Meta, para and ortho double exo nucleophilic additions of trimethylsilylester enolates derived from saturated and unsaturated carboxylic acids to tricarbonylchromium complexes of aryl ethers: dearomatizing cyclization to lactones

Article abstract of DOI:10.1016/S0022-328X(00)00848-2

Potassium enolates derived from saturated and unsaturated bis(trimethylsilyl) ketene acetals react with tricarbonylchromium complexes of anisole and diphenylether to give, in addition to α-arylcarboxylic acids, the mono addutcts, lactones, arising from a double exo nucleophilic addition. The latter were not observed in the case of benzenetricarbonylchromium. The intermediate dienol ethers could be isolated and fully characterized by X-ray crystallography. The influenece of the nature of the substituents on the ketene acetals, of the nature of the oxidant, and of the nature of the ester enolates on the course of the reaction has been established and will be discussed.

Full text of DOI:10.1016/S0022-328X(00)00848-2

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Journal of Organometallic Chemistry 621 (2001) 284–298
Meta, para and meta, ortho double exo nucleophilic additions of
trimethylsilylester enolates derived from saturated and unsaturated
carboxylic acids to tricarbonylchromium complexes of aryl ethers:
dearomatizing cyclization to lactones
Henri Rudler a,*, Virginie Comte a, Eva Garrier a,c, Moncef Bellassoued c,
Evelyne Chelain c, Jacqueline Vaissermann b
a Laboratoire de Synthe`se Organique et Organome´tallique, Uni6ersite´ Pierre et Marie Curie, 4 place Jussieu, UMR 7611, T 44-45, 75252 Paris,
Cedex 5, France
b Laboratoire de Chimie Inorganique et Mate´riaux Mole´culaires, Uni6ersite´ Pierre et Marie Curie, 4 place Jussieu, ESA 7071, 75252 Paris,
Cedex 5, France
c Laboratoire de Synthe`se Organome´tallique associe´ au CNRS, Uni6ersite´ de Cergy-Pontoise, 5 Mail Gay Lussac, Neu6ille-sur-Oise,
95031 Cergy-Pontoise, Cedex, France
Received 2 August 2000; accepted 14 September 2000
Abstract
Potassium enolates derived from saturated and unsaturated bis(trimethylsilyl) ketene acetals react with tricarbonylchromium
complexes of anisole and diphenylether to give, in addition to a-arylcarboxylic acids, the mono adducts, lactones, arising from a
double exo nucleophilic addition. The latter were not observed in the case of benzenetricarbonylchromium. The intermediate
dienol ethers could be isolated and fully characterized by X-ray crystallography. The influence of the nature of the substituents
on the ketene acetals, of the nature of the oxidant, and of the nature of the ester enolates on the course of the reaction has been
established and will be discussed. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Potassium enolates; Tricarbonylchromium complexes; Aryl ethers; Dearomatization; Dienol
3 via the formation of a carbonꢀcarbon single bond
1. Introduction
between
an
unsaturated
fragment
and
a
R3R4CHꢀCOOH group. This was followed by a cata-
lytic oxidation–cyclization with H2O2/MTO leading to
the formation of a carbonꢀoxygen bond and generating
d-hydroxy-g-lactones 4 (Eq. (1)).
Cyclofunctionalization reactions are very important
for the construction of elaborate molecules [1,2].
Among them, one can cite the formation of lactones by
the successive introduction of the RCH2COOH group
on an organic fragment containing a carbonꢀcarbon
double bond, followed by a cyclization reaction.
Recently, we described two approaches to lactones
involving such reactions [3–5]. First, a two-step cata-
lytic process, involving the interaction of p-allyl com-
plexes of palladium obtained from the allylic acetates 1
with bis(trimethylsilyl) ketene acetals 2 [6], which gave
(1)
Overall, and assuming that the first step occurs via an
SN2% reaction, this can be considered as a double nucleo-
philic addition of a dianion originating from a car-
boxylic acid to a carbonꢀcarbon double bond (Eq. (2)).
* Corresponding author. Tel.: +331-44-276197; fax: +331-44-
277089.
E-mail address: rudler@ccr.jussieu.fr (H. Rudler).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(00)00848-2

H. Rudler et al. / Journal of Organometallic Chemistry 621 (2001) 284–298
285
acetals bearing an extra carbonꢀcarbon double bond
towards tricarbonylchromium complexes of benzene,
anisole, and diphenylether.
(2)
A one pot, two-step stoichiometric sequence involving
arenetricarbonylchromium complexes 7 and enolates of
trimethylsilyl esters obtained from 2 and t-BuOK also
results in lactones. In this case, the first step involved is
a well documented, nucleophilic addition of enolates to
arenetricarbonylchromium [7–10] and is useful in the
synthesis of elaborate organic molecules. In the second
step, iodine was used as an oxidizing agent for the
demetallation of the organic substrates. Whereas in the
case of complexes of non-functionalized aromatic
derivatives the expected a-arylcarboxylic acids 6 were
obtained in high yield, surprisingly for the anisole
complex, the formation of tetrahydrobenzofuran-2,5-
diones 11 was observed via a dearomatization reaction,
double nucleophilic addition on an aromatic car-
bonꢀcarbon double bond and subsequent hydrolysis
(Eq. (3)).
2. Results and discussion
2.1. Isolation and characterization of dienol ethers.
The case of anisole
According to preliminary experiments [3,4], it was
concluded that success in the formation of lactones was
intimately linked to the nature of the substituents on
the starting ketene acetals 2; satisfactory yields of lac-
tones were observed from the acetal derived from cyclo-
hexanecarboxylic acid. Indeed, reduction of the size of
the substituents progressively suppressed the formation
of the lactones. This was demonstrated and confirmed
by the reaction of ketene acetal 2a bearing only a
methyl group with complex 7 which led to a single
product, the expected a-arylcarboxylic acid 8a in 48%
yield (Eq. (5)).
(3)
(5)
In the case of the formation of the lactones, to
confirm that indeed a double addition on the meta, para
positions of this complex took place, we attempted to
isolate the dienol ethers 9, the surmized precursors of
the lactones, and proceeded as follows. A THF solution
of anisoletricarbonylchromium (7) was treated with 1.5
equivalents of bis(trimethylsilyl) ketene acetal (2b),
derived from cyclohexanecarboxylic acid in the pres-
ence of a slight excess of t-BuOK (THF solution, 1.1
equivalents/2b), and DMF, at −70°C, then at −30°C
for 3 h. Addition of an excess of iodine in THF (5
equivalents/7) to the cloudy brownish solution, at
−70°C, followed by warming to room temperature and
stirring overnight gave, after treatment with sodium
dithionite to remove the excess of iodine and extraction
with diethyl ether, an oil which was chromatographed
on silica gel. Elution with P.E.–diethyl ether (98:2) led
to a white solid which was recrystallized in hexane–
dichloromethane to give the dienol ether 9b (36%, m.p.
Similarly, this methodology can be considered as a
double nucleophilic addition of a carboxylic acid dian-
ion, in this case, to a carbonꢀcarbon double bond of an
aromatic system with the formation of vicinal car-
bonꢀcarbon and carbonꢀoxygen bonds (Eq. (4)).
(4)
1
The purpose of this paper is first to demonstrate that
the formation of these lactones takes place via dienol
ethers which could be isolated and fully characterized in
the case of both anisole and diphenylether [11]. Sec-
ondly, to determine the structural features and the
conditions which drive the reaction towards the forma-
tion of these lactones (structure of the enolates and
nature of their substituents, nature of the oxidizing
agents) and finally, to examine the behaviour of ketene
75°C) which could be fully characterized by its H- and
1
13C-NMR data. The H-NMR spectrum disclosed sig-
nals for the three olefinic protons at l 5.97(dd),
5.91(dd), 4.50(m), and for the two protons at the ring
junction at l 5.06 and 3.21, together with a signal for
the methoxy group at l 3.55. From the mother liquor,
the second minor dienol ether 10b could be isolated as
1
an oil (B1%). Its H-NMR spectrum confirmed again
the presence of three olefinic protons at l 5.91 (ddd),

286
H. Rudler et al. / Journal of Organometallic Chemistry 621 (2001) 284–298
5.30 (dd) and 5.11(d) ppm, of the two protons at the
ring junction at l 4.85 and 3.25 ppm, and the singlet for
the methoxy group at l 3.59. Elution with P.E.–diethyl
ether (90/10) gave the acid 8b (5%) and finally with
P.E.–diethyl ether (20/80), the lactone 11b (8%) (Eq.
(6)).
2.2. Interaction of benzenetricarbonylchromium complex
with enolates deri6ed from crowded ketene acetals
(R3=H, R4=t-Bu, R3R4ꢁC5H10): exclusi6e high yield
formation of h-arylcarboxylic acids in high yield
We earlier observed that tricarbonylchromium com-
plexes derived from benzene led only to a-arylcar-
boxylic acids. We have now confirmed that even with
the most crowded ketene acetals, no products originat-
ing from a double nucleophilic addition were formed.
Thus, the ketene acetals 2b and 2d derived from cyclo-
hexanecarboxylic and t-butylacetic acid gave the ex-
pected acids 6b and 6d (Eq. (8)).
(6)
(8)
According to this result, a first prerequisite for the
formation of lactones appeared thus to be the presence
of an ether linkage in the starting complex.
Two observations have to be made at this point:
“ When the extraction was carried out as above and
the ethereal layer washed with dilute HCl, then only
the tetrahydrobenzofuran-2,5-dione 11b was isolated
in 51% yield together with 5% of the arylcarboxylic
acid 8b. The NMR data of these compounds were
fully consistent with their structures.
“ Such behaviour was also observed in the case of the
t-Bu-substituted ketene acetal 2d. In the case of the
ortho methylanisole complex, only the lactone 11%c
arising from the meta, ortho di-addition of the eno-
late derived from 2c was isolated, in low yield, the
2.3. Reaction of diphenylether complex with ketene
acetals
As already described, the behaviour of the complex
of diphenylether 12 paralleled that of the complex of
benzene, since even with moderately crowded enolates,
only arylcarboxylic acids of the type 13 were obtained.
Thus, complex 12 led to 13a, the well-known non-
steroidal anti-inflammatory drug fenoprofen in 79%
yield. Similar results were obtained from this complex
and a series of other ketene acetals (Eq. (9)).
(9)
However, a careful examination of the reaction mix-
ture obtained upon interaction of this complex with the
ketene acetal 2c (R3=H, R4=i-Pr) allowed us to
detect small amounts of the lactone 11c (B5%). Thus it
appeared clearly that even for this arylether, a double
nucleophilic addition could take place, albeit to a very
low extent, to give upon cleavage of the ether linkage a
conjugated ketone.
corresponding dienol ether being unstable under the
conditions used for the work up procedure (Eq. (7)).
(7)

H. Rudler et al. / Journal of Organometallic Chemistry 621 (2001) 284–298
287

288
H. Rudler et al. / Journal of Organometallic Chemistry 621 (2001) 284–298
Fig. 2. X-ray structure of 14d.
This interesting observation prompted us to examine
the most polar compound, obtained as a white solid in
11% yield, could be identified by its physical data to the
previously isolated lactone 11d and results from the
hydrolysis of the dienol ether 15d.
the behaviour of complex 12 towards the more crowded
ketene acetals 2d and 2b. The interaction of 2d with
complex 12 under the same conditions used for the
complex of anisole led surprisingly to four compound
after oxidative cleavage, two of moderate polarity, and
two of higher polarity.
Table 1
X-ray data for 14d (C17H16O3)
The two less polar compounds formed, respectively,
in 43 and 17% yield could be partially separated by
silica gel chromatography. The elemental analysis as
well as the NMR data of the less polar products were in
agreement with the structures 14d and 15d. Extensive
1H- and 13C-NMR spectroscopic techniques allowed the
assignment of all the signals. Thus, for the major
Formula weight
Crystal system
Space group
268.3
Monoclinic
P21/n
Unit cell dimensions
,
a (A)
5.409(3)
42.493(13)
6.643(4)
90
107.91(4)
90
1450(1)
4
0.78
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
V (A )
1
product 14d, the H-NMR spectrum (Fig. 1) disclosed
signals at l 7.28–7.00 for the five aromatic protons, at
l 5.69 (ddd), 5.18 (dd) and 5.01 (d) for the three
protons of the diene, at l 5.10 (d) and 3.38 (dddd) for
the two protons at the ring junction and at l 2.32 for
the proton on the carbon bearing the t-butyl group.
Crystals of this compound suitable for an X-ray
3
,
Z
Linear absorption coefficient v (cm−1
)
Density z (g cm−3
)
1.23
Diffractometer
CAD4
Enraf–Nonius
Mo–Ka
analysis
could
be
grown
from
hexane–
Radiation
dichloromethane. The molecular structure shown in
Fig. 2, confirmed the NMR data and thus the double
meta, ortho addition of the enolate with formation of a
g-lactone and a dienol ether. The X-ray data can be
found in Table 1.
,
(u=0.71069 A)
ꢀ/2q
Scan type
Scan range (°)
q Limits (°)
0.8+0.345 tgq
1–28
Temperature of measurement
Octants collected
Number of data collected
Number of unique data collected
295 K
0, 7; 0, 55; −8, 8
3907
The slightly more polar compound was assigned as
1
15d according to its NMR data. The H-NMR spec-
3488 (Rint=0.03)
trum disclosed signals, in addition to those for the
aromatic protons, at l 5.95 (dd), 5.83 (dd), and 4.74
(m) for the three protons of the diene, at l 5.13 (ddd)
and 3.23 (ddd) for the protons at the ring junction (Fig.
3).
Number of unique data used for refinement 1648
(Fo)2\3|(Fo)2
R=ꢀꢁꢁFoꢁ−ꢁFcꢁꢁ/ꢀꢁFoꢁ
Rw*=[ꢀw(ꢁFoꢁ−ꢁFcꢁ)2/ꢀwFo2]1/2 a
S
0.0544
0.0674
1.00
Extinction parameter
142
This product thus originates from a meta, para dou-
ble nucleophilic addition to the aromatic ring. The third
product, isolated in 17% yield as white crystals, corre-
sponds to the expected a-arylcarboxylic acid 13d result-
ing from a single nucleophilic addition of the enolate of
t-Butyl acetic acid on the chromium complex. Finally,
Number of variables
183
−0.16
0.18
−3
,
Dz min (e A
)
)
−3
,
Dz max (e A
a *w=w%[1−((ꢁꢁFoꢁ−ꢁFcꢁꢁ)/6|(Fo))2]2 with w%=1/ꢀrArTr(X) with 3
coefficients 8.48, 2.40 and 6.62 for a Chebyshev Series, for which X is
Fc/Fc(max).

H. Rudler et al. / Journal of Organometallic Chemistry 621 (2001) 284–298
289
Fig. 3. 1H-NMR spectrum of 15d (CDCl3, 400 MHz).
Surprisingly, in the reaction of acetal 2b with com-
plex 12, the mono-addition product 13b was the only
product obtained in 58% yield.
(10)
However, when the same reaction was carried out
starting from the corresponding trimethylsilylester 18b
this led to two compounds, the expected carboxylic acid
8b (5%) together with the lactone 11b (30%).
2.4. Influence of the structure of the enolates on the
course of the reaction: importance of the trimethylsilyl
group for the formation of the lactones
Interestingly, the dianion of cyclohexanecarboxylic
acid, which can be obtained from the corresponding
acid and LDA did not react at all with the complex of
anisole, even though the use of such dianions as enolate
equivalents is well documented [12] (Eq. (11)).
The nucleophilic addition of enolates derived from
carboxylic acid esters on arene tricarbonylchromium
complexes leading to a-arylcarboxylic esters is a well
established reaction [7–10]. No side products arising
from a double nucleophilic addition have, to the best of
our knowledge, been detected so far.
We confirmed this by carrying out a reaction involv-
ing the enolate of methylcyclohexanecarboxylate gener-
ated from the ester 16 and LDA, and complex 7. Under
the same conditions as above and as described in the
literature, only the expected arylester 17 could be iso-
lated after work up in 65% yield: no lactone even in
trace amounts could be detected (Eq. (10)).
(11)

290
H. Rudler et al. / Journal of Organometallic Chemistry 621 (2001) 284–298
It appears, therefore, that the trimethylsilyl ester
linked to oxygen is clearly indicated by three signals in
the 13C-NMR spectrum at l 147.3, 142.2 and 139.6.
Taken together, all these data agreed with the postu-
lated structure 19b (Eq. (13)).
group was able to interact as a nucleophile with the
aromatic ring during the oxidation step with formation
of a carbonꢀoxygen bond while a common alkoxy ester
was not, a result which confirms the beneficial influence
of the TMS group.
2.5. Influence of the nature of the oxidant
(13)
According to the early work of Semmelhack [13],
oxidants different from iodine could also be used to
carry out the final demetallation step after the nucleo-
philic additions to arene tricarbonylchromium com-
plexes. Among them, Fe(III) and Ce(IV) salts are re-
ported to give the best results.
Since the second step of the reactions leading to
lactones is the formation of a carbonꢀoxygen bond and
is likely to be induced by the oxidation of the metal, we
used, besides iodine, two other oxidants for the reaction
between anisoletricarbonylchromium and the ketene
acetal 2b, (Fe(DMF)3Cl2)(FeCl3) and Ce(NH4)2(NO3)6
(CAN). Surprisingly, in the latter two cases, only trace
amounts of the lactone 11b were detected, the main
product of the reaction is the arylcarboxylic acid 8b
(Eq. (12)).
That 19b probably originated from the enol ether 9b,
and is thus an over-oxidized product confirmed by the
following experiment: the oxidation of the dienol ether
9b in the presence of CAN as above led to a 1:3 mixture
of 19b and the lactone 11b.
The exact mechanism of this transformation,
which combines an aromatization, a demethylation
and a hydroxylation step, is still a matter of specula-
tions although demethylation–oxidation reactions
of methoxybenzenes by means of CAN are known
[14].
(12)
In the case of CAN, small amounts (8%) of a second
product having almost the same polarity as the lactone
11b was isolated. This new product was fully character-
ized by its spectroscopic data.
2.6. Reaction of arene tricarbonyl chromium complexes
with unsaturated ketene acetals: formation of
unsaturated arylcarboxylic acids and also of a
tetrahydrobenzofuran-1,5-dione containing an
unsaturated side chain
From analysis of mass spectra and NMR data, this
compound was determined to be 19b, an a-ortho-diphe-
1
nol containing a lactone. Both the H- and 13C-NMR
Having established the limitations of the addition of
enolates derived from various bis(trimethylsilyl) ketene
acetals and having discovered an unprecedented double
nucleophilic addition on a carbonꢀcarbon double bond
of aromatic ethers, we focused attention on the addi-
tion of enolates derived from unsaturated bis(trime-
thylsilyl) ketene acetals 20 which are easily synthesized
from the corresponding unsaturated carboxylic
acids[15], to a series of arenetricarbonylchromium com-
plexes. It is indeed known that enolates originating
from such ketene acetals behave like nucleophiles to-
wards aldehydes and ketones to give unsaturated d-
spectra confirmed the presence of the g-lactone but also
the absence of an extra carbonyl group and of the
methoxy group. Of significance were also the signals for
two vicinal olefinic protons at l 6.75 and 6.49 as two
doublets and of a broad signal at l 5.60 corresponding
to two protons, which split into two broad signals in
benzene. No other signals but those for the cyclohexyl
group appeared in the spectrum. According to the mass
spectrum, four oxygen atoms are present in the
molecule: besides the two oxygen atoms of the lactone,
two oxygen atoms belonging to two phenols are thus
required. The presence of three quaternary carbons

H. Rudler et al. / Journal of Organometallic Chemistry 621 (2001) 284–298
291
Table 2
As shown in Table 2 (entries 1–4), the expected conju-
gated arylcarboxylic acids 21 were obtained in satisfac-
tory yields in all the cases but for 21c (entry 3).
Conjugated arylcarboxylic acids 21a–23d from 20a–d
Entry
Compound R1
R2
R3 R4
X
Yield%
Under similar conditions, the same trend was ob-
served for the complex 12 derived from diphenylether.
The molecular structure of 23c was confirmed by an X-
ray analysis. Fig. 4 shows the meta addition of the eno-
late originating from 22c, via its g-carbon (Table 3).
However, in neither case did we observe, under these
conditions, products arising from a double nucleophilic
addition which indeed could only be formed upon an a-
enolate addition reaction. Finally we examined the be-
haviour of anisoletricarbonylchromium: again, a 41% of
the expected acid 22b was obtained from 20b. Since small
amounts of branched arylcarboxylic acids were only ob-
served at low temperature, we repeated several reactions
with the complexes derived from benzene and the
arylethers under such conditions. Thus reaction of the
acetal 20c with complex 5 gave the vinyl arylcarboxylic
acid 24. Similarly, with complex 7, besides the acid 25
(23%), a minor more polar product (15%) could be de-
tected. Its NMR data were akin to those of the bicyclic
compounds isolated so far and clearly indicating the
presence of a lactone and a cyclohexenone (Eq. (15)).
1
2
3
4
5
6
7
8
9
21a
21b
21c
21d
22b
23a
23b
23c
23d
H
Me
H
H
Me
H
Me
H
H
H
H
Me
H
H
H
H
Me
H
H
H
H
H
H
H
H
H
H
H
H
H
Me
H
H
H
H
Me
H
H
H
H
OMe
OPh
OPh
OPh
OPh
41
59
14
43
41
47
50
16
47
hydroxy acids (unpublished results from these
laboratories). In turn, and in relation with the above
results, their interaction with arenetricarbonylchro-
mium complexes might thus lead to arylacrylic acids 21–
23 which can be considered as precursors of important
pesticides [16].
We first examined the feasibility of such a transforma-
tion by reacting a series of unsaturated ketene acetals 20
with benzenetricarbonylchromium 5. Optimization of
the reaction conditions was achieved on the substrate
20a (R1=R2=R3=H). It appeared clearly that the best
yields of acids were obtained by using a slight excess of
acetal and by keeping the reaction mixture, before the
oxidation step, at room temperature for 5 h. Interest-
ingly, though the yields of addition products were low at
−35°C, products due to a 1,2-addition reactions, giving
branched unsaturated carboxylic acids, were detected
(Eq. (14)).
(15)
(14)
Fig. 4. X-ray structure of 23c.

292
H. Rudler et al. / Journal of Organometallic Chemistry 621 (2001) 284–298
Table 3
3. Discussion
X-ray data for 23c (C18H20O3)
The initial goal of these investigations was to synthe-
Formula weight
Crystal system
Space group
284.35
Triclinic
size a wide variety of saturated and unsaturated aryl-
carboxylic acids in order to test their possible biological
properties. This was achieved and additionally, we dis-
covered unexpectedly a direct, new type of carbonꢀ
carbon double bond difunctionalization of aromatic
systems, which appeared to be a double nucleophilic
exo addition reaction. This broadened even more the
scope of our approach since besides the a-arylcar-
boxylic acids, g-lactones were formed, the biological
properties of which are well-established [17].
(
P1
Unit cell dimensions
,
a (A)
8.469(3)
,
b (A)
10.491(2)
10.527(2)
117.11(2)
107.07(2)
96.42(2)
762.0(4)
2
0.78
1.24
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
Linear absorption coefficient v (cm−1
)
To summarize, both reactions have a common fea-
ture which is not new: the interaction of a nucleophile
with an arenetricarbonylchromium complex with the
formation of a carbonꢀcarbon bond.
Density z (g cm−3
Diffractometer
Radiation
)
CAD4 Enraf–Nonius
Mo–Ka (u=0.71069
,
A)
Scan type
Scan range (°)
q Limits (°)
Temperature of measurement
Octants collected
ꢀ/2q
The originality stems from two points:
0.8+0.345 tgq
1–26
295 K
0, 10; −12, 12; −12,
“ the use of bis(trimethylsilyl) ketene acetals to gener-
ate the enolates of TMS esters. This constitutes a
very clean and efficient approach to these intermedi-
ates since it has been shown in these laboratories
that they are formed in high yield upon the interac-
tion of the acetals with t-BuOK in THF. Confirma-
tion of this came from the results of the interaction
of the enolates generated in this way with aldehydes
and ketones which led almost quantitatively to a or
g-hydroxyacids [17].
12
3199
2984
Number of data collected
Number of unique data collected
Number of unique data used for
refinement
1628 (Fo)2\3|(Fo)2
R=?ꢁꢁFoꢁ−ꢁFcꢁꢁ/?ꢁFoꢁ
0.0493
0.0597
1.13
none
192
R*=[?w(ꢁFoꢁ−ꢁFcꢁ)2/_wFo2]1/2 a
w
S
Extinction parameter
“ the arylcarboxylic acids are obtained directly in high
to moderate yield, in a sequence which avoids the
transformation of esters or nitriles into acids under
severe conditions.
Number of variables
−3
,
Dz min (e A
)
)
−0.17
0.19
−3
,
Dz max (e A
a *w=w’[1−((ꢁꢁFoꢁ−ꢁFcꢁꢁ)/6|(Fo))2]2 with w’=1/ꢀrArTr(X) with 3
coefficients 5.06, 0.622 and 3.43 for a Chebyshev Series, for which X
is Fc/Fc(max).
3.1. Mechanism of the formation of the
tetrahydrobenzofuran-2,5-diones
Moreover, and as required for such a structure, two
extra signals corresponding to two olefinic protons and
to a methyl group (l 5.22, 5.19 and 1.79, respectively)
One of the benefits of these investigations is the
unexpected formation of lactones by a two-step se-
quence that occurs in situ, thus intermediates need not
to be isolated.
The first step of the reaction is common to both types
of products: it leads to a new carbonꢀcarbon bond. The
second step, the formation of a carbonꢀoxygen bond, is
specific to some ketene acetals and arenetricar-
bonylchromium complexes.
1
were present in the H-NMR spectrum. Thus, all these
data agreed with the structure of 26, the product of the
di-addition reaction. A similar behaviour was observed
in the case of 7 and 12 with 20b, the major products
being in this case, respectively, the lactone 28 isolated in
21% yield and the acid 29 obtained in 58% yield.
The first step involves the formation of cyclohexadi-
enyl complexes of chromium upon addition of the
enolate originating from the ketene acetal. Classically,
such an intermediate can be oxidized by iodine to give,
upon an aromatization reaction, the arylester. It can
also be protonated by strong acids to give dienol ethers
and, upon hydrolysis, cyclohexenones [11]. In the first
sequence, the metal is oxidized and loss of a proton
accounts for the rearomatization reaction [13], which
probably occurs rapidly.
(16)

H. Rudler et al. / Journal of Organometallic Chemistry 621 (2001) 284–298
293
Of interest, in the second step is the structure and the
reactivity of the intermediate oxidized chromium com-
plex, which is likely to be a tricarbonylcyclohexadi-
enylchromium(II) complex. Analogous complexes of
iron are known, and according to the pioneering work
of Pearson, they undergo nucleophilic addition reac-
tions leading to diene complexes [18,19]. There exists,
therefore, two ways for the oxidized intermediate to
evolve:
“ a rearomatization leading to an arylcarboxylic acid
with loss of a proton according to c
“ an intramolecular nucleophilic addition of the oxy-
gen of the ester group according to a and b (Eq.
(17)).
profitable conformers and increases the population of
conformers which can undergo ring closure. Applied to
the present cases, this means that the dialkylated ester
and the carbon-termini of the cyclohexadienyl ligand
must be in close proximity and hence increasing the
probability of bond formation.
Obviously, this is the trend for the various enolates
subjected to the nucleophilic addition to anisoletricar-
bonylchromium—increasing the number and the size of
the substituents from methyl to spirocyclohexyl on the
pendant carboxylate chain did indeed increase the yield
of the lactones, a result which can be directly inferred
to these kinetic effects.
A similar situation prevails in the case of the complex
12. However, less clear-cut results are observed since
small amounts of the expected lactone are observed
from the acetal 2c (R3=i-Pr, R4=H), and no lactone
at all is formed when 2b is used; the most significant
observations occurred upon the interaction of 2d with
12 which led mainly to cyclized products, the two
dienol ethers 14d and 15d and the lactone 11d. These
results might be due to the interaction of the more
crowded phenoxy group of 12 with the various sub-
stituents in the intermediate 30 (Eq. (16)), a situation
which does not occur with the less sterically demanding
methoxy group. Similar considerations might also ex-
plain the site-selective additions observed for the two
arylethers—route a for anisole, while for diphenylether
route b is predominant.
As far as the influence of the various oxidants is
concerned, iodine as well as Fe(III) and Ce(IV) are
suitable for the formation of arylcarboxylic acids. How-
ever, for the formation of the lactones not only their
oxidizing power but also their Lewis acidity has to be
taken into account. We observed indeed that iodine did
not interact with the trimethylsilylesters. Such is not the
case for Fe(III) and Ce(IV) which are powerful Lewis
acids. Since they are used in excess during the demetal-
lation reactions, they can interact directly with the
nucleophilic centre of the ester group and thus prevent
the formation of the lactones according to the second
step of the reaction.
(17)
According to our results, path a and b do not exist
for complexes derived from benzene. It is thus likely
that the lifetime of the intermediate ionic species is too
short in these cases to allow the second addition reac-
tion to occur.
Consequently, since aromatic ethers evolve in both
directions, the presence of the heteroatom slows down
the rate of the aromatization reaction by stabilizing the
ionic intermediate; competition between aromatization
and a second intramolecular nucleophilic reaction can
then take place.
The addition of the nucleophile, the oxygen atom of
the ester group at either end of the cyclohexadienyl
ligand might then lead to a five-membered ring lactone,
a very favourable transformation.
Surprisingly, however, only trace amounts of lactone
were observed for R3=H and R4=Me. To increase
the yield of lactone might be possible only by increasing
the rate of the intramolecular cyclization with respect
to the rate of the aromatization.
Evolutions of this type are well documented for
related intramolecular cyclization reactions. Indeed, for
the formation of five and six-membered ring systems, a
beneficial effect is usually observed by the introduction
of substituents giving rise to the gem dialkyl or Thorpe-
Ingold effects [20], which has more recently been dis-
cussed by Bruice and Lightstone [21]. According to
these authors, in such intramolecular reactions geminal
substitution decreases the population of kinetically un-
4. Conclusions
The results reported here confirm that lactones can
be formed upon a double exo nucleophilic addition to
arene complexes of potential dinucleophiles generated
from bis(trimethylsilyl) ketene acetals and t-BuOK, to-
gether with a-arylcarboxylic acids, the mono-addition
products. This reaction is not limited to anisole, but has
been extended to diphenylether. Moreover, ketene ac-
etals bearing a supplementary unsaturation can be sub-
jected to the same type of transformations, leading,
respectively to unsaturated arylcarboxylic acids and in

294
H. Rudler et al. / Journal of Organometallic Chemistry 621 (2001) 284–298
a few cases to lactones bearing various vinyl groups.
Since we observe a highly specific formation of three
contiguous chiral centres during the formation of the
bicyclic lactones, we are focusing our efforts towards
the asymmetric version of these reactions.
5.3. Preparation of 8, 9, 10 and 11
A solution of anisole·Cr(CO)3 7 (2 g, 7.8 mmol) and
ketene acetal 2 (12.3 mmol) in THF (40 ml) was treated
at −70°C with a slight excess (1.1 equivalents) of a
THF solution of t-BuOK (1 M) in the presence of
DMF (15 ml). After 3 h at −30°C, the mixture was
cooled to −70°C and a solution of I2 (8.3 g, 4 equiva-
lents) was slowly added. The solution was then progres-
sively warmed to r.t. overnight. The mixture was
treated with an aqueous sodium dithionite solution,
rapidly extracted with Et2O and washed (water, brine).
After drying over Na2SO4, the solvent was removed in
vacuo to give 8a or a mixture of four products, which
were purified by silica gel chromatography. The aryl-
carboxylic acids 8 were eluted with PE–Et2O (90/10), a
mixture of 9 and 10 with PE–Et2O (80/20) and tetrahy-
drobenzofuran-2,5-diones 11 with PE–Et2O (40/60).
Complexes 8 and 11, except 8a, were isolated as white
crystals after recrystallization in a mixture of Et2O–
hexane for 8 and CH2Cl2–hexane for 11.
5. Experimental
5.1. General
All reactions were performed under a dry argon
atmosphere. Solvents were distilled from sodium–ben-
zophenone ketyl (diethyl ether, tetrahydrofurane),
phosphorus pentoxide (CH2Cl2) and saturated with ar-
gon. Silica gel (Merck, type 60, 0.063–0.200 mm was
used for column chromatography. 1H-NMR: Bruker
ARX-400 (400 MHz), DPX 250 (250 MHz), AC-200
(200 MHz). 13C-NMR: Bruker ARX-400 (100 MHz),
DPX-250 (60 MHz), AC-200 (50MHz). All NMR spec-
tra were recorded in CDCl3 unless stated otherwise with
CHCl3 as internal standard. MS and HRMS were
recorded on a JEOL MS 700. Melting points were
performed on a Reichert apparatus and are uncor-
The two compounds 9 and 10 were separated by
preparative thin layer chromatography (hexane–
AcOEt, 80/20) and recrystallized in a mixture of Et2O–
hexane.
rected. TLC: 0.25 mm Merck silica gel plates 60 F254
.
2-(3-methoxy-phenyl)-propionic acid 8a (yellow oil,
1
45% yield) [24]: H-NMR (CDCl3, 400 MHz) l 7.18 (t,
J
HH=7.6 Hz, 1H, H8), 6.85 (d, JHH=7.6 Hz, 1H, H7),
5.2. Preparation of 6
6.83 (s, 1H, H5), 6.75 (dd, JHH=7.6 and 2.6 Hz, 1H,
H9), 3.72 (s, 3H, OCH3), 3.66 (q, JHH=7 Hz, 1H, H2),
1.44 (dd, JHH=7 Hz, 3H, CH3); 13C-NMR (CDCl3,
100 MHz) l 181.5 (C1, CO), 160.2 (C6ꢀOCH3), 141.7
(C4), 130.2 (C8), 120.4 (C7), 113.9 (C5), 113.1 (C9), 55.6
(OCH3), 45.7 (C2), 18.5 (CH3). MS Calc. for C10H12O3,
180 (M+). Found 180.
A solution of benzene·Cr(CO)3 5 (1.07 g, 5 mmol)
and ketene acetal 2 (10 mmol) in THF (10 ml) was
treated at −70°C with a slight excess (1.1 equivalents)
of a THF solution of t-BuOK (1 M) in the presence of
DMF (6 ml). After 2 h at −35°C, the mixture is cooled
to −70°C and a solution of I2 (6.35 g, 5 equivalents)
was slowly added. The solution was then progressively
warmed to room temperature (r.t.) overnight. The mix-
ture was treated with aqueous sodium dithionite solu-
tion, rapidly extracted by Et2O and washed (brine,
water). After drying over Na2SO4, the solvent was
removed in vacuo to give 6 that was purified by chro-
matography with PE–Et2O (90/10).
1-phenyl-cyclohexanecarboxylic acid 6b (white solid,
45% yield, m.p. 113°C) [22]: 1H-NMR (CDCl3, 400
MHz) l 7.48–7.25 (m, 5H, Ph), 2.48 (m, 2H, cyclo-
hexyl), 1.80–1.50 (m, 7H, cyclohexyl), 1.30 (m, 1H,
cyclohexyl); 13C-NMR (CDCl3, 100 MHz) l 180.9 (C2),
142.0 (C Ph), 128.6, 127.0 and 126.2 (CH Ph), 50.5
(C1), 34.3, 25.6 and 23.6 (CH2). HRMS Calc. for
C13H17O2 (MH+) 205.1229. Found 205.1229.
1-(3-methoxy-phenyl)-cyclohexanecarboxylic acid 8b
(white crystals, 5% yield, m.p. 75°C): 1H-NMR (CDCl3,
400 MHz) l 7.27 (t, JHH=7.9 Hz, 1H, H7), 7.03 (m,
2H, H4 and H6), 6.79 (dd, JHH=7.9 and 2.5 Hz, 1H,
H8), 3.80 (s, 3H, OCH3), 1.80–1.22 (m, 10H, CH2);
13C-NMR (CDCl3, 100 MHz) l 180.9 (C1, CO), 159.7
(C5ꢀOCH3), 144.7 (C3), 129.5 (C7), 118.6 (C6), 112.7
(C4), 111.9 (C8), 55.2 (OCH3), 50.5 (C2), 34.4 (2C,
CH2), 25.5 (1C, CH2), 23.6 (2C, CH2). Anal. Calc. for
C14H18O3: C, 71.76; H, 7.75. Found: C, 71.62; H,
7.81%.
2-(3-methoxy-phenyl)-3,3-dimethyl-butyric acid 8d
(white crystals, 20% yield, m.p. 100°C): 1H-NMR
(CDCl3, 400 MHz) l 7.24 (t, JHH=8 Hz, 1H, H9), 7.0
(m, 2H, H6 and H8), 6.85 (dd, JHH=8 and 2 Hz, 1H,
H10), 3.82 (s, 3H, OCH3), 1.05 (s, 9H, C(CH3)3); 13C-
NMR (CDCl3, 100 MHz) l 179.0 (C1, CO), 159.1
(C7ꢀOCH3), 137.2 (C5), 127.7 (C9), 121.6 (C10), 114.9
(C6), 111.4 (C8), 60.5 (C2), 54.2 (OCH3), 34.4
(C(CH3)3), 27.2 (3C, C(CH3)3). Anal. Calc. for
C13H18O3: C, 70.24; H, 8.16. Found: C, 70.17; H,
8.28%.
3,3-dimethyl-2-phenyl-butyric acid 6d (white solid,
1
75% yield) [23]: H-NMR (CDCl3, 250 MHz) l 7.40–
7.20 (m, 5H, Ph), 3.37 (s, 1H, H2), 0.94 (s, 9H, CH3);
13C-NMR (CDCl3, 60 MHz) l 179.4 (C1), 135.5 (C Ph),
129.8, 127.7 and 127.0 (CH Ph), 61.5 (C2), 34.1 (C3),
27.6 (3 CH3).

H. Rudler et al. / Journal of Organometallic Chemistry 621 (2001) 284–298
295
3,3%-cyclohexyl-5-methoxy-3a,7a-dihydro-3H-benzo-
furan-2-one 9b (white crystals, 36% yield, m.p. 70°C):
1H-NMR (CDCl3, 400 MHz) l 5.97 (dd, JHH=10 and
2.1 Hz, 1H, H6), 5.91 (dd, JHH=10 and 4.5 Hz, 1H,
H7), 5.06 (dd, JHH=8.6 and 4.5 Hz, 1H, H7a), 4.50 (m,
1H, H4), 3.55 (s, 3H, OCH3), 3.21 (dd, JHH=8.6 and
3.5 Hz, 1H, H3a), 1.84–1.65 (m, 6H, CH2), 1.53–1.37
(m, 4H, CH2); 13C-NMR (CDCl3, 100 MHz) l 180.5
(C2, CO), 152.3 (C5ꢀOCH3), 128.6 (C6), 123.0 (C7), 89.7
(C4), 72.2 (C7a), 54.4 (OCH3), 46.7 (C3), 42.4 (C3a),
33.4, 30.1, 25.3, 22.5 and 22.2 (1C, CH2). Anal. Calc.
for C14H18O3: C, 71.76; H, 7.75. Found: C, 71.59; H,
7.92%.
3,3%-cyclohexyl-7-methoxy-3a,7a-dihydro-3H-benzo-
furan-2-one 10b (white crystals, traces): 1H-NMR
(CDCl3, 400 MHz) l 5.91 (ddd, JHH=9.6, 6.6 and 3
Hz, 1H, H5), 5.30 (dd, JHH=9.6 and 3 Hz,1H, H4),
5.11 (d, JHH=6.6 Hz, 1H, H6), 4.85 (d, JHH=8 Hz,
1H, H7a), 3.59 (s, 3H, OCH3), 3.25 (ddd, JHH=8, 3 and
3 Hz, 1H, H3a), 1.84–1.50 (m, 10H, CH2); 13C-NMR
(CDCl3, 100 MHz) l 179.3 (C2, CO), 151.7 (C7ꢀOCH3),
122.5 (C5), 115.1 (C4), 95.0 (C6), 73.9 (C7a), 54.2
(OCH3), 46.0 (C3), 43.5 (C3a), 32.0, 29.3, 24.2, 21.6 and
21.0 (1C, CH2). HRMS Calc. for C14H19O3 (MH+)
235.1334. Found 235.1334.
1.04 (s, 9H, C(CH3)3); 13C-NMR (CDCl3, 100 MHz) l
196.1 (C5, CO), 175.6 (C2, CO), 142.3 (C7), 131.5 (C6),
71.8 (C7a), 54.5 (C3), 39.5 (C4), 36.3 (C3a), 33.7
(C(CH3)3), 27.7 (C(CH3)3). Anal. Calc. for C12H16O3:
C, 69.21; H, 7.74. Found: C, 69.16; H, 7.80%.
5.4. Preparation of complexes 13, 14, 15 and 11
Under the same conditions as for the anisole com-
plex, the diphenylether complex (2 g, 6.54 mmol) re-
acted with ketene acetal 2d (12.3 mmol) to give, after
work up, a mixture of 13d, 14d, 15d and 11d. Chro-
matography on silica gel allowed separation of the
compounds in the following order of elution: first, a
mixture of 14d and 15d (PE–Et2O 97/3), then 13d as
white crystals (PE–Et2O 95/5) and finally 11d. Com-
plexes 14d and 15d were isolated pure as white crystals
after separation with preparative thin layer (hexane–
AcOEt, 90/10) and recrystallization in a mixture Et2O–
hexane.
1-(3-phenoxy-phenyl)-cyclohexanecarboxylic
acid
1
(13b) (white crystals, 55% yield, m.p. 148°C): H-NMR
(CDCl3, 400 MHz) l 7.38–6.88 (m, 9H, Ph), 2.47 (m,
2H, cyclohexyl), 1.79–1.26 (m, 8H, cyclohexyl); 13C-
NMR (CDCl3, 100 MHz) l 181.7 (C2), 157.4 and 157.2
(CꢀO),145.3 (C Ph), 129.8, 129.7, 123.3, 121.3, 118.8,
117.3 and 117.2 (CH Ph), 50.6 (C1), 34.3, 25.7 and 23.6
(CH2). MS Calc. for C19H20O3, 296 (M+). Found 296.
2-(3-phenoxy-phenyl)-3,3%-dimethyl-butyric acid (13d)
(white crystals, 17% yield, m.p. 106°C) : 1H-NMR
(CDCl3, 400 MHz) l 7.17–6.82 (m, 9H, Ph), 3.33 (s,
1H, H2), 0.93 (s, 9H, C(CH3)3); 13C-NMR (CDCl3, 100
MHz) l 178.1 (C1, CO), 156.2 (CꢀO), 155.6 (CꢀO),
136.6 (C5), 128.7 (2C), 127.9, 123.9, 122.1, 119.8, 117.8,
117.6 and 116.7 (9C, CH, Ph), 60.4 (C2), 33.4 (C3), 26.8
(3C, C(CH3)3). MS Calc. for C18H20O3, 284 (M+).
Found 284.
3-tert-butyl-7-methoxy-3a,7a-dihydro-3H-benzo-
furan-2-one 10d (colorless oil, 5% yield): 1H-NMR
(CDCl3, 400 MHz) l 5.89 (ddd, JHH=9, 6.6 and 3 Hz,
1H, H5), 5.20 (dd, JHH=9 and 3 Hz, 1H, H4), 5.14 (d,
J
HH=6.6 Hz, 1H, H6), 4.97 (d, JHH=9.6 Hz, 1H, H7a),
3.66 (s, 3H, OCH3), 3.37 (dddd, JHH=9.6, 3, 3 and 3
Hz, 1H, H3a), 2.37 (d, JHH=3 Hz, 1H, H3), 1.13 (s, 9H,
C(CH3)3); 13C-NMR (CDCl3 100 MHz) l 177.3 (C2,
CO), 152.5 (C7ꢀOCH3), 122.0 (C5), 121.9 (C4), 95.7
(C6), 76.5 (C7a), 57.4 (C3), 55.6 (OCH3), 39.9 (C3a), 34.3
(C(CH3)3), 27.9 (3C, C(CH3)3). HRMS Calc. for
C13H19O3 (MH+) 223.1334. Found 223.1334.
3,3%-cyclohexyl-3,3a,4,7a-tetrahydro-benzofuran-2,5-
dione 11b (white crystals, 8% yield, m.p. 72°C): 1H-
NMR (CDCl3, 400 MHz) l 6.88 (dd, JHH=10 and 4.6
Hz, 1H, H7), 6.19 (d, JHH=10 Hz, 1H, H6), 4.94 (ddd,
3,-tert-butyl-7-phenoxy-3a,7a-dihydro-3H-benzo-
furan-2-one (14d) (white crystals, 24% yield, m.p.
1
98°C): H-NMR (CDCl3, 400 MHz) l 7.28–7.00 (m,
5H, Ph), 5.69 (ddd, JHH=9.6, 6.6 and 2.6 Hz, 1H, H5),
J
HH=5.6, 4.6 and 1 Hz, 1H, H7a), 2.83 (ddd, JHH
=
5.18 (dd, JHH=9.6 and 3 Hz, 1H, H4), 5.10 (d, JHH
=
11.2, 5.6 and 5.6 Hz, 1H, H3a), 2.44 (dd, JHH=15.6 and
5.6 Hz, 1H, H4/4%), 2.30 (dd, JHH=15.6 and 11.2 Hz,
1H, H4/4%), 1.80–1.36 (m, 10H, CH2); 13C-NMR
(CDCl3, 100 MHz) l 197.4 (C5, CO), 179.4 (C2, CO),
140.8 (C7), 133.2 (C6), 70.4 (C7a), 48.5 (C3), 41.0 (C3a),
35.4 (C4), 31.9, 28.4, 25.4, 22.5 and 22.2 (1C, CH2).
Anal. Calc. for C13H16O3: C, 70.89; H, 7.32. Found: C,
70.70; H, 7.33%.
9.6 Hz, 1H, H7a), 5.01 (d, JHH=6.6 Hz, 1H, H6), 3.38
(dddd, JHH=9, 3.6, 3 and 2.6 Hz, 1H, H3a), 2.32 (d,
J
HH=3.6 Hz, 1H, H3), 1.07 (s, 9H, C(CH3)3); 13C-
NMR (CDCl3, 100 MHz) l 175.9 (C2, CO), 153.2
(CꢀO), 150.7 (CꢀO), 128.8 (2C, CH, Ph), 123.9 (C4),
122.2 (C5), 120.1, 119.9 and 116.9 (1C, CH, Ph), 100.8
(C6), 74.6 (C7a), 56.0 (C3), 38.8 (C3a), 33.0 (C(CH3)3),
26.5 (C(CH3)3, 3C). Anal. Calc. for C14H18O3: C, 76.03;
H, 7.09. Found: C, 75.86; H, 7.29%.
3 - tert - butyl - 3,3a,4,7a - tetrahydro-benzofuran - 2,5-
1
dione 11d (white crystals, 23% yield, m.p. 128°C): H-
3-tert-butyl-5-phenoxy-3a,7a-dihydro-3H-benzo-
1
NMR (CDCl3, 400 MHz) l 6.71 (dd, JHH=10.2 and 3
Hz, 1H, H7), 6.13 (d, JHH=10.2 Hz, 1H, H6), 5.02
(ddd, JHH=7.2, 3 and 1 Hz, 1H, H7a), 3.03 (m, 1H,
H3a), 2.60 (m, 2H, H4/4%), 2.10 (d, JHH=8 Hz, 1H, H3),
furan-2-one (15d) (colorless oil, 19% yield): H-NMR
(CDCl3, 400 MHz) l 7.27–6.89 (m, 5H, Ph), 5.95 (dd,
J
HH=10 and 2 Hz, 1H, H6), 5.83 (dd, JHH=10 and 4
Hz, 1H, H7), 5.13 (ddd, JHH=10, 4 and 2 Hz, 1H,

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H. Rudler et al. / Journal of Organometallic Chemistry 621 (2001) 284–298
H7a), 4.74 (m, 1H, H4), 3.23 (ddd, JHH=10, 5.6 and 5.6
Hz, 1H, H3a), 2.29 (d, JHH=5.6 Hz, 1H, H3), 0.99 (s,
9H, C(CH3)3); 13C-NMR (CDCl3, 100 MHz) l 177.1
(C2, CO), 155.3 (CꢀO), 149.5 (C5), 128.8 (2C), 125.1,
123.8, 122.8, 1118.2 (2C) and 106.3 (CH, Ph), 73.8
(C7a), 56.7 (C3), 36.9 (C3a), 33.9 (C(CH3)3), 27.9
(C(CH3)3, 3C). MS Calc. for C18H20O3, 284 (M+).
Found 284.
held at r.t. after addition of t-BuOK. The products
were isolated after the analogous work up.
4-phenyl-but-2-enoic acid (21a) (white solid, 41%
1
yield, m.p. 54°C) [25]: H-NMR (CDCl3, 400 MHz) l
7.39–7.19 (m, 6H, H3 and Ph), 5.85 (d, JHH=15.5 Hz,
1H, H2), 3.58 (d, JHH=6.7 Hz, 2H, H4); 13C-NMR
(CDCl3, 100 MHz) l 172.1 (C1, CO), 150.4 (C3), 137.3
(C5), 128.9 (2C), 128.8 (2C) and 126.9 (1C) (CH, Ph),
121.7 (C2), 38.6 (C4).
5.5. Preparation of 17
2-methyl-4-phenyl-but-2-enoic acid (21b) (white solid,
59% yield, m.p. 71°C) [26]: 1H-NMR (CDCl3, 400
MHz) l 7.39–7.10 (m, 5H, Ph), 7.08 (m, 1H, H3), 3.60
(d, JHH=7.6 Hz, 2H, H4), 1.94 (s, 3H, CH3); 13C-NMR
(CDCl3, 100 MHz) l 173.8 (C1, CO), 143.0 (C3), 138.7
(C5), 128.6 (2C, CH, Ph), 128.6 (2C, CH, Ph), 128.3
(C2), 126.6 (1C, CH, Ph), 35.1 (C4), 11.7 (CH3). Anal.
Calc. for C11H12O2: C, 74.98; H, 6.86. Found: C, 74.88;
H, 6.87%.
3-methyl-4-phenyl-but-2-enoic acid (21c) (white solid,
14% yield, m.p. 72°C) [27]: 1H-NMR (CDCl3, 250
MHz) l 7.38–7.18 (m, 5H, Ph), 5.75 (m, 1H, H2), 3.49
(s, 2H, H4), 2.16 (s, 3H, CH3); 13C-NMR (CDCl3, 100
MHz) l 171.8 (C1, CO), 161.5 (C3), 137.5 (C5), 129.2
(2C), 128.7 (2C) and 126.9 (1C) (CH, Ph), 116.7 (C2),
47.4 (C4), 19.0 (CH3).
To a solution of lithium diisopropylamide (7.95
mmol) in THF (10 ml)was added dropwise a solution of
carboxylic ester 16 (7.95 mmol) in THF (10 ml) at
−70°C. The solution was stirred for 30 min at −70°C
and was added slowly to a solution of anisole·Cr(CO)3
(1.3 g, 5.3 mmol) at −70°C THF (10 ml) and DMF
(10 ml). The mixture was stirred for 3 h at −30°C.
After treatment with I2 (4 equivalents), the solution was
allowed to warm to r.t. overnight and was worked up
as above. Complex 17 was isolated as a yellow oil after
purification by chromatography.
1-(3-methoxy-phenyl)-cyclohexanecarboxylic
acid
methyl ester (17) (yellow oil, 65% yield): 1H-NMR
(CDCl3, 400 MHz) l 7.16 (t, JHH=8 Hz, 1H, H7), 6.89
(t, 1H, JHH=8 Hz, H6), 6.86 (s, 1H, H4), 6.69 (dd,
4-phenyl-pent-2-enoic acid (21d) (white solid, 43%
yield, m.p. 45°C): 1H-NMR (CDCl3, 250 MHz) l 7.27–
7.12 (m, 6H, H3 and Ph), 5.75 (dd, JHH=15.6 and 1.4
Hz, 1H, H2), 3.59 (m, 1H, H4), 1.38 (d, JHH=7Hz, 3H,
CH3); 13C-NMR (CDCl3, 60 MHz) l 172.0 (C1, CO),
155.7 (C3), 143.3 (C6), 129.1 (2C), 127.7 (2C) and 127.2
(1C) (CH, Ph), 119.7 (C2), 42.15 (C4), 20.4 (CH3).
4-(3-methoxy-phenyl)-2-methyl-but-2-enoic acid (22b)
J
HH=8 and 2.5 Hz, 1H, H8), 3.72 (s, 3H, COOCH3),
2.41–2.37 (m, 2H, CH2), 1.66–1.38 (m, 8H, CH2);
13C-NMR (CDCl3, 100 MHz) l 176.0 (C1, CO), 160.0
(C5ꢀOCH3), 154.9 (C3), 129.8 (C7), 118.6 (C6), 112.7
(C4), 111.9 (C8), 55.6 (OCH3), 52.45 5 (COOCH3),
51.32 (C2), 35.1 (2C), 25.9 and 24.1 (2C) (CH2). HRMS
Calc. for C15H21O3 (MH+) 249.1491. Found 249.1495.
1
(white solid, 41% yield, m.p. 48°C): H-NMR (CDCl3,
5.6. Preparation of 19b
400 MHz) l 7.26 (m, 1H, H9), 7.09 (m, 1H, H3), 6.80
(m, 2H, H8 and H10), 6.75 (m, 1H, H6), 3.82 (s, 3H,
OCH3), 3.55 (d, JHH=7.6 Hz, 2H, H4), 1.97 (s, 3H,
CH3); 13C-NMR (CDCl3, 100 MHz) l 173.6 (C1, CO),
159.9 (C7ꢀOCH3), 142.8 (C3), 140.2 (C5), 129.8 (1C,
CH, Ph), 127.8 (C2), 120.96, 114.3 and 111.8 (1C, CH,
Ph), 35.1 (C4), 12.2 (CH3). Anal. Calc. for C12H14O3: C,
69.89; H, 6.84. Found: C, 69.88; H, 6.92%.
4,5-dihydroxy-3,3%-cyclohexyl-3H-benzofuran-2-one
(19b) was obtained from complex 7 (4.4 mmol) and 2b
(6.6 mmol) upon oxidation with CAN (22 mmol) in
acetonitrile (55 ml) at −70°C; (white solid, 8% yield,
1
m.p. 101°C): H-NMR (CDCl3, 400 MHz) l 6.75 (d,
J
HH=8 Hz, 1H, H6 or H7), 6.50 (d, JHH=8 Hz, 1H,
H6 or H7), 5.60 (broad, 2H, OH), 2.31–1.36 (m, 10H,
CH2); 13C-NMR (CDCl3, 100 MHz) l 179.7 (C2, CO),
147.4, 142.2 and 139.6 (C4, C5 or C7a, CꢀO), 119.7
(C3a), 114.7 and 101.7 (C6 or C7), 47.2 (C3), 31.4 (2C),
25.3 and 20.9 (2C) (CH2). HRMS Calc. for C13H15O4
(MH+) 235.0970. Found 235.0970. This compound was
also obtained upon oxidation of 9b in acetonitrile with
CAN at r.t. for 12 h together with the lactone 11b and
identified by its NMR spectra.
4-(3-phenoxy-phenyl)-but-2-enoic acid (23a) (color-
less oil, 47% yield): 1H-NMR (CDCl3, 400 MHz) l
7.39–6.87 (m, 10H, H3 and Ph), 5.84 (d, JHH=15.6 Hz,
2H, H2), 3.54 (d, JHH=6.8 Hz, 2H, H4); 13C-NMR
(CDCl3, 100 MHz) l 172.1 (C1, CO), 157.7 (CꢀO),
157.1 (CꢀO), 149.9 (C3), 139.4 (C5), 130.1 (2C), 129.9
(2C), 123.7 (1C) and 123.5 (1C) (CH, Ph), 122.0 (C2),
119.3, 119.1 and 117.2 (1C, CH, Ph), 38.4 (C4). MS
Calc. for C16H14O3, 254 (M+). Found 254.
2-methyl-4-(3-phenoxy-phenyl)-but-2-enoic acid (23b)
1
5.7. Preparation of 21, 22 and 23
(white oil, 50% yield): H-NMR (CDCl3, 400 MHz) l
7.39–6.86 (m, 10H, H3 and Ph), 3.54 (d, JHH=7.6 Hz,
2H, H4), 1.96 (s, 3H, CH3); 13C-NMR (CDCl3, 100
MHz) l 173.6 (C1, CO), 157.5 (CꢀO), 157.1 (CꢀO),
The procedure is essentially the same as above with
saturated acetal except the reaction temperature was

H. Rudler et al. / Journal of Organometallic Chemistry 621 (2001) 284–298
297
142.5 (C3), 140.7 (C5), 130.0 (2C), 129.8 (2C), (CH,
Ph)), 128.1 (C2), 123.4 (2C), 119.0 (2C) and 116.9 (1C)
(CH, Ph), 34.9 (C4), 12.3 (CH3). Anal. Calc. for
C17H16O3: C, 76.10; H, 6.01. Found: C, 76.09; H,
6.15%.
(d, JHH=10.8 Hz, 1H, ꢁCHH%), 5.23 (d, JHH=17.4
Hz, 1H, ꢁCHH%), 5.23 (ddd, JHH=7.3, 2.9 and 1.5 Hz,
2H, H7a), 3.01 (ddd, JHH=7.3, 7.3 and 4.8 Hz,1H,
H3a), 2.66 (dd, JHH=17.4 and 7.3 Hz, 1H, H4/4%), 2.56
(dd, JHH=17.4 and 4.8 Hz, 1H, H4/4%), 1.42 (s, 3H,
CH3); 13C-NMR (CDCl3, 100 MHz) l 195.4 (C5), 177.6
(C2), 142.0 (C7), 134.1 (HCꢁ), 132.2 (C6), 119.1 (ꢁCH2),
71.7 (C7a), 49.3 (C3), 44.4 (C3a), 35.1 (C4), 22.5 (CH3).
HRMS Calc. for C11H13O3, 193.0865 (MH+). Found
193.0870.
3-methyl-4-(3-phenoxy-phenyl)-but-2-enoic acid (23c)
1
(white solid, 16% yield, m.p. 76°C): H-NMR (CDCl3,
400 MHz) l 7.39–6.88 (m, 9H, H3 and Ph), 5.74 (s, 1H,
H2), 3.46 (s 2H, H4), 2.16 (s, 3H, CH3); 13C-NMR
(CDCl3, 100 MHz) l 172.2 (C1, CO), 161.0 (C3), 157.5
(CꢀO), 157.1 (CꢀO), 139.5 (C5), 130.0 (2C), 129.9 (2C),
124.1, 123.4, 119.8, 119.0 and 117.2 (CH, Ph), 117.1
(C2), 47.1 (C4), 19.1 (CH3). MS Calc. for C17H16O3, 268
(M+). Found 268.
2-methyl-2-(3-phenoxy-phenyl)-but-3-enoic acid (29)
1
(colorless oil, 58% yield): H-NMR (CDCl3, 400 MHz)
l 7.38–6.89 (m, 9H, Ph), 6.42 (dd, JHH=17.6 and 10.6
Hz, 1H, H3), 5.36 (d, JHH=10.6 Hz, 1H, H4/4%), 5.24 (d,
4-(3-phenoxy-phenyl)-pent-2-enoic acid (23d) (white
J
HH=17.6 Hz, 1H, H4/4%), 1.69 (s, 3H, CH3); 13C-NMR
1
solid, 47% yield): H-NMR (CDCl3, 400 MHz) l 7.38–
(CDCl3, 100 MHz) l 180.9 (C1, CO), 157.3 (CꢀO),
157.1 (CꢀO), 144,8 (Cq, Ph),140.1 (C3), 129.8, 123.4,
121.6, 118.8, 117.7, 117.3 (CH, Ph), 115.8 (C4), 53.6
(C2), 23.2 (CH3). HRMS Calc. for C18H21O3, 285.1484
(M+CH+5 ). Found 285.1491.
6.86 (m, 10H, H3 and Ph), 5.82 (d, JHH=15.5 Hz, 1H,
H2), 3.64 (m, 1H, H4), 1.67 (d, JHH=6.5 Hz, 3H, CH3);
13C-NMR (CDCl3, 100 MHz) l 172.3 (C1, CO), 157.6
(CꢀO), 157.1 (CꢀO), 155.1 (C3), 145.1 (C6), 130.1,
129.9, 123.4 (2C) and 122.2 (CH,Ph), 119.7 (C2), 119.0
(2C), 118.0 and 117.1 (CH, Ph), 42.1 (C4), 20.1 (CH3).
HRMS Calc. for C17H16O3, 269.1173 (MH+). Found
269.1178.
6. Structure solution and refinement
3-methyl-2-phenyl-but-3-enoic acid (24) (white solid,
23% yield, m.p. 60°C) [28]: 1H-NMR (CDCl3, 400
MHz) l 7.38–7.28 (m, 5H, Ph), 5.06 (s, 1H, H4/4%), 4.96
(s, 1H, H4/4%), 4.36 (s,1H, H2), 1.79 (s, 3H, CH3);
13C-NMR (CDCl3, 100 MHz) l 178.5 (C1), 142.4 (C3),
136.6 (C Ph), 129.1, 128.9 and 128.0 (CH Ph), 114.8
(C4), 58.9 (C2), 22.1 (CH3). MS Calc. for C11H12O2, 176
(M+). Found 176.
For products 14d and 23c, accurate cell dimensions
and orientation matrices were obtained by least-squares
refinements of 25 accurately centred reflections. No
significant variations were observed in the intensities of
two checked reflections during data collection. Com-
plete data and collection parameters are listed in Table
2. Data was also collected for Lorentz and polarization
effects. Computations were performed by using the PC
version of CRYSTALS [30]. Scattering factors and correc-
tions for anomalous absorption were taken from Ref.
[31]. The structures were solved by Fo-Patterson tech-
nique or direct method (SHELXS [32]). Refinements were
carried out by full-matrix least squares. All non-hydro-
gen atoms were anisotropically refined, hydrogen atoms
were introduced in calculated positions. The drawing of
the molecules was carried out with the CAMERON pro-
gram [33].
2-(3-methoxy-phenyl)-3-methyl-but-3-enoic acid (25)
1
(colorless oil, 23% yield) [29]: H-NMR (CDCl3, 200
MHz) l 7.23 (m, 1H, H5%), 6.88 (m, 3H, H2%, H4% and
H6%), 5.03 (s, 1H, H4/4%), 4.95 (s, 1H, H4/4%), 3.79 (s, 3H,
OCH3), 1.76 (s, 3H, CH3); 13C-NMR (CDCl3, 50 MHz)
l 178.8 (C1), 158.8 (C3%), 142.0 (C3), 137.8 (C1%), 129.5
and 121.2 (CH Ph), 114.6 (C4), 114.5 and 112.9 (CH
Ph), 58.6 (C2), 55.2 (OCH3), 21.8 (CH3).
3-isopropenyl-3,3a,4,7a-tetrahydro-benzofuran-2,5-
dione (26) (white solid, 15% yield, m.p. 107°C): 1H-
NMR (CDCl3, 200 MHz) l 6.92 (dd, JHH=10 and 4.5
Hz, 1H,H7), 6.25 (d, JHH=10 Hz, 1H, H6), 5.22 (s, 1H,
ꢁCH2/2%), 5.19 (s, 1H, ꢁCH2/2%), 4.88 (m, 1H, H7a), 3.53
(d, JHH=7.1 Hz, 1H, H3), 3.19 (m, 1H, H3a), 2.26 (m,
2H, H4), 1.79 (s, 3H, CH3); 13C-NMR (CDCl3, 100
MHz) l 197.0 (C5), 173.7 (C2), 139.4 (C7), 135.1
(CꢁCH2), 133.8 (C6), 117.8 (ꢁCH2), 70.9 (C7a), 52.1
(C3), 37.2 (C4), 35.5 (C3a), 23.7 (CH3). HRMS Calc. for
C11H13O3, 193.0865 (MH+). Found 193.0865.
3-methyl-3-vinyl-3,3a,4,7a-tetrahydro-benzofuran-
2,5-dione (28) (white solid, 20% yield, m.p. 95°C):
1H-NMR (CDCl3, 400 MHz) l 6.83 (dd, JHH=10.4
and 2.9 Hz, 1H, H7), 6.15 (dd, JHH=10.4 and 1.5 Hz,
1H, H6), 5.68 (dd, JHH=17.4 and 10.8 Hz, HCꢁ), 5.27
7. Supplementary material
Fractional atomic coordinate anisotropic thermal
parameters for hydrogen and non-hydrogen atoms,
atomic coordinates for H atoms, complete lists of bond
distances and bond angles have been deposited with the
Cambridge Crystallographic data Centre, CCDC Nos
156560 for compound 14d and 156561 for compound
23c. Copies of the data may be obtained free of charge
from The Director, CCDC, 12 Union Road, Cam-
bridge CB2 1EZ, UK (Fax: +44-1223-336033; e-mail:
deposit@ccdc.cam.ac.uk or www: http://www.ccdc.
cam.ac.uk).

298
H. Rudler et al. / Journal of Organometallic Chemistry 621 (2001) 284–298
[14] P. Jacob, III, P.S. Callery, A.T. Shulgin, N. Castagnoli, Jr., J.
Acknowledgements
Org. Chem. Soc. 41 (1976) 3627.
[15] For the synthesis of unsaturated bis(trimethylsilyl)ketene acetals
see (a)W.T. Brady, M.O. Agho, J. Heterocycl. Chem. 20 (1963)
501. (b) M. Bellassoued, R. Enigrou, M. Gaudemar, J.
Organomet. Chem. 338 (1988) 149. (c) M. Bellassoued, R. Enni-
grou, M. Gaudemar, J. Organomet. Chem. 393 (1990) 19.
[16] J. Stetter, F. Lies, Angew. Chem. Int. Ed. Engl. 39 (2000) 1724
and references therein.
This research was supported by Centre National de
la Recherche Scientifique, MENRT, ANVAR and
AVENTIS-AGRO.
References
[17] R. Chamberlain, C. Koch, J. Org. Chem. 58 (1993) 2725.
[18] (a) A.J. Pearson, J. Chem. Soc. Chem. Commun. (1980) 488. (b)
A.J.Pearson, Chi Wi Ong, J. Org. Chem. 47 (1982) 3780. (c) A.J.
Pearson, A.R. Douglas, Organometallics, 17 (1998) 1448.
[19] M.-C.P. Yeh, L.W. Chuang, M.L. Lai, C.C. Chou,
Organometallics 16 (1997) 4435.
[20] G.S. Hammond, in: M.S. Newman (Ed.), Steric Effects on
Equilibrated Systems, Wiley, New York, 1956, p. 425.
[21] (a) F.C. Lightstone, T.C. Bruice, J. Am. Chem. Soc. 118 (1996)
2595. (b) T.C. Bruice, F.C. Lightstone, Acc. Chem. Res. 32
(1999) 127.
[22] S.N. Calderon, A.H. Newman, F.C. Tortella, J. Med. Chem. 34
(1991) 3159.
[23] C.F. Yao, K.H. Kao, J.T. Liu, C.M. Chu, Y. Wang, W.C. Chen,
Y.M. Lin, M.C. Yan, J.Y. Liu, M.C. Chuang, J.L. Shiue,
Tetrahedron 54 (1998) 791.
[24] W. Ku¨bler, O. Petrov, E. Winterfeldt, Tetrahedron 44 (1988)
4371.
[25] T.H. Black, Y. Zhang, J. Huang, D.C. Smith, B.E. Yates,
Synthetic Commun. 25 (1995) 15.
[26] R. Aumann, H.J. Weidenhaupt, Chem. Ber. 120 (1987) 23.
[27] M. Kuchar, B. Brunova, V. Rejholec, M. Jelinkova, J. Holubek,
O. Nemecek, Collect. Czech. Chem. Commun. 49 (1984) 122.
[28] R. Knorr, E. Lattke, Chem. Ber. 114 (1981) 2116.
[29] Sumimoto Chemical Co. Ltd. Ger. Offen. 2 335 347, 1974,
Japan, C.A. 80 (1974) 120746w.
[30] D.J. Watkins, C.K. Prout, J.R. Carruthers, P.W. Betteridge,
Crystals Issue 10, Chemical Crystallography Laboratory, Uni-
versity of Oxford, UK, 1966.
[1] See for example A.J. Pearson, S.L. Kole, T. Ray, J. Am. Chem.
Soc. 106 (1984) 6060 and references therein.
[2] For recent applications, see for example (a) S. Kudis, G. Helm-
chen, Tetrahedron, 54 (1998) 10449. (b) N. Gathergood, K.A.
Jorgensen, Chem. Commun. (1999) 1869. (c) C. Jonasson, M.
Ro¨nn, J.A. Ba¨ckvall, J. Org. Chem. Soc. 65 (2000) 2122 and
references cited therein.
[3] M. Bellassoued, E. Chelain, J. Collot, H. Rudler, J. Vaisser-
mann, Chem. Commun. (1999) 187.
[4] H. Rudler, V. Comte, M. Bellassoued, E. Garrier, J. Vaisser-
mann, J.C. Daran, C. R. Acad. Sci.Paris Serie IIc Chem. 3
(2000) 113.
[5] H. Rudler, A. Parlier, F. Cantagrel, P. Harris, M. Bellassoued,
Chem. Commun. (2000) 771.
[6] For the synthesis of bis(trimethylsilyl) ketene acetals see (a) C.
Ainsworth, Y.N. Kuo, J. Organomet. Chem. 46 (1973) 73. (b)
M. Bellassoued, M. Gaudemar, Tetrahedron Lett. 31 (1990)
209.
[7] M.F. Semmelhack, Ann. N.Y. Acad. Sci. 295 (1977) 36.
[8] G. Jaouen, Ann. N. Y. Acad. Sci. 295 (1977) 59.
[9] F. Rose-Munch, E. Rose, Curr. Org. Chem. 3 (1999) 445.
[10] E.P. Ku¨ndig, Pure Appl. Chem. 57 (1985) 1855.
[11] For the formation of dienol ethers from anisoletricar-
bonylchromium and enolates, upon protonation, see for example
(a) M.F. Semmelhack, A. Yamashita, J. Am. Chem. Soc. 102
(1980) 5924. (b) H.G. Schmalz, K. Schellhaas, Angew. Chem.
Int. Ed. Engl. 35 (1997) 2146. (c) A.J. Pearson, A.V.
Gontcharov, J. Org. Chem. 63 (1998) 152.
[31] D.T. Cromer, International Tables for X-ray crystallography,
vol. IV, Kynoch Press, UK, 1974.
[12] P.L. Creger, J. Am. Chem. Soc. 89 (1967) 2500.
[13] M.F. Semmelhack, H.T. Hall, Jr., R. Farina, M. Yoshifuji, G.
Clark, T. Bargar, K. Hirotsu, J. Clardy, J. Am. Chem. Soc. 101
(1979) 3535.
[32] G.M. Sheldrick, SHELXS-86, Program for Crystal Structure Solu-
tion, University of Go¨ttingen, 1986.
[33] D.J. Watkin, C.K. Prout, L.J. Pearce, Cameron Crystallography
Laboratory, University of Oxford, UK, 1996.
.