CF3 Oxonium Salts
(N2+), 1589, 1560, 1248, 1220, 1196, 1071 cm-1; MS (FAB) m/z
321 (M+ - SbF6); high MS M+ - SbF6 (C17H16F3N2O) 321.12033
(calcd 321.12147).
ethyl)dibenzofuranium Salts 1a,b, 2a-d, 3b, and 4a,b: A
Typical Procedure. A solution of 6.5 mg (12 µmol) of 18a and
1.1 mg (7.5 µmol) of benzotrifluoride (as an internal standard for
19F NMR analysis) in 0.6 mL of CD2Cl2 was placed into a Pyrex
glass NMR tube, then the tube was sealed after being purged with
N2. The tube was immersed in an EtOH-liquid N2 bath (a Pyrex
glass container) cooled to -106 °C, and irradiated for 45 min from
about 3.5 cm away with a high-pressure mercury lamp (400 W;
main light wavelength, 253.7 nm) positioned outside of the bath.
A bath temperature of -90 to -100 °C was maintained during the
irradiation. After the irradiation, the 19F NMR was measured at
-80 °C. The reaction solution in the NMR tube at the low
temperature of -90 to -106 °C was homogeneous both before
and after irradiation. The analysis of the NMR spectrum showed
2a was produced in 87% yield and 23 and 24 were produced in
9% and 3% yield, respectively.
5-tert-Butyl-2′-(trifluoromethoxy)biphenylyl-2-diazoniumhexaflu-
orophosphate (18c): mp 95.0-95.7 °C (CH3CN-Et2O); 1H NMR
δ 8.76 (1H, d, J ) 8.9 Hz), 7.94 (1H, dd, J ) 8.9, 1.9 Hz), 7.74
(1H, d, J ) 1.9 Hz), 7.72-7.68 (2H, m), 7.61 (1H, dt, J ) 1.1, 7.6
Hz), 7.53 (1H, m), 1.42 (9H s); 19F NMR δ -58.32 (3F, s), -72.81
(6F, d, J ) 712 Hz); IR (KBr) 2970, 2267, 1590, 1562, 1245, 1220,
1183, 1073 cm-1; low mass (FAB) m/z 321 (M+ - PF6); high MS
M+ - PF6 (C17H16F3N2O) 321.12116 (calcd 321.12147).
5-tert-Butyl-2′-(trifluoromethoxy)biphenylyl-2-diazonium tet-
1
rafluoroborate (18d): oily and sticky product; H NMR δ 8.91
(1H, d, J ) 8.9 Hz), 7.93 (1H, dd, J ) 8.9, 1.9 Hz), 7.79 (1H, dd,
J ) 7.7, 1.7 Hz), 7.73 (1H, d, J ) 1.9 Hz), 7.69 (1H, dt, J ) 1.7,
7.7 Hz), 7.61 (1H, dt, J ) 1.1, 7.7 Hz), 7.52 (1H, dd, J ) 1.1, 7.7
Hz), 1.42 (9H, s); 19F NMR δ -58.22 (3F, s), -151.60 (4F, s); IR
(KBr) 2971, 2268, 1589, 1562, 1260, 1220, 1178, 1072 cm-1; MS
(FAB) m/z 321 (M+ - BF4); high MS M+ - BF4 (C17H16F3N2O)
321.12209 (calcd 321.12147).
2-tert-Butyl-O-(trifluoromethyl)dibenzofuranium hexafluo-
roantimonate (2a): 1H NMR (CD2Cl2 at -70 °C) δ 8.30 (1H, dd,
J ) 7.6, 1.5 Hz, 5-H), 8.21 (1H, d, J ) 2.3 Hz, 1-H), 8.09 (1H,
dm, J ) 9.1 Hz, 8-H), 8.03 (1H, t, J ) 7.6 Hz, 6-H), 7.99 (1H, dq,
J ) 9.5, 2.3 Hz, 4-H), 7.92 (1H, ddd, J ) 9.1, 7.6, 1.5 Hz, 7-H),
7.89 (1H, dd, J ) 9.5, 2.3 Hz, 3-H), 1.44 (9H, s, 2-t-C4H9); 19F
NMR (CD2Cl2 at -70 °C) δ -52.65 (s, CF3). 5-tert-Butyl-2-fluoro-
5-Fluoro-2′-(trifluoromethoxy)biphenylyl-2-diazonium hexaflu-
oroantimonate (19a): mp 130-131 °C dec; 1H NMR (CD3CN) δ
7.58-7.89 (6H, m), 8.71 (1H, dd, J ) 9, 5 Hz); 19F NMR (CD3-
CN) δ -57.2 (3F, s, CF3), -82.2 (1F, td, J ) 8, 5 Hz, F), -102
to -144 (6F, m, SbF6); IR (KBr) 2272 (N2+) cm-1; MS (FAB)
m/z 283 (M+ - SbF6); high MS M+ - SbF6 (C13H7F4N2O)
283.04965 (calcd 283.04945).
1
2′-(trifluoromethoxy)biphenyl (23): H NMR δ 7.44-7.41 (2H,
m), 7.39-7.35 (3H, m), 7.33 (1H, dd, J ) 2.5, 7.1 Hz), 7.07 (1H,
t, J ) 9.1 Hz), 1.33 (9H, s, t-Bu); 19F NMR δ -57.66 (3F, s, CF3),
-21.22 (1F, s, 2-F); IR (neat) 3065, 2967, 1509, 1486, 1258, 1219,
1169, 823, 761 cm-1; GC-MS m/z 312 (M+), 297 (M+ - CH3),
269 (M+ - C3H7). O-(Trifluoromethyl)dibenzofuranium hexaflu-
oroantimonate (1a): 1H NMR (CD2Cl2 at -70 °C) δ 8.26 (2H, br
d, J ) 8 Hz, 4,5-H), 8.09 (2H, br d, J ) 8 Hz, 1,8-H), 8.00 (2H,
br t, J ) 8 Hz, 3,6-H), 7.91 (2H, br t, J ) 8 Hz, 2,7-H); 19F NMR
(CD2Cl2 at -70 °C) δ -52.38 (s, CF3). O-(Trifluoromethyl)-
dibenzofuranium undecafluorodiantimonate (1b): 1H NMR
(CD2Cl2 at -70 °C) δ 8.31 (2H, dd, J ) 1.4, 7.6 Hz, 4,5-H), 8.13
(2H, dd, J ) 2.3, 8.9 Hz, 1,8-H), 8.04 (2H, t, J ) 7.6 Hz, 3,6-H),
7.94 (2H, ddd, J ) 8.9, 7.6, 1.4 Hz, 2,7-H); 19F NMR (CD2Cl2 at
-70 °C) δ -51.99 (s, CF3). 2-tert-Butyl-O-(trifluoromethyl)-
dibenzofuranium undecafluorodiantimonate (2b): 19F NMR
(CD2Cl2 at -70 °C) δ -52.64 (s, CF3). 2-tert-Butyl-O-(trifluo-
romethyl)dibenzofuranium hexafluorophosphate (2c): 19F NMR
(CD2Cl2 at -70 °C) δ -52.96 (s, CF3). 2-tert-Butyl-O-(trifluo-
romethyl)dibenzofuranium tetrafluoroborate (2d): 19F NMR
(CD2Cl2 at -70 °C) δ -52.79 (s, CF3). 2-Fluoro-O-(trifluorom-
ethyl)dibenzofuranium undecafluorodiantimonate (3b): 19F NMR
(CD2Cl2 at -70 °C) δ -51.88 (s, CF3). 2-Methoxy-O-(trifluo-
romethyl)dibenzofuranium hexafluoroantimonate (4a): 1H NMR
(CD2Cl2 at -70 °C) δ 8.26 (1H, d, J ) 7 Hz, 5-H), 8.11 (1H, d, J
) 8 Hz, 4-H), 8.05-7.98 (2H, m, 6,8-H), 7.93 (1H, t, J ) 8 Hz,
5-Methoxy-2′-(trifluoromethoxy)biphenylyl-2-diazonium tet-
1
rafluoroborate (20): mp 65-67 °C; H NMR (CD3CN) δ 4.11
(3H, s), 7.32-7.50 (2H, m), 7.55 -7.85 (4H, m), 8.55 (1H, d, J )
9 Hz); 19F NMR (CD3CN) δ -57.2 (3F, s, CF3), -150.4 (4F, s,
BF4); IR (KBr) 2228 (N2+) cm-1; MS (FAB) m/z 295 (M+ - BF4);
high MS M+ - BF4 (C14H10F3N2O2) 295.07023 (calcd 295.06944).
5-Methoxy-2-(trifluoromethoxy)biphenylyl-2′-diazoniumhexaflu-
oroantimonate (21): mp 78-80 °C dec (CH2Cl2-CH3CN-Et2O);
1H NMR (CD3CN) δ 3.89 (3H, s), 7.18 (1H, d, J ) 3 Hz), 7.29
(1H, dd, J ) 9, 3 Hz), 7.56 (1H, dm, J ) 9 Hz), 7.98 (1H, dd, J
) 8, 1 Hz), 8.01 (1H, td, J ) 8, 1 Hz), 8.37 (1H, td, J ) 8, 1 Hz),
8.61 (1H, dd, J ) 8, 1 Hz); 19F NMR (CD3CN) δ -57.7 (3F, s,
CF3), -96 to -149 (6F, m, SbF6); IR (KBr) 2284 (N2+) cm-1; MS
(FAB) m/z 295 (M+ - SbF6); high MS M+ - SbF6 (C14H10F3N2O2)
295.06848 (calcd 295.06944).
5-Dimethylamino-2′-(trifluoromethoxy)biphenylyl-2-diazoni-
um hexafluoroantimonate (22): mp 136-139 °C (CH3CN-Et2O);
1H NMR (CD3CN) δ 8.10 (1H, d, J ) 9.7 Hz), 7.72-7.51 (4H,
m), 7.01 (1H, dd, J ) 9.7, 2.5 Hz), 6.82 (1H, d, J ) 2.5 Hz), 3.40
(3H, s), 3.35 (3H, s); 19F NMR (CD3CN) δ -57.92 (3F, s).
Counteranion Exchange Reaction of Diazonium Salt 17ds
Preparation of Diazonium Salts 17a and 17e: A Typical
Procedure. Into a stirred solution of 997 mg (5.7 mmol) of NaOTf
cooled at -20 °C was added 2.0 g (5.7 mmol) of 17d. The mixture
was gradually warmed to room temperature for a period of 2 h.
Some CH2Cl2 was added to the mixture and the insoluble solid
was removed by filtration. The filtrate was evaporated to dryness
under reduced pressure without heating. The residue was washed
with Et2O and recrystallized from CH2Cl2/Et2O to give 2.13 g (90%)
of 17e. Similarly, 17a was prepared in 71% yield from 17d with
NaSbF6 instead of NaOTf and agreed with the product (17a) from
the reaction of 10 and NOSbF6.
7-H), 7.65 (1H, s, 1-H), 7.33 (1H, m, 3-H), 4.04 (3H, s, CH3); 19
F
NMR (CD2Cl2 at -70 °C) δ -53.22 (s, CF3). 2-Methoxy-O-
(trifluoromethyl)dibenzofuranium tetrafluoroborate (4b): 19F
NMR (CD2Cl2 at -70 °C) δ -53.20 (s, CF3).
Measurement of Half-Life Time of O-(Trifluoromethyl)-
dibenzofuranium Salts. Into a NMR tube were placed the
diazonium salt (0.025 mmol), benzotrifluoride (1.5-2 µL) and CD2-
Cl2 (0.6 mL) containing a trace amount of CFCl3 as a standard for
19F NMR, then the NMR tube was sealed. The NMR tube was
irradiated with a high-pressure Hg lump in a bath of -90 to
-100 °C for 45 min. After the irradiation, the reaction mixture
was solidified by immersing the NMR tube into liquid nitrogen.
The NMR tube was set at -70 °C in the NMR instrument and its
NMR spectrum was measured to identify the O-(trifluoromethyl)-
dibenzofuranium salts. After that, the 19F NMR spectra were
measured at the designated temperature (-60 or -50 °C) succes-
sively with a time interval. A half-life time was determined as the
time when the amount of the O-CF3-dibenzofuranium salt was
reduced to half. The results are described in the text.
2-(Trifluoromethoxy)biphenylyl-2′-diazonium triflate (17e):
1
mp 76-78 °C dec (CH3CN-Et2O); H NMR (CD3CN) δ 7.63-
7.69 (3H, m), 7.80 (1H, ddd, J ) 8, 7, 3 Hz), 7.97 (1H, dd, J ) 8,
1 Hz), 8.01 (1H, td, J ) 8, 1 Hz), 8.37 (1H, td, J ) 8, 1 Hz), 8.63
(1H, d, J ) 8 Hz); 19F NMR (CD3CN) δ -57.1 (3F, s, OCF3),
-77.9 (3F, s, SCF3); IR (KBr) 2286 (N2+) cm-1; MS (FAB) m/e
265 (M+ - OSO2CF3). Anal. Calcd for C14H8F6N2O4S: C, 40.59;
H, 1.95; N, 6.76. Found: C, 40.61; H, 1.85; N, 6.89.
Photochemical Decomposition of 2-(Trifluoromethoxy)biphe-
nylyl-2′-diazonium SaltssIn Situ Synthesis of O-(Trifluorom-
J. Org. Chem, Vol. 72, No. 18, 2007 6915