52
Can. J. Chem. Vol. 80, 2002
1
Compound 10, which is both a m-hydroxystyrene and a
o,p-dimethoxystyrene, shows characteristics of both mecha-
nisms. However, the lifetime of the LFP intermediate shows
evidence of a m-QM rather than a carbocation intermediate.
mp 66–68°C. H NMR (CDCl3) δ: 3.81 (s, 3H, OCH3), 4.73
(s, 1H, OH), 5.35 (d, J = 6.6 Hz, 2H, =CH2), 6.78–6.92 (m,
5H, Ar), 7.16–7.26 (m, 3H, Ar). HRMS calcd. for C15H14O2:
226.0994; found: 226.0994.
3′-Hydroxy-2′′,4′′-dimethoxy-1,1-diphenylethanol (15)
The appropriate Grignard reagent was prepared from
1-bromo-2,4-dimethoxybenzene (9.0 mL, 62 mmol), Mg
(2.12 g, 87 mmol), and 3-hydroxyacetophenone (3.62 g,
27 mmol). The resulting crude oil was washed with benzene
to remove the byproduct dimethoxybenzene, resulting in 15
in a 60% yield. Recrystallization from ethanol and hexanes
gave pale green cubic crystals in 40% yield): mp 144–
Experimental
General
1H NMR spectra were recorded on a Bruker AC–300
(300 MHz) instrument. UV–vis spectra were obtained using
Cary 5 UV/Vis, Cary 1E UV/Vis, and Cary 50 Bio scanning
spectrophotometers in conjunction with fluorescence, LFP,
and ΦP measurements, respectively. The fluorescence spectra
were taken on a Photon Technology International A-1010
(PTI) Quanta MasterTM Luminescence Spectrometer. High
resolution mass spectra were obtained on a Kratos Concept
H (EI) instrument and the uncorrected melting points in a
Gallencamp melting point apparatus. IR spectra were re-
corded on a PerkinElmer Spectrum One FTIR spectrophoto-
meter either as KBr pellets (for solid compounds), or on
NaCl plates (as a neat oil). Photolyses were carried out in
100-mL quartz tubes using a Rayonet RPR 100 photochem-
ical reactor with 254 nm lamps (up to 16). The solvents
THF, CH3CN, and CH2Cl2 were distilled before use with
THF and CH3CN pre-drying over K and CaH2, respec-
tively. 3-Hydroxyacetophenone, 3-methoxyacetophenone,
acetophenone, 4-bromotoluene, 4-bromoanisole, and 1-bromo-
2,4-dimethoxybezene were purchased from Aldrich.
1
146°C. IR (cm–1): 3457 (s), 3310 (s). H NMR (CDCl3) δ:
1.77 (s, 3H, CH3), 3.58 (s, 3H, OCH3), 3.80 (s, 3H, OCH3),
4.48 (s, 1H, OH), 4.69 (s, 1H, OH), 6.45 (d, J = 2.9 Hz, 1H,
Ar), 6.50 (dd, J = 8.5, 2.5 Hz, 1H, Ar), 6.63 (dd, J = 8.1,
2.6 Hz, 1H, Ar), 6.79 (m, 2H, Ar), 7.09 (t, J = 8.1 Hz, 1H,
Ar), 7.30 (d, J = 8.8 Hz, 1H, Ar). HRMS calcd. for
C16H18O4: 274.1205; found: 274.1205.
3′-Hydroxy-2′′,4′′-dimethoxy-1,1-diphenylethene (10)
Molecule 15 (0.40 g, 1.4 mmol) was dissolved in THF
(120 mL) and a catalytic amount (one drop) of 10 N H2SO4
was added. The solution was heated at reflux for 2 h.
Quenching of the reaction with distilled water (100 mL),
neutralization with Na2CO3 (aq), and general workup (ex-
traction into CH2Cl2, drying with anhydrous MgSO4)
yielded 10 as on oil. Recrystallization from CHCl3 and hex-
anes gave light brown cubic crystals with an overall yield of
3′-Hydroxy-4′′-methyl-1,1-diphenylethene (8)
1
64%: mp 79–81°C. IR (cm–1): 3445 (s), 3097 (m). H NMR
The Grignard reagent was prepared by adding a solution
of 4-bromotoluene (5.5 mL, 45 mmol) in anhydrous THF
(25 mL) dropwise to Mg (0.87 g, 35.8 mmol) in anhydrous
THF (100 mL) under nitrogen. The resulting mixture was
heated at reflux for 2 h, then 3-hydroxyacetophenone
(1.82 g, 13.4 mmol) was added dropwise, and then the mix-
ture kept at reflux for more 2 h. Saturated aqueous NH4Cl
was added and the solution was subjected to standard
workup (extraction with CH2Cl2, washing of the organic
with saturated brine solution, drying (MgSO4), filtration, and
evaporation to dryness in vacuo), to afford the crude product
(CDCl3) δ: 3.62 (s, 3H, OCH3), 3.82 (s, 3H, OCH3), 4.59 (s,
1H, OH), 5.27 (d, J = 1.5 Hz, 1H), 5.63 (d, J = 1.5 Hz, 1H),
6.46–6.51 (m, 2H, Ar), 6.69–6.72 (m, 2H, Ar), 6.88 (d, J =
7.4 Hz, 1H, Ar), 7.11–7.15 (m, 2H, Ar). HRMS calcd. for
C16H16O3: 256.1099; found: 256.1101.
2′,3′′,4′-Trimethoxy-1,1-diphenylethanol (16)
The appropriate Grignard reagent was prepared from
1-bromo-2,4-dimethoxybenzene (2.4 mL, 17 mmol), Mg
(0.41 g, 17 mmol), and 3′-methoxyacetophenone (2 mL,
14 mmol) to afford the crude product alcohol. Purification
by column chromatography starting with CH2Cl2 and in-
creasing polarity with ethyl acetate yielded the clean product
alcohol
3′-hydroxy-4′′-methyl-1,1-diphenylethanol
(13)
(≈70%). Molecule 13 was refluxed in CH3CN with a cata-
lytic amount of dilute H2SO4, to yield the crude oil 8. Purifi-
cation by column chromatography in 9:1 CH2Cl2–EtOAc
1
oil 16 (~60%). H NMR (CDCl3) δ: 1.79 (s, 3H, CH3), 3.58
1
(s, 3H, OCH3), 3.76 (s, 3H, OCH3), 3.80 (s, 3H, OCH3),
4.49 (s, 1H, OH), 6.44 (d, J = 2.2 Hz, 1H, Ar), 6.50 (dd, J =
8.8, 2.2 Hz, 1H, Ar), 6.70 (d, J = 8.1 Hz, 1H, Ar), 6.79 (d,
J = 7.4 Hz, 1H, Ar), 6.92 (s, 1H, Ar), 7.13 (t, J = 8.0 Hz,
1H, Ar), 7.30 (d, J = 8.8 Hz, 1H, Ar). HRMS calcd. for
C17H20O4: 288.1362; found: 288.1362.
yielded pure material (oil). H NMR (CDCl3) δ: 2.35 (s, 3H,
CH3), 4.87 (s, 1H, OH), 5.39 (s, 2H, =CH2), 6.78 (m, 2H,
Ar), 6.90 (d, J = 8.0 Hz, 1H, Ar), 7.10–7.24 (m, 5H, Ar).
HRMS calcd. for C15H14O: 210.1045; found: 210.1047.
3′-Hydroxy-4′′-methoxy-1,1-diphenylethene (9)
The Grignard reagent was prepared as above using 4-
bromoanisole (5.8 mL, 46 mmol), Mg (0.87 g, 35.8 mmol),
and 3-hydroxyacetophenone (3.02 g, 22 mmol) to yield the
crude product alcohol 3′-hydroxy-4′′-methoxy-1,1-diphenyl-
ethanol (14). Molecule 14 was refluxed in CH3CN with a
catalytic amount of H2SO4 (aq) to yield the crude oil 9. Puri-
fication by column chromatography in 4:1 hexanes–EtOAc
yielded clean product, which was recrystallized from CH3Cl
and hexanes with an overall yield of 25% (1.35 g, 5 mmol):
2′,3′′,4′-Trimethoxy-1,1-diphenylethene (11)
Molecule 16 (2.21 g, 7.6 mmol) was heated at reflux in a
solution of CH3CN and dilute H2SO4. Quenching and
1
workup as for 10 yielded clean 11 in >80% yield. H NMR
(CDCl3) δ: 3.62 (s, 3H, OCH3), 3.76 (s, 3H, OCH3), 3.83 (s,
3H, OCH3), 5.29 (d, J = 1.5 Hz, 1H, =CH), 5.65 (d, J =
1.5 Hz, 1H, =CH), 6.48–6.52 (m, 2H, Ar), 6.79 (dd, J = 8.1,
1.5 Hz, 1H, Ar), 6.80–6.86 (m, 2H, Ar), 7.12–7.20 (m, 2H,
© 2002 NRC Canada