Synthesis of geminal enediynes with saturated and unsaturated carbocyclic backbones by palladium-catalyzed alkynylation of dibromoolefins

Article abstract of DOI:10.1055/s-1998-6094

The conversion of cyclic diketones 1 and 3 into the corresponding dibromoalkenes 2 and 4 via Corey-Fuchs procedure is described. Subsequent alkynylation of 2 and 4 as well as 9-(dibromomethylene)fluorene (6) yields the geminal enediynes 5a-e, 7a-e, and 8a

Full text of DOI:10.1055/s-1998-6094

SYNTHESIS
Papers
1362
Synthesis of Geminal Enediynes with Saturated and Unsaturated Carbocyclic
Backbones by Palladium-Catalyzed Alkynylation of Dibromoolefins
Richard Neidlein,* Moritz Winter
Pharmazeutisch-Chemisches Institut der Universität Heidelberg, Im Neuenheimer Feld 364, D-69120 Heidelberg, Germany
Tel. +49(6221)544850; Fax +49(6221)546430; E-mail: neidlein@convex.phazc.uni-heidelberg.de
Received 23 February 1998
Abstract: The conversion of cyclic diketones 1 and 3 into the cor-
responding dibromoalkenes 2 and 4 via Corey–Fuchs procedure is
described. Subsequent alkynylation of 2 and 4 as well as 9-
(dibromomethylene)fluorene (6) yields the geminal enediynes
5a–e, 7a–e, and 8a–c.The cyclohexane backbone of 5a,d can be
oxidized with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)
to the p-quinoid systems 9a,b.
Key words: dibromoalkenes, alkynylation, geminal enediynes,
oxidation
Scheme 2
In our earlier work,1, 2 we have explored the syntheses of
peri-ethynyl substituted 1,6-methano[10]annulene deriva-
tives and investigated the interactions between their acet-
ylene fragments. Several multi-ethynyl substituted deriv-
atives were synthesized and the properties of these and
other isolated products were investigated; we have also
synthesized some enediyne units as derivatives of 1,6-
methano[10]annulenes using palladium-catalyzed cross
coupling reactions.1, 2
hours, respectively, the dibromoalkenes 2 and 4 could be
isolated by filtration of the reaction mixtures, evaporation
of the filtrates and column chromatography on silica gel
in yields of 93% for 2 and 36% for 4. Dibromoalkenes 2
and 4 are colorless solids that are stable to air at ambient
temperature and melt at 140–145°C (subl.) and 73°C, re-
spectively.
Enediyne units can also be substructures in molecules de-
signed to serve as precursors to two-dimensional carbon
networks.3 Very often, substances of this type are made up
of tetraethynylethene building blocks.4 Carbon networks
prepared from this type of molecules would have distinc-
tive physical properties; selective substitution of the mo-
nomeric starting materials with cyclic aliphatic or aromat-
ic saturated or polyunsaturated groups could probably sig-
nificantly change the physical properties of the resulting
polymeric carbon networks.
Besides these two dibromoalkenes, 9-(dibromomethyl-
ene)-9H-fluorene5 (6) was chosen as an interesting start-
ing material for alkynylations.7 Substitution of bromine
atoms in 2, 4, and 6 was achieved by using different pal-
ladium catalysts, namely, Pd(PPh3)4, Pd(PPh3)2Cl2 and
Pd(PhCN)2Cl2. No systematic relation between the struc-
ture of the dibromoalkenes or the type of alkyne and the
best suited catalyst was observed; instead, the optimum
catalyst for a given reaction was found by comparison be-
tween several runs under different conditions. Reactions
were conducted in anhydrous benzene at temperatures be-
tween room temperature and 80°C. For elimination of the
HBr formed during the substitution reactions, various
amines were employed. Pure alkynylation products were
isolated by evaporation of the volatile portion of the reac-
tion mixtures and column chromatography of the residue
on silica gel. The resulting geminal enediynes 5a–e
(Scheme 3), 7a–e (Scheme 4), and 8a–c (Scheme 5) are
In order to prepare suitable precursors for such novel all
carbon networks, we chose to transform cyclohexane-1,4-
dione (1) and anthraquinone (3) into the corresponding di-
bromoalkenes (Schemes 1 and 2). These dibromoalkenes
as well as the known fluorene derivative 65 (Scheme 4)
should represent suitable starting materials for catalytic
alkynylation yielding novel cyclic geminal enediynes.
Scheme 1
According to known literature procedures,6 the ketones 1
and 3 were reacted with CBr4/PPh3 mixtures in anhydrous
benzene. After reaction at room temperature for 15 and 10 Scheme 3

SYNTHESIS
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1363
Table 1. Alkynylation Products 5a–e Prepared
with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ)
in anhydrous xylene at reflux. The resulting p-quinoid,
alkynyl-substituted systems 9a and 9b are intensively or-
ange colored, stable solids.
Com-
pound
R
Catalyst
Time
Temp. Yield
(°C)
(%)
5a
5b
5c
5d
5e
Ph
t-Bu
Pd(PPh3)2Cl2
Pd(PPh3)2Cl2
4 d
30 h
6 h
48 h
24 h
25
60
70
25
60
12
31
45
78
51
(CH2)5CH3 Pd(PhCN)2Cl2
SiMe3
Pd(PPh3)2Cl2
Pd(PPh3)2Cl2
Si(iPr)3
Scheme 6
Scheme 4
Table 2. Alkynylation Products 7a–e Prepared
In conclusion, it can be said that the transformation of ke-
tones 1 and 3 to dibromoalkenes 2 and 4 is easily achieved
by using reaction conditions analogous to those published
by Corey and Fuchs.3d Alkynylation of dibromoalkenes 2,
4, and 6 yields geminal enediynes with cyclohexane-1,4-
diyl, anthracene and fluorene backbones and various sub-
stituents on the alkynyl groups. These geminal enediynes
could possibly serve as interesting precursors to two-di-
mensional carbon networks. Geminal enediynes 5a and
5d were oxidized to p-quinoid molecules bearing substi-
tuted alkynyl groups.
Com-
pound
R
Catalyst
Time
Temp. Yield
(°C)
(%)
7a
7b
7c
7d
7e
Ph
t-Bu
Pd(PPh3)4
Pd(PPh3)2Cl2
7 d
3.5 h 70
5 h
24 h
3 h
25
12
47
16
54
71
(CH2)5CH3 Pd(PPh3)2Cl2
80
25
80
SiMe3
Pd(PPh3)2Cl2
Pd(PPh3)2Cl2
Si(iPr)3
All reactions were performed under N2 using standard Schlenk tech-
niques. Et2O and benzene were dried by distillation from sodium/ben-
zophenone, amines were distilled from CaH2. Reagents of commer-
cial quality were used unless otherwise stated. Analytical TLC: Ma-
cherey–Nagel Polygram Sil G/UV254 (0.2 mm silica with
fluorescence indicator); column chromatography: silica gel (60–
200 mesh), ICN Biomedicals. IR spectra were recorded on a Perkin–
Elmer FT-1600 IR spectrophotometer, mps were determined on a Re-
ichert melting point microscope and are uncorrected. UV-vis spectra
were recorded on a Hewlett–Packard HP 8452 A spectrophotometer.
1H and 13C NMR spectra were recorded on NMR spectrometers Bruk-
1
er AM 360 (360.12 MHz H and 90.56 MHz 13C), Bruker WM 250
Scheme 5
(250.13 MHz 1H and 62.89 MHz 13C) and Varian XL 300
(299.95 MHz 1H and 75.43 MHz 13C). The degree of substitution was
determined by J modulated spin-echo experiments. Chemical shifts
are given as δ in ppm rel. to TMS. MS were performed on a Varian
MAT 311 A mass spectrometer (ionization energy 70 eV).
Table 3. Alkynylation Products 8a–c Prepared
Com-
pound
R
Catalyst
Time
Temp. Yield
(°C)
(%)
Elemental analyses were obtained on a Foss–Heraeus Vario EL; all
compounds gave satisfactory microanalyses (C, H ± 0.3).
8a
8b
8c
Ph
t-Bu
SiMe3
Pd(PPh3)2Cl2
Pd(PPh3)2Cl2
Pd(PhCN)2Cl2
48h
8 h
6 h
25
80
80
29
32
26
1,4-Bis(dibromomethylene)cyclohexane (2):
To a solution of PPh3 (13.64 g, 52 mmol) in anhyd benzene (100 mL)
was added CBr4 (8.62 g, 26 mmol). After stirring at r.t. for 30 min,
cyclohexane-1,4-dione (1) (1.12 g, 10 mmol) was added and the mix-
ture was subsequently stirred for 15 h at r.t. The green precipitate was
removed from the solution by filtration, the filtrate was evaporated
under reduced pressure and the residue absorbed on Celite. Chroma-
tography (silica gel, 15 × 3 cm, hexane) yielded 2 (3.92 g, 92%) as
colorless crystals; mp 140–145°C (subl.).
yellowish to red solids, very soluble in hexane and can be
stored for extended periods of time at ambient tempera-
ture. Solutions of the above mentioned compounds de-
compose slowly.
The cyclohexane backbone of 5a and 5d is an interesting
target for attempts to transform it into a p-quinoid system.
Oxidation was brought about by reaction of 5a and 5d
UV-vis (hexane): λ (log ε) = 206 (4.03), 218 nm (3.96).
IR (KBr): ν = 2911 (C–H), 1713, 1463, 1377, 1252, 1195 cm–1.
1H NMR (300 MHz, CDCl3): δ = 2.50 (s, 8 H).

SYNTHESIS
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1364
13C NMR (75.43 MHz, CDCl3): δ = 32.3 (C-2,3,5,6); 84.3 (C-7,8);
141.4 (C-1,4).
MS (EI): m/z (%) = 430 (6), 429 (31) [M]+, 428 (100), 427 (5), 426
(14), 414 (3), 413 (9), 385 (7), 372 (15), 371 (44), [M – t-Bu]+, 358
(5), 357 (16), 356 (5), 341 (7), 327 (3), 316 (5), 315 (18) [M – 2 t-
Bu]+, 313 (5), 306 (7), 305 (28), 301 (7), 300 (6), 299 (8), 285 (7), 271
(6), 259 (6), 257 (5), 253 (9), 245 (5), 214 (5), 207 (4).
MS (EI): m/z (%) = 428 (4) [81Br4 M]+, 426 (16) [81Br379Br M]+, 424
(26) [81Br279Br2 M]+, 422 (19) [81Br79Br3 M]+, 420 (6) [79Br4 M]+,
347 (4), 345 (13), 343 (11) [M – 81Br]+, 341 (5), 266 (47), 265 (11),
264 (100) [M – 81Br79Br]+, 263 (12), 262 (50), 225 (4), 199 (4), 197
(3), 185 (10), 184 (14), 183 (13) [M – 81Br279Br]+.
HRMS: m/z = calcd for C32H44: 428.3443; found: 428.3443.
HRMS: m/z calcd for C8H881Br279Br2: 423.7318; found: 423.7317.
1,4-Bis[bis(oct-1-ynyl)methylene]cyclohexane (5c):
From 2 (0.21 g, 0.5 mmol) and oct-1-yne (0.55 g; 5.0 mmol); yield:
121 mg (45%); orange solid; mp 88°C.
9,10-Bis(dibromomethylene)-9,10-dihydroanthracene (4):
To a solution of PPh3 (2.73 g, 10.4 mmol) in anhyd benzene (30 mL)
was added CBr4 (1.72 g, 5.2 mmol). After stirring at r.t. for 30 min,
anthraquinone (3) (0.42 g, 2 mmol) was added and the mixture was
stirred at r.t. for 10 h. The precipitate was removed from the solution
by filtration and washed with benzene. Removal of the solvent under
reduced pressure and absorption of the residue on Celite, followed by
chromatography (silica gel, 5 × 25 cm, hexane) yielded 4 (0.37 g,
36%) as a colorless solid; mp 73°C.
UV-vis (hexane): λ (log ε) = 235 (3.50), 283 (4.21), 411 nm (3.96).
IR (KBr): ν = 2955 (s, C–H), 2933 (s, C–H), 2888 (m), 2855 (m),
2211 (w, C≡C), 1711 (s), 1616 (w), 1461 (w), 1433 (m), 1372 (w),
1344 (w), 1250 (s), 1194 (m), 1100 (w), 1022 cm–1 (w).
1H NMR (300 MHz, CDCl3): δ = 0.8–1.6 (br. m, 52 H, Alkyl-H); 2.50
(s, 8H, H-2,3,5,6).
13C NMR (62.89 MHz, CDCl3): δ = 14.0 (-CH3); 19.2, 22.5, 28.6,
29.7, 31.3, 32.3 (CH2); 65.3 (C-7,8); 77.6, 84.3 (C≡C–nHexyl,
C≡C–nHexyl); 141.6 (C-1,4).
UV-vis (CH2Cl2): λ (log ε) = 301 (4.09), 264 (4.08), 251 nm (4.20).
IR (KBr): ν = 3060 (w, C–H), 1718 (w), 1583 (m, arom. C=C), 1564
(m, arom. C=C), 1181 (m), 1162 cm–1 (m).
MS (EI): m/z (%) = 541 (100) [M]+, 512 (36), 504 (28), 500 (33), 468
(12), 416 (10), 386 (10), 385 (14), 353 (12), 352 (11), 324 (40), 302
(32), 298 (14), 232 (45).
1H NMR (300 MHz, CDCl3): δ = 7.25–7.88 (m, 8 H).
13C NMR (75.43 MHz, CDCl3): δ = 90.2 (C-11,12); 126.8, 127.4,
135.6 (arom. C); 139.3 (C-9,10).
HRMS: m/z = calcd for C40H60: 540.4695; found: 540.4695.
MS (EI): m/z (%) = 524 (10) [81Br4 M]+, 522 (34) [81Br379Br M]+, 520
(51) [81Br279Br2 M]+, 518 (36) [81Br79Br3 M]+, 516 (11) [79Br4 M]+,
362 (23), 361 (8), 360 (46) [M – 81Br79Br]+, 359 (4), 358 (24), 260 (4),
259 (3), 201 (16), 200 (100) [M – 81Br279Br2]+.
1,4-Bis[bis(trimethylsilylethynyl)methylene]cyclohexane (5d):
From 2 (0.20 g, 0.47 mmol) and trimethylsilylacetylene (0.36 g,
3.6 mmol); yield: 0.18 g (78%); yellow crystals; mp 93°C.
UV-vis (hexane): λ (log ε) = 234 (3.60), 280 nm (4.10).
IR (KBr): ν = 2960 (s, C–H), 2900 (m, C–H), 2844 (w, C–H), 2144
(m, C≡C), 1433 (m), 1295 (w), 1260 (w), 1249 (s), 1197 (m), 1104
(w), 1066 (w), 1020 cm–1 (w).
HRMS: m/z = calcd for C16H879Br281Br2: 519.7319; found: 519.7319.
gem-Enediynes 5a–e, 7a–e, 8a–c; General Procedure:
To a solution of amine, dibromoalkene and alkyne in anhyd benzene
(30 mL) were added the palladium catalyst (5 mol%) and CuI (10
mol%). The mixture was stirred at temperatures between 25 and 80°C
(Tables 1–3), concentrated in vacuo, and the residue was absorbed on
Celite. Column chromatography (silica gel, hexane) yielded the al-
kynylation products as colorless to yellow solids. Crude products
were recrystallized from mixtures of hexane and Et2O.
1H NMR (300 MHz, CDCl3): δ = 0.17–0.19 [m, 36 H, Si(CH3)3]; 2.48
(s, 8 H, CH2).
13C NMR (75.43 MHz, CDCl3): δ = –0.75 [Si(CH3)3]; 32.02 (CH2);
84.27 (C-7,8); 87.9, 100.63 (C≡C–SiMe3, C≡C–SiMe3); 159.25 (C-1,4).
MS (EI): m/z (%) = 493 (6) [M]+, 492 (18), 491 (25), 490 (52), 393
(4), 377 (4), 349 (4), 230 (1), 73 (100) [SiMe3]+.
HRMS: m/z = calcd for C28H44Si4: 492.2520; found: 492.2522.
1,4-Bis[bis(phenylethynyl)methylene]cyclohexane (5a):
From 2 (0.40 g, 0.94 mmol) and phenylacetylene (1 mL, 9.1 mmol);
yield: 60 mg (12%); red needles; mp 218°C.
1,4-Bis[bis(triisopropylsilylethynyl)methylene]cyclohexane (5e):
From 2 (0.40 g, 0.93 mmol) and triisopropylsilylacetylene (1.02 g,
5.6 mmol); yield: 0.39 g (51%); yellow needles; mp 96–98°C.
UV-vis (hexane): λ (log ε) = 251 (4.06), 265 (3.22), 281 nm (3.01).
IR (KBr): ν = 2945 (s, C–H), 2866 (s, C–H), 2062 (m, C≡C), 1465
(m), 1252 (w), 1073 (w), 1018 (m), 993 (m), 919 (w), 882 (m), 679
(s), 663 (s), 631 (m), 529 (w), 477 cm–1 (m).
UV-vis (hexane): λ (log ε) = 226 (5.06), 308 (4.05), 430 nm (4.04).
IR (KBr): ν = 3051 (w, arom. C–H), 3048 (w, arom. C–H), 2963 (s,
aliphat. C–H), 2105 (w, C≡C), 1489 (m), 1419 (w), 1261 (s), 1094 (s),
1022 cm–1 (s).
1H NMR (300 MHz, CDCl3): δ = 2.96 (s, 8 H, CH2); 7.17–7.56 (m,
20 H, arom. H).
1H NMR (300 MHz, CDCl3): δ = 1.09 [s, 84 H, Si(iPr)3]; 2.50 (s, 8 H,
CH2).
13C NMR (75.43 MHz, CDCl3): δ = 32.3 (C-2,3,5,6); 75.4 (C-7,8);
89.7, 99.1 (C≡C–Ph, C≡C–Ph); 121.7, 122.8, 125.6, 131.2 (arom. C);
143.7 (C-1,4).
13C NMR (75.43 MHz, CDCl3): δ = 11.3 [Si(CH(CH3)2)3]; 18.5
[Si(CH(CH3)2)3]; 32.2 (C-2,3,5,6); 81.5, 90.1 [C≡C–Si(iPr)3, C≡C–
Si(iPr)3]; 84.2 (C-7,8); 141.4 (C-1,4).
MS (EI): m/z (%) = 507 (10) [M – H]+, 506 (24), 395 (17), 394 (9),
393 (53), 392 (3), 379 (6), 378 (4), 377 (20), 365 (5), 364 (7), 362 (4),
351 (8), 350 (4), 349 (16), 333 (8), 214 (6), 213 (4).
HRMS: m/z = calcd for C40H28: 508.2191; found: 508.2191.
MS (EI): m/z (%) = 829 (9), 828 (100) [M]+, 827 (19), 727 (12), 724
(13), 626 (4), 363 (6), 362 (16), 321 (10), 320 (31), 291 (9), 277 (10),
263 (6), 250 (4), 249 (12), 235 (4).
HRMS: m/z = calcd for C52H92Si4: 828.6276; found: 828.6276.
1,4-Bis[bis(tert-butylethynyl)methylene]cyclohexane (5b):
From 2 (0.20 g, 0.47 mmol) and tert-butylacetylene (0.6 mL, 0.40 g,
4.8 mmol); yield: 63 mg (31%); yellow solid; mp 209°C.
UV-vis (CH2Cl2): λ (log ε) = 274 (4.34), 385 (3.53), 408 nm (3.49).
IR (KBr): ν = 2966 (vs., C–H), 2865 (s, C–H), 2211 (w, C≡C), 1457
(m), 1359 (m), 1324 (m), 1204 (m), 1096 cm–1 (m).
1H NMR (300 MHz, CDCl3): δ = 1.27 [s, 36 H, C(CH3)3]; 2.55 (s, 8
H, CH2).
9-[Bis(phenylethynyl)methylene]-9H-fluorene (7a):
From 6 (197 mg, 0.58 mmol) and phenylacetylene (0.14 g, 1.4 mmol);
yield: 27 mg (12%); red solid; mp 95–97°C.
UV-vis (hexane): λ (log ε) = 240 (4.11), 256 (4.00), 272 (4.04), 298
(3.70), 386 nm (3.92).
IR (KBr): ν = 3052 (w, arom. C–H), 3033 (w, arom. C–H), 2177 (w,
C≡C), 1700 (m), 1653 (m, aliphat. C=C), 1576 (m, arom. C=C), 1570
(m, arom. C=C), 1560 (w, arom. C=C), 1540 (m), 1533 (m), 1521
(m), 1507 (m), 1490 (s), 1457 (m), 1441 (vs.), 1354 (m), 1261 (s),
1092 (m), 1023 cm–1 (s).
13C NMR (75.43 MHz, CDCl3): δ = 28.1 [C(CH3)3]; 31.1 [C(CH3)3];
31.2 (C-2,3,5,6); 76.1 (C-7,8); 99.6, 100.1 (C≡C–t-Bu, C≡C–t-Bu);
154.2 (C-1,4).
1H NMR (300 MHz, CDCl3): δ = 6.4–7.8 (m, 18 H, arom. H).

SYNTHESIS
September 1998
1365
13C NMR (75.43 MHz, CDCl3): δ = 88.9, 97.8 (C-11,11',12,12');
101.2 (C-10); 119.5 (C-1,8); 122.8, 125.4, 127.4, 128.5, 129.0, 129.4,
131.7, 137.4, 140.1, (arom. C); 145.0 (C-9).
13C NMR (75.43 MHz, CDCl3): δ = 29.8 [Si(CH3)3]; 100.8 (C-10);
103.3, 104.5 (C-11,11',12,12'); 119.4, 125.8, 127.1, 129.6, 137.2,
140.1 (arom. C); 146.7 (C-9).
MS (EI): m/z (%) = 380 (5), 379 (30), 378 (100) [M]+, 377 (29), 376
(32), 375 (11), 374 (15), 350 (4), 348 (2), 301 (3), 300 (9) [M – Ph]+,
299 (2), 298 (3), 252 (2), 190 (3), 189 (8), 188 (13), 187 (16), 186 (3),
180 (4), 175 (5), 174 (4), 162 (2), 150 (2), 105(1).
MS (EI): m/z (%) = 373 (2), 372 (15), 371 (34), 370 (100) [M]+, 357
(3), 356 (6), 355 (18) [M – CH3]+, 340 (3), 339 (8), 325 (3), 323 (2),
309 (3), 298 (2), 297 (5), 296 (2), 295 (4), 293 (4), 283 (4), 282 (4),
281 (9), 280 (3), 279 (7), 269 (5), 268 (3), 267 (8), 266 (4), 265 (5),
257 (4), 256 (3), 255 (4), 253 (4), 252 (2), 243 (3), 242 (3), 241 (4),
239 (6), 229 (3).
HRMS: m/z = calcd for C30H18: 378.1409; found: 378.1408.
HRMS: m/z = calcd for C24H26Si2: 370.1573; found: 370.1572.
9-[Bis(tert-butylethynyl)methylene]-9H-fluorene (7b):
From 6 (0.34 g, 1 mmol) and tert-butylacetylene (0.62 mL, 0.41 g,
5 mmol); yield: 0.15 g (47%); yellow solid; mp 99°C.
UV-vis (hexane): λ (log ε) = 366 (4.32), 348 (4.22), 332 (3.86), 272
(4.20), 262 (4.14), 240 nm (4.25).
9-[Bis(triisopropylsilylethynyl)methylene]-9H-fluorene (7e):
From 6 (0.34 g, 1 mmol) and triisopropylsilylacetylene (1.1 mL,
0.9 g, 5 mmol); yield: 0.39 g (71%); yellow crystals; mp 112–113°C.
UV-vis (hexane): λ (log ε) = 238 (4.49), 272 (4.51), 356 (4.54),
376 nm (4.66).
IR (KBr): ν = 3054 (m, arom. C–H), 3031 (w, arom. C–H), 2968 (vs.,
aliphat. C–H), 2930 (s), 2866 (s), 2144 (m, C≡C), 1734 (w), 1718 (w),
1685 (w), 1653 (w), 1475 (s), 1444 (s), 1391 (w), 1362 (s), 1324 (w),
1285 (m), 1243 (vs.), 1201 (s), 1085 (m), 1035 cm–1 (w).
1H NMR (300 MHz, CDCl3): δ = 1.20 [s, 18 H, C(CH3)3]; 7.19–7.32
IR (KBr): ν = 3058 (m, arom. C–H), 2940 (s, aliphat, C–H), 2863 (s),
2122 (w, C≡C), 1701 (w), 1685 (w), 1654 (w), 1601 (m, arom. C=C),
1560 (m, arom. C=C), 1460 (s), 1448 (s), 1382 (m), 1355 (m), 1223
(s), 1192 (m), 1070 (m), 1012 cm–1 (m).
3
3
(m, 4 H, arom. H); 7.59 (d, J = 8 Hz, 2 H, arom. H); 8.68 (d, J =
8 Hz, 2 H, arom. H).
1H NMR (300 MHz, CDCl3): δ = 1.18 [br. s, 42 H, Si(iPr)3-H]; 7.22
(dt, 3J = 7.6 Hz, 4J = 1.1 Hz, 2 H, H-3,6); 7.34 (dt, 3J = 7.5 Hz, 4J =
1.0 Hz, 2 H, H-2,7); 7.63 (d, 3J = 7.5 Hz, 2 H, H-1,8); 8.83 (d, 3J =
7.8 Hz, 2 H, H-4,5).
13C NMR (75.43 MHz, CDCl3): δ = 30.6 [C(CH3)3]; 63.6 [C(CH3)3];
79.8 (C-10); 86.1, 106.8 (C-11,11',12,12'); 119.1, 124.8, 126.7, 128.5
137.6, 139.5 (arom. C); 142.7 (C-9).
MS (EI): m/z (%) = 340 (4), 339 (29), 338 (100) [M]+, 323 (4) [M –
CH3]+, 308 (3) [M – 2 CH3]+, 307 (2), 295 (2), 294 (3), 293 (8) [M –
3 CH3]+, 292 (2), 291 (3), 289 (2), 281 (4) [M – tBu]+, 280 (4), 279
(5), 278 (6), 277 (10), 276 (7), 268 (2), 267 (8), 266 (13), 265 (9), 264
(3), 263 (5), 254 (5), 253 (12), 252 (14), 250 (2), 240 (3), 239 (9), 229
(3), 228 (2), 227 (2), 226 (4), 215 (4), 203 (2), 202 (4).
HRMS: m/z = calcd for C26H26: 338.2036; found: 338.2036.
13C NMR (75.43 MHz, CDCl3): δ = 11.4 [Si–CH(CH3)2]; 18.7
[Si–CH(CH3)2]; 101.2 (C-10); 102.0, 105.4 (C-11,11',12,12'); 119.2,
125.8, 127.0, 129.3, 137.2, 139,9 (arom. C); 145.1 (C-9).
MS (EI): m/z (%) = 540 (19), 539 (51), 538 (100) [M]+, 495 (13), 454
(13), 453 (33), 439 (3), 425 (7), 412 (3), 411 (7), 383 (3), 369 (5), 355
(3), 341 (6), 339 (4), 327 (9), 326 (3), 325 (7), 313 (8), 199 (6), 297
(5), 295 (8), 283 (6), 281 (5), 269 (10), 257 (4), 255 (3), 226 (4).
HRMS: m/z = calcd for C36H50Si2: 538.3451; found: 538.3453.
9-[Bis(oct-1-ynyl)methylene]-9H-fluorene (7c):
From 6 (0.15 g, 0.45 mmol) and oct-1-yne (0.20 g; 1.79 mmol); yield:
28 mg (16%); colorless solid; mp 68°C.
UV-vis (hexane): λ (log ε) = 230 (4.70), 256 (4.40), 266 (4.33), 346
(3.96), 364 nm (3.96).
IR (film): ν = 3059 (m, arom. C–H), 2955 (s, aliphat. C–H), 2928 (vs.,
aliphat. C–H), 2857 (m, aliphat. C–H), 2204 (m, C≡C), 1943 (w),
1911 (w), 1876 (w), 1723 (w), 1609 (w, arom. C=C), 1580 (w, arom.
C=C), 1563 (w, arom. C=C), 1466 (m), 1446 (m), 1377 (w), 1352 (w),
1305 (w), 1222 (w), 1154 (w), 1108 (w), 1037 (w), 1007 cm–1 (w).
1H NMR (300 MHz, CDCl3): δ = 0.75–1.72 (br. m, 26 H, aliphat. H);
7.20–8.65 (m, 8 H, arom. H).
9,10-Bis[bis(phenylethynyl)methylene]-9,10-dihydroanthracene
(8a):
From 4 (0.26 g, 0.5 mmol) and phenylacetylene (0.36 g, 3.5 mmol);
yield: 88 mg (29%); yellow solid; mp 103°C.
UV-vis (hexane): λ (log ε) = 285 (4.13), 340 (3.60), 362 nm (3.90).
IR (KBr): ν = 3048 (w, C–H), 2133 (w, C≡C), 1653 (m), 1595 (m,
arom. C=C), 1507 (w), 1486 (w), 1449 (s), 1395 (w), 1316 (w), 1240
(m), 1204 (s), 1175 (s), 1068 (w), 1018 cm–1 (w).
1H NMR (300 MHz, CDCl3): δ = 7.17–7.97 (m, 28 H, arom. H).
13C NMR (75.43 MHz, CDCl3): δ = 82.1, 102.6 (C≡C–Ph, C≡C–Ph);
98.7 (C-11,12); 122.8, 127.6, 129.3, 130.2, 132.8, 121.5, 133.4 (arom.
C); 153.0 (C-9,10).
13C NMR (75.43 MHz, CDCl3): δ = 15.8 (C-18,18'); 22.4, 23.7, 28.7,
29.4, 32.6 (CH2); 71.5, 97.4 (C-11,11',12,12'); 102.1 (C-10); 118.6,
125.9, 126.8, 129.0, 136.2, 142.7 (arom. C); 147.2 (C-9).
MS (EI): m/z (%) = 396 (5), 395 (32), 394 (100) [M]+, 323 (11), 281
(2), 279 (2), 267 (6), 266 (3), 265 (4), 255 (6), 254 (4), 253 (13), 252
(9), 242 (3), 241 (14), 240 (5), 239 (6), 229 (3), 216 (3), 215 (9).
HRMS: m/z = calcd for C30H34: 394.2661; found: 394.2661.
MS (EI): m/z (%) = 604 (20) [M]+, 569 (30), 568 (15), 526 (6), 525
(10), 403 (16), 402 (22), 401 (11), 393 (9), 392 (25), 351 (13), 350
(34), 281 (8), 265 (6), 239 (9), 237 (6), 227 (10), 223 (8), 221 (5), 211
(8), 209 (9), 507 (6).
HRMS: m/z = calcd for C48H28: 604.2191; found: 604.2191.
9,10-Bis[bis(tert-butylethynyl)methylene]-9,10-dihydroan-
thracene (8b):
From 4 (0.5 g, 0.96 mmol) and tert-butylacetylene (0.8 g, 9.6 mmol);
yield: 0.16 g (32%); yellow needles; mp 118°C.
9-[Bis(trimethylsilylethynyl)methylene]-9H-fluorene (7d):
From 6 (0.20 g, 0.60 mmol) and trimethylsilylacetylene (0.5 mL,
0.35 g, 3.6 mmol); yield: 0.22 g (54%); yellow needles; mp 132–133°C.
UV-vis (hexane): λ (log ε) = 230 (4.50), 238 (4.50), 262 (4.46), 272
(4.53), 294 (3.70), 306 (3.72), 336 (4.21), 354 (4.54), 374 nm (4.64).
IR (KBr): ν = 3057 (w, arom. C–H), 2955 (m, aliphat. C–H), 2344
(w), 2124 (m, C≡C), 1792 (w), 1772 (w), 1751 (w), 1734 (w), 1718
(w), 1700 (w), 1696 (w), 1684 (w), 1653 (m), 1599 (m, arom. C=C),
1576 (m, arom. C=C), 1570 (w, arom. C=C), 1507 (m), 1448 (m),
1405 (w), 1362 (w), 1249 (s), 1225 (m), 1178 cm–1 (w).
UV-vis (hexane): λ (log ε) = 235 (4.69), 276 nm (3.45).
IR (film): ν = 3032 (w, arom. C–H), 2966 (s, aliphat. C–H), 2871 (s,
aliphat. C–H), 2216 (m, C≡C), 1947 (m), 1755 (m), 1737 (m), 1713
(m), 1626 (m), 1674 (m), 1556 (w, arom. C=C), 1479 (m), 1462 (m),
1393 (w), 1365 (w), 1202 (m), 1100 cm–1 (w).
1H NMR (300 MHz, CDCl3): δ = 1.2–1.4 [m, 36 H, C(CH3)3]; 7.15–
8.45 (m, 8 H, arom. H).
1H NMR (300 MHz, CDCl3): δ = 0.36 [s, 18 H, Si(CH3)3]; 7.26 (dt,
3J = 7.6 Hz, 4J = 1.2 Hz, 2 H, arom. H); 7.36 (dt, 3J = 7.4 Hz, 4J = 1.1
Hz, 2 H, arom. H); 7.64 (d, 3J = 7.6 Hz, 2 H, arom. H); 8.68 (d, 3J =
7.9 Hz, 2 H, arom. H).
13C NMR (75.43 MHz, CDCl3): δ = 27.5 [C(CH3)3]; 31.9 [C(CH3)3];
83.4, 107.4 [C≡C–C(CH3)3, C≡C–C(CH3)3]; 102.4 (C-11,12); 123.6,
132.9, 134.2 (arom. C); 153.6 (C-9,10).

SYNTHESIS
Papers
1366
MS (EI): m/z (%) = 524 (100) [M]+, 523 (11), 522 (28), 455 (3), 444
(5), 341 (3), 329 (3), 327 (3).
HRMS: m/z = calcd for C40H44: 524.3443; found: 524.3442.
MS (EI): m/z (%) = 488 (100) [M]+, 422 (6), 420 (5), 398 (17), 397
(13), 396 (4), 352 (10), 351 (8), 323 (16), 305 (25), 298 (17), 230 (3).
HRMS: m/z = calcd for C28H40Si4: 488.2207; found: 488.2206.
9,10-Bis[bis(trimethylsilylsilylethynyl)methylene]-9,10-dihy-
droanthracene (8c):
We would like to thank BASF AG, Bayer AG and Hoechst Marion
Roussel AG, the Verband der Chemischen Industrie, Fonds der Che-
mie as well as the Deutsche Forschungsgemeinschaft for support of
this work. Thanks to Hewlett Packard for providing a UV-vis spectro-
photometer. We would also like to thank Ms. U. Hertle and Dr. W.
Kramer for NMR measurements and Mr. H. Rudy and Mr. P. Weyrich
for mass spectra and elemental analyses. Dr. Amanda G. Brynant-
Friedrich is thanked for helpful discussions.
From 4 (0.25 g, 0.48 mmol) and trimethylsilylacetylene (0.47 g,
4.8 mmol); yield: 74 mg (26%); yellow crystals; mp 129°C.
UV-vis (hexane): λ (log ε) = 246 (3.42), 279 nm (4.09).
IR (KBr): ν = 3061 (w, arom. C–H), 2957 (m, aliphat. C–H), 2919 (m,
aliphat. C–H), 2849 (m), 2143 (m, C≡C), 1460 (w), 1449 (m), 1407
(w), 1247 (s), 1206 (s), 1123 (w), 1064 cm–1 (w).
1H NMR (300 MHz, CDCl3): δ = 0.23 [s, 36 H, Si(CH3)3]; 7.25–8.30
(m, 8 H, arom. H).
13C NMR (75.43 MHz, CDCl3): δ = –0.43 [Si(CH3)3]; 65.8 (C-11,12);
100.3, 103.6 (C≡C–SiMe3, C≡C–SiMe3); 126.7, 127.0, 134.0 (arom.
C); 147.3 (C-9,10).
(1) Neidlein, R.; Kux, U. Angew. Chem. 1993, 105, 1381; Angew.
Chem., Int. Ed. Engl. 1993, 32, 1324, and references cited therein.
Kux, U. Dissertation, Universität Heidelberg, 1993.
Neidlein, R.; Kux, U. Chem. Ber. 1994, 127, 1523; and references
cited therein.
MS (EI): m/z (%) = 591 (4), 590 (14), 589 (26) [M]+, 588 (48), 572
(3), 493 (3), 492 (5) [M – C≡C–SiMe3]+, 427 (1), 397 (2), 155 (1), 97
(2), 73 (100) [SiMe3]+, 59 (2), 45 (6).
Neidlein, R.; Kux, U. Helv. Chim. Acta 1994, 77, 1051.
Neidlein, R.; Gürtler, S. Synthesis 1995, 325.
HRMS: m/z = calcd for C36H44Si2: 588.2520; found: 588.2519.
Neidlein, R.; Gürtler, S. Synthesis 1995, 1389.
Gürtler, S. Dissertation, Universität Heidelberg, 1994.
(2) Bryant-Friedrich, A.C.; Neidlein, R. Synthesis 1995, 1506.
Bryant-Friedrich, A.C.; Neidlein, R. Helv. Chim. Acta 1997, 80,
128.
1,4-Bis[bis(phenylethynyl)methylene]cyclohexa-2,5-diene (9a):
DDQ (0.24 g, 1.06 mmol) was added to a solution of 5a (0.1 g,
0.26 mmol) in anhyd xylene (30 mL). The mixture was heated to re-
flux for 24 h and filtered after cooling; the solvent was evaporated in
vacuo and the residue absorbed on Celite. Column chromatography
(silica gel, hexane/EtOAc 10:1) gave an orange zone, evaporation of
the solvent in vacuo and recrystallization from Et2O yielded 9a
(85 mg, 64%); light orange needles; mp 105°C.
Bryant-Friedrich, A.C.; Neidlein, R. Helv. Chim. Acta 1997, 80,
1639.
Bryant-Friedrich, A.C., Dissertation, Universität Heidelberg,
1997.
(3) (a) Diederich, F.; Rubin, Y.; Knobler, C. B.; Whetten, R. L.;
Schriver, K. E.; Houk, K. N.; Li, Y. Science 1989, 245, 1088.
(b) Diederich, F.; Rubin, Y. Angew. Chem. 1992, 104, 1123; An-
gew. Chem., Int. Ed. Engl. 1992, 31, 1101.
UV-vis (hexane): λ (log ε) = 273 (4.392), 334 (3.467), 582 nm
(4.073).
IR (KBr): ν = 3057 (w, C–H), 3050 (w, C–H), 3046 (w, C–H), 2092
(m, C≡C), 1704 (w), 1630 (w), 1596 (m, arom. C=C), 1578 (w, arom.
C=C), 1566 (m, arom. C=C), 1489 (m), 1441 (m), 1333 (s), 1258 (w),
1205 (w), 1168 cm–1 (m).
(c) Diederich, F. Nature (London) 1994, 369, 199.
(d) Diederich, F.; Rubin, Y.; Chapman, O. L.; Goroff, N. S. Helv.
Chim. Acta 1994, 77, 1441.
1H NMR (300 MHz, CDCl3): δ = 6.53 (s, 4 H, H-2,3,5,6); 7.30–7.39
(m, 20 H, arom. H).
(4) Rubin, Y.; Knobler, C. B.; Diederich, F. Angew. Chem. 1991,
103, 708; Angew. Chem., Int. Ed. Engl. 1991, 30, 698.
Anthony, J.; Knobler, C.; Diederich, F. Angew. Chem. 1993, 105,
437; Angew. Chem., Int Ed. Engl. 1993, 32, 406.
van Loon, J. D.; Seiler, P.; Diederich, F. Angew Chem 1993, 105,
1235; Angew. Chem., Int. Ed. Engl. 1993, 32, 1187.
Anthony, J.; Boldi, A.; Rubin, Y.; Hobi, M.; Gramlich, V.; Knob-
ler, C.B.; Seiler, P.; Diederich, F. Helv. Chim. Acta 1995, 78, 13.
Faust, R.; Diederich, F.; Gramlich, V.; Seiler, P. Chem. Eur. J.
1995, 1, 111.
Tykwinski, R. R.; Schreiber, M.; Perez Carlon, M.; Diederich, F.;
Gramlich, V. Helv. Chim. Acta 1996, 79, 2249.
Tykwinski, R. R.; Diederich, F. Liebigs Ann. Chem. 1997, 649.
(5) Ried, W.; Appel, H. Liebigs Ann. Chem. 1964, 679, 51.
(6) Corey, E. J.; Fuchs, P. L. Tetrahedron Lett. 1972, 1373.
Posner, G. H.; Loomis, G. L.; Sawaya, H. S. Tetrahedron Lett.
1975, 1373.
13C NMR (75.43 MHz, CDCl3): δ = 82.6 (C-7,8); 105.8, 111.4
(C≡C–Ph, C≡C–Ph); 120.9, 129.8, 130.0, 131.6, 137.1 (arom. C);
149.5 (C-1,4).
MS (EI): m/z (%) = 504 (100) [M]+, 503 (20), 502 (9), 428 (12), 427
(23), 424 (20), 393 (10), 377 (6), 306 (14), 305 (12), 291 (26), 229
(20), 228 (18), 202 (32).
HRMS: m/z = calcd for C40H24: 504.1878; found: 504.1877.
1,4-Bis[bis(trimethylsilylethynyl)methylene]cyclohexa-2,5-diene
(9b):
DDQ (60 mg, 0.27 mmol) was added to a solution of 5d (0.1 g,
0.19 mmol) in anhyd xylene (25 mL). The mixture was heated to re-
flux for 24 h and filtered after cooling; the solvent was evaporated in
vacuo and the residue absorbed on Celite. Column chromatography
(silica gel, hexane) gave a yellow zone, evaporation of the solvent in
vacuo and recrystallization from Et2O/hexane yielded 9b (39 mg,
42%); orange needles; mp 97°C.
Mitchell, T. N.; Reimann, W. Organometallics 1986, 5, 1991.
Grandjean, D.; Pale, P.; Chuche, J. Tetrahedron Lett. 1994, 3529.
(7) Stephens, R. D.; Castro, C. E. J. Org. Chem. 1963, 38, 3313.
Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett.
1975, 4467.
UV-vis (hexane): λ (log ε) = 270 (4.32), 326 (3.67), 565 nm (3.84).
IR (film): ν = 3067 (w, C–H), 3055 (w), 2110 (m, C≡C), 1689 (m),
1593 (m, arom. C=C), 1542 (w), 1464 (m), 1377 (w), 1342 (w), 1292
(w), 1248 (w), 1225 (w), 1135 (m), 1075 (m), 1024 (w).
1H NMR (300 MHz, CDCl3): δ = 0.03 [s, 36 H, Si(CH3)3]; 6.91 (s, 4
H, H-2,3,5,6).
Tohda, Y.; Sonogashira, K.; Hagihara, N. Synthesis 1977, 777.
Austin, W. B.; Bilow, N.; Kellaghan, W. J.; Lau, K. S. Y. J. Org.
Chem. 1981, 46, 2280.
Satoh, Y.; Serizawa, H.; Miyaura, N.; Hara, S.; Suzuki, A. Tetra-
hedron Lett. 1988, 29, 1811.
13C NMR (75.43 MHz, CDCl3): δ = –0.01 [Si(CH3)3]; 102.8, 104.7
(C≡C–SiMe3, C≡C–SiMe3); 116.3 (C-7,8); 141.2 (C-2,3,5,6); 157.6
(C-1,4).