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Can. J. Chem. Vol. 91, 2013
8.03 (2H, d, J = 10, Z isomer), 8.28 (2H, d, J = 8.0, Z isomer), 8.32 (2H,
d, J = 8.0, E isomer). 13C NMR (100 MHz, CDCl3) ␦: 163.6, 161.1, 141.1,
140.8, 140.7, 139.7, 139.4, 138.1, 137.8, 137.5, 137.4, 129.8, 129.7,
126.8, 126.7, 120.9, 120.8, 120.7, 119.8, 119.7, 116.6, 116.5, 116.3, 113.4,
113.2. Isomer assignments were based on analogous comparison
with literature assignments made for (E)- and (Z)-2,2=-dibromo-
9,9=-bifluorenylidene (6).32
an orange solid (0.372 g, 76% yield): mp 309–312 °C. IR (ATR): 3034,
2952, 2902, 2864, 1605, 1465, 1402, 1362, 1326, 1300, 1250, 1201,
1131, 1107, 1086, 916, 878, 827, 690, 633, 416 cm−1. 1H NMR
(400 MHz, CDCl3) ␦: 1.42 (36H, s, t-Bu-H), 7.23 (4H, dd, J = 1.6, J = 8.4,
H-2,2=,7,7=), 7.72 (4H, s, H-4,4=,5,5=), 8.29 (4H, d, J = 8.8, H-1,1=,8,8=).
13C NMR (100 MHz, CDCl3) ␦: 152.2, 141.3, 139.1, 136.4, 126.3, 123.9,
116.3, 35.1, 31.4. Crystal structure obtained (CCDC 852344).
2,2=,7,7=-Tetra-tert-butyl-9,9=-bifluorenylidene (9)
9,9=-Bifluorenylidene (5)
Microwave-assisted synthesis. 2,7-Di-tert-butyl-9H-fluoren-9-one
synthesized according to literature25,35 (0.256 g, 0.875 mmol) and
LR (0.179 g, 0.443 mmol) were irradiated for 2 min 40 s, reaching a
maximum temperature of 162 °C. Purification by column chroma-
tography afforded title compound 9 as orange needles (0.202 g,
83% yield): mp 226–232 °C. IR (KBr): 2953, 2901, 2865, 1474, 1393,
Microwave-assisted synthesis. 9H-Fluoren-9-one (15) (0.272 g,
1.51 mmol) and LR (0.285 g, 0.705 mmol) were irradiated for 2 min
42 s, reaching a maximum temperature of 152 °C. Purification by
column chromatography afforded the title compound 5 as orange
needles (0.207 g, 84% yield): mp 185–186 °C (lit. 186–187 °C).33 IR
(KBr): 3055, 1597, 1553, 1477, 1444, 1350, 1282, 940, 787, 763, 745,
720, 639, 586 cm−1. 1H NMR (400 MHz, CDCl3) ␦: 7.19 (4H, t, J = 7.6,
H-3,3=,6,6=), 7.31 (4H, t, J = 7.6, H-2,2=,7,7=), 7.68 (4H, d, J = 8.0,
H-1,1=,8,8=); 8.36 (4H, d, J = 8.0, H-4,4=,5,5=). 13C NMR (100 MHz,
CDCl3) ␦: 141.3, 141.0, 138.2, 129.1, 126.8, 126.7, 119.9. Calcd. for
C26H16: C 95.09, H 4.91; found: C 94.90, H 4.84.
1
1254, 1186, 893, 818, 741, 694, 669, 491 cm−1. H NMR (400 MHz,
CDCl3) ␦: 1.28 (36H, s, t-Bu-H), 7.33 (4H, dd, J = 1.6, J = 8.0,
H-3,3=,6,6=), 7.58 (4H, d, J = 8.0, H-4,4=,5,5=); 8.29 (4H, s, H-1,1=,8,8=).
13C NMR (100 MHz, CDCl3) ␦: 149.5, 141.3, 139.0, 138.9, 126.7, 123.0,
119.3, 34.9, 31.5. Crystal structure obtained (CCDC 919566).
12-(12=H-dibenzo[c,g]fluorene-12=-ylidene)-12H-
(E)- and (Z)-2,2=-dibromo-9,9=-bifluorenylidene (6)
dibenzo[c,g]fluorene (10)
Microwave-assisted synthesis. 2-Bromo-9H-fluoren-9-one (0.240 g,
0.927 mmol) and LR (0.182 g, 0.450 mmol) were irradiated for
3 min 30 s, reaching a maximum temperature of 178 °C. Purifica-
tion by column chromatography afforded a 2:1 mixture of E and Z
isomers of title compound 6 as orange needles (0.113 g, 50% yield):
mp 230–232 °C. IR (ATR): 3047, 2921, 2851, 1720, 1458, 1439, 1097,
739, 611 cm−1. 1H NMR (400 MHz, CDCl3) ␦: 7.26 (2H, m, Ar-H), 7.35
(2H, m, Ar-H), 7.46 (2H, t, J = 8.0, Ar-H), 7.55 (2H, d, J = 8.4, Ar-H),
7.67 (2H, d, J = 7.6, Ar-H), 8.28 (2H, d, J = 7.6, E isomer), 8.34 (2H, d,
J = 8.0, Z isomer), 8.43 (2H, s, Z isomer), 8.47 (2H, s, E isomer).
13C NMR (100 MHz, CDCl3) ␦: 140.83, 140.80, 140.62, 140.56, 140.13,
140.10, 139.74, 139.55, 137.74, 137.65, 132.12, 129.84, 129.81, 129.43,
129.18, 127.51, 127.36, 126.73, 126.64, 121.19, 121.16, 120.70, 120.15,
120.08. Isomer assignments by the literature.32
Microwave-assisted synthesis. 7H-dibenzo[c,g]fluoren-7-one syn-
thesized according to the literature36 (0.105 g, 0.374 mmol) and LR
(0.077 g, 0.190 mmol) were irradiated for 13 min 00 s, reaching
a maximum temperature of 199 °C. Purification by column
chromatography afforded title compound 10 as dark purple needles
(0.059 g, 60% yield): mp 338–344 °C (decomposed). IR (ATR): 3044,
2921, 1553, 1403, 1365, 1209, 1180, 1156, 774, 742, 671, 524 cm−1.
1H NMR (400 MHz, CDCl3) ␦: 7.51 (8H, m, Ar-H), 7.70 (4H, d, J = 8.8,
Ar-H), 7.86 (4H, d, J = 8.4, Ar-H), 8.50 (8H, m, Ar-H). 13C NMR
(100 MHz, CDCl3) ␦: 143.8, 141.2, 138.8, 135.5, 128.9, 128.8, 127.6,
127.2, 126.3, 125.5, 124.6. Crystal structures of two polymorphs
obtained (CCDC 805494 and 805495).
N-propyl-9H-fluoren-9-imine (11)
A reaction of 9H-fluoren-9-one (1.0 g, 5.5 mmol, 2 equiv.) and
1-aminopropane (2.0 mL, 24 mmol, 9 equiv.) using TiCl4 (0.45 mL,
4.1 mmol, 1.3 equiv.) performed according to the literature37
afforded the title compound 11 as light yellow crystals (1.2 g,
95% yield): mp 55–58 °C. IR (KBr): 3056, 2963, 2870, 1717, 1639, 1600,
1450, 1380, 1367, 1309, 1284, 1101, 983, 917, 790, 726, 649 cm−1.
1H NMR (400 MHz, CDCl3) ␦: 1.05 (3H, t, J = 7.2, CH3), 1.88 (2H, m, CH2),
4.02 (2H, t, J = 7.2, NCH2), 7.21 (2H, m, H-2,7), 7.31 (2H, m, H-3,6) 7.48
(1H, d, J = 7.6, H-1), 7.57 (1H, d, J = 7.6, H-8), 7.73 (1H, d, J = 7.2, H-5), 7.78
(1H, d, J = 7.6, H-4). 13C NMR (100 MHz, CDCl3) ␦: 162.6, 143.5, 140.9,
138.5, 132.0, 131.0, 130.6, 128.2, 127.8, 127.6, 122.3, 120.3, 119.2, 55.2,
24.8, 12.2. Crystal structure obtained (CCDC 805492).
(E)- and (Z)-2,2=-di(ethoxycarbonyl)-9,9=-bifluorenylidene (7)
To a solution of 9H-fluoren-9-one-2-carboxylic acid (0.335 g,
1.493 mmol) in DMSO (9 mL) was added iodoethane (0.144 mL,
1.800 mmol) and K2CO3 (0.310 g, 2.250 mmol) according to the
literature.34 The reaction mixture was stirred overnight at room
temperature and quenched with water and 1% HCl. Extraction
with ether (3 × 25 mL) followed by concentration under vacuum
afforded 2-ethoxycarbonyl-9H-fluoren-9-one (0.363 g, 96% yield). A
test tube containing a solventless mixture of 2-ethoxycarbonyl-
9H-fluoren-9-one (0.300 g, 1.189 mmol) and LR (0.243 g, 0.601 mmol)
was placed in a sand bath preheated to 158 °C. Heating in the sand
bath was maintained for 22 min 00 s. The product was dissolved in
toluene and purified via column chromatography affording a 1:1
mixture of E and Z isomers of the title compound 7 as an orange
solid (0.281 g, 75% yield): mp 175–180 °C. IR (ATR): 3065, 2922, 2852,
1705, 1605, 1458, 1418, 1364, 1261, 1213, 1184, 1154, 1093, 1022, 923,
857, 746, 723 cm−1. 1H NMR (400 MHz, CDCl3) ␦: 1.37 (6H, t, J = 7.0,
CH3), 1.49 (6H, t, J = 7.0, CH3), 4.36 (4H, q, J = 7.1 OCH2), 4.71 (4H, q,
J = 7.1, OCH2), 7.32–8.38 (12H, m, Ar-H), 9.08 (2H, s, H-1,1=, Z isomer),
9.25 (2H, s, H-1,1=, E isomer). 13C NMR (100 MHz, CDCl3) ␦: 166.5,
144.8, 139.1, 130.7, 130.2, 129.7, 129.6, 128.0, 127.5, 120.9, 120.8,
119.6, 119.2, 68.5, 61.0, 14.3, 13.9. Isomer assignments were based
on analogous comparison with literature assignments for 6.32
Crystal structure obtained (CCDC 852345).
N-phenyl-9H-fluoren-9-imine (14)
A reaction of 9H-fluoren-9-one (14) (1.0 g, 5.5 mmol, 2 equiv.) and
aniline (2.2 mL, 24 mmol, 9 equiv.) using TiCl4 (0.50 mL, 4.6 mmol,
1.2 equiv.) performed according to the literature37 afforded the
title compound 14 as yellow crystals (1.3 g, 92% yield): mp 84–86 °C.
IR (KBr): 3050, 1674, 1609, 1484, 1451, 1304, 1105, 932, 756, 734, 699,
650 cm−1. 1H NMR (400 MHz, CDCl3) ␦: 6.55 (1H, d, J = 7.2, Ar-H), 6.90
(1H, t, J = 7.6, Ar-H), 6.98 (2H, d, J = 8.4, Ar-H), 7.20 (1H, m, Ar-H),
7.26–7.53 (5H, m, Ar-H), 7.57 (2H, d, J = 6.8, Ar-H), 7.90 (1H, d,
J = 7.2, Ar-H). 13C NMR (100 MHz, CDCl3) ␦: 162.8, 151.8, 143.8, 141.8,
137.4, 131.8, 131.7, 131.2, 129.3, 128.4, 127.6, 127.0, 124.0, 123.3, 120.2,
119.6, 118.2. Crystal structure obtained (CCDC 805493).
3,3=,6,6=-Tetra-tert-butyl-9,9=-bifluorenylidene (8)
X-ray diffraction crystallography
A test tube containing a solventless mixture of 3,6-di-tert-
butyl-9H-fluoren-9-one (0.518 g, 1.771 mmol) and LR (0.1875 g,
0.464 mmol) was placed in a sand bath preheated to 218–223 °C.
Heating in the sand bath was maintained for 5 min 00 s. Purifica-
tion by column chromatography afforded the title compound 8 as
Crystal structures were solved for compounds 7, 8, 10, 11, and
14 using a Bruker APEX 2 diffractometer equipped with a SMART
CCD area detector. The structure of compound 9 was solved at
Advanced Light Source (Lawrence Berkeley National Laboratory)
using synchrotron radiation and a D8 goniostat equipped with a
Published by NRC Research Press