6780 J. Am. Chem. Soc., Vol. 119, No. 29, 1997
Suzuki et al.
Trifluoromethanesulfonic acid (TFSA) was purchased from Central
Glass Co., Japan, and used after distillation twice under reduced pressure
with a Widmer condenser (bp 98 °C, 60 mmHg). Trifluoroacetic acid
(TFA) was obtained from Wako Pure Chemicals Co., Japan, and was
distilled at atomospheric pressure in the presence of a trace amount of
potassium permanganate (0.1 g per 1 kg of the acid), followed by
another distillation at atomospheric pressure without potassium per-
manganate (bp 72.5 °C).13
7.6 Hz), 7.82 (1H, d, 7.7 Hz). Anal. Calcd for C15H12O: C, 86.51;
H, 5.81. Found: C, 86.60; H, 5.73.
Reaction of 2-phenyl-1-[4-(trifluoromethyl)phenyl]-2-propen-1-
one (1c) in TFSA. 2c: mp 145-146 °C (recrystallized from CH2-
Cl2-n-hexane); 1H-NMR δ 3.36 (1H, dd, 4.2, 17.8 Hz), 3.77 (1H, dd,
8.4, 18.0 Hz), 3.97 (1H, dd, 4.4, 8.4 Hz), 7.18 (2H, d, 7.7 Hz), 7.28
(1H, dt, 0.7, 7.0 Hz), 7.34 (2H, t, 7.5 Hz), 7.69 (1H, d, 8.1 Hz), 7.82
(1H, s), 7.92 (1H, d, 8.1 Hz); HRMS calcd for C16H11F3O 276. 076,
found 276.075.
Preparation of 1-Phenyl-2-propen-1-one Derivatives. The precur-
sors of 1-phenyl-2-propen-1-ones, i.e., 2-subsitituted 3-(dimethylamino)-
1-propiophenones, were prepared by means of the Mannich reaction
as previously described.10 The hydrochloride salts of the precursor
amine (prepared by dissolving in 4 N aqueous HCl) were transformed
to 2-substituted 1-phenyl-2-propen-1-ones 1a-1h by the elimination
of the dimethylamine group, during steam distillation (in the case of
1a) or in the presence of sodium acetate at 95 °C for 15 min (in the
cases of 1b-1h).8,10
Reaction of 1-(4-methylphenyl)-2-phenyl-2-propen-1-one (1d) in
1
TFSA. 2d: mp 70-71 °C (recrystallized from n-hexane); H-NMR
δ 2.48 (3H, s), 3.21 (1H, dd, 4.0, 17.6 Hz), 3.64 (1H, dd, 8.2, 17.4
Hz), 3.88 (1H, dd, 3.9, 8.2 Hz), 7.18 (2H, td, 1.5, 7.0 Hz), 7.23-7.26
(2H, m), 7.29-7.33 (3H, m), 7.72 (1H, d, 7.7 Hz). Anal. Calcd for
C16 H14O: C, 86.45; H, 6.35. Found: C, 86.61; H, 6.33.
Reaction of 1-Phenyl-2-[4-(trifluoromethyl)phenyl]-2-propen-1-
one (1e) in TFSA. 2-[4-(Trifluoromethyl)phenyl]-1-indanone (2e): mp
1-Phenyl-2-propen-1-one (1a): 1H-NMR δ 5.94 (1H, dd, 1.8, 10.6
Hz), 6.45 (1H, dd, 1.8, 17.2 Hz), 7.17 (1H, dd, 10.6, 17.2 Hz), 7.49
(2H, td, 1.5, 7.7 Hz), 7.58 (1H, tt, 2.2, 7.3 Hz), 7.95 (2H, dd, 1.3, 8.2
Hz); HRMS calcd for C9H8O 132.058, found 132.057.
1
91-92 °C (recrystallized from n-hexane); H NMR δ 3.28 (1H, dd,
4.2, 17.4 Hz), 3.73 (1H, dd, 8.4, 17.2 Hz), 3.97 (1H, dd, 4.4, 8.4 Hz),
7.32 (2H, d, 8.1 Hz), 7.45 (1H, t, 7.0 Hz), 7.55 (1H, d, 7.7 Hz), 7.58
(2H, d, 8.1 Hz), 7.68 (1H, dt, 1.1, 7.3 Hz), 7.83 (1H, d, 7.3 Hz). Anal.
Calcd for C16H11F3O: C, 69.56; H, 4.01. Found: C, 69.58; H, 3.98.
Reaction of 1-(4-Methylphenyl)-1-phenyl-2-propen-1-one (1f) in
TFSA. 2-(4-Methylphenyl)-1-indanone (2f): mp 75-76 °C (recrystal-
lized from n-hexane); 1H-NMR δ 2.32 (3H, s), 3.25 (1H, dd, 4.1, 17.3
Hz), 3.68 (1H, dd, 8.3, 17.3 Hz), 3.86 (1H, dd, 4.1, 8.3 Hz), 7.07 (2H,
d, 8.1 Hz), 7.13 (2H, d, 8.5 Hz), 7.42 (1H, t, 7.5 Hz), 7.52 (1H, d, 7.7
Hz), 7.64 (1H, t, 7.5Hz), 7.81 (1H, d, 7.3 Hz). Anal. Calcd for
C16H14O: C, 86.45; H, 6.35. Found: C, 86.21; H, 6.33.
1,2-Diphenyl-2-propen-1-one (1b): mp 29 °C (recrystallized from
1
MeOH); H-NMR δ 5.65 (1H, s), 6.08 (1H, s), 7.32-7.38 (3H, m),
7.41-7.46 (4H, m), 7.54 (1H, tt, 1.3, 7.3 Hz), 7.91 (2H, dt, 1.5, 7.0
Hz). Anal. Calcd for C15H12O: C, 86.51; H, 5.81. Found: C, 86.35;
H, 5.76.
2-Phenyl-1-[4-(trifluoromethyl)phenyl]-2-propen-1-one (1c): mp
1
62-63 °C (recrystallized from n-hexane); H-NMR δ 5.71 (1H, s),
6.14 (1H, s), 7.34-7.41 (5H, m), 7.70 (2H, d, 8.4 Hz), 7.98 (2H, d,
8.1 Hz). Anal. Calcd for C16H11F3O: C, 69.56; H, 4.01. Found: C,
69.33; H, 3.93.
Reaction of 2-Methyl-1-phenyl-2-propen-1-one (1g) in TFSA.
1
2-Methyl-1-indanone (2g): bp 93-95 °C, 4 mmHg; H-NMR δ 1.32
1-(4-Methylphenyl)-2-phenyl-2-propen-1-one (1d): bp 129-135 °C,
0.07 mmHg; 1H-NMR δ 2.40 (3H, s), 5.60 (1H, s), 6.03 (1H, s), 7.23
(2H, d, 7.7 Hz), 7.31-7.36 (3H, m), 7.42 (2H, dd, 1.7,7.9 Hz), 7.82
(2H, d, 8.4 Hz). Anal. Calcd for C16H14O: C, 86.45; H, 6.35.
Found: C, 86.19; H, 6.21.
(3H, d, 7.3 Hz), 2.70-2.77 (2H, m), 3.41 (1H, dd, 8.8, 18.0 Hz), 7.37
(1H, t, 7.3 Hz), 7.46 (1H, d, 7.7 Hz), 7.59 (1H, dt, 1.1, 7.5 Hz), 7.76
(1H, d, 7.7 Hz); HRMS calcd for C10H10O 146.073, found 146.071.
Reaction of 2-Ethyl-1-phenyl-2-propen-1-one (1h) in TFSA.
2-Ethyl-1-indanone (2h): bp 90 °C, 3.5 mmHg; 1H-NMR δ 1.02 (3H,
dt, 0.86, 7.5 Hz), 1.52-1.58 (1H, m), 1.95-2.00 (1H, m), 2.60-2.64
(1H, m), 2.83 (1H, dd, 3.7, 17.2 Hz), 3.32 (1H, dd, 8.1, 17.2 Hz), 7.36
(1H, t, 7.5 Hz), 7.46 (1H, dd, 0.7, 7.0 Hz), 7.58 (1H, t, 7.5 Hz), 7.75
(1H, d, 7.7 Hz); HRMS calcd for C11H12O 160.089, found 160.093.
Kinetic Measurement. A mixture of the acid, TFSA, and TFA
was prepared in a polyethylene glovebox (AtomosBag, Aldrich) under
an argon atmosphere. To a weighted phenyl vinyl ketone (typically
6-10 mg) was added a precooled acid mixture (-45 °C, dry ice and
acetonitrile) (100 equiv, typically 2 mL) in the dry glovebox. After a
good solution was obtained, the solution was transferred to an NMR
tube which involved a small quantity of methanol-free methylene
chloride, as an internal standard of signal integrations. The spectra
were recorded at a specified temperature. The NMR probe temperature
was controlled with a variable-temperature apparatus, NM-ALTAS/L
and NM-AVT1A (JEOL, Japan). Errors in the controlled temperature
were (0.1 °C. The disappearance of the starting material was
monitored in terms of signal integration, with a GSX 500-MHz NMR
spectrometer.
Computational Methods. Geometries were initially optimized
without any symmetry restriction (except 10a and 10ts (C2 symmetry))
with the split valence HF/3-21G basis set, and with the heavy atom
d-polarized HF/6-31G* basis set.24 The geometries were further
optimized with a hybrid density-functional theory method, Becke3-
LYP (B3LYP) with the HF/6-31G* optimized geometries.26 In the
cases of divinyl derivatives 8-10 the structures were also optimized
in the second-order Møller-Plesset (MP2(Full)) perturbation. All the
structures of the reactants shown in Tables 4 and 6 were minima, and
the transition structures which represent rotation and cyclization
processes were characterized by frequency calculations. Zero-point
vibrational energies (ZPE) were scaled by 0.95 in the cases of the HF
and MP2 levels, and unscaled in the case of the B3LYP level.29
1-Phenyl-2-[4-(trifluoromethyl)phenyl]-2-propen-1-one (1e): mp
48-49 °C (recrystallized from MeOH); 1H-NMR δ 5.79 (1H, s), 6.18
(1H, s), 7.46 (2H, td, 1.5, 7.7 Hz), 7.55 (2H, d, 8.1 Hz), 7.59 (1H, td,
1.1, 7.3 Hz), 7.62 (2H, d, 8.4 Hz), 7.90 (2H, td, 1.5, 8.1 Hz). Anal.
Calcd for C16H11F3O: C, 69.56; H, 4.01. Found: 69.57; H, 3.75.
1-(4-Methylphenyl)-1-phenyl-2-propen-1-one (1f): mp 35 °C (re-
1
crystallized from n-hexane); H-NMR δ 2.34 (3H, s), 5.58 (1H, s),
6.02 (1H, s), 7.15 (2H, d, 7.7 Hz), 7.31 (2H, d, 8.1 Hz), 7.42 (2H, tt,
1.5, 7.5 Hz), 7.54 (1H, tt, 1. 5, 7.3 Hz), 7.90 (t 2H,d, 1.7, 8.4 Hz).
Anal. Calcd for C16H14O: C, 86.45; H, 6.35. Found: C, 86.33; H,
6.09.
1
2-Methyl-1-phenyl-2-propen-1-one (1g): bp 60 °C, 3 mmHg; H-
NMR δ 2.08 (3H, s), 5.63 (1H, s), 5.92 (1H, d, 1.5 Hz), 7.43 (2H, t,
7.5 Hz), 7.53 (1H, t, 7.3 Hz), 7.73 (2H, dd, 1.5, 7.0 Hz); HRMS calcd
for C10H10O 146.073, found 146.071.
2-Ethyl-1-phenyl-2-propen-1-one (1h): bp 85 °C, 5 mmHg; 1H-NMR
δ 1.13 (3H, t, 7.3 Hz), 2.50 (2H, q, 7.5 Hz), 5.58 (1H, d, 0.73 Hz),
5.83 (1H, s), 7.43 (2H, tt, 1.8, 7.5 Hz), 7.54 (1H, tt, 1.7, 7.5 Hz), 7.76
(2H, td, 1.7, 7.0 Hz); HRMS calcd for C11H12O 160.089, found 160.088.
Acid-Catalyzed Cyclization Reactions. Reaction of 1-Phenyl-2-
propen-1-one (1a) in TFSA. 1-Phenyl-2-propen-1-one (1a) (134 mg,
1 mmol) was added to TFSA ((9.0 mL, 100 mmol) at 25 °C with
stirring. The resultant solution was stirred at 25 °C for 120 h. The
whole was poured into ice-water and extracted with CH2Cl2 (150 mL).
The organic layer was washed with brine (100 mL), dried over Na2-
SO4, filtered, and evaporated to give a residue, which was flash-
chromatographed (CH2Cl2-n-hexane 1:2 to 1:1) to give 1-indanone
(2a) (84 mg, 63% yield), together with recovered 1a (8 mg, 6% yield).
1
2a: mp 40-42 °C (recrystallized from n-hexane); H-NMR δ 2.70
(2H, t, 5.9 Hz), 3.15 (2H, t, 5.5 Hz), 7.37 (1H, t, 7.7 Hz), 7.48 (1H, d,
7.7 Hz), 7.59 (1H, t, 7.7 Hz), 7.77 (1H, d, 7.7 Hz); HRMS calcd for
C9H8O 132.058, found 132.057.
Reaction of 1,2-Diphenyl-2-propen-1-one (1b) in TFSA. 2b: mp
76-77 °C (recrystallized from n-hexane); H-NMR δ 3.28 (1H, dd,
4.0, 17.6 Hz), 3.70 (1H, dd, 8.1, 17.6 Hz), 3.91 (1H, dd, 4.0, 8.4 Hz),
7.19 (2H, dt, 1.5, 7.0 Hz), 7.26 (1H, tt, 1.5, 7.4 Hz), 7.33 (2H, tt, 1.5,
7.2 Hz), 7.43 (1H, t, 7.0 Hz), 7.54 (1H, d, 7.7 Hz), 7.66 (1H, td, 1.1,
Supporting Information Available: Tables of total energies
and figures of optimized stuctures (6 pages). See any current
masthead page for ordering and Internet access instructions.
1
JA971100G