Facile synthetic access to multisubstituted benz[f]indenones and their application as ligands to the first synthesis of group(IV) metallocene complexes

Article abstract of DOI:10.1021/ol0352106

(Matrix presented) A very efficient method for the synthesis of benz[f]indenone derivatives was developed. This method allows the introduction of a variety of substituents to a molecule. The first zirconocene compound of benz[f]indene was synthesized.

Full text of DOI:10.1021/ol0352106

ORGANIC
LETTERS
2003
Vol. 5, No. 17
3151-3153
Facile Synthetic Access to
Multisubstituted Benz[f]indenones and
Their Application as Ligands to the First
Synthesis of Group(IV) Metallocene
Complexes
Do Han Kim, Seung Uk Son, and Young Keun Chung*
School of Chemistry and Center for Molecular Catalysis, Seoul National UniVersity,
Seoul 151-747, Korea
ykchung@plaza.snu.ac.kr
Received June 30, 2003
ABSTRACT
A very efficient method for the synthesis of benz[f]indenone derivatives was developed. This method allows the introduction of a variety of
substituents to a molecule. The first zirconocene compound of benz[f]indene was synthesized.
Benz[f]indenones and benz[f]indenes are potentially useful
building blocks in organic and organometallic synthesis.
However, their chemistry has not been much explored.
Recently, benz[f]indenones were used as important starting
materials in the synthesis of kinamycin antibiotics, which
showed excellent activity against gram-positive bacteria.1 The
use of benz[f]indene as a cyclopentadienyl ligand attracted
much attention because an annulated benzo ring might
increase both the stereocontrol and productivity of the
catalytic system.2 However, the use of benz[f]indene as a
cyclopentadienyl ligand in the synthesis of group IV metal
complexes was not successful. For example, attempts to use
benz[f]indene and 2-methylbenz[f]indene in the synthesis of
group IV metal complexes was unsuccessful, presumably due
to the instability of the product.3 Instead, a late transition
metal complex, benz[f]indenyldicarbonylrhodium, was
reported.3a We had envisioned that the substituents in benz-
[f]indenes might help to increase the stability of the product
and that it would be possible to isolate the product. However,
no general procedures to synthesize substituted benz[f]-
indenes are known.4 We herein report a general methodology
of the synthesis of multisubstituted benz[f]indenones and
benz[f]indenes by combination of well-known reactions,
Pauson-Khand and Diels-Alder reactions, and their use in
the synthesis of zirconium complexes.
Transition metal-catalyzed cycloaddition reactions are very
efficient and highly indispensable tools in organic synthesis.5
In particular, a carbocyclization of alkene, alkyne, and
carbonyl mediated by cobalt(0), known as the Pauson-
Khand (P-K) reaction, has been recognized as one of the
most powerful methods for the construction of five-
membered rings.6 Similarly, the Diels-Alder (D-A) reaction
has been one of the most popular reactions for the construc-
(3) (a) Foster, P.; Rausch, M. D.; Chien, J. C. W. J. Organomet. Chem.
1998, 569, 121. (b) Foster, P.; Chien, J. C. W.; Rausch, M. D. Organo-
metallics 1996, 15, 2404.
(4) For examples of the synthesis of benz[f]indenes, see: (a) Carpino,
L. A.; Lin, Y.-Z. J. Org. Chem. 1990, 55, 247. (b) Carpino, L. A.; Cohen,
B. J.; Lin, Y.-Z.; Stephens, K. E., Jr.; Triolo, S. A. J. Org. Chem. 1990,
55, 251. (c) Ghorai, S. K.; Hazra, N. K.; Mal, D. Tetrahedron Lett. 1998,
39, 689.
(1) Kitani, Y.; Morita, A.; Kumamoto, T.; Ishikawa, T. HelV. Chim. Acta
2002, 85, 1186.
(2) (a) Spaleck, W.; Kueber, F.; Winter, A.; Rohrmann, J.; Bachmann,
B.; Antberg, M.; Dolle, V.; Paulus, E. F. Organometallics 1994, 13, 954.
(b) Stehling, U.; Diebold, J.; Kristen, R.; Roell, W.; Brintzinger, H. H.;
Juengling, S.; Muelhaupt, R. Organometallics 1994, 13, 964.
10.1021/ol0352106 CCC: $25.00 © 2003 American Chemical Society
Published on Web 08/02/2003

tion of six-membered rings.7 Our strategy for the synthesis
of benz[f]indenones is based on a combination of these two
representative reactions: the D-A reaction and P-K reac-
tions (Scheme 1).
Table 1. Synthesis of Benz[f]indenones Using Various
Substrates
Scheme 1. Synthetic Strategy for Synthesis of
Benz[f]indenones
a Isolated yield. b Reaction conditions: 1.0 mmol of alkynes, 2.0 mmol
of oxabenzonorbornadienes, 50 µmol of Co2(CO)8, 130 °C, dichloromethane,
30 atm of CO pressure. c Reaction conditions: MeOH/hydrochloric acid
(15:1 v/v), reflux. d Compound synthesized is shown in parentheses.
Our novel method for the synthesis of benz[f]indenones
consists of the D-A reaction, P-K reaction, and dehydration
(Scheme 1 and Table 1). The D-A reactions were success-
fully carried out with good yields (see Supporting Informa-
tion). The P-K reaction is well-known for its stereo- and
regioselectivity: the P-K reaction products of alkyne,
norbornene, and carbon monoxide have an exo conformation,
and a bulky substituent of an alkyne is located at the
R-position to the ketone of the reaction product. When
oxabenzonorbornadienes were used as alkenes, the reaction
products showed an excellent exo regioselectivity, which was
confirmed by single-crystal X-ray analysis of 1b (see
Supporting Information).
Monosubstituted alkynes were excellent substrates (entries
1-4 and 6 in Table 1). However, an alkyne having a
hydroxyl group showed a moderate yield, presumably due
to the sensitivity of Co2(CO)8 to the hydroxyl group (entry
5 in Table 1). Disubstituted alkynes were anticipated to be
poor substrates due to their bulkiness. Contrary to our
expectation, they turned out to be good substrates and
resulted in excellent yields (entries 7-10).
Next we conducted dehydration of P-K reaction products
to obtain benz[f]indenones. The dehydration yields were very
dependent upon Y and Rs. When Y and Rs were H, the
dehydration yields were good. However, when Y was H and
Rs was not H, the products were isolated in moderate yields,
presumably due to a steric effect. Surprisingly, the substituent
Y dramatically improved the yield (entries 11-13), presum-
ably by enhancing aromatization. One of the dehydration
products was analyzed by a single-crystal X-ray diffraction
study (see Supporting Information).
Thus, we can introduce a variety of substituents to a
molecule in (a) specific position(s) through D-A and P-K
reactions from available materials. The substituents X and
Y can be introduced to benz[f]indenone in the D-A reaction
step, and various Rs and RL can be introduced in the P-K
reaction step.
(5) (a) Ojima, I.; Tzamarioudaki, M.; Li, Z.; Donavan, R. J. Chem. ReV.
1996, 96, 635. (b) Rosenthal, U.; Pellny, P.-M.; Kirchbauwe, F. G.;
Burlakov, V. V. Acc. Chem. Res. 2000, 33, 119. (c) Herndon, J. W.
Tetrahedron 2000, 56, 1257. (d) Harvey, D. F.; Sigano, D. Chem. ReV.
1996, 96, 271. (e) Bates, R. W.; Satcharoen, V. Chem. Soc. ReV. 2002, 31,
12. (f) Mongomery, J. Acc. Chem. Res. 2000, 33, 467. (g) Yet, L. Chem.
ReV. 2000, 100, 2963. (h) Li, C.-L.; Liu, R.-S. Chem. ReV. 2000, 100, 3127.
(i) Saito, S.; Yamamoto, Y. Chem. ReV. 2000, 100, 2901.
(6) For recent reviews, see: (a) Gibson, S. E.; Stevenazzi, A. Angew.
Chem., Int. Ed. 2003, 42, 1800. (b) Hanson, B. E. Comments Inorg. Chem.
2002, 23, 289. (c) Brummond, K. M.; Kent, J. L. Tetrahedron 2000, 56,
3263. (d) Chung, Y. K. Coord. Chem. ReV. 1999, 188, 297.
(7) For recent papers, see: (a) Tsuda, A.; Fukumoto, C.; Oshima, T. J.
Am. Chem. Soc. 2003, 125, 5811. (b) Heckrodt, T. J.; Mulzer, J. J. Am.
Chem. Soc. 2003, 125, 4680. (c) Juhl, K.; Jorgensen, K. A. Angew. Chem.,
Int. Ed. 2003, 42, 1498. (d) Northrup, A. B.; MacMillan, D. W. C. J. Am.
Chem. Soc. 2002, 124, 2458. (e) Faller, J. W.; Grimmond, B. J.; D’Alliessi,
D. G. J. Am. Chem. Soc. 2001, 123, 2525.
Benz[f]indenes were prepared from benz[f]indenones as
shown in Scheme 2.
Recently, benz[f]indenones and benz[f]indenes were used
as target molecules for computational chemistry.8 We expect
that our structural data may be useful to computational
chemists.
Next we investigated the use of benz[f]indenes as ligands
in the synthesis of organometallic compounds. Zirconocenes
especially attracted our attention because of their latent use
in olefin polymerization. As already mentioned, Rausch et
(8) Gonzales, J. M.; Barden, C. J.; Brown, S. T.; Schleyer, P. V. R.;
Schaefer, H. F., III; Li, Q.-S. J. Am. Chem. Soc. 2003, 125, 1064.
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Org. Lett., Vol. 5, No. 17, 2003

Scheme 2. Synthesis of Benz[f]indenes from Benz[f]indenones
Figure 1. ORTEP drawing of 5a.
bond distance of C(3)-C(12) is shorter than other C-C bond
distances of the Cp ring. This special pattern may originate
from an enhanced aromaticity of naphthalene ring compared
to other indenyl rings. Thus, the zirconium metal makes
regular bonds with three carbon atoms as in an η3-bonding
mode and relatively weak bonds with the remaining two
carbons as in an η2-bonding mode. This bonding situation
may explain the instability of zirconocene compounds of
benz[f]indenes. From a catalytic point of view, this bonding
situation may help an olefin to approach an active site and
eventually to enhance catalytic activity in olefin polymeri-
zation. Catalytic activity in olefin polymerization will be
discussed in due course.9
al. attempted to synthesize group IV metallocenes of benz-
[f]indenes.3 They used 2-methylbenz[f]indene to synthesize
a zirconocene derivative. However, none of their trials were
successful because of the instability of the product. Instead
of 2-methylbenz[f]indene, we used 2-phenylbenz[f]indene.
Unfortunately, we obtained a result similar to that of Rausch.
However, when we used benz[f]indene having a substituent
R, we could obtain the first zirconocene compound of benz-
[f]indene (Scheme 3).
In conclusion, we developed a very efficient method for
the synthesis of benz[f]indenone derivatives by using Pau-
son-Khand and Diels-Alder reactions. Our method allows
the introduction of a variety of substituents to a molecule.
Using the prepared benz[f]indenes, we could synthesize the
first zirconocene compound of benz[f]indenes and use them
as catalysts in the ethylene polymerization. Further investiga-
tions involving broadening the scope of the synthesis of
transition metal complexes of benz[f]indenes are currently
in progress.
Scheme 3. Synthesis of Zirconocene Compounds
Acknowledgment. We thank the Ministry of Commerce,
Industry, and Energy and the Korea Science and Engineering
Foundation through Center Molecular Catalysis. D.H.K. and
S.U.S. are grateful for a Brain Korea 21 fellowship.
As with other methods, there could be a problem in the
purification of the reaction product. When R was a phenyl
group, we failed to obtain a purified product. However, when
R was a methyl group, a purified product was obtained by
recrystallization and its structure was confirmed by a single-
crystal X-ray diffraction study (Figure 1).
Figure 1 shows an interesting bonding pattern between
Zr and the Cp ring. The Zr is significantly closer to carbons
C(1), C(2), and C(13) than carbons C(3) and C(12) [Zr-
C(1) ) 2.576 Å, Zr-C(2) ) 2.572 Å, Zr-C(3) ) 2.643 Å,
Zr-C(12) ) 2.592 Å, and Zr-C(13) ) 2.465 Å], and the
Supporting Information Available: Synthetic procedures
and spectral and analytical data. This material is available
free of charge via the Internet at http://pubs.acs.org.
OL0352106
(9) Preliminary results show a high activity in ethylene polymerization.
Kim, D. H.; Son, S. U.; Lee, B. Y.; Chung, Y. K. Manuscript in preparation.
Org. Lett., Vol. 5, No. 17, 2003
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