Synthesis and reactivity of cyclic and acyclic (1-(acyloxy)pentadienyl)Fe(CO)2LX and (1-alkoxypentadienyl)Fe(CO)2LX salts (L = CO, PPh3)

Article abstract of DOI:10.1021/om960336a

A variety of cyclic and acyclic [(pentadienyl)Fe(CO)₂L]X complexes (L = CO, PPh3) containing terminal acyloxy or alkoxy substituents have been prepared. In situ NMR studies indicate that for the acyclic series where L = CO, stability is limited by solvolysis reactions. The position of nucleophilic attack (ipso for alkoxy, internal for acyloxy) in the acyclic series indicates an electron-donating and electron-withdrawing nature for alkoxy and acyloxy substituents, respectively. In the cyclic series, the different regiodirecting powers of alkoxy and acyloxy groups provide access to regioisomeric substituted cyclohexadienyl salts. Crystal structures of the ψ-exo and ψ-endo stereoisomers of [5-(benzoyloxy)-2,4-hexadien-1-ol]Fe-(CO)₂PPh₃ (34 and 35) and of [(1,3,4,5-η)-1-(benzoyloxy)-2-methyl-3-pentene-1,5-diyl]Fe-(CO) ₂PPh₃ (57) have been determined.

Full text of DOI:10.1021/om960336a

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Organometallics 1996, 15, 4247-4257
4247
Syn th esis a n d Rea ctivity of Cyclic a n d Acyclic
(1-(a cyloxy)p en ta d ien yl)F e(CO)2LX a n d
(1-a lk oxyp en ta d ien yl)F e(CO)2LX Sa lts (L ) CO, P P h 3)
J ames A. S. Howell,* Andrew G. Bell, and Paula J . O’Leary
Chemistry Department, Keele University, Keele, Staffordshire ST5 5BG, Great Britain
G. Richard Stephenson,* Michelle Hastings, Philip W. Howard,
David A. Owen, and Andrew J . Whitehead
School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ , Great Britain
Patrick McArdle and Desmond Cunningham
Chemistry Department, University College, Galway, Ireland
Received May 7, 1996X
A variety of cyclic and acyclic [(pentadienyl)Fe(CO)2L]X complexes (L ) CO, PPh3)
containing terminal acyloxy or alkoxy substituents have been prepared. In situ NMR studies
indicate that for the acyclic series where L ) CO, stability is limited by solvolysis reactions.
The position of nucleophilic attack (ipso for alkoxy, internal for acyloxy) in the acyclic series
indicates an electron-donating and electron-withdrawing nature for alkoxy and acyloxy
substituents, respectively. In the cyclic series, the different regiodirecting powers of alkoxy
and acyloxy groups provide access to regioisomeric substituted cyclohexadienyl salts. Crystal
structures of the Ψ-exo and Ψ-endo stereoisomers of [5-(benzoyloxy)-2,4-hexadien-1-ol]Fe-
(CO)2PPh3 (34 and 35) and of [(1,3,4,5-η)-1-(benzoyloxy)-2-methyl-3-pentene-1,5-diyl]Fe-
(CO)2PPh3 (57) have been determined.
In tr od u ction
2-methoxy substituent is maintained in the acyclic
cation 3.4 Good regiocontrol, however, inevitably pre-
The efficient application of chiral electrophilic com-
plexes such as [(pentadienyl)Fe(CO)3]X salts in C-C
bond-forming reactions in asymmetric synthesis de-
pends on control of both regio- and stereoselectivity.1,2
Though the latter is usually guaranteed because of the
lateral coordination of the metal moiety, regioselectivity
has generally been controlled through the nature of the
substituent either on the pentadienyl ligand or on the
metal. Alkoxy substituents in particular have been
shown to exhibit high regiocontrol, promoting nucleo-
philic addition at C5 and C1 exclusively in complexes
11a and 2, respectively.3 This directing influence of the
X Abstract published in Advance ACS Abstracts, August 15, 1996.
(1) For reviews, see: (a) Pearson, A. J . Iron Compounds in Organic
Synthesis; Academic Press: London, 1994. (b) Gre´e, R.; Lellouche, J .
P. Advances in Metal-Organic Chemistry; Liebeskind, L. S., Ed.; J ai
Press: Greenwich, CT, 1995; Vol. 4, p 129. (c) Gre´e, R. Synthesis 1989,
341.
(2) For recent examples of applications in synthesis see: (a) Hachem,
A.; Toupet, L.; Gre´e, R. Tetrahedron Lett. 1995, 36, 1849. (b) Benvegnu,
T.; Schio, L.; Le Floch, Y.; Gre´e, R. Synlett 1994, 505. (c) Donaldson,
W. A.; Bell, P. T.; Wang, Z; Bennett, D. W. Tetrahedron Lett. 1994,
35, 5829. (d) Donaldson, W. A.; J in, M. J . Tetrahedron 1993, 49, 8787.
(e) Kno¨lker, H. J .; Baum, E.; Hoffmann, T. Tetrahedron Lett. 1995,
36, 5339. (f) Kno¨lker, H. J .; Baum, G.; Kosub, M. Synlett 1994, 1012.
(g) Kno¨lker, H. J .; El-Ahl, A. A.; Weingaertner, G. Synlett 1994, 194.
(h) McKillop, A.; Stephenson, G. R.; Tinkl, M. Synlett 1995, 669. (i)
Genet, J . P.; Hudson, R. D. A.; Meng, W. D.; Roberts, E.; Stephenson,
G. R.; Thorimbert, S. Synlett 1994, 631. (j) Franck-Neumann, M.;
Kastler, A. Synlett 1995, 61. (k) Roush, W. R.; Wada, C. K. J . Am.
Chem. Soc. 1994, 116, 2151.
cludes access to the alternative regioisomer series, thus
limiting synthetic applications if compounds from the
inaccessible regioisomer series are required. We wish
to report here our complete results5 on the preparation
and reactivity toward nucleophiles of cyclic and acyclic
1-acyloxy- and 1-alkoxy-substituted [(pentadienyl)Fe-
(CO)2L]X complexes (L ) CO, PPh3). The results
demonstrate a reversal of regioselectivity that offers
novel possibilities for complementary control strategies
in applications in asymmetric synthesis (since the
acyloxy and alkoxy series can be obtained from the same
precursors) and, for the acyloxy complexes, shows an
important variation in regioselectivity between the
cyclic and acyclic series.
(3) (a) Stephenson, G. R.; Howard, P. W.; Owen, D. A.; Whitehead,
A. J . J . Chem. Soc., Chem. Commun. 1991, 641. (b) Owen, D. A.;
Stephenson, G. R.; Finch, H.; Swanson, S. Tetrahedron Lett. 1990, 31,
3401. (c) Palatoi, I. M.; Stephenson, G. R.; Ross, W. J .; Tupper, D. E.
J . Organomet. Chem. 1989, 364, C11.
(4) Donaldson, W. A.; J in, M. J . Bull. Soc. Chim. Belg. 1993, 102,
297.
(5) For a preliminary communication, see ref 3a.
S0276-7333(96)00336-6 CCC: $12 00 © 1996 American Chemical Society

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4248 Organometallics, Vol. 15, No. 20, 1996
Howell et al.
Sch em e 1
acyclic as opposed to cyclic and of tricarbonyl as opposed
to dicarbonyl phosphine complexes has been noted by
other workers.7,8 The PPh3-substituted cation 23 does
undergo hydrolysis under more vigorous conditions,
though via deacylation to give a separable 7:1 mixture
of the (E)- and (Z)-pentadienal complexes 30 and 31.
Availability of the formyl derivatives 9-14 provides
potential access to 1-substituted dienyl salts via the
intermediacy of secondary alcohols produced by reaction
with Grignard or alkyllithium reagents. Thus, reaction
of 11 and 14 with MeMgI proceeds smoothly to yield
the separable diastereoisomeric Ψ-exo and Ψ-endo
products 32/33 and 34/35 in ratios of 1:1.3 and 2.1:1,
respectively (Scheme 3). The isolated yield of 1:3.3 for
32/33 is a result of more rapid decomposition of 32 on
chromatography. The change in the Ψ-exo/Ψ-endo
product ratio between tricarbonyl and dicarbonyl phos-
phine complexes has been observed previously in the
(sorbaldehyde)Fe(CO)2L series and may be associated
with the change in the s-cis/s-trans conformational
preference of the formyl moiety.9 Again, while proto-
nation of 34 proceeds cleanly to yield 36, no precipitates
are observed on protonation of either 32 or 33. Hy-
drolysis of 36 proceeds in a similar fashion as for 23 to
yield the separable (E,E)- and (E,Z)-(sorbaldehyde)Fe-
(CO)2PPh3 complexes 37 and 38, but in a ratio of 1:1.
(B) Cr ysta l a n d Molecu la r Str u ctu r es of 34 a n d
35. Reaction of (dienal)Fe(CO)3 complexes with Grig-
nard or alkyllithium reagents proceeds with poor ste-
reoselectivity in many cases to give Ψ-exo and Ψ-endo
mixtures which are usually easily separable. Crystal-
lographic determinations have confirmed the Ψ-exo or
Ψ-endo stereochemistry in several cases,2a,10a-c but we
are not aware of the structural characterization of both
diastereoisomers of the same complex.
The molecular structures of 34 and 35 (Figure 1)
confirm the assumed relative stereochemistries at iron
and C1. The staggered conformation at C1 relative to
the diene is in agreement with modeling predictions,11
with hydrogen occupying the most sterically demanding
position between the diene plane and the basal carbonyl.
The complexes exhibit the typical square-based-pyra-
midal structure of (diene)Fe(CO)2L complexes. While
35 crystallizes as a single basal phosphine isomer, the
solid-state structure of 34 contains an equimolar mix-
ture of axial and basal phosphine isomers. In both 35
and the basal isomer of 34, the phosphine occupies the
least sterically demanding basal position cis to the
benzoyloxy substituent, which is nearly coplanar with
the diene fragment.
Resu lts a n d Discu ssion
(A) Syn th esis. The cyclic cations 5 and 6 were
readily prepared as stable salts by alkylation or acyla-
tion of the easily available cyclohexadienone complex 4
(Scheme 1). Attempts to extend this to the acyclic series
were successful only in the acylation of (sorbaldehyde)-
Fe(CO)3 (7) to give 8 as a hygroscopic, unstable salt
which reverted easily to starting material on exposure
to moisture.
In order to improve stability and provide access to the
1-alkoxy series, an alternative synthetic strategy was
investigated in the acyclic series. NaBH4 reduction of
the 5-(acyloxy)- or 5-alkoxypentadienyl complexes 9-14
(all available inter alia from sodium glutaconaldehyde)6
gave the primary alcohol complexes 15-20 in good yield
(Scheme 2). The availability of 9-11 in homochiral
form may be noted.6 While protonation of the PPh3-
substituted complexes provided the pentadienyl salts
21-23 as yellow precipitates in good yield, no such
precipitates were observed in the cases of the tricarbonyl
analogues. Intermediacy of the required pentadienyl
cations 24-26 is indicated both by in situ NMR studies
(vide infra) and by the products generated on neutral-
ization. Evidence for intermediates 24 and 25 was also
obtained by FT-IR measurements on samples with-
drawn directly from the reaction mixture. Typical ν-
(CO) bands for [(pentadienyl)Fe(CO)3]+ complexes were
observed at 2119, 2072 and 2113, 2083 cm-1, respec-
tively. Infrared bands due to the neutral starting
materials were not present. In the case of the methoxy
complex, neutralization after reaction with HPF6 yields
the methyl ether 27 together with an inseparable
mixture of (E)- and (Z)-(pentadienal)Fe(CO)3 (28 and
29), while neutralization of 25 and 26 yields only
starting material. Given the water sensitivity of com-
plexes such as 8 and the aqueous nature of the proto-
nating medium, the results may perhaps best be inter-
preted as involving an equilibrium between protonated
and nonprotonated complex which in the case of the
methoxy complex collapses through alkylation of start-
ing complex 15 by cation 24 to give the observed
products. The greater sensitivity toward solvolysis of
Intermolecular hydrogen-bonded interactions involv-
ing OH and benzoyloxy CdO groups are shown in
Figure 2. The structure of 35 exhibits centrosymmetric
dimers with O---O contacts of 2.84 Å. The structure of
34 contains two molecules (axial and basal phosphine)
per asymmetric unit. The OH groups of the basal
(7) Donaldson, W. A.; Ramaswamy, M. Synth. React. Inorg. Met.-
Org. Chem. 1987, 17, 49.
(8) Donaldson, W. A.; Shang, L. Tetrahedron Lett. 1995, 36, 1575.
(9) Howell, J . A. S.; Squibb, A. D.; Bell, A. G.; McArdle, P.;
Cunningham, D.; Goldschmidt, Z.; Gottlieb, H. E.; Hezroni-Langerman,
D.; Gre´e, R. Organometallics 1994, 13, 4336.
(10) (a) Riley, P. E.; Davis, R. E. Acta Crystallogr. 1976, 32B, 381.
(b) Gre´e, D. M.; Martelli, J . T.; Gre´e, R. L.; Toupet, L. J . J . Org. Chem.
1995, 60, 2316. (c) Lellouche, J . P.; Breton, P.; Beaucourt, J . P.; Toupet,
L. J .; Gre´e, R. Tetrahedron Lett. 1988, 29, 2449. (d) Roush, W. R.;
Wada, C. K. Tetrahedron Lett. 1994, 35, 7347.
(6) Howell, J . A. S.; Bell, A. G.; O’Leary, P. J .; McArdle, P.;
Cunningham, D.; Stephenson, G. R. Organometallics 1994, 13, 1806.
(11) Clinton, N. A.; Lillya, C. P. J . Am. Chem. Soc. 1970, 92, 3058.

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(Acyloxy)- and Alkoxypentadienyl Complexes with Fe
Organometallics, Vol. 15, No. 20, 1996 4249
Sch em e 2
Sch em e 3
1:3.9), whereas for 35, the distribution is close to
equimolar (axial to basal ratio 1:1.4).
(C) In Situ P r oton a tion Stu d ies of Tr ica r bon yl
Com p lexes. The lack of precipitation of isolable salts
in the cases of complexes 15-17, 32, and 33 has
prompted in situ NMR studies using HSO3F/CD2Cl2 of
the species produced on protonation. The results con-
firm the formation of the required pentadienyl cation,
provide evidence for facile C-C rotational processes
which augment earlier work in this area, and also
indicate facile solvolysis reactions of the [(acyloxypen-
tadienyl)Fe(CO)3]+ cations.
Protonation of the Ψ-exo and Ψ-endo diastereoiso-
mers 32 and 33 at -20 °C (Scheme 4) yields spectra
which are fully consistent with the cis-syn, syn and cis-
syn, anti cations 39 and 40, respectively (Figure 3).
Particularly characteristic are the H5 resonances at 3.06
and 4.70 ppm with J 4-5 values of 13.7 and 9.3 Hz,
respectively. We have observed no resonances attribut-
able to the presumed initial trans cation under these
conditions.12 Cation 39 undergoes a smooth first-order
solvolysis at -20 °C (k2 ) 5.3 × 10-4 s-1) to give 41,
identified unambiguously by comparison with the spec-
trum of protonated (sorbaldehyde)Fe(CO)3 (7). Changes
in the spectrum of 40 with time show formation of both
39 and 41. The kinetics are in excellent agreement with
those expected for consecutive reactions;13 i.e., isomer-
ization of 40 to 39 is followed by solvolysis to 41 and no
direct conversion of 40 to 41 occurs (k1 ) 3.8 × 10-4
s-1, k2 ) 5.3 × 10-4 s-1). The phosphine-substituted
complexes are not stable to HSO3F, but in situ proto-
phosphine isomer form bifurcated hydrogen bonds with
the CdO and OH groups of molecules which have the
phosphine apical. The structure thus consists of cen-
trosymmetric tetramers with O- - -O contacts of 2.71 and
2.74 Å; the angle generated by the bifurcated hydrogen
bond is 102°. A feature of the hydrogen bonding is that
the 34 diene fragments of both unique molecules define
planes that make an angle of 54.2°. The tetramers are
packed to produce alternating hydrophobic and hydro-
philic layers containing the phosphine aryl rings and
the hydrogen-bonding regions, respectively. The prob-
able reason for the presence of both axial and basal
isomers is that the hydrogen-bonding arrangement
requires the relative rotation of the metal coordination
sphere, and to maintain the layer structure, the phos-
phines alternate between apical and basal positions. In
solution the isomer distribution is opposite; complex 34
exists mainly as the basal isomer (axial to basal ratio
(12) For in situ characterizations of trans cations, see: (a) Lillya,
C. P.; Sahatjian, R. A. J . Organomet. Chem. 1971, 32, 371. (b) Sorensen,
T. S.; J ablonski, C. R. J . Organomet. Chem. 1970, 25, C62. (c) Lillya,
C. P.; Sahatjian, R. A. J . Organomet. Chem. 1970, 25, C67. (d)
Brookhart, M.; Harris, D. L. J . Organomet. Chem. 1972, 42, 441.

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4250 Organometallics, Vol. 15, No. 20, 1996
Howell et al.
F igu r e 1. Molecular structures of 34 (basal) (top), 34
(axial), and 35 (bottom). Important bond lengths (Å) and
angles (deg): 34 basal, Fe-P ) 2.24, Fe-diene ) 2.14
(outer), 2.07 (inner), Fe-CO(av) ) 1.76, CO(ax)-Fe-P )
101, CO(ax)-Fe-CO(bas) ) 99, CO(bas)-Fe-P ) 90, C3-
C2-C101 ) 68; 34 axial, Fe-CO(av) ) 1.77, P-Fe-CO-
(bas) (av) ) 99.1, CO-Fe-CO ) 89, C103-C102-C101-
O101 ) 79; 35, Fe-P ) 2.24, Fe-diene ) 2.13 (outer), 2.06
(inner), Fe-CO(av) ) 1.77, CO(ax)-Fe-P ) 100, CO(ax)-
Fe-CO(bas) ) 102, CO(bas)-Fe-P ) 91, C3-C2-C1-O1
) 41.
F igu r e 2. Intermolecular hydrogen-bonded interactions
of 35 (top) and 34 (bottom).
goes a first-order solvolysis to give 45 (k1 ) 3.63 × 10-4
s-1).15 In the case of 16, solvolysis is sufficiently rapid
to preclude observation of 43 on the time scale of the
experiment. The methoxy cation 42 is resistant to
solvolysis.
A spectrum identical with that of 45 can be obtained
by in situ protonation of the E,Z complex 48, obtained
inter alia from ring opening of (pyrone)Fe(CO)3 (46)
(Scheme 5). Adaptation of this route to provide stable
salts in the PPh3 series is frustrated. Though the PPh3
complex 47 may be easily prepared, it does not undergo
ring opening under the same conditions used for 46.
Finally, it is of interest to compare the results on the
syn,anti to syn,syn isomerization of 40 to 39 with the
analogous isomerization process of the 1-methyl cations
51 and 52, which can be generated by in situ protonation
of the Ψ-exo and Ψ-endo diastereoisomers 49 and 50
(Scheme 6). In contrast to 40, 52 is configurationally
stable at -20 °C, only isomerizing to 51 with some
nation of 20 using CF3COOD/CD2Cl2 yields a spectrum
identical with that of the isolated cation 23.
In situ protonation of the primary alcohol complex 17
proceeds in a similar fashion to give 44, which under-
(13) Values of the first-order rate constants k1 and k2 were obtained
from plots of ln [A] against time for disappearance of 38 and 39,
respectively, using the integrated intensity of the methyl doublet as a
measure of concentration. Correlation coefficients greater than 0.994
were obtained. Kinetic analysis14 of a consecutive reaction series
indicates that the concentrations of A, B, and C with time can be
expressed by
at
[A]t ) [A]0 e-k
at
bt
e-k - e-k
[B]t ) [A]0ka
(
)
kb - ka
ka e-k - kb e-k
bt
at
[C]t ) [A]0 1 +
(14) Atkins, P. W. Physical Chemistry, 5th ed.; Oxford University
Press: Oxford, U.K., 1994; pp 883-884.
(15) The value of k1 was obtained from a plot of ln [A] against time
for the disappearance of 44 using the integrated intensity of the H3
resonances as a measure of concentration (correlation coefficient 0.998).
(
)
kb - ka
Using experimental values of k1 and k2, the experimentally observed
plots of concentration against time for 39, 38, and 40 match almost
exactly those predicted by the above equations.

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(Acyloxy)- and Alkoxypentadienyl Complexes with Fe
Organometallics, Vol. 15, No. 20, 1996 4251
Sch em e 5
Sch em e 6
F igu r e 3. 1H NMR spectra of cations 39-41 (CD2Cl2-
HSO3F, -20 °C).
Sch em e 4
cally pure deuterated cation 53 is also configurationally
stable, undergoing no deuterium scrambling over a
period of hours at room temperature.
The increased rates of isomerization of 52 and 40
relative to 53 thus indicate a steric acceleration in which
the ground-state cis-syn, anti cations lie closer in energy
to the transition state for the rotational process. The
increased rate of isomerization of 40 relative to 52 may
reflect an electronic contribution to the lowering of the
barrier.
(16) The value of k1 was obtained from a plot of ln [A] against time
for the disappearance of 52 using the integrated intensity of the methyl
resonances. Only three data points were obtained before decomposition
substantially broadened the spectrum. For previous characterization
of these cations, see ref 12b,c.
(17) Howell, J . A. S.; O’Leary, P. J .; Palin, M. G.; J aouen, G.; Top,
S. Tetrahedron: Asymmetry 1995, 7, 307.
decomposition at +15 °C (k1 ≈ 9 × 10-5 s-1).16 In other
work,17 we have recently shown that the enantiomeri-

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4252 Organometallics, Vol. 15, No. 20, 1996
Howell et al.
Ta ble 1
ratio and
entry
ref
nucleophile
MeLi
L
A
B
C
D
position of attack
a
b
c
d
e
f
g
h
i
18
18
8
CO
PPh3
CO
PPh3
CO
CO
CO
CO
CO
CO
CO
CO
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
1.2:1 B:A
>36:1 B:A
1.8:1 D:A
A only
A only
A only
D only
A only
A only
MeLi
malonate
malonate
malonate
malonate
malonate
malonate
malonate
malonate
malonate
H2CdCHCH2SiMe3
Me
Me
Ph
H
Me
Me
Ph
Ph
8
19
20
21
21
21
21
22
4
H
Me
Me
H
H
Me
H
Me
Me
H
j
k
l
1:1 A:C
>20:1 B:D
A only
CO2Me
Me
H
H
OMe
Sch em e 7
(D) Regioselectivity of Nu cleop h ilic Atta ck . For
acyclic cations, regioselectivity is greatly dependent on
the nucleophile, the pentadienyl substituent, and the
auxiliary ligands present on the metal. Nevertheless,
sufficient data exist in the series given in Table 1,
mainly for reaction with malonate, to delineate impor-
tant stereoelectronic influences.
The relatively poor regiodirecting influence of the
terminal methyl substituent is attributed to a relatively
weak electron-donating character that favors ipso attack
which is counterbalanced by a steric effect favoring
ω-attack at the other terminal carbon; 2- and 4-alkyl
substituents direct attack to the farthest terminus
through steric effects. Electron-withdrawing groups
direct attack to the internal carbon. The product of
internal attack in (entry j) is attributed to the perpen-
dicular orientation of Ph relative to the pentadienyl
ligand caused by the 2-methyl substituent; it thus acts
as an inductively electron-withdrawing substituent.
Our results are generally consistent with these ob-
servations. Thus, reaction of strong electron donor
cyclic and acyclic complexes 5 and 21 with RLi or
NaBH4 proceeds exclusively via ipso substitution to give
54a -c and 55 (Scheme 7). The regioselectivity is clearly
indicated by the multiplicity of the methyl groups
(singlet for 54a and doublet for 55), while the E,Z
stereochemistry of 55 is clearly indicated by the deshield-
ed H2 outer diene resonance at 2.45 ppm (J 2-3 ) 4.6
Hz). Lithium dimethylcuprate is less satisfactory. With
21, substantial dealkylation is observed to generate
(pentadienal)Fe(CO)2PPh3 (30:31 ) 8:1), while reaction
with 5 proceeds with loss of regioselectivity to give an
inseparable 1:1.5 mixture of 54a and 56.
Sch em e 8
Hammett σ+ values (indicative of the extent of reso-
nance between an electron-donor substituent and a
cationic reaction center (OMe (-0.78) > Me (-0.31) >
Ph (-0.18) > H (0) > CH3CO2 (+0.18)).23
The configuration of 57 has been confirmed by an
X-ray structure determination (Figure 4);24 exo addition
of the nucleophile is clearly evident. The structure is
essentially octahedral (average non-allyl L-M-L )
92°) with the allyl group occupying two positions with
Treatment of the acyloxy complexes 22 and 23 pro-
ceeds in good yield via internal attack to give the σ,π-
allyl complexes 57 and 58 (Scheme 8). Internal attack
suggests an electron-withdrawing nature for the acyloxy
substituent, which is consistent with the ordering of
(18) McDaniel, K. F.; Kracker, L. R.; Tharnburaj, P. K. Tetrahedron
Lett. 1990, 31, 2373.
(19) Donaldson, W. A.; Ramaswamy, M. Tetrahedron Lett. 1988, 29,
1343.
(23) Carey, F. A.; Sundberg, R. J . Advanced Organic Chemistry, 3rd
ed.; Plenum Press: New York, 1990; Part A, p 201.
(20) Donaldson, W. A. J . Organomet. Chem. 1990, 395, 187.
(21) Donaldson, W. A.; J in, M. Y.; Bell, P. T. Organometallics, 1993,
12, 1174.
(22) Donaldson, W. A.; Ramaswamy, M. Tetrahedron Lett. 1989, 30,
1343.
(24) The structure of an analogous tricarbonyl complex from the
reaction of P(OMe)3 with [(1-carbomethoxypentadienyl)Fe(CO)3]BF4
has been described: Pinsard, P.; Lellouche, J . P.; Beaucourt, J . P.;
Toupet, L.; Schio, L.; Gre´e, R. J . Organomet. Chem. 1989, 371, 219.

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(Acyloxy)- and Alkoxypentadienyl Complexes with Fe
Organometallics, Vol. 15, No. 20, 1996 4253
Sch em e 11
F igu r e 4. Crystal structure of 57.
Sch em e 9
products derived from nucleophilic attack at other sites
(including CO ligands) may be formed but not isolated.
In contrast to 17, the 31P NMR spectrum of 36 is
resolved into two resonances at -60 °C in the ratio 1:1.5,
indicating that both basal isomers 36a ,b are sub-
stantially populated. It has also recently been shown8
(entries c and d in Table 1) that phosphine substitution
to give the [(1-methylpentadienyl)Fe(CO)2PPh3]+ cation,
assigned structure 63 on the basis of NMR results,
selectively augments ipso attack at C1. The change in
regioselectivity observed between 8 and 36 indicates
that PPh3 selectively activates this ipso attack compared
to internal attack at C2. A substantial change in
regioselectivity is observed for the cyclic acyloxy cation
6, which reacts with LiCuMe2 exclusively at the unsub-
stituted terminus to give 64 (Scheme 10). Finally,
advantage may be taken of the different regiodirecting
powers of alkoxy and acyloxy groups in the cyclic series
to provide regioisomeric substituted cyclohexadienyl
salts. Thus, whereas protonation of 54a ,b provides
access to the 1-substituted salts 65a ,b in good yield,
protonation of 64 yields only the 3-substituted complex
66 (Scheme 11). This latter result is in accord with the
behavior of similar alkoxy-substituted complexes which
are known to rearrange extensively before loss of the
alkoxy group.25 As expected, reaction of the 1,4-
dimethoxy cation 67 with MeLi proceeds via ipso attack
to give 68, which itself is transformed on protonation
into the known 2-methoxy-5-methyl cation 69 (Scheme
12).
Sch em e 10
a bite angle of 62°. The phosphine occupies specifically
the position trans to the Fe-C σ-bond.
The 13C and 31P NMR spectra of cation 22 are
essentially independent of temperature and (on the
basis of observed axial and basal 13CO resonances) show
that only one basal isomer is populated, assigned as
shown above on the basis of minimization of steric
interactions between PPh3 and the acyloxy substituent.
It has been observed previously18 that for the unsub-
stituted [(pentadienyl)Fe(CO)2L]+ cation (entries a and
b in Table 1), PPh3 substitution significantly alters
regioselectivity toward the internal position. For 22 and
23, the PPh3 ligand may thus reinforce the directing
effect of the acyloxy substituent.
Reactions of salts 8 and 36 with MeLi provide
information on the relative directing power of acyloxy
and methyl substituents and the influence of PPh3 on
regioselectivity. The tricarbonyl salt 8 provides only the
σ,π-allyl complex 59 as the isolated product, thus
indicating the dominance of the directing effect of the
acyloxy substituent (Scheme 9). Reaction of the sub-
stituted salt 36 yields as isolated products a mixture of
60 and 62 together with a small amount of 61 derived
from 60 by phosphine displacement. Though insepa-
rable, the structures of 60 and 62 are clearly confirmed
by the NMR spectra. The low yields of the reactions of
both 8 and 36 with MeLi should be noted; unstable
Con clu sion s
The results thus demonstrate the stabilizing effect of
PPh3 substitution on the solvolysis of terminally sub-
stituted (acyloxy)- and alkoxypentadienyl complexes.
These substituents, introduced using common precur-
sors, provide complementary patterns of regioselectivity
in nucleophilic attack (internal (â) vs ipso (R) for acyclic
(25) Owen, D. A.; Stephenson, G. R.; Finch, H.; Swanson, S. J .
Organomet. Chem. 1989, 364, C11.

+
+
4254 Organometallics, Vol. 15, No. 20, 1996
Howell et al.
the product extracted with diethyl ether (3 × 50 mL). After
drying over MgSO4, the solvent was removed and the crude
product was purified by Chromatotron (4:1 petroleum ether
(30-40 °C)-ethyl acetate) to give 16 as a yellow solid (0.93 g,
77%). Mp: 90-92 °C. Anal. Found (calcd): C, 42.9 (42.6);
Sch em e 12
1
H, 3.79 (3.55). Infrared (CH2Cl2): 2055, 1985, 1979 cm-1. H
NMR (CDCl3): 3.5-3.8 (m, CH2), 0.98 (m, H2), 5.31 (dd, H3,
J 2-3 ) 9.0), 5.12 (dd, H4, J 3-4 ) 8.5), 4.05 (d, H5, J 4-5 ) 5.8),
2.02 (s, MeCO2). 13C NMR (CDCl3, -70 °C): 81.7, 84.8 (C3,
C4), 57.6 (C2), 63.6 (CH2), 73.7 (C5), 20.7, 168.9 (MeCO2), 215.0
(CO, axial), 208.6, 208.3 (CO, basal).
Complexes 15, 17, and 18-20 were prepared similarly.
15: yield 98%; yellow oil. M+ (calculated and found): m/ z
253.9874. Infrared (hexane): 2048, 1981, 1974 cm-1 1H NMR
.
(CDCl3): 3.6 (m, CH2), 0.70 (dd, H2), 5.04 (dd, H3), 5.17 (t,
H4), 3.12 (d, H5), 3.41 (s, MeO). 13C NMR (CD2Cl2, -70 °C):
56.7 (C1), 101.5, 79.5, 74.1, 63.9 (C2-C5), 60.4 (MeO), 216.9
(CO, axial), 209.4, 209.8 (CO, basal).
complexes, terminal (ω) vs ipso (R) for cyclic complexes)
which may have potential applications in synthesis.
17: yield 98%; mp 89-90 °C. Anal. Found (calcd): C, 52.6
(52.3); H, 3.34 (3.49). Infrared (hexane): 2051, 1995, 1981
cm-1 1H NMR (CDCl3): 3.4-3.8 (m, CH2), 1.10 (m, H2), 5.48
.
Exp er im en ta l Section
(dd, H3, J 2-3 ) 9.0), 5.18 (dd, H4, J 3-4 ) 8.4), 4.35 (d, H5, J 4-5
) 5.7), 7.3-8.0 (m, Ph).
All reactions involving iron complexes were carried out in
dry, degassed solvents under nitrogen. NMR spectra were
recorded on a J EOL GSX 270 spectrometer; temperatures were
measured using the built-in copper/constantan thermocouple.
1H and 13C chemical shifts are measured in ppm relative to
tetramethylsilane; 31P chemical shifts are measured in ppm
relative to 85% H3PO4. Where observed, J P-C values are given
in parentheses. All J values are given in Hz. Infrared spectra
were recorded on a Perkin-Elmer 257 spectrometer. Prepara-
tive thin-layer chromatography was performed on a Harrison
Research 7924 Chromatotron using 2 mm silica gel (type
PF60254) plates. The substrates 4,26 7,11 9-11,6 12, 14,11 46,
48,27 49, and 50,11 and 6728 were prepared as previously
reported.
18: yield 66%; yellow semisolid. Anal. Found (calcd): C,
64.6 (63.9); H, 5.36 (5.12). Infrared (hexane): 1984, 1926 cm-1
.
1H NMR (C6D6, +20 °C): 3.30-3.60 (m, br, CH2, H5), 0.05 (br,
H2), 4.58 (br, H3), 4.40 (dd, H4), 2.75 (s, MeO), 6.9-7.7 (m,
Ph).
19: yield 95%; mp 148-150 °C. Anal. Found (calcd): C,
62.7 (62.8); H, 4.93 (4.84). Infrared (hexane): 1983, 1927 cm-1
.
1H NMR (C6D6, +60 °C): 3.30 (m, br, CH2), -0.06 (m, H2),
4.90 (dd, H3), 4.68 (br, H4), 4.00 (t, br, H5), 1.31 (s, MeCO2).
20: yield 92%; mp 177-179 °C. Anal. Found (calcd): C,
66.7 (66.4); H, 4.59 (4.67). Infrared (hexane): 1983, 1923 cm-1
.
1H NMR (C6D6, +60 °C): 3.25 (d, CH2), -0.15 (m, H2), 4.93 (t,
br, H3), 4.70 (dd, H4), 4.08 (dd, H5, J P-5 ) 10.1), 6.8-8.0 (m,
Ph).
1. [5-(a cetyloxy)-2,4-p en ta d ien a l]F e(CO)2P P h 3 (13).
Complex 10 (0.5 g, 1.79 mmol) was added to a solution of PPh3
(0.95 g, 3.58 mmol) in acetone (40 mL), and the mixture was
heated to 50 °C; Me3NO‚2H2O (0.6 g, 5.37 mmol) was added
and the reaction monitored to completion by infrared spec-
troscopy (ca. 10 min). Diethyl ether (20 mL) was added and
the reaction mixture filtered through Celite. After removal
of solvent the crude product was purified by Chromatotron (4:1
petroleum ether (30-40 °C)-ethyl acetate) to give 13 as a
yellow solid (0.62 g, 67%). Mp: 127-128 °C. Anal. Found
(calcd): C, 62.8 (63.0); H, 4.63 (4.47). Infrared (hexane): 2011,
3. Rea ction of 11 w ith MeMgI. A solution of 11 (1.0 g,
2.9 mmol) in diethyl ether (30 mL) was cooled to -78 °C.
MeMgI (3.49 mmol, 1.16 mL of a 3 M solution in diethyl ether)
was added dropwise and the resulting solution stirred at -78
°C for 10 min. After it was warmed to room temperature, the
reaction mixture was quenched with saturated NH4Cl solution
(30 mL). The aqueous layer was extracted with diethyl ether
(2 × 30 mL). The combined ether extracts were dried over
MgSO4, and the solvent was removed. Purification of the
residue by Chromatotron (4:1 petroleum ether (30-40 °C)-
ethyl acetate) provided the two diastereoisomers 33 and 32 in
order of elution.
1951 cm-1
.
1H NMR (C6H6, +55 °C): 8.96 (d, H1, J 12 ) 4.1),
0.12 (br, H2), 5.23 (dd, H3), 4.78 (br, H4), 4.12 (br, H5), 1.40
(s, MeCO2), 6.9-7.6 (m, Ph). 31P NMR (CD2Cl2, -40 °C): 69.7,
62.3 in the ratio of 2.2:1 axial:basal isomers. The latter
resonance is further resolved into two (61.9 and 63.5) in the
ratio of 1:1.75 at -115 °C due to slowing of the s-cis/ s-trans
interconversion.9
(pyrone)Fe(CO)2PPh3 (47) was prepared in a similar way.
Yield: 58%. Mp: 184-185 °C. Anal. Found (calcd): C, 63.4
(63.8); H, 4.07 (4.04). Infrared (CH2Cl2): 2003, 1947 cm-1. 1H
NMR (C6D6, +55 °C): 2.48 (m, H1, J 1-2 ) 5.4), 5.12 (m, H2,
J 2-3 ) 6.8), 4.55 (m, H3, J 3-4 ) 5.0), 4.72 (m, H4), 6.9-7.3 (m,
Ph). 31P NMR (CD2Cl2, +20 °C): 66.7 (br). At -60 °C this is
resolved into two resonances at 61.7 and 71.9 ppm in the ratio
1:1.8, assignable to the two possible basal isomers.
33: yield 0.32 g, 43%; mp 115-116 °C. Anal. Found
(calcd): C 53.9 (53.7); H, 4.03 (3.91). Infrared (CH2Cl2): 2051,
1981 cm-1 1H NMR (CDCl3): 3.85 (m, CH), 1.06 (dd, H2, J 2-CH
.
) 8.8), 5.45 (t, H3, J 2-3 ) 6.1), 5.19 (dd, H4), 4.26 (t, H5), 1.32
(d, Me, J CH-Me ) 6.4), 7.4-8.0 (m, Ph).
32: yield 0.14 g, 14%; mp 112-113 °C. Anal. Found
(calcd): C 53.5 (53.7); H, 3.99 (3.91). Infrared (CH2Cl2): 2043,
1973 cm-1 1H NMR (CDCl3): 3.57 (m, CH), 0.95 (t, H2, J 2-CH
.
) 8.8), 5.45 (t, H3, J 2-3 ) 6.1), 5.25 (dd, H4), 4.36 (d, H5),
1.37 (d, Me, J CH-Me ) 6.3), 7.4-8.0 (m, Ph).
Reaction with the PPh3 derivative 14 was carried out in the
same way to give the two diastereoisomers 35 and 34 in order
of elution.
2. Syn th esis of 16. Complex 10 (1.2 g, 4.28 mmol) was
dissolved in methanol (50 mL) and the solution cooled to -10
°C. NaBH4 (0.16 g, 4.28 mmol) was added and the reaction
mixture stirred while it was warmed to room temperature.
After completion of the reaction, water (50 mL) was added and
35: yield 25%; mp 162-164 °C. Anal. Found (calcd): C,
67.3 (66.9); H, 4.91 (4.9). Infrared (hexane): 1977, 1915 cm-1
.
1H NMR (C6D6, +75 °C): 3.51 (m, br, CH), 0.21 (m, br, H2),
4.59 (dd, H3), 4.79 (br, H4), 4.0 (t, br, H5), 1.10 (d, CH3, J CH-Me
) 7.2), 6.9-8.0 (m, Ph). 31P NMR (CD2Cl2, +20°C): 65.2 (br).
At -60 °C this is resolved into two resonances at 65.7 and
64.1 in the ratio of 1.4:1.
(26) Birch, A. J .; Chamberlain, K. B.; Haas, M. A.; Thompson, D. J .
J . Chem. Soc., Perkin Trans. 1 1973, 1882.
(27) DePuy, C. H.; Parton, R. L.; J ones, T. J . Am. Chem. Soc. 1977,
99, 4070.
(28) Stephenson, G. R.; Finch, H.; Owen, D. A.; Swanson, S.
Tetrahedron 1993, 49, 5649.
34: yield 67%; mp 154-155 °C. Anal. Found (calcd): C,
66.9 (66.80); H, 5.00 (4.90). Infrared (hexane): 1975, 1917
cm-1 1H NMR (C6D6, +80 °C): 3.50 (q, br, CH), 0.10 (m, br,
.

+
+
(Acyloxy)- and Alkoxypentadienyl Complexes with Fe
Organometallics, Vol. 15, No. 20, 1996 4255
H2), 5.05 (dd, H3), 4.73 (br, H4), 4.25 (t, br, H5), 0.99 (d, br,
Me, J CH-Me ) 6.7), 6.9-8.0 (m, Ph). 13C NMR (CD2Cl2, -40
°C): 86.7 (8.0), 80.8, 78.0, 71.5 (C3, C4, C5, CH), 57.9 (6.0)
(C2), 24.5 (Me), 165.0 (PhCO2), 127-139 (Ph), 222.4 (6.8) (CO,
axial), 214.3 (25.7) (CO, basal). 31P NMR (CD2Cl2, +20 °C):
65.8 (br). At -60 °C this is resolved into two resonances at
66.1 and 65.7 ppm in the ratio 3.9:1.
mixture was then cooled to 0 °C, a solution of 4 (1.0 g, 4.3
mmol) in dry CH2Cl2 (2.0 mL) was added. After the mixture
was warmed to room temperature over 2 h, diethyl ether (30
mL) was added. The product 6 was collected as a yellow solid
(1.5 g, 88%) by filtration. Infrared (CH3CN): 2098, 2042 cm-1
.
1H NMR ((CD3)2CO): 7.01 (t, H3, J 2-3 ≈ J 3-4 ) 5.5), 6.28 (t,
H4, J 4-5 ) 5.5), 4.40 (d, H2), 4.14 (t, H5, J 4-5 ≈ J 5-6 ) 5.5),
â
3.37 (dd, H6â, J R-â ) 18), 2.90 (d, H6R), 2.06 (s, OAc).
Satisfactory microanalysis could not be obtained; the structure
is confirmed, however, by reduction of 6 to yield the known29
compound 54c.
4. Syn th esis of 22. Complex 19 (0.19 g, 0.37 mmol) was
dissolved in diethyl ether (10 mL) and the solution cooled to 0
°C, with stirring. HPF6 (0.37 mmol, 69 µL of 60% aqueous
HPF6) was added dropwise with stirring. After standing for
10 min, the yellow precipitate was collected by filtration and
washed with cold diethyl ether (0.21 g, 89%). Mp: 113-114
°C dec. Anal. Found (calcd): C, 49.6 (50.2); H, 4.33 (3.73).
8. Hyd r olysis of 23. Sodium bicarbonate (0.08 g) and
water (10 mL) were added to a solution of 23 (0.16 g, 0.22
mmol) in the minimum amount of acetone. After it was
warmed to 50 °C for 10 min, the yellow solution obtained was
extracted with diethyl ether (3 × 20 mL). After drying over
MgSO4 and evaporation of the solvent, the residue was purified
by Chromatotron (4:1 petroleum ether (30-40 °C)-ethyl
acetate) to give, in order of elution, the E isomer 30 (35 mg,
70%), identified by comparison with literature data,9 and the
Z isomer 31 (5 mg, 10%). Mp: 110-111 °C. Anal. Found
(calcd): C, 66.2 (65.8); H, 4.87 (4.60). Infrared (CH2Cl2): 1987,
Infrared (CH2Cl2): 2051, 2011 cm-1 13C NMR (CD2Cl2, -40
.
°C): 61.2 (C5), 86.3, 92.2, 101.2 (3.0), 102.3 (C1-C4), 20.8,
168.0 (MeCO2), 128-133 (Ph), 204.0 (31.6) (CO, basal), 213.8
(15.2) (CO, axial). 31P NMR (CD2Cl2, +20 °C): 60.0.
Complexes 21, 23, and 36 were prepared similarly.
21: yield 76%; mp 127-129 °C dec. Anal. Found (calcd):
C, 50.2 (50.6); H, 3.87 (3.90). Infrared (CH2Cl2): 2040, 1992
cm-1 13C NMR (CD2Cl2, -40 °C): 130.2 (C1), 79.8, 79.8, 99.5
.
1931 cm-1 1H NMR (C6D6, +20 °C): 9.21 (d, H1, J 1-2 ) 3.3),
.
(C2-C4), 62.4, 57.7 (C5, OMe), 128-133 (Ph), 205.4 (32.3) (CO,
basal), 221.1 (14.8) (CO, axial). 31P NMR (CD2Cl2, +20 °C):
63.6.
2.59 (m, H2, J 2-3 ≈ J 2-5 ) 5.2), 4.55 (br, H3, J 3-4 ) 5.3), 4.72
(br, H4), 2.5-2.6 (m, 2H5), 6.9-7.6 (m, Ph). 31P NMR (CD2-
Cl2, +20 °C): 68.5. At -100 °C, this is resolved into two
resonances at 63.6 and 72.5 ppm in the ratio 1:2.5.
23: yield 81%; mp 152-154 °C dec. Anal. Found (calcd):
C, 55.0 (54.4); H, 3.60 (3.68). Infrared (CH2Cl2): 2045, 2007
cm-1 1H NMR (CD2Cl2/CF3CO2D, -20 °C): 6.13 (d, H1, J 1-2
.
Similar treatment of 36 gave a 1:1 mixture of 37 and 38
which was separated by Chromatotron. Complex 37 was
identified by comparison with literature data.9 38: mp 124-
125 °C. Anal. Found (calcd): C, 66.8 (66.4); H, 5.05 (4.89).
) 8.6), 5.95 (t, H2, J 2-3 ≈ J 3-4 ) 8.0), 6.59, (t, H3), 5.10 (m,
H4), 1.11 (m, H5 inner), 2.45 (m, H5 outer), 7.3-8.2 (m, Ph)
(all peaks are broadened and J 4-5 values could not be mea-
sured). 13C NMR (CD2Cl2, -40 °C): 61.3 (C5), 86.9, 92.5, 100.4,
102.3 (C1-C4), 127-135 (Ph), 163.2 (PhCO2), 204.2 (33.6) (CO,
basal), 213.7 (14.8) (CO, axial). 31P NMR (CD2Cl2, +20 °C):
60.1.
Infrared (CH2Cl2): 1971, 1919 cm-1
°C): 9.08 (d, H1, J 1-2 ) 5.2), 2.45 (m, H2, 5, J 2-3 ) 6.0, J 4-5
.
1H NMR (C6D6, +20
)
10.8), 3.90 (m, H3, J 3-4 ) 6.5), 4.75 (dd, H5), 1.25 (d, Me, J 5-Me
) 6.3), 6.9-7.6 (m, Ph).
9. Attem p ted P r oton a tion of 15 a n d 17. (a) Complex
15 (0.54 g, 2.1 mmol) was dissolved in diethyl ether and the
solution cooled to 0 °C. With stirring, HPF6 (180 µL of a 60%
aqueous solution) was added dropwise; no precipitate was
observed after 1 h. Saturated NaHCO3 solution (30 mL) was
added and the product extracted with diethyl ether (3 × 50
mL). After drying over MgSO4 and evaporation, the residue
was purified by Chromatotron using 4:1 petroleum ether (30-
40 °C)-ethyl acetate to give, in order of elution, complex 27
(0.23 g, 41%) and an inseparable mixture of 28 and 29 in the
ratio of 1:2 (0.21 g, 45%).
36: yield 80%; mp 135-136 °C dec. Anal. Found (calcd):
C, 53.2 (55.0); H, 3.73 (3.90). Infrared (CH2Cl2) : 2039, 1999
cm-1 13C NMR (CD2Cl2, -65 °C): 84.3, 85.8, 86.9, 90.3, 92.8,
.
95.4, 95.5, 98.9, 102.1, 104.6 (C1-C5), 14.8, 20.5 (Me), 126-
135 (Ph), 163.3, 163.5 (PhCO2), 205.3 (35.5), 205.4 (35.0) (CO,
basal), 215.6 (15.4), 216.3 (13.4) (CO, axial). 31P NMR (CD2-
Cl2, +20 °C): 53.6. At -60 °C this is resolved into two
resonances at 54.3 and 55.2 ppm in the ratio of 1:1.5.
5. Syn th esis of 8. (sorbaldehyde)Fe(CO)3 (7; 1.0 g, 4.24
mmol) in acetic anhydride (4.5 mL) was cooled to -78 °C with
stirring. HPF6 (1.5 mL of a 60% aqueous solution) was added
dropwise to yield a dark solution, which later solidified. The
mixture was warmed to 0 °C over 1.5 h, and diethyl ether was
added in small portions to give a black precipitate. The solvent
was decanted and the residue triturated with a 2:1 mixture
of diethyl ether-CH2Cl2 to give eventually a yellow precipitate,
which was separated by filtration (1.4 g, 78%). Anal. Found
(calcd): C, 31.0 (31.2); H, 2.7 (2.6). Infrared (CH2Cl2): 2111,
27: orange oil. M+: m/ z 268.0030 (calculated and found).
Infrared (hexane): 2065, 2005, 1995 cm-1
.
1H NMR (C6D6):
0.40 (m, H2), 2.98, 3.21 (dd, CH2, J vic ) 10.7, J 1-CH2 ) 5.2, 4.4),
4.46 (dd, H3), 4.71 (t, H4), 2.72 (d, H5), 2.90, 3.00 (s, 2MeO).
13C NMR (CD2Cl2, -70 °C): 101.5, 79.9, 74.0, 73.7 (C3-C5,
CH2), 60.4, 57.8, 53.3 (C2, 2MeO), 216.9 (CO, axial), 209.4,
209.9 (CO, basal).
28/29: orange oil. M+: m/ z 221.9613 (calculated and found).
Infrared (hexane): 28, 2047, 1983, 1975 cm-1; 29, 2067, 2011,
2059 cm-1
.
1H NMR (CF3CO2D, +20 °C): 3.10 (m, H5,
J 5-Me ) 5.8, J 4-5 ) 12.8), 5.89, 6.16 (dd, t, H2, 4, J 2-3 ≈ J 3-4
)
1995 cm-1 1H NMR (C6D6): 28, 8.95 (d, H1, J 1-2 ) 3.4), 0.62
.
6.8), 5.98 (d, H1, J 1-2 ) 9.6), 7.10 (t, H3). The material is
hygroscopic, decomposing in undried solvents to regen-
erate 7.
(dd, H2), 5.22 (dd, H3), 4.43 (dd, H4), 0.02 (qd, H5i), 1.25 (qd,
H5o); 29, 8.89 (dd, H1, J 1-2 ) 2.2, J 1-3 ) 1.2), 2.22 (dd, H2,
J 2-3 ) 6.7), 4.43 (t, H3), 4.55 (m, H4), 1.31 (dd, H5i, J 4-5
10.0), 1.58 (m, H5o, J 4-5 ) 8.0, J vic ) 2.7).
)
6. Syn th esis of 5. Complex 4 (3.0 g, 12.8 mmol) was added
to a solution of Et3OPF6 (3.0 g, stabilized with 10% diethyl
ether, 10.9 mmol) in dry CH2Cl2 (50 mL). After it was stirred
for 70 h at room temperature, the solution was poured into
diethyl ether (160 mL). The precipitate was collected and
dried under vacuum to give 5 as a yellow powder (3.8 g, 85%).
Anal. Found (calcd): C, 32.4 (32.4); H, 2.5 (2.7). Infrared
(b) Complex 19 when subjected to protonation and NaHCO3
quenching as above, gave only recovered starting material.
10. Attem p ted P r ep a r a tion of [(1,5-d ia cetoxyp en ta -
d ien yl)F e(CO)3]P F 6. Acetoxyaldehyde complex 10 (1.05 g,
3.75 mmol) in ethanoic anhydride (2 mL) was added to a
preequilibrated (20 min), precooled (-30 °C) mixture of etha-
(CH3CN): 2100, 2045 cm-1 1H NMR ((CD3)2CO): 7.20 (t, H3,
.
J 2-3 ≈ J 3-4 ) 5.5), 6.43 (t, H4, J 4-5 ) 5.5), 4.84 (d, H2), 4.20-
4.44 (m, H5, CH2), 3.45 (dd, H6â, J 5-6 ) 5.5, J R-â ) 18), 2.95
(29) endo-alkoxy complexes may be formed by acid treatment of the
exo complex derived from nucleophilic attack on the [(cyclohexadienyl)-
Fe(CO)3]+ cation: (a) Burrows, A. L.; Parker, D. G.; Hine, K.; J ohnson,
B. F. G.; Lewis, J .; Poe, A.; Vichi, E. J . S. J . Chem. Soc., Dalton Trans.
1980, 1135. (b) Burrows, A. L.; J ohnson, B. F. G.; Lewis, J .; Parker,
D. G. J . Organomet. Chem. 1977, 127, C22.
(d, H6R), 1.44 (t, Me, J CH
) 7).
CH
2
3
7. Syn th esis of 6. HPF6 (2.0 mL, 75% aqueous, 10.3 mmol)
was added to acetic anhydride (10 mL) at -15 °C, and the
mixture was warmed to room temperature over 1 h. After this

+
+
4256 Organometallics, Vol. 15, No. 20, 1996
Howell et al.
noic anhydride (5 mL) and hexafluorophosphoric acid (2 mL).
After the mixture was stirred for 1 h, the reaction was
monitored by FT-IR and determined to be complete by the
54b: yield 89%; purified by flash chromatography (95:5
hexane-ethyl acetate). Anal. Found (calcd): C, 56.3 (56.3);
1
H, 6.55 (6.30). Infrared (hexane): 2052, 1990, 1973 cm-1. H
presence of bands at 2115 and 2074 cm-1
.
The reaction
NMR (CDCl3): 5.15-5.43 (m, H2,3), 2.81-3.67 (m, H1,4 and
solution was pipetted into ether, whereupon a black intractable
tar formed.
CH2CH3), 1.90 (dd, H6â, J 1-6 ) 4, J R-â ) 15), 1.55 (dd, H6R,
â
J 1-6R ) 2), 0.6-1.5 (m, Bun and CH2CH3).
68: yield 46%; purified by flash chromatography (7:3 hex-
ane-CH2Cl2); yellow oil. Anal. Found (calcd): C, 49.4 (49.0);
11. Rea ction of 21 w ith MeLi. A solution of 21 (0.5 g,
0.81 mmol) in CH2Cl2 (30 mL) was cooled to -78 °C. MeLi
(0.8 mL of a 1 M solution in diethyl ether) was added dropwise
with stirring. The solution was warmed to 10 °C and poured
into distilled water (50 mL). The product was extracted with
diethyl ether (3 × 50 mL) and dried over MgSO4. Removal of
solvent and crystallization from petroleum ether gave 55 as
orange crystals (0.28 g, 75%). Mp: 121-122 °C. Anal. Found
(calcd): C, 66.7 (66.7); H, 5.8 (5.6). Infrared (CH2Cl2): 1967,
H, 4.8 (4.8). Infrared (hexane): 2052, 1988, 1972 cm-1
.
1H
NMR (CDCl3): 5.03 (dd, H3, J 2-3 ) 7.0), 2.66 (d, H4), 3.22 (m,
H1), 1.88 (dd, H6â, J R-â ) 14.5, J 1-6 ) 3.5), 1.66 (dd, H6R,
â
J 1-6 ) 2.0), 1.18 (s, Me), 3.16 (s, 5-OMe), 3.65 (s, 2-OMe).
R
12. Rea ction of 5 a n d 6 w ith LiCu Me2. MeLi (2.86 mL,
1.40 M in diethyl ether, 4.0 mmol) was added slowly to a
suspension of CuI (380 mg, 2.0 mmol) in dry THF (10 mL) at
0 °C. After the mixture was stirred to obtain a colorless
solution, complex 5 (408 mg, 1.0 mmol) was added. After it
was stirred for 15 min, the mixture was poured into saturated
1911 cm-1
.
1H NMR (C6D6, +60 °C): 2.98 (m, H1, J 1-2 ≈ J 2-3
) 4.6, J 1-Me ) 6.2), 2.45 (m, H2), 4.48 (m, H3, J 3-4 ) 8.0), 4.80
(m, H4), 1.30 (m, H5outer, J 4-5(outer) ) 4.5), 1.03 (m, H5 inner,
J
4-5(inner) ) 9.5), 0.95 (d, Me), 3.37 (s, OMe), 6.9-7.6 (m, Ph).
NH
4Cl solution (10 mL) and diethyl ether (25 mL). After
13C NMR (CDCl3, +20 °C): 91.0, 83.6 (C3, C4), 75.8, 61.9, 56.1,
41.6 (C1, C2, C5, OMe), 24.8 (Me), 128-136 (Ph). 31P NMR
(CDCl3): 68.5.
filtration through Celite, the layers were separated and the
organic layer washed with water (10 mL) and brine (10 mL)
and dried over MgSO4. After removal of solvent, the residue
was purified by flash chromatography (97:3 petroleum ether
(30-40 °C)-ethyl acetate) to give (in order of elution) com-
plexes 54a (40 mg, 14%; see section 11) and 56 (62 mg, 22%).
Complex 56: semisolid. Anal. Found (calcd): C, 52.1 (51.8);
Reactions of 22, 23, 36, 8, 5, 6, and 67 with MeLi were
performed in a similar fashion. Complexes 61 and 60/62 were
separated by Chromatotron using 4:1 petroleum ether (30-
40 °C)-ethyl acetate, the tricarbonyl complex eluting first.
H, 5.1 (5.1). Infrared (hexane): 2041, 1973, 1967 cm-1
.
1H
57: yield 61%, purified by Chromatotron (4:1 petroleum
ether (30-40 °C)-ethyl acetate); mp 179-180 °C. Anal.
Found (calcd): C, 69.0 (68.8); H, 5.02 (5.03). Infrared (CH2-
NMR (CDCl3): 5.38 (dd, H2, J 2-3 ) 5), 5.00 (dd, H3, J 3-4
)
6.5), 2.85 (m, H4), 2.25 (m, H5), 2.48 (m, H6â, J gem ) 13.5),
1.35 (m, H6R), 0.95 (d, Me, J 5-Me ) 6.5), 1.22 (t, CH2CH3, J )
7), 3.35, 3.87 (dq, CH2CH3, J gem ) 9).
Cl2): 1983, 1927 cm-1 1H NMR (C6D6): 4.30 (m, H1, 3), 3.15
.
(m, H2, J 1-2 ≈ J 2-3 ) 6.3, J 2-Me ) 6.9), 3.60 (m, H4, J 3-4
)
Reaction of LiCuMe2 with 6 was performed in the same way.
Column chromatography (petroleum ether (30-40 °C) followed
by 6:4 petroleum ether-diethyl ether) gave (in order of elution)
complexes 64 (62%) and 4 (10%). Complex 64: yellow oil. Anal.
Found (calcd): C, 49.4 (49.3); H, 4.1 (4.1). Infrared (hexane):
6.3), 1.86 (m, H5 inner, J 4-5(inner) ) 12.3, J P-5(inner) ) 6.9),
2.51 (m, H5 outer, J 4-5(outer) ) 7.4, J P-5(outer) ) 2.9), 0.75
(d, Me, J Me-1 ) 6.84), 6.8-8.5 (m, Ph). 13C NMR (CD2Cl2):
96.5, 68.6, 66.8, 66.4 (C1, C3, C4, C5), 44.3 (C2), 23.8 (Me),
166.8 (PhCO2), 128-134 (Ph), 219.6 (16.8), 219.5 (12.1) (CO).
31P NMR (CD2Cl2): 55.3.
2058, 1999, 1970 cm-1 1H NMR (CDCl3): 5.43 (d, H2, J 2-3
. )
4), 5.07 (m, H3), 3.00 (m, H4), 2.45 (dd, H6â, J 5-6 ) 11.3, J R-â
â
58: yield 65%; purified by Chromatotron (4:1 petroleum
ether (30-40 °C)-ethyl acetate); mp 179-181 °C. Anal.
Found (calcd): C, 64.8 (65.3); H, 5.26 (5.25). Infrared (CH2-
) 13.4), 1.39 (dd, H6R, J 5-6 ) 3.1), 2.38 (m, H5), 0.98 (d, CH3,
R
J 5-Me ) 6.7), 2.04 (s, OAc).
13. Rea ction of 5 w ith Na BH4. NaBH4 (300 mg, 7.2
mmol) was added to a stirred solution of 5 (719 mg, 1.76 mmol)
in dry CH3CN (30 mL). After the mixture was stirred for 45
min at room temperature, solvent was removed and the
residue extracted with hexane (3 × 30 mL). Purification by
flash chromatography (95:5 hexane-diethyl ether) afforded the
product 54c29 (237 mg, 51%) as a yellow oil. Anal. Found
(calcd): C, 50.3 (50.0); H, 4.3 (4.6). Infrared (hexane): 2054,
Cl2): 1985, 1927 cm-1
5.8), 3.06 (m, H2, J 2-3 ) 6.9, J 2-Me ) 6.9), 4.26 (t, H3, J 3-4
6.3), 3.59 (m, H4), 1.81 (m, H5 inner, J 4-5(inner) ) 11.2,
.
1H NMR (C6D6): 4.00 (d, H1, J 1-2
)
)
J
J
P-5(inner) ) 6.3), 2.50 (m, H5 outer, J 4-5(outer) ) 7.9,
P-5(outer) ) 3.5), 0.75 (d, Me), 6.8-7.6 (m, Ph).
59: yield 30%; purified by Chromatotron (4:1 petroleum
ether (30-40 °C)-ethyl acetate); yellow oil. M+: m/ z 294.0191
(calculated and found). Infrared (CH2Cl2): 2052, 1979 cm-1
1H NMR (C6D6): 3.54 (d, H1, J 1-2 ) 6.1), 2.58 (m, H2, J 2-Me
.
)
1992, 1974 cm-1
H1), 3.30 (m, H4), 3.41 (m, H5 and CH2CH3), 1.95 (ddd, H6â,
J R-â ) 15.5, J 5-6 ) 7.0, J 1-6 ) 2.0), 1.57 (ddd, H6R, J 5-6
.
1H NMR (CDCl3): 5.27 (m, H2,3), 3.09 (m,
7.1, J 2-3 ) 4.6), 2.47 (m, H5, J 4-5 ) 9.6, J 5-Me ) 5.9), 3.60 (dd,
H4, J 3-4 ) 5.7), 3.75 (t, H3), 0.45 (d, Me(2)), 1.35 (d, Me(5)).
)
R
â
â
3.5, J 1-6 ) 2.0), 1.19 (t, CH2CH3, J ) 7.0).
R
61: yield 4%; yellow oil. (M-CO)+: m/ z 328. Infrared
14. Con ver sion of 54a in to 65a . Complex 54a (170 mg,
0.62 mmol) was added to trifluoroacetic acid (0.34 mL, 4.41
mmol) and shaken at room temperature for 15 min. The
reaction mixture was added to a solution of NH4PF6 (170 mg,
1.64 mmol) in water (2 mL), causing immediate formation of
a precipitate which was collected by filtration to afford complex
65a 30 as a yellow powder (202 mg, 85%). Infrared (CH3CN):
(CH2Cl2): 2047, 1979 cm-1 1H NMR (C6D6): 3.86 (d, H1, J 1-2
.
) 6.6), 2.65 (m, H2, J 2-Me ) 7.1, J 2-3 ) 4.5), 2.50 (m, H5, J 4-5
) 9.5, J 5-Me ) 6.0), 3.60 (dd, H4, J 3-4 ) 5.6), 3.80, (t, H3),
0.46 (d, Me(2)), 1.33 (d, Me(5)).
60/62: yield 59%; yellow semisolid. Infrared (CH2Cl2): 1979,
1919 cm-1 1H NMR (C6D6): 60, 4.32 (d, H1, J 1-2 ) 5.9), 3.10
.
2110, 2060 cm-1
) 5.5), 6.07 (t, H4, J 4-5 ) 6), 5.93 (d, H2), 4.55 (t, H5), 3.19
(dd, H6â, J R-â ) 16, J 5-6 ) 6), 2.40 (d, H6R), 1.97 (s, Me).
.
1H NMR ((CD3)2CO): 7.40 (t, H3, J 2-3 ≈ J 3-4
(m, H2, J 2-3 ) 6.8, J 2-Me ) 7.2, 3.70 (t, H3, J 3-4 ) 6.8), 3.35
(dd, H4, J 4-5 ) 9.5), 2.98 (m, H5, J 5-Me ) 5.9), 0.72 (d, Me(2)),
1.20 (d, Me(5)); 62, 4.10 (m, H1, J 1-2 ) 5.8, J 1-P ) 3.4), 5.46
(t, H2, J 2-3 ) 5.4), 5.64 (dd, H3, J 3-4 ) 6.8), 1.40 (m, br, CH,
J CH-Me ) 6.8), 0.65, 1.00 (d, 2Me). 31P NMR (CDCl3): 60, 53.3;
62, 68.5.
â
65b: yield 96%; yellow powder. Infrared (CH3CN): 2110,
2060 cm-1
. )
1H NMR ((CD3)2CO): 7.40 (t, H3, J 2-3 ) J 3-4
5.5), 6.18 (t, H4, J 4-5 ) 6), 5.89 (d, H2), 4.52 (t, H5), 3.14 (dd,
H6â, J R-â ) 16, J 5-6â ) 6), 2.37 (d, H6R), 0.6-1.7 (m, Bu).
69:31 yield 85%; yellow powder. Infrared (CH3CN): 2107,
54a : yield 84%; purified by flash chromatography (95:5
hexane-ethyl acetate); yellow oil. Anal. Found (calcd): C,
51.8 (52.0); H, 5.1 (5.2). Infrared (hexane): 2053, 1991, 1973
2056 cm-1 1H NMR ((CD3)2CO): 7.18 (dd, H3, J 2-3 ) 6), 5.99
.
cm-1 1H NMR (CDCl3): 5.36 (m, H3), 5.27 (ddd, H2, J 2-3
. )
4), 3.14 (d, H4, J 3-4 ) 7), 3.00 (m, H1, J 1-2 ) 6), 1.94 (dd, H6â,
J R-â ) 15, J 1-6 ) 4), 1.62 (dd, H6R, J 1-6 ) 2), 1.19 (s, Me),
(30) Herberich, G. E.; Muller, H. Chem. Ber. 1971, 104, 2781.
(31) Pearson, A. J . J . Chem. Soc., Perkin Trans. 1 1977, 2069.
(32) Birch, A. J .; Haas, M. A. J . Chem. Soc. C 1971, 2465.
â
R
1.20 (t, CH2CH3, J ) 7), 2.43, 3.35 (dd, CH2CH3, J gem ) 9).

+
+
(Acyloxy)- and Alkoxypentadienyl Complexes with Fe
Ta ble 2. Cr ysta l Da ta
Organometallics, Vol. 15, No. 20, 1996 4257
34
35
57
empirical formula
fw
C
33H29FeO5P
C33H29FeO5P
591.37
C33H29FeO4P
576.38
591.37
temp, K
293(2)
293(2)
293(2)
wavelength, Å
cryst syst
space group
0.710 69
monoclinic
P21/c
0.710 69
triclinic
P1h
0.710 69
orthorhombic
P212121
unit cell dimens
a, Å
b, Å
9.988(2)
20.182(2)
14.540(2)
90
94.030(10)
90
2923.7(8)
4
1.344
14.0720(10)
14.8560(10)
16.0540(10)
98.102(10)
112.118(10)
102.579(10)
2940.8(3)
4
11.394(2)
15.706(2)
16.051(2)
90
90
90
2872.2
4
1.333
0.617
1200
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
density (calcd), Mg/m3
abs coeff, mm-1
F(000)
1.338
0.607
1232
0.610
1228
cryst size, mm
θ range for data collecn, deg
index ranges
no. of rflns collected
no. of indep rflns
refinement method
no. of data/restraints/params
goodness of fita on F2
final R indices (I > 2σ(I))b
R indices (all data)
largest diff peak
and hole, e/Å3
0.28 × 0.34 × 0.41
0.32 × 0.24 × 0.41
0.45 × 0.15 × 0.1
2.02-27.98
2.11-21.99
2.19-31.95
0 e h e 13, 0 e k e 26, 19 e l e 19
7620
7032 (R(int) ) 0.0787)
full-matrix least-squares on F2
7032/0/366
0 e h e 14, -15 e k e 7, 16 e l e 15
6932
6390 (R(int) ) 0.0272)
full-matrix least-squares on F2
6390/0/725
4832
4347 (R(int) ) 0.0400)
full-matrix least-squares on F2
4347/0/356
0.955
0.613
0.779
R1 ) 0.0730, wR2 ) 0.1800
R1 ) 0.1140, wR2 ) 0.2003
1.36 and -1.214
R1 ) 0.0721, wR2 ) 0.2409
R1 ) 0.0826, wR2 ) 0.2730
0.902 and -0.713
R1 ) 0.0463, wR2 ) 0.1199
R1 ) 0.1112, wR2 ) 0.1459
0.408 and -0.338
a
2
2
b
Goodness of fit ) [∑w(|Fo | - |Fc |)2/(Nobs - Nparameters)]l/2
.
R indices: Rl ) [∑||Fo| - |Fc||]/∑|Fo| (based on F); wR2 ) [[∑w(|Fo
-
Fc|)2]/[∑w(|Fol)2]]1/2 (based on F2). w ) q/[(σFo)2 + (a*p)2 + b*P + d + e* sin θ].
(d, H2), 4.26 (m, H5), 3.23 (dd, H6â, J R-â ) 16, J 5-6â ) 5), 2.55
(d, H6R), 1.90 (s, Me), 3.96 (s, MeO).
45: 5.8-6.0 (m, H1,4, J 1-2 ) 10.3), 5.25 (dd, H2, J 2-3 ≈ J 3-4
) 7.1), 6.72 (t, H3), 1.50 (dd, H5 inner, J 4-5(inner) ) 11.7, J gem
) 3.5), 3.28 (dd, H5 outer, J 4-5(outer) ) 9.3). 1H NMR of
precursor 48 (C6D6): 5.09 (d, H1, J 1-2 ) 6.1), 4.90 (dd, H2,
J 2-3 ) 5.3), 4.35 (t, H3, J 3-4 ) 5.6), 2.17 (m, H4), 2.61, 3.13 (t,
15. Con ver sion of 64 in to 66. Aqueous HPF6 (0.5 mL of
75% solution, 2.7 mmol) was added at room temperature to a
stirred solution of 64 (200 mg, 0.68 mmol) in acetic anhydride
(2 mL). After 3 h, diethyl ether (10 mL) was added and the
product 66 was isolated by filtration as a yellow solid (159 mg,
dd, CH2, J 4-CH ) 4.9, 10.2, J vic ) 11.4), 1.48 (s, CO2Me).
2
51: 3.10 (m, H1/5, J 1/2-4/5 ) 12.2), 5.65 (dd, H2/4), 6.78 (t,
H3, J 2/4-3 ) 7.0), 1.75 (d, Me, J 1/5-Me ) 5.8).
52: 3.36 (m, H1, J 1-2 ) 11.7, J 1-Me ) 6.8), 5.80 (m, H2,4,
J 2-3 ≈ J 3-4 ) 7.5), 6.95 (t, H3), 4.25 (m, H5, J 4-5 ) 9.3, J 5-Me
) 5.9), 1.22 (d, Me(1)), 1.88 (d, Me(2)).
53: 3.11 (m, H1, J 1-2 ) 12.6, J 1-Me ) 6.4), 5.77 (dd, H2),
6.01 (dd, H4), 6.87 (t, H3, J 2-3 ≈ J 3-4 ) 7.0), 2.03 (d, H5, J 4-5
) 12.8), 1.85 (d, Me).
17. Cr ysta llogr a p h y. The structures were solved by
direct methods (SHELXS-86)33 and refined by full-matrix least
squares (SHELXL-93).34 Data were corrected for Lorentz and
polarization effects but not for absorption. Hydrogen atoms
were included in calculated positions with thermal parameters
30% larger than the atom to which they were attached. The
non-hydrogen atoms were refined anisotropically. All calcula-
tions were performed on a VAX 6610 computer. The ORTEX
program35 was used to obtain the drawings. Crystal data are
given in Table 2.
62%). Infrared (CH2Cl2): 2128, 2058 cm-1
.
1H NMR (CD3-
CN): 5.80 (t, H2/4, J 1/5-2/4 ) 7.2), 4.08 (t, H1/5), 3.00 (m, H6â,
J R-â ) 19, J 1/5-6 ) 7.0), 1.72 (d, H6R), 2.72 (s, Me).
â
16. In Situ NMR Stu d ies. The substrate (10-15 mg) was
dissolved in CD2Cl2 (1.5 mL) in a 5 mm NMR tube, and the
solution was degassed with nitrogen and cooled to -80 °C.
After addition of HSO3F (0.1 mL, triply distilled) by syringe,
the solution was mixed by shaking, placed in the NMR
spectrometer, and warmed to -20 °C. The mixture remains
two phases (yellow-orange CD2Cl2 layer over smaller orange
HSO3F layer) but nevertheless provides good-quality spectra.
1H NMR spectral data for cations characterized in situ are
given below.
39: 5.95 (d, H1, J 1-2 ) 8.7), 6.27 (t, H2, J 2-3 ≈ J 3-4 ) 7.5),
6.88 (t, H3), 5.79 (dd, H4, J 4-5 ) 13.7), 3.06 (m, H5, J 5-Me
5.9), 1.93 (d, Me), 7.6-8.3 (m, Ph).
)
40: 6.18 (d, H1, J 1-2 ) 8.2), 6.38 (t, H2, J 2-3 ≈ J 3-4 ) 6.8),
7.10 (t, H3), 5.90 (dd, H4, J 4-5 ) 9.3), 4.70 (m, H5, J 5-Me
6.8), 1.40 (d, Me), 7.6-8.3 (m, Ph).
)
Su p p or tin g In for m a tion Ava ila ble: Tables of crystal
data, atomic coordinates, bond lengths and angles, and aniso-
tropic displacement parameters for complexes 34, 35, and 57
(26 pages). Ordering information is given on any current
masthead page.
41: 5.90 (d, H1, J 1-2 ) 9.8), 5.23 (t, H2, J 2-3 ≈ J 3-4 ) 6.9),
6.52 (t, H3), 5.60 (dd, H4, J 4-5 ) 11.0), 2.46 (m, H5, J 5-Me
6.1), 1.74 (d, Me).
)
42: 5.66 (d, H1, J 1-2 ) 9.8), 5.19 (dd, H2, J 2-3 ≈ J 3-4 ) 6.5),
6.68 (t, H3), 5.93 (m, H4, J 4-5(outer) ) 9.4, J 4-5(inner)) 11.8),
1.51 (dd, H5 inner, J gem ) 4.0), 3.28 (dd, H5 outer)), 4.06 (s,
MeO).
OM960336A
(33) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467.
(34) Sheldrick, G. M. SHELXL-93. A Computer Program for Crystal
Structure Determination; University of Go¨ttingen, Go¨ttingen, Ger-
many, 1993.
44: 5.98 (d, H1, J 1-2 ) 8.5), 6.28 (t, H2, J 2-3 ≈ J 3-4 ) 7.0),
7.02 (t, H3), 6.11 (m, H4, J 4-5(outer) ) 9.5, J 4-5(inner) ) 13.5),
1.98 (dd, H5 inner, J gem ) 4.0), 3.85 (dd, H5 outer), 7.8-8.3
(m, Ph).
(35) McArdle, P. J . Appl. Crystallogr. 1993, 26, 752.