Reduction of acetals with samarium diiodide in acetonitrile in the presence of Lewis acids

Article abstract of DOI:10.1248/cpb.49.97

Transformation of acetals into ethers by partial reduction using a samarium diiodide-Lewis acids-acetonitrile system is described. The reaction with aromatic acetals occurred in good yields in the presence of aluminum chloride (2 eq) whereas the corresponding aliphatic, vinylic, and alkynyl derivatives did not afford ethers under the same conditions, β-Elimination to give an enol ether becomes predominant when aliphatic acetals that possess a hydrogen at the 2-position are treated with iodotrimethylsilane in the presence of SmI₂ or SmI₃.

Full text of DOI:10.1248/cpb.49.97

January 2001
Chem. Pharm. Bull. 49(1) 97—100 (2001)
97
Reduction of Acetals with Samarium Diiodide in Acetonitrile in the
Presence of Lewis Acids
Munetaka KUNISHIMA,* Daisuke NAKATA, Takayuki SAKUMA, Kazuhiro KONO, Shoichi SATO, and
Shohei TANI*
Faculty of Pharmaceutical Sciences and High Technology Research Center, Kobe Gakuin University, Nishi-ku, Kobe
651–2180, Japan. Received September 4, 2000; accepted October 6, 2000
Transformation of acetals into ethers by partial reduction using a samarium diiodide–Lewis acids–acetoni-
trile system is described. The reaction with aromatic acetals occurred in good yields in the presence of aluminum
chloride (2 eq) whereas the corresponding aliphatic, vinylic, and alkynyl derivatives did not afford ethers under
the same conditions. b-Elimination to give an enol ether becomes predominant when aliphatic acetals that pos-
sess a hydrogen at the 2-position are treated with iodotrimethylsilane in the presence of SmI2 or SmI3.
Key words samarium diiodide; reduction; dealkoxylation; acetal; ether
Partial reduction of acetals constitutes an important trans- follows: HMPA (38.8)ϾTHF (20.0)ϾCH3CN (14.1).6)
formation of ketones or aldehydes into ethers.1) Among vari-
Based on this consideration, we expected that addition of
ous methods, reaction using the powerful reducing agent Lewis acids stronger than samarium ions could activate the
samarium diiodide (SmI2)2) is very limited because acetals acetals. Thus, various Lewis acids as additives were exam-
have been recognized as stable to SmI2 in the absence of ad- ined to facilitate the transformation of diallyl acetal 1a into
ditives. Studer and Curran first reported that reduction of di- homoallyl alcohol 2a via [2,3]-Wittig rearrangement (Table
methyl acetals to methyl ethers proceeded using SmI2/ 1). Reactions were conducted until either 1a or the purple
tetrahydrofuran (THF) in the presence of trifluoroacetic acid color of SmI2 disappeared. Since SmI2 was consumed inde-
or water.3) Independently, we found that partial reduction of pendent of the disappearance of 1a in some cases, excess
diallyl acetals occurred without additives by simple refluxing SmI2 (5 eq) was used to obtain good yields. Although all
in acetonitrile giving a-allyloxy carbanions, which under- Lewis acids afforded yields lower than those observed in
went [2,3]-Wittig rearrangement leading to the formation of their absence, AlCl3 and BF3-Et2O allowed the reaction to
homoallyl alcohols.4) We also showed the first example of re- occur at room temperature.
duction of dithioacetals to sulfides with SmI2 in a related re-
We next attempted transformation of simple dialkyl acetal
action.5) We report here our efforts towards reductive 6a into ether 7a as shown in Table 2. Surprisingly, the yield
dealkoxylation of acetals with SmI2 in acetonitrile in the of 7a was much lower (13%) than that of 2a under the same
presence of Lewis acids.
conditions (refluxing in CH3CN: Table 2, run 1 vs. Table 1,
run 1). However, the observed solvent effect was similar to
Results and Discussion
Table 1. Activation of Diallyl Acetal by Lewis Acids
In previous work, we found that acetonitrile (CH3CN) as a
solvent is more effective than THF or benzene–hexam-
ethylphosphoric triamide (HMPA) for reduction of diallyl ac-
etals.4) In addition, reactions in CH3CN are completely sup-
pressed by addition of HMPA, a well known activator for
SmI2. Therefore, we proposed that the SmI2-induced [2,3]-
Wittig rearrangement, initiated by reductive cleavage of dial-
lyl acetals, could proceed by the mechanism illustrated in
Chart 1, in which activation of acetals by complexation with
a di- or trivalent samarium ion to generate 3 could be more
important than increasing the reducing potential of SmI2. Be-
cause of the strong coordinating ability of HMPA to samar-
ium ions, the formation of complex 3 could be prevented by
HMPA, therefore no reaction takes place. THF might also
have coordinating ability sufficient to inhibit the complexa-
tion, but the ability of CH3CN might be insufficient. This as-
sumption is supported by the order of the donor number as
Run Eq of SmI2 Additive (eq)
Conditions
Yield (%)a) of 2a
1
2
3
4
5
6
7
8
9
3
3
5
3
5
5
3
3
3
3
3
None
Reflux, 2 h
72
64
52
34
50
36
18
Ͻ2
0
SmI3 (1)
TMSCl (2)
TMSI (1)
AlCl3 (2)
Reflux, 40 min
Reflux, 30 min
Reflux, 15 min
r.t., 10 min
BF3·Et2O (2) r.t., 10 min
ZnCl2 (2)
SnOTf2 (2)
SnCl2 (2)
MgCl2 (2)
TiCl4 (2)
Reflux, 2 h
Reflux, 15 min
Reflux, 30 min
Reflux, 30 min
Reflux, 30 min
10
11
0
0
a) Isolated yield.
Chart 1
To whom correspondence should be addressed. e-mail: kunisima@kgu-p.pharm.kobegakuin.ac.jp
© 2001 Pharmaceutical Society of Japan

98
Vol. 49, No. 1
Table 2. Acetal Reduction with SmI2 under Various Conditions
Conditions
Temp.
Run
SmI2 (eq)
Additive (2eq)
Solvent
Yield (%)a)
Recovery (%)a)
Time
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
3
5
3
3
5
5
5
5
5
5
5
5
5
5
5
5
5
None
None
None
None
None
AlCl3
AlCl3 (1eq)
AlCl3
AlCl3
BF3·Et2O
TMSI
CH3CN
CH3CN
THF
Reflux
r.t.
Reflux
Reflux
Reflux
r.t.
r.t.
r.t.
r.t.
Reflux
r.t.
Ϫ20 °C
Ϫ20 °C
Reflux
Reflux
r.t.
30 min
24 h
2 h
2 h
2 h
30 min
10 min
20 min
24 h
10 min
15 min
15 min
2 h
15 min
10 min
30 min
4 min
13
0
8
0
0
80
14
41
0
72
6
62
15
52
43
20
30
24
91
76
84
93
0
CH3CN–HMPA
PhH–HMPA
CH3CN
CH3CN
THF
PhH–HMPA
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
b)
—
33
92
0
3
TMSI
17c)
71
0
TMSI (1eq)
CF3CO2H
CH3CO2H
TsOH
0
7
0
HCl (35%)
Reflux
a) Isolated yield. b) Not determined. c) Benzaldehyde (18%) was obtained.
Chart 2
Table 3. Reduction of Acetals Using the SmI2–AlCl3–CH3CN System
that using diallyl acetals 1. Reactions conducted in the pres-
ence of HMPA (CH3CN–HMPA or PhH–HMPA) resulted in
0% yield (runs 4, 5). Addition of 2 eq of AlCl3 successfully
promoted the reaction to give 7a in 80% yield whereas de-
creasing the amount of AlCl3 to 1 eq resulted in 14% yield.
When THF or benzen–HMPA (9 : 1) was used as a solvent,
the yields were decreased to 41% and 0%, respectively. BF3-
Et2O was also effective to give a 72% yield of 7a. Interest-
ingly, iodotrimethylsilane (TMSI; 2 eq) was found effective
at low temperature (Ϫ20 °C) affording 7a in 62% yield
whereas it was ineffective at room temperature (6%).
Brønsted acids promoted the reaction moderately.
Table 3 shows the scope of the reaction using the AlCl3–
SmI2–CH3CN system. Dialkyl acetals of aromatic aldehydes
or ketones underwent reduction to give the corresponding
ethers in good yields whereas those derived from aliphatic,
alkenyl, and alkynyl aldehydes afforded poor results.
6
Yield of Recovery
SmI2 Time
7 (%)a)
of 6 (%)a)
R1
R2 R3
b
c
Ph
Ph
H
Me
Bu
5
5
40 min
30 min
85b)
88
0
3
H
H
H
Bu
Bu
3
5
15 min
30 min
80
84
72b)
0
11
0
0
0
d
e
f
g
h
Me Me
5
5
5
5
4 h
2 h
2 h
1 h
0
7
16
0
PhCH2
Ph(CH2)2
H
H
H
Me
Bu
Bu
i
H
Et
5
2 h
0
79
As illustrated in Chart 2, the reduction of acetals may pro-
ceed by a mechanism similar to that for diallyl acetals. A net
two-electron transfer from SmI2 to the complex 8 with the
a) Isolated yield. b) Determined by GC.
liberation of an aluminum alkoxide followed by protonation Alternatively, metal-metal exchange between samarium ion
would give 7. The observed lower yield of 7a compared to 2a and aluminum ion would generate an alkylaluminum inter-
can be attributed to the facile decomposition of alkylsamar- mediates 10, which may be stable during the reaction. When
ium intermediates 9a under reflux conditions.7) Alkylsamari- 1 eq of AlCl3 was used, exclusive complexation of a liberated
ums possessing an a-allyloxy group such as 4 undergo [2,3]- alkoxy anion with aluminum ion may prevent the formation
sigmatropic rearrangement faster than decomposition and of 10, and therefore, may be responsible for the low yield.
product 2 was obtained in good yields. In the presence of
To achieve reduction of aliphatic acetals, we examined the
AlCl3, the reduction of 6 giving 9 might be completed effects of Lewis acids on the reduction of 6g under several
rapidly at room temperature before the decomposition of 9. conditions. Unfortunately, we could not find good conditions,

January 2001
99
Table 4. Elimination of Aliphatic Acetals Possessing b-Hydrogen
Run
Metal halide
Additive
Temp.
Time
Yield (%)
E/Z
Recovery (%)a)
Aldehyde (%)a)
b)
1
2
3
4
5
6
7
8
9
10
11
12
13
3SmI2
3SmI2
—
—
5SmI2
2TMSI
5TMSI
2TMSI
5TMSI
2TMSI
5TMSI
5TMSI
5TMSI
5TMSI
5TMSCl
5TMSI
2AlCl3
2AlCl3
r.t.
r.t.
r.t.
r.t.
Ϫ20°C
r.t.
r.t.
r.t.
r.t.
r.t.
4 h
45 min
2.5 h
25 min
4 h
20 min
45 min
30 min
30 min
75 min
1 h
20
60
0
0
0
64
0
0
0
37
0
30/70
27/73
—
—
—
34/66
—
—
—
30/70
—
4
14
8
8
83
8
11
16
2
—
21
75
48
6
3SmI3
10
65
68
88
33
3SmCl3
3SmCl3ϩ30LiI
9LiI
3SmI2
3SmI2ϩ12HMPA
5SmI2
7
b)
r.t.
r.t.
Reflux
96
16
21
—
2 h
2 h
0
30
—
35/65
14
b)
5SmI2
—
a) Isolated yield. b) Not determined.
but the formation of enol ether 11 was found to take place m), 3.50 (2H, dt, Jϭ9.4, 6.6 Hz), 3.58 (2H, dt, Jϭ9.4, 6.6 Hz), 3.54 (1H, s),
7.31—7.37 (1H, m), 7.40—7.46 (2H, m), 7.51—7.55 (2H, m), 7.56—7.62
when TMSI was used (Table 4). As Jung et al. reported that
(4H, m). 13C-NMR (CDCl3) d: 14.0, 19.5, 32.0, 65.3, 101.5, 127.0, 127.2
the reaction of acetals with TMSI gives ketones or aldehydes
(2C), 127.3, 128.8, 138.3, 141.0, 141.1. IR (film) cmϪ1: 3058, 3031, 2958,
2931, 2873, 1101, 1068, 1041, 1008. Anal. Calcd for C21H28O2: C, 80.73; H,
under non-aqueous conditions,8) 3-phenylpropionaldehyde
was obtained without any detectable formation of 11 when
the reaction was conducted in the absence of SmI2. SmI3 in
place of SmI2 was found to be useful, but SmCl3, LiI, and
SmI2–HMPA did not produce 11 at all. Chlorotrimethysilane
(TMSCl), which could generate TMSI in the reaction media,
was found to be effective. Miller and McKean reported that
b-elimination to give enol ether became predominant when
hexamethyldisilazane (HMDS) as a base was added to the re-
action of acetals and TMSI.9) In comparison with their re-
sults, it should be noted that our reaction enables the same
transformation under non-basic conditions. The stereoselec-
tivity, in which the Z-isomer is major, is similar to that ob-
served in the TMSI-HMDS system.
9.03. Found: C, 80.96; H, 9.12.
2-Naphthaldehyde Dibutyl Acetal (6d): A colorless oil. 1H-NMR (CDCl3)
d: 0.92 (6H, t, Jϭ7.4 Hz), 1.36—1.48 (4H, m), 1.58—1.67 (4H, m), 3.51
(2H, dt, Jϭ9.4, 6.6 Hz), 3.58 (2H, dt, Jϭ9.4, 6.6 Hz), 5.65 (1H, s), 7.43—
7.51 (2H, m), 7.55—7.60 (1H, m), 7.80—7.89 (3H, m), 7.94 (1H, s). 13C-
NMR (CDCl3) d: 14.0, 19.5, 32.0, 65.3, 101.7, 124.6, 125.9, 126.0, 126.1,
127.7, 128.0, 128.3, 133.1, 133.4, 136.7. IR (film) cmϪ1: 3060, 2958, 2933,
2871, 1170, 1126, 1099, 1066, 1043. Anal. Calcd for C19H26O2: C, 79.68; H,
9.15. Found: C, 79.66; H, 9.28.
Phenylpropionaldehyde Dibutyl Acetal (6g): A colorless oil. 1H-NMR
(CDCl3) d: 0.93 (6H, t, Jϭ7.4 Hz), 1.34—1.45 (4H, m), 1.52—1.61 (4H,
m), 1.90—1.98 (2H, m), 2.65—2.72 (2H, m), 3.42 (2H, dt, Jϭ9.3, 6.6 Hz),
3.58 (2H, dt, Jϭ9.3, 6.6 Hz), 4.47 (1H, t, Jϭ5.7 Hz), 7.14—7.22 (3H, m),
7.24—7.30 (2H, m). 13C-NMR (CDCl3) d: 13.9, 19.5, 31.1, 32.1, 35.1, 65.4,
102.4, 125.8, 128.4, 128.4, 141.9. IR (film) cmϪ1: 3033, 2958, 2871, 1128,
1043. Calcd for C17H28O2: C, 77.22; H, 10.67. Found: C, 77.26; H, 10.40.
Typical Procedure for [2,3]-Wittig Rearrangement in the Presence of
Lewis Acids Benzaldehyde diallyl acetal 1a (0.196 mmol) was added to a
solution of SmI2 (0.099 M, 0.979 mmol) and AlCl3 (0.392 mmol) in CH3CN
at room temperature. After 10 min, the reaction mixture was poured into
aqueous K2CO3, and extracted with ether. The organic layer was washed
with water and brine and dried over MgSO4. After evaporation, the residue
was purified by preparative TLC (hexane/AcOEtϭ8 : 2) to give 2a4) as a col-
orless oil (yield 50%). 1H-NMR (CDCl3) d: 2.09 (1H, br s), 2.45—2.58 (2H,
m), 4.73 (1H, dd, Jϭ7.6, 5.3 Hz), 5.11—5.19 (2H, m), 5.74—5.86 (1H, m),
7.24—7.37 (5H, m). IR (film) cmϪ1: 3380, 3080, 3040, 2940, 2920, 1640,
1500, 1460, 1320, 1200, 1050. HRMS Calcd for C10H12O m/z: 148.0888.
Found m/z: 148.0895.
General Procedure for Reduction of Dialkyl Acetals by the SmI2–
AlCl3–CH3CN System Benzaldehyde dibutyl acetal 6a (0.169 mmol) was
added to a solution of SmI2 (0.108 M, 0.846 mmol) in CH3CN followed by
addition of a solution of AlCl3 (0.338 mmol) in CH3CN at room tempera-
ture. After 30 min, the reaction mixture was poured into aqueous K2CO3,
and extracted with ether. The organic layer was washed with water and brine
and dried over MgSO4. After evaporation, the residue was purified by
preparative TLC (hexane/AcOEtϭ9 : 1) to give 7a as a colorless oil (yield
80%).13) 1H-NMR (CDCl3) d: 0.92 (3H, t, Jϭ7.4 Hz), 1.34—1.46 (2H, m),
1.56—1.65 (2H, m), 3.47 (2H, t, Jϭ6.6 Hz), 4.50 (2H, s), 7.24—7.36 (5H,
m). IR (film) cmϪ1: 3029, 2958, 2933, 2863, 1101.
Experimental
Acetals 1a, 6a, 6c, 6d, and 6g were prepared from the corresponding
aldehydes according to a method in the literature.10) Other acetals and chem-
icals were obtained from commercial sources and used as received unless
otherwise noted. CH3CN and HMPA were distilled from calcium hydride
prior to use. Benzene and THF were distilled from sodium/benzophenone
prior to use. 1,2-Diiodoethane was purified by treating with Na2S2O3. 1H-
NMR (400 MHz) and 13C-NMR (100 MHz) spectra were recorded in ppm
(d) downfield from tetramethylsilane as an internal standard using a Brüker
DPX 400 spectrometer. Infrared spectra were recorded on a JEOL JIR-100
FT-IR spectrometer. Preparative thin-layer chromatography was performed
on Merck precoated silica gel plates. GLC analysis was performed on a Hi-
tachi 263-50 Gas Chromatograph with 10% Silicone SE-30 on a Chro-
mosorb WAS DMCS (3 mmϫ1 m).
Benzaldehyde Diallyl Acetal (1a)11): A colorless oil. 1H-NMR (CDCl3) d:
4.06 (4H, dt, Jϭ5.5, 1.7 Hz), 5.18 (2H, dq, Jϭ10.4, 1.7 Hz), 5.31 (2H, dq,
Jϭ17.2, 1.7 Hz), 5.64 (1H, s), 5.94 (2H, ddt, Jϭ17.2, 10.4, 5.5 Hz), 7.29—
7.40 (3H, m), 7.47—7.52 (2H, m). IR (film) cmϪ1: 3081, 2867, 1646, 1095,
1074, 1041. MS m/z: 204 (Mϩ).
Benzaldehyde Dibutyl Acetal (6a)12): A colorless oil. 1H-NMR (CDCl3)
d: 0.91 (6H, t, Jϭ7.4 Hz), 1.35—1.46 (4H, m), 1.54—1.64 (4H, m), 3.53
(2H, dt, Jϭ9.4, 6.6 Hz), 3.47 (2H, dt, Jϭ9.4, 6.6 Hz), 5.50 (1H, s), 7.27—
7.38 (3H, m), 7.44—7.49 (2H, m). IR (film) cmϪ1: 3070, 3035, 2960, 2935,
2873, 1103, 1068, 1039. MS m/z: 236 (Mϩ). Anal. Calcd for C15H24O2: C,
76.23; H, 10.24. Found: C, 76.09; H, 10.37.
1
Butyl 4-Biphenylmethyl Ether (7c): A colorless oil. H-NMR (CDCl3) d:
0.92 (3H, t, Jϭ7.4 Hz), 1.35—1.47 (2H, m), 1.57—1.66 (2H, m), 3.50 (2H,
t, Jϭ6.6 Hz), 4.53 (2H, s), 7.29—7.36 (1H, m), 7.37—7.46 (4H, m), 7.53—
7.64 (4H, m). 13C-NMR (CDCl3) d: 14.0, 19.5, 31.9, 70.4, 72.6, 127.1,
1
4-Biphenylcarboxaldehyde Dibutyl Acetal (6c): A colorless oil. H-NMR
(CDCl3) d: 0.93 (6H, t, Jϭ7.4 Hz), 1.37—1.48 (4H, m), 1.57—1.66 (4H,

100
Vol. 49, No. 1
127.2, 127.3, 128.1, 128.8, 137.9, 140.5, 141.1. IR (film) cmϪ1: 3023, 2958,
2861, 1097. Anal. Calcd for C17H20O: C, 84.96; H, 8.39. Found: C, 85.24; H,
8.63.
Guide to Functional Group Preparations,” VCH Publishers, Inc., New
York, 1989.
2) For recent reviews on SmI2: Skrydstrup T., Angew. Chem., Int. Ed.
Engl., 36, 345—347 (1997); Molander G. A., Harris C. R., Tetrahe-
dron, 54, 3321—3354 (1998); Kunishima M., Tani S., J. Synth. Org.
Chem., Jpn., 57, 127—135 (1999); Krief A., Laval A.-M., Chem. Rev.,
99, 745—777 (1999).
3) Studer A., Curran D. P., Synlett, 1996, 255—257.
4) Hioki K., Kono K., Tani S., Kunishima M., Tetrahedron Lett., 39,
5229—5232 (1998).
5) Kunishima M., Nakata D., Hioki K., Tani S., Chem. Pharm. Bull., 46,
187—189 (1998).
6) Gutmann V., Angew. Chem., Int. Ed. Engl., 9, 843—860 (1970).
7) Curran D. P., Totleben M. J., J. Am. Chem. Soc., 114, 6050—6058
(1992).
Butyl 2-Naphthylmethyl Ether (7d): A colorless oil. 1H-NMR (CDCl3) d:
0.93 (3H, t, Jϭ7.4 Hz), 1.36—1.47 (2H, m), 1.58—1.67 (2H, m), 3.52 (3H,
t, Jϭ6.6 Hz), 4.66 (2H, s), 7.42—7.50 (3H, m), 7.77 (1H, s), 7.79—7.85
(3H, m). IR (film) cmϪ1: 2927, 2854, 1054. Anal. Calcd for C15H18O: C,
84.07; H, 8.47. Found: C, 83.84; H, 8.58.
Butyl Phenylpropyl Ether (7g)14): A colorless oil. 1H-NMR (CDCl3) d:
0.93 (3H, t, Jϭ7.4 Hz), 1.33—1.44 (2H, m), 1.52—1.61 (2H, m), 1.85—
1.94 (2H, m), 2.69 (2H, t, Jϭ7.7 Hz), 3.41 (2H, t, Jϭ6.6 Hz), 3.41 (2H, t,
Jϭ6.4 Hz), 7.14—7.21 (3H, m), 7.24—7.30 (2H, m). IR (film) cmϪ1: 3027,
2935, 2863, 1114. Calcd for C13H20O: C, 81.20; H, 10.48. Found: C, 81.27;
H, 10.65.
1
Butyl 3-Phenyl-1-Propenyl Ether (11): A colorless oil. H-NMR (CDCl3)
8) Jung M. E., Andrus W. A., Ornstein P. L., Tetrahedron Lett., 1977,
4175—4178.
9) Miller R. D., McKean D. R., Tetrahedron Lett., 23, 323—326 (1982).
10) Vogel A. I., J. Chem. Soc., 1948, 616—624.
11) Brogan J. B., Richard J. E., Zercher C. K., Synth. Commun., 25, 587—
593 (1995).
12) Adkins H., Nissen B. H., Org. Synth., Coll. Vol. 1, 1941, 1—2.
13) Barluenga J., Alonso-Cires L., Campos P. J., Asensio G., Synthesis,
1983, 53—55.
for E isomer: d: 0.93 (3H, t, Jϭ7.4 Hz), 1.34—1.47 (2H, m), 1.58—1.67
(2H, m), 3.26 (2H, d, Jϭ7.3 Hz), 3.66 (2H, t, Jϭ6.6 Hz), 4.92 (1H, dt,
Jϭ12.6, 7.3 Hz), 6.34 (1H, d, Jϭ12.6 Hz), 7.14—7.31 (5H, m). for Z iso-
mer: d: 0.94 (3H, t, Jϭ7.4 Hz), 1.34—1.47 (2H, m), 1.58—1.67 (2H, m),
3.43 (2H, d, Jϭ7.4 Hz), 3.77 (2H, t, Jϭ6.6 Hz), 4.55 (1H, td, Jϭ7.4, 6.2 Hz),
6.06 (1H, dt, Jϭ6.2, 1.4 Hz), 7.14—7.31 (5H, m). IR (E/Z mixture) (film)
cmϪ1: 3027, 2960, 2933, 2873, 1664, 1110. MS m/z: 190 (Mϩ).
Acknowledgement We thank Mr. Daisuke Higashiguchi for assistance
14) Akiyama T., Hirofuji H., Ozaki S., Bull. Chem. Soc. Jpn., 65, 1932—
1938 (1992).
in this research.
References and Notes
1) Larock R. C. (ed.), “Comprehensive Organic Transformations: A