Silica-gel supported sulfamic acid (SA/SiO2) as an efficient and reusable catalyst for conversion of ketones into oxathioacetals and dithioacetals

Article abstract of DOI:10.1080/00397911.2011.604458

A simple and efficient method for the conversion of carbonyl compounds to oxathioacetals and dithioacetals using SA/SiO² as an acid catalyst has been achieved. SA/SiO² is easily recovered from the reaction mixture and can be reused at least 15 times without loss of catalytic activity.

Full text of DOI:10.1080/00397911.2011.604458

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Silica-Gel Supported Sulfamic Acid
(SA/SiO2) as an Efficient and Reusable
Catalyst for Conversion of Ketones into
Oxathioacetals and Dithioacetals
Tadashi Aoyama a b , Toshihiko Suzuki a , Takashi Nagaoka a , Toshio
Takido a & Mitsuo Kodomari c
a Department of Materials and Applied Chemistry, College of Science
and Technology, Nihon University, Tokyo, Japan
b Center for Creative Materials Research, Research Institute of
Science and Technology, College of Science and Technology, Nihon
University, Tokyo, Japan
c Department of Bioscience and Engineering, Shibaura Institute of
Technology, Saitama, Japan
Accepted author version posted online: 13 Feb 2012.Version of
record first published: 08 Nov 2012.
To cite this article: Tadashi Aoyama , Toshihiko Suzuki , Takashi Nagaoka , Toshio Takido & Mitsuo
Kodomari (2013): Silica-Gel Supported Sulfamic Acid (SA/SiO2) as an Efficient and Reusable Catalyst
for Conversion of Ketones into Oxathioacetals and Dithioacetals, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 43:4, 553-566
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Synthetic Communications1, 43: 553–566, 2013
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2011.604458
SILICA-GEL SUPPORTED SULFAMIC ACID (SA/SiO2) AS
AN EFFICIENT AND REUSABLE CATALYST FOR
CONVERSION OF KETONES INTO OXATHIOACETALS
AND DITHIOACETALS
Tadashi Aoyama,1,2 Toshihiko Suzuki,1 Takashi Nagaoka,1
Toshio Takido,1 and Mitsuo Kodomari3
1Department of Materials and Applied Chemistry, College of Science and
Technology, Nihon University, Tokyo, Japan
2Center for Creative Materials Research, Research Institute of Science
and Technology, College of Science and Technology, Nihon University,
Tokyo, Japan
3Department of Bioscience and Engineering, Shibaura Institute of
Technology, Saitama, Japan
GRAPHICAL ABSTRACT
Abstract A simple and efficient method for the conversion of carbonyl compounds to
oxathioacetals and dithioacetals using SA/SiO2 as an acid catalyst has been achieved.
SA/SiO2 is easily recovered from the reaction mixture and can be reused at least 15 times
without loss of catalytic activity.
Keywords Acetal; protective group; sulfamic acid; supported reagent
INTRODUCTION
For environmental reasons, it is highly desirable to replace homogeneous catalysts
for organic synthesis with heterogeneous catalysts. Solid acid catalysts have many
Received June 13, 2011.
Address correspondence to Tadashi Aoyama, Department of Materials and Applied Chemistry,
College of Science and Technology, Nihon University, Kanda Surugadai, Chiyoda-ku, Tokyo 101-8308,
Japan. E-mail: aoyama.tadashi@nihon-u.ac.jp
553

554
T. AOYAMA ET AL.
advantages such as easy handling, decrease of corrosion, and environmentally safe dis-
posal. Many solid acids, therefore, have been developed. Among them, the development
of reusable inorganic solid-supported acid catalysts has attracted much attention.
Sulfamic acid [H2NSO3H (SA)] is a nonhygroscopic, nonvolatile, odorless, and
stable white crystalline solid that is inexpensive and readily commercially available.
Granular SA has been used as a heterogeneous catalyst in many organic prepara-
tions including protection of carbonyls,[1] alcohols,[2] and amines;[3] esterification;[4]
C-C bond formation;[5] and synthesis of heterocycles.[6] In many cases, products
are isolated from the reaction mixture by filtration, extraction, and washing. In some
cases, SA is recovered and reused after the reaction.
There are many advantages in a reaction using inorganic solid-supported cat-
alysts. The catalysts are easily separated from the reaction mixture by filtration, and
some of the catalysts recovered can be applied to subsequent reactions. Recently,
Niknam and coworkers developed silica-bonded N-propyl sulfamic acid (SBNPSA)
and reported efficient formylation and acetylation of alcohols and amines.[7]
Although SBNPSA is an efficient catalyst, toxic reagents are needed, and solvents
and long reaction times are required for the preparation of it. In continuation of
our studies on the application of inorganic solid-supported reagents to organic trans-
formations, we have developed inorganic solid-supported SA, which is easily pre-
pared and reusable.
The protection of carbonyl groups plays an important role in organic, med-
icinal, and drug design chemistry and multistep synthesis of many natural pro-
ducts.[8] Many methods for conversion of carbonyl compounds into oxathioacetals
and dithioacetals using silica-gel-supported reagents such as SOCl2=SiO2,[9]
CoBr2=SiO2,[10] ZrCl4=SiO2,[11] TaCl5=SiO2,[12] Cu(OTf)2=SiO2,[13] H3PW12O40=
SiO2,[14] and AlCl3=SiO2 have been reported.
[15]
Therefore, the efficient conversion of carbonyl compounds into oxathioacetals
and dithioacetals using SA=SiO2 shows the effectiveness of SA=SiO2 as an acid cata-
lyst, and comparison of SA=SiO2 with the other acid catalysts reported can be easily
made. In this article we describe the conversion of carbonyl compounds to oxathioa-
cetals and dithioacetals using SA=SiO2 as an acid catalyst. Initially the reaction of
benzaldehyde with 2-mercapto ethanol using SA=SiO2 was carried out in 1,2-dichlor-
oethane at room temperature. This reaction easily proceeded, and benzaldehyde was
converted quantitatively into the corresponding thioacetal in a minute. We employed
the reaction of acetophenone with 2-mercapto ethanol using SA=SiO2 to determine
optimum reaction conditions.
The effectiveness of several inorganic solid-supported SA systems for the reac-
tion was tested. The results obtained are summarized in Table 1. Both finely ground
SA and SiO2 were ineffective in promoting the reaction. SA=SiO2, however, gave 3aa
in good yield at room temperature within 2 h. The other solid supports such as neu-
˚
tral, acidic, and basic alumina and molecular sieves (4A) did not activate SA. The
activity of SA=SiO2 is significantly affected by the method of preparation of SA=
SiO2. When the reaction was carried out using SA=SiO2 prepared by Sadaphal’s
method,[16] 3aa was not obtained.
The reaction was carried out in various solvents such as 1,2-dichloroethane,
benzene, chlorobenzene, toluene, cyclohexane, and hexane to determine the most
effective solvent (Table 2). Hexane was the most effective among the solvents tested.

OXATHIOACETAL SYNTHESIS WITH SA/SiO2
555
Table 1. Comparison of effectiveness of solid supports for SAa
Entry
Catalyst
Yield of 3aa (%)b
1
2
3
4
5
6
7
8
9c
None
SA
SiO2
0
0
0
SA=SiO2
SA=n-Al2O3
SA=a-Al2O3
SA=b-Al2O3
SA=MS4A
SA=SiO2
69
0
0
0
0
0
aA mixture of 1a (2.0 mmol), 2a (2.4 mmol), and catalyst (1.5 mmol)
was stirred in 1,2-dichloroethane (DCE) at room temperature for 2 h.
bIsolated yield.
cSA=SiO2 was prepared by literature methods.[16]
When this reaction was carried out in hexane at 40 ꢀC for 1 h, 3aa was formed in 81%
yield.
The effect of loading ratio of SA=SiO2, amount of SA=SiO2, and molar ratio of
2a to 1a on the reaction of 1a with 2a was investigated (Table 3). When the reaction
was carried out at 40 ꢀC for 1 h in the presence of 75 mol% of SA=SiO2, which
was prepared in various loading ratios, 4.0 mmol=g SA=SiO2 was most effective
(entries 1–6). The yield of 3aa decreased according to the increase of loading ratio
Table 2. Synthesis of 3aa using SA=SiO2 in various solventsa
Entry
Solvent
Temp. (ꢀC)
Time (h)
Yield (%)b
1
2
3
4
5
6
7
1,2-Dichloroethane
Benzene
rt
rt
rt
rt
rt
rt
40
2
2
2
2
2
2
1
69
63
68
78
85
87
81
Chlorobenzene
Toluene
Cyclohexane
n-Hexane
n-Hexane
aIn all reactions 1a (2.0 mmol), 2a (2.4 mmol), SA=SiO2 (3.0 mmol=g,
0.5 g), and solvent (5 mL) were used.
bYields were determined by GLC.

556
T. AOYAMA ET AL.
Table 3. Determination of optimum reaction conditionsa
Loading ratio
(mmol=g)
Amount
(g)
Catalyst
(mol%)
Time
(h)
2a=1a
(mol=mol)
Yield of
3aa (%)b
Entry
1
2
1.5
3.0
4.0
5.0
7.0
10.0
4.0
4.0
4.0
4.0
4.0
4.0
4.0
4.0
1.00
0.50
0.37
0.30
0.22
0.15
0.10
0.20
0.30
0.40
0.50
0.3
75
75
75
75
75
75
20
40
60
80
100
60
60
60
1
1
1
1
1
1
6
5
1
1
1
1
1
1
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.0
1.1
1.5
68
81
89
85
73
56
74
80
89
89
89
74
85
88
3
4
5
6
7
8
9
10
11
12
13
14
0.3
0.3
aA mixture of 1a, 2a, and SA=SiO2 was stirred in hexane at 40 ꢀC.
bYields were determined by GLC.
of SA=SiO2. For instance, the 10.0 mmol=g SA=SiO2 gave 3aa in 56% yield. The
results of the reactions using 4.0 mmol=g SA=SiO2 show that at least 60 mol% of
SA against 1a is needed to afford 3aa in good yield (entries 3 and 7–11). Finally,
we determined the optimum molar ratio of 1a to 2a. The reaction using equivalent
moles of 1a and 2a afforded 3aa in 74% yield. Yield of 3aa increased according to
increasing amount of 2a but a larger excess amount of 2a was not required to obtain
3aa in good yield (entries 12–14). From these results, we decided that subsequent
reactions were carried out as follows: A mixture of 1a (2.0 mmol), 2a (2.4 mmol),
and SA=SiO2 (4.0 mmol=g, 0.3 g) in hexane was stirred at room temperature for 2 h.
We checked the reusability of SA=SiO2 in advance of reactions using a series of
various ketones. The results obtained are summarized in Table 4. SA=SiO2 was
recovered from the reaction mixture by filtration, regenerated with drying in vacuo
at 160 ꢀC for 1 h, and used for the next reaction. SA=SiO2 could be reused at least 15
times without loss of activity. The yield of 3aa in the 15th reaction was less than that
of the first reaction. The recovered amount of SA=SiO2 decreased step by step with
each treatment. In the 15th reaction, 0.23 g of SA=SiO2 was used. When reaction was
carried out using fresh SA=SiO2 (0.20 g), 3aa gave in 76% yield (entry 1).
To date, several homogeneous, solid, and supported acid catalysts have been
used for this reaction. To show the superiority of SA=SiO2 as catalyst, the efficiency
of SA=SiO2 was compared with efficiency of other catalysts in the conversion of
acetophenone with 2-mercapto ethanol into 3aa obtained by other workers. These
results are indicated in Table 5. Although a large amount of SA=SiO2 is required

OXATHIOACETAL SYNTHESIS WITH SA/SiO2
557
Table 4. Recycling of SA=SiO2 for the synthesis of 3aa
Entry
Catalysta
Amount (g)
Yield (%)b
1
2
3
4
5
6
7
8
9
SA=SiO2
SA=SiO2
0.20
0.30
0.30
0.29
0.29
0.28
0.27
0.25
0.23
76
89
88
87
87
86
87
85
79
SA=SiO2 (1)
SA=SiO2 (2)
SA=SiO2 (3)
SA=SiO2 (4)
SA=SiO2 (8)
SA=SiO2 (11)
SA=SiO2 (14)
aParenthetic numbers indicate the number of reuses of SA=SiO2.
bIsolated yield.
to complete the reaction, SA=SiO2 has some advantages, including mild reaction
conditions, good yield, simplicity in operation, and reusability.
A series of carbonyl compounds was used for acetalization with 2-mercaptho
ethanol (2a) and ethane-1,2-dithiol (2b) in the presence of SA=SiO2 (Table 6). All
of the carbonyls were converted into the corresponding acetals in good to excellent
yields. 4-Nitroacetophenone (1b) was the most inactive among the acetophenone
derivatives and gave 3ba and 3bb in 48% and 59% yield. Responsible for the poor
yields of 3ba and 3bb is the fact that 1b is slightly soluble in hexane. When the reac-
tion of 1b with 2a and 2b was carried out in hexane at reflux, 3ba and 3bb were
obtained in 99% yields within 1 h (entry 2). Reactions of 4-methoxyacetophenone
Table 5. Comparison between reported acid catalysts and SA=SiO2
Catalyst
x=mol (%)
Time
Yield (%)
Ref.
Sn(HPO4) H2O
H3PW12O40=SiO2
Fe(CF3CO2)3
Fe(CF3SO3)3
ZrCl4
5
6
110 min
24 h
190 min
3 h
10
50
82
81
88
60
82
93
89
17
14
18
18
19
20
21
12
5
5
10
10
5
14 h
1.5 h
5 h
HClO4
Yb(Otf)3
TaCl5=SiO2
SA=SiO2
2.5
60
1 h
2 h
This work

558
T. AOYAMA ET AL.
Table 6. Preparation of oxathioacetals and dithioacetalsa
Using 2a
Using 2b
Product
Entry
1
1
Substrate
Product
Yield (%)b
Yield (%)b
1a
89
93
2
1b
48 (98)c
59 (99)c
3
4
5
1c
1d
1e
90
58 (69)d
81
82
74 (99)e
76
6
1f
85
78
7
8
9
1g
1h
1i
70
81
42
99
35 (67)d
44 (99)d
10
11
1j
63
91
99
1k
98
(Continued )

OXATHIOACETAL SYNTHESIS WITH SA/SiO2
559
Table 6. Continued
Using 2a
Using 2b
Product
Entry
12
1
Substrate
Product
Yield (%)b
Yield (%)b
99
1l
99
aA mixture of 1a (2.0 mmol), 2a (2.4 mmol), and SA=SiO2 (4.0 mmol=g, 0.3 g) was stirred in hexane
(5 mL) at room temperature for 2 h.
bIsolated yield.
cReaction was carried out using 20 mL of hexane at reflux for 1 h.
dReaction was carried out at reflux for 2 h.
eReaction was carried out at 40 ꢀC for 12 h.
(1d) with 2a and 2b needed a high temperature and a long reaction time to obtain 3da
and 3db in good to excellent yields (Entry 4). Compound 3da was obtained in 69%
yield when the reaction was carried out at reflux for 2 h. Compound 3db was also
obtained in 99% yield at 40 ꢀC for 12 h. Benzaldehyde (1h) reacted with 2a to give
the corresponding acetal 3ha in 81% yield and 8% yield of benzaldehyde bis(2
-hydroxyethly)dithioacetal (30ha) as a by-product. Structure of 30ha was determined
1
by comparison with reported spectra of H and 13C NMR.[22] The reactivity of
benzophenone (1i) was poor, and in the reaction with 2a and 2b at room temperature
the yields of 3ia and 3ib were low (entry 9). However, the same reactions were carried
out at reflux to form 3ia and 3ib in 67% and 99% yields.
The reaction was further explored using acetophenone with various diols and
dithiols (Table 7). The reaction of 1a with 2a, 2b, and 1,3-dimercaptho propane
(2c) gave the desired products 3aa–ac in excellent yields (entries 1–3). Compound
3ac was obtained in 92% yield in 1 h. In the reaction of 1a with ethylene glycol
(2d) the desired product 3ad could not be isolated. When this reaction was carried
out under reflux for 35 h, 3ad gave 7%. The reaction with butane-2,3-diol (2e) gave
3ae in 25% yield (entries 4 and 5). When the reaction with 2e was carried out in hex-
ane under reflux for 1.5 h, 3ae was isolated in 89% yield. 2,2-Dimethyl propane-1,3-
diol (2f) gave the corresponding acetal 3af in moderate yield.
When a mixture of equimolar amounts of benzaldehyde and acetophenone was
allowed to react with ethane-1,2-dithiol in the presence of SA=SiO2 in hexane, only
2-phenyl-1,3-dithiolane was yielded (Scheme 1). Benzaldehyde was more reactive
than acetopenone.
In conclusion we have developed a simple and efficient method for the conver-
sion of carbonyl compounds into oxathioacetals and dithioacetals using SA=SiO2 as
an acid catalyst, which affords mild reaction conditions, good yields, simplicity in
operation, and utilization of inexpensive and reusable catalyst.
EXPERIMENTAL
Melting points were determined on a Yanako Micro melting-point apparatus.
Elemental analysis were performed on a Yanako CHN recorder MT-5. NMR

560
T. AOYAMA ET AL.
Table 7. Reaction of 1a with diols and dithiolsa
Entry
1
2
Product
Yield (%)b
2a
3aa
3ab
89
2
3
4
2b
2c
2d
93 (81)c
95 (92)c
Trace
3ac
3ad
5
6
2e
2f
3ae
3af
25 (89)d
59
aA mixture of 1a (2.0 mmol), 2a (2.4 mmol), and SA=SiO2 (4.0 mmol=g, 0.3 g) was stirred in hexane
(5 mL) at room temperature for 2 h.
bIsolated yield.
cReaction was running for 1 h.
dReaction was carried out hexane (10 mL) at reflux for 1.5 h.
Scheme 1. Chemoselective protection using SA=SiO2.

OXATHIOACETAL SYNTHESIS WITH SA/SiO2
561
spectra were recorded on a Jeol JNM-GX400 spectrometer or a Jeol JNM-ECX400.
Tetramethylsilane (d ¼ 0) was used as an internal standard for 1H NMR and CDCl3
(d ¼ 77.0) was used for 13C NMR. Mass analysis were performed on a Agilent G1969
LC=MDS TOF. Infrared (IR) spectra were recorded on a Thermo Electron Nicolet
380 spectrometer.
Preparation of silica-gel-supported SA: silica-gel [Wakogel C-200 (Wako Pure
Chemical Ind. Ltd.), 2.33 g] was added to a solution of SA (10 mmol, 1.48 g) in dis-
tilled water, and the mixture was stirred at room temperature for 0.5 h. The water
was removed by rotary evaporation under reduced pressure, and the resulting
reagent was dried in vacuo (10 mmHg) at 160 ꢀC for 2 h.
General Procedure for Synthesis of Oxathio- and Dithioacetals
A mixture of 1 (2.0 mmol), 2 (2.4 mmol), and SA=SiO2 (1.2 mmol) in hexane
(5 mL) was stirred at room temperature for 2 h, and then the supported reagent was
removed by filtration. The filtrate was concentrated and dried in vacuo to obtain 3.
Regeneration of used SA=SiO2:SA=SiO2 was recovered by filtration from the
reaction mixture, put in a 50-mL round-bottom flask, and dried in vacuo at
160 ꢀC for 1 h.
2-Methyl-2-phenyl-1,3-oxathiolane (3aa)
IR (neat): 2975, 1491, 1446, 1371, 1268, 1217, 1132, 1099, 1066, 763, 700 cmꢁ1
.
1H NMR (CDCl3): d ¼ 1.92 (3H, s), 3.04–3.12 (1H, m), 3.19–3.26 (1H, m),
3.99–4.07(1H, m), 4.32–4.39 (1H, m), 7.20–7.54 (5H, m). 13C NMR (CDCl3):
d ¼ 32.3, 34.4, 70.6, 95.5, 124.8, 127.2, 128.1, 146.7. HRMS (TOF-CI): m=z [M þ H]þ
calcd. for C10H13OS: 181.0687; found: 181.0686.
2-Methyl-2-phenyl-1,3-dithiolane (3ab)[23]
IR (neat): 3056, 2966, 2922, 1489, 1442, 1373, 1276, 1064, 699 cmꢁ1. 1H NMR
(CDCl3): d ¼ 2.14 (3H, s), 3.30–3.49 (4H, m), 7.17–7.24 (1H, m), 7.25–7.35 (2H, m),
7.71–7.77 (2H, m). 13C NMR (CDCl3): d ¼ 33.8, 40.2, 68.5, 126.7, 127.0, 127.9,
145.8. HRMS (TOF-CI): m=z [M þ H]þ calcd. for C10H13S2: 197.0458; found:
197.0452.
2-Methyl-2-(4-nitrophenyl)-1,3-oxathiolane (3ba)
White solid. Mp 50–51 ꢀC IR (neat): 2988, 2946, 1603, 1511, 1349, 1213, 1110,
1
1090, 1069, 851, 756, 702 cmꢁ1. H NMR (CDCl3): d ¼ 1.92 (3H, s), 3.07–3.11 (1H,
m), 3.25–3.30 (1H, m), 4.01–4.07 (1H, m), 4.36–4.41 (1H, m), 7.62–7.67 (2H, m),
8.16–8.21 (2H, m). 13C NMR (CDCl3): d ¼ 32.0, 34.7, 71.2, 94.5, 123.6, 125.9,
154.2. HRMS (TOF-CI): m=z [M þ H]þ calcd. for C10H12NO3S: 226.0537; found:
226.0533.

562
T. AOYAMA ET AL.
2-Methyl-2-(4-nitrophenyl)-1,3-dithiolane (3bb)
Yellow solid. Mp 56 ꢀC. IR (neat): 2976, 2937, 1591, 1513, 1484, 1353, 1114,
1075, 858, 695 cmꢁ1
.
1H NMR (CDCl3): d ¼ 2.16 (3H, s), 3.31–3.41 (2H, m),
3.48–3.56 (2H, m), 7.91–7.95 (2H, m), 8.14–8.18 (2H, m). 13C NMR (CDCl3):
d ¼ 33.2, 40.6, 67.7, 123.2, 127.9, 146.7, 153.8. HRMS (TOF-CI): m=z [M þ H]þ
calcd. for C10H12NO2S2: 242.0309; found: 242.0299.
2-(4-Chlorophenyl)-2-methyl-1,3-oxathiolane (3ca)
IR (neat): 2975, 2939, 2876, 1488, 1397, 1267, 1133, 1093, 1068, 1047, 1013,
1
832, 800 cmꢁ1. H NMR (CDCl3): d ¼ 1.88 (3H, s), 3.04–3.10 (1H, m), 3.20–3.26
(1H, m), 3.97–4.03 (1H, m), 4.31–4.35 (1H, m), 7.26–7.31 (2H, m), 7.40–7.44 (2H,
m). 13C NMR (CDCl3): d ¼ 32.2, 34.5, 70.7, 95.0, 126.4, 128.2, 132.9, 145.4. HRMS
(TOF-CI): m=z [M þ H]þ calcd. for C10H12OSCl: 215.0297; found: 215.0291.
2-(4-Chlorophenyl)-2-methyl-1,3-dithiolane (3cb)
1
IR (neat): 2966, 2923, 1489, 1446, 1397, 1373, 1277, 1094, 1012, 832 cmꢁ1. H
NMR (CDCl3): d ¼ 2.12 (3H, s), 3.30–3.39 (2H, m), 3.42–3.48 (2H, m), 7.26 (2H, dd,
J ¼ 8.7, 2.5 Hz), 7.69 (2H, dd, J ¼ 8.7, 2.5 Hz). 13C NMR (CDCl3): d ¼ 33.5, 40.4,
67.9, 128.0, 128.3, 132.8, 144.6. HRMS (TOF-CI): m=z [M þ H]þ calcd. for
C10H12S2Cl: 231.0068; found: 231.0065.
2-(4-Methoxyphenyl)-2-methyl-1,3-oxathiolane (3da)
IR (neat): 2972, 2875, 2835, 1609, 1210, 1463, 1302, 1249, 2276, 1132, 1034
1
833 cmꢁ1. H NMR (CDCl3): d ¼ 1.89 (3H, s), 3.02–3.10 (1H, m), 3.15–3.24 (1H,
m), 3.78 (3H, s), 3.96–4.04 (1H, m), 4.27–4.34 (1H, m), 6.81–6.86 (2H, m),
7.39–7.45 (2H, m). 13C NMR (CDCl3): d ¼ 32.2, 34.3, 55.1, 70.4, 95.4, 113.3,
126.2, 138.7, 158.6. HR-MS (TOF-CI): m=z [M þ H]þ calcd. for C11H15O2S:
211.0792; found: 211.0790.
2-(4-Methoxy-phenyl)-2-methyl-1,3-dithiolane (3db)
IR (neat): 2960, 2923, 2834, 1607, 1508, 1463, 1297, 1251, 1180, 1033, 833,
1
735 cmꢁ1. H NMR (CDCl3): d ¼ 2.14 (3H, s), 3.34–3.50 (4H, m), 3.79 (3H, s),
6.83 (2H, dd, J ¼ 9.2, 2.8 Hz), 7.67 (2H, dd, J ¼ 9.2, 2.8 Hz). 13C NMR (CDCl3):
d ¼ 33.9, 40.4, 55.2, 68.1, 113.2, 128.1, 137.7, 158.5. HRMS (TOF-CI): m=z [M þ H]þ
calcd. for C11H15OS2: 227.0564; found: 227.0558.
2-Methyl-2-p-tolyl-1,3-oxathiolane (3ea)
IR (neat): 2974, 2924, 2875, 1510, 1441, 1370, 1267, 1133, 1093, 1069, 1047,
1
818 cmꢁ1. H NMR (CDCl3): d ¼ 1.90 (3H, s), 2.33 (3H, s), 3.03–3.10 (1H, m),
3.18–3.24 (1H, m), 3.98–4.05 (1H, m), 4.31–4.35 (1H, m), 7.13 (1H, d, J ¼ 8.0 Hz),
7.38 (1H, d, J ¼ 8.0 Hz). 13C NMR (CDCl3): d ¼ 21.0, 32.3, 34.4, 70.6, 95.6, 124.8,

OXATHIOACETAL SYNTHESIS WITH SA/SiO2
563
128.8, 136.9, 143.8. HRMS (TOF-CI): m=z [M þ H]þ calcd. for C11H15OS: 195.0843;
found: 195.0837.
2-Methyl-2-p-tolyl-1,3-dithiolane (3eb)
IR (neat): 3022, 2965, 2921, 1682, 1508, 1444, 1372, 1275, 1186, 1072, 1018,
1
820, 732 cmꢁ1. H NMR (CDCl3): d ¼ 2.14 (3H, s), 2.32 (3H, s), 3.32–3.48 (4H,
m), 7.11 (1H, dd, J ¼ 8.2, 2.0 Hz), 7.63 (1H, dd, J ¼ 8.2, 2.0 Hz). 13C NMR (CDCl3):
d ¼ 20.9, 33.8, 40.3, 68.4, 126.6, 128.6, 136.7, 142.8. HRMS (TOF-CI): m=z [M þ H]þ
calcd. for C11H15S2: 211.0615; found: 211.0611.
2-Methyl-2-m-tolyl-1,3-oxathiolane (3fa)
1
IR (neat): 2974, 1606, 1486, 1444, 1370, 1270, 1131, 1047, 788, 705 cmꢁ1. H
NMR (CDCl3): d ¼ 1.90 (3H, s), 2.35 (3H, s), 3.05–3.10 (1H, m), 3.18–3.25 (1H,
m), 4.00–4.06 (1H, m), 4.32–4.37 (1H, m), 7.05 (1H, d, J ¼ 7.6 Hz), 7.20 (1H, t,
J ¼ 7.6 Hz), 7.27–7.30 (2H, m). 13C NMR (CDCl3): d ¼ 21.5, 32.4, 34.5, 70.7, 95.6,
121.9, 125.5, 128.0, 128.1, 137.8, 146.72. HRMS (TOF-CI): m=z [M þ H]þ calcd.
for C11H15OS: 195.0843; found: 195.0849.
2-Methyl-2-m-tolyl-1,3-dithiolane (3fb)
IR (neat): 2966, 2922, 1684, 1487, 1446, 1373, 1276, 1172, 1065, 790, 722 cmꢁ1
.
1H NMR (CDCl3): d ¼ 2.14 (3H, s), 2.36 (3H, s), 3.34–3.50 (4H, m), 7.04 (1H, d,
J ¼ 7.6 Hz), 7.20 (1H, t, J ¼ 7.6 Hz), 7.53–7.56 (2H, m). 13C NMR (CDCl3):
d ¼ 21.5, 34.1, 40.2, 68.5, 123.7, 127.4, 127.8, 127.89, 137.6, 145.7. HRMS (TOF-CI):
m=z [M þ H]þ calcd. for C11H15S2: 211.0615; found: 211.0622.
2-Methyl-2-o-tolyl-1,3-oxathiolane (3ga)
1
IR (neat): 2975, 2930, 2874, 1485, 1443, 1269, 1136, 1115, 1047, 759 cmꢁ1. H
NMR (CDCl3): d ¼ 1.93 (3H, s), 2.50 (3H, s), 3.00–3.07 (1H, m), 3.16–3.22 (1H, m),
3.96–4.02 (1H, m), 4.35–4.42 (1H, m), 7.14–7.19 (3H, m), 7.55–7.60 (1H, m). 13C
NMR (CDCl3): d ¼ 21.4, 31.2, 34.1, 70.2, 95.5, 124.1, 125.7, 127.2, 132.2, 134.3,
144.1. HRMS (TOF-CI): m=z [M þ H]þ calcd. for C11H15OS: 195.0843; found:
195.0842.
2-Methyl-2-o-tolyl-1,3-dithiolane (3gb)
IR (neat): 3057, 2968, 2922, 1684, 1480, 1452, 1371, 1278, 1058, 765, 729 cmꢁ1
.
1H NMR (CDCl3): d ¼ 2.18 (3H, s), 2.66 (3H, s), 3.28–3.25 (2H, m), 3.39–3.46 (2H,
m), 7.11–7.19 (3H, m), 7.90–7.92 (1H, dd, J ¼ 6.9, 1.8 Hz). 13C NMR (CDCl3):
d ¼ 22.6, 33.3, 39.7, 69.4, 125.5, 126.7, 127.4, 132.8, 136.2, 142.5. HRMS (TOF-CI):
m=z [M þ H]þ calcd. for C11H15S2: 211.0615; found: 211.0613.

564
T. AOYAMA ET AL.
2-Phenyl-1,3-oxathiolane (3ha)
IR (neat): 2920, 2851, 1455, 1232, 1065, 680 cmꢁ1. 1H NMR (CDCl3): d ¼ 3.14–
3.30 (2H, m), 3.90–3.97 (1H, m), 4.49–4.54 (1H, m), 6.04 (1H, s), 7.27–7.37 (3H, m)
7.44–7.48 (2H, m). 13C NMR (CDCl3): d ¼ 34.0, 71.9, 87.0, 126.6, 128.4, 128.6,
139.2. HRMS (TOF-CI): m=z [M þ H]þ calcd. for C9H11OS: 167.0530; found:
167.0531.
2-Phenyl-1,3-dithiolane (3hb)
IR (neat): 1663, 1492, 1445, 1057, 750, 696 cmꢁ1. 1H NMR (CDCl3): d ¼ 3.32–
3.41 (2H, m), 3.48–3.55 (2H, m), 5.64 (1H, s), 7.22–7.34 (3H, m), 7.51–7.55 (2H, m).
13C NMR (CDCl3): d ¼ 40.2, 56.2, 127.9, 128.0, 128.5, 140.3. HRMS (TOF-CI): m=z
[M þ H]þ calcd. for C9H11S2: 183.0302; found: 183.0308.
2,2-Diphenyl-1,3-oxathiolane (3ia)
White solid. Mp 45–46 ꢀC. IR (neat): 3028, 2942, 1487, 1447, 1235, 1056, 751,
705, 696 cmꢁ1
.
1H NMR (CDCl3): d ¼ 3.25 (2H, t, J ¼ 6.3 Hz), 4.22 (2H, t,
J ¼ 6.3 Hz), 7.22–7.33 (6H, m), 7.49–7.53(4H, m). 13C NMR (CDCl3): d ¼ 34.7,
70.2, 99.5, 126.7, 127.6, 128.0, 144.4. HRMS (TOF-CI): m=z [M þ H]þ calcd. for
C15H15OS: 243.0843; found: 243.0841.
2,2-Diphenyl-1,3-dithiolane (3ib)
1
White solid. Mp 107 ꢀC. IR (neat): 1483, 1442, 1237, 1078, 757, 701 cmꢁ1. H
NMR (CDCl3): d ¼ 3.41 (4H, s), 7.19–7.32 (6H, m), 7.58–7.63 (4H, m). 13C NMR
(CDCl3): d ¼ 40.1, 76.8, 127.1, 127.9, 128.1, 144.5. HR-MS (TOF-CI): m=z [M þ H]þ
calcd. for C15H15S2: 259.0615; found: 259.0615.
2-Styryl-1,3-oxathiolane (3ja)
IR (neat): 3026, 2939, 2971, 1714, 1496, 1449, 1269, 1204, 1165, 1058, 966, 759,
1
693 cmꢁ1. H NMR (CDCl3): d ¼ 3.09–3.20 (2H, m), 3.88–3.94 (1H, m), 4.38–4.43
(1H, m), 5.69 (1H, d, J ¼ 7.3 Hz), 6.27 (1H, dd, J ¼ 15.8, 7.3 Hz), 6.65 (1H, d,
J ¼ 15.8 Hz), 7.21–7.43 (5H, m). 13C NMR (CDCl3): d ¼ 33.7, 71.7, 86.3, 126.8,
127.1, 128.1, 128.6, 132.2, 135.9. HRMS (TOF-CI): m=z [M þ H]þ calcd. for
C11H13OS: 193.0687; found: 193.0690.
2-Styryl-1,3-dithiolane (3jb)
1
White solid. Mp 61–62 ꢀC. IR (neat): 1498, 1448, 969, 762, 731, 688 cmꢁ1. H
NMR (CDCl3): d ¼ 3.25–3.31 (2H, m), 3.33–3.40 (2H, m), 5.23 (1H, d, J ¼ 9.2 Hz),
6.21 (1H, dd, J ¼ 15.6, 9.2 Hz), 6.50 (1H, d, J ¼ 15.6 Hz), 7.20–7.39 (5H, m). 13C
NMR (CDCl3): d ¼ 39.6, 54.5, 126.6, 127.8, 128.5, 129.0, 130.2, 136.1. HRMS
(TOF-CI): m=z [M þ H]þ calcd. for C11H13S2: 209.0458; found: 209.0460.

OXATHIOACETAL SYNTHESIS WITH SA/SiO2
565
1-Oxa-4-thia-spiro[4,5]decane (3ka)
1
IR (neat): 2936, 2858, 1448, 1082 cmꢁ1. H NMR (CDCl3) d ¼ 1.22–1.57 (4H,
m), 1.73–1.91 (6H, m), 3.03 (2H, t, J ¼ 6.0 Hz), 4.17 (2H, t, J ¼ 6.0 Hz). 13C NMR
(CDCl3) d ¼ 24.9, 25.1, 32.9, 40.0, 69.5, 96.6. HRMS (TOF-CI): m=z [M þ H]þ calcd.
for C8H15OS: 159.0843; found 159.0844.
1,4-Dithia-spiro[4,5]decane (3kb)
1
IR (neat): 1447, 1423, 1276, 963, 895, 852 cmꢁ1. H NMR (CDCl3): d ¼ 1.37–
1.46 (2H, m), 1.63 (4H, quint, J ¼ 5.8 Hz), 2.00 (4H, J ¼ 5.8 Hz), 3.28 (4H, s). 13C
NMR (CDCl3): d ¼ 24.9, 26.1, 38.3, 42.8, 68.8. HR-MS (TOF-CI): m=z [M þ H]þ
calcd. for C8H15S2: 175.0615; found: 175.0613.
2,2-Dipropyl-1,3-oxathiolane (3la)
1
IR (neat): 1464, 1378, 1265, 1075 cmꢁ1. H NMR (CDCl3): d ¼ 0.93 (6H, t,
J ¼ 7.3 Hz), 1.31–1.52 (4H, m), 1.69–1.87 (4H, m), 3.00 (2H, t, J ¼ 5.7 Hz), 4.13
(2H, t, J ¼ 5.7 Hz). 13C NMR (CDCl3): d ¼ 14.3, 18.4, 33.7, 43.2, 70.5, 98.7. HRMS
(TOF-CI): m=z [M þ H]þ calcd. for C9H19OS: 175.1156; found: 175.1162.
2,2-Dipropyl-1,3-dithiolane (3lb)
1
IR (neat): 1463, 1276, 1139, 974, 853, 767 cmꢁ1. H NMR (CDCl3): d ¼ 0.93
(6H, t, J ¼ 7.3 Hz), 1.42–1.54 (4H, m), 1.86–1.91 (4H, m), 3.26 (4H, s). 13C NMR
(CDCl3): d ¼ 14.2, 20.2, 39.4, 45.8, 71.5. HR-MS (TOF-CI): m=z [M þ H]þ calcd.
for C9H19S2: 191.0928; found: 191.0924.
2-Methyl-2-phenyl-1,3-dithiane (3ac)
1
IR (neat): 3055, 2904, 2828, 1487, 1442, 1422, 1277, 1065, 765, 701 cmꢁ1. H
NMR (CDCl3): d ¼ 1.80 (3H, s), 1.90–2.00 (2H, m), 2.68–2.80 (4H, m), 7.23–7.29
(1H, m), 7.35–7.42 (2H, m), 7.93–7.98 (2H, m). 13C NMR (CDCl3): d ¼ 24.6, 28.0,
32.7, 54.0, 127.0, 127.7, 128.5, 143.7. HR-MS (TOF-CI): m=z [M þ H]þ calcd. for
C11H15S2: 211.0615; found: 211.0617.
2-Methyl-2-phenyl-1,3-dioxolane (3ad)
1
White solid. H NMR (CDCl3): d ¼ 1.66 (3H, s), 3.73–3.83 (2H, m), 3.99–4.09
(2H, m), 7.29–7.36 (3H, m), 7.46–7.51 (2H, m). 13C NMR (CDCl3): d ¼ 27.6, 64.4,
108.8, 125.2, 127.8, 128.2, 143.3. HR-MS (TOF-CI): m=z [M þ H]þ calcd. for
C10H13O2: 165.0915; found: 165.0916.
2,5,5-Trimethyl-2-phenyl-1,3-dioxane (3af)
IR (neat): 2954, 2864, 1472, 1445, 1371, 1252, 1214, 1183, 1129, 1083 1039,
1
1015, 874, 764, 704 cmꢁ1. H NMR (CDCl3): d ¼ 0.57 (3H, s), 1.27 (3H, s), 1.54

566
T. AOYAMA ET AL.
(3H, s), 3.33 (2H, d, J ¼ 11.0 Hz), 3.39 (2H, d, J ¼ 11.0 Hz), 7.26–7.46 (5H, m). 13C
NMR (CDCl3): d ¼ 21.8, 22.8, 29.8, 32.0, 71.6, 100.1, 126.7, 127.5, 128.5, 140.8.
HRMS (TOF-CI): m=z [M þ H]þ calcd. for C13H19O2: 207.1385; found: 207.1381.
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