M+], 165 (100) [C6H3(OMe)2CO+],
84 (20).
R. R., Eds.; Wiley-VCH: Weinheim, 2004.
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HRMS: calcd for C14H16O4: 248.1048.
(Z)-2-Cyclopropylethenyl 4-Aminobenzoate (23q)
Using 22 (291 mg, 4.40 mmol), 4-aminobenzoic acid (2q, 549 mg,
4.00 mmol), and C (52 mg, 2.0 mol%) in toluene (20 mL) and heat-
ing at 80 °C for 21 h and Kugelrohr distillation gave 23q (553 mg,
68%) as a colorless oil; bp 220 °C/0.2 mbar.
1H NMR (200 MHz, CDCl3): d = 0.40 (mc, 2 H, cPr-H), 0.79 (mc, 2
H, cPr-H), 1.86 (mc, 1 H, cPr-H), 4.32–4.40 (m, 3 H, H2¢, NH2),
6.60 (d, 3J = 8.5 Hz, 2 H, H3, H5), 7.22 (d, 3J = 6.3 Hz, 1 H, H1¢),
7.88 (d, 3J = 8.5 Hz, 2 H, H2, H6).
13C NMR (50.3 MHz, CDCl3): d = 7.05 (–, 2 C, cPr-C), 7.75 (+, cPr-
C), 113.88 (+, 2 C, C3, C5), 118.23 (+, C2¢), 132.10 (+, 2 C, C2,
C6), 132.40 (Cq, C1), 133.92 (+, C1¢), 151.80 (Cq, C4), 163.95 (Cq,
COO).
MS (70 eV): m/z (%) = 203 (3) [M+], 120 (100) [NH2C6H4CO+], 92
(8) Chatani, N.; Morimoto, T.; Muto, T.; Murai, S. J. Am. Chem.
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(28) [C6H4NH2 ], 65 (28).
Soc. 1994, 116, 6049.
HRMS: calcd for C12H13NO2: 203.0946.
Synthesis 2007, No. 22, 3574–3588 © Thieme Stuttgart · New York

3588
I. Emme et al.
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Synthesis 2007, No. 22, 3574–3588 © Thieme Stuttgart · New York