Indium-catalyzed cross-coupling reactions between α,β -unsaturated carbonyl compounds and aromatic aldehydes

Article abstract of DOI:10.1246/bcsj.76.1823

Cross-coupling reactions between α,β-unsaturated carbonyl compounds and aromatic aldehydes have been achieved in tetrahydrofuran (THF) at 25 °C under N₂ using a catalytic amount of InCl₃ (0. 05 molar amount to the substrate) in the presence of both chlorotrimethylsilane (TMSCl) and aluminum foil (Al). These reactions provide the corresponding β,γ-unsaturated ketones in moderate yields, together with pinacol-coupling products of aldehydes as side products. Chlorides other than TMSCl and AlCl₃, such as LiCl, CaCl₂, MgCl₂, and SOCl₂, are not effective at all. Without either TMSCl or Al, no reaction proceeds even in the presence of the catalyst.

Full text of DOI:10.1246/bcsj.76.1823

Ó 2003 The Chemical Society of Japan
Bull. Chem. Soc. Jpn., 76, 1823–1827 (2003) 1823
Indium-Catalyzed Cross-Coupling Reactions between ꢀ,ꢁ-Unsaturated
Carbonyl Compounds and Aromatic Aldehydes
ꢀ
Toshiyuki Ohe, Takuya Ohse, Kenji Mori, Seiji Ohtaka, and Sakae Uemura
Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University,
Sakyo-ku, Kyoto 606-8501
Received April 10, 2003; E-mail: uemura@scl.kyoto-u.ac.jp
Cross-coupling reactions between ꢀ,ꢁ-unsaturated carbonyl compounds and aromatic aldehydes have been
achieved in tetrahydrofuran (THF) at 25 ꢁC under N2 using a catalytic amount of InCl3 (0.05 molar amount to the sub-
strate) in the presence of both chlorotrimethylsilane (TMSCl) and aluminum foil (Al). These reactions provide the cor-
responding ꢁ,ꢂ-unsaturated ketones in moderate yields, together with pinacol-coupling products of aldehydes as side
products. Chlorides other than TMSCl and AlCl3, such as LiCl, CaCl2, MgCl2, and SOCl2, are not effective at all.
Without either TMSCl or Al, no reaction proceeds even in the presence of the catalyst.
The organic chemistry of indium is of current interest from
the viewpoint of organic synthesis. Many indium-mediated re-
actions have been reported, but the number of effective indi-
um-catalyzed reactions is still quite limited.1 We have recent-
ly reported some indium-catalyzed homo-coupling (pinacol-
type coupling) reactions of aromatic carbonyl compounds
and imines in the presence of chlorosilanes and either alumi-
num (Al foil) or magnesium (Mg turnings).2 The products
are the corresponding 1,2-diols or 1,2-diamines (dl/meso mix-
ture), which are supposed to be formed by reductive dimeriza-
tion of an intermediate ketyl or imino radical species. If the
radical species were trapped by suitable substrates like Mi-
chael acceptors, the corresponding cross-coupled products
might be produced in competition with the formation of the
homo-coupling products. Actually, when the above described
homo-coupling reaction of benzaldehyde was carried out in the
presence of methyl vinyl ketone, the formation of a cross-
coupled compound, 5-phenyl-4-penten-2-one, was observed
together with those of 1,2-diphenyl-1,2-ethanediols.3 During
this work, a report4 of similar reactions has appeared where
In/InCl3-mediated cross-coupling of various arenecarbalde-
hydes with methyl vinyl ketone afforded the corresponding
ꢁ,ꢂ-unsaturated ketones selectively in moderate to good
yields. The reported reaction is conceptually the same as that
of ours, but not catalytic in indium. As one of our continuing
studies on In-catalyzed reactions, we report here the results of
InCl3-catalyzed cross-coupling reactions between ꢀ,ꢁ-unsatu-
rated carbonyl compounds and aromatic aldehydes.
Results and Discussion
A mixture of benzaldehyde (1 molar amount) and methyl vi-
nyl ketone (MVK; 1 molar amount) was added to a mixture of
aluminum foil (Al, 4 molar amounts), chlorotrimethylsilane
(TMSCl, 4 molar amounts), and a catalytic amount of InCl3
(0.05 molar amount; 5 mol%) in tetrahydrofuran (THF) under
a nitrogen atmosphere. The resulting mixture was stirred at 25
ꢁC for 14 h (Method A). A cross-coupling product, 5-phenyl-
4-penten-2-one (1), and homo-coupling products, 1,2-diphen-
yl-1,2-ethanediols (2), were obtained in 24% and 26%
(dl/meso = 52/48) isolated yields, respectively (Scheme 1).
However, the results were not so reproducible and the range
of yields of the two products was 8–24% and 13–41%, respec-
tively (Table 1, Entry 1). Here, the concentration of each sub-
strate as well as the amount of TMSCl did not much affect the
results (Table 1, Entries 1–3). The yield as well as the selec-
tivity of 1 was improved by using a larger molar amount of
MVK (Table 1, Entries 1, 4, and 5). Thus, with 2 molar
amounts of MVK and 1 molar amount of benzaldehyde,
32% of 1 was obtained in one case with almost no by-products
(Table 1, Entry 5). However, the yield of 1 decreased to 18%
when 3 molar amounts of MVK and 1 molar amount of benz-
aldehyde were employed (Table 1, Entry 6). The presence of
Scheme 1.
Published on the web September 15, 2003; DOI 10.1246/bcsj.76.1823

1824 Bull. Chem. Soc. Jpn., 76, No. 9 (2003)
Indium-Catalyzed Cross-Coupling Reactions
Table 1. InCl3-Catalyzed Cross-Coupling between PhCHO
and MVK by Method Aa)
Table 3. InCl3-Catalyzed Cross-Coupling between PhCHO
and MVK, in the Presence of Various Metala)
MVK
mmol
Product yield/%b)
Product yield/%c)
Reaction
Entry
Chloride/mmol
Entry
Metal, Formb)
time/h
1a
8–24c)
17
24
2a
1a
2a
5–18d)
22
4
14
<25
—
1
2
3
4
5
6
7
1
1
1
1.5
2
TMSCl
TMSCl
TMSCl
TMSCl
TMSCl
TMSCl
AlCl3
4
2
8
4
4
4
1.33
13–41c)
18
29
1
2
3
4
5
6
Al
Al
In
F
P
P
P
T
P
3
2.5
4
1
8
20
54–56d)
45
63
26
16
<1–7c)
—
7
Zn
Mg
Fe
45
11
—
24–32c)
18
18
d)
3
1
a) InCl3 (0.05 mmol), metal (4 mmol), PhCHO (1 mmol),
MVK (2 mmol), TMSCl (4 mmol), and THF (10 mL) at 25
ꢁC under N2. b) F = foil, P = powder, T = turnings. c) Iso-
lated yield. d) Several runs.
a) InCl3 (0.05 mmolꢁ), Al (4 mmol), PhCHO (1 mmol), and
THF (10 mL) at 25 C for 14 h under N2. b) Isolated yield.
c) Several runs. d) Obtained as a complex mixture. The yield
of 2a is quite low.
Table 4. InCl3-Catalyzed Cross-Coupling between Various
ArCHO and MVK, in the Presence of Ala)
Table 2. InCl3-Catalyzed Cross-Coupling between PhCHO
and MVK by Method Ba)
Product yield/%c)
Reaction
Product yield/%b)
Entry
Ar
MVK
mmol
Reaction
time/h
time/h
Entry In species/mmol
1
2
1a
2a
5–18c)
5
1
2
3
4
5
6
7
Ph
3
1a, 54–56c) 2a, 5–18c)
1
2
3
4
5
6
7
8
9
InCl3
InCl3
InCl3
InCl3
InCl3
InCl3
In powder 0.05
In2O3 0.026
—
0.05
0.05
0.05
0.1
0.03
0.01
2
3
1.5
2
2
2
2
2
2
3
3
3.5
4
5.5
7
4
54–56c)
49
51
p-CH3C6H4
p-CH3OC6H4
p-FC6H4
p-ClC6H4
p-CF3C6H4
2-C4H3Od)
4
6
3.5
4
3.5
6.5
1b, 62
1c, 57
1d, 61
1e, 50
1f, 54
2b, 11
2c, <1
2d, 11
2e, 13
2f, 13
15
54
46
6
5
30
53
17
0
18
11
12
4
e)
e)
—
—
a) InCl3 (0.05 mmol), Al (4 mmol), ArCHO (1 mmol), MVK
(2 mmol), TMSCl (4 mmol), and THF (10 mL) at 25 ꢁC under
N2. b) Isolated yield. c) Several runs. d) Furfural. e) Ob-
tained as a complex mixture. The yields of both 1 and 2 could
not be determined.
19
11
a) Al (4 mmol), PhCHO (1 mmol), TMSCl (4 mmol), and THF
ꢁ
(10 mL) at 25 C under N2. b) Isolated yield. c) Several runs.
chloride anion was indispensable in the case of InCl3-cata-
lyzed homo-coupling of aldehydes.2 When the effect of vari-
ous chlorides was examined in this cross-coupling reaction, all
chlorides such as LiCl (4 molar amounts), CaCl2, MgCl2, and
SOCl2 (all, 2 molar amounts) were revealed to be ineffective,
except AlCl3 (1.33 molar amounts) which showed an almost
identical activity to that of TMSCl (Table 1, Entry 7). In other
solvents such as dioxane and diethyl ether, this cross-coupling
reaction failed.
During this investigation, we noticed that the yield of 1 was
affected by the order of addition of the reagents. Thus, when a
mixture of benzaldehyde and MVK was added to a mixture of
Al, InCl3, and THF, followed by the addition of TMSCl
(Method B), the yield of 1 was much improved (54–56%,
Table 2, Entry 1) and the data were more reproducible than
those provided by Method A. Although the exact reason for
this improvement was unclear, we decided to apply Method
B in subsequent investigations.
in place of Al (foil), were not effective (Table 3, Entries 5 and
6), while aluminum powder (Table 3, Entry 2), indium pow-
der4 (Table 3, Entry 3), and zinc powder (Table 3, Entry 4)
could be used in the same way as Al (foil) was used.
A variety of p-substituted aromatic aldehydes similarly af-
forded the corresponding expected products, 1 and 2, irrespec-
tive of the electron-releasing or electron-withdrawing nature of
the substituent (Table 4, Entries 1–6). The system could not be
applied to furfural (Table 4, Entry 7).
Ethyl vinyl ketone (EVK, 1-penten-3-one), 3-penten-2-one,
and 2-cyclohexen-1-one could also be employed in this cross-
coupling reaction with benzaldehyde to afford the correspond-
ing ꢁ,ꢂ-unsaturated ketones (3) such as 6-phenyl-5-hexen-3-
one, 3-methyl-5-phenyl-4-penten-2-one, and 2-(2-phenyl-
ethenyl)-1-cyclopentanone in moderate yields, respectively
(Table 5, Entries 2–4). A substituent at the ꢁ-position of
ꢀ,ꢁ-unsaturated ketones migrated to the ꢀ-position of the car-
bonyl groups of the corresponding ꢁ,ꢂ-unsaturated ketones (3)
in the latter two cases (Table 5, Entries 3 and 4; Scheme 2).
Similar reactions were also investigated using indium powder
in place of Al, but only EVK was reactive (Table 5, Entries 5
and 6), and other enones afforded very little 3 (Table 5, Entries
7 and 8).
The appropriate amount of MVK to benzaldehyde (Table 2,
Entries 1–3) and that of InCl3 to the aldehyde (Table 2, Entries
1, 4–6) were revealed to be 2 equiv. and 0.05 equiv.,
respectively. Other indium catalysts were tried; In (powder)
was as effective as InCl3 (Table 2, Entry 7), but In2O3 was
not effective (Table 2, Entry 8).
Other metals such as magnesium turnings and iron powder,
As to the reaction pathway for the formation of 1, Kang and

T. Ohe et al.
Bull. Chem. Soc. Jpn., 76, No. 9 (2003) 1825
Table 5. InCl3-Catalyzed Cross-Coupling between PhCHO
and Various Enone, in the Presence of Ala)
Experimental
General. The H and 13C NMR spectra were recorded with
1
Product yield/%b)
Reaction
JEOL JNM-AL300, JEOL EX-400, and JEOL GSX270 spectrom-
eters for solutions in CDCl3 with Me4Si as an internal standard.
Chemical shifts are reported in ꢃ ppm units downfield from
Me4Si. Analytical thin-layer chromatographies (TLC) were per-
formed with Merck silica gel 60 F-254 plates. The isolation of
a pure product was carried out with column chromatography on
SiO2 (Merck 60, 230–400 mesh, Merck KGaA.).
Materials. InCl3 was purchased from Aldrich and used with-
out further purification. Aluminum foil (0.1 mm ꢂ 0.8 mm) and
chlorotrimethylsilane (TMSCl) were purchased from Nacalai
Tesque and used without further purification. Tetrahydrofuran
(THF) was distilled from sodium diphenylketyl before use. All
carbonyl compounds were commercial products and were used
without further purification. The structures of 1,2-diols (2) were
determined by comparison of spectral data with those of the au-
thentic samples.2 All products (1 and 3) except 1f and 3c were
known compounds, the 1H and 13C NMR data being shown for
convenience.
Typical Procedure for a Cross-Coupling Reaction between
Methyl Vinyl Ketone with Benzaldehyde. Method A: A mix-
ture of aluminum (0.108 g, 4 mmol), InCl3 (11 mg, 0.05 mmol),
chlorotrimethylsilane (0.5 mL, 4 mmol), and THF (5 mL) in a
50 mL two necked round-bottomed flask was stirred for 5 min
at room temperature under N2. To this mixture was added a solu-
tion of methyl vinyl ketone (0.071 g, 1 mmol) and benzaldehyde
(0.106 g, 1 mmol) in THF (5 mL) at room temperature under N2.
The mixture was kept at room temperature with magnetic stirring
for 14 h. Aqueous HCl (ca. 1 mol dmꢃ3, 10 mL) was added to the
resulting mixture, which was stirred for 10 min, and the organic
layer was separated. The aqueous layer was extracted by diethyl
ether (20 mL ꢂ 3). The combined organic layer was washed with
saturated aqueous NaHCO3 (20 mL ꢂ 2), dried over MgSO4, and
then concentrated in vacuo. The residue was purified by column
chromatography on silica gel (eluent, hexane/ethyl acetate) to
Entry Metal
Enone
time/h
1a or 3
2a
1
2
3
4
5
6
7
8
Al
Al
Al
MVK
EVK
3-Penten-2-one
3
3
4
4
4
4
20
20
1a, 54–56c) 5–18c)
3a, 43
3b, 17
3c, 37
1a, 63
3a, 24
3b, 5
11
16
—
4
d)
Al 2-Cyclohexen-1-one
In
In
In
MVK
EVK
3-Penten-2-one
0
0
d)
In 2-Cyclohexen-1-one
3c,
3
—
a) InCl3 (0.05 mmol), metal (4 mmol), PhCHO (1 mmol),
enone (2 mmol), TMSCl (4 mmol), and THF (10 mL) at 25
ꢁC for 14 h under N2. b) Isolated yield. c) Several runs. d)
Obtained as a complex mixture and unable to be determined.
co-workers have proposed the radical cyclopropanation
(Scheme 3), the cyclopropanyl proton being detected by
1H NMR measurement.4 Our results of the formation of 3b
from 3-penten-2-one and 3c from 2-cyclohexen-1-one, where
alkyl migration proceeded, support this proposal as shown in
Scheme 4. Here a redox-active InCl3–metal alloy ([In], metal
= Al, Zn, In) is supposed to be an active indium species.2a,b,5
This indium species causes a one-electron reduction of an ꢀ,ꢁ-
unsaturated ketone to produce a ketyl radical, which might at-
tack an aldehyde to form an intermediate species I. This spe-
cies is intramolecularly cyclized and suffered one-electron re-
duction to form an ꢀ-hydroxybenzylic cyclopropanol. The cy-
clopropanol is protonated and dehydrated in aqueous HCl dur-
ing workup procedure to afford the product ꢁ,ꢂ-unsaturated
ketone as reported.6 The formation of pinacol-coupling prod-
uct 2 may be due to the coupling of a ketyl radical partly
formed from an aromatic aldehyde by an electron transfer from
the InCl3–metal alloy.2a,b
Scheme 2.
Scheme 3.

1826 Bull. Chem. Soc. Jpn., 76, No. 9 (2003)
Indium-Catalyzed Cross-Coupling Reactions
Scheme 4. Plausible reaction pathway.
give 5-phenyl-4-penten-2-one (1) (0.126–0.388 g, 0.079–0.242
mmol, 8–24% yield), 1,2-diphenyl-1,2-ethanediols (2) (0.135–
0.441 g, 0.063–0.206 mmol, 13–41% yield), and a complex mix-
ture containing benzyl alcohol and many unidentified compounds.
Typical Procedure for a Cross-Coupling Reaction between
Methyl Vinyl Ketone with Benzaldehyde. Method B: In a
two-necked 50 mL round-bottomed flask, equipped with a septum
inlet and a three-way stopcock, were placed aluminum foil (0.108
g, 4 mmol) and InCl3 (11 mg, 0.05 mmol). The system was then
evacuated and flushed several times with N2 from a N2-filled bal-
loon connected to the flask; THF (4 mL) and a solution of aromat-
ic aldehyde (1 mmol) and ꢀ,ꢁ-unsaturated ketone (2 mmol) in
THF (6 mL) were added and then chlorotrimethylsilane (0.5
mL, 4 mmol) was injected by a syringe. The reaction mixture
was then treated as above.
1H), 6.93–7.02 (t, J ¼ 8:8 Hz, 2H), 7.27–7.35 (dd, J ¼ 8:8, 5.5
Hz, 2H); 13C NMR (CDCl3) ꢃ 29.44, 47.36, 115.12–115.41 (d,
J ¼ 21:4 Hz), 121.57–121.60 (d, J ¼ 2:4 Hz), 127.56–127.67
(d, J ¼ 7:8 Hz), 132.33, 132.92–132.96 (d, J ¼ 3:7 Hz),
160.47–163.74 (d, J ¼ 246:6 Hz), 206.37.
5-(4-Chlorophenyl)-4-penten-2-one (1e):4,15 A pale yellow
1
oil; H NMR (CDCl3) ꢃ 2.19 (s, 3H), 3.30–3.34 (d, J ¼ 6:8 Hz,
2H), 6.22–6.33 (dt, J ¼ 16:0, 6.8 Hz, 1H), 6.36–6.43 (d,
J ¼ 16:0 Hz, 1H), 7.23–7.30 (m, 4H); 13C NMR (CDCl3) ꢃ
29.55, 47.37, 122.59, 127.35, 128.55, 132.32, 132.99, 135.26,
206.20.
5-(4-Trifluoromethylphenyl)-4-penten-2-one (1f):
A pale
yellow oil; 1H NMR (CDCl3) ꢃ 2.21 (s, 3H), 3.36–3.39 (d,
J ¼ 6:0 Hz, 2H), 6.36–6.47 (dt, J ¼ 16:0, 6.0 Hz, 1H), 6.46–
6.53 (d, J ¼ 16:0 Hz, 1H), 7.43–7.47 (d, J ¼ 8:1 Hz, 2H), 7.53–
7.57 (d, J ¼ 8:1 Hz, 2H); 13C NMR (CDCl3) ꢃ 29.76, 47.47,
122.47–133.27 (quartet, J ¼ 272:2 Hz), 124.92, 125.47–125.63
(quartet, J ¼ 3:7 Hz), 126.48, 128.73–130.01 (quartet, J ¼ 32:3
Hz), 132.40, 140.42, 206.10. HRMS (FAB) found: 229.0843.
Calcd for C12H12F3O (M + Hþ): 229.0840.
5-Phenyl-4-penten-2-one (1a):4,7–14
A pale yellow oil;
1H NMR (CDCl3) ꢃ 2.18 (s, 3H), 3.29–3.32 (d, J ¼ 7:0 Hz,
2H), 6.23–6.34 (dt, J ¼ 15:9, 7.0 Hz, 1H), 6.42–6.49 (d,
J ¼ 16:0 Hz, 1H), 7.18–7.38 (m, 5H); 13C NMR (CDCl3) ꢃ
29.59, 47.75, 121.86, 126.24, 127.55, 128.53, 133.79, 136.81,
206.67.
6-Phenyl-5-hexen-3-one (3a):4,16,17
A pale yellow oil;
5-(4-Methylphenyl)-4-penten-2-one (1b):4,9 A pale yellow
1H NMR (CDCl3) ꢃ 1.16–1.22 (t, J ¼ 7:3 Hz, 3H), 2.58–2.66
(quartet, J ¼ 7:3 Hz, 2H), 3.41–3.44 (d, J ¼ 7:0 Hz, 2H), 6.37–
6.48 (dt, J ¼ 16:0, 7.0 Hz, 1H), 6.55–6.61 (d, J ¼ 16:0 Hz,
1H), 7.31–7.50 (m, 5H); 13C NMR (CDCl3) ꢃ 7.64, 35.51,
46.49, 122.16, 126.15, 127.42, 128.46, 133.49, 136.86, 209.14.
3-Methyl-5-phenyl-4-penten-2-one (3b):10,18–20 A pale yel-
low oil; 1H NMR (CDCl3) ꢃ 1.25–1.29 (d, J ¼ 7:0 Hz, 3H),
2.20 (s, 3H), 3.30–3.40 (dt, J ¼ 8:5, 7.0 Hz, 1H), 6.12–6.21 (dd,
J ¼ 15:8, 8.5 Hz, 1H), 6.48–6.55 (d, J ¼ 15:8 Hz, 1H), 7.21–
7.39 (m, 5H); 13C NMR (CDCl3) ꢃ 16.15, 28.16, 51.34, 126.27,
127.66, 128.61, 128.79, 132.18, 136.80, 209.37.
1
oil; H NMR (CDCl3) ꢃ 2.16 (s, 3H), 2.31 (s, 3H), 3.26–3.29 (d,
J ¼ 7:0 Hz, 2H), 6.17–6.28 (dt, J ¼ 15:9, 7.0 Hz, 1H), 6.38–
6.45 (d, J ¼ 15:9 Hz, 1H), 7.07–7.11 (d, J ¼ 7:9 Hz, 2H), 7.23–
7.26 (d, J ¼ 7:9 Hz, 2H); 13C NMR (CDCl3) ꢃ 21.01, 29.37,
47.61, 120.70, 126.01, 129.10, 133.49, 133.96, 137.19, 206.63.
5-(4-Methoxyphenyl)-4-penten-2-one (1c):4,14 A pale yellow
1
oil; H NMR (CDCl3) ꢃ 2.18 (s, 3H), 3.26–3.30 (d, J ¼ 7:2 Hz,
2H), 3.56 (s, 3H), 6.08–6.19 (dt, J ¼ 15:9, 7.2 Hz, 1H), 6.36–
6.43 (d, J ¼ 15:9 Hz, 1H), 6.80–6.85 (d, J ¼ 8:8 Hz, 2H), 7.27–
7.31 (d, J ¼ 8:8 Hz, 2H); 13C NMR (CDCl3) ꢃ 29.39, 47.63,
55.11, 113.83, 119.48, 127.29, 129.56, 133.07, 159.05, 206.85.
5-(4-Fluorophenyl)-4-penten-2-one (1d):4 A pale yellow oil;
1H NMR (CDCl3) ꢃ 2.19 (s, 3H), 3.29–3.32 (d, J ¼ 7:0 Hz, 2H),
6.16–6.26 (dt, J ¼ 15:9, 7.0 Hz, 1H), 6.38–6.44 (d, J ¼ 15:9 Hz,
2-(2-Phenylethenyl)cyclopentan-1-one (3c): A pale yellow
oil; 1H NMR (CDCl3) ꢃ 1.75–2.36 (m, 6H), 2.86–2.96 (m, 1H),
6.16–6.25 (ddd, J ¼ 16:1, 6.1, 2.5 Hz, 1H), 6.41–6.48 (dd,
J ¼ 16:1, 1.3 Hz, 1H), 7.15–7.21 (t, J ¼ 7:0 Hz, 1H), 7.23–7.30

T. Ohe et al.
Bull. Chem. Soc. Jpn., 76, No. 9 (2003) 1827
(t, J ¼ 7:0 Hz, 2H), 7.33–7.37 (d, J ¼ 7:0 Hz, 2H); 13C NMR
(CDCl3) ꢃ 20.57, 29.48, 37.60, 52.27, 125.96, 126.00, 127.18,
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7
128.27, 131.72, 136.79, 217.83.
186.1039. Calcd for C13H14O (Mþ): 186.1045.
1,2-Bis(4-fluorophenyl)-1,2-ethanediol (2d)
HRMS (FAB) found:
8
(dl/meso
mixture):21 A colorless oil or a white solid: H NMR (CDCl3)
ꢃ 1.87 (s, br, 2H), 4.64 (dl isomer), 4.83 (meso isomer) (s, 2H),
6.88–7.19 (m, 8H).
1
1,2-Bis[4-(trifluoromethyl)phenyl]-1,2-ethanediol (2f) (dl/
meso mixture):22 A colorless oil or a white solid: 1H NMR
(CDCl3) ꢃ 2.43 (s, br, 2H), 4.75 (dl isomer), 4.95 (meso isomer)
(s, 2H), 7.42–7.63 (m, 8H).
12 T. Ueda, M. Kawakita, and Y. Otsuji, Nippon Kagaku
Kaishi, 1985, 271; Chem. Abstr., 104, 68982 (1986).
13 L. S. Hegedus and R. J. Perry, J. Org. Chem., 50, 4955
(1985).
References
1
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3
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