Sterically stabilized p-quinodimethanes by nucleophilic aromatic substitution

Article abstract of DOI:10.1002/ejoc.200600002

Triarylmethyl cations with a sterically shielded cationic center react with selected C- and N-nucleophiles under nucleophilic aromatic substitution. The resulting dipolar p-quinodimethanes represent highly functionalized extended π systems. Wiley-VCH Verl

Full text of DOI:10.1002/ejoc.200600002

FULL PAPER
DOI: 10.1002/ejoc.200600002
Sterically Stabilized p-Quinodimethanes by Nucleophilic Aromatic Substitution
Gerald Dyker,*[a] Marcel Hagel,[a] Oliver Muth,[a] and Christian Schirrmacher[a]
Keywords: Carbocations / Extended π systems / Nucleophilic Aromatic Substitution / p-Quinodimethanes
Triarylmethyl cations with a sterically shielded cationic cen- (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
ter react with selected C- and N-nucleophiles under nucleo-
philic aromatic substitution. The resulting dipolar p-quinodi-
methanes represent highly functionalized extended π sys-
tems.
Germany, 2006)
The importance of p-quinonoid compounds is based on benzylic cations 1 is of course strongly influenced by elec-
their general tendency to aromatize, thus exhibiting a high tronic effects of attached functional groups,[4] however, ste-
reactivity combined with interesting electronic properties. p- ric influence can be even more important for the regioselec-
Quinodimethanes, for instance, are regularly generated as tivity of a nucleophilic attack: while structure 3 represents
reactive intermediates for polymerization or cyclic oligo- the ordinary product[5] from the reaction with nucleophiles
merization reactions,[1] the latter being a versatile entry to 2, bulky groups R and/or RЈ should be able to favor attack
the strained [2.2]paracyclophanes.[2] With the ultimate goal in para position to give the intermediates 4. With a remain-
to synthesize extended conjugated π systems with multiple ing hydrogen atom at the nucleophilic center the final elimi-
coordination sites[3] for transition metals, we envisioned the nation should give the desired p-benzoquinodimethanes 5,[6]
nucleophilic aromatic substitution at triarylmethyl cations which are anticipated to be rather dipolar because of the
to be a versatile entry to dipolar p-quinodimethanes, a con- general acceptor character of the double-bonded “Nu”-
cept, which is depicted in Scheme 1. The electrophilicity of group. Triarylmethyl cations were chosen as easily access-
ible model compounds. Examples for the nucleophilic aro-
matic substitution at triarylmethyl cations are still very rare
in literature,[7] especially with C-nucleophiles.[8] A general
preparative investigation of scope and limitations of the
concept in Scheme 1 is clearly missing.
Results and Discussion
The dianisyl-substituted triarylmethyl salts 8 are ef-
ficiently accessible in just two preparative steps starting
from the corresponding benzophenone 6 (Scheme 2). The
reaction with malononitrile under basic conditions either
leads to the quarternary-centered products 9, or to the de-
sired p-quinodimethanes 10, depending on the steric hin-
drance at the central carbon atom: obviously both, the mes-
ityl- (in 8b) and the 9-anthryl substituent (in 8d) are bulky
enough for effectively shielding the benzylic position. How-
ever, the anthryl group itself was not completely inert, al-
lowing the formation of the semi-quinonoid by-product 11
(Scheme 3), which was identified by the diagnostic AB sig-
nal of the two methine protons at 4.23/4.44 ppm (J =
10 Hz). In order to enhance the structural diversity of appli-
cable C-nucleophiles bis(4-nitrophenyl)methane and fluo-
rene were tested in the reaction with 8b, leading to the suc-
cessful isolation of the extended π systems 12 and 13.
Scheme 1. Reaction pathways for the nucleophilic attack on ben-
zylic cations.
[a] Fakultät für Chemie, Ruhr-Universität Bochum,
Universitätsstrasse 150, 44780 Bochum, Germany
Fax: +49-234-32-14353
E-mail: gerald.dyker@ruhr-uni-bochum.de
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Sterically Stabilized p-Quinodimethanes by Nucleophilic Aromatic Substitution
FULL PAPER
Scheme 2. Dianisyl-substituted benzylic cations: product ratio in relation to steric hindrance.
Scheme 3. Additional products from dianisyl-substituted carbocations.
As model substrates for the synthesis of conjugated π
The bis(fluorophenyl)-substituted salt 25 is interesting
systems with coordinated metals we chose the ferrocenyl- both, from a spectroscopic and from a chemical point of
substituted triarylmethyl cations 18 and 19, which are view. The 1H and 13 C spectra in CDCl3 exhibit some broad
known as being especially stabilized and might be regarded signals and doubled sets of signals (in addition to C–F and
as cationic fulvene–iron complexes.[9] Nevertheless, the fluo- H–F couplings); presumably reversible coordination of
rophenyl group should guarentee a higher reactivity water is responsible for these dynamic NMR effects. Under
towards nucleophilic substitution and was compatible with neutral conditions 25 is not sensitive towards hydrolysis. We
the rather short synthetic pathways depicted in Scheme 4. tested 25 as substrate for a twofold nucleophilic aromatic
The steric hindrance of the two ferrocenyl substituents of substitution. Indeed, at room temperature an excess of de-
18 obviously is not sufficient for preventing the conven- protonated malononitrile gives the monosubstitution prod-
tional CC and CN bond formation[10] with relatively small uct 28. According to preliminary results the elevated tem-
nucleophiles like malononitrile and 8-aminoquinoline lead- perature of refluxing tetrahydrofuran is necessary. Under
ing to 20 and 21, respectively. On the other hand, the mes- the basic reaction conditions the crude product exhibits the
ityl group of 19 is an effective control element leading to intensive green color of the anion 26, with two symmetrical
the desired p-quinonoid compounds 22 and 23, the latter as dicyanomethyl-substituted phenylene groups according to
a 1:1 mixture of stereoisomers. The metallic lustre and deep 1H NMR spectroscopy. Acidification leads to the orange to
green (22) or purple color (23) of their crystals are macro- red neutral quinodimethane 27, which shows signals of two
1
scopic effects of the polar extended π systems.
distinguished phenylene groups in the H NMR spectrum
Eur. J. Org. Chem. 2006, 2134–2144
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G. Dyker, M. Hagel, O. Muth, C. Schirrmacher
FULL PAPER
Scheme 4. Test reactions with ferrocenyl-4-fluorophenyl-substituted benzylic cations (Fer = ferrocenyl); a: 3 equiv. ferrocenyl-Li, THF; b:
AlCl3, CH2Cl2; c: mesityllithium, THF; d: HBF4–diethyl ether, CH2Cl2; e: malononitrile, NaH, THF; f: 8-aminoquinoline, NaH, THF.
in CDCl3 solution. The signal of the CH(CN)2-group, regis- we are investigating the amphoteric behavior of 27 and the
tered at δ = 5.88 ppm, is very broad due to dynamic effects, complexating ability of tetracyano-substituted anion 26 for
presumably in connection with the acidity of 27. Currently transition metal cations (Scheme 5).
Scheme 5. Twofold SNAr reaction with a bis(fluorophenyl)-substituted benzylic cation; a: HBF4–etherate, CH2Cl2; b: malononitrile, NaH,
THF.
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Sterically Stabilized p-Quinodimethanes by Nucleophilic Aromatic Substitution
FULL PAPER
IR (KBr): ν = 3057 cm–1 (w), 3012 (w), 2949 (w), 2844 (w), 2727
˜
Conclusion
(w), 1606 (m), 1577 (s), 1507 (m), 1449 (m), 1373 (s), 1297 (s), 1164
(s), 1124 (s), 1084 (s), 1038 (m), 1005 (m), 916 (w), 853 (w), 833
(w), 756 (w), 595 (w). UV (acetonitrile): λmax (lgε) = 194 nm (4.77),
Functionalized p-quinodimethanes are easily accessible
by nucleophilic aromatic substitution with triarylmethyl
salts, sterically hindered at the central carbocation. This
method is compatible even with ferrocenyl substituents.
With two 4-fluorophenyl substituents – such as in 25 – it is
possible to perform two nucleophilic substitution reactions
successively, leaving the p-quinodimethane moiety intact.
Thus, we intend to use compound 25 as key substrate for
the synthesis of various donator-acceptor substituted p-qui-
nodimethanes.
1
253 (3.92, sh), 268 (4.07), 417 (4.22), 503 (4.89). H NMR (CDCl3,
500 MHz): δ = 1.94 ppm (s, 3 H, CH3), 4.17 (s, 6 H, OCH3), 7.11
(dd, J = 7.7, 1.4 Hz, 1 H), 7.36 (d, J = 8.7 Hz, 4 H), 7.41 (“t”, “J”
= 7.6 Hz, 1 H), 7.47 (d, J = 7.0 Hz, 1 H), 7.66 (“d”, br, “J” =
6.4 Hz, 4 H), 7.70 (dt, J = 7.5, 1.4 Hz, 1 H). 13C NMR (CDCl3,
125 MHz): δ = 20.93 ppm (q), 57.70 (q), 117.85 (d), 126.22 (d),
132.19 (d), 132.86 (s), 135.03 (d), 135.92 (d), 139.08 (s), 141.81 (s),
143.92 (d), 173.04 (s), 194.50 (s). MS (EI = 70 eV): m/z (%) = 337
(13), 336 (54) [M+ – BF3], 319 (9), 318 (41), 317 (48) [M+-BF4],
305 (11), 303 (16), 302 (34), 287 (17), 246 (17), 245 (100), 243 (12),
229 (17), 228 (12), 227 (31), 215 (10), 209 (16), 197 (10), 179 (14),
165 (11). C22H21BF4O2 (404.21): calcd. C 65.37, H 5.24; found C
65.08, H 5.21.
Experimental Section
General Remarks: M.p. (uncorrected): Reichert Thermovar. IR:
Perkin–Elmer 841 and 983. NMR: Bruker DPX-200, WM-300,
DRX-400, AM-500. 1H NMR spectra were recorded in CDCl3
with TMS as the internal standard. 13C NMR spectra were mea-
sured by using CDCl3 as the solvent and the internal standard.
MS: MAT 700 ITD (70 eV) and Varian MAT 311 A. For analytical
TLC precoated plastic sheets “POLYGRAM SIL G/UV254” from
“Macherey–Nagel” were used. EA: Elementar/Hanau Vario EL.
Bis(4-methoxyphenyl)(2,4,6-trimethylphenyl)methanol (7b): To
a
solution of 2-bromomesitylene (818 mg, 0.62 mL, 4.13 mmol) in
15 mL of dry THF a 15% solution of n-butyllithium in hexane
(2.8 mL, 4.5 mmol) was added within 5 min at –60 °C under argon.
After 1 h of stirring at –60 °C to –35 °C a solution of 4,4Ј-dimeth-
oxybenzophenone (6, 1.00 g, 4.13 mmol) in 20 mL of dry THF was
added dropwise within 15 min, and the reaction mixture was stirred
at room temperature for another 3.5 d. After hydrolysis with 20 mL
of a saturated aqueous (NH4)2HPO4 solution, the water layer was
extracted three times with 20 mL of dichloromethane and the com-
bined organic layers were dried with sodium sulfate, and the sol-
vents evaporated to dryness at the rotary evaporator: TLC (silica/
diethyl ether/hexane, 1:1) of the crude product: Rf = 0.37, 0.23. The
fraction with Rf = 0.37 was isolated by flash chromatography:
1.02 g (68%) of 7b as a reddish solid with m.p. 134–137 °C. IR
Bis(4-methoxyphenyl)-(2-methylphenyl)methanol (7a): To a solution
of 2-bromotoluene (700 mg, 0.49 mL, 4.05 mmol) in 20 mL of dry
THF, a 15% solution of n-butyllithium in hexane (2.63 mL,
4.2 mmol) was added within 5 min at –70 °C under argon. After
1 h of stirring at –70 °C to –55 °C a solution of 4,4Ј-dimethoxybe-
nzophenone (6, 1.01 g, 4.17 mmol) in 20 mL of dry THF was added
dropwise within 15 min and the reaction mixture was stirred at
room temperature for another 1.5 d. After hydrolysis with 20 mL
of a saturated aqueous (NH4)2HPO4 solution water layer was ex-
tracted three times with 20 mL of dichloromethane and the com-
bined organic layers were dried with sodium sulfate. Then the sol-
vents were evaporated to dryness at the rotary evaporator: TLC
(silica/diethyl ether/hexane, 1:1) of the crude product: Rf = 0.46,
0.35. The fraction with Rf = 0.46 was isolated by flash chromatog-
raphy: 920 mg (68%) of 7a a slightly yellow solid with m.p. 104 °C.
(KBr): ν = 2997 cm–1 (w), 2956 (w), 2933 (w), 2836 (w), 1608 (m),
˜
1582 (w), 1507 (s), 1462 (m, br), 1295 (m), 1249 (s), 1176 (s), 1115
(w), 1033 (m), 997 (w), 832 (m), 594 (w). UV (acetonitrile):
λmax (lgε) = 201 nm (4.88), 228 (4.35), 277 (3.22). 1H NMR
(CDCl3, 300 MHz): δ = 1.87 ppm (s, 6 H), 2.26 (s, 3 H), 2.65 (s, 1
H, OH), 3.80 (s, 6 H), 6.80 (s, 2 H), 6.82 (d, J = 9.0 Hz, 4 H), 7.13
(d, J = 9.0 Hz, 4 H). 13C NMR (CDCl3, 75.5 MHz): δ = 20.50 ppm
(q), 24.31 (q), 55.32 (q), 83.08 (s, C–OH), 113.52 (d), 129.12 (d),
131.34 (d), 136.09 (s), 138.17 (s), 140.44 (s), 141.58 (s), 158.88 (s).
MS (EI = 70 eV): m/z (%) = 363 (8) [M+ + 1], 362 (28) [M+], 346
(26), 345 (93), 331 (15), 330 (52), 315 (10), 255 (12), 253 (13), 244
(17), 243 (100), 237 (15), 223 (11), 222 (15), 215 (17), 214 (23), 179
(10), 165 (10), 149 (12), 147 (45), 136 (12), 135 (90), 121 (20), 77
(12). C24H26O3 (362.47): calcd. C 79.53, H 7.23; found C 79.34, H
7.28.
IR (KBr): ν = 3059 cm–1 (w), 3006 (w), 2957 (w), 2933 (w), 2836
˜
(w), 1608 (m), 1508 (s), 1462 (w), 1295 (m), 1252 (s), 1178 (s), 1032
(m), 831 (m), 763 (w), 610 (w), 588 (w). UV (acetonitrile): λmax (lgε)
= 198 nm (4.95), 228 (4.35, sh), 276 (3.53), 284 (3.46). 1H NMR
(CDCl3, 500 MHz): δ = 2.15 ppm (s, 3 H, CH3), 2.90 (s, 1 H, OH),
3.79 (s, 6 H, OCH3), 6.76 (dd, J = 7.8, 1.2 Hz, 1 H), 6.83 (d, J =
9.0 Hz, 4 H), 7.00–7.04 (m, 1 H), 7.12 (d, J = 9.1 Hz, 4 H), 7.15–
7.20 (m, 2 H). 13C NMR (CDCl3, 125 MHz): δ = 22.14 ppm (q,
CH3), 55.25 (q, OCH3), 82.55 (s, C–OH), 113.19 (d), 124.88 (d),
127.66 (d), 128.90 (d), 129.42 (d), 132.46 (d), 137.93 (s), 139.21 (s),
Bis(4-methoxyphenyl)(2,4,6-trimethylphenyl)methylium Tetrafluo-
roborate (8b): To a solution of the triarylmethyl alcohol 7b (300 mg,
0.828 mmol) in 3 mL of dry dichloromethane HBF4–diethyl ether
(0.33 mL, 2.4 mmol) was added at room temperature under nitro-
gen. After 10 min stirring at room temperature a layer of 9 mL of
diethyl ether was placed carefully on the surface of the reaction
mixture, leading to the formation of an oily precipitate within 1 d,
which solidified upon washing five times with 10 mL diethyl ether
and drying in vacuo (60 °C/0.04 mbar): 319 mg (89%) of 8b as an
144.91 (s), 158.53 (s). MS (EI = 70 eV): m/z (%) = 335 (9) [M+
+
1], 334 (35) [M+], 318 (10), 317 (25), 244 (18), 243 (100), 227 (18),
215 (15), 135 (83), 119 (13), 108 (9), 107 (14), 91 (13), 77 (15).
C22H22O3 (334.41): calcd. C 79.01, H 6.63; found C 79.04, H 6.58
Bis(4-methoxyphenyl)(2-methylphenyl)methylium Tetrafluoroborate
(8a): To a solution of the triarylmethyl alcohol 7a (600 mg,
1.79 mmol) in 5 mL of dry dichloromethane HBF4–diethyl ether
(0.63 mL, 4.6 mmol) was added at room temperature under nitro-
gen. After 10 min stirring at room temperature a layer of 15 mL of
diethyl ether was placed carefully on the surface of the reaction
mixture, leading to the formation of a solid precipitate within 1 d,
which was isolated by filtration and washing with 5 mL of diethyl
ether: 607 mg (84%) of 8a as a red to orange solid with m.p. 140 °C.
orange solid with m.p. 160–163 °C. IR (KBr): ν = 2944 cm–1 (w),
˜
2850 (w), 1626 (w), 1603 (m), 1576 (s), 1501 (w), 1444 (w), 1372
(s), 1316 (m), 1280 (s), 1160 (s), 1124 (s), 1084 (s), 1064 (w), 1036
(w), 1005 (w), 911 (w), 855 (w), 590 (w). UV (acetonitrile):
λmax (lgε) = 197 nm (4.88), 255 (3.97, sh), 270 (4.16), 330 (3.86),
442 (4.06, sh), 510 (4.96). 1H NMR (CDCl3, 500 MHz): δ =
1.81 ppm (s, 6 H), 2.42 (s, 3 H), 4.17 (s, 6 H), 7.05 (s, 2 H), 7.35
Eur. J. Org. Chem. 2006, 2134–2144
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G. Dyker, M. Hagel, O. Muth, C. Schirrmacher
FULL PAPER
(br. s, 4 H), 7.74 (br. s, 4 H). 13C NMR (CDCl3, 125 MHz): δ =
20.64 ppm (q), 21.39 (q) 57.78 (q, OCH3), 118.29 (d, broad), 129.71
(d), 133.01 (s), 136.09 (s), 138.68 (s), 143.51 (s), 173.40 (s), 195.02
(s). MS (EI = 70 eV): m/z (%) = 346 (30) [M+ + 1 – BF4], 345 (100)
9-Anthryl-bis(4-methoxyphenyl)methanol (7d): To a solution of 9-
bromoanthracene (1.12 g, 4.13 mmol) in 20 mL of dry THF, a 15%
solution of n-butyllithium in hexane (2.8 mL, 4.5 mmol) was added
within 5 min at –60 °C under argon. After 30 min of stirring at
[M+-BF4], 343 (10), 331 (16), 330 (51), 315 (11), 287 (9), 272 (6), –35 °C a solution of 4,4Ј-dimethoxybenzophenone (6, 1.00 g,
237 (9), 227 (6), 222 (11), 179 (6), 165 (7), 121 (6). C24H25BF4O2 4.13 mmol) in 25 mL of dry THF was added dropwise within
(432.27): calcd. C 66.69, H 5.83; found C 66.69, H 5.81.
15 min, and the reaction mixture was warmed up to room tempera-
ture within 1.5 d and was stirred for another 2 h at 50 °C. After
hydrolysis with 20 mL of a saturated aqueous (NH4)2HPO4 solu-
tion water layer was extracted three times with 20 mL of dichloro-
methane and the combined organic layers were dried with sodium
sulfate, and the solvents evaporated to dryness at the rotary evapo-
rator: TLC (silica/diethyl ether/hexane, 1:1) of the crude product:
Rf = 0.74 (anthracene), 0.49, 0.43 (6). The fraction with Rf = 0.43–
0.49 was isolated by flash chromatography and recrystallized from
diethyl ether/n-hexane (2:3): 1.14 g (66%) of 7d as colorless solid
Bis(4-methoxyphenyl)(1-naphthyl)methanol (7c): To a solution of 1-
bromonaphthalene (500 mg, 2.42 mmol) in 10 mL of dry THF a
15% solution of n-butyllithium in hexane (1.6 mL, 2.6 mmol) was
added within 5 min at –70 °C under argon. After 1 h of stirring
at –60 °C a solution of 4,4Ј-dimethoxybenzophenone (6, 585 mg,
2.42 mmol) in 15 mL of dry THF was added dropwise within
15 min, and the reaction mixture was warmed up to room tempera-
ture within 20 h and was stirred for another 2 h at 50 °C. After
hydrolysis with 20 mL of a saturated aqueous (NH4)2HPO4 solu-
tion water layer was extracted three times with 20 mL of dichloro-
methane and the combined organic layers were dried with sodium
sulfate and the solvents evaporated to dryness at the rotary evapo-
rator: TLC (silica/diethyl ether/hexane, 1:1) of the crude product:
Rf = 0.75, 0.41, 0.33. The fraction with Rf = 0.41 was isolated by
flash chromatography: 765 mg (86%) of 7c as colorless solid with
with m.p. 101 °C. IR (KBr): ν = 3045 cm–1 (w), 3002 (w), 2933 (w),
˜
2836 (w), 1604 (m), 1506 (s), 1459 (w), 1443 (w), 1304 (m, sh), 1251
(s), 1176 (s), 1033 (m), 929 (w), 890 (w), 833 (m), 771 (w), 739 (w),
606 (w), 583 (w). UV (acetonitrile): λmax (lgε) = 196 nm (4.86), 226
(4.48), 258 (4.85), 284 (4.24), 337 (3.34), 353 (3.55), 371 (3.70), 392
1
(3.65). H NMR (CDCl3, 300 MHz): δ = 2.99 ppm (s, 1 H, OH),
3.78 (s, 6 H), 6.81 (d, J = 8.9 Hz, 4 H), 7.05 (“ddd”, “J” = 7.9, 6.5,
1.4 Hz, 2 H), 7.21 (d, J = 9.0 Hz, 4 H), 7.23–7.31 (m, 2 H), 7.90–
7.95 (m, 4 H), 8.42 (s, 1 H). 13C NMR (CDCl3, 75.5 MHz): δ =
55.26 ppm (q, OCH3), 83.49 (s, C–OH), 113.70 (d), 123.93 (d),
124.17 (d), 128.17 (d), 128.65 (d), 128.93 (d), 129.12 (d), 130.75 (s),
132.09 (s), 139.49 (s), 141.05 (s), 158.82 (s). MS (EI = 70 eV):
m/z (%) = 420 (20) [M+], 404 (34), 403 (76), 389 (32), 388 (100),
387 (9), 359 (14), 315 (10), 313 (28), 312 (79), 295 (11), 281 (24),
253 (23), 252 (26), 243 (11), 178 (18), 135 (79). C29H24O3 (420.51):
calcd. C 82.83, H 5.75; found C 82.64, H 5.84
m.p. 158 °C. IR (KBr): ν = 3049 cm–1 (w), 3003 (w), 2956 (w), 2836
˜
(w), 1607 (m), 1583 (w), 1507 (s), 1459 (w), 1297 (m), 1250 (s), 1177
(s), 1034 (m), 1005 (w), 835 (m), 805 (m), 787 (w), 778 (m), 609
(w), 589 (w). UV (acetonitrile): λmax (lgε) = 197 nm (4.84), 204
(4.81, sh), 222 (4.85, sh), 227 (4.88), 273 (3.99, sh), 281 (4.05), 293
1
(3.80, sh). H NMR (CDCl3, 300 MHz): δ = 3.25 ppm (br. s, 1 H,
OH), 3.79 (s, 6 H), 6.83 (d, J = 8.9 Hz, 4 H), 6.88 (d, J = 7.4 Hz,
1 H), 7.18 (d, J = 8.9 Hz, 4 H), 7.20–7.29 (m, 2 H), 7.38 (ddd, “J”
= 8.1, 5.7, 1.2 Hz, 1 H), 7.81 (“dd”, “J” = 8.2, 7.2 Hz, 2 H), 8.13
(d, J = 8.7 Hz, 1 H). 13C NMR (CDCl3, 125 MHz): δ = 55.25 ppm
(q), 82.84 (s), 113.29 (d), 124.27 (d), 125.27 (d), 125.50 (d), 128.01 9-Anthryl-bis(4-methoxyphenyl)methylium Tetrafluoroborate (8d):
(d), 128.19 (d), 128.80 (d), 128.97 (d), 129.23 (d), 131.39 (s), 134.96 To a solution of the triarylmethyl alcohol 7d (450 mg, 1.07 mmol)
(s), 139.60 (s), 142.54 (s), 158.56 (s). MS (EI = 70 eV): m/z (%) =
370 (24) [M+], 354 (21), 353 (39), 263 (21), 262 (43), 261 (9),
245 (19), 244 (8), 243 (50), 231 (12), 215 (13), 202 (11), 155 (11),
in 3 mL of dry dichloromethane, HBF4–diethyl ether (0.50 mL,
3.7 mmol) was added at room temperature under nitrogen. After
5 min stirring at room temperature a layer of 10 mL of diethyl ether
136 (9), 135 (100), 128 (9), 127 (15), 107 (10), 77 (14). C25H22O3 was carefully placed on the surface of the reaction mixture, leading
(370.45): calcd. C 81.06, H 5.99; found C 81.08, H 5.95.
to the formation of an oily precipitate within 1 d, which solidified
upon washing five times with 10 mL diethyl ether in the ultrasonic
bath: 363 mg (69%) of 8d as dark green, metallic shining solid with
Bis(4-methoxyphenyl)(1-naphthyl)methylium Tetrafluoroborate (8c):
To a solution of the triarylmethyl alcohol 7c (630 mg, 1.70 mmol)
in 7 mL of dry dichloromethane, HBF4–diethyl ether (0.85 mL,
6.3 mmol) was added at room temperature under nitrogen. After
30 min stirring at room temperature a layer of 15 mL of pentane
was placed on the surface of the reaction mixture, leading to the
formation of an oily precipitate within 1 d. Recrystallization from
dichloromethane/diethyl ether gave 699 mg (93%) of 8c as dark
m.p. 115–120 °C. IR (KBr): ν = 3050 cm–1 (w), 2933 (w), 2847 (w),
˜
2731 (w), 1624 (m), 1605 (m), 1575 (s), 1443 (m), 1369 (s), 1280 (s),
1157 (s), 1123 (m), 1084 (s), 1003 (m), 910 (m), 863 (w), 841 (m),
742 (w), 600 (w). UV (acetonitrile): λmax (lgε) = 253 nm (5.09), 342
(4.14, sh), 369 (4.22), 388 (4.17, sh), 519 (4.90), 685 (3.70). 1H
NMR (CDCl3, 300 MHz): δ = 4.16 ppm (s, 6 H, OCH3), 7.29 (dd,
J = 8.9, 0.7 Hz, 4 H), 7.27–7.32 (br. m, 2 H), 7.41 (“ddd”, “J” =
7.9, 6.6, 1.3 Hz, 2 H), 7.54 (“ddd”, “J” = 8.4, 6.7, 1.0 Hz, 2 H),
7.75 (“s”, br, 4 H), 8.14 (d, J = 8.5 Hz, 2 H), 8.83 (s, 1 H). 13C
NMR (CDCl3, 125.8 MHz): δ = 57.85 ppm (q, OCH3), 118.49 (d),
125.53 (d), 126.25 (d), 129.11 (d), 130.79 (s), 132.58 (s), 132.70 (s),
134.30 (d), 134.88 (s), 173.51 (s), 191.50 (s). MS (EI = 70 eV):
m/z (%) = 404 (10), 403 (13) [M+ – BF4], 402 (11), 389 (32), 388
(100), 387 (11), 359 (15), 313 (10), 281 (21), 253 (18), 252 (21), 150
(12). C29H23BF4O2 (490.31): calcd. C 71.04, H 4.73; C29H23BF4O2
0.25 H2O (494.81): calcd. C 70.39, H 4.79; found C 70.43, H 4.59.
HRMS: calcd. 403.1698; found 403.1628.
green, metallic shining needles with m.p. 182–185 °C. IR (KBr): ν
˜
= 3056 cm–1 (w), 2937 (w), 2840 (w), 1605 (m), 1577 (s), 1505 (m),
1441 (m, br), 1373 (s), 1315 (m), 1279 (s, br), 1255 (w), 1161 (s),
1124 (s), 1084 (s, br), 1006 (m), 912 (w), 851 (w, br), 807 (w), 781
(w), 578 (w). UV (acetonitrile): λmax (lgε) = 204 nm (4.63, sh), 219
1
(4.71), 279 (4.07), 339 (3.87), 388 (3.63, sh), 494 (4.64). H NMR
(CDCl3, 300 MHz): δ = 4.15 ppm (s, 6 H), 7.28–7.47 (m, 7 H),
7.56–7.74 (m, 6 H), 8.03 (d, J = 8.2 Hz, 1 H), 8.33 (d, J = 8.2 Hz,
1 H). 13C NMR (CDCl3, 75.5 MHz): δ = 57.64 ppm (q), 117.76
(d), 125.11 (d), 125.74 (d), 127.65 (d), 129.02 (d), 129.15 (d), 133.60
(s), 133.75 (s), 134.17 (s), 137.31 (d), 137.45 (s), 137.83 (d), 143.94
(d), 172.87 (s), 192.66 (s). MS (EI = 70 eV): m/z (%) = 372 (4) [M+ –
BF3], 355 (24), 354 (92), 353 (50), 352 (100), 337 (18), 323 (19), 321
(25), 247 (11), 246 (14), 245 (25), 227 (25), 215 (19), 202 (18), 49
4-Fluorophenyl-bis(4-methoxyphenyl)methanol (7e): To a solution of
4-bromofluorobenzene (2.00 g, 11.4 mmol) in 5 mL of dry THF,
magnesium (340 mg, 14 mmol) was added, and the mixture stirred
(69), 48 (18). C25H21BF4O2 (440.24): calcd. C 68.21, H 4.81; found at reflux temperature for 45 min. A solution of 4,4Ј-dimethoxybe-
C 67.93, H 4.86 nzophenone (6, 2.00 g, 8.25 mmol) in 35 mL of dry THF was
2138
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2006, 2134–2144

Sterically Stabilized p-Quinodimethanes by Nucleophilic Aromatic Substitution
FULL PAPER
added, and the reaction mixture was stirred at reflux temperature
for 3.5 h and at room temperature for another 4 d. After hydrolysis
with of a saturated aqueous (NH4)2HPO4 solution (20 mL), the
water layer was extracted three times with 20 mL of dichlorometh-
ane, and the combined organic layers were dried with sodium sul-
fate, and the solvents evaporated to dryness at the rotary evapora-
tor: TLC (silica/diethyl ether/hexane, 1:2) of the crude product: Rf
= 0.30, 0.19. The fraction with Rf = 0.30 was isolated by flash
chromatography: 1.754 g (63%) of 7e as a highly viscous yellow oil.
234 (4.32), 275 (3.53), 286 (3.34, sh), 322 (2.90), 511 (2.75). 1H
NMR (300 MHz, CDCl3): δ = 1.78 ppm (s, 3 H), 3.82 (s, 6 H),
5.08 (s, 1 H), 6.89 (d, J = 8.9 Hz, 4 H), 7.16–7.28 (m, 4 H), 7.23
(d, J = 8.7 Hz, 4 H). 13C NMR (75.5 MHz, CDCl3): δ = 22.70 ppm
(q), 37.20 (d), 55.30 (q), 58.94 (s), 112.80 (s), 114.03 (d), 126.32 (d),
128.18 (d), 128.55 (d), 130.19 (d), 132.50 (s), 133.51 (d), 137.60 (s),
140.57 (s), 159.22 (s). MS (EI = 70 eV): m/z (%) = 382 (0.2) [M+],
350 (5), 319 (5), 318 (33), 317 (100) [M+ – C3HN2], 302 (6), 287 (6),
227 (8), 209 (8), 165 (5). C25H22N2O2 (382.46): calcd. C 78.51, H
IR (film): ν = 3039 cm–1 (w), 3001 (w), 2954 (w), 2933 (w), 2906 5.80, N 7.32; found C 78.54, H 5.82, N 7.57.
˜
(w), 2836 (w), 1606 (m), 1582 (w), 1503 (s), 1460 (m), 1442 (w),
1,1-Dicyano-2,2-bis(4-methoxyphenyl)-2-(1-naphthyl)ethane (9c):
1298 (m, sh), 1250 (s), 1225 (m), 1177 (m), 1158 (m), 1034 (m, sh),
906 (w), 828 (s). UV (acetonitrile): λmax (lgε) = 198 nm (5.12), 230
(4.54), 266 (3.62, sh), 275 (3.71), 283 (3.61). 1H NMR (CDCl3,
300 MHz): δ = 2.77 ppm (s, 1 H, OH), 3.78 (s, 6 H), 6.82 (“dd”,
“J” = 6.8, 2.3 Hz, 4 H), 6.94–6.99 (m, 2 H), 7.14 (“dd”, “J” = 6.8,
2.2 Hz, 4 H), 7.21–7.16 (m, 2 H). 13C NMR (CDCl3, 75.5 MHz):
δ = 55.29 ppm (q), 81.11 (s), 113.30 (d), 114.59 (d, 2JCF = 21.1 Hz),
Malononitrile (37 mg, 0.55 mmol) in 3 mL of dry THF was depro-
tonated at room temperature with 60% sodium hydride/mineral oil
(24 mg, 0.6 mmol. A deep red suspension of the tetrafluoroborate
8c (180 mg, 0.409 mmol) in 7 mL of dry THF was added, and the
reaction mixture was stirred for 24 h at room temperature. After
hydrolysis with a saturated aqueous (NH4)2HPO4 solution (20 mL),
the water layer was extracted three times with 20 mL of diethyl
ether and the combined organic layers were dried with sodium sul-
fate and the solvents evaporated to dryness at the rotary evapora-
tor: 160 mg (94%) of 9c as purple colored crystals (purity accord-
ing to 1H NMR Ͼ 95%); an analytically pure sample with m.p.
177–180 °C was obtained by recrystallization from diethyl ether/
3
4
129.07 (d), 129.58 (d, JCF = 8.0 Hz), 139.34 (s), 143.21 (s, JCF
=
1
3.3 Hz), 158.76 (s), 161.86 (s, JCF = 246.3 Hz). MS (EI = 70 eV):
m/z (%) = 339 (13) [M+ + 1], 338 (56) [M+], 322 (11), 321 (33), 244
(16), 243 (89), 231 (43), 215 (16), 136 (9), 135 (100), 123 (67), 108
(11), 107 (10), 95 (17). HRMS calcd. for C21H19FO3 (338.38):
338.1318; found 338.1284.
pentane (1:3). IR (KBr): ν = 3053 cm–1 (w), 3005 (w), 2931 (w),
˜
4-Fluorophenyl-bis(4-methoxyphenyl)methylium Tetrafluoroborate 2838 (w), 1608 (m), 1510 (s), 1461 (w), 1293 (m), 1258 (s), 1185
(8e): To a solution of the triarylmethyl alcohol 7e (571 mg,
1.69 mmol) in 5 mL of dry dichloromethane, HBF4–diethyl ether
(0.75 mL, 5.5 mmol) was added at room temperature under nitro-
gen. After 10 min stirring at room temperature a layer of 10 mL of
diethyl ether was placed carefully on the surface of the reaction
mixture, leading to the formation of a solid precipitate within 1 d,
which was isolated by filtration and washing with 5 mL of diethyl
ether: 634 mg (92%) of 8e as a orange solid with m.p. 171–177 °C.
(m), 1033 (m), 830 (m), 802 (m), 790 (m), 777 (m). UV (acetoni-
trile): λmax (lgε) = 199 nm (4.62), 225 (4.58), 274 (3.69, sh), 284
(3.76), 295 (3.53). 1H NMR (500 MHz, CDCl3): δ = 3.80 ppm (s, 6
H), 5.35 (s, 1 H), 6.87 (d, J = 9.1 Hz, 4 H), 7.15 (t, J = 7.5 Hz, 1
H), 7.32 (d, J = 9.0 Hz, 4 H), 7.33–7.39 (m, 2 H), 7.49 (t, J =
7.6 Hz, 2 H), 7.86 (d, J = 8.0 Hz, 1 H), 7.89 (d, J = 8.7 Hz, 1 H).
13C NMR (75.5 MHz, CDCl3): (two doublets are superimposed): δ
= 37.65 ppm (d), 55.36 (q), 59.18 (s), 112.91 (s), 114.02 (d), 124.86
IR (KBr): ν = 3057 cm–1 (w), 2953 (w), 2837 (w), 1581 (s, br), 1504 (d), 125.58 (d), 125.82 (d), 126.85 (d), 129.61 (d), 130.32 (d), 130.50
˜
(m), 1443 (w), 1414 (w), 1366 (m), 1316 (w), 1280 (s, br), 1251 (m), (d), 131.01 (s), 132.71 (s), 135.22 (s), 137.88 (s), 159.44 (s). MS (EI
1163 (s), 1124 (s), 1084 (s, br), 1037 (m), 917 (w), 831 (m). UV = 70 eV): m/z (%) = 417 (6) [M+ – 1], 416 (19), 386 (16), 379 (10),
(acetonitrile): λmax (lgε) = 196 nm (4.72), 228 (4.03, sh), 264 (3.87),
355 (33), 354 (100) [M+ – C3N2], 353 (26), 323 (20), 247 (14),
1
414 (4.29), 495 (4.65). H NMR (CDCl3, 300 MHz): δ = 4.14 ppm 246 (15), 245 (24), 227 (35), 226 (10), 215 (21), 202 (13), 66 (6).
(s, 6 H), 7.36 (d, J = 9.1 Hz, 4 H), 7.39–7.45 (m, 2 H), 7.53–7.58 C28H22N2O2 (418.49): calcd. C 80.36, H 5.30, N 6.69; found C
(m, 2 H), 7.64 (d, J = 8.8 Hz, 4 H). 13C NMR (CDCl3, 75.5 MHz):
80.16, H 5.30, N 6.70.
2
δ = 57.51 ppm (q), 117.44 (d), 117.45 (d, JCF = 2.3 Hz), 132.24
1,1-Dicyano-2-(4-fluorophenyl)-2,2-bis(4-methoxyphenyl)ethane
(9e): Malononitrile (38 mg, 0.57 mmol) in 3 mL of dry THF was
deprotonated at room temperature with 60% sodium hydride/min-
eral oil (26 mg, 0.65 mmol). A deep orange suspension of the tetra-
fluoroborate 8e (166 mg, 0.407 mmol) in 13 mL of dry THF was
added, and the reaction mixture was stirred for 24 h at room tem-
perature. After hydrolysis with 20 mL of a saturated aqueous
(NH4)2HPO4 solution, the water layer was extracted three times
with 20 mL of diethyl ether, and the combined organic layers were
dried with sodium sulfate and the solvents evaporated to dryness
at the rotary evaporator: TLC (silica; diethyl ether/n-hexane, 1:2):
Rf = 0.44 (7e), 0.27 (9e). The fraction with Rf = 0.27 was isolated
by flash chromatography to give 105 mg (67%) of 9e as slightly
3
(s), 135.21 (s), 140.98 (d, JCF = 10.4 Hz), 144.25 (d), 168.93 (s,
1JCF = 266.4 Hz), 172.39 (s), 192.81 (s). MS (EI = 70 eV): m/z (%)
= 341 (19), 340 (84) [M+ – BF3], 322 (38), 321 (54) [M+ – BF4], 309
(29), 291 (19), 246 (21), 245 (100), 234 (12), 233 (63), 227 (15), 215
(17), 214 (21), 213 (12), 199 (12), 189 (10), 183 (12), 171 (13), 170
(16), 135 (20). C21H18BF5O2 (408.17): calcd. C 61.79, H 4.44; found
C 61.58, H 4.50.
1,1-Dicyano-2,2-bis(4-methoxyphenyl)-2-(2-methylphenyl)ethane
(9a): Malononitrile (67 mg, 1.0 mmol) in 3 mL of dry THF was
deprotonated at room temperature with 60% sodium hydride/min-
eral oil (24 mg, 0.6 mmol). A deep red suspension of the tetrafluo-
roborate 8a (300 mg, 0.742 mmol) in 9 mL of dry THF was added,
and the reaction mixture was stirred for 21 h at room temperature.
After hydrolysis with 20 mL of a saturated aqueous (NH4)2HPO4
solution, the water layer was extracted three times with 20 mL of
diethyl ether and the combined organic layers were dried with so-
dium sulfate, and the solvents evaporated to dryness at the rotary
evaporator. The residue was recrystallized from diethyl ether/n-pen-
tane (1:5) to give 206 mg (73%) of 9a as purple needles with m.p.
yellow solid with m.p. 52 °C. IR (KBr): ν = 3053 cm–1 (w), 3005
˜
(w), 2959 (w), 2935 (w), 1606 (m), 1582 (w), 1508 (s), 1461 (m),
1299 (m), 1258 (s), 1186 (m), 826 (s), 738 (w). UV (acetonitrile):
λm a x (lg ε) = 198 nm (4.95), 225 (4.32), 275 (3.68). 1 H
NMR (300 MHz, CDCl3): δ = 3.81 ppm (s, 6 H), 5.05 (s, 1 H),
6.89 (d, J = 8.9 Hz, 4 H), 7.02–7.08 (m, 2 H), 7.13 (d, J = 8.9 Hz,
4 H), 7.21–7.27 (m, 2 H). 13C NMR (125 MHz, CDCl3): δ =
163–167 °C. IR (KBr): ν = 3059 cm–1 (w), 3006 (w), 2935 (w), 2839
35.96 ppm (d), 55.32 (q), 58.17 (s), 112.63 (s), 114.07 (d), 115.63 (d,
˜
(w), 1608 (m), 1511 (s), 1462 (w), 1293 (w), 1258 (s), 1185 (m), 1032 2JCF = 21.4 Hz), 129.85 (d), 130.62 (d, JCF = 8.0 Hz), 133.73 (s),
(m), 827 (m), 757 (w). UV (acetonitrile): λmax (lgε) = 199 nm (4.90), 138.09 (s), 159.20 (s), 162.13 (s, 1JCF = 248.8 Hz). MS (EI = 70 eV):
3
Eur. J. Org. Chem. 2006, 2134–2144
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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2139

G. Dyker, M. Hagel, O. Muth, C. Schirrmacher
FULL PAPER
m/z (%) = 386 (0.6) [M+], 322 (29), 321 (100), 142 (15), 135 (23),
86 (31), 84 (52), 66 (19). HMRS calcd. for C24H19FN2O2 (386.42):
321.12908 (for M – C3H2N2) and 66.02180 (for malononitrile frag-
ment); found 321.128586 and 66.012988.
(d), 130.51 (s), 131.23 (s), 132.21 (s), 133.31 (s), 133.62 (d), 133.95
(s), 136.02 (d), 137.23 (d), 155.59 (s), 159.47 (s), 162.31 (s). MS (EI
= 70 eV): m/z (%) = 438 (6), 437 (34) [M+ + 1], 436 (100) [M+], 329
(7), 328 (12), 252 (5). C31H20N2O (436.51): calcd. C 85.30, H 4.62,
N 6.42; found C 85.06, H 4.70, N 6.30.
α,α-Dicyano-β-(4-methoxyphenyl)-β-(2,4,6-trimethylphenyl)-p-benzo-
quinodimethane (10b): Malononitrile (17 mg, 0.25 mmol) in 1.5 mL
of dry THF was deprotonated at room temperature with 60% so-
dium hydride/mineral oil (11 mg, 0.28 mmol). A solution of the
tetrafluoroborate 8b (80 mg, 0.19 mmol) in 2.5 mL of dry THF was
added, and the reaction mixture was stirred for 20 h at room tem-
perature. After hydrolysis with 20 mL of water the aqueous layer
was extracted three times with 30 mL of diethyl ether and the com-
bined organic layers were dried with sodium sulfate and the sol-
vents evaporated. The residue was fractionated by flash chromatog-
raphy (silica/diethyl ether/n-hexane, 2:3). The fraction with Rf =
0.35 was isolated to give 10b (27 mg, 39%) as purple solid with
α-(4-Methoxyphenyl)-α-(2,4,6-trimethylphenyl)]-β,β-bis(4-nitro-
phenyl)-p-benzoquinodimethane (12): To a solution of bis(4-ni-
trophenyl)methane (168 mg, 0.65 mmol) in 6 mL of dry THF, a
solution of n-butyllithium (15% in n-hexane, 0.41 mL, 0.65 mmol)
was added at –20 °C under argon. The solution was warmed to
room temperature within 15 min, and a suspension of the tetrafluo-
roborate 8b (265 mg, 0.613 mmol) in 6 mL of dry THF was added.
The reaction mixture was stirred for another 4 d at room tempera-
ture and was hydrolyzed with 20 mL of a saturated aqueous
(NH4)2HPO4 solution. The water layer was extracted three times
with 20 mL of diethyl ether, and the combined organic layers were
m.p. 188–190 °C. IR (KBr): ν = 3045 cm–1 (w), 2926 (w), 2849 (w), dried with sodium sulfate and the solvents evaporated to dryness
˜
2209 (s), 1607 (m), 1591 (s), 1437 (s), 1414 (m), 1308 (w), 1291 (w),
1259 (m), 1203 (w), 1173 (s), 1028 (w), 841 (m), 604 (w). UV (aceto- Rf = 0.44, 0.17–0.05. The fraction with Rf = 0.44 was isolated by
nitrile): λmax (lgε) = 196 nm (4.85), 220 (4.23, sh), 244 (3.80, sh), flash chromatography to give 12 (84 mg, 39%) of as an orange solid
27 6 (3 . 7 4 . s h ), 3 0 1 ( 4. 10 ), 39 1 ( 3. 79 ), 50 8 ( 4. 55 ). 1 H with m.p. 211–214 °C. IR (KBr): ν = 3045 cm–1 (w), 2920 (w), 1596
at the rotary evaporator: TLC (silica; diethyl ether/n-hexane, 1:2):
˜
NMR (300 MHz, CDCl3): δ = 1.92 ppm (s, 6 H), 2.35 (s, 3 H),
3.88 (s, 3 H), 6.81 (dd, J = 9.6, 2.0 Hz, 1 H), 6.94 (d, ü, J = 8.8 Hz,
2 H), 6.95 (s, 2 H), 7.04 (dd, J = 9.6, 2.0 Hz, 1 H), 7.21 (dd, J = 199 nm (4.97), 221 (4.39, sh), 277 (4.29), 361 (4.06), 474 (4.55). H
(m), 1582 (m), 1512 (m), 1451 (w), 1340 (s), 1252 (m), 1174 (m),
1108 (w), 1032 (w), 846 (m), 702 (w). UV (CH3CN): λmax (lgε) =
1
9.7, 2.0 Hz, 1 H), 7.25 (d, J = 8.9 Hz, 2 H), 7.58 (dd, J = 9.6,
NMR (300 MHz, CDCl3): δ = 2.03 ppm (s, 6 H), 2.31 (s, 3 H),
2.0 Hz, 1 H). 13C NMR (75.5 MHz, CDCl3): δ = 20.24 ppm (q), 3.81 (s, 3 H, OCH3), 6.33 (dd, J = 10.0, 2.0 Hz, 1 H), 6.64 (dd, J
21.19 (q), 55.62 (q), 69.91 (s), 114.51 (d), 114.91 (s, C°N), 115.00
(s, C°N), 124.03 (d), 124.13 (d), 128.92 (d), 130.94 (s), 131.94 (s),
133.79 (d), 136.22 (s), 136.34 (d), 136.58 (s), 136.81 (d), 139.20 (s),
= 10.0, 2.1 Hz, 1 H), 6.77 (dd, J = 10.1, 2.1 Hz, 1 H), 6.85 (d, J =
8.9 Hz, 2 H), 6.91 (s, 2 H), 7.20 (d, J = 8.9 Hz, 2 H), 7.24 (dd, J =
10.1, 2.1 Hz, 1 H), 7.36 (ddd, J = 9.0, 2.1, 1.5 Hz, 2 H), 7.40 (ddd,
155.86 (s), 162.42 (s), 162.61 (s). MS (EI = 70 eV): m/z (%) = 380 J = 8.9, 2.4, 2.0 Hz, 2 H), 8.17 (dd, J = 8.9, 2.0 Hz, 2 H), 8.21 (dd,
(4), 379 (29), 378 (100) [M+], 363 (4), 348 (5), 305 (3), 270 (3), J = 8.9, 2.0 Hz, 2 H). 13C NMR (CDCl3, 298 K, 125.8 MHz): δ =
258 (4), 255 (6), 237 (4), 222 (3), 189 (4). C26H22N2O (378.48):
calcd. C 82.51, H 5.86, N 7.40; found C 82.60, H 5.90, N 7.38.
20.24 ppm (q), 21.12 (q), 55.35 (q, OCH3), 113.73 (d), 123.66 (d),
123.74 (d), 126.67 (d), 126.95 (d), 128.54 (d), 130.04 (d), 131.18 (d),
131.67 (s), 131.70 (d), 131.83 (s), 132.02 (d), 132.04 (d), 132.57 (s),
136.11 (s), 136.65 (s), 137.41 (s), 143.56 (s), 143.57 (s), 146.71 (s),
146.77 (s), 147.98 (s), 148.16 (s), 159.63 (s). MS (70 eV): m/z (%) =
571 (39), 570 (100) [M+], 524 (5), 285 (6), 237 (4), 222 (5), 150 (6).
C36H30N2O5 (570.64): calcd. C 75.77, H 5.30, N 4.91; found C
75.52, H 5.34, N 4.94.
β-(9-Anthryl)-α,α-dicyano-β-(4-methoxyphenyl)-p-benzoquinodimeth-
ane (10d): Malononitrile (37 mg, 0.55 mmol) in 3 mL of dry THF
were deprotonated at room temperature with 60% sodium hydride/
mineral oil (24 mg, 0.60 mmol). A suspension of the tetrafluorobo-
rate 8d (200 mg, 0.408 mmol) in 7 mL of dry THF was added, and
the reaction mixture was stirred for 21 h at room temperature. After
hydrolysis with 20 mL of water the aqueous layer was extracted
three times with 30 mL of diethyl ether, and the combined organic
layers were dried with sodium sulfate and the solvents evaporated.
The residue was fractionated by flash chromatography (silica/di-
ethyl ether/n-hexane, 3:2). The fraction with Rf = 0.39 gave 177 mg
of a mixture of two-products, identified by NMr analysis to consist
of p-quinodimethane 10d as main component (60% yield according
to integrals) and of the tetraarylethane 11 as byproduct (Ϸ 37%).
By recrystallization from diethyl ether/n-hexane (1:3) a pure sample
of 88 mg (49%) of 10d as green to purple metallic shining solid
4-(Fluoren-9-ylidene)-1-[(4-methoxyphenyl)(2,4,6-trimethylphenyl)]-
methylidenecyclohexa-2,5-diene (13): Fluorene (266 mg, 1.60 mmol)
and lithium (11 mg, 1.60 mmol) in 5 mL of dry THF were treated
in the ultrasonic bath for 1 h at 50 °C. Unreacted lithium was re-
moved, and a suspension of the tetrafluoroborate 8b (460 mg,
1.06 mmol) in 7 mL of dry THF was added. The reaction mixture
was stirred for another 20 h at room temperature and was hy-
drolyzed with a saturated aqueous (NH4)2HPO4 solution (20 mL).
The water layer was extracted three times with 20 mL of diethyl
ether, and the combined organic layers were dried with sodium sul-
fate and the solvents evaporated to dryness at the rotary evapora-
with m.p. 256 °C was obtained. IR (KBr): ν = 3054 cm–1 (w), 2935
˜
(w), 2839 (w), 2209 (s), 1609 (m), 1589 (s), 1505 (w), 1440 (s), 1414 tor: TLC (silica; diethyl ether/n-hexane, 1:9): Rf = 0.63 (fluorene),
(m), 1358 (w), 1308 (w), 1291 (w), 1261 (m), 1196 (w), 1173 (s), 0.38, 0.11–0.00. The fraction with Rf = 0.38 was isolated by flash
1025 (m), 907 (w), 890 (w), 834 (m), 787 (w), 738 (w). UV (acetoni-
chromatography and recrystallized from diethyl ether/pentane (1:3)
trile): λmax (lgε) = 190 nm (4.61), 223 (4.23), 253 (4.86), 305 (3.97), to give 60 mg (12%) of 13 as dark green crystals with m.p. 102–
1
348 (3.73), 366 (3.87), 387 (3.95), 499 (4.35). H NMR (500 MHz,
108 °C, pure enough for collecting significant spectroscopic data:
CDCl3): δ = 3.81 ppm (s, 3 H), 6.47 (dd, J = 9.6, 2.0 Hz, 1 H), IR (KBr): ν = 3052 cm–1 (w), 2920 (w), 2853 (w), 1731 (w), 1627
˜
6.84 (dd, J = 9.6, 2.1 Hz, 1 H), 6.87 (d, J = 9.0 Hz, 2 H), 7.31 (d,
J = 8.9 Hz, 2 H), 7.33 (dd, J = 9.7, 2.0 Hz, 1 H), 7.39 (ddd, J =
7.8, 5.4, 1.3 Hz, 2 H), 7.48 (ddd, J = 7.6, 5.5, 1.0 Hz, 2 H), 7.63
(dd J = 8.8, 0.8 Hz, 2 H), 7.86 (dd, J = 9.7, 1.9 Hz, 1 H), 8.07 (d,
J = 8.5 Hz, 2 H), 8.60 (s, 1 H). 13C NMR (125 MHz, CDCl3): δ =
55.55 ppm (q), 71.14 (s), 114.56 (s), 114.60 (d), 114.80 (s), 124.15
(d), 124.59 (d), 125.62 (d), 125.65 (d), 127.23 (d), 128.84 (d), 129.26
(s), 1599 (s), 1501 (m), 1474 (m), 1443 (s), 1391 (w), 1378 (w), 1346
(w), 1335 (w), 1288 (m), 1252 (s), 1173 (s), 1032 (m), 834 (m), 728
(m). UV (CH3CN): λmax (lg ε) = 199 nm (4.96), 247 (4.45), 256
(4.57), 383 (4.05), 490 (4.33). 1H NMR (300 MHz, CDCl3): δ =
2.05 ppm (s, 6 H), 2.35 (s, 3 H), 3.83 (s, 3 H), 6.56 (dd, J = 9.8,
1.6 Hz, 1 H), 6.89 (d, J = 8.8 Hz, 2 H), 6.95 (s, 2 H), 7.18–7.30 (m,
6 H), 7.49 (dd, J = 9.8, 1.5 Hz, 1 H), 7.68 (d, J = 8.8 Hz, 1 H),
2140
www.eurjoc.org
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2006, 2134–2144

Sterically Stabilized p-Quinodimethanes by Nucleophilic Aromatic Substitution
FULL PAPER
7.73 (“d”, “J” = 5.4 Hz, 2 H), 7.81 (d, J = 9.7 Hz, 1 H), 7.93 (d, J
methane was added dropwise within 1 h at room temperature. After
= 7.6 Hz, 1 H), 8.03 (“dd”, “J” = 8.4, 3.2 Hz, 1 H). 13C NMR 14 h of additional strirring the reaction mixture was poured on
(CDCl3, 298 K, 125.8 MHz): (one d is superimposed): δ =
20.32 ppm (q), 21.17 (q), 55.36 (q), 113.78 (d), 119.85 (d), 124.64
(d), 124.67 (d), 126.73 (d), 126.74 (d), 126.81 (d), 126.85 (d), 127.63
(d), 127.90 (d), 128.54 (d), 129.69 (d), 130.76 (d), 131.90 (d), 132.29
(s), 132.31 (s), 132.67 (s), 136.42 (s), 137.02 (s), 137.38 (s), 137.71
(s), 138.31 (s), 138.35 (s), 139.78 (s), 139.80 (s), 143.77 (s), 159.62
(s). MS (70 eV): m/z (%) = 478 (3) [M+], 332 (4), 331 (25), 330
100 g of crushed ice, and the precipitated aluminium hydroxide was
solubilized carefully by titrating with hydrochloric acid. The water
layer was extracted three times with 40 mL of dichloromethane and
the combined organic extracts were washed successively with
100 mL of brine, 100 mL of 2  aqueous sodium hydroxide solution
and again with 100 mL of brine. After drying with potassium car-
bonate the solvent was removed at the rotary evaporator, and the
(100), 315 (5), 287 (10), 272 (7), 271 (3), 257 (3), 250 (4), 237 (4), residue was treated with 50 mL of dry diethyl ether. Crystallization
229 (5), 222 (4), 180 (5), 179 (7), 178 (3), 165 (5), 136 (3), 121 (5).
for 1 d in the refrigerator, washing of the crystals with 10 mL of
dry diethyl ether and drying for 1 h at 70 °C in vacuo (0.056 mbar)
gave 7.63 g (82%) of orange to red plates of 16 with m.p. 114–
Diferrocenyl-(4-fluorophenyl)methanol (14): To a solution of ferro-
cene (2.23 g, 12.0 mmol) in 10 mL of dry THF, a solution of tert-
butyllithium in pentane (5.9 mL, 10.0 mmol, 1.7 ) was added
within 5 min at 0 °C under argon. After 1 h of stirring at 0 °C and
10 min at room temperature the reaction mixture was cooled to
–78 °C and a solution of 4-fluorobenzoyl chloride (15, 0.5 mL,
4.0 mmol) in 5 mL of dry THF was added dropwise within 10 min,
and the mixture was stirred for another 2 h at dry-ice temperature,
and then for 14 h at room temperature. After hydrolysis with 20 mL
of water, the water layer was extracted three times with 20 mL of
dichloromethane and the combined organic layers were dried with
sodium sulfate and the solvents evaporated to dryness at the rotary
evaporator: TLC (toluene/silica) of the crude product: Rf = 0.86,
0.52, 0.36. The fraction with Rf = 0.52 was isolated by flash
chromatography (column with length of 15 cm and diameter
of 2.5 cm). Compound 14 (0.72 g, 36%) was obtained as orange
116 °C. IR (KBr): ν = 3100 cm–1 (w), 3080 (w), 1625 (s), 1595 (s),
˜
1500 (w), 1495 (m), 1375 (w), 1295 (m), 1220 (m), 1170 (w), 1150
(m), 1095 (w), 1025 (w), 1005 (w), 965 (w), 850 (m), 825 (m), 770
(m), 670 (w), 635 (w), 620 (m). UV (acetonitrile): λmax (lg ε) =
1
201 nm (4.57), 244 (4.12), 276 (3.85, sh), 358 (3.10), 474 (2.85). H
NMR (300 MHz, CDCl3): δ = 4.21 ppm (s, 5 H, Cp-H), 4.60 (s, 2
H, Cp-H), 4.89 (s, 2 H, Cp-H), 7.15 (m, 2 H), 7.95 (m, 2 H). 13C
NMR (125 MHz, CDCl3): δ = 70.26 ppm, 71.44, 72.56 (all d, Cp),
78.10 (s), 115.26 [d, dCF, 2J(C,F) = 21.4 Hz], 130.53 [d, dCF, 3J(C,F)
4
1
= 7.9 Hz], 135.97 [s,dCF, J(C,F) = 4.0 Hz], 164.78 [s, dCF, J(C,F)
= 250.7 Hz], 197.40 (s). MS (EI = 70 eV): m/z (%) = 309 (20), 308
(100) [M+], 306 (7), 280 (6), 243 (7), 215 (6), 185 (7), 151 (7), 139
(13), 131 (5), 129 (5), 121 (9), 56 (11). C17H13FFeO (308.13): calcd.
C 66.27, H 4.25; found C 66.04, H 4.28.
crystals, decomposing at 180 °C. IR (KBr): ν = 3520 cm–1 (m), 3095
Ferrocenyl(4-fluorophenyl)mesitylmethanol (17): To a tert-butyllith-
ium solution in pentane (14.1 mL, 24.0 mmol, 1.7 ⁾, a solution of
2-bromomesitylene (1.8 mL, 12.0 mmol) in 25 mL of dry THF was
added at –78 °C within 5 min. After 1.5 h stirring at this tempera-
ture a solution of the ketone 16 (3.08 g, 10.0 mmol) in 15 mL of
dry THF was added within 10 min. After 2 h additional strirring
at –78 °C and 14 h at room temperature the mixture was hydrolyzed
with 25 mL of water and the water layer was extracted three times
with 40 mL of dichloromethane. The combined organic layers were
dried with sodium sulfate and the solvent was evaporated. The resi-
due was recrystallized from dichloromethane/diethyl ether to give
2.74 g (64%) orange crystals of 17 with m.p. 164–166 °C. IR (KBr):
˜
(w), 1600 (w), 1500 (m), 1390 (w), 1310 (w), 1225 (m), 1160 (w),
1105 (w), 1040 (w), 1000 (w), 850 (w), 820 (m), 795 (w), 670 (w),
660 (w). UV (acetonitrile): λmax (lgε) = 205 nm (4.83), 249 (3.82),
446 (2.30). 1H NMR (300 MHz, CDCl3): δ = 3.29 ppm (s, 1 H,
OH), 3.82 (m, 2 H, Cp-H), 4.11–4.19 (m, 16 H, Cp-H), 6.98 (m, 2
H), 7.39 (m, 2 H). 13C NMR (CDCl3, 75.5 MHz): δ = 67.17, 67.21,
68.09, 69.66 (all d, Cp), 73.36 (s), 99.75 (s), 113.66 [d, dCF, 2J(C,F)
= 21.5 Hz], 127.94 [d, dCF, 3J(C,F) = 7.7 Hz], 142.66 [s, dCF, 4J(C,F)
= 3.1 Hz], 161.46 [s, dCF,
1J(C,F) = 244.6 Hz]. MS (EI = 70 eV):
m/z (%) = 494 (51) [M+], 356 (100), 233 (18), 215 (10). C27H23FFe2O
(494.17): calcd. C 65.62, H 4.69; found C 65.54, H 4.49.
ν = 3470 (s), 3070 (w), 2910 (w), 1595 (m), 1500 (m), 1475 (w),
˜
Diferrocenyl-(4-fluorophenyl)methylium Tetrafluoroborate (18): To a
solution of the triarylmethanol 14 (0.74 g, 1.5 mmol) in 15 mL of
dry dichloromethane HBF4–diethyl ether (0.6 mL, 4.5 mmol) was
added under nitrogen. After 10 min stirring at room temperature
an overlayer of 15 mL of dry diethyl ether was carefully placed on
the surface of the reaction mixture. After one day of crystallization
in the refrigerator the precipitate wass isolated by filtration, washed
with 30 mL of dry diethyl ether and dried for 1 h at 90 °C in vacuo
(0.055 mbar). Compound 18 (0.83 g, 99%) was obtained as dark
1415 (w), 1380 (w), 1355 (w), 1225 (s), 1160 (w), 1105 (w), 1005
(w), 945 (w), 850 (w), 805 (m), 670 (w), 610 (w). UV (acetonitrile):
λmax (lg ε) = 205 nm (4.90), 249 (3.72, sh), 459 (2.11). 1H
NMR (300 MHz, CDCl3): δ = 1.95 ppm (s, 6 H), 2.21 (s, 3 H), 3.58
(br. s, 1 H, OH) 4.05 (br. s, 1 H, Cp-H), 4.21 (br. s, 1 H, Cp-H),
4.29 (br. s, 6 H, Cp-H) 4.42 (br. s, 1 H, Cp-H), 6.73 (s, 2 H), 7.01
(m, 2 H), 7.43 (m, 2 H). 13C NMR (75 MHz, CDCl3): δ =
20.47 ppm (q), 24.21 (q), 67.24, 68.42, 68.78, 69.15 (all d, Cp),
2
72.64 (s), 106.71 (s), 114.17 [d, dCF, J(C,F) = 21.3 Hz], 128.50 [d,
dCF,
3J(C,F) = 7.9 Hz], 131.19 (d), 136.04, 137.54, 140.10 (all s),
blue metallic shining needles, with m.p. 241–247 °C. IR (KBr): ν
˜
= 3104 cm–1 (m), 1594 (m), 1469 (s), 1412 (m), 1386 (m), 1332 (m),
1296 (m), 1227 (m), 1160 (m), 1084 (s), 1035 (s), 946 (w), 833 (m),
738 (m), 681 (m). UV (acetonitrile): λmax (lgε) = 194 nm (3.66), 261
(2.95), 376 (3.22), 728 (2.91). 1H NMR (300 MHz, CDCl3): δ =
4.47 ppm (br. s, 12 H, Cp-H), 5.10 (br. s, 2 H, Cp-H), 5.86 (br.
s, 4 H, Cp-H), 7.12 (2 H), 7.48 (2 H); throughout broad signals.
MS (LSIMS, NBA): m/z (%) = 477 (100) [M+], 356 (12), 123 (16),
108 (22). C27H22 BF5Fe2 (563.97): calcd. C 57.50, H 3.93; found C
57.11, H 3.86.
141.74 [s,dCF, 4J(C,F) = 3.1 Hz], 161.77 [s, dCF, 1J(C,F) = 245.1 Hz].
MS (EI = 70 eV): m/z (%) = 429 (25), 428 (76) [M+], 364 (17), 363
(67), 345 (25), 343 (26), 341 (11), 291 (14), 290 (60), 287 (16), 285
(15), 275 (36), 260 (15), 259 (13), 257 (10), 193 (9), 186 (10), 179
(11), 121 (9), 86 (43), 84 (76), 74 (23), 59 (46), 51 (27), 49 (100), 48
(9), 47 (15), 45 (26), 41 (16). C26H25FFeO (428.33): calcd. C 72.91,
H 5.88; found C 72.90, H 5.64.
Ferrocenyl(4-fluorophenyl)mesitylmethylium Tetrafluoroborate (19):
To a solution of the triarylmethanol 17 (2.57 g, 6.00 mmol) in
25 mL of dry dichloromethane HBF4–diethyl ether (1.8 mL,
13.0 mmol) was added under nitrogen. After 10 min stirring at
room temperature an overlayer of 25 mL of dry diethyl ether was
carefully placed on the surface of the reaction mixture. After one
Ferrocenyl 4-Fluorophenyl Ketone (16): To a solution of 4-fluo-
robenzoyl chloride (15, 3.6 mL, 30.0 mmol) and aluminium chlo-
ride (4.00 g, 30.0 mmol) in 30 mL of dry dichloromethane, a solu-
tion of ferrocene (5.58 g, 30.0 mmol) in 30 mL of dry dichloro-
Eur. J. Org. Chem. 2006, 2134–2144
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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2141

G. Dyker, M. Hagel, O. Muth, C. Schirrmacher
FULL PAPER
day of crystallization in the refrigerator the precipitate was isolated
by filtration, washed with 30 mL of dry diethyl ether and dried for
1 h at 70 °C in vacuo (0.064 mbar): 2.93 g (98%) dark green crys-
(d), 137.27 [s, dCF, 4J(C,F) = 3.0 Hz], 138.78 (q), 141.67 (q), 146.73
1
(d), 161.91 [s, dCF, J(C,F) = 245.3 Hz]. MS (EI = 70 eV): m/z (%)
= 621 (7), 620 (16) [M+], 479 (6), 478 (30), 477 (71), 475 (9), 409 (4),
tals of 19 with m.p. 212–215 °C. IR (KBr): ν = 3100 cm–1 (w), 2920 356 (9), 291 (17), 265 (19), 264 (100), 262 (7), 235 (5), 234 (8),
˜
(w), 1605 (m), 1590 (s), 1475 (m), 1340 (m), 1320 (m), 1230 (m),
233 (12), 215 (6), 199 (23), 144 (7), 121 (5). C36H29FFe2N2 (620.33):
calcd. C 69.70, H 4.71, N 4.52; found C 69.53, H 4.65, N 4.49.
1165 (m), 1070 (s), 1035 (s), 850 (m). UV (methanol): λmax (lgε) =
1
216 nm (4.42, sh), 229 (4.28, sh), 318 (4.19). H NMR: throughout
α,α-Dicyano-β-ferrocenyl-β-mesityl-p-benzoquinodimethane (22):
Malononitrile (132 mg, 2.00 mmol) in 20 mL of dry THF was de-
protonated at room temperature with 60% sodium hydride/mineral
oil (60 mg, 1.5 mmol). A solution of the tetrafluoroborate 19
(498 mg, 1.00 mmol) in 60 mL of dry THF was added within
10 min, and the reaction mixture was stirred for 20 h. After hydrol-
ysis with 20 mL of water the aqueous layer was extracted three
times with 30 mL of dichloromethane, and the combined organic
layers were dried with sodium sulfate and the solvents evaporated.
The residue was recrystallized from 25 mL diethyl ether to give
300 mg (66%) of 22 as dark green metallic shining crystals with
broad signals. MS (LSIMS, NBA): m/z (%) = 456 (6), 411 (100)
[M+], 290 (6), 194 (4), 136 (5), 121 (4). C26H24 BF5Fe (498.12):
calcd. C 62.69, H 4.86; found C 62.86, H 5.11.
1,1-Dicyano-2,2-diferrocenyl-2-(4-fluorophenyl)ethane (20): Ma-
lononitrile (132 mg, 2.00 mmol) in 20 mL of dry THF was depro-
tonated at room temperature with 60% sodium hydride/mineral oil
(60 mg, 1.5 mmol). A solution of the tetrafluoroborate 18 (564 mg,
1.00 mmol) in 50 mL of dry THF was added within 10 min, and
the reaction mixture was stirred for 19 h. After hydrolysis with
20 mL of water the aqueous layer was extracted three times with
30 mL of dichloromethane and the combined organic layers were
dried with sodium sulfate and the solvents evaporated. The residue
was crystallized from 20 mL dichloromethane/diethyl ether (1:1) to
give 385 mg (71%) of 20 as orange crystals with mp. 200 °C (dec.).
m.p. 204 °C. IR (KBr): ν = 3070 cm–1 (w), 2910 (w), 2200 (s),
˜
1595 (s), 1435 (s), 1395 (m), 1370 (m), 1340 (w), 1320 (w), 1320 (w),
1260 (w), 1210 (m), 1180 (s), 935 (w), 830 (m), 680 (m). UV (aceto-
nitrile): λmax (lg ε) = 196 nm (3.91), 282 (3.02), 357 (2.82), 467
IR (KBr): ν = 3073 cm–1 (w), 2911 (w), 1604 (m), 1508 (s), (3.27), 512 (3.32), 720 (3.01). 1H NMR (500 MHz, CDCl3): δ =
˜
1412 (w), 1235 (m), 1172 (m), 1109 (m), 1039 (m), 1004 (m), 824 (s), 1.97 ppm (s, 6 H), 2.33 (s, 3 H), 4.29 (s, 5 H, Cp-H), 4.47 (s, 2 H,
794 (s). UV (acetonitrile): λmax (lgε) = 205 nm (4.85), 244 (3.93, sh). Cp-H), 4.79 (s, 2 H, Cp-H), 6.60 (dd, J = 9.5 Hz, 1.9 Hz), 6.90 (s,
1H NMR (500 MHz, CDCl3): δ = 4.18 ppm (br. s, 12 H, Cp-H),
2 H), 6.95 (dd, J = 9.5 Hz, 2.0 Hz), 7.35 (dd, J = 9.6 Hz, 1.9 Hz),
4.32–4.36 (m, 6 H, Cp-H), 5.48 [s, 1 H, –CH(CN)2], 7.07 (m, 2 H), 8.53 (dd, J = 9.7 Hz, 1.7 Hz). 13C NMR (125 MHz, CDCl3): δ =
7.53 (m, 2 H). 13C NMR (125 MHz, CDCl3): δ = 38.57 ppm [d,
20.02 ppm (q), 21.07 (q), 67.50 (s), 71.38 (d, several C), 73.72 (d),
–CH(CN)2], 50.32 [s, C–CH(CN)2], 67.67, 68.56, 68.69, 69.21, 74.62 (d), 81.96 (s), 116.10 (s, CN), 116.30 (s, CN), 122.34 (d),
69.76 (all d), 94.82 (s), 113.14 (s, CN), 114.64 [d, dCF
,
2J(C,F) =
122.98 (d), 128.44 (d, mesityl-H), 130.68 (s), 134.80 (d), 135.37 (s),
3
4
21.4 Hz], 129.73 [d, dCF, J(C,F) = 8.0 Hz], 137.38 [s, dCF, J(C,F) 136.26 (d), 136.94 (s), 138.54 (s), 155.88 (s), 169.74 (s). MS (EI
= 3.0 Hz], 162.00 [s, dCF
,
1J(C,F) = 248.8 Hz]. MS (EI = 70 eV):
= 70 eV): m/z (%) = 456 (100) [M+], 315 (12), 186 (7), 121 (23).
C29H24FeN2 (456.37): calcd. C 76.32, H 5.30, N 6.14; found
C 76.13, H 5.38, N 6.05.
m/z (%) = 543 (12), 542 (34) [M+], 478 (42), 477 (100), 475 (13),
409 (6), 357 (22), 356 (84), 355 (16), 354 (17), 291 (31), 235 (12),
234 (32), 233 (44), 215 (21), 186 (22), 139 (5), 121 (25), 86 (32),
84 (57), 74 (15), 66 (67), 59 (17), 56 (11), 51 (21), 49 (64), 45 (15),
39 (13), 38 (10). C30H23FFe2N2 (542.22): calcd. C 66.45, H 4.28, N
5.17; found C 66.30, H 4.34, N 5.08.
4-[Ferrocenyl(mesityl)methylene]-1-[(quinolin-8-yl)imino]cyclohexa-
2,5-diene (23): 8-Aminoquinoline (288 mg, 2.00 mmol) in 30 mL of
dry THF was deprotonated with 60% sodium hydride/mineral oil
(60 mg, 1.5 mmol) for 3 h at reflux temperature. A solution of the
tetrafluoroborate 19 (498 mg, 1.00 mmol) in 60 mL of dry THF
was added within 5 min at room temperature, and the reaction mix-
ture was stirred for 6 h at room temperature. After hydrolysis with
30 mL of water the aqueous layer was extracted three times with
30 mL of dichloromethane and the combined organic layers were
dried with sodium sulfate and the solvents evaporated. The residue
8-[Diferrocenyl-(4-fluorophenyl)methylamino]quinoline (21): 8-Ami-
noquinoline (288 mg, 2.00 mmol) in 30 mL of dry THF were de-
protonated with 60 % sodium hydride/mineral oil (60 mg,
1.5 mmol) within 3 h at reflux temperature. A solution of the tetra-
fluoroborate 18 (564 mg, 1.00 mmol) in 60 mL of dry THF was
added within 5 min, and the reaction mixture was stirred for 7 h at
reflux temperature. After hydrolysis with 30 mL of water the aque- was fractionated by flash chromatography with first toluene, then
ous layer was extracted three times with 30 mL of dichloromethane,
and the combined organic layers were dried with sodium sulfate
and the solvents evaporated. The residue was fractionated by flash
chromatography; TLC (toluene/silica) Rf = 0.87, 0.60, 0.33, 0.20.
The fraction with Rf = 0.87 crystallized from 30 mL of diethyl ether
ethyl acetate as eluent; TLC (toluene/silica) Rf = 0.87, 0.77, 0.62,
0.38, 0.13–0.00. The fraction with Rf = 0.52 (ethyl acetate/silica)
was isolated and crystallized from 20 mL diethyl ether at –18° to
give 150 mg (28%) of 23 as dark purple metallic crystals with m.p.
193 °C (dec.). IR (KBr): ν = 3080 cm–1 (w), 3040 (w), 2910 (w),
˜
to give 220 mg (35%) of 21 as golden to yellow crystals with m.p. 2850 (w), 1605 (rn), 1565 (rn), 1490 (s), 1445 (rn), 1380 (rn), 1335
225 °C (dec.). IR (KBr): ν = 3364 cm–1 (m), 3092 (w), 1603 (w), (w), 1310 (w), 1285 (w), 1245 (w), 1180 (rn), 1105 (w), 1080 (w),
˜
1571 (m), 1511 (s), 1478 (s), 1380 (s), 1337 (w), 1226 (m), 1159 (m), 1050 (w), 1000 (w), 940 (w), 835 (rn), 800 (rn), 750 (w), 665 (w).
1107 (m), 1000 (w), 818 (s), 748 (w). UV (acetonitrile): λmax (lgε) =
201 nm (5.02), 254 (4.48), 374 (3.67). 1H NMR (500 MHz, CDCl3):
δ = 3.99 ppm (br. s, 2 H, Cp-H), 4.10 (m, 2 H, Cp-H), 4.12 (s, 10
UV (acetonitrile): λmax (lgε) = 198 nm (4.93), 243 (4.43), 283 (3.98),
397 (4.35), 551 (3.66). H NMR (500 MHz, CDCl3): δ = 2.02 ppm
(s, 6 H), 2.29 (s, 3 H), 4.22 (s, 5 H, Cp-H), 4.30 (s, 2 H, Cp-H),
1
H, Cp-H), 4.20 (m, 2 H, Cp-H), 4.43 (br. s, 2 H, Cp-H), 6.11 (dd, 4.48 (s, 2 H, Cp-H), 6.44 (rn, br, 1 H), 6.60 (very br, 1 H), 6.86 (s,
4
3
4
3J = 7.7, J = 1.2 Hz, 1 H, H-7), 6.93 (dd, J = 8.2, J = 1.2 Hz, 1 2 H), 7.00 (very br, 1 H), 7.22 (m, lH), 7.39–7.58 (m, 3 H), 8.15 (d,
H, H-5), 7.01 (m, 1 H), 7.05 (m, 2 H), 7.39 (m, 1 H), 7.76 (m, 2
J = 8.2 Hz, 1 H), 8.47 (rn, br, 1 H), 8.91 (br. s, 1 H). 13C
3
4
H), 8.05 (dd, J = 8.3, J = 1.7 Hz, 1 H, H-4), 8.25 (s, 1 H, N–H), NMR (125 MHz, CDCl3): δ = 20.05 ppm (q), 21.11 (q), 70.43 (d),
3
8.85 (dd, J = 4.2, 4J = 1.7 Hz, 1 H, H-2). 13C NMR (125 MHz,
71.03 (d), 72.93 (d), 82.60 (s), 118.12 (d), 121.35 (d), 123.41 (s),
126.65 (d), 128.00 (d), 128.18 (d, mesityl-H), 129.26 (s), 129.41 (s),
132.53 (d), 135.51 (s), 136.05 (d), 137.36 (s), 137.86 (s), 142.06 (s),
149.74 (d), 160.94 (s). MS (EI = 70 eV): m/z (%) = 534 (0.1) [M+],
CDCl3): δ = 61.25 (s), 66.77, 68.78, 68.86, 69.19 (all d), 99.52 (s),
108.71 (d), 113.19 (d), 114.00 [d, dCF
(d), 127.02 (d), 128.68 (q), 130.68 [d, dCF, 3J(C,F) = 7.5 Hz], 136.10
,
2J(C,F) = 21.4 Hz], 121.21
2142
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© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2006, 2134–2144

Sterically Stabilized p-Quinodimethanes by Nucleophilic Aromatic Substitution
186 (100), 144 (35), 121 (57), 93 (8), 56 (22). C35H30FeN2 (534.48): sodium sulfate and the solvents evaporated to dryness at the rotary
FULL PAPER
calcd. C 78.65, H 5.66, N 5.24; found C 78.43, H 5.94, N 5.04.
evaporator: TLC (silica; diethyl ether/n-hexane, 1:3): Rf = 0.26,
0.10. Fractionated by flash chromatography.
Bis(4-fluorophenyl)(2,4,6-trimethylphenyl)methanol (24): To a solu-
tion of 1-bromomesitylene (2.74 g, 2.10 mL, 13.7 mmol) in 20 mL
of dry THF a 15% solution of n-butyllithium in hexane (5.2 mL,
13.0 mmol) was added within 5 min at –55 °C under argon. After
30 min of stirring at –55 °C a solution of 4,4Ј-difluorobenzophe-
none (2.00 g, 9.16 mmol) in 30 mL of dry THF was added dropwise
at –30 °C within 15 min, and the reaction mixture was stirred at
room temperature for another 5 d. After hydrolysis with 20 mL of a
saturated aqueous (NH4)2HPO4 solution water layer was extracted
three times with 40 mL of dichloromethane and the combined or-
ganic layers were dried with sodium sulfate and the solvents evapo-
rated to dryness at the rotary evaporator: TLC (silica/toluene) of
the crude product: Rf = 0.56, 0.48. The fraction with Rf = 0.56 was
isolated by flash chromatography: 2.46 g (79%) of 24 as colorless
First Fraction: Rf = 0.26. Compound 28 (100 mg, 62%) was ob-
tained as dark green crystals with metallic lustre and m.p. 75 °C.
IR (KBr): ν = 2923 cm–1 (w), 2212 (s), 1607 (m), 1592 (s), 1501
˜
(w), 1444 (s), 1235 (m), 1202 (m), 1181 (m), 1159 (m), 843 (m).
UV (acetonitrile): λmax (lgε) = 196 nm (4.99), 283 (4.12), 357 (3.98,
sh), 470 (4.70). 1H NMR (300 MHz, CDCl3): δ = 1.95 ppm (s, 6
H), 2.35 (s, 3 H), 6.83 (dd, J = 9.7, 1.7 Hz, 1 H), 6.96 (s, 2 H),
7.05–7.15 (m, 3 H), 7.20–7.32 (m, 3 H), 7.52 (dd, J = 9.7, 1.7 Hz,
1 H). 13C NMR (75.5 MHz, CDCl3): δ = 20.29 ppm (q), 21.14 (q),
72.24 (s), 114.34 (s, C°N), 114.40 (s, C°N), 116.12 (d, JCF
2
=
21.8 Hz), 124.58 (d), 124.68 (d), 129.05 (d), 132.68 (s), 133.59 (d,
4
3JCF = 8.8 Hz), 134.39 (s, JCF = 3.3 Hz), 135.68 (d), 135.88 (s),
136.38 (s), 136.61 (d), 139.40 (s), 155.55 (s), 160.32 (s), 164.17 (s,
1JCF = 255.0 Hz). MS (EI = 70 eV): m/z (%) = 367 (27) [M+ + 1],
366 (100) [M+], 351 (8), 336 (6), 270 (7), 246 (5), 225 (10), 219 (6),
210 (7), 147 (6), 123 (12), 109 (5). C25H19FN2 (366.44): calcd. C
81.94, H 5.23, N 7.64; found C 81.70, H 5.17, N 7.45.
crystals with m.p. 137–140 °C. IR (KBr): ν = 3555 cm–1 (m, OH),
˜
3045 (w), 2967 (w), 2934 (w), 1600 (s), 1502 (s), 1375 (w), 1231 (s),
1263 (s), 1155 (m), 1032 (w), 1014 (w), 1002 (m), 851 (m), 835 (s),
826 (s). 812 (w), 586 (m). UV (acetonitrile): λmax (lgε) = 196 nm
(4.92), 217 (4.44, sh), 265 (3.25), 274 (3.11). 1H NMR (CDCl3,
500 MHz): δ = 1.85 ppm (s, 6 H), 2.26 (s, 3 H), 2.69 (s, 1 H, OH),
6.81 (s, 2 H), 6.96–7.04 (m, 4 H), 7.15–7.22 (m, 4 H). 13C NMR
(CDCl3, 125 MHz): δ = 20.51 ppm (q), 24.34 (q), 82.75 (s, C–OH),
Second Fraction: with Rf = 0.10: 25 mg (16%) of a yellow solid
with 119–123 °C, identified as the hydrolysis product 4-[(4-fluo-
rophenyl)-(2,4,6-trimethylphenyl)]methylidene-2,5-cyclohexadien-
1-one.
2
3
115.05 (d, JCF = 21.0 Hz), 129.50 (d, JCF = 8.0 Hz), 131.54 (d),
4
4-[(4-Fluorophenyl)-(2,4,6-trimethylphenyl)]methylidene-2,5-cyclo-
136.62 (s), 137.85 (s), 140.74 (s), 143.41 (s, JCF = 3.5 Hz), 162.03
hexadien-1-one: IR (KBr): ν = 3049 cm–1 (w), 2920 (w), 1629 (s),
(s, JCF = 246.8 Hz). MS (EI = 70 eV): m/z (%) = 338 (10) [M+],
1
˜
1608 (w), 1595 (m), 1500 (m, sh), 1430 (w), 1379 (w), 1230 (m),
1159 (m), 865 (m), 839 (w), 811 (w), 586 (w). UV (acetonitrile):
λmax (lgε) = 196 nm (4.85), 220 (4.23, sh), 250 (4.22), 367 (4.47).
1H NMR (300 MHz, CDCl3): δ = 2.00 ppm (s, 6 H, CH3), 2.34 (s,
3 H, CH3), 6.35 (dd, J = 10.0, 2.0 Hz, 1 H), 6.51 (dd, J = 10.0,
2.0 Hz, 1 H), 6.95 (s, 2 H), 6.96 (dd, J = 9.9, 2.7 Hz, 1 H), 7.06–
7.14 (m, 2 H), 7.24–7.30 (m, 2 H), 7.61 (dd, J = 10.0, 2.7 Hz, 1 H).
13C NMR (75.5 MHz, CDCl3): δ = 20.27 ppm (q), 21.10 (q), 115.71
321 (23), 320 (62), 305 (36), 243 (16), 226 (10), 225 (46), 224 (31),
220 (14), 219 (87), 210 (14), 148 (9), 147 (54), 123 (100), 120 (24),
105 (11), 95 (30). C22H20F2O (338.40): calcd. C 78.09, H 5.96;
found C 78.13, H 5.88.
Bis(4-fluorophenyl)(2,4,6-trimethylphenyl)methylium Tetrafluorobo-
rate (25): To a solution of the triarylmethyl alcohol 24 (1.09 g,
3.23 mmol) in 14 mL of dry dichloromethane HBF4–diethyl ether
(1.26 mL, 9.26 mmol) was added at room temperature under nitro-
gen. After 5 min stirring at room temperature a layer of 40 mL of
diethyl ether was placed carefully on the surface of the reaction
mixture, leading to the formation of a solid precipitate within 1 d,
which was isolated by filtration and was washed with 10 mL of
diethyl ether: Compound 25 (1.160 g, 88%) was obtained as dark
2
(d, JCF = 21.8 Hz, C-3ЈЈ/C-5ЈЈ), 128.84 (d), 129.06 (d), 129.38 (d),
4
130.45 (s), 133.24 (d, 3JCF = 8.2 Hz, C-2ЈЈ/C-6ЈЈ), 134.29 (s, JCF
=
3.5 Hz, C-1ЈЈ), 136.01 (s), 136.21 (s), 137.66 (d), 138.49 (d), 138.80
1
(s), 157.92 (s), 163.62 (s, JCF = 252.7 Hz, C-4ЈЈ), 187.10 (s, C=O).
MS (EI = 70 eV): m/z (%) = 319 (24) [M+ + 1], 318 (100) [M+], 303
(15), 275 (26), 260 (18), 259 (11). C22H19OF (318.39): calcd. C
82.99, H 6.01; found C 82.86, H 5.96.
green, metallic shining crystals with m.p. 144–150 °C. IR (KBr): ν
˜
= 3039 cm–1 (w), 2919 (w), 2856 (w), 1627 (m), 1599 (s), 1582 (s,
sh), 1496 (w, sh), 1421 (m), 1375 (s), 1349 (m), 1240 (m), 1172 (m),
1156 (s), 1123 (m), 1084 (s, br), 910 (w), 864 (w). UV (acetonitrile):
λmax (lgε) = 196 nm (4.85), 247 (4.04), 266 (3.55, sh), 307 (3.80),
435 (4.68), 482 (4.21). 1H NMR (CDCl3, 500 MHz): partially
broadened double set of signals; δ = 1.81 ppm (s, 6 Ha), 1.83 (s, 6
Hb), 2.42 (s, 3 Hb), 2.47 (s, 3 Ha), 7.07 (s, 2 Hb), 7.16 (s, 2 Ha), 7.33
(dd, J = 9.2, 2.4 Hz, 1 Hb), 7.40 (“t”, “J” = 8.4 Hz), 7.52 (dd, J =
9.3, 2.4 Hz, 1 Hb), 7.58–7.61 (m), 7.69 (s, br), 8.04 (dd, J = 9.2,
2.4 Hz, 1 Hb), 8.15 (br. s, 1 H). MS (EI = 70 eV): m/z (%) = 340
(24) [M+ – BF3], 321 (34) [M+ – BF4], 319 (25), 318 (100), 303 (14),
275 (22), 260 (14), 225 (14), 221 (33), 210 (14), 201 (11). C22H19BF6
(408.19): calcd. C 64.73, H 4.69; found C 64.41, H 4.69.
α,α-Dicyano-β-(4-dicyanomethylphenyl)-β-mesityl-p-benzoquinodi-
methane (27): In an orientating experiment malononitrile (142 mg,
2.11 mmol) in 3 mL of dry THF was deprotonated at room tem-
perature with 60% sodium hydride/mineral oil (84 mg , 2.11 mmol).
A
solution of the monosubstitution product 28 (200 mg,
0.528 mmol) in 5 mL of dry THF was added, and the reaction mix-
ture was stirred under reflux for 20 h, resulting in a dark green
reaction mixture. The solvent was removed at the rotatory evapora-
tor. The residue was solubilized in 20 mL methanol, the solution
was filtered through silica and concentrated to give a dark green
solid with m.p. Ͼ 330 °C, whose 1H NMR spectrum is in agreement
with the resonance stabilized symmetrical anion 26. 1H
NMR (300 MHz, [D4]MeOH): δ = 1.88 ppm (s, 6 H), 2.34 (s, 3 H),
6.98 (s, 2 H), 6.99 (d, J = 8.7, 4 H), 7.18 (d, J = 8.7, 4 H). Acidify-
ing the dark green THF solution with half concentrated hydrochlo-
ric acid let to a change in color to deep orange. Isolation of the
neutral product by flash chromatography failed due to a tendency
to decomposition by hydrolysis, however, mass spectrum and 1H
NMR spectrum of the crude product with about 90% purity were
in agreement with structure 28 (which is of course less mesomeric
stabilized compared to structures 10 and 22): 1H NMR (300 MHz,
α,α-Dicyano-β-(4-fluorophenyl)-β-mesityl-p-benzoquinodimethane
(28): Malononitrile (66 mg, 0.98 mmol) in 5 mL of dry THF were
deprotonated at room temperature with 60% sodium hydride/min-
eral oil (40 mg, 1.0 mmol). A suspension of the tetrafluoroborate
25 (200 mg, 0.490 mmol) in 8 mL of dry THF was added, and the
reaction mixture was stirred for 20 h. After hydrolysis with 20 mL
of water the aqueous layer was extracted three times with 20 mL
of diethyl ether and the combined organic layers were dried with
Eur. J. Org. Chem. 2006, 2134–2144
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2143

G. Dyker, M. Hagel, O. Muth, C. Schirrmacher
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Received: January 2, 2006
Published Online: March 3, 2006
2144
www.eurjoc.org
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2006, 2134–2144