Reaction of 2-alkoxypropenals with 2-mercaptoethanol

Article abstract of DOI:10.1023/A:1013909715161

The reaction between 2-alkoxypropenals and 2-mercaptoethanol was studied at 20 and 60°C by means of ¹HNMR and GC-MS methods. Under kinetically controlled conditions (20°C, 7-30 days) with no catalyst the addition of 2-mercaptoethanol to 2-alkox

Full text of DOI:10.1023/A:1013909715161

Russian Journal of Organic Chemistry, Vol. 37, No. 12, 2001, pp. 1693 1699. Translated from Zhurnal Organicheskoi Khimii, Vol. 37, No. 12, 2001,
pp. 1774 1780.
Original Russian Text Copyright
2001 by Keiko, Funtikova, Stepanova, Chuvashev, Albanov, Voronkov.
Reaction of 2-Alkoxypropenals with 2-Mercaptoethanol*
N. A. Keiko, E. A. Funtikova, L. G. Stepanova, Yu. A. Chuvashev,
A. I. Albanov, and M. G. Voronkov
Faworsky Irkutsk Institute of Chemistry, Siberian Division, Russian Academy of Sciences, Irkutsk, 664033 Russia
Received January 29, 2001
Abstract The reaction between 2-alkoxypropenals and 2-mercaptoethanol was studied at 20 and 60 C by
1
means of H NMR and GC-MS methods. Under kinetically controlled conditions (20 C, 7 30 days) with no
catalyst the addition of 2-mercaptoethanol to 2-alkoxypropenals occurs along Markownikoff rule. The arising
2 -hydroxyethylthio-2-alkoxypropanal undergoes isomerization into the 2-hydroxy-3-alkoxy-3-methyl-1,4-
oxathiane that at heating in the presence of catalytic amounts of acids is converted into 2-methyl-2-formyl-
1,3-oxathiolane. The reaction of 2-alkoxypropenals with 2-mercaptoethanol at heating (60 C, 3 h) in the
presence of acids affords 2-methyl-2,2 -bi(1,3-oxathiolane) even at 2-mercaptoethanol deficit. At the
double excess of the latter the 2-methyl-2,2 -bi(1,3-oxathiolane) was obtained in quantitative yield. The
presumable schemes of conversion of 2-hydroxy-3-alkoxy-3-methyl-1,4-oxathiane into 2-methyl-2-formyl-
1,3-oxathiolane and 2-acetyl-1,3-oxathiolane are discussed.
The reactions of mercapto groups of glutathione
[1] and cysteine [2] with , -unsaturated aldehydes
govern the biological activity of the latter.
a bifunctional reagent, 2-mercaptoethanol, in the
neutral and acidic media. If the substrate molecule is
regarded as an -formyl-substituted vinyl ether then
the expected reaction would be addition of the
sulfhydryl group along Markownikoff rule as in reac-
tions with thiols [3] and alcohols [6] (path a).
However further route of the reaction remained
unclear. If the system under study is regarded as an
acryl one then it is presumable that occurs 1,2-addi-
tion [7, 8, 9] in the presence of acids (path b) or
1,4-addition [10] in the absence of a catalyst (path c);
the latter direction is characteristic of unsubstituted
acrolein in reactions with thiols [7, 10], dithiols [10],
or diols [11].
2-Alkoxypropenals combine in their structure
the fragments of the vinyl ether and the acrolein.
Depending on a reagent or reaction conditions this
highly reactive bonds system with electron-donor
and electron-acceptor substituents can react in
three directions: Markownikoff addition [3],
Michael addition [4], and addition to the carbonyl
group [4, 5].
The target of this study was elucidation of the
regiodirection in reaction of 2-alkoxypropenals with
*
The study was carried out under financial support from the Russian Foundation for Basic Research, grant no. 99-03-33057.
1070-4280/01/3712-1693$25.00 2001 MAIK Nauka/Interperiodica

1694
KEIKO et al.
The reaction was studied by an example of 2-eth-
assumption that in a small amount arises a bicyclic
methylglyoxal acetal, 2-methyl-2,2 -bi(1,3-oxathio-
lane) (V), whose ketal fragment suffers hydrolysis
under the reaction conditions (path d). In the absence
of an acid catalyst a hydrolysis of the vinyloxy group
of the initial substrate I and formation of thioacetal
at the aldehyde group to afford thioacetal VI is less
probable (path e). An intramolecular rearrangement
of semiacetal III into acetal VI along the scheme
given above is also presumable.
oxypropenal. The reaction progress was monitored
1
by H NMR and GC-MS methods. In the absence of
catalyst at room temperature the reaction of 2-ethoxy-
propenal (I) and 2-mercaptoethanol occurs with heat
evolution. Therewith in the first stage the sulfhydryl
group of the reagent adds to the double bond of the
substrate along the Markownikoff rule. Then follows
an intramolecular addition of the hydroxy group of
intermediate II to the carbonyl group yielding
2-hydroxy-3-methyl-3-ethoxy-1,4-oxathiane (III).
At cautious evaporation from the reaction mixture
of the solvent (ether, benzene) or at keeping the
reaction mixture without solvent for 6 7 days semi-
acetal III crystallized. Therefore we were able to
purify it and to have good elemental analyses. In the
1H NMR spectrum of the crystalline substance as a
rule appear signals corresponding to one of the dia-
stereomers. The thermal stability of this cyclic
semiacetal was sufficiently high to be heated to 100 C
(in DMSO) for 1 min in the NMR tube; no changes
in the spectrum was observed after such treatment.
However at heating in benzene at 70 C for 2 h one
diastereomer to 60% is converted into the other
diastereomeric form.
This sequence of stages is evidenced by dis-
appearance in the IR spectrum of the reaction mixture
of the absorption bands belonging to 2-ethoxy-
1
propenal (
1610 and
1710 cm ) and
C= C
C= O
appearance of a single broad band of the OH group
1
(3350 cm ). The structure of cyclic semiacetal III
1
was also confirmed by the data of H NMR spectrum
1
and GC-MS. According to H NMR semiacetal III
arises in two diastereomeric forms in the ratio from
1: 14 to 3: 1 depending on the preparation conditions
(see Experimental). The semiacetal III formation to
complete consumption of the initial reactants in the
absence of a catalyst takes two months at 20 C and
5 h at 60 C. Therewith in the cold semiacetal III
forms regiospecifically and diastereoselectively, and
at heating its content in the reaction mixture in 3 h
amounts to 60% (see the table, run no. 2a) and
further its content decreases presumably due to the
thermal isomerization into semithioketal II that
subsequently is converted through intramolecular
trans-acetalization into a cyclic semithioketal of
methylglyoxal, 2-methyl-2-formyl-1,3-oxathiolane
(IV). Besides at heating is also observed formation
of an admixture of isomeric methylglyoxal thioacetal,
As should be expected at vacuum distillation semi-
acetal III is decomposed yielding 2-hydroxyethylthio-
1
2-ethoxypropanal (II). It is evidenced by H NMR
spectrum of the freshly distilled fraction. In the
spectrum besides the weak signals of semiacetal III
appears a signal with the chemical shift 9.65 ppm
not observed in the other compounds obtained in this
series of transformations; the signals inherent to the
cyclic conformations of compound III (groups SCH2
and OCH2) nearly completely disappear, and are
present the signals from the group OCH2CH2S sub-
jected to free rotation (2.8 m CSH2 and 3.7 m OCH2).
In the IR spectrum is observed an absorption band of
1
2-acetyl-1,3-oxathiolane (VI). According to H NMR
data after 5 h of heating the reaction mixture contains
compounds III, IV, and VI in 3: 7: 1 ratio. The
formation of thioacetal VI may be rationalized by
1
the carbonyl group (1740 cm ) and a strong band
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 12 2001

REACTION OF 2-ALKOXYPROPENALS WITH 2-MERCAPTOETHANOL
Reaction of 2-mercaptoethanol with 2-ethoxypropenal at equimolar ratio
1695
Run
no.
Solvent
(molecular
sieves)
Reaction
time
Reaction products and their ratio in
the reaction mixture, mol%, (1H NMR data)
Catalyst
T,
C
III
IV
V
VI
1
Benzene
20
60 days
Quantitative
2a
2b
3
Benzene
Benzene
60
60
20
20
3 h
5 h
4 days
24 h
58
27
70
80
4
64
30
15
1
9
4
CF3COOH
(5 mol%)
p-TsOH
(1 mol%)
p-TsOH
(5 mol%)
p-TsOH
(7 mol%)
p-TsOH
Benzene
Ether
5
20
50
20
60
5 h
82
5
15
6
Ether
3 h
80
7a
8a
Ether
mol. sieves 4A
Benzene
7 days
2 h
Quantitative
Quantitative
(5 mol%)
a
Double (molar) excess of 2-mercaptoethanol.
1
of associated OH group (3430 cm ). Presumably the
GC-MS method also registered isomer II as the main
peak with the molecular weight 178 (90% of the
fraction) since the temperature in the vaporizer and
the column of the mass spectrometer is sufficiently
high (250 C and 70 280 C respectively).
tionally occur due to intramolecular rearrangements
of acetal III depicted in the scheme.
The mechanism similar to the path g was previous-
ly assumed to explain the formation of cyclic di-
thioketal of methylglyoxal VII in the reaction of
alkylglyoxals with ethanedithiol proceeding via
intermediate semiketal (A) [11]. The formation of the
hypothetical intermediate (A) was not proved spectral-
ly or by its isolation.
The heating of semiacetal III to 100 C in DMSO
in the presence of 5 mol% of p-TsOH within 5 min
resulted in conversion of compound III into acetals
IV and VI at the ratio (III): (IV): (VI) of 1: 4: 1. The
similar high yield of ketal IV (67%) was obtained at
heating semiacetal III to 60 C for 3 h in the presence
of p-TsOH. The latter two observations suggest that
alongside the previously mentioned possible paths
leading to monocyclic acetals IV and VI may addi-
In our series of conversions that undergoes
methylglyoxal semiacetal III in the absence of
Bro/ nsted acids their role is apparently played by the
sulfhydryl group of 2-mercaptoethanol. This assump-
tion was proved experimentally. The heating of the
reaction mixture at 60 C for 5 h (see the table, run
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 12 2001

1696
KEIKO et al.
no. 2b) results in reaction products among which
acetal IV amounts to 64%. The similar heating of
an individual diastereomerically pure semiacetal III
led only to its isomerization to 66% into the other
diastereomer.
compounds I and II, and methylglyoxal bisacetal (V)
becomes the principal reaction product even at deficit
of 2-mercaptoethanol in the reaction mixture.
To optimize the yield of bisacetal V we carried out
the reaction with double molar excess of 2-mercapto-
ethanol with respect to 2-ethoxyacrolein in the
presence of p-TsOH (7 mol%) at 20 C. According to
1H NMR and GC-MS data after 7 days the only reac-
tion product was bisacetal V, yield quantitative (see
the table, run no. 17). At 60 C the same result was
attained in 2 h (run no. 8).
To increase the yield of thioketal IV and accelerate
its formation we studied catalysis by acids of the
reaction between 2-mercaptoethanol and 2-ethoxy-
propenal. This reaction in the presence of trifluoro-
acetic acid (5 mol%) in benzene at 20 C in 24 h gives
rise to a mixture of acetals III and IV in 5: 1 ratio at
complete consumption of the initial compounds. The
reaction catalyzed by p-toluenesulfonic acid (p-TsOH)
(1 mol%) at 20 C in 5 h afforded crystalline semi-
acetal III in 72% yield. The mother liquor according
to GC-MS data contained equal weights of semiacetal
III and ketal IV. The yield of the latter same as in the
preceding experiment was around 15%. The attempt
to separate the products by rectification furnished
ketal IV in 7% yield and a fraction containing
according to GC-MS data two isomers of molecular
weight 178. They are probably isomers II and III.
Overall yield amounts to 65%.
Thus in the reaction under investigation 2-ethoxy-
propenal behaved as a vinyl ether with an -carbonyl
group and as a chemical equivalent of methylglyoxal.
The study of methylglyoxal thioacetals as models of
natural analogs is especially interesting for the
methylglyoxal is one of metabolites of glyoxalase
system and is widely spread in the cells of living
organisms, in particular, it reacts with the sulfhydryl
group of glutathione and takes part in controlling the
cell growth [12].
EXPERIMENTAL
On heating equimolar mixture of the initial
reagents to 50 C for 3 h in the presence of p-TsOH
(5 mol%) without solvent arose a mixture of products
where by GC-MS data the main component (80% of
the mixture) was 2-methyl-2,2 -bi(1,3-oxathiolane)
(V), and the ratio thereof with its three isomers was
37: 5: 4: 3. These are presumable diastereomers
pairs of structures V and VIII.
1H NMR spectra were registered on spectrometer
Bruker DPX-400 (400 MHz) from solutions in
DMSO and CDCl3, internal reference HMDS. IR
spectra were measured on spectrometer Specord
75IR. GC-MS measurements were carried out on
Hewlett-Packard HP 5971A instrument (electron
impact at 70 eV, mass-selective detector), chromato-
graph HP-5890, column Ultra-2 (stationary phase 5%
of phenylmethylsilicone), vaporizer temperature
250 C, oven temperature 70 280 C, heating rate
On the chromatogram among the impurities is
clearly seen the methylglyoxal diethylacetal. It can
be generated by hydrolytic decomposition of the
vinyloxy group of substrate I or of the ketal fragment
in thioketal II followed by acetal formation at the
aldehyde group with the liberated ethanol. Thus at
heating the reaction mixture in the presence of acids
into the reaction are involved the carbonyl groups of
1
20 deg min .
Preparation of 2-hydroxy-3-methyl-1,4-oxathiane
(III) at 20 C in benzene (Procedure A). To a solu-
tion of 0.5 ml (4.85 mmol) of 2-ethoxypropenal in
1 ml of benzene was added 0.34 ml (4.85 mmol) of
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 12 2001

REACTION OF 2-ALKOXYPROPENALS WITH 2-MERCAPTOETHANOL
1697
3
2-mercaptoethanol. The mixture was left standing at
20 C till complete consumption of the initial com-
pounds (monitoring by H NMR and GC-MS). After
standing for 2 months from the mixture precipitated
crystals. The crystalline compound is one of dia-
stereomers of semiacetal III, the mother liquor
contained a mixture of diastereomers III in 1: 3 ratio
(see spectra below). Yield quantitative.
DMSO, , ppm: 1.15 t [3H, CH3(Et), J 7.0 Hz],
2
1.26 s (3H, CH3), 2.19 d.t [1H, SCH2 (He), Ja e
13.4, J 2.1 Hz], 2.76 d.d.d [1H, SCH2 (Ha), Ja e
13.4, Ja a 11.9, Ja e 3.2 Hz], 3.41 and 3.70 two d.q
1
3
2
2
3
2
3
[2H, OCH2(OEt), JAB 11.0, J 7.1 Hz], 3.76 t.d
2
3
[1H, CH2O (Ha), Ja e
=
3Ja a = 11.8 Hz, Ja e
2
2.1 Hz], 4.15 d.d.d [1H, CH2O (He), Je a 11.8, Je a
3
3.3, Je e 2.2 Hz), 4.59 d (1H, C_HOH, JCH OH
Reaction of 2-ethoxypropenal with 2-mercapto-
ethanol at heating. (Procedure B). To a solution of
2 ml (19.5 mmol) of 2-ethoxypropenal in 6 ml of
benzene was added 1.36 ml (19.5 mmol) of
2-mercaptoethanol. The mixture was heated to 60 C
8.2 Hz), 6.14 d (1H, OH_ , 3J 8.2 Hz).
Conversion of semiacetal III into ketal IV at
heating in the presence of acids. The solution in
DMSO of crystalline semiacetal III prepared along
procedure B was heated for 5 min in an NMR tube in
the presence of 5 mol% of p-TsOH. According to the
1H NMR spectrum in the resulting solution the ratio
of compounds III:IV:VI = 1: 4: 1. The following
1
for 3 h. As showed H NMR spectrum, after 3 h in
the mixture were still present the initial compounds,
and the reaction products III, IV, and VI were in the
ratio 58: 4: 1. The heating to 60 C was continued
for 2 h more, the initial compounds were totally
consumed, and the products were present in the ratio
(III): (IV): (VI) = 3: 7: 1. After evaporation of
benzene in 7 days from the reaction mixture was
isolated 0.81 g (23%) of colorless needle-like crystals
of compound III as a pure diastereomer, mp 102 C.
1H NMR spectrum, DMSO, , ppm: 1.16 s [3H,
CH3(Et), J 7.0 Hz], 1.29 s (3H, CH3), 2.23 d.d.d
1
signals in the H NMR spectrum in DMSO were
assigned to compound VI, , ppm: 2.16 s (3H, CH3)
and 5.22 s (1H, OCHS); in CDCl3, , ppm: 2.18 s
(3H, CH3CO) and 5.38 s. (1H, OCHS); the OCH2 and
SCH2 signals are overlapped by stronger resonances
of isomer IV. Mass spectrum, m/z (Irel, %): 132 (3)
[M]+ , 89 (57) [M CH3CO]+ , 61 (90), 45 (65), 43
(100) [CH3CO]+ . The spectra of isomer IV are given
below.
3
3
[1H, SCH2 (He), JAB 13.2, Je a 2.3, Je 3e 3.1 Hz],
2
2.8 d.d.d [1H, SCH2 (Ha), JAB 13.2, Ja a 11.3,
Reaction of 2-ethoxypropenal (I) with 2-mer-
captoethanol without solvent. To 3.59g (35.9mmol)
of aldehyde I was added 2.51 ml (35.9 mmol) of
2-mercaptoethanol. The reaction mixture was heated
to 50 C. After 12 days the vacuum distillation of the
reaction mixture afforded 2.2 g (yield 35%) of the
fraction with bp 98 101 C (1 mm Hg), n2D0 1.5139.
According to GC-MS data the fraction contained 70%
of compound with molecular weight M 178. Mass
3Je a 3.1 Hz), 3.50 and 3.73 two d.q [2H, OCH2(Et),
3
2JAB 9.15, J 7.0 Hz], 3.61 d.t [1H, CH2O (He),
3
3
3Je a 11.5, Je e 3.1, Je3 a 3.1 Hz], 4.1 t.d [1H,
2
3
CH2O (Ha), Ja e 11.5, Ja a 11.3, Ja e 2.3 Hz],
4.55 d (1H, C_HOH, J 5.2 Hz), 6.48 d (1H, CHO_H,
3
3J 5.2 Hz).13C NMR spectrum (DMSO), C, ppm:
16.16 [CH3(Et)], 22.25 (CH3C), 24.51 (SCH2), 57.18
and 58.51 (OCH2), 82.88 (SCO), 93.84 (OCO). Mass
spectrum, m/z (Irel, %): 178 (1) [M]+ , 151
(1), 149 (19) [M CHO]+ , 133 (3) [M OEt]+ , 105
(64), 104 (49) [M CHO OEt]+ , 89 (9), 77 (11)
spectrum, m/z (Irel, %): 178 (1) [M]+ , 150 (2)
+
+
[M CH2CH2] , 132 (1) [M EtOH] , 103 (32)
[M CHO EtOH]+ , 85 (9), 75 (25), 72 (22), 61 (52),
59 (26), 45 (58) [EtO]+ , 29 (100) [CHO]+ . The
molecular weight and the fragmentation pattern cor-
respond to 2 -hydroxyethylthio-2-ethoxypropanal (II).
In the IR spectrum of the compound (from thin film)
[SCH2CH2OH] , 61 (51), 43 (100) [CH3CO]+.
+
Found, %: C 47.22; H 8.07; S 18.23. C7H12O3S.
Calculated, %: C 47.19; H 7.87; S 17.98.
1
were observed absorption bands at 3440 cm (OH),
1
1
1
The crystals obtained in this run were dissolved in
DMSO, and the solution was heated in the NMR tube
1710 cm (CHO), 1080 cm (C O C). H NMR
spectrum (CDCl3), , ppm: 1.37 s (3H, CH3), 9.65 s
(1H, CHO), 2.8 m (SCH2), 3.68 m (OCH2), are
present poorly resolved signals from EtO group.
1
to 100 C for 1 min; no changes in the H NMR
spectrum appeared after heating.
The benzene solution of these crystals was heated
to 60 70 C for 2 h. On evaporating the solution the
1H NMR spectrum revealed the presence of two dia-
stereomers of compound III in 1: 2 ratio, and the new
diastereomer prevailed. Its 1H NMR spectrum,
Reaction of 2-ethoxypropenal (I) with 2-mer-
captoethanol in the presence of acids. (a) In the
presence of CF3COOH. To a solution of 0.5 ml
(4.85 mmol) of 2-ethoxypropenal in 3 ml of benzene
was added 27 mg (5mol%) of CF3COOH and 0.34 ml
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 37 No. 12 2001

1698
KEIKO et al.
spectrum (CDCl3), , ppm: 1.71 s (3H, CH3);
(4.85 mmol) of 2-mercaptoethanol. The mixture self-
heated to 30 C. After keeping the mixture for 24 h
at 20 C according to H NMR data the yield of semi-
acetal III was 80%, that of 2-methyl-2-formyl-1,3-
oxathiolane (IV) 15%.
2
3
3
2.59 d.d.d (2H, SCH2, J 13.5, J 7.0, J 2.7 Hz),
1
2
3
3
2.84 d.d.d (2H, SCH2, J 13.5, J 7.0, J 3.1 Hz),
2
3
3.96 and 4.30 two d.d.d (4H, OCH2, J 12.0, J 7.0,
3J 3.1 Hz); 3.81 s (1H, CH). According to GC-MS
the substance contained two diastereomers of
molecular weight 192 in 95: 5 ratio. Mass spectrum
(b) In the presence of p-TsOH. To a solution of
4.94 ml (49 mmol) of 2-ethoxypropenal in 20 ml of
anhydrous ether was added 0.42 g (5 mol%) of
p-TsOH and 3.96 ml (49 mmol) of 2-mercaptoethanol.
The mixture self-heated to 30 C. After 5 h at 20 C
precipitated crystals of semiacetal III. They were
filtered off and dried in a vacuum. They weighed
1.65 g. The evaporation of the mother liquor
provided more 4.7 g of compound III crystals, over-
all yield 72%. In the IR spectrum of the crystals
(pelleted with KBr) the absorption bands of C=O and
C=C groups were lacking, and was observed a
of the major diastereomer, m/z (Irel, %): 192(7) [M]+ ,
+
+
164 (1) [M CH2CH2] , 116 (3) [M 2(CH2)2] , 103
+
+
(5) [CH3 CSCH2CH2O] , 88 (11) [CSCH2CH2O] ,
76 (4), 61 (12) [SCHO]+ , 45 (32), 43 (100)
+
[CH3CO] .
(b) At heating. To a solution of 0.24 g (5 mol%)
of p-TsOH in benzene was added 2 ml (28.2 mmol)
of 2-mercaptoethanol and 1.5 ml (14.1 mmol) of
2-ethoxypropenal. The reaction occurred with heat
evolution (up to 60 C). Then the reaction mixture
was heated to 80 C for 2 h. According to GC-MS and
1H NMR data the only product in solution was bi-
cyclic acetal V. In 1 h the mixture separated in two
layers. The bottom layer was removed. After neutra-
lization with potassium carbonate in the upper
benzene layer began crystals formation. The crystals
according to 1H NMR spectrum consist of one
diastereomer of bicyclic compound V, mp 78 C.
1H NMR spectrum (DMSO), , ppm: 1.58 s (3H,
1
strong narrow band at 3330 cm with a shoulder
1
1
at 3340 cm . According to H NMR data the dia-
stereoisomer excess in the sample of compound III
obtained was 80%.
The distillation of the mother liquor after neutra-
lization with potassium carbonate provided the frac-
tion of 2-methyl-2-formyl-1,3-oxathiolane (IV) , bp
44 C (2 mm Hg), n2D0 1.4917. 1H NMR spectrum
(CDCl3), , ppm: 1.67 s (3H, CH3); 3.11 and
2
3
CH3); 2.6 and 2.76 d.d.d (2H, SCH2, J 13.3, J 7.0,
2
2
3
3J 2.9 Hz), 2.76 d.d.d (2H, SCH2, J 13.3, J 7.2,
3.17 q.t (q AB, split in t) (2H, CH2S, J 10.35,
3JSH -CH O 5.65, JSH
6.17 Hz); 4.30 and
d.d.d (2H, CH2O, J 9.2, J 5.65, J 6.1 Hz);
3
2
3
3J 2.9 Hz), 3.84 d.d.d (2H, OCH2, J 12.1, J 7.0,
CH2O
2
a
2
c
3J 2.9 Hz); 3.99 s (1H, CH); 4.15 d.d.d (2H, OCH2,
3
3
4.33
2J 12.1, J 7.2, J 2.9 Hz). Found, %: C 44.28;
H 6.27; S 33.96. C7H12O2S2. Calculated, %: C
43.72; H 6.29; S 33.96.
3
3
9.19 s (1H, CHO). Mass spectrum, m/z (Irel, %):
103 (29) [M CHO]+ , 61 (11), 59 (34), 43 (100)
+
[CH3CO] . Found, %: C 45.07; H 6.24; S 23.90.
C5H8O2S. Calculated, %: C 45.45; H 6.05; S 24.26.
REFERENCES
Reaction of 2-ethoxypropenal with equimolar
amount of 2-mercaptoethanol at heating. To 1 ml
(9.7 mmol) of 2-ethoxypropenal was added 83 mg
(5 mol%) of p-TsOH and 0.68 ml (9.7 mmol) of
2-mercaptoethanol. The reaction mixture was heated
to 50 C for 3 h. According to GC-MS data the
content in the mixture of four isomers of molecular
weight 192 amounted to 80%, their ratio was
37: 5: 4: 3.
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calcined molecular sieves 4A. After standing for
1
7 days at 20 C according to the data of H and
GC-MS the reaction mixture was a solution of
2-methyl-2,2 -bi(1,3-oxathiolane) (V). 1H NMR
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REACTION OF 2-ALKOXYPROPENALS WITH 2-MERCAPTOETHANOL
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