1400
X. Hao et al. / Journal of Fluorine Chemistry 128 (2007) 1396–1401
and turned into two liquid phases within 5 min, i.e., an upper
chlorobenzene and a lower SV 135 phase. Pure p-methox-
yacetophenone was obtained from the upper phase after silica
gel chromatography (120.1 mg, 80% isolated yield). The lower
fluorous phase containing the catalyst was reused in the
subsequent recycling reactions, to which chlorobenzene
(1.5 ml), anisole (108.1 mg, 1.0 mmol) and acetic anhydride
(204.2 mg, 2.0 mmol) were added, respectively. The other
operations and procedure (e.g., stirring at 100 8C for 1 h,
product separation) were the same as described above for the
first cycle. Such a procedure was repeated further four times.
Substantially, the yields of p-methoxyacetophenone were 81%,
79%, 78% and 80% in the succeeding four times, respectively.
In addition, about 1.0 wt.% leaching of Hf[N(SO2C8F17)2]4
catalyst into the chlorobenzene phase was observed (deter-
mined by atomic emission spectrometry) on each cycle, and
94% of Hf[N(SO2C8F17)2]4 remained in the flask after the fifth
run.
4.5.2. (2RS,4SR,6RS)-2,4,6-Trimethyl-4-phenyl-1,3-
dioxane
1H NMR (CDCl3): d 1.21 (d, J = 6.5 Hz, 3H), 1.33 (d,
J = 5 Hz, 3H), 1.40 (s, 3H), 1.67 (dd, J = 11.5 Hz, J = 14 Hz,
1H), 2.32 (dd, J = 2 Hz, J = 14 Hz, 1H), 3.65 (ddq (12 lines),
J = 2 Hz, J = 11.5 Hz, J = 6.5 Hz, 1H), 4.70 (q, J = 5 Hz, 1H),
7.19–7.26 (m, 1H), 7.31-7.37 (m, 4H).
13C NMR (CDCl3): d 21.1, 21.6, 34.3, 41.0, 68.9, 76.4, 93.6,
125.8, 126.8, 128.6, 144.4.
4.5.3. (2RS,4RS,6RS)-2,4,6-Trimethyl-4-phenyl-1,3-
dioxane
1H NMR (CDCl3): d 1.22 (d, J = 6 Hz, 3H), 1.41 (d,
J = 5 Hz, 3H), 1.58 (s, 3H), 1.60 (dd, J = 11.5 Hz, J = 13 Hz,
1H), 1.79 (dd, J = 2.5 Hz, J = 13 Hz, 1H), 4.00 (ddq [12 lines],
J = 2.5 Hz, J = 11.5 Hz, J = 6 Hz, 1H), 5.18 (q, J = 5 Hz, 1H),
7.18–7.25 (m, 1H), 7.29–7.37 (m, 2H), 7.42–7.46 (m, 2H).
13C NMR (CDCl3): d 21.6, 21.8, 23.2, 43.6, 68.5, 74.5, 92.2,
123.9, 126.6, 128.1, 148.9.
4.5. Typical procedure for Hf[N(SO2C8F17)2]4-catalyzed
Prins reaction
4.5.4. (2RS,4SR,6SR)-2,4,6-Trimethyl-4-phenyl-1,3-
dioxane
To a mixture of GALDEN1 SV 135 (1.5 ml) and 1,2-
dichloroethane (1.5 ml) were added Hf[N(SO2C8F17)2]4 (20.5
mg, 0.005 mmol), a-methylstyrene (118.2 mg, 1.0 mmol),
paraformaldehyde (60.0 mg, corresponding to 2 mmol equiva-
lents of formaldehyde). The mixture was stirred at 35 8C for
0.5 h. Once the stirring was stopped, the mixture settled down at
room temperature and turned into two liquid phases, i.e., an
upper 1,2-dichloroethane and a lower SV 135 phase. The
upper 1,2-dichloroethane phase was evaporated to give a
crude oil. The crude product was purified by commercially
available TLC (silica gel) to afford pure 4-methyl-4-phenyl-
1,3-dioxane product (153.9 mg, 0.86 mmol), which was
characterized by GC/MS, 1H and 13C NMR. The lower
fluorous phase containing the catalyst was reused in the
subsequent recycling reactions, to which 1,2-dichloroethane
(1.5 ml), a-methylstyrene (118.2 mg, 1.0 mmol), parafor-
maldehyde (60.0 mg, 2.0 mmol) were added, respectively.
The other operations and procedure (e.g., stirring at 35 8C for
0.5 h, product separation) were the same as described above
for the first cycle. Such a procedure was repeated further 25
times, and the yields were as described above in Table 2.
In addition, a 0.8 wt.% leaching of Hf[N(SO2C8F17)2]4
catalyst into 1,2-dichloroethane phase was observed (deter-
mined by atomic emission spectrometry) in the first cycle,
and 85% of Hf[N(SO2C8F17)2]4 remained in the flask after
the 15th cycle. The catalyst recover studies are still under
progress.
1H NMR (CDCl3): d 1.15 (d, J = 6.5 Hz, 3H), 1.37 (d,
J = 5 Hz, 3H), 1.48 (s, 3H), 2.16 (dd, [B-part of an AB
Specturm]), J = 8 Hz, J = 14 Hz, 1H), 2.19 (dd [A-part of an
AB Specturm]), J = 5 Hz, J = 14 Hz, 1H), 4.26 (ddq [14 lines]),
J = 5 Hz, J = 8 Hz, J = 14 Hz, 1H), 5.01 (q, J = 5 Hz, 1H),
7.22–7.29 (m, 1H), 7.33–7.38 (m, 4H).
13C NMR (CDCl3): d 21.4, 21.9, 29.3, 42.2, 68.6, 75.3, 92.9,
124.5, 126.8, 128.4, 147.9.
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