The first synthesis of cyclopropanone acetals from the reaction of Fischer carbene complexes with ketene acetals

Article abstract of DOI:10.1016/j.jorganchem.2005.08.025

The reaction of iso-propoxy stabilized Fischer carbene complexes with ketene acetals gives moderate to excellent yields of cyclopropanone acetals when carried out under a carbon monoxide atmosphere. This is in contrast to the known reaction of methoxy substituted complexes which give cyclic ortho esters under the same conditions. A mechanism is proposed which involves a branch point between the two products as the zwitterionic intermediate resulting from nucleophilic addition of the ketene acetal to the carbene carbon. A 1,3-migration of the methoxyl group to the cationic center leads to the ortho ester and a ring closure by backside attack leads to the cyclopropanone acetal. A double-labeling experiment shows that the 1,3-migration occurs by an intramolecular process that is proposed to involve a bridging oxonium ion. The effect of the isopropoxy group is thus interpreted to be to sterically hinder the formation of a bridged oxonium ion.

Full text of DOI:10.1016/j.jorganchem.2005.08.025

Journal of Organometallic Chemistry 690 (2005) 6101–6110
www.elsevier.com/locate/jorganchem
The first synthesis of cyclopropanone acetals from the reaction
of Fischer carbene complexes with ketene acetals
Siu Ling B. Wang, Daniel R. Goldberg, Xuejun Liu, Jing Su, Qi-Huang Zheng,
*
Vincent Liptak, William D. Wulff
Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
Received 15 July 2005; accepted 3 August 2005
Available online 30 September 2005
Abstract
The reaction of iso-propoxy stabilized Fischer carbene complexes with ketene acetals gives moderate to excellent yields of cyclopropa-
none acetals when carried out under a carbon monoxide atmosphere. This is in contrast to the known reaction of methoxy substituted com-
plexes which give cyclic ortho esters under the same conditions. A mechanism is proposed which involves a branch point between the two
products as the zwitterionic intermediate resulting from nucleophilic addition of the ketene acetal to the carbene carbon. A 1,3-migration
of the methoxyl group to the cationic center leads to the ortho ester and a ring closure by backside attack leads to the cyclopropanone acetal.
A double-labeling experiment shows that the 1,3-migration occurs by an intramolecular process that is proposed to involve a bridging oxo-
nium ion. The effect of the isopropoxy group is thus interpreted to be to sterically hinder the formation of a bridged oxonium ion.
Ó 2005 Elsevier B.V. All rights reserved.
Keywords: Cyclopropanone acetals; Fischer carbene complexes; Cross-over experiment; Ketene acetals; Zwitterionic intermediate
1. Introduction
acetals by this reaction [7]. We herein wish to report a solu-
tion to this problem and the first synthesis of cyclopropa-
none acetals from the reaction of Fischer carbene
complexes with ketene acetals (see Scheme 1).
The formal transfer of a carbene to an alkene represents
one of the key methods for the synthesis of cyclopropanes
[1,2]. The first method involving an isolated transition me-
tal carbene complex was reported by Fischer for a chro-
mium pentacarbonyl complex [3–5]. Cyclopropanation
with Fischer carbene complexes has been extensively inves-
tigated mechanistically and synthetically. However, ketene
acetals have never been reported as substrates [2]. These
would be valuable substrates for this reaction since the
products, cyclopropanone acetals, are useful synthetic
intermediates for a variety of reactions [6]. In earlier inves-
tigations, we found that the reactions of Fischer carbene
complexes with ketene acetals unexpectedly gave butyro-
lactones, thwarting our efforts to prepare cyclopropanone
The first step in the mechanism that was proposed to ac-
count for the formation of butyrolactones is the attack of
the ketene acetal on the carbene carbon to give the zwitter-
ionic intermediate 5 in Scheme 2 [7]. A 1,3-migration of the
methoxyl group would give the unstablized carbene com-
plex 7, which upon C–H insertion would produce the cyclic
ortho ester 8 that after hydrolysis would provide a butyro-
lactone [7,8]. The 1,3-migration of the methoxyl group
may occur via a bridged oxonium ion as indicated in
Scheme 2, via an intermolecular transfer or via dissociation
of methoxyl to form an ion pair. The dissociation into ion
pairs may be facilitated by the replacement of the methoxyl
substituent with a bulkier alkoxide, but if an oxonium ion is
involved, a bulkier alkoxide may slow down the 1,3-migra-
tion. This would then be expected to favor cyclopropane
*
Corresponding author.
E-mail address: wulff@chemistry.msu.edu (W.D. Wulff).
0022-328X/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.08.025

6102
S.L.B. Wang et al. / Journal of Organometallic Chemistry 690 (2005) 6101–6110
R1H2CO OCH2R1
OCH3
In either event, the mechanism in Scheme 2 would predict
that cyclopropane formation from ketene acetals would
be favored with carbene complexes with sterically larger
oxygen stabilizing groups on the carbene carbon.
OCH2R1
OCH2R1
OCH3
R2
R2
3
(CO)5Cr
+
Cyclopropanone acetals could indeed be obtained from
the reaction of ketene acetals with Fischer carbene com-
plexes derived from secondary alcohols as shown by the
data in Tables 1 and 2. Complexes 11, 15 and 16 were pre-
pared in good yields by the procedure of Connor [9] utiliz-
ing isopropanol or menthol and complexes 17 and 18 were
prepared by Fischer original synthesis [10] employing iso-
propyl triflate [11] as alkylating agent. The data in Table 1
reveal that there is a correlation between the size of the alk-
oxy group and the partition between the cyclopropanone
acetal and butyrolactone products.
R2
1
2
O
R1
O
4
Scheme 1.
R2
R2
CH3
OCH3
(CO)5Cr
O
(CO)5Cr
OCH2R1
OCH2R1
Chromium carbene complex 11 provides a much more
efficient transfer of phenyl(isopropoxy)methylene to diethyl
ketene acetal than does either of the corresponding molyb-
denum or tungsten complexes 15 and 16 (Table 2). The
electron rich 2-furyl carbene complex 17 is unreactive and
is recovered in high yield after 96 h at 75 °C, but a slow
reaction was observed at 100 °C. The n-butyl carbene com-
plex is also slower than the aryl complex although moder-
ate yields of the cyclopropanone acetal could be obtained.
The secondary alkyl complex 32c does not give a cyclo-
propanone acetal but rather suffers an internal proton
transfer to give the enol ether 33 (Scheme 3). The more hin-
dered carbene complex 11f derived from L-menthol gave
excellent yield with dimethyl ketene acetal, but disappoint-
ingly only a 2:1 stereoselectivity was observed and the rel-
ative stereochemistry of the major product was not
determined. A higher selectivity (4:1) is seen with the o-xy-
lyl ketene acetal 20 but the yield is reduced. No further
increase in asymmetric induction is observed with the
9-phenylmentholoxy carbene complex 11g.
OCH2R1
OCH2R1
6
5
R2
OCH3
R2
(CO)5Cr
OCH3
OCH2R1
OCH2R1
OCHR1
OCH2R1
7
9
H
R2
OCH3
R2
R1
OCH2R1
OCH3
(CO)nCr
R1H2CO
R1H2CO
O
10
8
Scheme 2.
formation since it is thought to occur either via a direct ring
closure by backside attack in the zwitterionic intermediate 5
or via reductive elimination from the metallacycle 10. This
metallacycle could be formed by closure from zwitterion 5
or by direct [2+2] cycloaddition with the carbene complex.
It proved possible to probe the mechanism of the reac-
tion with the finding that small amounts of the cycloprop-
anone acetal 35 could be obtained from the reaction of the
methoxy carbene complex 11a with the acetal 20 if the
Table 1
Cyclopropanone acetals from Fischer carbene complexesa
O
EtO OEt
OR1
Ph
CO (500 psi)
THF, 80 ˚C
OEt
OEt
O
OR1
Ph
+
+
(CO)5Cr
11
Ph
Me
12
13
14
Carbene complex
R1
Time (h)
13
Yield of 13 (%)b
Yield of 14 (%)b
11a
11b
11c
11d
11e
a
Methyl
Ethyl
Isopropyl
Cyclopentyl
Cyclopentyl
22
20
24
72
48
13a
13b
13c
13d
13e
0
26
75
47
71
76
60
0
0
0
Unless otherwise specified all reactions were carried out at 0.1 M in carbene complex in THF with 1.2 equiv of ketene acetal at 80 °C under 500 psi of
CO in a Paar bomb. The reaction mixture was deoxygented before transfer to bomb.
b
Isolated yields.

S.L.B. Wang et al. / Journal of Organometallic Chemistry 690 (2005) 6101–6110
6103
Table 2
Cyclopropanone acetals from Fischer carbene complexesa
R3O OR3
OR1
R2
OR1
(CO)5M
OR3
OR3
CO (500 psi)
THF, 80 ˚C
+
R2
Carbene complex
M
R1
R2
Acetal
R3
Time (h)
Product
Product yield
Rec (%)
11c
11c
15c
16c
17c
17c
11c
11e
18c
11f
11f
11f
11g
a
Cr
Cr
Mo
W
Cr
Cr
Cr
Cr
Cr
Cr
Cr
Cr
Cr
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
i-Pr
Cy
Ph
Ph
Ph
Ph
2-Fu
2-Fu
Ph
Ph
n-Bu
Ph
19
Et
Et
Et
Et
24
24
24
22
96
48
69
24
92
22
72
72
72
22
75
0
0
30
49
97
0
–
–
–
–
69b
39
19
Et
23
24
25
26
27
28
29
30
31
0
20
o-Xylyl
o-Xylyl
o-Xylyl
o-Xylyl
Me
Et
o-Xylyl
o-Xylyl
13c
76
77
48
98d
75e
40f
24g
i-Pr
L-Menthol
L-Menthol
L-Menthol
Phenmenh
21
19
20
Ph
Ph
1Ph
–
–
–
Unless otherwise specified all reactions were carried out at 0.1 M in carbene complex in THF with 1.2 equiv of ketene acetal at 75–80 °C under 500 psi
of CO in a Paar bomb. The reaction mixture was deoxygented before transfer to bomb.
b
Reaction performed in the presence of 10 equiv of i-Propanol.
Reaction at 100 °C, 22% of iso-propyl-2-furoate also obtained.
2.0:1 mixture of diastereomers.
2.2:1 mixture of diastereomers.
4.0:1 mixture of diastereomers.
4.4:1 mixture of diastereomers.
9-Phenylmentholoxy carbene complex.
c
d
e
f
g
h
O
OMe
Ph
O
O
+
CO (500 psi)
THF, 80 ˚C
(CO)5Cr
11a
OEt
(CO)5Cr
O
+
OEt
20
19
33 (90%)
32c
25 ˚C, 5 d
1000 psi CO
(87% with 20)
Scheme 3.
O
+
reaction is run at room temperature rather than at 70 °C
(Scheme 4) [7]. Small amounts of 35 were found in the
reactions in THF and acetonitrile but not in hexane, which
is not consistent with a mechanism in which the ortho ester
34 is formed from the zwitterion 5 and the cyclopropanone
acetal formed by the direct [2+2] cycloaddition of 11a with
20 to give 10 (Scheme 2). The metallacycle 10 can be an
intermediate in the reaction, however, as indicated by the
isolation of the metathesis product 36 in the absence of
carbon monoxide [12]. In this case, the metallacycle 10
must be unsaturated (n = 4) since under 1000 psi of CO
the formation of carbene complex 36 is completely sup-
pressed [2]. The reaction of 11a with 20 was also carried
out in THF in the presence of 10 equivalents of metha-
nol-d4 in an effort to trap the oxonium cation in the zwit-
terion 5. However, both the ortho ester 34 and the
cyclopropanone acetal 35 showed no detectable amount
of deuterium incorporation in the methoxyl group. Thus,
if the 1,3-migration of the methoxyl group in 5 involves
O
OMe
O
Ph
O
Ph
34
OMe
35
Solvent
Yield 34 (cis:trans) Yield 35
60 (7 : 1)
78 (6 : 1)
56 (8 : 1)
26 (5 : 1) b
hexanes
THF
Š 1
17
CH3CN
6
THF a
62 b
a (10 equiv CD3OD) b Š 5% CD3 incorporation
O
Cr(CO)5
O
36
Scheme 4.

6104
S.L.B. Wang et al. / Journal of Organometallic Chemistry 690 (2005) 6101–6110
Future studies will focus on establishing the scope of
this reaction for the preparation of cyclopropanone acetals
and its application in synthesis.
OR1
O
O
+
(CO)5Cr
20
R2
37 R1 = CD3, R2 = H
2. Experimental
R1 = CH3, R2 = OCH3
38
All experiments were performed under an argon atmo-
sphere. Benzene, THF, and Et2O were distilled from sodium
benzophenone ketyl under nitrogen. Methylene chloride
was distilled from calcium hydride under nitrogen. i-Propa-
70 ˚C, 36 h
800 psi CO
THF
37:38 = 1.8:1
˚
nol was distilled from NaBH4 onto 4 A MS. Other reagents
were purified by simple distillation or passing through a pad
of activated silica gel. Diethyl ketene acetal was purchased
from Fluka, and distilled prior to use. Ketene-[o-xylyleneac-
etal] was prepared as described in the literature [13]. Penta-
carbonyl-[(1R,2S,5R)-(ꢀ)-menthyloxybenzylidene]-chromium
(0) and [(1R,2S,5R)-(ꢀ)-phenylmenthyloxybenzylidene]-chro-
mium (0) were prepared as described by Do¨tz and Stinner
[14]. All glassware was washed with aqueous KOH, flame
dried under vacuum and cooled under an argon atmosphere
prior to use.
O
O
+
OCD3
O
O
OCD3
40
39
60% (Š5% H)
7% (<5% H)
O
O
OCH3
1H and 13C NMR spectra were recorded on a General
OCH3
+
1
Electric QE-300 (300 MHz H, 75.5 MHz 13C) or Bruker
O
O
Avance (400 MHz 1H, 100 MHz 13C) spectrometer in
CDCl3 using residual CHCl3 (7.25 ppm 1H, 77.25 ppm
13C) as an internal reference unless otherwise stated.
Elemental analyses were performed by Galbraith Labora-
tories, Inc., Knoxville, TN. Analytical thin-layer chroma-
tography (TLC) was performed on Merck silica gel plates
with F-254 indicator. Components were visualized by illu-
mination with long wave ultraviolet light, exposure to io-
dine vapor, or by staining with one of the following
reagents (followed by heating): p-anisaldehyde (or vanillin)
in ethanol/sulfuric acid; 7% phosphomolybdic acid in eth-
anol; 0.04 M ammonium molybdate in 10% sulfuric acid.
Solvents for extraction and chromatography were reagent
grade and used as received. Flash column chromatography
was performed by the method of Still [15] using E. Merck
silica gel 60 (230–400 mesh).
OCH3
41
23% (>95% H)
42
H3CO
29% (>95% H)
Scheme 5.
the dissociation of methoxide to give an ion pair, the inter-
nal return is so efficient that external methanol cannot
compete. Perhaps the most interesting aspect of this exper-
iment is the observation that the presence of 10 equivalents
of methanol-d4 increases the ratio of cyclopropanone ace-
tal to ortho ester by a factor of 11. While this is not under-
stood, it did not prove to be a general phenomenon. The
reaction of 11c with 19 in the presence of 10 equiv of iso-
propanol did not lead to an increased yield of 22 (Table 2,
entry 2). The use of methanol in this reaction lead to
scrambling of the alkoxy group in the carbene complex.
The possibility of a 1,3-migration of methoxyl by an
intermolecular exchange was tested with the double-label-
ing experiment shown in Scheme 5. A 1.8:1 mixture of
the complexes 37 and 38 was allowed to react with excess
ketene acetal 20 at 70 °C for 36 h. The para-methoxyphenyl
complex 38 was found to give a much greater proportion of
the cyclopropanone acetal than the phenyl complex.
However, neither the ortho ester 41 or the cyclopropanone
acetal 42 contained any detectable amount of deuterium in
the methoxyl attached to the sp3-carbon. Similarly, neither
the ortho ester 39 or the cyclopropanone acetal 40 were
found to contain any detectable loss of deuterium in the
methoxyl group. Therefore, the 1,3-migration of the meth-
oxyl group in the zwitterion 5 must occur by an intramolec-
ular process.
3. General experimental for synthesis of iso-propoxy carbene
complexes – illustrated for complex 11c
To a flame dried 250 mL round bottom flask with stir -
bar was suspended 10 g (45.5 mmol) of chromium hexacar-
bonyl in 65 mL of Et2O. The reaction was cooled to
ꢀ78 °C, and 28 mL (1.62 M, 45.5 mmol) of phenyllithium
was added dropwise. The initially canary yellow suspension
was warmed to room temperature, and then became a deep
brown-red solution. After 2 h at room temperature, the
reaction was concentrated on the roto evaporator and then
dried at 5 mm Hg for 0.5 h. After this time, 200 mL of dis-
tilled water was added, and the reaction was filtered
through Celite directly on to 7.7 g (50 mmol) of tetrameth-
ylammonium bromide. The resulting orange suspension
was stirred for 15 min, then the solid was collected on a
Buchner funnel, and dried overnight to provide 7.1 g
¨

S.L.B. Wang et al. / Journal of Organometallic Chemistry 690 (2005) 6101–6110
6105
(42%) of the tetramethyl ammonium salt as a bright orange
solid.
2942 cmꢀ1. Anal. Calc. for C18H16CrO6: C, 56.85; H,
4.24. Found: C, 56.79; H, 4.34%.
To a flame dried 250 mL three-neck flask with constant
addition funnel and stir bar, was charged 6.1 g (16.4 mmol)
of the tetramethylammonium salt and 31 mL of CH2Cl2.
The suspension was cooled to ꢀ65 °C, and 2.2 g
(18.1 mmol) of acetyl bromide in 31 mL of CH2Cl2 was
added dropwise. The resulting blood red suspension was
stirred for an additional 15 min, and then 1.1 g (18.1 mmol)
of i-propanol was added dropwise, and the reaction was
warmed to ꢀ20 °C. After 24 h, the crude reaction was fil-
tered through 1:1/Celite:SiO2 with 100 mL hexanes, and
concentrated to approximately 1/3 the original volume
then chromatographed directly (50 mm column, 600 SiO2,
100% hexanes) by collecting the resulting red band which
was concentrated in vacuo to provide a red solid. Recrys-
tallization with 95:5/pentane:CH2Cl2 provided 2.5 g
(45%) of the title compound as a bright orange solid;
3.3. Pentacarbonyl-[isopropoxybenzylidene]-molybdenum
(0) (15c)
This complex was isolated in 28% yield from the tetra-
methylammonium salt following the procedure for the
chromium analog. Orange-rust crystals, mp 62–64 °C
(sharp). 1H NMR (300 MHz, CDCl3) d 1.67 (d, 6H,
CH(CH3)2, J = 6.2 Hz), 6.15 (m, 1H, CH(CH3)2), 7.49
(m, Ar–CH, 3H), 7.56 (m, Ar–CH, 1H); 13C NMR
(100 MHz, CDCl3) d 22.3 (CH(CH3)2), 88.3 (CH(CH3)2),
125.8 (Ar–C), 128.0 (Ar–C), 131.5 (Ar–C), 153.9 (Cipso),
205.6 (CO), 213.8 (CO), 332.8 (Ccarb); IR (thin film,
cmꢀ1) 2071m, 1992m, 1965s, 1928s, 1211w; mass spectrum
m/z (% rel. int.) 386 (M+, 98Mo, 10), 358 (M+ ꢀ CO, 98Mo,
35), 330 (98Mo, 19), 302 (98Mo, 40), 154 (84), 136 (46), 105
(100); HRMS calcd for C15H12MoO6 m/z 385.9692, measd
385.9687. Anal. Calc. for C15H12MoO6: C, 46.79; H, 3.10;
Mo, 24.97. Found: C, 45.31; H, 3.10; Mo, 23.84%.
1
m.p. 45–46 °C (sharp): H NMR (300 MHz, CDCl3) d 1.7
(d, 6H, CH(CH3)2, J = 6.4 Hz), 5.7 (m, CH(CH3)2, 1H),
7.2–7.5 (m, 5H, Ar–CH); 13C NMR (75 MHz, CDCl3) d
22.6 (CH(CH3)2), 85.7 (CH(CH3)2), 122.4 (Ar–C), 128.1
(Ar–C), 129.7 (Ar–C), 153.8 (Cipso), 216.3 (CO), 224.4
(CO), 345.8 (Ccarb); mass spectrum m/z (% rel. int.) 312
(M+ ꢀ CO, 3), 284 (11), 256 (3), 230 (1), 228 (18), 200
(90), 178 (20), 158 (41), 157 (30), 129 (75), 118 (22), 105
(30), 86 (62), 84 (100); IR (thin film, cmꢀ1) 2061s, 1924s,
1246w, 1079w, 653m. Anal. Calc. for C15H12CrO6: C,
52.82; H, 3.55. Found: C, 52.71; H, 3.65%.
3.4. Pentacarbonyl-[isopropoxybenzylidene]-tungsten (0)
(16c)
This complex was isolated in 28% yield from the tetram-
ethylammoniium salt following the procedure for the chro-
1
mium analog. Orange powder, mp 76–77 °C (sharp). H
NMR (300 MHz, CDCl3) d 1.62 (d, 6H, CH(CH3)2,
J = 6.4 Hz), 5.91 (m, 1H, CH(CH3)2), 7.42–7.50 (m, Ar–
3.1. Pentacarbonyl-[cyclopentyloxybenzylidene]-chromium
(0) (11d)
CH, 5H); 13C NMR (100 MHz, CDCl3)
d
22.4
(CH(CH3)2), 88.8 (CH(CH3)2), 125.9 (Ar–C), 128.0 (Ar–
C), 131.4 (Ar–C), 155.4 (Cipso), 197.2 (t, CO,
JCW = 127 Hz), 203.7 (CO), 316.1 (Ccarb); IR (thin film,
cmꢀ1) 2069m, 1989m, 1959s, 1922s, 1256w; mass spectrum
m/z (% rel. int.) 472 (M+, 184W, 2), 444 (4, 184W), 373 (35,
184W), 309 (36), 279 (25), 195 (21), 155 (84), 135 (66), 119
(100); HRMS calcd for C15H12184WO6 m/z 472.0140,
measd 472.0143. Anal. Calc. for C15H12WO6: C, 38.09;
H, 2.56. Found: C, 37.88; H, 2.49%.
This compound was obtained according to the proce-
dure for 11c and was isolated in 83% yield from the tetra-
methyl ammonium salt as a yellow crystal. Spectral data
for 11d: 1H NMR (300 MHz, CDCl3) d 1.70–1.90 (m,
2H), 1.90–2.05 (m, 2H), 2.05–2.20 (m, 4H), 5.85 (m, 1H),
7.10–7.30 (m, 2H), 7.30–7.55 (m, 3H); 13C NMR
(75 MHz, CDCl3) d 24.2, 34.2, 94.5, 122.4, 128.1, 129.6,
153.7, 216.3, 224.6, 345.6; IR (film) 455, 621, 654, 692,
702, 762, 897, 1148, 1240, 1273, 1325, 1441, 1917, 1950,
2082, 2878, 2969 cmꢀ1. Anal. Calc. for C17H14CrO6: C,
55.74; H, 3.85. Found: C, 55.49; H, 4.10%.
3.5. Pentacarbonyl-[isopropoxy-2-furanyl-methylidene]-
chromium (0) (17c)
This complex was isolated in 90% yield from 620 mg
(9.1 mmol) of furan, 2 g (9.1 mmol) of chromium hexacar-
bonyl and 3.5 g (18.2 mmol) of isopropyl triflate. The cru-
rde product was chromatorgraphed directly (50 mm
column, 600 SiO2, 95:5/hexanes:CH2Cl2) and collection of
the resulting red-purple band as described above gave a
purple solid. Recrystallization from pentane provides pur-
ple needles, mp 88–90 °C (sharp). 1H NMR (300 MHz,
CDCl3) d 1.57 (d, 6 H, CH(CH3)2, J = 6.0 Hz), 6.00 (sept,
1H, CH(CH3)2), 6.59 (bs, 1H, CH-2), 7.04 (d, 1H, CH-3,
J = 2.7 Hz), 7.89 (s, 1H, CH-1); 13C NMR (100 MHz,
CD2Cl2) d 22.7 (CH(CH3)2), 85.1 (CH(CH3)2), 112.8 (C-
1), 113.2, 150.3, 164.5 (C-4), 217.2 (CO), 224.6 (CO),
3.2. Pentacarbonyl-[cyclohexyloxybenzylidene]-chromium
(0) (11e)
This compound was obtained according to the proce-
dure for 11c and was isolated in 48% yield from the tetra-
methyl ammonium salt as a yellow crystal. Spectral data
for 11e: 1H NMR (300 MHz, CDCl3) d 1.70–2.20 (m,
10H), 5.85 (m, 1H), 7.10–7.32 (m, 2H), 7.32–7.55 (m,
3H); 13C NMR (75 MHz, CDCl3) d 23.4, 24.9, 32.4, 90.4,
122.7, 128.1, 129.9, 153.7, 216.3, 224.4, 345.6; IR (film)
410, 619, 655, 760, 864, 903, 937, 951, 1150, 1173, 1181,
1208, 1232, 1248, 1277, 1443, 1451, 1917, 2080, 2865,

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S.L.B. Wang et al. / Journal of Organometallic Chemistry 690 (2005) 6101–6110
307.9 (Ccarbene); IR (thin film, cmꢀ1) 2060w, 1992w, 1925s,
1889m, 1545w, 1223m, 643m; mass spectrum m/z (% rel.
int.) 330 M+ (28), 307 (34), 302 (32), 274 (16), 246 (35),
218 (55), 190 (24), 154 (100), 136 (85), HRMS calcd for
C13H10CrO7 m/z 329.9831, measd 329.9831.
4. General experimental for cyclopropanation reaction with
ketene acetals – illustrated for 1,1-diethyoxy-2-isopropoxy-
2-phenyl-cyclopropane 13c
To a flame dried 25 mL Schlenk flask with a stir bar and
septa was charged 430 mg (1.3 mmol) of pentacarbonyl-
[isopropoxybenzylidene]-chromium (0) 11c, 13 mL of
THF and 177 mg (1.52 mmol) of diethyl ketene acetal.
The clear orange solution was deoxygenated by the
freeze–pump–thaw method (three cycles) and then trans-
ferred into a Parr high pressure reactor filled with argon,
sealed, and pressurized to 500 psi of CO. The reactor was
heated at 75 °C for 24 h, cooled to room temperature and
then the contents were concentrated in vacuo. The crude
green-yellow solution was chromatographed (30 mm col-
umn, 400 SiO2, 20:1/hexanes:EtOAc) to provide 245 mg
(74%) of the title compound as a clear, very light yellow li-
quid. TLC (SiO2, 5:1/hexanes:EtOAc, Rf = 0.45). 1H NMR
(CDCl3, 300 MHz) d 0.8 (t, 3H, CH3, J = 7.1 Hz), 1.0 (d,
3H, CH(CH3)2, J = 6.2 Hz), 1.2 (d, 3H, CH(CH3)2,
J = 6.1 Hz), 1.3 (t, 3H, CH2CH3, J = 7.1 Hz), 1.36 (d, 1H,
CH2, J = 7.2 Hz), 1.7 (d, 1H, CH2, J = 7.2 Hz), 3.17 (m,
1H, OCH2), 3.50 (m, 1H, OCH2), 3.73 (m, 2H,
CH(CH3)2 + OCH2CH3), 3.87 (m, 1H, OCH2), 7.20–7.32
(m, 3H), 7.4 (m, 2H); 13C NMR (CDCl3, 75 MHz) d 15.0
(OCH2CH3), 15.6 (OCH2CH3), 21.3 (C-3, JCH = 158 Hz),
23.3 (i-Pr-CH3), 23.6 (i-Pr-CH3), 61.6 (OCH2CH3), 62.9
(OCH2CH3), 69.4 (C-2), 70.6 (OCH(CH3)2), 92.7 (C-1),
3.6. Pentacarbonyl-[1-isopropoxy-n-pentylidene]-chromium
(0) (18c)
To a flame dried 50 mL round bottom flask equipped
with a stir bar and septa was suspended 2.8 g (12.8 mmol)
of chromium hexacarbonyl in 50 mL of Et2O. The reac-
tion was cooled to ꢀ78 °C, and 5.8 mL (2.19 M,
12.8 mmol) of butyllithium was added dropwise. The ini-
tially canary yellow suspension was warmed to room tem-
perature which then became a deep brown-red solution.
After 1.5 h at RT, the reaction was filtered through a
pad of Celite, concentrated and then dried at 5 mm Hg
for 0.5 h. After this time, the brown solid was suspended
in 50 mL of CH2Cl2, and the mixture reaction was cooled
to 0 °C. To the brown-yellow solution was added 3.7 g
(19.3 mmol) of isopropyl triflate [16] in 10 mL of CH2Cl2
dropwise. After the addition was complete, the now red
reaction mixture was warmed to RT for 1 h. After this
time, the reaction was filtered through 1:1/Celite:SiO2
with 100 mL hexanes, concentrated to approximately
1/3 the original volume, then chromatographed directly
(30 mm column, 400 SiO2, 100% hexanes) by collecting
the resulting yellow-orange band which was concentrated
to provide 1.7 g (41%) of the title compound as bright
yellow crystals, mp 34–36 °C (sharp). 1H NMR
(300 MHz, CDCl3) d 0.92 (t, 3H, J = 7.1 Hz, Butyl
CH3), 1.38 (m, 2H, CH2), 1.46 (m, 2H, CH2), 1.64 (d,
6H, CH(CH3)2, J = 5.6 Hz), 3.27 (t, 2H, J = 7.2 Hz,
CH2Ccarbene), 5.84 (brs, 1H, CH(CH3)2); 13C NMR
(125 MHz, CDCl3) d 14.1 (CH3), 22.5 (CH(CH3)2), 22.8
(CH2), 28.6 (CH2), 63.5 (CcarbeneCH2), 87.8 (CH(CH3)2),
217.1 (CO), 224.2 (CO), 355.4 (Ccarb); IR (thin film,
cmꢀ1) 2061s, 1978m, 1923s, 1261m; mass spectrum m/z
(% rel. int.) 320 M+ (7), 292 (13), 264 (9), 236 (5), 208
(21), 180 (100), 138 (33), HRMS calcd for C13H16CrO6
m/z 320.0351, measd 320.0351. Anal. Calc. for
C13H16CrO6: C, 48.75; H, 5.03, Cr, 16.24. Found: C,
48.38; H, 5.03; Cr, 16.70%.
126.8 (C–Ar), 127.7 (C–Ar), 138.4 (Cipso); IR (neat, cmꢀ1
)
2974s, 2930s, 2886m, 1448m, 1368m, 1267w, 1209s, 1119s,
1050s, 698s; mass spectrum m/z (% rel. int.) 221 (M ꢀ
i-Pr)+ (30), 193 (19), 147 (14), 105 (100). Anal. Calc. for
C16H24O3: C, 72.69; H, 9.15. Found: C, 73.03; H, 9.11%.
4.1. c1,1-Diethyoxy-2-isopropoxy-2-phenyl-cyclopropane
(13d)
Colorless oil, 47% yield. Spectral data for 13d: 1H NMR
(300 MHz, CDCl3) d 0.84 (t, J = 7.1 Hz, 3H), 1.26–1.46 (m,
4H), 1.31 (t, J = 7.1 Hz, 3H), 1.43 (d, J = 7.1 Hz, 1H),
1.54–1.80 (m, 4H), 1.68 (d, J = 7.1 Hz, 1H), 3.12–3.24
(m, 1H), 3.46–3.60 (m, 1H), 3.72–3.82 (m, 1H), 3.84–3.92
(m, 1H), 3.93–4.04 (m, 1H), 7.20–7.45 (m, 5H); 13C
NMR (75 MHz, CDCl3) d 14.9, 15.5, 21.5, 23.0, 23.3,
33.0, 61.5, 62.8, 69.9, 80.3, 92.8, 126.6, 127.4, 127.6, 138.3
(1 aliphatic C not located). Anal. Calc. for C18H26O3: C,
74.45; H, 9.02. Found: C, 74.48; H, 9.21%.
3.7. Pentacarbonyl-[isopropoxy-cyclohexyl-methylidene]-
chromium (0) (32c)
Yellow crystal. Spectral data for 32c: 1H NMR
(300 MHz, CDCl3) d 1.00–1.40 (m, 10H), 1.53 (d,
J = 5.7 Hz, 3H), 1.78 (d, J = 5.7 Hz, 3H), 3.83 (m, 1H),
5.80 (m, 1H); 13C NMR (75 MHz, CDCl3) d 22.1, 25.6,
25.9, 28.3, 71.3, 86.8, 216.5, 223.5, 357.3; IR (film) 590,
648, 666, 853, 914, 982, 1062, 1100, 1258, 1325, 1368,
1443, 1916, 2080, 2857, 2934 cmꢀ1. Anal. Calc. for
C15H18CrO6: C, 52.03; H, 5.24. Found: C, 51.89; H,
5.37%.
4.2. 1-o-Xyleneacetal-2-isopropoxy-2-furanyl-cyclopropane
(24)
This compound was isolated in 13% yield as a light yel-
low liquid using the procedure described above with
200 mg (0.61 mmol) of pentacarbonyl-[isopropoxyfura-
nyl]-chromium (0) 17c, 8 mL of THF and 197 mg
(1.21 mmol) of ketene acetal. The reaction was performed
1
at 100 °C under 500 psi CO for 48 h. H NMR (CDCl3,

S.L.B. Wang et al. / Journal of Organometallic Chemistry 690 (2005) 6101–6110
6107
300 MHz) d 1.08 (d, 3H, CH(CH3)2,J = 6.2 Hz), 1.15 (d,
3H, CH(CH3)2,J = 6.2 Hz), 1.55 (d, 1H, CH2,
J = 7.1 Hz), 1.73 (d, 1H, CH2, J = 7.1 Hz), 3.84 (hept,
1H, CH(CH3)2, J = 6.1 Hz), 4.53 (2, 1H, CH2,
J = 14.1 Hz), 4.93 (2, 1H, CH2, J = 14.1 Hz), 5.00 (2, 1H,
CH2, J = 14.0 Hz), 5.20 (2, 1H, CH2, J = 14.1 Hz), 6.32
(m, 1H, furyl), 6.38 (m, 1H, furyl), 7.09 (m, 1H, Ar–CH),
7.19 (m, 3H, Ar–CH), 7.40 (bs, 1H, furyl); 13C NMR
(CDCl3, 100 MHz) d 21.9 (CH3), 24.6 (C-3, JCH = 160 Hz),
71.1, 71.5, 72.1, 77.5, 95.8, 109.3 (C-furyl), 110.7 (C-furyl),
127.5 (2xC–Ar), 127.6 (C–Ar), 127.6 (C–Ar), 138.7 (Cipso),
139.0 (Cipso), 142.3 (C-furyl), 152.2 (Cipso-furyl); IR (thin
film, cmꢀ1) 2964m, 1372w, 1266w, 1132m, 1062w, 1027w;
mass spectrum m/z (% rel. int.) 300 (88), 257 (24), 241
(33), 183 (69), 171 (67), 155 (51), 146 (28), 137 (100),
HRMS calcd for C18H20O4 m/z 300.1356, measd 300.1361.
200 mg (0.62 mmol) of pentacarbonyl-[isopropoxy-butyli-
dene]-chromium (0) 18c, 8 mL of THF and 111 mg
(0.69 mmol) of ketene acetal 20. The reaction was per-
formed at 75 °C under 500 psi CO for 92 h. TLC (SiO2,
4:1/Hexanes:EtOAc, Rf = 0.28). 1H NMR (CDCl3,
300 MHz) d 0.89 (m, 4H), 1.21 (m, 7H), 1.36 (m, 2H),
1.52 (m, 2H), 1.67 (m, 2H), 3.81 (sept, 1H, J = 6.2 Hz,
CH(CH3)2), 4.69–5.05 (m, 4H, OCH2), 7.04–7.22 (m,
Ar–CH, 4H); 13C NMR (CDCl3, 75 MHz) d 14.3 (butyl-
CH3), 23.1, 23.9, 24.0, 24.2, 27.9, 30.7, 68.4 (C-2), 70.4
(OCH(CH3)2), 70.7 (OCH2), 71.6 (OCH2), 97.2 (C-1),
127.3 (Ar–C), 127.4 (Ar–C), 127.5 (Ar–C), 138.8 (Cipso),
139.2 (Cipso); IR (thin film, cmꢀ1) 2957s, 2928s, 2861s,
1446m, 1367m, 1213w, 1168s, 1152s, 1069s, 1039s,
745m; mass spectrum (FAB) m/z (% rel. int.) 289 (8),
247 (14), 231 (10), 185 (8), 154 (51), 136 (36), 135 (34),
104 (100), HRMS calcd for C18H26O3 m/z 289.1803,
measd 289.1803.
4.3. 1-o-Xyleneacetal-2-isopropoxy-2-phenyl-cyclopropane
(25)
4.6. 1,1-Dimethoxy-2-mentholoxy-2-phenyl-cyclopropane (28)
This compound was isolated in 76% yield as a colorless
liquid using the procedure described above with 216 mg
(0.32 mmol) of pentacarbonyl-[isopropoxybenzylidene]-
chromium (0) 11c, 12 mL of THF and 90 mg (0.64 mmol)
of ketene acetal. The reaction was performed at 50 °C under
640 psi CO for 69 h. 1H NMR (CDCl3, 300 MHz) d 1.07 (d,
3H, CH(CH3)2), 1.19 (d, 3H, CH(CH3)2), 1.57 (d, 1H, CH2,
J = 7 Hz), 1.84 (d, 1H, CH2, J = 7 Hz), 3.81 (hept, 1H,
CH(CH3)2, J = 6 Hz), 4.51 (m, allylic CH2, 2H), 5.10 (m,
allylic CH2, 2H), 7.01 (d, Ar–CH, 1H), 7.1–7.5 (m, Ar–
CH, 8H); 13C NMR (CDCl3, 75 MHz) d 23.0 (C-
3,JCH = 159 Hz), 23.5, 69.2, 70.4, 70.4, 71.9, 95.7, 127.2,
127.2, 127.3, 127.3, 127.4, 128.0, 137.8, 138.6, 138.9 (1 aryl
C not located); IR (thin film, cmꢀ1) 2972s, 1496m, 1447s,
1424m, 1380m, 1369s. Anal. Calc. for C20H22O3: C, 77.39;
H, 7.14. Found: C, 77.41; H, 7.29%.
This cyclopropanone acetal 28 was isolated in 98% yield
as a colorless oil using the procedure described above with
160 mg (0.37 mmol) of pentacarbonyl-[(1R,2S,5R)-(ꢀ)-
menthyloxybenzylidene]-chromium (0) 11f, 5 mL of THF
and 65 mg (0.74 mmol) of dimethoxy ketene acetal 21.
The reaction was performed at 80 °C under 380 psi CO
for 24 h. Acetal 28 was isolated as a 2:1 mixture of isomers
which could be separated by preparative TLC with a 1:1:20
mixture of ether, methylene chloride and hexanes. Major
1
isomer: H NMR (CDCl3, 300 MHz) d 0.66 (d, 3H), 0.77
(d, 3H), 0.92 (d, 3H), 0.6–1.6 (m, 10H), 2.33 (m, 1H),
3.13 (s, 3H), 3.21 (m, 1H), 3.52 (s, 3H), 7.2–7.4 (m, 5H);
13C NMR (CDCl3, 75 MHz) d 15.9, 19.7, 21.4, 22.9, 23.1,
24.7, 31.6, 34.4, 42.4, 48.3, 52.9, 54.3, 69.4, 78.2, 94.1,
126.8, 127.5, 127.7, 139.7; IR (neat, cmꢀ1) 2954s, 2933s,
2870m, 1448m, 1225m; mass spectrum m/z (% rel. int.)
219 (M+ ꢀ C10H19, 3), 193 (68), 169 (8), 131 (11), 105
(100) (thick colorless oil). Minor isomer: 1H NMR (CDCl3,
300 MHz) d 0.42 (d, 3H, J = 7 Hz), 0.7–1.6 (m, 9H), 0.85
(d, 3H, J = 7 Hz), 0.88 (d, 3 H, J = 7 Hz), 2.2–2.7 (m,
2H), 3.07 (m, 1H), 3.19 (s, 3H), 3.61 (s, 3H), 7.3–7.4 (m,
5H); 13C NMR (CDCl3, 75 MHz) d 15.6, 21.3, 22.6, 22.7,
25.0, 31.3, 34.4, 40.8, 48.0, 52.7, 54.3, 67.9, 75.5, 91.4,
127.6, 128.1, 129.4, 136.3 (1 aliphatic C not located); IR
(neat, cmꢀ1) 2954s, 2933s, 2870m, 1448m, 1224m.
4.4. 1-o-Xyleneacetal-2-cyclohexyloxy-2-phenyl-
cyclopropane (26)
1
Colorless oil, 77% yield. Spectral data for 26: H NMR
(300 MHz, CDCl3) d 0.84–0.96 (m, 1H), 1.10–1.56 (m, 6H),
1.62 (d, J = 7.0 Hz, 1H), 1.64–1.80 (m, 2H), 1.87 (d,
J = 7.0 Hz, 1H), 1.88–1.98 (m, 1H), 3.45–3.55 (m, 1H),
4.39 (d, J = 14.2 Hz, 1H), 4.64 (d, J = 14.0 Hz, 1H), 5.04
(d, J = 14.2 Hz, 1H), 5.20 (d, J = 14.2 Hz, 1H), 7.02 (d,
J = 7.2 Hz, 1H), 7.15–7.25 (m, 3H), 7.25–7.42 (m, 3H),
7.55 (d, J = 7.7 Hz, 2H); 13C NMR (75 MHz, CDCl3) d
23.0, 24.4, 25.6, 33.2, 33.5, 69.0, 70.4, 71.9, 76.4, 95.8,
127.0, 127.1, 127.2, 127.8, 127.83, 138.0, 138.5, 138.9 (three
carbons not located). Anal. Calc. for C23H26O3: C, 78.83;
H, 7.48. Found: C, 78.99; H, 7.21%.
4.7. 1-o-Xyleneacetal-2-mentholoxy-2-phenyl-cyclopropane
(30)
Major isomer, 33% yield, colorless oil. Spectral data for
30 (major): 1H NMR (300 MHz, CDCl3) d 0.72 (d,
J = 6.6 Hz, 3H), 0.83 (d, J = 6.9 Hz, 3H), 0.99 (d,
J = 7.1 Hz, 3H), 0.90–1.32 (m, 3H), 1.36–1.48 (m, 1H),
1.52–1.70 (m, 4H), 1.60 (d, J = 7.7 Hz, 1H), 1.85 (d,
J = 7.7 Hz, 1H), 2.45 (pd, J = 7.1, 2.8 Hz, 1H), 3.30 (td,
J = 10.4, 3.8 Hz, 1H),4.33 (d, J = 14.0 Hz, 1H),4.54 (d,
4.5. 1-o-Xyleneacetal-2-isopropoxy-2-butyl-cyclopropane (27)
Cyclopropanone acetal 27 was isolated in 48% yield as
a yellow liquid using the procedure described above with

6108
S.L.B. Wang et al. / Journal of Organometallic Chemistry 690 (2005) 6101–6110
J = 13.7 Hz, 1H), 4.88 (d, J = 14.2 Hz, 1H), 5.19 (d,
J = 14.0 Hz, 1H), 7.03 (d, J = 6.9 Hz, 1H), 7.14–7.40 (m,
6H), 7.48–7.54 (m, 2H); 13C NMR (75 MHz, CDCl3) d
15.8, 21.3, 22.3, 22.9, 24.9, 31.5, 34.4, 42.0, 48.2, 68.6,
70.8, 72.3, 77.6, 96.7, 126.5, 126.6, 127.2, 127.4, 127.6,
127.8, 138.8, 139.2, 139.8 (1 aryl and 1 alkyl C not located);
IR (film) 632, 644, 737, 764, 898, 990, 1028, 1063, 1074,
1129, 1144, 1181, 1262, 1329, 1370, 1447, 1495, 2868,
2918, 2953 cmꢀ1. Anal. Calc. for C27H34O3: C, 79.76; H,
8.43. Found: C, 80.02; H, 8.22%. Minor isomer. Colorless
oil, 8% yield. Spectral data for 30 (minor): 1H NMR
(300 MHz, CDCl3) d 0.50 (d, J = 6.9 Hz, 3H), 0.89 (d,
J = 2.5 Hz, 3H), 0.91 (d, J = 1.9 Hz, 3H),0.70–1.70 (m,
8H),1.54 (d, J = 7.1 Hz, 1H), 1.88 (d, J = 7.1 Hz,
1H),2.24–2.32 (m,1H),2.36 (pd, J = 6.9,4.4 Hz, 1H),3.25
(td, J = 10.4, 4.4 Hz, 1H), 4.53 (d, J = 14.0 Hz, 1H), 4.74
(d, J = 14.0 Hz, 1H), 5.04 (d, J = 14.0 Hz, 1H), 5.24 (d,
J = 14.2 Hz, 1H), 7.04 (d, J = 6.9 Hz, 1H), 7.16–7.24 (m,
3H), 7.30–7.42 (m, 3H), 7.44–7.50 (m, 2H); 13C NMR
(75 MHz, CDCl3) d 15.8, 21.3, 22.5, 22.8, 24.3, 25.0, 31.3,
34.3, 40.9, 48.1, 67.8, 70.0, 72.0, 75.7, 94.2, 127.1, 127.3,
127.31, 127.6, 128.1, 129.2, 136.1, 138.6, 138.9 (1 aryl C
not located); IR (film) 642, 700, 745, 764, 909, 982, 1001,
1034, 1063, 1134, 1183, 1262, 1345, 1360, 1447, 1495,
2853, 2923, 2953, cmꢀ1. Anal. Calc. for C27H34O3: C,
79.76; H, 8.43. Found: C, 79.88; H, 8.21%.
1183, 1262, 1345, 1360, 1447, 1495, 2853, 2923, 2953,
3025 cmꢀ1. Anal. Calc. for C33H38O3: C, 82.12; H, 7.94.
Found: C, 81.88; H, 8.21%.
4.9. Reaction of complex 11a with ketal acetal 20 at room
temperature
Carbene complex 11a (0.1159 g) was dissolved in 7.4 mL
THF with 1.0 eq of 20. The solution was deoxygenated by
the freeze–thaw method (three cycles). The solution was
then stirred at room temperature until the complete con-
sumption of the carbene complex was observed (5 days).
The crude mixture was then purified by chromatography.
Ortho ester 34 was isolated in 54% (cis:trans = 10:1) yield
along with a-methoxystyrene (not quantified) and 36 in
25% yield. cis-34: 1H NMR (CDCl3) d 2.46 (dd, 1H,
J = 6.2, 13.2 Hz), 2.70 (t, 1H, J = 12.8 Hz), 3.58 (s, 3H),
4.09–4.14 (m, 1H, d), 5.41 (d, 1H, J = 13.7 Hz), 5.65 (d,
1H, J = 9.2 Hz), 6.13 (d, 1H, J = 7.6 Hz), 6.75 (t, 1H,
J = 7.4 Hz), 6.95–7.04 (m, 7 H); 13C NMR (CDCl3) d
42.2, 47.9, 51.3, 65.5, 85.0, 122.6, 126.35, 126.43, 126.56,
126.97, 127.85 (2 carbons), 127.88, 137.0, 138.5, 139.4; IR
(CH2Cl2) 1640m, 1574m, 1318m, 1304s, 1286s cmꢀ1; mass
spectrum m/z (% rel. int.) M+ 282 (3), 251 (2), 208 (41),
163 (35), 149 (7), 121 (100), 104 (27). Anal. Calc. for
C18H18O3: C, 76.56; H, 6.43. Found: C, 76.31; H, 6.51%.
1
White solid, mp 70 °C (dec.). trans-34: H NMR (CDCl3)
4.8. 1-o-Xyleneacetal-2-(9-phenylmentholoxy)-2-phenyl-
cyclopropane (31)
d 2.25 (dd, 1H, J = 9.3, 12.1 Hz), 2.67 (dd, 1H, J = 8.7,
12.0 Hz), 3.44–3.49 (m, 1H), 3.59 (s, 3H), 4.50 (d, 1H,
J = 14.0 Hz), 5.24 (d, 1H, J = 4.1 Hz), 5.40 (d, 1H,
J = 14.0 Hz), 6.90–6.91 (m, 1H), 7.10–7.36 (m, 8H); 13C
NMR (CDCl3) d 43.0, 52.26, 52.33, 65.6, 87.4, 122.5,
125.5, 126.9, 127.0, 127.4, 127.5, 127.6, 129.0, 136.4,
142.4, 143.8; IR (CH2Cl2) 1446m cmꢀ1; mass spectrum
m/z (% rel. int.) M+ 282 (5), 264 (14), 200 (50), 162 (42),
122 (30), 121 (100), 120 (28), 119 (98). White solid, mp
Major isomer, 20% yield, colorless oil. Spectral data for
1
31 (major): H NMR (300 MHz, CDCl3) d 0.60–1.00 (m,
3H), 0.75 (d, J = 6.6 Hz, 3H), 1.15–1.50 (m, 3H), 1.46 (s,
3H), 1.72 (d, J = 7.7 Hz, 1H), 1.74 (s, 3H), 1.85 (d,
J = 7.7 Hz, 1H), 1.90–2.00 (m, 2H), 3.50 (td, J = 10.4,
3.8 Hz, 1H), 4.50 (q, J = 13.7 Hz, 2H), 4.84 (d,
J = 14.0 Hz, 1H), 5.16 (d, J = 14.0 Hz, 1H), 7.03 (d,
J = 6.8 Hz, 1H), 7.10–7.55 (m, 13H); 13C NMR (75 MHz,
CDCl3) d 20.9, 22.0, 22.4, 27.9, 30.9, 31.5, 34.8, 40.8,
41.9, 52.1, 67.1, 70.3, 72.0, 78.9, 96.6, 124.9, 126.1, 126.4,
126.8, 127.1, 127.3, 127.6, 127.7, 138.7, 140.5, 151.8 (2 aryl
C not located); IR (film) 632, 644, 737, 764, 898, 990, 1028,
1063, 1074, 1129, 1144, 1181, 1262, 1329, 1370, 1447, 1495,
2868, 2918, 2953 cmꢀ1. Anal. Calc. for C33H38O3: C, 82.12;
H, 7.94. Found: C, 82.01; H, 8.02%. Minor isomer. 4%
yield, colorless oil. Spectral data for 31 (minor): 1H
NMR (300 MHz, CDCl3) d 0.65–1.45 (m, 6H), 0.90 (d,
J = 6.6 Hz, 3H), 1.30 (s, 3H), 1.54 (d, J = 7.1 Hz, 1H),
1.63 (s, 3H), 1.83 (d, J = 7.1 Hz, 1H), 1.90–2.00 (m, 1H),
2.45–2.55 (m, 1H), 3.42 (td, J = 10.4, 4.2 Hz, 1H), 4.78
(q, J = 14.0 Hz, 2H), 4.92 (d, J = 14.2 Hz, 1H), 5.20 (d,
J = 14.2 Hz, 1H), 7.04 (d, J = 6.9 Hz, 1H), 7.10–7.60 (m,
13H); 13C NMR (75 MHz, CDCl3) d 22.4, 22.44, 25.0,
27.5, 31.2, 31.7, 34.6, 41.0, 41.1, 51.5, 66.3, 69.5, 71.3,
77.5, 93.5, 124.9, 125.7, 126.8, 127.1, 127.9, 128.1, 129.9,
135.4, 138.4, 138.6, 152.1 (3 aryl C not located); IR (film)
642, 700, 745, 764, 909, 982, 1001, 1034, 1063, 1134,
1
67 °C (dec.). Compound 36: H NMR (CDCl3) d 5.7 (s,
4H), 7.5 (s, 4H); 13C NMR (CDCl3) d 74.9, 128.3, 130.4,
135.6, 216.7, 221.9, 268.7; IR (CH2Cl2) 2064s,
1998br,s cmꢀ1; mass spectrum m/z (% rel. int.) 340 M+
(25), 312 (5), 256 (12), 228 (52), 220 (20), 200 (100), 199
(95), 201 (27). Anal. Calc. for C14H8CrO7: C, 49.42; H,
2.37. Found: C, 49.32; H, 2.56%. Pale yellow solid: mp
126.5 °C (dec.).
4.10. Reaction of complex 11a with ketal acetal 20 at room
temperature under 1000 psi of carbon monoxide
A solution of 0.1410 g of 11a and 0.0744 g of 20 in
8.4 mL THF was prepared under an argon atmosphere
and then transferred to the Parr reactor under inert atmo-
sphere. The reactor was then charged to a pressure of
1000 psi of CO. The reaction was then set aside for five
days at room temperature. After the pressure was released
from the reactor, the crude mixture was then purified on
silica gel to give a 78% yield of 34 (cis:trans = 7:1) and a
1
17% yield of 35. Spectral data for 35: H NMR (CDCl3)

S.L.B. Wang et al. / Journal of Organometallic Chemistry 690 (2005) 6101–6110
6109
d 1.5 (d, 1H, J = 7 Hz), 1.7 (d, 1H, J = 7 Hz), 3.3 (s, 3H),
4.5 (m, 2H), 5.1 (m, 2H), 7.1–7.5 (m, 9H); 13C NMR
(CDCl3) d 23.2 (JCH = 160 Hz), 54.6, 71.2, 72.0, 72.7,
98.0, 128.23, 128.26, 128.32, 128.37, 128.44, 128.94,
129.0, 137.2, 139.9, 140.2 (colorless oil).
Repeating the reaction under the same conditions in
hexane as solvent gave a 60% yield of 34 as a 7:1 mixture
of cis:trans isomers. Less than <1% yield of 35 was ob-
served by 1H NMR. Repeating the reaction under the same
conditions in acetonitrile as solvent gave a 56% yield of 34
as an 8:1 mixture of cis:trans isomers along with a 6% yield
of 35.
yield 42, a 60% yield of 39 and a 23% yield of 41. Com-
pounds 42 and 39 were not separable and the yields were
calculated from the 1H NMR spectrum. The 1H NMR inte-
gration of the OCH3 on the sp3-carbon in each product was
used to calculate the percentage of methoxyl group ex-
change during the reaction. Compounds 39 and 40 con-
tained greater than 95% deuterium and compounds 41
and 42 contained less than 5% deuterium. Other than the
1
deuterated methoxyl group, the H NMR spectrum of 39
and 40 were identical to those of their protio analogs cis-
34 and 35, respectively.
When the reaction was carried out as described above in
THF in the presence of of 10 eq of CD3OD the products
were purified to give 34 in 26% yield which contained less
than 5% deuterium in the methoxyl group and a 62% yield
of 35 which contained less than 10% deuterium in the meth-
oxyl group.
Acknowledgement
This work was supported by the National Institutes of
Health (GM 33589).
References
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The orthoester 41 was formed as a single diastereomer
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1
(cis:trans P 10:1). Spectral data for 41: H NMR (CDCl3)
d 2.40 (dd, 1H), 2.69 (dd, 1H), 3.67 (s, 3H), 3.71 (s, 3H),
4.07 (m, 1H), 4.48 (d, 1H, J = 17 Hz), 5.42 (d, 1H,
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J = 7 Hz), 6.53 (d, 2H, J = 7 Hz), 6.80 (t, 1H, J = 7 Hz),
6.85 (d, 1H, J = 7 Hz), 6.95–7.05 (m, 3H); 13C NMR
(CDCl3) d 42.1, 47.1, 51.6, 54.6, 65.6, 85.4, 112.9, 114.8,
122.2, 122.6, 126.3, 126.5, 126.9, 128.0, 129.9, 131.2,
136.9, 137.5, 158.9; IR (CH2Cl2) 1612w, 1513m cmꢀ1 (col-
orless oil). Spectral data for 42: 40% yield, 1H NMR
(CDCl3) d 1.44 (d, 1H, J = 7 Hz), 1.68 (d, 1H, J = 7 Hz),
3.27 (s, 3H), 3.83 (s, 3H), 4.55 (d, 1H, J = 18 Hz), 4.67
(d, 1H, J = 18 Hz), 5.05 (d, 1H, J = 17 Hz), 5.13 (d, 1H,
J = 17 Hz), 6.93 (d, 2H, J = 7 Hz), 7.06 (d, 1H, J = Hz),
7.15–7.25 (m, 3H), 7.38 (d, 2H, J = 7 Hz); 13C NMR
(CDCl3) d 22.6, 54.6, 55.3, 63.0, 70.7, 72.1, 96.9, 113.7,
127.3, 127.4, 127.5, 127.6, 129.0, 129.3, 138.6, 138.7,
159.0; IR (neat) 1610m, 1513s, 1459m, 1431m, 1302m,
1247s, 1176s cmꢀ1. Anal. Calc. for C19H20O4: C, 73.06;
H, 6.45. Found: C, 73.01; H, 6.41%. Colorless oil.
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THF under 800 psi CO at 70 °C for 36 h. The crude reac-
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(f) M.A. Sierra, J.C. del Amo, M.J. Mancheno, M. Gomez-Gallego,
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6110
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