Enhancing the solubility for hypervalent ortho-sulfonyl iodine compounds

Article abstract of DOI:10.1016/j.tet.2010.04.087

The synthesis and characterization of new hypervalent iodine reagents ArINTs (2a), ArIO (3a), and ArIO₂ (4a) (Ar=2-tert-butylsulfonyl-5- tert-butylphenyl) are described. These reagents are compared to previously reported analogous set of reagen

Full text of DOI:10.1016/j.tet.2010.04.087

Tetrahedron 66 (2010) 5768e5774
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Enhancing the solubility for hypervalent ortho-sulfonyl iodine compounds
*
Bindu V. Meprathu, John D. Protasiewicz
Department of Chemistry, Case Western Reserve University, Cleveland, OH 44106, United States
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 6 April 2010
Received in revised form 20 April 2010
Accepted 21 April 2010
Available online 24 April 2010
The synthesis and characterization of new hypervalent iodine reagents ArINTs (2a), ArIO (3a), and ArIO2
(4a) (Ar¼2-tert-butylsulfonyl-5-tert-butylphenyl) are described. These reagents are compared to pre-
viously reported analogous set of reagents Ar¼2-tert-butylsulfonylphenyl and found to have significantly
enhanced solubility and similar chemical reactivity. The X-ray crystal structures of 4a and of ArI (1a)
(Ar¼2-tert-butylsulfonyl-5-tert-butylphenyl) are discussed and compared. These reagents find use in
atom and group transfer reactions.
Keywords:
Polyvalent organoiodine compounds
Iodyl benzene
Ó 2010 Elsevier Ltd. All rights reserved.
Iodoxybenzene
Iodosylbezene
1. Introduction
promoting the solubility of these reagents (while maintaining the
desired reactivity), we have thus examined the impact of a tert-
Polyvalent organoiodine compounds are an extremely impor-
tant class of compounds finding many uses for organic synthesis.1
In 1999, we found that strategic placement of an ortho-tert-butyl
sulfonyl group into the aromatic ring of polyvalent iodobenzenes
could markedly improve their solubility in organic media and af-
ford opportunities to study their crystal structures.2,3 Their en-
hanced solubility have led others to capitalize on these favorable
properties for improving selectivity and to better understand
transition metal catalyzed atom and group transfer reactions in-
volving organoiodine(III) reagents.4e21 The strategy of introducing
elements bringing intramolecular I/E bonds to influence the re-
activity and physical properties of hypervalent iodine compounds
has grown immensely.22,23 In this contribution we present simple
means for enhancing the solubility (and perhaps utility) of ortho-
tert-butyl sulfonyl substituted polyvalent iodobenzenes.
butyl group in the 5-position on the phenyl ring. During this work it
was important to make all steps easy and high yielding in order to
maximize the utility of the reagent.
Iodoarene 1a was prepared by the synthetic route outlined in
Scheme 1. 4-tert-Butylbromobenzene was subjected to halogen/
lithium exchange using Schumann’s protocol and treated with di-
tert-butyldisulfide (t-BuS)2 to obtain intermediate i in 95% yield.
Thioether i was easily oxidized to sulfone ii using excess peracetic
acid. Sulfone ii was transformed to iodoarene 1a, in good yields, by
taking advantage of the ortho-metal directing ability of the
tert-butylsulfone moiety.
Compound 1a served as a convenient entryway to the desired
polyvalent iodine compound. Specifically, it could be readily oxi-
dized to the diacetoxyiodoarene iii, using peracetic acid. This in-
termediate was not isolated, but was prepared and used in situ to
obtain (tosyliminoiodo)arene 2a and iodosylarene 3a (Scheme 2).
These new iodanes were readily identified and characterized by 1H
2. Results and discussion
[ O ]
1) Li
t-Bu
S
t-Bu
Br
Our original attempt at improving the solubility of ortho-tert-
butyl sulfonyl substituted polyvalent iodobenzenes focused on
placement of the p-CF3 group onto the parent iodobenzene ring.24
While a modest gain in solubility was obtained for the iodo-
sylbenzene (ca. 3.7ꢀ), the ArI]NTs species was found to actually be
less soluble. Furthermore, the p-CF3 bearing iodosylbenzene was
less stable than the parent compound. With the objective of further
2) ( t-BuS)2
t-Bu
i, 95 %
I
1) n-BuLi
t-Bu
SO2
t-Bu
t-Bu
SO2
t-Bu
2) I2
ii, 87 %
1a, 78 %
* Corresponding author. E-mail address: protasiewicz@case.edu (J.D.
Protasiewicz).
Scheme 1.
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.04.087

B.V. Meprathu, J.D. Protasiewicz / Tetrahedron 66 (2010) 5768e5774
5769
_
O
IO2
O
I
+
O
O
O
S
I NTs
NaOCl
AcOH
S
S
O
t-Bu
t-Bu
t-Bu
TsNH2 / KOH
MeOH
t-Bu
4a, 94 %
t-Bu
t-Bu
1a
2a, 71 %
O
S
I(OAc)2
O
AcOOH
Scheme 3.
1a
_
O
t-Bu
+
O
S
I
t-Bu
The structure of 4a was conclusively established by an X-ray
structural analysis performed on a crystal of 4a$H2O grown from
a solution in chloroform. As expected, secondary bonding was evi-
dent from one of the sulfonyl oxygen atoms (O3) to the electro-
O
iii
NaOH (aq)
t-Bu
t-Bu
3a, 86 %
ꢀ
positive iodine center (dI/O¼2.704(4) A) (Fig. 1). For comparative
Scheme 2.
purposes, the X-ray structure of compound 1a was also determined
from a crystal grown from slow evaporation of a solution of 1a in
a 1:1 mixture of methanol/dichloromethane, and the results are
shown in Figure 2. Clearly such an interaction is absent in 1a (closest
and 13C NMR spectroscopy, as well by elemental analysis. In par-
ticular, 13C{1H} NMR spectral data for 2a and 3a in CDCl3 display
resonances shifted downfield for the ipso-aromatic carbon atoms at
d 117.8, respectively, relative to 1a (d 94.8) that signal
oxidation of I(I) to I(III).
Iodanes 2a and 3a were found to have pronounced solubility in
chloroform, ca. 8e13 times that of the original soluble analogues 2b
and 3b, respectively (Table 1). Solutions of these oxidants could be
ꢀ
dI/O¼3.190(4) A). The intramolecular secondary bonding in 4a in-
d
115.7 and
duces the I1, C1, C2, S, and O3 atoms to be coplanar, thereby, closely
resembling some cyclic iodyl structures (4b and 5b Chart 1).27,28
Compound 5a is unusual in that the O3/I vector nearly bisects
the O1eIeO2 angle. Most secondary bonds are directed so as to
direct electron density into an IeO
s
*
orbital.25,26 Due to the
Table 1
Comparative solubility data (data for 2b, 3b are from reference3, data for para-CF3 compound are from reference24).
ArI]NTs
Solubility (M) CHCl3
Relative solubility
ArI]O
Solubility (M) CHCl3
0.08
Relative solubility
1
_
NTs
_
O
+
+
O
O
I
O
S
I
O
S
0.14
1
t-Bu
t-Bu
3b
2b
_
NTs
_
O
+
+
I
O
O
I
O
S
O
S
1.06
0.05
7.6
1.08
0.30
13.5
3.7
t-Bu
t-Bu
t-Bu
t-Bu
3a
2a
_
NTs
_
O
+
I
+
I
O
S
O
S
O
O
0.36
t-Bu
t-Bu
CF3
CF3
prepared up to 1 M in chloroform (as determined by integration in
1H NMR spectra using 1,4-dimethoxybenzene as an internal stan-
dard). Solutions of 2a were moderately stable in chloroform,
showing some decomposition (<30%) when monitored over 24 h.
Solutions of 3a in CDCl3, however, were found to rapidly dis-
proportionate, to iodoarene 1a and iodylarene 4a, in the presence
of 1,4-dimethoxybenzene. The solubility of iodosylarene 3a was
determined by measuring the amount of solvent required to form
a homogeneous mixture with a known amount of 3a. Iodanes 2a
and 3a, however, did not display a significant increase in solubility
in acetonitrile over compounds 2b and 3b, respectively. For ex-
ample, a 0.05 M solution of 2a could be prepared in acetonitrile,
which is about twice that of 2b in acetonitrile. It is unclear why the
presence of 1,4-dimethoxybenzene should promote the dispro-
portionation reaction of 3a.
The iodylarene 4a that results from the decomposition of 3a can
be produced more directly by oxidation of 1a with bleach in acetic
acid (Scheme 3) in near quantitative yield. Compound 4a is rea-
sonably soluble in chloroform, and the 13C{1H} NMR spectra of 4a in
CDCl3 display resonance shifted downfield for the ipso-aromatic
Figure 1. X-ray crystal structure of iodylarene 4a$H2O (H2O molecule omitted for
ꢁ
ꢀ
clarity). Selected distances [A] and angles [ ]: I1eO1 1.800(3), I1eO2 1.803(3), I1/O3
2.704(4), I1eC1 2.158(4), S1eO3 1.436(3), S1eO4 1.439(3); C1eI1eO1 95.2(1),
O1eI1eO2 99.3(1), C1eI1eO2 96.1(1), O(1)eI(1)eO(3) 168.2(2).
carbon atoms at
d 146.8 relative to 1a (d 94.8) that indicate oxida-
tion of I(I) to I(V).

5770
B.V. Meprathu, J.D. Protasiewicz / Tetrahedron 66 (2010) 5768e5774
butylphosphine was instantaneously oxidized when treated with
2a to afford 4-methyl-N-(tri-n-butyl phosphoranylidene)-benze-
nesulfonamide in good yields. Triphenylphosphine was also
oxidized to 4-methyl-N-(triphenylphosphoranylidene)-benzene-
sulfonamide, although the reaction took 2 h for completion. CuOTf
catalyzed aziridination of styrene and trans-stilbene using 2a
yielded N-(para-tolylsulfonyl)-2-phenylaziridine and trans-N-
(para-tolylsulfonyl)-2,3-diphenylaziridine in yields comparable to
that obtained by using 4a or PhINTs.
Iodosylarene 3a was found to act as an effective oxo precursor,
readily yielding sulfoxides and triphenylphosphine oxide
(Scheme 5). Manganese catalyzed epoxidations of styrene and
trans-stilbene using 3a as oxidant slowly yielded the corresponding
epoxides over a 2e4 day period. Elevated temperatures decreased
reaction times to 6e12 h, but caused a drop in yields. These yields
are comparable to those obtained by using iodosylarene 4b as the
oxidant under the same reaction conditions.
Iodylarene 4a was also established to serve as a useful oxo do-
nor. Triphenylphosphine was readily oxidized to triphenylphos-
phine oxide upon the addition of a solution of 4a in CDCl3.
Iodoxyarene 4a oxidizes thioethers and olefins (under manganese
ꢀ
Figure 2. X-ray crystal structure of iodoarene 1a. Selected distances [A]: I1eC1 2.109
(4), S1eO1 1.427(3), S1eO2 1.440(3).
_
_
_
_
_
O
O
O
O
2
2
O
2
2
2
_
_
_
_
_
2+
2+
2+
2+
O
O
2+
3
O
O
O
O
3
3
O
I
3
3
O
I
O
I
O
I
1
1
O
I
1
1
1
S
O
O
O
O
S
S
S
S
N
p-Tolyl
i-Pr
t-Bu
N
t-Bu
N
CO2Me
CO2Me
t-Bu
4b
4a
5a
5b
6
Bond
Lengths
4b
(ref 2)
4a
5a*
(ref 27)
5b
(ref 27)
6
(this work)
(ref 28)
dI-O1 (Å)
dI-O2 (Å)
dI-O3 (Å)
1.796
1.806
1.845,
1.832
1.820
1.807
1.822
2.693
1.807
2.709
1.799,
1.793
1.795
2.871
1.786
3.035
3.084,
3.010
*Two independent molecules per asymmetric unit
Chart 1. Comparison of intramolecular I/O]S secondary bonds in some iodylarenes.
increased ring pseudo-size (from 5 to 6 atoms), the geometry of 6
catalysis) to the corresponding sulfoxides and epoxides (Scheme 6).
Epoxidation reactions required long reaction times (days) for
complete consumption of the oxidant. An optimum yield of the
styrene epoxide (57%) was obtained when the reaction was allowed
to proceed for 4 days at room temperature. At elevated temperature
(65 ꢁC) the reaction was complete in 1 h but the yield of epoxide
obtained was reduced to 33%. In the oxidation processes 4a loses
both its oxygen atoms, reducing back to iodoarene 1a.
departs from the others in that the pseudo-ring cannot be planar.
ꢀ
The two IeO bond lengths in 4a were determined to be 1.800(3) A
ꢀ
and 1.803(3) A, which is comparable to the range of such distances
in related compounds having I/O]S contacts (Chart 1).28 Com-
pound 4a, like other iodyl compounds, features additional in-
termolecular contacts in the crystal lattice that yield a pseudo
octahedral geometry for the iodine center in 4a (Fig. 3). Also of note,
molecules of 4a cocrystallize with one molecule of H2O, consistent
with the results of elemental analysis. While hydrogen atoms on the
oxygen atom of the included water were not successfully located,
3. Conclusions
ꢀ
the shortest O/O distance (3.07 A) involves O1, and could indicate
New soluble iodanes containing two substituents in the
iodoarene residue were synthesized and assessed to be moderately
effective oxidants. The added tert-butyl group in iodanes 2a and 3a
provide greater solubility of iodosylarenes and (tosyliminoiodo)
arenes, and importantly, does not significantly change the chemical
reactivity of the reagents. The impact of this group was also evident
in the solubility of iodylarene 4a. This solubility of iodylarenes
should facilitate the further study of these reagents as oxidants. Our
possible HOeH/OeI hydrogen bonding.
Compounds 2a, 3a, and 4a were studied as atom and group
transfer sources in various reactions under conditions that we have
previously reported, and products were identified by 1H NMR
spectroscopy in comparisons to authentic samples.3 (Tosylimi-
noiodo)arene 2a was found to act as a nitrene precursor under
CuOTf catalysis yielding sulfimines in good yields (Scheme 4). Tri-n-

B.V. Meprathu, J.D. Protasiewicz / Tetrahedron 66 (2010) 5768e5774
5771
strategy should also find merit for those seeking to further enhance
the properties of other hypervalent reagents.
4. Experimental section
4.1. General procedures
Alkyllithium reagents were purchased from Aldrich and titrated
with diphenylacetic acid prior to use. Reactions involving the ma-
nipulation of air and water sensitive reagents were performed
under a nitrogen atmosphere using Schlenk techniques. THF was
distilled from sodium benzophenone ketyl. CH2Cl2 and CH3CN were
distilled from calcium hydride. The identities of aziridines, sulfili-
mines, and phosphinimines synthesized in this work were con-
firmed by comparison of spectra and melting points with literature
values. 1H and 13C{1H} NMR spectra were recorded on Varian XL200
or Varian XL 300 spectrometers. Chemical shifts were referenced
internally to residual solvent signals (1H). HRMS spectra were
recorded on a Carlo-Erba Mass Spectrometer. GCeMS spectra were
recorded on an HP5890 Series II Gas Chromatograph equipped with
an HP 5972 Mass Selective Detector. Elemental analyses were
performed by Qualitative Technologies Inc. (QTI), Whitehouse, NJ.
4.2. 4-tert-Butylphenyl tert-butyl thioether (i)
This synthesis was adapted from a literature procedure. In
a 100 mL two-neck flask fitted with a reflux condenser were placed
Li wire (0.208 g, 30.0 mmol) and dry diethyl ether (25 mL) under
argon. To this flask was added 4-tert-butylbromobenzene (2.6 g,
12 mmol) via syringe with constant stirring and the mixture
maintained under reflux conditions to obtain a brown solution. This
solution was then transferred dropwise via cannula into a flask
containing di-tert-butyldisulfide (1.67 g, 9.36 mmol) and the re-
sultant suspension was stirred at ꢂ40 ꢁC for 2 h. The suspension
was then allowed to warm to room temperature and 1 M HCl
(10 mL) and water (10 mL) added. The organic layer was separated
and the aqueous layer extracted with diethyl ether (3ꢀ10 mL). The
combined organic extracts were washed with brine and dried over
MgSO4. The solvents were removed in vacuo to obtain a pale yellow
solid. Recrystallization from diethyl ether yielded a colorless i.
Figure 3. Packing diagram of iodylarene 4a$H2O (hydrogen0 atoms and H2O molecules
0
ꢀ
ꢃꢃꢃ
ꢃꢃꢃ
have been omitted for clarity). Selected distances [A]: I1 O1 2.672(4), I1 O2 2.615(4).
R3P
R3P=NTs
R = Ph, 60 %
R = n-Bu, ~ 95 %
CDCl3
-
O
I
NTs
O
Ar =Ph, R' = Me, 83%
Ar = p-Tolyl, R' = Me, 85%
Ar = Ph, R' = CH2Ph 34%
S
ArSR'
ArR'S=NTs
Ts
t-Bu
CuOTf
R
t-Bu
Yield: 2.11 g (95%). 1H NMR (CDCl3, 200 MHz):
d 7.46 (d, 2H,
2a
N
R
Ph
CuOTf
R = H, 90%
R = Ph, 21%
3JHH¼8.6 Hz), 7.34 (d, 2H, 3JHH¼8.6 Hz), 1.33 (s, 9H), 1.29 (s, 9H). 13
C
Ph
Scheme 4.
{1H} NMR (CDCl3, 50.2 MHz):
31.4, 31.0.
d 151.8, 137.2, 129.2, 125.5, 45.7, 34.7,
Ph3P
4.3. 4-tert-Butylphenyl tert-butylsulfone (ii)
Ph3P=O
~95%
-
To a 100 mL beaker charged with i (1.5 g, 6.7 mmol) were added
30% H2O2 (3 mL) and glacial AcOH (3 mL) and the suspension stir-
red at 80 ꢁC for 3 h. This mixture was allowed to cool to room
temperature and crushed ice was added to precipitate a white solid.
The solid was isolated by filtration, washed successively with water
and cold hexanes. Recrystallization from EtOH afforded a colorless
ArSR'
Ar = Ph, R' = Me, 94%
Ar = p-Tolyl, R' = Me, 88%
Ar = Ph, R' = CH2Ph, 80%
O
I
O
ArS(=O)R'
O
S
t-Bu
R
t-Bu
O
R
R = H, 28%
R = Ph, 28%
Ph
[Mn(Salen)Cl]
3a
Ph
Scheme 5.
ii. Yield: 1.5 g (87%). 1H NMR (CDCl3, 300 MHz):
d 7.79 (d, 2H,
3JHH¼8.6 Hz), 7.55 (d, 2H, 3JHH¼8.6 Hz), 1.35 (s, 18H).
4.4. 2-(tert-Butylsulfonyl)-5-tert-butyliodobenzene (1a)
Ph3P
Ph3P=O
~95%
CDCl3
To a solution of ii (0.500 g, 1.96 mmol) in THF (30 mL) cooled to
ꢂ78 ꢁC was added n-BuLi (0.91 mL of 2.5 M solution in hexanes,
2.3 mmol) dropwise with vigorous stirring. The yellow reaction
mixture was stirred at ꢂ78 ꢁC for 1 h and a solution of iodine
(0.730 g, 2.85 mmol) in THF (20 mL) slowly added via cannula. The
dark brown reaction mixture was stirred at ꢂ78 ꢁC for 1 h and
allowed to warm to room temperature. Excess iodine was quenched
with aqueous Na2S2O3. The organic layer separated and the
ArSR'
Ar = Ph, R' = Me, >95%
Ar = p-Tolyl, R' = Me, >95%
Ar = Ph, R' = CH2Ph, 94%
O
IO2
Ar(S=O)R'
O
CDCl3
S
t-Bu
R
t-Bu
O
R
R = H, 57%
R = Ph, 23%
Ph
[Mn(Salen)Cl]
4a
Ph
Scheme 6.

5772
B.V. Meprathu, J.D. Protasiewicz / Tetrahedron 66 (2010) 5768e5774
aqueous layer extracted with diethyl ether (3ꢀ20 mL). The com-
bined organic extracts were washed with brine and dried over
MgSO4. The solvents were removed in vacuo to obtain a yellow
solid. Recrystallization of this material from EtOH yielded a color-
123.3, 62.1, 36.7, 31.2, 23.9. Anal. Calcd for C14H19O3SI$H2O: C,
40.78; H, 5.13. Found: C, 39.59; H, 5.14.
4.8. Reactions involving 2a
less 1a. Yield: 0.586 g (78%). 1H NMR (CDCl3, 300 MHz):
d 8.11 (d,
4
3
1H, JHH¼2.0 Hz), 7.98 (d, 1H, JHH¼8.4 Hz), 7.52 (dd, 1H,
4.8.1. N-(para-Tolylsulfonyl)-2-phenylaziridine. To a suspension of
4JHH¼1.9 Hz, JHH¼8.4 Hz), 1.42 (s, 9H), 1.33 (s, 9H). 13C{1H} NMR
2a (0.100 g, 0.18 mmol), styrene (0.11 mL, 0.91 mmol), and 4 A
3
ꢀ
(CDCl3, 75.5 MHz):
d
158.3, 141.1, 134.8, 134.2, 125.5, 94.8, 62.4, 34.9,
molecular sieves in CH3CN (1 mL) was injected a solution of
30.9, 24.3. Anal. Calcd for C14H21O2IS: C, 44.22; H, 5.56. Found C,
44.31; H, 5.83.
CuOTf$½C6H6 (4.5 mg, 9 mmol) in toluene (1 mL) to result in a green
suspension. The reaction mixture was stirred at room temperature
for 3 h until all of 2a was consumed and diethyl ether (5 mL) added
to it. The suspension was filtered through a plug of silica gel and
eluted with diethyl ether (5 mL). The solvents were removed in
vacuo and the yield of N-(para-tolylsulfonyl)-2-phenylaziridine was
determined by the addition of 1,4-dimethoxybenzene as an internal
standard to be 90%.
4.5. 2-(tert-Butylsulfonyl)-5-tert-butyl-(tosylimino)
iodobenzene (2a)
Acetic anhydride (2.4 mL) and 30% H2O2 (0.6 mL) were stirred at
42 ꢁC for 4 h. To the resulting solution was added 1a (0.729 g,
1.92 mmol) and the reaction mixture stirred at 30 ꢁC for 24 h
resulting in a pale yellow solution. The progress of the reaction was
monitored by TLC (benzene/silica gel plate) to ensure complete
oxidation of 1a. The solvents were removed in vacuo and the white
pasty solid obtained was treated with an ice-cooled solution of
para-toluenesulfonamide (0.342 g, 2.01 mmol) and KOH (0.360 g,
6.40 mmol) in MeOH (10 mL). The reaction mixture was stirred for
1 h at 0 ꢁC and for 1 h at room temperature to give a pale yellow
precipitate. This material was washed with water and diethyl ether
and dried in vacuo to obtain a yellow solid. Yield: 0.749 g (71%). 1H
4.8.2. trans-N-(para-Tolylsulfonyl)-2,3-diphenylaziridine. To a sus-
pension of 2a (0.08 g, 0.14 mmol), stilbene (0.131 g, 0.729 mmol),
ꢀ
and 4 A molecular sieves in CH3CN (1 mL) was added via syringe
a solution of CuOTf$½C6H6 (3.6 mg, 7.3 mmol) in toluene (1 mL) to
result in a green suspension. The reaction mixture was stirred at
room temperature for 3 h until all of 2a was consumed and diethyl
ether (5 mL) added to it. The suspension was filtered through a plug
of silica gel and eluted with diethyl ether (5 mL). The solvents were
removed in vacuo and the yield of N-(para-tolylsulfonyl)-2,3-
diphenylaziridine determined by 1H NMR integration by using 1,4-
dimethoxybenzene as an internal standard to be 21%.
NMR (CDCl3, 200 MHz):
d
8.44 (d, 1H, 4JHH¼1.18 Hz), 7.85e7.79 (m,
3H), 7.70e7.66 (m, 1H), 7.27e7.21 (m, 2H), 2.39 (s, 3H), 1.45 (s, 9H),
1.41 (s, 9H). 13C{1H} NMR (CDCl3, 75.5 MHz):
d 161.5, 142.0, 140.5,
4.8.3. Methyl phenyl sulfimine. To
a solution of 2a (0.08 g,
133.3, 129.4, 128.8, 128.0, 126.8, 125.9, 115.7, 63.4, 36.5, 30.9, 23.5,
and 21.5. Anal. Calcd for C21H28O4NIS2: C, 45.90; H, 5.13; N, 2.55.
Found: C, 45.77; H, 5.09; N, 2.41. Solubility extent: 0.18 mL of CDCl3
was required to completely dissolve 105 mg of 4. Thus a 1.06 M
solution of 2a in CDCl3 could be prepared.
0.14 mmol) and thioanisole (18.0 mg, 0.15 mmol) in dichloro-
methane (2 mL) was added via syringe a solution of CuOTf$½C6H6
(3.7 mg, 7.3 mmol) in toluene (0.4 mL) to result in a pale yellow
colored solution. The reaction mixture was stirred at room tem-
perature for 48 h, diluted with diethyl ether (2 mL), and passed
through a short plug of silica gel to remove the copper catalyst. The
solvents were removed in vacuo and the yield of methyl phenyl
sulfimine determined by 1H NMR spectrum integration using 1,4-
dimethoxybenzene as an internal standard to be 83%.
4.6. 2-(tert-Butylsulfonyl)-5-tert-butyliodosylbenzene (3a)
Acetic anhydride (6.36 mL, 67.4 mmol) and 30% H2O2 (1.45 mL,
14.2 mmol) were stirred at 42 ꢁC for 4 h. To the resulting solution
was added 1a (2.01 g, 5.28 mmol) and the reaction mixture stirred
at 30 ꢁC for 24 h to result in a pale yellow solution. The progress of
the reaction was monitored by TLC (benzene/silica gel plate) to
ensure complete oxidation of 1a. The solvents were removed in
vacuo and the white pasty solid obtained was treated with aqueous
3 N NaOH (5 mL) at 0 ꢁC to obtain a yellow precipitate. The reaction
mixture was stirred at 0 ꢁC for 1 h and allowed to warm to room
temperature. The yellow solid was isolated by filtration, washed
4.8.4. Benzyl phenyl sulfimine. To
a solution of 2a (0.08 g,
0.14 mmol) and benzyl phenyl sulfide (29.2 mg, 0.15 mmol) in
dichloromethane (2 mL) was added via syringe a solution of
CuOTf$½C6H6 (3.7 mg, 7.3 mmol) in toluene (0.4 mL) to result in
a pale yellow colored solution. The reaction mixture was stirred at
room temperature for 48 h, diluted with diethyl ether (2 mL), and
passed through a short plug of silica gel to remove the copper
catalyst. The solvents were removed in vacuo and the yield of
benzyl phenyl sulfimine determined by 1H NMR spectrum in-
tegration using 1,4-dimethoxybenzene as an internal standard to
be 34%.
with water and diethyl ether and air-dried. Yield: 1.801 g (86%). 1H
4
NMR (CDCl3, 200 MHz):
d
8.06 (d, 1H, JHH¼1.7 Hz), 7.77 (d, 1H,
4
2
2JHH¼8.1 Hz), 7.60 (dd, 1H, JHH¼1.7 Hz, JHH¼8.1 Hz), 1.41 (s, 18H).
13C{1H} NMR (CDCl3, 75.5 MHz):
d 160.4, 132.5, 128.8, 127.0, 124.2,
117.8, 63.2, 36.3, 30.9, 23.5. Anal. Calcd for C15H22O3Cl3IS$CHCl3: C.
34.94; H, 4.3. Found: C, 35.26; H, 4.71.
4.8.5. Methyl para-tolyl sulfimine. To a solution of 2a (0.08 g,
0.14 mmol) and methyl para-tolyl sulfide (29.2 mg, 0.15 mmol) in
dichloromethane (2 mL) was added via syringe a solution of
4.7. 2-(tert-Butylsulfonyl)-5-tert-butyliodylbenzene (4a)
CuOTf$½C6H6 (3.7 mg, 7.3 mmol) in toluene (0.4 mL) to result in
a pale yellow colored solution. The reaction mixture was stirred at
room temperature for 48 h, diluted with diethyl ether (2 mL), and
passed through a short plug of silica gel to remove the copper cat-
alyst. The solvents were removed in vacuo and the yield of methyl
para-tolyl sulfimine determined by 1H NMR spectrum integration
using 1,4-dimethoxybenzene as an internal standard to be 85%.
This synthetic procedure was adapted from the literature. To
a vigorously stirred suspension of 1a (0.500 g, 1.37 mmol) in com-
mercial bleach (5.25% aqueous NaOCl, 3.3 mL, 2.3 mmol) was added
glacial acetic acid (0.66 mL). A white precipitate was seen imme-
diately. The reaction mixture was stirred for 16 h at room temper-
ature, and the white solid isolated by filtration, washed with water
(3ꢀ25 mL), acetone, diethyl ether, and air-dried. Yield: 0.508 g
4 . 8 . 6 . 4 - M e t h yl - N - ( t r i - n - b u t yl p h o s p h o ra n yl i d e n e ) -
benzenesulfonamide. To a solution of 2a (93 mg, 0.17 mmol) in
CDCl3 (0.4 mL) was added tri-n-butylphospine (5.0 mL, 0.2 mmol)
(94%). 1H NMR (CDCl3, 200 MHz):
d
8.69 (s, 1H), 7.76 (m, 2H), 1.40 (s,
18H). 13C{1H} NMR (CDCl3, 75.5 MHz):
d
160.7, 146.8, 131.4, 129.7,

B.V. Meprathu, J.D. Protasiewicz / Tetrahedron 66 (2010) 5768e5774
5773
via syringe. 31P{1H} NMR spectrum recorded after mixing the re-
agents indicated instantaneous oxidation. 1,4-Dimethoxybenzene
(8.0 mg, 0.05 mmol) was added as an internal standard and yield
was determined by 1H NMR spectrum integration to be >95%.
triphenylphosphine oxide in near quantitative yield. 3a was ob-
served to have completely reduced to iodoarene 1a from the 1H
NMR spectrum.
4.10. Reactions involving 4a
4.8.7. 4-Methyl-N-(triphenylphosphoranylidene)-benzenesulfona-
mide. To a solution of 2a (0.01 g, 0.02 mmol) in CDCl3 (0.4 mL) was
added triphenylphosphine (8.0 mg, 0.03 mmol) and the progress of
reaction monitored by periodically recording its 31P{1H} and 1H
NMR spectra. The reaction required several hours to complete at
room temperature and the yield of 4-methyl-N-(triphenylphos-
phoranylidene)-benzenesulfonamide was determined to be 60% by
1H NMR spectral analysis.
4.10.1. Epoxidation of styrene. To a suspension of styrene (0.14 mL,
1.3 mmol) and (1R,2R)-(ꢂ)-[1,2-cyclohexanediamino-N,N0-bis(3,5-
di-tert-butylsalicylidene)]manganese(III)
chloride
(7.9 mg,
12 mmol) in CHCl3 (5 mL) was added 4a (0.10 g, 0.24 mmol) and the
resulting dark brown solution stirred at room temperature for 4
days until all of 4a was consumed. To the solution was added
hexane (10 mL) and passed through a short column of silica gel to
remove the catalyst. The column was eluted with 1:1 mixture of
diethyl ether/hexanes (10 mL). The solvents were removed in vacuo
and to the solid obtained was added 1,4-dimethoxybenzene as an
internal standard and the yield of styrene epoxide determined by
1H NMR integration to be 57%.
4.9. Reactions involving 3a
4.9.1. Epoxidation of styrene. To a suspension of styrene (0.14 mL,
1.3 mmol) and (1R,2R)-(ꢂ)-[1,2-cyclohexanediamino-N,N0-bis(3,5-
di-tert-butylsalicylidene)]manganese(III)
chloride
(7.9 mg,
4.10.2. Epoxidation of stilbene. To a suspension of trans-stilbene
(0.225 g, 1.27 mmol) and (1R,2R)-(ꢂ)-[1,2-cyclohexanediamino-N,
12 mmol) in CH2Cl2 (5 mL) was added 3a (0.100 g, 0.254 mmol), and
the resulting dark brown solution stirred at room temperature (for
2 days), until all of 3a was consumed. To the solution was added
hexane (10 mL), and passed through a short column of silica gel to
remove the catalyst. The column was eluted with of 1:1 mixture of
diethyl ether/hexanes (10 mL). The solvents were removed in vacuo
and to the solid obtained was added 1,4-dimethoxybenzene as an
internal standard and the yield of styrene epoxide determined by
1H NMR spectrum integration to be 28%.
N0-bis(3,5-di-tert-butylsalicylidene)]manganese(III)
chloride
(7.9 mg, 12 mmol) in CHCl3 (5 mL) was added 4a (0.100 g,
0.24 mmol), and the resulting dark brown mixture stirred at 65 ꢁC
for 4 days. To the solution was added 10 mL hexane and passed
through a short column of silica gel to remove the catalyst. The
column was eluted with 1:1 mixture of diethyl ether/hexanes
(10 mL). The solvents were removed in vacuo and to the solid
obtained was added 1,4-dimethoxybenzene as an internal stan-
dard, and the yield of epoxide determined by 1H NMR integration to
be 23%.
4.9.2. Epoxidation of stibene. To a suspension of trans-stilbene
(0.225 g, 1.25 mmol) and (1R,2R)-(ꢂ)-[1,2-cyclohexanediamino-N,
N0-bis(3,5-di-tert-butylsalicylidene)]manganese(III)
chloride
4.10.3. Methyl phenyl sulfoxide (method a). To a solution of 4a
(7.9 mg, 12
mmol) in CH2Cl2 (5 mL) was added 3a (0.100 g,
(18.8 mg, 0.046 mmol) in CDCl3 (0.8 mL) placed in an NMR tube
0.254 mmol), and the resulting dark brown mixture stirred at room
temperature for 4 days. To the solution was added hexane (10 mL)
and passed through a short column of silica gel, to remove the
catalyst. The column was eluted with 1:1 mixture of diethyl ether/
hexanes (10 mL). The solvents were removed in vacuo and to the
solid obtained was added 1,4-dimethoxybenzene as an internal
standard and the yield of stilbene epoxide determined by 1H NMR
spectrum integration to be 28%.
was added thioanisole (5.3 mL, 0.05 mmol) and the tube placed in
an oil bath held at 65 ꢁC. The progress of the reaction was moni-
tored by periodically recording the 1H NMR spectrum. In 48 h all of
thioanisole was oxidized to methyl phenyl sulfoxide and 50% of 4a
remained unreacted.
4.10.4. Methyl phenyl sulfoxide (method b). To a solution of 4a
(14.3 mg, 0.035 mmol) in CDCl3 (0.8 mL) placed in an NMR tube
was added thioanisole (8.2 mL, 0.07 mmol) and the tube placed in
4.9.3. Methyl phenyl sulfoxide. To
0.06 mmol) in CH2Cl2 (2 mL) was added thioanisole (7.6
a
solution of 3a (25 mg,
L,
an oil bath held at 65 ꢁC. The progress of the reaction was moni-
tored by periodically recording the 1H NMR spectrum. In 12 h all of
4a was consumed to quantitatively oxidize thioanisole to methyl
phenyl sulfoxide.
m
0.07 mmol) and the resulting solution stirred at room temperature
for 8 h until all the oxidant was consumed. To the clear solution was
added a measured amount of 1,4-dimethoxybenzene as an internal
standard, and the solvents removed in vacuo. The solid obtained
was dissolved in CDCl3 (0.8 mL) and the yield of methyl phenyl
sulfoxide determined by 1H NMR integration to be 94%.
4.10.5. Methyl para-tolyl sulfoxide (method a). To a solution of 4a
(15.6 mg, 0.038 mmol) in CDCl3 (0.8 mL) placed in an NMR tube
was added methyl para-tolyl sulfide (5.1 mL, 0.04 mmol) and the
tube placed in an oil bath held at 65 ꢁC. The progress of the reaction
was monitored by periodically recording the 1H NMR spectrum. In
48 h all of thioanisole was oxidized to methyl para-tolyl sulfoxide
and 50% of 6 remained unreacted.
4.9.4. Methyl para-tolyl sulfoxide. To a solution of 3a (20 mg,
0.05 mmol) in CH2Cl2 (2 mL) was added methyl para-tolyl sulfide
(7.1 mL, 0.05 mmol), and the resulting solution stirred at room
temperature for 5 h until all of the oxidant was consumed. To the
clear solution was added a measured amount of 1,4-dimethox-
ybenzene as an internal standard, and the solvents removed in
vacuo. The solid obtained was dissolved in CDCl3 (0.8 mL) and the
yield of methyl para-tolyl sulfoxide determined by 1H NMR in-
tegration to be 88%.
4.10.6. Methyl para-tolyl sulfoxide (method b). To a solution of 4a
(15.2 mg, 0.036 mmol) in CDCl3 (0.8 mL) placed in an NMR tube
was added methyl para-tolyl sulfide (9.9 mL, 0.07 mmol) and the
tube placed in an oil bath held at 65 ꢁC. The progress of the reaction
was monitored by periodically recording the 1H NMR spectrum. In
12 h all of 4a was consumed to quantitatively oxidize thioanisole to
methyl para-tolyl sulfoxide.
4.9.5. Triphenylphosphine oxide. To
a solution of 3a (12 mg,
0.03 mmol) in CDCl3 was added triphenylphophine (15 mg,
0.06 mmol) and 1H and 31P{H} NMR spectra recorded after mixing.
4.10.7. Triphenylphosphine oxide. To
a solution of 4a (15 mg,
The
phosphine
was
instantaneously
oxidized
to
0.04 mmol) in CDCl3 (0.4 mL) was added triphenylphophine

5774
B.V. Meprathu, J.D. Protasiewicz / Tetrahedron 66 (2010) 5768e5774
(19 mg, 0.07 mmol) and 1H and 31P{H} NMR spectra recorded after
mixing. The phosphine was instantaneously oxidized to triphe-
nylphosphine oxide in near quantitative yield. Compound 4a was
observed to have completely reduced to iodoarene 1a from the 1H
NMR spectrum.
References and notes
1. Varvoglis, A. The Organic Chemistry of Polycoordinated Iodine; VCH: New York,
NY, 1992.
2. Macikenas, D.; Skrzypczak-Jankun, E.; Protasiewicz, J. D. Angew. Chem., Int. Ed.
2000, 11, 2007e2010.
3. Macikenas, D.; Skrzypczak-Jankun, E.; Protasiewicz, J. D. J. Am. Chem. Soc. 1999,
121, 7164e7165.
4. England, J.; Martinho, M.; Farquhar, E. R.; Frisch, J. R.; Bominaar, E. L.; Munck, E.;
Que, L., Jr. Angew. Chem., Int. Ed. 2009, 48, 3622e3626 S3622/1eS3622/16.
5. Mechanisms in Homogenous and Heterogeneous Epoxidation Catalysis, Oyama,
S. T., ed. 2008, Elsevier, Amsterdam.
6. Lee, S. J.; Cho, S.-H.; Mulfort, K. L.; Tiede, D. M.; Hupp, J. T.; Nguyen, S. T. J. Am.
Chem. Soc. 2008, 130, 16828e16829.
7. Han, H.; Park, S. B.; Kim, S. K.; Chang, S. J. Org. Chem. 2008, 73, 2862e2870.
8. Avenier, F.; Goure, E.; Dubourdeaux, P.; Seneque, O.; Oddou, J.-L.; Pecaut, J.;
Chardon-Noblat, S.; Deronzier, A.; Latour, J.-M. Angew. Chem., Int. Ed. 2008, 47,
715e717.
9. Zdilla, M. J.; Dexheimer, J. L.; Abu-Omar, M. M. J. Am. Chem. Soc. 2007, 129,
11505e11511.
10. Zdilla, M. J.; Abu-Omar, M. M. J. Am. Chem. Soc. 2006, 128, 16971e16979.
11. Collman, J. P.; Zeng, L.; Wang, H. J. H.; Lei, A.; Brauman, J. I. Eur. J. Org. Chem.
2006, 2707e2714.
4.11. X-ray crystallography
Data were collected with a Bruker P4 diffractometer (Mo K
a
ꢀ
radiation l¼0.71073 A). Crystals were mounted at the end of a glass
fiber with superglue. Crystals were judged to be acceptable based
on omega scans and rotation photography. Random search located
reflections to generate reduced primitive cells, cell lengths being
corroborated by axial photography. Additional reflections with 2
q
values between 24.5ꢁ and 25ꢁ were appended to the reflection ar-
rays and yielded the refined cell constants. The symmetry of the
unit cells was confirmed by further examination on the diffrac-
tometer. Data were corrected for absorption (empirical
j scan).
12. Cho, S.-H.; Ma, B.; Nguyen, S. T.; Hupp, J. T.; Albrecht-Schmitt, T. E. Chem.
Direct methods (Siemens SHELXTL PLUS, Version 5.1) revealed all of
the non-hydrogen atoms for 1a and 4a. All non-hydrogen atoms
were refined anisotropically for 1a and 4a, and full crystallographic
details for compounds 1a and 4a are provided within the cif files as
Supplementary data.
Commun. 2006, 2563e2565.
13. Merlau, M. L.; Cho, S.-H.; Sun, S.-S.; Nguyen, S. T.; Hupp, J. T. Inorg. Chem. 2005,
44, 5523e5529.
14. Cho, S.-H.; Walther, N. D.; Nguyen, S. T.; Hupp, J. T. Chem. Commun. 2005,
5331e5333.
15. Cho, S.-H.; Nguyen, S. T.; Hupp, J. T. Top. Catal. 2005, 34, 101e107.
16. Leca, D.; Song, K.; Amatore, M.; Fensterbank, L.; Lacote, E.; Malacria, M. Chem.d
Eur. J. 2004, 10, 906e916.
17. Conry, R. R.; Tipton, A. A.; Striejewske, W. S.; Erkizia, E.; Malwitz, M. A.; Caf-
faratti, A.; Natkin, J. A. Organometallics 2004, 23, 5210e5218.
18. Avenier, F.; Latour, J.-M. Chem. Commun. 2004, 1544e1545.
19. Avenier, F.; Dubois, L.; Latour, J.-M. New J. Chem. 2004, 28, 782e784.
20. Dauban, P.; Dodd, R. H. Synlett 2003, 1571e1586.
21. Gillespie, K. M.; Sanders, C. J.; O’Shaughnessy, P.; Westmoreland, I.; Thickitt, C.
P.; Scott, P. J. Org. Chem. 2002, 67, 3450e3458.
22. Ladziata, U.; Zhdankin, V. V. ARKIVOC (Gainesville, FL, US) 2006, 26e58.
23. Zhdankin, V. V.; Stang, P. J. Chem. Rev. 2002, 102, 2523e2584.
24. Meprathu, B. V.; Protasiewicz, J. D. ARKIVOC (Gainesville, FL, US) 2003, 83e90.
25. Landrum, G. A.; Goldberg, N.; Hoffmann, R.; Minyaev, R. M. New J. Chem. 1998,
22, 883e890.
5. Supplementary data available
Supplementary X-ray structural data for 1a and 4a are avail-
able from the Cambridge Crystallographic Data Centre, 12 Union
Road, Cambridge CB2 1EZ, England (fax: þ44 1223 336033), on
request quoting the deposition numbers CCDC 768414 and CCDC
768415.
Acknowledgements
26. Landrum, G. A.; Hoffmann, R. Angew. Chem., Int. Ed. 1998, 37, 1887e1890.
27. Koposov, A. Y.; Nemykin, V. N.; Zhdankin, V. V. New J. Chem. 2005, 29,
998e1000.
28. Mailyan, A. K.; Geraskin, I. M.; Nemykin, V. N.; Zhdankin, V. V. J. Org. Chem.
2009, 74, 8444e8447.
We thank the CWRU Department of Chemistry and the donors of
The Petroleum Research Fund, administered by the ACS, for support
of this work. We also thank Nihal Deligonul for assistance with the
crystallography files.