Synthesis of Unsymmetrical 1,4-Diarylbutadiynes by Stille Coupling

Full text of DOI:10.1021/jo970549p

J . Org. Chem. 1997, 62, 7471-7474
7471
Sch em e 1. F or m a tion of Un sym m etr ica l
Dia r ylbu ta d iyn es (R ) e.g. H, Cu , Zn Cl, Sn R′3)
Syn th esis of Un sym m etr ica l
1,4-Dia r ylbu ta d iyn es by Stille Cou p lin g
Adelheid Godt
Max-Planck-Institut fu¨r Polymerforschung,
Ackermannweg 10, 55128 Mainz, Germany
Received March 25, 1997
sponding arylbutadiynes.1e,11 This paper reports on the
synthesis of the appropriate arylbutadiynes and their use
in the formation of the angular molecules 9.
In the context of catenane synthesis we are interested
in shape persistent,1 angular molecules like 9, containing
substituted arylbutadiyne moieties attached to a central
phenylene ring. A common method for the synthesis of
such unsymmetrically substituted 1,4-diarylbutadiynes
uses the Cadiot-Chodkiewicz coupling of arylethyne with
1-aryl-2-bromoethyne (Scheme 1, path a).2,3 The yields
are often moderate to good, depending on the actual
substituents at the arylethyne and the bromoethyne. In
a well known side reaction the bromoethyne dimerizes
to give symmetrical 1,4-diarylbutadiyne. To no surprise,
the reaction of 3,5-diethynyl-4-[(4-methoxybenzyl)oxy]-
benzoic acid with 1-(4-iodophenyl)-2-bromoethyne under
the typical Cadiot-Chodkiewicz conditions gave a con-
siderable amount of 1,4-bis(4-iodophenyl)butadiyne. Use
of 1-(4-iodophenyl)-2-iodoethyne instead of 1-(4-iodophe-
nyl)-2-bromoethyne under conditions5,6 reported not to
give the dimerization product of the iodoethyne compo-
nent resulted in a mixture of products including the
dimerization product 1,4-bis(4-iodophenyl)butadiyne. This
waste of rather precious arylethyne, troubles with the
separation of the desired product from the dimerization
product when working on a large scale, and the inherent
problems of using reactions with only moderate yields
on molecules with two to-be-transformed functionalities
made us search for a better approach. Alternatively to
the alkyne-alkyne coupling reaction, as in the mentioned
Cadiot-Chodkiewicz coupling, one can consider an aryl-
alkadiyne coupling to form diarylbutadiyne (Scheme 1,
path b). Proper substituents R at the arylbutadiyne unit
may be for example H, Cu, ZnCl, SnR′3. Those substit-
uents are known to allow for the coupling of arylethynes
with aryl halides to give diarylethynes.7-10 Little is
known about such coupling reactions using the corre-
Resu lts a n d Discu ssion
The approach outlined in Scheme 1 as path b requires
arylbutadiynes as prefabricated building blocks. These
were synthesized starting from para-substituted aryl
halides 1 (Scheme 2). In a first step the aryl halides 1
were coupled with propargyl alcohol or with (trimethyl-
silyl)acetylene to give the disubstituted acetylenes 2 and
3, respectively.7 The monosubstituted acetylenic com-
pounds 4 were formed by reaction of compounds 2 with
MnO2 and KOH12 or by reaction of compounds 3 with
K2CO3 or NaOH. The acetylenes 4 were subsequently
coupled with 3-bromoprop-2-ynol under the conditions of
the Cadiot-Chodkiewicz reaction2,13 to give diacetylenes
5. The conversion of 4 was found to be nearly quantita-
tive only when a large excess (3 equiv) of 3-bromoprop-
2-ynol had been used. This is partly due to the unavoid-
able formation of the dimerization product hexa-2,4-
diyne-1,6-diol. However, 3-bromoprop-2-ynol is a rather
inexpensive reagent and separation of hexa-2,4-diyne-
1,6-diol was easily achieved either by chromatography,
distillation, or recrystallization. The reverse reaction of
propargyl alcohol with 1-aryl-2-bromoethyne is possible,
as tested for 5a ,b. However, as expected, in this case
part of the valuable 1-bromo-2-(4-bromophenyl)ethyne or
1-bromo-2-tolylethyne was consumed by dimerization,
and the isolation of pure 5a ,b became more tedious.
Treatment of 5 with suspended MnO2 and KOH12,13 for
about 1 h gave the deprotected butadiynes 6 in a clean
and quantitative reaction. Therefore storable compounds
5 appear to be valuable precursors for compounds 6,
which turned out to be rather instable when isolated free
of solvent. The transformation is compatible with a
variety of functionalities and protecting groups (Scheme
2). This synthesis of arylbutadiynes 6 via 5 starting from
arylethynes 4 is a suitable alternative to the synthesis
of butadiynes by cross-coupling of alkynes with 1-chloro-
2-iodoethylene or 1,2-dichloroethylene followed by HCl-
elimination from the 1-chloro-1-buten-3-yne derivatives
(1) E.g. (a) Diederich, Nature 1994, 369, 199. (b) Wu, Z.; Moore, J .
S. Angew. Chem. 1996, 108, 320. (c) Schumm, J . S.; Pearson, D. L.;
Tour, J . M. Angew. Chem. 1994, 106, 1445. (d) Bartik, T.; Bartik, B.;
Brady, M.; Dembinski, R.; Gladysz, J . A. Angew. Chem. 1996, 108, 467.
(e) Bunz, U. H. F.; Enkelmann, V. Organometallics 1994, 13, 3823. (f)
Ho¨ger, S. Angew. Chem. 1995, 107, 2917. (g) de Meijere, A.; Kozhush-
kov, S.; Puls, C.; Haumann, T.; Boese, R.; Cooney, M. J .; Scott, L. T.
Angew. Chem. 1994, 106, 934. (h) Vo¨gtle, F.; Michel, I.; Berscheid, R.;
Nieger, M.; Rissanen, K.; Kotila, S.; Airola, K.; Armaroli, N.; Maestri,
M.; Balzani, V. Liebigs Ann. 1996, 1697. (i) Harriman, A.; Ziessel, R.
Chem. Commun. 1996, 1707.
(2) (a) Chodkiewicz, W. Ann. Chim. 1957, 2 (13. Se´rie), 819. For
reasons unknown to us, the yield of 3-bromoprop-2-ynol ranged from
nearly 0% to 70%. (b) Eglington. G.; MacCrae, W. in Advances in
Organic Chemistry, Methods and Results; Raphael, R. A., Taylor, E.
C., Wynberg, H., Eds.; Wiley: New York, 1963; vol. 4, p 225.
(3) The strategy via dialkynylborates4 is not compatible with the
functional groups used in this paper.
(4) Sinclair, J . A.; Brown, H. C. J . Org. Chem. 1976, 41, 1079. Pelter,
A.; Hughes, R.; Smith, K.; Tabata, M. Tetrahedron Lett. 1976, 48, 4385.
(5) Alami, M.; Ferri, F. Tetrahedron Lett. 1996, 37, 2763.
(6) Wityak, J ; Chan, J . B. Synth. Commun. 1991, 21, 977.
(7) E.g. Takahashi, S.; Kuroyama, Y.; Sonogashira, K.; Hagihara,
N. Synthesis 1980, 627. Alami, M.; Ferri, F.; Linstrumentelle, G.
Tetrahedron Lett. 1993, 34, 6403. Rossi, R.; Carpita, A.; Bellina, F.
Org. Prep. Proc. Int. 1995, 27, 127.
by NaNH2/NH3 or Bu4NF.15 Compound 6a and phe-
14
nylbutadiyne were isolated free of solvent by filtering the
reaction suspension of the acetylene deprotection step
(10) (a) Stille, J . K.; Simpson, J . H. J . Am. Chem. Soc. 1987, 109,
2138. (b) Stille, K. Angew. Chem. 1986, 98, 504. (c) Mitchell, T. N.
Synthesis 1992, 803.
(11) Boese, R.; Green, J . R.; Mittendorf, J .; Mohler, D. L.; Vollhardt,
K. P. C. Angew. Chem. 1992, 104, 1643. Diercks, R.; Vollhardt, K. P.
C. J . Am. Chem. Soc. 1986, 108, 3150.
(12) Bumagin, N. A.; Ponomaryov, A. B.; Beletskaya, I. P. Synthesis
1984, 728.
(13) Vereshchagin, L. I.; Buzilova, S. R.; Bol’shedvorskaya, R. L.;
Kirillova, L. P. J . Org. Chem. USSR (Engl. Transl.) 1976, 12, 1174.
(14) Negishi, E.; Okukado, N.; Lovich, S. F.; Luo, F.-T. J . Org. Chem.
1984, 49, 2629.
(8) Stephens, R. D.; Castro, C. E. J . Org. Chem. 1963, 28, 3313.
(9) King, A. O.; Negishi, E. J . Org. Chem. 1978, 43, 358. Russell, C.
E.; Hegedus, L. S. J . Am. Chem. Soc. 1983, 105, 943.
(15) Kende, A. S.; Smith, C. A. J . Org. Chem. 1988, 53, 2655.
S0022-3263(97)00549-5 CCC: $14.00 © 1997 American Chemical Society

7472 J . Org. Chem., Vol. 62, No. 21, 1997
Notes
Sch em e 2a
Ta ble 1. Isola ted Yield s (%) of th e Key Com p ou n d s 5, 7,
a n d 9
a
b
c
d
e
f
5
65
47
83
70
64
79
88
89
79
85
53
64
7a
9
47b
70
80
82
43c
31d
a
b
Overall yield starting from 5. One reaction out of six gave a
yield of 60%. c The reaction of 7e with 8 was incomplete (ca. 80%
1
conversion, estimated from the H NMR spectrum). Therefore the
isolation of pure 9e resulted in a relatively low yield. Compound
d
9f was synthesized only once. The not optimized workup may
account for the low yield.
and fractional distillation of the filtrate. The products
were stored under argon in a freezer and used the next
day for the coupling reaction. At room temperature the
pure compounds turned partly insoluble within few
hours.
For the synthesis of tolanes the most convenient
method is the Pd/Cu-catalyzed coupling of arylethynes
with aryl halides.7 The analogous reaction of an aryl-
butadiyne (Scheme 1: R ) H) with an aryl iodide had
been reported.11 However, the reaction of 6a with 8 at
room temperature in piperidine with Pd(PPh3)2Cl2 and
CuI as catalysts yielded starting material 8 and a
considerable amount of olefinic products instead of
product 9a . The model reaction of phenylbutadiyne with
the simple aryl iodide 1b under the same conditions gave
also a mixture of several products including alkenes.
As an alternative, the Stille coupling10 between 1-aryl-
2-(trimethylstannyl)butadiyne and aryl halide is sug-
gested by the work of Bunz et al.1e The syntheses of
stannylbutadiynes 7 were accomplished by treatment of
6 with (N,N-dimethylamino)trimethylstannane10 using
the filtrate of the conversion reaction of 5 to 6. The
possibility to skip aqueous workup prior to addition of
an air- and water-sensitive reagent renders this proce-
dure convenient and advantageous to other reported
methods for the preparation of 6.14,15 The stannyl-
butadiynes 7 can be used either directly after removing
the solvent or after distillation. The stannanes 7 were
isolated in good yields with the exception of 7a (Table
1). For unknown reasons, compound 7a was reproducibly
isolated in comparatively low yields. One factor might
be the greater acidity of the acceptor-substituted aryl-
butadiyne 6a compared to the other arylbutadiynes 6b-
f. Because no byproducts could be detected in the
solution of 6a , the compounds 5a or 6a must have been
either partially trapped in the MnO2/KOH precipitate or
turned into insoluble material during the acetylene
deprotection step. The stannylbutadiynes were stored
in a freezer under argon for several months without any
sign of decomposition. They also proofed stable at room
temperature for several days when stored under argon.
Reaction of the stannanes 7 with the diiodide 8 in THF
16
in the presence of Pd2(dba)3/AsPh3 gave the angular
molecules 9 usually in good yields (Table 1). The reaction
of 7a with 8 shows that the iodide-bromide-selectivity,17
used for the synthesis of 1e and 2a , works as well in this
case of the Stille coupling. Other reaction conditions that
had been reported for the Stille coupling,10a,18 e.g. DMF
instead of THF or Pd(CH3CN)2Cl2 instead of Pd2(dba)3/
AsPh3, resulted in a very slow formation of 9.
a
Key: PMB ) 4-Methoxybenzyl; (a) HOCH2CCH, Pd(PPh3)2Cl2,
CuI, piperidine, THF, 0 °C f rt, 83-88%; (b) for 3c: 1c, TMSCCH,
Pd(PPh3)2Cl2, CuI, piperidine, rt, 86%; for 3d ,f: 1d , f, TMSCCH,
Pd(PPh3)2Cl2, CuI, Et2NH, rt, 78% and 67%, respectively; for 3e:
(1) 1a , TMSCCH, Pd(PPh3)2Cl2, CuI, PPh3, piperidine, 0 °C f rt;
(2) TIPSCCH, 60 °C, 72%; (c) MnO2, KOH, Et2O, 77-85%; (d)
K2CO3 or KOH, MeOH, 81-86%; (e) CuCl, NH2OH‚HCl, 70%
aqueous EtNH2, MeOH, additional THF in the case of 4f, for yields
see Table 1; (f) MnO2, KOH, Et2O, additional CH2Cl2 in the case
of 5c and f; (g) Me3SnNEt2, Et2O, additional CH2Cl2 in the case
of 5c and f, for yields see Table 1; (h) Pd2(dba)3, AsPh3, THF, 60
°C, for yields see Table 1.
(16) Farina, V.; Krishnan, B. J . Am. Chem. Soc. 1991, 113, 9585.
Farina, V. Pure Appl. Chem. 1996, 68, 73.
(17) E.g. ref 1f. Bedard, T. C.; Moore, J . S. J . Am. Chem. Soc. 1995,
117, 10662.
(18) Lo Sterzo, C.; Stille, J . K. Organometallics 1990, 9, 687.

Notes
In this paper a convenient and general way to a variety
of arylbutadiynes 6 and their stannane derivatives 7 is
described. The latter proved to be useful arylbutadiyne
construction blocks for the synthesis of unsymmetrical
1,4-diarylbutadiynes as in compound 9. The reported
synthetic strategy is efficient, feasible on the gram scale,
and compatible with a range of functionalities.
J . Org. Chem., Vol. 62, No. 21, 1997 7473
70.5, 72.1, 78.7, 80.0, 96.1, 114.1, 116.4, 134.1, 157.8. Anal.
Calcd for C16H16O3: C, 74.98; H, 6.29. Found: C, 74.92, H, 6.25.
5-[4-[2-(Tr iisop r op ylsilyl)e t h yn yl]p h e n yl]p e n t a -2,4-
d iyn ol (5e). Heating of the second eluted fraction under
vacuum (60 °C/0.01 mbar) to remove hexa-2,4-diyne-1,6-diol gave
5d (53%) as a brown oily residue: 1H NMR δ 1.10 (s, 21H), 2.04
(br s, 1H), 4.40 (s, 2H), 7.39 (s, 4H); 13C NMR δ 11.3, 18.6, 51.6,
70.3, 74.9, 78.1, 81.4, 93.9, 106.3, 121.1, 124.5, 132.0, 132.3. Anal.
Calcd for C22H28OSi: C, 78.51; H, 8.39. Found: C, 78.57, H,
8.29.
5-[4-(3,3-Te t r a m e t h yle n e t r ia ze n o)p h e n yl]p e n t a -2,4-
d iyn ol (5f). Recrystallization of the second eluted fraction from
ethanol gave 5f (64%) as yellow needles: mp 144 °C; 1H NMR20
δ 2.02 (br t, 4H), 2.23 (br s, 1H), 3.78 (br s, 4H), 4.38 (s, 2H),
7.35 and 7.44 (AA′BB′, 2H each); 13C NMR δ 23.7, 47 and 51
(very broad signals20), 51.5, 70.6, 73.0, 79.3, 80.5, 117.3, 120.3,
133.4, 152.0. Anal. Calcd for C15H15N3O: C, 71.13; H, 5.97; N,
16.59. Found: C, 71.09, H, 6.09; N, 16.66.
Exp er im en ta l Section
Gen er a l. All experiments were carried out under inert
atmosphere (argon or nitrogen). Piperidine and dichloromethane
were distilled from CaH2. THF and diethyl ether were dried
over sodium/benzophenone. The petroleum ether used had a
boiling range of 30-40 °C. Activated MnO2, Pd2(dba)3, and
AsPh3
were
purchased
from
Aldrich.
Me3Sn-
NEt219 and 3-bromoprop-2-ynol2a were synthesized according to
the literature. For flash chromatography, Merck silica gel (mesh
70-230) was used. TLC was performed on silica gel coated
aluminum foil (Merck aluminum foils 60 F254). If not otherwise
mentioned, 1H and 13C NMR spectra were recorded in CDCl3 as
solvent and internal standard on a 300 MHz spectrometer.
DEPT experiments were run to determine the multiplicity in
the 13C NMR spectra.
Gen er a l P r oced u r e for th e P r ep a r a tion of (4-Ar ylbu ta -
1,3-d iyn yl)tr im eth ylsta n n a n es 7a -f. The reactions were
carried out starting from 3-5 g of compounds 5.
Compounds 5a ,b,d ,e (10 mmol) were dissolved in diethyl ether
(47 mL), 5c (10 mmol) was dissolved in diethyl ether (14 mL)
and methylene chloride (41 mL), and 5f (10 mmol) was dissolved
in diethyl ether (38 mL) and methylene chloride (19 mL). These
solutions were cooled in an ice bath, and MnO2 (100 mmol) and
powdered KOH (50 mmol) were added. The suspensions were
stirred well at rt, and the reactions were monitored by TLC
(petroleum ether/diethyl ether 1:1). Usually they were complete
after 1 h. If not, some more MnO2 (10-50 mmol) and powdered
KOH (5-25 mmol) were added. Upon completion of the reac-
tions (usually after further 15 min), the precipitates were filtered
off under inert atmosphere by use of a double-ended frit and
washed several times with diethyl ether. (N,N-Diethylamino)t-
rimethylstannane (11-13 mmol) was added to the slightly yellow
filtrates. After 1 h of stirring at rt, the solvent was distilled off
giving brown solids (7a -d ,f) or a brown, very viscous oil (7e).
[4-(4-Br om op h en yl)bu ta -1,3-d iyn yl]tr im eth ylsta n n a n e
(7a ). Distillation (150 °C bath temp/0.001 mbar) gave 7a (47%;
one reaction out of six gave a yield of 60%) as a pale yellow
solid: mp 80 °C; 1H NMR δ 0.35 (s with Sn satellites,21 9H),
7.31 and 7.42 (AA′BB′, 2H each); 13C NMR δ -7.68 (signal with
Sn satellites21), 73.06, 75.53, 90.98, 93.27, 120.79, 123.47, 131.69,
Gen er a l P r oced u r e for th e P r ep a r a tion of 5-Ar ylp en ta -
2,4-d iyn ols 5a -f. The reactions were carried out using 2-10
g of starting material 4.
Arylethyne 4 (10 mmol) was added to a degassed mixture of
hydroxylamine hydrochloride (12 mmol) and CuCl (0.4 mmol)
in methanol (5.5 mL) and aqueous 70% ethylamine (2.9 mL). In
the case of 4f, THF (4 mL) was added. To this intensely yellow
suspension 3-bromoprop-2-ynol (30 mmol) diluted with methanol
(36 mL) was added over the course of 20-30 min. The inside
temperature was kept at 15-20 °C with the help of an dry ice/
2-propanol bath. In case that the color changed to greenish,
some additional hydroxylamine hydrochloride was added. After
complete addition of 3-bromoprop-2-ynol, the cooling bath was
removed and the suspension was stirred at rt for another 4 h.
For workup, the suspension was poured into saturated aqueous
NH4Cl, the aqueous phase was extracted with diethyl ether (5b-
f) or methylene chloride (5a ), and the combined organic phases
were washed with saturated aqueous NH4Cl, dried (Na2SO4),
and filtered. After removal of the solvent in vacuo, the residue
was purified by flash chromatography (5a ,b: methylene chloride;
5c-f: petroleum ether/diethyl ether 1:1 v/v). The first fraction
contained unreacted 4 and the second the diyne 5.
133.98. Anal. Calcd for
Found: C, 42.15; H, 3.02.
C13H13BrSn: C, 42.45; H, 3.56.
[4-(4-Me t h y lp h e n y l)b u t a -1,3-d iy n y l]t r im e t h y ls t a n -
n a n e (7b). Distillation (104 °C bath temp/0.001 mbar) gave 7b
1
(83%) as a pale yellow solid: mp 62 °C; H NMR δ 0.35 (s with
Sn satellites,21 9H), 2.34 (s, 3H), 7.10 and 7.36 (AA′BB′, 2H each);
13C NMR δ -7.7 (signal with Sn satellites21), 21.6, 73.7, 74.6,
91.3, 91.7, 118.5, 129.1, 132.5, 139.4. Anal. Calcd for
5-(4-Br om op h en yl)p en ta -2,4-d iyn ol (5a ). Heating of the
second eluted fraction under vacuum (70 °C/0.01 mbar) to
remove hexa-2,4-diyne-1,6-diol gave 5a (65%) as a pale yellow
1
solid residue: mp 138 °C (lit.13: 128-130 °C); H NMR δ 1.83
C
14H16Sn: C, 55.50; H, 5.32. Found: C, 55.61; H, 5.26.
[4-[4-(E t h yloxy)p h en yl]b u t a -1,3-d iyn yl]t r im et h ylst a n -
(br s, 1H), 4.41 (s, 2H), 7.33, 7.45 (AA′BB′, 2H each); 13C NMR
(DMSO-d6) δ 49.5, 67.8, 74.4, 76.3, 84.7, 119.7, 123.4, 131.9,
134.2. Anal. Calcd for C11H7BrO: C, 56.20; H, 3.00. Found:
C, 56.14; H, 2.94.
n a n e (7c). Distillation (160-170 °C bath temp/0.001 mbar)
gave 7c (79%) as a colorless solid: mp 66 °C; 1H NMR δ 0.33 (s
with Sn satellites,21 9H), 1.37 (t, J ) 7.0 Hz, 3H), 3.98 (q, J )
7.0 Hz, 2H), 6.77 and 7.36 (AA′BB′, 2H each); 13C NMR δ -7.68
(signal with Sn satellites21), 14.7, 63.5, 73.2, 74.6, 91.2, 91.7,
113.4, 114.6, 134.2, 159.7. Anal. Calcd for C15H18OSn: C, 54.10;
H, 5.45. Found: C, 54.46, H, 5.37.
[4-[4-(Tet r a h yd r op yr a n -2-yloxy)p h en yl]b u t a -1,3-d iyn -
yl]tr im eth ylsta n n a n e (7d ). Distillation (175 °C bath temp/
0.001 mbar) gave 7d (79%) as a slightly yellow solid: mp 107
°C; 1H NMR δ 0.34 (s with Sn satellites,21 9H), 1.5-2.1 (m, 6H),
3.59 (m, 1H), 3.84 (m, 1H), 5.41 (t, J ) 3.0 Hz, 1H), 6.96 and
7.39 (AA′BB′, 2H each); 13C NMR δ -7.7 (signal with Sn
satellites21), 18.6, 25.1, 30.2, 62.0, 73.2, 74.5, 91.3, 91.5, 96.2,
5-(4-Meth ylp h en yl)p en ta -2,4-d iyn ol (5b). Recrystalliza-
tion of the second eluted fraction from petroleum ether contain-
ing a small amount of diethyl ether gave 5b (47%) as pale yellow
1
flaky crystals: mp 82 °C; H NMR δ 1.95 (s, 1H), 2.34 (s, 3H),
4.41 (s, 2H), 7.11 and 7.37 (AA′BB′, 2H each); 13C NMR δ 21.6,
51.6, 70.6, 72.6, 78.9, 80.1, 118.2, 129.2, 132.5, 139.8. Anal.
Calcd for C12H10O: C, 84.68; H, 5.92. Found: C, 84.72; H, 5.91.
5-[4-(Eth yloxy)p h en yl]p en ta -2,4-d iyn ol (5c). The diyne
5c (64%) was obtained as a brownish solid: mp 109-110 °C; 1H
NMR δ 1.40 (t, J ) 7.0 Hz, 3H), 1.86 (br s, 1H), 4.02 (q, J ) 7.0
Hz, 2H), 4.40 (s, 2H), 6.81 and 7.40 (AA′BB′, 2H each); 13C NMR
δ 14.7, 51.7, 63.6, 70.8, 72.0, 79.0, 79.8, 113.1, 114.6, 134.2, 159.9.
Anal. Calcd for C13H12O2: C, 77.98; H, 6.04. Found: C, 77.94,
H, 6.00.
5-[4-(Te t r a h yd r op yr a n -2-yloxy)p h e n yl]p e n t a -2,4-d i-
yn ol (5d ). Diyne 5d (89%) was obtained as an off-white solid:
mp 97 °C; 1H NMR δ 1.5-2.1 (m, 6H), 3.59 (m, 1H), 3.84 (m,
1H), 4.39 (d, J ) 6.2 Hz, 2H), 5.43 (t, J ) 3.1 Hz, 1H), 6.98 and
7.41 (AA′BB′, 2H each); 13C NMR δ 18.5, 25.0, 30.1, 51.5, 62.0,
(20) Temperature dependent measurements of 3f in C2D2Cl4 re-
vealed coalescence of the two signals at 47 and 51 ppm at higher
temperature. At 80 °C they give a rather sharp signal with δ ) 49.0.
Furthermore the signal at 24 ppm sharpens when the temperature is
raised. Similarly, the 1H signals at 2 and 4 ppm get considerably
narrower with temperature increase. This observation is explained
with the conformational flexibility of the pyrrolidine ring.
(21) The satellites showed the expected coupling constants of 58 and
60 Hz for 2J (H, Sn) and 388 and 406 Hz for 1J (CH3, Sn). The signal to
noise ration of the 13C NMR spectra was usually too low for detection
of the Sn satellites of the alkyne signal.
(19) J ones, K.; Lappert, M. F. J . Chem. Soc. 1965, 1944.

7474 J . Org. Chem., Vol. 62, No. 21, 1997
Notes
114.4, 116.4, 134.1, 157.7. Anal. Calcd for C18H22O2Sn: C,
55.57; H, 5.70. Found: C, 55.61, H, 5.73.
1.42 (t, J ) 7.0 Hz, 6H), 3.78 (s, 3H), 4.04 (q, J ) 7.0 Hz, 4H),
4.35 (q, J ) 7.1 Hz, 2H), 5.38 (s, 2H), 6.85 and 7.48 (AA′BB′, 4H
each), 6.90 and 7.50 (AA′BB′, 2H each), 8.10 (s, 2H); 13C NMR δ
14.3, 14.7, 55.2, 61.4, 63.6, 72.6, 75.8, 76.1, 79.7, 83.6, 113.2,
113.8, 114.7, 117.1, 126.0, 128.4, 130.5, 134.2, 136.1, 159.8, 160.0,
164.5, 165.7. Anal. Calcd for C41H34O6: C, 79.08; H, 5.50.
Found: C, 78.96, H, 5.51.
An gu la r Molecu le 9d . Flash chromatography (methylene
chloride) gave 9d (85%) as a yellow-brown solid contaminated
with catalyst, clearly to be seen in the 1H NMR spectrum:22 1H
NMR δ 1.37 (t, J ) 7.1 Hz, 3H), 1.5-2.1 (m, 12H), 3.61 (m, 2H),
3.78 (s, 3H); 3.86 (m, 2H), 4.35 (q, J ) 7.1 Hz, 2H), 5.38 (s, 2H),
5.45 (t, J ) 3.0 Hz, 2H), 6.90 and 7.50 (AA′BB′, 2H each), 7.02
and 7.48 (AA′BB′, 4H each), 8.10 (s, 2H); 13C NMR δ 14.3, 18.6,
25.1, 30.2, 55.3, 61.4, 62.1, 72.7, 75.9, 76.1, 79.7, 83.5, 96.3, 113.9,
114.2, 116.6, 117.1, 126.0, 128.4, 130.5, 134.1, 136.2, 158.1, 159.8,
164.6, 165.8.
An gu la r Molecu le 9e. Purification by flash chromatography
(diethyl ether/petroleum ether 1:10 v/v) and subsequent recrys-
tallization from ethanol containing some ethyl acetate gave 9e
(43%) as a greyish solid: mp 98 °C; 1H NMR δ 1.12 (s, 42H),
1.38 (t, J ) 7.1 Hz, 3H), 3.78 (s, 3H), 4.35 (q, J ) 7.1 Hz, 2H),
5.39 (s, 2H), 6.89 (half of an AA′BB′ system, 2H), 7.46 (m, 10
H), 8.12 (s, 2H); 13C NMR (CD2Cl2) δ 11.7, 14.4, 18.8, 55.6, 61.9,
75.5, 76.6, 77.8, 79.4, 83.1, 94.7, 106.7, 114.2, 117.1, 121.6, 125.1,
126.7, 128.7, 130.9, 132.4, 132.8, 136.8, 160.4, 164.6, 166.4.
Anal. Calcd for C59H66O4Si2: C, 79.15; H, 7.43. Found: C, 78.95,
H, 7.29.
An gu la r Molecu le 9f. Purification by flash chromatography
(starting with petroleum ether/diethyl ether 1:2 v/v and increas-
ing the polarity with increasing the portion of diethyl ether) and
subsequent recrystallization from acetone yielded 9f (31%) as
brown needles: mp 172 °C; 1H NMR20 δ 1.38 (t, J ) 7.1 Hz,
3H), 2.03 (br s, 8H), 3.70 (br s, 4H), 3.78 (s, 3H), 3.90 (br s, 4H),
4.35 (q, J ) 7.1 Hz, 2H), 5.39 (s, 2H), 6.91 (half part of an AA′BB′
system, 2H), 7.39 (half part of an AA′BB′ system, 4H), 7.50 (two
half parts of two AA′BB′ systems, 6H), 8.11 (s, 2H); 13C NMR20
(CH2Cl2) δ 14.4, 24.1 (br), 46.9 (br), 51.7 (br), 55.6, 61.8, 73.7,
76.4, 76.9, 79.9, 84.5, 114.2, 117.37, 117.41, 120.8, 126.7, 128.8,
130.9, 133.9, 136.5, 152.9, 160.4, 164.7, 166.2. Anal. Calcd for
[4-[4-[2-(Tr iisop r op ylsilyl)eth yn yl]p h en yl]bu ta -1,3-d iy-
n yl]tr im eth ylsta n n a n e (7e). The brown oil was heated to 80
°C/0.001 mbar in order to remove excess stannane reagent and
trapped solvent. Product 7d (80%) was obtained as a very
viscous, black oil which was used without further purification:
1H NMR δ 0.35 (s with Sn satellites,21 9H), 1.11 (s, 21 H), 7.39
(s, 4H); 13C NMR δ -7.7 (signal with Sn satellites21), 11.3, 18.6,
73.8, 76.1, 91.1, 93.5, 93.7, 106.4, 121.6, 124.2, 131.9, 132.4. Anal.
Calcd for C24H34SiSn: C, 61.42; H, 7.30. Found: C, 61.39, H,
7.33.
[4-[4-(3,3-Tetr a m eth ylen etr ia zen o)p h en yl]bu ta -1,3-d iy-
n yl]tr im eth ylsta n n a n e (7f). The crude material (82%) was
used for further reactions. For elemental analysis a small
portion was distilled (140 °C bath temp/0.001 mbar) to yield a
yellow-brown solid: mp 128 °C; 1H NMR20 δ 0.33 (s with Sn-
satellites,21 9H), 2.00 (br s, 4H), 3.78 (br m, 4H), 7.31 and 7.41
(AA′BB′, 2H each); 13C NMR δ -7.8 (signal with Sn-satellites21),
23.6, 47 and 51 (very broad signals20), 74.1, 75.1, 91.5, 91.9,
117.7, 120.4, 133.5, 152.0. Anal. Calcd for C17H21N3Sn: C,
52.89; H, 5.48; N, 10.88. Found: C, 52.93, H, 5.48; N, 10.79.
Gen er a l P r oced u r e for th e Syn th esis of th e An gu la r
Molecu les 9a -f. The reactions were carried out using 1.6-
3.5 g of starting compound 8.
To a cooled (ice bath) solution of 8 (1 mmol) in THF (6.5 mL)
were added Pd2(dba)3 (0.02 mmol) and AsPh3 (0.16 mmol). The
ice bath was removed, and the deep red mixture was stirred at
rt until all of the catalyst had dissolved and the color had turned
green. This solution was again cooled with an ice bath, and
stannane 7 (2.1-2.2 mmol) was added. The reaction mixture
was heated to 60 °C for 11-15 h whereupon it turned black.
The solvent and most of the trimethyliodostannane were re-
moved in vacuo. In the case of 9a , the black residue was
dissolved in THF (7.7 mL), and the product was precipitated by
addition of diethyl ether. In the cases of 9b-f the black residue
was suspended in ethanol (2-5.4 mL; compound 9e solidified
in ethanol after cooling for some time to -18 °C), and the brown
solid was isolated.
An gu la r Molecu le 9a . Compound 9a (70%) was obtained
as a brownish solid: mp 170 °C; 1H NMR δ 1.38 (t, J ) 7.1 Hz,
3H), 3.78 (s, 3H), 4.35 (q, J ) 7.1 Hz, 2H), 5.38 (s, 2H), 6.89 and
7.46 (AA′BB′, 2H each), 7.39 and 7.49 (AA′BB′, 4H each), 8.12
(s, 2H); 13C NMR δ 14.3, 55.2, 61.5, 74.8, 76.0, 77.1, 79.1, 82.0,
113.8, 116.7, 120.4, 124.0, 126.0, 128.2, 130.4, 131.8, 133.9, 136.5,
159.8, 164.4, 165.9. Anal. Calcd for C37H24Br2O4: C, 64.18; H,
3.49. Found: C, 63.94, H, 3.69.
C
45H40O4N6: C, 74.16; H, 5.53; N, 11.53. Found: C, 73.77, H,
5.37; N, 11.35.
Ack n ow led gm en t. I like to thank J . Thiel for his
help in the laboratory, B. Ederer for carefully reading
the manuscript, and the Deutsche Forschungsgemein-
schaft for financial support and a fellowship.
An gu la r Molecu le 9b. The solid was purified by flash
chromatography (methylene chloride) and then recrystallized
from ethyl acetate giving 9b (70%) as brownish needles: mp
127-128 °C; 1H NMR δ 1.38 (t, J ) 7.1 Hz, 3H), 2.38 (s, 6H),
3.77 (s, 3H), 4.35 (q, J ) 7.1 Hz, 2H), 5.39 (s, 2H), 6.91 and 7.50
(AA′BB′, 2H each), 7.16 and 7.45 (AA′BB′, 4H each), 8.12 (s, 2H);
13C NMR δ 14.2, 21.6, 55.2, 61.4, 73.1, 75.9, 76.2, 79.5, 83.5,
113.8, 116.9, 118.4, 125.9, 128.3, 129.3, 130.5, 132.5, 136.2, 139.9,
159.8, 164.5, 165.8. Anal. Calcd for C39H30O4: C, 83.25; H, 5.37.
Found: C, 82.85, H, 5.33.
Su p p or tin g In for m a tion Ava ila ble: Experimental pro-
cedures and full characterization for the compounds 1-4 and
8 (9 pages). This material is contained in libraries on
microfiche, immediately follows this article in the microfilm
version of the journal, and can be ordered from the ACS; see
any current masthead page for ordering information.
J O970549P
An gu la r Molecu le 9c. Filtration through silica gel (meth-
ylene chloride/petroleum ether 1:1 v/v) yielded 9c (88%) as a
brown solid: mp 120 °C; 1H NMR δ 1.37 (t, J ) 7.1 Hz, 3H),
(22) Although 9d could not be obtained as a pure compound, 9 (R )
OH) synthesized from 9d in 91% yield was an analytically pure
compound.