Preparation, crystal structures, and spectroscopic and chemical properties of 2,4,6-trifluorophenyl-or 4-(methoxycarbonyl)-Phenyl-substituted (E)-1-(3-guaiazulenyl)ethylene and (2E,4E)-1-(3-guaiazulenyl)-1,3-butadiene derivatives

Article abstract of DOI:10.1246/bcsj.20100069

Wittig reactions in general provide a mixture of E and Z geometric isomers, while reactions of 2,4,6-trifluorobenzaldehyde [and (E)-3-(2,4,6- trifluorophenyl)propanal] with the Wittig reagent (3-guaiazulenyl) triphenylphosphonium bromide in ethanol containing NaOEt at 25 °C for 24 h under argon give only new E (and 2E,4E)-forms selectively, i.e., (E)-1-(3-guaiazulenyl)-2-(2,4,6-trifluorophenyl)ethylene and (2E,4E)-1-(3-guaiazulenyl)-4-(2,4,6-trifluorophenyl)-1,3-butadiene. For comparative purposes, Wittig reactions of methyl 4-formylbenzoate, 4-(dimethylamino)benzaldehyde, methyl 4-[(E)-2-formylethenyl]benzoate, and (E)-3-[4-(dimethylamino)phenyl]propanal: namely, possessing an electronwithdrawing (-COOCH₃) {or an electron-donating [-N(CH ₃)₂]} group at the C-4 position of the benzene ring, with (3-guaiazulenyl)triphenylphosphonium bromide in methanol (or ethanol) containing NaOMe (or NaOEt) at 25°C for 24h under argon afford a mixture of the corresponding geometric isomers respectively. Along with spectroscopic properties and crystal structures of the isolated products, the chemical behavior of those products toward 1,1,2,2-tetracyanoethylene (TCNE) in benzene at 25°C for 24 h under argon is reported with a view to comparative study.

Full text of DOI:10.1246/bcsj.20100069

1248 Bull. Chem. Soc. Jpn. Vol. 83, No. 10, 1248–1263 (2010)
© 2010 The Chemical Society of Japan
Preparation, Crystal Structures, and Spectroscopic and Chemical
Properties of 2,4,6-Trifluorophenyl- or 4-(Methoxycarbonyl)-
phenyl-Substituted (E)-1-(3-Guaiazulenyl)ethylene and
(2E,4E)-1-(3-Guaiazulenyl)-1,3-butadiene Derivatives
Shin-ichi Takekuma,*1 Hiroto Matsuoka,1 Syoutarou Ogawa,1
Yasutaka Shibasaki,1 and Toshie Minematsu2
1Department of Applied Chemistry, Faculty of Science and Engineering, Kinki University,
3-4-1 Kowakae, Higashi-Osaka 577-8502
2School of Pharmaceutical Sciences, Kinki University, 3-4-1 Kowakae, Higashi-Osaka 577-8502
Received March 11, 2010; E-mail: takekuma@apch.kindai.ac.jp
Wittig reactions in general provide a mixture of E and Z geometric isomers, while reactions of 2,4,6-trifluoro-
benzaldehyde [and (E)-3-(2,4,6-trifluorophenyl)propanal] with the Wittig reagent (3-guaiazulenyl)triphenylphosphonium
bromide in ethanol containing NaOEt at 25 °C for 24 h under argon give only new E (and 2E,4E)-forms selectively, i.e.,
(E)-1-(3-guaiazulenyl)-2-(2,4,6-trifluorophenyl)ethylene and (2E,4E)-1-(3-guaiazulenyl)-4-(2,4,6-trifluorophenyl)-1,3-
butadiene. For comparative purposes, Wittig reactions of methyl 4-formylbenzoate, 4-(dimethylamino)benzaldehyde,
methyl 4-[(E)-2-formylethenyl]benzoate, and (E)-3-[4-(dimethylamino)phenyl]propanal: namely, possessing an electron-
withdrawing (-COOCH3) {or an electron-donating [-N(CH3)2]} group at the C-4 position of the benzene ring, with
(3-guaiazulenyl)triphenylphosphonium bromide in methanol (or ethanol) containing NaOMe (or NaOEt) at 25 °C for 24 h
under argon afford a mixture of the corresponding geometric isomers respectively. Along with spectroscopic properties
and crystal structures of the isolated products, the chemical behavior of those products toward 1,1,2,2-tetracyanoethylene
(TCNE) in benzene at 25 °C for 24 h under argon is reported with a view to comparative study.
In previous papers,1-22 we reported facile preparation and
crystal structures as well as spectroscopic, chemical, and
electrochemical properties of new conjugated ³-electron sys-
tems possessing a 3-guaiazulenyl (=5-isopropyl-3,8-dimeth-
ylazulen-1-yl)1-16,18-22 [or an azulen-1-yl8,15 or a 3-(methoxy-
carbonyl)azulen-1-yl17] group. During the course of our basic
and systematic investigations on azulenes, we found that 17,8
18,8 19,18 and 2018 (Chart 1) serve as strong two electron
donors and one electron acceptors (or a two electron acceptor
for 17) respectively and further that the reactions of 17-20 with
2 equivalents of TCNE, which serves as a strong electron
acceptor,11,12 in benzene at 25 °C for 24 h under argon give
unique cycloaddition products 21,12 22,12 23,18 and 2418
(Chart 2), possessing interesting molecular structures selec-
tively. Similar to our products 21-24, in 2009 Shoji et al.
reported that the reaction of 1,3,6-tri-tert-butylazulene with
TCNE in ethyl acetate at room temperature for 15 h afford-
a considerable extent;24 however, none have really been
documented for the accurate crystal structures as well as the
detailed spectroscopic and chemical properties of those com-
pounds. Along with the above basic studies,1-24 we quite
recently found that the Wittig reactions of 2,4,6-trifluorobenz-
aldehyde (5) [and (E)-3-(2,4,6-trifluorophenyl)propanal (11)]
with (3-guaiazulenyl)triphenylphosphonium bromide (4) in
ethanol containing NaOEt at 25 °C for 24 h under argon
gave only new E (and 2E,4E)-forms selectively, i.e., (E)-1-
(3-guaiazulenyl)-2-(2,4,6-trifluorophenyl)ethylene (7; 63%
isolated yield) (Chart 1) and (2E,4E)-1-(3-guaiazulenyl)-4-
(2,4,6-trifluorophenyl)-1,3-butadiene (13; 54% isolated yield)
(Chart 3). On the other hand, regiospecific photoisomerization
of fluorinated (2E,4E)-1,4-diphenyl-1,3-butadienes25 and crys-
tal structures and emission properties of fluorinated diphenyl-
polyenes26 have been documented; however, the fluorinated ³-
electron systems 7 and 13, possessing a 3-guaiazulenyl group,
have not yet been synthesized. Thus, our next challenge has
been focused on the following clarification: namely, (i) the
difference between the Wittig reactions of 5 (and 11), methyl
4-formylbenzoate (6) {and methyl 4-[(E)-2-formylethenyl]-
benzoate (12)}, and 4-(dimethylamino)benzaldehyde [and (E)-
3-[4-(dimethylamino)phenyl]propanal27] with the reagent 4 in
ethanol (or methanol) containing NaOEt (or NaOMe) at 25 °C
for 24 h under argon; (ii) the difference between the spectro-
scopic properties and the crystal structures of new fluorinated
ed
3,5,9-tri-tert-butyltricyclo[6.2.2.02,6]dodeca-2,4,6,9-tetra-
ene-11,11,12,12-tetracarbonitrile,23 quantitatively, whose pro-
posed reaction mechanism was quoted from our literature.12
Furthermore, in relation to the conjugated ³-electron systems
17-20, for example, preparation and anticancer activity of (E)-
1-aryl-2-(3-guaiazulenyl)ethylenes (=1-[(E)-2-arylethenyl]-5-
isopropyl-3,8-dimethylazulenes) and (2E,4E)-1-aryl-4-(3-
guaiazulenyl)-1,3-butadienes (=1-[(1E,3E)-4-aryl-1,3-butadi-
enyl]-5-isopropyl-3,8-dimethylazulenes) have been studied to
Published on the web October 5, 2010; doi:10.1246/bcsj.20100069

S. Takekuma et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 10 (2010) 1249
F
1
1
1"
1"
6"
F
2"
4"
4"
F
MeOOC
7
8
MeO
1'''
7'''
3'''
4''
1
4'''
1
1"
3''
7''
1"
4"
MeO
N
17
18
1'''
7'''
3'''
1
1
4'''
1"
1"
4"
4"
N
N
19
20
Chart 1.
³-electron systems 7 and 13 and those of (E)-1-(3-guaiazule-
nyl)-2-[4-(methoxycarbonyl)phenyl]ethylene (8) (Chart 1),
(2E,4E)-1-(3-guaiazulenyl)-4-[4-(methoxycarbonyl)phenyl]-
1,3-butadiene (14) (Chart 3), (E)-1-(3-guaiazulenyl)-2-[4-(di-
methylamino)phenyl]ethylene18 (19) (Chart 1), and (2E,4E)-1-
(3-guaiazulenyl)-4-[4-(dimethylamino)phenyl]-1,3-butadiene27
(25) (Chart 3): namely, possessing an electron-withdrawing
(-COOCH3) or an electron-donating [-N(CH3)2] group; and
(iii) the difference between the chemical behavior of 7, 8,
13, 14, 19, and 25 toward TCNE in benzene at 25 °C for 24 h
under argon and further, a plausible reaction pathway for the
formation of the resulting products 9, 10, 15, 16, 23,18 and 2627
(Charts 2 and 3). We now wish to report detailed comparative
studies of the above three points (i)-(iii).
and 125 MHz for 13C) and JNM-ECA700 (700 MHz for 1H and
1
176 MHz for 13C) cryospectrometer at 25 °C. H NMR spectra
were assigned using computer-assisted simulation (software:
gNMR developed by Adept Scientific plc) on a DELL Dimen-
sion 9150 personal computer with a Pentium IV processor.
Preparation of (E)-1-(3-Guaiazulenyl)-2-(2,4,6-trifluoro-
phenyl)ethylene (7). To a solution of 2,4,6-trifluorobenz-
aldehyde (5) (38 mg, 237 ¯mol) in ethanol (5 mL) was added a
solution of (3-guaiazulenylmethyl)triphenylphosphonium bro-
mide22,27 (4) (131, 237 ¯mol) in ethanol (5 mL) containing
sodium ethoxide (32 mg, 470 ¯mol). The mixture was stirred at
25 °C for 24 h under argon. After the reaction, distilled water
was added to the mixture and the resulting product was then
extracted with dichloromethane (10 mL © 3). The extract was
washed with distilled water, dried (MgSO4), and evaporated in
vacuo. The residue thus obtained was carefully separated by
silica gel column chromatography with hexane-benzene (9:1,
vol/vol) as an eluant. The crude product 7 was recrystallized
from acetonitrile to provide pure 7 (53 mg, 150 ¯mol, 63%
yield) as stable single crystals.
Experimental
General. Melting points were taken on a Yanagimoto MP-
S3 instrument. FAB- and EI-MS spectra were taken on a JEOL
The Tandem Mstation JMS-700 TKM data system. UV-vis and
IR spectra were taken on a Beckman DU640 spectrophotometer
and a Shimadzu FTIR-4200 Grating spectrometer. NMR
Compound 7: Dark-green needles [Rf = 0.38 on silica gel
TLC (solv. hexane:benzene = 9:1, vol/vol)]; mp 85 °C; UV-
1
spectra were recorded with a JNM-ECA500 (500 MHz for H

1250 Bull. Chem. Soc. Jpn. Vol. 83, No. 10 (2010)
New Fluorinated ³-Electron Systems
CN
CN
CN CN
CN CN
NC
NC
10a
10a
1
1
F
9
9
CN
CN
CN
CN
3
3
9a
6
9a
6
4b
4b
4a
4a
1'
1'
11
11
CN
4'
4'
CN
F
F
MeOOC
NC
NC
10
9
CN
MeO 4"
CN
1
CN
CN
CN
1
9a
9
CN 10a
CN
CN 10a
CN
CN
4'
3
4b
1"
1'
9a
6
9
CN
CN
4a
7'
3
4b
3'
11
CN
4a
11
CN
6
NC
1'
NC
4'
OMe
21
22
CN
1
N
CN
4"
CN
CN
NC
1
9a
NC
NC
10a
9
10a
4b
CN
CN
CN
3
9
1"
CN
CN
4a
3
4b
9a
1'
4a
11
CN
1'
11
CN
4'
6
NC
N
6
NC
4'
N
24
23
Chart 2.
vis -max/nm (log ¾) in CH2Cl2: 227 (4.20), 267 (4.31), 329
(4.41), 414 (4.41), and 635 (2.66); IR ¯max/cm¹1 (KBr): 2959-
2866 (C-H), 2959, 826 (-CH=CH-), 1585, 1443 (C=C), and
1161, 1115, 1026 (C-F); exact EI-MS (70 eV), found: m/z
354.1575; calcd for C23H21F3: M+, m/z 354.1595; 500 MHz
1H NMR (acetonitrile-d3), signals resulting from a 3-guaiazule-
nyl group: ¤ 1.31 (6H, d, J = 6.9 Hz, (CH3)2CH-7¤), 2.57 (3H,
br s, Me-1¤), 2.95 (3H, s, Me-4¤), 3.02 (1H, sept, J = 6.9 Hz,
(CH3)2CH-7¤), 6.92 (1H, d, J = 10.6 Hz, H-5¤), 7.32 (1H, dd,
J = 10.6, 2.3 Hz, H-6¤), 7.94 (1H, br s, H-2¤), and 8.06 (1H,
d, J = 2.3 Hz, H-8¤); signals resulting from a 2,4,6-trifluoro-
phenyl group: ¤ 6.85 (2H, t, J = 9.2 Hz, H-3¤¤,5¤¤); and signals
resulting from an (E)-ethylene unit: ¤ 6.80 (1H, d, J = 16.4 Hz,
H-2) and 8.30 (1H, d, J = 16.4 Hz, H-1); 125 MHz 13C NMR
(acetonitrile-d3): ¤ 174.2 (C-4¤¤), 172.3 (C-2¤¤,6¤¤), 158.8 (C-4¤),
154.7 (C-7¤), 153.5 (C-8a¤), 147.9 (C-6¤), 147.5 (C-2¤), 146.7
(C-8¤), 145.7 (C-3a¤), 144.6 (C-1), 140.8 (C-5¤), 139.4 (C-1¤),
138.3 (C-3¤), 125.5 (C-1¤¤), 123.2 (C-2), 113.2 (C-3¤¤,5¤¤), 50.0
((CH3)2CH-7¤), 40.3 (Me-4¤), 36.2 ((CH3)2CH-7¤), and 24.7
(Me-1¤).
Mo K¡ radiation (- = 0.71069 ¡, rotating anode: 50 kV,
180 mA) at ¹75 °C. The structure was solved by direct
methods (SIR92)28 and expanded using Fourier techniques
(DIRDIF99).29 Non-hydrogen atoms were refined anisotropi-
cally. Hydrogen atoms were included but not refined. The final
cycle of full-matrix least-squares refinement was based on F2.
All calculations were performed using the teXsan crystallo-
graphic software package.30 Crystallographic data have been
deposited with Cambridge Crystallographic Data Center:
Deposition number CCDC-670806 for compound No. 7.
Copies of the data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/conts/retrieving.html (or from the
Cambridge Crystallographic Data Centre, 12, Union Road,
Cambridge, CB2 1EZ, U.K.; Fax: +44 1223 336033; e-mail:
deposit@ccdc.cam.ac.uk).
Crystallographic data for 7: C23H21F3 (FW: 354.41), dark-
green prism (the crystal size, 0.20 © 0.20 © 0.20 mm3), triclin-
ꢀ
ic, P1 (#2), a = 10.336(3) ¡, b = 16.863(5) ¡, c = 5.336(2) ¡,
¡ = 97.21(3)°, ¢ = 96.83(3)°, £ = 101.09(2)°, V = 895.6(5)
¹1
¡3, Z = 2, Dcalcd = 1.314 g cm¹3, ®(Mo K¡) = 0.964 cm
,
X-ray Crystal Structure of (E)-1-(3-Guaiazulenyl)-2-
(2,4,6-trifluorophenyl)ethylene (7). A total 4332 reflections
with 2ªmax = 55.0° were collected on a Rigaku AFC-5R auto-
mated four-circle diffactometer with graphite monochromated
scan width: (1.21 + 0.30 tan ª)°, scan mode: ½-2ª, scan rate:
4.0°/min, measured reflections: 4332, observed reflectons:
4107, No. of parameters: 257, R1 = 0.0623, wR2 = 0.0942,
goodness of fit indicator: 1.000.

S. Takekuma et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 10 (2010) 1251
1'
7'
1'
1'
7'
7'
2
3'
2
3'
2
3'
4'
1
4
4'
4'
1
1
4
4
F
3
6"
4"
3
3
1"
1"
1"
F
2"
4"
4"
N
F
MeOOC
14
25
13
1
1
1''
CN
CN
CN
CN CN
NC
CN CN
CN CN
7
NC
NC
7
7''
6'
1'
3
6'
1'
5'
4'
3
3''
F
1"
1"
4
4'
4
4'
4
1'
4''
4"
4"
1
N
F
F
MeOOC
15
16
26
Chart 3.
Preparation of (E)-1-(3-Guaiazulenyl)-2-[4-(methoxycar-
bonyl)phenyl]ethylene (8). To a solution of methyl 4-
from an (E)-ethylene unit: ¤ 7.03 (1H, d, J = 16.1 Hz, H-2) and
8.22 (1H, d, J = 16.1 Hz, H-1); 125 MHz 13C NMR (aceto-
nitrile-d3): ¤ 167.5 (H3COOC-4¤¤), 147.3 (C-4¤), 144.5 (C-1¤¤),
143.1 (C-7¤), 142.0 (C-8a¤), 136.34 (C-2¤), 136.27 (C-6¤), 135.0
(C-8¤), 134.2 (C-3a¤), 130.7 (C-3¤¤,5¤¤), 129.4 (C-1), 129.1 (C-
5¤), 128.7 (C-4¤¤), 127.7 (C-1¤), 126.6 (C-2¤¤,6¤¤), 126.5 (C-3¤),
125.6 (C-2), 52.5 (H3COOC-4¤¤), 38.3 ((CH3)2CH-7¤), 28.8
(Me-4¤), 24.5 ((CH3)2CH-7¤), and 13.1 (Me-1¤).
formylbenzoate (6) (57 mg, 347 ¯mol) in methanol (5 mL) was
added a solution of (3-guaiazulenylmethyl)triphenylphospho-
nium bromide22,27 (4) (180 mg, 325 ¯mol) in methanol (5 mL)
containing sodium methoxide (37 mg, 685 ¯mol). The mixture
was stirred at 25 °C for 24 h under argon. After the reaction,
distilled water was added to the mixture and then, the resulting
product was extracted with dichloromethane (10 mL © 3). The
extract was washed with distilled water, dried (MgSO4), and
evaporated in vacuo. The residue thus obtained was carefully
separated by silica gel column chromatography with hexane-
ethyl acetate (9:1, vol/vol) as an eluant. The crude product 8
was recrystallized from hexane to provide pure 8 (53 mg,
148 ¯mol, 46% yield) as stable single crystals.
X-ray Crystal Structure of (E)-1-(3-Guaiazulenyl)-2-[4-
(methoxycarbonyl)phenyl]ethylene (8).
A total 4787
reflections with 2ªmax = 55.0° were collected on a Rigaku
AFC-5R automated four-circle diffractometer with graphite
monochromated Mo K¡ radiation (- = 0.71069 ¡, rotating
anode: 50 kV, 180 mA) at ¹75 °C. The structure was solved
by direct methods (SIR92)28 and expanded using Fourier
techniques (DIRDIF94).31 Non-hydrogen atoms were refined
anisotropically. Hydrogen atoms were included but not
refined. The final cycle of full-matrix least-squares refinement
was based on F2. All calculations were performed using the
teXsan crystallographic software package.30 Deposition num-
ber CCDC-670966 for compound No. 8.
Compound 8: Dark-green needles [Rf = 0.23 on silica gel
TLC (solv. hexane:ethyl acetate = 9:1, vol/vol)]; mp 128 °C;
UV-vis -max/nm (log ¾) in CH2Cl2: 235 (4.41), 280 (4.49),
¹1
335 (4.40), 436 (4.67), and 600 (2.90); IR ¯max/cm (KBr):
2959-2870 (C-H), 2959, 953 (-CH=CH-), 1717 (C=O), 1589
(C=C), and 1281, 1177 (C-O); exact FAB-MS (3-nitrobenzyl
alcohol matrix), found: m/z 358.1932; calcd for C25H26O2:
M+, m/z 358.1933; 500 MHz 1H NMR (acetonitrile-d3), signals
based on a 3-guaiazulenyl group: ¤ 1.32 (6H, d, J = 6.9 Hz,
(CH3)2CH-7¤), 2.59 (3H, br s, Me-1¤), 3.036 (1H, sept, J =
6.9 Hz, (CH3)2CH-7¤), 3.038 (3H, s, Me-4¤), 6.96 (1H, d,
J = 10.6 Hz, H-5¤), 7.35 (1H, dd, J = 10.6, 2.0 Hz, H-6¤), 7.98
(1H, br s, H-2¤), and 8.07 (1H, d, J = 2.0 Hz, H-8¤); signals
arising from a 4-(methoxycarbonyl)pheny group: ¤ 3.86 (3H, s,
H3COOC-4¤¤), 7.62 (2H, dd, J = 8.3, 2.4 Hz, H-2¤¤,6¤¤), and
7.95 (2H, dd, J = 8.3, 2.4 Hz, H-3¤¤,5¤¤); and signals arising
Crystallographic data for 8: C25H26O2 (FW: 358.48), dark-
3
ꢀ
green plate (crystal size: 0.30 © 0.20 © 0.10 mm ), triclinic, P1
(#2), a = 8.942(3) ¡, b = 14.892(5) ¡, c = 7.726(4) ¡, ¡ =
102.44(4)°, ¢ = 94.16(5)°, £ = 77.57(3)°, V = 980.7(7) ¡3,
Z = 2, Dcalcd = 1.214 g cm¹3, ®(Mo K¡) = 0.751 cm¹1, scan
width: (1.26 + 0.30 tan ª)°, scan mode: ½-2ª, scan rate:
8.0°/min, measured reflections: 4787, observed reflections:
4499, No. of parameters: 349, R1 = 0.0602, wR2 = 0.2108,
goodness of fit indicator: 0.987.
Reaction of (E)-1-(3-Guaiazulenyl)-2-(2,4,6-trifluoro-

1252 Bull. Chem. Soc. Jpn. Vol. 83, No. 10 (2010)
New Fluorinated ³-Electron Systems
phenyl)ethylene (7) with 1,1,2,2-Tetracyanoethylene
(TCNE). To a solution of 7 (11 mg, 31 ¯mol) in benzene
(5 mL) was added a solution of TCNE (8 mg, 62 ¯mol) in
benzene (5 mL) under argon. The mixture was stirred at 25 °C
for 24 h under argon. After the reaction, the reaction solution
was evaporated in vacuo. The crude product thus obtained was
recrystallized from benzene-dichloromethane (5:1, vol/vol) to
provide pure 1,1,2,2,11,11,12,12-octacyano-3-(2,4,6-trifluoro-
phenyl)-8-isopropyl-5,10-dimethyl-1,2,3,6,9,10a-hexahydro-6,9-
ethanobenz[a]azulene (9) (5 mg, 8 ¯mol, 26% yield) as stable
crystals.
(50 mg, 312 ¯mol) in toluene (5 mL) was added a solution of
(triphenylphosphoranediyl)acetaldehyde (106 mg, 348 ¯mol) in
toluene (5 mL). The mixture was refluxed for 2 h under argon.
After the reaction, the reaction solution was evaporated in
vacuo. The residue thus obtained was carefully separated by
silica gel column chromatography with hexane-ethyl acetate
(5:1, vol/vol) as an eluant, providing pure 11 (48 mg,
258 ¯mol, 83% yield).
Compound 11: White powder; exact FAB-MS (3-nitrobenzyl
alcohol matrix), found: m/z 186.0279; calcd for C9H5OF3: M+,
m/z +186.0292.
Compound 9: Colorless plates; mp >222 °C (decomp); UV
max/nm (log ¾) in CH2Cl2: 291 (4.16); IR ¯max/cm (KBr):
Preparation of Methyl 4-[(E)-2-Formylethenyl]benzoate
(12). To a solution of methyl 4-formylbenzoate (6) (52 mg,
317 ¯mol) in toluene (5 mL) was added a solution of (tri-
phenylphosphoranediyl)acetaldehyde (100 mg, 329 ¯mol) in
toluene (5 mL). The mixture was refluxed for 2 h under argon.
After the reaction, the reaction solution was evaporated in
vacuo. The residue thus obtained was carefully separated by
silica gel column chromatography with hexane-ethyl acetate
(5:1, vol/vol) as an eluant, providing pure 12 (47 mg, 247
¯mol, 78% yield).
¹1
-
2966-2878 (C-H), 2253 (C¸N), 1632 (C=C), and 1172, 1130
(C-F); exact EI-MS (70 eV), found: m/z 610.1871; calcd for
C35H21N8F3: M+, m/z 610.1841; 700 MHz 1H NMR (dichloro-
methane-d2): ¤ 1.14 (6H, d, J = 6.6 Hz, (CH3)2CH-8), 2.27
(3H, s, Me-5), 2.40 (3H, s, Me-10), 2.62 (1H, sept, J = 6.6 Hz,
(CH3)2CH-8), 3.82 (1H, d, J = 7.8 Hz, H-6), 4.13 (1H, s,
H-10a), 4.33 (1H, d, J = 1.2 Hz, H-9), 4.96 (1H, s, H-3), 6.30
(1H, s, H-4), 6.38 (1H, dd, J = 7.8, 1.2 Hz, H-7), and 6.89
(1H, t, J = 8.6 Hz, H-3¤,5¤); 176 MHz 13C NMR (benzene-d6): ¤
163.4 (C-4¤), 160.6 (C-2¤,6¤), 146.0 (C-8), 137.4 (C-9a), 136.1
(C-4b), 135.5 (C-4a), 130.4 (C-5), 122.8 (C-7), 122.1 (C-3),
111.9 (2CN-11), 111.6 (2CN-12), 111.0 (2CN-2), 109.9
(2CN-1), 107.2 (C-1), 101.5 (C-3¤,5¤), 51.3 (C-10a), 50.4
(C-6), 45.6 (C-9), 45.5 (C-2), 45.3 (C-11), 44.8 (C-12), 39.4
(C-4), 34.3 ((CH3)2CH-8), 23.5 (Me-5), 19.9 ((CH3)2CH-8),
and 13.3 (Me-10). The C-10 and C-1¤ carbon signals are
included in other signals.
Reaction of (E)-1-(3-Guaiazulenyl)-2-[4-(methoxycarbon-
yl)phenyl]ethylene (8) with 1,1,2,2-Tetracyanoethylene
(TCNE). To a solution of 8 (15 mg, 42 ¯mol) in benzene
(5 mL) was added a solution of TCNE (10 mg, 78 ¯mol) in
benzene (5 mL) under argon. The mixture was stirred at 25 °C
for 24 h under argon. After the reaction, the reaction solution
was evaporated in vacuo. The crude product thus obtained was
recrystallized from hexane-dichloromethane (5:1, vol/vol)
to provide pure 1,1,2,2,11,11,12,12-octacyano-3-[4-(methoxy-
carbonyl)phenyl]-8-isopropyl-5,10-dimethyl-1,2,3,6,9,10a-hexa-
hydro-6,9-ethanobenz[a]azulene (10) (13 mg, 21 ¯mol, 50%
yield) as stable crystals.
Compound 12: White powder; exact FAB-MS (3-nitrobenzyl
alcohol matrix), found: m/z 190.0633; calcd for C11H10O3: M+,
m/z 190.0630.
Preparation of (2E,4E)-1-(3-Guaiazulenyl)-4-(2,4,6-tri-
fluorophenyl)-1,3-butadiene (13). To a solution of (E)-3-
(2,4,6-trifluorophenyl)propanal (11) (57 mg, 306 ¯mol) in
ethanol (5 mL) was added a solution of (3-guaiazulenyl-
methyl)triphenylphosphonium bromide22,27 (4) (170 mg, 307
¯mol) in ethanol (5 mL) containing sodium ethoxide (42 mg,
617 ¯mol). The mixture was stirred at 25 °C for 24 h under
argon. After the reaction, distilled water was added to the
mixture and then, the resulting product was extracted with
dichloromethane (20 mL © 3). The extract was washed with
distilled water, dried (MgSO4), and evaporated in vacuo. The
residue thus obtained was carefully separated by silica gel
column chromatography with hexane-ethyl acetate (9:1, vol/
vol) as an eluant. The crude product 13 was recrystallized from
methanol-chloroform (5:1, vol/vol) (several times) to provide
pure 13 (63 mg, 166 ¯mol, 54% yield) as stable single crystals.
Compound 13: Dark-green needles [Rf = 0.50 on silica gel
TLC (solv. hexane:ethyl acetate = 9:1, vol/vol)]; mp 115 °C;
UV-vis -max/nm (log ¾) in CH2Cl2: 237 (4.34), 281 (4.39), 326
Compound 10: Colorless needles; mp >155 °C (decomp);
UV -max/nm (log ¾) in CH2Cl2: 233 (4.54) and 277 (4.22);
¹1
(4.45), 339 (4.54), 439 (4.72), and 639 (2.85); IR ¯max/cm
¹1
IR ¯max/cm (KBr): 2954-2878 (C-H), 2257 (C¸N), 1717
(KBr): 2959-2870 (C-H), 2959, 980 (-CH=CH-), 1589,
1547 (C=C), and 1188, 1165, 1115 (C-F); exact FAB-MS
(3-nitrobenzyl alcohol matrix), found: m/z 380.1732; calcd for
(C=O), 1612, 1435 (C=C), and 1288, 1115 (C-O); exact
FAB-MS (3-nitrobenzyl alcohol matrix), found: m/z 614.2158;
1
1
calcd for C37H26O2N8: M+, m/z 614.2179; 700 MHz H NMR
C25H23F3: M+, m/z 380.1752; 500 MHz H NMR (dichloro-
(dichloromethane-d2): ¤ 1.14, 1.21 (3H each, d, J = 6.7 Hz,
(CH3)2CH-8), 2.11 (3H, d, J = 1.8 Hz, Me-5), 2.26 (3H, d,
J = 1.6 Hz, Me-10), 2.55 (1H, br sept, J = 6.7 Hz, (CH3)2CH-
8), 3.75 (1H, dd, J = 7.8, 1.8 Hz, H-6), 3.94 (3H, s, H3COOC-
4¤), 4.32 (1H, br s, H-10a), 4.760, 4.764 (0.5H each, d,
J = 2.7 Hz, H-3), 6.28 (1H, br s, H-9), 6.33 (1H, ddd, J = 7.8,
1.6, 1.6 Hz, H-7), 7.057, 7.061 (0.5H each, d, J = 2.7 Hz, H-4),
7.57 (2H, dd, J = 8.3, 1.8 Hz, H-2¤,6¤), and 8.21 (2H, dd,
J = 8.3, 1.8 Hz, H-3¤,5¤).
methane-d2), signals from a 3-guaiazulenyl group: ¤ 1.33 (6H,
d, J = 6.9 Hz, (CH3)2CH-7¤), 2.59 (3H, br s, Me-1¤), 2.989 (3H,
s, Me-4¤), 2.993 (1H, sept, J = 6.9 Hz, (CH3)2CH-7¤), 6.86 (1H,
J = 10.6 Hz, H-5¤), 7.25 (1H, dd, J = 10.6, 2.3 Hz, H-6¤), 7.88
(1H, br s, H-2¤), and 7.98 (1H, d, J = 2.3 Hz, H-8¤); signals
from a 2,4,6-trifluorophenyl group: ¤ 6.71 (2H, t, J = 9.2 Hz,
H-3¤¤,5¤¤); and signals from a (2E,4E)-1,3-butadiene unit: ¤
6.52 (1H, d, J = 15.8 Hz, H-4), 6.83 (1H, d, J = 14.9, 10.9 Hz,
H-2), 7.29 (1H, dd, J = 15.8, 10.9 Hz, H-3), and 7.65 (1H, d,
J = 14.9 Hz, H-1); 125 MHz 13C NMR (dichloromethane-d2):
¤ 161.3 (C-4¤¤), 159.3 (C-2¤¤,6¤¤), 145.9 (C-4¤), 141.5 (C-7¤),
Preparation of (E)-3-(2,4,6-Trifluorophenyl)propanal
(11).
To a solution of 2,4,6-trifluorobenzaldehyde (5)

S. Takekuma et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 10 (2010) 1253
140.8 (C-8a¤), 136.5 (C-3), 134.9 (C-2¤), 134.8 (C-6¤), 133.5
(C-8¤), 132.5 (C-3a¤), 131.6 (C-1), 127.6 (C-5¤), 127.3 (C-2),
126.4 (C-1¤), 125.5 (C-3¤), 114.2 (C-4), 112.0 (C-1¤¤), 100.1,
100.0 (C-3¤¤,5¤¤), 37.3 ((CH3)2CH-7¤), 28.0 (Me-4¤), 23.8
((CH3)2CH-7¤), and 12.4 (Me-1¤).
(1H, d, J = 15.5 Hz, H-4), 6.88 (1H, dd, J = 14.9, 10.9 Hz,
H-2), 7.19 (1H, dd, J = 15.5, 10.9 Hz, H-3), and 7.69 (1H, d,
J = 14.9 Hz, H-1); 125 MHz 13C NMR (dichloromethane-d2): ¤
166.4 (H3COOC-4¤¤), 145.9 (C-4¤), 142.4 (C-1¤¤), 141.6 (C-7¤),
140.9 (C-8a¤), 134.8 (C-6¤,2¤), 133.5 (C-8¤), 133.2 (C-3), 132.6
(C-3a¤), 131.8 (C-1), 129.5 (C-3¤¤,5¤¤), 127.8 (C-4,5¤), 127.7 (C-
4¤¤), 126.5 (C-1¤), 126.2 (C-2), 125.6 (C-3¤), 125.4 (C-2¤¤,6¤¤),
51.5 (H3COOC-4¤¤), 37.3 ((CH3)2CH-7¤), 28.0 (Me-4¤), 23.8
((CH3)2CH-7¤), and 12.4 (Me-1¤).
Reaction of (2E,4E)-1-(3-Guaiazulenyl)-4-(2,4,6-trifluo-
rophenyl)-1,3-butadiene (13) with 1,1,2,2-Tetracyanoethyl-
ene (TCNE). To a solution of 13 (20 mg, 53 ¯mol) in benzene
(5 mL) was added a solution of TCNE (15 mg, 117 ¯mol) in
benzene (5 mL) under argon, turning the green solution of 13
into a blue solution gradually. The mixture was stirred at 25 °C
for 24 h under argon. After the reaction, the reaction solution
was evaporated in vacuo. The crude product thus obtained
was recrystallized from hexane-ethyl acetate (5:1, vol/vol)
to provide pure 3-[5,5,6,6-tetracyano-cis-4-(2,4,6-trifluoro-
phenyl)-2-cyclohexenyl]guaiazulene (15) (18 mg, 35 ¯mol,
66% yield) as a stable powder.
X-ray Crystal Structure of (2E,4E)-1-(3-Guaiazulenyl)-4-
(2,4,6-trifluorophenyl)-1,3-butadiene (13).
The X-ray
measurement of a single crystal 13 was made on a Rigaku
Saturn CCD area detector with graphite monochromated
Mo K¡ radiation (- = 0.71075 ¡) at ¹140 « 1 °C. The struc-
ture was solved by direct methods (SIR92)28 and expanded
using Fourier techniques (DIRDIF99).29 Non-hydrogen atoms
were refined anisotropically. Hydrogen atoms were included
but not refined. The final cycle of full-matrix least-squares
refinement was based on F2. All calculations were performed
using the CrystalStructure crystallographic software package
developed by Rigaku corporation, Japan. Deposition number
CCDC-744863 for compound No. 13.
Crystallographic data for 13: C25H23F3 (FW: 380.45), dark-
green needle (the crystal size: 0.53 © 0.27 © 0.19 mm3),
ꢀ
triclinic, P1 (#2), a = 7.4137(12) ¡, b = 7.9708(14) ¡, c =
17.117(3) ¡,
¡ = 94.5313(14)°,
¢ = 95.550(3)°,
£ =
Compound 15: Blue powder; mp >129 °C (decomp); UV-
vis -max/nm (log ¾) in benzene: 295 (4.59), 307 (4.47), 353
(3.82), 370 (3.88), 446 (2.59), 552 (2.65), 587 (2.73), 638
(2.64), and 712 (2.07); IR ¯max/cm¹1 (KBr): 3035-2963 (C-H),
2252 (C¸N), 1632, 1601 (C=C), and 1173, 1126 (C-F); exact
FAB-MS (3-nitrobenzyl alcohol matrix), found: m/z 508.1903;
¹3
103.328(2)°, V = 974.3(3) ¡3, Z = 2, Dcalcd = 1.297 g cm
,
®(Mo K¡) = 0.936 cm¹1, measured reflections: 9490, ob-
served reflectons: 3208, No. of parameters: 277, R1 =
0.0453, wR2 = 0.1486, goodness of fit indicator: 0.959.
Preparation of (2E,4E)-1-(3-Guaiazulenyl)-4-[4-(methoxy-
1
carbonyl)phenyl]-1,3-butadiene (14).
To a solution of
calcd for C31H23N4F3: M+, m/z 508.1875; 700 MHz H NMR
methyl 4-[(E)-2-formylethenyl]benzoate (12) (33 mg, 174
¯mol) in methanol (5 mL) was added a solution of (3-
guaiazulenylmethyl)triphenylphosphonium bromide22,27 (4)
(97 mg, 175 ¯mol) in methanol (5 mL) containing sodium
methoxide (20 mg, 370 ¯mol). The mixture was stirred at 25 °C
for 24 h under argon. After the reaction, distilled water was
added to the mixture and the resulting product was then
extracted with dichloromethane (20 mL © 3). The extract was
washed with distilled water, dried (MgSO4), and evaporated in
vacuo. The residue thus obtained was carefully separated by
silica gel column chromatography with hexane-ethyl acetate
(9:1, vol/vol) as an eluant. The crude product 14 was
recrystallized from methanol-chloroform (5:1, vol/vol) (sev-
eral times) to provide pure 14 (9 mg, 24 ¯mol, 14% yield).
Compound 14: Dark-green needles [Rf = 0.26 on silica gel
TLC (solv. hexane:ethyl acetate = 9:1, vol/vol)]; mp 121 °C;
UV-vis -max/nm (log ¾) in CH2Cl2: 228 (4.36), 249 (4.30), 275
(benzene-d6), signals from a 3-guaiazulenyl group: ¤ 1.39 (6H,
d, J = 7.0 Hz, (CH3)2CH-7), 2.67 (3H, br s, Me-1), 3.140 (3H,
s, Me-4), 3.144 (1H, sept, J = 7.0 Hz, (CH3)2CH-7), 7.18 (1H,
J = 10.9 Hz, H-5), 7.54 (1H, dd, J = 10.9, 2.2 Hz, H-6), 7.78
(1H, br s, H-2), and 8.32 (1H, d, J = 2.2 Hz, H-8); signals from
a 2,4,6-trifluorophenyl group: ¤ 6.93 (2H, t, J = 9.0 Hz, H-
3¤¤,5¤¤); and signals from a cis-1,4-disubstituted 5,5,6,6-tetra-
cyano-2-cyclohexene unit: ¤ 5.04 (1H, m, H-4¤), 5.86 (1H, m,
H-1¤), 6.04 (1H, m, H-3¤), and 6.28 (1H, m, H-2¤); 176 MHz
13C NMR (benzene-d6): ¤ 164.6 (C-4¤¤), 162.6 (C-2¤¤,6¤¤), 144.2
(C-4), 142.4 (C-7), 139.4 (C-8a), 137.3 (C-2), 135.5 (C-6),
134.8 (C-8), 133.8 (C-3a), 129.7 (C-5), 129.0 (C-2¤), 125.5 (C-
1), 123.8 (C-3¤), 115.6 (C-3), 110.6, 110.3, 109.8, 109.6 (CN
each), 105.6 (C-1¤¤), 101.6 (C-3¤¤,5¤¤), 47.8 (C-6¤), 45.0 (C-5¤),
40.6 (C-1¤), 38.0 (C-4¤), 37.5 ((CH3)2CH-7), 27.6 (Me-4), 24.0
((CH3)2CH-7), and 12.5 (Me-1).
Reaction of (2E,4E)-1-(3-Guaiazulenyl)-4-[4-(methoxy-
carbonyl)phenyl]-1,3-butadiene (14) with 1,1,2,2-Tetra-
(4.34), 294 (4.36), 347 (4.33), 459 (4.65), and 633 (2.83); IR
¹1
¯
max/cm (KBr): 2959-2870 (C-H), 2959, 980 (-CH=CH-),
cyanoethylene (TCNE).
To a solution of 14 (15 mg,
1713 (C=O), 1574 (C=C), and 1277, 1173 (C-O); exact FAB-
MS (3-nitrobenzyl alcohol matrix), found: m/z 384.2070;
calcd for C27H28O2: M+, m/z 384.2089; 500 MHz 1H NMR
(dichloromethane-d2), signals originating from a 3-guaiazule-
nyl group: ¤ 1.33 (6H, d, J = 6.9 Hz, (CH3)2CH-7¤), 2.59 (3H,
br s, Me-1¤), 3.00 (1H, sept, J = 6.9 Hz, (CH3)2CH-7¤), 3.01
(3H, s, Me-4¤), 6.87 (1H, d, J = 10.6 Hz, H-5¤), 7.26 (1H, dd,
J = 10.6, 2.0 Hz, H-6¤), 7.90 (1H, br s, H-2¤), and 7.98 (1H, d,
J = 2.0 Hz, H-8¤); signals arising from a 4-(methoxycarbonyl)-
phenyl group: ¤ 3.88 (3H, s, H3COOC-4¤¤), 7.50 (2H, dd,
J = 8.3, 1.9 Hz, H-2¤¤,6¤¤), 7.96 (2H, dd, J = 8.3, 1.9 Hz, H-
3¤¤,5¤¤); and signals from a (2E,4E)-1,3-butadiene unit: ¤ 6.62
39 ¯mol) in benzene (5 mL) was added a solution of TCNE
(10 mg, 78 ¯mol) in benzene (5 mL) under argon, turning the
green solution of 14 into a blue solution gradually. The mixture
was stirred at 25 °C for 24 h under argon. After the reaction, the
reaction solution was evaporated in vacuo. The crude product
thus obtained was recrystallized from hexane-ethyl acetate
(5:1, vol/vol) to provide pure methyl 4-[5,5,6,6-tetracyano-
cis-4-(3-guaiazulenyl)-2-cyclohexenyl]benzoate (16) (14 mg,
27 ¯mol, 69% yield) as a stable powder.
Compound 16: Blue powder; mp >202 °C (decomp); UV-
vis -max/nm (log ¾) in benzene: 295 (4.66), 307 (4.55), 353
(3.92), 370 (3.98), 470 (2.68), 589 (2.90), 638 (2.82), and 704

1254 Bull. Chem. Soc. Jpn. Vol. 83, No. 10 (2010)
New Fluorinated ³-Electron Systems
CHO
POCl3
in DMF
at 0 °C for 1 h
under argon
1
2
CH2OH
NaBH4
Ph3P HBr
2
P
in EtOH
at 25 °C for 1 h
in CHCl3
reflux, for 1 h
under argon
Br
3
4
CHO
R3
R1
R2
5: R1=R2=R3=F
6: R1=R3=H, R2=COOMe
NaOEt (or NaOMe)
7 (or 8)
4
in EtOH (or MeOH)
at r.t. for 15 min
under argon
in EtOH (or MeOH)
at r.t. for 24 h
under argon
Scheme 1. The preparation of the Wittig reagent 4 and the reaction of 5 (or 6) with 4 in ethanol (or methanol) in the presence of
sodium ethoxide (or sodium methoxide) at 25 °C for 24 h under argon.
¹1
(2.45); IR ¯max/cm (KBr): 2959-2808 (C-H), 2245 (C¸N),
1612 (C=O), and 1215, 1169 (C-O); exact FAB-MS (3-
nitrobenzyl alcohol matrix), found: m/z 512.2205; calcd for
C33H28O2N4: M+, m/z 512.2212; 700 MHz 1H NMR (benzene-
d6), signals from a 3-guaiazulenyl group: ¤ 1.137, 1.140 (3H
each, J = 7.0 Hz each, (CH3)2CH-7¤¤), 2.52 (3H, br s, Me-1¤¤),
2.72 (1H, sept, J = 7.0 Hz, (CH3)2CH-7¤¤), 3.01 (3H, s, Me-4¤¤),
6.73 (1H, J = 10.8 Hz, H-5¤¤), 7.11 (1H, dd, J = 10.8, 2.2 Hz,
H-6¤¤), 7.91 (1H, br s, H-2¤¤), and 8.14 (1H, d, J = 2.2 Hz,
H-8¤¤); signals from a 4-substituted methyl benzoate: ¤ 3.51
(3H, s, H3COOC-1), 7.09 (2H, dd, J = 8.2, 1.8 Hz, H-3,5), and
8.03 (2H, dd, J = 8.2, 1.8 Hz, H-2,6); and signals from a cis-
1,4-disubstituted 5,5,6,6-tetracyano-2-cyclohexene unit: ¤ 4.29
(1H, m, H-1¤), 5.19 (1H, m, H-2¤), 5.80 (1H, m, H-3¤), and
5.94 (1H, m, H-4¤); 176 MHz 13C NMR (benzene-d6): ¤ 165.7
(H3COOC-1), 144.8 (C-4¤¤), 142.5 (C-7¤¤), 140.3 (C-8a¤¤),
138.0 (C-2¤¤), 137.7 (C-4), 135.8 (C-6¤¤), 135.2 (C-8¤¤), 134.8
(C-3a¤¤), 132.4 (C-1), 131.0 (C-3¤), 130.7 (C-2,6), 130.5 (C-5¤¤),
129.7 (C-3,5), 125.9 (C-1¤¤), 124.9 (C-2¤), 116.3 (C-3¤¤), 111.6,
111.3, 111.0, 110.4 (CN each), 51.8 (H3COOC-1), 47.7 (C-5¤),
47.2 (C-1¤,6¤), 41.3 (C-4¤), 37.8 ((CH3)2CH-7¤¤), 28.1 (Me-4¤¤),
24.4 ((CH3)2CH-7¤¤), and 13.0 (Me-1¤¤).
nium bromide in ethanol containing NaOEt at 25 °C for 24 h
under argon gave the E and Z isomers of 2-[4-(dimethylamino)-
phenyl]-1-(3-guaiazulenyl)ethylene, while only the E form 19
could be isolated as single crystals in 12% yield (Chart 1).18
Quite recently, we further found that the reversed Wittig
reaction of 4-(dimethylamino)benzaldehyde with (3-guaiazule-
nyl)triphenylphosphonium bromide22,27 (4), which can be
derived via the materials 1-3 (Scheme 1), under the same
reaction conditions as the above afforded the same results.
Similarly, the Wittig reaction of methyl 4-formylbenzoate (6)
with 4 in methanol containing NaOMe at 25 °C for 24 h under
argon gave a ca. 2:1 mixture of the corresponding E and Z
isomers and similar to 19, only the E form 8 could be isolated
as single crystals in 46% yield (Scheme 1);32 however, the
reaction of 2,4,6-trifluorobenzaldehyde (5) with 4 in ethanol
containing NaOEt at 25 °C for 24 h under argon provided only
the E form 7 as single crystals in 63% yield (Scheme 1). The
great difference between the above Wittig reactions can be
inferred that the reaction of 4-(dimethylamino)benzaldehyde
(or 6) with 4 yields a mixture of the corresponding geometric
isomers, i.e., (E)- and (Z)-2-[4-(dimethylamino)phenyl]-1-(3-
guaiazulenyl)ethylenes {or (E)- and (Z)-1-(3-guaiazulenyl)-2-
[4-(methoxycarbonyl)phenyl]ethylenes}, via trans- and cis-
oxaphosphetane intermediates, while the reaction of 5 with 4
provides only the E form 7, whose structure is derived from the
trans-oxaphosphetane a, forming an intramolecular CH£FC
hydrogen bond at the two positions, illustrated in Chart 4. In
relation to our studies, in 1994 Karatsu, Tokumaru et al.
Results and Discussion
Preparation and Spectroscopic Properties of 7 and 8. In
2008 we reported that the Wittig reaction of guaiazulene-3-
carbaldehyde (=5-isopropyl-3,8-dimethylazulene-1-carbalde-
hyde) (2) with [4-(dimethylamino)benzyl]triphenylphospho-

S. Takekuma et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 10 (2010) 1255
reported that 1-styrylazulene and 3-styrylguaiazulene (=7-
isopropyl-1,4-dimethyl-3-styrylazulene) underwent one-way
isomerization from the Z to E isomer on triplet sensitization,
whose triplet states as intermediates of the isomerization were
observed by laser flash photolysis.33 In our case, a rapid one-
way isomerization from the resulting (Z)-1-(3-guaiazulenyl)-2-
(2,4,6-trifluorophenyl)ethylene to the E isomer 7 under the
above reaction conditions cannot be excluded completely, the
phenomenon of which is currently under intensive investiga-
tion. The molecular structures of 7 and 8 were established on
the basis of spectroscopic data [UV-vis, IR, EI- (or FAB-) MS,
unit, the signals of which were carefully assigned using H-H
COSY and computer-assisted simulation based on first-order
analysis. As a result, the Me-1¤, H-2¤, Me-4¤, and H-8¤ proton
signals of 7 coincided with those of 19; however, the six proton
signals [H-5¤, H-6¤, (CH3)2CH-7¤, (CH3)2CH-7¤, H-3¤¤,5¤¤, and
H-1] of 7 showed downfield shifts and the H-2 proton signal of
7 revealed an upfield shift in comparison with those of 19
(Table 1). The 13C NMR spectrum of 7 exhibited 20 carbon
signals assigned using HMQC and HMBC (Tables 2 and 3).
The C-3¤¤,5¤¤ carbon signal of 7 coincided with that of 19. The
C-1¤¤ and C-2 carbon signals of 7 showed upfield shifts in
comparison with those of 19, while the other carbon signals of
7 showed downfield shifts in comparison with those of 19. An
1
and H and 13C NMR including 2D NMR (i.e., H-H COSY,
HMQC, and HMBC)].
1
The fluorinated compound 7 was obtained as dark-green
needles. The spectroscopic properties of 7 compared with those
of 19 are described as follows. The UV-vis spectrum of 7
showed that the spectral pattern of 7 resembled that of 19; the
longest absorption wavelength of 7 revealed a hypsochromic
shift (¦ 19 nm) and a slight hypochromic effect (¦ log ¾ =
0.14) in comparison with that of 19 (Figure 1). The IR
spectrum showed specific bands from the C-H, -CH=CH-,
C=C, and C-F bonds, the wavenumbers (C-H, -CH=CH-,
and C=C) of which revealed slight high and low frequency
shifts in comparison with those of 19. The molecular formula
C23H21F3 was determined by exact EI-MS spectrum. The
1H NMR spectrum showed signals from a 3-guaiazulenyl and
2,4,6-trifluorophenyl group and signals from an (E)-ethylene
apparent difference between the UV-vis spectrum and the H
and 13C NMR chemical shifts (¤) of 7 and those of 19 is owing
to the influence of the 2,4,6-trifluorophenyl substituent, which
serves as an electron-withdrawing group, and the 4-(dimethyl-
amino)phenyl substituent, which serves as an electron-donating
group. The detailed spectroscopic analyses for 7 led to the
molecular structure illustrated in Chart 1.
Compound 8 was obtained as dark-green needles. The
spectroscopic properties of 8 compared with those of 7 and 19
are described as follows. The UV-vis spectrum of 8 showed
that the spectral pattern of 8 resembled those of 7 and 19; the
longest absorption wavelength of 8 revealed a hypsochromic
shift (¦ 54 nm) and a slight hyperchromic effect (¦ log ¾ =
0.10) in comparison with that of 19 (Figure 1). The IR
spectrum showed specific bands from the C-H, -CH=CH-,
C=C, C=O, and C-O bonds, the wavenumbers (C-H,
-CH=CH-, and C=C) of which revealed slight high shifts
in comparison with those of 19. The molecular formula
C25H26O2 was determined by exact FAB-MS spectrum. The
1H NMR spectrum showed signals from a 3-guaiazulenyl and
4-(methoxycarbonyl)phenyl group and signals from an (E)-
ethylene unit, the signals of which were carefully assigned
using similar analyses to 7. As a result, although the Me-1¤,
H-2¤, and H-2¤¤,6¤¤ proton signals of 8 coincided with those of
19, the eight proton signals [Me-4¤, H-5¤, H-6¤, (CH3)2CH-7¤,
(CH3)2CH-7¤, H-8¤, H-3¤¤,5¤¤, and H-1] of 8 showed downfield
shifts and the proton H-2 signal of 8 revealed an upfield shift in
Ph: Phenyl group, Gu3: 3-Guaiazulenyl group
Chart 4.
Figure 1. (a) The UV-vis spectra of 7 and 8 in CH2Cl2. Concentrations, 7: 0.10 g L¹1 (282 ¯mol), 8: 0.08 g L¹1 (223 ¯mol). Length
of the cell, 0.1 cm each. Each log ¾ value is given in parenthesis. (b) The UV-vis spectra of 19 in CH2Cl2. Concentration, 19:
¹1
0.10 g L (291 ¯mol). Length of the cell, 0.1 cm. log ¾ value is given in parenthesis.

1
Table 1. The H NMR Spectral Data (¤) of 7 and 8 in Acetonitrile-d3, 13 and 14 in Dichloromethane-d2, 19 and 25 in Benzene-d6
3-Guaiazulenyl group
H-5¤ H-6¤ (CH3)2CH-7¤ (CH3)2CH-7¤ H-8¤
Aryl group
Butadiene (or ethylene) part
Compound
Me-1¤ H-2¤
Me-4¤
H-2¤¤,6¤¤ (CH3)2N-4¤¤ H-3¤¤,5¤¤ H3COOC-4¤¤
H-1
H-2
H-3
H-4
7
8
13
14
19
25
2.57
2.59
2.59
2.59
2.56
2.523
7.94
7.98
7.88
7.90
8.01
7.98
2.95
3.038
2.989
3.01
2.88
2.81
6.92
6.96
6.86
6.87
6.56
6.55
7.32
7.35
7.25
7.26
7.00
6.97
3.02
3.036
2.993
3.00
2.73
2.71
1.31
1.32
1.33
1.33
1.20
1.19
8.06
8.07
7.98
7.98
7.97
7.93
®
®
®
6.85
7.95
6.71
7.96
6.67
6.61
®
3.86
®
8.30
8.22
7.65
7.69
8.10
7.67
6.80
7.03
6.83
6.88
7.15
7.07
®
®
®
®
7.62
®
®
®
7.29
7.19
®
6.52
6.62
®
7.50
7.57
7.47
3.88
®
2.56
2.519
®
7.15
6.77
Table 2. The 13C NMR Spectral Data (¤) of 7 and 8 in Acetonitrile-d3, 13 and 14 in Dichloromethane-d2, 19 and 25 in Benzene-d6
3-Guaiazulenyl group
Compound
C-1¤
Me-1¤
C-2¤
C-3¤
C-3a¤
C-4¤
Me-4¤
C-5¤
C-6¤
C-7¤
(CH3)2CH-7¤
(CH3)2CH-7¤
C-8¤
C-8a¤
7
8
13
14
19
25
139.4
127.7
126.4
126.5
126.1
126.5
24.7
13.1
12.4
12.4
13.1
13.1
147.5
136.34
134.9
134.8
136.7
136.4
138.3
126.5
125.5
125.6
128.4
126.5
145.7
134.2
132.5
132.6
132.7
132.8
158.8
147.3
145.9
145.9
146.2
146.4
40.3
28.8
28.0
28.0
28.4
28.4
140.8
129.1
127.6
127.8
126.9
127.3
147.9
136.27
134.8
134.8
134.6
134.7
154.7
143.1
141.5
141.6
140.1
140.6
50.0
38.3
37.3
37.3
37.9
37.9
36.2
24.5
23.8
23.8
24.5
24.4
146.7
135.0
133.5
133.5
133.4
133.4
153.5
142.0
140.8
140.9
141.2
141.6
Table 3. The 13C NMR Spectral Data (¤) of 7 and 8 in Acetonitrile-d3, 13 and 14 in Dichloromethane-d2, 19 and 25 in Benzene-d6
Aryl group
Butadiene (or ethylene) part
Compound
C-1¤¤
C-2¤¤,6¤¤
C-3¤¤,5¤¤
C-4¤¤
(CH3)2N-4¤¤
H3COOC-4¤¤
H3COOC-4¤¤
C-1
C-2
C-3
C-4
7
8
13
14
19
25
125.5
144.5
112.0
142.4
128.4
127.4
172.3
126.6
159.3
125.4
127.4
127.7
113.2
130.7
100.0, 100.1
129.5
174.2
128.7
161.3
127.7
149.9
150.1
®
®
®
52.5
®
®
167.5
®
144.6
129.4
131.6
131.8
123.0
128.7
123.2
125.6
127.3
126.2
128.0
129.2
®
®
®
®
®
®
136.5
133.2
®
114.2
127.8
®
51.5
®
166.4
®
®
113.2
113.0
40.2
40.1
®
127.5
131.2

S. Takekuma et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 10 (2010) 1257
(a)
(b)
(c)
(d)
Figure 2. (a) The ORTEP drawing (30% probability thermal ellipsoids) of 7. (b) The space filling molecular structure of 7. The two
different views [(c) and (d)] for the packing molecular structures of 7. Hydrogen atoms are omitted for reasons of clarity.
comparison with those of 19 (Table 1). The 13C NMR spectrum
exhibited 22 carbon signals assigned using HMQC and HMBC
(Tables 2 and 3). The C-3¤, C-4¤¤, and C-2 carbon signals of 8
showed upfield shifts in comparison with those of 19, while the
ten carbon signals [C-1¤, C-3a¤, C-4¤, C-5¤, C-6¤, C-7¤, C-8¤,
C-1¤¤, C-3¤¤,5¤¤, and C-1] of 8 showed downfield shifts in
comparison with those of 19. The other carbon signals of 8
coincided with those of 19. An apparent difference between
the UV-vis spectrum and the 1H and 13C NMR chemical
shifts (¤) of 8 and those of 19 results from the influence of the
4-(methoxycarbonyl)phenyl substituent, which serves as an
electron-withdrawing group, and the 4-(dimethylamino)phenyl
substituent, which serves as an electron-donating group. The
detailed spectroscopic analyses for 8 led to the molecular
structure illustrated in Chart 1.
X-ray Crystal Structures of 7 and 8. The recrystallization
(several times) of 7 from acetonitrile provided single crystals
suitable for X-ray crystallographic analysis, while the recrys-
tallization (several times) of 8 from hexane provided single
crystals suitable for that purpose. The crystal structures of 7
and 8 were then determined by X-ray diffraction, producing
accurate structural parameters. The ORTEP drawings of 7 and
8, indicating the molecular structures illustrated in Chart 1, are
shown in Figures 2a and 3a, 3b along with the selected bond
lengths (Tables 4 and 5). As a result, it was found that from the
dihedral angles between the least-squares planes, the planes of
the 3-guaiazulenyl groups of 7 and 8 twisted by 6 and 46° from
those of the benzene rings. Although the C-C bond alternation
patterns observed for the azulene rings of 7, 8, and 19 were
slightly different (Table 4), owing to the influence of the 2,4,6-
trifluorophenyl, 4-(methoxycarbonyl)phenyl, and 4-(dimethyl-
amino)phenyl substituents, the average C-C bond length of
the seven-membered ring for the 3-guaiazulenyl group of
7 (1.411 ¡) coincided with those of 8 (1.407 ¡) and 19
(1.407 ¡). The C-C bond length of the five-membered ring for
the 3-guaiazulenyl group of 7 appreciably varied between
1.368 and 1.509 ¡; in particular, the C1¤-C2¤ bond length
(1.368 ¡) was characteristically shorter than the average C-C
bond length for the five-membered ring (1.430 ¡), the results of
which coincided with those of 19. Similar to 7 and 19, the C-C
bond length of the five-membered ring for the 3-guaiazulenyl
group of 8 appreciably varied between 1.367 and 1.491 ¡; in
particular, the C1¤-C2¤ bond length (1.367 ¡) was character-
istically shorter than the average C-C bond length for the
five-membered ring (1.425 ¡). The C1-C2 bond lengths of 7
(1.331 ¡) and 8 (1.342 ¡) were longer than that of 1918
(1.325 ¡) (Table 5). The C1H£F7¤¤C2¤¤ and C2H£F9¤¤C6¤¤
distances of 7 (2.23 and 2.38 ¡) and the space-filling molecular
structure of 7 shown in Figure 2b were suggested to form an
intramolecular CH£FC hydrogen bond between them. Along
with the ORTEP drawings of 7 and 8, the packing molecular
structures of 7 and 8 are shown in Figures 2c, 2d and 3c,
3d. Figures 2c and 2d revealed that each average interplane
distance between the overlapping molecules, whose direc-
tions were the same, was 5.34 ¡ for 7, suggesting that each
molecule forms a weak ³-stacking structure in the single
crystal; however, Figure 3d revealed that each average inter-
plane distance between the overlapping molecules, which were

1258 Bull. Chem. Soc. Jpn. Vol. 83, No. 10 (2010)
New Fluorinated ³-Electron Systems
Figure 3. The two different [top (a) and side (b)] views of the ORTEP drawings (30% probability thermal ellipsoids) of 8. The two
different [top (c) and side (d)] views for the packing molecular structures of 8. Hydrogen atoms are omitted for reasons of clarity.
Table 4. The C-C Bond Lengths (¡) of 7, 8, 13, 19, and 25
Table 5. The C-C, C-F, C-O, and C-N Bond Lengths (¡)
of 7, 8, 13, 19, and 25
Atom
7
8
13
19
25
Atom
7
8
13
19
25
C1¤-C2¤
C2¤-C3¤
1.368(3) 1.367(3) 1.380(2) 1.373(4) 1.375(3)
1.419(4) 1.421(4) 1.425(2) 1.418(4) 1.419(2)
C1-C2
C2-C3
C3-C4
C1-C3¤
C4-C1¤¤
C2-C1¤¤
1.331(4) 1.342(3) 1.348(2) 1.325(4) 1.342(3)
C3¤-C3a¤ 1.430(4) 1.414(3) 1.417(2) 1.408(3) 1.421(3)
C3a¤-C4¤ 1.390(4) 1.410(4) 1.410(2) 1.411(4) 1.402(2)
C4¤-C5¤
C5¤-C6¤
C6¤-C7¤
C7¤-C8¤
C8¤-C8a¤ 1.385(3) 1.379(3) 1.390(2) 1.381(3) 1.379(3)
C8a¤-C1¤ 1.423(4) 1.431(4) 1.416(2) 1.419(4) 1.423(2)
C1¤-C9¤
C4¤-C10¤ 1.523(3) 1.510(4) 1.505(2) 1.523(5) 1.521(3)
C7¤-C11¤ 1.530(3) 1.528(3) 1.525(2) 1.520(4) 1.532(3)
C11¤-C12¤ 1.514(4) 1.514(4) 1.528(2) 1.518(5) 1.505(4)
C11¤-C13¤ 1.527(4) 1.514(3) 1.507(2) 1.529(6) 1.518(4)
C8a¤-C3a¤ 1.509(3) 1.491(3) 1.502(2) 1.503(4) 1.505(2)
®
®
®
®
1.443(2)
1.337(2)
®
®
1.436(3)
1.349(3)
1.407(4) 1.397(3) 1.402(2) 1.380(4) 1.395(3)
1.402(3) 1.397(3) 1.397(2) 1.403(5) 1.402(3)
1.383(4) 1.378(4) 1.380(2) 1.370(5) 1.376(3)
1.399(4) 1.394(4) 1.404(2) 1.398(4) 1.403(3)
1.457(3) 1.452(3) 1.454(2) 1.457(4) 1.447(3)
®
®
1.460(2)
®
®
1.458(4)
1.455(3)
®
1.460(3) 1.469(3)
C1¤¤-C2¤¤ 1.396(4) 1.402(4) 1.395(2) 1.389(5) 1.393(3)
C2¤¤-C3¤¤ 1.379(4) 1.385(3) 1.369(2) 1.372(4) 1.387(3)
C3¤¤-C4¤¤ 1.373(5) 1.386(3) 1.362(2) 1.408(4) 1.398(3)
C4¤¤-C5¤¤ 1.360(5) 1.385(4) 1.378(2) 1.382(6) 1.403(4)
C5¤¤-C6¤¤ 1.377(4) 1.386(3) 1.378(2) 1.378(5) 1.387(3)
C6¤¤-C1¤¤ 1.392(4) 1.394(3) 1.404(2) 1.391(4) 1.395(3)
C2¤¤-F7¤¤ 1.357(4)
C4¤¤-F8¤¤ 1.365(3)
C6¤¤-F9¤¤ 1.358(3)
C4¤¤-C7¤¤
C7¤¤-O8¤¤
C7¤¤-O9¤¤
O9¤¤-C10¤¤
C4¤¤-N7¤¤
N7¤¤-C8¤¤
N7¤¤-C9¤¤
1.502(4) 1.498(4) 1.499(2) 1.495(5) 1.494(2)
®
®
1.3565(18)
1.357(2)
1.3561(19)
®
®
®
®
®
®
®
®
®
®
®
®
®
®
®
®
®
®
®
®
®
®
1.482(3)
1.196(4)
1.338(3)
1.440(4)
®
®
®
®
®
®
®
®
overlapped so that those dipole moments might be negated
mutually, was 3.97 ¡ for 8, suggesting that each molecule
forms a ³-stacking structure in the single crystal. Furthermore,
Figure 3c showed that the distance between the intermolecular
methoxycarbonyl groups was 4.59 ¡, suggesting the formation
of a weak C¤+£:O coordinate bond illustrated in that figure.
1.377(4) 1.380(3)
1.461(6) 1.444(3)
1.427(5) 1.432(3)
®
®

S. Takekuma et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 10 (2010) 1259
TCNE
7 (or 8)
9 (or 10)
in benzene
at r.t. for 24 h
under argon
P
CHO
O
Scheme 2. The reaction of 7 (or 8) with 2 equivalents of
TCNE in benzene at 25 °C for 24 h under argon.
R3
5 (or 6)
R1
in toluene
reflux, for 2 h
R2
Reactions of 7 and 8 with TCNE. In 2008 we reported
that the reaction of 19 with 2 equivalents of TCNE in benzene
at 25 °C for 24 h under argon gave product 23 (Chart 2) in 41%
isolated yield and further, a plausible reaction pathway for
the formation of 23 was proposed.18 Along with the spectro-
scopic properties of 23, the crystal structure of 23 could be
determined. For comparative purposes, the reactions of 7 and 8
with 2 equivalents of TCNE were carried out under the same
reaction conditions as for 19 (Scheme 2), affording new 23
analogs 9 and 10 (Chart 2), in 26 and 50% isolated yields, the
molecular structures of which were established on the basis of
similar spectroscopic analyses to those of 7 and 8. A similar
reaction pathway to 2318 can be inferred for the formation of 9
and 10.
under argon
11: R1=R2=R3=F
12: R1=R3=H, R2=COOMe
Scheme 3. The Wittig reaction of 5 (or 6) with (triphenyl-
phosphoranediyl)acetaldehyde in toluene at reflux temper-
ature for 2 h under argon, providing the corresponding
cinnamaldehydes 11 and 12.
NaOEt (or NaOMe)
11 (or 12)
13 (or 14)
4
in EtOH (or MeOH)
at r.t. for 24 h
in EtOH (or MeOH)
at r.t. for 15 min
under argon
under argon
Scheme 4. The Wittig reaction of 11 (or 12) with 4 in
ethanol (or methanol) in the presence of sodium ethoxide
(or sodium methoxide) at 25 °C for 24 h under argon.
Compound 9 was obtained as colorless plates, while 10
was obtained as colorless needles. The characteristic UV-vis
absorption bands of guaiazulene34 (1) and 7 were not observed
for 9 and the longest UV absorption wavelength appeared at
-
291 nm (log ¾ = 4.16). Similar to 9, the characteristic
Similar to the above, the Wittig reaction of methyl 4-[(E)-2-
formylethenyl]benzoate (12) with 422,27 in methanol containing
NaOMe at 25 °C for 24 h under argon afforded a ca. 1:1
mixture of the corresponding 2E,4E- and 2Z,4E-isomers and
similar to 25, only the 2E,4E-form 14 could be isolated as
single crystals in 14% yield (Scheme 4);35 however, the
reaction of (E)-3-(2,4,6-trifluorophenyl)propanal (11) with the
Wittig reagent 4 in ethanol containing NaOEt at 25 °C for
24 h under argon provided only the 2E,4E-form 13 as single
crystals in 54% yield (Scheme 4). Similar to 7, 8, and the
previously reported 19,18 the great difference between the
above Wittig reactions can be inferred that the reaction of (E)-
3-[4-(dimethylamino)phenyl]propanal (or 12) with 4 yields a
mixture of the corresponding geometric isomers, i.e., (2E,4E)-
and (2Z,4E)-4-[4-(dimethylamino)phenyl]-1-(3-guaiazulenyl)-
1,3-butadienes {or (2E,4E)- and (2Z,4E)-1-(3-guaiazulenyl)-4-
[4-(methoxycarbonyl)phenyl]-1,3-butadienes}, via trans- and
cis-oxaphosphetane intermediates, while the reaction of 11 with
4 provides only the 2E,4E-form 13, whose structure is derived
from the trans-oxaphosphetane b, forming an intramolecular
CF£HC£HC hydrogen bond at the two positions, illustrated in
Chart 4. Similar to 7, a rapid one-way isomerization from the
yielded (2Z,4E)-1-(3-guaiazulenyl)-4-(2,4,6-trifluorophenyl)-
1,3-butadiene to the 2E,4E-isomer 13 under the above reaction
conditions cannot be excluded completely, the phenomenon of
which is also currently under intensive investigation. The
molecular structures of 13 and 14 were established on the basis
of similar analyses to 7 and 8.
max
UV-vis absorption bands of 134 and 8 were not observed for 10
and the longest UV absorption wavelength appeared at -max
277 nm (log ¾ = 4.22). The IR spectra of 9 and 10 showed
specific bands from the C-H, -C¸N, C=C, and C-F bonds for
9 and specific bands from the C-H, -C¸N, C=C, C=O, and
C-O bonds for 10. The molecular formula C35H21N8F3 of 9
was determined by exact EI-MS spectrum and the molecular
formula C37H26O2N8 of 10 was determined by exact FAB-MS
spectrum. The H and 13C NMR spectra of 9 showed signals
1
from a 3-(2,4,6-trifluorophenyl) group and a 1,1,2,2,11,11,-
12,12-octacyano-8-isopropyl-5,10-dimethyl-1,2,3,6,9,10a-hexa-
hydro-6,9-ethanobenz[a]azulene unit and the 1H NMR spec-
trum of 10 revealed signals from a 3-[4-(methoxycarbonyl)-
phenyl] group and an 8-isopropyl-5,10-dimethyl-1,2,3,6,9,10a-
hexahydrobenz[a]azulene unit, the signals of which were
carefully assigned using conventional methodology. Thus, the
detailed spectroscopic analyses of 9 and 10 indicated similar
structures to that of 23, illustrated in Chart 2.
Preparation of 11 and 12. A facile preparation of the
starting materials 11 and 12 of the target compounds 13 and 14
is as follows. The reactions of 5 and 6 with an equivalent of
(triphenylphosphoranediyl)acetaldehyde were carried out under
the same reaction conditions (Scheme 3), affording the (E)-
cinnamaldehydes 11 and 12 in 83 and 78% isolated yield.
Preparation and Spectroscopic Properties of 13 and 14.
Quite recently, we reported that the Wittig reaction of (E)-3-[4-
(dimethylamino)phenyl]propanal with the reagent 4 in ethanol
containing NaOEt at 25 °C for 24 h under argon gives the
2E,4E- and 2Z,4E-isomers of 4-[4-(dimethylamino)phenyl]-1-
(3-guaiazulenyl)-1,3-butadiene, while only the 2E,4E-form 25
could be isolated as single crystals in 19% yield (Chart 3).27
The fluorinated compound 13 was obtained as dark-green
needles. The spectroscopic properties of 13 compared with
those of 25 are as follows. The UV-vis spectrum of 13 showed
that the spectral pattern of 13 resembled that of 25; the longest

1260 Bull. Chem. Soc. Jpn. Vol. 83, No. 10 (2010)
New Fluorinated ³-Electron Systems
¹1
¹1
Figure 4. (a) The UV-vis spectra of 13 and 14 in CH2Cl2. Concentrations, 13: 0.10 g L (263 ¯mol), 14: 0.10 g L (260 ¯mol).
Length of the cell, 0.1 cm each. Each log ¾ value is given in parenthesis. (b) The UV-vis spectrum of 25 in CH2Cl2. Concentration,
¹1
25: 0.11 g L (298 ¯mol). Length of the cell, 0.1 cm. log ¾ value is given in parenthesis.
absorption wavelength of 13 revealed a hypsochromic shift
(¦ 20 nm) and a slight hyperchromic effect (¦ log ¾ = 0.08) in
comparison with that of 25 (Figure 4). The IR spectrum
showed specific bands from the C-H, -HC=CH-, C=C, and
C-F bonds, the wavenumbers (C-H, -HC=CH-, and C=C)
of which revealed slight high and low frrequency shifts in
comparison with those of 25. The molecular formula C25H23F3
was determined by exact FAB-MS spectrum. The 1H NMR
spectrum showed signals arising from a 3-guaiazulenyl and
2,4,6-trifluorophenyl group and signals from a 2E,4E-butadiene
unit, the signals of which were carefully assigned using H-H
COSY and computer-assisted simulation based on first-order
analysis. Although the Me-1¤, H-8¤, and H-1 proton signals
coincided with those of 25,27 the seven proton signals [Me-4¤,
H-5¤, H-6¤, (CH3)2CH-7¤, (CH3)2CH-7¤, H-3¤¤,5¤¤, and H-3] of
13 showed downfield shifts and the H-2¤, H-2, and H-4 proton
signals of 13 revealed upfield shifts in comparison with those
of 25 (Table 1). The 13C NMR spectrum exhibited 23 carbon
signals assigned using HMQC and HMBC (Tables 2 and 3).
Although the six carbon (C-2¤, C-3¤, C-1¤¤, C-3¤¤,5¤¤, C-2, and
C-4) and four carbon (C-2¤¤,6¤¤, C-4¤¤, C-1, and C-3) signals of
13 showed up- and downfield shifts in comparison with those
of 25, the other carbon signals of 13 coincided with those of 25.
In particular, the C-3 and C-4 carbon signals of 13 were
apparently down- and upfield shifts in comparison with those
of 25. Similar to the difference between 7 and 19, an apparent
difference between the UV-vis spectrum and the 1H and
13C NMR chemical shifts (¤) of 13 and those of 25 result from
the influence of the 2,4,6-trifluorophenyl and 4-(dimethyl-
amino)phenyl substituents. Besides the above, an apparent
difference between the UV-vis spectrum and the 1H and
13C NMR chemical shifts (¤) of the (2E,4E)-1,3-butadiene 13
and those of the (E)-ethylene 7 was also observed (Figures 1, 4
and Tables 1-3). The detailed spectroscopic analyses for 13
led to the molecular structure illustrated in Chart 3.
shift (¦ 26 nm) and a slight hyperchromic effect (¦ log ¾ =
0.06) in comparison with that of 25 (Figure 4). The IR
spectrum showed specific bands arising from the C-H,
-CH=CH-, C=C, C=O, and C-O bonds, the frequencies
(C-H, -CH=CH-, and C=C) of which revealed slight high and
low shifts in comparison with those of 13 and 25. The
molecular formula C27H28O2 was determined by exact FAB-
1
MS spectrum. The H NMR spectrum showed signals from a
3-guaiazulenyl and 4-(methoxycarbonyl)phenyl group and
signals from a 2E,4E-butadiene unit, the signals of which
were carefully assigned using H-H COSY and computer-
assisted simulation based on first-order analysis. Although
the six proton signals (Me-1¤, H-2¤, H-8¤, H-2¤¤,6¤¤, H-1, and
H-3) of 14 coincided with those of 25, the six proton signals
[Me-4¤, H-5¤, H-6¤, (CH3)2CH-7¤, (CH3)2CH-7¤, and H-3¤¤,5¤¤]
of 14 showed downfield shifts and the H-2 and H-4 proton
signals of 14 showed upfield shifts in comparison with those
of 25 (Table 1). The 13C NMR spectrum exhibited 22 carbon
signals assigned using HMQC and HMBC (Tables 2 and 3).
Although the five carbon signals (C-7¤, C-1¤¤, C-3¤¤,5¤¤, C-1, and
C-3) of 14 showed downfield shifts in comparison with those
of 25, the five carbon signals (C-2¤, C-2¤¤,6¤¤, C-4¤¤, C-2, and
C-4) of 14 revealed upfield shifts in comparison with those
of 25. The other carbon signals of 14 coincided with those of
25. Similar to the difference between 8 and 19, an apparent
difference between the UV-vis spectrum and the 1H and
13C NMR chemical shifts (¤) of 14 and those of 25 arise from
the influence of the 4-(methoxycarbonyl)phenyl and 4-(di-
methylamino)phenyl substituents. Besides the above, an appa-
1
rent difference between the UV-vis spectrum and the H and
13C NMR chemical shifts (¤) of the (2E,4E)-1,3-butadiene 14
and those of the (E)-ethylene 8 was also observed (Figures 1, 4
and Tables 1-3). The detailed spectroscopic analyses of 14 led
to the molecular structure illustrated in Chart 3.
X-ray Crystal Structure of 13. The crystal structure of 14
has not yet been elucidated because of difficulty in obtaining
a single crystal suitable for X-ray crystallographic analysis,
while the recrystallization of 13 from a mixed solvent of
chloroform and methanol (1:5, vol/vol) provided single
crystals suitable for that purpose. The crystal structure of 13
Compound 14 was obtained as dark-green needles. The
spectroscopic properties of 14 compared with those of 25
are as follows. The UV-vis spectrum of 14 showed that
the spectral pattern of 14 resembled those of 13 and 25; the
longest absorption wavelength of 14 revealed a hypsochromic

S. Takekuma et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 10 (2010) 1261
was then determined by means of X-ray diffraction, producing
accurate structural parameters. The ORTEP drawing of 13, with
a numbering scheme, indicating the molecular structure
illustrated in Chart 3, is shown in Figure 5 along with selected
bond lengths (Tables 4 and 5). As a result, it was found that
from the dihedral angles between the least-squares planes, the
plane of the 3-guaiazulenyl group of 13 twisted by 5° from that
of the benzene ring. The average C-C bond length of the seven-
membered ring for the 3-guaiazulenyl group of 13 (1.412 ¡)
coincided with those of 7 (1.410 ¡) and 25 (1.409 ¡). The C-C
bond length of the five-membered ring for the 3-guaiazulenyl
group of 13 appreciably varied between 1.380 and 1.502 ¡; in
particular, the C1¤-C2¤ bond length for the five-membered ring
(1.380 ¡) was characteristically shorter than the average C-C
bond length for the five-membered ring (1.428 ¡), whose
results were similar to those of 7 and 25. The C1-C2 and C2-
C3 bond lengths of 13 were slightly longer than those of 25,
while the C3-C4 bond length of 13 was slightly shorter than
that of 25. The bond alternation pattern observed for the 3-
guaiazulenyl and 2,4,6-trifluorophenyl groups of 13 coincided
with that of 25. Although the C4H£F9¤¤C6¤¤ and C3H£F7¤¤C2¤¤
distances of 13 (2.41 and 2.33 ¡) were slightly longer than the
C2H£F9¤¤C6¤¤ and C1H£F7¤¤C2¤¤ distances of 7, the results
of which were suggested to form an intramolecular CH£FC
hydrogen bond between them. Along with the ORTEP drawing
of 13, the packing molecular structures of 13, illustrated using a
space-filling molecular structure (Figures 6a and 6b) and a
ball and stick molecular structure (Figures 6c and 6d), showed
that each molecule formed a ³-stacking structure and an
intermolecular hydrogen bond between C12¤H£F8¤¤C4¤¤ (and
C13¤H£F8¤¤C4¤¤) in the single crystal, and revealed that the
average interplane and hydrogen bond distances between the
overlapping molecules, which were overlapping so that those
dipole moments might be negated mutually, were 3.35 ¡ (for
the ³-stacking structure) and 2.60 ¡ (for the hydrogen bond).
Therefore, an apparent difference between the packing mo-
lecular structures of 7 and those of 13 could be observed.
Reactions of 13 and 14 with TCNE. Quite recently, we
reported that the reaction of 25 with 2 equivalents of TCNE in
benzene at 25 °C for 24 h under argon gave a Diels-Alder
Figure 5. The ORTEP drawing (30% probability thermal
ellipsoids) of 13.
Figure 6. The two different [side (a) and top (b)] views for the packing molecules of the space-filling molecular structure 13. The
two different [side (c) and top (d)] views for the packing molecules of the ball and stick molecular structure 13. Hydrogen atoms are
omitted for reasons of clarity.

1262 Bull. Chem. Soc. Jpn. Vol. 83, No. 10 (2010)
New Fluorinated ³-Electron Systems
TCNE
13 (or 14)
15 (or 16)
in benzene
at r.t. for 24 h
under argon
Scheme 5. The reaction of 13 (or 14) with 2 equivalents of
TCNE in benzene at 25 °C for 24 h under argon.
Figure 8. The UV-vis spectrum of 16 in benzene. Con-
¹1
centration, 16: 0.10 g L (195 ¯mol). Length of the cell,
0.1 cm. Each log ¾ value is given in parenthesis.
using conventional methodology. Thus, the detailed spectro-
scopic analyses of 15 and 16 indicated similar structures to that
of 26, illustrated in Chart 3.
Conclusion
Figure 7. The UV-vis spectrum of 15 in benzene. Con-
centration, 15: 0.10 g L (218 ¯mol). Length of the cell,
¹1
We have reported the following three interesting points for
the title chemistry: namely, (i) the Wittig reactions in general
provide a mixture of E and Z geometric isomers, while the
reactions of 2,4,6-trifluorobenzaldehyde (5) [and (E)-3-(2,4,6-
trifluorophenyl)propanal (11)] with the Wittig reagent (3-
guaiazulenyl)triphenylphosphonium bromide (4) in ethanol
containing NaOEt at 25 °C for 24 h under argon gave only E
(and 2E,4E)-forms selectively, i.e., (E)-1-(3-guaiazulenyl)-
2-(2,4,6-trifluorophenyl)ethylene (7) and (2E,4E)-1-(3-guai-
azulenyl)-4-(2,4,6-trifluorophenyl)-1,3-butadiene (13); (ii) for
comparative purposes, the Wittig reactions of methyl 4-
formylbenzoate and methyl 4-[(E)-2-formylethenyl]benzoate,
possessing an electron-withdrawing group (-COOCH3), with
reagent 4 in methanol containing NaOMe at 25 °C for 24 h
under argon afforded a mixture of the corresponding geometric
isomers, i.e., (E)- and (Z)-1-(3-guaiazulenyl)-2-[4-(methoxy-
carbonyl)phenyl]ethylenes and (2E,4E)- and (2Z,4E)-1-(3-
guaiazulenyl)-4-[4-(methoxycarbonyl)phenyl]-1,3-butadienes,
the results of which coincided with those of the reactions
of 4-(dimethylamino)benzaldehyde and (E)-3-[4-(dimethyl-
amino)phenyl]propanal, possessing an electron-donating group
[-N(CH3)2], with 4. A reaction mechanism for the formation
of 7 (and 13) via the trans-oxaphosphetane intermediates a
(and b), forming an intramolecular CH£FC hydrogen bond
at the two positions illustrated in Chart 4, was proposed; and
(iii) along with the spectroscopic properties and the crystal
structures of the isolated ³-electron systems 7, 8, 13, and 14
compared with those of the previously reported 19 and 25,
the chemical properties of 7, 8, 13, and 14 toward 1,1,2,2-
tetracyanoethylene (TCNE) compared with those of 19 and 25,
yielding the resulting cycloaddition products 9, 10, 15, and 16,
were reported.
0.1 cm. Each log ¾ value is given in parenthesis.
adduct 26 (Chart 3) in 59% isolated yield.27 Along with the
spectroscopic properties of 26, the crystal structure of 26 was
determined. For comparative purposes, the reactions of 13 and
14 with 2 equivalents of TCNE were carried out under the same
reaction conditions as for 25 (Scheme 5), affording new Diels-
Alder adducts 15 and 16 in 66 and 69% isolated yields, the
molecular structures of which were established on the basis of
similar spectroscopic analyses to those of 13 and 14. A similar
reaction pathway (i.e., [³4 + ³2] cycloaddition reaction) to
that of 2627 can be inferred for the formation of the resulting
products 15 and 16.
Compounds 15 and 16 were obtained as a blue powder.
Similar to 26, the characteristic UV-vis absorption bands of
13 were not observed for 15, while those from guaiazulene34
(1) with a band (446 nm, log ¾ = 2.59) were observed as
shown in Figure 7 and the longest visible absorption wave-
length appeared at -max 587 nm (log ¾ = 2.73). Similar to 15,
the characteristic UV-vis absorption bands of 14 were not
observed for 16, while those from 134 with a band (470 nm,
log ¾ = 2.68) were observed as shown in Figure 8 and the
longest visible absorption wavelength appeared at -max 589 nm
(log ¾ = 2.90). The IR spectra showed specific bands from the
C-H, -C¸N, C=C, and C-F bonds for 15 and specific bands
from the C-H, -C¸N, C=C, C=O, and C-O bonds for 16. The
molecular formulas C31H23N4F3 (for 15) and C33H28O2N4 (for
1
16) were determined by exact FAB-MS spectra. The H NMR
(including NOE) and 13C NMR spectra showed signals from a
2,4,6-trifluorophenyl and 3-guaiazulenyl group and a cis-1,4-
disubstituted 5,5,6,6-tetracyano-2-cyclohexene unit for 15 and
signals from a 4-(methoxycarbonyl)phenyl and 3-guaiazulenyl
group and a cis-1,4-disubstituted 5,5,6,6-tetracyano-2-cyclo-
hexene unit for 16, the signals of which were carefully assigned
This work was partially supported by a Grant-in-Aid for
Scientific Research from the Ministry of Education, Culture,
Sports, Science and Technology, Japan.

S. Takekuma et al.
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Bull. Chem. Soc. Jpn. Vol. 83, No. 10 (2010) 1263
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