Vol. 64, No. 4 (2016)
Chem. Pharm. Bull.
373
Table 2. Substrate Scope of Olefinsa)
a) Yield (%)=isolation yield.
ducts. This mild and neutral condition offers the advantage of
General Procedure of Co-Catalyzed Hydrotrifluo-
functional group tolerance. For now, there is room to improve roethoxylatin of Olefins To a solution of 2a (44.5mg,
in terms of substrate scope. The results show that the stabi- 0.250mmol, 1eq) in 2,2,2-trifluoroethanol (1.5mL) was added
lization of the carbocationic intermediate is required toward complex 1 (4.5mg, 0.00750mmol, 3mol%) and N-fluoro-2,4,6-
TFE addition. In the case of styrene substrates, the plausible trimethylpyridinium tetrafluoroborate (114mg, 0.50mmol,
benzyl cation species should be stabilized by the neighboring 2.0eq), followed by another portion of 2,2,2-trifluoroethanol
aromatic ring. In the case of phenylpropanoids, there is a non- (1.0mL). The solution was bubbled with Ar for 10min, after
classical interaction between the homobenzyl carbocationic which 1,1,3,3-tetramethyldisiloxane (0.088mL, 0.50mmol,
species and aromatic ring.15) On the other hand, loss of these 2.0eq) was added over 30s at 0°C under Ar. The resulting
contributions in substrates 6 or 8 is the reason for the failure mixture was stirred at room temperature (r.t.) and the reaction
of the desired reaction. Further investigation will focus on was monitored by TLC. After completion, the solvent was
expanding the substrate scope and optimizing the reaction evaporated and the residue was purified by flash column chro-
conditions.
matography to give 3a (56.5mg, 81%) as pale yellow oil.
Compound 3a
Pale yellow oil, IR (attenuated total reflectance (ATR))
Experimental
General All reactions were carried out under an argon νmax=2636, 1515, 1263, 1138cm−1; 1H-NMR (400MHz,
atmosphere with dry solvents using anhydrous conditions un- CDCl3) δ: 6.71–6.80 (m, 3H), 3.861 (s, 3H), 3.854 (s, 3H),
less otherwise stated. Reagents were purchased at the highest 3.68–3.80 (m, 3H), 2.83 (dd, 1H, J=14.0, 6.8Hz), 2.65 (dd, 1H,
commercial quality and used without further purification, J=13.6, 5.2Hz), 1.19 (d, 3H, J=6.4Hz); 13C-NMR (100MHz,
unless otherwise stated. Yields refer to chromatographically CDCl3) δ: 148.7, 147.6, 130.8, 124.0 (J=277Hz), 121.3, 112.8,
and spectroscopically homogeneous materials, unless other- 111.1, 79.2, 66.6 (J=34.3Hz), 55.8, 55.7, 42.6, 19.4; HR-MS
wise stated. Reactions were monitored by TLC carried out on [direct analysis in real time (DART)(+)] Calcd for C13H18F3O3
Merck silica gel plates (60F-254) using UV light as the visual- (M+H+): 279.1203. Found 279.1203.
izing agent and an acidic mixture of anisaldehyde and ceric
ammonium molybdate, and heat as developing agents. Kanto
Compound 3a′
Pale yellow oil, IR (ATR) νmax=2939, 1516, 1191cm−1;
Chemical Silica gel 60N (spherical, neutral 0.040–0.050mm) 1H-NMR (400MHz, CDCl3) δ: 6.79 (d, 1H, J=8.0Hz),
was used for flash column chromatography and Yamazen 6.70–6.73 (m, 2H), 4.10 (sept, 1H, J=6.0Hz), 3.98 (sext, 1H,
EPCLC-AI-580S. NMR spectra were recorded on JEOL J=6.0Hz), 3.87 (s, 6H), 2.92 (dd, 1H, J=13.6, 6.0Hz), 2.72
ECX-400 and calibrated using residual undeuterated solvent (dd, 1H, J=13.6, 6.4Hz), 1.21 (d, 3H, J=6.4Hz); 13C-NMR
1
as an internal reference (CHCl3@7.26ppm H-NMR, 77.0ppm (100MHz, CDCl3) δ: 148.7, 147.7, 129.6, 121.5, 112.7,
13C-NMR). The following abbreviations (or combinations 111.0, 81.7, 74.3 (J=32.4Hz), 55.8, 55.7, 42.4, 18.9; HR-MS
thereof) were used to explain the multiplicities: s=singlet, [DART(+)] Calcd for C14H17F6O3 (M+H+): 347.1076. Found
d=doublet, t=triplet, q=quartet, quint=quintet, sext=sextet, 347.1076.
sept=septept, m=multiplet, br=broad. High-resolution (HR)-
MS were recorded on JEOL AccuTOF. IR spectra were re-
Compound 3b
Pale yellow oil, IR (ATR) νmax=2935, 1513, 1268, 1155cm−1;
corded on a JASCO FT/IR-4100. Melting points were recorded 1H-NMR (400MHz, CDCl3) δ: 7.05 (d, 1H, J=8.0Hz), 6.78
on a JASCO P-1020 melting point apparatus. Optical rotations (d, 1H, J=1.6Hz), 6.70 (dd, 1H, J=8.0, 1.6Hz), 5.20 (s, 3H),
were measured on a JASCO P-2000 digital polarimeter with 3.86 (s, 3H), 3.69–3.80 (m, 3H), 3.51 (s, 3H), 2.84 (dd, 1H,
a sodium lamp. 1, 2c, 4, 6 and 8 are prepared according to J=13.6, 6.8Hz), 2.64 (dd, 1H, J=13.6, 5.6Hz), 1.19 (d, 3H,
a previously reported literature.4) 2a, d–g are commercially J=6.0Hz); 13C-NMR (100MHz, CDCl3) δ: 149.5, 145.0,
available and used as received.
132.5, 124.0 (J=277Hz), 121.5, 116.3, 113.1, 95.6, 79.1, 66.5