Synthesis of cyclo-1,3-dien-5-ynes

Article abstract of DOI:10.1002/1521-3765(20011015)7:20<4378::AID-CHEM4378>3.0.CO;2-I

Cyclo-1,3-dien-5-ynes with ring sizes from 10 to 14 (6a-e) have been prepared for the first time by using a five-step synthesis starting from the alkynols 7a-e. The final ring-closure was achieved by McMurry coupling of the α,ω-dialdehydes 12a-e with the complex TiCl₃(DME)_1.5. Thermal isomerization of the cyclodienynes leads to the corresponding benzocycloalkenes, and it has been shown that the ring size has a considerable influence on the temperature necessary for thermocylization.

Full text of DOI:10.1002/1521-3765(20011015)7:20<4378::AID-CHEM4378>3.0.CO;2-I

FULL PAPER
Synthesis of Cyclo-1,3-dien-5-ynes**
Henning Hopf* and Anke Krüger[a]
Dedicated to Professor Siegfried Hünig on the occasion of his 80th birthday
Abstract: Cyclo-1,3-dien-5-ynes with ring sizes from 10 to 14 (6a ± e) have been
prepared for the first time by using a five-step synthesis starting from the alkynols
7a ± e. The final ring-closure was achieved by McMurry coupling of the a,w-
dialdehydes 12a ± e with the complex TiCl3(DME)1.5 . Thermal isomerization of the
cyclodienynes leads to the corresponding benzocycloalkenes, and it has been shown
that the ring size has a considerable influence on the temperature necessary for
thermocylization.
Keywords: alkynes ´ bridged furans
cyclodienynes cyclization
McMurry coupling
´
´
´
sufficientº, no external hydrogen source being necessary for
its cyclization. Having studied the mechanism of the 1 ! 3
cyclization in great detail[4, 5] and having, furthermore, used
this process for the synthesis of a number of novel aromatic
hydrocarbons,[5, 8] we became interested in incorporating the
hexa-1,3-dien-5-yne unit into cyclic ring systems. Since the
terminal carbon atoms of 1 have to be joined during the
isomerization step, it appears reasonable to assume that the
interconnection of these positions through a molecular bridge
should facilitate the process. Comparable experiments have
been carried out for the Bergman cyclization, and it has been
shown that the cyclization temperature required can be
reduced significantly (from ca. 2008C for the parent hydro-
carbon[9] to room temperature for cyclodeca-1,5-diyne-3-ene,
for example[10]). Before we began our preparative efforts to
find a route to the cyclo-1,3-dien-5-ynes, we carried out
semiempirical calculations[11] on the stability of these unsatu-
rated hydrocarbons. According to these estimates, the ring
strain in cyclodeca-1,3-dien-5-yne (C10H12) should be suffi-
ciently low to permit the isolation of this hydrocarbon. In fact,
this compound is the only currently known isolable member
of this series, having been prepared by Hanack and co-
workers many years ago.[12] However, the reaction sequence
published at that time is quite elaborate and not easily
adapted to other ring sizes. In this paper, we report on a
general synthesis of the cyclo-1,3-dien-5-ynes with ring sizes of
between ten and fourteen members, and present exploratory
experiments on their thermal cyclization.
Introduction
The thermal cyclization of hexa-1,3-dien-5-yne (1) to benzene
(3) is the ªdihydro variantº of the celebrated Bergman
cyclization.[2] At temperatures above 2008C this electrocycli-
zation begins with the formation of isobenzene (2, cyclohexa-
1,2,4-triene),[3] which subsequently stabilizes itself by a hydro-
gen shift process to 3.[4±7] (Scheme 1).
Whereas in the Bergman cyclization of hex-3-en-1,5-diynes
the cycloaromatization requires the ªadditionº of external
hydrogen atoms (which may be furnished either by simple
hydrogen donors, such as cyclohexa-1,4-diene, or also by very
complex ones, such as DNA[2]), the substrate 1 is ªself
Scheme 1. The thermal cyclization of hexa-1,3-dien-5-yne (1) to benzene
(3).
[a] Prof. Dr. H. Hopf, Dr. A. Krüger
Institut für Organische Chemie, Technische Universität Braunschweig
Hagenring 30, 38106 Braunschweig (Germany)
Fax : (‡49)531-391-5388
Results and Discussion
Since the base-catalyzed isomerization of hexa-1,5-diyne (4)
to 1 is a very well known process in hydrocarbon chemistryÐit
is in fact the fundamental process of Sondheimerꢀs annulene
E-mail: h.hopf@tu-bs.de
[**] Alkynes and Cumulenes, Part XXIV; for Part XXIII see ref. [1].
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Chem. Eur. J. 2001, 7, No. 20

4378±4385
chemistry[13] and has also been studied extensively from the
mechanistic viewpoint[14]Ðwe initially thought that it should
be effortlessly adaptable to converting cyclo-1,5-diynes 5 into
their conjugated isomers 6. The starting materials 5 are now
readily available, thanks to the synthetic efforts of Gleiter and
co-workers.[15] As a model compound, cycloundeca-1,5-diyne
(5, n ˆ 5) was selected. However, to our surprise, all isomer-
ization reactions, with a large variety of bases and different
conditions, failed.[16] Either the starting cyclodiyne did not
rearrange at all, or isomerization would set in uncontrollably,
leading to a product mixture containing numerous isomer-
ization products that could not be separated. After a series of
other unsuccessful approachesÐincluding inter alia pinacoli-
zation, Barbier and Sonogashira coupling reactions, and ring-
closing metathesis of appropriately functionalized precursor
systems[11]Ðthe sequence summarized in Scheme 2 was finally
successful.
The starting materials were the alkynols 7, all of them
readily available commercially or from propargyl alcohol by
standard treatments. These were first subjected to an acetyl-
ene zipper reaction[17] by using Abramsꢀ method, which
involves treatment of the acetylenic alcohols with lithium
powder and potassium tert-butoxide in 1,3-diaminopropane
(DAP).[18] The advantage of this variant over Brownꢀs classical
procedure[17] is the improved safety and the consistently good
to excellent yield of the desired terminal alkynols; yields in
the 80 ± 100% range are typically achieved after purification
by distillation; this permits preparation of the starting
materials on the multigram scale. Subsequent Swern oxida-
tion[19] of 8a ± e afforded the corresponding aldehydes 9a ± e,
which could be used without further purification, again in
good yield. However, these intermediates are unstable toward
oxygen and can only be stored for prolonged periods when
kept under argon. The higher homologues of 9 crystallize on
standing in the freezer.
The next step involved chain elongation with the ylide
prepared from the phosphonium salt 10, a process often used
to prepare a,w-unsaturated aldehydes.[20] In contrast to the
procedures reported in the literature, work up was carried out
under neutral conditions to avoid removal of the protecting
group. The yields of the ketals 11, isolated as colorless oils,
were around 80%, and they were produced as mixtures of E
and Z isomers in ca. 2.5:1 ratios (GC analysis). It was not
possible to separate the diastereomers by preparative gas
chromatography but, when solutions of them in tetrahydro-
furan were treated with aqueous oxalic acid, the deprotected
E aldehydes were generated in a pure state. This observation
was put to use when the derivatives 11 were subjected to a
second chain extension step to give the dialdehydes 12. The
ketals 11 were metallated with butyl lithium in diethyl ether,
and the resulting acetylides were quenched with DMF. Work
up under acidic conditions removed the protecting group and
induced Z ! E isomerization, resulting in the formation of the
dialdehydes 12, which, after rapid chromatographic purifica-
tion at low temperature, were obtained as colorless oils. They
could only be stored for a limited time under argon in the
refrigerator and, hence, should be used as quickly as possible.
The synthesis of the desired cyclo-1,3-dien-5-ynes 6 was
finally accomplished by means of a McMurry-type coupling of
12, by using TiCl3(DME)1.5 (DME ˆ dimethoxyethane) as the
titanium source and a zinc/copper couple as the reducing
agent.[21] Whereas 6a and 6b were formed even at room
temperature, the higher homologues required boiling DME.
The yields of the cyclodienynes (see Scheme 2) do not show
any particular trend. For the
lower members of the series,
their low thermal stabilities
(see below) and their high vol-
atilities certainly contributed to
a
yield reduction. Complete
removal of the solvent was only
possible with heavy losses of
product. We also noted the
formation of higher-molecular-
weight material, but found no
evidence that this was produced
by the formation of dimers or
trimers. The products 6a ± e
were characterized by the usual
spectroscopic methods as de-
scribed in the Experimental
Section. The assignment of the
(1E,3Z) stereochemistry shown
in Scheme 2 is largely based on
the coupling constants between
the olefinic protons. Whereas
the coupling constants between
the protons at C-3 and C-4
amount to 10.5 Æ 0.5 Hz, con-
stants of 15.8 Æ 0.1 Hz are ob-
served between the protons at
Scheme 2. The preparation of the cyclodienynes 6.
Chem. Eur. J. 2001, 7, No. 20
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4379

H. Hopf, A. Krüger
FULL PAPER
C-1 and C-2. Furthermore, the
1H NMR spectrum of (7Z,9E)-
octadeca-7,9-dien-5-yne,
an
open-chain model for the cyclo-
dienynes 6, has recently be-
come available.[22] For this di-
enyne, a value of 10.3 Hz was
observed for Jcis and one of
15.4 Hz for Jtrans; this is in ex-
cellent agreement with the data
for the cyclic hydrocarbons 6.
Over all five steps, the hydro-
carbons 6 could be prepared in
isolated yields between 2%
(n ˆ 4) and 22% (n ˆ 8), no
optimization so far having been
attempted. Because of their
trans-configured double bonds,
the dienynes 6 are inherently
chiral. However, attempts to
resolve them on a chiral col-
umn (cyclodextrin)[23] have so
far met with failure. Whether
this is due to a low enantiomer-
ization barrier or to not yet
having found the right resolu-
tion conditions is unknown at
present.
Scheme 3. Furan formation during McMurry coupling of the unsaturated dialdehydes 12 and 15.
Interestingly, when other
conditions for the McMurry
coupling were applied, differ-
ent results were obtained. For
example, in a qualitative ex-
periment under the conditions
proposed by Lenoir[24] (TiCl4,
Scheme 4. Mechanism of furan formation.
Zn powder, pyridine, terahydrofuran), 12c provided a com-
plex mixture comprising 6c and two oxygen-containing
compounds. Structures 13 and 14 (Scheme 3) were assigned
to these, largely on the basis of GC/MS analysis. Although
they could not be obtained in pure form, we are confident
about our structure assignment, largely because of the
similarity of their spectroscopic and analytical data to those
of the acetylene 18 (see below). To reduce the complexity of
the product mixture, we replaced 12c with the more sym-
metrical dialdehyde 15 in a second experiment. In this case the
McMurry coupling provided the corresponding products 16
(2.6%), 17 (16%), and 18 (7%). Again, it was easy to assign a
furan structure to the last product, but the ring positions in
which the bridging alkynyl chain was anchored were not
initially obvious. Comparison with the NMR spectra of model
compounds,[25] however, indicated that structure 18 must be
correct. For the alternative 19 a coupling constant of about
3.4 Hz would be expected for the furan-ring hydrogen atoms,
whereas in 20 it should amount to 0.9 Hz and in 21 to 1.5 Hz.
For 18 a value of 1.8 Hz was observed.
The process begins with the formation of radical 22 on the
surface of the activated titanium. This intermediate may be
reduced a second time to provide the corresponding diyl,
which can collapse to the intermediate that, on hydrolysis, will
furnish the diol 17 or the endiyne 16. Alternatively, the radical
centre in 22 may be trapped intramolecularly by the
unreduced ynal function to provide the cyclic radical 23. This
stabilizes itself through a 1,3-hydrogen shift, and the resulting
radical 24 $ 25 can undergo terminal ring-closure to 18 by
deoxygenation. It seems likely that the cyclization products
6c, 13, and 14 are produced by a similar mechanism in the case
of 12c.
The anticipated thermal cyclizations of the monocyclic
precursor hydrocarbons 6 to the corresponding benzocycloal-
kenes were studied in a series of exploratory experiments by
heating the starting materials in tetradeuterio-ortho-dichloro-
1
benzene and monitoring the cycloaromatization by H NMR
spectroscopy. As shown in Scheme 5Ðand already mentioned
aboveÐthe ten-membered ring system 6a already begins to
aromatize at room temperature.
Although no mechanistic studies were undertaken to
elucidate the mechanism of formation of the unexpected
ªfuranophanesº, we believe that the interpretation offered in
Scheme 4 for 18 is reasonable.
As expected, the higher homologues require higher tem-
peratures, a trend that has also been observed in the Bergman
cyclization of cyclic endiynes.[10] For a thorough understanding
of the cyclization process it will now be necessary to
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Chem. Eur. J. 2001, 7, No. 20

Synthesis of Cyclo-1,3-dien-5-ynes
4378±4385
1
726 (m), 628 cm (s); UV/Vis (MeCN): lmax(lg e) ˆ 192 (2.52), 208 (1.72),
‡
226 nm (1.16); MS (70 eV, EI): m/z (%): 125 [M H] (1), 107 (24), 93 (48),
79 (100), 67 (62), 55 (39), 43 (9).
Non-8-yn-1-ol (8c): This compound was synthesized according to the
general procedure: Li (3.08 g, 0.44 mol), diaminopropane (220 mL),
tBuOK (28.6 g, 0.26 mol), and 7c (9.16 g, 65.6 mmol) provided 8c (8.57 g,
61.2 mmol, 94%). 1H NMR (200 MHz, CDCl3): d ˆ 1.20 ± 1.53 (m, 10H;
2-H to 6-H), 1.70 (brs, 1H; OH), 1.88 (t, 4J ˆ 2.7 Hz, 1H; 9-H), 2.12 (dt,
3J ˆ 6.8, 4J ˆ 2.6 Hz, 2H; 7-H), 3.56 (t, 3J ˆ 6.5 Hz, 2H; 1-H); 13C NMR
(50.3 MHz, CDCl3): d ˆ 18.3 (C-7), 25.6 (C-6), 28.3, 28.6, 28.8 (C-3, C-4,
C-5), 32.6 (C-2), 62.8 (C-1), 68.1 (C-9), 84.6 (C-8); IR (film): nÄ ˆ 3350 (s,
br), 3310 (s), 3302(s), 2934 (vs), 2859 (s), 2118 (w), 1464 (w), 1058 (w),
Scheme 5. Thermal cyclization of the cyclodienynes 6 to the benzocyclo-
alkenes 26.
1
625 cm (s); UV/Vis (MeCN): lmax(lg e) ˆ 202 (2.22), 222 (1.76), 244 nm
‡
(1.48); MS (70 eV, EI): m/z (%): 121 [M H3O] (2), 107 (28), 79 (100), 67
investigate the kinetics of the reaction. We hope to report on
these results in due course.
(59), 55 (71).
Dec-9-yn-1-ol (8d): This compound was prepared according to the general
procedure: Li (1.54 g, 0.22 mol), diaminopropane (110 mL), tBuOK (14.3 g,
0.13 mol), and 7d (5.05 g, 32.0 mmol) provided 8d (3.86 g, 25.1 mmol,
1
76%). H NMR (200 MHz, CDCl3): d ˆ 1.22 ± 1.55 (m, 12H; 2-H to 7-H),
4
3
4
Experimental Section
1.90 (t, J ˆ 2.6 Hz, 1H; 10-H), 2.00 (brs, 1H; OH), 2.14 (dt, J ˆ 6.9, J ˆ
2.6 Hz, 2H; 8-H), 3.57 (t, 3J ˆ 6.6 Hz, 2H; 1-H); 13C NMR (50.3 MHz,
CDCl3): d ˆ 18.3 (C-8), 25.6 (C-7), 28.4, 28.6, 29.0, 29.2 (C-3, C-4, C-5, C-6),
32.7 (C-2), 62.8 (C-1), 68.1 (C-10), 84.7 (C-9); IR (film): nÄ ˆ 3346 (s, br),
General remarks: All moisture-sensitive reactions were carried out in
flame-dried glassware under nitrogen or argon. When necessary, commer-
cially available reagents and solvents were purified and dried by standard
methods immediately prior to use. IR: Nicolet 320 FT-IR spectrometer.
UV/Vis: HP 8452A Diode Array spectrophotometer. 1H and 13C NMR:
Bruker AC 200 or Bruker DRX 400 spectrometer at 200.1 and 50.3, or
400.1 and 100.6 MHz, respectively; chemical shifts refer to TMS as internal
standard, while NMR signal assignments were performed with the aid of
COSYand COLOQ experiments. MS: Finnigan MAT 8430. GC/MS: Carlo
Erba HRGC 5160 in combination with a Finnigan 4515 mass spectrometer;
HRMS: Finnigan MAT 8430 with the peak-matching method. Elemental
analyses: Institute of Inorganic and Analytical Chemistry of the Technical
1
3312 (s), 2933 (vs), 2858 (vs), 2118 (w), 1465 (m), 1433 (m), 628 cm (s);
UV/Vis (MeCN): lmax(lg e) ˆ 202 (2.04), 214 (1.55), 244 nm (1.26); MS
‡
(70 eV, EI): m/z (%): 155 [M‡H] (1), 121 (11), 107 (18), 93 (56), 79 (100),
67 (80), 55 (88).
General procedure for the preparation of the aldehydes 9: A solution of
anhydrous DMSO in anhydrous dichloromethane (10 mL) was slowly
added to a solution of oxalyl chloride in anhydrous dichloromethane
(100 mL) at 608C. The mixture was stirred for 10 min, and a solution of
the alkynols 8 in anhydrous dichloromethane (20 mL) was added. After this
had been stirred for 30 min at 608C, triethylamine was added, and the
reaction mixture was allowed to warm to 08C. After addition of diethyl
ether (150 mL) and water (100 mL), the layers were separated, and the
aqueous phase was extracted carefully with diethyl ether (3 Â 100 mL). The
combined organic layers were washed with 15% aq. HCl, 5% aq. soda
solution, and saturated brine, then dried with sodium sulfate. After removal
of the solvent in vacuo, the crude product was purified by distillation.
Although the products 9 have all been described in the literature, the
analytical data are incomplete and were recorded under different
conditions. We have therefore repeated/completed these data for the
whole set of homologous compounds 9.
University of Braunschweig. Undec-10-yn-1-ol (8e) is
a commercial
product (Lancaster Synthesis) and was used without further purification.
General procedure for the preparation of the alkynols 8: Lithium powder
was placed under nitrogen in a three-necked flask, and 1,3-diaminopropane
was added. The mixture was stirred at 808C for 2 h; during which the initial
blue color faded and a pale grey suspension was formed. After this had
cooled to RT, potassium tert-butoxide was added, and the mixture was
stirred for 15 min. The alkynol 7 was added and, after 2 h at RT, the orange
reaction mixture was cautiously poured into ice water (50 mL). After
extraction with chloroform (4 Â 50 mL), the combined organic layers were
washed with water, 10% aq. HCl, satd. NaHCO3 solution, and saturated
brine solution, then dried over sodium sulfate. After removal of the solvent
at reduced pressure, the crude product was purified by distillation.
Although the products 8 have all been described in the literature, the
analytical data are incomplete and were recorded under different
conditions. We have therefore repeated/completed these data for the
whole set of homologous compounds 8.
Hept-6-yn-al (9a): This compound was prepared according to the general
procedure: oxalyl chloride (2.1 mL, 23.1 mmol), DMSO (3.6 mL), NEt3
(14 mL, 0.1 mol), and 8a (2.36 g, 21 mmol) produced 9a (2.29 g, 20.8 mmol,
98%). 1H NMR (200 MHz, CDCl3): d ˆ 1.42 ± 1.77 (m, 4H; 3-H, 4-H), 1.91
(t, 4J ˆ 2.6 Hz, 1H; 7-H), 2.14 (dt, 3J ˆ 6.8, 4J ˆ 2.6 Hz, 2H; 5-H), 2.40 (t,
3J ˆ 7.1 Hz, 2H; 2-H), 9.69 (pseudo s, 1H; 1-H); 13C NMR (50.3 MHz,
CDCl3): d ˆ 18.1 (C-5), 21.0 (C-3 or C-4), 27.7 (C-3 or C-4), 43.2 (C-2), 68.7
(C-7), 83.7 (C-6), 202.0 (C-1); IR (film): nÄ ˆ 3297 (s), 2943 (s), 2868 (s), 2117
(w), 1712 (vs), 1655 (m), 1649 (m), 1638 (m), 1461 (m), 1433 (m), 1413 (m),
1356 (m), 1331 (m), 1291 (m), 1234 (m), 1198 (m), 1140 (m), 1080 (m),
Hept-6-yn-1-ol (8a): This compound was synthesized according to the
general procedure: Li (0.42 g, 60 mmol), diaminopropane (30 mL), tBuOK
(3.9 g, 35 mmol), and 7a (1.0 g, 9.0 mmol) provided 8a (0.97 g, 8.66 mmol,
97%). 1H NMR (200 MHz, CDCl3): d ˆ 1.36 ± 1.65 (m, 6H; 2-H, 3-H, 4-H),
1
635 cm (s). UV/Vis (MeCN): lmax(lg e) ˆ 192 (2.45), 220 (1.85), 276 nm
4
3
4
1.93 (t, 1H; J ˆ 2.6 Hz, 7-H), 2.18 (dt, J ˆ 6.7, J ˆ 2.6 Hz, 2H; 5-H), 3.62
(t, 3J ˆ 6.3 Hz, 2H; 1-H); 13C NMR (50.3 MHz, CDCl3): d ˆ 18.3 (C-5), 24.8
(C-3 or C-4), 28.2 (C-3 or C-4), 32.1 (C-2), 62.7 (C-1), 68.3 (C-7), 84.4 (C-6);
IR (film): nÄ ˆ 3300 (vs), 2940 (vs), 2864 (s), 2117 (w), 1433 (m), 1401 (m),
1073 (m), 1052 (m), 626 cm 1 (s); UV/Vis (MeCN): lmax(lg e) ˆ 192 (2.49),
‡
‡
(1.07); MS (70 eV, EI): m/z (%): 111 [M‡H] (100), 110 [M] (15), 109
(46), 93 (76), 83 (48), 79 (26), 77 (16), 67 (57), 55 (60).
Oct-7-yn-al (9b): This compound was prepared according to the general
procedure: oxalyl chloride (1.5 mL, 16.5 mmol), DMSO (2.5 mL), NEt3
(10 mL, 71.4 mmol), and 8b (1.8 g, 14.3 mmol) provided 9b (1.67 g,
13.5 mmol, 94%). 1H NMR (400 MHz, CDCl3): d ˆ 1.36 ± 1.62 (m, 6H;
3-H, 4-H, 5-H), 1.88 (t, 4J ˆ 2.5 Hz, 1H; 8-H), 2.13 (dt, 3J ˆ 6.9, 4J ˆ 2.7 Hz,
‡
220 (0.79), 276 nm (0.65); MS (70 eV, EI): m/z (%): 112 [M] (2), 97 (14), 93
(11), 83 (17), 79 (100), 67 (31), 55 (59).
Oct-7-yn-1-ol (8b): This compound was synthesized according to the
general procedure: Li (2.21 g, 0.32 mol), diaminopropane (160 mL),
tBuOK (20.6 g, 0.19 mol), and 7b (5.94 g, 47 mmol) provided 8b (4.87 g,
38.6 mmol, 82%). 1H NMR (200 MHz, CDCl3): d ˆ 1.33 ± 1.54 (m, 8H; 2-H,
3-H, 4-H, 5-H), 1.89 (t, 4J ˆ 2.6 Hz, 1H; 8-H), 2.01 ± 2.16 (m, 2H; 6-H),
3.52 ± 3.59 (m, 2H; 1-H); 13C NMR (50.3 MHz, CDCl3): d ˆ 18.3 (C-6), 25.2
(C-5), 28.3 (C-3 or C-4), 28.4 (C-3 or C-4), 32.5 (C-2), 62.7 (C-1), 68.2 (C-8),
84.5 (C-7); IR (film): nÄ ˆ 3348 (s, br), 3301 (vs), 2937 (vs), 2861 (vs), 2117
(w), 1463 (m), 1433 (m), 1328 (m), 1074 (m), 1056 (m), 1033 (m), 1002 (m),
3
3
3
2H; 6-H), 2.38 (dt, J ˆ 7.3, J ˆ 1.6 Hz, 2H; 2-H), 9.71 (t, J ˆ 1.5 Hz, 1H;
1-H); 13C NMR (100.6 MHz, CDCl3): d ˆ 18.1 (C-6), 21.5 (C-5), 28.0 (C-3 or
C-4), 28.1 (C-3 or C-4), 43.6 (C-2), 68.4 (C-8), 84.1 (C-7), 202.4 (C-1); IR
(film): nÄ ˆ 3298 (s), 2939 (vs), 2862 (s), 2117 (w), 1710 (vs), 1464 (m), 1433
(m), 1412 (m), 1363 (m), 1352 (m), 1270 (m), 1245 (m), 1206 (m), 1176 (m),
1
1133 (s), 1087 (m), 630 cm (s); UV/Vis (MeCN): lmax(lg e) ˆ 192 (2.67),
‡
222 nm (2.39); MS (70 eV, EI): m/z (%): 124 [M] (7), 109 (10), 101 (20), 95
(72), 80 (100), 67 (35), 60 (35), 55 (83).
Chem. Eur. J. 2001, 7, No. 20
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4381

H. Hopf, A. Krüger
FULL PAPER
Non-8-yn-al (9c): This compound was prepared according to the general
procedure: oxalyl chloride (2.3 mL, 24.4 mmol), DMSO (3.9 mL), NEt3
(15 mL, 107 mmol), and 8c (3.1 g, 22.1 mmol) provided 9c (2.94 g,
21.3 mmol, 96%). 1H NMR (200 MHz, CDCl3): d ˆ 1.27 ± 1.65 (m, 8H;
3-H to 6-H), 1.88 (t, 4J ˆ 2.6 Hz, 1H; 9-H), 2.12 (dt, 3J ˆ 6.8, 4J ˆ 2.6 Hz,
(8.08 g, 72.4 mmol), and 9b (3.48 g, 28.1 mmol) provided 11b (4.50 g,
23.2 mmol, 83%). 1H NMR (200 MHz, CDCl3): d ˆ 1.40 ± 1.60 (m, 6H; 4-H,
5-H, 6-H), 1.93 (t, 4J ˆ 2.6 Hz, 1H; 9-H), 2.13 ± 2.44 (m, 4H; 3-H, 7-H),
3.83 ± 4.04 (m, 4H; CH2 dioxolane ring), 5.15 ± 5.96 (m, 3H; -OCHO-, 1-H,
2-H); 13C NMR (50.3 MHz, CDCl3): d ˆ 18.3 (C-7), 27.6 (C-3), 28.2 (2
signals), 28.9 (C-4, C-5, C-6), 64.9 (CH2 dioxolane ring), 68.2 (C-9), 84.8
(C-8), 99.2 (-OCHO-), 126.0 (C-1), 137.3 (C-2); IR (film): nÄ ˆ 3290 (m),
2937 (vs), 2888 (s), 2861 (s), 2117 (w), 1463 (m), 1430 (m), 1347 (m), 1224
3
3
3
2H; 7-H), 2.37 (dt, J ˆ 7.4, J ˆ 1.7 Hz, 2H; 2-H), 9.70 (t, J ˆ 1.7 Hz, 1H;
1-H); 13C NMR (50.3 MHz, CDCl3): d ˆ 18.2 (C-7), 21.8 (C-6), 28.1, 28.3,
28.5 (C-3, C-4, C-5), 43.7 (C-2), 68.2 (C-9), 84.4 (C-8), 202.5 (C-1); IR
(film): nÄ ˆ 3299 (s), 2937 (vs), 2861 (s), 2117 (w), 1710 (vs), 1464 (m), 1433
(m), 1401 (m), 1355 (m), 1328 (m), 1296 (m), 1259 (m), 1234 (m), 1172 (m),
1
(s), 1212 (s), 1128 (s), 1102 (s), 1042 (s), 985 (s), 625 cm (s); UV/Vis
(MeCN): lmax(lg e) ˆ 192 (3.88), 228 nm (2.08); MS (70 eV, EI): m/z (%):
1
‡
1133 (s), 1092 (m), 632 cm (s). UV/Vis (MeCN): lmax(lg e) ˆ 192 (2.83),
193 [M H] (3), 179 (4), 155 (22), 137 (4), 125 (8), 113 (47), 99 (100), 86
‡
236 (2.18), 266 nm (1.76); MS (70 eV, EI): m/z (%): 138 [M] (1), 109 (12),
(14), 79 (10), 73 (32), 69 (12), 55 (12); elemental analysis calcd (%) for
C12H18O2: C 74.19, H 9.34; found C 74.13, H 9.14.
94 (29), 79 (100), 67 (63), 55 (61).
(E,Z)-2-Dec-1-en-9-ynynl-[1.3]dioxolane (11c): This compound was pre-
pared according to the general procedure: 10 (11.9 g, 27.7 mmol), tBuOK
(3.0 g, 26.9 mmol), and 9c (1.43 g, 10.4 mmol) provided 11c (1.72 g,
8.27 mmol, 80%). 1H NMR (200 MHz, CDCl3): d ˆ 1.15 ± 1.62 (m, 8H;
4-H to 7-H), 1.91 (t, 4J ˆ 2.5 Hz, 1H; 10-H), 2.01 ± 2.18 (m, 4H; 3-H, 8-H),
3.83 ± 4.00 (m, 4H; CH2 dioxolane ring), 5.13 ± 5.98 (m, 3H; -OCHO-, 1-H,
2-H); 13C NMR (50.3 MHz, CDCl3): d ˆ 18.3 (C-8), 27.7 (C-3), 28.3, 28.5,
29.3, 31.9 (C-4 to C-7), 64.9 (CH2 dioxolane ring), 68.1 (C-10), 84.8 (C-9),
99.2 (-OCHO-), 125.9 (C-1), 137.5 (C-2); IR (film): nÄ ˆ 3291 (m), 2934 (vs),
2888 (s), 2859 (s), 2117 (w), 1464 (w), 1430 (w), 1347 (w), 1211 (w), 1127 (s),
1106 (s), 1047 (m), 995 (w), 626 cm 1 (m); UV/Vis (MeCN): lmax(lg e) ˆ 192
Dec-9-yn-al (9d): This compound was prepared according to the general
procedure: oxalyl chloride (1.5 mL, 16.5 mmol), DMSO (2.2 mL), NEt3
(9.7 mL. 69 mmol), and 8d (2.2 g, 14.3 mmol) provided 9d (1.87 g,
12.3 mmol, 86%). 1H NMR (200 MHz, CDCl3): d ˆ 1.29 ± 1.65 (m, 10H;
4
4
3-H to 7-H), 1.92 (t, J ˆ 2.6 Hz, 1H; 10-H), 2.16 (dt, 3J ˆ 6.9, J ˆ 2.6 Hz,
3
2H; 8-H), 2.40 (dt, 3J ˆ 7.2, 3J ˆ 0.8 Hz, 2H; 2-H), 9.76 (t, J ˆ 0.8 Hz, 1H;
1-H); 13C NMR (50.3 MHz, CDCl3): d ˆ 18.3 (C-8), 22.0 (C-7), 28.3, 28.4,
28.7, 29.0 (C-3 to C-6), 43.8 (C-2), 68.1 (C-10), 84.5 (C-9), 202.7 (C-1); IR
(film): nÄ ˆ 3294 (m), 2935 (vs), 2869 (s), 2117 (w), 1725 (vs), 1465 (m), 1432
1
(m), 1411 (m), 1391 (m), 723 cm (m); UV/Vis (MeCN): lmax(lg e) ˆ 192
‡
(2.59), 222 (1.45), 238 nm (1.24); MS (70 eV, EI): m/z (%): 153 [M‡H]
‡
(3.84), 218 (2.24), 276 nm (2.18); MS (70 eV, EI): m/z (%): 208 [M] (1), 169
(42), 135 (91), 107 (40), 97 (63), 81 (68), 67 (100), 55 (80).
(19), 152 (6), 125 (11), 113 (56), 99 (100), 86 (18), 73 (48), 55 (31); elemental
analysis calcd (%) for C13H20O2: C 74.95, H 9.68; found C 74.38, H 9.76.
Undec-10-yn-al (9e): This compound was prepared according to the
general procedure: oxalyl chloride (4.4 mL, 48.4 mmol), DMSO (7.4 mL),
NEt3 (29.0 mL, 0.21 mol), and 8e (7.0 g, 41.7 mmol) provided 9e (6.04 g,
36.4 mmol, 86%). 1H NMR (200 MHz, CDCl3): d ˆ 1.30 ± 1.63 (m, 12H;
(E,Z)-2-Undec-1-en-10-ynyl-[1.3]dioxolane (11d): This compound was
prepared according to the general procedure: 10 (16.7 g, 38.9 mmol),
tBuOK (4.20 g, 37.6 mmol), and 9d (2.25 g, 14.8 mmol) provided 11d
4
4
3-H to 8-H), 1.92 (t, J ˆ 2.6 Hz, 1H; 11-H), 2.15 (dt, 3J ˆ 6.9, J ˆ 2.6 Hz,
2H; 9-H), 2.40 (dt, 3J ˆ 7.4, 3J ˆ 1 .8 Hz, 2H; 2-H), 9.72 (t, 3J ˆ 1.8 Hz, 1H;
1-H); 13C NMR (50.3 MHz, CDCl3): d ˆ 18.3 (C-9), 22.0 (C-8), 28.4, 28.6,
28.8, 29.0, 29.1 (C-3 to C-7), 43.8 (C-2), 68.1 (C-11), 84.6 (C-10, 202.7 (C-1);
IR (film): nÄ ˆ 3286 (m), 2934 (vs), 2924 (vs), 2850 (s), 2138 (w), 1726 (vs),
1465 (m), 1363 (m), 1158 (m), 1134 (m), 1128 (m), 1121 (m), 698 (m),
1
(2.86 g, 12.88 mmol, 87%). H NMR (200 MHz, CDCl3): d ˆ 1.33 (m, 4H;
4
6-H, 7-H), 1.42 (m, 4H; 5-H, 8-H), 1.54 (m, 2H; 4-H), 1.96 (t, J ˆ 2.6 Hz,
1H; 11-H), 2.20 (m, 4H; 3-H, 9-H), 3.89 ± 4.08 (m, 4H; CH2 dioxolane
ring), 5.43 ± 5.57 (m, 2H; -OCHO-, 1-H), 5.78 (dt, 3J ˆ 7.7, 3J ˆ 11.0 Hz, 1H;
2-H); 13C NMR (50.3 MHz, CDCl3): d ˆ 18.3 (C-9), 27.7 (C-3), 28.4 (C-4),
28.5, 28.8, 28.9, 29.3 (C-5 to C-8), 64.9 (CH2 dioxolane ring), 68.0 (C-11),
84.6 (C-10), 99.1 (-OCHO-), 125.7 (C-1), 137.6 (C-2); IR (film): nÄ ˆ 3298
(m), 2932 (vs), 2890 (s), 2117 (w), 1465 (w), 1430 (w), 1347 (w), 1212 (w),
1
670 cm (m); UV/Vis (MeCN): lmax(lg e) ˆ 192 (2.83), 228 (2.47), 256 nm
‡
(1.58); MS (70 eV, EI): m/z (%): 167 [M‡H] (17), 133 (20), 117 (36), 109
(32), 95 (63), 91 (60), 81 (100), 67 (97), 55 (76).
1
1126 (m), 1108 (m), 1052 (m), 959 (w), 723 cm (w); UV/Vis (MeCN):
General procedure for the preparation of the 1,3-dioxolanes 11: The
phosphonium salt 10[20] was placed under nitrogen in a three-necked, flame-
dried flask, then anhydrous THF (200 mL) was added. Potassium tert-
butoxide was added to the suspension with ice cooling (color change to
deep yellow), and the mixture was stirred for 30 min. A solution of the
aldehyde 9 in anhydrous THF (50 mL) was added over 20 min, and the
reaction mixture was stirred for 6 h at room temperature. After decom-
position with water (250 mL), the product was isolated by careful
extraction with pentane (5 Â 100 mL). The organic phases were combined,
reduced to approximately one third of the original volume and passed
through a short silica gel column (removal of the triphenylphosphine
oxide). After the column had been washed with pentane, the solvent was
removed in vacuo, and the remaining brown oil was purified by flash
chromatography on silica gel with pentane/diethyl ether (10:1, v/v); the
products 11 were obtained as colorless oils. For the NMR data only the
signals for the main (E) isomer are given.
lmax(lg e) ˆ 192 nm (3.80), 216 (2.09); MS (70 eV, EI): m/z (%): 221 [M
‡
H] (5), 179 (6), 155 (5), 125 (9), 113 (47), 99 (100), 93 (25), 81 (83), 79 (42),
73 (41), 55 (70); elemental analysis calcd (%) for C14H22O2: C 75.63, H 9.97;
found C 75.45, H 9.97.
(E,Z)-2-Dodec-1-en-11-ynyl-[1.3]dioxolane (11e): This compound was
prepared according to the general procedure: 10 (30.3 g, 70.6 mmol),
tBuOK (7.6 g, 68.1 mmol), and 9e (4.38 g, 26.4 mmol) provided 11e (5.7 g,
24.2 mmol, 92%). 1H NMR (200 MHz, CDCl3): d ˆ 1.28 ± 1.62 (m, 12H;
4-H to 9-H), 1.92 (t, 4J ˆ 2.6 Hz, 1H; 12-H), 2.04 ± 2.20 (m, 4H; 3-H, 10-H),
3.80 ± 4.07 (m, 4H; CH2 dioxolane ring), 5.15 ± 5.99 (m, 3H; -OCHO-, 1-H,
2-H); 13C NMR (50.3 MHz, CDCl3): d ˆ 18.3 (C-10), 27.7 (C-3), 28.4, 28.7,
28.9, 29.0, 29.2, 29.4 (C-4 to C-9), 64.9 (CH2 dioxolane ring), 68.0 (C-12),
84.7 (C-11), 99.2 (-OCHO-), 125.8 (C-1), 137.6 (C-2); IR (film): nÄ ˆ 3291
(m), 2929 (vs), 2857 (vs), 2117 (w), 1719 (m), 1465 (m), 1430 (m), 1347 (m),
1210 (m), 1126 (s), 1110 (s), 1057 (s), 996 (m), 958 (s), 722 (m), 625 cm 1 (s);
UV/Vis (MeCN): lmax(lg e) ˆ 192 (3.87), 218 nm (2.72); MS (70 eV, EI): m/z
‡
(E,Z)-2-Oct-1-en-7-ynyl-[1.3]dioxolane (11a): This compound was pre-
pared according to the general procedure: 10 (30.3 g, 70.7 mmol), tBuOK
(7.6 g, 68.0 mmol), and 9a (2.9 g, 26.4 mmol) provided 11a (3.37 g,
18.7 mmol, 71%). 1H NMR (200 MHz, CDCl3): d ˆ 1.52 (m, 4H; 4-H,
5-H), 1.92 (t, 4J ˆ 2.6 Hz, 1H; 8-H), 2.08 ± 2.24 (m, 4H; 3-H, 6-H), 3.82 ±
4.06 (m, 4H; CH2 dioxolane ring), 5.15 ± 5.98 (m, 3H; -OCHO-, 1-H, 2-H);
13C NMR (50.3 MHz, CDCl3): d ˆ 18.1 (C-6), 27.2 (C-3), 27.7, 28.4 (C-4,
C-5), 64.9 (CH2 dioxolane ring), 68.3 (C-8), 84.2 (C-7), 99.1 (-OCHO-),
126.2 (C-1), 136.9 (C-2); IR (film): nÄ ˆ 3290 (s), 2941 (s), 2868 (m), 2115
(w), 2093 (w), 1655 (m), 1455 (m), 1435 (m), 1401 (m), 1377 (m), 1275 (s),
1186 (s), 1082 (s), 1041 (s), 983 (m), 886 (m), 634 cm 1 (s); UV/Vis (MeCN):
(%): 236 [M] (2), 193 (8), 179 (6), 155 (14), 125 (10), 113 (45), 99 (100), 73
(27), 55 (8); elemental analysis calcd (%) for C15H24O2: C 76.23, H 10.23;
found C 75.24, H 10.07.
General procedure for the preparation of the dialdehydes 12: A solution of
the alkyne 11 in anhydrous diethyl ether (200 mL) was placed in a three-
necked flask under nitrogen. A solution of n-butyl lithium (1.6m) in hexane
was added at 508C, and the mixture was stirred for 30 min at this
temperature, before being taken down to 708C to cause precipitation of
the acetylide. N,N-Dimethylformamide was added in one portion, and the
reaction mixture was allowed to warm to 10 158C, which resulted in
dissolution of the precipitate. After 2 h, the product mixture was hydro-
lyzed with sulfuric acid/ice water, then the two-phase mixture was stirred
vigorously overnight. Neutralization with NaHCo3 solution, separation of
the organic phase, careful extraction of the aqueous phase with diethyl
ether, and drying of the combined organic phase with sodium sulfate
concluded the workup. The solvent was removed by rotary evaporation and
‡
lmax(lg e) ˆ 208 nm (3.68); MS (70 eV, EI): m/z (%): 180 [M] (3), 179 (24),
135 (27), 133 (25), 121 (28), 107 (37), 105 (44), 99 (28), 91 (47), 79 (28), 73
(100), 67 (58), 55 (48).
(E,Z)-2-Non-1-en-8-ynyl-[1.3]dioxolane (11b): This compound was pre-
pared according to the general procedure: 10 (32.2 g, 75.1 mmol), tBuOK
4382
ꢁ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
0947-6539/01/0720-4382 $ 17.50+.50/0
Chem. Eur. J. 2001, 7, No. 20

Synthesis of Cyclo-1,3-dien-5-ynes
4378±4385
the remaining yellow oil was purified by column chromatography on silica
gel (pentane/etherˆ 2:1, v/v). The dialdehydes 12 were obtained as
colorless, unstable oils, which did not give satisfactory elemental analyses.
158.8 (C-3), 177.2 (C-14), 194.1 (C-1); IR (film): nÄ ˆ 2930 (vs), 2857 (s), 2280
(w), 2236 (w), 2201 (m), 1691 (vs), 1670 (vs), 1466 (m), 1422 (m), 1283 (m),
1231 (m), 1139 (m), 977 cm 1 (m); UV/Vis (MeCN): lmax(lg e) ˆ 220 (4.00),
246 nm (3.04, sh).
Dec-2-en-8-ynedial (12a): This compound was prepared according to the
general procedure: 11a (3.2 g, 17.8 mmol), nBuLi (1.6m, 11.3 mL,
18.1 mmol), DMF (1.64 g, 22.5 mmol), and H2SO4 (96%, 4.4 g) in ice
water (90 mL) provided 12a (2.07 g, 12.6 mmol, 71%). 1H NMR (200 MHz,
CDCl3): d ˆ 1.58 ± 1.71 (m, 4H; 5-H, 6-H), 2.30 ± 2.47 (m, 4H; 4-H, 7-H),
6.10 (ddt, 3J ˆ 15.6, 3J ˆ 7.9, 4J ˆ 1.5 Hz, 1H; 2-H), 6.81 (dt, 3J ˆ 6.7, 3J ˆ
15.6 Hz, 1H; 3-H), 9.15 (t, 5J ˆ 0.8 Hz, 1H; 10-H), 9.48 (d, 3J ˆ 7.9 Hz, 1H;
1-H); 13C NMR (50.3 MHz, CDCl3): d ˆ 18.9 (C-7), 26.8, 26.9 (C-5, C-6),
32.0 (C-4), 81.9 (C-9), 98.0 (C-8), 133.3 (C-2), 157.4 (C-3), 177.0 (C-10),
193.8 (C-1); IR (film): nÄ ˆ 2943 (s), 2866 (s), 2281 (s), 2236 (s), 2203 (s),
1694 (vs), 1691 (vs), 1463 (m), 1418 (s), 1396 (s), 1355 (s), 1286 (s), 1243 (s),
1210 (s), 1138 (s), 1088 (m), 1077 (m), 1021 (m), 981 (s), 905 cm 1 (m); UV/
Vis (MeCN): lmax(lg e) ˆ 218 (4.03), 230 (3.86, sh), 244 nm (3.12, sh).
General procedure for the preparation of the cyclo-1,3-dien-5-ynes 6: A
flame-dried three-necked flask (1 L) was charged under argon with
TiCl3(DME)1.5 , prepared according to [21], and with a zinc/copper couple.
The two components were mixed thoroughly. Freshly distilled DME was
added, and the mixture was heated under reflux for 5 h, during which time
it turned black. The suspension was cooled to room temperature, and a
solution of the bisaldehyde 12 in DME (20 mL) was added slowly by means
of a motor-driven syringe (ca. 30 h). The reaction mixture was stirred until
the substrate 12 had been consumed completely, while the process was
monitored by GC analysis. After dilution with pentane (250 mL), the
product mixture was filtered through silica gel, and the column was washed
carefully with pentane. The organic solvents were removed in vacuo, and
the remaining oil was purified by preparative thick-layer chromatography
on silica gel with pentane. The cyclodienynes 6 were isolated as colorless
oils. In all cases the volatile products contained varying amounts of solvent
(DME, as shown by 1H NMR analysis); this made the determination of
elemental analyses impossible.
Undec-2-en-9-ynedial (12b): This compound was prepared according to the
general procedure: 11b (4.4 g, 22.7 mmol), nBuLi (1.6m, 14.7 mL,
23.5 mmol), DMF (2.1 g, 28.8 mmol), and H2SO4 (96%, 5.0 g) in ice water
(100 mL) provided 12b (1.66 g, 9.33 mmol, 41%). 1H NMR (200 MHz,
CDCl3): d ˆ 1.39 ± 1.67 (m, 6H; 5-H, 6-H, 7-H), 2.21 ± 2.62 (m, 4H; 4-H,
8-H), 5.78 ± 6.16 (m, 1H; 2-H), 6.76 ± 7.10 (m, 1H; 3-H), 9.14 (t, 5J ˆ 0.8 Hz,
1H; 11-H), 9.46 (d, 3J ˆ 7.9 Hz, 1H; 1-H); 13C NMR (50.3 MHz, CDCl3):
d ˆ 18.5 (C-8), 27.2 (2 signals), 28.2 (C-5, C-6, C-7), 32.4 (C-4), 81.8 (C-10),
98.7 (C-9), 133.0 (C-2), 158.4 (C-3), 177.2 (C-11), 194.2 (C-1); IR (film): nÄ ˆ
3022 (m), 2937 (vs), 2863 (s), 2281 (w), 2235 (m), 2202 (s), 1692 (vs), 1670
(vs), 1458 (m), 1426 (m), 1390 (m), 1373 (m), 1236 (s), 1168 (m), 1139 (s),
Cyclodeca-1,3-dien-5-yne (6a): This compound was prepared according to
the general procedure: TiCl3(DME)1.5 (13.0 g, 44.9 mmol), Zn/Cu couple
(17.1 g, 0.27 mol), and 12a (1.6 g, 9.78 mmol) in DME (220 mL) provided
6a (60 mg, 0.45 mmol, 5%). 1H NMR (200 MHz, CDCl3): d ˆ 1.71 (m, 4H;
3
8-H, 9-H), 2.10 (m, 2H; 10-H), 2.18 (m, 2H; 7-H), 5.28 (dm, J ˆ 10.2 Hz,
3
1H; 4-H), 5.53 (dm, J ˆ 15.9 Hz, 1H; 2-H), 6.31 (m, 1H; 1-H), 6.41 (dm,
1
1093 (m), 1072 (m), 1017 (m), 979 (m), 756 cm (m); UV/Vis (MeCN):
3J ˆ 10.2 Hz, 1H; 3-H); 13C NMR (50.3 MHz, CDCl3): d ˆ 21.9 (C-7), 26.9,
30.8 (C-8, C-9), 33.0 (C-10), 84.1 (C-5), 97.5 (C-6), 112.0 (C-4), 123.1 (C-2),
141.8 (C-1), 142.6 (C-3); IR (film): nÄ ˆ 2934 (vs), 2864 (s), 2251 (w), 2205
(w), 1720 (vs), 1679 (vs), 1449 (m), 1408 (m), 1392 (m), 1351 (m), 1326 (m),
1260 (m), 1232 (m), 1212 (m), 1167 (m), 1140 (m), 1099 (m), 1079 (m), 1031
(m), 1013 (m), 914 (m), 733 (s), 647 cm 1 (m); UV/Vis (MeCN): lmax(lg e) ˆ
‡
lmax(lg e) ˆ 218 nm (3.93); MS (70 eV, EI): m/z (%): 178 [M] (1), 177 (2),
149 (20), 135 (32), 121 (46), 107 (72), 91 (68), 79 (100), 67 (43), 55 (89).
Dodec-2-en-10-ynedial (12c): This compound was prepared according to
the general procedure: 11c (3.0 g, 14.4 mmol), nBuLi (1.6m, 9.1 mL,
14.6 mmol), DMF (1.33 g, 18.2 mmol), and H2SO4 (96%, 2.5 g) in ice water
(65 mL) provided 12c (2.39 g, 12.4 mmol, 86%). 1H NMR (200 MHz,
CDCl3): d ˆ 1.30 ± 1.60 (m, 8H; 5-H to 8-H), 2.31 (pseudo qd, 3J ˆ 7.1, 3J ˆ
7.1, 4J ˆ 1.5 Hz, 2H; 4-H), 2.38 (dt, 3J ˆ 6.9, 5J ˆ 0.8 Hz, 2H; 9-H), 6.07 (ddt,
3J ˆ 15.7, 3J ˆ 7.9, 4J ˆ 1.5 Hz, 1H; 2-H), 6.81 (dt, 3J ˆ 6.9, 3J ˆ 15.6, 1H;
3-H), 9.13 (brs, 1H; 12-H), 9.46 (d, 3J ˆ 7.9 Hz, 1H; 1-H); 13C NMR
(50.3 MHz, CDCl3): d ˆ 19.0 (C-9), 27.3, 27.5, 28.4, 28.5 (C-5 to C-8), 32.5
(C-4), 81.7 (C-10), 98.9 (C-11), 133.0 (C-2), 158.5 (C-3), 177.1 (C-12), 194.0
(C-1); IR (film): nÄ ˆ 2935 (vs), 2860 (s), 2280 (w), 2235 (w), 2201 (s), 1690
‡
192 (3.94), 212 (3.52, sh), 226 nm (3.29); MS (GC/MS): m/z (%): 132 [M]
(80), 115 (24), 104 (100), 91 (65), 78 (17), 65 (16).
Cycloundeca-1,3-dien-5-yne (6b): This compound was prepared according
to the general procedure: TiCl3(DME)1.5 (5.2 g, 17.9 mmol), Zn/Cu couple
(3.8 g, 58 mmol), and 12b (0.4 g, 2.2 mmol) in DME (220 mL) provided 6b
(121 mg, 0.83 mmol, 38%). 1H NMR (200 MHz, CDCl3): d ˆ 1.34 (m, 2H;
10-H), 1.49 (m, 2H; 8-H), 1.60 (m, 2H; 9-H), 2.08 (m, 2H; 11-H), 2.28 (m,
2H; 7-H), 5.34 (dm, 3J ˆ 10.6 Hz, 1H; 4-H), 5.61 (dm, 3J ˆ 15.7 Hz, 1H;
2-H), 5.87 (m, 1H; 1-H), 6.33 (dm, 3J ˆ 10.5 Hz, 1H; 3-H); 13C NMR
(50.3 MHz, CDCl3): d ˆ 17.7 (C-7), 22.0 (C-9), 23.9 (C-10), 26.4 (C-8), 32.2
(C-11), 82.8 (C-5), 93.5 (C-6), 111.2 (C-4), 125.6 (C-2), 137.9 (C-1), 140.9
(C-3); IR (film): nÄ ˆ 3018 (m), 2929 (vs), 2860 (s), 2219 (w), 2205 (w), 2170
(w), 1682 (s), 1648 (m), 1456 (m), 1443 (m), 1346 (m), 1018 (m), 968 (m),
921 (m), 765 cm 1 (m); UV/Vis (MeCN): lmax(lg e) ˆ 198 (3.77), 242 (3.56),
1
(vs), 1670 (vs), 1464 (w), 1448 (s), 1390 (w), 1159 (m), 1138 (m), 978 cm
(m); UV/Vis (MeCN): lmax(lg e) ˆ 220 (4.14), 248 (3.11, sh), 266 nm (2.78,
‡
‡
sh); MS (70 eV, EI): m/z (%): 193 [M‡H] (5), 192 [M] (1), 191 (4), 173
(4), 161 (19), 149 (21), 133 (36), 135 (36), 121 (52), 107 (51), 91 (67), 81
(100), 67 (57), 55 (75); HRMS: m/z calcd for C12H16O2 192.1150; found
192.1150.
‡
268 nm (3.52); MS (GC/MS): m/z (%): 146 [M] (5), 145 (6), 131 (28), 117
Tridec-2-en-11-ynedial (12d): This compound was prepared according to
the general procedure: 11d (2.7 g, 12.2 mmol), nBuLi (1.6m, 7.9 mL,
12.7 mmol), DMF (1.13 g, 15.5 mmol), and H2SO4 (3.0 g, 96%) in ice water
(60 mL) provided 12d (1.57 g, 7.63 mmol, 63%). 1H NMR (200 MHz,
CDCl3): d ˆ 1.18 ± 1.57 (m, 10H; 5-H to 9-H), 2.22 ± 2.64 (m, 4H; 4-H,
10-H), 5.73 ± 6.15 (m, 1H; 2-H), 6.55 ± 6.97 (m, 1H; 3-H), 9.15 (t, 5J ˆ
0.8 Hz, 1H; 13-H), 9.48 (d, 3J ˆ 7.9 Hz, 1H; 1-H); 13C NMR (50.3 MHz,
CDCl3): d ˆ 19.0 (C-10), 27.4, 27.7, 28.6, 28.7, 28.9 (C-5 to C-9), 32.6 (C-4),
81.7 (C-12), 99.2 (C-11), 132.9 (C-2), 158.9 (C-3), 177.2 (C-13), 194.3 (C-1);
IR (film): nÄ ˆ 2932 (vs), 2858 (s), 2281 (w), 2235 (m), 2201 (s), 1690 (vs),
1670 (vs), 1465 (m), 1423 (m), 1283 (m), 1235 (m), 1139 (m), 976 cm 1 (m);
UV/Vis (MeCN): lmax(lg e) ˆ 222 nm (4.18), 248 (3.03, sh); MS (70 eV, EI):
(100), 104 (36), 91 (66), 78 (28), 65 (15).
Cyclododeca-1,3-dien-5-yne (6c): This compound was prepared according
to the general procedure: TiCl3(DME)1.5 (11.0 g, 37.9 mmol), Zn/Cu couple
(14.6 g 0.22 mol), and 12c (1.6 g, 8.33 mmol) in DME (220 mL) provided 6c
1
(210 mg, 1.31 mmol, 16%). H NMR (200 MHz, CDCl3): d ˆ 1.47 (m, 6H;
8-H, 9-H, 10-H), 1.60 (m, 2H; 11-H), 2.11 (m, 2H; 12-H), 2.21 (m, 2H;
7-H), 5.34 (d, 3J ˆ 11.0 Hz, 1H; 4-H), 5.75 (dm, 3J ˆ 15.8 Hz, 1H; 2-H), 6.10
(dm, 3J ˆ 11.0 Hz, 1H; 3-H), 6.41 (dm, 3J ˆ 15.8 Hz, 1H; 1-H); 13C NMR
(50.3 MHz, CDCl3): d ˆ 19.7 (C-7), 25.6, 25.7, 27.1, 27.2, 32.4 (C-8 to C-12),
80.7 (C-5), 94.8 (C-6), 108.8 (C-4), 125.1 (C-2), 138.4 (C-1), 138.6 (C-3); IR
(film): nÄ ˆ 2927 (vs), 2858 (s), 2208 (w), 1712 (m), 1683 (m), 1656 (m), 1459
(m), 1445 (m), 1348 (m), 1320 (m), 1132 (m), 1117 (m), 1110 (m), 1091 (m),
‡
m/z (%): 205 [M H] (1), 204 (1), 183 (6), 171 (5), 159 (4), 145 (8), 131
1
(100), 117 (84), 91 (79), 79 (36), 67 (28).
1050 (m), 1024 (m), 970 (m), 911 (m), 733 cm (m); UV/Vis (MeCN):
‡
lmax(lg e) ˆ 244 (3.54), 264 nm (3.55); MS (GC/MS): m/z (%): 160 [M] (6),
Tetradec-2-en-12-ynedial (12e): This compound was prepared according to
the general procedure: 11e (0.52 g, 2.2 mmol), nBuLi (1.6m, 1.4 mL,
2.2 mmol), DMF (0.20 g, 2.76 mmol), and H2SO4 (96%, 0.4 g) in ice water
(10 mL) provided 12e (234 mg, 1.06 mmol, 48%). 1H NMR (200 MHz,
CDCl3): d ˆ 1.31 ± 1.83 (m, 12H; 5-H to 10-H), 2.26 ± 2.58 (m, 4H; 4-H, 11-
H), 6.10 (ddt, 3J ˆ 15.6, 3J ˆ 7.9, 4J ˆ 1.5 Hz, 1H; 2-H), 6.84 (dt, 3J ˆ 6.8, 3J ˆ
15.6 Hz, 1H; 3-H), 9.16 (t, 5J ˆ 0.8 Hz, 1H; 14-H), 9.50 (d, 3J ˆ 7.9 Hz, 1H;
1-H); 13C NMR (50.3 MHz, CDCl3): d ˆ 19.1 (C-11), 27.4, 27.7, 28.7, 28.8,
29.0, 29.1 (C-5 to C-10), 32.6 (C-4), 81.7 (C-13), 99.2 (C-12), 133.0 (C-2),
145 (7), 131 (39), 117 (100), 104 (27), 91 (91), 79 (41), 65 (17).
Cyclotrideca-1,3-dien-5-yne (6d): This compound was prepared according
to the general procedure: TiCl3(DME)1.5 (5.74 g, 19.8 mmol), Zn/Cu couple
(4.19 g, 64 mmol), and 12d (0.5 g, 2.43 mmol) in DME (150 mL) provided
6d (156 mg, 0.90 mmol, 37%). 1H NMR (200 MHz, CDCl3): d ˆ 1.13 ± 1.57
(m, 10H; 8-H to 12-H), 2.13 ± 2.49 (m, 4H; 7-H, 13-H), 5.22 (dm, 3J ˆ
10.1 Hz, 1H; 4-H), 5.99 ± 6.85 (m, 3H; 1-H, 2-H, 3-H); 13C NMR
(50.3 MHz, CDCl3): d ˆ 19.9 (C-7), 25.4, 25.7, 26.1, 27.6, 29.1, 30.1 (C-8 to
Chem. Eur. J. 2001, 7, No. 20
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4383

H. Hopf, A. Krüger
FULL PAPER
C-13), 78.8 (C-5), 98.4 (C-6), 108.4 (C-4), 126.6 (C-2), 135.1 (C-1), 139.2 (C-
3); IR (film): nÄ ˆ 3017 (w), 2931 (vs), 2859 (vs), 2204 (w), 1683 (m), 1645
(m), 1462 (m), 1449 (m), 1347 (m), 1322 (m), 1108 (m), 1080 (m), 1051 (m),
1012 (m), 985 (m), 734 cm 1 (m); UV/Vis (MeCN): lmax(lg e) ˆ 264 (3.67),
(ratio 6c/14 56:44, GC analysis). Compound 6c was identified by its mass
spectrum, which could be superimposed on that obtained above.
Thermal cyclization of the cyclodienynes 6: A solution of 6 (10 4 m) in
perdeuterated o-dichlorobenzene was placed in an NMR tube under
nitrogen, and the tube was heated in an oil bath at the temperature given in
Scheme 5. Product formation was monitored by 1H NMR spectroscopy, and
the benzocycloalkenes 26 were identified by their NMR spectroscopic data,
‡
268 nm (3.87); MS (GC/MS): m/z (%): 174 [M] (23), 145 (23), 131 (64),
117 (70), 105 (36), 91 (100), 79 (45), 67 (26).
Cyclotetradeca-1,3-dien-5-yne (6e): This compound was prepared accord-
ing to the general procedure: TiCl3(DME)1.5 (0.84 g 2.89 mmol), Zn/Cu
couple (1.12 g, 17.1 mmol), and 12e (0.14 g, 0.64 mmol) in DME (50 mL)
provided 6e (53 mg, 0.28 mmol, 44%). 1H NMR (200 MHz, CDCl3): d ˆ
1.30 ± 1.66 (m, 12H; 8-H to 13-H), 2.21 (m, 2H; 14-H), 2.41 (m, 2H; 7-H),
5.29 (dm, 3J ˆ 10.4 Hz, 1H; 4-H), 5.94 (dm, 3J ˆ 15.7 Hz, 1H; 2-H), 6.42 (m,
1H; 3-H), 6.76 (m, 1H; 1-H); IR (film): nÄ ˆ 2933 (vs), 2929 (vs), 2859 (vs),
2280 (w), 2234 (m), 2203 (m), 1707 (s), 1702 (s), 1695 (s), 1671 (s), 1641 (m),
1462 (m), 1426 (m), 1361 (m), 1322 (m), 1215 (m), 1205 (m), 1137 (m), 1091
with the commercially available 26a (tetralin) used as
a reference
compound.
Acknowledgement
We thank the Fonds der Chemischen Industrie for support of our work;
A.K. in particular is grateful for a dissertation scholarship.
1
(m), 1064 (m), 985 (m), 631 cm (m); UV/Vis (MeCN): lmax(lg e) ˆ 194
‡
(4.26), 214 (3.70, sh), 268 nm (3.79); MS (GC/MS): m/z (%): 188 [M] (36),
145 (28), 131 (42), 117 (57), 105 (43), 91 (100), 79 (44), 67 (22).
[1] H. Hopf, R. Stamm, P. G. Jones, Chem. Ber. 1991, 124, 1471 ± 1475.
[2] Reviews: a) K. C. Nicolaou, A. L. Smith in Modern Acetylene
Chemistry (Eds.: P. J. Stang, F. Diederich), VCH, Weinheim, 1995,
203 ± 283; b) J. W. Grissom, G. U. Gunawardena, D. Klingberg, D.
Huang, Tetrahedron 1996, 52, 6453 ± 6518; c) K. K. Wang, Chem. Rev.
1996, 96, 207 ± 222.
McMurry coupling of the dialdehyde 15 under Lenoir conditions:[24]
Anhydrous THF (200 mL) was placed under nitrogen in a flame-dried,
three-necked flask (500 mL), and titanium(iv) chloride (0.93 mL,
8.43 mmol) was added at 08C. The color of the solution changed to intense
yellow. Zinc dust (1.01 g, 15.47 mmol) and anhydrous pyridine (0.52 g,
6.63 mol) were added. The color of the initially grey suspension changed to
[3] H. Hopf, H. Musso, Angew. Chem. 1969, 81, 704; Angew. Chem. Int.
Ed. Engl. 1969, 8, 680.
dark brown within 15 min.
A solution of 15 (1.26 g, 6.63 mmol) in
[4] H. Hopf, W. R. Roth, C. Horn, Chem. Ber. 1994, 127, 1765 ± 1779.
[5] H. Hopf, H. Berger, G. Zimmermann, U. Nüchter, P. G. Jones, I. Dix,
Angew. Chem. 1997, 109, 1236 ± 1238; Angew. Chem. Int. Ed. Engl.
1997, 36, 1187 ± 1190.
[6] Review: G. Zimmermann, Eur. J. Org. Chem. 2001, 457 ± 471.
[7] For the first generation of isobenzene as a reactive intermediate see:
M. Christl, M. Braun, G. Müller, Angew. Chem. 1992, 104, 471 ± 473;
Angew. Chem. Int. Ed. Engl. 1992, 31, 473 ± 476. For the synthesis of
various benzannelated and heteroatom-substituted isobenzenes see:
B. Miller, X. Shi, J. Am. Chem. Soc. 1987, 109, 578 ± 579; M. Christl, S.
Drinkuth, Eur. J. Org. Chem. 1998, 63, 237 ± 241; W. Pan, M. Balci,
P. B. Shevlin, J. Am. Chem. Soc. 1997, 119, 5035 ± 5036. For the
preparation of an isolable diphosphaisobenzene see: M. A. Hofmann,
anhydrous THF (90 mL) was added over 4 h, and the reaction mixture
was stirred overnight at room temperature. After hydrolysis with aqueous
potassium carbonate solution (35 mL, 25%), the solid precipitate was
removed by filtration and decomposed by treatment with HCl (2 n,
120 mL). The resulting solution (combined with the mother liquors) was
extracted with pentane, and the organic phases were combined, washed
successively with saturated bicarbonate solution and brine, then dried with
MgSO4. The solvent was removed in vacuo, and the resulting oily product
mixture was separated by column chromatography on silica gel with
pentane/diethyl ether (1:1, v/v) to provide two fractions: a) cyclododeca-
3,11-diyne-1,2-diol (17) as a waxy solid: yield: 240 mg, 16%, 1.25 mmol;
m.p. 25 ± 308C; 1H NMR (200 MHz, CDCl3): d ˆ 1.53 (m, 8H; 6-H to 9-H),
2.20 ± 2.32 (m, 4H; 5-H, 10-H), 4.33 (m, 2H; 1-H, 2-H); 13C NMR
(50.3 MHz, CDCl3): d ˆ 18.0 (C-5, C-10), 25.5, 26.2 (C-6 to C-9), 67.7 (C-1,
C-2), 78.7 (C-4, C-11), 87.9 (C-3, C-12); IR (KBr): nÄ ˆ 3389 (vs, br), 2935
(vs), 2857 (s), 2235 (m), 1716 (m), 1711 (m), 1702 (m), 1446 (m), 1432 (m),
1334 (m), 1273 (m), 1268 (m), 1241 (m), 1237 (m), 1161 (m), 1140 (m), 1057
Â
U. Bergsträsser, G. J. Reiss, L. Nyulaszi, M. Regitz, Angew. Chem.
2000, 112, 1318 ± 1320; Angew. Chem. Int. Ed. 2000, 39, 1261 ± 1263;
see also: R. Hoffmann, P. Laszlo, Angew. Chem. 2001, 113, 1065 ±
1068; Angew. Chem. Int. Ed. 2001, 40, 1033 ± 1036.
‡
(vs), 1011 (m), 1002 cm 1 (m); MS (GC/MS, 70 eV): m/z (%): 192 [M] (1),
[8] H. Hopf, H. Berger, unpublished results.
[9] R. R. Jones, R. G. Bergman, J. Am. Chem. Soc. 1972, 94, 660 ± 661; cf.
R. G. Bergman, Acc. Chem. Res. 1973, 6, 25 ± 31.
[10] a) K. C. Nicolaou, G. Zuccarelleo, Y. Ogawa, E. J. Schweiger, T.
Kumazawa, J. Am. Chem. Soc. 1988, 110, 4866 ± 4868; b) K. C.
Nicolaou, G. Zuccarello, C. Riemer, V. A. Estevez, W. M. Dai, J.
Am. Chem. Soc. 1992, 114, 7360 ± 7371.
[11] A. Krüger, PhD Dissertation, University of Braunschweig (Germa-
ny), 2000, available on the net under: http://www.biblio.tu-bs.de/ediss/
data/20000630a/20000630a.html.
[12] M. Hanack, R. Rieth, Chem. Ber. 1987, 120, 1659 ± 1666; cf. M.
Hanack, R. Rieth, J. Chem. Soc. Chem. Commun. 1985, 1487 ± 1489.
For the formation of cycloocta-1,3-dien-5-yne as a highly reactive
intermediate see: N. Hanold, H. Meier, Chem. Ber. 1985, 118, 198 ±
209; cf. H. Meier, N. Hanold, H. Kolshorn, Angew. Chem. 1982, 94,
67 ± 68; Angew. Chem. Int. Ed. Engl. 1982, 21, 66 ± 67.
[13] Reviews: a) F. Sondheimer in Aromaticity, Special Publication No. 21,
The Chemical Society, London, 1967, 75 ± 107; b) P. J. Garratt,
Aromaticity, Wiley, London, 1986, Chapter 4, pp. 84 ± 124; c) D. Lloyd,
The Chemistry of Conjugated Cyclic Compounds, Wiley, Chichester,
1989, Chapter 6, pp. 61 ± 82.
[14] H. Hopf, Chem. Ber. 1971, 104, 3087 ± 3095; cf. H. Hopf, Tetrahedron
Lett. 1970, 1107 ± 1109.
[15] R. Gleiter, D. Kratz, V. Schehlmann, Tetrahedron Lett. 1988, 29,
2813 ± 2816. We thank Professor Gleiter for making his procedures for
preparing various cyclo-1,5-diynes available to us.
173 (1), 164 (2), 145 (2), 131 (3), 117 (5), 105 (8), 95 (16), 79 (16), 70 (100),
55 (15). b) the 2,3-bridged furan 18 as a colorless oil: yield: 71 mg, 7%,
0.41 mmol; 1H NMR (200 MHz, CDCl3): d ˆ 1.54 ± 1.83 (m, 8H; 8-H, 9-H,
10-H, 11-H), 2.45 (m, 2H; 7-H or 12-H), 2.60 (m, 2H; 7-H or 12-H), 6.18 (d,
3J ˆ 1.8 Hz, 1H; 4-H), 7.16 (d, 3J ˆ 1.8 Hz, 1H; 5-H); 13C NMR (50.3 MHz,
CDCl3): d ˆ 20.1 (C-7), 24.3, 25.1, 25.2, 27.9 (C-8 to C-12), 76.2 (C-5), 101.5
(C-6), 113.4 (C-3), 131.2 (C-2), 133.4 (C-1), 140.8 (C-4); IR (film): nÄ ˆ 2930
(vs), 2906 (s), 2863 (s), 2227 (w), 2215 (w), 1678 (w), 1583 (w), 1085 (m),
1
‡
740 cm (m); MS (70 eV, EI): m/z (%): 174 [M] (88), 159 (24), 146 (53),
131 (100), 117 (45), 105 (20), 91 (56), 77 (33), 63 (17), 51 (19). The formation
of cyclododeca-3-ene-1,5-diyne (16; ca. 2.6% by GC analysis) was inferred
by comparison of the spectral data with those reported in ref. [10b].
When the same coupling experiment was carried out with 12c in THF at
room temperature, a complex product mixture 13/14 (85:15, GC analysis)
was obtained, which could not be fully characterized. The following
analytical data were obtained: Cyclodeca-3-en-11-yne-1,2-diol (13): GC/
‡
MS (40 eV): m/z (%): 193 [M H] (1), 175 (2), 163 (2), 147 (7), 133 (10),
123 (12), 110 (20), 91 (28), 83 (44), 70 (100), 57 (48), 41 (32), identical to the
spectrum reported in ref. [10]. 4,5,6,7,8,9-Hexahydrocyclodeca[b]furan
(14): 1H NMR (200 MHz, CDCl3): d ˆ 1.17 ± 1.65 (m, 8H; 9-H to 12-H),
1.90 ± 2.07 (m, 2H; 13-H), 2.10 ± 2.28 (m, 2H; 8-H), 5.78 ± 5.93 (m, 1H;
7-H), 6.07 ± 6.00 (m, 2H; 4-H, 6-H), 7.16 (d, 3J ˆ 1.8 Hz, 1H; 5-H); 13C NMR
(50.3 MHz, CDCl3): d ˆ 20.8, 23.5, 23.6, 26.1, 28.2 (C-9 to C-13), 31.8 (C-8),
111.0 (C-6), 113.5 (C-4), 119.9 (C-3), 120.9 (C-2), 139.9 (C-5), 141.4 (C-7);
‡
GC/MS (40 eV): m/z (%): 176 [M] (68), 161 (9), 147 (25), 133 (68), 119
[16] That this process worked so well in Sondheimerꢀs numerous cases
probably has two main reasons. On the one hand, the rings involved in
annulene chemistry are usually larger and, hence, presumably less
(25), 105 (28), 91 (100), 77 (33), 65 (19), 55 (19). When the reaction was
carried out in THF under reflux, 6c was obtained in place of the diol 13
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Chem. Eur. J. 2001, 7, No. 20

Synthesis of Cyclo-1,3-dien-5-ynes
4378±4385
strained than in our examples. On the other hand, the generated
dehydroannulenes are fully conjugated, and in most cases aromatic.
[17] C. A. Brown, A. Yamashita, J. Am. Chem. Soc. 1975, 97, 891 ± 892.
[18] S. R. Abrams, Can. J. Chem. 1984, 62, 1333 ± 1334.
[19] A. J. Manusco, S.-L. Huang, D. Swern, J. Org. Chem. 1978, 43, 2480 ±
2482.
[22] A. Kasatkin, R. J. Whitby, J. Am. Chem. Soc. 1999, 121, 7039 ± 7049.
[23] We thank Prof. Dr. W. A. König (University of Hamburg) for these
separation experiments on the following cyclodextrin phases: hepta-
kis(6-O-tert-butyldimethylsilyl-2,3-di-O-methyl)-b-cyclodextrin, octa-
kis(6-O-methyl-2,3-di-O-pentyl)-b-cyclodextrin, and heptakis(2,6-di-
O-methyl-3-O-pentyl)-b-cyclodextrin.
[20] a) T. M. Cresp, M. V. Sargent, P. Vogel, J. Chem. Soc. Perkin Trans. 1
1974, 37 ± 41; b) H. Higuchi, M. Kondo, H. Yonehara, J. Ojima, M.
Iyoda, Bull. Chem. Soc. Jpn. 1993, 66, 275 ± 281; c) N. Daubresse, C.
Francesch, C. Rolando, Tetrahedron 1998, 54, 10761 ± 10770.
[21] T. Lectka in Active Metals (Ed.: A. Fürstner), VCH, Weinheim, 1996,
p. 92.
[24] D. Lenoir, Synthesis 1977, 553 ± 554.
[25] E. Pretsch, J. Seibl, W. Simon, Th. Clerc, Tabellen zur Strukturauf-
klärung organischer Verbindungen, Springer, Berlin, 1986, 3rd ed.,
p. H265.
Received: March 7, 2001 [F3113]
Chem. Eur. J. 2001, 7, No. 20
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4385