Zirconocene-mediated macrocyclizations of diynes containing Di-o-methylphenylene spacers

Full text of DOI:10.1021/jo802715m

The reductive coupling of alkynes by zirconocene results in
zirconacyclopentadienes which can be transformed to a wide
array of conjugated structures and heterocycles.13 The efficient
synthesis of macrocycles via the zirconocene coupling route is
based on the coupling of silicon-substituted diynes. This process
involves the formation of C-C bonds, and with silyl-substituted
alkynyl groups, the coupling is highly regioselective and
reversible.14,15 It is the reversible nature of these couplings that
provides efficient, high-yield routes to macrocyclic structures.
Although the silicon substituents have these desirable effects
on the zirconocene coupling, the resulting zirconacyclopenta-
dienes possessing silyl groups in the R position are difficult to
derivatize4,16 and successful derivatizations can be low-yielding.9
Therefore, it is of interest to develop new synthetic methodolo-
gies that do not depend on bulky R-directing groups.
Zirconocene-Mediated Macrocyclizations of
Diynes Containing Di-o-Methylphenylene Spacers
Adam D. Miller, Jennifer L. McBee, and T. Don Tilley*
Department of Chemistry, UniVersity of California,
Berkeley, California 94720-1460
tdtilley@berkeley.edu
ReceiVed December 10, 2008
ꢀ-Directing groups have the potential to promote macrocycle
formation while leaving the metal center sterically accessible
for further chemical transformations. Previous studies with
electron-withdrawing aryl groups (i.e., -C6F5) demonstrate the
desired ꢀ selectivity, but these groups do not promote revers-
ibility.17 Subsequent investigations have revealed that the mesityl
group preferentially couples into the ꢀ-position and enhances
the reversibility of alkyne couplings.18 In this contribution, we
describe the synthesis of macrocycles via the coupling of diynes
containing di-o-methylated phenylene spacers as analogues of
the mesityl group.
Two diynes, containing biphenyl and terphenyl spacers, were
synthesized. The diyne 3,3′,5,5′-tetramethyl-4,4′-di(pent-1-
ynyl)biphenyl (4) was synthesized by the route shown in Scheme
1. 4,4′-Diiodo-3,3′,5,5′-tetramethylbiphenyl (2) was synthesized
from 3,3′,5,5′-tetramethylbenzidine (1) via a Sandmeyer-type
iodination. Although the direct coupling of 1-pentyne with
biphenyl 2 would have been the most direct route to diyne 4,
this reaction proved too low-yielding to give any appreciable
amount of product. Thus, the alkynyl groups were introduced
via Sonogashira coupling of Me3SiCt CH to give 3,3′,5,5′-
tetramethyl-4,4′-bis(trimethylsilyl-2-ethyne-1-yl)biphenyl (3) in
62% yield. The alkynes were then deprotected by removal of
the -SiMe3 groups under basic conditions, and the propyl
groups were introduced by a nucleophilic substitution reaction
between lithium acetylide and 1-bromopropane.
The diynes 3,3′,5,5′-tetramethyl-4,4′-di(pent-1-ynyl)biphenyl
(4) and 3,3′′,5,5′′-tetramethyl-4,4′′-di(hex-1-ynyl)terphenyl
(9) undergo coupling with Cp2Zr(η2-Me3SiCt CSiMe3)(py)
to give dimeric macrocycles in moderate yields (16% for 4
and 26% for 9).
Macrocycles and cyclophanes are desirable synthetic targets
for a wide variety of investigations and applications including
(for example) aromaticity, host-guest chemistry, and supramo-
lecular chemistry.1 However, the preparation of these molecules
is often fraught with difficult procedures (e.g., high dilution),
low yields, and laborious purification.2 Previously, we have
described the preparation of zirconium-containing macrocycles
and cyclophanes from the zirconocene coupling of diynes.3-12
This method provides simple, high-yield routes to macrocycles
that can vary considerably in size and shape.
Macrocycle 5 was prepared by coupling of diyne 4 with
Rosenthal’s Cp2Zr(η2-Me3SiCt CSiMe3)(py).19 Although the
resulting zirconium-containing macrocycle precipitated out of
benzene upon formation, it was relatively impure. This mac-
rocycle was demetalated by protonolysis with TFA to give
macrocycle 5 in 16% yield after purification by column
chromatography. The dimeric nature of the macrocycle was
(1) Gleiter, R.; Hopf, H. Modern Cyclophane Chemistry; Wiley-VCH:
Weinheim, Germany, 2004.
(2) Parker, D. Macrocycle Synthesis: A Practical Approach; Oxford Uni-
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(3) Liu, F. Q.; Harder, G.; Tilley, T. D. J. Am. Chem. Soc. 1998, 120, 3271–
3272.
(4) Mao, S. S. H.; Liu, F. Q.; Tilley, T. D. J. Am. Chem. Soc. 1998, 120,
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(5) Mao, S. S. H.; Tilley, T. D. J. Am. Chem. Soc. 1995, 117, 5365–5366.
(6) Nitschke, J.; Tilley, T. D. J. Org. Chem. 1998, 63, 3673–3676.
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2145.
(8) Nitschke, J. R.; Tilley, T. D. J. Am. Chem. Soc. 2001, 123, 10183–10190.
(9) Nitschke, J. R.; Tilley, T. D. J. Organomet. Chem. 2003, 666, 15–22.
(10) Nitschke, J. R.; Zurcher, S.; Tilley, T. D. J. Am. Chem. Soc. 2000, 122,
10345–10352.
(11) Schafer, L. L.; Nitschke, J. R.; Mao, S. S. H.; Liu, F. Q.; Harder, G.;
Haufe, M.; Tilley, T. D. Chem.sEur. J. 2002, 8, 74–83.
(12) Schafer, L. L.; Tilley, T. D. J. Am. Chem. Soc. 2001, 123, 2683–2684.
(13) Negishi, E.; Takahashi, T. Bull. Chem. Soc. Jpn. 1998, 71, 755–769.
(14) Erker, G.; Zwettler, R. J. Organomet. Chem. 1991, 409, 179–188.
(15) Erker, G.; Zwettler, R.; Kruger, C.; Hyla-Kryspin, I.; Gleiter, R.
Organometallics 1990, 9, 524–530.
(16) Sava, X.; Mezailles, N.; Maigrot, N.; Nief, F.; Ricard, L.; Mathey, F.;
Le Floch, P. Organometallics 1999, 18, 4205–4215.
(17) Johnson, S. A.; Liu, F. Q.; Suh, M. C.; Zurcher, S.; Haufe, M.; Mao,
S. S. H.; Tilley, T. D. J. Am. Chem. Soc. 2003, 125, 4199–4211.
(18) Miller, A. D.; Tannaci, J. F.; Johnson, S. A.; Lee, H.; McBee, J. L.;
Tilley, T. D. J. Am. Chem. Soc. Accepted for publication.
(19) Rosenthal, U.; Ohff, A.; Baumann, W.; Tillack, A.; Gorls, H.; Burlakov,
V. V.; Shur, V. B. Z. Anorg. Allg. Chem. 1995, 621, 77–83.
2880 J. Org. Chem. 2009, 74, 2880–2883
10.1021/jo802715m CCC: $40.75 2009 American Chemical Society
Published on Web 03/11/2009

SCHEME 1. Synthesis and Cyclodimerization of Diyne 4a
SCHEME 3. Synthesis of Macrocycles 10 and 11a
a Conditons: (g) Cp2Zr(η2-Me3SiCt CSiMe3)(py), toluene, 26%; (h) TFA,
THF, 23% (overall).
a Conditions: (a) NaNO2, KI, H2SO4, H2O, 24%; (b) PdCl2(PPh3)2, CuI,
PPh3, Me3SiCt CH, Et3N, 62%; (c) (i) K2CO3, THF, MeOH, (ii) n-BuLi,
pentane, (iii) 1-bromopropane, TMEDA, THF, 30%; (d) (i) Cp2Zr(η2-
Me3SiCt CSiMe3)(py), benzene, (ii) TFA, THF, 16%.
SCHEME 2. Synthesis of Diyne 9a
FIGURE 1. ORTEP depiction of the solid-state molecular structure
of 10. Hydrogen atoms are omitted for clarity. Ellipsoids are drawn
with 50% probabilities.
a Conditions: (e) PdCl2, X-Phos, Cs2CO3, 1-hexyne, AcCN, 59%; (f) 8,
Pd2(dba)3, X-Phos, Cs2CO3, DMF, 69%.
terphenyl spacer (Figure 1). The phenylene rings in the
ꢀ-positions of the zirconacyclopentadiene are bent by 11.2 and
17.4° (defined as the angle between the planes formed by the
ipso and two ortho C’s of the phenylene group), while the
middle phenylene ring is significantly more planar (bent by
2.9°). On the other hand, the zirconacyclopentadiene moiety
exhibits relatively little strain with a nearly planar framework.
Zirconocene-mediated macrocyclizations may be driven by
precipitation of the macrocycle from solution. Thus, in an
attempt to improve the yield of 10, the relatively poor solvent
diethyl ether was employed in the reaction of diyne 9 with
Cp2Zr(η2-Me3SiCt CSiMe3)(py). In fact, this reaction led to
significantly more precipitate, but the yield of the macrocycle
10 was not improved. Analysis of the resulting solid by mass
spectrometry (MALDI-TOF) indicated that the major byproducts
were oligomers (n ) 3-7). The crude solid was subsequently
demetalated with TFA, and the resulting macrocycle was
isolated from the oligomeric byproducts by column chroma-
tography to give 11 in 23% yield.
Compared to other zirconocene-mediated cyclizations of
diynes containing silicon substituents, the cyclizations of diynes
containing o-methylphenylene spacers are rather low-yielding.
It has been observed that (alkyl)Ct CMes will couple with the
mesityl group in the ꢀ-position under kinetic conditions (ambient
temperature) such that the ꢀꢀ regioisomer is the major product
(Cp2Zr[2,5-Pr2-3,4-Mes2C4]). Heating solutions of these zir-
conacycles gives the Rꢀ regiosomer, Cp2Zr[2,4-Mes2-3,5-Pr2C4],
as the apparent thermodynamic product.18 Similarly, heating
solutions of diyne 9 and Cp2Zr(η2-Me3SiCt CSiMe3)(py) to 80
°C in C6D6 did not lead to an increase in macrocycle yield and
established by EI-MS (including HRMS). The short, two-carbon
spacer between the tetramethylbiphenyl groups in macrocycle
5 probably causes considerable strain within the molecule, which
may decrease the yield of the cyclization step.
An analogous diyne with a terphenyl spacer was synthesized
by the route in Scheme 2. In the first step, 1-hexyne was coupled
to 4-chloro-1-iodo-2,6-dimethylbenzene (6) via a palladium
coupling route using Buchwald’s X-Phos ligand.20 Although
these reaction conditions were optimized for coupling terminal
alkynes to chloroarenes, we observed the coupling to prefer-
entially occur at the sterically hindered iodo site. Diyne 9 was
then obtained through two consecutive couplings of chloroarene
7 to diboronic ester 8 under anhydrous conditions.
The synthesis of macrocycle 10 resulted from the cyclodimer-
ization of diyne 9 with Cp2Zr(η2-Me3SiCt CSiMe3)(py) in
toluene (Scheme 3). This macrocycle has no appreciable
solubility in common organic solvents, which prevented char-
acterization by mass spectrometry and NMR spectroscopy.
Macrocycle 10 was demetalated by protonolysis with TFA to
afford macrocycle 11. Removal of the zirconocene moiety led
to a considerable increase in solubility and allowed for
characterization of macrocycle 11 by routine techniques (1H and
13C{1H} NMR, MALDI-TOF, and combustion analysis).
To further characterize 10, X-ray quality crystals were
obtained by layering a toluene solution of diyne 9 over a toluene
solution of Cp2Zr(η2-Me3SiCt CSiMe3)(py). The resulting cen-
trosymmetric structure exhibits conformational strain along the
(20) Gelman, D.; Buchwald, S. L. Angew. Chem., Int. Ed. 2003, 42, 5993–
5996.
J. Org. Chem. Vol. 74, No. 7, 2009 2881

(3.0 mL, 4.9 mmol) was added dropwise via syringe. The cold bath
was removed after 10 min, and the reaction mixture was stirred at
ambient temperature for 2 h. The solvent was then removed by
cannula filtration, and the resulting solid was suspended in THF
(25 mL). To this suspension was added 1-bromopropane (0.44 mL,
4.9 mmol), and the reaction mixture was heated at 60 °C for 16 h.
The reaction was monitored by GC-MS. TMEDA (0.73 mL, 4.8
mmol) was added to the reaction mixture, and this was heated at
reflux for 20 h. 1-Bromopropane (0.15 mL, 1.6 mmol) was added
to the reaction mixture, and this was heated at reflux for an
additional 16 h. The solvent was then removed, and the resulting
oil was dissolved in diethyl ether. This solution was washed with
a saturated solution of NaHCO3, water, 2 N NaOH, and brine. The
organic layer was collected, dried with MgSO4, filtered, and
concentrated. The resulting crude oil was purified by column
chromatography (silica gel, hexanes/toluene) to give a light yellow
solid in 30% yield (0.25 g, 0.73 mmol): 1H NMR (500 MHz, C6D6)
δ 7.36 (s, 4H), 2.57 (s, 12H), 2.30 (t, J ) 6.8 Hz, 4H), 1.49 (tq, J
) 7.2 Hz, 4H), 0.98 (t, J ) 7.2 Hz, 6H); 13C{1H} NMR (125.8
MHz, CDCl3) δ 140.5, 139.4, 125.4, 123.0, 99.6, 78.5, 22.7, 22.0,
21.5, 13.8; GC-MS m/z ) 342 (M+); HRMS calcd for C26H30
342.2348, found 342.2354.
eventually led to decomposition of any macrocycle that had
formed. Therefore, it seems reasonable to assume that macro-
cycle formation with diynes containing o-methylphenylene
spacers is under kinetic rather than thermodynamic control.
In conclusion, we have demonstrated that the zirconocene
coupling of diynes containing di-o-methylphenylene spacers
results in dimeric macrocycles that can be demetalated to give
all-carbon-based structures. This new method is complementary
to the coupling of diynes terminated with silicon substituents,
which generally give trimeric macrocycles with p-phenylene
spacers of four rings or less.6,8,10,11
Experimental Section
4,4′-Diiodo-3,3′,5,5′-tetramethylbiphenyl (2). Biphenyl 1 (1.50
g, 6.2 mmol) was dissolved in toluene (5 mL) and acetone (10
mL), and to this solution were added water (20 mL) and H2SO4
(1.3 mL, 25.0 mmol), which caused the solid to precipitate out of
solution. The reaction mixture was cooled to 0 °C, and a solution
of NaNO2 (1.55 g, 22.5 mmol) in water (8 mL) was added dropwise.
This was stirred at 0 °C for 3 h. To this reaction mixture was slowly
added a solution of KI (2.50 g, 15.0 mmol) in water (10 mL) over
10 min. The reaction mixture was then heated at 40 °C for 1 h and
then at 80 °C until the solid dissolved. The reaction mixture was
diluted with water and then extracted with diethyl ether. The organic
layers were combined and then washed with a saturated solution
of Na2S2O3, water, 2 N NaOH, and brine. The organic layer was
collected, dried with MgSO4, filtered, and concentrated. The
resulting crude product was filtered through a plug of silica with
hexanes as the eluent to give a yellow solid in 24% yield (0.68 g,
Macrocycle 5. Biphenyl 4 (0.10 g, 0.29 mmol) and Cp2Zr(py)(η2-
Me3SiCt CSiMe3) (0.14 g, 0.29 mmol) were loaded into a Teflon-
sealed tube and dissolved in benzene (2 mL). Reaction occurred at
ambient temperature over 16 h, during which time precipitate
formed. The solvent was removed by filtration on a fritted funnel,
and the resulting solid was washed with benzene and diethyl ether
to give an orange powder in 17% crude yield (0.028 g, 0.025 mmol).
This solid was loaded into a Schlenk tube and dissolved in THF (5
mL). To this solution was added TFA (18 µL, 0.25 mmol), and the
reaction mixture was stirred at ambient temperature for 2.5 h. The
solvent and excess acid were removed under vacuum. The resulting
crude solid was purified by column chromatography (silica gel,
hexanes/toluene) to give a white solid in 16% overall yield (0.016
g, 0.023 mmol): 1H NMR (500 MHz, CDCl3) δ 6.54 (s, 8H), 6.29
(t, J ) 7.2 Hz, 4H), 2.14 (s, 24H), 2.01 (dt, J ) 7.2 Hz, 8H), 1.51
(tq, J ) 7.4 Hz, 8H), 0.95 (t, J ) 7.5 Hz, 12H); 13C{1H} NMR
(125.8 MHz, CDCl3) δ 140.4, 140.1, 136.6, 135.9, 127.6, 125.7,
32.7, 23.0, 21.1, 14.4; EI-MS m/z ) 688 (M+); HRMS calcd for
C52H64 688.5008, found 688.5015.
1
1.5 mmol): H NMR (400 MHz, C6D6) δ 7.07 (s, 4H), 2.38 (s,
12H); 13C{1H} NMR (125.8 MHz, C6D6) δ 143.0, 140.4, 126.2,
108.0, 30.2; GC-MS m/z ) 462 (M+). Anal. Calcd for C16H16I2:
C, 41.59; H, 3.49. Found: C, 41.94; H, 3.45.
3,3′,5,5′-Tetramethyl-4,4′-bis(trimethylsilyl-2-ethyne-1-yl)biphe-
nyl (3). Biphenyl 2 (2.00 g, 4.3 mmol), CuI (0.020 g, 0.09 mmol),
PPh3 (0.050 g, 0.17 mmol), and PdCl2(PPh3)2 (0.070 g, 0.09 mmol)
were loaded into a flask. These solids were dissolved/suspended in
triethylamine (50 mL), and trimethylsilylacetylene (1.3 mL, 9.5
mmol) was added via syringe. The flask was equipped with a reflux
condenser, and the reaction mixture was heated at reflux. The
reaction progress was monitored by GC-MS. At 8 and 24 h
intervals, CuI (0.020 g, 0.09 mmol), PPh3 (0.050 g, 0.17 mmol),
PdCl2(PPh3)2 (0.070 g, 0.09 mmol), and trimethylsilylacetylene (0.5
mL, 3.5 mmol) were added. The reaction mixture was heated at
reflux for a total of 44 h. The reaction was quenched with a saturated
solution of NH4Cl (50 mL), and this was stirred for 10 min. The
reaction mixture was then filtered through a plug of silica gel. The
organic layer was collected and washed with a saturated solution
of NH4Cl, a dilute solution of HCl, water, and brine. The organic
layer was collected, dried with MgSO4, filtered, and concentrated.
The crude solid was adsorbed onto silica gel and purified by column
chromatography (silica gel, hexanes/diethyl ether) to give a light
yellow solid in 62% yield (1.09 g, 2.7 mmol): 1H NMR (500 MHz,
CDCl3) δ 7.25 (s, 4H), 2.48 (s, 12H), 0.28 (s, 18H); 13C{1H} NMR
(125.8 MHz, CDCl3) δ 141.2, 140.1, 125.5, 122.3, 103.7, 103.0,
21.4, 0.4; GC-MS m/z ) 402 (M+). Anal. Calcd for C26H34Si2: C,
77.54; H, 8.51. Found: C, 77.14; H, 8.58.
3,3′,5,5′-Tetramethyl-4,4′-di(pent-1-ynyl)biphenyl (4). Biphe-
nyl 3 (1.00 g, 2.5 mmol) and K2CO3 (0.34 g, 2.5 mmol) were loaded
into a flask and dissolved/suspended in THF (15 mL) and methanol
(15 mL). The reaction mixture was stirred at ambient temperature
for 4 h, and then the solvent was removed. The crude solid was
extracted with diethyl ether, and this was washed with water, a
saturated solution of NaHCO3, and brine. The organic layer was
collected, dried over MgSO4, filtered, and concentrated. The
resulting solid was loaded into a Schlenk flask and dissolved in
pentane (20 mL). This solution was cooled in to 0 °C, and BuLi
5-Chloro-2-(hex-1-ynyl)-1,3-dimethylbenzene (7). 2-Dicyclo-
hexylphosphino-2′,4′,6′-triisopropylbiphenyl (0.54 g, 1.1 mmol),
PdCl2 (67 mg, 0.40 mmol), and Cs2CO3 (16.0 g, 48.9 mmol) were
loaded into a flask and suspended in acetonitrile (40 mL). To this
suspension was added 4-chloro-1-iodo-2,6-dimethylbenzene (6)21
(5.00 g, 18.8 mmol), and the reaction mixture was stirred for 10
min. 1-Hexyne (2.8 mL, 24.4 mmol) was then added via syringe,
and the reaction mixture was heated at 80 °C for 16 h. The reaction
mixture was allowed to cool to ambient temperature and then diluted
with water. The aqueous layer was extracted with diethyl ether.
The organic layers were combined, dried with MgSO4, filtered, and
concentrated. The resulting crude product was purified by column
chromatography (silica gel, hexanes) to give a yellow oil in 59%
1
yield (2.45 g, 11.1 mmol): H NMR (400 MHz, C6D6) δ 6.91 (s,
2H), 2.25 (m, 8H), 1.36 (m, 4H), 0.81 (t, J ) 7.0 Hz, 3H); 13C{1H}
NMR (125.8 MHz, C6D6) δ 142.3, 133.2, 127.5, 123.3, 100.2, 78.4,
31.6, 22.6, 21.4, 19.9, 14.1; GC-MS m/z ) 220 (M+). Anal. Calcd
for C14H17Cl: C, 76.18; H, 7.76. Found: C, 76.14; H, 7.69.
3,3′′,5,5′′-Tetramethyl-4,4′′-di(hex-1-ynyl)terphenyl (9). 1,4-
Bis(4,4,5,5-tetramethyl-1,3-dioxaborolan-2-yl)benzene (8) (0.067 g,
0.20 mmol), Pd2(dba)3 (3 mg, 3 µmol), 2-dicyclohexylphosphino-
2′,4′,6′-triisopropylbiphenyl (9 mg, 18 µmol), and Cs2CO3 (0.39 g,
1.2 mmol) were loaded into a flask. A separate flask was loaded
with alkyne 7 (0.090 g, 0.40 mmol); this flask was washed with
DMF (2 × 4 mL), and the resulting solutions were transferred by
(21) Zhang, Y.; Burgess, J. P.; Brackeen, M.; Gilliam, A.; Mascarella, S. W.;
Page, K.; Seltzman, H. H.; Thomas, B. F. J. Med. Chem. 2008, 51, 3526–3539.
2882 J. Org. Chem. Vol. 74, No. 7, 2009

cannula to the flask containing the reagents. The solution was
degassed by three freeze/pump/thaw cycles, and then the flask
was sealed and heated at 95 °C for 16 h. The reaction mixture was
filtered through diatomaceous earth and diluted with ethyl acetate.
This was then washed with a saturated solution of NaHCO3 and
brine. The organic layer was collected, dried with MgSO4, filtered,
and concentrated. The resulting crude product was purified by
column chromatography (silica gel, hexanes/diethyl ether) to give
temperature for 16 h, during which time an orange precipitate
formed. The solvent was removed by cannula filtration, and the
crude solid was dried under vacuum. This solid was suspended in
THF (15 mL), and to this was added TFA (0.10 mL, 1.3 mmol).
This was stirred at ambient temperature for 1 h, during which time
the solid dissolved into solution. The solvent and excess acid were
removed under vacuum, and the resulting yellow solid was purified
by column chromatography (silica gel, hexanes/toluene) to give a
1
1
a light yellow solid in 69% yield (0.061 g, 0.14 mmol): H NMR
light yellow solid in 23% yield (0.035 g, 0.039 mmol): H NMR
(500 MHz, C6D6) δ 7.61 (s, 4H), 7.36 (s, 4H), 2.59 (s, 12H), 2.38
(t, J ) 7.0 Hz, 4H), 1.45 (m, 8H), 0.86 (t, J ) 7.0 Hz, 6H); 13C{1H}
NMR (125.8 MHz, C6D6) δ 141.1, 140.6, 140.1, 128.2, 126.2,
124.0, 100.1, 79.5, 31.8, 22.6, 21.9, 20.1, 14.1; GC-MS m/z )
446 (M+). Anal. Calcd for C34H38: C, 91.42; H, 8.58. Found: C,
91.07; H, 8.46.
(400 MHz, CDCl3) δ 7.11 (s, 8H), 6.76 (s, 8H), 6.26 (t, J ) 7.0
Hz, 4H), 2.13 (s, 24H), 2.03 (dt, J ) 7.3 Hz, 8H), 1.50 (tt, J ) 7.6
Hz, 8H), 1.38 (tq, J ) 7.2 Hz, 8H), 0.86 (t, J ) 7.2 Hz, 12H);
13C{1H} NMR (100.6 MHz, CDCl3) δ 140.3 (two overlapping
peaks), 139.5, 137.3, 136.2, 128.1, 127.5, 125.6, 32.1, 30.2, 23.0,
20.8, 14.4; MALDI-TOF m/z ) 896 (M+). Anal. Calcd for C68H80:
C, 91.01; H, 8.99. Found: C, 90.63; H, 9.10.
Macrocycle10.Terphenyl9(0.25g,0.56mmol)andCp2Zr(py)(η2-
Me3SiCt CSiMe3) (0.26 g, 0.56 mmol) were loaded into a flask
and dissolved in toluene (8 mL). This mixture was stirred at ambient
temperature for 16 h, during which time precipitate formed. The
solvent was removed by cannula filtration, and the resulting solid
was washed with toluene to give an orange powder in 26% yield
(0.081 g, 0.061 mmol). Attempts at characterization by NMR
spectroscopy were unsuccessful due to low solubility. Anal. Calcd
for C88H96Zr2: C, 79.10; H, 7.24. Found: C, 78.98; H, 7.19.
Macrocycle11.Terphenyl9(0.15g,0.34mmol)andCp2Zr(py)(η2-
Me3SiCt CSiMe3) (0.16 g, 0.34 mmol) were loaded into separate
flasks. The diyne was dissolved in diethyl ether (15 mL), and a
solution of the Cp2Zr(pyr)(η2-Me3SiCt CSiMe3) in diethyl ether
(5 mL) was added via cannula. This was stirred at ambient
Acknowledgment. To John Tannaci and Andrew Halff for
helpful discussions. This work was supported by the National
Science Foundation research grant CHE0314709.
Supporting Information Available: General experimental
methods, copies of 1H and 13C{1H} NMR spectra, tables of bond
lengths and angles, and the X-ray crystallographic data for
compound 10 in the form of CIF files. This material is available
free of charge via the Internet at http://pubs.acs.org.
JO802715M
J. Org. Chem. Vol. 74, No. 7, 2009 2883