Blue LED-Promoted Oxathiacetalization of Aldehydes and Ketones

Article abstract of DOI:10.1002/ejoc.202000218

In synthetic chemistry, the protection of aldehydes and ketones is crucial during multistep synthesis of complex molecules. Organic chemists have paid substantial attention to the synthesis of 1,3-oxathiolanes and 1,3-oxathianes because of their considera

Full text of DOI:10.1002/ejoc.202000218

European Journal of Organic Chemistry
Accepted Article
Accepted Article
Title: Blue LEDs-Promoted Oxathiacetalization of Aldehydes and
Ketones
Authors: You-Chen Liu, Daggula Mallikarjuna Reddy, Xin-An Chen, Yi-
Chen Shieh, and Chin-Fa Lee
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To be cited as: Eur. J. Org. Chem. 10.1002/ejoc.202000218
Link to VoR: https://doi.org/10.1002/ejoc.202000218
01/2020

10.1002/ejoc.202000218
European Journal of Organic Chemistry
FULL PAPER
Blue LEDs-Promoted Oxathiacetalization of Aldehydes and
Ketones
You-Chen Liu,a Daggula Mallikarjuna Reddy,a Xin-An Chen,a Yi-Chen Shieh,a and Chin-Fa Leea,b,c,
*
a
Department of Chemistry, National Chung Hsing University, Taichung, Taiwan 402, R.O.C
Tel: +886 4 2284-0411 ext. 810
Fax: +886 4 2286-2547
E-mail: cfalee@dragon.nchu.edu.tw
Research Center for Sustainable Energy and Nanotechnology (RCSEN)
Innovation and Development Center of Sustainable Agriculture (IDCSA)
b
c
Abstract: In synthetic chemistry, the protection of aldehydes and
ketones is crucial during multistep synthesis of complex molecules.
Organic chemists have paid substantial attention to the synthesis of
1,3-oxathiolanes and 1,3-oxathianes because of their considerable
stability under acidic conditions and ease of removal of protecting
groups. In this paper, we report the mild and efficient
oxathiacetalization of aldehydes with 2-mercaptoethanol and 3-
aforementioned methods have several shortcomings: low yield
of products,[6d] harsh reaction conditions,[6a,6c] long reaction
times,[6g] and use of either stoichiometric[6c,6f] or expensive[6d, 6e]
reagents. Therefore, synthetic and medicinal chemists have
focused on developing methodologies for effective protection of
carbonyl groups by valuable oxathioacetals.
In the development of organic methodologies, visible-light-
promoted photoredox catalysis has recently received
considerable attention because of its mildness and high
functional group tolerance.[7] It acts as a single-electron transfer
(SET) system that blocks undesired reaction pathways, thus
accomplishing simple and clean organic transformation
processes,[8] and its homogenous nature increases the catalyst
efficiency for the lowest catalyst loading in the reaction system.
Visible-light-driven reactions have emerged as versatile methods
of C–S[9] and C–O[10] bond formation. Lei et al.[11a] developed the
visible-light-promoted acetalization of aldehydes with alcohols
through the photoacid- mediated nucleophilic addition pathway
(Scheme 1a). Recently, Kokotos and co-workers[11b]
demonstrated highly efficient acetalization of aldehydes using
thioxanthenone as the photocatalyst and inexpensive household
lamps as the light source (Scheme 1a). Very recently, we
reported the environmental friendly thioacetalization of
aldehydes with thiols through visible-light-driven eosin–Y
catalyzed C–S bond formation at ambient temperature under
metal-free and solvent-free conditions (Scheme 1b).[12]
Encouraged by these two results, we anticipated that the
installation of –OH and –SH in photoredox catalysis under
uniform blue light irradiation may activate 2-mercaptoethanol
through SET, radical addition to aldehyde[13] and facilitating
access to 1,3-oxathiolanes. As part of our ongoing progress in
the field of C–S and C–O bond coupling reactions,[14,15] in this
paper, we report the mild and efficient oxathiacetalization of
aldehydes with 2-mercaptoethanol and 3-mercaptopropan-1-ol
through visible-light-driven eosin–Y catalyzed C–S and C–O
bond formation at ambient temperature under metal-free
conditions (Scheme 1c). We also successfully achieved the
oxathiacetalization of ketone. Notably the thiacetalization of
ketones was unsuccessful under the optimized reaction
conditions used for the oxathiacetalization of ketones.
mercaptopropan-1-ol
through
visible-light-promoted
eosin–Y
catalyzed C–S and C–O bond formation at ambient temperature
under metal-free conditions. This catalytic system also affords
oxathiacetalization of ketones through photoredox catalysis.
Introduction
Protection of carbonyl functional groups from nucleophilic attack
until their electrophilic nature can be exploited is major challenge
for organic chemists during the multistep synthesis of complex
molecules. Among the various carbonyl–protecting groups, 1,3-
oxathiolanes, and 1,3-oxathianes have long been used,[1,2] they
are considerably more stable than the O,O-acetals under acidic
conditions, and easier to remove than S,S-acetals.[3]
Furthermore, in the pioneering work by Eliel and others, the use
of oxathioacetals in organic synthesis was clearly demonstrated;
that is chiral 1,3-oxathioacetals were used as chiral auxiliaries
for the enantioselective synthesis of α-hydroxy acids and
glycols.[4,5] Although, abundant methods are available for the
protection and deprotection of carbonyl compounds such as
S,S-acetals, few methods have been developed for
oxathioacetals.[1,2] The existing methods for oxathioacetals
employ HClO4,[6a] TsOH,[6b] BF3·OEt2,[6c] Bu4NBr3,[6d] TMSOTf,[6e]
SO2,[6f] ZrCl4,[6g] ZnCl2–Na2SO4,[6h]
–Brønsted acidic ionic
liquid,[6i] heterogeneous acid catalyst,[6j] iodine,[6k] N-
bromosaccharin,[6l]
Amberlyst®15[6n]
montmorillonite
–and Sc(OTf)3
K-10
as catalysts or
clay,[6m]
[6o]
–
stoichiometric reagents. Regardless of their advancements, the
[a]
Y.-C. Liu, Dr. D. M. Reddy, X.-A. Chen, Y.-C. Shieh, Prof. Dr. C.-F.
Lee
Department of Chemistry, National Chung Hsing University
145 Xingda Rd., South Dist., Taichung City 402, Taiwan (R.O.C.)
E-mail: cfalee@dragon.nchu.edu.tw
Homepage: www.nchu.edu.tw/chem/cflee.htm
Prof. Dr. C.-F. Lee
Research Center for Sustainable Energy and Nanotechnology
(RCSEN)
Prof. Dr. C.-F. Lee
[b]
[c]
Innovation and Development Center of Sustainable Agriculture
(IDCSA)
Supporting information for this article is given via a link at the end of
the document.((Please delete this text if not appropriate))
1
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10.1002/ejoc.202000218
European Journal of Organic Chemistry
FULL PAPER
withdrawing substituents at the ortho-, meta-, and para-positions
and the reaction generated corresponding products in moderate
to high yields (3g–3o). The use of 1-, 2-naphthaldehydes for the
oxathiacetalization of aldehydes generated, the corresponding
1,3- oxathiolanes (3p and 3q) in high yields. Vinyl and alkyl
aldehydes could also be used as substrates for the reaction with
2-mercaptoethanol; the reaction provided the relevant
oxathiacetals in high yields (3r, 3s and 3t). Notably, multi
substituted benzaldehyde (1u) as well as heterocyclic aldehydes
(1v and 1w) could be used for oxathiacetalization and afforded
the corresponding products in high yields (3u–3w). The
chemoselective protection of aldehydes in the presence of
ketone was also successfully achieved under the optimized
reaction conditions and provided corresponding product (3x) in
good yield.
Scheme 1. Photoredox Catalyzed Protection of Carbonyl Compounds.
Table 1. Optimization of oxathiacetalization of benzaldehyde (1a) with 2-
mercaptoethanol (2)[a]
Results and Discussion
Initially, oxathiacetalization of aldehydes with 2-mercaptoethanol
was examined. Benzaldehyde (1a) and 2-mercaptoethanol (2)
were selected as model substrates under solvent-free conditions,
and the reaction was conducted using 1.0 mol% eosin Y as the
photoredox catalyst under illumination provided by 10-W white
LEDs, this resulted in the desired product 1,3-oxathiolane–, (3a)-,
in 54% yield under nitrogen atmosphere (Table 1, entry 1).
Replacing the light source with 10-W blue LEDs-, led to the
Entry
1[c]
2
Photocatalyst
Solvent
Yield (%)[b]
54
Eosin Y
-
Eosin Y
-
57
3
Rose bengal
Acr-Mes+ ClO4
-
Trace
52
-
4
-
product yield increasing slightly to 57% (Table 1, entry 2).
A
5
Rhodamine B
-
Trace
23
trace amount of the product was detected when the other photo
catalysts such as eosin B, rose bengal and rhodamine B were
used-, instead of eosin Y (Table 1, entries 3–5). Compared with
6
Methylene blue
Eosin B
Eosin Y
Eosin Y
Eosin Y
Eosin Y
Eosin Y
Eosin Y
Eosin Y
Eosin Y
Eosin Y
Eosin Y
Eosin Y
Eosin Y
Eosin Y
Eosin Y
Eosin Y
-
7
-
Trace
54
8[d]
9[e]
10[f]
11[g]
12
13
14
15
16
17
18
19[h]
20[i]
21[j]
22[k]
-
-
eosin Y, Acr-Mes+ ClO4 –and methylene blue as photo–catalyst
-
56
for the oxathiacetalization of benzaldehyde, generated the
product in low yield (Table 1, entries 6 and 7). Varying the
catalyst loading and reaction time did not enhance the yield of
the product (Table 1, entries 8–11). Next we tested the reaction
by using various solvents such as toluene, THF, 1,4-dioxane,
DMF, CH2Cl2, CH3CN and H2O. Among all solvents, only 1,4-
dioxane provided favourable results, with 82% yield (Table 1,
entry 12). Inferior results were obtained when other solvents
were used compared with solvent free conditions (Table 1,
entries 13–18). The reaction performed under aerobic conditions
generated lower yield of the product (Table 1, entries 19 and 20).
Only trace amount of product was detected either the reaction
was performed under dark conditions or thermal conditions
under dark conditions (Table 1, entries 21 and 22).
-
15
-
51
Toluene
THF
48
46
1,4-Dioxane
DMF
82
14
CH2Cl2
CH3CN
H2O
51
25
13
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
1,4-Dioxane
74
47
Trace
Trace
[a]Reaction conditions: 1a (1 mmol), 2 (1.1 equiv) at rt for 12 h. [b]Isolated
yields. [c]White LEDs. [d]0.5 mol % catalyst is used. [e]1.5 mol % catalyst is
used. [f]6 h of reaction time. [g]24 h of reaction time. [h]Air balloon is used.
[i]Under open air conditions. [j]Under dark conditions. [k]In dark at 60 °C.
Under the optimized reaction conditions, the oxathiacetalization
of various aldehydes (1) was first evaluated with 2-
mercaptoethanol (2). As demonstrated in Scheme 2, the
photoredox catalyzed reaction generated the corresponding
products in moderate to high yields. The substrates bearing
halogens at the ortho-, meta-, and para-position of substituted
aromatic rings worked well under the reaction conditions (3b–
3d). Notably, the reaction of 2-nitrobenzaldehyde or 2-
hydroxybenzaldehyde with 2-mercaptoethanol under photoredox
catalysis generated the corresponding products (i.e., 1,3-
oxathiolanes) in low yields (3e and 3f). This may have been due
to either steric hindrance or reduction of the aldehydic character
of benzaldehyde. We next evaluated the reaction by using
various benzaldehydes bearing electron-donating and electron-
The scope and generality of the photoredox- catalyzed
oxathiacetalization reaction were further demonstrated by
employing 3-mercaptopropan-1-ol (4) as the substrate in the
reaction with various aldehydes (Scheme 3). In this regard, we
selected various aldehydes to react with 3-mercaptopropan-1-ol
(4); the reaction proceeded smoothly to give the corresponding
1,3-oxathianes (5a–5i) in moderate to high yields.
2
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10.1002/ejoc.202000218
European Journal of Organic Chemistry
FULL PAPER
the yield of the product (Table 2, entries 6–9). The choice of
photocatalyst is crucial for this oxathiacetalization. For this
transformation, we used CH2Cl2 as the solvent-, and other
photocatalysts such as rose bengal, eosin B, rhodamine 6G, and
methylene blue resulting in, none of the desired product being
obtained (Table 2, entries 10–13). However, when Acr-Mes+
-
ClO4 was used as the photo catalyst, the product was obtained
in low yield compared with the use of eosin Y (Table 2, entry 14).
When the catalyst loading was reduced to 0.1 mol% (Table 2,
entry 15), the product was obtained in lower yield. The yield of
the product increased to 85% when the catalyst loading was 2
mol% (Table 2, entry 16). With further increase in the catalyst
loading, the product was obtained in lower yield (Table 2, entry
17). Decreasing or increasing the reaction time generated the
product in lower yields (Table 2, entries 18 and 19).
–
Performing the reaction under more dilution or aerobic
conditions provided the product in decreased yield (Table 2,
entries 20 and 21). Very little improvement in the yield of
product was observed when degassed dichloromethane was
used (Table 2, entry 22). No product was detected when the
reaction was performed without a catalyst (Table 2, entry 23).
Only trace amount of product was detected either the reaction
was performed under dark conditions or thermal conditions
under dark conditions (Table 2, entries 24 and 25).
Scheme 2. Scope of aldehydes (1) with 2-mercaptoethanol (2) for
oxathiacetalization. [a]Isolated yields are reported. [b]Reaction conditions: 1 (1.0
mmol), 2 (1.1 equiv), eosin Y (1 mol%), 1,4-dioxane (3 mL), blue LEDs, under
N2, rt, 12 h.
Table 2. Optimization of oxathiacetalization of acetophenone (6a) with 2-
mercaptoethanol (2)[a]
Entry
1
Photocatalyst (mol%)
Eosin Y (1)
Solvent
1,4-Dioxane
DMF
Yield (%)[b]
11
2
Eosin Y (1)
N.R.
N.R.
N.R.
77
3
Eosin Y (1)
H2O
Eosin Y (1)
4
EtOH
5
Eosin Y (1)
Eosin Y (1)
Eosin Y (1)
Eosin Y (1)
Eosin Y (1)
Rose Bengal (1)
Eosin B (1)
Acr-Mes+ ClO4- (1)
Rhodamine 6G (1)
Methylene blue (1)
Eosin Y (0.1)
Eosin Y (2)
Eosin Y (3)
Eosin Y (2)
Eosin Y (2)
Eosin Y (2)
Eosin Y (2)
Eosin Y (2)
-
CH2Cl2
Toluene
CH3CN
DCE
6
33
7
28
8
21
9
-
51
10
11
12
13
14
15
16
17
18[c]
19[d]
20[e]
21[f]
22[g]
23
24[h]
25[i]
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
N.R.
N.R.
41
Scheme 3. Scope of aldehydes (1) with 3-mercaptopropan-1-ol (4) for
oxathiacetalization. [a]Isolated yields are reported. [b]Reaction conditions: 1 (1.0
mmol), 4 (1.1 equiv), eosin Y (1 mol%), 1,4-dioxane (3 mL), blue LEDs, under
N2, rt, 12 h.
N.R.
Trace
67
Based on the aforementioned results we next used ketones (6)
as substrates instead of aldehydes for photoredox-catalyzed
oxathiacetalization with 2-mercaptoethanol (2). We first selected
acetophenone (6a) as the model substrate, and it was reacted
with 2-mercaptoethanol (2) under the optimized conditions of
aldehydes, which yielded the corresponding 1,3-oxathiolane (7a)
in low yield (Table 2, entry 1). On the basis of this result, we
further optimized the reaction conditions. Different solvents were
tested first, and the desired product (7a) was not obtained when
DMF, H2O, and ethanol were used as the solvent (Table 2,
entries 2–4). However, when CH2Cl2 was used as the solvent,
the product was obtained in 77% yield (Table 2, entry 5). The
use of other solvents such as toluene, CH3CN, and
dichloroethane or the solvent-free condition could not improve
85
48
34
63
67
69
69
N.R.
Trace
Trace
Eosin Y
Eosin Y
[a]Reaction conditions: 6a (1 mmol), 2 (1.1 equiv) at rt for 12 h. [b]Isolated
yields. [c]At 6 h. [d]At 24 h. [e]At 24 h using degassed DCM. [f]Under air. [g]Use of
6 mL solvent. [h]Under dark conditions. [i]In dark at 60 °C.
3
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10.1002/ejoc.202000218
European Journal of Organic Chemistry
FULL PAPER
Subsequently, we explored the scope of the photoredox
oxathiacetalization reaction of various ketones (6) with 2-
mercaptoethanol (2) when using 2 mol% eosin Y as the catalyst
and CH2Cl2 as the solvent (Scheme 4). Halogen-substituted
acetophenones (6b–6g) were converted into the desired
products (7b–7f) in high yield under the optimized conditions. 3-
Methyl acetophenone (6g) also reacted to generate the
corresponding product (7g) in high yield. However, in the case of
electron-rich, methyl, methoxy, and methylthio-substituted
acetophenones (6h–6k), the products (7h–7k) were obtained in
relatively low yields. Other acetylarenes, namely, 4’-tert-
butylacetophenone (6l) and 2-acetylnaphthalene (6m),
successfully reacted to form the desired products (7l and 7m).
However, when (E)-4-phenylbut-3-en-2-one (6n) was used as
the ketone source, the corresponding product (7n) was obtained
in low yield. When electron-deficient acetylarenes such as 4’-
cyanoacetophenone (6o) and 4’-nitroacetophenone (6p) were
used as substrates, the desired products (7o and 7p) were not
obtained. Other arylketones, namely-, propiophenone (7q) and
4’-chloropropiophenone (7r) reacted to form the corresponding
products in high yield. Aliphatic ketones (6s and 6t) were also
used for this oxathiacetalization, and the related products (7s
and 7t) were obtained in high yield. Finally, we employed ethyl
acetoacetate (6u) as the ketone source and it reacted to form
the corresponding product (7u) in low yield.
moderate yields (Scheme 5). Further decreasing the catalyst
loading resulted reduced the product yield.
Scheme 5. Scope of ketones (6) with 3-mercaptopropan-1-ol (4) for
oxathiacetalization. [a]Isolated yields are reported. [b]Reaction conditions: 6 (1.0
mmol), 2 (1.1 equiv), eosin Y (1 mol%), CH2Cl2 (3 mL), blue LEDs, under N2, rt,
12 h.
To determine the plausible mechanism of this photoredox-
catalyzed oxathiacetalization of aldehydes and ketones, various
control experiments were performed by choosing acetophenone
as the substrate. Thioacetalization with thiols (Scheme 6a),
acetalization with alcohols (Scheme 6b) and oxathiacetalization
with a mixture of alcohols and thiols (Scheme 6c), did not
generate, the desired product under the optimized reaction
conditions of ketones. Furthermore, the addition of TEMPO (9)
to
a
reaction mixture containing acetophenone (6a), 2-
(2) and photocatalyst stopped
mercaptoethanol
a
oxathiacetalization (Scheme 6d). indicating that the reaction
proceeds through a radical pathway. A similar type of control
experiments were also performed with benzaldehyde and
corresponding results were presented in Scheme 7.
Scheme 4. Scope of ketones (6) with 2-mercaptoethanol (2) for
oxathiacetalization. [a]Isolated yields are reported. [b]Reaction conditions: 6 (1.0
mmol), 2 (1.1 equiv), eosin Y (1 mol%), CH2Cl2 (3 mL), blue LEDs, under N2, rt,
12 h.
To further demonstrate the generality of the photoredox
oxathiacetalization reaction, 3-mercaptopropan-1-ol (4) was
used as the substrate, and reacted with various ketones (6a–6d,
6g, 6m, 6s and 6t), generating the desired products in moderate
yields (8a–8d, 8g, 8m, 8s and 8t respectively). Notably, the
products were obtained in low yields when 2 mol% of the
catalyst was used, whereas when the catalyst loading was
decreased to 0.5 mol% the desired products were obtained in
Scheme 6. Control experiments with acetophenone
4
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10.1002/ejoc.202000218
European Journal of Organic Chemistry
FULL PAPER
eminent features of the present protocol include the simple and
convenient operation, low catalyst loading, and high functional
group tolerance.
Experimental Section
General Information
Merck silica gel 60 (230–400 mesh) were used to purify the compounds
by column chromatography. All commercial chemicals were used as such.
GC-MS analyses were undertaken on Agilent Technologies 5977A GC
equipped with Agilent 7890B MS. Varian Unity Inova-600 or a Varian
Mercury-400 NMR instrument were used to record NMR by using CDCl3
solvent and multiplicity were determined as singlet s, doublet d, triplet t,
double of doublet dd, multiplet m and broad brs. Chemical shifts and
coupling constant values are determined in parts per million (ppm) and in
hertz (Hz). High-resolution mass spectra (HRMS) were analyzed on a
Jeol JMS-HX 110 spectrometer by the services provided at the National
Chung Hsing University.
Scheme 7. Control experiments with benzaldehyde
Based on the aforementioned control experiments, we
propose a plausible mechanism for this transformation as
follows: interaction of 2-mercaptoethanol (2) with blue light
induces the formation of excited organophotocatalyst II
through the SET process; this generates radical cation
species IV, which in turn undergoes deprotonation to form
the hydroxythiyl radical IVa. The formed hydroxythiyl radical
IVa reacts with 1 or 6 to form the intermediate V. The
intermediate V interacts with reduced organophotocatalyst III
through an SET process to generate species Va, which in
turn captures the proton followed by removal of water
molecule forms the desired 1,3-oxathiolane 3 or 7 (Scheme
8).
General Procedure for the Synthesis of Compounds 3 and 5
Aldehyde 1 (1 mmol), mercaptoalcohol 2 or 4 (1.1 mmol) and eosin Y (1
mol%) were added to the Schlenk tube containing a Teflon-coated
magnetic stir bar and was purged by evacuating the tube and back filled
with nitrogen. To the mixture, 1,4-dioxane (3 mL) was added and it was
kept for stirring under 10 W blue LEDs irradiation at room temperature for
12 hours. After completion of the reaction, the crude reaction mixture was
purified by silicagel column chromatography to afford the pure product 3
or 5.
2-Phenyl-1,3-oxathiolane (3a):[16] This compound is obtained as
colorless liquid by the reaction of benzaldehyde (1a) with 2-
mercaptoethanol (2) following the general procedure for 3 and 5. Yield:
82%. 1H NMR (400 MHz, CDCl3): δ 3.15-3.29 (m, 2H), 3.90-3.96 (m, 1H),
4.49-4.54 (m, 1H), 6.04 (s, 1H), 7.29-7.37 (m, 3H), 7.45-7.47 (m, 2H). 13
C
NMR (100MHz, CDCl3): δ 34.1, 72.0, 87.0, 126.7, 128.5, 128.7, 139.2.
2-(3-Chlorophenyl)-1,3-oxathiolane (3b): This compound is obtained
as light yellow liquid by the reaction of 3-chlorobenzaldehyde (1b) with 2-
mercaptoethanol (2) following the general procedure for 3 and 5. Yield:
83%. 1H NMR (400 MHz, CDCl3): δ 3.11-3.24 (m, 2H), 3.87-3.93 (m, 1H),
4.44-4.49 (m, 1H), 5.98 (s, 1H), 7.22-7.30 (m, 3H), 7.50 (d, J = 2 Hz, 1H).
13C NMR (100MHz, CDCl3): δ 33.8, 71.9, 85.8, 124.6, 126.5, 128.4,
129.5, 134.1, 141.4. HRMS (EI) calcd for C9H9ClOS [M]+ 200.0063, found
200.0068.
2-(4-Bromophenyl)-1,3-oxathiolane (3c):[17] This compound is obtained
as colorless liquid by the reaction of 4-bromobenzaldehyde (1c) with 2-
mercaptoethanol (2) following the general procedure for 3 and 5. Yield:
76%. 1H NMR (400 MHz, CDCl3): δ 3.13-3.17 (m, 1H), 3.19-3.26 (m, 1H),
3.86-3.94 (m, 1H), 4.45-4.50 (m, 1H), 5.97 (s, 1H), 7.31 (d, J = 8.4 Hz,
2H), 7.46 (d, J = 8.4 Hz, 2H). 13C NMR (100MHz, CDCl3): δ 33.9, 71.8,
86.1, 122.3, 128.2, 131.4, 138.3.
Scheme 8. Plausible Mechanism
2-(2-Bromophenyl)-1,3-oxathiolane (3d): This compound is obtained
as yellow liquid by the reaction of 2-bromobenzaldehyde (1d) with 2-
mercaptoethanol (2) following the general procedure for 3 and 5. Yield:
84%. 1H NMR (400 MHz, CDCl3): δ 3.15-3.19 (m, 2H), 3.95-4.01 (m, 1H),
4.57-4.61 (m, 1H), 6.30 (s, 1H), 7.12-7.16 (m, 1H), 7.32 (t, J = 7.6 Hz,
1H), 7.51 (d, J = 8 Hz, 1H), 7.63 (d, J = 8 Hz, 1H). 13C NMR (100MHz,
CDCl3): δ 33.4, 72.2, 85.3, 121.6, 126.9, 127.6, 129.4, 132.4, 139.5.
HRMS (EI) calcd for C9H9BrOS [M]+ 243.9557, found 243.9552.
Conclusion
In summary, we developed a mild and efficient protocol for
oxathiacetalization of aldehydes and ketones using a visible-
light-promoted metal-free photoredox catalyst. A wide range of
aldehydes containing aromatic, heteroaromatic, aliphatic, and
α,β-unsaturated aromatic rings are all well tolerated under the
reaction conditions employed. In this report, we have also
demonstrated an efficient route for protection of less reactive
ketones with mercaptoalcohols. The control experimental
studies validated the insight of the reaction mechanism. The
2-(2-Nitrophenyl)-1,3-oxathiolane (3e):[18] This compound is obtained
as yellow solid by the reaction of 2-nitrobenzaldehyde (1e) with 2-
mercaptoethanol (2) following the general procedure for 3 and 5. Yield:
16%. m.p.: 60-62 °C. 1H NMR (400 MHz, CDCl3): δ 3.11-3.15 (m, 2H),
5
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10.1002/ejoc.202000218
European Journal of Organic Chemistry
FULL PAPER
4.01-4.07 (m, 1H), 4.57-4.61 (m, 1H), 6.57 (s, 1H), 7.43-7.47 (m, 1H),
7.63-7.67 (m, 1H), 7.87 (d, J = 8 Hz, 1H), 8.02 (d, J = 8.4Hz, 1H). 13C
NMR (100MHz, CDCl3): δ 33.0, 72.5, 81.7, 124.5, 127.0, 128.5, 133.8,
137.4, 146.4.
2-mercaptoethanol (2) following the general procedure for 3 and 5. Yield:
53%. 1H NMR (400 MHz, CDCl3): δ 3.14-3.17 (m, 2H), 3.85 (s, 3H), 3.94-
4.00 (m, 1H), 4.52-4.56 (m, 1H), 6.34 (s, 1H), 6.86 (d, J = 8.4 Hz, 1H),
6.98 (t, J = 7.6 Hz, 1H), 7.25-7.29 (m, 1H), 7.56 (d, J = 8 Hz, 1H). 13C
NMR (100MHz, CDCl3): δ 33.1, 55.3, 71.7, 81.0, 110.1, 125.4, 128.4,
128.9, 156.0. HRMS (EI) calcd for C10H12O2S [M]+ 196.0558, found
196.0562.
2-(1,3-Oxathiolan-2-yl)phenol (3f):[19] This compound is obtained as
colorless liquid by the reaction of 2-hydroxybenzaldehyde (1f) with 2-
mercaptoethanol (2) following the general procedure for 3 and 5. Yield:
35%. 1H NMR (400 MHz, CDCl3): δ 3.20-3.27 (m, 2H), 3.86-3.92 (m, 1H),
4.53-4.57 (m, 1H), 6.13 (s, 1H), 6.83-6.89 (m, 2H), 7.16 (dd, J1 = 7.6 Hz,
J2= 0.8 Hz, 1H), 7.20-7.24 (m, 1H), 7.31 (s, 1H). 13C NMR (100MHz,
CDCl3): δ 33.4, 71.6, 87.0, 117.1, 120.0, 121.5, 128.1, 130.2, 155.0.
2-(4-Methoxyphenyl)- 1,3-oxathiolane (3n):[20] This compound is
obtained as colorless liquid by the reaction of p-anisaldehyde (1n) with 2-
mercaptoethanol (2) following the general procedure for 3 and 5. Yield:
30%. 1H NMR (400 MHz, CDCl3): δ 3.14-3.19 (m, 1H), 3.23-3.29 (m, 1H),
3.78 (s, 3H), 3.86-3.92 (m, 1H), 4.47-4.52 (m, 1H), 5.99 (s, 1H), 6.87 (dd,
J1 = 6.8 Hz, J 2= 2 Hz, 2H), 7.39-7.41 (m, 2H). 13C NMR (100MHz,
CDCl3): δ 33.9, 55.2, 71.6, 86.7, 113.7, 128.1, 130.9, 159.8.
3-(1,3-Oxathiolan-2-yl)benzonitrile (3g): This compound is obtained as
colorless liquid by the reaction of 3-cyanobenzaldehyde (1g) with 2-
mercaptoethanol (2) following the general procedure for 3 and 5. Yield:
83%. 1H NMR (400 MHz, CDCl3): δ 3.22-3.28 (m, 2H), 3.96-4.02 (m, 1H),
4.51-4.56 (m, 1H), 6.05 (s, 1H), 7.46 (t, J = 7.6 Hz, 1H), 7.60 (d, J =
7.6Hz, 1H), 7.67 (d, J = 7.6 Hz, 1H), 7.77 (s, 1H). 13C NMR (100MHz,
CDCl3): δ 34.0, 72.1, 85.4, 112.4, 118.5, 129.1, 130.1, 130.9, 132.0,
141.2. HRMS (EI) calcd for C10H9NOS [M]+ 191.0405, found 191.0412.
Methyl 3-(1,3-Oxathiolan-2-yl)benzoate (3o): This compound is
obtained as colorless liquid by the reaction of methyl 3-formylbenzoate
(1o) with 2-mercaptoethanol (2) following the general procedure for 3 and
5. Yield: 44%. 1H NMR (400 MHz, CDCl3): δ 3.19-3.23 (m, 1H), 3.26-3.32
(m, 1H), 3.92 (s, 3H), 3.94-4.00 (m, 1H), 4.53-4.56 (m, 1H), 6.09 (s, 1H),
7.43 (t, J = 7.8 Hz, 1H), 7.65 (d, J = 7.6 Hz, 1H), 7.99 (d, J = 7.6Hz, 1H),
8.13 (s, 1H). 13C NMR (100MHz, CDCl3): δ 34.0, 52.1, 72.0, 86.3, 127.7,
128.5, 129.7, 130.3, 131.1, 139.9, 166.7.
4-(1,3-Oxathiolan-2-yl)benzonitrile (3h):[20] This compound is obtained
as colorless liquid by the reaction of 4-cyanobenzaldehyde (1h) with 2-
mercaptoethanol (2) following the general procedure for 3 and 5. Yield:
49%. 1H NMR (400 MHz, CDCl3): δ 3.19-3.28 (m, 2H), 3.96-4.02 (m, 1H),
4.50-4.55 (m, 1H), 6.07 (s, 1H), 7.52-7.54 (m, 2H), 7.63 (dd, J 1= 6.4 Hz,
J 2= 2 Hz, 2H). 13C NMR (100MHz, CDCl3): δ 33.9, 72.1, 85.4, 111.9,
118.4, 126.9, 132.1, 144.8.
2-(Naphthalene-1-yl)-1,3-oxathiolane (3p):[19] This compound is
obtained as pale yellow liquid by the reaction of 1-naphthaldehyde (1p)
with 2-mercaptoethanol (2) following the general procedure for 3 and 5.
Yield: 91%. 1H NMR (400 MHz, CDCl3): δ 3.06-3.13 (m, 2H), 3.85-3.91
(m, 1H), 4.44-4.49 (m, 1H), 6.62 (s, 1H), 7.38-7.48 (m, 3H), 7.71-7.78 (m,
3H), 7.98 (d, J = 8.4 Hz, 1H). 13C NMR (100MHz, CDCl3): δ 33.5, 71.5,
84.2, 122.4, 123.1, 125.2, 125.5, 126.0, 128.4, 128.5, 130.0, 133.4,
134.8.
2-(m-Tolyl)-1,3-oxathiolane (3i):[6o] This compound is obtained as
colorless liquid by the reaction of m-tolualdehyde (1i) with 2-
mercaptoethanol (2) following the general procedure for 3 and 5. Yield:
60%. 1H NMR (400 MHz, CDCl3): δ 2.32 (s, 3H), 3.08-3.12 (m, 1H), 3.16-
3.23 (m, 1H), 3.83-3.89 (m, 1H), 4.43-4.48 (m, 1H), 5.98 (s, 1H), 7.09 (d,
J = 6.8 Hz, 1H), 7.18-7.24 (m, 2H), 7.27 (s, 1H). 13C NMR (100MHz,
CDCl3): δ 21.1, 33.8, 71.6, 86.8, 123.5, 126.9, 128.0, 129.1, 137.8, 138.8.
2-(Naphthalene-2-yl)-1,3-oxathiolane (3q): This compound is obtained
as white solid by the reaction of 2-naphthaldehyde (1q) with 2-
mercaptoethanol (2) following the general procedure for 3 and 5. Yield:
88%. m.p.: 98-99 °C. 1H NMR (400 MHz, CDCl3): δ 3.20-3.23 (m, 1H),
3.26-3.31 (m, 1H), 3.96-4.02 (m, 1H), 4.54-4.58 (m, 1H), 6.21 (s, 1H),
2-(o-Tolyl)-1,3-oxathiolane (3j): This compound is obtained as pale
liquid by the reaction of o-tolualdehyde (1j) with 2-mercaptoethanol (2)
following the general procedure for 3 and 5. Yield: 62%. 1H NMR (400
MHz, CDCl3): δ 2.35 (s, 3H), 3.18-3.24 (m, 2H), 3.89-3.95 (m, 1H), 4.56-
4.60 (m, 1H), 6.19 (s, 1H), 7.12-7.13 (m, 1H), 7.17-7.23 (m, 2H), 7.58-
7.60 (m, 1H). 13C NMR (100MHz, CDCl3): δ 19.1, 33.7, 71.7, 84.3, 125.3,
126.1, 128.1, 130.3, 134.9, 137.3. HRMS (EI) calcd for C10H12OS [M]+
180.0609, found 180.0615.
7.45-7.47 (m, 2H), 7.57-7.59 (m, 1H), 7.80-7.85 (m, 3H), 7.88 (s, 1H). 13
C
NMR (100MHz, CDCl3): δ 34.1, 72.1, 87.2, 124.3, 125.6, 126.2, 126.24,
127.7, 128.1, 128.4, 132.9, 133.4, 136.6. HRMS (EI) calcd for C13H12OS
[M]+ 216.0609, found 216.0603.
(E)-2-Styryl-1,3-oxathiolane (3r):[20] This compound is obtained as
yellow liquid by the reaction of (E)-cinnamaldehyde (1r) with 2-
mercaptoethanol (2) following the general procedure for 3 and 5. Yield:
84%. 1H NMR (400 MHz, CDCl3): δ 3.08-3.18 (m, 2H), 3.85-3.91 (m, 1H),
4.36-4.40 (m, 1H), 5.68 (d, J = 7.6 Hz, 1H), 6.24-6.30 (m, 1H), 6.64 (d, J
= 15.6 Hz, 1H), 7.24-7.26 (m, 1H), 7.29-7.33 (m, 2H), 7.38-7.40 (m, 2H).
13C NMR (100MHz, CDCl3): δ 33.6, 71.6, 86.2, 126.7, 127.0, 128.1,
128.5, 132.1, 135.8.
2-(p-Tolyl)- 1,3-oxathiolane (3k):[20] This compound is obtained as pale
liquid by the reaction of p-tolualdehyde (1k) with 2-mercaptoethanol (2)
following the general procedure for 3 and 5. Yield: 45%. 1H NMR (400
MHz, CDCl3): δ 2.32 (s, 3H), 3.10-3.15 (m, 1H), 3.18-3.23 (m, 1H), 3.84-
3.91 (m, 1H), 4.44-4.48 (m, 1H), 5.99 (s, 1H), 7.13 (d, J = 7.2 Hz, 2H),
7.35 (t, J =5.6 Hz, 2H). 13C NMR (100MHz, CDCl3): δ 21.1, 33.8, 71.6,
86.9, 126.5, 128.9, 136.0, 138.2.
2-(n-Heptyl)-1,3-oxathiolane (3s): This compound is obtained as
colorless liquid by the reaction of n-octanal (1s) with 2-mercaptoethanol
(2) following the general procedure for 3 and 5. Yield: 79%. 1H NMR (400
MHz, CDCl3): δ 0.88 (t, J = 6.8 Hz, 3H), 1.28-1.49 (m, 11H), 1.72-1.96 (m,
1H), 3.01-3.04 (m, 2H), 3.74-3.81 (m, 1H), 4.31-4.36 (m, 1H), 5.06 (t, J =
6.2 Hz, 1H). 13C NMR (100MHz, CDCl3): δ 14.0, 22.6, 26.5, 29.1, 29.4,
31.7, 32.5, 36.4, 71.1, 87.1.
2-(3,5-Dimethoxyphenyl)- 1,3-oxathiolane (3l): This compound is
obtained
as
colorless
liquid
by
the
reaction
of
3,5-
dimethoxybenzaldehyde (1l) with 2-mercaptoethanol (2) following the
general procedure for 3 and 5. Yield: 55%. 1H NMR (400 MHz, CDCl3): δ
3.10-3.15 (m, 1H), 3.17-3.24 (m, 1H), 3.76 (s, 6H), 3.87-3.93 (m, 1H),
4.44-4.49 (m, 1H), 5.97 (s, 1H), 6.39 (t, J =2.4 Hz, 1H), 6.61 (d, J = 2.4
Hz, 2H). 13C NMR (100MHz, CDCl3): δ 33.6, 55.1, 71.6, 86.5, 100.4,
104.0, 141.5, 160.5. HRMS (EI) calcd for C11H14O3S [M]+ 226.0664,
found 226.0667.
2-(Cyclohexyl)-1,3-oxathiolane (3t): This compound is obtained as
colorless liquid by the reaction of cyclohexyl carboxaldehyde (1t) with 2-
mercaptoethanol (2) following the general procedure for 3 and 5. Yield:
72%. 1H NMR (400 MHz, CDCl3): 1H NMR (400 MHz, CDCl3): δ 0.98-
1.33 (m, 5H), 1.61-1.80 (m, 5H), 1.97-2.01 (m, 1H), 2.90-3.02 (m, 2H),
3.72-3.78 (m, 1H), 4.31-4.35 (m, 1H), 4.84 (d, J = 6.8 Hz, 1H), 13C NMR
2-(2-Methoxyphenyl)- 1,3-oxathiolane (3m): This compound is
obtained as colorless liquid by the reaction of o-anisaldehyde (1m) with
6
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10.1002/ejoc.202000218
European Journal of Organic Chemistry
FULL PAPER
(100MHz, CDCl3): δ 25.6, 25.7, 26.2, 29.4, 29.8, 31.9, 43.6, 71.3, 91.8.
2-(3-Chlorophenyl)- 1,3-oxathiane (5d): This compound is obtained as
yellow liquid by the reaction of 3-chlorobenzaldehyde (1b) with 3-
mercaptopropan-1-ol (4) following the general procedure for 3 and 5.
Yield: 79%. 1H NMR (400 MHz, CDCl3): δ 1.70 (dd, J1 = 14 Hz, J2 = 0.8
Hz, 1H), 2.00-2.08 (m, 1H), 2.77 (dd, J1 =13.2 Hz, J2 = 1.6 Hz, 1H), 3.11-
3.18 (m, 1H), 3.67-3.74 (m, 1H), 4.25-4.29 (m, 1H), 5.72 (s, 1H), 7.21-
7.26 (m, 2H), 7.30-7.32 (m, 1H), 7.48 (s, 1H). 13C NMR (100MHz,
CDCl3): δ 25.2, 28.8, 70.3, 83.1, 124.0, 126.1, 128.2, 129.4, 133.9, 141.2.
HRMS (EI) calcd for C10H11ClOS [M]+ 214.0219, found 214.0217.
HRMS (EI) calcd for C9H16OS [M]+ 172.0922, found 172.0913.
2,4-Dichloro-6-(1,3-oxathiolan-2-yl)phenol (3u): This compound is
obtained as white solid by the reaction of 3,5-dichloro-2-
hydroxybenzaldehyde (1u) with 2-mercaptoethanol (2) following the
general procedure for 3 and 5. Yield: 72%. m.p.: 97-99 °C. 1H NMR (400
MHz, CDCl3): δ 3.19-3.23 (m, 2H), 3.94-4.01 (m, 1H), 4.53-4.58 (m, 1H),
6.20 (s, 1H), 6.61 (s, 1H), 7.28 (t, J = 2.4 Hz, 2H). 13C NMR (100MHz,
CDCl3): δ 33.3, 72.0, 82.6, 121.0, 125.1, 125.5, 127.5, 128.5, 147.9.
HRMS (EI) calcd for C9H8Cl2O3S [M]+ 249.9622, found 249.9626.
3-(1,3-Oxathian-2-yl)benzonitrile (5e): This compound is obtained as
white solid by the reaction of 3-cyanobenzaldehyde (1g) with 3-
mercaptopropan-1-ol (4) following the general procedure for 3 and 5.
Yield: 83%. m.p.:75-78°C. 1H NMR (400 MHz, CDCl3): δ 1.75-1.81 (m,
1H), 2.01-2.13 (m, 1H), 2.80-2.86 (m, 1H), 3.18-3.26 (m, 1H), 3.75-3.81
(m, 1H), 4.30-4.35 (m, 1H), 5.80 (s, 1H), 7.43 (t, J = 7.6 Hz, 1H), 7.55-
7.58 (m, 1H), 7.67 (d, J = 7.6 Hz, 1H), 7.77 (d, J = 1.6 Hz, 1H). 13C NMR
(100MHz, CDCl3): δ 24.8, 28.5, 69.9, 82.1, 111.8, 118.0, 128.6, 129.1,
129.9, 131.2, 140.4. HRMS (EI) calcd for C11H11NOS [M]+205.0561,
found 205.0564.
2-(Furan-2-yl)- 1,3-oxathiolane (3v):[20] This compound is obtained as
yellow liquid by the reaction of furfural (1v) with 2-mercaptoethanol (2)
following the general procedure for 3 and 5. Yield: 63%. 1H NMR (400
MHz, CDCl3): δ 3.09-3.15 (m, 1H), 3.21-3.27 (m, 1H), 4.01-4.07 (m, 1H),
4.27-4.32 (m, 1H), 6.11 (s, 1H), 6.33-6.34 (m, 1H), 6.45-6.46 (m, 1H),
7.42 (dd, J1 = 1.6 Hz, J 2= 0.8 Hz, 1H). 13C NMR (100MHz, CDCl3): δ
33.3, 71.1, 78.9, 109.0, 110.2, 143.2, 152.0. HRMS (EI) calcd for
C11H14O3S [M]+ 226.0664, found 226.0667.
2-(Thiophen-2-yl)- 1,3-oxathiolane (3w):[20] This compound is obtained
as yellow liquid by the reaction of thiophene-2-carbaldehyde (1w) with 2-
mercaptoethanol (2) following the general procedure for 3 and 5. Yield:
51%. 1H NMR (400 MHz, CDCl3): δ 3.13-3.18 (m, 1H), 3.25-3.31 (m, 1H),
3.95-4.01 (m, 1H), 4.37-4.42 (m, 1H), 6.31 (s, 1H), 6.95 (dd, J1 = 4.8 Hz,
2-(Naphthalen-2-yl)-1,3-oxathiane (5f): This compound is obtained as
white solid by the reaction of 2-naphthaldehyde (1q) with 3-
mercaptopropan-1-ol (4) following the general procedure for 3 and 5.
Yield: 48%. m.p.: 113-116°C. 1H NMR (400 MHz, CDCl3): δ 1.67-1.72 (m,
1H), 2.06-2.14 (m, 1H), 2.77-2.81 (m, 1H), 3.15-3.22 (m, 1H), 3.72-3.79
(m, 1H), 4.30-4.34 (m, 1H), 5.90 (s, 1H), 7.42-7.45 (m, 2H), 7.56 (d, J =
8.8 Hz, 1H), 7.77-7.83 (m, 3H), 7.93 (s, 1H). 13C NMR (100MHz, CDCl3):
δ 25.5, 29.1, 70.5, 84.4, 123.9, 125.0, 126.0, 126.1, 127.5, 128.0, 128.1,
133.0, 133.2, 136.8. HRMS (EI) calcd for C14H14OS [M]+230.765, found
230.0758.
J = 3.6 Hz, 1H), 7.13 (d, J = 3.2 Hz, 1H), 7.31 (d, J = 5.2 Hz, 1H). 13C
2
NMR (100MHz, CDCl3): δ 33.9, 71.3, 82.1, 126.3, 126.4, 126.5, 143.6.
1-(3-(1,3-Oxathiolan-2-yl)phenyl)ethanone (3x): This compound is
obtained as colorless liquid by the reaction of 3-acetylbenzaldehyde (1x)
with 2-mercaptoethanol (2) following the general procedure for 3 and 5.
Yield: 65%. 1H NMR (400 MHz, CDCl3): δ 2.59 (s, 3H), 3.16-3.29 (m, 2H),
3.91-3.97 (m, 1H), 4.50-4.55 (m, 1H), 6.07 (s, 1H), 7.43 (t, J = 7.8 Hz,
1H), 7.63-7.66 (m, 1H), 7.88-7.90 (m, 1H), 8.03 (t, J = 1.6 Hz, 1H). 13C
NMR (100MHz, CDCl3): δ 26.6, 34.0, 72.0, 86.2, 126.3, 128.4, 128.6,
131.2, 137.1, 140.0, 197.6. HRMS (EI) calcd for C11H12O2S [M]+
208.0558, found: 208.0554
2-(Naphthalen-1-yl)-1,3-oxathiane (5g): This compound is obtained as
yellow liquid by the reaction of 1-naphthaldehyde (1p) with 3-
mercaptopropan-1-ol (4) following the general procedure for 3 and 5.
Yield: 57%. 1H NMR (400 MHz, CDCl3): δ1.73 (d, J = 14.4 Hz, 1H), 2.13-
2.16 (m, 1H), 2.81 (d, J = 13.6 Hz, 1H), 3.22-3.29 (m, 1H), 3.80-3.86 (m,
1H), 4.34-4.39 (m, 1H), 6.36 (s, 1H), 7.42-7.53 (m, 3H), 7.76-7.82 (m,
3H), 8.28 (d, J = 8.4 Hz, 1H). 13C NMR (100MHz, CDCl3): δ 25.7, 29.2,
70.9, 82.3, 123.7, 124.4, 125.3, 125.5, 125.9, 128.6, 128.9, 129.4, 133.6,
134.9. HRMS (EI) calcd for C14H14OS [M]+ 230.0765, found 230.0762.
2-Phenyl-1,3-oxathiane (5a): This compound is obtained as colorless
liquid by the reaction of benzaldehyde (1a) with 3-mercaptopropan-1-ol
(4) following the general procedure for 3 and 5. Yield: 78%. 1H NMR (400
MHz, CDCl3): δ1.54-1.59 (m, 1H), 1.89-1.99 (m, 1H), 2.64-2.67 (m, 1H),
3.01-3.08 (m, 1H), 3.61 (m, 1H), 4.15-4.19 (m, 1H), 5.65 (s, 1H), 7.15-
7.25 (m, 3H), 7.36 (d, J = 7.6 Hz, 2H). 13C NMR (100MHz, CDCl3): δ 25.3,
28.9, 70.3, 84.1, 125.8, 128.1, 128.2, 139.3. HRMS (EI) calcd for
C10H12OS [M]+180.0609, found 180.0605.
2,4-Dichloro-6-(1,3-oxathian-2-yl)phenol (5h): This compound is
obtained as white solid by the reaction of 3,5-dichloro-2-
hydroxybenzaldehyde (1t) with 3-mercaptopropan-1-ol (4) following the
general procedure for 3 and 5. Yield: 77%. m.p.: 123-125 °C. 1H NMR
(400 MHz, CDCl3): δ 1.80-1.84 (m, 1H), 2.09-2.14 (m, 1H), 2.82-2.86 (m,
1H), 3.19-3.26 (m, 1H), 3.77-3.84 (m, 1H), 4.35-4.38 (m, 1H), 5.95 (s,
1H), 7.17-7.18 (m, 1H), 7.29-7.30 (m, 1H), 7.33 (d, J = 2.8 Hz, 1H). 13C
NMR (100MHz, CDCl3): δ 25.4, 28.7, 70.9, 81.9, 121.9, 124.7, 126.0,
126.1, 129.3, 148.6. HRMS (EI) calcd for C10H10Cl2O2S [M]+ 263.9779,
found 263.9777.
2-(2-Bromophenyl)-1,3-oxathiane (5b): This compound is obtained as
colorless liquid by the reaction of 2-bromobenzaldehyde (1d) with 3-
mercaptopropan-1-ol (4) following the general procedure for 3 and 5.
Yield: 42%. 1H NMR (400 MHz, CDCl3): δ 1.72-1.76 (m, 1H), 2.05-2.14
(m, 1H), 2.81 (d, J = 13.6 Hz, 1H), 3.20-3.27 (m, 1H), 3.78-3.85 (m, 1H),
4.29-4.33 (m, 1H), 6.03 (s, 1H), 7.12-7.16 (m, 1H), 7.31-7.35 (m, 1H),
7.50 (d, J = 8 Hz, 1H), 7.69 (d, J = 7.6 Hz, 1H). 13C NMR (100MHz,
CDCl3): δ 25.5, 29.0, 70.7, 83.6, 121.1, 127.7, 128.6, 129.7, 132.4, 138.5.
HRMS (EI) calcd for C10H11BrOS [M]+ 257.9714, found 257.9705.
(E)-2-Styryl-1,3-oxathiane (5i): This compound is obtained as colorless
liquid by the reaction of (E)-cinnamaldehyde (1r) with 3-mercaptopropan-
1-ol (4) following the general procedure for 3 and 5. Yield: 30%. 1H NMR
(400 MHz, CDCl3): δ 1.66-1.72 (m, 1H), 1.95-2.05 (m, 1H), 2.73-2.79 (m,
1H), 3.01 (m, 1H), 3.64-3.71 (m, 1H), 4.21-4.26 (m, 1H), 5.43-5.45 (m,
1H), 6.23-6.28 (m, 1H), 6.76 (d, J = 15.6 Hz, 1H), 7.21-7.25 (m, 1H),
7.28-7.32 (m, 2H), 7.38 (d, J = 7.2 Hz, 2H). 13C NMR (100MHz, CDCl3): δ
25.4, 8.2, 69.8, 82.1, 126.1, 126.5, 127.8, 128.3, 131.4, 135.9. HRMS
(EI) calcd for C12H14OS [M]+ 206.0765, found 206.0768.
2-(4-Bromophenyl)- 1,3-oxathiane (5c): This compound is obtained as
white solid by the reaction of 4-bromobenzaldehyde (1c) with 3-
mercaptopropan-1-ol (4) following the general procedure for 3 and 5.
Yield: 82%. m.p.: 76-79°C. 1H NMR (400 MHz, CDCl3): δ 1.75 (d, J =
14.4 Hz, 1H), 2.06-2.16 (m, 1H), 2.81 (d, J = 13.6 Hz, 1H), 3.16-3.23 (m,
1H), 3.76 (t, J = 12.4 Hz, 1H), 4.30-4.33 (m, 1H), 5.73 (s, 1H), 7.33 (d, J
= 8 Hz, 2H), 7.47 (d, J = 8.4 Hz, 2H). 13C NMR (100MHz, CDCl3): δ 25.4,
29.0, 70.5, 83.5, 122.2, 127.7, 131.4, 138.4. HRMS (EI) calcd for
C10H11BrOS [M]+ 257.9714, found 257.9707.
General Procedure for the Synthesis of Compounds 7 and 8
Ketone 6 (1 mmol), mercaptoalcohol 2 or 4 (1.1 mmol) and eosin Y (2
mol%) were added to the Schlenk tube containing a Teflon-coated
7
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10.1002/ejoc.202000218
European Journal of Organic Chemistry
FULL PAPER
magnetic stir bar and was purged by evacuating the tube and back filled
with nitrogen. To the mixture, CH2Cl2 (3 mL) was added and it was kept
for stirring under 10 W blue LEDs irradiation at room temperature for 12
hours. After completion of the reaction, the crude reaction mixture was
purified by silicagel column chromatography to afford the pure product 7
or 8.
7.21 (d, J = 11.2 Hz, 2H). 13C NMR (100MHz, CDCl3): δ 21.4, 32.3, 34.3,
70.5, 95.5, 121.8, 125.4, 127.8, 127.9, 137.6, 146.6.
2-Methyl-2-(o-tolyl)-1,3-oxathiolane (7h):[21] This compound is obtained
as colorless liquid by the reaction of 2’-methylacetophenone (6h) with 2-
mercaptoethanol (2) following the general procedure for 7 and 8. Yield:
1
42%. H NMR (400 MHz, CDCl3): δ 1.95 (s, 3H), 2.52 (s, 3H), 3.04-3.06
2-Methyl-2-phenyl-1,3-oxathiolane (7a):[21] This compound is obtained
as colorless liquid by the reaction of acetophenone (6a) with 2-
mercaptoethanol (2) following the general procedure for 7 and 8. Yield:
85%. 1H NMR (400 MHz, CDCl3): δ 1.82 (s, 3H), 2.94-2.99 (m, 1H), 3.08-
3.14 (m, 1H), 3.89-3.95 (m, 1H), 4.21-4.26 (m, 1H), 7.11-7.15 (m, 1H),
7.20-7.24 (m, 2H), 7.39-7.41 (m, 2H). 13C NMR (100MHz, CDCl3): δ 32.3,
34.4, 70.6, 95.5, 124.8, 127.1, 128.1, 146.7.
(m, 1H), 3.17-3.23 (m, 1H), 3.97-4.03 (m, 1H), 4.37-4.42 (m, 1H), 7.16-
7.18 (m, 3H), 7.29-7.60 (dd, J = 6.2, 1.6 Hz, 1H). 13C NMR (100MHz,
CDCl3): δ 21.3, 31.1, 34.1, 70.1, 95.4, 124.1, 125.7, 127.2, 132.1, 134.2,
144.0.
2-(3,4-Dimethylphenyl)-2-methyl-1,3-oxathiolane (7i): This compound
is obtained as colorless liquid by the reaction of 3’,4’-
dimethylacetophenone (6i) with 2-mercaptoethanol (2) following the
general procedure for 7 and 8. Yield: 43%. 1H NMR (400 MHz, CDCl3): δ
1.89 (s, 3H), 2.23 (s, 3H), 3.26 (s, 3H), 3.05-3.09 (m, 1H), 3.17-3.23 (m,
1H), 4.00-4.06 (m, 1H), 4.30-4.35 (m, 1H), 7.06-7.08 (d, J = 8.0 Hz, 1H),
7.20-7.25 (m, 2H). 13C NMR (100MHz, CDCl3): δ 19.3, 19.9, 32.4, 34.4,
70.6, 95.5, 122.2, 126.1, 129.4, 135.5, 136.3, 144.2. HRMS (EI) calcd for
C12H16OS [M]+ 208.0922, found 208.0918.
2-(4-Chlorophenyl)-2-methyl-1,3-oxathiolane (7b):[21] This compound
is obtained as colorless liquid by the reaction of 4’-chloroacetophenone
(6b) with 2-mercaptoethanol (2) following the general procedure for 7 and
1
8. Yield: 79%. H NMR (400 MHz, CDCl3): δ 1.87 (s, 3H), 3.03-3.08 (m,
1H), 3.18-3.23 (m, 1H), 3.97-4.01 (m, 1H), 4.29-4.34 (m, 1H), 7.25-7.29
(m, 2H), 7.41-7.44 (m, 2H). 13C NMR (100MHz, CDCl3): δ 32.1, 34.4,
70.7, 95.0, 126.4, 128.2, 132.9, 145.3.
2-(4-Methoxyphenyl)-2-methyl-1,3-oxathiolane (7j):[21] This compound
is obtained as colorless liquid by the reaction of 4’-methoxyacetophenone
(6j) with 2-mercaptoethanol (2) following the general procedure for 7 and
2-(4-Bromophenyl)-2-methyl-1,3-oxathiolane (7c):[22] This compound
is obtained as colorless liquid by the reaction of 4’-bromoacetophenone
(6c) with 2-mercaptoethanol (2) following the general procedure for 7 and
1
8. Yield: 43%. H NMR (400 MHz, CDCl3): δ 1.89 (s, 3H), 3.04-3.09 (m,
1
8. Yield: 75%. H NMR (400 MHz, CDCl3): δ 1.87 (s, 3H), 3.04-3.08 (m,
1H), 3.17-3.23 (m, 1H), 3.78 (s, 3H), 3.98-4.04 (m, 1H), 4.28-4.33 (m,
1H), 6.82-6.86 (m, 2H), 7.40-7.43 (m, 2H). 13C NMR (100MHz, CDCl3): δ
32.2, 34.3, 55.1, 70.4, 95.4, 113.3, 126.2, 138.7, 158.6.
1H), 3.17-3.21 (m, 1H), 3.97-4.00 (m, 1H), 4.29-4.33 (m, 1H), 7.35-7.37
(m, 2H), 7.41-7.44 (m, 2H). 13C NMR (100MHz, CDCl3): δ 32.1, 34.4,
70.7, 95.0, 121.0, 126.7, 131.1, 145.9. HRMS (EI) calcd for C10H11BrOS
[M]+ 257.9714, found 257.9706.
2-((4-Methylthio)phenyl)-2-methyl-1,3-oxathiolane
(7k):
This
compound is obtained as colorless liquid by the reaction of 4’-
(methylthio)acetophenone (6k) with 2-mercaptoethanol (2) following the
general procedure for 7 and 8. Yield: 47%. 1H NMR (400 MHz, CDCl3): δ
1.88 (s, 3H), 2.45 (s, 3H), 3.02-3.07 (m, 1H), 3.16-3.22 (m, 1H), 3.96-
4.01 (m, 1H), 4.28-4.33 (m, 1H), 7.18-7.21 (m, 2H), 7.39-7.42 (m, 2H).
13C NMR (100MHz, CDCl3): δ 15.7, 32.0, 34.3, 70.5, 95.2, 12.4, 126.2,
137.2, 143.6. HRMS (EI) calcd for C11H14OS2 [M]+ 226.0486, found
226.0494.
2-(4-Iodophenyl)-2-methyl-1,3-oxathiolane (7d): This compound is
obtained as colorless liquid by the reaction of 4’-iodoacetophenone (6d)
with 2-mercaptoethanol (2) following the general procedure for 7 and 8.
Yield: 64%. 1H NMR (400 MHz, CDCl3): δ 1.87 (s, 3H), 3.04-3.08 (m, 1H),
3.18-3.24 (m, 1H), 3.96-4.01 (m, 1H), 4.30-4.35 (m, 1H), 7.23-7.26 (m,
1H), 7.62-7.66 (m, 1H). 13C NMR (100MHz, CDCl3): δ 32.1, 34.5, 70.7,
92.7, 95.1, 127.0, 137.2, 146.6. HRMS (EI) calcd for C10H11IOS [M]+
305.9576, found 305.9582.
2-(4-tert-Butylphenyl)-2-methyl-1,3-oxathiolane (7l): This compound is
obtained as white solid by the reaction of 4’-(tert-butyl)acetophenone (6l)
with 2-mercaptoethanol (2) following the general procedure for 7 and 8.
Yield: 51%. m.p.: 43.1 °C. 1H NMR (400 MHz, CDCl3): δ 1.30 (s, 9H),
1.90 (s, 3H), 3.05-3.09 (m, 1H), 3.17-3.23 (m, 1H), 4.00-4.06 (m, 1H),
4.30-4.35 (m, 1H), 7.32-7.34 (m, 1H), 7.39-7.42(m, 1H). 13C NMR
(100MHz, CDCl3): δ 31.3, 32.3, 34.3, 34.4, 70.6, 95.5, 124.5, 125.0,
143.6, 145.0. HRMS (EI) calcd for C14H20OS [M]+ 236.1235, found
236.1227.
2-(4-Fluorophenyl)-2-methyl-1,3-oxathiolane (7e): This compound is
obtained as colorless liquid by the reaction of 4’-fluoroacetophenone (6e)
with 2-mercaptoethanol (2) following the general procedure for 7 and 8.
Yield: 70%. 1H NMR (400 MHz, CDCl3): δ 1.87 (s, 3H), 3.02-3.08 (m, 1H),
3.17-3.22 (m, 1H), 3.96-4.01 (m, 1H), 4.28-4.33 (m, 1H), 6.95-7.00 (m,
2H), 7.44-7.48 (m, 2H). 13C NMR (100 MHz, CDCl3): δ 32.2, 34.3, 70.5,
95.0, 114.7 (d, J = 21.2 Hz), 126.7 (d, J = 8 Hz), 142.5 (d, J = 3 Hz),
161.8 (d, J = 244.4 Hz). 19F NMR (376 MHz, CDCl3): δ -117.1. HRMS
(EI) calcd for C10H11FOS [M]+ 198.0515, found 198.0506.
2-Methyl-2-(naphthalene-2-yl)-1,3-oxathiolane (7m): This compound is
obtained as colorless liquid by the reaction of 2-acetylnaphthalene (6m)
with 2-mercaptoethanol (2) following the general procedure for 7 and 8.
Yield: 514%. 1H NMR (400 MHz, CDCl3): δ 2.03 (s, 3H), 3.08-3.13 (m,
1H), 3.23-3.29 (m, 1H), 4.08-4.14 (m, 1H), 4.38-4.43 (m, 1H), 7.46-7.50
(m, 2H), 7.59-7.61 (m, 1H), 7.81-7.87 (m, 3H), 7.98-7.99 (m, 1H). 13C
NMR (100MHz, CDCl3): δ 32.1, 34.5, 70.8, 95.7, 122.9, 123.9, 125.9,
126.2, 127.5, 128.1, 128.2, 132.6, 132.9, 143.9. HRMS (EI) calcd for
C14H14OS [M]+ 230.0765, found 230.0762.
2-(2-Chlorophenyl)-2-methyl-1,3-oxathiolane (7f): This compound is
obtained as colorless liquid by the reaction of 2’-chloroacetophenone (6f)
with 2-mercaptoethanol (2) following the general procedure for 7 and 8.
Yield: 53%. 1H NMR (400 MHz, CDCl3): δ 1.91 (s, 3H), 2.84-2.89 (m, 1H),
3.01-3.08 (m, 1H), 3.87-3.93 (m, 1H), 4.28-4.33 (m, 1H), 7.04-7.15 (m,
2H), 7.26-7.28 (d, J = 8.0 Hz, 1H), 7.50-7.51 (d, J = 7.6 Hz, 1H). 13C
NMR (100MHz, CDCl3): δ 30.1, 33.9, 70.5, 93.5, 124.4, 126.7, 128.2,
131.0, 131.5, 143.5. HRMS (EI) calcd for C10H11ClOS [M]+ 214.0219,
found 214.0216.
(E)-2-Methyl-2-styryl-1,3-oxathiolane (7n):[23] This compound is
obtained as colorless liquid by the reaction of (E)-4-phenylbut-3-en-2-one
(6n) with 2-mercaptoethanol (2) following the general procedure for 7 and
2-Methyl-2-(m-tolyl)-1,3-oxathiolane (7g):[21] This compound is
obtained as colorless liquid by the reaction of 3’-methylacetophenone
(6g) with 2-mercaptoethanol (2) following the general procedure for 7 and
8. Yield: 53%. 1H NMR (400 MHz, CDCl3): δ 1.80 (s, 3H), 2.25 (s, 3H),
2.94-2.98 (m, 1H), 3.06-3.11 (m, 1H), 3.89-3.94 (m, 1H), 4.20-4.25 (m,
1H), 6.93-6.95 (d, J = 7.6 Hz, 1H), 7.08-7.12 (t, J = 7.6 Hz, 1H), 7.18-
1
8. Yield: 21%. H NMR (400 MHz, CDCl3): δ 1.81 (s, 3H), 3.12-3.17 (m,
2H), 4.14-4.17 (m, 1H), 4.23-4.27 (m, 1H), 6.30-6.34 (d, J = 15.6 Hz, 1H),
6.60-6.64 (d, J = 16.0 Hz, 1H), 7.22-7.24 (m, 1H), 7.28-7.32 (t, J = 7.4 Hz,
2H), 7.37-7.39 (d, J = 7.2 Hz, 2H). 13C NMR (100MHz, CDCl3): δ 28.8,
34.2, 70.8, 93.2, 126.6, 127.2, 127.6, 128.5, 133.6, 136.3.
8
This article is protected by copyright. All rights reserved.

10.1002/ejoc.202000218
European Journal of Organic Chemistry
FULL PAPER
2-Ethyl-2-phenyl-1,3-oxathiolane (7q): This compound is obtained as
colorless liquid by the reaction of propiophenone (6q) with 2-
mercaptoethanol (2) following the general procedure for 7 and 8. Yield:
72%. 1H NMR (400 MHz, CDCl3): δ 0.57-0.90 (t, J = 7.2 Hz, 3H), 2.09-
2.15 (t, J = 7.6 Hz, 2H), 2.98-3.03 (m, 1H), 3.09-3.15 (m, 1H), 3.88-3.94
(m, 1H), 4.30-4.35 (m, 1H), 7.19-7.23 (m, 1H), 7.28-7.32 (m, 2H), 7.42-
7.44 (m, 2H). 13C NMR (100MHz, CDCl3): δ 9.6, 33.9, 37.4, 70.6, 99.6,
125.5, 127.0, 127.9, 145.5. HRMS (EI) calcd for C11H14OS [M]+ 194.0766,
found 194.0769.
CDCl3): δ 24.9, 25.2, 33.1, 63.2, 84.5, 121.4, 128.8, 131.5, 142.6. HRMS
(EI) calcd for C11H13BrOS [M]+ 271.9871, found 271.9869.
2-(4-Iodophenyl)-2-methyl-1,3-oxathiane (8d): This compound is
obtained as white solid by the reaction of 4’-iodoacetophenone (6d) with
3-mercaptopropan-1-ol (4) following the general procedure for 7 and 8.
Yield: 47%. m.p.: 83.9 °C. 1H NMR (400 MHz, CDCl3): δ 1.57-1.63 (m,
1H), 1.66 (s, 3H), 1.92-2.02(m, 1H), 2.59-2.75 (m, 2H), 3.60-3.66 (m, 1H),
3.86-3.91 (m, 1H), 7.42-7.46 (m, 2H), 7.69-7.73 (m, 2H). 13C NMR
(100MHz, CDCl3): δ 25.0, 25.3, 33.2, 63.3, 84.7, 93.3, 129.2, 137.6,
143.4. HRMS (EI) calcd for C11H13IOS [M]+ 319.9732, found 319.9730.
2-(4-Chlorophenyl)-2-ethyl-1,3-oxathiolane (7r): This compound is
obtained as colorless liquid by the reaction of 4’-chloropropiophenone
(6r) with 2-mercaptoethanol (2) following the general procedure for 7 and
8. Yield: 60%. 1H NMR (400 MHz, CDCl3): δ 0.86-0.89 (t, J = 7.6 Hz, 3H),
2.07-2.12 (t, J = 7.2 Hz, 2H), 3.02-3.05(m, 1H), 3.11-3.15 (m, 1H), 3.87-
2-Methyl-2-(m-tolyl)-1,3-oxathiane (8e): This compound is obtained as
colorless liquid by the reaction of 3’-methylacetophenone (6g) with 3-
mercaptopropan-1-ol (4) following the general procedure for 7 and 8.
Yield: 38%. 1H NMR (400 MHz, CDCl3): δ 1.56-1.61 (m, 1H), 1.69 (s, 3H),
1.92-2.00 (m, 1H), 2.38 (s, 3H), 2.59-2.64 (m, 1H), 2.72-2.79 (m, 1H),
3.65-3.72 (m, 1H), 3.85-3.90 (m, 1H), 7.09 (d, J = 7.6 Hz, 1H), 7.27 (t, J =
7.6 Hz, 1H), 7.47-7.51 (m, 2H). 13C NMR (100MHz, CDCl3): δ 21.5, 25.1,
25.4, 33.2, 63.2, 85.2, 124.0, 127.5, 128.1, 128.4, 138.1, 143.4. HRMS
(EI) calcd for C12H16OS [M]+ 208.0922, found 208.0929.
3.93 (m, 1H),4.31-4.36 (m, 1H), 7.27-7.29 (m, 2H), 7.37-7.39 (m, 2H). 13
C
NMR (100MHz, CDCl3): δ 9.6, 34.0, 37.4, 70.7, 99.2, 127.1, 128.1, 132.9,
144.1. HRMS (EI) calcd for C11H13ClOS [M]+ 228.0375, found 228.0378.
2-(n-Hexyl)-2-methyl-1,3-oxathiolane (7s):[22] This compound is
obtained as colorless liquid by the reaction of octan-2-one (6s) with 2-
mercaptoethanol (2) following the general procedure for 7 and 8. Yield:
59%. 1H NMR (400 MHz, CDCl3): δ 0.80-0.83 (t, J = 6.8 Hz, 3H), 1.22-
1.28 (m, 6H), 1.31-1.39 (m, 2H), 1.50 (s, 3H), 1.71-1.77 (m, 2H), 2.92-
3.02 (m, 2H), 4.01-4.13 (m, 2H). 13C NMR (100MHz, CDCl3): δ 14.0, 22.5,
25.4, 28.8, 29.4, 31.7, 33.8, 43.3, 70.1, 95.3. HRMS (EI) calcd for
C10H20OS [M]+ 188.1235, found 188.1232.
2-Methyl-2-(naphthalene-2-yl)-1,3-oxathiane (8f): This compound is
obtained as white solid by the reaction of 2-acetylnaphthalene (6m) with
3-mercaptopropan-1-ol (4) following the general procedure for 7 and 8.
Yield: 32%. m.p.: 64.5 °C. 1H NMR (400 MHz, CDCl3): δ 1.54-1.60 (m,
1H), 1.81 (s, 3H), 1.97-2.07 (m, 1H), 2.63-2.68 (m, 1H), 2.80-2.87 (m,
1H), 3.66-3.73 (m, 1H), 3.92-3.96 (m, 1H), 7.49-7.52 (m, 2H), 7.75-7.78
(m, 1H), 7.84-7.91 (m, 3H), 8.29 (s, 1H). 13C NMR (100MHz, CDCl3): δ
25.1, 25.4, 33.3, 63.5, 85.4, 124.6, 126.0, 126.1, 126.6, 127.4, 128.2,
128.5, 132.7, 133.3, 140.8. HRMS (EI) calcd for C15H16OS [M]+ 244.0922,
found 244.0915.
1-Oxa-4-thiaspiro[4,5]decane (7t):[21] This compound is obtained as
colorless liquid by the reaction of cyclohexanone (6t) with 2-
mercaptoethanol (2) following the general procedure for 7 and 8. Yield:
61%. 1H NMR (400 MHz, CDCl3): δ 1.22-1.29 (m, 1H), 1.35-1.44 (m, 3H),
1.65-1.84 (m, 6H), 2.93-2.96 (t, J = 6.0 Hz, 2H), 4.07-4.10 (t, J = 5.8 Hz,
2H). 13C NMR (100MHz, CDCl3): δ 24.6, 24.8, 32.7, 39.7, 69.2, 96.2.
2-Ethyl-2-phenyl-1,3-oxathiane (8g): This compound is obtained as
colorless liquid by the reaction of 3’-methylacetophenone (6g) with 3-
mercaptopropan-1-ol (4) following the general procedure for 7 and 8.
Ethyl 2-(2-methyl-1,3-oxathiolan-2-yl)acetate (7u): This compound is
obtained as pale yellow liquid by the reaction of ethylacetoacetate (6u)
with 2-mercaptoethanol (2) following the general procedure for 7 and 8.
Yield: 21%. 1H NMR (400 MHz, CDCl3): δ 1.28 (t, J = 7.0 Hz, 3H), 1.75 (s,
1
Yield: 45%. H NMR (400 MHz, CDCl3): δ 0.64 (t, J =7.6 Hz, 3H), 1.44-
1.48 (m, 1H), 1.81-1.93 (m, 3H), 2.48-2.63 (m, 2H), 3.56-3.62 (m, 1H),
3.72-3.76 (m, 1H), 7.14-7.18 (m, 1H), 7.27 (t, J =7.6 Hz, 2H), 7.53-7.55
(m, 2H). 13C NMR (100MHz, CDCl3): δ 7.8, 24.8, 25.4, 38.0, 62.8, 88.9,
127.1, 127.7, 128.2, 141.5. HRMS (EI) calcd for C12H16OS [M]+ 208.0922,
found 208.0929.
3H), 2.89 (q, J = 14.5 Hz, 2H), 3.06-3.13 (m, 2H), 4.14-4.21 (m, 4H). 13
C
NMR (100MHz, CDCl3): δ 14.1, 29.1, 33.8, 48.0, 60.5, 70.3, 91.4, 169.7.
2-Methyl-2-phenyl-1,3-oxathiane (8a): This compound is obtained as
colorless liquid by the reaction of acetophenone (6a) with 3-
mercaptopropan-1-ol (4) following the general procedure for 7 and 8.
Yield: 49%.1H NMR (400 MHz, CDCl3): δ 1.44-1.50 (m, 1H), 1.59 (s, 3H),
1.81-1.91 (m, 1H), 2.47-2.53 (m, 1H), 2.60-2.67 (m, 1H), 3.53-3.60 (m,
1H), 3.75-3.80 (m, 1H), 7.15-7.19 (m, 1H), 7.26-7.30 (m, 2H), 7.58-7.61
(m, 2H). 13C NMR (100MHz, CDCl3): δ 25.1, 25.3, 33.3, 63.2, 85.1, 126.9,
127.3, 128.4, 143.4. HRMS (EI) calcd for C11H14OS [M]+ 194.0765, found
194.0774.
2-(n-Hexyl)-2-methyl-1,3-oxathiane (8h): This compound is obtained as
colorless liquid by the reaction of octan-2-one (6s) with 3-
mercaptopropan-1-ol (4) following the general procedure for 7 and 8.
Yield: 41%. 1H NMR (400 MHz, CDCl3): δ 0.80-0.83 (m, 3H), 1.23-1.29
(m, 6H), 1.30-1.38 (m, 2H), 1.48 (s, 3H), 1.65-1.74 (m, 3H), 1.84-1.91 (m,
1H), 2.75-2.84 (m, 2H), 3.72-3.83 (m, 2H). 13C NMR (100MHz, CDCl3): δ
13.9, 22.4, 23.3, 24.2, 25.2, 25.5, 29.3, 31.6, 40.7, 61.6, 81.5. HRMS (EI)
calcd for C11H22OS [M]+ 202.1391, found 202.1397.
2-(4-Chlorophenyl)-2-methyl-1,3-oxathiane (8b): This compound is
obtained as colorless liquid by the reaction of 4’-chloroacetophenone
(6b) with 3-mercaptopropan-1-ol (4) following the general procedure for 7
and 8. Yield: 51%. 1H NMR (400 MHz, CDCl3): δ 1.47-1.53 (m, 1H), 1.57
(s, 3H), 1.82-1.91 (m, 1H), 2.49-2.65 (m, 2H), 3.49-3.56 (m, 1H), 3.76-
3.81 (m, 1H), 7.22-7.26 (m, 2H), 7.51-7.55 (m, 2H). 13C NMR (100MHz,
CDCl3): δ 25.0, 25.3, 33.1, 63.2, 84.5, 128.4, 128.6, 133.1, 142.1. HRMS
(EI) calcd for C11H13ClOS [M]+ 228.0375, found 228.0382.
1-Oxa-5-thiaspiro[5,5]undecane (8i): This compound is obtained as
colorless liquid by the reaction of cyclohexanone (6t) with 3-
mercaptopropan-1-ol (4) following the general procedure for 7 and 8.
Yield: 40%. 1H NMR (400 MHz, CDCl3): δ 1.33-1.57 (m, 6H), 1.72-1.83
(m, 4H), 1.90-1.95 (m, 2H), 2.76 (t, J =6.0 Hz, 2H), 3.80 (t, J =5.6 Hz, 2H).
13C NMR (100MHz, CDCl3): δ 22.0, 23.7, 25.6, 36.5, 60.9, 81.6. HRMS
(EI) calcd for C9H16OS [M]+ 172.0922, found 172.0927.
Benzaldehyde didodecyldithioacetal (10):[24] This compound is
obtained as colorless liquid by the reaction of benzaldehyde (1.0 mmol)
with dodecane-1-thiol (2.2 equiv) following the general procedure for 3
and 5. Yield: 76%.1H NMR (400 MHz, CDCl3): δ 0.91 (t, J =6.8 Hz, 6H),
1.28-1.38 (m, 36H), 1.53-1.61 (m, 4H), 2.49-2.64 (m, 4H), 4.90 (s, 1H),
7.26 (t, J = 7.8 Hz, 1H), 7.33 (t, J = 8.0 Hz, 2H), 7.45-7.47 (m, 2H). 13C
NMR (100MHz, CDCl3): δ 14.1, 22.7, 28.9, 29.1, 29.2, 29.3, 29.4, 29.5,
29.6, 31.9, 32.2, 53.1, 127.6, 127.7, 128.4, 140.6.
2-(4-Bromophenyl)-2-methyl-1,3-oxathiane (8c): This compound is
obtained as colorless liquid by the reaction of 4’-bromoacetophenone
(6c) with 3-mercaptopropan-1-ol (4) following the general procedure for 7
and 8. Yield: 48%. 1H NMR (400 MHz, CDCl3): δ 1.47-1.53 (m, 1H), 1.57
(s, 3H), 1.82-1.91 (m, 1H), 2.49-2.65 (m, 2H), 3.49-3.56 (m, 1H), 3.76-
3.81 (m, 1H), 7.38-7.42 (m, 2H), 7.46-7.49 (m, 2H). 13C NMR (100MHz,
9
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10.1002/ejoc.202000218
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Acknowledgements
This work was financially supported by the Ministry of Science
and Technology, Taiwan (Most 107-2113-M-005-019-MY3),
National Chung Hsing University, Research Center for
Sustainable Energy and Nanotechnology (RCSEN), and the
“Innovation and Development Center of Sustainable Agriculture
(IDCSA)” from The Featured Areas Research Center Program
within the framework of the Higher Education Sprout Project by
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Entry for the Table of Contents
Photoredox catalysis: A visible-light-promoted oxathiacetalization of aldehydes and ketones with 2-mercaptoethanol and 3-
mercaptopropan-1-ol in the presence of eosin Y as catalyst is described leading to the formation of 1,3-oxathiolanes and 1,3-
oxathianes at ambient temperature and under metal-free conditions. The solvent is playing vital role in the protection of carbonyl
compounds with mercaptoalcohol.
11
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