Base-Induced Cyclization of Propargyl Alkenylsulfones: A High-Yielding Synthesis of 4,5-Disubstituted 2H-Thiopyran 1,1-Dioxides

Article abstract of DOI:10.1002/ejoc.201500633

A convenient synthesis of 4,5-disubstituted 2H-thiopyran 1,1-dioxides is reported through a base induced process starting from eneyne sulfones. Except for strongly electron-withdrawing groups, the reaction tolerated a wide variety of substituents in the t

Full text of DOI:10.1002/ejoc.201500633

FULL PAPER
DOI: 10.1002/ejoc.201500633
Base-Induced Cyclization of Propargyl Alkenylsulfones: A High-Yielding
Synthesis of 4,5-Disubstituted 2H-Thiopyran 1,1-Dioxides
Ishita Hatial,[a][‡] Joyee Das,[a][‡] Ananta K. Ghosh,[b] and Amit Basak*[a]
Keywords: Sulfur heterocycles / Cyclization / Electrocyclic reactions / Alkynes / Allylic compounds
A convenient synthesis of 4,5-disubstituted 2H-thiopyran
1,1-dioxides is reported through a base induced process
starting from eneyne sulfones. Except for strongly electron-
withdrawing groups, the reaction tolerated a wide variety of
substituents in the two aryl rings. This finding represents a
major departure from the behaviour of the corresponding
ethers. The reaction most probably proceeds through a 6π-
electrocyclization from an in-situ-generated 1,3,5-trienyl
sulfinate.
Introduction
molecular Diels–Alder reaction mechanism to explain the
The reactivity of bispropargyl sulfones, ethers, and sul- selectivity of the cyclization of propargyl alkenyl ethers,
fonamides has been well studied, especially in recent which, upon treatment with a suitable base, generate prod-
years.[1] The reaction leads to the formation of two C–C ucts following a similar pathway (Scheme 3). Because of the
bonds in high yield under mild conditions, and is popularly
known as the Garratt–Braverman (GB) cyclization.[2] The
synthetic utility of the reaction has recently been reported
in a series of papers.[3] Although doubts remain about the
exact mechanism of the reaction, a diradical mechanism in-
volving a bis-allene intermediate (Scheme 1), as proposed
initially by Garratt and Braverman and later supported by
computations and selectivity profiles,[4] is the generally ac-
cepted one. In 2007, while studying the rearrangement of
ethers, Kudoh et al.[5] proposed an anionic intramolecular
Diels–Alder mechanism involving a monoallenyl anion
(Scheme 2); this mechanism has the support of deuterium-
labelling experiments as well as computations based on the
HUMO–LUMO gap. The same authors also used the intra-
Scheme 2. Mechanism proposed by Kudoh et al.
Scheme 1. Mechanism proposed by Garratt and Braverman.
[a] Department of Chemistry, Indian Institute of Technology,
Kharagpur 721302, India
E-mail: absk@chem.iitkgp.ernet.in
http://www.chemistry.iitkgp.ac.in/~absk/
http://www.iitkgp.ac.in/
[b] Department of Biotechnology, Indian Institute of Technology,
Kharagpur 721302, India
[‡] Equal contribution
Scheme 3. Reaction with eneyne–ether system, as reported by Ku-
doh et al.[5]
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201500633.
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I. Hatial, J. Das, A. K. Ghosh, A. Basak
FULL PAPER
reported differences between the reactivity and selectivity
profiles of bis-propargyl sulfones vis-à-vis ethers,[6] we be-
came curious to know whether similar products would be
obtained when propargyl alkenyl sulfones were treated with
base. With this idea in mind, we synthesized several prop-
argyl alkenyl sulfones 11A–11M. On treatment with a base
(NaH/DMSO), these sulfones gave disubstituted thiopyran
1,1-dioxides 7A–7M, instead of the aryl(dihydro)naphthal-
enes as was observed for the corresponding ethers. This
method offers a convenient procedure for the synthesis of
thiopyran dioxide derivatives with a variety of substituents,
which are reported to be important in medicinal[7] and ma-
terials chemistry.[8] It has also been reported that that cyclic
Results and Discussion
The starting propargyl alkenyl sulfones (i.e., 11A–11M)
were prepared by the sequence of steps shown in Scheme 4.
The key step was a K2CO3-mediated S-alkylation[10] of an
alkenyl thiol, generated in situ from the corresponding
thioacetate[11] 8A–8C, with a propargyl bromide 9A–9M (all
the bromides are reported in the literature[4,12]). Subsequent
oxidation of the crude sulfides (i.e., 10A–10M) gave the tar-
get sulfones (i.e., 11A–11M), which were isolated pure by
chromatography. Sulfonamide 11N was prepared by N-alk-
ylation of phenyl propargylamine p-toluenesulfonamide de-
rivative 9Y with cinnamyl bromide.
The reactivity of the sulfones under basic conditions was
sulfones are attractive options for medicinal chemistry.[9] In then probed, starting with compound 11A. Initial attempts
this article, we describe our results along with possible to induce cyclization by treatment with Et3N (catalytic or
mechanistic descriptions. A rationale for the differences in 1 equiv.) at room temp. failed. The use of stronger bases like
the reactivity profiles of sulfones and ethers is also pro- DBU or DBN did not lead to cyclization, even at elevated
vided.
temperatures; only decomposition of the starting material
Scheme 4. Synthesis of propargyl alkenyl sulfones.
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Base-Induced Cyclization of Propargyl Alkenylsulfones
Table 1. Base-catalysed cyclization of propargyl alkenyl sulfones.
was observed. Gratifyingly, upon treatment with NaH in
DMSO at ice-cold temperature for 10 min, the sulfone
underwent a clean reaction to give a single product, which
was isolated pure by chromatography. Analysis by NMR
spectroscopy and mass spectrometry confirmed the struc-
ture as 5-benzyl-4-phenyl-2H-thiopyran 1,1-dioxide (7A).
The experiment was repeated with other sulfones, which
also gave thiopyran-1,1-dioxide derivatives in decent yields.
The results summarized in Table 1 show that the reactions
of the alkenyl propargyl sulfones do not follow a GB path-
way like the corresponding ethers. Rather, the reaction takes
a different route involving the formation of only one new
C–C bond to produce the thiopyran derivatives. The reac-
tion is quite general, and it tolerated a large number of sub-
stituents on the phenyl rings of both the alkyne part as well
as the cinnamoyl moiety; the yields ranged from moderate
to excellent. Regarding the use of an electron-withdrawing
aromatic system in the alkyne unit, we obtained the desired
product only for a p-chloro-substituted (mildly with-
drawing) derivative.[13] We wanted to study systems with
more strongly electron-withdrawing groups like nitro and
cyano. However, we were unable to synthesize the mixed
sulfide of the nitro derivative, despite trying different reac-
tion conditions. For the cyano derivative we could success-
fully synthesize the sulfone, but the cyclization reaction did
not work; the starting material decomposed. The feasibility
of the reaction was also investigated by using solvents of
different polarities. The reaction failed to proceed in nonpo-
lar solvents like dichloromethane, but it did work in moder-
ately polar solvents like THF to give similar yields. While
carrying out the reaction in THF, we isolated exomethylene
compound 25 (structure confirmed by X-ray crystallogra-
phy) from the reaction of 11G. Interestingly, the corre-
sponding sulfonamide (i.e., 11N) followed the GB pathway
like its ether counterpart to give aryl dihydronaphthalene
derivative 7N.
Thiopyran derivatives have been reported[14] to be fully hy-
drogenated under atmospheric pressure in the presence of Pd/
C (10%) catalyst in methanol to give the corresponding satu-
rated tetrahydrothiopyran 1,1-oxides. Following that pro-
cedure, thiopyran 1,1-dioxide 7B was subjected to hydrogen-
ation, which gave rise to a mixture of products (Scheme 5).
[a] NaH/ DMSO, ice-cold. [b] DBU, toluene, reflux. [c] Sulfone 11P
was prepared by S-alkylation of phenylpropargylthiol, generated
from the corresponding thioacetate, with β-methyl-substituted cin-
namyl bromide.
Scheme 5. Hydrogenation of 5-(4-methylbenzyl)-4-phenyl-2H-thio-
pyran 1,1-dioxide.
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Fractional crystallization of the crude mixture produced erature.[17] The proposed mechanism is supported by the
a white solid, which was identified as dihydrothiopyran de- isolation of exomethylene derivative 25, which could have
rivative 12, obtained by incomplete but selective hydrogen- been generated by 1,3-protonation after the electrocycliza-
ation. The mother liquor contained an inseparable mixture tion. We carried out the reaction in deuterated solvents. Un-
of cis- and trans-tetrahydrothiopyran 1,1-oxides. Both the fortunately, we were unable to reproduce the reaction in the
partially saturated and fully saturated skeletons are known deuterated protic solvent [D4]methanol. However, when the
to have biological activities.[15]
reaction was repeated in [D6]DMSO/NaH and quenched
Regarding the mechanism, we believe that the reaction with water (H2O), no incorporation of deuterium into the
1
proceeds by an exothermic 6π-electrocyclization[16] process product could be observed, as revealed by H NMR spec-
(Scheme 6, path a). The 1,3,5-triene framework required for troscopy. The reaction was next carried out in the presence
the electrocyclization is produced by propargyl–allene isom- of [D6]DMSO/NaH and quenched with D2O. This time we
erization followed by sulfinate generation. It appears that obtained a product with complete deuterium incorporation
the 6π-electrocyclization is easier than the intramolecular at the benzylic CH2 and at the CH2 group adjacent to the
Diels–Alder mechanism (Scheme 6, path b) unless the triene sulfone moiety. However, as the product itself undergoes
generation is not possible. This is consistent with the inabil- deuterium exchange at these two positions when treated
ity of the ether or sulfonamide to undergo a similar process. with [D6]DMSO/NaH and subsequent quenching with
In these cases, the allylic anion cannot generate a 1,3,5- D2O, the deuterium-labelling experiments remain incon-
triene system, thus ruling out the 6π-electrocyclization pro- clusive regarding the mechanistic pathway (all relevant
cess (see inset, Scheme 6). Hence the alternative GB-like NMR spectra are included in the Supporting Information).
process occurs for these systems. It may be mentioned here We also checked the reactivity of β-methyl cinnamyl deriva-
that although there is controversy regarding the nature of tive 11P, hoping to isolate intermediate 26. However, the
sulfone moiety, i.e., whether it is electron-withdrawing or reaction failed to produce any well-defined product.
-delocalizing, the involvement of such a sulfinate formation
through electron delocalization has been reported in the lit-
Conclusion
A new high-yielding method for the synthesis of disubsti-
tuted 2H-thiopyran 1,1-dioxide has been developed, start-
ing from propargyl alkenyl sulfones. A 6π-electrocyclization
mechanism for the reaction has been proposed that also
explains the inability of the corresponding ethers or sulfon-
amides to undergo a similar reaction. The synthesized
thiopyran derivatives will be screened for biological activity
in the future.
Experimental Section
General Remarks: 1H 13C NMR spectra were obtained with 200,
400, and 600 MHz Bruker NMR instruments, using [D]chloroform
and [D3]acetonitrile as solvents. The following abbreviations are
used to describe peak patterns where appropriate: s = singlet, d =
doublet, t = triplet, q = quartet, m = multiplet, br. = broad signal.
All coupling constants (J) are given in Hz. Mass spectra were re-
corded in ESI+ mode (ion trap).
General Procedure for Sulfonation. Synthesis of Compounds 11A–
11P: Oxone (767 mg, 2.5 equiv.) was added to an ice-cold solution
of crude sulfide 10A–10P (1 mmol) in THF/H2O (1:1; 20 mL), and
the mixture was stirred at room temperature under a nitrogen at-
mosphere. After 12 h, the reaction mixture was diluted with di-
chloromethane, and the organic layer was washed with brine, and
dried with anhydrous sodium sulfate. The solvent was removed,
and the crude residue was purified by column chromatography (sil-
ica gel, petroleum ether/ethyl acetate mixture as eluent).
Selected Spectroscopic Data
4-[3-(3-Phenylprop-2-ene-1-sulfonyl)prop-1-ynyl]benzene
(11A):
White gummy mass (252 mg, 85%). IR (neat): ν = 3056, 2920,
˜
2850, 2235, 1623, 1447, 1301, 1121, 750 cm–1. 1H NMR (400 MHz,
[D]chloroform): δ = 7.52–7.31 (m, 10 H), 6.83 (d, J = 15.9 Hz, 1
H), 6.32 (dt, J = 15.6, 7.6 Hz, 1 H), 4.12 (d, J = 7.8 Hz, 4 H)
Scheme 6. Proposed 6π-electrocyclization-based mechanism
(IMDAR = intramolecular Diels–Alder reaction).
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Base-Induced Cyclization of Propargyl Alkenylsulfones
ppm. 13C NMR (100 MHz, [D]chloroform): δ = 139.9, 135.8, 132.3,
J = 2.5 Hz, 1 H) ppm. 13C NMR (100 MHz, [D]chloroform): δ =
140.0, 135.6, 129.1, 129.0, 128.9, 127.0, 114.8, 76.96, 76.94, 76.90,
71.8, 55.6, 43.4 ppm. HRMS: calcd. for C12H13O2S+ [M + H]+
221.0631; found 221.0648.
129.6, 129.1, 128.8, 127.1, 121.9, 115.1, 88.2, 77.9, 56.1, 44.9 ppm.
HRMS: calcd. for C18H17O2S+ [M
297.0945.
+
H]+ 297.0944; found
1-Methyl-4-[3-(3-phenylprop-2-ene-1-sulfonyl)prop-1-ynyl]benzene
(E)-1-Bromo-4-[3-(3-phenylprop-2-ynylsulfonyl)prop-1-enyl]benzene
(11B): White solid (279 mg, 90%), m.p. 111–112 °C. IR (neat): ν (11H): Yellow solid (300 mg, 80%), m.p. 94–95 °C. IR (neat): ν =
˜
= 3058, 2927, 2851, 2240, 1620, 1445, 1309, 750 cm–1. 1H NMR
(400 MHz, [D]chloroform): δ = 7.44–7.31 (m, 7 H), 7.16 (d, J =
˜
3045, 2967, 2245, 1635, 1445, 1312, 755, 550 cm–1
.
1H NMR
(600 MHz, [D]chloroform): δ = 7.49 (d, J = 12 Hz, 3 H), 7.43–7.40
8.0 Hz, 2 H), 6.83 (d, J = 15.9 Hz, 1 H), 6.30 (dt, J = 15.6, 7.6 Hz, (m, 1 H), 7.38–7.35 (m, 2 H), 7.30 (d, J = 12 Hz, 2 H), 7.28 (s, 1
1 H), 4.11 (d, J = 7.6 Hz, 2 H), 4.08 (s, 2 H), 2.38 (s, 3 H) ppm. H), 6.78 (d, J = 18 Hz, 1 H), 6.32 (dt, J = 18, 6 Hz, 1 H), 4.12 (d,
13C NMR (50 MHz, [D]chloroform): δ = 139.8, 135.6, 132.0, 129.9,
129.4, 128.9, 126.9, 118.6, 114.9, 88.3, 75.9, 55.7, 44.7, 21.7 ppm.
HRMS: calcd. for C19H19O2S+ [M + H]+ 311.1100; found
311.1090.
J = 6 Hz, 2 H), 4.11 (s, 2 H) ppm. 13 C NMR (150 MHz,
[D]chloroform): δ = 138.5, 134.4, 131.9, 129.3, 128.5, 128.3, 122.8,
121.4, 115.6, 88.15, 76.4, 55.7, 44.8 ppm. HRMS: calcd. for
C18H16BrO2S+ [M + H]+ 375.0054; found 375.0060.
1-Methoxy-4-[3-(3-phenylprop-2-ene-1-sulfonyl)prop-1-ynyl]benzene
(E)-1-Bromo-4-{3-[3-(4-methoxyphenyl)prop-2-ynylsulfonyl]prop-1-
enyl}benzene (11I): Pale yellow solid (282 mg, 70 %), m.p. 145–
(11C): Yellow sticky mass (277 mg, 85%). IR (neat): ν = 3056,
˜
2926, 2855, 2227, 1605, 1513, 1444, 1306, 1178, 1030, 743 cm–1. 1H 146 °C. IR (neat): ν = 3087, 2975, 2950, 2835, 2219, 1610, 1313,
˜
NMR (400 MHz, [D]chloroform): δ = 7.43–7.25 (m, 8 H), 6.87 (d, 1159, 1130, 1050, 725, 575 cm–1. 1H NMR (600 MHz, [D]chloro-
J = 8.2 Hz, 2 H), 6.58 (d, J = 16 Hz, 1 H), 6.25 (dt, J = 15.3,
form): δ = 7.49 (d, J = 8.4 Hz, 2 H), 7.41 (d, J = 9 Hz, 2 H), 7.30
7.5 Hz, 1 H), 3.81 (d, J = 3.7 Hz, 3 H), 3.55 (d, J = 7.7 Hz, 2 H), (d, J = 8.4 Hz, 2 H), 6.88 (d, J = 9 Hz, 2 H), 6.78 (d, J = 16.2 Hz,
3.48 (s, 2 H) ppm. 13C NMR (100 MHz, [D]chloroform): δ = 160.4,
139.7, 135.6, 133.6, 128.9, 128.8, 126.9, 114.9, 114.2, 113.6, 88.2,
75.1, 55.7, 55.4, 44.7 ppm. HRMS: calcd. for C19H19O3S+ [M + H]+
327.1049; found 327.1046.
1 H), 6.32 (dt, J = 16.2, 6 Hz, 1 H), 4.12 (d, J = 6 Hz, 2 H), 4.09
(s, 2 H), 3.85 (s, 3 H) ppm. 13C NMR (150 MHz, [D]chloroform):
δ = 160.4, 138.4, 134.4, 133.5, 131.9, 128.3, 122.8, 115.7, 114.2,
113.4, 88.2, 75.0, 55.6, 55.4, 44.9 ppm. HRMS: calcd. for
C19H18BrO3S+ [M + H]+ 405.0160; found 405.0167.
1,2-Dimethyl-4-[3-(3-phenylprop-2-ene-1-sulfonyl)prop-1-ynyl]benz-
ene (11D): Off-white solid (253 mg, 78%), m.p. 86–87 °C. IR (neat):
(E)-1-Bromo-4-[3-(3-p-tolylprop-2-ynylsulfonyl)prop-1-enyl]benzene
1
ν = 3059, 2921, 2849, 2234, 1620, 1445, 1306, 1122, 753 cm–1. H
(11J): White solid (291 mg, 75%), m.p. 180–181 °C. IR (neat): ν =
˜
˜
NMR (400 MHz, [D]chloroform): δ = 7.43 (d, J = 7.4 Hz, 2 H), 3077, 2974, 2850, 2220, 1659, 1440, 1323, 1126, 752, 560 cm–1. H
1
7.35 (q, J = 9.1, 7.9 Hz, 3 H), 7.29–7.20 (m, 2 H), 7.11 (d, J =
7.7 Hz, 1 H), 6.84 (d, J = 15.8 Hz, 1 H), 6.31 (dt, J = 15.5, 7.6 Hz, 7.38 (d, J = 7.8 Hz, 2 H), 7.30 (d, J = 8.4 Hz, 2 H), 7.18 (d, J =
1 H), 4.11 (d, J = 7.6 Hz, 2 H), 4.08 (s, 2 H), 2.29 (s, 3 H), 2.26 (s, 7.8 Hz, 2 H), 6.77 (d, J = 15.6 Hz, 1 H), 6.32 (dt, J = 15.6, 6 Hz,
3 H) ppm. 13C NMR (100 MHz, [D]chloroform): δ = 139.9, 138.6, 1 H), 4.12 (d, J = 6 Hz, 2 H), 4.09 (s, 2 H), 2.40 (s, 3 H) ppm. 13C
NMR (600 MHz, [D]chloroform): δ = 7.49 (d, J = 8.4 Hz, 2 H),
137.1, 135.7, 133.12, 129.9, 129.6, 129.0, 128.9, 127.0, 118.9, 115.1,
88.6, 75.7, 55.8, 44.9, 29.9, 20.0, 19.8 ppm. HRMS: calcd. for
C20H21O2S+ [M + H]+ 325.1257; found 325.1247.
NMR (150 MHz, [D]chloroform): δ = 139.7, 138.4, 134.4, 131.9,
131.8, 129.2, 128.3, 122.8, 118.3, 115.6, 88.4, 75.7, 55.6, 44.9,
21.6 ppm. HRMS: calcd. for C19H18BrO2S+ [M + H]+ 389.0211;
found 389.0217.
2,4-Dimethoxy-1-[3-(3-phenylprop-2-ene-1-sulfonyl)prop-1-ynyl]-
benzene (11E): Yellow solid (299 mg, 84 %), m.p. 97–98 °C. IR
(E)-1-Methyl-4-[3-(3-p-tolylallylsulfonyl)prop-1-ynyl]benzene (11K):
(neat): ν = 3082, 2970, 2921, 2836, 2220, 1609, 1312, 1161, 1125, Off-white solid (217 mg, 67%), m.p. 157–158 °C. IR (neat): ν =
˜
˜
3075, 2956, 2850, 2221, 1620, 1445, 1363, 1128, 753 cm–1. 1H NMR
(600 MHz, [D]chloroform): δ = 7.40 (d, J = 7.8 Hz, 2 H), 7.34 (d,
J = 7.2 Hz, 2 H), 7.18 (d, J = 7.8 Hz, 4 H), 6.82 (d, J = 16.2 Hz,
1 H), 6.26 (dt, J = 16.2, 7.2 Hz, 1 H), 4.12 (d, J = 7.2 Hz, 2 H),
4.09 (s, 2 H), 2.40 (s, 3 H), 2.38 (s, 3 H) ppm. 13C NMR (150 MHz,
[D]chloroform): δ = 139.6, 139.5, 138.9, 132.7, 131.9, 129.5, 129.2,
126.8, 118.5, 113.7, 88.2, 75.8, 55.7, 44.5, 21.6, 21.3 ppm. HRMS:
calcd. for C20H21O2S+ [M + H]+ 325.1262; found 325.1269.
1050, 723 cm–1. 1H NMR (400 MHz, [D]chloroform): δ = 7.43–
7.26 (m, 6 H), 6.95 (d, J = 15.9 Hz, 3 H), 6.47 (d, J = 7.7 Hz, 2
H), 6.32 (dt, J = 15.7, 7.8 Hz, 1 H), 4.19 (d, J = 7.8 Hz, 2 H), 4.09
(s, 2 H), 3.90 (s, 3 H), 3.87 (s, 3 H) ppm. 13C NMR (100 MHz,
[D]chloroform): δ = 162.2, 162.1, 139.8, 135.9, 134.8, 128.9, 127.0,
115.4, 105.2, 103.5, 98.7, 85.1, 79.3, 55.9, 55.7, 55.1, 44.9 ppm.
HRMS: calcd. for C20H21O4S+ [M + H]+ 357.1155; found
357.1144.
1-Chloro-4-[3-(3-phenylprop-2-ene-1-sulfonyl-1-ynyl)]benzene (11F):
(E)-1-Methoxy-4-[3-(3-p-tolylallylsulfonyl)prop-1-ynyl]benzene
White gummy mass (248 mg, 75 %). IR (neat): ν = 2950, 2867, (11L): Pale yellow solid (245 mg, 72%), m.p. 115–116 °C. IR (neat):
˜
1
1
2237, 1635, 1456, 1313, 1121, 810, 752 cm–1. H NMR (400 MHz, ν = 3078, 2925, 2235, 1656, 1456, 1320, 1125, 1055, 753 cm–1. H
˜
[D]chloroform): δ = 7.43–7.26 (m, 9 H), 6.81 (d, J = 15.8 Hz, 1 H),
NMR (600 MHz, [D]chloroform): δ = 7.44 (d, J = 9 Hz, 2 H), 7.32
(d, J = 7.8 Hz, 2 H), 7.18 (d, J = 7.8 Hz, 2 H), 6.89 (d, J = 8.4 Hz,
2 H), 6.81 (d, J = 15.6 Hz, 1 H), 6.26 (dt, J = 15.6, 7.8 Hz, 1 H),
4.11 (d, J = 7.8 Hz, 2 H), 4.08 (s, 2 H), 3.85 (s, 3 H), 2.38 (s, 3 H)
6.30 (dt, J = 15.4, 7.6 Hz, 1 H), 4.10 (d, J = 7.4 Hz, 4 H) ppm. 13
C
NMR (100 MHz, [D]chloroform): δ = 139.9, 135.6, 135.6, 133.4,
129.1, 129.1, 129.0, 128.8, 127.0, 120.2, 114.9, 87.1, 77.0, 56.3,
44.7 ppm. HRMS: calcd. for C18H16ClO2S+ [M + H]+ 331.0554; ppm. 13C NMR (150 MHz, [D]chloroform): δ = 160.3, 139.6, 138.9,
found 331.0544.
133.5, 132.8, 129.5, 126.8, 114.1, 113.7, 113.6, 88.0, 75.1, 55.7, 55.4,
44.5, 21.3 ppm. HRMS: calcd. for C20H21O3S+ [M + H]+ 341.1211;
found 341.1213.
[3-(Prop-2-yne-1-yne-sulfonyl)propenyl]benzene (11G): Pale yellow
solid (187 mg, 85%), m.p. 74–75 °C. IR (neat): ν = 3270, 3053,
˜
2921, 2135, 1510, 1418, 1303, 1125, 760 cm–1. 1H NMR (400 MHz, (E)-1-Methyl-4-[3-(3-phenylprop-2-ynylsulfonyl)prop-1-enyl]benz-
[D]chloroform): δ = 7.43 (d, J = 7.2 Hz, 2 H), 7.34 (dq, J = 14.0, ene (11M): Off-white solid (239 mg, 77%), m.p. 110–111 °C. IR
7.0 Hz, 3 H), 6.81 (d, J = 15.9 Hz, 1 H), 6.25 (dt, J = 15.7, 7.7 Hz, (neat): ν = 3045, 2937, 2878, 2234, 1630, 1456, 1312, 1125,
˜
1 H), 4.08 (d, J = 7.6 Hz, 2 H), 3.85 (d, J = 2.2 Hz, 2 H), 2.58 (t,
750 cm–1. 1H NMR (600 MHz, [D]chloroform): δ = 7.50 (d, J =
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I. Hatial, J. Das, A. K. Ghosh, A. Basak
FULL PAPER
8.4 Hz, 2 H), 7.43–7.34 (m, 5 H), 7.18 (d, J = 7.8 Hz, 2 H), 6.82
(d, J = 15.6 Hz, 1 H), 6.27 (dt, J = 15.6, 7.2 Hz, 1 H), 4.12 (d, J =
13C NMR (100 MHz, [D]chloroform): δ = 159.7, 143.0, 140.1,
137.4, 130.6, 129.4, 128.6, 128.3, 128.2, 127.7, 118.3, 114.3, 105.0,
7.8 Hz, 2 H), 4.10 (s, 2 H), 2.38 (s, 3 H) ppm. 13C NMR (150 MHz, 100.2, 55.5, 52.4, 52.4 ppm. HRMS: calcd. for C19H19O3S+ [M +
[D]chloroform): δ = 139.6, 139.0, 132.7, 132.0, 129.5, 129.3, 128.5,
126.8, 121.6, 113.7, 88.0, 76.5, 55.8, 44.4, 21.3 ppm. HRMS: calcd.
for C19H19O2S+ [M + H]+ 311.1106; found 311.1108.
H]+ 327.1049; found 327.1058.
5-(3,4-Dimethylbenzyl)-4-phenyl-2H-thiopyran 1,1-Dioxide (7D):
White solid (85 mg, 88%), m.p. 142–143 °C. IR (neat): ν = 3035,
˜
1
4-Methyl-N-(3-phenyl-allyl)-N-(3-phenylprop-2-ynyl)benzenesulfon-
amide (11N): White solid (305 mg, 76%) m.p. 89–90 °C. IR (neat):
2912 1620, 1445, 1320, 1121, 845, 751 cm–1. H NMR (400 MHz,
[D]chloroform): δ = 7.40–7.34 (m, 5 H), 7.12 (d, J = 8.2 Hz, 1 H),
ν = 3056, 3039, 2928, 2852, 2247, 1605, 1445, 1345, 1322, 1158, 6.96 (d, J = 6.8 Hz, 2 H), 6.65 (s, 1 H), 5.71 (t, J = 4.6 Hz, 1 H),
˜
766 cm–1. 1H NMR (400 MHz, [D]chloroform): δ = 7.83 (d, J =
8.0 Hz, 2 H), 7.31 (dq, J = 31.3, 7.3 Hz, 10 H), 7.10 (d, J = 6.9 Hz,
2 H), 6.63 (d, J = 15.8 Hz, 1 H), 6.18 (dt, J = 14.2, 6.8 Hz, 1 H),
4.24 (s, 2 H), 3.95 (d, J = 4.5 Hz, 2 H), 2.26 (s, 3 H), 2.25 (s, 3 H)
ppm. 13C NMR (100 MHz, [D]chloroform): δ = 143.0, 140.1, 137.9,
137.1, 137.1, 132.8, 130.3, 130.1, 129.4, 128.7, 128.6, 128.3, 126.6,
4.36 (s, 2 H), 4.08 (d, J = 6.7 Hz, 2 H), 2.36 (s, 3 H) ppm. 13C 118.5, 52.5, 52.3, 29.9, 19.9, 19.8 ppm. HRMS: calcd. for
NMR (100 MHz, [D]chloroform): δ = 143.8, 136.4, 136.3, 135.1,
131.7, 129.8, 128.8, 128.7, 128.3, 128.1, 126.8, 123.4, 122.4, 86.1,
82.1, 49.2, 37.1, 21.7 ppm. HRMS: calcd. for C25H24NO2S+ [M +
H]+ 402.1522; found 402.1518.
C20H21O2S+ [M + H]+ 325.1257; found 325.1281.
5-(2,4-Dimethoxybenzyl)-4-phenyl-2H-thiopyran 1,1-Dioxide (7E):
White solid (101 mg, 95%), m.p. 133–134 °C. IR (neat): ν = 3031,
˜
2965, 2859, 1627, 1449, 1323, 1156, 1035, 750 cm–1
.
1H NMR
(E)-[3-(3-Phenylbut-2-enylsulfonyl)prop-1-ynyl]benzene (11P): Yel-
(400 MHz, [D]chloroform): δ = 7.38 (s, 5 H), 7.15 (d, J = 8.4 Hz,
low liquid (186 mg, 60%). IR (neat): ν = 3055, 2928, 2855, 2243, 1 H), 6.67 (s, 1 H), 6.49 (d, J = 8.4 Hz, 1 H), 6.42 (s, 1 H), 5.68 (t,
˜
1
1623, 1447, 1311, 755 cm–1. H NMR (600 MHz, [D]chloroform):
J = 4.5 Hz, 1 H), 4.12 (s, 2 H), 3.94 (d, J = 4.4 Hz, 2 H), 3.81 (s,
δ = 7.47 (dd, J = 9, 6 Hz, 4 H), 7.4–7.28 (m, 6 H), 5.95 (t, J = 3 H), 3.74 (s, 3 H) ppm. 13C NMR (100 MHz, [D]chloroform): δ
6 Hz, 1 H), 4.19 (d, J = 6 Hz, 2 H), 4.09 (s, 2 H), 2.26 (s, 3 H)
ppm. 13C NMR (150 MHz, [D]chloroform): δ = 145.2, 141.9, 131.9,
129.2, 128.5, 128.2, 126.0, 121.5, 112.5, 87.6, 76.6, 52.2, 44.8,
16.8 ppm. HRMS: calcd. for C19H19O2S+ [M + H]+ 311.1106;
found 311.1114.
= 161.5, 158.7, 143.1, 140.1, 134.2, 131.1, 129.5, 128.5, 128.2, 127.9,
117.7, 117.1, 104.6, 98.8, 55.7, 53.6, 52.8, 52.5, 29.9 ppm. HRMS:
calcd. for C20H21O4S+ [M + H]+ 357.1155; found 357.1165.
5-(4-Chlorobenzyl)-4-phenyl-2H-thiopyran 1,1-Dioxide (7F): White
solid (60 mg, 60%), m.p. 144–145 °C. IR (neat): ν = 2967, 2851,
˜
General Procedure for the Preparation of Thiopyran 1,1-Dioxides:
Sodium hydride (60 % in oil; 9 mg, 0.36 mmol, 1.2 equiv.) was
added to an ice-cold solution of the respective sulfone (0.3 mmol,
1.0 equiv.) in dry DMSO (10 mL), and the mixture was stirred for
the specifed time. After TLC showed that the reaction was com-
plete, it was quenched with water (10 mL), and the mixture was
diluted with EtOAc (30 mL). The organic layer was separated,
washed with brine (3ϫ 10 mL), dried (Na2SO4), and concentrated
under vacuum. The residue was purifed by silica gel column
chromatography using petroleum ether/EtOAc as eluent to give the
final product.
1620, 1443, 1312, 1119, 800, 754 cm–1 1H NMR (400 MHz,
.
[D]chloroform): δ = 7.42–7.04 (m, 9 H), 6.64 (s, 1 H), 5.77 (t, J =
5.6 Hz, 1 H), 4.15 (s, 2 H), 3.95 (d, J = 4.0 Hz, 2 H) ppm. 13C
NMR (150 MHz, [D]chloroform): δ = 142.5, 139.5, 136.2, 133.5,
130.3, 129.2, 128.9, 128.5, 128.3, 119.1, 52.3, 52.1 ppm. HRMS:
calcd. for C18H16ClO2S+ [M + H]+ 331.0554; found 331.0538.
5-Methyl-4-phenyl-2H-thiopyran 1,1-Dioxide (7G) and 3-Methyl-4-
phenyl-2H-thiopyran 1,1-Dioxide (7GЈ): White gummy mass (50 mg,
75%). IR (neat): ν = 3268, 2915, 1613, 1416, 1308, 1124, 759 cm–1.
˜
1H NMR (600 MHz, [D]chloroform): δ = 7.39 (ddt, J = 21.3, 14.8,
7.6 Hz, 6 H), 7.30–7.16 (m, 4 H), 6.74 (d, J = 10.8 Hz, 1 H), 6.63–
5-Benzyl-4-phenyl-2H-thiopyran 1,1-Dioxide (7A): White solid 6.48 (m, 2 H), 6.16 (t, J = 5.0 Hz, 1 H), 1.96 (s, 3 H), 1.88 (s, 3 H)
(67 mg, 75 %), m.p. 155 °C (decomposed). IR (neat): ν = 3059,
ppm. 13C NMR (150 MHz, [D]chloroform): δ = 146.8, 140.6, 138.9,
˜
2944, 2852, 1618, 1444, 1319, 1120, 753 cm–1. 1H NMR (400 MHz, 138.5, 138.3, 132.7, 131.4, 128.9, 128.7, 128.7, 128.5, 128.2, 126.4,
[D3]acetonitrile): δ = 7.58–7.21 (m, 10 H), 6.62 (s, 1 H), 5.80 (t, J 125.9, 122.9, 55.8, 50.6, 23.0, 22.6 ppm. HRMS: calcd. for
= 4.6 Hz, 1 H), 4.20 (s, 2 H), 3.95 (d, J = 4.6 Hz, 2 H) ppm. 13C C12H13O2S+ [M + H]+ 221.0631; found 221.0626.
NMR (100 MHz, [D3]acetonitrile): δ = 141.9, 140.4, 135.9, 135.6,
5-Benyl-4-(4-bromophenyl)-2H-thiopyran 1,1-Dioxide (7H): White
130.8, 129.4, 129.1, 128.9, 128.7, 128.3, 128.2, 120.5, 52.1,
solid (73 mg, 65%), m.p. 195–196 °C. IR (neat): ν = 3065, 2943,
˜
52.0 ppm. HRMS: calcd. for C18H17O2S+ [M + H]+ 297.0944;
found 297.0950.
1655, 1448, 1305, 752, 556 cm–1. 1H NMR (600 MHz, [D]chloro-
form): δ = 7.56 (d, J = 12 Hz, 2 H), 7.39 (t, J = 6 Hz, 2 H), 7.33
(t, J = 6 Hz, 1 H), 7.25 (d, J = 6 Hz, 2 H), 7.23 (d, J = 12 Hz, 2
5-(4-Methylbenzyl)-4-phenyl-2H-thiopyran 1,1-Dioxide (7B): White
solid (80 mg, 85%), m.p. 166–167 °C. IR (neat): ν = 3036, 2914, H), 6.7 (s, J = 1 Hz), 5.76 (t, J = 6 Hz, 1 H), 4.22 (s, 2 H), 3.97 (d,
˜
1615, 1441, 1319, 1109, 839, 757 cm–1 1H NMR (400 MHz, J = 6 Hz, 2 H) ppm. 13C NMR (150 MHz, [D]chloroform): δ =
.
[D]chloroform): δ = 7.41–7.34 (m, 5 H), 7.18–7.10 (m, 4 H), 6.67 141.7, 138.6, 137.7, 134.9, 131.7, 130.9, 129.1, 128.9, 128.7, 128.3,
(s, 1 H), 5.72 (t, J = 4.6 Hz, 1 H), 4.22 (s, 2 H), 3.95 (d, J = 4.6 Hz, 122.4, 119.2, 52.1, 30.9 ppm. HRMS: calcd. for C18H15BrNaO2S+
2 H), 2.35 (s, 3 H) ppm. 13C NMR (100 MHz, [D]chloroform): δ
= 143.0, 140.0, 138.4, 137.8, 132.4, 129.6, 129.5, 129.1, 128.9, 128.6,
128.4, 118.6, 52.4, 52.4, 21.5 ppm. HRMS: calcd. for C19H19O2S+
[M + H]+ 311.1100; found 311.1095.
[M + Na]+ 396.9874; found 396.9875.
4-(4-Bromophenyl)-5-(4-methoxybenzyl)-2H-thiopyran 1,1-Dioxide
(7I): Off-white solid (84 mg, 70%), m.p. 178–179 °C. IR (neat): ν =
˜
3037, 2961, 2855, 1635, 1445, 1367, 1132, 1050, 855, 751, 560 cm–1.
5-(4-Methoxybenzyl)-4-phenyl-2H-thiopyran 1,1-Dioxide (7C):
1H NMR (600 MHz, [D]chloroform): δ = 7.55 (d, J = 7.8 Hz, 2
White solid (88 mg, 90%), m.p. 173–174 °C. IR (neat): ν = 2961, H), 7.24 (d, J = 8.4 Hz, 2 H), 7.18 (d, J = 8.4 Hz, 2 H), 6.92 (d, J
˜
2845, 1612, 1447, 1306, 1132, 1026, 845, 750 cm–1
.
1H NMR = 8.4 Hz, 2 H), 6.61 (s, 1 H), 5.71 (t, J = 4.2 Hz, 1 H), 4.23 (s, 2
H), 3.96 (d, J = 3.6 Hz, 2 H), 3.84 (s, 3 H) ppm. 13C NMR
(400 MHz, [D]chloroform): δ = 7.41–7.33 (m, 5 H), 7.33–7.15 (m,
2 H), 6.90–6.87 (m, 2 H), 6.64 (s, 1 H), 5.70 (dd, J = 5.2, 3.9 Hz, (150 MHz, [D]chloroform): δ = 159.6, 141.9, 138.7, 137.4, 131.6,
1 H), 4.22 (s, 2 H), 3.95 (d, J = 4.6 Hz, 2 H), 3.81 (s, 3 H) ppm. 130.9, 130.4, 127.6, 127.2, 122.3, 118.5, 114.2, 55.3, 52.2, 52.1 ppm.
6022
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© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2015, 6017–6024

Base-Induced Cyclization of Propargyl Alkenylsulfones
HRMS: calcd. for C19H17BrO3SNa+ [M + Na]+ 426.9974; found
426.9976.
comprised an inseparable mixture of cis and trans tetrahydropyran
derivatives 13.
4-(4-Bromophenyl)-5-(4-methylbenzyl)-2H-thiopyran 1,1-Dioxide Data for 12: White solid (5 mg, 30%), m.p. 145–146 °C. IR (neat):
(7J): Pale brown solid (87 mg, 75%), m.p. 172–173 °C. IR (neat): ν = 3039, 2934 1634, 1447, 1334, 1120, 752 cm–1. 1H NMR
˜
ν = 3026, 2914, 1632, 1439, 1330, 1110, 845, 754, 562 cm–1. 1H
(600 MHz, [D]chloroform): δ = 7.43 (t, J = 6 Hz, 2 H), 7.35 (d, J
˜
NMR (600 MHz, [D]chloroform): δ = 7.56 (d, J = 7.8 Hz, 2 H), = 12 Hz, 1 H), 7.32 (d, J = 12 Hz, 2 H), 7.22 (d, J = 6 Hz, 2 H),
7.25 (d, J = 7.8 Hz, 2 H), 7.19 (d, J = 7.8 Hz, 2 H), 7.12 (d, J = 7.17 (d, J = 6 Hz, 2 H), 6.41 (s, 1 H), 4.08 (d, J = 12 Hz, 1 H),
7.8 Hz, 2 H), 6.65 (s, 1 H), 5.73 (t, J = 4.2 Hz, 1 H), 4.23 (s, 2 H),
3.96 (d, J = 4.2 Hz, 2 H), 2.37 (s, 3 H) ppm. 13C NMR (150 MHz,
[D]chloroform): δ = 141.8, 138.7, 138.4, 137.8, 131.9, 131.7, 130.9,
129.4, 128.9, 128.4, 122.4, 188.8, 52.2, 52.1, 21.3 ppm. HRMS:
calcd. for C19H17BrO2SNa+[M + Na]+ 411.0030; found 411.0034.
3.88 (d, J = 18 Hz, 1 H), 3.70 (d, J = 18 Hz, 1 H), 3.34–3.23 (m, 2
H), 2.79–2.73 (m, 1 H), 2.53–2.58 (m, 1 H), 2.36 (s, 3 H) ppm. 13C
NMR (150 MHz, [D]chloroform): δ = 138.9, 137.5, 133.4, 132.4,
131.9, 129.2, 129.0, 128.8, 128.0, 127.4, 54.3, 53.4, 51.1, 48.1, 28.2,
21.2 ppm. HRMS: calcd. for C19H20O2SNa+ [M + Na]+ 335.1082;
found 335.1089.
5-(4-Methylbenzyl)-4-p-tolyl-2H-thiopyran 1,1-Dioxide (7K): Sticky
white mass (65 mg, 67%). IR (neat): ν = 3037, 2922 1623, 1455,
˜
Data for 13 (cis and trans): Gummy mass (5 mg, 30%). IR (neat):
˜
1
1323, 1120, 847, 751 cm–1. H NMR (600 MHz, [D]chloroform): δ
1
ν = 3056, 2945 1665, 1458, 1320, 745 cm–1. H NMR (400 MHz,
= 7.26 (d, J = 7.8 Hz, 2 H), 7.22 (d, J = 7.8 Hz, 2 H), 7.18 (d, J =
7.8 Hz, 2 H), 7.13 (d, J = 8.4 Hz, 2 H), 6.72 (s, 1 H), 5.72 (t, J =
4.2 Hz, 1 H), 4.23 (s, 2 H), 3.96 (d, J = 4.2 Hz, 2 H), 2.41 (s, 3 H),
2.37 (s, 3 H) ppm. 13C NMR (150 MHz, [D]chloroform): δ = 142.7,
138.1, 138.0, 137.5, 136.9, 132.3, 129.3, 129.1, 128.9, 128.7, 117.9,
52.2, 21.3, 21.2 ppm. HRMS: calcd. for C20H20O2SNa+ [M + Na]+
347.1076; found 347.1076.
[D]chloroform): δ = 7.43–7.41 (m, 3 H), 7.34–7.24 (m, 6 H), 7.12–
7.05 (m, 3 H), 6.94 (d, J = 8 Hz, 2 H), 6.84 (d, J = 8 Hz, 1 H),
3.30–3.01 (m, 9 H), 2.79–2.58 (m, 4 H), 2.53–2.48 (m, 1 H), 2.44–
2.28 (m, 8 H), 2.24–2.17 (m, 1 H), 2.10–2.01 (m, 2 H) ppm. 13C
NMR (100 MHz, [D]chloroform): δ = 141.8, 136.3, 136.0, 129.6,
129.4, 129.1, 129.0, 127.8, 127.3, 55.3, 53.6, 52.3, 51.9, 48.7, 44.6,
43.9, 29.9, 25.0, 22.9, 21.2, 14.3 (some peaks may have overlapped)
ppm. HRMS: calcd. for C19H23O2S+ [M + H]+ 315.1413; found
315.1407.
5-(4-Methoxybenzyl)-4-p-tolyl-2H-thiopyran 1,1-Dioxide (7L):
Sticky white mass (70 mg, 69%). IR (neat): ν = 3037, 2921, 1633,
˜
1442, 1332, 1109, 847, 755 cm–1. 1H NMR (600 MHz, [D]chloro-
form): δ = 7.26 (d, J = 7.8 Hz, 2 H), 7.21 (d, J = 7.8 Hz, 2 H), 7.18
(d, J = 8.4 Hz, 2 H), 6.90 (d, J = 9.0 Hz, 2 H), 6.69 (s, 1 H), 5.70
(t, J = 4.8 Hz, 1 H), 4.23 (s, 2 H), 3.96 (d, J = 4.8 Hz, 2 H), 3.84
(s, 3 H), 2.40 (s, 3 H) ppm. 13C NMR (150 MHz, [D]chloroform):
δ = 159.5, 142.8, 138.0, 137.1, 136.9, 130.4, 129.1, 128.0, 127.6,
117. 6, 114. 1, 55.3, 52.2, 21.2 ppm. HRMS: calcd. for
C20H20O3SNa+ [M + Na]+ 363.1031; found 363.1031.
3-Methylene-4-phenyl-3,6-dihydro-2H-thiopyran 1,1-Dioxide (25):
Pale yellow solid (176 mg, 80%), m.p. 135–136 °C. IR (neat): ν =
˜
3210, 2945, 1615, 1420, 1310, 1125, 760 cm–1. 1H NMR (600 MHz,
[D]chloroform): δ = 7.39–7.37 (m, 3 H), 7.30–7.28 (m, 2 H), 5.74
(t, J = 4.2 Hz, 1 H), 5.40 (s, 1 H), 5.20 (s, 1 H), 3.98 (s, 2 H), 3.94
(d, J = 4.2 Hz, 2 H) ppm. 13C NMR (150 MHz, [D]chloroform): δ
= 141.4, 139.2, 135.9, 128.9, 128.3, 128.2, 123.3, 119.2, 57.0,
52.2 ppm. HRMS: calcd. for C12H12O2SNa+ [M + Na]+ 243.0450;
found 243.0452.
5-Benzyl-4-p-tolyl-2H-thiopyran 1,1-Dioxide (7M): Off-white solid
(70 mg, 76%) m.p. 147–148 °C. IR (neat): ν = 3032, 2912, 1614,
˜
1442, 1320, 1110, 840, 750 cm–1. 1H NMR (600 MHz, [D]chloro-
form): δ = 7.38 (d, J = 7.8 Hz, 2 H), 7.32–7.22 (m, 7 H), 6.75 (s, 1
H), 5.74 (t, J = 4.2 Hz, 1 H), 4.22 (s, 2 H), 3.97 (d, J = 4.2 Hz, 2
H), 2.40 (s, 3 H) ppm. 13C NMR (150 MHz, [D]chloroform): δ =
142.6, 138.1, 137.5, 136.8, 135.2, 129.4, 129.1, 128.9, 128.6, 128.1,
118.3, 52.3, 52.1, 21.3 ppm. HRMS: calcd. for C19H18O2SNa+ [M
+ Na]+ 333.0925; found 333.0925.
Acknowledgments
A. B. is grateful to the Council of Scientific and Industrial Research
(CSIR), New Delhi, for funding, and to the Department of Science
and Technology (DST), New Delhi, for a J. C. Bose fellowship.
I. H. and J. D. thank the CSIR for a research fellowship (NET).
The DST is also thanked for the funds for a 400 MHz NMR facil-
ity under the IRPHA program.
9-Phenyl-2-(p-tolylsulfonyl)-2,3,3a,4-tetrahydro-1H-benzo[f]isoind-
ole (7N): White solid (66 mg, 55%), m.p. 200 °C (decomposed). IR
1
(neat): ν = 3062, 2928, 2836, 1602, 1441, 1342, 1158, 757 cm–1. H
˜
[1] T. Mitra, J. Das, M. Maji, R. Das, U. K. Das, P. K. Chattaraj,
A. Basak, RSC Adv. 2013, 3, 19844.
NMR (600 MHz, [D]chloroform): δ = 7.72–7.18 (m, 5 H), 7.16 (dd,
J = 12.7, 7.1 Hz, 4 H), 7.09 (t, J = 7.2 Hz, 1 H), 6.77 (d, J = 7.6 Hz,
1 H), 4.32 (d, J = 17.3 Hz, 1 H), 4.01 (t, J = 8.8 Hz, 1 H), 3.66
(dd, J = 15.7, 2.5 Hz, 1 H), 3.15 (dd, J = 15.3, 7.0 Hz, 1 H), 2.92
(d, J = 9.1 Hz, 1 H), 2.65 (t, J = 15.1 Hz, 1 H), 2.45 (s, 3 H)
ppm. 13C NMR (150 MHz, [D]chloroform): δ = 143.9, 137.9, 136.9,
135.9, 134.3, 133.4, 132.4, 129.9, 128.8, 127.9, 127.8, 127.3, 126.9,
125.9, 54.5, 50.8, 39.2, 32.9, 21.8 ppm. HRMS: calcd. for
C25H24NO2S+ [M + H]+ 402.1522; found 402.1519.
[2] a) S. Braverman, D. Segev, J. Am. Chem. Soc. 1974, 96, 1245;
b) P. J. Garratt, S. B. Neoh, J. Am. Chem. Soc. 1975, 97, 3255;
c) S. Braverman, Y. Duar, D. Segev, Tetrahedron Lett. 1976, 17,
3181; d) P. J. Garratt, S. Neoh, J. Org. Chem. 1979, 44, 2667;
e) Y. S. P. Cheng, P. J. Garratt, S. B. Neoh, V. H. Rumjanek, Isr.
J. Chem. 1985, 26, 101; f) S. Braverman, Y. Duar, J. Am. Chem.
Soc. 1990, 112, 5830; g) Y. Zafrani, H. E. Gottlieb, M. Spre-
cher, S. Braverman, J. Org. Chem. 2005, 70, 10166.
[3] a) Y. Zafrani, H. E. Gottlieb, M. Sprecher, S. Braverman, J.
Org. Chem. 2005, 70, 10166; b) S. Mondal, T. Mitra, R. Mukh-
erjee, P. S. Addy, A. Basak, Synlett 2012, 23, 2582; c) S. Mon-
dal, A. Basak, S. Jana, A. Anoop, Tetrahedron 2012, 68, 7202;
d) P. S. Addy, S. Dutta, K. Biradha, A. Basak, Tetrahedron
Lett. 2012, 53, 19; e) S. Mondal, M. Maji, A. Basak, Tetrahe-
dron Lett. 2010, 52, 1183; f) R. K. Mohamed, P. W. Peterson,
I. V. Alabugin, Chem. Rev. 2013, 113, 7089.
5-(4-Methylbenzyl)-4-phenyl-3,4-dihydro-2H-thiopyran 1,1-Dioxide
(12) and 3-(4-Methylbenzyl)-4-phenyl-tetrahydro-thiopyran 1,1-Di-
oxide (cis and trans) (13): A solution of thiopyran 1,1-dioxide 7B
(20 mg, 0.06 mmol) in dry methanol (5 mL) was hydrogenated with
Pd/C (10%; 8 mg) for 1 h at room temperature. Filtration followed
by evaporation gave a crude mixture, from which partially hydroge-
nated sulfone 12 was isolated in pure form by fractional crystalli-
zation from dichloromethane/petroleum ether. The mother liquor
[4] M. Maji, D. Mallick, S. Mandal, A. Anoop, S. S. Bag, A. Ba-
sak, E. D. Jemmis, Org. Lett. 2011, 13, 888.
Eur. J. Org. Chem. 2015, 6017–6024
© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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I. Hatial, J. Das, A. K. Ghosh, A. Basak
FULL PAPER
[5]
arov, V. I. Minkin, Chem. Heterocycl. Compd. (N. Y., NY,
U. S.) 1982, 18, 779; c) an alternative mechanism that could
have been considered involves a 6-exo-dig process (favourable
according to Baldwin’s rules: J. E. Baldwin, J. Chem. Soc.,
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Received: May 15, 2015
Published Online: August 14, 2015
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Eur. J. Org. Chem. 2015, 6017–6024