Synthesis of functionalized aryliron complexes by palladium-catalyzed transmetalation between [CpFe(CO)2I] and arylzinc or arylboron reagents

Article abstract of DOI:10.1021/om800916r

Transmetalation between [CpFe(CO)₂I] and arylzinc reagents or arylboronic acids under palladium catalysis yields the corresponding aryliron complexes [CpFe(CO)2Ar]. The reactions offer easy and reliable accesses to a variety of [CpFe(CO)₂Ar] species bearing a functionalized aryl group.

Full text of DOI:10.1021/om800916r

6050
Organometallics 2008, 27, 6050–6052
Synthesis of Functionalized Aryliron Complexes by
Palladium-Catalyzed Transmetalation between [CpFe(CO)2I] and
Arylzinc or Arylboron Reagents
Yoshihiro Asada, Shigeo Yasuda, Hideki Yorimitsu,* and Koichiro Oshima*
Department of Material Chemistry, Graduate School of Engineering, Kyoto UniVersity,
Kyoto-daigaku Katsura, Nishikyo-ku, Kyoto 615-8510, Japan
ReceiVed September 19, 2008
Summary: Transmetalation between [CpFe(CO)2I] and arylzinc
reagents or arylboronic acids under palladium catalysis yields
the corresponding aryliron complexes [CpFe(CO)2Ar]. The
reactions offer easy and reliable accesses to a Variety of
[CpFe(CO)2Ar] species bearing a functionalized aryl group.
The rich coordination chemistry of dicarbonylcyclopentadi-
enylorganoiron complexes [CpFe(CO)2R] has been attracting
significant interest.1 Among them, the corresponding aryliron
complexes [CpFe(CO)2Ar] are interesting not only as funda-
mental organometallic compounds2 but also as potentially useful
arylmetal reagents in organic synthesis.3 However, little is
known about the concise synthesis of [CpFe(CO)2Ar].4
Figure 1. Reactions of [CpFe(CO)2I] (1) with phenylzinc reagents.
Recently, we have developed an easy and efficient method
for the synthesis of [CpFe(CO)2Ar], the palladium-catalyzed
transmetalation between [CpFe(CO)2I] and arylmagnesium
reagents.5 However, the functional group compatibility of the
reaction is not sufficiently wide because of the high reactivity
of arylmagnesium reagents. Moreover, ortho-substituted aryl-
magnesium reagents reacted sluggishly with [CpFe(CO)2I] under
the palladium catalysis. Here we report palladium-catalyzed
arylation reactions of [CpFe(CO)2I] with arylzinc or arylboron
reagents, the mild reactivities of which should ensure high
functional group compatibility.6
iodide-lithium chloride complexes. Reaction of [CpFe(CO)2I]
(1) with phenylzinc iodide-lithium chloride proceeded very
smoothly under conditions that are similar to those in the
previous report (Figure 1).5 [CpFe(CO)2Ph] (2a) was obtained
in 100% NMR yield (90% isolated yield) by the action of 0.25
mol % of palladium acetate and 0.50 mol % of diamine 4.8
The use of Knochel’s arylzinc reagent was essential to attain
high yield. It is worth noting that commercially available lithium
chloride free phenylzinc iodide was less reactive, and dimer 3
was formed as a byproduct. The reactivity of the commercially
supplied phenylzinc iodide could be improved upon mixing with
lithium chloride at 50 °C for 24 h prior to the reaction.
The arylzinc reagents used were prepared according to the
procedure of Knochel:7 treatment of iodoarenes with zinc
powder and lithium chloride afforded the corresponding arylzinc
The scope of arylzinc reagents is summarized in Table 1.
Sterically demanding arylzinc reagents reacted with 1 with
reasonable efficiency (entries 2, 3, and 11), which we had failed
to attain by the arylation with Grignard reagents.5 Thanks to
* To whom correspondence should be addressed. E-mail: yori@orgrxn.
mbox.media.kyoto-u.ac.jp (H.Y.); oshima@orgrxn.mbox.media.kyoto-u.
ac.jp (K.O.).
(1) Kerber, R. C. In ComprehensiVe Organometallic Chemistry II; Abel,
E. W., Stone, F. G. A., Wilkinson, G., Eds.; Elsevier: Oxford, U.K., 1995;
Vol. 7, Chapter 2.
(2) Kerber, R. C. In ComprehensiVe Organometallic Chemistry II,; Abel,
E. W., Stone, F. G. A., Wilkinson, G., Eds.; Elsevier: Oxford, U.K., 1995;
Vol. 7, pp 163-176.
(3) Butler, I. R.; Cullen, W. R.; Lindsell, W. E.; Preston, P. N.; Rettig,
S. J. J. Chem. Soc., Chem. Commun. 1987, 439–441.
(4) The reaction of [CpFe(CO)2I] with phenylmagnesium bromide was
reported to result in a less than 12% yield of [CpFe(CO)2Ph]: (a) Li, H.-J.;
Turnbull, M. M. J. Organomet. Chem. 1991, 419, 245–249. The reaction
with highly reactive aryllithium: (b) Butler, I. R.; Lindsell, W. E.; Preston,
P. N. J. Chem. Res. Synop. 1981, 185. The palladium-catalyzed reactions
of aryl iodides with [CpFe(CO)2]ZnCl, the preparation of which requires
NaK2.8: (c) Artamkina, G. A.; Mil’chenko, A. Y.; Bumagin, N. A.;
Beletskaya, I. P.; Reutov, O. A. Organomet. Chem., USSR 1988, 1, 17–20.
The reactions of diaryliodonium or triarylsulfonium salts with [CpFe(CO)2]Na:
(d) Nesmeyanov, A. N.; Chapovsky, Y. A.; Polovyanyuk, I. V.; Makarova,
L. G. J. Organomet. Chem. 1967, 7, 329–337. Decarbonylation of
[CpFe(CO)2(ArCO)], which is available from [CpFe(CO)2]Na and ArCOCl: (e)
Hunter, A. D.; Szigety, A. B. Organometallics 1989, 8, 2670–2679, and
references cited therein.
(6) Palladium-catalyzed alkynylation reactions of [CpFe(CO)2I] with
1-alkynylstannanes are known: (a) Lo Sterzo, C. J. Chem. Soc., Dalton
Trans. 1992, 1989–1990. (b) Crescenzi, R.; Lo Sterzo, C. Organometallics
1992, 11, 4301–4305. (c) Ricci, A.; Angelucci, F.; Bassetti, M.; Lo Sterzo,
C. J. Am. Chem. Soc. 2002, 124, 1060–1071, and references cited therein. (d)
Long, N. J.; Williams, C. K. Angew. Chem., Int. Ed. 2003, 42, 2586–2617.
(7) Krasovskiy, A.; Malakhov, V.; Gavryushin, A.; Knochel, P. Angew.
Chem., Int. Ed. 2006, 45, 6040–6044.
(8) Experimental procedure: THF (1.0 mL) was placed in a 20 mL
reaction flask under argon. [CpFe(CO)2I] (1; 152 mg, 0.50 mmol), palladium
acetate (0.050 M THF solution, 0.025 mL, 0.0013 mmol), diamine 4 (0.050
M THF solution, 0.050 mL, 0.0025 mmol), and phenylzinc iodide-lithium
chloride complex (0.66 M THF solution, 1.14 mL, 0.75 mmol) were
sequentially added at 0 °C. After the mixture was stirred for 15 min, a
saturated ammonium chloride solution (1 mL) was added, and the product
was extracted with ethyl acetate (10 mL × 3). The combined organic layers
were passed through a pad of anhydrous sodium sulfate/Florisil and
concentrated. 1H NMR analysis of the crude product by using 1,1,2,2-
tetrabromoethane as an internal standard indicated that 2a was quantitatively
formed. The crude oil was purified in air on silica gel by using carbon
disulfide as an eluent to yield 2a (114 mg, 0.45 mmol, 90%) as a brown
solid.
(5) Yasuda, S.; Yorimitsu, H.; Oshima, K. Organometallics 2008, 27,
4025–4027.
10.1021/om800916r CCC: $40.75
2008 American Chemical Society
Publication on Web 10/31/2008

Communications
Organometallics, Vol. 27, No. 23, 2008 6051
Table 1. Palladium-Catalyzed Arylation of 1 with ArZnI · LiCl
Table 3. Self- and Cross-Metathesis of 2p under Ruthenium
Catalysis
entry
Ar
2
isolated yield /%
1
2
3
4
5
6
C6H5
1-naphthyl
2-MeC6H4
4-MeOC6H4
3-CF3C6H4
2a
2b
2c
2d
2e
2f
90 (100a)
92
73b
94
94
92
4-BrC6H4
7
8
9
10
11
12
4-NCC6H4
2g
2h
2i
2j
2k
2l
94
82
4-EtOC(dO)C6H4
3-EtOC(dO)C6H4
2-EtOC(dO)C6H4
2-FC6H4
90
tracec
74
2-thienyl
79
a
Yield determined by H NMR analysis of the crude product. b With
1
3.0 equiv of the zinc reagent. c 94% of 1 was recovered.
Table 2. Palladium-Catalyzed Arylation of 1 with ArB(OH)2
a
1
Yield determined by H NMR.
reactions (entries 4, 7, and 8).11,12 It is worth noting that
transmetalation from 2-(ethoxycarbonyl)phenylboronic acid to
1 proceeded smoothly by the action of 5 and copper(I) iodide
(entry 9). Iron complex 2j could not be prepared from the
corresponding arylzinc reagent (Table 1, entry 10). Styrene
derivative 2p was prepared from 4-vinylphenylboronic acid in
good yield (entry 10). Unfortunately, arylboronic acids having
a hydroxy or amino group failed to react with 1.
entry
Ar
2
isolated yield /%a
Further transformations of the functional groups on the phenyl
ring could increase the diversity of [CpFe(CO)2Ar].
1
2
3
4
5
6
7
8
9
10
C6H5
1-naphthyl
2-MeC6H4
4-MeOC6H4
4-CF3C6H4
4-MeC6H4
4-MeOCH2C6H4
4-EtOC(dO)C6H4
2-EtOC(dO)C6H4
4-CH2dCHC6H4
2a
2b
2c
2d
2m
2n
2o
2h
2j
88
82
76
68 (82)
80
Treatment of 2h with diisobutylaluminum hydride (DIBAL-
H) or butyllithium afforded the benzylic alcohol 2q or 2r,
respectively, in high yield (eq 1). The CpFe(CO)2 moiety
remained untouched under these reaction conditions, and
selective nucleophilic attacks to the ester moiety took place.
79
73 (86)
67 (87)
(75)
2p
72 (83)
a Yields obtained in the presence of 0.40 equiv of CuI are given in
parentheses.
the mild reactivity of organozinc reagents, aryliron complexes
having a bromo (2f), cyano (2g), and ethoxycarbonyl (2h,i)
group were readily prepared. However, the reaction of o-
ethoxycarbonyl-substituted arylzinc reagent resulted in recovery
of 1 (entry 10). The heteroaryliron complex 2l was obtained in
high yield (entry 12).
The vinylphenyliron complex 2p underwent metathesis in the
presence of ruthenium catalyst 6 (Table 3).13 Self-metathesis
(10) Experimental procedure: [CpFe(CO)2I] (1; 152 mg, 0.50 mmol),
phenylboronic acid (122 mg, 1.0 mmol), 5 (17 mg, 0.025 mmol), and cesium
carbonate (489 mg, 1.50 mmol) were placed in a 20 mL reaction flask under
an atmosphere of argon. 1,4-Dioxane was then added, and the resulting
mixture was stirred for 2 h at 60 °C. The reaction was quenched with a
saturated ammonium chloride solution (1 mL). Extractive workup followed
by silica gel column purification (eluent: carbon disulfide) afforded 2a (104
mg, 0.41 mmol) in 82% yield.
(11) (a) Hodgson, P. B.; Salingue, F. H. Tetrahedron Lett. 2004, 45,
685–687. (b) Yamamoto, Y.; Takizawa, M.; Yu, X.-Q.; Miyaura, N. Angew.
Chem., Int. Ed. 2008, 47, 929–931. (c) Liu, X.-X.; Deng, M.-Z. Chem.
Commun. 2002, 622–623. (d) Boland, G. M.; Donnelly, D. M. X.; Finet,
J.-P.; Rea, M. D. J. Chem. Soc., Perkin Trans. 1 1996, 2591–2597.
(12) We assume that arylcopper species generated from CuI and
arylboronic acids would undergo the more efficient transmetalation with
the iodopalladium intermediate: (a) Liebeskind, L. S.; Fengl, R. W. J. Org.
Chem. 1990, 55, 5359–5364. (b) Kang, S.-K.; Yamaguchi, T.; Kim, T.-H.;
Ho, P.-S. J. Org. Chem. 1996, 61, 9082–9083.
We next turned our attention to transmetalation from orga-
noboron compounds. After extensive screening of the reaction
conditions, we found that palladium complex 5,9 having a bulky
N-heterocyclic carbene ligand, showed the highest catalytic
activity for the reaction of phenylboronic acid with the aid of
cesium carbonate (Table 2, entry 1).10 Other arylboronic acids
underwent the transmetalation with high efficiency (entries 2,
3, 5, and 6). When the yields of the products were unsatisfactory,
the addition of copper(I) iodide improved the efficiency of the
(9) (a) O’Brien, C. J.; Kantchev, E. A. B.; Valente, C.; Hadei, N.; Chass,
G. A.; Lough, A.; Hopkinson, A. C.; Organ, M. G. Chem. Eur. J. 2006,
12, 4743–4748. (b) Kantchev, E. A. B.; O’Brien, C. J.; Organ, M. G. Angew.
Chem., Int. Ed. 2007, 46, 2768–2813.

6052 Organometallics, Vol. 27, No. 23, 2008
Communications
of 2p proceeded smoothly to yield the stilbene derivative 2s in
91% yield (entry 1). A cross-metathesis reaction with ethyl
acrylate provided the (E)-cinnamoyl ester 2t in good yield (entry
2). A cross-metathesis reaction of 2p with 1-octene required a
large excess of 1-octene to obtain a satisfactory amount of
desired product 2u, due to the much lower reactivity of 1-octene
in the metathesis reaction (entry 3). Allyltrimethylsilane also
participated in cross-metathesis14 to furnish the bimetallic
styrene 2v, which can undergo a number of further transforma-
tions (entry 4). Notably, all the reactions proceeded with
exclusive E selectivity. Again, the CpFe(CO)2 moiety of the
aryliron complex 2p has thus proved to be compatible under
typical conditions for metathesis.
In summary, the palladium-catalyzed transmetalation between
[CpFe(CO)2I] and arylzinc or arylboron reagents has emerged
as an efficient method for the synthesis of various functionalized
iron complexes. The sufficient stability of the carbon-iron
bonds of [CpFe(CO)2Ar] allows for selective transformations
of the functional groups on the phenyl ring to prepare a wider
variety of functionalized aryliron complexes. The iron com-
plexes thus synthesized could find applications in organic
synthesis as well as in materials chemistry.
Acknowledgment. This work was supported by Grants-
in-Aid for Scientific Research and for GCOE Research from
the MEXT and JSPS.
(13) (a) Scholl, M.; Ding, S.; Lee, C. W.; Grubbs, R. H. Org. Lett. 1999,
1, 953–956. (b) Grubbs, R. H.; Chang, S. Tetrahedron 1998, 54, 4413–
4450. (c) Trnka, T. M.; Grubbs, R. H. Acc. Chem. Res. 2001, 34, 18–29.
(14) (a) Crowe, W. E.; Goldberg, D. R.; Zhang, Z. J. Tetrahedron Lett.
1996, 37, 2117–2120. (b) BouzBouz, S.; De Lemos, E.; Cossy, J. AdV.
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Supporting Information Available: Text and figures giving
characterization data for new compounds. This material is available
free of charge via the Internet at http://pubs.acs.org.
OM800916R