A reaction of 3,6-di(tert-butyl)-4-chloro-1,2-benzoquinone with potassium ethyl xanthate. New sulfur-containing o-quinones

Article abstract of DOI:10.1007/s11172-006-0317-9

In a reaction of 3,6-di(tert-butyl)-4-chloro-1,2-benzoquinone with potassium ethyl xanthate, the halogen atom was replaced by the ethyl xanthate group. Acid hydrolysis of the product gave 4,7-di(tert-butyl)-5,6-dihydroxy-1,3- benzodithiol-2-one containing

Full text of DOI:10.1007/s11172-006-0317-9

Russian Chemical Bulletin, International Edition, Vol. 55, No. 4, pp. 708—711, April, 2006
708
A reaction of 3,6ꢀdi(tertꢀbutyl)ꢀ4ꢀchloroꢀ1,2ꢀbenzoquinone
with potassium ethyl xanthate. New sulfurꢀcontaining oꢀquinones
V. A. Kuropatov,ꢀ V. K. Cherkasov, Yu. A. Kurskii, G. K. Fukin, L. G. Abakumova, and G. A. Abakumov
G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences,
49 ul. Tropinina, 603950 Nizhnii Novgorod, Russian Federation.
Fax: +7 (831 2) 12 7497. Eꢀmail: viach@iomc.ras.ru
In a reaction of 3,6ꢀdi(tertꢀbutyl)ꢀ4ꢀchloroꢀ1,2ꢀbenzoquinone with potassium ethyl
xanthate, the halogen atom was replaced by the ethyl xanthate group. Acid hydrolysis of the
product gave 4,7ꢀdi(tertꢀbutyl)ꢀ5,6ꢀdihydroxyꢀ1,3ꢀbenzodithiolꢀ2ꢀone containing a pyrocatꢀ
echol fragment, which was oxidized into the corresponding quinone. When irradiated in soluꢀ
tion with visible light, this quinone quantitatively eliminated a CO molecule with contraction
of the ring to a fiveꢀmembered one. The quinones obtained were studied as ligands in coordinaꢀ
tion spheres of metals by ESR spectroscopy.
Key words: sterically hindered oꢀquinones and pyrocatechols, 1,3ꢀdithiole, metal comꢀ
plexes with oꢀsemiquinones.
In recent years, investigations of complexes of transiꢀ
Results and Discussion
tion and Main Group elements with sterically hindered
ligands genetically related to oꢀquinones have become a
separate area of coordination chemistry. Such rapt attenꢀ
tion is due to at least two reasons.
1. When entering the coordination sphere of a metal,
these variableꢀvalence ligands conform their valences to
the redox potential of the metal in the rest of the ligand
environment. Thus, the structure of a redox ligand allows
one to control the valences in the complex.
When equimolar amounts of the reagents were mixed
in THF at room temperature, the starting oꢀquinone (1)
virtually completely converted into quinone 2 in 20 min
(Scheme 1).
Scheme 1
2. Bringing the valences of a metal and a redox ligand
to thermodynamic agreement is usually accompanied by
intramolecular electron transfer. With consideration that
stable radical species are conveniently detected by the
ESR method, this provides a powerful source of informaꢀ
tion on the structure and dynamics of the coordination
sphere of the metal.
Extension of the range of the redox properties of
ligands attracts attention to the problem of functionaliꢀ
zation of oꢀquinones. The range of the latter can be subꢀ
stantially extended by using reactions of 3,6ꢀdi(tertꢀbuꢀ
tyl)ꢀ1,2ꢀbenzoquinone with organometallic compounds
and CH acids.1,2 An alternative is nucleophilic displaceꢀ
ment of the halogen from positions 4 and 5 of sterically
hindered oꢀquinone. We employed this reaction for the
synthesis of sulfurꢀcontaining oꢀquinones. 3,6ꢀDi(tertꢀ
butyl)ꢀ4ꢀchloroꢀ1,2ꢀbenzoquinone (1) was used as a subꢀ
strate and potassium ethyl xanthate was used as a nucleoꢀ
philic reagent. In the present work, we studied new synꢀ
thetic potentialities associated with subsequent hydrolysis
of the substitution product.
Quinone 2 is a dark red crystalline solid with
m.p. 83 °C, which is soluble in common organic solvents.
Its acid hydrolysis occurs anomalously. It is known3 that
the hydrolysis of xanthates mainly yields thiols through
cleavage of the C—S bond in the sulfide fragment. Howꢀ
ever, quinone 2 in the presence of dilute HCl underwent
closure of the 1,3ꢀdithiole ring to give pyrocatechol 3.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 683—686, April, 2006.
1066ꢀ5285/06/5504ꢀ0708 © 2006 Springer Science+Business Media, Inc.

Sulfurꢀcontaining oꢀquinones and catechols
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 4, April, 2006
709
Scheme 3
The suggested mechanism of the reaction is shown in
Scheme 2.
Scheme 2
The structure of quinone 4 was confirmed by Xꢀray
diffraction analysis. According to the crystallographic data,
its molecule is virtually planar; the bond lengths in the
quinone ring distinctly alternate, which is typical of the
oꢀquinone structure (Fig. 1) (C(3)—C(2), 1.358(3) Å;
C(3)—C(4), 1.479(3) Å; C(4)—C(4A), 1.535(5) Å;
C(2)—C(2A), 1.508(4) Å). The bond lengths in the fiveꢀ
membered ring are typical of 1,3ꢀdithiole rings.5
When a solution of compound 4 in toluene was irradiꢀ
ated with visible light (a KGMꢀ24ꢀ150 halogen lamp),
the oꢀquinone ring eliminated a CO molecule to give
bright red dienone 5 (Scheme 4).
Scheme 4
The reaction proceeded almost quantitatively over sevꢀ
eral hours (TLC data). A similar process is known for
3,6ꢀdi(tertꢀbutyl)ꢀ1,2ꢀbenzoquinone;6 however, it requires
more drastic conditions (UV irradiation) and is followed
by the Diels—Alder dimerization of the resulting dienone.7
O(2A)
O(2)
The overall equation of the process has the form
C(8A)
C(7A)
C(8)
C(7)
C(4A)
C(3A)
C(5A)
C(4)
C(3)
2 + H2O → 3 + EtOH.
The formation of such 1,3ꢀdithiole rings from dithioꢀ
carbamate derivatives of substituted pyridines has been
reported earlier.4
C(5)
C(2A)
C(2)
C(6)
Like most of the known analogs, pyrocatechol 3 is a
colorless crystalline solid with m.p. 110 °C. Its IR specꢀ
trum shows characteristic bands of the C=O stretchꢀ
ing vibrations in the dithiole ring (1630 cm–1) and
of the stretching vibrations of the sterically hindered
OH groups of pyrocatechol (3420 and 3250 cm–1). The
compound is easily oxidized with alkali metal ferricyanide
in ethereal solution into the corresponding oꢀquinone 4
(Scheme 3).
C(6A)
S(1A)
S(1)
C(1)
O(1)
Fig. 1. General view of structure 4.

710
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 4, April, 2006
Kuropatov et al.
C(13)
C(11)
C(12)
C(10)
S(2)
C(4)
C(5)
O(1)
O(2)
C(14)
S(1)
copper to give copper(II) catecholate complex 7. In this
complex, the unpaired electron is localized at the Cu atom
(d9 configuration), which is evident from the parameters
of the ESR spectrum (see Table 1).
C(3)
C(2)
C(1)
C(9)
Thus, we studied the reaction of 3,6ꢀdi(tertꢀbutyl)ꢀ4ꢀ
chloroꢀ1,2ꢀbenzoquinone with potassium ethyl xanthate
and obtained two novel oꢀquinones. These oꢀquinones
can be used as ligands in the coordination spheres of
metals.
C(8)
C(6)
C(7)
Fig. 2. General view of structure 5.
Experimental
Table 1. Parameters of the isotropic ESR spectra of metal comꢀ
plexes with quinones 2 and 4 in THF at 290 K
3,6ꢀDi(tertꢀbutyl)ꢀ1,2ꢀbenzoquinone was prepared as deꢀ
scribed earlier8 and used for the synthesis of 3,6ꢀdi(tertꢀbutyl)ꢀ
4ꢀchloroꢀ1,2ꢀbenzoquinone (1) according to a known proceꢀ
dure.9 Solvents were purified in standard ways.10 Highꢀpurity
potassium ethyl xanthate was used. A KGMꢀ24ꢀ150 lamp with a
focusing unit served as a light source. A radiation with λ > 440 nm
was isolated by an appropriate light filter. ESR spectra were
recorded on a Bruker ER 200DꢀSRC spectrometer. The g factor
was determined with dinitrophenylpicrylhydrazyl (DPPH) as
the standard. Samples of semiquinone and catecholate comꢀ
plexes for ESR studies were prepared according to known proceꢀ
dures.11,12 IR spectra were recorded on a Specord Mꢀ80 specꢀ
trometer (Nujol). 1H and 13C NMR spectra were recorded
on a Bruker Avance DPXꢀ200 instrument (200 (1H) and
50 MHz (13C)) in CDCl3. Xꢀray diffraction analysis was carried
out on a Smart Apex diffractometer (Bruker AXS) at 100 K. All
structures were solved by the direct method and refined by the
Quinone Metalꢀ
containing
g Factor
aH
aM
aL
mT
fragment
2
4
K
Tl
K
2.0049
2.0001
2.0046
1.9995
2.0059
2.0999
0.27
0.30 6.30
—
—
—
—
—
—
—
—
—
—
6.11
1.11 1.86
8.74 0.88
Tl
Cu(PPh3)2
Cu(bpy)
The structure of compound 5 was unambiguously deterꢀ
mined by IR and NMR spectroscopy and Xꢀray diffracꢀ
tion analysis (Fig. 2).
leastꢀsquares method on F2 in the anisotropic approximation
Like most of the sterically hindered oꢀquinones studꢀ
ied, compounds 2 and 4 in solution can be reversibly
reduced successively in two oneꢀelectron steps with alkali
metals and thallium amalgam to give radical anions of
oꢀsemiquinones and catecholate dianions. The paramꢀ
eters of the ESR spectra of complexes of compounds 2
and 4 in THF are given in Table 1. The character of these
spectra is typical of oꢀsemiquinones. Because derivatives 4
contain no ring protons or other magnetic nuclei (exꢀ
cept 13C and 33S), the hyperfine structure is only due to
splitting on the magnetic nuclei of metal cations. In addiꢀ
tion, the lines in the ESR spectra of derivatives 4 are very
narrow and thus the new quinone is of purely methodical
interest for analysis of complex ESR multiplets when exꢀ
cessive lines of a radical ligand proper should be get rid of
as far as possible. An example of such systems are semiꢀ
quinone copper complexes with phosphine ligands (6).
Like a number of other oꢀquinones, compound 4 in
THF in the presence of α,α´ꢀbipyridyl dissolves metallic
hkl
for all nonꢀhydrogen atoms. The H atoms were located from an
electronꢀdensity difference map and refined isotropically. All
calculations were performed with the SHELXTL program packꢀ
age (v. 6.10). Atomic coordinates have been deposited with the
Cambridge Crystallographic Data Center.
Sꢀ[2,5ꢀDi(tertꢀbutyl)ꢀ3,4ꢀdioxocyclohexaꢀ1,5ꢀdienꢀ1ꢀyl]
Oꢀethyl dithiocarbonate (2). Compound 1 (5 g, 20 mmol) and
potassium ethyl xanthate (3.1 g, 20 mmol) were dissolved in
THF (20 mL) and the solution was stirred for 45 min. The
degree of conversion of the starting quinone was checked by
TLC. The mixture was filtered and the filtrate was concentrated.
The product was recrystallized from hexane to form redꢀbrown
crystals. The yield was 9.03 g (85%), m.p. 83—84 °C. Found (%):
C, 59.21; H, 6.97; S, 19.02. C17H24O3S2. Calculated (%):
C, 59.97; H, 7.10; S, 18.83. IR,
1H NMR, : 1.22, 1.39 (both s, 9 H each, But); 1.44 (t, 3 H,
OCH2CH3, J = 7.3 Hz); 4.72 (q, 2 H, OCH2CH3, J = 7.3 Hz);
6.86 (s, 1 H, C=CH). 13C NMR,
: 14.0 (OCH2CH3); 29.1,
ν
/cm–1: 1680, 1660 (C=O).
δ
δ
31.0 (C(5)C(CH3)3, C(2)C(CH3)3); 35.2, 38.0 (C(5)C(CH3)3,
C(2)C(CH3)3); 72.1 (OCH2CH3); 144.1 (C(6)); 138.7, 147.0,

Sulfurꢀcontaining oꢀquinones and catechols
Russ.Chem.Bull., Int.Ed., Vol. 55, No. 4, April, 2006
711
157.5 (C(1), C(2), C(5)); 184.9, 187.7 (C(3), C(4));
208.8 (C=S).
dent of the Russian Federation (Program for State Supꢀ
port of Leading Scientific Schools of the Russian Federaꢀ
tion, Grant 1649.2003.3).
4,7ꢀDi(tertꢀbutyl)ꢀ5,6ꢀdihydroxyꢀ1,3ꢀbenzodithiolꢀ2ꢀone (3).
Dilute HCl (20 mL) was added to a solution of compound 2
(6.8 g, 20 mmol) in THF (20 mL). The mixture was stirred with
a magnetic stirring bar for 20 min and diluted with water
(100 mL). The organic material was extracted with ether. The
ethereal solution was washed with water to a neutral reaction.
The solvent was removed and the colorless crystals that formed
were recrystallized from methanol. The yield was 4.99 g (80%),
m.p. 110—111 °C. Found (%): C, 57.80; H, 6.51; S, 20.67.
References
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C
ν
15H20O3S2. Calculated (%): C, 57.66; H, 6.45; S, 20.53. IR,
1
/cm–1: 3420, 3250 (OH); 1630 (C=O). H NMR,
δ
: 1.59 (s,
18 H, But); 6.28 (s, 2 H, OH). 13C NMR,
δ: 31.3 (C(CH3)3);
38.0 (C(CH3)3); 124.0, 129.1, 143.7 (C arom.); 192.1 (C=O).
4,7ꢀDi(tertꢀbutyl)ꢀ5,6ꢀdihydroꢀ1,3ꢀbenzodithioleꢀ2,5,6ꢀ
trione (4). Compound 3 (6.2 g, 20 mmol) was dissolved in diꢀ
ethyl ether (50 mL). A solution of K3[Fe(CN)]6 (0.04 mol) and
NaHCO3 (0.08 mol) in water (100 mL) was added. The mixture
was stirred with a magnetic stirring bar for 1 h. The ethereal
layer was separated, washed with water, dried over CaCl2, and
concentrated. The residue (dark red tabular crystals) was recrysꢀ
tallized from hexane. The yield was 6.01 g (97%), m.p. 84—85 °C
Found (%): C, 57.95; H, 5.91; S, 20.59. C15H18O3S2. Calcuꢀ
lated (%): C, 58.04; H, 5.84; S, 20.66. IR,
/cm–1: 1690, 1660,
: 1.55 (s, 18 H, But). 13C NMR,
.
6. V. B. Vol´eva, V. V. Ershov, I. S. Belostotskaya, and N. L.
Komissarov, Izv. Akad. Nauk SSSR, Ser. Khim., 1974, 739
[Bull. Acad. Sci. USSR, Div. Chem. Sci., 1974, 23 (Engl.
Transl.)].
ν
1
1640 (C=O). H NMR,
δ
δ:
31.24 (C(CH3)3); 37.98 (C(CH3)3); 124.01, 128.78 (C=C);
7. G. A. Abakumov, N. N. Vavilina, L. N. Zakharov, Yu. A.
Kurskii, V. I. Nevodchikov, and A. S. Shavyrin, Izv. Akad.
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Transl.)].
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Cherkasov, L. G. Abakumova, and Yu. A. Kurskii, Izv. Akad.
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Transl.)].
191.43 (SC(O)S); 193.44 (CC(O)C(O)C).
The molecular formula: C15H18O3S2, M = 310.41, orthoꢀ
rhombic crystals, space group Pnma. At 100 K: a
=
7.5066(19)
Å
, b = 20.914(5)
Å
, c = 9.411(2)
σ), wR2 = 0.1403 (for all
Å
, V =
1477.5(6) Å3, Z = 4, R1 = 0.0651 (I > 2
reflections).
4,6ꢀDi(tertꢀbutyl)ꢀ5Hꢀcyclopenta[d][1,3]dithioleꢀ2,5ꢀdione
(5). A solution of compound 4 (3.12 g, 10 mmol) in toluene
(100 mL) was exposed for 8 h to light emitted by a halogen lamp.
The solvent was removed and the bright red needleꢀlike crystals
that formed were recrystallized from ether. The yield was 2.78 g
(98%), m.p. 90—91 °C. Found (%): C, 59.47; H, 6.45; S, 22.20.
C
ν
14H18O2S2. Calculated (%): C, 59.54; H, 6.42; S, 22.71. IR,
1
/cm–1: 1720, 1695 (C=O). H NMR,
δ
: 1.24 (s, 18 H, But).
: 29.55 (C(CH3)3); 32.67 (C(CH3)3); 130.19,
(O)S); 193.60 (CC(O)C).
The molecular formula: C14H18O2S2, M = 282.42, monoꢀ
13C NMR,
δ
145.60 (C=C); 190.50 (S
C
clinic crystals, space group P2(1)/c. At 100 K: a = 9.9560(8)
b = 10.4078(9) , c = 13.8278(12) = 90 = 92.470(2)
= 90
, V = 1431.5(2) Å3, Z = 4, R1 = 0.0368 (I > 2
wR2 = 0.0864 (for all reflections).
Å
°
,
,
12. G. A. Abakumov, V. K. Cherkasov, A. V. Lobanov, and
G. A. Razuvaev, Izv. Akad. Nauk SSSR, Ser. Khim., 1984,
1610 [Bull. Acad. Sci. USSR, Div. Chem. Sci., 1984, 33, 1478
(Engl. Transl.)].
Å
Å
,
α
°
,
β
γ
°
σ),
This work was financially supported by the Russian
Foundation for Basic Research (Project Nos. 04ꢀ03ꢀ32409
and 04ꢀ03ꢀ32413) and the Council on Grants of the Presiꢀ
Received November 9, 2005;
in revised form March 23, 2006