Transformation of the carboxyl group adjacent to the (η4-diene)Fe(CO)3 moiety: A convenient route to (η4-diene)Fe(CO)3 complexes containing α,β- and β,γ-unsaturated carbonyl groups, and 1,3-dicarbonyl groups

Article abstract of DOI:10.1016/s0020-1693(99)00026-2

Acyl halides adjacent to an (η⁴-diene)Fe(CO)₃ moiety react with allylsilanes, vinylsilanes and enamines to give the corresponding allyl ketones, vinyl ketones and 1,3-diketones in high yields, respectively. The allylation reaction proceeds smoothly under neutral conditions without a Lewis acid as an activating agent, while the vinylation reaction takes place in the presence of a Lewis acid.

Full text of DOI:10.1016/s0020-1693(99)00026-2

www.elsevier.nl/locate/ica
Inorganica Chimica Acta 291 (1999) 231–237
Transformation of the carboxyl group adjacent to the
(h4-diene)Fe(CO)3 moiety: a convenient route to (h4-diene)Fe(CO)3
complexes containing a,b- and b,g-unsaturated carbonyl groups,
and 1,3-dicarbonyl groups
Saburo Nakanishi *, Katsuhisa Kumeta, Toshikazu Takata
Department of Applied Chemistry, College of Engineering, Osaka Prefecture Uni6ersity, 1-1 Gakuen-cho, Sakai, Osaka 599-8531, Japan
Received 11 August 1998; accepted 4 November 1998
Abstract
Acyl halides adjacent to an (h4-diene)Fe(CO)3 moiety react with allylsilanes, vinylsilanes and enamines to give the correspond-
ing allyl ketones, vinyl ketones and 1,3-diketones in high yields, respectively. The allylation reaction proceeds smoothly under
neutral conditions without a Lewis acid as an activating agent, while the vinylation reaction takes place in the presence of a Lewis
acid. © 1999 Elsevier Science S.A. All rights reserved.
Keywords: Iron complexes; Carbonyl complexes; Diene complexes; Unsaturated carbonyl group complexes; 1,3-Dicarbonyl group complexes
is the functionalization of a carboxyl group adjacent to
1. Introduction
the (h4-diene)Fe(CO)3 moiety. In contrast to the (h4-
2,4-pentadienal)Fe(CO)3 complex, the (h4-2,4-penta-
dienoic acid)Fe(CO)3 complex and its homologs have
rarely been utilized because the solubility of these com-
plexes is poor in most organic solvents and transforma-
tion of the carboxyl group into other functional groups
is relatively restricted. In the context of a program
dealing with the use of the (h4-diene)Fe(CO)3 complex
in organic synthesis, we have found a remarkable pro-
moting effect of the (h4-diene)Fe(CO)3 moiety on ally-
lation of acyl halides with allylsilanes [4]. This
observation prompted us to apply the functionalization
of carboxyl groups for the preparation of (h4-di-
ene)Fe(CO)3 complexes having a variety of carbonyl
fragments. In this paper, we wish to report the details
of the synthesis of (h4-diene)Fe(CO)3 complexes con-
taining a,b- and b,g-unsaturated ketones and 1,3-dike-
tones via reactions of acyl halides adjacent to a
(h4-diene)Fe(CO)3 moiety with vinylsilanes, allylsilanes
and enamines.
Much attention has been focused on (h4-diene)-
Fe(CO)3 complexes because of the stability of these
complexes, application of planar chiral properties of the
complexes for asymmetric transformation, and intro-
duction of 1,3-diene groups into organic compounds
via facile removal of the Fe(CO)3 fragment [1]. The
(h4-diene)Fe(CO)3 complexes having carbonyl groups
are well utilized in organic synthesis among the (h4-di-
ene)Fe(CO)3 complexes. For the preparation of such
complexes, a Friedel–Crafts type acylation [2] of diene
complexes and palladium-catalyzed acylation [3] of 2-
stannylated diene complexes have been developed.
However, these processes have their inherent limitation
in their applicability. One of the attractive routes to the
(h4-diene)Fe(CO)3 complexes bearing carbonyl groups
* Corresponding author. Tel.: +81-722-54 9295; fax: +81-722-54
9910.
0020-1693/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0020-1693(99)00026-2

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S. Nakanishi et al. / Inorganica Chimica Acta 317 (1999) 231–237
2. Experimental
2.1. General
2.4. Hydrolysis of ester complexes
A solution containing the ester complexes 1b–e (6
mmol) in 0.5 M KOH aqueous ethanol (20 ml of
ethanol and 7 ml of water) was heated at 50°C for 2
h. After filtration, the filtrate was washed twice with
diethyl ether. Acidification of the aqueous solution
precipitated the (h4-2,4-dienoic acid)Fe(CO)3 com-
plexes 2b–e which were crystallized from dichloro-
methane–hexane.
The IR spectra were recorded on a JASCO IRA-16
spectrometer. The NMR spectra were measured at
270 MHz on a JEOL JNM-GX 270 and at 500 MHz
on a JEOL a500 with TMS as the internal standard.
Elemental analyses were carried out on a Yanaco
CHN analyzer.
2b: Yellow solid. M.p. 215–217°C. IR (KBr); 2058,
1
2.2. Materials
1978 (CO), 1669 (CꢀO) cm−1. H NMR (270 MHz,
DMSO-d6); 1.73 (1H, d, CHꢀ, J=8.5 Hz), 2.98 (1H,
d, CHꢀ, J=9.8 Hz), 5.91 (1H, dd, CHꢀ, J=8.5, 4.8
Hz), 6.36 (1H, dd, CHꢀ, J=9.8, 4.8 Hz), 7.16–7.42
(5H, m, Ph). Anal. Calc. for C14H10FeO5: C, 53.54;
H, 3.21. Found: C, 53.60; H, 3.29%.
2,4-Dienoic acid esters were prepared by the
Horner–Emmons reaction of the corresponding a,b-
unsaturated aldehydes with phosphorous ylids by lit-
erature methods [5]. (h4-2,4-Hexadienoic acid)Fe(CO)3
complex 2a was prepared by the literature method [6].
Allylsilanes, vinylsilanes and enamines were prepared
by the usual methods.
2c: Yellow solid. M.p. 152–155°C. IR (KBr); 2058,
1
1978 (CO), 1674 (CꢀO) cm−1. H NMR (270 MHz,
DMSO-d6); 0.85 (3H, t, CH3, J=6.9 Hz), 1.23 (1H,
d, CHꢀ, J=8.5 Hz), 1.35–1.78 (5H, m, CH2, CHꢀ),
5.50 (1H, dd, CHꢀ, J=5.1, 8.5 Hz), 5.73 (1H, dd,
CHꢀ, J=5.1, 8.3 Hz). Anal. Calc. for C11H12FeO5: C,
47.18; H, 4.32. Found: C, 47.05; H, 4.55%.
2.3. Preparation of (p4-substituted-2,4-dienoic ester)-
Fe(CO)3 complexes
A mixture of 2,4-dienoic ethyl ester (10 mmol),
Fe(CO)5 (12 mmol) and acetone (10 ml) was irradi-
ated with UV light (\280 nm) at room temperature
(r.t.) for 1–2 days. After evaporation of the solvent
the residue was isolated by column chromatography
on silica gel to give the (h4-2,4-dienoic acid es-
ter)Fe(CO)3 complex from dichloromethane as eluent.
1b: Red oil. IR (neat); 2058, 1980 (CO), 1700
2d: Yellow solid. M.p. 212–216°C. IR (KBr); 2057,
1
1978 (CO), 1682 (CꢀO) cm−1. H NMR (270 MHz,
DMSO-d6); 1.32 (1H, s, CHꢀ), 2.54 (3H, s, CH3),
2.78 (1H, d, CHꢀ, J=9.3 Hz), 6.25 (1H, d, CHꢀ,
J=9.3 Hz), 7.16–7.41 (5H, m, Ph). Anal. Calc. for
C15H12FeO5: C, 54.91; H, 3.69. Found: C, 54.88; H,
3.77%.
2e: Yellow solid. M.p. 190–194°C. IR (KBr); 2061,
1
1
(CꢀO) cm−1. H NMR (270 MHz, CDCl3); 1.27 (3H,
1982 (CO), 1669 (CꢀO) cm−1. H NMR (270 MHz,
t, CH3, J=7.3 Hz), 1.25–1.30 (1H, m, CHꢀ), 2.35
(1H, d, CHꢀ, J=8.0 Hz), 4.05–4.20 (2H, m, CH2),
5.91–5.98 (2H, m, CHꢀ), 7.16–7.29 (5H, m, Ph).
1c: Red oil. IR (neat); 2057, 1978 (CO), 1711
DMSO-d6); 1.56 (1H, d, CHꢀ, J=8.6 Hz), 3.00 (1H,
d, CHꢀ, J=9.2 Hz), 5.88 (1H, dd, CHꢀ, J=5.2, 8.6
Hz), 6.06 (1H, dd, CHꢀ, J=5.2, 9.2 Hz), 6.37–6.38
(2H, m, CHꢀ), 7.56 (1H, s, CHꢀ). Anal. Calc. for
C12H8FeO6: C, 47.41; H, 2.65. Found: C, 47.25; H,
2.55%.
1
(CꢀO) cm−1. H NMR (270 MHz, CDCl3); 0.95 (3H,
t, CH3, J=7.3 Hz), 1.24 (3H, t, CH3, J=7.0 Hz),
1.29–1.52 (2H, m, CH2), 1.58–1.68 (2H, m, CH2),
1.50–1.80 (2H, m, CHꢀ), 4.08–4.13 (2H, m, CH2),
5.20 (1H, dd, CHꢀ, J=8.6, 5.0 Hz), 5.75 (1H, dd,
CHꢀ, J=8.5, 5.0 Hz).
2.5. Allylation of acyl halide complexes with
allylsilanes
1d: Red oil. IR (neat); 2058, 1978 (CO), 1700
To a suspension of (h4-2,4-dienoic acid)Fe(CO)3
(2a–d) (2.0 mmol) in dichloromethane (20 ml) was
added oxalyl chloride (4.0 mmol). The mixture was
stirred at r.t. for 1 h. The complex dissolved com-
pletely and was converted into the acyl chloride dur-
ing the procedure. After removal of the excess oxalyl
chloride and the solvent, dichloromethane (20 ml) and
AlCl3 (2.0 mmol), if necessary, were added to the
residue. Allyltrimethylsilane (4) (2.4 mmol) was added
to the solution at −60°C. The resulting mixture was
stirred at −60°C for 3 h and then gradually warmed
to r.t. The reaction mixture was poured over ice. The
organic solution was washed with aqueous NH4Cl so-
1
(CꢀO) cm−1. H NMR (270 MHz, CDCl3); 1.08 (1H,
s, CHꢀ), 1.32 (3H, t, CH3, J=7.0 Hz), 2.25 (1H, d,
CHꢀ, J=8.0 Hz), 2.64 (3H, s, CH3), 4.15–4.22 (2H,
m, CH2), 5.80 (1H, d, CHꢀ, J=8.0 Hz), 7.28–7.59
(5H, m, Ph).
1e: Red oil. IR (neat); 2060, 1980 (CO), 1711
1
(CꢀO) cm−1. H NMR (270 MHz, CDCl3); 1.16 (1H,
d, CHꢀ, J=7.7 Hz), 1.25 (3H, t, CH3, J=7.3 Hz),
2.36 (1H, d, CHꢀ, J=8.2 Hz), 4.10–4.23 (2H, m,
CH2), 5.87–5.94 (2H, m, CHꢀ), 6.42–6.43 (1H, m,
CHꢀ), 6.67–6.69 (1H, m, CHꢀ), 7.30–7.32 (1H, m,
CHꢀ).

S. Nakanishi et al. / Inorganica Chimica Acta 317 (1999) 231–237
233
lution and dried over anhydrous Na2SO4. The allylated
products 5a–i were isolated by column chromatography
on silica gel using dichloromethane as eluent.
88.87, 117.12, 117.20, 137.01 137.47 (Cꢀ), 205.29, 206.50
(CO), 208.54–211.70 (CO). Anal. Calc. for C17H22FeO4:
C, 58.98; H, 6.40. Found: C, 58.77; H, 6.25%.
5f: Yellow oil. IR (neat); 2056, 1980 (CO), 1673
(CꢀO) cm−1. 1H NMR (270 MHz, CDCl3); 1.57 (1H, d,
CHꢀ, J=6.5 Hz), 2.47 (1H, d, CHꢀ, J=7.7 Hz), 3.18
(2H, dt, CH2, J=7.3, 1.2 Hz), 5.17–5.25 (2H, m, CHꢀ),
5.89–6.04 (3H, m, CHꢀ), 7.13–7.31 (5H, m, Ph). Anal.
Calc. for C17H14FeO4: C, 60.38; H, 4.17. Found: C,
60.25; H, 3.99%.
5a: Yellow oil. IR (neat); 2056, 1972 (CO), 1678
(CꢀO) cm−1. 1H NMR (270 MHz, CDCl3); 1.25 (1H, d,
CHꢀ, J=8.1 Hz), 1.48 (3H, d, CH3, J=5.3 Hz),
1.48–1.61 (1H, m, CHꢀ), 3.11 (2H, d, CH2, J=6.8 Hz),
5.10–5.23 (2H, m, CH2ꢀ), 5.24 (1H, dd, CHꢀ, J=8.0,
4.8 Hz), 5.79 (1H, dd, CHꢀ, J=8.4, 4.8 Hz), 5.78–6.00
(1H, m, CHꢀ). 13C NMR (67 MHz, CDCl3); 19.11
(CH3), 47.70 (CH2), 52.49, 59.34, 81.27, 88.92, 118.75,
131.20 (Cꢀ), 203.27, 218.33 (CO). Anal. Calc. for
C12H12FeO4: C, 52.21; H, 4.38. Found: C, 52.35; H,
4.26%.
5g: Red oil. IR (neat); 2055, 1984 (CO), 1678 (CꢀO)
1
cm−1. H NMR (270 MHz, CDCl3); 0.95 (3H, t, CH3,
J=7.1 Hz), 1.24 (1H, d, CHꢀ, J=8.5 Hz), 1.43–1.71
(5H, m, CH2CH2, CHꢀ), 3.10 (2H, d, CH2, J=7.3 Hz),
5.12–5.28 (3H, m, CH2ꢀ, CHꢀ), 5.78–5.96 (2H, m,
CHꢀ). Anal. Calc. for C14H16FeO4: C, 55.29; H, 5.30.
Found: C, 55.43; H, 5.27%.
5h: Red oil. IR (neat); 2058, 1974 (CO), 1669 (CꢀO)
cm−1. 1H NMR (270 MHz, CDCl3); 1.21 (1H, s, CHꢀ),
2.33 (1H, d, CHꢀ, J=9.3 Hz), 2.61 (3H, s, CH3), 3.22
(2H, dt, CH2, J=7.3, 1.2 Hz), 5.20 (2H, m, CH2ꢀ), 5.78
(1H, d, CHꢀ, J=9.3 Hz), 5.90–6.05 (1H, m, CHꢀ),
7.16–7.31 (5H, m, Ph). Anal. Calc. for C18H16FeO4: C,
61.39; H, 4.58. Found: C, 61.24; H, 4.61%.
5b: Red oil. IR (neat); 2056, 1976 (CO), 1647 (CꢀO)
1
cm−1. H NMR (270 MHz, CDCl3); 1.37 (1H, d, CHꢀ,
J=8.1 Hz), 1.50 (3H, d, CH3, J=5.2 Hz), 1.53–1.61
(1H, m, CHꢀ), 1.78 (3H, s, CH3), 3.08 (2H, s, CH2),
4.88 (1H, s, CHꢀ), 4.98 (1H, s, CHꢀ), 5.30 (1H, dd,
CHꢀ, J=5.2, 8.1 Hz), 5.80 (1H, dd, CHꢀ, J=5.2, 8.1
Hz). 13C NMR (67 MHz, CDCl3); 18.95, 22.25 (CH3),
52.21 (CH2), 52.25, 59.22, 81.54, 88.67, 114.97, 139.51
(Cꢀ), 203.01, 210.10 (CO). Anal. Calc. for C13H14FeO4:
C, 53.83; H, 4.86. Found: C, 53.86; H, 4.59%.
5c: Red oil. IR (neat); 2058, 1982 (CO), 1669 (CꢀO)
1
cm−1. H NMR (270 MHz, CDCl3); 0.80–0.88 (1H, m,
2.6. Vinylation of acyl halide complexes with
6inylsilanes
CHꢀ), 1.18 (3H, s, CH3), 1.25 (3H, s, CH3), 1.42 (1H, d,
CHꢀ, J=8.2 Hz), 1.46 (3H, d, CH3, J=6.1 Hz),
5.10–5.33 (3H, m, CHꢀ, CH2ꢀ), 5.75 (1H, dd, CHꢀ,
J=8.2, 4.2 Hz), 5.95 (1H, dd, CHꢀ, J=10.2, 18.8 Hz).
13C NMR (67 MHz, CDCl3); 19.01, 23.97, 24.35 (CH3),
49.58 (C), 50.05, 59.04, 82.93, 88.92, 113.76, 143.21
(Cꢀ), 208.55 (CO), 220.11 (CO). Anal. Calc. for
C14H16FeO4: C, 55.29; H, 5.30. Found: C, 55.41; H,
5.42%.
5d: Yellow oil. IR (neat); 2056, 1995 (CO), 1673
(CꢀO) cm−1. 1H NMR (270 MHz, CDCl3); 1.16 (1H, d,
CHꢀ, J=8.1 Hz), 1.35 and 1.36 (3H, d, CH3, J=7.3
Hz), 1.34–1.36 (1H, m, CHꢀ), 4.25 (1H, d, CH, J=8.1
Hz), 5.05 (1H, dd, CHꢀ, J=10.5, 17.3 Hz), 5.11–5.19
(2H, m, CHꢀ), 5.70 (1H, m, CHꢀ), 6.19 (1H, m, CHꢀ),
7.23 (5H, m, Ph). 13C NMR (67 MHz, CDCl3); 18.77,
18.87 (CH3), 52.27, 52.65 (CH), 59.00, 59.28, 62.63,
63.02, 81.29, 82.02, 88.71, 88.90, 117.05, 127.10, 117.16
(Cꢀ), 128.11–138.66 (Ph), 203.31, 204.20 (CO), 208.22–
212.55 (CO). Anal. Calc. for C18H16FeO4: C, 61.39; H,
4.58. Found: C, 61.22; H, 4.69%.
To a mixture of the acyl chloride complex 3a (10
mmol), generated as mentioned above, AlCl3 (12 mmol)
and dichloromethane (20 ml) were added vinylsilanes
6a,b at 0°C. The resulting mixture was stirred for 15
min at 0°C and then at r.t. for 1 h. a,b-Unsaturated
ketones 7a–d were obtained by the usual work up.
7a: Yellow solid. M.p. 39–40°C. IR (KBr); 2056,
1
1980 (CO), 1667 (CꢀO) cm−1. H NMR (270 MHz,
CDCl3); 1.43 (1H, d, CHꢀ, J=9.1 Hz), 1.50 (3H, d,
CH3, J=6.1 Hz), 1.58–1.67 (1H, m, CHꢀ), 5.29 (1H,
dd, CHꢀ, J=9.1, 4.9 Hz), 5.72 (1H, dd, CH2ꢀ, J=9.7,
1.9 Hz), 5.91 (1H, m, CHꢀ), 6.21 (1H, dd, CH2ꢀ,
J=17.8, 1.9 Hz), 6.34 (1H, dd, CHꢀ, J=17.8, 9.7 Hz).
13C NMR (67 MHz, CDCl3); 19.20 (CH3), 52.19, 59.40,
81.50, 89.12, 126.90, 136.16 (Cꢀ), 194.62 (CO), 219.33
(CO). Anal. Calc. for C11H10FeO4: C, 50.42; H, 3.85.
Found: C, 50.50; H, 3.99%.
7b: Yellow solid. M.p. 59–60°C. IR (KBr); 2054,
1
1982 (CO), 1661 (CꢀO) cm−1. H NMR (270 MHz,
5e: Red oil. IR (neat); 2058, 1974 (CO), 1676 (CꢀO)
CDCl3); 1.51 (3H, d, CH3, J=6.0 Hz), 1.50–1.54 (1H,
m, CHꢀ), 1.62–1.70 (1H, m, CHꢀ), 5.30 (1H, dd, CHꢀ,
J=9.1, 5.0 Hz), 5.93–5.98 (1H, m, CHꢀ), 6.69 (1H, d,
CHꢀ, J=15.7 Hz), 7.39–7.57 (5H, m, Ph), 7.59 (1H, d,
CHꢀ, J=15.7 Hz). 13C NMR (67 MHz, CDCl3); 19.22
(CH3), 54.02, 59.36, 81.60, 89.02 (Cꢀ), 125.99–141.60
(Ph), 194.13 (CO), 218.38 (CO). Anal. Calc. for
C17H14FeO4: C, 60.38; H, 4.17. Found: C, 60.22; H,
4.26%.
1
cm−1. H NMR (270 MHz, CDCl3); 0.87 (3H, t, CH3,
J=6.8 Hz), 1.25–1.71 (11H, m, CH3, CH2), 1.48 (1H,
d, CHꢀ, J=6.0 Hz), 1.75 (1H, m, CHꢀ), 3.00 (1H, m,
CH), 5.07–5.19 (2H, m, CH2ꢀ), 5.27 (1H, dd, CHꢀ,
J=8.2, 4.8 Hz), 5.62–5.80 (2H, m, CHꢀ). 13C NMR
(67 MHz, CDCl3); 13.86, 18.95 (CH3), 22.39, 26.67,
26.74, 31.14, 31.45, 31.51, 31.57 (CH2), 52.51, 52.69
(CH), 57.58, 57.93, 59.00, 59.14, 81.60, 81.64, 88.69,

234
S. Nakanishi et al. / Inorganica Chimica Acta 317 (1999) 231–237
7c: Red solid. M.p. 104–108°C. IR (KBr); 2055, 1980
9c: Red oil. IR (neat); 2055, 1980 (CO), 1713 (CꢀO)
(CO), 1667 (CꢀO) cm−1. H NMR (270 MHz, CDCl3);
1.75 (1H, d, CHꢀ, J=7.7 Hz), 2.56 (1H, d, CHꢀ, J=9.3
Hz), 5.77 (1H, dd, CH2ꢀ, J=10.0, 1.8 Hz), 6.00–6.09
(2H, m, CHꢀ), 6.20 (1H, dd, CH2ꢀ, J=17.5, 1.8 Hz), 6.36
(1H, dd, CHꢀ, J=17.5, 10.0 Hz), 7.25 (5H, s, Ph). Anal.
Calc. for C16H12FeO4: C, 59.29; H, 3.73. Found: C, 59.19;
H, 3.88%.
cm−1. H NMR (270 MHz, CDCl3); 0.90 (1H, d, CHꢀ,
1
1
J=8.0 Hz), 1.32 (1H, d, CHꢀ, J=6.0 Hz), 1.48 (3H, d,
CH3, J=5.6 Hz), 1.49 (6H, s, CH3), 5.25 (1H, dd, CHꢀ,
J=4.7, 9.3 Hz), 5.81 (1H, dd, CHꢀ, J=4.7, 9.4 Hz), 9.59
(1H, s, CHO). 13C NMR (67 MHz, CDCl3); 19.10, 19.74,
19.90 (CH3), 44.22 (C), 49.33, 59.81, 82.49, 89.16 (Cꢀ),
200.70, 201.58 (CO), 210.54, 210.88 (CO). Anal. Calc. for
C13H14FeO5: C, 51.01; H, 4.61. Found: C, 51.29; H,
4.52%.
7d: Red oil. IR (neat); 2056, 1995 (CO), 1651 (CꢀO)
1
cm−1. H NMR (270 MHz, CDCl3); 0.95 (3H, t, CH3,
J=7.3 Hz), 1.39–1.74 (6H, m, CHꢀ, CH2), 5.25 (1H, dd,
CHꢀ, J=4.8, 8.5 Hz), 5.70 (1H, dd, CH2ꢀ, J=9.8, 1.8
Hz), 5.90 (1H, dd, CHꢀ, J=4.8, 8.6 Hz), 6.20 (1H, dd,
CH2ꢀ, J=17.0, 1.8 Hz), 6.35 (1H, dd, CHꢀ, J=17.0, 9.8
Hz). Anal. Calc. for C13H14FeO4: C, 53.82; H, 4.86.
Found: C, 53.64; H, 4.86%.
2.8. Decomplexation of the (p4-diene)Fe(CO)3 complex
A methanol solution containing 5c (1.0 mmol) and
cerium ammonium nitrate (3.0 mmol) was stirred for
3 h at r.t. The reaction mixture was poured on ice-water
and then extracted with dichloromethane. Evaporation
of the extract gave 1,3-pentadienyl 1,1-dimethyl-2-
propenyl ketone in a 95% yield.
2.7. Reaction of acyl halide complexes with enamines
1
Colorless oil. IR (neat); 1671 (CꢀO) cm−1. H NMR
To a mixture of the acyl chloride complex 3a (2 mmol)
and dichloromethane (10 ml) were added enamines 8a–c
(2.4 mmol) at 0°C, the resulting mixture was stirred at
0°C for 20 h. Usual work up of the reaction mixture gave
1,3-diketone complexes 9a–c.
(270 MHz, CDCl3); 1.25 (6H, s, CH3), 1.86 (3H, d,
J=4.43 Hz, CH3), 5.14–5.19 (2H, m, CH2ꢀ), 5.93 (1H,
dd, CHꢀ, J=17.8, 10.4 Hz), 6.19–6.42 (2H, m, CHꢀ),
6.42 (1H, d, J=15.3 Hz), 7.22–7.26 (1H, m, CHꢀ).
9a: Yellow oil. IR (neat); 2056, 1980 (CO), 1715 (CꢀO)
cm−1. H NMR (270 MHz, CDCl3); 1.30 (1H, d, CHꢀ,
1
3. Results and discussion
J=8.5 Hz), 1.49 (3H, d, CH3, J=6.1 Hz), 1.53–1.60
(1H, m, CHꢀ), 1.71–1.91 (4H, m, CH2), 2.27–2.37 (4H,
m, CH2), 5.28 (1H, dd, CHꢀ, J=4.3, 8.5 Hz), 5.95 (1H,
dd, CHꢀ, J=4.3, 7.9 Hz), 16.5 (1H, s, OH). 13C NMR
(67 MHz, CDCl3); 19.15 (CH3), 25.00, 27.02, 31.59, 41.98
(CH2), 49.92, 58.98, 81.31, 88.65, 105.98 (Cꢀ), 194.23
(ꢀC–O), 212.12 (CO), 219.86 (CO). Anal. Calc. for
C15H16FeO5: C, 54.24; H, 4.86. Found: C, 54.33; H,
4.78%.
3.1. Preparation of (p4-substituted-2,4-pentadienoic
acid)Fe(CO)3 complexes
(h4-2,4-Hexadienoic acid)Fe(CO)3 complex 2a (R1=
CH3, R2=H) was prepared by complexation of sorbic
acid with Fe(CO)5 in acetone upon irradiation with UV
light. (h4-Substituted-2,4-pentadienoic acid)Fe(CO)3
complexes 2b–e were prepared starting from 2,4-dienoic
esters [5] as outlined in Scheme 1. It is worth noting that
hydrolysis of the ester groups of complexes 1b–e was
conducted in aqueous ethanol solution at 50°C without
decomposition of the iron complexes. Acidification of the
reaction mixture precipitated acid complexes 2b–e which
were sparingly soluble in most organic solvents and pure
enough for further reaction. In addition, the planar
chirality of the (h4-diene)Fe(CO)3 complexes was main-
tained during the hydrolysis [1k]. Yields of these iron
9b: Red oil. IR (neat); 2052, 1980 (CO), 1711 (CꢀO)
cm−1. 1H NMR (270 MHz, CDCl3); 1.14 (1H, dd, CHꢀ,
J=9.3, 0.8 Hz), 1.49 (3H, d, CH3, J=6.1 Hz), 1.61–1.72
(1H, m, CHꢀ), 1.88–1.98 (2H, m, CH2), 2.35–2.55 (4H,
m, CH2), 5.23 (1H, dd, CHꢀ, J=4.8, 9.3 Hz), 5.87 (1H,
dd, CHꢀ, J=4.8, 9.3 Hz), 16.55 (OH). 13C NMR (67
MHz, CDCl3); 18.97 (CH3), 19.88, 25.46, 36.59 (CH2),
50.61, 58.61, 79.62, 87.62, 108.69 (Cꢀ), 175.31 (ꢀC–O),
203.43 (CO), 210.25 (CO). Anal. Calc. for C14H14FeO5:
C, 52.86; H, 4.44. Found: C, 52.71; H, 4.36%.
Scheme 1.

S. Nakanishi et al. / Inorganica Chimica Acta 317 (1999) 231–237
235
Table 1
solved in the solvent and complete dissolution of 2
indicated thorough conversion of 2 to 3. Conversion of
2 to 3 failed using thionyl chloride, phosphorous pen-
tachloride, phosphorous trichloride, and phosphorous
oxychloride in place of oxalyl chloride (Scheme 2).
Allylation of acyl halides with allylsilanes is a useful
method for the preparation of b,g-unsaturated ketones
[7]. Acyl chlorides thus generated were allowed to react
subsequently with allylsilanes to give (h4-diene)Fe(CO)3
complexes having b,g-unsaturated ketones in good
yields. The results are shown in Table 2. The reaction
has some remarkable features: although acyl halides
generally react with allylsilanes in the presence of a
Lewis acid as the activating agent, the present reaction
proceeds under neutral conditions without a Lewis
acid, indicating that the (h4-diene)Fe(CO)3 moiety acti-
vates the acyl group for the allylation reaction. Car-
bon–carbon bond formation takes place only at the
g-position of the allylsilanes in the usual fashion. The
reaction of sterically hindered allylsilanes such as
prenyl-, 2-octenyl- and cinnamyltrimethylsilanes gave
the corresponding ketones in low yields. However, the
yields can be improved by using AlCl3 without decom-
position of the complexes. This allylation reaction pro-
vides a route to (h4-diene)Fe(CO)3 complexes bearing
b,g-unsaturated acyl groups, and 1,3-butadienyl allyl
ketones can be obtained via decomplexation of the
Preparation of iron complexes 1 and 2
R1
R2
Yield of complex Yield of complex
(%)a
(%)a
Ph
n-C3H7
Ph
H
H
CH3
H
1b
1c
1d
1e
73
72
78
75
2b
2c
2d
2e
87
81
25
65
2-Furyl
a Isolated yield.
complexes 1 and 2 are given in Table 1. The acid
complexes 2 were obtained in good yields except for 2d
which was gradually decomposed in the reaction mix-
ture.
3.2. Allylation of acyl halides with allylsilanes leading
to (p4-diene)Fe(CO)3 complexes with i,k-unsaturated
ketones
Although the solubility of the acid complexes 2a–e is
poor in most organic solvents, the corresponding acyl
chloride complexes 3 are soluble in organic solvents.
Thus, formation of complexes 3 was attained satisfacto-
rily on treatment of complexes 2 suspended in dichloro-
methane with oxalyl chloride except for 2e (R1=2-
furyl). During the reaction, solids of 2 gradually dis-
Scheme 2.
Table 2
Reaction of acyl chlorides with allylsilanes
Complex
R1
Allylsilane
R3
Yield (%)a
Complex
R1
Allylsilane
R3
Yield (%)a
R2
R4
R5
R2
R4
R5
CH3
CH3
CH3
CH3
CH3
CH3
H
H
H
H
H
H
H
H
H
CH3
CH3
C6H5
H
H
H
CH3
CH3
H
H
H
CH3
H
H
5a
5a
5b
5c
5c
5d
86
CH3
CH3
CH3
C6H5
n-C3H7
C6H5
H
H
H
H
H
CH3
C6H5
n-C5H11
n-C5H11
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
5d
5e
5e
5f
5g
5h
89b
92b
87
67
89b
83
83
80
23
70b
60
H
a Isolated yields.
b In the presence of AlCl3.

236
S. Nakanishi et al. / Inorganica Chimica Acta 317 (1999) 231–237
asymmetric induction. The diastereomers could not be
separated by column chromatography (Scheme 2).
3.3. Vinylation of acyl halides with 6inylsilanes leading
to (p4-diene)Fe(CO)3 complexes with h,i-unsaturated
ketones
Scheme 3.
Table 3
It is well known that acyl halides react with vinylsi-
lanes in the presence of a Lewis acid to give a,b-unsat-
urated ketones [8]. This vinylation reaction was applied
to the synthesis of (h4-diene)Fe(CO)3 complexes bear-
ing an a,b-unsaturated ketone fragment (Scheme 3).
The results are given in Table 3. The Friedel–Crafts/
desilylation reaction occurred at the a-carbon of the
vinylsilane in the usual manner. Vinylated complexes 7
were produced in moderate yields using AlCl3 as the
Lewis acid. The use of TiCl4 or SnCl4 was ineffective
for this reaction. The a,b-unsaturated ketones adjacent
to (h4-diene)Fe(CO)3 complexes thus obtained are use-
ful reagents as dienophiles for the Diels–Alder reac-
tion, in which effective asymmetric reaction has been
attained using planar chiral (h4-diene)Fe(CO)3 com-
plexes [1f].
Reaction of acyl chlorides with vinylsilanes
Complex
R1
Vinylsilane
R2
Lewis acid
Yield (%)a
CH3
CH3
C6H5
n-C3H7
CH3
H
C6H5
H
H
H
AlCl3
AlCl3
AlCl3
AlCl3
none
7a
7b
7c
7d
7a
7a
7a
50
40
48
28
0
CH3
CH3
H
H
TiCl4
SnCl4
0
0
a Isolated yields.
3.4. (p4-Diene)Fe(CO)3 complexes with 1,3-diketones
6ia reaction of acyl halides with enamines
Introduction of 1,3-diketone units into (h4-diene)-
Fe(CO)3 complexes can be easily achieved by the reac-
tion of the acyl chlorides with enamines [9]. The results
are illustrated in Scheme 4. Complexes 9a and 9b exist
in the enol form (enol protons exhibit signals at 16.55
ppm in their 1H NMR spectra). 1,3-Diketones thus
obtained are versatile reagents for organic synthesis, for
example, alkylation provides a construction of a qua-
ternary carbon. It was discovered that asymmetric alky-
lation of 1,3-dienes adjacent to (h4-diene)Fe(CO)3
complexes was induced by the planar chiral (h4-di-
ene)Fe(CO)3 moiety [10].
Scheme 4.
(h4-diene)Fe(CO)3 fragment. For example, treatment of
5c with cerium ammonium nitrate in methanol gave the
1,3-pentadienyl allyl ketone in a 95% yield. The iron
carbonyl moiety serves not only as an activating agent
on the allylation reaction but also as a protecting agent
of the 1,3-butadiene group in the reaction.
4. Conclusion
Transformation of the carboxyl group adjacent to the
(h4-diene)Fe(CO)3 moiety can be easily performed via
the acyl chloride into a,b-unsaturated ketones, a,b-un-
saturated ketones and 1,3-diketones, which offers the
advantage that the planar chiral (h4-diene)Fe(CO)3
moiety can induce asymmetric reactions.
Many asymmetric transformations can be induced by
planar chiral (h4-diene)Fe(CO)3 complexes [1a]. Com-
plexes 5d and 5e consist of
a mixture of the
diastereomeric complexes due to the chiral allylic car-
bon in a ratio of 3:2, regardless of the Lewis acid. 13C
NMR spectra showed a pair of signals for each carbon
due to diastereomers. However, only partial protons of
the diastereomers can be discriminated in their 1H
NMR spectra. Further, the reaction of planar chiral
(2S)-(h4-2,4-hexadienoic acid)Fe(CO)3 [7] with cin-
namyltrimethylsilane and 2-octenyltrimethylsilane af-
forded a mixture of the diastereomeric complexes 5d
and 5e, respectively, in a ratio of 3:2, indicating little
References
[1] Recent reviews, for examples, (a) R. Gre´e, Synthesis (1989) 341.
(b) H.-J. Kno¨lker, in: K.H. Do¨tz, W. Hoffmann (Eds.), Organic
Synthesis via Organometallics, Vieweg, Braunschweig, 1991. (c)
R. Gre´e, J.P. Lellouche, Acyclic Diene Tricarbonyliron Com-

S. Nakanishi et al. / Inorganica Chimica Acta 317 (1999) 231–237
237
plexes in Organic Synthesis, in: L.S. Liebeskind (Ed.), Advances
in Metal-Organic Chemistry, JAI Press, Connecticut, 1995, pp.
129–273. Recent papers, for examples (d) H.-J. Kno¨lker, H.
Hermann, Angew. Chem., Int. Ed. Engl. 35 (1996) 341. (e) A.
Hachem, L. Toupet, R. Gre´e, Tetrahedron Lett. 36 (1995) 1849.
(f) Y. Takemoto, N. Yoshikawa, C.J. Iwata, Chem. Soc., Chem.
Commun. (1995) 631. (g) M. Frank-Neumann, C. Gateau, L.
Miesch-Gross, Tetrahedron Lett. 38 (1997) 8077. (h) B. Das-
gupta, W.A. Donaldson, Tetrahedron Lett. 39 (1998) 343. (i)
M.P. Yeh, L.W. Chuang, M.L. Lai, C.C. Chou, Organometallics
16 (1997) 4435. (j) S. Nakanishi, K. Kumeta, Y. Sawai, T.
Takata, J. Organomet. Chem. 515 (1996) 99. (k) S. Nakanishi,
K. Kumeta, J. Nakanishi, T. Takata, Tetrahedron: Asymmetry 6
(1996) 2097.
[4] S. Nakanishi, K. Kumeta, Y. Otsuji, Tetrahedron Lett. 35 (1994)
3727.
[5] J. Boutagy, R. Thomas, Chem. Rev. 74 (1974) 87.
[6] A. Musco, R. Palumbo, G. Paiaro, Inorg. Chim. Acta 5 (1971)
157.
[7] (a) R. Calas, J. Dunogues, J.P. Pillot, C. Biran, F. Pisciatti, B.
Arreguy, J. Organomet. Chem. 85 (1975) 145. (b) J.-P. Pillot, J.
Dunogues, R. Calas, Tetrahedron Lett. (1976) 1871. (c) I. Ojima,
M. Kumagai, Y. Miyazawa, Tetrahedron Lett. (1977) 1385.
[8] (a) I. Fleming, A. Pearce, J. Chem. Soc., Chem. Commun. (1975)
633. (b) I. Fleming, A. Pearce, J. Chem. Soc., Perkin Trans. I
(1980) 2485. (c) T.H. Chan, P.W.K. Lau, W. Mychajlowskij,
Tetrahedron Lett. (1977) 3317.
[9] (a) G. Stork, A. Brizzolara, H. Landesman, J. Szmuszkovicz, R.
Terrell, J. Am. Chem. Soc. 85 (1963) 207. (b) J. Szmuszkovicz,
Adv. Org. Chem. 4 (1963) 1.
[2] R.E. Graf, C.P. Lillya, J. Organomet. Chem. 122 (1976) 377.
[3] P.J. Colson, M. Franck-Neumann, M. Sedrati, Tetrahedron
Lett. 30 (1989) 2393.
[10] Unpublished results.
.