Stepwise assembly of site specifically functionalized dehydrobenzo [18] annulenes

Article abstract of DOI:10.1021/ja991749g

Site specifically functionalized dehydrobenzo[18]annulenes (DBAs) with previously inaccessible topologies (C(2v) and C(s) symmetry) were prepared by utilizing an in situ protiodesilylation/alkynylation reaction. By application of a stepwise synthetic route, donor and/or acceptor functional groups were introduced to the annulenic core in a designed manner. The electronic absorption spectra of the DBAs revealed moderate to dramatic changes in the electronic structure of the [18]annulene core when subtle changes were made in substitution patterns and/or functional groups. Macrocycles containing C(2v) symmetry exhibited progressive and predictable bathochromic shifts ranging from 20 to 80 nm along with increasing intramolecular excited state change transfer (CT) behavior. Asymmetric (C(s)) molecules presented more interesting absorption behavior, such as accentuation of bands in the visible region. X-ray crystal structures of [18]DBAs 20, 22, 23, and 25 showed normal bond lengths and bond angles within the planar annulenic core. A solid-state thermal study indicated ordered polymerization of the DBAs between 164 and 240 °C.

Full text of DOI:10.1021/ja991749g

8182
J. Am. Chem. Soc. 1999, 121, 8182-8192
Stepwise Assembly of Site Specifically Functionalized
Dehydrobenzo[18]annulenes†
Joshua J. Pak, Timothy J. R. Weakley,‡ and Michael M. Haley*
Contribution from the Department of Chemistry, UniVersity of Oregon, Eugene, Oregon 97403-1253
ReceiVed May 26, 1999
Abstract: Site specifically functionalized dehydrobenzo[18]annulenes (DBAs) with previously inaccessible
topologies (C2V and Cs symmetry) were prepared by utilizing an in situ protiodesilylation/alkynylation reaction.
By application of a stepwise synthetic route, donor and/or acceptor functional groups were introduced to the
annulenic core in a designed manner. The electronic absorption spectra of the DBAs revealed moderate to
dramatic changes in the electronic structure of the [18]annulene core when subtle changes were made in
substitution patterns and/or functional groups. Macrocycles containing C2V symmetry exhibited progressive
and predictable bathochromic shifts ranging from 20 to 80 nm along with increasing intramolecular excited
state change transfer (CT) behavior. Asymmetric (Cs) molecules presented more interesting absorption behavior,
such as accentuation of bands in the visible region. X-ray crystal structures of [18]DBAs 20, 22, 23, and 25
showed normal bond lengths and bond angles within the planar annulenic core. A solid-state thermal study
indicated ordered polymerization of the DBAs between 164 and 240 °C.
Introduction
subject of this study, can be achieved only through easy access
to different topologies of the macrocycles as well as total control
over substitution pattern specificity.
Although 40 years have elapsed since Eglinton’s pioneering
research on diacetylenic DBAs (e.g., 1),7b,8 most systems are
still constructed via Cu-mediated cyclooligomerization of an
o-diethynylbenzene.1-5 While this intermolecular route usually
Recent studies have shown diacetylenic dehydrobenzoannu-
lenes (DBAs)1 and related phenylacetylene macrocycles2 to be
useful precursors for a variety of carbon-rich polymeric systems,
such as ladder polymers,3 molecular tubes,4 and novel allotropes
of carbon.5 In addition, these and other highly conjugated
organic molecules and polymers have been actively investigated
for possible application toward the next generation of electronics
and photonics.6 To exploit the technological potential of these
discoveries, it is not only necessary to have ready availability
to an ample supply of the desired materials (greater than
milligram scale) but also to tailor and fine-tune the chemical
and physical properties of the DBA precursors. The former
concern has been addressed with our recent report on an
intramolecular synthetic process which allowed construction of
previously inaccessible DBA structures.7 The latter concern, the
† Dedicated to Professor Virgil Boekelheide on the occasion of his 80th
birthday.
‡ To whom inquiries about the X-ray crystal structures should be
addressed.
requires a small number of synthetic steps, the complex mixture
of products, the difficulty of separating structurally related
macrocycles,3,5b and the low isolated yield of a given DBA5a
often outweigh the synthetic advantage. More importantly, the
substitution pattern of the desired molecule is absolutely
restricted by obligatory symmetry of the starting building block;
thus, product symmetries other than Dnh (n ) 2-4), such as Cs
or even C2V, are impossible to obtain.9
(1) Haley, M. M. Synlett 1998, 557-568.
(2) Haley, M. M.; Pak, J. J.; Brand, S. C. In Carbon-Rich Compounds
II; Topics in Current Chemistry 201; de Meijere, A., Ed.; Springer-Verlag:
Berlin, 1999; pp 81-130.
(3) Zhou, Q.; Carroll, P. J.; Swager, T. M. J. Org. Chem. 1994, 59, 1294-
1301.
(4) Baldwin, K. P.; Matzger, A. J.; Scheiman, D. A.; Tessier, C. A.;
Vollhardt, K. P. C.; Youngs, W. J. Synlett 1995, 1215-1218.
(5) (a) Boese, R.; Matzger, A. J.; Vollhardt, K. P. C. J. Am. Chem. Soc.
1997, 119, 2052-2053. (b) Tovar, J. D.; Jux, N.; Jarrosson, T.; Khan, S.
I.; Rubin, Y. J. Org. Chem. 1997, 62, 3432-3433. (c) Tobe, Y.; Nakagawa,
N.; Naemura, K.; Wakabayashi, T.; Shida, T.; Achiba, Y. J. Am. Chem.
Soc. 1998, 120, 4544-4545. (d) Rubin, Y.; Parker, T. C.; Pastor, S. J.;
Jalisatgi, S.; Boulle, C.; Wilkins, C. L. Angew. Chem., Int. Ed. 1998, 37,
1226-1229.
(6) (a) Conjugated Polymers and Related Materials: The Interconnection
of Chemical and Electronic Structure; Salaneck, W. R., Lundstro¨m, I.,
Ranby, B., Eds.; Oxford University Press: Oxford, U.K., 1993. (b) Photonic
and Optoelectronic Polymers; Jenekhe, S. A., Wynne, K. J., Eds.; American
Chemical Society: Washington, DC, 1995. (c) Electronic Materials: The
Oligomer Approach; Mu¨llen, K., Wegner, G., Eds.; Wiley-VCH: Weinheim,
Germany, 1998.
The growing interest in preparing extended π-conjugated
systems containing a variety of electron donor and acceptor
(7) (a) Haley, M. M.; Bell, M. L.; English, J. J.; Johnson, C. A.; Weakley,
T. J. R. J. Am. Chem. Soc. 1997, 119, 2956-2957. (b) Haley, M. M.; Brand,
S. C.; Pak, J. J. Angew. Chem., Int. Ed. Engl. 1997, 36, 836-838.
(8) (a) Eglinton, G.; Galbraith, A. R. Proc. Chem. Soc. 1957, 350-351.
(b) Behr, O. M.; Eglinton, G.; Raphael, R. A. Chem. Ind. 1959, 699-700.
(c) Eglinton, G.; Galbraith, A. R. J. Chem. Soc. 1960, 3614-3625.
(9) In theory, both higher and lower symmetries are possible; in practice,
macroscopic amounts of systems other than Dnh (n ) 2-4) have proven
elusive via the cyclooligomerization route.
10.1021/ja991749g CCC: $18.00 © 1999 American Chemical Society
Published on Web 08/31/1999

Functionalized Dehydrobenzo[18]annulenes
J. Am. Chem. Soc., Vol. 121, No. 36, 1999 8183
functional groups10,11 inspired our preparation and study of
substituted [18]DBAs. Discreet placement of these moieties
should lead to distinct changes in the electronic characteristics
and materials properties of the DBAs. Most notably, there have
been extensive studies on linear π-conjugated systems containing
donor-acceptor substituents.10-12 However, due to the lack of
viable preparative methods to produce functionalized macro-
cyclic systems, augmented studies of such classes of molecules
have been difficult at best. As part of our continuing program
exploring the chemistry of dehydrobenzoannulenes,1,2,7,13 we
report herein a synthetic method that allows efficient and
versatile construction of site-specifically functionalized [18]-
DBAs originating from simple building blocks. The character-
ization of the resultant donor and/or acceptor macrocycles and
elucidation of their solution and solid-state physiochemical
properties provide the first fundamental investigation of sub-
stituted dehydrobenzoannulenes. We describe our insights
toward understanding the structure-property relationship (SPR)
of these DBA derivatives through study of their electronic
absorption spectra. We also examine the solid-state behavior
of the novel macrocycles by X-ray crystallography and dif-
ferential scanning calorimetry (DSC).
Scheme 1a
a (a) ICl, AcOH; (b) [i] NaNO2, HCl, [ii] pyrrolidine, K2CO3; (c)
i-Pr3SiCtCH, PdCl2(PPh3)2, CuI, Et3N; (d) MeI, 120 °C; (e)
Me3SiCtCCtCH, PdCl2(PPh3)2, CuI, Et3N.
Scheme 2a
Results and Discussion
Synthesis of Building Blocks. To overcome the aforemen-
tioned synthetic difficulties in DBA assembly, we employed a
stepwise construction method in which functionality is intro-
duced from phenylbutadiyne and diiodoarene synthons (2 and
3, respectively) and is then carried over to the corresponding
macrocycles via intramolecular cyclization of the intermediate
silyl-protected R,ω-polyynes. In addition to the known triyne
2a,7b we also desired phenylbutadiyne synthons substituted with
acceptor (2b) and donor (2c) substituents. Unlike the parent
triyne 2a, construction of the functionalized triynes required
additional synthetic transformations. Scheme 1 illustrates the
preparation of nitro-triyne 2b. Commercially available 4-ni-
troaniline was treated with 1 equiv of ICl to give 2-iodo-4-
nitroaniline (4) in 76% yield.14 Diazonium ion formation with
HCl and NaNO2 followed by trapping with pyrrolidine afforded
N,N-tetramethylene-N′-(2-iodo-4-nitrophenyl)triazene (5).15 Tri-
azene 5 underwent Pd-catalyzed cross-coupling16 with (triiso-
propylsilyl)acetylene smoothly to give trisubstituted phenyl-
acetylene 6 in almost quantitative yield. Subsequent triazene
decomposition15 with iodomethane at 120 °C generated iodo-
benzene 7 in 86% yield. The final alkynylation with (trimeth-
a (a) BuBr, NaHCO3, THF, DMSO; (b) i-Pr3SiCtCH, PdCl2(PPh3)2,
CuI,Et3N;(c)(BnNEt3)+ICl2-,CaCO3,MeOH,CH2Cl2;(d)Me3SiCtCCtCH,
PdCl2(PPh3)2, CuI, Et3N.
ylsilyl)butadiyne17 furnished the nitro-functionalized triyne 2b
in 32% overall yield for the five steps.
As shown in Scheme 2, donor synthon 2c can be prepared
readily from 3-iodoaniline. Alkylation with 1-bromobutane in
a THF/DMSO solution in the presence of NaHCO3 generated
N,N-dibutyl-3-iodoaniline (8) in 94% yield. Cross-coupling of
aniline 8 with (triisopropylsilyl)acetylene gave 9. Compound 9
was conveniently iodinated by use of the mild reagent
- 18
(BnNEt3)+ICl2
to provide the desired 4-iodoaniline 10 in
near-quantitative yield. A second Sonogashira coupling with
(trimethylsilyl)butadiyne furnished building block 2c in 78%
overall yield for the four steps.
(10) (a) Stiegman, A. E.; Miskowski, V. M.; Perry, J. W.; Coulter, D.
R. J. Am. Chem. Soc. 1987, 109, 5884-5886. (b) Graham, E. M.;
Miskowski, V. M.; Perry, J. W.; Coulter, D. R.; Stiegman, A. E.; Schaefer,
W. P.; Marsh, R. E. J. Am. Chem. Soc. 1989, 111, 8771-8779. (c) Stiegman,
A. E.; Graham, E.; Perry, K. J.; Khundkar, L. R.; Cheng, L.-T.; Perry, J.
W. J. Am. Chem. Soc. 1991, 113, 7658-7666.
(11) (a) Tykwinski, R. R.; Schreiber, M.; Carlo´in, R. P.; Diederich, F.;
Gramlich, V. HelV. Chim. Acta 1996, 79, 2249-2281. (b) Tykwinski, R.
R.; Diederich, F. Liebigs Ann./Recl. 1997, 649-661.
(12) Prasad, P. N.; Williams, D. J. Introduction to Nonlinear Optical
Effects in Molecules and Polymers; Wiley: New York, 1991; Chapter 7,
pp 132-174.
(13) (a) Pak, J. J.; Weakley, T. J. R.; Haley, M. M. Organometallics
1997, 16, 4505-4507. (b) Haley, M. M.; Bell, M. L.; Brand, S. C.; Kimball,
D. B.; Pak, J. J.; Wan, W. B. Tetrahedron Lett. 1997, 38, 7483-7486. (c)
Wan, W. B.; Kimball, D. B.; Haley, M. M. Tetrahedron Lett. 1998, 39,
6795-6798.
(14) Sandin, R. B.; Drake, W. V.; Leger, F. In Organic Syntheses; Blatt,
A. H., Ed.; Wiley: New York, 1943; Collect. Vol. 2, pp 196-197.
(15) Moore, J. S.; Weinstein, E. J.; Wu, Z. Tetrahedron Lett. 1991, 32,
2465-2466.
(16) (a) Tsuji, J. Palladium Reagents and Catalysts; Wiley: New York,
1995. (b) Modern Cross-Coupling Reactions; Stang, P. J., Diederich, F.,
Eds.; VCH: Weinheim, Germany, 1997.
Synthesis of Functionalized [18]DBAs. With triynes 2a-c
in hand, we assembled an array of functionalized [18]DBAs
(Table 1). First, we applied our in situ coupling route to generate
C2V-substituted DBAs (11-18 and 25). A typical synthetic
representation is illustrated in Scheme 3. Diiodoveratrole (3c)
was treated with 2 equiv of 2b using the in situ protiodesilyl-
ation/alkynylation reaction under pseudo-high-dilution condi-
tions.1,7 Thus, slow addition via syringe pump of the triyne
solution to a triethylamine/THF mixture containing both pal-
ladium catalyst and aqueous potassium hydroxide afforded the
tetrafunctionalized R,ω-polyyne 27. Macrocycle precursor 27
was then desilylated with tetrabutylammonium fluoride in THF/
ethanol solution. After aqueous workup, the crude material was
filtered through a short plug of silica gel. Without further
(17) Brandsma, L. PreparatiVe Acetylenic Chemistry; Elsevier: Am-
sterdam, 1988; pp 118-119.
(18) Kajigaeshi, S.; Kakinami, T.; Yamasaki, H.; Fujisaki, S.; Okamoto,
T. Bull. Chem. Soc. Jpn. 1988, 61, 600-602.

8184 J. Am. Chem. Soc., Vol. 121, No. 36, 1999
Pak et al.
Scheme 4a
Table 1. Yields for in Situ Pd-Catalyzed Cross-Coupling Reaction
and Cu-Mediated Intramolecular Cyclization
a (a) 2c, aqueous KOH, PdCl2(PPh3)2, CuI, Et3N; (b) 2b, aqueous
KOH, PdCl2(PPh3)2, CuI, Et3N; (c) Bu4NF, EtOH, THF; (d) Cu(OAc)2,
CuCl, pyridine.
substituted annulene 17 as bright red-orange microcrystals in
97% yield. The cyclization reactions were exceptionally efficient
in most cases, providing only the desired products with no
detection of higher cyclooligomers or catenanes.
The assembly of DBAs with lower symmetry illustrates the
versatility of this route and is best exemplified by the preparation
of Cs macrocycle 20 (Scheme 4). Selective and sequential
Sonogashira cross-coupling of 2c and 2b to diiodobenzene 3a19
using in situ desilylation/alkynylation reaction conditions fur-
nished the asymmetrically functionalized R,ω-polyyne 29 in
62% overall yield. It is noteworthy that only dibenzotriyne 28
was isolated and that no product of double alkynylation was
detected from the first cross-coupling reaction. This fact can
be attributed to the greater tendency of electron-poor arenes to
undergo Pd-catalyzed cross-coupling reactions much faster than
the corresponding electron-rich arenes.16 Polyyne 29 underwent
the standard protiodesilylation/cyclization steps, generating
tetrasubstituted annulene 20 as deep red crystals in 84% yield.
Using this strategy, we were able to assemble various Cs-
symmetric donor/acceptor macrocycles (Table 1, DBAs 19-
24).
a Combined yield for sequential cross-coupling reactions. b Combined
yield for protiodesilylation/intramolecular cyclization.
Scheme 3a
Attempts to prepare the C2V-donor/acceptor DBA 30 from
1,2-diiodo-4,5-dinitrobenzene (31) using analogous chemistry
were unsuccessful; instead, an unusually broad triplet at 8.01
ppm in the proton NMR spectrum suggested formation of
hydroxy-containing macrocycle 26 (Figure 1). The presence of
the hydroxyl group in 26 was confirmed by a deuterium
exchange experiment. The proton NMR spectrum of the resultant
molecule showed the disappearance of the broad triplet while
the remaining signals were virtually unchanged. Arene 31 is
known to undergo facile substitution under certain conditions
in the presence of nucleophiles (e.g., reaction of 31 with
dibutylamine yields 3a).19 Thus, under our standard reaction
conditions for coupling triyne synthons, hydroxide ion first
replaces one of the nitro groups in 31 and then cross-coupling
with desilylated 2c occurs.
Upon cyclization of the gummy acyclic precursors, the
product macrocycles were obtained as solids of variable
solubility in common organic solvents. We circumvented low
solubility problems by adjoining decyl, alkoxy, and dibutylamino
groups to the annulenic core. Although incorporation of alkoxy
a (a) 2b, aqueous KOH, PdCl2(PPh3)2, CuI, Et3N; (b) Bu4NF, EtOH,
THF; (c) Cu(OAc)2, CuCl, pyridine.
purification, cyclization of the desilylated R,ω-polyyne was
carried out via Cu-mediated intramolecular oxidative dimeriza-
tion under pseudo-high-dilution conditions, generating tetra-
(19) Senskey, M. D.; Bradshaw, J. D.; Tessier, C. A.; Youngs, W. J.
Tetrahedron Lett. 1995, 36, 6217-6220.

Functionalized Dehydrobenzo[18]annulenes
J. Am. Chem. Soc., Vol. 121, No. 36, 1999 8185
Figure 1. Unsuccessful attempt to synthesize donor-acceptor DBA
30 using the in situ protiodesilylation/alkynylation route.
Figure 2. Electronic absorption spectra of DBA 1 and C2V DBAs 11-
14.
groups helped reduce the solubility problem of the macrocycles,
the DBA products were found to be somewhat unstable, slowly
decomposing under ambient conditions over the course of a few
days. Conversely, DBAs containing both alkoxy and nitro
groups exhibited increased stability without any detectable
decomposition after months under analogous conditions. How-
ever, incorporation of the nitro moieties significantly decreased
the solubility of the final products. Inclusion of dialkylamino
groups (DBAs 19-26), on the other hand, dramatically in-
creased DBA solubility.
Clearly, judicious choice of the coupling partners (triynes
2a-c and diiodobenzenes 3a-c) can furnish [18]DBAs with
one, two, or three benzene rings bearing one or two functional
groups. Depending on the viability of multisubstituted building
blocks, it should be possible to produce even more complicated
topologies not only of [18]annulene derivatives but also of other
DBA sizes as well.7a The latter avenue is currently under further
exploration.
Table 2. Selected λmax Values (nm) and Molar Extinction
Coefficients (L mol-1 cm-1) of DBAs 1, 11-14, 16-18, and 25 in
CH2Cl2
DBA
peak 1
peak 2
peak 3
peak 4
1
11
12
13
14
16
17
18
25
312 (44 900) 331 (72 200)
315 (46 700) 334 (74 600)
316 (35 800) 338 (70 900)
318 (57 100) 339 (104 900) 374 (21 900) 402 (12 900)
317 (73 100) 339 (136 500) 373 (27 600) 402 (14100)
310 (34 000) 349 (54 100)
309 (11 800) 351 (12 100)
311 (18 200) 352 (17 200)
311 (40 700) 351 (54 200)
359 (22 200) 370 (23 900)
363 (22 300) 373 (24 400)
372 (13 400) 401 (7300)
364 (58 400) 414 (20 200)
370 (13 700) 433 (6100)
372 (20 400) 435 (8600)
387 (57 500) 437 (22 900)
Electronic Characteristics of DBAs. To design organic
materials possessing desired properties, it is absolutely critical
to have a systematic understanding of the structure-property
relationship (SPR) of a given class of compounds. Previously,
most of the efforts in the acetylenic area were focused on linear
and acyclic systems.10-12 The advent of our synthetic method
to generate DBAs substituted in various positions provided us
with the opportunity to conduct an inclusive study on the planar
[18]annulene system for the first time.
In a previous report we discussed that the electronic absorp-
tion spectra of dodecadehydro[18]annulenes possess a charac-
teristic pattern of four absorption bands,7b which are attributable
primarily to π f π* transitions.10a,c,20 This pattern includes the
trend in peak intensity of decreasing order of second, first, third,
and fourth peak, as shown for 1 in Figure 2. The alkyl
substituents of DBA 11 did not alter the electronic absorption
spectra significantly and showed very good agreement with
spectra of 1. All four peaks only deviated within 3 or 4 nm
with essentially the same molar extinction coefficient (ꢀ) (Table
2) as alkyl groups are known to be only slightly electron
donating. Comparison with the spectra of alkoxy containing
DBAs such as 12-14 showed the same pattern for the [18]-
annulenic core but exhibited a general bathochromic shift for
the diagnostic peaks. For example, peak 4 shifted 32 nm from
370 nm for 13. The end absorption points of 12-14 also
displayed shifts of ca. 30 nm to lower energy. Retention of the
Figure 3. Electronic absorption spectra of C2V DBAs 16-18 and 25.
general annulenic core pattern of the spectra suggests that most
of the electron-donating ability of the alkoxy groups is localized
in the benzene ring.
The electronic absorption spectrum of dibutylamino-contain-
ing DBA 25 presented a somewhat more interesting spectrum
(Figure 3). DBA 25, which contains two donor groups, showed
a large bathochromic shift as well as lack of the characteristic
pattern. The strongest absorption band appeared at 387 nm in
comparison to 330 nm (for 1 and 11) and 340 nm (for 12-14).
Along with significant shifting of the peaks, a general broaden-
ing of the bands was also observed, suggesting strong intramo-
lecular excited-state charge-transfer (CT) activities. The above
observations indicate that the effect of the dibutylamino groups
is much more influential on the electronic circuit of [18]DBA
(20) Hoshi, T.; Okubo, J.; Kobayashi, M.; Tanizaki, Y. J. Am. Chem.
Soc. 1986, 108, 3867-3872.

8186 J. Am. Chem. Soc., Vol. 121, No. 36, 1999
Pak et al.
Figure 4. Electronic absorption spectra of asymmetric DBAs 19-23
and diyne model 32.
Table 3. Selected λmax Values (nm) and Molar Extinction
Coefficients (L mol-1 cm-1) of DBAs 19-23 and 32 in CH2Cl2
DBA
peak 1
peak 2
peak 3
peak 4
19
20
21
22
23
32
340 (77 900) 360 (75 600) 451 (19 400) 529 (6200)
308 (44 700) 324 (48 300) 348 (42 700) 422 (57 300)
338 (59 200) 357 (50 200) 409 (10 200) 474 (4000)
339 (67 900) 362 (51 400) 400 (26 700) 435 (16 500)
315 (24 000) 327 (20 900) 367 (14 200) 483 (10 200)
326 (32 500) 341 (34 200)
435 (15 200)
Figure 5. Electron delocalization pathways in DBAs 19-23 and linear
component 32. The arrows denote the possible delocalization pathways
in each DBA.
than that of alkoxy groups. The positioning of the functional
groups also emerges as an important component in tailoring
the electronic properties, as DBA 25 carries only one substituent
per benzene ring and yet causes considerable CT behavior.21
To study the affects of nitro groups on the DBA electronic
circuit, we assembled compound 15 but could not isolate pure
material due to its extreme insolubility. A logical soluble alter-
native was didecyl derivative 16. Due to its substitution pattern,
the spectrum of 16 exhibited largely broadened CT bands (Fig-
ure 3). In comparison to its amino-substituted analogue 25, the
end absorption point extended only to 460 nm, about 15 nm
short of its counterpart. When alkyl groups were replaced with
alkoxy groups, as represented by DBAs 17 and 18, the end
absorption points were extended beyond 475 nm, accompanied
by severe broadening of absorption bands throughout the spectra.
Up to this point, all of the macrocycles examined were
symmetrically substituted systems (C2V) and exhibited reason-
ably uncomplicated and somewhat predictable electronic ab-
sorption spectra. By introducing asymmetry to the annulenic
core, we expected that more intricate and intriguing electronic
behavior might transpire; this indeed proved to be the case. The
UV-vis spectra of annulenes 19 and 20 displayed end absorp-
tion points extending beyond 600 and 560 nm, respectively
(Figure 4). More interestingly, the spectrum of 20 exhibited a
broad yet very strong CT absorption band at 422 nm with a
molar extinction coefficient of 57 300 M-1 cm-1, the strongest
low-energy level absorption we have observed in an annulene
derivative (Table 3).
electron delocalization pathways contained in DBAs 19 and 20
(Figure 5). Analysis of the spectra of nonlinearly arranged
macrocycles 21 and 22 revealed that the two DBAs displayed
very similar absorption patterns but with extremely distinct
extinction coefficients (Table 3). Spectrum 21 was accompanied
by an extremely weak CT band at 474 nm. Since both functional
groups on 21 are positioned on a single benzene ring ortho to
each other, most of the donating and accepting effects were
localized in the six-membered ring (pathway a). In the case of
22, the large increase in the degree of absorption throughout
the spectrum was remarkable. The effects of the donor-acceptor
groups appear to be very minor on the DBA electronic circuit
through the shortest delocalization pathway (pathway b) since
it is cross-conjugated, which is known to be much less efficient
than a conjugated pathway.11 However, the extreme differences
between 21 and 22 may be explained by accounting for the
cumulative effect of the single linear donor (c) and acceptor
(d) pathways. A qualitative comparison between the spectra of
19 and 22 shows very little deviation from each other and thus
is in accordance with the above interpretation.
Examination of the absorption spectra of molecules 23 and
32, which contain linear donor-acceptor components (pathway
e), exhibited moderately strong, broad CT transitions at 483
and 435 nm, respectively, with end absorptions greater than 550
nm. Comparison of DBA 23 with the parent donor-acceptor
diyne 32 showed that the magnitude of the donor-acceptor
conjugation, as approximated by the position of the CT bands,
was strengthened when the chromophore was locked into
planarity. Therefore, incorporation of the donor-acceptor unit
of 32 into the DBA skeleton resulted in a significant batho-
chromic shift of nearly 50 nm. Although conjugation in the
extended macrocycle might play a role in this shift, we feel it
is minimal as (1) the parent DBA 1 displayed no absorption
To investigate systematically the topological origin of this
phenomenon, we prepared annulenes 21-23 as well as linear
donor-acceptor component 3211c and acquired their electronic
absorption spectra (Figure 4). Compounds 21-23 and 32
represent segments of the conjugated and cross-conjugated
(21) Anthony, J. E.; Khan, S. I.; Rubin, Y. Tetrahedron Lett. 1997, 38,
3499-3502.

Functionalized Dehydrobenzo[18]annulenes
J. Am. Chem. Soc., Vol. 121, No. 36, 1999 8187
Figure 6. Molecular structure of DBA 20; ellipsoids drawn at the 30% level.
bands above 400 nm and (2) the alternate resonance pathway
in 23 is the less efficient, cross-conjugated route.
is little or no intramolecular ground-state charge transfer, similar
to what was found with acyclic donor-acceptor polyynes.10,11,23
Of the four structures examined, only macrocycle 22 pos-
sessed a noncentrosymmetric arrangement in the solid state
(Figure 7). The organization of 22 contains a mirror plane
through the planar sheet of macrocycles with no point of
inversion. The unit cell of DBA 23 contains two macrocycles
arranged in a centrosymmetric manner with no net dipole
moment. Likewise, annulene 25 contains two molecules per
centrosymmetric unit cell. A view from the top of the planar
molecule shows an interesting “Star of David” arrangement.
Solid-State Behavior of DBAs. In conjunction with X-ray
structural analyses, we also examined the thermal solid-state
behavior of [18]DBAs. Dehydrobenzoannulenes and other
phenylacetylene macrocycles potentially can be useful precursors
to carbon-rich polymers. In addition, the rigid core may serve
as building blocks for tubular liquid crystals and porous
molecular crystals. In our study, all macrocycles exhibited sharp,
irreversible exothermic transitions as determined by differential
scanning calorimetry (DSC). The maximum heights for these
peaks were observed between 164 and 240 °C (Table 4). The
enthalpy associated with these reactions range from 389 to 740
kJ mol-1, showing relatively high thermal reactivity. The half-
widths of the exotherms ranged from 3 to 15 °C, suggesting
the occurrence of well-ordered polymerizations. Interestingly,
only macrocycles containing decyl groups (DBAs 11 and 16)
exhibited melting transitions at 135 and 93 °C, respectively.
Attempts to examine thermoproducts from the DSC experi-
ments were severely hampered due to complete insolubility of
What then, is the origin for the large extinction coefficient
of the CT absorption band in macrocycle 20? Individually, the
electron delocalization (resonance) pathways contained in DBAs
21-23 do not appear to contribute significantly, nor does a
simple summation of these effects. However, it seems that a
synergistic influence of the two donor-acceptor groups, when
placed judiciously on the macrocycle, is likely responsible for
the intriguing electronic behavior illustrated by DBA 20.
Crystal Structures of [18]DBAs. Prior to this study, the only
crystal structures reported for diacetylenic DBAs were limited
to smaller macrocycles3,4,5b,22 or nonplanar systems.5a,7a To gain
further understanding of the structural effects of donor-acceptor
functionalization on the bonding and molecular packing, we
sought to perform X-ray structural analyses of the macrocycles.
In our previous studies with planar DBAs, efforts to grow
crystals of the parent hydrocarbons that were suitable for X-ray
analysis had proven fruitless. Fortunately, inclusion of the
dialkylamino groups on the [18]DBA skeleton greatly facilitated
crystal formation, which was achieved by slow diffusion of
hexanes into a concentrated dichloromethane solution of the
appropriate DBA. Gratifyingly, we were able to obtain structural
data for DBAs 20, 22, 23, and 25.
The molecular structures of the substituted [18]DBAs, for
which macrocycle 20 is illustrative (Figure 6), revealed that the
annulenic cores are essentially planar. For example, the mean
deviation in 20 was less than 0.070 Å. The bond lengths and
bond angles are typical for those found in other strain-free
dehydrobenzoannulenes.3-5,7 These results indicate that there
(23) Dehu, C.; Meyers, F.; Bre´das, J. L. J. Am. Chem. Soc. 1993, 115,
6198-6206.
(22) Bunz, U. H. F.; Enkelmann, V. Chem. Eur. J. 1999, 5, 263-266.

8188 J. Am. Chem. Soc., Vol. 121, No. 36, 1999
Pak et al.
Figure 7. Crystal packing diagrams for macrocycles 22 (a, left), 23 (b, middle), and 25 (c, right).
Table 4. Selected DSC Data for Functionalized [18]DBAs
charge-transfer behavior in the electronic ground state. The
electronic absorption spectra of donor-acceptor DBAs also
displayed larger bathochromic shifts as stronger donor-acceptor
functionalities were incorporated. The increasingly broad and
intense low-energy absorption in the spectra is attributed to the
increasing polarization of the conjugated backbone from the
donor to the acceptor groups in the excited state. We also
observed unexpected changes in absorption spectra in the case
of DBA 20 showing unusually strong CT behavior around 422
nm. The strong absorption may be the result of synergistic
cooperation of the particular asymmetric substitution pattern in
which the partial pattern exhibited only weak to moderate CT
behavior. In conclusion, we were able to show the ability to
effectively tailor the electronic structure of [18]DBAs by rational
design of the substitution pattern. We are currently exploring
the nonlinear optical activity of this unique class of molecules
to add to the present structure-property relationship studies.
We are also pursuing the study of DBA thermal products to
better understand the solid-state polymerization process. These
results will be presented in due course.
DBA
Tmax (°C)a
Tmin (°C)b
w1/2
∆Hrxn (kJ mol-1
)
11
13
14
16
19
20
21
22
23
24
164
186
211
227
240
230
206
230
230
214
135
7
3
12
6
4
4
15
15
13
13
442
430
463
488
601
618
552
561
740
389
93
a Exotherm; thermal polymerization. b Endotherm; melting transition.
the shiny, black materials in common organic solvents. There-
fore, the structures of these thermoproducts as well as the nature
of thermal transformation remain uncertain. In-depth studies are
required to determine whether the DBAs undergo topochemical
solid-state polymerization to form polydiacetylenes; these studies
are currently underway.
Conclusions
Experimental Section
Herein we have described an efficient and versatile synthetic
method for generating highly functionalized dehydrobenzo[18]-
annulenes. The route allows placement of functionality to be
determined at the building block level. With suitably function-
alized building blocks, an R,ω-polyyne with a specific substitu-
tion pattern can be generated. Subsequent cyclization affords a
rationally designed [18]DBA. Compared with the more com-
monly used one-pot cyclooligomerization approach, our method
provides vital reaction efficiency, product purity, ease of product
separation, and complete control over the ring substitution.
Utilizing the synthetic advances, a large series of donor-
acceptor DBAs were prepared, permitting the first detailed SPR
studies of these macrocycles. X-ray structure analyses of donor-
acceptor DBAs exhibited the expected planarity with normal
bond lengths and angles, indicating the absence of intramolecular
General Considerations. H and 13C NMR spectra were recorded
1
using a Varian Inova 300 NMR (1H, 299.94 MHz; 13C, 75.43 MHz)
spectrometer. Chemical shifts (δ) are expressed in ppm downfield from
tetramethylsilane using the residual solvent as internal standard
1
(chloroform-d, H 7.27 ppm and 13C 77.0 ppm; dichloromethane-d2,
1H 5.32 ppm, 13C 54.0 ppm; tetrahydrofuran-d8, 1H 3.58 ppm, 13C 67.57
ppm). Coupling constants are expressed in hertz. IR spectra were
recorded using a Nicolet Magna-FTIR 550 spectrometer. UV-vis
spectra were recorded using a Hewlett-Packard 8453 UV-vis spec-
trophotometer in CH2Cl2. Melting points were determined on a Meltemp
II apparatus. All melting points are uncorrected. MS spectra were
recorded using a Kratos MS50 spectrometer. DSC analyses were
performed using a TA Instruments DSC 2920 Modulated DSC.
Elemental analyses were performed by Robertson Microlit Laboratories,
Inc. Dichloromethane, triethylamine, and pyridine were distilled from

Functionalized Dehydrobenzo[18]annulenes
J. Am. Chem. Soc., Vol. 121, No. 36, 1999 8189
calcium hydride under an atmosphere of nitrogen prior to use.
Tetrahydrofuran was distilled from sodium and benzophenone under
an atmosphere of nitrogen prior to use. All other chemicals were of
reagent quality and used as obtained from the manufacturers. Column
chromatography was performed on Whatman reagent grade silica gel
(230-400 mesh). Rotary chromatography was performed on a Chro-
matotron using silica gel (60 PF254) plates (1-4 mm). Baker precoated
silica gel plates were used for analytical (200 × 50 × 0.25 mm) thin-
layer chromatography. Reactions were carried out under an inert
atmosphere (dry nitrogen or argon) when necessary.
N,N-Tetramethylene-N′-(2-iodo-4-nitrophenyl)triazene (5). Aniline
4 (5.28 g, 20 mmol) was dissolved in concentrated HCl (5.6 mL) and
H2O (10 mL) and then cooled to 0 °C. An ice-cold solution of NaNO2
(1.52 g, 22 mmol) in H2O (4.0 mL) was added dropwise to the mixture.
After it was stirred at 0 °C for 30 min, the brown reaction mixture was
poured into a solution of pyrrolidine (2.20 g, 31 mmol) and K2CO3
(5.11 g, 37 mmol) in H2O (25 mL) and stirred for 30 min. The mixture
was filtered, and the solid was washed with H2O (20 mL) and ether
(20 mL). Product 5 was air-dried to give a yellow solid (3.81 g, 55%
1
yield). Mp: 180.8-181.6 °C. H NMR (CDCl3): δ 8.69 (d, J ) 2.7
Hz, 1H), 8.11 (dd, J ) 9.0, 2.7 Hz, 1H), 7.43 (d, J ) 9.0 Hz, 1H),
4.01 (t, J ) 6.3 Hz, 2H), 3.79 (t, J ) 6.6 Hz, 2H), 2.24-2.02 (m, 4H).
13C NMR (CDCl3): δ 155.37, 144.36, 134.79, 124.15, 116.09, 94.77,
51.66, 47.98, 23.91, 23.32. IR (KBr): ν 3091, 2972, 2873, 1501, 1375,
1295 cm-1. MS (EI, 70 eV): m/z 346 (M+, 42), 276 (76), 248 (100).
N,N-Tetramethylene-N′-[4-nitro-2-((triisopropylsilyl)ethynyl)-
phenyl]triazene (6). Triazene 5 (621 mg, 1.7 mmol) was treated with
(triisopropylsilyl)acetylene (650 mg, 3.6 mmol) using acetylene coupling
procedure A. Chromatography on silica gel (9:1 hexanes:CH2Cl2)
afforded 6 (667 mg, 98% yield) as a yellow solid. Mp: 111.5-113.7
°C. 1H NMR (CDCl3): δ 8.34 (d, J ) 9.0 Hz, 1H), 8.07 (dd, J ) 9.0,
2.4 Hz, 1H), 7.56 (d, J ) 2.4 Hz, 1H), 4.01 (t, J ) 5.7 Hz, 2H), 3.75
(t, J ) 5.7 Hz, 2H), 2.18-2.01 (m, 4H), 1.15 (s, 21H). 13C NMR
(CDCl3): δ 157.43, 143.71, 129.53, 124.04, 118.62, 116.74, 102.91,
96.94, 51.60, 47.46, 23.89, 23.41, 18.71, 11.26. IR (KBr): ν 2939,
2873, 2164, 1507 cm-1. MS (FAB): m/z 401 (M+ + H, 100), 330 (36).
2-Iodo-4-nitro-1-[(triisopropylsilyl)ethynyl]benzene (7). Com-
pound 6 (341 mg, 0.85 mmol) was dissolved in freshly distilled
iodomethane (26 mL) and was heated in a pressure tube at 120 °C for
48 h. The cooled reaction mixture was then filtered through a cake of
silica gel using a 1:1 hexanes-CH2Cl2 mixture. Chromatography on
silica gel (3:2 hexanes-CH2Cl2) gave arene 7 (313 mg, 86% yield) as
General Acetylene Coupling Procedure A. A round-bottom flask
was charged with iodoarene (1 equiv), bis(triphenylphosphine)palla-
dium(II) chloride (0.03 equiv), copper(I) iodide (0.06 equiv), and
triethylamine (0.1 M). After the mixture was bubbled with N2 for 30
min, the silyl-protected terminal acetylene (1.1-1.3 equiv) was added
by syringe under a nitrogen atmosphere. The reaction mixture was
stirred at 50 °C for 2-12 h and was monitored by TLC. Upon
completion, the reaction mixture was cooled and concentrated in vacuo.
The dark residue was redissolved in CH2Cl2 and the solution filtered
through a thin cake of silica gel using CH2Cl2. The solution was
concentrated and then chromatographed on silica gel.
General in Situ Protiodesilylation/Alkynylation Procedure B.
Iodoarene (1 equiv) and [(trimethylsilyl)butadiynyl]arene (1.1 equiv)
were dissolved in H2O/THF/triethylamine (0.01:1:5) solutions in
separate vessels. The solutions were degassed vigorously by either
bubbling of nitrogen or by three freeze-pump-thaw cycles. The
acetylene solution was added via syringe pump to the iodoarene solution
charged with bis(triphenylphosphine)palladium(II) chloride (0.03 equiv),
copper(I) iodide (0.06 equiv), and KOH (10 equiv per silyl group) over
12-24 h under a nitrogen atmosphere at 50 °C. Upon completion, the
mixture was concentrated in vacuo and redissolved in CH2Cl2. The
dark residue was filtered through a thin cake of silica gel using CH2-
Cl2, concentrated, and then chromatographed on silica gel.
1
a reddish solid. Mp: 123.2-124.5 °C. H NMR (CDCl3): δ 8.26 (d,
J ) 2.4 Hz, 1H), 8.05 (d, J ) 8.7 Hz, 1H), 7.81 (dd, J ) 8.7, 2.4 Hz,
1H), 1.18 (s, 21H). 13C NMR (CDCl3): δ 147.61, 139.72, 131.74,
127.09, 123.20, 109.18, 105.82, 99.17, 18.63, 11.18. IR (KBr): ν 2943,
2865, 2164 cm-1. MS (FAB): m/z 386 (M+ - C3H7, 84), 358 (35),
340 (83), 300 (22).
General Macrocyclization Procedure C. A 0.01 M solution of the
bis(silyl)-protected R,ω-polyyne in THF/MeOH (10:1 v:v) was treated
with 2.5 equiv of tetrabutylammonium fluoride (1 M THF solution) at
room temperature. The reaction was monitored by TLC and was
typically complete within 30 min. The reaction mixture was diluted
with diethyl ether (ca. 25 mL per mmol substrate), washed three times
with water and twice with brine, and dried over magnesium sulfate.
The solution was concentrated in vacuo, and the resultant oil was
redissolved in pyridine (ca. 10 mL). The pyridine solution was slowly
added via syringe pump to a round-bottom flask charged with 25 equiv
of Cu(OAc)2, 20 equiv of CuCl, and pyridine (ca. 250 mL per mmol
of R,ω-polyyne) at 60 °C. The addition was done under house air over
10-20 h. Upon completion, the mixture was concentrated in vacuo
and then redissolved in CH2Cl2. The mixture was filtered through a
thin cake of silica gel using CH2Cl2, concentrated, and chromatographed
on silica gel.
4-Nitro-2-[(triisopropylsilyl)ethynyl]-1-[4-(trimethylsilyl)-1,3-
butadiynyl]benzene (2b). Ethynylbenzene 7 (301 mg, 0.70 mmol) was
reacted with (trimethylsilyl)butadiyne17 (171 mg, 1.4 mmol) using
acetylene coupling procedure A. Chromatography on silica gel (3:1
hexanes-CH2Cl2) yielded 2b (270 mg, 91% yield) as a yellow gum.
1H NMR (CDCl3): δ 8.30 (d, J ) 2.4 Hz, 1H), 8.01 (dd, J ) 8.7, 2.4
Hz, 1H), 7.60 (d, J ) 8.7 Hz, 1H), 1.18 (s, 21H), 0.25 (s, 9H). 13C
NMR (CDCl3): δ 147.00, 133.35, 130.91, 128.91, 126.96, 122.50,
102.19, 99.83, 95.13, 87.16, 82.74, 73.22, 18.63, 11.21, -0.57. IR
(KBr): ν 2953, 2866, 2104 cm-1. Anal. Calcd for C24H33NO2Si2: C,
68.03; H, 7.85; N, 3.31. Found: C 67.81; H, 7.83; N, 3.25.
N,N-Dibutyl-3-iodoaniline (8). A mixture of 3-iodoaniline (1.97
g, 9.0 mmol), NaHCO3 (2.27 g, 27 mmol), and 1-bromobutane (12.3
g, 90 mmol) in a 5:1 THF-DMF solution (60 mL) was stirred at reflux
for 7 days. The cooled reaction mixture was washed with H2O (3 ×
50 mL) and extracted with ether (50 mL). The organic layer was dried
over MgSO4 and concentrated. Chromatography on silica gel (9:1
hexanes-CH2Cl2) gave N,N-dibutyl-3-iodoaniline (2.79 g, 94% yield)
as a light yellow oil. 1H NMR (CDCl3): δ 6.97-6.70 (m, 3H), 6.62-
6.51 (m, 1H), 3.22 (t, J ) 7.5 Hz, 4H), 1.62-1.46 (m, 4H), 1.43-1.23
(m, 4H), 0.96 (t, J ) 7.5 Hz, 6H). 13C NMR (CDCl3): δ 149.30, 130.48,
123.86, 120.28, 110.81, 95.78, 50.61, 29.20, 20.29, 13.97. IR (neat):
ν 2952, 2872, 1586 cm-1. MS (EI, 70 eV): m/z 331 (M+, 9), 288 (100),
246 (57).
N,N-Dibutyl-4,5-diiodo-2-nitroaniline (3a).19 A mixture of 1,2-
diiodo-4,5-dinitrobenzene (31;24 151 mg, 0.36 mmol) and dibutylamine
(92 mg, 0.72 mmol) in THF (10 mL) was stirred at room temperature
for 4 h. The reaction mixture was concentrated and chromatographed
on silica gel (2:1 hexanes-CH2Cl2), furnishing 3a (162 mg, 90% yield)
1
as a red-orange oil. H NMR (CDCl3): δ 8.03 (s, 1H), 7.58 (s, 1H),
3.07 (t, J ) 7.2 Hz, 4H), 1.62-1.40 (m, 4H), 1.32-1.20 (m, 4H), 0.89
(t, J ) 7.2 Hz, 6H). 13C NMR (CDCl3): δ 144.66, 141.34, 135.19,
131.87, 113.72, 92.28, 51.58, 29.28, 19.97, 13.76. IR (neat): ν 2966,
2866, 1580, 1448, 1348 cm-1. MS (EI, 70 eV): m/z 502 (M+, 13),
485 (19), 459 (100), 443 (18), 416 (24), 402 (27).
2-Iodo-4-nitroaniline (4). 4-Nitroaniline (4.15 g, 30 mmol) was
treated with ICl (4.87 g, 30 mmol) according to a literature procedure,14
yielding 4 (6.01 g, 76% yield) as a light green powder. Mp: 157.2-
N,N-Dibutyl-3-[(triisopropylsilyl)ethynyl]aniline (9). N,N-Dibutyl-
3-iodoaniline (1.69 g, 5.1 mmol) was reacted with (triisopropylsilyl)-
acetylene (1.40 g, 7.7 mmol) using acetylene coupling procedure A.
Chromatography on silica gel (2:1 hexanes-CH2Cl2) afforded com-
1
159.7 °C. H NMR (CDCl3): δ 8.57 (d, J ) 2.7 Hz, 1H), 8.06 (dd, J
) 9.3, 2.7 Hz, 1H), 6.71 (d, J ) 9.3 Hz), 4.85 (bs, 2H). 13C NMR
(CDCl3): δ 152.30, 135.49, 135.26, 125.71, 112.23, 80.53. IR (KBr):
ν 3484, 3368, 2820, 2556, 1525 cm-1. MS (EI, 70 eV): m/z 264 (M+,
100), 234 (49), 91 (30).
1
pound 9 (1.93 g, 98% yield) as a light brown oil. H NMR (CDCl3):
δ 7.17 (t, J ) 8.4 Hz, 1H), 6.94-6.78 (m, 2H), 6.66 (dd, J ) 8.4, 2.4
Hz, 1H), 3.31 (t, J ) 7.6 Hz, 4H), 1.70-1.53 (m, 4H), 1.51-1.31 (m,
4H), 1.21 (s, 21H), 1.05 (t, J ) 6.5 Hz, 6H). 13C NMR (CDCl3): δ
147.84, 128.95, 124.03, 118.98, 115.07, 112.15, 108.57, 88.66, 50.63,
(24) Arotsky, J.; Butler, R.; Darby, A. C. J. Chem. Soc. 1970, 1480-
1485.

8190 J. Am. Chem. Soc., Vol. 121, No. 36, 1999
Pak et al.
29.28, 20.30, 18.67, 13.96, 11.37. IR (neat): ν 2946, 2873, 2150 cm-1
Anal. Calcd for C25H43NSi: C, 77.85; H, 11.24; N, 3.63. Found: C,
77.92; H, 11.34; N, 3.58.
.
7.09 (s, 2H), 4.18 (bs, 4H), 3.94 (bs, 4H), 3.77 (bs, 8H). 13C NMR
(CD2Cl2): δ 149.62, 132.66, 132.47, 128.73, 128.57, 125.27, 124.99,
118.81, 116.17, 81.01, 80.69, 80.42, 78.30, 78.04, 77.16, 70.98, 70.12,
68.95, 68.65. IR (KBr): ν 2920, 2865, 2215, 2196, 2147 cm-1. HRMS
(FAB): calcd for C38H26O5 562.1780, found 562.1781.
Dehydrobenzo[18]annulene 15. The corresponding R,ω-polyyne
(90 mg, 0.12 mmol) was subjected to macrocyclization reaction
procedure C. Although observation of the reaction mixture under UV
light indicated formation of the product DBA, the material proved to
be insoluble in a variety of organic solvents and thus could not be
isolated in pure form.
N,N-Dibutyl-4-iodo-3-[(triisopropylsilyl)ethynyl]aniline (10). Com-
pound 9 (540 mg, 1.4 mmol) was treated with (BnNEt3)+ICl2- 18 (462
mg, 1.4 mmol) and CaCO3 (200 mg, 2.0 mmol) in 5:1 CH2Cl2-MeOH
solution (30 mL). The reaction mixture was stirred for 2 h and then
filtered. The filtrate was concentrated and washed with 5% NaHSO3
solution (30 mL), which was back-extracted with ether (3 × 30 mL).
The combined organic layers were dried over MgSO4 and concentrated
in vacuo. Chromatography on silica gel (2:1 hexanes-CH2Cl2) gave
aniline 10 (687 mg, 96% yield) as a light yellow oil. 1H NMR
(CDCl3): δ 7.53 (d, J ) 9.0 Hz, 1H), 6.78 (d, J ) 3.0 Hz, 1H), 6.34
(d, J ) 9.0, 3.0 Hz, 1H), 3.23 (t, J ) 7.2 Hz, 4H), 1.58-1.47 (m, 4H),
1.40-1.28 (m, 4H), 1.18 (s, 21H), 0.96 (t, J ) 7.2 Hz, 6H). 13C NMR
(CDCl3): δ 147.60, 138.68, 129.95, 116.61, 114.10, 109.00, 93.22,
81.77, 50.57, 29.09, 20.22, 18.71, 13.91, 11.35. IR (neat): ν 2953,
2866, 2157 cm-1. HRMS (FAB): calcd for C25H42INSi 511.2133, found
511.2131.
Dehydrobenzo[18]annulene 16. The corresponding R,ω-polyyne
(37 mg, 0.035 mmol) was subjected to macrocyclization reaction
procedure C. The product DBA (25 mg, 96% yield) was isolated as a
bright yellow solid after chromatography on silica gel (3:1 hexanes-
1
CH2Cl2). H NMR (CD2Cl2): δ 8.50 (d, J ) 2.4 Hz, 2H), 8.23 (dd, J
) 8.4, 2.4 Hz, 2H), 7.80 (d, J ) 8.4 Hz, 2H), 7.48 (s, 2H), 2.64 (bt,
J ) 7.8 Hz, 4H), 1.68-1.49 (m, 4H), 1.46-1.24 (m, 28H), 0.90 (bt, J
) 6.0 Hz, 6H). 13C NMR (CD2Cl2): δ 146.67, 143.54, 133.54, 133.35,
131.55, 127.72, 125.94, 123.55, 122.12, 84.12, 83.54, 79.68, 79.54,
78.52, 76.79, 32.59, 31.91, 30.62, 29.64 (2), 29.56, 29.48, 29.34, 22.69,
14.12. IR (KBr): ν 2955, 2926, 2853, 2210, 2197 cm-1. HRMS
(FAB): calcd for C50H50N2O4 742.3771, found 742.3780.
N,N-Dibutyl-3-[(triisopropylsilyl)ethynyl]-4-[4-(trimethylsilyl)-
1,3-butadiynyl]aniline (2c). Iodoaniline 10 (333 mg, 0.65 mmol) was
reacted with (trimethylsilyl)butadiyne17 (119 mg, 0.97 mmol) using
acetylene coupling procedure A. Chromatography on silica gel (2:1
hexanes-CH2Cl2) yielded triyne 2c (276 mg, 89% yield) as a light
r,ω-Polyyne 27. Triyne 2c (113 mg, 0.28 mmol) was reacted with
o-diiodoveratrole (44 mg, 0.11 mmol) via in situ protiodesilylation/
alkynylation reaction procedure B. Chromatography on silica gel (1:1
hexanes-CH2Cl2) gave polyyne 27 (72 mg, 82% yield) as a red gum.
1H NMR (CDCl3): δ 8.33 (d, J ) 2.4 Hz, 2H), 8.11 (dd, J ) 8.7, 2.4
Hz, 2H), 7.65 (d, J ) 8.7 Hz, 2H), 6.98 (s, 2H), 3.93 (s, 6H), 1.17 (s,
42H). 13C NMR (CDCl3): δ 150.19, 146.93, 133.31, 131.11, 128.48,
127.13, 122.54, 117.98, 115.12, 102.32, 99.78, 83.28, 82.78, 79.62,
76.57, 56.13, 18.67, 11.21. IR (neat): ν 2946, 2873, 2197 cm-1. HRMS
(FAB): calcd for C50H56N2O6Si2 836.3677, found 836.3679.
1
brown oil. H NMR (CDCl3): δ 7.28 (d, J ) 8.7 Hz, 1H), 6.67 (d, J
) 2.4 Hz, 1H), 6.49 (dd, J ) 8.7, 2.4 Hz, 1H), 3.27 (t, J ) 7.2 Hz,
4H), 1.61-1.48 (m, 4H), 1.45-1.30 (m, 4H), 1.19 (s, 21H), 0.97 (t, J
) 7.2 Hz, 6H), 0.23 (s, 9H). 13C NMR (CDCl3): δ 147.95, 133.98,
128.60, 114.54, 111.39, 109.76, 105.60, 93.97, 89.47, 89.15, 77.23,
75.64, 50.49, 29.21, 20.19, 18.69, 13.88, 11.34, -0.29. IR (neat): ν
2953, 2866, 2197, 2157, 2091 cm-1. Anal. Calcd for C32H51NSi2: C,
75.97; H, 10.16; N, 2.77. Found: C, 75.60; H, 10.32; N, 2.59.
Dehydrobenzo[18]annulene 11. The corresponding R,ω-polyyne
(100 mg, 0.10 mmol) was subjected to macrocyclization reaction
procedure C. The product DBA (54 mg, 83% yield) was isolated as a
bright yellow microcrystalline solid after chromatography on silica gel
(3:1 hexanes-CH2Cl2). 1H NMR (CDCl3): δ 7.72-7.63 (m, 4H), 7.46
(s, 2H), 7.44-7.37 (m, 4H), 2.62 (t, J ) 8.1 Hz, 4H), 1.59 (bt, J ) 8.1
Hz, 4H), 1.44-1.01 (m, 28H), 0.90 (t, J ) 7.2 Hz, 6H). 13C NMR
(CDCl3): δ 143.70, 133.85, 133.37, 133.24, 129.65, 129.49, 125.70,
125.43, 122.65, 81.95, 81.34, 80.79, 78.50, 78.16, 77.16, 33.08, 32.49,
31.31, 30.26, 30.15, 30.03 (2), 29.91, 23.26, 14.45. IR (KBr): ν 2926,
2866, 2215, 2198 cm-1. HRMS (FAB): calcd for C50H52 652.4069,
found 652.4073.
Dehydrobenzo[18]annulene 17. R,ω-Polyyne 27 (60 mg, 0.075
mmol) was subjected to the standard macrocyclization reaction
procedure C. The product DBA (38 mg, 97% yield) was isolated as a
bright red-orange microcrystalline solid after chromatography on silica
gel (1:1 hexanes-CH2Cl2). Once purified, the product exhibited very
1
poor solubility, thus precluding complete characterization. H NMR
(CDCl3): δ 8.58 (s, 2H), 8.23 (d, J ) 8.4 Hz, 2H), 7.83 (d, J ) 8.4
Hz, 2H), 7.17 (s, 2H), 3.98 (s, 6H). IR (KBr): ν 2960, 2926, 2853,
2190, 2158 cm-1
.
Dehydrobenzo[18]annulene 18. The corresponding R,ω-polyyne
(40 mg, 0.039 mmol) was subjected to macrocyclization reaction
procedure C. The product DBA (13 mg, 46% yield) was isolated as a
bright red-orange microcrystalline solid after chromatography on silica
gel (1:1 hexanes-CH2Cl2). Once purified, the product exhibited very
Dehydrobenzo[18]annulene 12. The corresponding R,ω-polyyne
(175 mg, 0.23 mmol) was subjected to macrocyclization reaction
procedure C. The product DBA (38 mg, 38% yield) was isolated as a
bright yellow microcrystalline solid after chromatography on silica gel
(9:1 hexanes-CH2Cl2). 1H NMR (CD2Cl2): δ 7.74-7.68 (m, 4H),
7.51-7.44 (m, 4H), 7.14 (s, 2H), 3.91 (s, 6H). 13C NMR (CD2Cl2): δ
150.88, 133.36, 133.13, 129.61, 129.43, 125.62, 125.29, 118.79, 115.11,
81.82, 81.32, 80.96, 78.46, 78.14, 76.97, 56.64. IR (KBr): ν 2966,
2913, 2853, 2213, 2197 cm-1. HRMS (FAB): calcd for C32H16O2
432.1150, found 432.1154.
1
poor solubility, thus precluding complete characterization. H NMR
(THF-d8): δ 8.64 (d, J ) 2.1 Hz, 2H), 8.36 (dd, J ) 8.4, 2.1 Hz, 2H),
7.94 (d, J ) 8.4 Hz, 2H), 7.30 (s, 2H), 4.10 (t, J ) 6.3 Hz, 4H), 1.98-
1.27 (m, 28H), 0.91 (bt, J ) 6.9 Hz, 6H). IR (KBr): ν 2956, 2922,
2853, 2196, 2160 cm-1. HRMS (FAB): calcd for C46H42N2O6 718.3043,
found 718.3046.
Dehydrobenzo[18]annulene 19. The corresponding R,ω-polyyne
(50 mg, 0.044 mmol) was subjected to macrocyclization reaction
procedure C. The product DBA (29 mg, 93% yield) was isolated as a
dark red solid after chromatography on silica gel (4:1 hexanes-CH2-
Dehydrobenzo[18]annulene 13. The corresponding R,ω-polyyne
(250 mg, 0.31 mmol) was subjected to macrocyclization reaction
procedure C. The product DBA (143 mg, 73% yield) was isolated as
a bright yellow solid after chromatography on silica gel (4:1 hexanes-
1
Cl2). H NMR (CD2Cl2): δ 8.47 (d, J ) 2.1 Hz, 1H), 8.20 (dd, J )
1
CH2Cl2). H NMR (CD2Cl2): δ 7.72-7.63 (AA′ m, 4H), 7.45-7.37
8.7, 2.1 Hz, 1H), 7.93 (s, 1H), 7.71 (d, J ) 8.7 Hz, 1H), 7.45 (d, J )
8.7 Hz, 1H), 7.34 (s, 1H), 6.86 (d, J ) 2.4 Hz, 1H), 6.69 (dd, J ) 8.7,
2.4 Hz, 1H), 3.32 (t, J ) 7.2 Hz, 4H), 3.17 (t, J ) 7.2 Hz, 4H), 1.65-
1.48 (m, 8H), 1.46-1.23 (m, 8H), 0.98 (t, J ) 7.2 Hz, 6H), 0.90 (t, J
) 7.2 Hz, 6H). 13C NMR (CD2Cl2): δ 148.78, 147.68, 144.58, 141.00,
134.50, 134.38, 131.09, 130.86, 128.22, 127.99, 127.28, 125.88, 125.37,
123.73, 115.43, 115.08, 113,50, 110.70, 84.23, 83.46, 82.86, 82.34,
80.85, 80.41, 79.08, 79.00, 78.94, 78.29, 76.21, 75.99, 52.26, 51.25,
29.96, 29.67, 20.79, 20.63, 14.27, 14.11. IR (KBr): ν 2959, 2926, 2866,
2203, 2144 cm-1. Anal. Calcd for C46H44N4O4: C, 77.07; H, 6.19; N,
7.82. Found: C, 76.47; H, 6.17; N, 7.69.
(BB′ m, 4H), 7.10 (s, 2H), 4.03 (t, J ) 6.6 Hz, 4H), 1.80-1.68 (m,
4H), 1.57-1.32 (m, 20H), 0.91 (t, J ) 6.6 Hz, 6H). 13C NMR (CD2-
Cl2): δ 149.87, 132.67, 132.44, 128.71, 128.49, 125.39, 125.00, 118.32,
115.91, 81.41, 80.74, 80.30, 78.48, 78.10, 76.73, 69.18, 31.80, 29.25,
28.95, 25.92, 22.65, 17.67, 14.09. IR (KBr): ν 2957, 2927, 2856, 2213,
2197 cm-1. HRMS (FAB): calcd for C46H44O2 628.3341, found
628.3347.
Dehydrobenzo[18]annulene 14. The corresponding R,ω-polyyne
(100 mg, 0.12 mmol) was subjected to macrocyclization reaction
procedure C. The product DBA (63 mg, 93% yield) was isolated as a
bright yellow solid after chromatography on silica gel (4:1 hexanes-
THF). 1H NMR (CD2Cl2): δ 7.70-7.63 (m, 4H), 7.41-7.38 (m, 4H),
Dibenzotriyne 28. Triyne 2c (128 mg, 0.25 mmol) was reacted with
diiodoarene 3a (115 mg, 0.23 mmol) via in situ desilylation/alkynylation

Functionalized Dehydrobenzo[18]annulenes
J. Am. Chem. Soc., Vol. 121, No. 36, 1999 8191
reaction procedure B. Chromatography on silica gel (5:1 hexanes-
79.77, 79.45, 78.45, 77.41, 76.07, 51.26, 29.67, 20.79, 14.27. IR
(KBr): ν 2954, 2928, 2870, 2206, 2191, 2142 cm-1. Anal. Calcd for
C38H28N2O2: C, 83.80; H, 5.18; N, 5.14. Found: C, 83.88; H, 5.30; N,
5.04.
1
CH2Cl2) gave compound 28 (158 mg, 85% yield) as a reddish oil. H
NMR (CDCl3): δ 8.10 (s, 1H), 7.35 (d, J ) 9.0 Hz, 1H), 7.20 (s, 1H),
6.69 (d, J ) 2.4 Hz, 1H), 6.53 (dd, J ) 9.0, 2.4 Hz, 1H), 3.30 (t, J )
7.2 Hz, 4H), 3.08 (t, J ) 7.2 Hz, 4H), 1.64-1.18 (m, 16H), 1.19 (s,
21H), 0.97 (t, J ) 7.2 Hz, 6H), 0.89 (t, J ) 7.2 Hz, 6H). 13C NMR
(CDCl3): δ 148.32, 144.50, 141.26, 135.56, 134.26, 133.70, 128.49,
126.26, 114.74, 111.48, 109.30, 105.56, 94.31, 86.03, 84.79, 81.63,
81.50, 74.86, 51.87, 50.53, 29.21, 20.19, 20.06, 18.78, 13.88, 13.79,
11.35. IR (neat): ν 2953, 2873, 2197, 2150 cm-1. HRMS (FAB): calcd
for C43H62IN3O2Si 807.3656, found 807.3651.
r,ω-Polyyne 29. Triyne 2b (109 mg, 0.22 mmol) was reacted with
compound 28 (136 mg, 0.20 mmol) via in situ desilylation/alkynylation
reaction procedure B. Chromatography on silica gel (5:1 hexanes-
CH2Cl2) gave polyyne 29 (151 mg, 73% yield) as a red gum. 1H NMR
(CDCl3): δ 8.32 (d, J ) 2.4 Hz, 1H), 8.10 (dd, J ) 9.0, 2.4 Hz, 1H),
7.88 (s, 1H), 7.66 (d, J ) 9.0 Hz, 1H), 7.35 (d, J ) 8.4 Hz, 1H), 7.15
(s, 1H), 6.69 (d, J ) 2.4 Hz, 1H), 6.52 (dd, J ) 8.4, 2.4 Hz, 1H), 3.30
(t, J ) 7.5 Hz, 4H), 3.18 (t, J ) 7.5 Hz, 4H), 1.63-1.51 (m, 8H),
1.44-1.25 (m, 8H), 1.19 (s, 21H), 1.17 (s, 21H), 0.97 (t, J ) 7.2 Hz,
6H), 0.91 (t, J ) 7.2 Hz, 6H). 13C NMR (CDCl3): δ 148.31, 146.80,
144.88, 139.21, 134.19, 133.41, 132.04, 131.30, 130.32, 128.53, 128.38,
127.01, 124.63, 122.43, 114.72, 112.57, 111.44, 109.30, 105.54, 102.27,
99.90, 94.23, 89.08, 83.10, 82.45, 82.21, 79.54, 78.14, 76.60, 75.16,
51.67, 50.51, 29.45, 29.20, 20.18, 20.03, 18.71, 18.63, 13.87, 13.75,
11.33, 11.21. IR (neat): ν 2958, 2937, 2864, 2204, 2155 cm-1. Anal.
Calcd for C64H86N4O4Si2: C, 74.52; H, 8.40; N, 5.43. Found: C, 74.88;
H, 8.46; N, 5.06.
Dehydrobenzo[18]annulene 23. The corresponding R,ω-polyyne
(10 mg, 0.012 mmol) was subjected to macrocyclization reaction
procedure C. The product DBA (6.5 mg, 99% yield) was isolated as a
bright yellow solid after chromatography on silica gel (2:1 hexanes-
1
CH2Cl2). H NMR (CD2Cl2): δ 8.49 (d, J ) 2.4 Hz, 1H), 8.20 (dd, J
) 8.7, 2.4 Hz, 1H), 7.77 (d, J ) 8.7 Hz, 1H), 7.74-7.67 (m, 2H),
7.53-7.44 (m, 3H), 6.89 (d, J ) 2.7 Hz, 1H), 6.70 (dd, J ) 9.0, 2.7
Hz, 1H), 3.34 (t, J ) 7.2 Hz, 4H), 1.63-1.51 (m, 4H), 1.42-1.34 (m,
4H), 0.98 (t, J ) 7.2 Hz, 6H). 13C NMR (CD2Cl2): δ 148.47, 147.14,
134.51, 132.98, 132.72, 132.66, 132.10, 129.16, 128.80, 127.52, 126.84,
125.69, 125.50, 124.82, 123.18, 114.75, 112.36, 109.69, 86.74, 85.04,
81.93, 81.82, 80.11, 80.00, 78.83, 78.74, 78.40, 77.21, 76.75, 75.80,
50.79, 29.21, 20.27, 13.97. IR (KBr): ν 2959, 2926, 2860, 2190 cm-1
.
HRMS (FAB): calcd for C38H28N2O2 544.2151, found 544.2155.
Dehydrobenzo[18]annulene 24. The corresponding R,ω-polyyne
(100 mg, 0.14 mmol) was subjected to macrocyclization reaction
procedure C. The product DBA (42 mg, 60% yield) was isolated as a
bright yellow-green solid after chromatography on silica gel (4:1
hexanes-THF). 1H NMR (CD2Cl2): δ 7.73-7.66 (m, 4H), 7.52-7.40
(m, 5H), 6.88 (d, J ) 2.4 Hz, 1H), 6.69 (dd, J ) 8.7, 2.4 Hz, 1H), 3.32
(t, J ) 7.5 Hz, 4H), 1.66-1.54 (m, 4H), 1.46-1.33 (m, 4H), 0.98
(t, J ) 6.9 Hz, 6H). 13C NMR (CD2Cl2): δ 148.86, 134.63, 133.35,
133.28, 132.76, 129.61, 129.61, 129.55, 129.51, 128.87, 126.58, 126.30,
125.59, 125.53, 124.84, 115.27, 113.20, 110.41, 83.71, 82.60, 81.63,
81.19, 80.65, 80.45, 79.51, 78.42, 78.29, 77.96, 76.61, 75.97, 51.26,
29.70, 20.80, 14.29. IR (KBr): ν 2957, 2929, 2872, 2861, 2210, 2190,
2135 cm-1. HRMS (FAB): calcd for C38H29N 499.2300, found
499.2296.
Dehydrobenzo[18]annulene 20. R,ω-Polyyne 29 (134 mg, 0.13
mmol) was subjected to macrocyclization reaction procedure C. The
residual solid was purified by chromatography on silica gel (4:1 to 1:1
hexanes-CH2Cl2 gradient). Macrocycle 20 (78 mg, 84% yield) was
1
isolated as a bright red microcrystalline solid. H NMR (CD2Cl2): δ
Dehydrobenzo[18]annulene 25. The corresponding R,ω-polyyne
(60 mg, 0.064 mmol) was subjected to macrocyclization reaction
procedure C. The product DBA (37 mg, 92% yield) was isolated as a
bright yellow solid after chromatography on silica gel (2:1 hexanes-
8.42 (d, J ) 2.4 Hz, 1H), 8.15 (dd, J ) 8.4, 2.4 Hz, 1H), 7.97 (s, 1H),
7.75 (d, J ) 8.4 Hz, 1H), 7.44 (d, J ) 8.7 Hz, 1H), 7.28 (s, 1H), 6.84
(d, J ) 2.4 Hz, 1H), 6.67 (dd, J ) 8.7, 2.4 Hz, 1H), 3.32 (t, J ) 6.9
Hz, 4H), 3.19 (t, J ) 6.9 Hz, 4H), 1.66-1.50 (m, 8H), 1.46-1.22 (m,
8H), 0.99 (t, J ) 6.9 Hz, 6H), 0.91 (t, J ) 6.9 Hz, 6H). 13C NMR
(CD2Cl2): δ 149.10, 147.15, 145.66, 139.48, 134.88, 133.89, 132.21,
131.77, 130.60, 127.94, 126.59, 126.54, 124.00, 123.76, 115.49, 113.38,
112.22, 109.99, 85.47, 83.66, 83.59, 81.98, 80.41, 79.64 (3), 78.69,
76.94, 76.35, 76.05, 52.26, 51.28, 29.98, 29.67, 20.79, 20.60, 14.29,
14.11. IR (KBr): ν 2957, 2928, 2869, 2204, 2189 cm-1. Anal. Calcd
for C46H44N4O4: C, 77.07; H, 6.19; N, 7.82. Found: C, 76.87; H, 6.36;
N, 7.64.
1
CH2Cl2). H NMR (CD2Cl2): δ 7.63 (AA′ m, 2H), 7.48 (d, J ) 9.0
Hz, 2H), 7.38 (BB′ m, 2H), 6.86 (d, J ) 3.0 Hz, 2H), 6.69 (dd, J )
9.0, 3.0 Hz, 2H), 3.32 (t, J ) 7.5 Hz, 8H), 1.65-1.37 (m, 8H), 1.40-
1.28 (m, 8H), 0.98 (t, J ) 7.5 Hz, 12H). 13C NMR (CD2Cl2): δ 148.80,
134.62, 132.68, 128.83, 126.63, 125.62, 115.19, 113.10, 110.46, 83.50,
81.94, 80.71, 79.15, 76.77, 75.95, 51.26, 29.70, 20.80, 14.29. IR
(KBr): ν 2953, 2926, 2864, 2193, 2141, 1590 cm-1. HRMS (FAB):
calcd for C46H46N2 626.3661, found 626.3665.
Dehydrobenzo[18]annulene 26. The corresponding R,ω-polyyne
(80 mg, 0.095 mmol) was subjected to macrocyclization reaction
procedure C. The product DBA (101 mg, 45% yield) was isolated as
a dark red solid after chromatography on silica gel (2:1 hexanes-CH2-
Cl2). 1H NMR (CD2Cl2): δ 8.41 (s, 1H), 8.07 (t, J ) 5.1 Hz, 1H), 7.46
(d, J ) 9.0 Hz, 1H), 7.44 (d, J ) 9.0 Hz, 1H), 7.08 (s, 1H), 6.85-6.81
(m, 2H), 6.68 (d, J ) 2.1 Hz, 1H), 6.65 (d, J ) 1.8 Hz, 1H), 3.42-
3.22 (m, 8H), 1.65-1.52 (m, 8H), 1.43-1.31 (m, 8H), 0.98 (t, J ) 7.2
Hz, 12H). 13C NMR (CD2Cl2): δ 149.18, 148.65, 144.92, 135.01,
134.40, 132.55, 131.40, 131.28, 127.19, 126.32, 117.72, 115.31, 115.17,
113.20, 113.01, 111.55, 110.78, 109.76, 86.16, 82.78, 82.56, 82.22,
81.62, 79.99, 79.51, 77.15, 77.05, 76.59, 76.05, 75.89, 51.25, 29.71,
Dehydrobenzo[18]annulene 21. The corresponding R,ω-polyyne
(175 mg, 0.20 mmol) was subjected to macrocyclization reaction
procedure C. The product DBA (95 mg, 87% yield) was isolated as a
bright red solid after chromatography on silica gel (4:1 hexanes-CH2-
1
Cl2). H NMR (CD2Cl2): δ 8.00 (s, 1H), 7.71-7.64 (m, 4H), 7.49-
7.41 (m, 4H), 7.34 (s, 1H), 3.19 (t, J ) 7.2 Hz, 4H), 1.60-1.52 (m,
4H), 1.35-1.24 (m, 4H), 0.90 (t, J ) 7.2 Hz, 6H). 13C NMR (CD2-
Cl2): δ 145.20, 140.34, 133.55, 133.44, 133.36, 133.17, 131.70, 130.05,
129.74, 129.67, 129.50, 129.46, 125.88, 125.71, 125.28, 125.15, 124.97,
113.66, 82.54, 81.52, 81.21, 81.09, 80.29, 80.19, 80.03, 78.49, 78.46,
78.10, 77.78, 77.53, 52.28, 30.00, 20.60, 14.11. IR (KBr): ν 2955,
2929, 2871, 2853, 2213, 2194, 2156, 2142 cm-1. Anal. Calcd for
C38H28N2O2: C, 83.80; H, 5.18; N, 5.14. Found: C, 83.60; H, 5.37; N,
4.98.
20.79, 14.27. IR (KBr): ν 3370, 2959, 2926, 2866, 2190, 2137 cm-1
MS (FAB): m/z 687 (M+, 57), 671 (22).
.
N,N-Dibutyl-4-[4-(4-nitrophenyl)-1,3-butadiynyl]aniline (32). N,N-
Dibutyl-4-iodoaniline (50 mg, 0.15 mmol), prepared in a manner
analogous to that for 8, was reacted with 1-[4-(trimethylsilyl)-1,3-
butadiynyl]-4-nitrobenzene (44 mg, 0.18 mmol) via in situ protiode-
silylation/alkynylation reaction procedure B. Chromatography on silica
gel (3:1 hexanes-CH2Cl2) gave butadiyne 32 (47 mg, 84%) as a light
Dehydrobenzo[18]annulene 22. The corresponding R,ω-polyyne
(60 mg, 0.070 mmol) was subjected to the standard macrocyclization
reaction procedure C. The product DBA (36 mg, 94% yield) was
isolated as a bright red solid after chromatography on silica gel (4:1
1
hexanes-CH2Cl2). H NMR (CD2Cl2): δ 8.49 (d, J ) 2.4 Hz, 1H),
1
8.21 (dd, J ) 8.7, 2.4 Hz, 1H), 7.79 (d, J ) 8.7 Hz, 1H), 7.68-7.62
(m, 2H), 7.49 (d, J ) 8.7 Hz, 1H), 7.47-7.7.37 (m, 2H), 6.86 (d, J )
2.7 Hz, 1H), 6.67 (dd, J ) 8.7, 2.7 Hz, 1H), 3.32 (t, J ) 7.2 Hz, 4H),
orange solid. H NMR (CDCl3): δ 8.20 (d, J ) 9.0 Hz, 2H), 7.63 (d,
J ) 9.0 Hz, 2H), 7.39 (d, J ) 9.0 Hz, 2H), 6.56 (d, J ) 9.0 Hz, 2H),
3.30 (t, J ) 7.8 Hz, 4H), 1.62-1.51 (m, 4H), 1.40-1.31 (m, 4H), 0.97
(t, J ) 7.8 Hz, 6H). 13C NMR (CDCl3): δ 148.90, 134.25, 133.18,
132.79, 132.63, 128.54, 123.63, 111.09, 87.31, 80.49, 78.72, 71.57,
50.67, 29.26, 20.26, 13.96. IR (KBr): ν 2958, 2931, 2874, 2855, 2210,
1.65-1.54 (m, 4H), 1.44-1.33 (m, 4H), 1.00 (t, J ) 7.2 Hz, 6H). 13
C
NMR (CD2Cl2): δ 148.90, 147.43, 134.68, 134.19, 133.59, 132.83,
131.54, 130.17, 138.94, 127.98, 126.88, 126.66, 126.12, 124.25, 123.77,
115.44, 113.53, 110.50, 84.30, 83.98, 83.75, 83.03, 80.56, 80.33 (2),
2186 cm-1
.

8192 J. Am. Chem. Soc., Vol. 121, No. 36, 1999
Pak et al.
Table 5. Crystallographic Data for DBAs 20, 22, 23, and 25
parameters are given in Table 5. Structure refinements (C atoms
anisotropic, H atoms riding) were accomplished with the TEXSAN
program suite (version 5.0). Further details are contained in the
Supporting Information. All crystals were weakly diffracting and
exhibited disorder in the butyl groups.
20
22
23
25
empirical
formula
fw
cryst syst
space group P1h
C46H44N4O4‚ C38H28N2O2 C38H28N2O2 C46H46N2
CH2Cl2
801.81
544.65
monoclinic
Ia
544.65
triclinic
P1h
626.89
triclinic
P1h
triclinic
Acknowledgment. We thank the National Science Founda-
tion (Grant No. CHE-9704171), the donors of the Petroleum
Research Fund, administered by the American Chemical Society,
and The Camille and Henry Dreyfus Foundation (Teacher-
Scholar Award 1998-2003 to M.M.H.) for support of this
research. J.J.P. acknowledges the ACS Division of Organic
Chemistry for a Graduate Fellowship (1998-1999), sponsored
by Organic Syntheses.
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
10.0234(11) 9.7761(10)
13.9218(16) 31.232(4)
16.5767(19) 10.954(3)
10.769(2)
11.449(3)
14.308(2)
70.55(2)
9.420(3)
12.022(4)
18.224(3)
73.26(2)
82.47(2)
74.29(3)
1899(1)
2
74.555(9)
86.062(9)
79.957(10)
2192.5(9)
2
90
114.464(14) 78.93(1)
90
3044.2(9)
4
64.78(2)
1502(1)
2
T (K)
GOF
R(F)
294
1.69
0.101
0.053
294
295
1.37
0.147
0.067
295
3.15
0.095
0.093
Supporting Information Available: Figures giving X-ray
crystal structures and tables of atomic coordinates, thermal
parameters, bond lengths, and bond angles of 20, 22, 23, and
25 and crystallographic files, in CIF format, for these com-
pounds. This material is available free of charge via the Internet
at http://pubs.acs.org.
1.35
0.053
0.045
Rw(F)
X-ray Structure Determinations. Data were collected on an Enraf-
Nonius CAD-4 diffractometer using graphite-monochromated Mo KR
radiation (0.710 73 Å). Pertinent crystallographic data and refinement
JA991749G