Syntheses and structures of sulfilimine, sulfone diimine, and sulfoximine derivatives of a monocyclic thiophene, 3,4-di-tert-butylthiophene

Article abstract of DOI:10.1002/hc.1052

The reaction of 3,4-di-tert-butylthiophene (6a) with N-[(p-tolylsulfonyl)imino]-phenyliodinane (TsN=IPh) in the presence of Cu(MeCN)₄PF₆ in MeCN at room temperature provided 3,4-di-tert-butyl-1-[(p-tolylsulfonyl)imino]-1,1-dihydrothiophene (3b), 3,4-di-tert-butyl-1,1-bis[(p-tolylsulfonyl)imino]-1,1-dihydrothiophene (5a), and 1-(p-tolylstdfonyl)-3,4-di-tert-butylpyrrole (7a) as the principal products. The use of 20 molar amounts of 6a gave 3b in an increased yield of 61%. Treatment of 3,4-di-tert-butylthiophene 1-oxide (1a) with (CF₃CO)₂O or (CF₃SO₂)₂O, followed by reactions with RSO₂NH₂, ROC(=O)NH₂, or RCONH₂, furnished a series of S-imino derivatives (3b,c,e-h) of 6a, which carry an electron-withdrawing substituent on the imino nitrogen atom. Treatment of the S-imino derivative 3f (substituent on the nitrogen atom = CO₂¹Bu) with CF₃CO₂H gave an aminosulfonium salt (13), whose deprotonation led to the parent N-unsubstituted 1-imide derivative (3n). Treatment of 2,4-di-tert-butylthiophene 1-oxide (1b) with TsN = IPh in the presence of Cu(MeCN)₄PF₆, in MeCN at room temperature provided 2,4-di-tert-butyl-1-[(p-toluenesulfonyl)imino]-1,1-dihydrothiophene 1-oxide (4e) in 81% yield. Hydrolysis of 4e by concentrated H₂SO₄ at room temperature furnished 2,4-di-tert-butyl-1-imino-1,1-dihydrothiophene 1-oxide (4f) in 89% yield. A pair of enantiomers of 4f were separated by high-performance liquid chromatography (HPLC) on a chiral column, and their absolute configurations were determined by an X-ray crystallographic analysis. Structures of sulfilimine, sulfone diimine, and sulfoximine derivatives of monocyclic thiophenes, obtained in these ways, are discussed based on spectroscopies (IR and ¹H and ¹³C NMR) and X-ray crystallographic analyses.

Full text of DOI:10.1002/hc.1052

Heteroatom Chemistry
Volume 12, Number 5, 2001
Syntheses and Structures of Sulfilimine,
Sulfone Diimine, and Sulfoximine Derivatives
of a Monocyclic Thiophene, 3,4-Di-tert-
butylthiophene
Juzo Nakayama, Takashi Otani, Yoshiaki Sugihara, Yuki Sano,
Akihiko Ishii, and Akira Sakamoto
Department of Chemistry, Faculty of Science, Saitama University, Urawa, Saitama 338-8570, Japan
Received 28 November 2000
temperature provided 2,4-di-tert-butyl-1-[(p-toluene-
sulfonyl)imino]-1,1-dihydrothiophene 1-oxide (4e) in
ABSTRACT: The reaction of 3,4-di-tert-butylthio-
phene (6a) with N-[(p-tolylsulfonyl)imino]-phenyliod-
81% yield. Hydrolysis of 4e by concentrated H2SO4 at
inane (TsNסIPh) in the presence of Cu(MeCN)4PF6 in
room temperature furnished 2,4-di-tert-butyl-1-imino-
MeCN at room temperature provided 3,4-di-tert-butyl-
1,1-dihydrothiophene 1-oxide (4f) in 89% yield. A pair
1-[(p-tolylsulfonyl)imino]-1,1-dihydrothiophene (3b),
3,4-di-tert-butyl-1,1-bis[(p-tolylsulfonyl)imino]-1,1-di-
hydrothiophene (5a), and 1-(p-tolylsulfonyl)-3,4-di-
tert-butylpyrrole (7a) as the principal products. The
use of 20 molar amounts of 6a gave 3b in an increased
yield of 61%. Treatment of 3,4-di-tert-butylthiophene
1-oxide (1a) with (CF3CO)2O or (CF3SO2)2O, followed
by reactions with RSO2NH2, ROC(סO)NH2, or
of enantiomers of 4f were separated by high-perfor-
mance liquid chromatography (HPLC) on a chiral col-
umn, and their absolute configurations were deter-
mined by an X-ray crystallographic analysis.
Structures of sulfilimine, sulfone diimine, and sulfox-
imine derivatives of monocyclic thiophenes, obtained
in these ways, are discussed based on spectroscopies
1
(IR and H and 13C NMR) and X-ray crystallographic
RCONH2, furnished a series of S-imino derivatives
(3b,c,e–h) of 6a, which carry an electron-withdrawing
substituent on the imino nitrogen atom. Treatment of
analyses. ᭧ 2001 John Wiley & Sons, Inc. Hetero-
atom Chem 12:333–348, 2001
the S-imino derivative 3f (substituent on the nitrogen
atom ס CO2 Bu) with CF3CO2H gave an aminosulfon-
INTRODUCTION
t
ium salt (13), whose deprotonation led to the parent
N-unsubstituted 1-imide derivative (3n). Treatment of
2,4-di-tert-butylthiophene 1-oxide (1b) with TsNסIPh
in the presence of Cu(MeCN)4PF6 in MeCN at room
The chemistry of thiophene 1,1-dioxides (2) has been
extensively studied both experimentally and theoret-
ically and is thus well documented [1]. A recent ex-
haustive literature survey has revealed that more
than 300 articles have been published on the chem-
istry of 2 [1a]. Recently, thiophene 1-oxides (1) have
been attracting much interest from the standpoints
of syntheses, structures, synthetic applications, and
biochemistry [1b,2]. Substitution of the oxygen atom
of 1 by an imino group leads to sulfilimine deriva-
tives (3). Substitution of one of the two oxygen atoms
of 2 by an imino group provides sulfoximine deriv-
Dedicated to Prof. Emeritus Naoki Inamoto of the University of
Tokyo on the occasion of his 72nd birthday.
Correspondence to: Juzo Nakayama.
Contract Grant Sponsor: Ministry of Education, Science, Sports
and Culture, Japan.
Contract Grant Sponsor: Japanese Society for the Promotion of
Science for Young Scientists (T.O.).
᭧ 2001 John Wiley & Sons, Inc.
333

334 Nakayama et al.
atives (4), whereas substitution of both oxygen at-
oms by imino groups leads to the sulfone diimine
derivatives (5) (Scheme 1). When we planned a syn-
thetic study of 3–5 in 1997, the following had been
reported on these compounds [3,4]. Meth-Cohn et al.
obtained sulfilimines (3a) by thermolyses of azides
in tetrachlorothiophene [3a], which were the only
sulfilimine derivatives of monocyclic thiophenes,
and they investigated the reactivities of these sulfi-
limines toward dienophiles in some detail [3c]. They
also obtained the sulfoximine (4a) by oxidation of 3a
(R ס CO2Et) [3b]. Sulfone diimines (5) were still un-
known and had remained to be synthesized.
netically by steric protection. Indeed, this strategy
worked well to lead to the successful preparation of
3–5 [6]. Reported here are experimental details of
this synthetic study. Structures of 3–5 are also dis-
cussed in some detail based on spectroscopies (IR
1
and H and 13C NMR) and X-ray crystallographic
analyses.
RESULTS AND DISCUSSION
Preparation of Sulfilimine and Sulfone Diimine
Derivatives
Preparation of Sulfilimine and Sulfone Diimine
Derivatives by Direct Imination of 3,4-Di-tert-bu-
tylthiophene. Thermolyses of organic azides in
tetrachlorothiophene afforded the desired sulfilimi-
nes (3a) [3a]. Thermolyses in other thiophenes, how-
ever, all failed to give the corresponding sulfilimines
[3a,7,8]. This would be at least partly due to the ex-
pected thermal instability of sulfilimines, which may
not allow their survival under the thermolysis con-
ditions (130–150ꢀC). Reportedly, N-[(p-tolylsulfonyl)-
imino]phenyliodinane (TsNסIPh) [9] generates the
tosyl nitrene or its equivalent at a lower temperature
in the presence of a Cu(I) or Cu(II) catalyst [10]. We
therefore first examined the imination of 3,4-di-tert-
butylthiophene (6a) by this reagent. Thus, 6a and
TsNסIPh were allowed to react in varying molar ra-
tios in the presence of 5 mol % of Cu(MeCN)4PF6
[(Cu(I)] [11] or Cu(OTf)2 [Cu(II)] (Tf ס SO2CF3) in
MeCN. The reaction took place at room temperature
in every case. Purification of the resulting complex
mixtures provided the expected sulfilimine 3b, to-
gether with unexpected formation of the sulfone di-
imine 5a and the pyrrole 7a [8] (Scheme 2 and Table
1). Compounds 8, 9, and TsNH2 were also isolated in
small amounts. Structures of 3b, 5a, and 9 were es-
tablished by X-ray crystallographic analyses. Better
total yields of the products were obtained by using
the Cu(I) catalyst rather than the Cu(II) (entries 2
and 3, Table 1). The yield of 3b, based on TsNסIPh,
increased with an increasing molar ratio of 6a; a sat-
isfactory yield of 61% was attained by use of 20 mo-
lar amounts of 6a. The sulfilimine 3b was more sta-
ble thermally than we had initially expected and
melted at 130–131ꢀC without decomposition. Com-
pound 5a provided the first example of a sulfone di-
imine derivative of a thiophene. It was also thermally
stable and had a melting point of 155.0–155.5ꢀC. As
for the structures of 8 and 9, the corresponding tau-
tomeric forms 8a and 9a are possible. However, com-
pound 8 exists exclusively in the imino form, as re-
vealed by IR and NMR spectral analyses, at the
sacrifice of the aromaticity of one of the thiophene
The parent thiophene 1,1-dioxide and monosub-
stituted thiophene 1,1-dioxides undergo very rapid
[4 ם 2] self-dimerization, where one molecule acts
as a diene and the other as a dienophile, and thus
they are labile and are not isolated at room tempera-
ture [1b,5]. Many stable and isolable di-, tri- and
tetra-substituted thiophene 1,1-dioxides are known
[1]. Thiophene 1-oxides are much more reactive than
the corresponding thiophene 1,1-dioxides [1b,2]. By
analogy, nitrogen-substituted compounds 3–5 are
expected to be labile species. Therefore, in order to
obtain stable and isolable derivatives of 3–5, the dou-
ble bonds of these compounds should be deactivated
either kinetically or electronically. Taking this into
account, we have chosen 3,4- and 2,4-di-tert-butyl-
thiophenes (6a and 6b) as starting materials for our
synthetic study since the double bonds of 3–5, de-
rived from these compounds, would be stabilized ki-
SCHEME 1

Sulfilimine, Sulfone Diimine, and Sulfoximine Derivatives of a Monocyclic Thiophene, 3,4-Di-tert-butylthiophene 335
SCHEME 2
TABLE 1 Reactions of 6a with TsNסIPh under a Variety of
Conditions
discussed later, would be more reactive than that of
6a toward the nitrene or TsNסIPh. Therefore, 3b
would react further to give the sulfone diimine 5a. A
separate reaction of 3b with an equimolar amount
of TsNסIPh in the presence of 5 mmol % of the Cu(I)
catalyst gave 5a in 10% yield with recovered 3b in
48% yield; the pyrrole 7a and TsNH2 were also
formed in 18 and 43% yields, respectively (Scheme
3). The formation of sulfone diimines by reaction of
sulfides with TsNסIPh is unprecedented to our
knowledge. Previously, we reported that the pyrrole
7a is formed in a low yield by thermolysis of tosyl
azide in 6a at 150ꢀC [8]. At that time, we thought that
7a would be formed by the secondary self-reaction
of the initial product 3b as one of the plausible path-
ways. However, this pathway might now be ruled out
because the sulfilimine 3b was not converted to 7a
by heating its benzene solution at 160ꢀC for 3 hours
in a sealed tube. Also, the conversion of 3b to 7a was
not brought about by the action of the Cu(I) catalyst
at room temperature. These observations lead to a
conclusion that 7a is formed by reaction of 3b with
TsNסIPh. In order to look into the mechanism of
the formation of 7a, 3b was allowed to react with
PhSO2NסIPh in the presence of the Cu(I) catalyst.
The reaction gave sulfone diimine 5b in 6% yield and
a mixture of pyrroles 7a and 7b in 14% yield in the
ratio 15:85, with recovery of 3b in 72% yield
(Scheme 3). The predominant formation of 7b over
7a is suggestive of the mechanism. One of the plau-
sible mechanisms, based on this observation, in-
volves the 1,4-addition of the benzenesulfonyl ni-
trene to 3b. The resulting adduct (10) would produce
Isolated Yield
(%)b
Molar Ratio
Entry (6a/TsNסIPh) Catalysta 3b 5a 7a
8
9
1
2
3
4
5
2.5
5.0
5.0
7.5
Cu(I)
Cu(I)
Cu(II)
Cu(I)
Cu(I)
23
9
9
2
3
3
4
3
םc
םc
3
38 18 10
32
50
61
8
9
7
4
10
5
םc
4
20
aCu(I) ס Cu(MeCN)4PF6, Cu(II) ס Cu(OTf)2.
bBased on TsNסIPh.
cNo effort was made to isolate 9 (detected by TLC).
rings. Release from steric repulsions between the
two thiophene rings that carry bulky tert-butyl
groups serves to explain the existence of 8 in the im-
ino form. Previously, we reported that the two thio-
phene rings of 3,4,3Ј,4Ј-tetra-tert-butyl-2,2Ј-bithio-
phene are nearly perpendicular to each other to
avoid steric repulsions. Compound 9 exists in the
amino–imino form, as revealed by X-ray crystallo-
graphic analysis, to avoid steric repulsions among
the substituents. Any evidence for the existence of
the diamino form 9a in solution was also not found
by 1H and 13C NMR spectral analyses. Thus, 8 and 9
contradict the fact that 2-amino derivatives of thio-
phene generally exist in the amino form [12].
The sulfilimine 3b would be formed by addition
of the tosyl nitrene to the thiophene 6a. The sulfur
atom of 3b, whose thiophene ring is not aromatic as

336 Nakayama et al.
7b with extrusion of TsNסS, although the concom-
itant formation of 7a in a small amount still remains
to be explained.
ter reaction gave a complex mixture from which a
sulfilimine (3d) was isolated in 20% yield.
Mechanisms of the formation of 8 and 9 are not
clear, although many tentative explanations are pos-
sible. For example, the simplest explanation would
be provided by insertion of a carbene (11) into the
C␣–H bond of the thiophene 6a and into the N–H
bond of TsNH2, which affords 8 and 9, respectively,
although it is not easy to explain how 11 was
produced.
The reactions of 6a with PhSO2NסIPh and of
2,4-di-tert-butylthiophene (6b) with TsNסIPh were
also examined, though not in great detail (Scheme
4). The former reaction gave sulfilimine (3c), sulfone
diimine (5c), pyrrole (7b); and PhSO2NH2 in 38, 5, 7,
and 33% yields, respectively, by use of five molar
amounts of 6a and the Cu(I) as the catalyst. The lat-
Preparation of Sulfilimine Derivatives from 3,4-
Di-tert-butylthiophene 1-Oxide. The synthesis, de-
scribed previously, required the use of 20 molar
amounts of the thiophene 6a to obtain 3b in 61%
yield. Another drawback to this method is that 3b
cannot be converted to the N-unsubstituted deriva-
tive by conventional methods of detosylation [13].
These considerations prompted us to develop an al-
ternative synthesis of S-iminated thiophenes. Previ-
ously, we reported that the oxidation of 6a with m-
chloroperbenzoic acid (MCPBA) in the presence of
BF3 •Et2O affords the corresponding thiophene 1-ox-
ide (1a) in good yield [14]. We therefore examined
the conversion of 1a to 3b and the related sulfilimi-
nes [15].
SCHEME 3
SCHEME 4

Sulfilimine, Sulfone Diimine, and Sulfoximine Derivatives of a Monocyclic Thiophene, 3,4-Di-tert-butylthiophene 337
The thiophene 1-oxide 1a was allowed to react
expected compounds 3k or 3l was formed. In these
cases, the initial products 3j and 3k are probably
converted to 3i by the action of TFAA or CF3CO2H.
An analogy is found in the reaction of DMSO with
TFAA, followed by treatment with H2NCONH2 in
CH2Cl2, which gave Me2SסNCOCF3 in 80% yield
[15e]. The reaction of 1a with MeNH2, after treat-
ment with TFAA, also failed to give the expected sul-
filimine (3m), with quantitative recovery of 1a being
realized. Conversion of 3b to 3e was done in 85%
yield by treatment of 3b with TFAA and then with 10
molar amounts of H2NCO2Et. Thus, desirable mu-
tual conversions between sulfilimine derivatives
seem possible.
with two molar amounts of (CF3CO)2O (TFAA) at
מ78ꢀC to form a sulfonium salt or a sulfurane (12)
(RЈ ס COCF3), which was treated in situ with two
molar amounts of TsNH2 at the same temperature
(Scheme 5). The mixture was warmed slowly to
room temperature, and the reaction was quenched
by addition of water. Purification of the mixture gave
3b in 86% yield (Table 2, run 1). The reaction, in
which (CF3SO2)2O (Tf2O) was used instead of TFAA,
under similar conditions, also afforded 3b in 79%
yield (run 2). In these ways, a series of sulfilimines
3b,c,e–h were synthesized in satisfactory yields, as
shown in Table 2.
Although the previous synthesis seemed to be
quite general and unsatisfactory, but interesting, ex-
ceptions were found. Thus, treatment of 1a with
TFAA and then with H2NCN yielded the trifluoro-
acetyl derivative (3i) in 85% yield, but not the ex-
pected cyano derivative (3j) (Scheme 6). Similarly,
treatment of 1a with TFAA, and then with
H2NCONH2, also gave 3i in 83% yield. Neither of the
In order to obtain the parent N-unsubstituted
compound (3n), the N-Boc substituted 3f was
treated with CF3CO2H [16]. The reaction satisfacto-
rily yielded an aminosulfonium salt (13) quantita-
tively, which provided the first example of amino-
sulfonium salt of a monocyclic thiophene. Treatment
of a solution of 13 in CH2Cl2 with aqueous NaOH
gave the expected sulfilimine 3n and the thiophene
6a in the ratio 30:1 in a quantitative total yield,
whereas treatment of 13 with NaH in ether gave 3n
and 6a in the ratio 58:42 (Scheme 7). The formation
of 6a, in addition to 3n, indicates that the nucleo-
philes attack not only the amino hydrogen atom but
also the amino nitrogen atom as depicted in Figure
1; in other words, 13 possesses the potential to serve
as an amination reagent. The compound 3n provides
the first example of an N-unsubstituted sulfilimine
of a thiophene. It is converted to 3b in 84% yield by
SCHEME 5
TABLE 2 Preparation of a Variety of N-Substituted 1-Imino
Derivatives 3b,c,e–h from 3,4-Di-tert-butylthiophene 1-Oxide
(1a)
1-Imino
Derivative
Acid
Ahydride
Yield
(%)
Run
R
1
2
3
4
5
6
7
3b
3b
3c
3e
3f
3g
3h
SO2C6H4CH3(p)
SO2C6H4CH3(p)
SO2C6H5
TFAA
Tf2O
Tf2O
TFAA
TFAA
TFAA
TFAA
86
79
74
90
82
53
74
CO2Et
COt2Bu
COCH3
COC6H4CH3(p)
SCHEME 6

338 Nakayama et al.
SCHEME 7
[13a,b] to form the parent sulfoximide (4c) in 95%
ם
מ
yield. Treatment of 4c with Me3O BF4 gave the N-
methylated compound 4d in 43% yield, with a 40%
yield recovery of 4c.
Similarly, the unsymmetrically substituted thio-
phene 1-oxide (1b) also afforded the sulfoximine (4e)
in 81% yield on reaction with TsNסIPh in the pres-
ence of the Cu(I) catalyst. Treatment of 4e with con-
centrated H2SO4 gave the parent sulfoximide (4f) in
89% yield. Both 4c and 4f were not very stable ther-
mally; 4c decomposed completely, when heated in
boiling toluene for several hours, to give at least 10
products.
FIGURE 1
treatment with TsCl (Scheme 8). Thus, it seems pos-
sible to derive a variety of sulfilimine derivatives
from 3n by alkylation and acylation. The sulfilimine
3n is storable at below מ20ꢀC at least for one month
without any appreciable decomposition, but it was
converted to the thiophene 6a quantitatively through
hydrolysis by contaminating water, when its CDCl3
solution was heated at 50ꢀC for 6 hours. The hydro-
lysis probably involves an aminosulfonium ion (14).
Spectroscopies and X-Ray Crystallographic
Analyses of Sulfilimine, Sulfone Diimine, and
Sulfoximine
1H and 13C NMR Spectra. Table 3 summarizes
chemical shift values of a series of S-substituted de-
rivatives of 3,4-di-tert-butylthiophene (6a). The
chemical shift values of the ␣-hydrogen atoms of the
Preparation of Sulfoximines by Imination of
2,4- and 3,4-Di-tert-butylthiophene 1-Oxides
1
A great number of sulfoximines have been synthe-
sized, and their chemistry has been attracting much
interest from a variety of standpoints, such as struc-
tures, stereochemistry, reactivities, and applications
to organic syntheses [17]. However, synthetic study
of sulfoximine derivatives of thiophenes has been
surprisingly neglected. To our knowledge, the sulfox-
imine (4a) [3b] is the only sulfoximine derivative of
a monocyclic thiophene ever synthesized [4a]. De-
scribed in the following paragraphs is our synthetic
study.
The reaction of the thiophene 1-oxide 1a with
TsNסIPh (1.2 molar amounts) proceeded smoothly
in the presence of the Cu(I) catalyst [Cu(MeCN)4PF6]
in MeCN at room temperature to furnish the ex-
pected thiophene sulfoximine (4b) in 67% yield.
These results show that the imination of 1a takes
place more effectively than that of the corresponding
1-imide 3b. A conventional method, which employs
tosyl azide (three molar amounts) in the presence of
an activated copper powder in refluxing methanol
[18], worked only in a sluggish way to produce 4b in
a moderate yield of 35%. The tosyl group of 4b was
eliminated by hydrolysis with concentrated H2SO4
thiophene ring in H NMR and those of the ␣- and
b-carbon atoms in 13C NMR spectra are given. For
comparison, the chemical shift values of 3,4-di-
tert-butylthiophene 1,1-dioxide (2a) [19] are also
included.
The thiophene 1-oxide 1a and the sulfilimine 3n
are isoelectronic to each other, and their ring ␣-hy-
drogen atoms resonate at d 6.93 and 6.81, respec-
tively, upper fields than those of the parent thiophene
6a, which resonate at d 7.16. The observed upfield
shift ongoing from 6a to 1a and 3n is indicative of
the disappearance of the ring current effect of the
thiophene ring in 1a and 3n, namely, the loss of ar-
omaticity. The resonance of the ␣-hydrogen atoms of
3n at an upper field than that of 1a by 0.12 ppm
would be due to the smaller electronegativity of the
nitrogen atom than that of the oxygen atom. The ␣-
hydrogen atoms of N-acyl substituted sulfilimines
3g–i resonate in the range d 7.10–7.22, comparable
values with those of 6a, d 7.16. This reflects that the
␣-carbon atoms of 3g–i are more electron deficient,
thus, the hydrogen atoms attached to them are more
acidic than those of the other sulfilimines due to the
contribution of the canonical structure (15); need-

Sulfilimine, Sulfone Diimine, and Sulfoximine Derivatives of a Monocyclic Thiophene, 3,4-Di-tert-butylthiophene 339
SCHEME 8
SCHEME 9
TABLE 3 Relevant 1H and 13C NMR Data for a Series of S-
Substituted Derivatives of 3,4-Di-tert-butylthiophene (6a).a
less to say, this does not mean that these compounds
are aromatic.
The ␣-hydrogen atoms of the aminosulfonium
salt 13 resonate at an upper field of d 6.97 than those
of 6a by 0.19 ppm. The thiophene ring of 13, in
which the sulfur atom has tetrahedral hybrid orbit-
als, also would not be aromatic.
The thiophene 1,1-dioxide 2a, the sulfoximine
4c, and the sulfone diimine 5a, in which two pairs
of lone-pair electrons on the sulfur atom are con-
sumed for bond formation with heteroatoms, are
isoelectronic to each other and are also not aro-
matic. Interestingly, the ␣-hydrogen atoms of 2a and
4c resonate at d 6.44 and 6.53, respectively, upper
fields than those of the thiophene 1-oxide 1a and the
sulfilimine 3n, despite the fact that their sulfur atom
carries two electronegative heteroatoms. The ␣-hy-
drogen atoms of the sulfone diimine 5a resonates at
a lower field of d 7.13.
1H NMR
13C NMR
Compounds
␣-Hydrogens
␣-Carbons
b-Carbons
6a
1a
3n
3b
3c
3e
3f
3g
3h
3i
13
2a
4c
4b
4d
5a
7.16
6.93
6.81
6.70
6.70
6.92
6.92
7.10
7.22
7.15
6.97
6.44
6.53
6.92
6.57
7.13
134.4
122.3
150.6
158.4
158.4
160.4
162.0
162.4
162.2
162.7
162.4
164.7
165.7
156.8
155.0
158.9
155.4
160.4
135.1
b
b
128.5
128.8
129.1
b
125.2
126.5
127.5
129.4
b
126.5
b
The ␣-carbon atoms of a series of S-substituted
compounds resonate in the range d 122.3–129.4,
which is at a higher field than those of the thiophene
aChemical shifts are given in d values with TMS as the internal stan-
dard and with CDCl3 as the solvent.
bNot assigned.

340 Nakayama et al.
6a, d 134.4. An exception is the ␣-carbon atoms of
the sulfilimine 3n, which resonate at d 135.1. On the
contrary, the b-carbon atoms of S-substituted com-
pounds, which carry a bulky tert-butyl group, reso-
nate at lower fields, d 155.4–165.7, than those of the
thiophene 6a, d 150.6, without any exception.
C(sp3)-H bonds is 21. These findings prompted us to
carry out ab initio calculations (B3LYP/6-31G*) on
the infrared spectrum of the simplest sulfilimine (16)
[21]. The calculations predicted that the C–Ha
מ1
stretching vibration of 16 appears at 3181 cm
(scaling factor, 0.96) and 5.8 times enhanced, com-
pared to the C–Ha stretching vibration of the parent
thiophene (17), while the C-Hd stretching vibration
of 16 appears at 3159 cmמ1, only 1.8 times enhanced.
Therefore, the very intense absorption of 3g at 3097
מ1
cm would be assigned to the stretching vibration
of the C–Ha bond that faces to the carbonyl side. Al-
though the reason for the enhanced absorption is not
clear, it is certainly related to the presence of the
CסO group since such enhancement was not ob-
served with 3b,c [22].
Infrared Spectra. Table 4 summarizes the CסO
stretching vibrations of sulfilimines 3e–i. The CסO
stretching frequencies of 3e,f and those of 3g–i are
מ1
more than 50 cm smaller than the corresponding
carbamates (R2NCO2RЈ) and amides (R2NCORЈ)
[20], respectively, suggesting that the canonical
structure 15 is the principal contributor of 3e–i, in
accordance with the same conclusion reached by 1H
NMR spectral analysis.
Here it would be worthy of mention that C(sp2)–
H stretching vibrations of the sulfilimines 3e–i, par-
ticularly of 3g,h, appeared abnormally enhanced.
Figure 2 shows the infrared spectrum of 3g, in which
a very intense C(sp2)–H stetching vibration is ob-
served at 3097 cmמ1; consider that there exist only
two C(sp2)–H bonds in 3g, whereas the number of
X-Ray Crystallographic Analyses.
An ORTEP
structure of 3b is given in Figure 3, along with the
relevant bond lengths and angles data. For compar-
ison, the outline structure of 3b and that of 1a [14],
which is isoelectronic with the former, are also
shown in Figure 3. Crystal data of 3b are summa-
rized in Table 5. The geometry of 3b is similar to that
of 1a with a pyramidal configuration at the sulfur
atom. In both 3b and 1a, although four carbon atoms
of the thiophene ring form a quasi-plane, the sulfur
atom is placed out of the plane. Their C2–C3 bond
TABLE 4 Carbonyl Stretching Vibrations of Sulfilimines 3e–
i in the IR Spectra
˚
lengths, 1.53–1.54 A, and C1–C2 (C3–C4) bond
Compounds
3e
3f
3g
3h
3i
˚
lengths, 1.33–1.34 A, are almost equal to the com-
מ1
a
mCסO (cm
)
1636
1639
1573
1541
1627
mon single and double bond lengths [23], respec-
tively, revealing a bond alternation. Pyramidal ge-
ometry of the sulfur atom, nonplanar structure of
the thiophene ring, and the bond alternation data
lead to the conclusion that both 3b and 1a are not
aromatic, in agreement with the conclusion reached
by 1H NMR data analyses. Interestingly, the benzene
and thiophene rings of 3b exist in a face-to-face con-
formation. If this conformation is the preferred one
in solution, the shielding effect by the benzene ring
would explain the fact that the thiophene ring ␣-hy-
drogen atoms of 3b and 3c resonate at a higher field
d 6.70 than do the corresponding hydrogens of 3n, d
6.81 (Table 3). In this connection, we are currently
investigating how this conformation influences the
p-face selectivity in cycloadditions of 3b.
aTaken for KBr disks.
FIGURE 2 Infrared Spectrum of 3g.

Sulfilimine, Sulfone Diimine, and Sulfoximine Derivatives of a Monocyclic Thiophene, 3,4-Di-tert-butylthiophene 341
The tetracoordinated sulfur atom of 4f is chiral;
thus, an effort was made to separate a pair of enan-
tiomers. High-performance liquid chromatography
(HPLC) on a chiral column gave two well-separated
peaks due to a pair of enantiomers and allowed us
their easy separation. Both enantiomers, on slow
evaporation of a hexane solution, provided good
crystals for an X-ray crystallographic analysis. The
analysis disclosed that the second-eluted enantiomer
has an (S)-configuration with the g value defined by
Rogers [25] being 1.03(6) [26]. The (R) configuration
is therefore assigned to the first-eluted enantiomer.
An ORTEP structure of (S)-4f is given in Figure 6,
along with the relevant bond lengths and bond an-
gles data. Crystal data of (S)-4f are summarized in
Table 5. The thiophene ring of the compound is pla-
nar, as in many thiophene 1,1-dioxides [24], as well
as in the sulfone diimine 5a, which is isoelectronic
˚
with 4f. The bond length data (1.32 A for C2–C3 and
˚
C4–C5, 1.49 A for C3–C4) are indicative of a bond
alternation, that is, nonaromaticity of the thiophene
ring. The S–O and S–N bond lengths are 1.45 and
˚
1.54 A, respectively, and are comparable with those
of other sulfoximides [26]. The O–S–N bond angle of
119ꢀ is larger than those of acyclic sulfoximides. The
sulfur atom of 1b is also chiral. However, attempted
separation of a pair of enantiomers was fruitless be-
cause of the low inversion barrier that is character-
istic of the sulfur atom in monocyclic thiophene 1-
oxides [27]. Attempted separation of a pair of
enantiomers of 3d also failed, probably because of
the same reason as that for 1b.
FIGURE 3 (a) ORTEP structure of 3b. (b) Outline structure
of 3b. (c) Outline structure of 1a. Selected bond lengths data
of 3b: S–N, 1.595(7); S–C1, 1.744(7); S–C4, 1.742(8); C1–
C2, 1.332(11); C2–C3, 1.535(10); C3–C4, 1.329(10). Bond
angles data of 3b (ꢀ): C1–S–C4, 90.7(4); S–C1–C2, 113.6(6);
C1–C2–C3, 109.9(7); C2–C3–C4, 111.7(7); C3–C4–S,
112.6(6).
(R)-4f and (S)-4f both had a melting point of
114–115ꢀC, which was much higher than that of the
racemate 4f (m.p. 82.5–83.5ꢀC), and showed specific
rotations of מ48.6ꢀ and ם48.6ꢀ (c 0.10 g/100 mL,
CHCl3, 26ꢀC), respectively. The UV–is spectrum of
the racemate 4f showed absorption maxima at ca.
315 (sh), 279, and 245 nm (Figure 7). Thus, (מ)-(R)-
4f showed the negative first Cotton effect at 315, the
positive second one at 279, and the negative third
one at 236 nm in the circular dichroism (CD) spec-
trum, while (ם)-(S)-4f gave the exactly reverse pat-
tern (Figure 7).
The present study has developed rather general
syntheses of sulfilimine and sulfoximine derivatives
of monocyclic thiophenes. These compounds are not
aromatic but are cyclic dienes. In addition, they
show equally characteristic properties of sulfilimines
and sulfoximines. Taking these properties into ac-
count, a special emphasis of the future study of these
compounds should be placed on their applications
to organic syntheses to open a new field of hetero-
cyclic and heteroatom chemistry. Particularly, their
An ORTEP structure of 5a and its outline struc-
ture are given in Figure 4, along with the relevant
bond lengths and angles data. Crystal data of 5a are
summarized in Table 5. The thiophene ring of the
sulfone diimine 5a is nearly planar as is true of most
thiophene 1,1-dioxides [24]. The S–N1 and S–N2
˚
bond lengths are 1.55 A and are nearly equal to the
˚
bond length (1.54 A) of the common S–N bonds [23]
that are conventionally expressed by a double bond.
The bond alternation in the thiophene ring is evident
from the bond lengths data: C1–C2, 1.34; C2–C3,
˚
1.52 A.
An ORTEP structure of 9 is shown in Figure 5,
along with the relevant bond lengths and angles
data. Crystal data of 9 are summarized in Table 5.
The ORTEP structure shows that 9 exists in the
amino–imino form in the solid state. Thus, C4–N2 is
typical of a double bond with a bond length of 1.29
˚
A, while the C1–N1 is typical of a single bond with a
˚
bond length of 1.46 A [23].

342 Nakayama et al.
TABLE 5 Crystal Data of 3b, 5a, 9, and (S)-4f
3b
C19H27NO2S2
365.56
Needles
5a
9
(S)-4f
C12H21NOS
227.40
Needles
Chemical formula
Formula weight
Crystal form
C26H34N2O4S3
534.77
C26H34N2O4S3
534.77
Needles
Needles
Crystal size (mm3)
Crystal system
Space group
0.29 ן 0.08 ן 0.08 0.16 ן 0.08 ן 0.08 0.34 ן 0.15 ן 0.15 0.58 ן 0.16 ן 0.10
Triclinic
P1
Monoclinic
P21/n
10.246(2)
11.848(1)
22.677(3)
Monoclinic
P21/a
12.355(1)
17.297(1)
13.864(1)
Orthorhombic
P212121
13.491(3)
17.019(4)
5.802(1)
˚
a (A)
9.696(1)
14.071(3)
15.614(4)
105.811(9)
100.32(1)
98.07(1)
1975.9(7)
4
˚
b (A)
˚
c (A)
␣ (ꢀ)
b (ꢀ)
c (ꢀ)
95.132(7)
108.502(4)
3
˚
V (A )
2741.8(6)
4
2809.7(3)
4
1332.2(5)
4
1.133
1553
1361
1450
192
Z
D
מ3
calc (Mg m
)
1.229
8212
3087
1.295
7608
2859
5953
350
1.264
7380
5060
6702
452
No. of measured reflections
No. of independent reflections
No. of observed reflections (I ꢁ 2rI) 6639
No. of parameters
487
R
Rw
GOF
Dqmax
Dqmin
0.079
0.075
2.045
0.61
0.071
0.060
1.714
0.41
0.047
0.051
1.396
0.55
0.055
0.065
1.526
0.41
מ0.44
מ0.69
מ0.42
מ0.46
FIGURE 5 ORTEP structures of 9. Selected bond length
(A): N1–C1, 1.455(2); C1–C2, 1.521(3); C2–C3, 1.359(2);
C3–C4, 1.485(2); C4–N2, 1.292(2); C1–S, 1.815(2); S–C4,
1.730(2). Bond angles (ꢀ): N1–C1–C2, 109.6(2); N1–C1–S,
113.3(2); S–C1–C2, 108.4(1); C1–C2–C3, 113.7(2); C2–C3–
C4, 110.3(2); C3–C4–S, 113.7(1); C3–C4–N2, 121.3(2); S–
C4–N2, 124.8(2).
˚
FIGURE 4 (a) ORTEP structure of 5a. (b) Outline structure
of 5a. Selected bond lengths (A): S–N1, 1.551(6); S–N2,
1.557(5); S–C1, 1.737(7); S–C4, 1.728(7); C1–C2, 1.339(10);
C2–C3, 1.524(11); C3–C4, 1.343(9). Bond angles (ꢀ): N1–S–
N2, 121.5(3); C1–S–C4, 93.1(4); S–C1–C2, 111.7(5); C2–
C3–C4, 111.7(6); C3–C4–S, 111.7(5).
˚

Sulfilimine, Sulfone Diimine, and Sulfoximine Derivatives of a Monocyclic Thiophene, 3,4-Di-tert-butylthiophene 343
or a Perkin Elmer System 2000 FT-IR spectrometer.
UV–vis spectra were determined on a JASCO V-560
spectrophotometer. CD spectra were determined on
a JASCO J-600 spectropolarimeter. Mass spectra
were recorded on a JEOL JMS-DX303 spectrometer
operating at 70 eV in the EI mode. Elemental anal-
yses were performed by the Chemical Analysis Cen-
ter of Saitama University.
Imination of 3,4-Di-tert-butylthiophene (6a) by
N-[(p-tolylsulfonyl)imino]phenyliodinane
(TsNסIPh)
FIGURE 6 ORTEP structure of (ם)-(S)-4f. Selected bond
lengths (A): S–O, 1.445(3); S–N, 1.536(3); S–C1, 1.796(3);
˚
S–C4, 1.739(3); C1–C2, 1.321(3); C2–C3, 1.492(3); C3–C4,
1.319(4); C1–C5, 1.520(4); C3–C6, 1.507(4). Bond angles (ꢀ):
O–S–N, 119.3(2); C1–S–C4, 92.9(2); S–C1–C2, 107.3; C1–
C2–C3, 116.4(2); C2–C3–C4, 111.5(3), C3–C4–S, 111.9(2);
S–C1–C5, 123.2(2); C2–C3–C6, 121.5(2).
Cu(MeCN)4PF6 as the Catalyst. The thiophene
6a and TsNסIPh in a variety of molar ratios were
allowed to react in the presence of 5 mol % of
Cu(MeCN)4PF6. The following are experimental de-
tails of the 20:1 molar ratio reaction. A mixture of
3.92 g (20 mmol) of 6a, 373 mg (1 mmol) of
TsNסIPh, and 20 mg (0.05 mmol) of Cu(MeCN)4PF6
in 25 mL of MeCN was stirred for 3 hours at room
temperature. The reaction was quenched by addition
of water. The resulting mixture was extracted with
ether (50 mL). The extract was washed with water,
dried over MgSO4, and evaporated. Chromatography
was performed on the residue on a column of silica
gel (100 g). The column was first eluted with hexane
to remove excess 6a and iodobenzene. The column
was then eluted with a 9:1 mixture of hexane and
CH2Cl2 to give 18 mg (5%) of 7a and 17 mg (3%) of
8, in that order. The column was further eluted with
CH2Cl2 to give 10 mg (4%) of 9, 18 mg (7%) of 5a,
TsNH2, and 238 mg (61%) of 3b in that order. Sepa-
ration of all of these products by single column chro-
matography was not complete, and thus repurifica-
tion of the mixture parts by further column
chromatography was required in many cases.
FIGURE 7 CD Spectra of (מ)-(R)- and (ם)-(S)-4f (c 0.010
g/100 mL, CH2Cl2) and UV–vis Spectrum of the Racemate 4f
(CH2Cl2)
Compound 3b: m.p. 130–131ꢀC (from cyclohex-
1
ane); H NMR (400 MHz, CDCl3) d ס 1.37 (s, 18H),
2.40 (s, 3H), 6.70 (s, 2H), 7.24 (d, J ס 8 Hz, 2H), 7.76
(d, J ס 8 Hz, 2H); 13C NMR (100.6 MHz, CDCl3) d ס
21.4 (CH3), 31.8 (CH3), 36.4 (C), 127.0 (CH), 128.4
(CH), 129.2 (CH), 140.3 (C), 142.2 (C), 161.8 (C).
Anal. calcd for C19H27NO2S2: C, 62.43; H, 7.45; N,
3.83. Found: C, 62.37; H, 7.44; N, 3.81.
cycloaddition chemistry would be of much interest
in comparison with those of thiophene 1-oxides and
1,1-dioxides.
EXPERIMENTAL
Solvents were purified and dried in the usual man-
ner. All of the reactions were carried out under ar-
gon. Silica-gel column chromatography was per-
formed on silica gel 7734 (Merck, 70–230 mesh).
Melting points were determined on a Mel-Temp cap-
illary tube apparatus and are uncorrected. 1H and 13C
NMR spectra were recorded on a Bruker ARX400, a
Bruker AM400, or a Bruker AM300 spectrometer us-
ing CDCl3 as the solvent with TMS as the internal
standard. IR spectra were taken on a Hitachi 270-50
Compound 5a: m.p. 155.0–155.5ꢀC (from Et2O/
hexane); H NMR (400 MHz, CDCl3) d ס 1.38 (s,
1
18H), 2.40 (s, 6H), 7.13 (s, 2H), 7.21 (d, J ס 8 Hz,
4H), 7.72 (d, J ס 8 Hz, 4H); 13C NMR (100 MHz,
CDCl3) d ס 21.6 (CH3), 31.3 (CH3), 36.7 (C), 125.9
(CH), 126.9 (CH), 129.3 (CH), 139.6 (C), 143.2 (C),
160.4 (C). Anal. calcd for C26H34N2O4S3: C, 58.40; H,
6.41; N, 5.24. Found: C, 58.47; H, 6.42; N, 5.34.
Compound 8: m.p. 140–141ꢀC (from pentane);
1H NMR (400 MHz, CDCl3) d ס 1.34 (s, 9H), 1.47 (s,

344 Nakayama et al.
9H), 1.51 (s, 9H), 1.63 (s, 9H), 2.42 (s, 3H), 6.57 (s,
1H), 7.07 (s, 1H), 7.29 (d, J ס 8 Hz, 2H), 7.85 (d, J
ס 8 Hz, 2H); 13C NMR (100 MHz, CDCl3) d ס 21.6
(CH3), 31.7 (CH3), 33.3 (CH3), 34.58 (CH3), 34.61
(CH3), 36.9 (C), 37.1 (C), 37.3 (C), 38.6 (C), 57.2 (CH),
121.3 (CH), 127.0 (CH), 129.3 (CH), 137.5 (C), 138.2
(C), 143.2 (C), 145.7 (C), 149.0 (C), 152.1 (C), 167.0
(C), 183.8 (C). Anal. calcd for C31H45NO2S3: C, 66.50;
H, 8.10; N, 2.50. Found: C, 66.67; H, 8.20; N, 2.40.
Compound 9: m.p. ꢁ 167ꢀC (dec) (from Et2O/
hexane); 1H NMR (400 MHz, CDCl3) d ס 1.37 (s, 9H),
1.47 (s, 9H), 2.42 (s, 3H), 2.50 (s, 3H), 4.38 (d, J ס
12 Hz, 1H), 6.04 (d, J ס 12 Hz, 1H), 7.27 (d, J ס 8
Hz, 2H), 7.40 (d, J ס 8 Hz, 2H), 7.74 (d, J ס 8 Hz,
2H), 7.76 (d, J ס 8 Hz, 2H); 13C NMR (100 MHz,
CDCl3) d ס 21.6 (CH3), 21.8 (CH3), 31.6 (CH3), 32.3
(CH3), 36.9 (C), 37.7 (C), 67.0 (CH), 127.1 (CH), 127.8
(CH), 129.4 (CH), 130.4 (CH), 135.5 (C), 137.3 (C),
(m, 2H), 7.83–7.85 (m, 4H). 13C NMR (CDCl3, 100.6
MHz) d 31.3, 36.7, 125.8, 126.8, 128.8, 132.6, 142.3,
160.7. Anal. calcd for C24H30N2O4S3: C, 56.89; H, 5.97;
N, 5.53. Found: C, 56.62; H, 5.89; N, 5.37.
Compound 7b: m.p. 147–148ꢀC; colorless crys-
tals (from hexane); 1H NMR (CDCl3, 400 MHz) d 1.32
(s, 18H), 6.95 (s, 2H), 7.48–7.52 (m, 2H), 7.57–7.61
(m, 1H), 7.80–7.82 (m, 2H); 13C NMR (CDCl3, 100.6
MHz) d 32.3, 32.6, 118.6, 126.6, 129.2, 133.4, 138.2,
139.4. Anal. calcd for C18H25NO2S: C, 67.67; H, 7.89;
N, 4.38. Found: C, 67.59; H, 7.88; N, 4.32.
Imination of 2,4-Di-tert-butylthiophene (6b) by
N-[(p-tolylsulfonyl)imino]phenyliodinane
(TsNסIPh)
A mixture of 400 mg (2 mmol) of 6b, 373 mg (1
mmol) of TsNסIPh, and 20 mg (0.05 mmol) of
Cu(MeCN)4PF6 in 10 mL of MeCN was stirred at
room temperature for 1 hour. The resulting mixture
was purified by silica-gel column chromatography to
give 76 mg (20%) of the sulfilimine 3d. Structures of
other products, which were obtained in small
amounts or in pure form, could not be elucidated.
Compound 3d: m.p. 111–113ꢀC; colorless crys-
tals (from ether/hexane); 1H NMR (CDCl3, 400 MHz)
d 1.21 (s, 9H), 1.35 (s, 9H), 2.40 (s, 3H), 6.12 (d, J ס
1 Hz, 1H), 6.57 (d, J ס 1 Hz, 1H), 7.25 (d, J ס 8 Hz,
2H), 7.80 (d, J ס 8 Hz, 2H); 13C NMR (CDCl3, 100.6
MHz) d 21.4, 28.3, 30.6, 34.3, 35.9, 120.3, 126.7,
127.0, 129.2, 140.7, 142.0, 158.7, 161.4. Anal. calcd
for C19H27NO2S2: C, 62.43; H, 7.45; N, 3.83. Found:
C, 62.35; H, 7.49; N, 3.78.
143.7 (C), 145.3 (C), 149.9 (C), 163.5 (C), 181.2 (C);
מ1
IR (KBr) 3216 cm
(N-H). Anal. calcd for
C26H34N2O4S3: C, 58.40; H, 6.41; N, 5.24. Found: C,
58.44; H, 6.41; N, 5.17.
Cu(OTf)2 as the Catalyst. A mixture of 500 mg
(2.5 mmol) of 6a, 200 mg (0.54 mmol) of TsNסIPh,
and 15 mg (0.04 mmol) of Cu(OTf)2 in 5 mL of MeCN
was stirred for 2 hours at room temperature. The
reaction mixture was worked up in a manner similar
to that described previously give 64 mg (32%) of 3b,
12 mg (8%) of 5a, 7 mg (4%) of 7a, 9 mg (3%) of 8,
and 4 mg (3%) of 9.
Imination of 3,4-Di-tert-butylthiophene (6a) by
N-[(benzenesulfonyl)imino]phenyliodinane
(PhSO2NסIPh)
Reaction of Sulfilimine 3b with TsNסIPh
A mixture of 1.00 g (5 mmol) of 6a, 0.36 g (1 mmol)
of PhSO2NסIPh, and 18 mg (0.05 mmol) of
Cu(MeCN)4PF6 in 20 mL of MeCN was stirred at
room temperature for 1 hour. The resulting reaction
mixture was purified in a manner similar to that of
the reaction of 6a with TsNסIPh to give 133 mg
(38%) of the sulfilimine 3c, 12 mg (5%) of the sulfone
diimine 5c, 22 mg (7%) of the pyrrole 7b, and 52 mg
(33%) of PhSO2NH2.
Compound 3c: m.p. 133–135ꢀC; colorless crys-
tals (from cyclohexane); 1H NMR (CDCl3, 400 MHz)
d 1.37 (s, 18H), 6.70 (s, 2H), 7.43–7.53 (m, 3H), 7.88–
7.90 (m, 2H); 13C NMR (CDCl3, 100.6 MHz) d 31.8,
36.5, 126.9, 128.3, 128.6, 131.6, 143.2, 162.0. Anal.
calcd for C18H25NO2S2: C, 61.50; H, 7.17; N, 3.99.
Found: C, 61.39; H, 7.15; N, 3.93.
A mixture of 183 mg (0.5 mmol) of 3b, 183 mg (0.5
mmol) of TsNסIPh, and 9 mg (0.03 mmol) of
Cu(MeCN)4PF6 in 5 mL of MeCN was stirred for 5
hours at room temperature. Purification of the mix-
ture by silica-gel column chromatography gave 26
mg (10%) of 5a, 88 mg (48%) of 3b, 28 mg (18%) of
7a, and 37 mg (43%) of TsNH2.
Reaction of Sulfilimine 3b with PhSO2NסIPh
A mixture of 366 mg (1.0 mmol) of 3b, 360 mg (1.0
mmol) of PhSO2NסIPh, and 20 mg (0.05 mmol) of
Cu(MeCN)4PF6 in 10 mL of MeCN was stirred for 8
hours at room temperature. Purification of the mix-
ture by silica-gel column chromatography gave 45
mg (14%) of a mixture of pyrroles 7a and 7b in the
ratio of 15:85, 32 mg (6%) of sulfone diimine 5b, 102
mg (67%) of a mixture of PhSO2NH2 and TsNH2 in
the ratio of 9:1, and 264 mg (72%) of sulfilimine 3b.
Compound 5c: m.p. 184–187ꢀC; colorless crys-
1
tals (from hexane); H NMR (CDCl3, 400 Hz) d 1.38
(s, 18H), 7.15 (s, 2H), 7.42–7.46 (m, 4H), 7.52–7.55

Sulfilimine, Sulfone Diimine, and Sulfoximine Derivatives of a Monocyclic Thiophene, 3,4-Di-tert-butylthiophene 345
Compound 5b: m.p. 124–126ꢀC; colorless crys-
By Use of (CF3SO2)2O. To a solution of 170 mg
(0.6 mmol) of (CF3SO)2O in 10 mL of CH2Cl2, cooled
at 0ꢀC, was added 106 mg (0.5 mmol) of 1a all at
once. After the mixture had been stirred for 10 min-
utes at 0ꢀC, a solution of 103 mg (0.6 mmol) of TsNH2
in 10 mL of CH2Cl2 was added. The mixture was
warmed slowly to room temperature. The reaction
was quenched by addition of ice water. The organic
layer was separated, washed with water and then
with aqueous NaHCO3, dried over MgSO4, and evap-
orated. The resulting residue was purified by passing
it through a short column of silica gel to give 144 mg
(79%) of 3b. Sulfilimine 3c was also prepared in a
similar manner.
tals (from hexane); 1H NMR (400 MHz, CDCl3) d 1.37
(s, 18H), 2.39 (s, 3H), 7.20 (d, J ס 8.0 Hz, 2H), 7.41–
7.45 (m, 2H), 7.51–7.55 (m, 1H), 7.70–7.73 (m, 2H),
7.85 (d, J ס 8.0 Hz, 2H); 13C NMR (100.6 MHz,
CDCl3) d 21.5, 31.3, 36.7, 125.9, 126.82, 126.84, 128.7,
129.3, 132.5, 139.5, 142.4, 143.3, 160.5. Anal. calcd
for C25H32N2O4S3: C, 57.66; H, 6.19; N, 5.38. Found:
C, 57.79; H, 6.24; N, 5.22.
Preparation of Sulfilimines 3b,c,e–h from 3,4-
Di-tert-butylthiophene 1-Oxide (1a)
By Use of (CF3CO)2O. To a solution of 210 mg
(1.0 mmol) of (CF3CO)2O in 5 mL of CH2Cl2, cooled
at מ78ꢀC was added 105 mg (0.5 mmol) of 1a all at
once. After the mixture had been stirred for 10 min-
utes at מ78ꢀC, 171 mg (1.0 mmol) of TsNH2 was
added quickly. The mixture was warmed slowly to
room temperature. The reaction was quenched by
addition of ice water. The organic layer was sepa-
rated, washed with water, and then with aqueous
NaHCO3, dried over MgSO4, and evaporated. The re-
sulting residue was purified by passing it through a
short column of silica gel to give 156 mg (86%) of
3b. Sulfilimines 3c,e–h were prepared in similar
manners. In the case of 3g, the reaction was
quenched at מ20ꢀC; quenching of the reaction at
room temperature may result in a decrease of the
yield because of partial decomposition of the
product.
Preparation of Sulfilimine 3i
To a solution of 210 mg (1.0 mmol) of (CF3CO)2O in
10 mL of CH2Cl2, cooled at מ78ꢀC, was added 106
mg (0.5 mmol) of 1a all at once. After the mixture
had been stirred for 1 hour at מ78ꢀC, a solution of
42 mg (1.0 mmol) of NCNH2 in 10 mL of CH2Cl2 was
added. The mixture was stirred at the same tem-
perature for 2 hours and then warmed slowly to
room temperature. The reaction was quenched by
addition of ice water. The organic layer was sepa-
rated, washed with water and then with aqueous
NaHCO3, dried over MgSO4, and evaporated. The re-
sulting crystalline residue was purified by passing it
through a short column of silica gel to give 130 mg
(85%) of 3i: m.p. 158–160ꢀC (from cyclohexane); 1H
NMR (400 MHz, CDCl3) d 1.46 (s, 18H), 7.15 (s, 2H);
13C NMR (100.6 MHz, CDCl3) d 31.8, 36.9, 117.0 (q,
1
Compound 3e: viscous oil; H NMR (400 MHz,
CDCl3) d 1.27 (t, J ס 7.1 Hz, 3H), 1.42 (s, 18H), 4.13
(q, J ס 7.1 Hz, 2H), 6.92 (s, 2H); 13C NMR (100.6
MHz, CDCl3) d 14.7, 32.0, 36.5, 62.1, 128.5, 162.4,
166.0. HRMS calcd for C15H25NO2S m/z 283.1606
5
1J(C,F) ס 286 Hz), 125.2 (dt, J(C,F) ס 19, 86 Hz),
2
164.7, 167.3 (q, J(C,F) ס 35 Hz). Anal. calcd for
C14H20F3NOS: C, 54.71; H, 6.56; N, 4.56. Found: C,
54.80; H, 6.56; N, 4.44.
ם
(M ); Found, 283.1597. 3f: m.p. 129–131ꢀC (from
hexane); 1H NMR (400 MHz, CDCl3) d 1.42 (s, 18H),
1.49 (s, 9H), 6.92 (s, 2H); 13C NMR (100.6 MHz,
CDCl3) d 28.4, 32.0, 36.4, 79.4, 128.8, 162.2, 165.6.
Anal. calcd for C17H29NO2S: C, 65.55; H, 9.38; N, 4.50.
Found: C, 65.63; H, 9.35; N, 4.49.
In a similar manner, 128 mg (83%) of 3i was ob-
tained from 106 mg (0.5 mmol) of 1a and 50 mg (0.8
mmol) of H2NCONH2.
Mutual Conversion between Sulfilimines:
Conversion of 3b to 3e
1
Compound 3g: m.p. 90–91ꢀC (from hexane); H
NMR (400 MHz, CDCl3) d 1.44 (s, 18H), 2.14 (s, 3H)
7.10 (s, 2H); 13C NMR (100.6 MHz, CDCl3) d 23.4,
31.9, 36.5, 12.9, 162.7, 182.1. Anal. calcd for
C14H23NOS: C, 66.36; H, 9.15; N, 5.53. Found: C,
66.55; H, 9.34; N, 5.48.
Compound 3h: m.p. 110–111ꢀC (from hexane);
1H NMR (400 MHz, CDCl3) d 1.46 (s, 18H), 2.37 (s,
3H), 7.16 (d, J ס 8 Hz, 2H), 7.22 (s, 2H), 7.97 (d, J
ס 8 Hz, 2H); 13C NMR (100.6 MHz, CDCl3) d 21.5,
32.1, 36.6, 127.4, 128.6, 128.8, 132.8, 141.0, 162.4,
177.4. Anal. calcd for C26H34N2O4S3: C, 72.90; H, 8.26;
N, 4.25. Found: C, 72.63; H, 8.35; N, 4.23.
To a solution of 105 mg (0.5 mmol) of (CF3CO)2O in
5 mL of CH2Cl2, cooled at מ78ꢀC, was added 92 mg
(0.25 mmol) of 3b all at once. After the mixture had
been stirred for 10 minutes at מ78ꢀC, a solution of
225 mg (2.5 mmol) of H2NCO2Et in 5 mL of CH2Cl2
was added. The mixture was warmed slowly to
מ10ꢀC. The reaction was quenched by addition of
ice water. The organic layer was separated, washed
with aqueous NaHCO3, and evaporated. The result-
ing residue was dissolved in 10 mL of ether, and the
solution was washed with 2M NaOH, dried over

346 Nakayama et al.
MgSO4, and evaporated. The resulting residue was
purified by passing it through a short column of sil-
ica gel to give 60 mg (85%) of 3e.
added to the reaction mixture, and the resulting mix-
ture was washed with brine, dried over Na2SO4, and
evaporated. Chromatography was performed on the
residue on a column of silica gel (15 g). Elution of
the column with a 1:3 mixture of AcOEt and hexane
gave 124 mg (67%) of 4b: m.p. 140.0–140.5ꢀC; col-
Preparation of the Aminosulfonium Salt 13
1
To a solution of 156 mg (0.5 mmol) of 3f in 2.5 mL
of CH2Cl2 was added 0.5 mL of CF3CO2H. After stir-
ring for 3 hours, the volatiles were removed by evap-
oration. Dilution of the residue by 3 mL of cold ether
gave 107 mg (66%) of the aminosulfonium salt 13:
m.p. 123–126ꢀC (decomp.); colorless needles (from
orless needles (from hexane); H NMR (400 MHz,
CDCl3) d 1.41 (s, 18H), 2.41 (s, 3H), 6.92 (s, 2H), 7.29
(d, J ס 8 Hz, 2H), 7.89 (d, J ס 8 Hz, 2H); 13C NMR
(100.6 MHz, CDCl3) d 21.5, 31.5, 36.2, 126.6, 126.7,
129.4, 140.5, 143.0, 158.9; IR (KBr) 3110, 2867, 1316,
1303, 1266, 1222, 1153, 1081, 1061, 831, 745, 657
cmמ1. Anal. calcd for C19H27NO3S2: C, 59.81; H, 7.13;
N, 3.67. Found: C, 59.97; H, 7.14; N, 3.67.
The sulfoximine 4e was prepared in 81% yield
by stirring a mixture of 212 mg (1 mmol) of 1b, 453
mg (1.2 mmol) of TsNסIPh, and 8.7 mg of
Cu(MeCN)4PF6 in 5 mL of MeCN for 20 minutes at
room temperature.
1
ether/hexane); H NMR (400 MHz, CDCl3) d 1.44 (s,
18H), 6.97 (s, 2H), 7.16 (broad s, 2H); 13C NMR
(100.6 MHz, CDCl3) d 31.7, 37.0, 116.7 (q, 1J(C,F) ס
2
294 Hz), 126.5, 161.8 (q, J(C,F) ס 34 Hz), 165.7.
Anal. calcd for C14H22F3NO2S: C, 51.68; H, 6.82; N,
4.31. Found: C, 51.67; H, 6.79; N, 4.31.
Compound 4e: m.p. 124.5–126.0ꢀC; colorless
needles (from hexane); 1H NMR (300 MHz, CDCl3) d
1.19 (s, 9H), 1.36 (s, 9H), 2.42 (s, 3H), 6.55 (d, J ס 1
Hz, 1H), 6.96 (d, J ס 1 Hz, 1H), 7.29 (d, J ס 8 Hz,
2H), 7.89 (d, J ס 8 Hz, 2H); 13C NMR (100.6 MHz,
CDCl3) d 21.5, 27.6, 29.5, 33.7, 35.6, 121.3, 124.9,
126.5, 129.3, 141.0, 142.7, 153.3, 153.9. Anal. calcd
for C19H27NO3S2: C, 59.81; H, 7.13; N, 3.67. Found:
C, 59.83; H, 7.20; 3.66.
Preparation of the Sulfilimine 3n
To a suspension of 110 mg (0.34 mmol) of 13 in 10
mL of ether was added 10 mL of 0.1 M NaOH at
room temperature. The mixture was stirred for 3
minutes, and the organic layer was separated,
washed with water, dried over MgSO4, and evapo-
rated. The resulting residue was washed with pen-
tane to give 63 mg (88%) of 3n as a viscous oil that
solidified in a refrigerator; 1H NMR (400 MHz,
CDCl3) d 1.44 (s, 18H), 2.34 (broad s, 1H, NH), 6.81
(s, 2H); 13C NMR (100.6 MHz, CDCl3) d 32.1, 35.9,
135.1, 158.4. HRMS calcd for C12H21NS m/z 211.1395
Preparation of Sulfoximine 4b from 1a and
TsN3
ם
(M ); Found, 211.1392.
Activated copper, prepared from 2.11 g of CuSO4
•5H2O and 0.78 g of zinc powder, was washed with
2 M HCl, water, and MeOH successively, and sus-
pended in 20 mL of MeOH. To this suspension were
added 213 mg (1.0 mmol) of 1a and 591 mg (2.9
mmol) of TsN3. The mixture was heated at reflux for
3 hours and filtered while hot. The insoluble mate-
rials were washed with CH2Cl2. The filtrate and
washings were combined, washed with water, dried
over Na2SO4, and evaporated. The resulting residue
was choromatographed on a column of silica gel
(50 g) with CH2Cl2 as the eluent to give 138 mg (35%)
of 4b.
Conversion of 3n to 3b (Tosylation of 3n)
To a stirred and ice-cooled solution of 63 mg (0.3
mmol) of 3n in 5 mL of CH2Cl2 was added dropwise
a solution of 86 mg (0.5 mmol) of tosyl chloride in 5
mL of CH2Cl2. The mixture was warmed slowly to
room temperature and stirred for 2 hours. The re-
action was quenched by addition of ice water. The
organic layer was separated, washed with aqueous
NaHCO3, dried over MgSO4, and evaporated. The re-
sulting residue was purified by passing it through a
short column of silica gel to give 92 mg (84%) of 3b.
Conversion of Sulfoximines 4b and 4e to the
Corresponding N-Unsubstituted Sulfoximines
4c and 4f
Preparation of Sulfoximines 4b and 4e from 1a
and 1b, respectively, by Treatment with
TsNסIPh
Sulfoximine 4b (77 mg, 0.20 mmol) was added to 1.0
mL of concentrated H2SO4 under stirring. The re-
sulting homogeneous mixture was added slowly to
20 mL of a 20% NaOH solution under ice-cooling.
The mixture was extracted with CH2Cl2, and the ex-
A mixture of 103 mg (0.49 mmol) of 1a, 215 mg (0.58
mmol) of TsNסIPh, and 4.8 mg (0.01 mmol) of
Cu(MeCN)4PF6 in 4 mL of MeCN was stirred for 15
minutes at room temperature. AcOEt (30 mL) was

Sulfilimine, Sulfone Diimine, and Sulfoximine Derivatives of a Monocyclic Thiophene, 3,4-Di-tert-butylthiophene 347
tract was washed with water, dried over Na2SO4, and
were carried out to collect enough samples for de-
termination of CD spectra and X-ray crystallo-
graphic analysis.
evaporated to give 43 mg (95%) of the N-unsubsti-
tuted sulfoximine 4c: m.p. 95.5–96.0ꢀC; colorless
needles (from hexane); 1H NMR (400 MHz, CDCl3) d
1.40 (s, 18H), 2.97 (broad s, 1H, NH), 6.53 (s, 2H);
13C NMR (100.6 MHz, CDCl3) d 31.6, 35.4, 129.4,
X-Ray Crystallographic Analyses of 3b, 5a, 9,
and (S)-4f
155.0; IR (KBr) 3156 (NH), 3112, 2964, 1238, 1222,
מ1
Crystal data are for 3b, 5a, 9, and (S)-4f are given in
Table 5.
1210, 1006 (SO), 994 cm
. Anal. calcd for
C12H21NOS: C, 63.39; H, 9.31; 6.16. Found: C, 63.49;
H, 9.41; N, 6.15.
The N-unsubstituted sulfoximine 4f was pre-
pared in 89% yield by treatment of 299 mg of 4e with
3 mL of concentrated H2SO4.
The crystal data for 3b, 5a, and 9 were recorded
on a Mac Science DIP3000 diffractometer equipped
with a graphite monochrometer. Oscillation and
nonscreen Weissenberg photographs were recorded
on the imaging plates of the diffractometer by using
Compound 4f: m.p. 82.5–83.5ꢀC (racemate); col-
˚
1
Mo K␣ radiation (k ס 0.71073 A), and the data re-
orless needles (from hexane); H NMR (400 MHz,
duction was made by the MAC DENZO program sys-
tem. Cell parameters were determined and refined
by using the MAC DENZO for all observed reflec-
tions. The structure was solved by direct methods
using SIR in the CRYSTAN-GM program system.
The atomic coordinates and anisotropic thermal pa-
rameters of the non-H atoms were refined by full-
matrix least squares.
CDCl3) d 1.17 (s, 9H), 1.42 (s, 9H), 2.96 (broad s, 1H,
NH), 6.12 (d, J ס 1 Hz, 1H), 6.29 (d, J ס 1 Hz, 1H);
13C NMR (100.6 MHz, CDCl3) d 27.7, 29.6, 33.1, 35.1,
120.1, 122.8, 152.7, 156.0; UV–vis (CH2Cl2) kmax (e)
245 (1880), 279 (2130), 315 nm (sh). Anal. calcd for
C12H21NOS: C, 63.39; H, 9.31; 6.16. Found: C, 63.56;
H, 9.42; N, 6.12.
The crystal data for (S)-4f was recorded on a Mac
Science MXC3K diffractometer, Cu K␣ radiation (k
ס 1.54178 A) with a graphite crystal monochrono-
Preparation of 4d: N-Methylation of 4b
˚
A mixture of 62 mg (0.27 mmol) of 4b and 81 mg
ם
מ
meter in the incident beam. The unit cell dimensions
were obtained by a least-squares fit of 22 automati-
cally centered reflections in the range of 56.5 ꢂ 2h ꢂ
59.9ꢀ. Intensity data were collected using x-2h scan
method in the range 3 ꢂ 2h ꢂ 40ꢀ. The scan width,
Dx, for each reflection was 2.34 ם 0.2tan h, with a
scan speed of 6.0ꢀ minמ1. The structure was solved
by direct methods using SIR92 [28] in the CRYSTAN-
GM program system. The atomic coordinates and
the anisotropic thermal parameters of the non-H at-
oms were refined by full-matrix least squares [29] to
minimize functions Rw(|Fo| מ |Fc|)2.
(0.55 mmol) of Me3O BF4 in 6 mL of CH2Cl2 was
stirred overnight at room temperature. Since the
progress of the methylation was sluggish, an addi-
ם
מ
tional 81 mg (0.55 mmol) of Me3O BF4 was added,
and the mixture was stirred for an additional 8
hours. The reaction was quenched by addition of wa-
ter. The organic layer was washed with water, dried
over Na2SO4, and evaporated. The residue was pu-
rified by preparative thin-layer chromatography
(TLC) with a 1:1 mixture of AcOEt and hexane as the
eluent to give 28 mg (43%) of 4d and 25 mg (40%)
of 4b.
Compound 4d: m.p. 117–118ꢀC; yellow powder
(from hexane); 1H NMR (400 MHz, CDCl3) d 1.23 (s,
18H), 2.95 (s, 3H), 6.57 (s, 2H); 13C NMR (100.6 MHz,
CDCl3) d 31.1, 31.7, 35.5, 126.5, 155.4. Anal. calcd for
C13H23N2S: C, 64.68; H, 9.60; N, 5.80. Found: C,
64.78; H, 9.69; N, 5.76.
REFERENCES
[1] (a) Nakayama, J.; Sugihara, Y. Top Curr Chem 1999,
205, 131; (b) Nakayama, J. J Bull Chem Soc Jpn 2000,
73, 1.
[2] (a) Nakayama, J.; Sugihara, Y. Sulfur Reports 1997,
19, 349; (b) Nakayama, J. Sulfur Reports 2000, 22,
123.
[3] (a) Meth-Cohn, O.; van Vuuren, G. J Chem Soc Chem
Commun 1984, 190; (b) Meth-Cohn, O.; van Vuuren,
G. J Chem Soc Perkin Trans 1 1986, 233; (c) Meth-
Cohn, O.; van Vuuren, G. J Chem Soc Perkin Trans 1
1986, 245; (d) Meth-Cohn, O.; van Vuuren, G. Tetra-
hedron Lett 1986, 27, 1105; (e) Dillen, J. L. M.; Meth-
Cohn, O.; van Vuuren, G. J Chem Soc Perkin Trans 1
1987, 2659.
Optical Resolution of (R)-4f and (S)-4f
Optical resolution was done by HPLC on a chiral col-
umn CHIRALPAK AD (4.6 mm i.d. ן 250 mm; Dai-
cel Chemical Industries, Ltd.) using a UV detector of
254 nm. A 1.3 mg sample of 4f was charged, with a
98.5:1.5 mixture of hexane and ethanol being used
as the eluent at a flow rate of 1.0 mL/min. Under
these conditions, retention times of (R)-4f and (S)-
4f were 44 and 54 minutes, respectively. Many runs
[4] (a) For dibenzo derivatives, see Stoss, P.; Satzinger,
G. Tetrahedron Lett 1974, 1973; (b) Svoronos, P.;
Horak, V. Synthesis 1979, 596; (c) Svoronos, P.;

348 Nakayama et al.
Horak, V. Phosphorus Sulfur Silicon 1989, 42, 139;
Molecules; Chapman and Hall: London, 1975; Part 2;
(b) Dolphin, D.; Wick, A. Tabulation of Infrared Spec-
tral Data, Wiley; New York, 1977; Chapter 4.
(d) Klein, R. F. X.; Svoronos, P. D. N.; Horak, V.; Jame-
son, G. B. J Org Chem 1991, 56, 3259.
[5] (a) Nakayama, J.; Nagasawa, H.; Sugihara, Y.; Ishii,
A. J Am Chem Soc 1997,119, 9077; (b) Nagasawa, H.;
Sugihara, Y.; Ishii, A.; Nakayama, J. J Bull Chem Soc
Jpn 1999, 72, 1919; (c) Nakayama, J.; Nagasawa, H.;
Sugihara, Y.; Ishii, A. Heterocycles 2000, 52, 365.
[6] (a) For preliminary reports, Otani, T.; Sugihara, Y.;
Ishii, A.; Nakayama, J. Tetrahedron Lett 1999, 40,
5549; (b) Otani, T.; Sugihara, Y.; Ishii, A.; Nakayama,
J. Tetrahedron Lett 2000, 41, 8461; (c) Nakayama, J.;
Sano, Y.; Sugihara, Y.; Ishii, A. Tetrahedron Lett 1999,
40, 3785.
[7] (a) Hafner, K.; Kaiser, W. Tetrahedron Lett 1964,
2185; (b) Meth-Cohn, O.; van Vuuren, G. Tetrahedron
Lett 1986, 27, 1105.
[8] Nakayama, J.; Sugihara, Y.; Terada, K.; Clennann,
E. L. Tetrahedron Lett 1990, 31, 4473.
[21] The calculations have been performed by using the
GAUSSIAN 98 (Revision A.7) program on homemade
workstations running RedHat Linux 6.0. All the ge-
ometry optimization and vibrational frequency cal-
culations have been carried out at the B3LYP/6-31G*
level. All the calculated frequencies are multiplied by
0.9613. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.;
Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Za-
krzewski, V. G.; Montgomery, J. A., Jr.; Stratmann,
R. E.; Burant, J. C.; Dapprich, S.; Millam, J. M.; Dan-
iels, A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.;
Tomasi, J.; Barone, V.; Cossi, M.; Cammi, R.; Men-
nucci, B.; Pomelli, C.; Adamo, C.; Clifford, S.; Och-
terski, J.; Petersson, G. A.; Ayala, P. Y.; Cui, Q.; Mo-
rokuma, K.; Malick, D. K.; Rabuck, A. D.;
Raghavachari, K.; Foresman, J. B.; Cioslowski, J.; Or-
tiz, J. V.; Baboul, A. G.; Stefanov, B. B.; Liu, G.; Liash-
enko, A.; Piskorz, P.; Komaromi, I.; Gomperts, R.;
Martin, R. L.; Fox, D. J.; Keith, T.; Al-Laham, M. A.;
Peng, C. Y.; Nanayakkara, A.; Gonzalez, C.; Challa-
combe, M.; Gill, P. M. W.; Johnson, B.; Chen, W.;
Wong, M. W.; Andres, J. L.; Gonzalez, C.; Head-Gor-
don, M.; Replogle, E. S.; Pople, J. A. GAUSSIAN98,
Revision A.7; Gaussian, Inc.: Pittsburgh, 1998.
[22] Discussion will be made in more detail elsewhere.
[23] Allen, F. H.; Kennard, O.; Wattson, D. G.; Brammer,
L.; Orpen, A. G.; Taylor, R. J Chem Soc Perkin Trans
2 1987, S1.
[24] (a) Kronfeld, L. R.; Sass, R. L. Acta Cryst 1968, B24,
981; (b) Goldberg, I.; Schmueli, U. Acta Cryst 1971,
B27, 2173; (c) Faghi, M. S. E. A. E.; Geneste, P.; Olive´,
J. L.; Dubourg, A.; Rambaud, J.; Declercq, J.-P. Acta
Cryst 1987, C43, 2421; (d) Faghi, M. S. E. A. E.; Ge-
neste, P.; Olive´, J. L.; Rambaud, J.; Declercq, J.-P. Acta
Cryst 1988, C44, 498; (e) Douglas, G.; Frampton,
C. S.; Muir, K. W. Acta Cryst 1993, C49, 1197; (f) For
a congested thiophene 1,1-dioxide, see Krebs, A. W.;
Franken, E.; Mu¨ller, M.; Colberg, H.; Cholcha, W.;
Wilken, J.; Ohrenberg, J.; Albrecht, R.; Weiss, E. Tet-
rahedron Lett 1992, 33, 5947.
[9] Yamada, Y.; Yamamoto, T.; Okawara, M. Chem Lett
1975, 361.
[10] (a) Evans, D. A.; Faul, M. M.; Bilodeau, M. T. J Org
Chem 1991, 56, 6744; (b) Takada, H.; Nishibayashi,
Y.; Ohe, K.; Uemura, S. J Org Chem 1997, 62, 6512.
[11] Kubas, G. J. Inorg Synth 1979, 19, 90.
[12] Brunett, E. W.; Altwein, D. M.; McCarthy, W. C. J Het-
erocycl Chem 1973, 10, 1067.
[13] (a) Cram, D. J.; Day, J.; Rayner, D. R.; von Schlitz,
D. M.; Duchamp, D. J.; Garwood, D. C. J Am Chem
Soc 1970, 92, 7369; (b) Yoshimura, T.; Omata, T.; Fu-
rukawa, N.; Oae, S. J Org Chem 1976, 41, 1728; (c)
Otani, T.; Sugihara, Y.; Ishii, A.; Nakayama, J. Chem
Lett 2000, 744.
[14] Nakayama, J.; Yu, T.; Sugihara, Y.; Ishii, A. Chem Lett
1997, 499.
[15] (a) For conversion of sulfoxides to sulfilimines, see
Claus, P.; Vycudilik, W. Monatsh Chem 1970, 101,
396; (b) Lerch, U.; Moffatt, J. G. J Org Chem 1971,
36, 3391; (c) Lerch, U.; Moffatt, J. G. J Org Chem
1971, 36, 3686; (d) Lerch, U.; Moffatt, J. G. J Org
Chem 1971, 36, 3861; (e) Sharma, A. K.; Ku, T.; Daw-
son, A. D.; Swern, D. J Org Chem 1975, 40, 2758.
[16] Bach, T.; Ko¨rber, C. Eur J Org Chem 1999, 1033.
[17] (a) Johnson, C. R. In Comprehensive Organic Chem-
istry; Jones, D. N., Ed.; Pergamon Press: Elmsford,
NY, 1979; Vol. 3, Part 11.11, p 223; (b) Oae, S. In Yuki-
iou Kagaku (Hanno-kiko Hen), Kagakudojin: Kyoto,
Japan, 1982; Chapter 3; (c) Kise, M. In Yuki-iou Ka-
gaku (Gosei-hanno Hen); Oae, S., Ed., Kagakudojin:
Kyoto, Japan 1982; Chapter 7.
[25] Rogers, D. Acta Cryst 1987, A37, 734.
[26] Christiansen, B. W.; Kajaer, A. J Chem Soc Chem
Commun 1969, 169.
[27] (a) Mock, W. L. J Am Chem Soc 1970, 92, 7610; (b)
Jenks, W. S.; Matsunaga, N.; Gordon, M. J Org Chem
1996, 61, 1275; (c) Bongini, A.; Barbarella, G.; Zam-
bianchi, M.; Arbizzani, C.; Mastragostino, M. J Chem
Soc Chem Commun 2000, 439.
[28] Altomare, A.; Cascarano, G.; Giacovazzo, O.; Guag-
liard, A.; Burla, M. C.; Polidori, G.; Camalli, M. J Appl
Cryst 1984, 27, 435.
[18] (a) Kwart, H.; Kahn, A. A. J Am Chem Soc 1967, 89,
1950; (b) Johnson, C. R.; Kirchhoff, R. J.; Reischer,
R. J.; Katekar, G. F. J Am Chem Soc 1973, 95, 4287.
[19] Nakayama, J.; Hasemi, R.; Yoshimura, K.; Sugihara,
Y.; Yamaoka, S. J Org Chem 1998, 63, 4912.
[29] Mallinson, P. R.; Muir, K. W. J Appl Cryst 1985, 28,
31.
[20] (a) Bellamy, L. J. The Infra-red Spectra of Complex