G Model
FLUOR-8412; No. of Pages 11
G.K.S. Prakash et al. / Journal of Fluorine Chemistry xxx (2014) xxx–xxx
9
Fig. 6. MP2/cc-pVTZ calculated structures of 28–33.
data with those of the authentic samples (in the case of known
compounds). Some of the reactions were also repeated in presence
of TfOH (7 equivalents, Table 2). Since dichlorobenzene is a solid
aromatic compound, it was dissolved in dichloromethane and the
solution was used in the reaction.
2,2-Bis(20,40-dimethylphenyl)acetic acid (13) [38,39]: 1H NMR
(400 MHz, CDCl3):
d
2.22 (s, 6H), 2.29 (s, 6H), 5.24 (s,1H), 6.97–7.00
19.5, 21.0,
(m, 6H), 10.79 (br, 1H); 13C NMR (100 MHz, CDCl3):
d
50.1, 126.9, 128.1, 131.4, 132.9, 136.2, 137.0, 179.2; GC–MS (EI), m/
z, 268.05 (M+).
2,2-Bis(40-fluorophenyl)acetic acid (14) [37,40]: 1H NMR
4.3. General procedure for the PVP-TfOH catalyzed reactions of acetyl
chloride with arenes
(400 MHz, CDCl3): d 5.00 (s, 1H), 7.00–7.04 (m, 4H), 7.25–7.29
(m, 4H), 10.36 (br, 1H); 13C NMR (100 MHz, CDCl3):
d
55.3, 115.7 (d,
3
4
2JC–F = 21.4 Hz), 130.2 (d, JC–F = 7.6 Hz), 133.4 (d, JC–F = 3.1 Hz),
1
Acetyl chloride (20 mmol, 1.57 g) was added to arene (50 mmol)
in a Nalgene1 bottle. The solution was cooled to 0 8C and then PVP-
TfOH (1:10) complex (4.81 g, 30 mmol) was added slowly. The
mixture was stirred at 0 8C and gradually allowed to warm up to
room temperature and continued for specific period of time
(Table 3). Reaction of benzene (50 mmol) with acetylchloride
(20 mmol, 1.57 g) was repeated in presence of pure TfOH (30 mmol)
for comparison. Progress of the reactions was monitored by TLC (4:1
hexane/ethyl acetate). After the reaction was complete the reaction
mixture was carefully filtered into ice water, neutralized with
solution of sodium bicarbonate, and extracted with diethyl ether
(3 ꢃ 15 mL). The organic extracts were combined, washed with
water and dried over anhydrous Na2SO4. The solvent was removed
by vacuum evaporation and crude products were purified with
column chromatography using silica gel and hexane/ethyl acetate
(85:15) as eluent. All products were characterized by comparing the
spectral data with those of the authentic samples.
162.2 (d, JC–F = 247.2 Hz), 178.5; 19F NMR (376 MHz, CDCl3):
d
ꢀ115.0 (m); GC–MS (EI), m/z, 248.05 (M+).
2,2-Bis(chlorophenyl)acetic acids (15) [37,40]: A mixture was
obtained with para–para isomer as a major product along with
other regioisomers. 1H NMR (400 MHz, CDCl3):
d
4.97 (s, 1H), 5.48
(s, 1H), 7.22–7.25 (m, 7H), 7.29–7.33 (m, 9H), 10.86 (brs, 2H); 13C
NMR (100.5 MHz, CDCl3): 55.33, 55.82, 127.33, 129.20, 129.32,
d
129.95, 130.07, 130.159, 130.61, 134.01, 134.50, 135.00, 135.59,
136.06, 177.97, 178.26; GC–MS (EI), m/z, 280.20 (M+).
2,2-Bis(20,50-difluorophenyl)acetic acid (16): 1H NMR (400 MHz,
CDCl3):
(100 MHz, CDCl3):
d
5.50 (s, 1H), 6.95–7.10 (m, 6H), 10.10 (br, 1H); 13C NMR
2
d
43.3, 116.2–117.0 (m),124.9 (dd, JC–
F = 17.9 Hz, 3JC–F = 8.0 Hz),156.44 (dd, 1JC–F = 243.4 Hz, 4JC–
F = 2.7 Hz), 158.6 (dd, JC–F = 243.4 Hz, JC–F = 2.3 Hz); 19F NMR
1
4
(376 MHz, CDCl3):
d
ꢀ118.0 (m), ꢀ122.4 (m); GC–MS (EI), m/z,
284.15 (M+); HRMS (ESI), m/z calcd for C13H7F4 (M+—45) 239.0484,
observed 239.0476.
2,2-Diphenylacetic acid (10) [35,36]: 1H NMR (400 MHz, CDCl3):
2,2-Bis(20,50-dichlorophenyl)acetic acid (17): 1H NMR (400 MHz,
d
5.04 (s, 1H), 7.25–7.33 (m, 10H), 11.37 (brs, 1H); GC–MS (EI), m/z,
212.00 (M+).
2,2-Bis(methylphenyl)acetic acids (11) [37–39]: A mixture with
para–para isomer as a major product along with other regioi-
somers. 1H NMR (400 MHz, CDCl3):
2.28 (s, 6H), 2.30 (s, 6H), 4.96
(s, 1H), 5.18 (s,1H), 7.11 (d, J = 7.63 Hz, 7H), 7.17–7.21 (m, 8H),
7.26–7.29 (m, 1H) 11.30 (brs, 2H); 13C NMR (100.5 MHz, CDCl3):
CDCl3):
J = 2.4 Hz, 2H), 7.38 (d, J = 8.5 Hz, 2H), 9.37 (br, 1H); 13C NMR
(100 MHz, CDCl3): 51.2, 129.6, 129.7, 131.1, 133.0, 133.2, 135.5,
175.9; GC–MS (EI), m/z, 305.95 (M+—44); HRMS (ESI), m/z calcd for
13H8Cl4 (M—44) 303.9380, observed 303.9369.
d 5.80 (s, 1H), 7.12 (d, J = 2.3 Hz, 2H), 7.28 (dd, J = 8.5 Hz,
d
d
C
d
5. Conclusions
19.78, 21.01, 53.28, 56.25, 126.22, 127.47, 128.04, 128.45, 128.80,
129.29, 130.67, 134.20 135.09, 136.40 137.08, 179.26, 179.30; GC–
MS (EI), m/z, 239.55 (M+).
A novel solid superacidic system, poly(4-vinylpyridinium)
poly(triflic acid) (PVP-TfOH) was developed by immobilization
of triflic acid on poly(4-vinylpyridine). Being much safer to handle,
the polymer supported triflic acid was found to be very convenient
and effective solid acid catalyst for Friedel–Crafts hydroxyalkyla-
tion and acetylation reactions. One pot solvent-free synthesis of
wide variety of diarylacetic acids in high yields can be achieved by
2,2-Bis(20,50-dimethylphenyl)acetic acid (12) [38,39]: 1H NMR
(400 MHz, CDCl3):
7.00 (dd, J = 7.7 Hz, J = 1.1 Hz, 2H), 7.07 (d, J = 7.8 Hz, 2H), 10.82 (br,
1H); 13C NMR (100 MHz, CDCl3):
19.1, 21.2, 50.8, 128.2, 128.9,
130.4, 133.3, 135.5, 135.6, 178.9; GC–MS (EI), m/z, 268.25 (M+).
d2.21(s, 6H), 2.26(s, 6H), 5.27(s,1H), 6.91(s, 2H),
d