Thia-Diels–Alder reactions of hetaryl thioketones with nonactivated 1,3-dienes leading to 3,6-dihydro-2H-pyrans: evidence for a diradical mechanism

Article abstract of DOI:10.1007/s10593-017-2086-9

[Figure not available: see fulltext.] Dihetaryl thioketones possessing thiophen-2-yl and selenophen-2-yl rings react as “superdienophilic” reagents with nonactivated 1,3-dienes such as 2,3-dimethylbuta-1,3-diene, cyclopentadiene, and mixtures of isomeric

Full text of DOI:10.1007/s10593-017-2086-9

DOI 10.1007/s10593-017-2086-9
Chemistry of Heterocyclic Compounds 2017, 53(5), 518–525
Thia-Diels–Alder reactions of hetaryl thioketones
with nonactivated 1,3-dienes leading to 3,6-dihydro-2H-pyrans:
evidence for a diradical mechanism
1
1
2
2
Grzegorz Mlostoń *, Paulina Grzelak , Anthony Linden , Heinz Heimgartner
1
Department of Organic and Applied Chemistry, University of Łódź,
1
2 Tamka, Łódź PL-91-403, Poland; e-mail: gmloston@uni.lodz.pl
2
Department of Chemistry, University of Zurich,
90 Winterthurerstrasse, Zurich CH-8057, Switzerland
e-mail: heinz.heimgartner@chem.uzh.ch
1
Published in Khimiya Geterotsiklicheskikh Soedinenii,
017, 53(5), 518–525
Submitted December 21, 2016
Accepted February 21, 2017
2
Dihetaryl thioketones possessing thiophen-2-yl and selenophen-2-yl rings react as ''superdienophilic'' reagents with nonactivated
1
2
,3-dienes such as 2,3-dimethylbuta-1,3-diene, cyclopentadiene, and mixtures of isomeric hexa-2,4-dienes to produce the expected
H-thiopyrans in moderate to excellent yields. In the latter case, the corresponding cis-2,2-dihetaryl-3,6-dimethyl-3,6-dihydro-2H-
thiopyrans are formed as the sole products in a stereoconvergent thia-Diels–Alder reaction. A stepwise mechanism via delocalized
diradical intermediates is postulated to rationalize the observed reaction course. Treatment of 4,5-dimethyl-2,2-di(thiophen-2-yl)-
3
,6-dihydro-2H-thiopyran with excess of m-CPBA at room temperature leads to the oxidation of the C=C bond and the sulfur atom in the
six-membered ring.
Keywords: cyclic sulfones, 3,6-dihydro-2H-thiopyrans, thioketones, reaction mechanisms, thia-Diels–Alder reactions.
The thia-Diels–Alder reactions constitute an important
group of hetero-Diels–Alder reactions and can be used to
1,3-dienes.10a The analogous reactions were observed with
α,α,α-trifluorothioacetophenone and α,α,α-trifluorothio-
1
10b
synthesize six-membered sulfur-containing compounds.
acetone. Various 3,6-dihydro-2H-thiopyrans have been
These chemical transformations arouse special interest for
preparation of 3,6-dihydro-2H-thiopyrans, which are known
as relevant components of natural and biologically active
prepared via the reaction of in situ generated thioketones
bearing an electron-withdrawing group and 2,3-dimethyl-
11
1,3-butadiene (1a). Furthermore, several thia-Diels–Alder
2
products. In general, thia-Diels–Alder reactions can be
reactions of adamantanethione with substituted buta-1,3-dienes
3
12
performed with thiabutadienes or thiadienophiles as
were reported. Alkyl trimethylsilyl as well as phenyl tri-
4
starting materials. In the latter case, activated thioesters,
methylsilyl thioketones undergo the (4+2) cycloaddition
with diene 1a, and the obtained 2-silylated 3,6-dihydro-2H-
thiopyrans have been converted into 2H-thiopyrans by treat-
4,5
6
dithioesters, and thioamides, as well as thiourea deriva-
7
tives, are known as prone dienophiles in reactions with
13
nonactivated 1,3-dienes. In addition, application of some
ment with m-chloroperbenzoic acid (m-CPBA). The
relatively stable diaryl thioketones react efficiently with
diverse 1,3-dienes14 and on the basis of kinetic measure-
8
aromatic thioketones as heterodienophiles is also described,
but reactions with simple enolizable, aliphatic thioketones
9
a
15
are rarely reported, as their handling is difficult.
ments have been named as ''superdienophiles'' by Sauer.
Nevertheless, the reaction of thioacetone with 2,3-dimethyl-
In a recent study, the volume parameters of the thiobenzo-
phenone reaction with isoprene were determined, and
authors concluded that a concerted reaction mechanism is
plausible.16
buta-1,3-diene (1a) was reported to afford the expected
9b
cycloadduct. On the other hand, hexafluorothioacetone
reacts easily with compound 1a and some other
0
009-3122/17/53(05)-0518©2017 Springer Science+Business Media New York
5
18

Chemistry of Heterocyclic Compounds 2017, 53(5), 518–525
In addition to the aforementioned, asymmetric thia-Diels–
Scheme 2
1
7
Alder reactions of activated dithioesters as well as aryl
1
8
and hetaryl thioketones with in situ generated chiral
trienamines were presented. In the first case, Jørgensen,
according to DFT calculations, suggested a stepwise
1
7
mechanism involving zwitterionic intermediates. On the
other hand, in the case of hetaryl thioketones and activated
1
,3-dienes (i.e., trienamines), a stepwise reaction mecha-
18
nism via diradical intermediates was proposed. The goal
of the present study was to examine thia-Diels–Alder
reactions of nonactivated dienes with a series of dihetaryl
and hetaryl phenyl thioketones, which have been used as
1
8
heterodienophiles only in a single study.
Symmetric and nonsymmetric dihetaryl thioketones
exploited in this study were obtained from the cor-
responding ketones by thionation with Lawesson's reagent
1
9
(
LR). The already reported method, which relies on
heating a mixture of the ketone and LR in PhCH , was
3
2
0
improved by applying microwave irradiation. In that case,
the reaction times were drastically reduced to two minutes,
and the desired thioketones were obtained in moderate to
high yields. However, in contrast to the reported data, the
desired thiofluorenone could not be obtained, instead the
formation of bisfluorenylidene was observed.
In a typical experiment, a solution of 2,3-dimethylbuta-
,3-diene (1a) (2 mmol) and di(thiophen-2-yl)methane-
activated 1,3-dienes, additional experiments involving
(2E,4E)-hexa-2,4-diene ((E,E)-1b) were performed. The
concerted (4+2) cycloaddition predicts stereospecific
formation of a single product in each case. On the other
hand, disruption of the concertedness would lead to
mixtures of stereoisomeric products as a result of the
appearance of intermediate zwitterionic or diradical
species. The reaction of diene (E,E)-1b with thiobenzo-
phenone (6a) has been reported to afford 3,6-dimethyl-
2,2-diphenyl-3,6-dihydro-2H-thiopyran in 60% yield, but
the configuration of the product has not been deter-
mined.1 In a more recent study, cis configuration of the
stereospecifically formed analogous products from diaryl
21
1
thione (2a) (1 mmol) in THF was stirred at room tempe-
rature for 24 h (Scheme 1). After chromatographic
purification, the sole product 3a was obtained as a solid
1
material in 82% yield. The H NMR spectrum confirmed
the presence of the expected 4,5-dimethyl-2,2-di(thiophen-
4b
2
-yl)-3,6-dihydro-2H-thiopyran (3a), and the structure was
13
further proven by C NMR and IR spectra and elemental
analysis. Similarly, reactions of diene 1a with di(seleno-
phen-2-yl)methanethione (2b) and di(furan-2-yl)methane-
thione (2c) led to the desired 2H-thiopyrans 3b,c in 89 and
1
selenoketones was established on the basis of H NMR
data.22 However, similar reactions performed with the less
reactive (2Z,4E)-hexa-2,4-diene ((Z,E)-1b) and diaryl
selenoketones or diaryl thioketones provided the cis-
configured major products – 3,6-dihydro-2H-seleno- and
3,6-dihydro-2H-thiopyrans, respectively – together with
small amounts of the corresponding trans-isomers. These
results of a stereoconvergent reaction have been explained
by a concerted cycloaddition in the case of diene (E,E)-1b
and a two-step radical pathway via reversible formation
of diradical intermediates in the case of the less reactive
8
5% yields, respectively. However, the attempted
(
4+2) cycloaddition of di(N-methylpyrrol-2-yl) thioketone
and reactant 1a was unsuccessful, and the thioketone was
recovered from the reaction mixture.
Scheme 1
Me
S
Me
CH2
CH2
S
X
+
Me
22
THF
diene (Z,E)-1b. In our recent publications, a nonconcerted
Me
X
X
X
rt, 24 h
mechanism involving diradical intermediates of formal
8
2–89%
(
4+2) and (3+2) cycloadditions with hetaryl thioketones
1
a
2a–c
3a–c
18,23
has been proposed and described.
a X = S, b X = Se, c X = O
In continuation of this research, the reaction of hetaryl
thioketones 2a,b with excess of diene (E,E)-1b (2.2 equiv;
as a mixture containing ca. 40% (Z,E)- and 5% (Z,Z)-1b)
was performed without any solvent at room temperature for
24 h and in each case led to a single product, which was
isolated in quantitative yield (Scheme 3). Based on the
spectroscopic and elemental analysis data, the structures of
the products were assigned to 2,2-dihetaryl-3,6-dimethyl-
3,6-dihydro-2H-thiopyrans 8a,b, respectively. Comparison
In another series of experiments, hetaryl phenyl thio-
ketones 4a–c were used in the reaction with 1,3-diene 1a
leading solely to products 5a–c in 84–88% yield.
Furthermore, thiobenzophenone (6a) and thiodibenzo-
suberone (6b) were converted into the corresponding
2
H-thiopyrans 7a,b (90 and 95% yield) under the same
conditions (Scheme 2).
1
In order to examine the mechanism of the studied thia-
Diels–Alder reaction of hetaryl thioketones with non-
of their H NMR spectra with those of the corresponding
2,2-diaryl-2H-selenopyrans described in literature22
5
19

Chemistry of Heterocyclic Compounds 2017, 53(5), 518–525
Scheme 3
allowed the cis configuration to be ascribed to products
a,b. Finally, the structure of cis-3,6-dimethyl-2,2-di-
8
(
thiophen-2-yl)-3,6-dihydro-2H-thiopyran (cis-8a) was
confirmed by X-ray crystallography (Fig. 1).
The ratio of isomeric hexa-2,4-dienes 1b, including
diene (E,E)-1b, in the starting material was compared with
the ratio determined in the sample after completion of the
reaction with thioketones 2a,b. Calculations performed for
both reaction mixtures showed that, in the course of the
studied (4+2) cycloadditions, the amount of (E,E)-isomer
increased by ca. 12 mol %, whereas the amounts of (Z,E)-
and (Z,Z)-isomers were reduced in total by ca. 12 mol %.
These results strongly suggest that the amounts of the
obtained products cis-8a,b are higher than expected for the
consumed compound (E,E)-1b, based on the contents of
the starting mixture.
2
4
Figure 1. ORTEP representation of the molecular structure of
conformation A of 3,6-dihydro-2H-thiopyran cis-8a (with 50%
probability ellipsoids; arbitrary numbering of atoms).
most reactive) compound (E,E)-1b in the reaction mixture
is also acceptable.22 Both interpretations, however, support
the proposed stepwise diradical mechanism of the formal
(4+2) cycloadditions of nonactivated, electron-rich
1,3-dienes and hetaryl thioketones.
Another experiment was performed using equimolar
amounts of thioketone 2a and hexa-2,4-diene 1b as a
mixture of (E,E)-, (Z,E)-, and (Z,Z)-isomers in a ratio of
2
2:70:8. The mixture of compounds 2a and 1b was heated
in a closed reaction tube at 80°C for 18 h. After this time,
Scheme 4
the green color of the starting material 2a completely
disappeared, and the H NMR analysis of the crude
1
reaction mixture with a weighed internal standard (1,1,2,2-
tetrachloroethane) revealed the formation of product cis-8a
in 84% yield. Two characteristic doublets (1.31 and 1.04 ppm)
of this previously described product were accompanied by
2
another pair of low intensity doublets ( JHH = 6.0 Hz)
located at 1.31 and 1.16 ppm, respectively, which could be
attributed to the isomeric product trans-8a. The location of
these signals and the difference in chemical shifts were
similar to the data reported for the trans-isomer of the
analogous product, obtained from diene 1b and
2
2
thiobenzophenone (6a). Based on the comparison of the
intensities of these signals and the signal of CH groups in
2
the standard used for the quantitative analysis, the
calculated yield of the postulated product trans-8a was ca.
6
%. This result points out that, in the course of the studied
reaction, a substantial amount of hexadiene (Z,E)-1b,
present in the starting mixture, underwent isomerization in
the course of the reaction and was subsequently consumed
yielding an additional portion of product cis-8a.
A likely explanation of the observed results is a stepwise
cycloaddition of the less reactive compounds (Z,E)- and
(
Z,Z)-1b and subsequent C–C bond rotation in the
intermediate diradicals 9 leading to the formation of cis-
configured thiopyrans 8a,b (Scheme 4). On the other hand,
the postulated reversible formation of intermediate
diradicals leading to the increase of the most stable (and
5
20

Chemistry of Heterocyclic Compounds 2017, 53(5), 518–525
As a third 1,3-diene, freshly prepared cyclopentadiene
11) was used in reactions with symmetric di(thiophen-
-yl)methanethione (2a) and nonsymmetric phenyl(thiophen-
1,3-dienes. The (4+2) cycloadditions can be performed
under mild conditions in the absence of any catalyst. The
results obtained for the reactions with (2E,4E)-hexa-
2,4-diene that give cis-configured 3,6-dimethyl-3,6-dihydro-
2H-thiopyrans suggest a concerted (4+2) cycloaddition.
However, the enhanced amounts of the isolated cis-products
in reactions with mixtures of isomeric hexa-2,4-dienes
indicate that some isomerization processes might occur
during the course of the reactions. The postulated diradical
intermediates, formed in the initial step of the reaction,
may either isomerize to the most stable precursors of the
cis-configured (4+2) cycloadducts or, in a reversible process,
may be converted into more reactive (2E,4E)-hexa-2,4-diene.
The latter may subsequently react with the starting thio-
ketone in a concerted, stereospecific manner. In contrast to
dihetaryl thioketones bearing thiophen-2-yl, selenophen-2-yl,
or furan-2-yl rings, the analogous di(N-methylpyrrol-2-yl)
thioketone does not display reactivity of a ''superdieno-
philic'' reagent and the expected 2H-thiopyran derivative
does not form in the reaction with 2,3-dimethylbuta-
(
2
2
-yl)methanethione (4a) to afford bicyclic products 12a,b
in reasonable yields (71 and 89%, respectively) (Scheme 5).
In the second case, a mixture of two stereoisomeric
1
products exo- and endo-12b in a 7:3 ratio ( H NMR) was
obtained after chromatographic purification. Similarly to
the experiment with 2,3-dimethylbuta-1,3-diene (1a), the
attempted (4+2) cycloaddition of cyclopentadiene (11) and
di(N-methylpyrrol-2-yl) thioketone in THF solution at
room temperature was unsuccessful and even after 24 h
only the starting thioketone was recovered.
Scheme 5
1
,3-diene. Treatment of 3,6-dihydro-2H-thiopyrans with an
excess of m-CPBA at room temperature leads to the
oxidation of the S atom as well as the C=C bond to produce
bicyclic oxiranes containing a sulfonyl group.
The commercially available (1E,3E)-1,4-diphenylbuta-
1
,3-diene, which is known to display low reactivity toward
25
nonactivated dienophiles, was also tested in the reaction
with thioketone 2a in THF solution at room temperature. In
that case, however, no formation of the expected
Experimental
IR spectra were recorded on a Thermo Nicolet NEXUS
1
13
(
4+2) cycloadduct was observed even after 24 h. Instead,
470 FT IR spectrometer in KBr pellets. H and C NMR
spectra were obtained on a Bruker Avance III instrument
only gradual decomposition of the starting material 2a was
observed.
(600 and 150 MHz, respectively) in CDCl . Chemical shifts
3
Finally, 2H-thiopyrans 3a and 7a were oxidized by
were referenced to the residual non-deuterated solvent
signals (7.26 and 77.0 ppm, respectively). The multiplicity
treatment with excess of m-CPBA in CH
2
Cl at room
2
13
temperature for 48 h (Scheme 6). In each case, a single
of C signals was deduced from DEPT experiments sup-
ported by HMQC spectra. Mass spectra were recorded on a
Varian 500-MS IT mass spectrometer (ESI, 50 eV). Elemental
analyses were performed in the Microanalytical Laboratory
of the Chemistry Faculty in Łódź using a VARIO ELIII
apparatus (Elementar Analysensysteme GmbH). Melting
points were determined in a capillary using a Sigma-Aldrich
MEL-TEMP apparatus and are uncorrected. Microwave-
supported syntheses of thioketones 2a–c, 4a–c, and 6a,b
were performed in a Discover SP microwave reactor.
product was isolated as a crystalline material in high yield
1
(
90 and 95%, respectively). The H NMR spectra of both
products revealed two AX systems attributed to two CH
2
1
3
groups. In addition, in the C NMR spectra, five signals
were observed between 40 and 70 ppm instead of expected
3
three signals for the Csp atoms of the heterocycle. Based
on these data, structures of the bicyclic oxiranes 13a,b
were postulated and subsequently confirmed by elemental
analysis. These structures indicate that oxidation of the S
atom in compounds 3a and 7a to the sulfone group occurs
along with the formation of the corresponding oxiranes.
Similar course of oxidation of variously substituted
Applied dienes such as (1E,3E)-1,4-diphenylbuta-
1,3-diene, 2,3-dimethylbuta-1,3-diene (1a), and hexa-
2,4-diene 1b (mixture of (E,E)-, (Z,E)-, and (Z,Z)-isomers
in a ratio of 55:40:5), inorganic reagents, and solvents are
commercially available (Sigma-Aldrich) and were used as
received. The (Z,E)-1b enriched mixture of (E,E)-, (Z,E)-,
and (Z,Z)-isomers in a ratio of 22:70:8, was prepared from
®
26
3
,6-dihydro-2H-thiopyrans with Oxone , as well as
27,28
m-CPBA
has been reported.
Scheme 6
29
the commercial sample based on a reported protocol. The
ratio of isomeric hexa-2,4-dienes 1b was established based
1
on the H NMR spectrum registered in CDCl
3
solution.
Cyclopentadiene (11) was freshly prepared by distillation
of the commercially available dimer according to a known
protocol.30
Synthesis of thioketones 2a–c, 4a–c, and 6a,b (General
method).20 A solution of the corresponding ketone
(1 mmol) and Lawesson's reagent (LR) (1 mmol) in dry
In conclusion, the presented study shows that, similarly
to aryl thioketones, hetaryl analogs are superior hetero-
dienophiles in thia-Diels–Alder reactions with nonactivated
PhCH (2 ml) was placed in a microwave reaction tube. All
3
5
21

Chemistry of Heterocyclic Compounds 2017, 53(5), 518–525
–
1
reactions were performed at 150 W for 2 min. After
cooling the reaction mixture to room temperature, the
solvent was evaporated in vacuo. The residue was purified
by column chromatography (silica gel) using a mixture of
mp 74–75°C. IR spectrum, ν, cm : 3058 (w), 2896 (m),
1
1490 (m), 1443 (s), 1221 (m), 700 (s). H NMR spectrum,
δ, ppm: 1.67 (3H, s, CH
3
); 1.77 (3H, s, CH ); 2.88–3.07
3
(4H, m, 2CH ); 6.99–7.00 (1H, m, H Ar); 7.11–7.13 (1H,
2
petroleum ether and CHCl
3
(7:3) as the eluent.
m, H Ar); 7.23–7.25 (1H, m, H Ar); 7.29–7.32 (2H, m,
H Ar); 7.49–7.51 (2H, m, H Ar); 7.90–7.91 (1H, m, H Ar).
Synthesis of 2H-thiopyrans 3a–c, 5a–c, and 7a,b
13
(
General method). A solution of the corresponding thio-
C NMR spectrum, δ, ppm: 19.2, 20.4 (2CH ); 32.5, 47.6,
3
3
2
ketone 2, 4, or 6 (1 mmol) and 2,3-dimethylbuta-1,3-diene
52.6 (3Csp ); 123.3, 126.1 (2Csp ); 127.1, 127.2, 127.6,
128.1, 128.8, 130.5 (8CH Ar); 145.7, 159.6 (2C Ar).
(
1a) (0.2 ml, 2 mmol) in dry THF (1 ml) was stirred at
room temperature for 24 h. After this time, the solvent was
Found, %: C 61.07; H 5.33; S 9.90. C17
H18SSe. Calculated,
evaporated in vacuo. The residue was purified by column
%: C 61.26; H 5.40; S 9.61.
chromatography (silica gel) using CH
2
Cl
2
as the eluent.
2-(4,5-Dimethyl-2-phenyl-3,6-dihydro-2H-thiopyran-
2-yl)furan (5c). Yield 238 mg (88%), orange solid, mp 62–
4
,5-Dimethyl-2,2-di(thiophen-2-yl)-3,6-dihydro-2H-thio-
–1
pyran (3a). Yield 239 mg (82%), green solid, mp 80–81°C.
63°C. IR spectrum, ν, cm : 3021 (w), 2888 (m), 1491 (s),
–
1
1
IR spectrum, ν, cm : 3084 (w), 2864 (m), 1425 (m), 1231
1445 (s), 1154 (s), 1013 (s), 747 (s), 705 (s). H NMR
1
(
s), 708 (s). H NMR spectrum, δ, ppm (J, Hz): 1.66 (3H, s,
spectrum, δ, ppm (J, Hz): 1.68 (3H, s, CH
3
); 1.76 (3H, s,
);
CH
CH
3
); 1.75 (3H, s, CH
3
); 3.06 (2H, s, CH
2
); 3.10 (2H, s,
CH
3
); 2.83 (1H, d, J = 16.8) and 2.90–2.98 (3H, m, 2CH
2
2
); 6.90–6.91 (2H, m, H Ar); 6.98 (2H, dd, J = 3.6,
6.24 (1H, d, J = 3.0, H Ar); 6.32 (1H, dd, J = 3.6, J = 1.8,
J = 1.2, H Ar); 7.22 (2H, dd, J = 5.4, J = 1.2, H Ar).
H Ar); 7.22–7.25 (1H, m, H Ar); 7.29–7.31 (2H, m, H Ar);
1
3
13
C NMR spectrum, δ, ppm: 19.3, 20.5 (2CH
3
); 33.2, 47.9,
8.4 (3Csp ); 122.8, 125.8 (2Csp ); 125.0, 125.4, 126.5
6CH Ar); 151.1 (2C Ar). Found, %: C 61.61; H 5.45;
S 32.97. C15 . Calculated, %: C 61.59; H 5.52; S 32.88.
,5-Dimethyl-2,2-di(selenophen-2-yl)-3,6-dihydro-2H-
thiopyran (3b). Yield 343 mg (89%), dark-red solid,
7.35–7.36 (3H, m, H Ar). C NMR spectrum, δ, ppm:
3
2
3
4
(
19.3, 20.3 (2CH
3
); 31.8, 44.1, 49.2 (3Csp ); 123.0, 126.1
2
(2Csp ); 108.0, 110.1, 127.0, 127.2, 128.3, 142.0 (8CH Ar);
H S
16 3
144.0, 156.5 (2C Ar). Found, %: C 75.29; H 6.63; S 12.09.
4
C H18OS. Calculated, %: C 75.55; H 6.66; S 11.85.
17
4,5-Dimethyl-2,2-diphenyl-3,6-dihydro-2H-thiopyran
–
1
14b,31
mp 68–69°C. IR spectrum, ν, cm : 3051 (w), 2863 (m),
(7a).
(mp 52–53°C (hexane) ). H NMR spectrum, δ, ppm: 1.70
(3H, s, CH ); 1.83 (3H, s, CH ); 2.78 (2H, s, CH ); 2.94
(2H, s, CH
Yield 252 mg (90%), white solid, mp 50–51°C
1
31 1
1
1
3
445 (s), 1227 (s), 705 (s). H NMR spectrum, δ, ppm (J, Hz):
.67 (3H, s, CH ); 1.74 (3H, s, CH ); 3.07 (2H, s, CH );
.12 (2H, s, CH ); 7.12–7.14 (4H, m, H Ar); 7.92 (2H, dd,
3
3
2
3
3
2
2
2
); 7.23–7.25 (2H, m, H Ar); 7.29–7.32 (4H, m,
1
3
J = 5.4, J = 1.8, H Ar). C NMR spectrum, δ, ppm: 19.3,
H Ar); 7.37–7.39 (4H, m, H Ar).
3
2
(
0.6 (2CH
3
); 33.6, 49.7, 51.7 (3Csp ); 122.8, 125.8
3',6',10,11-Tetrahydro-4',5'-dimethylspiro[dibenzo-
[a,d][7]annulene-5,2'-thiopyran] (7b). Yield 291 mg
(95%), colorless crystals, mp 89–90°C (MeOH). IR spectrum,
2
2Csp ); 127.4, 129.0, 130.7 (6CH Ar); 159.2 (2C Ar).
Found, %: C 46.83; H 4.41; S 8.66. C15
lated, %: C 46.64; H 4.18; S 8.30.
H
16SSe . Calcu-
2
–
1
ν, cm : 3056 (w), 2871 (m), 1484 (s), 1446 (s), 729 (s).
1
2
,2'-(4,5-Dimethyl-3,6-dihydro-2H-thiopyran-2,2-diyl)-
H NMR spectrum, δ, ppm (J, Hz): 1.64 (3H, s, CH
(3H, s, CH ); 2.76 (2H, s, CH ); 3.01–3.08 (2H, m,
CH CH ); 3.35 (2H, s, CH ); 4.20–4.27 (2H, m, CH CH );
7.05–7.08 (2H, m, H Ar); 7.10–7.14 (4H, m, H Ar); 7.19 (2H,
3
); 1.96
difuran (3c). Yield 211 mg (85%), orange solid, mp 53–
3
2
–
1
5
4°C. IR spectrum, ν, cm : 3118 (w), 2911 (m), 1498 (s),
2
2
2
2
2
1
1
146 (s), 1014 (s), 737 (s). H NMR spectrum, δ, ppm: 1.67
13
(
3H, s, CH
2H, s, CH
3
); 1.74 (3H, s, CH
3
); 2.95 (2H, s, CH
2
); 2.99
d, J = 7.8, H Ar). C NMR spectrum, δ, ppm: 19.0, 20.7
3
(
2
); 6.20–6.21 (2H, m, H Ar); 6.30–6.31 (2H, m,
(2CH ); 32.7, 33.1, 44.3, 50.3 (5Csp ); 124.1, 126.5
3
1
3
2
H Ar); 7.35 (2H, br. s, H Ar). C NMR spectrum, δ, ppm:
(2Csp ); 125.6, 126.1, 127.5, 132.0 (8CH Ar); 140.0, 141.4
3
1
(
9.4, 20.4 (2CH
3
); 31.5, 41.0, 44.8 (3Csp ); 122.6, 125.4
(4C Ar). Found, %: C 82.20; H 7.12; S 10.71. C21
Calculated, %: C 82.29; H 7.25; S 10.46.
H22S.
2
2Csp ); 107.4, 110.3, 142.1 (6CH Ar); 154.9 (2C Ar).
Found, %: C 69.28; H 6.14; S 12.28. C15
lated, %: C 69.20; H 6.19; S 12.32.
H
16
O
2
S. Calcu-
Synthesis of 2H-thiopyrans cis-8a,b (General method).
A solution of the corresponding thioketone 2 (1.0 mmol) in
hexa-2,4-diene 1b (0.25 ml, 2.2 mmol) as a mixture of
(E,E)-, (Z,E)-, and (Z,Z)-isomers in a ratio of 55:40:5 was
stirred at room temperature for 24 h. Diene 1b was
evaporated in vacuo, and the residue was recrystallized
from MeOH.
4
,5-Dimethyl-2-phenyl-2-(thiophen-2-yl)-3,6-dihydro-
2
H-thiopyran (5a). Yield 213 mg (84%), green solid,
–1
mp 74–75°C. IR spectrum, ν, cm : 3053 (w), 2894 (m),
1
1
1
442 (s), 1256 (m), 720 (s). H NMR spectrum, δ, ppm (J, Hz):
.69 (3H, s, CH ); 1.80 (3H, s, CH ); 2.91 (1H, d, J = 15.6)
); 6.92–6.94 (2H, m, H Ar);
.23–7.29 (2H, m, H Ar); 7.32–7.35 (2H, m, H Ar); 7.48–
3
3
and 3.01–3.11 (3H, m, 2CH
2
cis-3,6-Dimethyl-2,2-di(thiophen-2-yl)-3,6-dihydro-
2H-thiopyran (cis-8a). Yield 292 mg (>99%), colorless
7
7
1
3
–1
.49 (2H, m, H Ar). C NMR spectrum, δ, ppm: 19.3, 20.4
crystals, mp 76.0–76.5°C (MeOH). IR spectrum, ν, cm :
3
2
(
2CH
3
); 32.4, 47.2, 50.8 (3Csp ); 123.3, 126.2 (2Csp );
3101 (w), 2961 (w), 2857 (w), 1445 (m), 1429 (m), 1239
1
1
1
25.0, 125.7, 126.2, 127.1, 127.2, 128.2 (8CH Ar); 145.6,
51.5 (2C Ar). Found, %: C 71.28; H 6.29; S 22.20.
(s), 1223 (s), 1093 (m), 761 (m), 707 (s). H NMR
spectrum, δ, ppm (J, Hz): 1.04 (3H, d, J = 6.6, CH
3
); 1.31
); 3.29–
); 5.52 (1H, dt, J = 10.8, J = 1.8,
CH=CH); 5.84–5.87 (1H, m, CH=CH); 6.88 (1H, dd,
C
17
4
H
18
S
2
. Calculated, %: C 71.33; H 6.29; S 22.38.
(3H, d, J = 7.2, CH
3
); 3.08–3.12 (1H, m, CHCH
3
,5-Dimethyl-2-phenyl-2-(selenophen-2-yl)-3,6-dihydro-
3.34 (1H, m, CHCH
3
2
H-thiopyran (5b). Yield 280 mg (84%), dark-red solid,
5
22

Chemistry of Heterocyclic Compounds 2017, 53(5), 518–525
J = 4.8, J = 3.6, H Ar); 6.90 (1H, dd, J = 4.8, J = 3.6,
54.8; 59.4; 64.4; 124.5; 124.6; 124.7; 126.1; 126.5; 126.6;
133.1; 138.5; 151.6; 154.1. Found, %: C 61.06; H 4.38;
H Ar); 6.97 (1H, dd, J = 3.6, J = 1.2, H Ar); 7.13 (1H, dd,
J = 3.6, J = 1.2, H Ar); 7.19 (1H, dd, J = 5.4, J = 1.2,
S 34.84. C14
H
12
S . Calculated, %: C 60.83; H 4.37; S 34.80.
3
1
3
H Ar); 7.21 (1H, dd, J = 4.8, J = 1.2, H Ar). C NMR
3-Phenyl-3-(thiophen-2-yl)-2-thiabicyclo[2.2.1]hept-
5-ene (12b). Yield 240 mg (89%), orange solid, mp 79–81°C.
The compound consisted of a mixture of two stereoisomers
spectrum, δ, ppm: 19.1, 19.7 (2CH
3
); 35.5, 40.4, 54.1
3
(
3Csp ); 124.1, 124.9, 125.1, 125.3, 125.7, 126.3, 129.1,
2
–1
1
32.6 (2Csp , 6CH Ar); 150.9, 153.4 (2C Ar). Found, m/z:
(endo- and exo-12b) in a ratio 7:3. IR spectrum, ν, cm :
+
3
15.0307 [M+Na] . C15
H16NaS
3
. Calculated, m/z: 315.0306.
3047 (w), 2939 (w), 1594 (w), 2896 (m), 1489 (m), 1442
1
Found, %: C 61.72; H 5.55; S 32.89. C15
H
16
S
3
. Calculated, %:
(s), 1331 (m), 1223 (m), 717 (s), 698 (s). H NMR
C 61.60; H 5.51; S 32.89.
spectrum, δ, ppm (J, Hz) (values for the minor isomer in
cis-3,6-Dimethyl-2,2-di(selenophen-2-yl)-3,6-dihydro-
H-thiopyran (cis-8b). Yield 386 mg (>99%), colorless
italics): 1.99–2.00 (2H, m, major,minor-CH
A
); 2.10 (1H, d,
);
2
J = 9.0, major-CH
B
); 2.35 (1H, d, J = 9.0, minor-CH
B
–1
crystals, mp 97.8–98.3°C (MeOH). IR spectrum, ν, cm :
4.11 (1H, br. s, minor-CH); 4.14 (1H, br. s, major-CH);
4.30 (2H, br. s, major,minor-CH); 5.79–5.83 (2H, m,
major,minor-CH=CH); 6.41 (1H, dd, J = 5.4, J = 3.0,
minor-CH=CH); 6.59 (1H, dd, J = 5.4, J = 2.4, major-
CH=CH); 6.79–6.80 (1H, m, H Ar); 6.86–6.87 (1H, m,
H Ar); 6.92–6.94 (1H, m, H Ar); 7.03–7.05 (1H, m, H Ar);
7.12 (2H, d, J = 4.8, H Ar); 7.18 (1H, d, J = 5.4, H Ar);
7.21–7.37 (5H, m, H Ar); 7.50 (2H, d, J = 7.2, H Ar); 7.59
3
006 (w), 2968 (w), 1445 (m), 1239 (s), 1226 (m), 1084
1
(
w), 758 (m), 688 (s). H NMR spectrum, δ, ppm (J, Hz):
1
.09 (3H, d, J = 6.6, CH
.06 (1H, m, CHCH ); 3.41–3.45 (1H, m, CHCH
3
); 1.32 (3H, d, J = 7.2, CH
3
); 3.02–
); 5.53
3
3
3
(
1H, dt, J = 10.8, J = 1.8, CH=CH); 5.85–5.88 (1H, m,
CH=CH); 7.10 (1H, dd, J = 5.4, J = 3.6, H Ar); 7.13–7.16
2H, m, H Ar); 7.23–7.24 (1H, m, H Ar); 7.89–7.91 (2H,
(
1
3
13
m, H Ar). C NMR spectrum, δ, ppm: 19.5, 19.7 (2CH
3
);
(2H, d, J = 7.8, H Ar). C NMR spectrum, δ, ppm: 50.7;
3
3
1
6.0, 40.8, 57.6 (3Csp ); 125.7, 126.7, 128.3, 128.9, 129.1,
51.5; 53.5; 55.0; 55.5; 57.6; 67.8; 69.2; 124.4; 124.5;
126.2; 126.5; 126.6 (2C); 126.7; 127.9; 128.3; 128.7;
133.2; 133.3; 137.8; 139.1; 145.7; 148.0; 152.8; 155.5.
2
30.6, 130.8, 132.6 (2Csp , 6CH Ar); 159.0, 162.7 (2C Ar).
Found, %: C 46.69; H 4.11; S 8.35. C15
Calculated, %: C 46.64; H 4.18; S 8.30.
H
16SSe .
2
Found, %: C 71.06; H 5.43; S 23.56. C16
%: C 71.06; H 5.23; S 23.71.
H
14
2
S . Calculated,
Test experiment with equimolar amounts of
thioketone 2a and a mixture of hexa-2,4-dienes (Z,E)-,
Oxidation of 2H-thiopyrans 3a and 7a with m-CPBA
(General method). A solution of 2H-thiopyran 3a (292 mg,
1 mmol) or 7a (280 mg, 1 mmol) and m-CPBA (70%
(
1
E,E)-, and (Z,Z)-1b. A solution of thioketone 2a (210 mg,
2
9
mmol) in a freshly prepared mixture of hexa-2,4-dienes
(
Z,E)-, (E,E)-, and (Z,Z)-1b (70:22:8; 0.1 ml, 1 mmol) was
purity; 740 mg, 3 mmol) in CH
2
2
Cl (3 ml) was stirred at
placed into a closed reaction tube. The solution was heated
in an oil bath at 80°C for 18 h. After this time, the mixture
was cooled to room temperature, and 1,1,2,2-tetra-
chloroethane (58 mg, 0.34 mmol) was added as a standard.
room temperature for 48 h. The reaction mixture was
extracted with saturated aqueous NaHCO solution (3 × 10 ml)
and distilled water (1 × 10 ml). The organic phase was
3
dried over anhydrous Na
2
SO and concentrated in vacuo.
4
1
The H NMR spectrum of this mixture was obtained in
Products 13a,b were purified by recrystallization from
petroleum ether.
CDCl solution.
3
Synthesis of 2-thiabicyclo[2.2.1]hept-5-enes 12a,b
General method). Freshly distilled cyclopentadiene (11)
0.2 ml, 2 mmol) was added at 0°C to a solution of
1,6-Dimethyl-4,4-di(thiophen-2-yl)-7-oxa-3-thiabicyclo-
[4.1.0]heptane 3,3-dioxide (13a). Yield 306 mg (90%),
white crystals, mp 171–172°C (petroleum ether).
(
(
–1
thioketone 2a (210 mg, 1 mmol) or 4a (204 mg, 1 mmol) in
dry THF (1 ml). The mixture was stirred at 0°C for 2 h,
then at room temperature for 24 h. The solvent was
evaporated in vacuo, and the residue was purified by
IR spectrum, ν, cm : 3083 (w), 2925 (s), 1459 (m), 1432
1
(m), 1308 (s), 1120 (s), 851 (m), 700 (s). H NMR
spectrum, δ, ppm (J, Hz): 1.33 (3H, s, CH
3
); 1.53 (3H, s,
); 3.28 and
); 7.02 (1H, dd, J = 5.4,
J = 4.2, H Ar); 7.06 (1H, dd, J = 5.4, J = 4.2, H Ar); 7.35–
CH
3
); 3.27 and 3.62 (2H, AX, J = 18.0, 5-CH
2
column chromatography (NEt
mixture of petroleum ether and Et
2a) or CH Cl (for compound 12b) as the eluent.
,3-Di(thiophen-2-yl)-2-thiabicyclo[2.2.1]hept-5-ene (12a).
Yield 196 mg (71%), orange solid, mp 66−69°C (decomp.,
3
-treated silica gel) using a
3.48 (2H, AX, J = 18.0, 2-CH
2
2
O (1:1) (for compound
13
1
2
2
7.40 (3H, m, H Ar); 7.41–7.42 (1H, m, H Ar). C NMR
3
spectrum, δ, ppm: 20.8, 21.4 (2CH ); 46.0, 53.0, 60.2, 61.1,
3
3
65.2 (5Csp ); 127.1, 127.2, 127.5, 127.6, 128.9, 130.0
–
1
green coloration). IR spectrum, ν, cm : 3101 (m), 2970
m), 2924 (s), 2854 (m), 1802 (m), 1572 (w), 1519 (w),
434 (s), 1328 (s), 1331 (m), 1229 (s), 807 (s), 694 (s).
(6CH Ar); 139.2, 139.5 (2C Ar). Mass spectrum, m/z (Irel, %):
+
+
(
1
363 [M+Na] (100), 364 [M+H+Na] (10). Found, %:
C 52.96; H 4.72; S 28.35. C15
C 52.91; H 4.75; S 28.25.
H
16
O
3
S . Calculated, %:
3
1
H NMR spectrum, δ, ppm (J, Hz): 1.92 (1H, dt, J = 9.6,
J = 2.4, CH ); 2.15–2.17 (1H, m, CH ); 3.92–3.93 (1H, m,
CH); 4.28–4.29 (1H, m, CH); 5.80–5.81 (1H, m, CH=CH);
.48–6.50 (1H, m, CH=CH); 6.83 (1H, dd, J = 4.8, J = 3.6,
A
B
1,6-Dimethyl-4,4-diphenyl-7-oxa-3-thiabicyclo[4.1.0]-
heptane 3,3-dioxide (13b). Yield 312 mg (95%), white
–1
6
solid, mp 191–192°C (petroleum ether). IR spectrum, ν, cm :
H Ar); 6.85 (1H, dd, J = 3.6, J = 1.8, H Ar); 6.94 (1H, dd,
J = 4.8, J = 3.6, H Ar); 7.08 (1H, dd, J = 5.4, J = 1.2,
H Ar); 7.14 (1H, dd, J = 3.6, J = 1.2, H Ar); 7.18 (1H, dd,
3060 (w), 2926 (m), 1497 (m), 1446 (m), 1308 (s), 1124
1
(s), 893 (m), 697 (s). H NMR spectrum, δ, ppm (J, Hz):
1.33 (3H, s, CH
3
); 1.49 (3H, s, CH ); 3.13 and 3.52 (2H,
3
1
3
J = 5.4, J = 1.2, H Ar). C NMR spectrum, δ, ppm: 51.4;
AX, J = 18.0, 5-CH ); 3.25 and 3.51 (2H, AX, J = 18.0,
2
5
23

Chemistry of Heterocyclic Compounds 2017, 53(5), 518–525
2
-CH
2
); 7.30–7.37 (6H, m, H Ar); 7.52–7.54 (2H, m,
reflections 3712, reflections with I > 2σ(I) 3660, reflections
1
3
H Ar); 7.59–7.61 (2H, m, H Ar). C NMR spectrum,
used in refinement 3712, parameters refined 184, restraints
2
δ, ppm: 21.0, 21.5 (2CH
3
); 43.4, 54.5, 60.5, 60.9, 70.1
26, R(F) (I > 2σ(I) reflections) 0.0214, wR(F ) (all data)
3
2
2
2
–1
(
5Csp ); 128.2, 128.4, 128.5, 128.7, 129.2, 129.5 (10CH Ar);
0.0561 (w = (σ (F
o
) + (0.0340P) + 0.2427P) , where
2
2
1
37.5, 137.9 (2C Ar). Mass spectrum, m/z (Irel, %): 246
P = (F
o
+ 2F )/3), goodness of fit 1.041, final Δmax/σ 0.001,
Δρ (max; min) 0.22; –0.25 e·Å .
c
+
+
–3
(
25), 351 [M+Na] (100), 352 [M+H+Na] (20). Found, %:
C 69.33; H 5.99; S 9.67. C19
C 69.47; H 6.15; S 9.76.
H
20
O
3
S. Calculated, %:
The crystallographic data and refinement parameters of
compound cis-8a have been deposited at the Cambridge
Crystallographic Data Center (deposit CCDC-1523861).
These data can be obtained free of charge via
www.ccdc.cam.ac.uk/getstructures
X-ray crystal structure determination of compound
cis-8a. Suitable single crystals of compound cis-8a were
obtained by slow evaporation of a solution of the com-
pound in MeOH. All measurements were performed on a
Rigaku Oxford Diffraction SuperNova area-detector
The authors thank the National Science Center (Cracow,
PL) for financial support within the project Maestro (Grant
Number: Dec-2012/06/A/ST5/00219). This work is a part
of the planned PhD thesis of Paulina Grzelak, University of
Łódź.
32
diffractometer using MoKα radiation (λ 0.71073 Å) from
a micro-focus X-ray source and an Oxford Instruments
Cryojet XL cooler. Data reduction was performed with
CrysAlisPro.32 Intensities were corrected for Lorentz and
polarization effects, and an empirical absorption correction
References
3
2
using spherical harmonics was applied. Equivalent
reflections, other than Friedel pairs, were merged. The
1
. Blond, G.; Gulea, M.; Mamane, V. Curr. Org. Chem. 2016,
2
0, 2161.
structure was solved by dual space methods using
SHELXT-2014,33 which revealed the positions of all non-
2.
(a) Block, E. In Science of Synthesis, Molander, G. A., Ed.;
G. Thieme Verlag: Stuttgart, 2007, vol. 33, ch. 33, p. 235.
hydrogen atoms. One of the thiophene rings is disordered
through a rotation of approximately 180° about the ring
pivot axis, thus interchanging the positions of the S atom
and a C atom. Two positions were defined for these atoms,
and the site occupation factor of the major conformation
refined to 0.847(3). Similarity restraints were applied to the
chemically equivalent bond lengths involving the
disordered atoms, while neighboring atoms from the two
conformations of the disordered ring were restrained to
have similar atomic displacement parameters. 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 C atom (1.5Ueq for the
methyl groups). The refinement of the structure was carried
(
b) Tavakolinia, F.; Baghipour, T.; Hossaini, Z.; Zareyee, D.;
Mohammad, A.; Khalilzadeh, M. A.; Rajabi, M. Nucleic Acid
Ther. 2012, 22, 265.
3. (a) Bogdanowicz-Szwed, K.; Budzowski, A. Wiad. Chem.
2003, 57, 435 (PL-ISSN 0043-5104). (b) Mlostoń, G.;
Grzelak, P.; Heimgartner, H. J. Sulfur Chem. 2017, 38, 1.
4
5
6
.
.
.
Timoshenko, V. M.; Siry, S. A.; Rozhenko, A. B.;
Shermolovich, Y. G. J. Fluorine Chem. 2010, 131, 172.
Dentel, H.; Chataigner, I.; Lohier, J.-F.; Gulea, M.
Tetrahedron 2012, 68, 2326.
(a) Kanishchev, O. S.; Sanselme, M.; Bouillon, J.-P.
Tetrahedron 2013, 69, 1322. (b) Mikhailichenko, S. S.;
Bouillon, J.-P.; Besson, T.; Shermolovich, Y. G. Tetrahedron
Lett. 2010, 51, 990.
Larsen, C.; Harpp, D. N. J. Org. Chem. 1980, 45, 3713.
(a) Schönberg, A.; König, B. Chem. Ber. 1968, 101, 725.
7.
.
8
(
b) König, B.; Martens, J.; Praefcke, K.; Schönberg, A.;
2
Schwarz, H.; Zeisberg, R. Chem. Ber. 1974, 107, 2931.
out on F by using full-matrix least-squares procedures,
(
(
c) Praefcke, K.; Weichsel, C. Liebigs Ann. Chem. 1979, 784.
d) Weinreb, S. M.; Staib, R. R. Tetrahedron 1982, 38, 3087.
2
2 2
which minimized the function Ʃw(F
o
–F ) . A correction
c
for secondary extinction was not applied. Refinement of the
(
e) Metzner, P. Synthesis 1992, 1185. (f) Itoh, T.; Fujikawa, K.;
34
absolute structure parameter yielded a value of 0.03(2), which
confidently confirms that the refined model represents the
true absolute structure. Neutral atom scattering factors for
Kubo, M. J. Org. Chem. 1996, 61, 8329. (g) Mlostoń, G.;
Grzelak, P.; Hamera-Fałdyga, R.; Jasiński, M.; Pipiak, P.;
Urbaniak, K.; Albrecht, Ł.; Hejmanowska, J.; Heimgartner, H.
Phosphorus, Sulfur Silicon Relat. Elem. 2017, 192, 204.
3
5
non-hydrogen atoms were taken from ref. , and the
36
9. (a) Baumann, K.; Fromm, E. Ber. Dtsch. Chem. Ges. 1889,
22, 2593. (b) Gaumont, A. C.; Wazneh, L.; Denis, J. M.
Tetrahedron 1991, 47, 4927.
scattering factors for H atoms were taken from ref.
37
Anomalous dispersion effects were included in F
c
;
the
3
8
values for f' and f'' were those of ref. The values of the
1
0. (a) Middleton, W. J. J. Org. Chem. 1965, 30, 1390.
b) Schuler, B.; Sundermeyer, W. Chem. Ber. 1990, 123, 177.
1. (a) Larsen, S. D.; Fisher, P. V.; Libby, B. E.; Jensen, R. M.;
Mizsak, S. A.; Watt, W. J. Org. Chem. 1996, 61, 4725.
(b) Huang, N.-Z.; Lakshmikantham, M. V.; Cava, M. P.
J. Org. Chem. 1987, 52, 169.
39
mass attenuation coefficients are those of ref. The
(
4
0
SHELXL-2016 program was used for all calculations.
Crystal data for compound cis-8a: C15 , M 292.46,
1
H
S
16 3
crystallized from methanol, colorless, prism, crystal
dimensions 0.16 × 0.18 × 0.25 mm, monoclinic, space group
Ia, Z 4, reflections for unit cell determination 7331, 2θ range
for unit cell determination 7–61°, a 15.2401(4), b 8.36686(16),
12. (a) Sasaki, T.; Eguchi, S.; Katada, T. Heterocycles 1984, 21,
6
82. (b) Katada, T.; Eguchi, S.; Sasaki, T. J. Org. Chem.
3
1986, 51, 314.
c 12.1476(3) Å, β 111.886(3)°, V 1437.33(6) Å , T 160(1) K,
–3
–1
13. (a) Bonini, B. F.; Mazzanti, G.; Zani, P.; Maccagnani, G.
J. Chem. Soc., Perkin Trans. 1 1989, 2083. (b) Bonini, B. F.;
Lenzi, A.; Maccagnani, G.; Barbaro, G.; Giorgianni, P.;
Macciantelli, D. J. Chem. Soc., Perkin Trans. 1 1987, 2643.
D
2
X
1.352 g×cm , μ(MoKα) 0.495 mm , scan type ω,
θ
max 60.8°, transmission factors (min; max) 0.923; 1.000,
total reflections measured 9233, symmetry independent
5
24

Chemistry of Heterocyclic Compounds 2017, 53(5), 518–525
1
4. (a) Ito, S.; Okujima, T.; Kikuchi, S.; Shoji, T.; Morita, N.;
26. Li, H.; Silver, J. E.; Watson, W. H.; Kashyap, R. P.;
Le Noble, W. J. J. Org. Chem. 1991, 56, 5932.
Asao, T.; Ikoma, T.; Tero-Kubota, S.; Kawakami, J.; Tajiri, A.
J. Org. Chem. 2008, 73, 2256. (b) Breu, J.; Höcht, P.;
Rohr, U.; Schatz, J.; Sauer, J. Eur. J. Org. Chem. 1998, 2861.
5. (a) Schatz, J.; Sauer, J. Tetrahedron Lett. 1994, 35, 4767.
27. (a) Petrov, V. A.; Lustig, S.; Marshall, W. J. Fluorine Chem.
2007, 128, 1227. (b) Schwab, M.; Sundermeyer, W. Chem.
Ber. 1986, 119, 2458.
1
1
(b) Rohr, U.; Schatz, J.; Sauer, J. Eur. J. Org. Chem. 1998, 2875.
28. Block, E.; Wall, A. Tetrahedron Lett. 1985, 26, 1425.
29. Alder, K.; Vogt, W. Liebigs Ann. Chem. 1951, 571, 137.
30. Magnusson, G. J. Org. Chem. 1985, 50, 1998.
31. Biellmann, J. F.; Ducep, J. B.; Vicens, J. J. Tetrahedron 1976,
32, 1801.
32. CrysAlisPro, Version 1.171.38.43c; Rigaku Oxford Diffraction:
Abingdon, 2015.
33. Sheldrick, G. M. Acta Crystallogr. Sect. A 2015, 71, 3.
34. Parsons, S.; Flack, H. D.; Wagner, T. Acta Crystallogr. Sect.
B 2013, 69, 249.
35. Maslen, E. N.; Fox, A. G.; O'Keefe, M. A. In International Tables
for Crystallography, Wilson, A. J. C., Ed.; Kluwer Academic
Publishers: Dordrecht, 1992, vol. C, Table 6.1.1.1, p. 477.
36. Stewart, R. F.; Davidson, E. R.; Simpson, W. T. J. Chem.
Phys. 1965, 42, 3175.
37. Ibers, J. A.; Hamilton, W. C. Acta Crystallogr. 1964, 17, 781.
38. Creagh, D. C.; McAuley, W. J. In International Tables for
Crystallography; Wilson, A. J. C., Ed.; Kluwer Academic
Publishers: Dordrecht, 1992, vol. C, Table 4.2.6.8, p. 219.
39. Creagh, D. C.; Hubbell, J. H. In International Tables for
Crystallography; Wilson, A. J. C., Ed.; Kluwer Academic
Publishers: Dordrecht, 1992, vol. C, Table 4.2.4.3, p. 200.
40. Sheldrick, G. M. Acta Crystallogr., Sect. C: Struct. Chem.
2015, C71, 3.
6. Kiselev, V. D.; Kashaeva, E. A.; Potapova, L. N.;
Iskhakova, G. G.; Konovalov, A. I. Russ. Chem. Bull., Int. Ed.
2
005, 54, 2034. [Izv. Akad. Nauk, Ser. Khim. 2005, 1973.]
1
1
1
2
7. Jiang, H.; Cruz Cruz, D.; Li, Y.; Lauridsen, V. H.;
Jørgensen, K. A. J. Am. Chem. Soc. 2013, 135, 5200.
8. Hejmanowska, J.; Jasiński, M.; Mlostoń, G.; Albrecht, Ł. Eur.
J. Org. Chem. 2017, 950.
9. Mlostoń, G.; Urbaniak, K.; Gębicki, K.; Grzelak, P.;
Heimgartner, H. Heteroat. Chem. 2014, 25, 548.
0. Hamera-Fałdyga, R.; Grzelak, P.; Pipiak, P.; Mlostoń, G.
Phosphorus, Sulfur Silicon Relat. Elem. 2017, 192, 197.
1. Varma, R. S.; Kumar, D. Org. Lett. 1999, 1, 697.
2
2
2
2. Wilker, S.; Erker, G. J. Am. Chem. Soc. 1995, 117, 10922.
3. (a) Mlostoń, G.; Urbaniak, K.; Linden, A.; Heimgartner, H.
Helv. Chim. Acta 2015, 98, 453. (b) Mlostoń, G.; Pipiak, P.;
Linden, A.; Heimgartner, H. Helv. Chim. Acta 2015, 98, 462.
(
c) Mlostoń, G.; Pipiak, P.; Heimgartner, H. Beilstein J. Org.
Chem. 2016, 12, 716. (d) Mlostoń, G.; Hamera-Fałdyga, R.;
Linden, A.; Heimgartner, H. Beilstein J. Org. Chem. 2016, 12,
1
421.
2
4. Johnson, C. K. ORTEPII, Report ORNL-5138: Oak Ridge
National Laboratory: Oak Ridge, Tennessee, 1976.
2
5. Praefcke, K.; Weichsel, C. Liebigs Ann. Chem. 1980, 1604.
5
25