The synthesis of a novel strained diyneparacyclophane and its dimer by metal-mediated coupling

Article abstract of DOI:10.1002/(SICI)1521-3773(20000117)39:2<385::AID-ANIE385>3.0.CO;2-I

Relieve strain with a twist! Synthesis of the paracyclophane 1 and its dimer 2 employed a sequence of metal-mediated couplings. The X-ray analysis of 2 revealed a helical twist inherent in this structure, which created extended arms, that trapped a molecule of solvent. A carboxylic acid derivative of 1 was also prepared, and its structure indicated the diyne rod moiety of 1 is distorted more than in analogous compounds.

Full text of DOI:10.1002/(SICI)1521-3773(20000117)39:2<385::AID-ANIE385>3.0.CO;2-I

COMMUNICATIONS
1996, 108, 110; Angew. Chem. Int. Ed. Engl. 1996, 35, 65; d) P. J.
Brothers, K. Hübler, U. Hübler, B. C. Noll, M. M. Olmstead, P. P.
Power, Angew. Chem. 1996, 108, 2528; Angew. Chem. Int. Ed. Engl.
1996, 35, 2355.
substituents on the indium atoms. The synthesis and structure
of 1 also suggest that the extrusion of part of the ligand array
in simple clusters such as R2MMR2 (M ˆ Ga, In) or (InR)n to
give higher clusters that incorporate unsubstituted metal
atoms may be a general phenomenon in these sterically
crowded species. Another distinctive feature of the synthesis
of 1 is that an InI compound was employed as starting
material. This already has a 1:1 metal:ligand ratio and is closer
stoichiometrically to the more highly aggregated cluster
product 1 than are the higher valent starting materials, which
usually carry two substituents per metal atom. It now seems
likely that further examples of these interesting species will be
isolated not only for indium but also for the other Group 13
metals.
[9] A. F. Wells, Structural Inorganic Chemistry, 5th ed., Clarendon,
Oxford, 1984, p. 1278.
[10] W. Uhl, A. Jantschak, W. Saak, M. Kaupp, R. Wartchow, Organo-
metallics 1998, 17, 5009.
[11] J. Ebenhöch, G. Müller, J. Riede, H. Schmidbaur, Angew. Chem. 1984,
96, 367; Angew. Chem. Int. Ed. Engl. 1984, 23, 386.
[12] Some prominent recent examples for Al and Ga are given in: A.
Ecker, L. Weckert, H. Schnöckel, Nature 1997, 387, 379; C. Klemp, R.
Koppe, E. Weckert, H. Schnöckel, Angew. Chem. 1999, 111, 1851;
Angew. Chem. Int. Ed. 1999, 38, 1740; W. Kostler, G. Linti. Angew.
Chem. 1997, 109, 2758; Angew. Chem. Int. Ed. Engl. 1997, 36, 2644.
[13] H. Schumann, C. Janiak, F. Görlitz, J. Loebel, A. Dietrich, J.
Organomet. Chem. 1989, 363, 243.
[14] O. T. Beachley, R. Blom, M. R. Churchill, J. Fettinger, J. C. Pazik, L.
Victoriano, J. Am. Chem. Soc. 1986, 108, 4666.
[15] N. Wiberg, H.-W. Lerner, H. Nöth, W. Ponikwar, Angew. Chem. 1999,
111, 887; Angew. Chem. Int. Ed. 1999, 38, 839.
Experimental Section
Under anaerobic and anhydrous conditions, a pale yellow solution of
LiC6H3-2,6-Mes2 (1.60 g, 4.99 mmol) in THF (20 mL) was cooled to ca.
788C and added dropwise to a yellow suspension of InCl (0.82 g,
5.5 mmol) in THF (5 mL) at ca. 788C. The solution became dark orange-
brown upon addition and was stirred for 30 min. The solution was warmed
to 158C, and the THF was removed under reduced pressure. The orange-
brown solid was extracted with hexanes (100 mL) and gravity filtered
through a Celite pad. The volume of the orange-brown solution was
reduced to 30 mL. Cooling to ca. 08C for 12 h produced dark brown crystals
of 1 (0.55 g, 0.25 mmol, 36.8% yield based on InCl). M.p. 207 ± 2108C;
1H NMR (399.77 MHz, C6D6, 258C, TMS): d ˆ 0.88 (t, hexane), 1.22 (m,
hexane), 1.88 (s, 24H, p-Me, Mes), 2.12 (brs, 24H, o-Me, Mes), 2.29 (brs,
24H, o-Me, Mes), 6.75 (d, 3J (H, H) ˆ 7.2 Hz, 8H, m-C6H3), 6.86 (s, m-Mes,
16H), 7.05 (t, 3J(H, H) ˆ 7.2 Hz, 4H, p-C6H3); 13C{1H} NMR (100.53 MHz,
C6D6, 258C, TMS): d ˆ 21.29 (p-Me, Mes), 21.65 (o-Me, Mes), 129.28 (m-
Mes), 136.59 (m-C6H3), 137.13 (o-Mes), 137.23 (p-C6H3), 141.53 (p-Mes),
144.97 (i-Mes), 148.77 (o-C6H3), 189.88 (i-C6H3); UV/Vis (hexanes): lmax
(e) ˆ 305sh (1000).
[16] N. Wiberg, T. Blank, A. Purath, G. Stösser, H. Schnöckel, Angew.
Chem. 1999, 111, 2745; Angew. Chem. Int. Ed. 1999, 38, 2563.
The Synthesis of a Novel Strained
Diyneparacyclophane and Its Dimer by
Metal-Mediated Coupling**
Shawn K. Collins, Glenn P. A. Yap, and Alex G. Fallis*
Diverse families of cyclophanes[1] and assorted cage com-
pounds[2] with novel structures and properties continue to be
topics of wide-spread interest.[3] Earlier, we reported the
synthesis of a novel class of enediyne cyclophanes by
sequential palladium- or copper-mediated coupling.[4] In
contrast to normal [n.m]paracyclophanes, the rotation of the
benzene ring in these molecules is not restricted by the
bridging bonds. Consequently they were christened revolv-
eneynes 1 as the aromatic rings rotate freely, with ªskipping
ropeº-type properties, in which the bridging units and one
aromatic ring may swing around each other. The unsaturated
bonds in these bridges impart a helical twist to the structures.
As a result, they possess helical chirality, a property that is
shared with related D2-symmetric olefinic paracyclophanes.[5]
In a related area, we[6] and others[7] have attemped to extend
these syntheses to multibridged systems in order to prepare
potential precursors to fullerenes such as C60, but with limited
success. However, Vollhardt and co-workers[8] have demon-
strated that 2 decomposed explosively to form carbon onions
when heated, and cobalt alkyne complexes afforded carbon
nanotubes.
Received: August 30, 1999 [Z13942]
[1] B. Schiemenz, P. P. Power, Organometallics 1998, 15, 958.
[2] a) S. T. Haubrich, P. P. Power, J. Am. Chem. Soc. 1998, 120, 2202; b) M.
Niemeyer, P. P. Power, Angew. Chem. 1998, 110, 1291; Angew. Chem.
Int. Ed. 1998, 37, 1277.
[3] W. Uhl, Angew. Chem. 1993, 105, 1449; Angew. Chem. Int. Ed. Engl.
1993, 32, 1386; C. Dohmeier, D. Loos, H. Schnöckel, Angew. Chem.
1996, 108, 141; Angew. Chem. Int. Ed. Engl. 1996, 35, 129.
[4] B. T. Twamley, S. T. Haubrich, P. P. Power, Adv. Organomet. Chem.
1999, 44, 1.
[5] K. Ruhlandt-Senge, J. J. Ellison, R. J. Wehnschulte, F. Pauer, P. P.
Power, J. Am. Chem. Soc. 1993, 115, 11353.
[6] Crystal data for 1 (190 K) with MoKa (l ˆ 0.71073 Š) radiation: a ˆ
14.0174(5), b ˆ 15.5917(5), c ˆ 23.7818(8) Š, a ˆ 92.047(1), b ˆ
Å
104.734(1), g ˆ 107.703(1)8, Z ˆ 2, space group P1, R1 ˆ 0.052 for
7389 data with I > 2s(I). Crystallographic data (excluding structure
factors) for the structures reported in this paper have been deposited
with the Cambridge Crystallographic Data Centre as supplementary
publication no. CCDC-135535. Copies of the data can be obtained free
of charge on application to CCDC, 12 Union Road, Cambridge
CB21EZ, UK (fax: (‡44)1223-336-033; e-mail: deposit@ccdc.cam.
ac.uk).
[*] Prof. Dr. A. G. Fallis, S. K. Collins, G. P. A. Yap
Department of Chemistry, University of Ottawa
10 Marie Curie, Ottawa, Ontario K1N 6N5 (Canada)
Fax : (‡ 1)613-562-5170
[7] For example: K. S. Hagen, J. G. Reynolds, R. H. Holm, J. Am. Chem.
Soc. 1981, 103, 4054; B.-K. Teo, J. C. Calabrese, J. Am. Chem. Soc.
1975, 97, 1256.
[8] a) W. Uhl, M. Layh, W. Hiller, J. Organomet. Chem. 1989, 368, 139;
b) R. D. Schluter, A. H. Cowley, D. A. Atwood, R. A. Jones, M. R.
Bond, C. J. Carrano, J. Am. Chem. Soc. 1993, 115, 2070; c) N. Wiberg,
K. Amelunxen, H. Nöth, H. Schmidt, H. Schwenk, Angew. Chem.
E-mail: afallis@science.uottawa.ca
[**] We are grateful to the Natural Sciences and Engineering Research
Council of Canada for financial support of this research. S. K. Collins
thanks NSERC for a Graduate Scholarship.
Angew. Chem. Int. Ed. 2000, 39, No. 2
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
0570-0833/00/3902-0385 $ 17.50+.50/0
385

COMMUNICATIONS
ed the silyl-protected derivatives 7 (80 ± 90% yield). This
organozinc protocol[11] was superior to traditional tributyl- or
trimethyltin coupling methods because it avoided the difficult
chromatographic separations encountered from the co-elu-
tion of alkyltin byproducts and the phenylacetylenes. Re-
moval of the triisopropylsilyl protecting groups was accom-
plished by treatment with tetra-n-butylammonium fluoride in
THF, although traces of triisopropylsilyl fluoride complicated
the separation. Removal of the trimethylsilyl groups was
accomplished efficiently with K2CO3 in THF/MeOH/H2O at
218C, thus protection using the trimethysilyl was preferred.
The diacetylene 8, was then subjected to oxidative coupling
using CuII(OAc)2[12] and by refluxing in pyridine/diethyl ether
(3/1). A single product was isolated in 90% yield whose
spectral features suggested it was the monomer 3[17] and not
the anticipated dimer 4 which would be formed from an
intermolecular coupling. Thus the strained system 3 from the
intramolecular coupling of the terminal acetylenes formed
preferentially. In order to understand this preference various
reaction conditions were examined, as summarized in Table 1.
n
n = 1 or 2
n
2
1
3
Herein we report an extension of our initial investigations
which culminated in the synthesis of the strained diyne system
3 in 90% yield. Modification of the coupling conditions
afforded the corresponding dimer 4 which is the benzenoid
analogue of 1 for n ˆ 2. A variety of related bis-acetylene
systems are also known[9] and the relevant bond angles are
compared with those of 3 and 4.
Table 1. Effect of oxidative-coupling conditions on product ratios.
Coupling conditions[a]
Yields [%]
3
4
The synthesis of 3 is outlined in Scheme 1 and commenced
with commercially available 1-bromo-2-iodobenzene (5).
908C, 3 h
218C, 3 d
218C, 3 d (protected from light)
90
43 ± 58
54
0
18 ± 26
17 ± 21
Br
[a] CuII(OAc)2, 6 equiv; pyridine/diethyl ether 3/1.
Br
I
b)
a)
Variation of the reaction temperature afforded consider-
able control over the ratio of inter- versus intramolecular
coupling. Reactions protected from light produced emerald
green solutions, while in reactions left unprotected the
solution remained the characteristic sapphire blue of the
CuII(OAc)2, although the total yields and product mixtures
were similar. CuI/O2 mediated couplings,[7, 13] in contrast, gave
a complex ªsoupº of products with no trace of 3, although a
disappointing 10% yield of the dimer 4 was isolated.
R
5
6a R = TIPS
6b R = TMS
R
R
7a R = TIPS
7b R = TMS
c)
d)
Crystals of the dimer 4[17] suitable for X-ray analysis were
grown from a dichloromethane/methanol solution. It was
anticipated that the unsaturated bonds in the bridges would
impart a helical twist to the molecule as observed previously
for the revolveneynes. Thus, the two central benzene rings
were expected to be aligned in an overlapping manner,
superimposed on each other but slightly offset. The crystal
structure analysis revealed the dimer, which co-crystallized
with dichloromethane in a 2:1 ratio, was indeed helical but the
spacial arrangement of the ªouterº rings created two ªarmsº
(Figure 1).[14] This stereochemical relationship appears to
result from a twisting of the molecule to facilitate through-
space alignment between two of the ªouterº benzene rings of
the bridges. This creates a pincer-like structure,[15] with one
molecule of dichloromethane within the cavity of every
second molecule dispersed uniformly throughout the lattice of
the crystal. The helical conformation of the dimer helps to
relieve strain within the acetylene bonds. The bond angles at
the four triple bonds are as follows: C(19)-C(20)-C(21) 177.78,
C(20)-C(21)-C(22) 177.18, C(41)-C(42)-C(43) 175.98, C(42)-
C(43)-C(44) 178.78.
H
H
3
8
Scheme 1. Synthesis of strained cyclophane 3. a) TMSA (or TIPSA),
[Pd(PPh3)2Cl2], CuI, THF, DEA, 558C, 15 h, 90% for R ˆ TMS, 80% for
R ˆ TIPS; b) 1) nBuLi, THF, 788C, 30 min, 2) ZnBr2, THF, 08C, 15 min,
3) [Pd(PPh3)4], 1,4-dibromobenzene, THF, 658C, 15 h, 90% for R ˆ TMS,
80% for R ˆ TIPS; c) For R ˆ TIPS: TBAF, THF, 3 h, 100%; for R ˆ TMS:
K2CO3, MeOH, THF, H2O, 3 h, 100%; d) CuII(OAc)2 (6 equiv), pyridine/
diethyl ether 3/1, 908C, 3 h, 90%.
Selective reaction at the iodine center by palladium(0)-
mediated coupling in the presence of copper iodide with
triisopropylsilyl- or trimethylsilylacetylene provided the phe-
nyl acetylenes 6a and 6b[10] in yields of 80 and 90%,
respectively. The most efficient procedure for the coupling
of 6a with 1,4-dibromobenzene involved the use of an
organozincate generated in situ by halogen ± metal exchange
with nBuLi followed by transmetalation with ZnBr2. Subse-
quent addition of tetrakis(triphenylphosphane)palladium(0)
and 1,4-dibromobenzene followed by a 15-hour reflux afford-
386
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
0570-0833/00/3902-0386 $ 17.50+.50/0
Angew. Chem. Int. Ed. 2000, 39, No. 2

COMMUNICATIONS
lized from dichloromethane as monoclinic crystals for X-ray
analysis.[14]
Figure 2 illustrates the influence of the free acid group
which, as expected, forms hydrogen bonded dimers through
intermolecular association. This clearly establishes the struc-
ture of both 3 and 13.[15] The inherent strain in this unique ring
Figure 1. Structure of 4 in the crystal: view from the side with a co-
crystallized molecule of dichloromethane (left), and from above without a
molecule of dichloromethane (right).
Several attempts to crystallize 3 were unsuccessful and
resulted in the formation of a material assumed to be a
polymer. In order to assign the structure of 3 unambiguously, a
new analogue was synthesized containing a carboxylic acid
group. This facilitated crystallization, allowed X-ray structural
analysis of the crystal, and provided insight into the hydrogen
bonding of the acid dimers in the crystal. The acid 13 was
assembled using a parallel set of reactions (Scheme 2) to those
CO2Me
Br
CO2Me
Br
a)
9
Figure 2. Structure of 13 in the crystal (top) and intermolecular hydrogen
bonding within the lattice (bottom).
R
R
10
11
R =TMS
R = H
b)
system is reflected in the deviation from planarity observed
between the two outer benzene rings which lie perpendicular
to the central ring and the connecting bonds. The bond
between C(7) C(8) is bent 17.88 out of the plane of the central
ring, while the C(4) C(23) bond is distorted by 18.78. The
acetylene bonds are also strained as the angles C(14)-C(15)-
C(16) and C(15)-C(16)-C(17) are 163.78 and 163.58, respec-
tively. However, the carbon ± carbon bond lengths fall within
the normal range. The corresponding bond angles in a related
[4.4]orthocyclophane bisdiyne system prepared by Zhou,
Carroll, and Swager[9b] were 165.88 and 166.78, respectively,
while the [3.4]paracyclophane diynes synthesized by Ueda,
Katayama, and Tanaka[9d] are also bowed, but the deforma-
tion is less, with bond angles of 172.88 and 173.98, respectively.
In conclusion, this palladium-coupling sequence provided a
rapid route to novel benzene ± diyne bridged cyclophanes that
possess interesting geometric features. It is anticipated that
current investigations will lead to more highly functionalized
systems with unique properties, capable of binding transition
metals[16] and acting as multidentate ligands when hetero-
atoms are present. In addition, with appropriate functionality,
these methods will provide access to novel liquid crystals.
c)
CO2R'
12
13
R' = Me
R' = H
d)
Scheme 2. Synthesis of the carboxylic acid cyclophane derivative 13.
a) 1) 6b, nBuLi, THF, 788C, 30 min, 2) ZnBr2, THF, 08C, 15 min,
3) [Pd(PPh3)4], methyl 2,5-dibromobenzoate, THF, 658C, 15 h, 80%;
b) K2CO3, MeOH, THF, H2O, 3 h, 99%; c) CuII(OAc)2 (6 equiv), pyri-
dine/diethyl ether 3/1, 908C, 3 h, 64%; d) LiOH, H2O, MeOH, 508C, 3 h,
25%.
described above. The organozinc derivative of 6b (Scheme 2)
was prepared as previously and the solution treated with
tetrakis(triphenylphosphane)palladium(0) and methyl 2,5-di-
bromobenzoate (reflux, 15 h) to afford 10[17] in 80% yield.
Removal of the trimethylsilyl groups and oxidative coupling
with CuII(OAc)2 in refluxing pyridine/diethyl ether (3/1) gave
12[17] in 64% yield. Saponification of the methyl ester with
lithium hydroxide required warming to reflux in methanol
over 3 h to produce the carboxylic acid 13 in a modest 25%
yield. More vigorous conditions and alternative bases (KOH,
NaOH) caused decomposition. The carboxylic acid crystal-
Received: August 17, 1999 [Z13894]
Angew. Chem. Int. Ed. 2000, 39, No. 2
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
0570-0833/00/3902-0387 $ 17.50+.50/0
387

COMMUNICATIONS
[1] a) Top. Curr. Chem. 1983, 113; Top. Curr. Chem. 1983, 115; b) Cyclo-
phanes, Vols. I, II (Eds.: P. M. Keehn, S. M. Rosenfeld), Academic
Press, New York, 1983; c) F. Diederich, Cyclophanes, Royal Society of
Chemistry, Cambridge, UK, 1991; d) F. Vögtle, Cyclophane Chemistry,
Wiley, New York, 1993; e) Top. Curr. Chem. 1994, 172; f) G. J.
Bodwell, Angew. Chem. 1996, 108, 2221 ± 2224; Angew. Chem. Int. Ed.
Engl. 1996, 35, 2085 ± 2088; g) A. de Meijere, B. König, Synlett 1997,
1221 ± 1232.
[2] a) C. Seel, F. Vögtle, Angew. Chem. 1992, 104, 542 ± 563; Angew.
Chem. Int. Ed. Engl. 1992, 31, 528 ± 549; b) Frontiers in Supra-
molecular Organic Chemistry and Photochemistry (Eds.: H. J.
Schneider, H. Dürr), VCH, Weinheim. 1991.
a ˆ 12.879(4), b ˆ 10.168(3), c ˆ 13.466(4) Š, b ˆ 114.545(4)8, Vˆ
1604.2(8) Š3, Z ˆ 4, 1calcd ˆ 1.326 gcm 3, m ˆ 0.084 mm 1, 3482 unique
reflections at 808C, of which 3482 were taken as observed [Io >
2.00s(I)], R ˆ 0.0563, Rw ˆ 0.0983 (this value is a consequence of the
traces of polymer that appear to adhere to the crystal surface).
Crystallographic data (excluding structure factors) for the structures
reported in this paper have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication nos.
CCDC-133375 (4) and CCDC-133376 (13). Copies of the data can
be obtained free of charge on application to CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK (fax: (‡44)1223-336-033; e-mail: deposit@
ccdc.cam.ac.uk).
[3] a) B. König, Top. Curr. Chem. 1998, 196, 96 ± 136; b) T. Tsuji, Adv.
Strained Interesting Org. Mol. 1999, 7, 103 ± 152; c) Modern Acetylene
Chemistry (Eds.: P. J. Stang, F. Diederich), VCH, Weinheim, 1995.
[4] M. A. Romero, A. G. Fallis, Tetrahedron Lett. 1994, 35, 4711 ± 4714.
[5] D. Malaba, A. Djebli, L. Chen, E. A. Zarate, C. A. Tessier, W. J.
Youngs, Organometallics 1993, 12, 1266 ± 1276.
[15] For an example of ªpincerº-shaped molecules, see R. Rathore, S. V.
Lindeman, J. K. Kochi, Angew. Chem. 1998, 110, 1665 ± 1667; Angew.
Chem. Int. Ed. 1998, 37, 1585 ± 1587.
[16] J. Schulz, F. Vögtle in ref. [1e], pp. 41 ± 86.
[17] Physical data for the new compunds. 3: White solid, m. p. 167 ± 1708C;
1H NMR (200 MHz, CDCl3): d ˆ 7.39 (m, 9H), 7.72 (m, 3H); 13C NMR
(50 MHz, CDCl3): d ˆ 84.1, 98.1, 124.8, 126.4, 126.9, 127.4, 128.7, 129.8,
141.5, 150.9 ; IR (CHCl3): nÄ ˆ 2965, 2921, 1508, 1457, 1260, 1099,
1019 cm 1; MS (70 eV): m/z (%): 276 (100), 248 (6), 198 (1), 162 (10),
137 (14), 99 (2), 70 (2), 31 (6); HRMS for C22H12: calcd: 276.0940;
found: 276.0938. 4: Yellow solid, m. p. 257 ± 2608C; 1H NMR
(500 MHz, CDCl3): d ˆ 7.27 (m, 4H), 7.36 (m, 8H), 7.53 (s, 8H), 7.58
(d, J ˆ 7.4 Hz, 4H); 13C NMR (125 MHz, CDCl3): d ˆ 76.7, 81.3, 120.4,
127.1, 128.8, 129.2, 129.5, 133.7, 139.3, 145.2; IR (CHCl3): nÄ ˆ 3055,
3029, 2924, 2854, 2216, 1468, 1439, 1220, 840 cm 1; MS (FAB): m/z
(%): 551 (3), 461 (1), 391 (1), 369 (1), 338 (1), 277 (5), 246 (5), 219 (3).
10: Pale yellow solid, m. p. 113 ± 1168C; 1H NMR (500 MHz, CDCl3):
d ˆ 0.02 (s, 9H), 0.11 (s, 9H), 3.66 (s, 3H), 7.30 (m, 4H), 7.40 (m, 3H),
7.48 (dm, 1H), 7.58 (dm, 1H), 7.83 (dd, J ˆ 2.0, 7.9 Hz, 1H), 8.20 (d, J ˆ
1.8 Hz, 1H); 13C NMR (125 MHz, CDCl3): d ˆ 0.40, 0.32, 51.9,
97.6, 98.1, 103.8, 104.4, 121.5, 122.3, 126.9, 127.3, 128.4, 128.4, 128.9,
129.3, 130.3, 130.7, 130.8, 131.6, 132.4, 133.4, 139.6, 141.0, 143.0, 145.0,
167.5; IR (CHCl3): nÄ ˆ 3006, 2957, 2156, 1722, 1474, 1437, 1312, 1248,
1208, 1118 cm 1; MS (70 eV): m/z (%): 480 (23), 465 (25), 435 (23), 407
(6), 391 (10), 376 (32), 348 (54), 333 (30), 319 (13), 303 (20), 289 (30),
263 (16), 225 (10), 201 (7), 147 (7), 89 (43), 73 (100), 59 (36); HRMS
for C30H34O2Si2: calcd: 480.1942; found: 480.1927; elemental analysis
for C30H34O2Si2: calcd: C 74.95, H 6.71; found: C 75.05, H 6.65. 12:
Yellow solid, m. p. 143 ± 1468C; 1H NMR (500 MHz, CDCl3): d ˆ 3.66
(s, 3H), 7.24 (m, 2H), 7.33 (m, 3H), 7.45 (m, 3H), 7.69 (d, J ˆ 6.8 Hz,
1H), 7.73 (d, J ˆ 7.1 Hz, 1H), 7.95 (d, J ˆ 1.7 Hz, 1H); 13C NMR
(125 MHz, CDCl3): d ˆ 51.8, 83.3, 84.8, 97.9, 98.0, 123.1, 124.9, 126.4,
126.9, 127.0, 127.0, 127.2, 127.8, 128.6, 128.8, 130.9, 132.0, 132.3, 133.4,
142.1, 142.7, 149.4, 150.5, 166.4; IR (CHCl3): nÄ ˆ 2999, 2954, 2858,
2169, 1720, 1436, 1308, 1213, 1140 cm 1; MS (70 eV): m/z (%): 334
(35), 303 (4), 274 (41), 218 (1), 143 (30), 112 (12), 69 (100), 40 (16);
HRMS for C24H14O2: calcd: 334.0094; found: 334.1018.
[6] A. G. Fallis, Can. J. Chem. 1999, 77, 159 ± 177.
[7] a) Y. Rubin, T. C. Parker, S. I. Khan, C. L. Holliman, S. W. McElvany,
J. Am. Chem. Soc. 1996, 118, 5308 ± 5309; b) Y. Rubin, Chem. Eur. J.
1997, 3, 1009 ± 1016; c) Y. Tobe, N. Nakagawa, K. Naemura, T.
Wakabayashi, T. Shida, Y. Achiba, J. Am. Chem. Soc. 1998, 120, 4544 ±
4545; d) Y. Rubin, T. C. Parker, S. J. Pastor, S. Jalisatgi, C. Boulle,
C. L. Wilkins, Angew. Chem. 1998, 110, 1353 ± 1356; Angew. Chem.
Int. Ed. 1998, 37, 1226 ± 1229.
[8] a) R. Boese, A. J. Matzger, K. P. C. Vollhardt, J. Am. Chem. Soc. 1997,
119, 2052 ± 2053; b) P. I. Dosa, C. Erben, V. S. Iyer, K. P. C. Vollhardt,
I. M. Wasser, J. Am. Chem. Soc. 1999, 121, 10430 ± 10431.
[9] a) L. Guo, J. D. Bradshaw, C. A. Tessier, W. J. Youngs, J. Chem. Soc.
Chem. Commun. 1994, 243 ± 244; b) Q. Zhou, P. J. Carroll, T. M.
Swager, J. Org. Chem. 1994, 59, 1294 ± 1301; c) H. Hopf, P. G. Jones, P.
Bubenitschek, C. Werner, Angew. Chem. 1995, 107, 2592 ± 2594;
Angew. Chem. Int. Ed. Engl. 1995, 34, 2367 ± 2368; d) H. Ueda, C.
Katayama, J. Tanaka, Bull. Chem. Soc. Jpn. 1981, 54, 891 ± 896.
[10] Compound 6b is now commercially available from Aldrich.
[11] S. Sengupta, V. Snieckus, J. Org. Chem. 1990, 55, 5680 ± 5683.
[12] a) G. Eglington, W. McRae, Adv. Org. Chem. 1963, 4, 225 ± 338;
b) O. M. Behrr, G. Eglington, A. R. Galbraith, R. A. Raphael, J.
Chem. Soc. 1960, 3614 ± 3625.
[13] a) A. S. Hay, J. Org. Chem. 1960, 25, 1275 ± 1276; b) A. S. Hay, J. Org.
Chem. 1962, 27, 3320 ± 3321.
[14] X-ray crystal structural analyses: Dimer 4: crystal size 0.30 Â 0.04 Â
0.04 mm3, orthorhombic, space group Pbca, scan range 3.96 < 2q <
41.988, a ˆ 15.201(5), b ˆ 20.611(6), c ˆ 21.317(6) Š, Vˆ 6679(3) Š3,
Z ˆ 8, 1calcd ˆ 1.268 gcm 3, m ˆ 0.226 mm 1, 3586 unique reflections at
808C, of which 3586 were taken as observed [Io > 2.00s(I)], R ˆ
0.1125, Rw ˆ 0.2685; monomer 13: crystal size 0.20  0.20  0.20 mm3,
monoclinic, space group P21/c, scan range 5.3 < 2q < 57.288,
388
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
0570-0833/00/3902-0388 $ 17.50+.50/0
Angew. Chem. Int. Ed. 2000, 39, No. 2