Rapid and convenient thioester synthesis under phase-transfer catalysis conditions

Article abstract of DOI:10.1080/10426501003713072

Various thioesters were obtained through an efficient phase-transfer catalysis method, by treating several thiophenols with different acyl chlorides, in a biphasic system composed of 10% aqueous NaOH and dichloromethane in the presence of tetrabutylammonium chloride. The thiolation reaction was complete in only 5 minutes, at 0C. Taylor & Francis Group, LLC.

Full text of DOI:10.1080/10426501003713072

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Rapid and Convenient Thioester
Synthesis Under Phase-Transfer Catalysis
Conditions
Cristian Simion a , Iwao Hashimoto b , Yoshiharu Mitoma c , Alina
Marieta Simion a & Naoyoshi Egashira c
a Department of Organic Chemistry , “Politehnica” University of
Bucharest , Bucharest, Romania
b Department of Material Science , Wakayama National College of
Technology , Goboh City, Wakayama, Japan
c Department of Environmental Sciences , Faculty of Life and
Environmental Sciences, Prefectural University of Hiroshima ,
Shobara City, Hiroshima, Japan
Published online: 19 Nov 2010.
To cite this article: Cristian Simion , Iwao Hashimoto , Yoshiharu Mitoma , Alina Marieta Simion &
Naoyoshi Egashira (2010) Rapid and Convenient Thioester Synthesis Under Phase-Transfer Catalysis
Conditions, Phosphorus, Sulfur, and Silicon and the Related Elements, 185:12, 2480-2488, DOI:
10.1080/10426501003713072
To link to this article: http://dx.doi.org/10.1080/10426501003713072
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Phosphorus, Sulfur, and Silicon, 185:2480–2488, 2010
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426501003713072
RAPID AND CONVENIENT THIOESTER SYNTHESIS
UNDER PHASE-TRANSFER CATALYSIS CONDITIONS
Cristian Simion,1 Iwao Hashimoto,2 Yoshiharu Mitoma,3
Alina Marieta Simion,1 and Naoyoshi Egashira3
1Department of Organic Chemistry, “Politehnica” University of Bucharest,
Bucharest, Romania
2Department of Material Science, Wakayama National College of Technology,
Goboh City, Wakayama, Japan
3Department of Environmental Sciences, Faculty of Life and Environmental
Sciences, Prefectural University of Hiroshima, Shobara City, Hiroshima, Japan
Various thioesters were obtained through an efficient phase-transfer catalysis method, by
treating several thiophenols with different acyl chlorides, in a biphasic system composed of
10% aqueous NaOH and dichloromethane in the presence of tetrabutylammonium chloride.
The thiolation reaction was complete in only 5 minutes, at 0◦C.
Keywords S-Acylation; phase transfer catalysis; tetrabutylammonium chloride; thioesters
INTRODUCTION
Among the different forms of organic sulfur, thioesters seem to be of a particular
importance, considering the key role that these molecules played in the mystery of the origin
of life on Earth (“The thioester world,” as Nobel prize laureate Christian de Duve has named
this primordial period of time1) and also the role they play in metabolic processes of living
organisms centered around the well-known coenzyme A.2 Therefore, much research has
been devoted to expanding the number of thiolation methods (the synthesis of thioesters by
acylation of thiols). Thus, various S-acylation methods of thiols have been proposed, starting
from carboxylic acids,3 anhydrides,4 or acyl chlorides.5 Comparatively, with the formation
of their oxygenated counterparts, syntheses of thioester are even more damaged by the
presence of water, this being the reason why most of the modern methods of thiolation either
need anhydrous solvents3a–c,4b,4e,4h,5b,5c or are completely solvent-free reactions.4a,4c,4d,4f,4g,5a
Nevertheless, the inconveniences that arise from the use of anhydrous solvents or free-
solvent conditions can be circumvented if a method is applied that proved to be successful
Received 6 January 2010; accepted 17 February 2010.
Address correspondence to Cristian Simion, Department of Organic Chemistry, “Politehnica” Uni-
versity of Bucharest, Spl. Independentei 313 060042, Bucharest, Romania. E-mail: c simion@chim.upb.ro
and Yoshiharu Mitoma, Department of Environmental Sciences, Faculty of Life and Environmental Sciences,
Prefectural University of Hiroshima, 562 Nanatsuka-Cho, Shobara City, Hiroshima 727-0023, Japan. E-mail:
mitomay@pu-hiroshima.ac.jp
2480

THIOLATION UNDER PHASE-TRANSFER CATALYSIS
2481
for the O-acylation of alcohols and phenols with acyl chlorides: phase-transfer catalysis.6
Over the past several years, we have developed our own protocol for the O-acylation of
phenols,7 the main advantages of which are the use of equimolecular amounts of phenol
and acyl chloride, dichloromethane as organic solvent, and less toxic tetrabutylammonium
chloride as the phase-transfer catalyst (PTC). Low temperatures (0◦C) and extremely short
reaction time (only 5 min) complete the abbreviated description of our method. Since the
results we obtained in the O-acylation of alcohols, as well as of mono- and poly-substituted
phenols with various mono- and di-alkanoyl chlorides in a biphasic system of aqueous
NaOH:CH2Cl2 were extremely successful (almost quantitative yields),7 we decided to
apply the same reaction protocol to the S-acylation of thiophenols.
It is known that coenzyme A functions in living organisms as a carrier of the acetyl
group mainly through the existence of a thioester moiety formed between the thiol group
of the coenzyme and the carbonyl function of the acetyl group. The formation, namely the
rupture of this thioester function, occurs in the cell environment, which is an aqueous one,
under the influence of an enzymatic catalyst. Researchers tried to replicate this process on
a laboratory scale, Ouyang et al. having had the idea of using a two-phase aqueous–organic
system in which they combined enzymatic and phase-transfer catalysis.8 To the best of our
knowledge, there are only two other examples of phase-transfer catalysis thiolation: the
ring-closure condensation of phthalic chloride with 4,4ꢁ-thiobisbenzenethiol, which was
carried out in a high dilution conditions to obtain a cyclic S-thioester dimer in only 56%
yield,9 and the formation of terephtaloyl dithioesters in 80% yield, in a mixture of aqueous
NaOH and chloroform.10
We report in this article the details of a rapid and convenient method for preparing
various thioesters by S-acylation of thiols with different acyl chlorides, in a biphasic system
and using tetrabutylammonium chloride as phase-transfer catalyst.
RESULTS AND DISCUSSIONS
Reversible protein acetylation is a ubiquitous means for the rapid control of diverse
cellular processes. Acetyltransferase enzymes transfer the acetyl group from acetyl-CoA
to lysine residues, while deacetylase enzymes catalyze removal of the acetyl group by
hydrolysis or by an NAD+-dependent reaction. A modification in this process, resulting
in the inactivation of a specific enzyme, can lead to important perturbances of distinct
functions in the regulation of biological processes.11 An example of such a modification is
the replacement of an acetyl group with a propionyl group.12 These are the reasons why
we decided to start our investigation not with the acetylation of thiophenol, but with the
propionylation of the same S-substrate.
All reactions were carried out using an equimolecular stoichiometry between thiophe-
nol and n-propionyl chloride in a 1:1 mixture of aqueous NaOH and dichloromethane, in the
presence of a tetraalkylammonium salt such as PTC. The reaction temperature was 0◦C, and
the duration was only 5 min. As we previously noted,7 vigorous stirring is a very important
parameter, so the reaction mixture was kept at 400 rpm magnetic stirring. A confirmation
of the optimum conditions for the thiolation process was attempted by double-checking all
reaction conditions through the S-benzoylation of thiophenol. The results obtained in these
various attempts are presented in Table I.
When no PTC was used, the yield in thioester was only 43%, but an extra 1.5 mmol
BNCl increased the yields to over 90%. BNBr was not as effective as BNCl, so the latter

2482
C. SIMION ET AL.
Table I Phase-transfer catalysis S-propionylation and S-benzoylation of thiophenol with propionyl chloride and
benzoyl chloride
Biphasic system (mL)
PTCa (mmol)
Yield (%)
Temp.
(◦C)
Entry
aq. NaOH (%)
CH2Cl2
BnCl
BnBr
S-propionylation
S-benzoylation
1
2
3
4
5
6
7
8
9
10
11
12
13c
20 (10%)
20 (10%)
20 (10%)
20 (10%)
–
20 (10%)
20 (10%)
20 (10%)
20 (5%)
10 (10%)
40 (10%)
20 (20%)
20 (10%)
20
20
20
20
20
–
20
20
20
20
20
20
20
–
1.5
–
–
–
1.5
–
–
–
–
–
–
–
0
0
0
0
0
0
5
10
0
0
43
92
71
87
7
86
100
100
100
13
39
86
84
3.0
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
10
71
72
73
78
63
73
b
–
–
b
–
–
–
0
0
25
b
–
–
95
95
b
aBnCl = tetrabutylammonium chloride; BnBr = tetrabutylammonium bromide.
bNot attempted.
cReaction time = 20 min.
was kept for the rest of the experiments. An enhancement of the quantity of PTC did not
lead to significant changes, but the yields decreased dramatically when only one solvent of
the biphasic system was used. A slight diminution of the overall yield was recorded when
the temperature was increased by 5 or 10◦C. The ssame results were recorded when the
quantity or the concentration of the NaOH solution was lowered, while a higher quantity
of NaOH solution accentuated the tendency of the yields to diminish; this is probably due
to the competition between the hydroxide and thiophenoxide anions. Results obtained in
the S-benzoylation of thiophenol proved to be superior to the ones for S-propionylation
of the same substrate. Some parallels can be made: The biphasic system is extremely
important—in both cases, the yields were extremely low when only one component was
used.
It is safe to assume that S-acylation of thiophenol occurs according to the general
mechanism of phase transfer catalysis, which could be represented, for this case, as is
shown in Scheme 1.
p-X-C6H4-S-Na+
p-X-C6H4-S-N+(n-Bu)4 + NaCl
+ H2O
p-X-C6H4-SH
p-X-C6H4-S-Na+
+
NaOH
Aqueous phase
Organic phase
+
(n-Bu)4N+Cl-
p-X-C6H4-S-N+(n-Bu)4 + R-CO-Cl
p-X-C6H4-S-CO-R + (n-Bu)4N+Cl-
Scheme 1 General mechanism for the phase-transfer catalysis process of S-acylation.
The first step is the formation of an ion pair between the quaternary ammonium cation
and the thiophenoxide ion (PhS−) in the aqueous layer. Following the transfer of the ion pair
to the organic layer, the reaction with the acyl chloride would yield the S-phenyl thioester.
Simultaneously with the thioester formation, the PTC is regenerated and subsequently
transferred back into the aqueous phase. Two types of mechanisms can be expected for

THIOLATION UNDER PHASE-TRANSFER CATALYSIS
2483
Table II S-Acylation of thiophenols
Entry
1 (X-)
2 (R-)
Yield (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
H
H
H
H
H
H
H
H
H
CH3
CH3CH2
95
92
93
87
90
88
95
91
100
96
92
94
95
96
CH3CH2CH2
(CH3)2CH
CH3(CH2)2CH2
(CH3)2CHCH2
(CH3)3C
cyclo-C6H11
C6H5
CH3CH2
CH3CH2
CH3CH2
CH3CH2
CH3CH2
CH3
CH3O
Cl
Br
ortho-CH3
the rate-determining step of the process, which is the formation of the thioester (a reaction
occurring in the organic layer, which is slower than the formation of the thiophenoxide
anion in the aqueous layer): a classical addition–elimination mechanism (determined by
the nucleophilic attack of the thiophenoxide anion)7c or an electron transfer process.12
However, considering the high speed of the process (almost quantitative transformation in
just 5 min), the second hypothesis could be discarded.
Once the general reaction condition was established (equimolecular amounts of
reagents, 10% PTC, 0◦C, 5 min duration, under intense stirring), we proceeded to the
study of the scope and limitations of this process by reacting different substituted thiophe-
nols with various acyl chlorides (Scheme 2, Table II).
(n-Bu)4N+Cl-
p-X-C6H4-S-COR
p-X-C6H4-SH + R-COCl
aq. NaOH / CH2Cl2
1
2
3
0°C, 5 min
Scheme 2 S-Acylation process.
Every S-acylation in the presence of PTC proceeded in a clear-cut manner and gave
the corresponding S-phenyl thioester in high yield. However, no clear correlation between
the electronic effect of substituents present on the thiophenols or on the carboxyl moiety
and the product yields could be established. One probable reason is that the ion-pair p-
X-PhS−N+(n-Bu)4 participating in the rate-determining step of this process is very tight
and exists as a highly polarized salt. In such a tight ion pair, the electronic effect of the
substituent on the reactivity would appear weaker than that of the free anion (in a dissociated
system) or of a loose ion pair.13 Therefore, since electronic effects became more discrete,
the partition of the ion pairs between the two layers (depending on the hydrophobic effects
of the hydrocarbonated chain, on the rate of mass transfer between the two layers and on the
superficial tension) turned out to be the dominant factor. Therefore, the use of the appropriate
organic solvent (which, in PTC conditions, proved to be dichloromethane6m,6o,7c) and a low
temperature would favor the formation of such a tight ion pair.13 Nevertheless, the high
yields, mild conditions, and rapidity of the thioster formation surpasses precedent methods

2484
C. SIMION ET AL.
Table III S-Acylation of 1-propanethiol and thiophenol with dicarboxylic acid chlorides under PTC conditions∗
Dithioester (%)
N in
Classic
PTC
Entry
Thiol
(CH2)n(COCl)2
Schotten–Baumann
process
1
2
3
4
5
6
CH3CH2CH2 SH
2
3
4
2
3
4
85
79
81
92
87
86
92
92
95
100
100
98
C6H5-SH
∗BnC, 3 mmol; thiol, 3 mmol; (CH2)n(COCl)2, 1.5 mmol; 20 mL 10% NaOH aq., 20 mL CH2Cl2; 0◦C, 5 min.
(e.g., the formation of same S-phenyl thioacetate and parent compounds, using palladium-
mediated couplings of aryl halides with potassium thioacetate in dioxane at 100◦C for
several hours14).
As an application of the above S-esterification under PTC conditions, the reactions
of 1-propanethiol and thiophenol with some dicarboxylic acid chlorides were carried out.
Isolation of practically pure reaction products was simple and straightforward. Data for
conversions are summarized in Table III, from which it can be seen that the yields of
dithioesters are generally excellent, comparing favorably to those obtained by classical
thiolation methods.
Bis-thiolation at both ends of a α,ω-dicarboxylic acid chlorides was effective in only
5 min, presenting higher yields than the classic Schotten–Baumann process, which was
carried out simultaneously, but whose duration was at least 1 h.
Overall, our results showed that S-acylation of substituted thiophenols as well as
bis-thiolation with aromatic and aliphatic thiols is highly effective under PTC conditions,
with tetrabutylammonium chloride as catalyst in a mixture of 10% aqueous NaOH and
dichloromethane, in only 5 minutes reaction time at 0◦C.
EXPERIMENTAL
In all reactions, commercially available substituted thiophenols and alkanoyl chloride
were used, after being purified by distillation or recrystallization. Analytical gas–liquid
chromatography was carried out on a Yanagimoto G-180F fitted with an FS-WCOT column
(0.25 mm i.d., length 25 m) coated Silicon OV-1701 or Yanagimoto G-80 packed column
gas chromatograph (Apiezon grease L, 10%, 1.5 m or silicone SE-30, 10%, 1 m). NMR
spectra were recorded on a Varian Unity-300 (300 MHz), with CDCl3 internal standard.
IR spectra were recorded on a Shimadzu 8100M FT-IR in KBr or in a NaCl cell. All
reaction products were identified by comparison with GLC retention times of the authentic
samples, either purchased or previously obtained through classic Schotten–Baumann or
other thioesterification procedures,3a while, for the sake of comparison, thioesters (R-CS-
ORꢁ) were obtained in classical manner, such as treatment of corresponding ester with
P4S10 or Lawesson’s reagent.15

THIOLATION UNDER PHASE-TRANSFER CATALYSIS
2485
General Procedure for the Preparation of Thioesters
The thiophenol (15 mmol) was dissolved in 20 mL of 10% aqueous sodium hydroxide
solution in a 100 mL flask. The solutions of tetra-n-butylammonium chloride (1.5 mmol) and
acyl chloride (15 mmol) in dichloromethane (5 and 15 mL, respectively) were independently
prepared. After cooling all solutions at 0◦C, they were mixed together at once. The reaction
mixture was kept under vigorous magnetic stirring (400 rpm) at 0◦C for 5 min, and then
poured over 50 mL of icy water. The organic layer was separated, and the aqueous layer
was extracted twice with 40 mL of ethyl ether. The combined organic phases were washed
with saturated NaCl solution. After drying on Na2SO4, the solvent was evaporated, and
the residue was analyzed directly by GLC. Quantitative analyses were carried out using
internal standard method. The products were also identified by IR, NMR, and GC-mass
analyses. All thioesters presented in GC analyses showed at least a 99.5% degree of purity.
S-Phenyl thiopropionate16. Bp 130–131◦C/25 mbar; IR (NaCl): 927, 1012,
1
1441, 1447, 1583, 1712 (CO), 2939, 2980 cm−1; H NMR (300 MHz, CDCl3): δ =
1.23 (t, J = 7.6Hz, 3H), 2.69 (q, J = 7.6Hz, 2H), 7.40 (s, 5H); MS (EI, 70 eV): m/z (%) =
166 (M+, 14), 110 (28), 57 (100).
S-Phenyl thiobenzoate17. Mp 52–53◦C; IR (KBr): 893, 1199, 1439, 1579, 1664,
3059 cm−1; 1H NMR (300 MHz, CDCl3): δ = 7.47 (m, 8H), 8.03 (m, 2H); MS (EI, 70 eV):
m/z (%) = 214 (M+, 8), 105 (100), 77 (72).
S-Phenyl thioacetate14. Bp 161–161.5◦C/150 mbar; IR (NaCl): 951, 1115, 1441,
1477, 1709, 3060 cm−1; 1H NMR (300 MHz, CDCl3): δ = 2.42 (s, 3H), 7.41 (s, 5H); MS
(EI, 70 eV): m/z (%) = 152 (M+, 17), 110 (100), 66 (28).
S-Phenyl thio-n-butyrate18. Bp 165◦C/150 mbar; IR (NaCl): 995, 1113, 1441,
1447, 1709, 2934 cm−1; 1H NMR (300 MHz, CDCl3): δ = 0.99 (t, J = 7.2Hz, 3H), 1,76
(sext, J = 7.2Hz, 2H), 2,64 (t, J = 7.2Hz, 2H), 7,41 (s, 5H); MS (EI, 70 eV): m/z (%) =
180 (M+, 12), 110 (23), 71 (100).
S-Phenyl thio-iso-butyrate19. Bp 164.5◦C/65 mbar; IR (NaCl): 960, 1094, 1441,
1447, 1701, 2974 cm−1; 1H NMR (300 MHz, CDCl3): δ = 1.26 (d, J = 6.9Hz, 6H), 2.83
(t, J = 6.9Hz, 1H), 7.40 (s, 5H); MS (EI, 70 eV): m/z (%) = 180 (M+, 16), 110 (37), 71
(100).
S-Phenyl thio-n-valerate. Bp 173.5–174◦C/65 mbar; IR (NaCl): 958, 1014, 1441,
1477, 1709, 2959 cm−1; 1H NMR (300 MHz, CDCl3): δ = 0.93 (t, J = 7.1Hz, 3H), 1.40
(sext, J = 7.1Hz, 2H), 1.71 (qv, J = 7.1Hz, 2H), 2.65 (t, J = 7.1Hz, 2H), 7.41 (s, 5H); MS
(EI, 70 eV): m/z (%) = 194 (M+, 10), 110 (18), 85 (69), 57 (100).
S-Phenyl thio-iso-valerate. Bp 135.5–136◦C/15 mbar; IR (NaCl): 999, 1132,
1441, 1477, 1709, 2959 cm−1; 1H NMR (300 MHz, CDCl3): δ = 1.00 (d, J = 6.6Hz, 6H),
2.21 (oct, J = 6.6Hz, 1H), 2.54 (d, J = 6.6Hz, 2H), 7.40 (s, 5H); MS (EI, 70 eV): m/z
(%) = 194 (M+, 11), 110 (18), 85 (67), 57 (100).
S-Phenyl thio-tert-butyrate20. Bp 127.5–128◦C/15 mbar; IR (NaCl): 931, 1025,
1441, 1477, 1697, 2970 cm−1; 1H NMR (300 MHz, CDCl3): δ = 1.32 (s, 9H), 7.39 (s, 5H);
MS (EI, 70 eV): m/z (%) = 194 (M+, 25), 110 (61), 85 (100), 65 (14).
S-Phenyl thiocyclohexanecarboxylate21. Mp 31–32◦C; IR (KBr): 962, 1138,
1439, 1477, 1693, 2936 cm−1; 1H NMR (300 MHz, CDCl3): δ = 1.24 (m, 2H), 1.47 (m,
2H), 1,64 (m, 2H), 1,81 (m, 2H), 2.00 (m, 2H), 2.60 (t, 1H), 7.40 (s, 5H); MS (EI, 70 eV):
m/z (%) = 220 (M+, 10), 111 (36), 83 (100), 55 (73).
S-p-Tolyl thiopropionate. Bp 174–176◦C/40 mbar; IR (NaCl): 925, 1182, 1377,
1460, 1493, 1599, 1709, 2980 cm−1; 1H NMR (300 MHz, CDCl3): δ = 1.22 (t, J = 7.4Hz,

2486
C. SIMION ET AL.
3H), 2.37 (s, 3H), 2.68 (q, J = 7.4Hz, 2H), 7.21 (d, J = 8.1Hz, 2H), 7.29 (d, J = 8.1Hz,
2H); MS (EI, 70 eV): m/z (%) = 180 (M+, 19), 124 (28), 91 (12), 77 (6), 57 (100).
S-p-Anisyl thiopropionate. Bp 99–101◦C/3 mbar; IR (NaCl): 927, 1174, 1290,
1408, 1496, 1574, 1701, 2837 cm−1; 1H NMR (300 MHz, CDCl3): δ = 1.21 (t, J = 7.2Hz,
3H), 2.65 (q, J = 7.2Hz, 2H), 3.81 (s, 3H), 6.93 (d, J = 8.7Hz, 2H), 7.31 (d, J = 8.7Hz,
2H); MS (EI, 70 eV): m/z (%) = 196 (M+, 53), 140 (100), 125 (65), 96 (42), 57 (98).
S-p-Chlorophenyl thiopropionate. Bp 156–158◦C/40 mbar; IR (NaCl): 819,
925, 1012, 1390, 1458, 1477, 1576, 1713, 2982 cm−1; 1H NMR (300 MHz, CDCl3): δ =
1.25 (t, J = 7.5Hz, 3H), 2.70 (q, J = 7.5Hz, 2H), 7,19 (m, 5H); MS (EI, 70 eV): m/z (%) =
202 (M++2, 20), 200 (M+, 59), 144 (96), 108 (77), 69 (33), 57 (100).
S-p-Bromophenyl thiopropionate. Bp 102–104◦C/3 mbar; IR (NaCl): 925,
1008, 1387, 1412, 1471, 1568, 1703, 2980 cm−1; 1H NMR (300 MHz, CDCl3): δ = 1.23
(t, J = 6.0Hz, 3H), 2.68 (q, J = 6.0Hz, 2H), 7. 24 (d, J = 7.2Hz, 2H), 7.46 (d, J = 7.2Hz,
2H); MS (EI, 70 eV): m/z (%) = 246 (M++2, 24), 244 (M+, 24), 190 (56), 188 (55), 108
(59), 69 (28), 57 (100).
S-o-Tolyl thiopropionate. Bp 115–116◦C/3 mbar; IR (NaCl): 925, 1088, 1280,
1379, 1475, 1591, 1709, 2980 cm−1; 1H NMR (300 MHz, CDCl3): δ = 1.23 (t, J = 7.5Hz,
3H), 2.34 (s, 3H), 2.68 (q, J = 7.5Hz, 2H), 7.30 (m, 5H); MS (EI, 70 eV): m/z (%) = 180
(M+, 66), 124 (100), 91 (91), 77 (56), 57 (99).
Di-S-Phenyl thiosuccinate. Mp 90.0◦C; IR (KBr): 978, 1023, 1447, 1488, 1700,
3021 cm−1; 1H NMR (300 MHz, CDCl3): δ = 3.01 (s, 4H), 7.42 (s, 10H); MS (EI, 70 eV):
m/z (%) = 302 (M+, 2), 194 (93), 109 (100), 77 (19), 65 (31), 55 (99).
Di-S-Phenyl thioglutarate. Mp 33.0–33.4◦C; IR (KBr): 968, 1083, 1447, 1483,
1699, 3023 cm−1; 1H NMR (300 MHz, CDCl3): δ = 2.09 (t, J = 7.5Hz, 2H), 2.75 (t, J =
7.5Hz, 4H), 7.40 (s, 10H); MS (EI, 70 eV): m/z (%) = 316 (M+, 2), 207 (91), 179 (18), 109
(100), 97 (53), 77 (14), 65 (27), 55 (89).
Di-S-Phenyl thioadipate22. Mp 81.2–82.2◦C; IR (KBr): 910, 1049, 1241, 1410,
1441, 1477, 1712, 2980 cm−1; 1H NMR (300 MHz, CDCl3): δ = 1.80 (m, 4H), 2.64 (m,
4H), 7.41 (s, 10H); MS (EI, 70 eV): m/z (%) = 330 (M+, 1), 221 (34), 174 (54), 137 (12),
109 (100), 77 (32), 65 (96), 55 (99).
Di-S-Propyl thiosuccinate. Mp 89.8–90.0◦C; IR (KBr): 991, 1410, 1458, 1689,
1
2964 cm−1; H NMR (300 MHz, CDCl3): δ = 0.96 (t, J = 7.2Hz, 6H), 1.61 (sext, J =
7.2Hz, 4H), 2.87 (t, J = 7.2Hz, 4H), 2.91 (s, 4H); MS (EI, 70 eV): m/z (%) = 234 (M+, 1),
159 (81), 117 (67), 89 (25), 71 (33), 55 (100).
Di-S-Propyl thioglutarate. Mp 31.2–32.5◦C; IR (NaCl): 976, 1084, 1412, 1456,
1690, 2965 cm−1; 1H NMR (300 MHz, CDCl3): δ = 0.97 (t, J = 7.4Hz, 6H), 1.58 (sext,
J = 7.4Hz, 4H), 2.01 (qv, J = 7.2Hz, 2H), 2.60 (t, J = 7.4Hz, 4H), 2.86 (t, J = 7.2Hz, 4H);
MS (EI, 70 eV): m/z (%) = 248 (M+, 1), 173 (26), 145 (23), 103 (17), 97 (11), 69 (15), 55
(100).
Di-S-Propyl thioadipate. Mp 81–82◦C; IR (NaCl): 951, 1012, 1452, 1693, 2991
cm−1; 1H NMR (300 MHz, CDCl3): δ = 0.96 (t, J = 7.5Hz, 6H), 1.58 (sext, J = 7.5Hz,
4H), 1.61 (m, 4H), 2.54 (t, J = 7.5Hz, 4H), 2.85 (m, 4H); MS (EI, 70 eV): m/z (%) = 262
(M+, 1), 167 (45), 141 (31), 111 (100), 83 (21, 55 (83).
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