Preparation and spectroscopic properties of some new diaroylmethanatoboron difluoride derivatives

Article abstract of DOI:10.1016/j.jfluchem.2012.04.010

Five diaroylmethanatoboron difluoride derivatives were prepared from aryl methyl ketones via Claisen condensation with aromatic esters and followed by complexation with boron trifluoride etherate. Their structures and spectroscopic properties were studied

Full text of DOI:10.1016/j.jfluchem.2012.04.010

Journal of Fluorine Chemistry 140 (2012) 49–53
Contents lists available at SciVerse ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Preparation and spectroscopic properties of some new diaroylmethanatoboron
difluoride derivatives
*
Dun-Jia Wang , Ben-Po Xu, Xian-Hong Wei, Jing Zheng
Hubei Key Laboratory of Pollutant and Reuse Technology, College of Chemistry and Environmental Engineering, Hubei Normal University, Huangshi 435002, PR China
A R T I C L E I N F O
A B S T R A C T
Article history:
Five diaroylmethanatoboron difluoride derivatives were prepared from aryl methyl ketones via Claisen
condensation with aromatic esters and followed by complexation with boron trifluoride etherate. Their
structures and spectroscopic properties were studied by elemental analysis, IR, NMR, ESI–MS, UV and
fluorescence spectroscopy. The results showed that these boron complexes had strong fluorescent peaks
in the 400–500 nm range in chloroform and high quantum yields. The emission peaks for boron
complexes containing naphthyl group exhibited considerable red shift as compared to those of
containing phenyl group.
Received 9 February 2012
Received in revised form 18 April 2012
Accepted 19 April 2012
Available online 26 April 2012
Keywords:
Diaroylmethanatoboron difluoride
Preparation
ß 2012 Elsevier B.V. All rights reserved.
Diaroylmethanes
Spectroscopic properties
1. Introduction
2. Results and discussion
The boron difluoride
b
-diketonates, especially the diaroyl-
2.1. Preparation of diaroylmethanatoboron difluoride derivatives
methanatoboron difluoride derivatives, are of great attention to
the chemists because they exhibit high luminescence in the visible
range of spectrum and can be used as fluorescent electrolumines-
cent emitters, photoconductivity and fluorescent probes [1–3].
Preparation of the title compounds is outlined in Scheme 1. The
diaroylmethanatoboron difluoride derivatives were obtained by
the reaction of boron trifluoride diethyl ether complex (BF3ꢀEt2O)
with the corresponding diaroylmethanes in dichloromethane. The
diaroylmethanes were prepared from aryl methyl ketones via
Claisen condensation with aromatic esters [12,13]. After recrys-
tallization from ethanol, pure boron complexes were isolated in
moderate to good yields. All products and intermediates were
characterized by elemental analysis, FTIR, NMR, and mass
spectroscopy.
Boron difluoride
b-diketonates have been known since 1924 and
the methods of their preparation are considerably well known and
systematized [3–6]. Recently, Ono et al. [7] and Zhang et al. [8,9]
reported synthesis and photoluminescence properties of some
new difluoroboron
b-diketonates. In addition, a variety of solid
state structures of difluoroboron complexes with 1,3-diketones are
also studied [10,11]. With the purpose of investigation into the
influence of aromatic substituent groups (including strong
electron-withdrawing fluorophenyl, electron-donating tert-butyl
phenyl and fused naphthalene ring) on the luminescene intensity,
we report the preparation and spectroscopic properties of some
new diaroylmethanatoboron difluoride derivatives. Structures and
properties of the obtained compounds were established by means
of the elemental analysis, IR, NMR, ESI–MS, UV and fluorescence
spectroscopy.
2.2. IR spectra
The IR spectra of diaroylmethanatoboron difluoride derivatives
show marked changes in comparison with those of the diaroyl-
methanes. The characteristic, strong bands of the diaroylmethanes
and their boron complexes are summarized in Table 1. Their IR
spectra showed several weak vibrations in the range of 3100–
2800 cmꢁ1 assigned to the stretching vibrations for saturated C–H
and unsaturated C–H. In the range of 1650–500 cmꢁ1, their spectra
are substantially different. The strong absorption bands in the
regions of 1629–1599 cmꢁ1 and 1546–1500 cmꢁ1 belonged to the
C55O and enolic C55C stretching vibrations [14,15]. However, the
C55O and C55C stretching frequencies of the boron complexes were
* Corresponding author. Tel.: +86 714 6515602; fax: +86 714 6573832.
E-mail address: dunjiawang@163.com (D.-J. Wang).
0022-1139/$ – see front matter ß 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jfluchem.2012.04.010

50
D.-J. Wang et al. / Journal of Fluorine Chemistry 140 (2012) 49–53
F
F
O
O
O
O
B
1) NaNH
2) H
2
BF / Et O
3
2
O
O
+
R
OCH
R
R
2
CH Cl
R
1
1
2
3
2
2
R
1
R
2
1a - 5a
1b - 5b
CH
1: R =
R =
F
3
1
2
CH
Cl
2: R =
R =
3
1
2
OCH3
3: R =
R =
2
1
OCH3
4: R =
R =
2
C(CH )
1
3 3
CH O
5: R =
R =
C(CH )
3 3
2
1
2
Scheme 1. Synthetic routes for compounds 1b–5b.
red-shifted 1–5 cmꢁ1 with respect to those of the corresponding
diaroylmethanes. These results indicated that the C55O bond in the
diaroylmethanes was weakened due to boron complex formation
arising from the withdraw of electronic density from the chelate
ring by the fluorine atoms, and the vibration frequency was
decreased. The strong absorptions of the boron complexes in the
region of 1371–1366 cmꢁ1 were due to the B–O stretching
vibrations and those in the region of 1203–1180 cmꢁ1 were
attributed to the B–F stretching vibrations [14,16]. Obviously,
there were no strong absorptions in these regions for the
diaroylmethane compounds.
corresponding vinylic signal in the parent enol [14,15]. This is also
explained by the effect of electronegative fluorine atoms on the
electron density of the quasiaromatic cycle of the boron complex.
2.4. UV–vis spectra
The UV–vis spectra data for compounds 1a–5a and 1b–5b in
chloroform are summarized in Table 3. The results showed that
there were a strong broad absorption bands at 364–370 nm and
392–422 nm in compounds 1a–5a and 1b–5b, respectively, which
assigned to
p
p* transitions in the conjugated ring system. The UV
ꢁ
spectra of the boron complexes are similar to those of the
corresponding diaroylmethanes, but bands are red-shifted about
40–50 nm, which indicated that the boron complex forms an
2.3. 1H NMR spectra
In the 1H NMR spectra of the diaroylmethanes and their boron
complexes, their chemical shifts of the phenyl and naphthenyl ring
protons were very similar. However, the chemical shifts of the
enolic OH proton, the keto-CH2 proton and the vinylic proton in
enol exhibited pronounced difference (Table 2). In the diaroyl-
effective p-conjugation between the two aryl groups via the BF2-
chelating moiety.
2.5. Fluorescence spectra and quantum yields
methanes, the enolic protons displayed a single peak at
17.10 ppm and the keto-CH2 protons also revealed a single peak at
= 4.56–4.70 ppm. But in the boron complexes, they did not show
the presence of not only the enolic proton but also the keto-CH2
proton signals. The vinylic protons for the diaroylmethanes and
d
= 16.98–
The fluorescence spectra of compounds 1b–5b were recorded in
chloroform at a concentration of 2.0 ꢂ 10ꢁ5 mol Lꢁ1 (Fig. 1 and
Table 4). The results showed that the boron complexes 1b–5b are
strong fluorescent in the range of 400–500 nm and their quantum
d
yields are good-to-excellent, attributed to their extended
p-
their boron complexes exhibited a single peak at
6.99 ppm, whereas the vinylic proton signal for boron complexes
was shifted 0.24–0.34 ppm to lower field with respect to the
d
= 6.78–
conjugated molecules. The emission maxima, intensity and
quantum yield of 1b were much analogous to those of 2b, assigned
to their similar structure and substituents. As for 5b, its emission
Table 1
Table 2
Comparison of the characteristic IR data for compounds 1a–5a and 1b–5b.
Comparison of 1H NMR parameters for compounds 1a–5a and 1b–5b.
Compound
n
(C5O), cmꢁ1
n
(C5C), cmꢁ1
n
(B–O), cmꢁ1
n
(B–F), cmꢁ1
Compound
d
(keto-CH2), ppm
d
(C5C–H), ppm
d (O–H), ppm
1a
1b
2a
2b
3a
3b
4a
4b
5a
5b
1602 (s)
1599 (s)
1605 (s)
1600 (s)
1628 (s)
1627 (s)
1629 (s)
1625 (s)
1605 (s)
1600 (s)
1505 (s)
1500 (s)
1509 (s)
1506 (s)
1541 (s)
1537 (s)
1545 (s)
1541 (s)
1506 (s)
1501 (s)
–
–
1a
1b
2a
2b
3a
3b
4a
4b
5a
5b
4.56
–
6.78
7.02
6.78
7.05
6.99
7.25
6.97
7.25
6.78
7.12
17.06
–
1368 (s)
1180 (s)
–
1366 (s)
–
–
1186 (s)
–
4.61
–
17.03
–
4.70
–
17.05
–
1371 (s)
–
1203 (s)
–
4.70
–
17.10
–
1369 (s)
–
1198 (s)
–
4.65
–
16.98
–
1370 (s)
1184 (s)

D.-J. Wang et al. / Journal of Fluorine Chemistry 140 (2012) 49–53
51
Table 3
Table 4
UV–vis spectra data for compounds 1a–5a and 1b–5b.
Fluorescence spectra data and quantum yields for compounds 1b–5b.
Compound
lmax (nm)
log emax
Compound
lex (nm)
lem (nm)
fF
1a
2a
3a
4a
5a
358
360
368
370
364
4.73
4.75
4.35
4.30
4.58
1b
2b
3b
4b
5b
400
402
420
422
404
425
425
485
483
426
0.68
0.76
0.33
0.29
0.46
1b
2b
3b
4b
5b
400
402
420
422
404
4.63
4.65
4.21
4.18
4.54
13C NMR spectra were measured on a Varian Mercury-Plus 400
NMR nuclear magnetic resonance instrument in CDCl3 solution
with TMS as internal standard. Infrared spectra were recorded at
1 cmꢁ1 resolution on a Nicolet FTIR 5700 spectrophotometer with
KBr pellets. Low-resolution electrospray ionization mass spectra
(ESI–MS) were determined with a Finnigan LCQ ADVANTAGE MAX
spectrometer. Reagents were of analytical grade and were used
without further purification.
2b
1b
1.0
0.8
0.6
0.4
0.2
0.0
The UV–vis spectra were obtained with Hitachi U-3010
spectrometer. The emission spectra of the sample were carried
5b
out on a Varian Cary Eclipse fluorescence spectrometer. The
values were determined according to literature method using
quinine sulfate in 0.1 mol Lꢁ1 sulfuric acid
ST = 0.55,
ex = 366 nm, at room temperature) as a standard [17]. The
f
3b
4b
(f
l
fluorescence quantum yields
shown in Eq. (1):
f were calculated from the relation
DX ꢂ AST ꢂ n2X
FF
¼
ꢂ
FST
(1)
DST ꢂ AX ꢂ n2ST
400
450
500
550
600
Wavelength (nm)
where the subscripts
X and ST denote test and standard
respectively, is the fluorescence quantum yield, A is the
f
Fig. 1. Normalized emission spectra for compounds 1b–5b.
absorbance at the excitation wavelength, D is the integrated
emission spectrum, and n is the refractive index for the solvent.
intensity and quantum yield were lower than that of 1b and 2b,
owing to steric hindrance of benzyl and tert-butyl groups.
However, the emission maxima for 3b and 4b were red-shifted
about 60 nm as compared to those of compounds 1b, 2b and 5b,
4.2. Preparation of dibenzoylmethanes
The mixture of aryl methyl ketones (0.04 mol), aromatic esters
(0.04 mol), NaNH2 (1.95 g, 0.05 mol) and toluene (50 mL) was
stirred at 80 8C for 6 h. The reaction mixture was cooled to room
temperature, acidified with dilute hydrochloric acid and then
stirred until all solids dissolved. The toluene layer was separated,
washed with a saturated NaHCO3 solution, dried over anhydrous
MgSO4 and the solvent was removed by evaporation. The residual
oil solidified on standing and the solid was recrystallized from
ethanol to obtain the dibenzoylmethanes.
because of their much larger
p-conjugated systems. On the
contrary, their fluorescent intensities and quantum yields were
much lower than those of compounds 1b and 2b, these results in
accordance with the literature [3].
3. Conclusions
In summary, some new diaroylmethanatoboron difluoride
compounds were prepared, and their structures and spectroscopic
properties were investigated by UV–vis, IR, NMR and fluorescence
spectroscopy. These boron complexes exhibited intense fluores-
cence in the 400–500 nm range and high quantum yields. The
absorption and emission maxima of compounds 3b and 4b were
considerably red-shifted as compared to those of compounds 1b,
4.2.1. 1-(4-Methyl-phenyl)-3-(4-fluoro-phenyl)-propane-1,3-dione
(1a)
Colorless crystals, yield 72%, mp 125–126 8C; IR (KBr):
n 3452
(w), 3078 (m), 2961 (m), 2870 (w), 1602 (s), 1540 (m), 1505 (s),
1456 (m), 1365 (w), 1226 (s), 1158 (s), 1104 (m), 1011 (m), 850 (s),
794 (s) cmꢁ1; 1H NMR (400 MHz, CDCl3):
d2.36 (s, 3H, CH3), 4.56 (s,
2b and 5b, suggesting
a
much extended
p
-conjugation in
0.14H, keto CH2), 6.78 (s, 1H, enol CH), 7.10–7.13 (m, 2H), 7.50 (d,
2H, Ar–H, J = 8.4 Hz), 7.81 (d, 2H, Ar–H, J = 8.4 Hz), 7.96–7.99 (m,
2H), 17.06 (br s, 1H, enol OH) ppm; ESI–MS: m/z 257.11 [M + 1]+;
Anal. calcd. for C16H13FO2: C, 74.99; H, 5.11; found: C, 75.46; H,
5.03.
complexes 3b and 4b. They could be used as fluorescent
electroluminescent materials because of their strong fluorescent
property and high quantum yields. The further investigation of
their potential application is in progress.
4. Experimental
4.2.2. 1-(4-Methyl-phenyl)-3-(4-chloro-phenyl)-propane-1,3-dione
(2a)
4.1. Chemicals and methods
Colorless crystals, yield 78%, mp 136–137 8C; IR (KBr): n 3469
(w), 3065 (m), 2952 (m), 2860 (w), 1605 (s), 1545 (m), 1509 (s),
1463 (m), 1369 (w), 1231 (m), 1150 (m), 1100 (s), 1021 (s), 856 (s),
Melting points were determined using X-4 digital melting point
apparatus and uncorrected. Elemental analysis (C, H, N) was
performed using a Perkin-Elmer 2400 elemental analyzer. 1H and
798 (s) cmꢁ1
;
1H NMR (400 MHz, CDCl3):
d
2.35 (s, 3H, CH3), 4.61
(s, 0.16H, keto CH2), 6.78 (s, 1H, enol CH), 7.06–7.09 (m, 2H), 7.48

52
D.-J. Wang et al. / Journal of Fluorine Chemistry 140 (2012) 49–53
(d, 2H, Ar–H, J = 8.4 Hz), 7.90 (d, 2H, Ar–H, J = 8.4 Hz), 7.99–8.02 (m,
2H), 17.03 (br s, 1H, enol OH) ppm; ESI–MS: m/z 273.68 [M + 1]+;
Anal. calcd. for C16H13ClO2: C, 70.46; H, 4.80; found: C, 70.93; H,
4.75.
4.3.2. Boron difluoride 1-(4-methyl-phenyl)-3-(4-chloro-phenyl)-
propane-1,3-dionate (2b)
Yellow green powder, yield 65%, mp 23–239 8C; IR (KBr): n 3032
(w), 2953 (m), 2865 (w), 1600 (s), 1553 (s), 1506 (s), 1458 (m),
1366 (s), 1243 (m), 1186 (s), 1102 (s), 1023 (s), 850 (s), 796
(s) cmꢁ1; 1H NMR (400 MHz, CDCl3):
d 2.36 (s, 3H, CH3), 7.05 (s, 1H,
4.2.3. 1-(6-Methoxy-naphthalen-2-yl)-3-phenyl-propane-1,3-dione
(3a)
C55CH), 7.10–7.12 (m, 2H), 7.51 (d, 2H, Ar–H, J = 8.4 Hz), 7.96 (d,
2H, Ar–H, J = 8.4 Hz), 8.05–8.08 (m, 2H) ppm; 13C NMR (100 MHz,
Pale yellow crystals, yield 52%, mp 143–144 8C; IR (KBr):
n
3490 (w), 3063 (w), 2975 (w), 2852 (w), 1628 (s), 1599 (m),
1541 (s), 1480 (m), 1391 (s), 1267 (s), 1234 (s), 1197 (s), 1022
CDCl3): d 20.6, 92.5, 128.2, 128.9, 129.2, 130.6, 134.5, 135.7, 138.7,
145.3, 183.6, 184.2 ppm; ESI–MS: m/z 321.45 [M + 1]+; Anal. calcd.
(s), 857 (s), 770 (s) cmꢁ1
;
1H NMR (400 MHz, CDCl3):
d
3.96 (s,
for C16H12BClF2O2: C, 59.96; H, 3.77; found: C, 60.12; H, 3.75.
3H, OCH3), 4.70 (s, 0.14H, keto CH2), 6.99 (s, 1H, enol CH), 7.17–
7.18 (m, 2H), 7.51–7.53 (m, 3H), 7.81 (d, 1H, Ar–H, J = 8.4 Hz),
7.88 (d, 1H, Ar–H, J = 9.6 Hz), 7.99–8.04 (m, 3H), 8.48 (s, 1H),
17.05 (br s, 1H, enol OH) ppm; ESI–MS: m/z 305.03 [M + 1]+;
Anal. calcd. for C20H16O3: C, 78.93; H, 5.30; found: C, 79.18; H,
5.16.
4.3.3. Boron difluoride 1-(6-methoxy-naphthalen-2-yl)-3-phenyl-
propane-1,3-dionate (3b)
Earth yellow powder, yield 51%, mp 230–231 8C; IR (KBr):
n
3011 (w), 2949 (w), 2845 (w), 1627 (s), 1599 (m), 1537 (s), 1491 (s),
1390 (s), 1371 (s), 1273 (s), 1203 (s), 1131 (s), 1035 (s), 845 (m),
; d 3.99 (s, 3H,
820 (m), 776 (m) cmꢁ1 1H NMR (400 MHz, CDCl3):
4.2.4. 1-(4-tert-Butyl-phenyl)-3-(6-methoxy-naphthalen-2-yl)-
OCH3), 7.20 (s, 1H, Ar–H), 7.25 (s, 1H, C55CH), 7.31 (s, 1H, Ar–H),
7.56–7.60 (m, 2H, Ar–H), 7.70 (m, 1H, Ar–H), 7.85 (d, 1H, Ar–H,
J = 9.2 Hz), 7.92 (d, 1H, Ar–H, J = 8.8 Hz), 8.08 (d, 1H, Ar–H,
J = 8.8 Hz), 8.19 (d, 2H, Ar–H, J = 7.6 Hz), 8.72 (s, 1H, Ar–H) ppm;
propane-1,3-dione (4a)
Pale yellow crystals, yield 48%, mp 146–147 8C; IR (KBr):
n
3473 (w), 3071 (w), 2950 (s), 2865 (w), 1629 (s), 1608 (m), 1545
(s), 1526 (m), 1481 (m), 1459 (m), 1362 (m), 1300 (m), 1269 (s),
1199 (s), 1111 (s), 1028 (s), 913 (s), 855 (s), 808 (s), 786
13C NMR (100 MHz, CDCl3):
d 56.1, 94.7, 106.8, 120.7, 125.0, 126.5,
128.0, 128.2, 129.5, 129.8, 132.0, 132.4, 132.7, 136.0, 139.0, 161.2,
181.6, 182.9 ppm; ESI–MS: m/z 353.09 [M + 1]+; Anal. calcd. for
(s) cmꢁ1
;
1H NMR (400 MHz, CDCl3):
d
1.37 (s, 9H, C(CH3)3), 3.96
(s, 3H, OCH3), 4.70 (s, 0.14H, keto CH2), 6.97 (s, 1H, enol CH),
7.17–7.23 (m, 2H), 7.53 (d, 2H, Ar–H, J = 8.0 Hz), 7.82 (d, 1H, Ar–
H, J = 8.4 Hz), 7.88 (d, 1H, Ar–H, J = 9.2 Hz), 7.96–8.01 (m, 3H),
8.47 (s, 1H), 17.10 (br s, 1H, enol OH) ppm; ESI–MS: m/z 361.06
[M + 1]+; Anal. calcd. for C24H24O3: C, 79.97; H, 6.71; found: C,
80.45; H, 6.62.
C20H15BF2O3: C, 68.22; H, 4.29; found: C, 68.41; H, 4.27.
4.3.4. Boron difluoride1-(4-tert-butyl-phenyl)-3-(6-methoxy-
naphthalen-2-yl)-propane-1,3-dionate (4b)
Bright yellow needles, yield 68%, mp 243–244 8C; IR (KBr):
3022 (w), 2960 (w), 2865 (w), 1625 (s), 1606 (m), 1541 (s), 1388 (s),
1369 (s), 1269 (s), 1198 (s), 1029 (s), 848 (s), 788 (s) cmꢁ1; 1H NMR
n
4.2.5. 1-(4-Benzyloxy-phenyl)-3-(4-tert-butyl-phenyl)-propane-1,3-
(400 MHz, CDCl3): d 1.38 (s, 9H, C(CH3)3), 3.98 (s, 3H, OCH3), 7.18–
dione (5a)
7.23 (m, 2H, Ar–H), 7.25 (s, 1H, C55CH), 7.56 (d, 2H, Ar–H,
J = 8.8 Hz), 7.82 (d, 1H, Ar–H, J = 8.8 Hz), 7.90 (d, 1H, Ar–H,
J = 8.8 Hz), 8.05 (d, 1H, Ar–H, J = 8.4 Hz), 8.11 (d, 2H, Ar–H,
White crystals, yield 62%, mp 99–101 8C; IR (KBr):
n 3425 (m),
3010 (w), 2961 (m), 2843 (m), 1605 (s), 1506 (s), 1481 (m), 1452
(s), 1379 (w), 1264 (s), 1230 (s), 1174 (s), 1109 (m), 1027 (m), 895
(m), 790 (s) cmꢁ1
C(CH3)3), 4.65 (s, 0.10H, keto CH2), 5.15 (s, 2H, OCH2), 6.78 (s, 1H,
enol CH), 7.06 (d, 2H, Ar–H, J = 8.8 Hz), 7.39–7.46 (m, 5H), 7.50 (d,
2H, Ar–H, J = 8.4 Hz), 7.91 (d, 2H, Ar–H, J = 8.4 Hz), 7.97 (d, 2H, Ar–
H, J = 8.8 Hz), 16.98 (br s, 1H, enol OH) ppm; ESI–MS: m/z 387.12
[M + 1]+; Anal. calcd. for C26H26O3: C, 80.80; H, 6.78; found: C,
81.38; H, 6.70.
J = 8.4 Hz), 8.68 (s,1H, Ar–H) ppm; 13C NMR (100 MHz, CDCl3):
d
;
1H NMR (400 MHz, CDCl3):
d
1.36 (s, 9H,
31.0, 35.4, 55.5, 92.9, 105.9, 120.4, 124.3, 126.2, 126.8, 127.6, 127.9,
128.8, 129.3, 131.3, 131.7, 138.5, 159.4, 160.8, 181.2, 182.5 ppm;
ESI–MS: m/z 409.06 [M + 1]+; Anal. calcd. for C24H23BF2O3: C,
70.61; H, 5.68; found: C, 70.78; H, 5.65.
4.3.5. Boron difluoride 1-(4-benzyloxy-phenyl)-3-(4-tert-butyl-
phenyl)-propane-1,3-dionate (5b)
Yellow green powder, yield 79%, mp 219–220 8C; IR (KBr):
n
4.3. Preparation of diaroylmethanatoboron difluoride
3068 (w), 3030 (w), 2960 (m), 2867 (m), 1600 (s), 1562 (m), 1501
(s), 1370 (s), 1321 (s), 1260 (s), 1184 (s), 1129 (s), 1030 (s), 800 (s),
Boron trifluoride diethyl etherate (1 mL, 7 mmol) was added to
a solution of dibenzoylmethanes (5 mmol) in dry dichloromethane
(10 mL). The reaction mixture was stirred at 40 8C for 3 h. After
removal of the solvent, the residue was filtered and crystallized
from ethanol. The solid was sublimation at 200 8C under
10ꢁ3 mmHg to provide the boron complexes.
819 (s) cmꢁ1 1H NMR (400 MHz, CDCl3):
; d 1.37 (s, 9H, C(CH3)3),
5.20 (s, 2H, OCH2), 7.09 (d, 2H, Ar–H, J = 6.4 Hz), 7.12 (s, 1H, C55CH),
7.42–7.44 (m, 5H, Ar–H), 7.55 (d, 2H, Ar–H, J = 8.4 Hz), 8.06 (d, 2H,
Ar–H, J = 8.4 Hz), 8.15(d, 2H, Ar–H, J = 8.8 Hz) ppm; 13C NMR
(100 MHz, CDCl3):
d 31.0, 35.4, 70.4, 92.2, 115.4, 124.5, 126.1,
127.5, 128.5, 128.7, 128.8, 129.4, 131.5, 135.6, 159.2, 164.6, 180.5,
181.2 ppm; ESI–MS: m/z 435.17 [M + 1]+; Anal. calcd. for
4.3.1. Boron difluoride 1-(4-methyl-phenyl)-3-(4-fluoro-phenyl)-
propane-1,3-dionate (1b)
C26H25BF2O3: C, 71.86; H, 5.80; found: C, 72.09; H, 5.79.
Yellow microcrystalline powder, yield 69%, mp 223–224 8C;
Acknowledgment
IR (KBr):
(s), 1478 (m), 1368 (s), 1316 (s), 1279 (s), 1245 (s), 1180 (s),
1038 (m), 845 (s), 791 (s) cmꢁ1 1H NMR (400 MHz, CDCl3):
n 3070 (w), 2965 (w), 2866 (w), 1599 (s), 1548 (s), 1500
Financial support for this work from the Natural Science
Foundation of the Educational Commission of Hubei Province, PR
China (No. CXY2009B029).
;
d
2.37 (s, 3H, CH3), 7.02 (s, 1H, C55CH), 7.13–7.16 (m, 2H), 7.52 (d,
2H, Ar–H, J = 8.4 Hz), 7.90 (d, 2H, Ar–H, J = 8.4 Hz), 8.02–8.05 (m,
2H) ppm; 13C NMR (100 MHz, CDCl3):
d 20.6, 92.8, 116.0/115.7,
128.3, 128.9, 131.9/131.8, 132.5, 135.2, 145.1, 167.1/163.7,
184.5, 185.1 ppm; ESI–MS: m/z 305.02 [M + 1]+; Anal. calcd. for
C16H12BF3O2: C, 63.20; H, 3.98; found: C, 63.36; H, 3.95.
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