Synthesis, structure, and thermolysis of tris(dimethylphenylsilyl)methyl sulfenyl chloride

Article abstract of DOI:10.1246/cl.170188

Sulfenyl chlorides, i.e., di-coordinated sulfur(II) chlorides are useful precursors for a variety of organic sulfur compounds. Herein, the synthesis, structure, and reactivity of a sulfenyl chloride that bears a bulky tris(dimethylphenylsilyl)methyl group on the sulfur atom are reported. The thermolysis of this sulfenyl chloride resulted in the generation of the corresponding bissilylthioketone via the 1,2-elimination of chlorodimethylphenylsilane.

Full text of DOI:10.1246/cl.170188

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Synthesis, Structure, and Thermolysis of Tris(dimethylphenylsilyl)methyl Sulfenyl Chloride
Koh Sugamata* and Shigeru Ishii
Advance Publication on the web March 25, 2017
doi:10.1246/cl.170188
© 2017 The Chemical Society of Japan
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1
Synthesis, Structure, and Thermolysis of Tris(dimethylphenylsilyl)methyl Sulfenyl Chloride
Koh Sugamata*, Shigeru Ishii
Faculty of Science and Engineering, Toyo University, Kawagoe, Saitama, 350-8585
(E-mail: sugamata@toyo.jp)
Sulfenyl chlorides, i.e., di-coordinated sulfur(II)
chlorides are useful precursors for a variety of organic sulfur
compounds. Herein, the synthesis, structure, and reactivity of
In this paper, we report the synthesis and X-ray
crystallographic analysis of a sulfenyl chloride that bears a
bulky tris(dimethylphenylsilyl)methyl group (Tpsi),7 which is
much bulkier than the C(SiMe3)3 group. The generation of a
bissilylthioketone upon thermolysis of the sulfenyl chloride
was confirmed by a trapping reaction with 2,3-dimethyl-1,3-
a
sulfenyl
chloride
that
bears
a
bulky
tris(dimethylphenylsilyl)methyl group on the sulfur atom is
reported. The thermolysis of this sulfenyl chloride resulted in
the generation of the corresponding bissilylthioketone via the
1,2-elimination of chlorodimethylphenylsilane.
butadiene,
which
afforded
the
corresponding
[4+2]cycloadduct.
Sulfur is abundant in nature, and biologically the most
important chalcogen.
A rich variety of organosulfur
compounds has been used in organic chemistry, biochemistry,
and material chemistry. For the synthesis of organic sulfur
compounds, sulfenyl halides represent a crucial starting
material.1 Compared to the other sulfenyl halides,2 which are
unstable and highly reactive, sulfenyl chlorides are
remarkably stable, and it is therefore not surprising that the
synthesis and characterization of various sulfenyl chlorides
has already been reported.3 But despite the number of
examples, thorough structural analyses of sulfenyl chlorides
with single-crystal X-ray diffraction techniques have not yet
been reported. Silylthioketones, on the other hand, are key
intermediates for the organic synthesis of vinylsilanes,
dienophiles, and radical trapping agents.4 However, only a
few synthetic studies on bissilylthioketones have been
reported to date. Ricci and co-workers have reported the
thermolysis of tris(trimethylsilyl)methyl sulfenylbromide
(TsiSBr; 1) to afford bis(trimethylsilyl)thioketone (2) and
small amounts of its dimer, i.e., the corresponding dithietane
derivative (3).5 Attempts to purify the bissilylthioketone by
column chromatography on Florisil remained unsuccessful,
due to the instability of 2 under these conditions. Brook et al.
have carried out trapping reactions of in-situ-generated
bissilylthioketone 2 upon heating bis(trimethylsilyl)methyl
alkanethiosulfinate esters (4) (Scheme 1).6
Scheme 2. Synthesis of TpsiSCl (3)
The Tpsi-substituted thiol (TpsiSH; 6), was prepared
according to a modification of the method reported by Tang et
al.:8 MeLi in Et2O was added to a THF solution of TpsiH (5)
at room temperature. The mixture was heated to reflux for 3 h,
and then cooled to room temperature. The resulting mixture
was treated with 1.2 equivalents of elemental sulfur. The
reaction mixture was stirred for 1 h, before it was quenched
with an aqueous solution of NH4Cl. The crude mixture was
recrystallized from CH2Cl2/hexane to furnish TpsiSH (6) as
colorless crystals in 75% yield (Scheme 2), which is a
remarkable improvement compared to the 10% yield reported
in the literature. A THF solution of TpsiSLi, prepared by the
treatment of TpsiSH with 1.1 equiv. of MeLi, was treated with
1.1 equivalents of SO2Cl2, to give the corresponding sulfenyl
chloride (TpsiSCl; 7) as yellow crystals in 99% yield.
Although du Mont et al. have recently reported the synthesis
of TsiSCl via the chlorination of TsiSH with SOCl2 in Et2O,9
this reaction did not occur in our case.
The structure of sulfenyl chloride 7 was unequivocally
determined by spectroscopic and X-ray crystallographic
analyses (Figure 1).10 In contrast to TsiSI,11 sulfenyl chloride
7 exist as a monomer in the crystalline state. The S-Cl
[2.0472(8) Å] and C-S bond lengths [1.828(2) Å] suggest an
intermediate position for 7 between triphenylmethyl- (8) and
phenyl-substituted sulfenyl chloride (9) (Table 1).12
Theoretical calculations were carried out at the B3PW91/6-
311G(2d,p) level of theory in order to compare the bond
lengths of these sulfenyl chlorides. In the thus obtained
optimized structures, a similar trend was observed for the C-S
bond lengths of these compounds. In contrast, the
experimentally observed S-Cl bond lengths are shortened
relative to the optimized ones. The Si1···Cl1 distance (~3.6
Å) in the solid state is shorter than the sum of van der Waals
Scheme 1. Previously reported methods for the synthesis of
bissilylthioketones

2
radii of Si and Cl atoms (4.31 Å), indicating an intramolecular
interaction between these atoms.13 Theoretical calculations
were carried out at the B3PW91/6-311G(2d,p) level of theory
in order to gain further structural information on 7, and the
theoretically optimized structural parameters of 7 are in good
agreement with the experimentally observed values (Table 1).
kcal·mol–1) relative to TpsiSCl (7), and therefore the 1,2-
elimination of chlorosilane should be exothermic.
A
combined consideration of the aforementioned results and the
previous reports, renders the conclusion feasible that
bissilylthioketone 10 should be generated from the
thermolysis of 7 via a 1,2-elimination of Me2PhSiCl.
Therefore, we examined the trapping reaction of
bissilylthioketone 10 with 2,3-dimethyl-1,3-butadiene. For
that purpose, a toluene solution of sulfenyl chloride 7 was
heated to 100 °C in the presence of an excess of 2,3-dimethyl-
1,3-butadiene. After 2 h, the color of the solution changed
from pale yellow to colorless. After removal of all volatiles,
the crude product was recrystallized from MeOH to afford the
corresponding cyclic product 2,2-bissilyl-4,5-dimethyl-3,6-
dihydro-2H-thiopyran (11) in 83% yield. The efficiency of the
formation of 11 was remarkably improved relative to the
method reported by Block et al. (46%).8 Thus, the formation
of 11 should most likely be interpreted in terms of the
intermediacy of bissilylthioketone 10, which should be
generated by the thermolysis of sulfenyl chloride 7 (Scheme
3). Compound 11 was characterized by multinuclear NMR
spectroscopy and high-resolution mass spectrometry. Finally,
the molecular structure of diene adduct 11 was confirmed by
single-crystal X-ray diffraction analysis (Figure 2).15
Figure 1. Molecular structure of 7 with thermal ellipsoids set at
50% probability. Hydrogen atoms are omitted for clarity.
Table 1. Selected bond distances (Å) and angles (º) for sulfenyl
halides 7-9.
Scheme 3. Generation and trapping of 10 as the corresponding
bissilylthioketone (11)
Lewis acids such as AlCl3 can promote the catalytic 1,2-
elimination of chlorosilane from chlorophosphines to furnish
the corresponding phosphaalkenes.14 In contrast, the
attempted
Lewis-acid-catalyzed
1,2-elimination
of
chlorosilane from sulfenyl chloride
7
to furnish
bissilylthioketone 10 was not successful. However, thermal
reactions of 7 in solution (in CDCl3 in a degassed and sealed
tube; 100 °C) or in the solid state (100 ºC) induced the 1,2-
elimination of Me2PhSiCl, under concomitant formation of
complicated product mixtures, which could not be identified,
even on the basis of applying several spectroscopic analysis
techniques. Since the melting point of TsiSCl (152 °C) is
higher than that of TpsiSCl (102 °C, dec.), we tentatively
assigned a higher thermal stability to TsiSCl than to TpsiSCl.
Theoretical calculations at the B3PW91/6-311G(2d,p) level of
theory predicted the formation of bissilylthioketone 10 and
Me2PhSiCl to be thermodynamically more stable (37.2
Figure 2. Molecular structure of 2,2-bissilyl-4,5-dimethyl-3,6-
dihydro-2H-thiopyran 11 with atomic displacement parameters
set at 50% probability. Hydrogen atoms are omitted for clarity.
Selected bond lengths (Å) and bond angles (º): C(1)-C(2)
1.555(7), C(1)-S(1) 1.852(5), C(2)-C(3) 1.509(6), C(3)-C(4)
1.327(7), C(3)-C(6) 1.501(6), C(4)-C(5) 1.509(7), C(4)-C(7)
1.538(7), C(5)-S(1) 1.820(5). C(2)-C(1)-S(1) 106.5(3), C(2)-
C(1)-Si(1) 111.3(3), S(1)-C(1)-Si(1) 111.7(2), C(3)-C(2)-C(1)
117.6(4), C(4)-C(3)-C(6) 123.1(4), C(4)-C(3)-C(2) 122.4(4),
C(6)-C(3)-C(2) 114.4(4), C(3)-C(4)-C(5) 126.1(4), C(3)-C(4)-

3
11
12
Both the shortest intermolecular S···S and S···Cl distances are ~ 8
Å.
a) Williams, C. R.; Britten, J. F.; Harpp, D. N. J. Org. Chem.1994,
59, 806-812. b) Zaripov, N. M.; Popik, M. V.; Vilkov, I. V. J.
Struct. Chem. 1980, 21, 728-732.
C(7) 124.1(5), C(5)-C(4)-C(7) 109.8(4), C(4)-C(5)-S(1) 117.9(3),
C(5)-S(1)-C(1) 103.7(2).
In summary, sulfenyl chloride 7 was obtained from
the chlorination of the corresponding thiol (6), and its solid-
state structure was unambiguously determined. The
thermolysis of 7 in the presence of 2,3-dimethyl-1,3-butadiene
afforded the corresponding [4+2] cycloadduct of the
bissilylthioketone (11), suggesting that bissilylthioketone 10
should be generated via the elimination of 1,2-chlorosilane
from PhMe2SiCl. Further investigations into the synthesis and
isolation of stable bissilylthioketone derivatives, which
contain sterically demanding substituents, are currently in
progress.
13
14
For values of atomic van der Waals radii, see: Batsanov, S. S.
Inorganic Materials 2001, 37, 871-885.
a) Sugamata, K.; Sasamori, T.; Tokitoh, N. Chem. Lett. 2014, 43,
95-96. b) Sasamori, T.; Villalba Franco, J. M.; Guo, J.-D.; Nagase,
S.; Streubel, R.; Tokitoh, N. Eur. J. Inorg. Chem. 2016, 678-684.
Crystal data for 11: C23H31SSi2, M = 364.47, T = 90(2) K, Triclinic,
P-1, a = 7.066(3) Å, b = 10.375(4) Å, c = 16.720(7) Å,  =
78.841(6)°,  = 83.460(6)°,  = 83.184(6)°, V = 1188.8(8)Å3, Z = 2,
Dcalcd = 1.018 Mg/m3,  = 0.238 mm-1,  = 0.78224 Å, 2max = 52°,
measured/independent reflections = 6835/3358 (Rint = 0.0726), 241
refined parameters, GOF = 1.016, R1 = 0.0575 [I > 2(I)], wR2 =
0.1753[for all data], largest diff. peak and hole 0.431 and -0.394
e.Å-3 [CCDC-1482691]
15
Acknowledgement
We would like to express our sincere gratitude to Prof. Dr.
Mao Minoura (Rikkyo University) and to Prof. Dr. Takahiro
Sasamori (Kyoto University) for their advice and fruitful
discussions. Synchrotron radiation experiments were carried
out at the BL40XU beam line of SPring-8 with the approval
of the Japan Synchrotron Radiation Research Institute
(JASRI; proposal 2015B1074).
Supporting
Information
is
available
on
http://dx.doi.org/10.1246/cl.******.
References and Notes
1
Devillanova, F. (ed.) Handbook of Chalcogen Chemisry: New
Perspectives in Sulfur, Selenium and Tellurium (Royal Society of
Chemisry, 2006).
2
3
a) Reno, D. S.; Pariza, R. J.; Org. Synth. 1998, 9, 662. b) Sase, S.;
Aoki, Y.; Abe, N.; Goto, K. Chem. Lett. 2009, 38, 1188-1189.
a) Drabowicz, J; Kiełbasiński, P; Łyżwa, P; Mikołajczyk, M.;
Zając, A., Science of Synthesis 2009, 42, 679-778. b) Kambe, N,
Science of Synthesis, 2008, 39, 544-550.
4
a) Barbaro, G.; Battaglia, A.; Giorgianni, P.; Maccagnani, G.;
Macciantelli, D. J. Chem. Soc. Perkin Trans 1 1986, 381-385. b)
Bonini, B. F.; Mazzanti, G.; Zani, P.; Maccagnani, G. J. Chem.
Soc., Chem. Commun. 1988, 365-367. c) Ricci, A.; Degl’Innocenti,
A.; Capperucci, A.; Reginato, G. J. Org. Chem. 1989, 54, 20-21. d)
Alberti, A.; Benaglia, M. J. Organomet. Chem. 1992, 151-158. e)
Bonini, B. F.; Comes-Franchini, M.; Fochi, M.; Mazzanti, G.; Ricci,
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Degl’Innocenti, A.; Capperucci, A.; Oniciu, D. C.; Katritzky, A. R.
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5
Ricci, A.; Degl’Innocenti, A.; Fiorenza, M. Dembech, P.; Ramadan,
N.; Seconi, G.; Walton, D. R. M. Tetrahedron Lett. 1985, 26, 1091-
1092.
6
7
Block, E.; Aslam, M. Tetrahedron Lett., 1985, 26, 2259-2262.
Al-Juaid, S. S.; Eaborn, C.; Habtemariam, A.; Hitchcock, P. B.;
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8
9
Tang, K.; Aslam, M.; Block, A. E.; Nicholson, T.; Zubieta, Inorg.
Chem. 1987, 26, 1488-1497.
Wismach, C.; Jones, P. G.; du Mont, W-W.; Mugesh, G.; Papke,
U.; Linden, H. B.; Arca, M.; Lippolis, V. Eur. J. Inorg. Chem.
2014, 1399-1406.
10
Crystal data for 7: C25H33ClSSi3, M = 485.29, T = 100(2) K,
monoclinic, P21/c, a = 14.8132(4) Å, b = 13.2259(3) Å, c =
13.5650(4) Å,  = 99.0580(10)°, V = 2624.48(12)Å3, Z = 4, Dcalcd
=
1.228 Mg/m3,  = 3.412 mm-1,  = 1.54178 Å, 2max = 66.57°,
measured/independent reflections = 16973/4616 (Rint = 0.0311),
277 refined parameters, GOF = 1.035, R1 = 0.0437 [I > 2(I)], wR2
= 0.1281[for all data], largest diff. peak and hole 0.531 and -0.304
e.Å-3 [CCDC-1482690]