Rare earth metal trifluoromethanesulfonates catalyzed benzyl-etherification.

Article abstract of DOI:10.1248/cpb.50.380

Rare earth metal trifluoromethanesulfonates [rare earth metal triflate, RE(OTf)3] were found to be efficient catalyst for benzyl-etherification. In the presence of a catalytic amount of RE(OTf)3, condensation of benzyl alcohols and aliphatic alcohols proceeded smoothly to afford the benzyl ethers. The condensation between benzyl alcohols and thiols also proceeded, and thio ethers were obtained in good yield. In these reactions, RE(OTf)3 could be recovered easily after the reactions were completed and could be reused without loss of activity.

Full text of DOI:10.1248/cpb.50.380

380
Chem. Pharm. Bull. 50(3) 380—383 (2002)
Vol. 50, No. 3
Rare Earth Metal Trifluoromethanesulfonates Catalyzed
Benzyl-Etherification
b
Atsushi KAWADA, ,a Kayo YASUDA,b Hitoshi ABE,b and Takashi HARAYAMA
*
Nippon Steel Chemical Co., Ltd., Research & Development Laboratories,a 46–80 Nakabaru Sakinohama, Tobata-ku,
Kitakyushu 804–8503, Japan and Faculty of Pharmaceutical Sciences, Okayama University,b 1–1–1 Tsushima-naka,
Okayama 700–8530, Japan. Received November 1, 2001; accepted January 4, 2002
Rare earth metal trifluoromethanesulfonates [rare earth metal triflate, RE(OTf)3] were found to be efficient
catalyst for benzyl-etherification. In the presence of a catalytic amount of RE(OTf)3, condensation of benzyl alco-
hols and aliphatic alcohols proceeded smoothly to afford the benzyl ethers. The condensation between benzyl al-
cohols and thiols also proceeded, and thio ethers were obtained in good yield. In these reactions, RE(OTf)3 could
be recovered easily after the reactions were completed and could be reused without loss of activity.
Key words rare earth metal trifluoromethanesulfonate; benzyl-etherification; recyclable catalyst; benzyl alcohol; benzyl ether;
Lewis acid
Etherification by direct condensation of alcohols is one of The results are summarized in Table 1. Acetonitrile, di-
the most used method.1) This reaction is commonly achieved chloromethane, toluene, N,N-dimethylformamide (DMF), or
by use of small amounts of an organic or inorganic acid.1) On 1,3-dimethyl-2-imidazolidinone (DMI) was used as a sol-
the other hand, Lewis acid-catalyzed etherification by direct vent. In each set of conditions, the reaction proceeded and 4-
condensation has also been reported.2) In most cases, these [(2-isopropoxyethoxy)methyl]phenol (2) and bis(4-hydroxy-
reactions required stoichiometric amounts of catalyst, be- benzyl) ether (3) were obtained. It should be noted that only
cause the Lewis acid was decomposed by water which was a 0.01 molar amount of Yb(OTf)3 was required as catalyst in
formed as a co-product in the condensation of alcohols. Kim this reaction. The yields of 2 were increased in accordance
et al. reported that etherification by direct condensation of al- with the amount of 2-isopropoxyethanol. When a 1.0 molar
cohols proceeded by using a catalytic amount of zinc chlo- amount of 2-isopropoxyethanol was used, the yield of 2 was
ride as the Lewis acid; however, catalytic etherification was 34% (entry 1). On the other hand, when a 5.0 molar amount
limited to activated benzyl alcohols.2a) Quite recently, of 2-isopropoxyethanol was used, the yield of 2 was im-
Maruoka and co-workers reported that a small amount of proved to 81% (entry 4). Reaction temperature also affected
MeAl(NTf2)2, as a strong Lewis acid, catalyzed etherification
by direct condensation.2d)
Table 1. Yb(OTf)3 Catalyzed Etherification of 1
It is known that rare earth metal trifluoromethanesul-
fonates [rare earth metal triflate, RE(OTf)3] are stable in
water and therefore do not decompose under aqueous work-
up conditions, which are different from conventional Lewis
acids. In this decade, there have been many reports that
RE(OTf)3 as a Lewis acid catalyst has been successfully ap-
plied to several synthetic reactions.3) Recently, we have de-
veloped RE(OTf)3 catalyzed Friedel–Crafts acylation and
alkylation; these reactions proceed smoothly in the presence
of small amounts of RE(OTf)3.4) It has also been demon-
strated that the catalyst can be easily recovered by aqueous
Yield/%a)
work-up from the reaction mixture and reused without de-
Entry
Solvent
Temp./°C
crease in its catalytic activity. From these reports, we ex-
pected that RE(OTf)3 would work as a Lewis acid efficiently
even in the presence of water as the co-product in condensa-
tion of alcohols. Very recently, Sharma et al. examined ytter-
bium (III) trifluoromethanesulfonates [ytterbium (III) triflate;
Yb(OTf)3] catalyzed benzyl-etherification by condensation of
alcohols as described in preliminary report independently
from us.5) Therefore, we would like to report the etherifica-
tion of benzyl alcohols fully employing the characteristic fea-
tures of RE(OTf)3 efficiently.6)
2
3
1b)
2c)
3
4
5
6
7
8
9
MeCN
MeCN
MeCN
MeCN
CH2Cl2
Toluene
Toluene
Toluene
DMF
80
80
50
80
Reflux
50
80
Reflux
50
100
50
100
34
72
68
81
70
68
82
7
5
6
20
2
19
3
7
Trace
Trace
16
5
1
10
11
12
DMF
42
11
85
DMId)
DMId)
Results and Discussion
1
In the first place, several reaction conditions were exam-
ined in the reaction of 4-hydroxybenzyl alcohol (1) and 2-
a) Yields were determined by HPLC using the internal standard method. b) 1.0
molar amount of 2-isopropoxyethanol was used. c) 3.0 molar amounts of 2-iso-
isopropoxyethanol with catalytic amounts of Yb(OTf)3.7) propoxyethanol was used. d) 1,3-Dimethyl-2-imidazolidinone.
To whom correspondence should be addressed. e-mail: kawadaat@nscc.co.jp
© 2002 Pharmaceutical Society of Japan

March 2002
381
Table 2. Effect of Rare Earth Metal Triflate
Table 3. Catalytic Activity Of Yb(OTf)3 and Sc(OTf)3
Yield/%a)
Yield/%a)
Yield/%a)
RE
RE
Entry
Time
RE
2
3
2
3
2
3
Sc
Y
La
Pr
Nd
Sm
Eu
61
79
75
80
77
74
85
9
6
9
9
12
5
Gd
Dy
Ho
Er
Tm
Yb
Lu
78
79
75
80
65
81
76
4
1
2
3
4
5
6
7
8
9
5 min
5 min
10 min
10 min
30 min
1 h
2 h
5 h
5 h
Yb
Sc
Yb
Sc
Yb
Yb
Yb
Yb
Sc
18
78
37
76
65
61
79
81
61
8
3
3
6
12
2
5
15
Trace
16
14
8
8
9
2
9
a) Yields were determined by HPLC using the internal standard method.
a) Yields were determined by HPLC using the internal standard method.
Table 4. Reuse of Yb(OTf)3 in Etherification in 1
the yield. For example, while the reaction of 1 and 2-iso-
propoxyethanol in toluene at 80 °C gave 82% of 2 (entry 7),
the reaction under reflux condition gave only 7% (entry 8).
The result of gel permeation chromatography (GPC) analysis
of the reaction mixture in entry 9 showed that a polymeriza-
tion product was formed. We presumed that 1 or 2 was poly-
merized at high temperature and the yield of 2 was decreased.
Other RE(OTf)3 were then examined as a catalyst in the
reaction of 1 with 2-isopropoxyethanol (Table 2). Each
RE(OTf)3 was prepared by the reaction of the corresponding
rare earth metal oxide with trifluoromethanesulfonic acid in
an aqueous solution.7) All the RE(OTf)3 listed were effective
catalysts in the reaction of 1 and 2-isopropoxyethanol; 2 was
obtained in moderate yield.
Yield/%a)
No. of times
used
Recovery of
Yb(OTf)3/%
2
3
The difference of catalytic activity between Yb(OTf)3 and
scandium (III) trifluoromethanesulfonate [scandium (III) tri-
flate; Sc(OTf)3] is clearly shown in Table 3. This table shows
that Sc(OTf)3 is a more active catalyst than Yb(OTf)3. For ex-
ample, while the Sc(OTf)3-catalyzed reaction in 5 min
yielded 78% of 2 (entry 2), Yb(OTf)3 catalyzed reaction gave
only 18% (entry 1). On the other hand, the yields of the
Yb(OTf)3 catalyzed reaction increased in accordance with
the extension of reaction time; the reaction in 5 h gave 81%
of 2 (entry 8). However, the yields of the Sc(OTf)3 catalyzed
reaction decreased in accordance with the extension of reac-
tion time; the reaction of 5 h gave only 61% of 2 (entry 9).
The result of GPC analysis of the reaction mixture in entry 9
showed that a polymerization product was formed. These re-
sults showed that 2 was polymerized by Sc(OTf)3 because of
its strong Lewis acidity,8) thus the yield of 2 was decreased.
Reusability of the catalyst is one of the main advantages of
using RE(OTf)3. RE(OTf)3 could be easily recovered from
the reaction mixture by simple extraction and removing
water, which could be reused without further purification
(see Experimental). Efficiency of the recovery and catalytic
activity of reused Yb(OTf)3 were examined in the reaction of
1 with 2-isopropoxyethanol using Yb(OTf)3 as a representa-
1
2
3
85
84
81
4
4
5
72
70
70
a) Yields were determined by HPLC using the internal standard method.
tive RE(OTf)3. As shown in Table 4, the yields of etherifica-
tion product 2 in the second and third uses were almost the
same as those in the first use. However, the recovery of
Yb(OTf)3 was only 70%. We presumed that the catalyst was
soluble in the organic layer. The organic layer contained ethyl
acetate, 2-isopropoxyethanol, and water, because 2-iso-
propoxyethanol is highly soluble in ethyl acetate and water.
Therefore, a part of the catalyst was dissolved in the organic
layer, and the amount of the recovered catalyst decreased.
The reactivity of several kinds of benzyl alcohols was
examined in RE(OTf)3 catalyzed etherification. The results
are shown in Table 5. Although the etherification of benzyl
alcohol did not occur, introduction of a hydroxy or alkoxy
group to the benzene ring, such as hydroxybenzyl alcohol or
methoxybezyl alcohol, was effective for promoting the reac-
tion. For example, 1 reacted with methanol smoothly to

382
Vol. 50, No. 3
Table 5. Yb(OTf)3 Catalyzed Etherification of Benzylalcohols and Table 6. Yb(OTf)3 Catalyzed Etherification of 1 with Various Alcohols
Methanol
Entry
1
ROH
Product
Yield/%a)
85
Entry
1
Product
Yield/%a)
85
MeOH
4
10
11
2
3
65
70
1
5
4
2
3
27
37
6
NDb)
4
62
15
64
7
12
13
4
5
tert-BuOH
8
9
a) Isolated yield. b) Not detected.
6
14
a) Isolated yield.
Chart 1. A Possible Stable Complex of ortho-Substituted Benzyl Alcohols
Table 7. Yb(OTf)3 Catalyzed Reaction of 1 with Thiols
give 4-(methoxymethyl)phenol (4) in good yield (entry 1).
This table also shows that Yb(OTf)3 catalyzed etherifica-
tion is influenced strongly by the position of a hydroxy or
alkoxy group on the benzene ring. For example, the etherifi-
cation of 2-hydroxybenzyl alcohol (5) gave a low yield of 2-
(methoxymethyl)phenol (entry 2). As for the reaction of
methoxybenzyl alcohols, while 4-methoxybenzyl alcohol (8)
reacted to give 1-methoxy-4-(methoxymethyl)benzene (9), 2-
methoxybenzyl alcohol (7) did not react (entries 3, 4). From
these results, we assume that 5 or 7 would be stabilized by
bidentate chelation of Yb(OTf)3 shown in Chart 1.
The results of the Yb(OTf)3 catalyzed etherification with 1
and various aliphatic alcohols are summarized in Table 6. Al-
though the etherification with methanol proceeded smoothly,
the reaction with isopropyl alcohol or 1,1-dimethylethanol
gave lower yield product (entries 1, 4, 5). For example,
methanol gave 85% yield of 4-(methoxymethyl)phenol, but
1,1-dimethylethanol gave only 15% yield of 4-(tert-butoxy-
methyl)phenol (13). These results show that a sterically hin-
dered aliphatic alcohol influences the yield of the product.
Etherification using an allyl alcohol or a keto alcohol also
proceeded and gave the corresponding product in moderate
yield (entries 3, 6).
Entry
1
RSH
Product
Yield (%)a)
93
n-BuSH
15
16
2
tert-BuSH
89
a) Isolated yield.
responding thio ethers were obtained quantitatively.
Conclusions
We have demonstrated the RE(OTf)3 catalyzed etherifica-
tion of hydroxybenzyl alcohols and aliphatic alcohols by di-
rect condensation, which was found to be have specific fea-
tures as follows.
1) The reaction proceeds smoothly using a catalytic amount
of RE(OTf)3.
2) Sc(OTf)3 is the most active catalyst among the
RE(OTf)3.
3) RE(OTf)3 is easily recovered and reused without de-
crease in its catalytic activity.
RE(OTf)3 was also found to be an excellent catalyst in
condensation between benzyl alcohols and thiols.9) The re-
sults are summarized in Table 7. Butane-1-thiol or 1,1-di-
methylethane-1-thiol was used as thiols. As might be ex-
pected, both reactions proceeded quite smoothly, and the cor-

March 2002
383
[M]ϩ. Anal. Calcd for C10H14O2: C, 72.26; H, 8.48%. Found: C, 72.40; H,
8.50%.
4) RE(OTf)3 is also effective in thio etherification.
Experimental
4-(tert-Butoxymethyl)phenol (13): mp 62—65 °C (ether–n-hexane); IR
1
(KBr) 3280, 1620, 1520, 1250, 1040 cmϪ1; H-NMR (CDCl3) d: 1.29 (9H,
Melting points were measured with a Yanagimoto micro melting point ap-
paratus. IR spectra were recorded on a JASCO FT/IR-350. 1H-NMR spectra
[tetramethylsilane (TMS) as an internal standard] were recorded on a Varian
VXR-500 spectrometer. Chemical shifts are given in ppm. Mass spectra
were measured on a VG-70SE spectrometer. Elemental analyses were car-
ried out using a Yanaco MT-5. For thin layer chromatography (TLC) analy-
s), 4.36 (2H, s), 5.12 (1H, br s), 6.72 (2H, d, Jϭ8.5 Hz), 7.16 (2H, d,
Jϭ8.5 Hz). FAB-MS (positive ion mode) m/z: 180 [M]ϩ. High resolution
FAB-MS. Found: m/z 180.1186 [M]ϩ. Calcd for C11H16O2: 180.1150.
4-Hydroxybenzyloxy-2-butanone (14): Colorless oil. IR (neat) 3320,
2880, 1700, 1620, 1520, 1230 cmϪ1; 1H-NMR (CDCl3) d: 2.18 (3H, s), 2.71
(2H, t, Jϭ6.5 Hz), 3.71 (2H, t, Jϭ6.5 Hz), 4.42 (2H, s), 5.06 (1H, br s), 6.76
(2H, d, Jϭ8.5 Hz), 7.17 (2H, d, Jϭ8.5 Hz). FAB-MS (positive ion mode)
m/z: 194 [M]ϩ.
ses throughout this work, Merck precoated TLC plates (silica-gel 60 F254
)
were used. HPLC analysis for the determination of yield was carried out on
a SHIMADZU LC-6A and an UV detector of 254 nm. GPC analysis was
carried out on a TOSOH HLC-8020. Silica-gel column chromatography was
performed using Merck Kieselgel 60 (70—230 mesh).
All of the RE(OTf)3 were prepared from the corresponding rare earth
metal oxide (Soekawa Chemicals Co., Ltd.) and trifluoromethanesulfonic
acid (Kanto Chemicals Co., Ltd.) in water according to the literature.7)
Reagents used in this work were commercially available.
4-(Butylthiomethyl)phenol (15): Yellow oil. IR (KBr) 3360, 1620,
1520 cmϪ1 1H-NMR (CDCl3) d: 0.88 (3H, t, Jϭ15.0 Hz), 1.37 (2H, sext,
;
Jϭ7.5 Hz), 1.54 (2H, quint, Jϭ7.5 Hz), 2.41 (2H, t, Jϭ15.0 Hz), 3.65 (2H,
s), 4.86 (1H, br s), 6.77 (2H, d, Jϭ8.5 Hz), 7.16 (2H, d, Jϭ8.5 Hz). FAB-MS
(positive ion mode) m/z: 197 [Mϩ1]ϩ. High resolution FAB-MS. Found: m/z
197.1003 [Mϩ1]ϩ. Calcd for C11H16OS: 197.1000.
A Typical Experimental Procedure for the RE(OTf)3 Catalyzed Ben-
zyl-Etherification Typical experimental procedure is described for the re-
action of 4-hydroxybenzyl alcohol with 2-isopropoxyethanol; Yb(OTf)3 was
prepared from the ytterbium (III) oxide (Yb2O3) and trifluoromethanesul-
fonic acid.7) A mixture of Yb(OTf)3 (124 mg, 0.2 mmol), 2-isopropoxy-
ethanol (11.6 ml, 100 mmol) and 4-hydroxybenzyl alcohol (2.48 g, 20 mmol)
in acetonitrile (20 ml) was stirred at 80 °C for 5 h. After dilution with water,
the mixture was extracted with ethyl acetate. After removal of the solvents,
the crude products were purified by column chromatography on silica-
gel using ether–dichloromethane (1 : 10) as eluent to afford 4-[(2-iso-
propoxyethoxy)methyl]phenol (2) (85% yield) and bis(4-hydroxybenzyl)
ether (3) (4% yield). The aqueous layer was concentrated in vacuo to give a
crystalline residue, which was finally heated at 180 °C for 48 h in vacuo to
afford 89 mg (72%) of Yb(OTf)3 as colorless crystals. The recovered
Yb(OTf)3 was reused in the next reaction.
4-(tert-Butylthiomethyl)phenol (16): mp 94.5—95.5 °C (ether–n-hexane);
1
IR (KBr) 3200, 1520 cmϪ1; H-NMR (CDCl3) d: 1.34 (9H, s), 3.71 (2H, s),
4.76 (1H, br s), 6.75 (2H, d, Jϭ8.5 Hz), 7.2 (2H, d, Jϭ8.5 Hz). FAB-MS
(positive ion mode) m/z: 197 [Mϩ1]ϩ. High resolution FAB-MS. Found: m/z
197.1003 [Mϩ1]ϩ. Calcd for C11H16OS: 197.1000.
Acknowledgement We are grateful to the SC-NMR Laboratory of
Okayama University for high-field NMR experiments.
References and Notes
1) a) Smith M. B., March J., “Advanced Organic Chemistry,” 5th edition,
Wiley-Interscience, New York, 2001, pp. 479—480; b) Larock R. C.,
“Comprehensive Organic Transformations,” 2nd edition, Wiley-Inter-
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Maruoka K., Heterocycles, 52, 575—578 (2000).
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Soc. Jpn., 67, 2342—2344 (1994); b) Hachiya I., Kobayashi S., J. Org.
Chem., 58, 6958—6966 (1993); c) Manabe K., Oyamada H., Sugita
K., Kobayashi S., ibid., 64, 8054—8057 (1999); d) Kobayashi S., Ishi-
tani H., Hachiya I., Araki M., Tetrahedron, 50, 11623—11633 (1994).
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8944 (1999); b) Sharma G. V. M., Prasad T. R., Mahalingam A. K.,
Tetrahedron Lett., 42, 759—761 (2001).
6) We have already applied for Japanese patents for the rare earth metal
triflates catalyzed benzyl-etherification. Kawada A., Tomiku T.,
Ishikawa S., JP Patent 2000-204055 (2000) [Chem. Abstr,. 133,
104871 (2000)].
7) a) Forsberg J. H., Spaziano V. T., Balasubramanian T. M., Liu G. K.,
Kinsley S. A., Duckworth C. A., Poteruca J. J., Brown P. S., Miller J.
L., J. Org. Chem., 52, 1017—1021 (1987); b) Thom K. F., U.S. Patent
3615169 (1971) [Chem. Abstr., 76, 5436a (1972)].
8) It was already known that Sc(OTf)3 is the strongest Lewis acid among
rare earth metal triflates. a) Tsuruta H., Yamaguchi K., Imamoto T., J.
Chem. Soc., Chem. Commun., 1999, 1703—1704; b) Kobayashi S.,
Hachiya I., Ishitani H., Araki M., Synlett, 1993, 472—474; c)
Kobayashi S., Hachiya I., Araki M., Ishitani H., Tetrahedron Lett., 34,
3755—3758 (1993); d) Kobayashi S., Ishitani H., Nagayama S., Syn-
thesis, 1995, 1195—1202; e) Kobayashi S., Eur. J. Org. Chem., 1999,
15—17; see also Refs. 4b and 4d.
4-[(2-Isopropoxyethoxy)methyl]phenol (2): Yellow oil. IR (KBr) 3300,
1620, 1520, 1220, 1080 cmϪ1; 1H-NMR (CDCl3) d: 1.18 (6H, d, Jϭ6.0 Hz),
3.58—3.67 (5H, m), 4.47 (2H, s), 5.70—5.75 (1H, br s), 6.74 (2H, d,
Jϭ8.5 Hz), 7.16 (2H, d, Jϭ8.5 Hz). High resolution FAB-MS. Found: m/z
210.1255 [M]ϩ. Calcd for C12H18O3: 210.1270.
Bis(4-hydroxybenzyl) Ether (3)10): mp 84—85 °C (ether–n-hexane) (lit.
63—65 °C); IR (KBr) 3200, 1620, 1520, 1250, 1060 cmϪ1 1H-NMR
;
(CD3OD) d: 4.39 (4H, s), 4.87 (2H, s), 6.75 (4H, d, Jϭ8.5 Hz), 7.15 (4H, d,
Jϭ8.5 Hz), FAB-MS (positive ion mode) m/z: 230 [M]ϩ. Anal. Calcd for
C14H14O3·1/2H2O: C, 70.27; H, 6.31%. Found: C, 70.39; H, 6.15%.
4-(Methoxymethyl)phenol (4)10): mp 82—83 °C (ether–n-hexane) (lit.
81—83 °C); IR (KBr) 3240, 1620, 1520, 1070 cmϪ1 1H-NMR (CDCl3) d:
;
3.37 (3H, s), 4.39 (2H, s), 5.37 (1H, s), 6.77 (2H, d, Jϭ8.5 Hz), 7.16 (2H, d,
Jϭ8.5 Hz). FAB-MS (positive ion mode) m/z: 138 [M]ϩ. Anal. Calcd for
C8H10O2: C, 69.54; H, 7.29%. Found: C, 69.62; H, 7.35%.
2-(Methoxymethyl)phenol (6)11): Colorless oil. IR (CHCl3) 3400, 3000,
2920, 1600, 1490, 1240, 1080 cmϪ1; 1H-NMR (CDCl3) d: 3.45 (3H, s), 4.67
(2H, s), 6.85 (1H, dt, Jϭ7.5, 1.5 Hz), 6.90 (1H, dd, Jϭ7.5, 1.5 Hz), 7.02
(1H, dd, Jϭ7.5, 1.5 Hz), 7.22 (1H, dt, Jϭ7.5, 1.5 Hz), 7.45 (1H, br s). FAB-
MS (positive ion mode) m/z: 138 [M]ϩ.
1-Methoxy-4-(methoxymethyl)benzene (9)12): Colorless oil. IR (CHCl3)
1
3000, 2920, 2840, 1620, 1520, 1240, 1080 cmϪ1; H-NMR (CDCl3) d: 3.35
(3H, s), 3.80 (3H, s), 4.39 (2H, s), 6.88 (2H, d, Jϭ8.5 Hz), 7.26 (2H, d,
Jϭ8.5 Hz). Anal. Calcd for C9H12O2: C, 71.02; H, 7.94%. Found: C, 71.03;
H, 7.85%.
4-(2-Methoxyethoxymethyl)phenol (10)13): Yellow oil. IR (KBr) 3300,
1
1610, 1510, 1240, 1080 cmϪ1; H-NMR (CDCl3) d: 3.39 (3H, s), 3.60 (4H,
s), 4.47 (2H, s), 5.74 (1H, br s), 6.74 (2H, d, Jϭ8.5 Hz), 7.16 (2H, d,
Jϭ8.5 Hz). FAB-MS (positive ion mode) m/z: 182 [M]ϩ. Anal. Calcd for
C10H14O3·1/5H2O: C, 64.63; H, 7.81%. Found: C, 64.80; H, 7.64%.
(4-Allyloxymethyl)phenol (11): Colorless oil. IR (KBr) 3300, 1610, 1510,
9) Guindon et al. reported that ZnI2 as Lewis acid worked efficiency for the
preparation of thioethers from thiols and alcohols. Guindon Y., Frenette
R., Fortin R., Rokach J., J. Org. Chem., 48, 1357—1359 (1983).
10) Torii S., Inokuchi T., Horike H., Kuroda H., Uneyama K., Bull. Chem.
Soc. Jpn., 60, 2173—2188 (1987).
1
1240, 1080 cmϪ1; H-NMR (CDCl3) d: 4.02 (2H, ddd, Jϭ5.5, 2.0, 1.0 Hz),
4.45 (2H, s), 5.21 (1H, ddd, Jϭ10.0, 3.0, 1.0 Hz), 5.30 (1H, ddd, Jϭ17.0,
3.0, 2.0 Hz), 5.59 (1H, br s), 5.95 (1H, ddt, Jϭ17.0, 10.0, 5.5 Hz), 6.76 (2H,
d, Jϭ8.5 Hz), 7.16 (2H, d, Jϭ8.5 Hz). FAB-MS (positive ion mode) m/z: 164
[M]ϩ. Anal. Calcd for C10H12O2·1/10H2O: C, 72.35; H, 7.40%. Found: C,
72.14; H, 7.37%.
11) Taguchi H., Yoshida I., Yamasaki K., Kim I. H., Chem. Pharm. Bull.,
29, 55—62 (1981).
(4-Isopropoxymethyl)phenol (12): mp 61.5—62.5 °C (ether–n-hexane);
12) Sparfel D., Baranne-Lanfont J., Coung N. K., Capdevielle P., Maumy
M., Tetrahedron, 46, 793—802 (1990).
13) Saá J. M., Llobera A., García-Raso A., Costa A., Deyá P. M., J. Org.
1
IR (KBr) 3200, 1620, 1520, 1040 cmϪ1; H-NMR (CDCl3) d: 1.12 (6H, d,
Jϭ6.0 Hz), 3.69 (1H, sept, Jϭ6.0 Hz), 4.43 (2H, s), 5.23 (1H, s), 6.75 (2H,
d, Jϭ8.5 Hz), 7.16 (2H, d, Jϭ8.5 Hz). FAB-MS (positive ion mode) m/z: 166
Chem., 53, 4263—4273 (1988).