Synthesis of [Ethylene-1-(η 5-4,5,6,7-tetrahydro-1-indenyl)-2-(η5-4′ ,5′,6′,7′-tetrahydro-2′-indenyl)]titanium Dichloride, the Elusive Isomer of the Brintzinger-Type ansa-Titanocenes

Article abstract of DOI:10.1021/jo034975o

We present a short synthesis of 1-(2-indenyl)-2-(3-indenyl)ethane (5) and a method for its conversion to the ansa-metallocene [ethylene(η ⁵-inden-1-yl)(η⁵-inden-2-yl)] titanium dichloride (13). The synthetic strategy applied to prepa

Full text of DOI:10.1021/jo034975o

Syn th esis of [Eth ylen e-1-(η5-4,5,6,7-tetr a h yd r o-1-in d en yl)-2-
(η5-4′,5′,6′,7′-tetr a h yd r o-2′-in d en yl)]tita n iu m Dich lor id e, th e Elu sive
Isom er of th e Br in tzin ger -Typ e a n sa -Tita n ocen es
Patrick A. Kelly, Gideon O. Berger, J ustin K. Wyatt,† and Michael H. Nantz*
Department of Chemistry, University of California, Davis, California 95616
mhnantz@ucdavis.edu
Received J uly 7, 2003
We present a short synthesis of 1-(2-indenyl)-2-(3-indenyl)ethane (5) and a method for its conversion
to the ansa-metallocene [ethylene(η5-inden-1-yl)(η5-inden-2-yl)]titanium dichloride (13). The syn-
thetic strategy applied to prepare bisindene 5 relies on the efficient alkylation of 2-(phenylsulfonyl)-
indane followed by HMPA-assisted E1cB-elimination of phenylsulfinate. This tandem sequence
circumvents the predisposition of indene to undergo C(1)-alkylation and enables access to C(2)-
substituted indenes. The key step in the synthesis of the title ansa-titanocene (4) features a
previously unreported equilibration step to generate the bis(indenide anion) of 5. Complexation
with TiCl4‚(THF)2 followed by hydrogenation of the product metallocene furnishes ansa-titanocene
4.
In tr od u ction
The use of titanocene- and zirconocene-based catalysts
in the polymerization of R-olefins is considerably impor-
tant for the production of commercial polymers, and
much effort continues to be devoted toward preparing
new metallocene catalysts to obtain greater control over
polymer properties.1 Enantioenriched group 4 metal-
locenes also have utility as catalysts for a variety of
stereoselective organic transformations.2 A major focus
of research in these areas has been the study of alkyl-
and silyl-bridged (aka ansa) bis(cyclopentadienyl) and,
in particular, ethylene-bridged bis(indenyl) systems.3 The
syntheses of such bridged systems often involve difficult
or low-yielding steps that deliver the ansa-metallocenes
as mixtures of rac- and meso-diastereomers. These
problems are evident in the synthesis of the prototypical
ansa-titanocene dichlorides 1 and 2 (Figure 1), first
F IGURE 1.
disclosed by Brintzinger in 1982.4 Refinements5 to the
synthetic and optical resolution protocols have led to the
widespread availability of nonracemic 1 and its promi-
nent use in catalysis.6
Our interests in this field led us to develop synthetic
routes to the isomeric bis(2-indenyl) complex 3 (Figure
1) and chiral 1-alkyl analogues thereof.7 These syntheses,
however, also were complicated by the formation of rac-
* To whom correspondence should be addressed. Phone: 530-752-
6357. FAX: 530-752-8995.
† Present address: Department of Chemistry and Biochemistry, The
College of Charleston, Charleston, SC 29424.
(1) (a) Organometallic Complexes and Olefin Polymerization; Blom,
R., Follestad, A., Rytter, E., Tilset, M., Ystenes, M., Eds.; Springer:
Berlin, Germany, 2001. (b) Halterman, R. L. In Metallocenes; Togni,
A., Halterman, R. L., Eds.; Wiley-VCH: New York, 1998; pp 455-
544. (c) Kaminsky, W. J . Chem. Soc., Dalton Trans. 1998, 1413. (d)
Brintzinger, H. H.; Fischer, D.; Mu¨lhaupt, R.; Rieger, B.; Waymouth,
R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143.
(4) Wild, F. R. W. P.; Zsolnai, L.; Huttner, G.; Brintzinger, H. H. J .
Organomet. Chem. 1982, 232, 233.
(2) (a) Yun, J .; Buchwald, S. L. J . Org. Chem. 2000, 65, 767. (b)
Troutman, M. V.; Appella, D. H.; Buchwald, S. L. J . Am. Chem. Soc.
1999, 121, 4916. (c) Hicks, F. A.; Buchwald, S. L. J . Am. Chem. Soc.
1999, 121, 7026. (d) Catalytic Enantioselective Alkylation of Alkenes
by Chiral Metallocenes; Beller, M., Bolm, C., Eds.; Wiley-VCH: Wein-
heim, Germany, 1998. (e) Hoveyda, A. H.; Morken, J . P. Angew. Chem.,
Int. Ed. Engl. 1996, 35, 1263. (f) Duthaler, R. O.; Hafner, A. Chem.
Rev. 1992, 92, 807. (g) Willoughby, C. A.; Buchwald, S. L. J . Am. Chem.
Soc. 1992, 114, 7562. (h) Hollis, T. K.; Robinson, N. P.; Bosnich, B.
Tetrahedron Lett. 1992, 43, 6423. (i) Grossman, R. B.; Davis, W. M.;
Buchwald, S. L. J . Am. Chem. Soc. 1991, 113, 2321.
(5) (a) Scha¨fer, A.; Karl, E.; Zsolnai, L.; Huttner, G.; Brintzinger,
H. H. J . Organomet. Chem. 1987, 328, 87. (b) Collins, S.; Kuntz, B. A.;
Taylor, N. J .; Ward, D. G. J . Organomet. Chem. 1988, 342, 21. (c)
Collins, S.; Kuntz, B. A.; Hong, Y. J . Org. Chem. 1989, 54, 4154. (d)
Grossman, R. B.; Doyle, R. A.; Buchwald, S. L. Organometallics 1991,
10, 1501.
(6) The corresponding enantioenriched titanocene difluoride, and the
titanocene and zirconocene binaphthyl-2,2′-diolates are available com-
mercially.
(7) (a) Nantz, M. H.; Hitchcock, S. R.; Sutton, S. C.; Smith, M. D.
Organometallics 1993, 12, 5012. (b) Hitchcock, S. R.; Situ, J . J .; Covel,
J . A.; Olmstead, M. M.; Nantz, M. H. Organometallics 1995, 14, 3732.
(3) Shapiro, P. J . Coord. Chem. Rev. 2002, 231, 67.
10.1021/jo034975o CCC: $25.00 © 2003 American Chemical Society
Published on Web 10/02/2003
J . Org. Chem. 2003, 68, 8447-8452
8447

Kelly et al.
F IGURE 3.
SCHEME 1 a
F IGURE 2.
and meso-isomers at the stage of titanium complexation.
Interestingly, the only Brintzinger-type ethylene-bridged
bis(indene) capable of forming a chiral complex yet
incapable of forming a diastereomeric mixture on meta-
lation has not been reported. Specifically, ansa-titanocene
4 would be formed on titanium complexation of 1-(2-
indenyl)-2-(3-indenyl)ethane (5) and subsequent hydro-
genation of the arene rings. We present herein the results
of our efforts to synthesize 5 and on its metalation to
arrive at the novel titanocene dichloride 4.
a
Reagents and conditions: (a) (i) n-BuLi, THF; (ii) 1,2-dibro-
moethane. (b) (i) n-BuLi (1.05 equiv), THF, -78 °C to room
temperature; (ii) epoxide, -78 °C to room temperature, 15 h. (c)
12a , I2, PPh3, imidazole, Et2O, CH3CN, 80%. (d) Lithium indenide
(2 equiv), THF, HMPA, -78 °C to room temperature, 4 h, 81%.
Resu lts a n d Discu ssion
We envisioned that synthesis of 5 would follow the
retrosynthetic plan A outlined in Figure 2. The strategy
requires a phenyl sulfone-mediated alkylation by 3-(2′-
bromoethyl)indene (8)8 followed by elimination of phe-
nylsulfinate (6 f 5) to deliver the 2-indenyl ring. We have
previously demonstrated use of the phenylsulfonyl group
in the synthesis of 2-substituted indenes.9,10
We prepared 2-(phenylsulfonyl)Indane (7) from 2-in-
danyl phenyl sulfide11 using a modified literature proce-
dure.12 Unfortunately, our attempts to alkylate the
derived R-sulfonyl anion of 7 using bromide 8 failed to
deliver any of the desired coupling product 6, rather
indene 913 was the major product in this reaction (75%,
philic side chain to the ring bearing the phenyl sulfone
group. As indicated by retrosynthetic analysis path B
(Figure 3), alkylation of indene by halide 10 avoids the
possibility of a spirocyclization event.
Metalation of sulfone 7 with n-BuLi followed by addi-
tion of excess 1,2-dibromoethane afforded a mixture of
products containing only a trace quantity of desired
product 10a . The major product was identified as R-bro-
mo sulfone 11 (Scheme 1), presumably the consequence
of a direct attack on bromine.15 Adjusting our approach
once more, we pursued attachment of the electrophilic
side chain using a two-step sequence involving epoxide
ring-opening followed by alcohol-to-iodide conversion. In
contrast to analogous epoxide cleavage reactions, treat-
ment of R-lithiated 7 with ethylene oxide in THF pro-
ceeded without the need for Lewis acid assistance to give
adduct 12a in 70% yield.16,17 The derived R-sulfonyl anion
of 7 proved to be an excellent nucleophile for epoxide
cleavage reactions as evidenced by the regioselective
reactions with the epoxides of 1-propene and styrene,
giving good yields of adducts 12b and 12c, respectively.
The significance of these reactions lies in the potential
for using this approach to furnish the ansa-bridge with
unoptimized). This result is not entirely unexpected since
others have noted the propensity of 1-substituted indenes
appropriately fitted with leaving groups to undergo
spirocyclization.14
We next examined a complementary approach to
prepare bisindene 5 wherein we transferred the electro-
(14) (a) Rheingold, A. L.; Robinson, N. P.; Whelan, J .; Bosnich, B.
Organometallics 1992, 11 1869. (b) Lee, I. M.; Gauthier, W. J .; Ball, J .
M.; Iyengar, B.; Collins, S. Organometallics 1992, 11, 2115. (c)
Halterman, R. L.; Schumann, H.; Du¨bner, F. J . Organomet. Chem.
2000, 604, 12.
(15) In similar fashion, 1,2-dibromoethane is reported to brominate
an ester enolate anion, see: Greene, A. E.; Muller, J . C.; Ourisson, G.
J . Org. Chem. 1974, 39, 186.
(8) Sugie, A.; Shimomura, H.; Katsube, J .; Yamamoto, H. Tetrahe-
dron Lett. 1977, 18, 2759.
(9) (a) Palandoken, H.; McMillen, W. T.; Nantz, M. H. Org. Prep.
Proc. Intl. 1996, 28 702. (b) Palandoken, H.; Wyatt, J . K.; Hitchcock,
S. R.; Olmstead, M. M.; Nantz, M. H. J . Organomet. Chem. 1999, 579,
338.
(10) Several strategies have been reported for substitution of indene
at the 2-position; for examples, see: (a) Greifenstein, L. G.; Lambert,
J . B.; Nienhuis, R. J .; Fried, H. E.; Pagani, G. A. J . Org. Chem. 1981,
46, 5125. (b) Adamczyk, M.; Watt, D. S.; Netzel, D. A. J . Org. Chem.
1984, 49, 4226. (c) Kaminsky, W.; Rabe, O.; Schauwienold, A. M.;
Schupfner, G. U.; Hanss, J .; Kopf, J . J . Organomet. Chem. 1995, 497,
181. (d) Halterman, R. L.; Zhu, C. Tetrahedron Lett. 1999, 40, 7445.
(11) McCullough, K. J . Tetrahedron Lett. 1982, 23, 2223.
(12) Trost, B. M.; Curran, D. P. Tetrahedron Lett. 1981, 22, 1287.
(13) Kauffman, T.; Berghus, K.; Rensing, A. Chem. Ber. 1985, 118,
3737.
(16) Achmatowicz, B.; Marczak, S.; Wicha, J . J . Chem. Soc., Chem.
Commun. 1987, 1226.
(17) An exothermic reaction occurred when BF3‚Et2O was added to
i. The THF cleavage product ii was isolated on aqueous workup. For
an analogous reaction with THF, see: Christoffers, J .; Do¨tz, K. H.
Organometallics 1994, 13, 4189.
8448 J . Org. Chem., Vol. 68, No. 22, 2003

1-(2-Indenyl)-2-(3-indenyl)ethane
SCHEME 3 a
TABLE 1. Ba se-Med ia ted Con ver sion of Su lfon e 6 f 5
entry
base (equiv)
conditions
yield (%)a
1
2
3
4
KOt-Bu (4.05) THF, 10 °C f rt, 2 h
6
46
50
86
KDA (3.05)
n-BuLi (5.0)
n-BuLi (4.1)
THF, -78 °C f 0 °C, 1 h
THF, -78 °C f 0 °C, 1.5 h
9:1 THF:HMPA, -78 °C, 2 h
a
Chromatographed.
a
Reagents and conditions: (a) (i) n-BuLi (1.95 equiv), THF, -78
SCHEME 2
°C to room temperature, 12 h; (ii) TiCl4‚THF2 (1.0). (b) H2, cat.
PtO2, THF, rt, 57%.
starting bisindene. To our dismay, attempts to metalate
5a with other protocols for titanocene formation, which
included reactions with TiCl3 (direct and inverse addi-
tion)24 and TiCl3/NaH,25 also failed to furnish the corre-
sponding ansa-titanocene.
In concurrent attempts to synthesize the ansa-zir-
conocene, application of the zirconation conditions de-
1
veloped by J ordan26 with periodic analysis by H NMR
(5a + Zr(NMe2)4, toluene-d8, 100 °C) indicated possible
metallocene formation; however, continued reaction re-
sulted in disappearance of the characteristic signals.27
This result led us to examine metalation of 5a using a
Ti(IV) source. Unfortunately treatment of the dianion of
a stereogenic center, a structural feature that modulates
metallocene formation18 and reactivity.3 Alcohol 12a was
converted uneventfully into iodide 10b by using Corey’s
method.19 Treatment of 10b with lithium indenide in
THF resulted in a low yield of the displacement product
6. However, we were gratified to observe that addition
of HMPA to the anion solution led to smooth alkylation
on addition of 10b, giving adduct 6 in good yield.
Treatment of homoallylic- or homobenzylic-positioned
phenylsulfonyl groups with KOt-Bu in THF generally is
sufficient to effect elimination of phenylsulfinate.18b,20
However, the base-mediated elimination of tertiary cy-
clopentyl phenyl sulfones is particularly capricious.21
Indeed, treatment of sulfone 6 with KOt-Bu (Table 1,
entry 1) failed to adequately effect the desired elimina-
tion. Treatment with KDA (entry 2) provided a modest
yield of the elimination product as a mixture (ca. 1:1) of
double bond isomers 5a and 5b and led us to pursue the
use of n-BuLi. The optimal n-BuLi condition for phenyl-
sulfinate elimination (entry 4) gave 5a as the exclusive
regioisomer (Scheme 2). In summary, bisindene 5 was
prepared in four steps from sulfone 7 in 39% overall yield
without the assistance of column chromatography: the
product of each transformation was obtained by simple
recrystallization of the reaction mixture.
5a with either TiCl4‚2THF22 or TiCl4 followed by either
4
a standard workup or a nonaqueous, nonoxidative work-
up failed to deliver a Ti complex. To our surprise the
desired titanocene complex 13 was obtained only when
bisindene 5a was treated with 1.95 equiv of basesinstead
of the more traditional approach using g2 equivs
followed by an equilibration protocol that involved stir-
ring at room temperature. One possible explanation to
account for the uniform, aforementioned problems in
metalation is that the 2-alkyl indene ring of 5a undergoes
loss of a proton from the R-bridging methylene instead
of from its benzylic position under kinetic deprotonation
conditions to give rise to a dianion incapable of metal-
1
locene formation. H NMR analysis of the crude product
supports assignment of structure 13 as the principal
product of the complexation reaction (Scheme 3). The four
distinct C5-indenyl signals are in agreement with the C1-
symmetric ansa-metallocene structure (Table 2). At-
tempts to purify complex 13 to obtain crystals suitable
for X-ray analysis were unsuccessful and led to decom-
position giving rise to unidentifiable material. The sensi-
tive nature of complex 13 led us to examine whether it
is compatible with the aqueous acid, oxidative workup
procedures of our earlier Ti(III) complexation attempts.
Exposure of 13 to 6 N HCl and air resulted in significant
decomposition.
With the bisindene system available, we turned our
attention to methods for titanocene formation. We and
others previously used the reagent TiCl3‚3THF22 with
great success to obtain ethylene-bridged ansa-titano-
cenes.7,23 However, attempted complexation of 5a with
this reagent under a variety of conditions led only to
intractable material, and in some cases to recovery of
Catalytic hydrogenation of crude 13 with Adams
catalyst under ambient conditions afforded a more robust
metallocene. Purification of the resultant bis(tetrahy-
(18) (a) Hollis, T. K.; Rheingold, A. L.; Robinson, N. P.; Whelan, J .;
Bosnich, B. Organometallics 1992, 11, 2812. (b) Sutton, S. C.; Nantz,
M. H.; Parkin, S. R. Organometallics 1993, 12, 2248. (c) Chen, Z.;
Halterman, R. L. Organometallics 1994, 13, 3932. (d) Shapiro, P. J .;
Kane, K. M.; Vij, A.; Stelck, D.; Matare, G. J .; Hubbard, R. L.; Caron,
B. Organometallics 1999, 18, 3468.
(24) (a) Halterman, R. L.; Vollhardt, K. P. C. Organometallics 1988,
7, 883. (b) Chen, Z.; Halterman, R. L. J . Am. Chem. Soc. 1992, 114,
2276.
(19) Singh, A. K.; Bakshi, R. K.; Corey, E. J . J . Am. Chem. Soc. 1987,
109, 6187.
(20) Magnus, P. D. Tetrahedron 1977, 33, 2019.
(21) Radisson, X.; Kwiatkowski, P. L.; Fuchs, P. L. Synth. Commun.
1987, 17, 39.
(25) Chen, Z. C.; Eriks, K.; Halterman, R. L. Organometallics 1991,
10, 3449.
(26) (a) Diamond, G. M.; Rodewald, S.; J ordan, R. F. Organometallics
1995, 14, 5. (b) Diamond, G. M.; J ordan, R. F.; Petersen, J . L. J . Am.
Chem. Soc. 1996, 118, 8024.
(22) Manzer, L. E. Inorg. Synth. 1982, 21, 135.
(23) Collins, S.; Hong, Y.; Taylor, N. J . Organometallics 1990, 9,
2695.
(27) Emerging resonances at δ 5.84 (d, J ) 2.4 Hz, 1H), 5.94 (d, J
) 2.6 Hz), 6.11 (d, J ) 2.9 Hz), and 6.45 (d, J ) 2.9 Hz, 1H) within 3
h suggest zirconocene formation.
J . Org. Chem, Vol. 68, No. 22, 2003 8449

Kelly et al.
TABLE 2. Select 1H NMR Da ta a
a
p ) present work.
at -78 °C was added dropwise n-BuLi (4.8 mL of a 2.5 M
solution in hexane, 11.9 mmol). The reaction mixture was
stirred 0.5 h at 0 °C and 0.5 h at room temperature, and then
recooled to 0 °C whereupon a solution of dibromoethane (21.8
g, 11.6 mmol) in THF (12 mL) at 0 °C was added dropwise via
cannula. The reaction was slowly warmed to room temperature
and stirred 5 h, and then quenched by addition of saturated
aq NH4Cl. The reaction mixture was extracted with three
portions of CHCl3 and the combined organic extract was
washed successively with H2O and brine and then dried
(MgSO4). The solvents were removed by rotary evaporation.
Recrystallization of the residue from 95% EtOH yielded 2.9 g
(75%) of 11 as brown needles; mp 133-134 °C; 1H NMR δ 3.42
(d, J ) 17.0 Hz, 2H), 4.23 (d, J ) 17.0 Hz, 2H), 7.20-7.27 (m,
4H), 7.59-7.76 (m, 3H), 8.09-8.13 (m, 2H); 13C NMR δ 45.9,
81.5, 124.7, 127.7, 128.9, 131.0, 134.5, 134.9, 137.6; IR (KBr)
3070, 2969, 1583, 1446, 1322, 1228, 1178, 1149 cm-1. Anal.
Calcd for C15H13BrO2S: C, 53.42; H, 3.89. Found: C, 53.50;
H, 3.96.
droindenyl) titanocene dichloride was accomplished by
using a combination of filtration (Celite) and chromatog-
raphy (BioBeads SX-1). Spectral analysis of the product
confirms the structural assignment as the elusive Brintz-
inger isomer, ansa-titanocene 4.
Attempts to recrystallize complex 4 from various
combinations of pentane, hexane, cyclohexane, isooctane,
dichloromethane, diethyl ether, benzene, and toluene
were unsuccessful. Recrystallization with the solvent
mixture 20:1 isooctane:toluene did result in microcrystals
of 4; however, under close inspection these were deemed
unsuitable for X-ray diffraction studies.
In conclusion, we have described an efficient synthesis
of 1-(2-indenyl)-2-(3-indenyl)ethane using a (phenyl)-
sulfone alkylation-elimination tandem sequence to couple
differentially substituted indene rings. In the course of
attempting to metalate this novel bisindene, we found
that a thermodynamic equilibration of the derived dian-
ion is crucial prior to metallocene formation. This obser-
vation may be of practical use for the complexation of
C(2)-substituted bisindene systems. Indeed, we used this
approach to prepare the last isomer of the Brintzinger
family of ansa-titanocenes, ethylene-1-(η5-4,5,6,7-tetrahy-
dro-1-indenyl)-2-(η5-4′,5′,6′,7′-tetrahydro-2′-indenyl)]tita-
nium dichloride.
Column chromatography (hexane:EtOAc, 6:1) on a small
quantity of the crude residue afforded a minor amount of 10a
suitable for characterization; mp 107-110 °C; 1H NMR 2.42-
2.48 (m, 2H), 2.95 (d, J ) 16.4 Hz, 2H), 3.23-3.29 (m, 2H),
3.82 (d, J ) 16.4 Hz, 2H), 7.09-7.15 (m, 4H), 7.51-7.65 (m,
3H), 7.89 (d, J ) 8.21 Hz, 2H); 13C NMR δ 27.3, 39.3, 40.0,
72.7, 124.5, 127.7, 129.4, 130.2, 134.3, 136.3, 139.1; IR (KBr)
3062, 2940, 1446, 1294, 1147 cm-1. Anal. Calcd for C17H17
BrO2S: C, 55.90; H, 4.48. Found: C, 55.71; H, 4.48.
-
Exp er im en ta l Section
P r ep a r a t ion of 2-(2-H yd r oxyet h yl)-2-(p h en ylsu lfo-
n yl)in d a n e (12a ). To a solution of sulfone 7 (40.0 g, 155 mmol)
in THF (516 mL) at -78 °C was added dropwise n-BuLi (70.1
P r epar ation of 2-Br om o-2-(ph en ylsu lfon yl)in dan e (11).
To a solution of sulfone 7 (3.0 g, 11.6 mmol) in THF (47 mL)
8450 J . Org. Chem., Vol. 68, No. 22, 2003

1-(2-Indenyl)-2-(3-indenyl)ethane
mL of a 2.32 M solution in hexane, 163 mmol). The reaction
mixture was stirred 2 h at -78 °C and 0.5 h at 0 °C, and then
recooled to -78 °C whereupon a solution of ethylene oxide (7.16
g, 163 mmol) in THF (325 mL) at -78 °C was added dropwise
via cannula. The reaction was slowly warmed to room tem-
perature, stirred 15 h, and then quenched by addition of
saturated aqueous NH4Cl. The reaction mixture was extracted
with three portions of EtOAc and the combined organic extract
was washed successively with H2O and brine and then dried
(MgSO4). The solvents were removed by rotary evaporation.
Recrystallization of the residue from 95% EtOH yielded 32.6
in THF (200 mL) at -78 °C was added dropwise n-BuLi (43.1
mL of a 2.32 M solution in hexane, 100.1 mmol). The yellow
slurry was stirred 10 min, warmed to room temperature, and
stirred 45 min, and then cooled to -40 °C before addition of
HMPA (44.6 mL). The reaction solution was then added
dropwise via cannula to a stirred solution of iodo-sulfone 10b
(20.0 g, 49.0 mmol) in THF (245 mL) at -78 °C. The amber
reaction mixture turned deep red as it was allowed to warm
to room temperature over 4 h. The reaction was quenched by
addition of aq NH4Cl and then extracted with two portions of
EtOAc. The combined organic extract was washed with H2O
and brine, and then dried (MgSO4). The solvents were removed
by rotary evaporation. The crude residue was dissolved in a
minimum amount of CH2Cl2 and crystallization was induced
by addition of EtOH, yielding 15.8 g (81%) of 6 as a white
powder; mp 137-139 °C; 1H NMR δ 2.20 (m, 2H), 2.43 (m,
2H), 3.01 (d, J ) 17.0 Hz, 2H), 3.19 (s, 2H), 3.84 (d, J ) 17.0
Hz, 2H), 7.05-7.17 (m, 7H), 7.33-7.52 (m, 4H), 7.83-7.85 (m,
2H); 13C NMR δ 22.7, 34.2, 37.7, 39.3, 72.2, 118.7, 123.7, 124.1,
124.7, 126.0, 127.2, 127.9, 128.8, 130.0, 133.6, 136.5, 139.7,
143.2, 144.2, 144.7; IR (KBr) 3066, 2931, 1446, 1297, 1143
cm-1. Anal. Calcd for C26H24O2S: C, 77.97; H, 6.04. Found:
C, 77.85; H, 6.09.
1
g (70%) of 12a as white crystals; mp 163-166 °C; H NMR δ
1.93 (s, 1H), 2.16 (t, J ) 6.2 Hz, 2H), 3.03 (d, J ) 17.0 Hz,
2H), 3.64 (t, J ) 6.5 Hz, 2H), 3.81 (d, J ) 16.4 Hz, 2H), 7.07-
7.10 (m, 4H), 7.50-7.60 (m, 3H), 7.88-7.91 (m, 2H); 13C NMR
δ 38.4, 39.6, 58.8, 71.6, 124.1, 127.2, 128.9, 130.0, 133.8, 136.0,
139.2; IR (KBr) 3516, 3060, 2949, 1446, 1294, 1141 cm-1. Anal.
Calcd for C17H18O3S: C, 67.52; H, 6.00. Found: C, 67.49; H,
6.05.
P r ep a r a tion of 2-(2-Hyd r oxyp r op yl)-2-(p h en ylsu lfo-
n yl)in d a n e (12b). Epoxide adduct 12b was prepared analo-
gously to 12a from 7 (3.0 g, 11.6 mmol) with propylene oxide
(0.73 g, 12.5 mmol): yield 76% (2.78 g) as a white solid; mp
174.5-175.5 °C; 1H NMR δ 1.15 (d, J ) 5.9 Hz, 3H), 1.97-
2.12 (m, 2H), 2.33 (d, J ) 4.1 Hz, 1H), 3.12 (d, J ) 17.0 Hz,
1H), 3.20 (d, J ) 17.0 Hz, 1H), 3.74 (d, J ) 17.0 Hz, 1H), 3.83
(d, J ) 17.0 Hz, 1H), 4.05-4.12 (m, 1H), 7.01-7.08 (m, 4H),
7.46 (m, 2H), 7.57 (m, 1H), 7.88 (m, 2H); 13C NMR δ 24.9, 39.9,
40.4, 44.5, 64.4, 72.4, 124.1, 124.2, 127.1, 127.2, 128.8, 130.1,
133.7, 136.2, 139.4, 139.6; IR (KBr) 3542, 3052, 2969, 1448,
1267, 1137 cm-1. Anal. Calcd for C18H20O3S: C, 68.33; H, 6.24.
Found: C, 67.96; H, 6.24.
P r ep a r a tion of 1-(2-In d en yl)-2-(3-in d en yl)eth a n e (5a ).
To a solution of sulfone 6 (13.5 g, 33.7 mmol) in THF (170 mL)
at -78 °C was added HMPA (17 mL) followed by dropwise
addition of n-BuLi (58.8 mL of a 2.32 M solution in hexane,
136.5 mmol). The deep red solution was stirred 2 h before
quenching by addition of 10% HCl. The reaction mixture was
extracted with two portions of Et2O and the combined organic
extract was washed with H2O and brine, and then dried
(MgSO4). The solvents were removed by rotary evaporation.
The crude product was recrystallized from EtOH-acetone
P r ep a r a t ion of 2-(2-P h en yl-2-h yd r oxyet h yl)-2-(p h e-
n ylsu lfon yl)in d a n e (12c). Epoxide adduct 12c was prepared
analogously to 12a from 7 (1.65 g, 6.4 mmol) with styrene oxide
(0.85 g, 7.0 mmol): yield 64% (1.56 g, recrystallized from
1
yielding 7.5 g (86%) of 5a ; mp 85-87 °C; H NMR δ 2.88 (s,
4H), 3.32 (s, 2H), 3.36 (s, 2H), 6.24 (s, 1H), 6.58 (s, 1H), 7.10-
7.47 (m, 8H); 13C NMR δ 27.1, 29.6, 37.8, 41.1, 118.8, 120.0,
123.4, 123.7, 123.8, 124.6, 126.0, 126.2, 126.4, 128.0, 143.0,
143.7, 144.4, 145.3, 145.5, 150.1; IR (KBr) 3062, 3016, 2898,
1610, 1461, 1392 cm-1. Anal. Calcd for C20H18: C, 92.98; H,
7.02. Found: C, 92.97; H, 7.01.
1
EtOH), as a white solid; mp 144.4-146.3 °C; H NMR δ 2.34
(d, J ) 5.8 Hz, 2H), 2.53 (d, J ) 3.5 Hz, 1H), 3.21 (d, J ) 11.7
Hz, 1H), 3.27 (d, J ) 11.1 Hz, 1H), 3.76 (d, J ) 17.0 Hz, 1H),
3.87 (d, J ) 17.0 Hz, 1H), 5.00 (m, 1H), 6.99-7.09 (m, 4H),
7.20-7.31 (m, 5H), 7.43 (m, 2H), 7.54 (dt, J ) 7.6, 1.2 Hz, 1H),
7.85 (m, 2H); 13C NMR δ 40.1, 40.2, 44.9, 70.9, 72.5, 124.1,
124.2, 125.6, 127.0, 127.1, 127.6, 128.5, 128.8, 130.1, 133.7,
136.2, 139.5, 139.6, 144.5; IR (KBr) 3511, 3027, 2942, 1448,
1282, 1135. Anal. Calcd for C23H22O3S: C, 72.99; H, 5.86.
Found: C, 72.21; H, 5.74.
P r ep a r a tion of [Eth ylen e-1-(η5-in d en -1-yl)-2-(η5-in d en -
2′-yl)]tita n iu m Dich lor id e (13). To a solution of bisindene
5a (797 mg, 3.08 mmol) in THF (20 mL) at -78 °C was added
n-BuLi (2.6 mL of a 2.32 M solution in hexane, 5.95 mmol).
The reaction mixture was stirred 15 min to result in a pink
slurry that was then warmed to room temperature. The
resultant deep red solution was stirred 12 h. In a separate
flask, TiCl4‚2THF (1.03 g, 3.10 mmol) was dissolved in THF
(55 mL). The bisindene dianion and TiCl4 solutions were
simultaneously added dropwise over 30 min via cannula to a
third flask containing 15 mL of THF cooled to -40 °C. The
reaction mixture was warmed to room temperature and stirred
an additional 1.5 h. The reaction solvent was removed by
distillation in vacuo. The dark red residue was redissolved in
CH2Cl2 and filtered through a pad of Celite. The filtrate was
condensed in vacuo and the solids washed with Et2O to afford
778 mg (67%) of the crude titanocene, which was used in the
next reaction without further purification; 1H NMR δ 3.46 (m,
2H), 3.85 (m, 2H), 6.19 (d, J ) 2.3 Hz, 1H), 6.48 (d, J ) 3.5
Hz, 1H), 6.50 (d, J ) 2.3 Hz, 1H), 6.97 (d, J ) 3.5 Hz, 1H),
7.24-7.69 (m, 8H); 13C NMR δ 28.2, 31.5, 107.1, 113.2, 115.7,
121.5, 122.7, 123.5, 125.7, 125.9, 126.4, 127.8, 127.9, 128.4,
128.8, 129.4, 129.8, 131.8, 133.2, 140.2.
P r ep a r a tion of [Eth ylen e-1-(η5-4,5,6,7-tetr a h yd r oin -
d en -1-yl)-2-(η5-4,5,6,7-t et r a h yd r o-in d en -2′-yl)]t it a n iu m
Dich lor id e (4). A mixture of titanocene 13 (600 mg, 1.60
mmol) and PtO2 (73 mg, 0.32 mmol) in THF (8.0 mL) was
stirred under hydrogen at room temperature and ambient
pressure for 36 h. The reaction mixture was filtered through
a pad of Celite and the filtrate was condensed in vacuo. The
deep red residue was dissolved in toluene and passed through
a short column of BioBeads SX-2 (∼4 g), eluting with toluene.
P r ep a r a tion of 2-(2-Iod oeth yl)-2-(p h en ylsu lfon yl)in -
d a n e (10b). To a solution of hydroxysulfone 12 (27.0 g, 89.3
mmol) in a 1:1 mixture of Et2O:CH3CN (446 mL) at room
temperature was added Ph3P (70.3 g, 268 mmol) and imidazole
(18.2 g, 268 mmol). The solution was cooled to 0 °C and I2 (68.0
g, 268 mmol) was added in one portion. The dark brown
reaction mixture was immediately warmed to room tempera-
ture and stirred 3 h before quenching by addition of aq NH4-
Cl. The reaction mixture was extracted with two portions of
EtOAc and the combined organic extract was washed succes-
sively with H2O and brine and then dried (MgSO4). The
solvents were removed by rotary evaporation. The crude
product was washed in a fritted glass funnel with cold absolute
ethanol and the retentate was collected. The ethanol filtrate
was evaporated and the solid residue was again washed in a
funnel with cold ethanol. The two retentate crops were
combined and recrystallized from ethanol to obtain 29.4 g
(80%) of 10b as fine white needles; mp 140-143 °C; 1H NMR
δ 2.49 (m, 2H), 2.94 (d, J ) 17.0 Hz, 2H), 3.02 (m, 2H), 3.81
(d, J ) 16.4 Hz, 2H), 7.07-7.105 (m, 4H), 7.52-7.67 (m, 3H),
7.87-7.90 (m, 2H); 13C NMR δ -2.24, 38.8, 41.2, 73.5, 124.2,
127.4, 129.1, 129.9, 134.0, 136.0, 139.0; IR (KBr) 3053, 2902,
1448, 1288, 1135 cm-1. Anal. Calcd for C17H17IO2S: C, 49.52;
H, 4.16. Found: C, 49.51; H, 4.15.
P r ep a r a tion of 2-(2-In d en -3-yleth yl)-2-(p h en ylsu lfo-
n yl)in d a n e (6). To a solution of indene (11.7 g, 100.5 mmol)
J . Org. Chem, Vol. 68, No. 22, 2003 8451

Kelly et al.
After ca. three column volumes, a deep red solution eluted and
was collected. Removal of solvent afforded 358 mg (57%) of
ansa-titanocene 4; H NMR δ 1.48-1.66 (m, 4H), 1.76-1.93
Ack n ow led gm en t. P.A.K. is grateful for the award
of an R. Bryan Miller Graduate Fellowship. We thank
Professor Peter Somfai (Royal Institute of Technology,
KTH, Stockholm, Sweden) for his valuable contributions
to the project.
1
(m, 3H), 2.00 (m, 1H), 2.26 (m, 1H), 2.42-2.58 (m, 3H), 2.67
(m, 1H), 2.96-3.25 (m, 7H), 5.30 (d, J ) 2.5 Hz, 1H), 5.67 (d,
J ) 2.3 Hz, 1H), 5.89 (d, J ) 2.9 Hz, 1H), 6.57 (d, J ) 2.7 Hz,
1H); 13C NMR δ 21.7, 21.8, 21.9 (2), 24.2, 24.7, 24.8, 25.2, 28.1,
30.8, 110.9, 111.9, 114.3, 125.3, 129.0, 133.9, 136.8, 137.6,
Su p p or tin g In for m a tion Ava ila ble: NMR spectra for
obtained compounds. This material is available free of charge
via the Internet at http://pubs.acs.org.
137.8, 139.0; IR (KBr) 3077, 2932, 2861, 1445, 1429 cm-1
;
HRMS (EI) calcd for C20H24ClTi [M - Cl]+ 347.1046, found
347.1037.
J O034975O
8452 J . Org. Chem., Vol. 68, No. 22, 2003