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was added, followed by Et3N (0.866 mL, 0.210 mmol). The tempera-
ture was allowed to reach RT. The resulting strongly red reaction
mixture (which contained 11) was heated to reflux for 1 h to con-
vert 11 into 3, whereafter it was concentrated under vacuum. Pu-
rification by dry column vacuum chromatography (silica 15–40 mm,
12.6 cm2, 0–100% CHCl3/heptanes, 5% steps, 40 mL fractions) gave
3 (1.24 g) as a yellow solid with some impurities. An analytically
pure sample was obtained by recrystallization from boiling CHCl3
(50 mL) and 96% EtOH (100 mL), which gave 3 (498 mg, 40%) as
a bright yellow crystalline powder. TLC (CH2Cl2): Rf =0.73 (yellow to
orange-red). M.p. >2308C, darkens at 215–2188C; 1H NMR
(500 MHz, CDCl3): d=8.04 (t, J=1.9 Hz, 1H), 7.80 (dd, J=7.9,
1.9 Hz, 2H), 7.61 (t, J=7.9 Hz, 1H), 6.97 (s, 2H), 6.60 (dd, J=11.2,
6.2 Hz, 2H), 6.51 (dd, J=11.2, 6.2 Hz, 2H), 6.42 (d, J=6.2 Hz, 2H),
6.33 (ddd, J=10.2, 6.1, 2.2 Hz, 2H), 5.83 (dd, J=10.2, 3.8 Hz, 2H),
3.82 ppm (m, 2H) (the coupling constants are not paired as the
spin systems could not be assigned); 13C NMR (125 MHz, CDCl3):
d=139.01, 139.00, 138.33, 138.31, 133.95, 131.82, 131.52, 131.03,
131.02, 130.43, 127.92, 127.49, 123.99, 122.09, 119.64, 119.62,
115.09, 115.07, 112.71, 112.69, 51.21, 45.38 ppm (signals missing
due to overlap); HRMS (MALDI+): m/z calcd for C30H18N4Na+:
457.14237; found: 457.14262 [M+Na+]; elemental analysis calcd
(%) for C30H18N4 (434.49): C 82.93, H 4.18, N 12.89; found: C 82.82,
H 4.32, N 12.86.
641.2663 [M+Na+]; elemental analysis calcd (%) for C44H34N4: C
85.41, H 5.54, N 9.05; found C: 85.35, H 5.28, N 9.04.
2,2’-[(2E,2’E)-1,4-Phenylenebis(3-phenylallyl-1-ylidene)]dima-
lononitrile (8)
Tritylium tetrafluoroborate (142 mg, 0.430 mmol) was added to
a dry and argon-degassed solution of compound 7 (103 mg,
0.166 mmol) in DCE (45 mL) under argon. The mixture was heated
to reflux for 2 h and was then washed with brine (2ꢁ50 mL), dried
with MgSO4, and concentrated under vacuum. The residue was
then purified by flash chromatography (20% EtOAc, 80% heptane)
and recrystallized from CH2Cl2/heptane to give compound 8
(24 mg, 25%). 1H NMR (500 MHz, CDCl3): d=7.64 (d, J=15.6 Hz,
2H), 7.59 (s, 4H), 7.58–7.54 (m, 4H), 7.50–7.38 (m, 6H), 6.90 ppm
(d, J=15.6 Hz, 2H); 13C NMR (126 MHz, CDCl3) d=169.93, 150.18,
135.94, 134.07, 132.32, 129.74, 129.47, 129.24, 124.03, 113.24,
112.44, 83.22 ppm; HRMS (MALDI+): m/z calcd for C30H18N4Na+:
457.14237; found 457.14255 [M+Na+].
2,2’-[1,3-Phenylenebis(ethan-1-yl-1-ylidene)]dimalononitrile
(9)
NH4OAc (10.0 g, 130 mmol) and AcOH (30 mL, 500 mmol) were
added to
a stirred mixture of 1,3-diacetylbenzene (8.61 g,
53.3 mmol) and malononitrile (14.97 g, 226.6 mmol) in toluene. The
flask was equipped with a Dean–Stark trap, and the reaction mix-
ture was heated to reflux overnight. The reaction mixture was
cooled for about 30 min, and while still hot it was poured into
a mixture of brine (100 mL) and diethyl ether (100 mL) in a separa-
tion funnel. Diethyl ether (100 mL) was cautiously poured into the
hot flask and the mixture was left at boiling for a few minutes to
extract the product from the oil that formed in the flask and was
transferred into the separation funnel. The ether phase was sepa-
rated and washed with water (100 mL) and brine (100 mL), then
dried with MgSO4, filtered, and concentrated under vacuum. The
resulting yellow residue was purified (in two separate batches) by
means of dry column vacuum chromatography (silica 15–40 mm,
12.6 cm2, 0–36% EtOAc/heptanes, 3% steps, 40 mL fractions),
which gave 9 (9.91 g, 38.4 mmol, 72%) as a slightly yellow crystal-
line powder. Alternatively, the crude product could be purified by
a fractional recrystallization from CH2Cl2/heptanes or boiling EtOH
(150 mL) (Note 1), which gave 9 (6.73 g, 53%) as slightly yellow
crystals. M.p. 1518C (EtOH); 1H NMR (500 MHz, CDCl3): d=7.73–
7.65 (m, 4H), 2.68 ppm (s, 6H); 13C NMR (125 MHz, CDCl3): d=
173.76, 136.99, 130.65, 130.39, 126.29, 112.44, 112.11, 86.73,
24.46 ppm; HRMS (MALDI+): m/z calcd for C16H10N4Na+: m/z:
281.07977; found: 281.07983 [M+Na+]. Note 1: The residue was
first attempted purified by recrystallization from boiling EtOAc/
heptanes (1:5).
2,2’-[1,4-Phenylenebis(ethan-1-yl-1-ylidene)]dimalononitrile
(4)
1,1,1,3,3,3-Hexamethyldisilazane (3.29 mL, 15.8 mmol) was added
to acetic acid (7.54 mL, 131 mmol) while keeping the temperature
under 758C. 4-Acetylacetophenone (2.10 g, 13.0 mmol), malononi-
trile (1.71 g, 25.9 mmol), and acetic acid (3.76 mL, 65.7 mmol) were
added to this mixture. The mixture was heated to 708C for 29 h,
after which the reaction mixture was poured into water (100 mL).
The precipitate was collected, washed with water (4ꢁ50 mL), and
then quickly with 40% EtOH (40 mL), which gave 4 (3.28 g, 98%)
1
as a white powder. M.p. 193–1968C; H NMR (500 MHz, CDCl3): d=
7.67 ppm (s, 4H), 2.66 ppm (s, 6H); 13C NMR (126 MHz, CDCl3): d=
173.61, 139.15, 128.20, 112.31, 112.18, 86.64, 24.35 ppm; HRMS
(ESP+): m/z calcd for C16H11N4Na+: 281.0798; found: 281.0744
[M+Na+]; elemental analysis calcd (%) for C16H10N4 (258.09): C
74.40, H 3.90, N 21.69; found: C 74.28, H 3.75, N 21.46.
2,2’-{1,4-Phenylenebis[2,2-di(cyclohepta-2,4,6-trien-1-yl)e-
than-1-yl-1-ylidene]}dimalononitrile (7)
Et3N (0.45 mL, 3.2 mmol) was added to a solution of 4 (165 mg,
0.638 mmol) and tropylium tetrafluoroborate (575 mg, 3.23 mmol)
in CH2Cl2 (100 mL) at RT. After 2 h, four spots were observed on
TLC, and more tropylium tetrafluoroborate (135 mg, 0.759 mmol)
and Et3N (0.12 mL, 0.86 mmol) were added. After a further 16 h,
there was one main spot on TLC. The mixture was quenched with
saturated aqueous NH4Cl (50 mL) and washed with water, then
dried with MgSO4 and concentrated under vacuum. The residue
was purified by flash chromatography (20% EtOAc, 80% heptane)
and recrystallized from chloroform and heptane, which gave com-
pound 7 (291 mg, 74%) as a yellow solid. A small amount was re-
crystallized from THF/heptane for X-ray crystallography. M.p. 171–
1728C; 1H NMR (500 MHz, CDCl3): d=7.21 (s, 4H), 6.74–6.68 (m,
8H), 6.28–6.23 (m, 8H), 5.26 (dd, J=9.1, 6.8 Hz, 4H), 4.87 (t, J=
8,12 Hz, 4H), 3.76 (t, J=9.3 Hz, 2H), 2.10 ppm (s, 4H); 13C NMR
(125 MHz, CDCl3): d=180.20, 131.59, 130.86, 128.40, 126.39, 125.97,
119.99, 118.16, 111.59, 111.55, 48.54, 40.54 ppm (two signals miss-
ing); HRMS (ESP+): m/z calcd for C44H34N4Na+: 641.2676; found:
2,2’-{1,3-Phenylene-bis[2-(cyclohepta-2,4,6-trien-1-yl)ethan-
1-yl-1-ylidene]}dimalononitrile (10)
Et3N (0.866 mL, 6.210 mmol) was added to a stirred suspension of
9 (801.9 mg, 3.105 mmol) and freshly mortared tropylium tetra-
fluoroborate (1.436 g, 8.072 mmol) in CH2Cl2 (175 mL) at ꢁ788C,
and the reaction mixture was allowed to slowly warm to RT over-
night. Saturated aqueous NH4Cl (50 mL) was added, and the organ-
ic phase was separated and concentrated under vacuum. Purifica-
tion by means of dry column vacuum chromatography (silica 15–
40 mm, 12.6 cm2, 0–50% EtOAc/heptanes, 5% steps, 40 mL frac-
tions) gave 10 (790 mg, 58%) as a yellow solid. The desired com-
pound could also be isolated by fractional recrystallization from
Chem. Eur. J. 2015, 21, 3968 – 3977
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