The unusual influence of hetaryl groups on the direct conversion of some secondary alcohols into thiols with Lawesson’s reagent: elucidation of the reaction mechanism

Article abstract of DOI:10.1080/17415993.2017.1313257

A series of hetaryl-substituted methanols were used for direct conversion into the corresponding thiols by treatment with Lawesson’s reagent in boiling toluene. Unexpectedly, the respective sulfides were formed exclusively. In the case of chiral alcohols,

Full text of DOI:10.1080/17415993.2017.1313257

Journal of Sulfur Chemistry
ISSN: 1741-5993 (Print) 1741-6000 (Online) Journal homepage: http://www.tandfonline.com/loi/gsrp20
The unusual influence of hetaryl groups on the
direct conversion of some secondary alcohols into
thiols with Lawesson’s reagent: elucidation of the
reaction mechanism
Grzegorz Mlostoń, Róża Hamera-Fałdyga, Małgorzata Celeda, Anthony
Linden & Heinz Heimgartner
To cite this article: Grzegorz Mlostoń, Róża Hamera-Fałdyga, Małgorzata Celeda, Anthony Linden
& Heinz Heimgartner (2017): The unusual influence of hetaryl groups on the direct conversion
of some secondary alcohols into thiols with Lawesson’s reagent: elucidation of the reaction
mechanism, Journal of Sulfur Chemistry, DOI: 10.1080/17415993.2017.1313257
To link to this article: http://dx.doi.org/10.1080/17415993.2017.1313257
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Date: 18 April 2017, At: 10:26

JOURNAL OF SULFUR CHEMISTRY, 2017
http://dx.doi.org/10.1080/17415993.2017.1313257
The unusual influence of hetaryl groups on the direct
conversion of some secondary alcohols into thiols with
Lawesson’s reagent: elucidation of the reaction mechanism
Grzegorz Mlostońa, Róża Hamera-Fałdygaa∗, Małgorzata Celedaa, Anthony Lindenb
and Heinz Heimgartnerb
aDepartment of Organic and Applied Chemistry, University of Łódź, Łódź, Poland; bDepartment of Chemistry,
University of Zurich, Zurich, Switzerland
ABSTRACT
ARTICLE HISTORY
Received 16 February 2017
Accepted 27 March 2017
A series of hetaryl-substituted methanols were used for direct con-
version into the corresponding thiols by treatment with Lawesson’s
reagent in boiling toluene. Unexpectedly, the respective sulfides
were formed exclusively. In the case of chiral alcohols, the sulfides
were obtained as 1:1-mixtures of meso- and dl-diastereoisomers.
In contrast to hetaryl-substituted alcohols, the analogous protocol
applied for benzhydryl alcohol led to a mixture of the expected sec-
ondary thiol and a bis(diphenylmethyl) trithiophosphonate. Finally,
the analogous reactions with ferrocenyl(phenyl)methanol and difer-
rocenylmethanol, respectively, led to the corresponding thiols in
good yield.
KEYWORDS
Lawesson’s reagent;
secondary alcohols;
secondary thiols; organic
sulfides; hetaryl substituents
Ph
Ph
S
P
Ar = Ph
SH
+
MeO
SCHPh2
Ph
SCHPh2
OH
L. R.
+
Het =
Ar/Het
S
S
S
S
Ph
Ph
d,l and meso
1. Introduction
Thiols are an important class of organic compounds with great significance for organic
syntheses. Diverse methods are known for their preparation [1], and in recent years, asym-
metric syntheses of thiols have been studied extensively [2,3]. It is well known that many
thiols are biologically active substances [4] and some of them are of special interest as
odorous compounds [5].
CONTACT Grzegorz Mlostoń
gmloston@uni.lodz.pl
Department of Organic and Applied Chemistry, University
of Łódź, Tamka 12, PL-91-403 Łódź, Poland
*Part of the planned Ph.D. Thesis of R. H.-F. (University of Łódź).
© 2017 Informa UK Limited, trading as Taylor & Francis Group

2
G. MLOSTOŃ ET AL.
It is generally known that the treatment of primary, secondary or tertiary alcohols with
Lawesson’s reagent (LR) is a straightforward method for their conversion into the corre-
sponding thiols [6,7]. In some recent publications, we described the synthesis of hetaryl and
ferrocenyl ketones and their conversions into the sulfur analogues, i.e. thioketones [8,9].
The latter were tested as precursors of thiols by treatment with diverse reducing agents,
and in the cases of aromatic and cycloaliphatic thioketones, only LDA gave satisfactory
results [10]. In order to get an alternative, straightforward access to hetarylmethanethi-
ols, the direct conversion of the corresponding secondary alcohols into the required thiols
using Lawesson’s reagent should be examined.
2. Results and discussion
The study started with the preparation of a series of hetaryl- and ferrocenyl-substituted
ketones 1 via lithiated hetarenes [8] or via the in situ-generated mixed anhydrides [9].
The obtained ketones 1a–1e were converted into the corresponding secondary alco-
hols 2a–2e via reduction with NaBH4 in THF solution (Scheme 1, Table 1) or alternatively,
in the case of phenyl/ferrocenyl ketones 1f–1h, with lithium aluminum hydride. In the
first thiolation experiment, di(thiophen-2-yl)methanol (2a) was treated with ca. equimolar
amounts of LR in boiling dry toluene. The progress of the reaction was monitored by TLC,
and after 15 min, the starting material 2a was completely consumed. The crude reaction
mixture, after removal of toluene, was analyzed by 1H NMR spectroscopy, which evidenced
the formation of only one product. Along with two doublets and a triplet for the thiophene
ring, the spectrum showed a singlet at 5.43 ppm. Surprisingly, the expected IR absorption
band for the SH group at ca. 2500–2600 cm−1 was missing. The elemental analysis of the
purified sample showed a significantly reduced value for sulfur in comparison with that cal-
culated for the desired thiol (40.99 instead of 47.09%). This value corresponded, however,
to the molecular formula C18H14S5 of the sulfide 3a.
Scheme 1. Preparation of disubstituted methanols 2 and their transformations into sulfides 3 or
thiols 4.

JOURNAL OF SULFUR CHEMISTRY
3
Table 1. Aryl/hetaryl and ferrocenyl-substituted methanols 2, sulfides 3, and thiols 4.
1
Hetar or Ar1
Ar or Ar2
2
Yield (%)a
3
4
Yield (%)a
75
a
b
c
d
e
f
Thiophen-2-yl
Thiophen-2-yl
Furan-2-yl
Phenyl
Phenyl
Phenyl
Thiophen-2-yl
Selenophen-2-yl
Selenophen-2-yl
Thiophen-2-yl
Selenophen-2-yl
Phenyl
a [11,12]
b [12]
c
d [11,12]
e [13]
f [14]
79
94
65
93
68
99
84
89
a
–
–
b
c
–
–
–
–
–
–
–
–
a [6]
b
c
b
–
–
b
92
75
90
58
56
g
h
Ferrocenyl
Ferrocenyl
Phenyl
Ferrocenyl
g [15]
h [16]
aYield of isolated product.
bOnly non-identified decomposition products were obtained.
A similar reaction course was observed in the case of hetaryl(phenyl)methanols 2d–2e
(Table 1). However, in both cases, 1:1-mixtures of two diastereoisomeric products 3b and
3c (meso and dl) were obtained. These mixtures could not be separated by means of stan-
dard chromatographic methods. For example, the 1H NMR spectrum of sulfide 3b showed
− −
two equally intense singlets at 5.11 and 5.12 ppm, which are attributed to the CH S CH
fragment in the two diastereoisomers. In addition, the 13C NMR spectrum revealed two
signals for this fragment at 49.79 and 49.82 ppm, respectively.
The presented results differ significantly from the reported formation of diphenyl-
methanethiol (4a) from benzhydryl alcohol (2f) under similar conditions [6]. For that
reason, the experiment with 2f was repeated in boiling dry toluene, and the TLC analy-
sis showed that already after 15 min the starting material was completely consumed, and
two new spots evidenced the formation of two new products. After chromatographic sepa-
ration, the less polar fraction was identified as the known diphenylmethanethiol (4a) [6] as
the major product. The more polar fraction, obtained as the minor product, was isolated
as a colorless solid, and the 31P NMR spectrum indicated the presence of a P-atom by a
signal at 78.2 ppm, i.e. in the region of aryltrithiophosphonates [17–20]. In the 1H NMR
spectrum, signals of a MeO group (3.78 ppm) and of a 4-MeOC6H4 residue (6.66–6.68 and
7.60–7.65 ppm) suggested the presence of a monomeric unit of Lawesson’s reagent. In addi-
tion, comparison of the intensities of the MeO and the CHPh2 groups (doublet at 5.79 ppm)
proved the ratio 3:2 for the respective H-atoms. Based on these data, structure 5 (Scheme 2)
was attributed to this product (cf. [19]). The elemental analysis supported the molecular
formula C33H29OPS3. Finally, the proposed structure was unambiguously confirmed by
X-ray crystallography (Figure 1). The corresponding bis(diphenylmethyl) phenyltrithio-
phosphonate of type 5 has been obtained in a two-step reaction from phenylphosphine
and thiobenzophenone [19].
The formation of product 5 or its analogues has not been reported in earlier publications
[6,22] on the direct conversion of 2f and other secondary alcohols into the corresponding
Scheme 2. Reaction of benzhydryl alcohol (2f) with Lawesson’s reagent (LR) in abs. toluene.

4
G. MLOSTOŃ ET AL.
Figure 1. ORTEP plot [21] of the molecular structure of 5 (with 50% probability ellipsoids; arbitrary
numbering of atoms).
thiols. As a matter of fact, in supplementary experiments performed with 2f in wet toluene,
the formation of 5 has not been observed, and thiol 4a was isolated as the only product in
good yield (90%), in agreement with the reported results. In a test experiment, the isolated
compound 5 was heated in wet toluene over 0.5 h, but in this case the starting compound
was recovered. Thus, thiol 4a is not a product of hydrolysis of the initially formed 5. In
order to check whether the latter can be formed from thiol 4a and monomeric LR, both
reagents, used in a molar ratio of 2:1 were heated in boiling toluene until 4a completely
disappeared from the reaction mixture (TLC monitoring). In fact, the formation of 5 was
evidenced by TLC, however, many other spots revealed a rather complicated outcome of
the reaction. Based on this observation we conclude that the formation of 5 occurs via an
intermediate formed in the initial step of the reaction from alcohol 2f (and not from the in
situ-formed thiol 4a), and Lawesson’s reagent. The detailed mechanism of this conversion
is not yet clear.
Finally, the experiment with ferrocenyl(phenyl)methanol (2g) led to the correspond-
ing thiol 4b, which was isolated in 58% yield (Scheme 1, Table 1). In the reaction mixture,
non-identified decomposition products were also present, but neither a sulfide of type 3 nor
an analogue of 5 could be identified. An analogous result was obtained with diferrocenyl-
methanol (2h), and in this case diferrocenylmethanethiol (4c) was isolated in a comparable
yield (Table 1).

JOURNAL OF SULFUR CHEMISTRY
5
Ar
Hetar
SH
S
P
4
Ar'
SH
OH
A
SH
O
L.R.
route B
B
Ar
Hetar
Ar
Hetar
Ar
O
Toluene
reflux
Hetar
-
Ar'
P
S
6
2
4
S
-
Ar'
P
OH
route A
SH
Hetar
S
Hetar
Ar
Ar
3
Scheme 3. Proposed reaction mechanisms for the competitive formation of sulfides 3 and thiols 4.
The results of the present study show that the presence of a hetaryl residue in the sec-
ondary alcohols 2 changes the reactivity of the system, and instead of methanethiols of
type 4, sulfides 3 are formed as unexpected products. It seems likely that the intermediate
aryl dithiophosphonate 6 is attacked by the in situ-formed secondary thiol of type 4 to give
the sulfide 3 (route A). Its formation suggests that intermediate 6 acts as a trapping agent
for the nucleophilic thiol 4 (Scheme 3). This interpretation leads to the conclusion that the
intermolecular S-attack is a competitive pathway to the intramolecular one, which leads to
the formation of the thiol 4 (route B).
In the reaction with benzhydryl alcohol (2f) in dry toluene, the initially formed
diphenylmethanethiol (4a) behaves differently and reacts with the monomer of Lawes-
son’s reagent to give, after elimination of H2S, dibenzhydryl (4-methoxyphenyl)trithio-
phosphonate (5, Scheme 2). However, in the presence of water 4a is the exclusive product.
A similar example of the formation of a trithiophosphonate from Lawesson’s reagent and
an in situ-generated pyrazole-3-thiol has already been described [23].
3. Conclusions
In continuation of our recent studies on hetaryl-substituted organic systems, the pre-
sented results demonstrate that hetaryl groups, in comparison with aryl groups, strongly
modify the reactivity of such systems. The known protocol for the direct conversion of
secondary diphenyl alcohols (benzhydryl alcohols) into the corresponding thiols by treat-
ment with Lawesson’s reagent leads, in the case of hetaryl analogues, to the corresponding
sulfides as final products. The initially formed thiols are trapped by an activated inter-
mediate generated from the starting alcohol and Lawesson’s reagent. The importance
of a hetaryl group is emphasized by the fact that both benzhydryl alcohol and ferro-
cenyl(phenyl)methanol behaved similarly, and in both cases only the respective thiols were

6
G. MLOSTOŃ ET AL.
formed. These results point out that the presence of the hetaryl groups strongly modifies
the reactivity of the SH moiety, very likely by the enhancement of its nucleophilicity. It
should be emphasized that in a similar study performed with ferrocenyl/hetarylmethanols
of type 2 and LR, another mechanism governs the reaction course and the formation of
tetra-substituted ethane derivatives was observed [24]. All these results point out that
the type of products obtained from secondary alcohols, derived from methanol, strongly
depends on the substitution pattern and both hetaryl and ferrocenyl groups are of special
importance.
4. Experimental
4.1. General
All solvents were dried over appropriate drying agents and distilled before use. Melting
points were determined in a capillary using a StewartꢀR SMP 30 and they are uncorrected.
The IR spectra were recorded on a Nexus FT-IR spectrophotometer. The 1H, 13C and 31
P
NMR spectra were measured on a Bruker Avance III instrument (600, 150 and 243 MHz,
respectively), using the solvent signal and H3PO4, respectively, as reference. The elemental
analyses were recorded on a Vario Micro Cube. ESI-MS were recorded on a Varian 500-MS
IT mass spectrometer. Column chromatography (CC) was carried out using Silica gel 60
(Sigma-Aldrich, 230–400 mesh). The notation Fc in this study represents the ferrocenyl
residue. The applied ferrocenyl- and hetaryl-substituted ketones were obtained by known
methods according to the literature protocols [8,9]. Other reagents used in the present
study were commercially available.
4.2. Synthesis of secondary alcohols 2a–2f
To a solution of the corresponding ketone 1 (1 mmol) in THF (2 mL), water (0.06 mL)
and NaBH4 (1.25 mmol, 0.047 g) were added. The mixture was heated at reflux for 2 h.
Then, the solution was diluted with water (10 mL) and THF was evaporated. The residue
was extracted with ethyl acetate. The combined organic layers were dried over MgSO4.
The solvent was evaporated and crude products were purified by CC (SiO2, petroleum
ether/ethyl acetate 8:2).
4.2.1. Di(thiophen-2-yl)methanol (2a)
Colorless solid; yield: 147 mg (79%); m.p. 50.0–52.0°C (petroleum ether/CH2Cl2) ([12]:
1
3
m.p. 53°C). H NMR (600 MHz, CDCl3): δ 2.76 (d, JH,H = 4.2 Hz, OH), 6.30 (d,
JH,H = 4.2 Hz, CH O), 6.99 (dd, JH,H = 3.6 Hz, 3JH,H = 4.8 Hz, 2CHarom), 7.02–7.05
3
3
−
(m, 2CHarom), 7.30 (d, 3JH,H = 4.8 Hz, 2CHarom) ppm. 13C{ H} NMR (150 MHz, CDCl3):
1
−
δ 68.5 (CH O), 125.0, 125.4, 126.6 (6CHarom), 147.1 (2Carom) ppm. IR (KBr): υ 3243s
(OH), 3101m, 2923m, 2854m, 2357m, 2027w, 1945w, 1792w, 1733w, 1673w, 1606w, 1537w,
1439m, 1363m, 1347m, 1271m, 1230m, 1163m, 1135m, 1075m, 1006s, 850m, 796m, 752m,
701vs cm−1. Anal. calcd for C9H8OS2 (196.29): C 55.07, H 4.11, S 32.67; found: C 55.25,
H 4.18, S 32.51.

JOURNAL OF SULFUR CHEMISTRY
7
4.2.2. (Selenophen-2-yl)(thiophen-2-yl)methanol (2b)
Pale yellow solid; yield: 228 mg (94%); m.p. 58.0–60.0°C (petroleum ether/CH2Cl2) ([12]:
1
3
m.p. 62.5°C). H NMR (600 MHz, CDCl3): δ 2.74 (d, JH,H = 3.6 Hz, OH), 6.30 (d,
3
−
JH,H = 3.6 Hz, CH O), 6.97–7.01 (m, 1CHarom), 7.04–7.07 (m, 1CHarom), 7.17–7.19 (m,
1CHarom), 7.20–7.23 (m, 1CHarom), 7.30 (dd, 4JH,H = 1.2 Hz, 3JH,H = 5.4 Hz, 1CHarom),
7.99 (dd, JH,H = 1.2 Hz, JH,H = 5.4 Hz, 1CHarom) ppm. 13C{ H} NMR (150 MHz,
4
3
1
−
CDCl3): δ 70.3 (CH O), 124.9, 125.5, 126.6, 126.9, 129.1, 130.9 (6CHarom), 147.5, 154.6
(2Carom) ppm. IR (KBr): υ 3500s (OH), 3414s, 3098m, 3069m, 2955w, 2920w, 2854w,
1815w, 1736w, 1673w, 1606w, 1543m, 1447m, 1372m, 1347m, 1292m, 1261s, 1217s, 1173m,
1125s, 1066m, 1014m, 986s, 856m, 834s, 807m, 755m, 698vs cm−1
4.2.3. (Furan-2-yl)(selenophen-2-yl)methanol (2c)
.
Isolated as a viscous oil turning brownish when stored at ambient conditions; yield:
1
3
148 mg (65%). H NMR (600 MHz, CDCl3): δ 2.72 (d, JH,H = 4.8 Hz, OH), 6.07 (d,
3
−
JH,H = 4.8 Hz, CH O), 6.31–6.33 (m, 1CHarom), 6.35–6.38 (m, 1CHarom), 7.17–7.19 (m,
4
1CHarom), 7.20–7.24 (m, 1CHarom), 7.41–7.42 (m, 1CHarom), 8.00 (dd, JH,H = 0.6 Hz,
JH,H = 6.0 Hz, 1CHarom) ppm. 13C{ H} NMR (150 MHz, CDCl3): δ 68.1 (CH O), 107.2,
3
1
−
110.3, 127.1, 129.1, 131.0, 142.5 (6CHarom), 151.7, 155.1 (2Carom) ppm. IR (KBr): υ 3430s
(OH), 3107w, 3050w, 2930w, 1720s, 1701s, 1502m , 1448m, 1369m, 1233m, 1144m, 1071m,
1011m, 986m, 922m, 805m, 739s, 691vs cm−1. All attempts to prepare this product as an
analytically pure sample were unsuccessful.
4.2.4. Phenyl(thiophen-2-yl)methanol (2d)
Pale yellow solid; yield: 177 mg (93%); m.p. 58.0–60.0°C (petroleum ether/CH2Cl2) ([12]:
1
−
m.p. 62.5°C). H NMR (600 MHz, CDCl3): δ 2.53–2.56 (m, OH), 6.03–6.07 (m, CH O),
6.88–6.91 (m, 1CHarom), 6.94–6.98 (m, 1CHarom), 7.24–7.29 (m, 1CHarom), 7.31–7.35
(m, 1CHarom), 7.36–7.41 (m, 2CHarom), 7.43–7.49 (m, 2CHarom) ppm. 13C{ H} NMR
1
−
(150 MHz, CDCl3): δ 72.4 (CH O), 124.8, 125.3, 126.3, 126.6, 127.9, 128.5 (8CHarom),
143.1, 148.1 (2Carom) ppm. IR (KBr): υ 3256s (OH), 2664w, 2357m, 2338m, 2145w, 1958w,
1894w, 1796w, 1768w, 1600w, 1486m, 1458m, 1435m, 1353m, 1280m, 1258m, 1201m,
1144m, 1033m, 1008vs, 916m, 853m, 824m, 786m, 726m, 694vs, 590m, 527m cm−1. Anal.
calcd for C11H10OS (190.26): C 69.44, H 5.30, S 16.85; found: C 69.45, H 5.31, S 16.95.
4.2.5. Phenyl(selenophen-2-yl)methanol (2e)
Pale yellow solid; yield: 161 mg (68%); m.p. 64.0–66.0°C ([13]: m.p. 60–61°C). 1H NMR
−
(600 MHz, CDCl3): δ 2.58 (brs, OH), 6.04 (brs, CH O), 7.04–7.08 (m, 1CHarom), 7.19
3
3
(dd, JH,H = 3.6 Hz, JH,H = 6.0 Hz, 1CHarom), 7.31–7.35 (m, 1CHarom), 7.37–7.41 (m,
2CHarom), 7.46–7.49 (m, 2CHarom), 7.97 (dd, 4JH,H = 1.2 Hz, 3JH,H = 6.0 Hz, 1CHarom
)
ppm. 13C{ H} NMR (150 MHz, CDCl3): δ 74.2 (CH O), 126.2, 126.6, 128.0, 128.5, 129.1,
130.6 (8CHarom), 143.5, 155.8 (2Carom) ppm. IR (KBr): υ 3215s (OH), 2866m, 2664w,
1958w, 1888w, 1784w, 1600w, 1587w, 1546w, 1496m, 1448s, 1328m, 1293m, 1258m,
1204m, 1195m, 1147m, 1081m, 1033m, 1021s, 922w, 821s, 758m, 707vs, 691vs, 637m,
580m cm−1. Anal. calcd for C11H10OSe (237.16): C 55.71, H 4.25; found: C 55.87, H 4.25.
1
−

8
G. MLOSTOŃ ET AL.
4.2.6. Diphenylmethanol (benzhydryl alcohol) (2f)
1
Colorless solid; yield: 182 mg (99%); m.p. 62.0–63.0°C ([14]: m.p. 65–66°C). H NMR
3
−
(600 MHz, CDCl3): δ 2.37 (d, JH,H = 3.0 Hz, OH), 5.85 (brs, CH O), 7.27–7.31 (m,
2CHarom), 7.33–7.38 (m, 4CHarom), 7.39–7.42 (m, 4CHarom) ppm.
4.3. Synthesis of ferrocenyl(phenyl)methanol (2g) and diferrocenylmethanol (2h)
A solution of a ferrocenyl-substituted ketone (1 mmol) in dry THF (4 mL) was placed in an
ice bath, and the reducing agent LiAlH4 (1.2 mmol, 0.6 mL of a 2 M solution in THF) was
added under an argon atmosphere. A color change from red to yellow was observed. The
reaction was monitored by TLC, and after complete reaction, a saturated aqueous solution
of MgSO4 (4 mL) was added. The crude mixture was filtered through Celite, the solvent
was evaporated, and alcohols 2g–2h were obtained as analytically pure samples.
4.3.1. Ferrocenyl(phenyl)methanol (2g)
1
Yellow solid; yield: 245 mg (84%); m.p. 74.2–75.9°C ([15]: m.p. 78–80°C). H NMR
3
(600 MHz, CDCl3): δ 2.45 (d, JH,H = 3.0 Hz, OH), 4.18–4.19 (m, 1CHFc), 4.20–4.21
3
−
(m, 2CHFc), 4.22–4.23 (m, 1CHFc), 4.24 (s, 5CHFc), 5.49 (d, JH,H = 3.0 Hz, CH O),
7.26–7.28 (m, CHarom), 7.32–7.36 (m, 2CHarom), 7.39–7.41 (m, 2CHarom) ppm. 13C{ H}
1
−
NMR (150 MHz, CDCl3): δ 66.0, 67.4, 68.1, 68.2, 72.0 (4CHFc, CH O), 68.5 (s, 5CHFc),
94.3 (CFc), 126.2, 127.4, 128.2 (5CHarom), 143.3 (Carom) ppm. IR (KBr): υ 3392m (OH),
3082w, 3053w, 3025w, 2920w, 2851w, 1492m, 1454m, 1407m, 1382m, 1363m, 1318m,
1182m, 1100m, 1043m, 1005s, 926m, 821s, 723s, 701vs, 501s, 479vs cm−1. Anal. calcd for
C17H16OFe (292.15): C 69.89, H 5.52; found: C 70.01, H 5.57.
4.3.2. Diferrocenylmethanol (2h)
Yellow solid; yield: 356 mg (89%); m.p. 171–173°C (decomp.) ([16]: m.p. 174–176°C). 1H
3
NMR (600 MHz, CDCl3): 2.38 (d, JH,H = 3.0 Hz, OH), 4.15–4.17 (m, 6CHFc), 4.20 (s,
3
1
10CHFc), 4.25–4.26 (m, 2CHFc), 5.22 (d, JH,H = 3.0 Hz, CH O) ppm. 13C{ H} NMR
−
−
(150 MHz, CDCl3): δ 66.1, 67.2, 67.6, 67.8 (8CHFc), 68.1 (CH O), 68.5 (s, 10CHFc), 93.0
(2CFc) ppm. IR (KBr): υ 3458s (OH), 3104m, 3089m, 2925m, 2853m, 1640m, 1407s, 1319m,
1282m, 1199m, 1162m, 1103vs, 1046s, 1037s, 1024s, 1000vs, 910m, 818vs, 749m, 738m,
525s, 453vs cm−1. Anal. calcd for C21H20OFe2 (400.07): C 63.04, H 5.04, found: C 63.23,
H 5.14.
4.4. Synthesis of sulfides 3a–3c
To a solution of the corresponding alcohol (1 mmol) in dry toluene (5 mL), under an argon
atmosphere, Lawesson’s reagent (0.6 mmol, 0.24 g) was added. The mixture was heated at
reflux and the reaction monitored by TLC. When the alcohol was completely consumed,
the solvent was evaporated and the crude products were purified by CC (SiO2, petroleum
ether/ethyl acetate 8:2).
4.4.1. Bis[di(thiophen-2-yl)methyl]sulfide (3a)
1
−
Colorless oil; yield: 146 mg (75%). H NMR (600 MHz, CDCl3): δ 5.19 (brs, 1CH S),
3
3
−
5.44 (brs, 1CH S), 6.78–6.87 (m, 2CHarom), 6.96 (dd, JH,H = 3.6 Hz, JH,H = 4.8 Hz,

JOURNAL OF SULFUR CHEMISTRY
9
4
2CHarom), 6.97–7.05 (m, 3CHarom), 7.07–7.10 (m, 1CHarom), 7.12 (dd, JH,H = 1.2 Hz,
3JH,H = 4.8 Hz, 1CHarom), 7.28 (dd, 4JH,H = 1.2 Hz, 3JH,H = 4.8 Hz, 2CHarom), 7.30 (dd,
1
4JH,H = 1.2 Hz, 3JH,H = 4.8 Hz, 1CHarom) ppm. 13C{ H} NMR (150 MHz, CDCl3): δ 45.1
−
(2CH S), 125.5, 126.2, 126.6 (12CHarom), 144.5 (4Carom) ppm. IR (film): υ 3104m, 3066m,
2927w, 2854w, 2464w, 2429w, 2287w, 2151w, 2075w, 1894w, 1793m, 1730w, 1676w,
1597m, 1527m, 1432s, 1363m, 1350m, 1277m, 1236s, 1102m, 1081m, 1043s, 853s, 755m,
698s cm−1. Anal. calcd for C18H14S5 (390.63): C 55.34, H 3.61, S 41.04; found: C 55.07, H
3.88, S 40.99.
4.4.2. (1:1)-Mixture of meso- and d,l-bis[phenyl(thiophen-2-yl)methyl]sulfide (3b)
1
−
Pale yellow oil; yield: 174 mg (92%). H NMR (600 MHz, CDCl3): δ 5.10 (brs, 1CH S), 5.11
−
(brs, 1CH S), 6.93–7.00 (m, 4CHarom), 7.26–7.28 (m, 2CHa1rom), 7.29–7.33 (m, 2CHarom),
7.34–7.39 (m, 4CHarom), 7.40–7.46 (m, 4CHarom) ppm. 13C{ H} NMR (150 MHz, CDCl3):
−
δ 49.79, 49.82 (2CH S), 125.2, 125.3, 125.9, 126.0, 126.6, 126.7, 127.6, 127.7, 128.2, 128.5,
128.6 (16CHarom), 140.5, 140.6, 145.1, 145.2 (4Carom) ppm. IR (KBr): υ 3104m, 3059m,
3025m, 2921m, 2851m, 1945w, 1879w, 1798w, 1635w, 1598m, 1493s, 1454s, 1432m, 1264m,
1230m, 1075m, 1029m, 853m, 821m, 698vs, 637m, 590m, 512m cm−1. Anal. calcd for
C22H18S3 (378.57): C 69.80, H 4.79, S 25.41; found: C 69.69, H 4.87, S 25.40.
4.4.3. (1:1)-Mixture of meso- and d,l-bis[phenyl(selenophen-2-yl)methyl]sulfide (3c)
1
Colorless, viscous oil; yield: 177 mg (75%). H NMR (600 MHz, CDCl3): δ 5.18 (brs,
−
−
1CH S), 5.19 (brs, 1CH S), 7.03–7.08 (m, 2CHarom), 7.14–7.21 (m, 2CHarom), 7.29–7.38
1
(m, 6CHarom), 7.40–7.46 (m, 4CHarom), 7.92–7.97 (m, 2CHarom) ppm. 13C{ H} NMR
−
(150 MHz, CDCl3): δ 52.2, 52.3 (2CH S), 127.6, 127.7, 128.0, 128.1, 128.2, 128.3, 128.6,
128.7, 129.1, 130.8, 130.9 (16CHarom), 141.0, 152.8, 152.9 (4Carom) ppm. IR (film): υ
3060m, 3028m, 2923m, 1951w, 1888w, 1806w, 1727w, 1600m, 1540w, 1492m, 1451s,
1333w, 1261m, 1230m, 1106m, 1074m, 1030m, 805m, 739m, 698vs cm−1. Anal. calcd for
C22H18SSe2 (472.36): C 55.94, H 3.84, S 6.79; found: C 55.88, H 4.12, S 7.09.
4.5. Synthesis of diphenylmethanethiol (4a)
A solution of benzhydryl alcohol (2f) (1 mmol, 0.18 g) in a mixture of toluene (5 mL) and
water (1.4 mmol, 0.025 g) with Lawesson’s reagent (2.4 mmol, 0.97 g) was heated at reflux
for 30 min. Next, the toluene was evaporated under reduced pressure. The crude product
was purified by CC (SiO2, petroleum ether/ethyl acetate 9:1). Colorless oil; yield of 4a
[6]: 180 mg (90%). 1H NMR (600 MHz, CDCl3): δ 2.29 (d, 3JH,H = 4.8 Hz, SH), 5.47 (d,
3
−
JH,H = 4.8 Hz, CH S), 7.24–7.28 (m, 2CHarom), 7.31–7.36 (m, 4CHarom), 7.42–7.46 (m,
4CHarom) ppm.
4.6. Synthesis of ferrocenyl(phenyl)methanethiol (4b) and
diferrocenylmethanethiol (4c)
Lawesson’s reagent (0.6 mmol, 0.24 g) was added to a solution of ferrocenyl-substituted
methanols 2g or 2h (1 mmol) in dry toluene (5 mL) under argon and heated at reflux for
10 min. Then, the solvent was evaporated and the crude product was purified by CC (SiO2,

10
G. MLOSTOŃ ET AL.
petroleum ether/CH2Cl2 7:3). Both products undergo decomposition, even when stored
at −78°C (dry ice) for a longer time.
4.6.1. Ferrocenyl(phenyl)methanethiol (4b)
Viscous yellow oil; yield: 179 mg (58%). 1H NMR (600 MHz, CDCl3): δ 2.38 (d,
3JH,H = 4.2 Hz, SH), 4.09 (brs, 1CHFc), 4.14 (brs, 1CHFc), 4.18 (s, 5CHFc), 4.20 (brs,
3
−
1CHFc), 4.43 (brs, 1CHFc), 5.17 (d, JH,H = 4.2 Hz, CH S), 7.20–7.24 (m, 1CHarom),
7.28–7.32 (m, 2CHarom), 7.33–7.38 (m, 2CHarom) ppm. 13C{ H} NMR (150 MHz, CDCl3):
1
−
δ 44.1 (CH S), 67.7, 67.8, 67.9, 68.1 (4CHFc), 69.0 (5CHFc), 91.8 (CFc), 127.1, 127.3, 128.4
(5 CHarom), 144.6 (Carom) ppm. IR (KBr): υ 3091m, 3028m, 2965m, 2923m, 2854w, 2566w,
1951w, 1875w, 1641m, 1600m, 1496m, 1451s, 1413m, 1268m, 1103s, 1027s, 995m, 821vs,
707vs cm−1. Anal. calcd for C17H16FeS (308.22): C 66.25, H 5.23, S 10.40; found: C 66.08,
H 5.24, S 10.27.
4.6.2. Diferrocenylmethanethiol (4c)
1
Viscous yellow oil; yield: 233 mg (56%). H NMR (600 MHz, C6D6): δ 2.40 (brs, SH),
3.89–3.95 (m, 6CHFc), 4.08 (s, 10CHFc), 4.25 (brs, 2CHFc), 4.73 (brs, CH S) ppm. 13C{ H}
1
−
−
NMR (150 MHz, C6D6): δ 67.4, 67.5, 67.9, 68.2 (8CHFc), 69.3 (10 CHFc), 69.5 (CH S), 93.7
(2CFc) ppm. IR (KBr): υ 3085m, 2920m, 2847m, 2569w, 1613m, 1461m, 1410m, 1258m,
1103s, 1021m, 1002m, 818s, 479vs cm−1. Anal. calcd for C21H20Fe2S (416.14): C 60.61, H
4.84, S 7.71; found: C 60.48, H 4.74, S 7.52.
4.7. Synthesis of dibenzhydryl 4-methoxyphenyltrithiophosphonate (5)
To a solution of benzhydryl alcohol (2f) (1 mmol, 0.18 g) in absolute toluene (5 mL),
Lawesson’s reagent (2.4 mmol, 0.97 g) was added, and the mixture was heated at reflux.
After 15 min, the solvent was evaporated and the crude products were separated by CC
(SiO2, petroleum ether/ethyl acetate 9:1). Yield of 4a: 122 mg (61%). 5: Colorless solid;
yield: 104 mg (18%); m.p. 109.0–110.0°C. 1H NMR (600 MHz, CDCl3): δ 3.78 (s, CH3O),
−
−
5.79 (brs, 1CH S), 5.81 (brs, 1CH S), 6.67–6.71 (m, 2CHarom), 7.09–7.16 (m, 6CHarom),
7.19–7.25 (m, 6CHarom), 7.26–7.30 (m, 4CHarom), 7.32–7.36 (m, 4CHarom), 7.61–7.68 (m,
2CHarom) ppm. 13C{ H} NMR (150 MHz, CDCl3): δ 55.4 (CH3O), 56.8, 56.9 (2CH S),
1
−
113.4, 113.5, 127.0, 127.2, 128.2, 128.3, 128.7, 128.9, 132.8, 132.9 (24CHarom), 140.5, 140.6,
140.8, 140.9, 162.4, 162.5 (6Carom) ppm. 31P NMR (243 MHz, CDCl3): δ 78.22 ppm. IR
(KBr): υ 3056w, 3022w, 2996w, 2873w, 1597s, 1499m, 1492m, 1451m, 1309m, 1264s,
1182m, 1100s, 1024m, 831m, 698vs, 530s cm−1. Anal. calcd for C33H29OPS3 (568.75): C
69.69, H 5.14, S 16.91; found: C 69.66, H 5.26, S 16.67.
4.8. Attempted reaction of diphenylmethanethiol (4a) with Lawesson’s reagent
A sample of pure 4a (190.0 mg, 1.0 mmol) and Lawesson’s reagent (242.0 mg, 0.6 mmol)
were dissolved in 6 mL of dry toluene and the mixture was heated at reflux. The disappear-
ance of 4a was monitored by TLC (SiO2, petroleum ether/ethyl acetate 9:1), and after 15
min, no starting material (Rf = 0.70) could be detected. The formation of the expected
trithiophosphonate 5 was evidenced by comparison with a pure sample (Rf = 0.40).

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11
4.9. X-ray crystal structure determination of compound 5 [25]
All measurements were made on Rigaku Oxford Diffraction SuperNova area-detector
diffractometer [26] using MoKα radiation (λ = 0.71073 Å) from a micro-focus X-ray
source and an Oxford Instruments Cryojet XL cooler. The data collection and refinement
parameters are given below [25] and a view of the molecule is shown in Figure 1. Data
reduction was performed with CrysAlisPro [26]. The intensities were corrected for Lorentz
and polarization effects, and an empirical absorption correction using spherical harmon-
ics [26] was applied. Equivalent reflections were merged. The structure was solved by dual
space methods using SHELXT-2014 [27], which revealed the positions of all non-hydrogen
atoms. The non-hydrogen atoms were refined anisotropically. All of the H-atoms were
placed in geometrically calculated positions and refined by using a riding model where
each H-atom was assigned a fixed isotropic displacement parameter with a value equal to
1.2Ueq of its parent atom (1.5Ueq for the methyl group). The refinement of the structure
was carried out on F2 by using full-matrix least-squares procedures, which minimized the
ꢀ
function w(Fo2 − Fc2)2. A correction for secondary extinction was not applied. Neutral
atom scattering factors for non-H-atoms were taken from [28], and the scattering factors
for H-atoms were taken from [29]. Anomalous dispersion effects were included in Fc [30];
the values for f ꢀ and f ꢀꢀ were those of [31]. The values of the mass attenuation coefficients
are those of [32]. All calculations were performed using the SHELXL-2014 program [33].
Crystal data for 5: C33H29OPS3, M = 568.71, crystallized from petroleum ether/
CH2Cl2, colorless, prism, crystal dimensions 0.15 × 0.25 × 0.26 mm, triclinic, space
¯
group P1, Z = 2, reflections for cell determination 21105, 2θ range for cell determi-
nation 5–65°, a = 10.2285(2) Å, b = 10.8866(2) Å, c = 14.7543(3) Å, α = 80.4281(18),
β = 84.6407(17), γ = 62.910(2)°, V = 1442.04(6) Å3, T = 160(1) K, DX = 1.310 g cm−3
μ(MoKα) = 0.338 mm−1, scan type ω, 2θ(max) = 64.9°, transmission factors (min;
max) = 0.955; 1.000, total reflections measured 45,039, symmetry independent reflec-
tions 9732, reflections with I > 2σ(I) 8001, reflections used in refinement 9732, param-
eters refined 344, R(F) [I > 2σ(I) reflections] = 0.0340, wR(F2) [all data] = 0.0886
(w = [σ2(Fo2) + (0.0357P)2 + 0.5162P]−1, where P = (Fo2 + 2Fc2)/3), goodness of fit
,
1.042, final ꢀmax/σ 0.002, ꢀρ (max; min) = 0.36; −0.25 e Å−3
.
Acknowledgement
Skillful performance of elemental analysis of all new compounds by Ms Agnieszka Cieślińska and
Ms Hanna Jatczak (University of Łódź) is gratefully acknowledged.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
The authors thank the National Science Center (Cracow, Poland) for generous financial support
[grant Maestro-3 (Dec-2012/06/A/ST5/00219)].
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