New chiral hypervalent iodine(V) compounds as stoichiometric oxidants

Article abstract of DOI:10.1016/j.tet.2010.05.079

The synthesis and application of some new hypervalent iodine compounds bearing chiral and achiral ester motives derived from easily accessible starting materials is presented. The oxidation is carried out using dimethyldioxirane as an oxidant providing the desired compounds in moderate to high yields. A crystal structure analysis for one iodine(V) derivative is investigated. The λ⁵-iodanes are applied as stoichiometric reagents in the oxidation of thioanisole to phenylmethyl sulfoxide, benzyl alcohol to benzaldehyde, and meso-hydrobenzoine to benzaldehyde, benzyl, and benzoin.

Full text of DOI:10.1016/j.tet.2010.05.079

Tetrahedron 66 (2010) 5902e5907
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
New chiral hypervalent iodine(V) compounds as stoichiometric oxidants
*
€
Sabine M. Altermann, Sascha Schafer, Thomas Wirth
School of Chemistry, Cardiff University, Park Place, Main Building, Cardiff CF10 3AT, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis and application of some new hypervalent iodine compounds bearing chiral and achiral
ester motives derived from easily accessible starting materials is presented. The oxidation is carried out
using dimethyldioxirane as an oxidant providing the desired compounds in moderate to high yields.
Received 12 March 2010
Received in revised form 14 May 2010
Accepted 20 May 2010
A crystal structure analysis for one iodine(V) derivative is investigated. The l
5-iodanes are applied as
Available online 25 May 2010
stoichiometric reagents in the oxidation of thioanisole to phenylmethyl sulfoxide, benzyl alcohol to
benzaldehyde, and meso-hydrobenzoine to benzaldehyde, benzyl, and benzoin.
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Hypervalent
Iodine
Oxidation
Dimethyldioxirane
1. Introduction
menthol or borneol. A variety of alcohols was oxidized by penta-
valent iodine compounds bearing ester moieties in the presence of
Pentavalent iodine compounds have proven to be mild oxidizing
agents.1 The iodyl (IOþ2 )-moiety is isoelectronic to ozone and,
therefore, it is likely that reactions employing iodyl compounds
proceed via a comparable mechanism. Iodylarenes are usually
polymeric and cannot be dissolved in ordinary solvents.1c,2 They are
thermally stable unless heated in the absence of solvents: melting
points usually are explosion points.3
TFA, KBr or BF3-etherate.14 As an example, benzaldehyde was
obtained exclusively when benzyl alcohol was stirred together with
KBr as catalyst in chloroform at 50 ꢀC.14 IBX amides oxidized suc-
cessfully primary and secondary alcohols to the corresponding al-
dehydes and ketones without the presence of an acid, in contrast to
non-cyclic iodylarenes such as iodylbenzene (PhIO2). Iodylbenzene
only reacts after appropriate activation such as stirring in DMSO,
since the strong intermolecular bonding between the iodine atom
and an oxygen atom occupies the coordination site at the iodine
atom necessary for reactions.1f,15 After the reaction using penta-
valent iodine compounds bearing chiral amides in the side chain,
the remaining alcohol showed some enantioenrichment of 9%,
when 1-phenylethanol was oxidized in CDCl3 at room temperature
over a time period of 18 h.12
The first iodyl compound, PhIO2, was synthesized by Willgerodt
in 1900.4 Usually, iodylarenes are prepared by treatment of iodoar-
enes with strong oxidants such as peracetic acid,5 sodium hypo-
chlorite,6 peroxymonosulfates7 or diacetyl peroxide.8 One of the
best known iodine(V) compounds is the well-established and
widely used DesseMartin periodinane (DMP).9 The advantage of
DMP is the enhanced stability as well as safety since iodoxybenzoic
acid was experienced to be explosive under excessive heating or
impact.3 Cyclic iodylarenes possess an enhanced stability because
the pentavalent iodine atom is part of a five-membered ring; non-
cyclic iodylarenes have beenreported tohaveexplosiveproperties.10
Some years ago, the synthesis and employment of IBX1f as well
as the corresponding IBX-esters11 and IBX amides12 has been
reported. These esters belong to a new class of pentavalent iodine
compounds with a pseudo-benziodoxole structure and have been
employed successfully in oxidizing alcohols to the respective car-
bonyl derivatives in excellent yields of 95e100%.13 The ester moiety
in these IBX reagents can be derived from chiral moieties such as
A range of differently substituted iodoarenes can be oxidized
with suitable oxidants to obtain
l
5-iodane derivatives. These
hypervalent iodine compounds can then be used in different oxi-
dations or functionalizations.
2. Results and discussion
Some hypervalent (2-iodosylphenyl)acetic acid derivatives
bearing a stereocenter in the benzylic position have been prepared
recently.16 As iodyl compounds are usually prepared by direct ox-
idation of the corresponding iodoarenes with strong oxidizing
agents, we investigated different oxidants such as sodium period-
ate,17 potassium bromate,18 sodium hypochlorite,6 oxone,19 and
dimethyldioxirane (DMDO).20 Iodoarenes are initially oxidized to
* Corresponding author. Tel./fax: þ44 29 2087 6968; e-mail address: wirth@cf.
ac.uk (T. Wirth).
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.05.079

S.M. Altermann et al. / Tetrahedron 66 (2010) 5902e5907
5903
Table 1
Synthesis of iodylarenes 2
the corresponding iodosylarenes, which then disproportionate to
iodylarenes either at room temperature or at elevated tempera-
tures21 or under metal catalysis.22
The starting materials for the iodosylarenes 2aei were synthe-
sized by esterification of either (2-iodophenyl)acetic acid or
2-iodobenzoyl chloride (1a, 1feh) and subsequent deprotonation
in benzylic position and reaction with alkylhalogenides to gain
access to 1b and 1c.23 A secondary alkyl moiety was introduced,
applying the same method, to obtain compounds 1dee.23
Skulski and co-workers have developed a synthetic method
toward iodyl compounds using sodium periodate in water under
reflux in good yields (up to 91%).17 This method was applied to the
disubstituted ester 1d. Unfortunately the 1H NMR analysis of the
crude product showed only traces of the desired iodane. The oxi-
dation of iodoarene 1d with potassium bromate and sulfuric acid
under heating for about 4 h returned only starting material.18 The
mono- and disubstituted methylesters 1b and 1d have also been
treated with oxone16,19 in an aqueous solution at elevated tem-
peratures. In both reactions, only starting material was isolated
after work-up. For the oxidation with sodium hypochlorite,6
(2-iodophenyl)acetic acid was employed as starting material, but
could not be oxidized under these conditions; starting material was
recovered. Compound 1d could also not be oxidized with this
method, the starting material was recovered. Only 1i could be ox-
idized with sodium hypochlorite to the corresponding iodyl com-
pound 2i in 60% yield.
Entry
1
AreI
Product AreIO2
Yield [%]
44
67
2
3
4
5
63
74
98
Dimethyldioxirane (DMDO) has been used in the past to oxidize
iodoarenes to l l
3- and 5-iodanes.20 DMDO was prepared according
to a procedure developed by Murray and Singh from acetone, oxone,
NaHCO3, and water.24 Concentrations of DMDO solutions are gen-
erally low,25 0.07e0.09 M are reported. This is probably due to the
high volatility and inherent instability of the oxidant. In order to
achieve optimumyields, extra care and constant vigilance was taken
with regards to the sealing of the reaction apparatus as well as to
efficient stirring of the reaction mixture using an overhead stirrer.
The product mixture of DMDO in acetone has to be stored at ꢁ20 ꢀC.
A range of iodoarenes was oxidized using a freshly prepared so-
lution of DMDO in acetone. The oxidation of methylester 1d in the
presence of acetic acid in the DMDO-reaction mixture was supposed
to result in the corresponding (diacetoxy)iodo derivative as de-
scribed earlier.20 However, the addition of acetic acid did not make
any difference and the corresponding iodyl compound was formed
as confirmed by 1H NMR spectroscopy (low-field shift of the aro-
6
54
7
8
64
99
matic ortho-proton to
acteristic CeI signal around
d
z8.0 ppm), 13C NMR (absence of the char-
¼95 ppm), IR (strong peak at
d
769 cmꢁ1), and mass spectrometry. Therefore, all reactions were
performed without the addition of acetic acid (Table 1). After re-
action completion, the solvent was evaporated to give colorless
solids; remains of starting materials were removed by washing with
diethyl ether. Yields achieved ranged from promising 44% for 2a
(Table 1, entry 1) to excellent 99% for compound 2i (Table 1, entry 8).
Not all iodyl derivatives could be fully characterized due to the
sometimes very small amounts of iodoarenes and not achieving full
reaction conversion or also due to the possibility of decomposition
of the iodyl compounds.
9a
60
a
Synthesized using 2 equiv NaOCl in AcOH/CH2Cl2 at rt, 3 days.
chloroform or dichloromethane and therefore offering the possi-
bility of mild reaction conditions when used as oxidizing reagents.
Although being a fairly stable compound, a crystal structure was
obtained of the dimethyl-substituted iodylarene 2d (Fig. 1).26
A similar distance between the iodine atom and the ester oxygen
has been found in 2d (2.611e2.933 Å) and some IBX-esters.11 Also,
intermolecular secondary I/O bonding interactions have been
detected. The interaction distance from the iodine atom to iodyl
oxygen atoms of neighboring molecules has been found to range
from 2.654e3.100 Å. The angle of the 3c4e-bond of O10eI3eO9 has
been found to be 101.5(2)ꢀ.
The solubility properties of hypervalent iodine compounds have
generally been found to be low in many organic solvents.1c,2 The
analysis of the crystal structures of iodosyl and iodyl compounds
can explain their poor solubility properties, which are caused by
strong secondary IeO bonds forming a polymer. The effects of the
latter have been investigated thoroughly in the past.21b The solu-
bility of the iodyl compounds 2aei is dependent on structural
features: methylesters with only one or no substituent did not
dissolve in solvents other than dimethylsulfoxide (Table 1, entries
1e3), whereas esters with two or bulkier alkyl substituents as well
as all iodoarenes with a terpene moiety were easily dissolved in

5904
S.M. Altermann et al. / Tetrahedron 66 (2010) 5902e5907
have been carried out. In some cases, the sulfoxides were con-
taminated with impurities, which could not be removed by pre-
parative TLC and a determination of the enantiomeric excess was
not possible.
Initially two reactions were conducted using 1 equiv of mono-
and disubstituted methylesters rac-2b and rac-2e (Table 2, entries 2
and 5) resulting in complete conversions. For the following re-
actions, the amount of oxidant was reduced: 0.8 equiv of achiral
ester 2a also resulted in complete conversion (Table 2, entry 1),
whereas the use of 0.7 equiv seems to be sufficient only for some
reactions (Table 2, entries 4, 6, and 7). The mono-substituted
methylesters rac-2c led to good conversions of 94% (Table 2, entry
3). The difference of the conversion was high, when terpene esters
with a shorter side chain were used: complete conversion was
achieved using the bornyl ester 2f (Table 2, entry 6), whereas only
19% were observed from the use of the respective fenchylester 2h
(Table 2, entry 7). Only 0.5 equiv of methylester rac-2b achieved
a moderate 57% conversion (Table 2, entry 3). The employment of
1 equiv of FIBX resulted in excellent conversion of 99% and 90%
yield (Table 2, entry 8).27
If 1 equiv of oxidant is used, usually excellent conversions were
achieved; the use of lower amounts gave mixed results with no
clear trends being observed. In case of 0.7 equiv, already small
structural differences seem to result in dramatic changes of con-
versions, e.g., the introduction of a methyl group at the benzylic
position in the ortho side chain. The enantiomeric excess for the
reaction with 2h could not be determined due to overlapping sig-
nals with 1h.
IBX was employed in the oxidation of primary and secondary
alcohols at room temperature in dimethylsulfoxide by Frigerio and
Santagostino.28 In order to investigate the oxidation properties of
iodylarenes described here, a range of reagents was employed as
oxidants in the oxidation of benzyl alcohol (Table 3). All reactions
were conducted in dichloromethane or in acetonitrile at room
temperature or at elevated temperature with 1 equiv of an iodyl
derivative.
Figure 1. Crystal structure analysis of 2d indicating secondary interactions.
Bonding features discovered in 2d are very similar to the ones
obtained from the IBX-esters.11 The distances between the iodine
atom and the ester oxygens range between 2.6 and 3.1 Å, distances
to other iodyleoxygen moieties are between 2.6 and 2.9 Å. Like-
wise, 2d can be dissolved in commonly used solvents such as
dichloromethane and chloroform.
Unlike DMP or IBX, iodyl compounds 2aei have not been found
to be explosive, neither when scratched with a spatula nor on
impact. When heated above 150 ꢀC, combustion has been observed
for some iodylarenes, but in most cases only melting or degradation
under discoloration has been observed.
To test possible reactions with compounds 2aei, thioanisole was
oxidized to phenylmethyl sulfoxide. About 0.5e1.0 equiv of the
oxidant was used in order to determine the minimum amount
necessary for a full conversion. The reactions were conducted by
stirring in acetonitrile at 0 ꢀC to improve enantioselectivity, but
then had to be heated up to 50 ꢀC, since conversions were too small
(Table 2). In order to examine the dissolving behavior and oxidation
ability of iodylarenes 2aei, the reactions were performed without
addition of TFA (trifluoroacetic acid), which supports the dissolving.
With enantiomerically pure iodylarenes stereoselective reactions
Table 3
Oxidation of benzyl alcohol to benzaldehyde
Entry
Solvent
Temp
Equiv TFA
Iodylarene
Conversiona
%
1
2
3
4
5
6
7
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH3CN
rt
Reflux
rt
Reflux
rt
Reflux
Reflux
d
2a
2a
rac-2b
rac-2c
2d
11
51
35
100
2
51
Table 2
1.0
d
Oxidation of thioanisole 3 to phenylmethyl sulfoxide 4
1.0
d
d
2d
2i
d
0.2
a
Determined by 1H NMR.
Entry
Equiv
Iodylarene
Conversion %a
4 eec [%]
The employment of the unsubstituted methylester 2a resulted
in only small conversion of 11% if stirred at room temperature. The
addition of trifluoroacetic acid (TFA) and heating improved the
conversion to moderate 51% (Table 3, entries 1 and 2). Moderate
35% conversion was achieved with the methylated ester rac-2b at
room temperature in absence of TFA (Table 3, entry 3). Ethyl ester
rac-2c achieved complete conversion by refluxing in presence of
TFA (Table 3, entry 4). The importance of heating the reaction
mixture was again shown in the reaction of the disubstituted
iodylarene 2d firstly at room temperature resulting in only 2%
conversion, which was improved to 51% conversion simply by
1
2
3
4
5
6
7
8
0.8
1.0
0.5
0.7
1.0
0.7
0.7
1.0
2a
99
99
57
94
99
99
d
d
d
d
d
rac-2b
rac-2b
rac-2c
rac-2e
2f
0
d
2h
FIBX
19
99 (90)b
d
a
Determined by 1H NMR and HPLC.
Yield.
Determined by HPLC on a chiral column (Chiracel OD).
Determination was not possible.
b
c
d

S.M. Altermann et al. / Tetrahedron 66 (2010) 5902e5907
5905
heating (Table 3, entries 5 and 6). On the other hand, the iodyl
derivative 2i resulted in no conversion, even though the reaction
mixture was refluxed overnight (Table 3, entry 7).
sulfoxides, aldehydes, and ketones. However, even though the
iodylarenes employed in the oxidation of thioanisole were enan-
tiomerically pure, the enantiomeric excess could not be determined.
A crystal structure analysis for 2d was obtained and analyzed.
In the following reaction series, some iodylarenes were tested as
suitable oxidants for the enantioselective oxidation of meso-hydro-
benzoin.29 For this purpose, diol 7 was stirred together with the
iodylarene in dichloromethane or acetonitrile at room temperature
or elevated temperatures with or without trifluoroacetic acid (TFA)
(Table 4). Only benzaldehyde 6 was recovered from the reaction
conducted at 65 ꢀC using 2a as oxidant without TFA (Table 4, entry
1); at 40 ꢀC and in the presence of 1 equiv a 1:2 mixture of 6 and 8
was detected (Table 4, entry 2). If TFA was added to the reaction
mixture and stirred at room temperature only benzil 8 was found
(Table 4, entry 3). A product mixture with similar ratios was ob-
served, when methyl- and ethyl-substituted methylesters rac-2b and
rac-2c were employed in refluxing dichloromethane in the presence
of TFA (Table 4, entries 4 and 5). On the other hand, the employment
of FIBX as oxidant at room temperature without TFA resulted in
a product mixture of 6 (30%) and benzoin 9 (70%) (Table 4, entry 6).27
Compound 9 was not detected in any other oxidation reaction.
4. Experimental part
4.1. General
Air-insensitive reactions were conducted in loosely covered
vials. Inert reactions were conducted under an atmosphere of argon
in oven dried glassware. A Büchi GKR-50 Kugelrohr distillation
apparatus was employed for Kugelrohr distillations. Dichloro-
methane was dried over calcium hydride, THF, and diethyl ether
over sodium and benzophenone. All other high purity solvents and
also all chemicals used were purchased from SigmaeAldrich, Alfa
Aesar, Fluka or Acros. NMR spectroscopy was performed on Bruker
DPX 500, DPX 400 or Bruker DPX 250. The chemical shifts
d are
given in parts per million relative to tetramethylsilane. Coupling
constants J are given in Hertz. The multiplicity of signals is desig-
nated: s¼singlet, d¼doublet, t¼triplet, q¼quartet, dt¼doublet of
triplets, td¼triplet of doublets, sex¼sextet, m¼multiplet. Mass
spectroscopic measurements have been performed on Waters LCR
Premier XEdtof. High resolution mass spectrometry for some
compounds was carried out by EPSRC Swansea. Gas Chromatog-
raphy Mass Spectrometry was collected on a PerkineElmer 8700,
beta-column. High Pressure Liquid Chromatography was done on
Shimadzu Class VP. Analytical chiral columns (0.46 cmꢂ25 cm)
were used for separation of enantiomers (Chiracel OB, OB-H, OD-H,
AD) at solvent flow rates of 0.5 mL/min; for preparative separations
Table 4
Oxidation of meso-hydrobenzoin using iodylarenes with and without TFA
Entry Solvent Temperature Equiv Iodyl-arene Yield 6a Yield 8a Yield 9a
[ꢀC]
TFA
[%]
[%]
[%]
1
2
3
4
5
6
CH3CN Reflux
CH3CN 40
CH3CN 20
CH2Cl2 Reflux
CH2Cl2 Reflux
CH3CN 20
d
2a
2a
2a
rac-2b
rac-2c
FIBX
100
32
d
d
d
d
d
of enantiomers
a chiral preparative Chiracel OD column
1.0
1.0
1.0
1.0
d
68
(2 cmꢂ25 cm) was used, the solvent flow rate was 3 mL/min. IR
spectra were collected on a PerkineElmer 1600 series FTIR. Wave
numbers are quoted in cmꢁ1; samples were measure either neat or
as KBr disc. Melting points were measured on a Gallenkamp vari-
able heater and are uncorrected.
d
100
68
65
d
32
35
30 (20)b
70 (64)b
Determined by 1H NMR.
Yield.
a
b
4.2. General procedures (GP)
It is obvious that the temperature as well as the presence of TFA
4.2.1. GP 1: alkylation in benzylic position. To a freshly prepared
LDA solution (1.8 mmol, 1.2 equiv) was added dropwise a solution
of the respective iodoarene ester (1.5 mmol, 1 equiv) in dry THF
at ꢁ78 ꢀC and stirred for 30 min at this temperature. Then the
alkylhalogenide (1.8 mmol, 1.2 equiv) was added dropwise and the
mixture was stirred at room temperature for 2e3 h. After reaction
completion, the mixture was poured into aqueous saturated NH4Cl
(10 mL) and extracted with CH2Cl2 (3ꢂ8 mL). The combined or-
ganic layers were dried over MgSO4 and the solvent was removed
after filtration. If the ester was alkylated twice, the procedure was
repeated with the crude reaction mixture without further purifi-
cation. The crude product was purified by flash chromatography
(petroleum etherediethyl ether 4:1).
takes crucial influence on the products observed. Apart from the
reaction employing FIBX as oxidant, product mixtures of benzal-
dehyde and benzil were found, the latter being the major fraction,
when the product mixtures where heated in presence of TFA. Only
reactions either being heated or conducted in presence of TFA at
room temperature resulted in either benzaldehyde or benzil. When
FIBX was employed at room temperature without TFA, the major
fraction of the reaction mixture was the originally desired product
9. These results suggest the oxidation strength of iodylarenes
synthesized in this project to be greater than the one of FIBX, since
only compounds resulting from over-oxidation of meso-hydro-
benzoin were observed.
Iodylarene 2a was also employed in oxidation reactions of sec-
ondary alcohols, such as cyclopentanol and 2,3-butanediol together
with TFA in dichloromethane at 40 ꢀC, but only starting material
was recovered from these reactions.
4.2.2. GP 2: oxidation using DMPO. An iodoarene was stirred in
a solution of DMDO (1e3 equiv, depending on reaction progress) in
acetone at room temperature for 8 h. After reaction completion, the
solvent was evaporated and the resulting solid washed with diethyl
ether.
3. Conclusion
Several commonly used oxidation methods have been applied to
4.2.3. GP 3: oxidation using NaOCl. CH2Cl2 was added to a vigor-
ously stirred suspension of an iodoarene (1 equiv, 0.5 mmol) and
a 4% aq sodium hypochlorite solution (2 mL) and then acetic acid
(0.5 mL) was added dropwise during 10 min at room temperature.
The resulting mixture was stirred overnight. The reaction mixture
was then extracted with CH2Cl2 (5ꢂ10 mL). The combined extracts
were washed with aqueous saturated NaHCO3 solution (6 mL),
iodoarenes. The desired l
5-iodanes could be synthesized and iso-
lated in good to excellent yields. These iodylarenes were sub-
sequently employed as oxidants for different substrates, in order to
determine their oxidative potential. Sulfides like thioanisole, pri-
maryalcohols, such as benzyl alcohol and secondaryalcohols such as
meso-hydrobenzoin were oxidized successfully to the respective

5906
S.M. Altermann et al. / Tetrahedron 66 (2010) 5902e5907
dried over MgSO4. The solvent was evaporated under reduced
pressure after filtration to afford the crude product.
together with acetic acid (258
room temperature. Yield: 74% (507 mg, 1.51 mmol), colorless solid.
Decomposition point: 150 ꢀC. IR (neat) (
): 3417.5 (m) (H2O), 2965.6
mL, 4.50 mmol, 2.2 equiv) for 24 h at
n
4.2.3.1. 2-Methyl-(2-iodophenyl)propionic acid methylester 1d.
Synthesisaccording toGP 1 from1a (338 mg,1.20 mmol) andmethyl
iodide (208 mg,1.50 mmol). After work-up and solvent evaporation,
the procedure was repeated. The product was purified by flash col-
umn chromatography (petrol ether:diethyl ether 4:1). Yield: 75%
(m), 1699.5 (s),1458.4 (s),1433.3 (m),1282.7 (s),1252.6 (s), 1152.1 (s),
1101.9 (m), 976.4 (m), 850.9 (m), 775.5 (s), 740.4 (s) cmꢁ1. 1H NMR
(500 MHz, CDCl3):
d
¼1.77 (s, 6H, 4,5-CH3), 3.82 (s, 3H, 1-CH3),
7.49e7.55 (m, 3H, 7,8,9-CH), 8.37 (d, 1H, J¼7.5 Hz, 10-CH). 13C NMR
(125 MHz, CDCl3):
d
¼29.1 (4,5-C), 47.2 (3-C), 54.5 (1-C), 127.5, 127.6,
(274 mg, 900
m
mol), yellowoil.1H NMR (250 MHz, CDCl3):
d
¼1.63 (s,
129.7, 133.0, 142.6 (6-C), 150.1 (11-C), 180.5 (2-C) ppm. m/z (ESI)¼
337.0(6),322.0(45), 305.0(3),196.1(100),177.0(7),119.1(4), 52.1(41),
44.1 (8). Exact mass within error limits could not be determined.
6H, 4,5-CH3), 3.67 (s, 3H, 1-CH3), 6.79 (td, 1H, J¼7.8, 2.2 Hz, 9-CH),
7.33e7.43 (m, 2H, 7,8-CH), 7.77 (dd,1H, J¼7.8,1.2 Hz,10-CH) ppm.13C
NMR (62.5 MHz, CDCl3):
d
¼26.6 (4,5-C), 49.4 (3-C), 52.2 (1-C), 98.6
(11-C), 126.3, 127.3, 129.6, 132.9, 145.9 (6-C), 176.3 (2-C) ppm. Ma-
terial was used directly in oxidation reaction.
4.2.3.6. (ꢃ)-2-(2-Iodoxyphenyl)-2-propylpropionic acid methyl-
ester rac-2e. According to GP 2 rac-1e (83.9 mg, 218 mmol) was
stirred in a solution of DMDO in acetone (53.2 mM, 4.1 mL,
218 mol, 1 equiv) for 8 h at room temperature. Yield: 54%
(48.8 mg,117
mol), colorless solid. Decomposition point: 153 ꢀC. IR
(KBr) ( ): 3434.6 (m), 3053.1 (w), 2944.1 (s), 2856.9 (m), 1709.0 (s),
1469.2 (m), 1452.8 (s), 1431.0 (s), 1371.1 (w), 1294.8 (m), 1267.5 (s),
1245.7 (s), 1202.1 (m), 1136.7 (s), 1076.8 (m), 973.2 (m), 929.6 (w),
853.3 (w), 771.6 (s), 722.5 (s), 586.3 (w) cmꢁ1. 1H NMR (500 MHz,
4.2.3.2. (2-Iodoxyphenyl)acetic acid methylester 2a. Synthesis
m
according to GP 2 1a (190 mg, 690
DMDO in acetone (65.7 mM, 21.0 mL, 1.38 mmol, 2 equiv) for 8 h at
room temperature. Yield 44% (94.2 mg, 306 mol), colorless solid.
Decomposition point: 141e142 ꢀC. IR (KBr) (
): 3374.3 (m) (H2O),
2922.6 (m), 1699.5 (s), 1673.0 (m), 1439.1 (s), 1358.2 (s), 1278.1 (s),
1250.6 (s), 1160.9 (s), 989.3 (s), 786.3 (s), 755.5 (s) cmꢁ1 1H NMR
(500 MHz, DMSO-d6):
mmol) was stirred in a solution of
m
n
m
n
.
CDCl3):
d
¼0.91 (t, 3H, 6-CH3), 1.08e1.13 (m, 1H, 5-CHA), 1.21e1.28
d
¼3.73 (s, 3H, 9-CH3), 4.24 (s, 2H, 7-CH2),
(m,1H, 5-CHB),1.75 (s, 3H, 7-CH3), 2.02e2.15 (m, 2H, 4-CH2), 3.87 (s,
3H, 1-CH3), 7.49 (dd, 1H, J¼7.9, 1.4 Hz, 9-CH), 7.59 (td, 1H, J¼7.9,
1.4 Hz, 10- or 11-CH), 7.67 (td, 1H, J¼7.2, 1.4 Hz, 10- or 11-CH), 8.45
(dd, 1H, J¼8.0, 1.4 Hz, 12-CH) ppm. 13C NMR (125 MHz, CDCl3):
7.40 (d, 1H, J¼7.5 Hz, 5-CH), 7.52 (t, 1H, J¼7.4 Hz, 3- or 4-CH), 7.61 (t,
1H, J¼7.6 Hz, 3- or 4-CH), 7.99 (d, 1H, J¼7.8 Hz, 2-CH) ppm. 13C NMR
(125 MHz, DMSO-d6):
d
¼38.6 (7-C), 53.2 (9-C), 127.7, 129.1, 132.3,
132.4, 134.0 (6-C), 151.1 (1-C), 173.6 (8-C) ppm. m/z (EI)¼276.0 (5),
231.8 (5), 216.9 (33), 149.0 (100), 121.0 (46), 90.0 (53), 63.0 (32).
Molecular peak could not be obtained. HRMS (ESI): found [MþH]þ
308.9619, C9H10O4I requires 308.9618.
d
¼14.5 (6-C), 18.5 (5-C), 25.2 (7-C), 45.3 (4-C), 51.3 (1-C), 54.5 (3-C),
127.5, 128.4, 129.9, 133.2, 133.7 (8-C), 141.3 (13-C), 180.8 (2-C) ppm.
m/z (ESI)¼729.0 (100), 365.0 (79), 331.0 (1), 232.0 (3), 205.1 (64).
HRMS (ESI): [MþH]þ found 365.0235, C13H18O4I requires 365.0250.
4.2.3.3. (ꢃ)-2-(2-Iodoxyphenyl)propionic acid methylester rac-
4.2.3.7. 2-Iodoxyphenyl-1-(1S)-endo-bornylether 2f. According
2b. According to GP 2 rac-1b (200 mg, 690
m
mol) was stirred in
to GP 2 1f (83.9 mg, 218
acetone (53.2 M, 4.1 mL, 218
perature. Yield: 54% (48.8 mg, 117
(c 0.205, DMSO). IR (KBr) ( ): 3434.6 (m), 3053.1 (w), 2955.0 (s),
mmol) was stirred in a solution of DMDO in
a solution of DMDO in acetone (65.7 mM, 21.0 mL, 1.38 mmol,
2 equiv) for 8 h at room temperature. Yield: 67% (150 mg,
m
mol, 1 equiv) for 8 h at room tem-
25
m
mol). Mp 150 ꢀC. [
a
]
ꢁ2.0
D
465
m
mol) colorless solid. Mp 158 ꢀC. IR (KBr) (
n
): 3448.6 (m) (H2O),
n
3060.0 (s), 2947.7 (m), 1734.7 (m), 1457.9 (s), 1432.9 (m), 1282.4 (s),
2867.8 (m), 2355.5 (w), 1725.4 (m), 1681.8 (s), 1583.7 (m), 1458.3
(m), 1376.6 (m), 1311.2 (s), 1251.2 (m), 1142.2 (s), 1109.5 (s), 1038.6
(m), 1016.8 (m), 973.2 (m), 886.0 (w), 771.6 (s), 744.3 (s), 678.9 (m),
1263.6 (s),1204.8 (s),1115.6 (m),1078.0 (s), 724.6 (m) cmꢁ1. 1H NMR
(500 MHz, DMSO-d6):
d
¼1.56 (d, 3H, J¼7.0 Hz, 4-CH3), 3.67 (s, 3H,
1-CH3), 4.67 (q, 1H, J¼7.0 Hz, 3-CH), 7.46 (dd, 1H, J¼7.2, 1.5 Hz,
6-CH), 7.54e7.60 (m, 2H, 7,8-CH), 8.07 (dd, 1H, J¼7.5, 1.8 Hz, 9-CH)
635.3 (w) cmꢁ1. 1H NMR (500 MHz, CDCl3):
d¼0.91 (s, 3H, 10-CH3),
0.93 (s, 3H, 8-CH3), 0.96 (s, 3H, 100-CH3), 1.17 (dd, 1H, J¼13.9, 3.5 Hz,
bornyl), 1.27e1.34 (m, 1H, bornyl), 1.42e1.48 (m, 1H, bornyl),
1.73e1.86 (m, 2H, bornyl), 2.01e2.13 (m, 1H, bornyl), 2.47e2.53
(m, 1H, bornyl), 5.17e5.22 (m 1H, 2-CH), 7.72 (t, 1H, J¼7.5 Hz, 14-
CH), 7.95e8.00 (m, 1H, 13-CH), 8.13 (d, 1H, J¼7.6 Hz, 12-CH), 8.50 (d,
ppm. 13C NMR (125 MHz, DMSO-d6):
d
¼18.7 (4-C), 49.7 (3-C), 53.0
(1-C), 128.2, 128.9, 129.5, 132.6, 140.0 (5-C), 151.2 (10-C), 174.4 (2-C)
ppm. m/z (ESI)¼509.0 (2), 413.3 (7), 391.3 (52), 345.0 (26), 323.0
(100), 319.0 (68), 305.0 (21), 161.1 (10). HRMS (ESI): [MþH]þ found
322.9778, C10H12O4I requires 322.9775.
1H, J¼7.8 Hz, 15-CH) ppm. 13C NMR (125 MHz, CDCl3):
¼14.0 (8-C),
d
19.2 (10- or 100-C), 20.0 (100- or 10-C), 27.6, 28.3, 37.0, 45.2, 48.4,
49.7, 84.8 (2-C), 123.2, 125.2, 127.3, 130.8, 133.2 (11-C), 135.5 (16-C),
168.8 (17-C) ppm. m/z (ESI)¼480.0 (30), 417.0 (9), 384.9 (3), 343.9
(6), 321.9 (100), 304.9 (22), 263.9 (16), 232.0 (5), 213.0 (4). HRMS
(ESI): [MþH]þ found 417.0554, C17H22O4I requires 417.0563.
4.2.3.4. (ꢃ)-1-Ethyl-1-(2-iodoxyphenyl)acetic acid methylester
rac-2c. According to GP 3 rac-1c (208 mg, 684 mmol) was stirred in
a solution of DMDO in acetone (54.0 mM, 12.0 mL, 648
1.06 equiv) for 24 h at room temperature. Yield: 63% (144 mg,
428 ):
mol), colorless solid. Combustion point: 166 ꢀC. IR (KBr) (
2969.8 (m), 2945.3 (m), 2875.8 (s), 1734.2 (m), 1470.0 (s), 1431.9 (s),
1318.1 (s), 1263.6 (s), 1245.8 (s), 1203.9 (s), 1155.6 (m), 734.3 (m) cmꢁ1
1H NMR (500 MHz, DMSO-d6):
mmol,
m
n
4.2.3.8. 2-Iodoxybenzoic acid (2R,4R,7R)-menthylester 2g. Acc-
.
ording to GP 2 1g (65.4 mg, 169
DMDO in acetone (54.5 M, 3.1 mL,169
temperature. Yield: 64% (45.1 mg, 108 mmol), colorless solid. De-
mmol) was stirred in a solution of
d
¼0.88 (t, 3H, J¼7.3 Hz, 5-CH3),
mmol,1 equiv) for 8 h at room
1.83e1.92 (m,1H, 4-CHA), 2.09e2.18 (m,1H, 4-CHB), 3.61 (s, 3H,1-CH3),
4.25 (dd,1H, J¼8.4, 6.5 Hz, 3-CH), 7.41 (dd,1H, J¼6.2,1.3 Hz, aromatic),
7.48e7.54 (m, 3H, aromatic), 8.03e8.05 (m, 1H, 10-CH) ppm. 13C NMR
composition point: 180 ꢀC. [
a
]
25 þ20.0 (c 0.10, DMSO). IR (KBr) (
n):
D
2965.0 (m), 2924.0 (m), 2876.3 (m),1607.4 (m),1562.5 (s),1438.2 (s),
(125 MHz, DMSO-d6):
d
¼11.8 (5-C), 24.7 (4-C), 49.5 (3-C), 52.0 (1-C),
1340.8 (m), 832.1 (m), 742.0 (s), 695.2 (s) cmꢁ1. 1H NMR (500 MHz,
124.9,128.1, 128.2, 131.7, 137.2 (6-C), 150.7 (11-C), 172.9 (2-C) ppm. m/z
(ESI)¼391.3 (3), 359.0 (9), 337.0 (100), 333.0 (11), 303.0 (4), 175.1 (6).
HRMS (ESI): [MþH]þ found 336.9934, C11H14O4I requires 336.9931.
CDCl3):
d
¼0.79 (d, 3H, J¼6.9 Hz, 10-CH3), 0.82e0.88 (m, 1H,
menthyl), 0.93 (d, 3H, J¼7.0 Hz, 9-CH3), 0.95 (d, 3H, J¼6.9 Hz, 90-
CH3), 1.12e1.18 (m, 1H, menthyl), 1.21 (t, 1H, J¼6 Hz, menthyl),
1.54e1.65 (m, 2H, menthyl), 1.74e1.79 (m, 2H, menthyl), 1.86e1.93
(m, 1H, menthyl), 2.15e2.22 (m, 1H, menthyl), 5.05 (td, 1H, J¼11.1,
4.6 Hz, 2-CH), 7.76 (td, 1H, J¼7.5, 1.0 Hz, 14-C), 8.00 (td, 1H, J¼7.5,
1.3 Hz, 13-C), 8.14 (dd, 1H, J¼7.6, 1.2 Hz, 12-C), 8.53 (d, 1H, J¼7.9 Hz,
4.2.3.5. 1,1-Dimethyl-1-(2-iodoxyphenyl)acetic acid methylester
2d. According to GP 2 1d (622 mg, 2.05 mmol) was stirred in a solu-
tion of DMDO in acetone (69.0 mM, 60 mL, 4.09 mmol, 2 equiv)

S.M. Altermann et al. / Tetrahedron 66 (2010) 5902e5907
5907
15-C) ppm. 13C NMR (125 MHz, CDCl3):
d
¼16.9 (10-C), 21.0 (9- or 90-
Hypervalent Iodine Chemistry: Modern Developments in Organic Synthesis;
Wirth, T., Ed.; Springer: Berlin, Heidelberg, 2003; (e) Wirth, T. Angew. Chem.
2005, 117, 3722e3731; Angew. Chem., Int. Ed. 2005, 44, 3656e3665; (f) Wirth, T.
Angew. Chem. 2001, 113, 2893e2895; Angew. Chem., Int. Ed. 2001, 40,
2812e2814.
2. (a) Nicolaou, K. C.; Baran, P. S.; Zhong, Y.-L.; Sugita, K. J. Am. Chem. Soc. 2002,
124, 2212e2220; (b) Nicolaou, K. C.; Baran, P. S.; Zhong, Y.-L. J. Am. Chem.
Soc. 2002, 124, 2221e2232; (c) Nicolaou, K. C.; Montagnon, T.; Baran, P. S.
Angew. Chem. 2002, 114, 993e996; Angew. Chem., Int. Ed. 2002, 41,
1035e1038; (d) Nicolaou, K. C.; Baran, P. S.; Zhong, Y.-L.; Barluenga, S.; Hunt,
K. W.; Kranich, R.; Vega, J. A. J. Am. Chem. Soc. 2002, 124, 2233e2244;
(e) Nicolaou, K. C.; Baran, P. S.; Zhong, Y.-L.; Sugita, K. J. Am. Chem. Soc. 2002,
124, 2245e2258.
C), 22.2 (90- or 9-C), 23.9, 26.9, 31.9, 34.3, 40.9, 47.5, 79.5 (2-C),125.1,
130.8, 133.5, 135.5, 139.5 (11-C), 147.7 (16-C), 167.8 (1-C) ppm. m/z
(ESI)¼482.1 (79), 419.1 (24), 384.9 (12), 343.9 (48), 321.9 (100), 305.9
(54), 288.9 (48), 264.9 (40), 247.9 (38), 232.0 (4), 213.0 (6). HRMS
(ESI): [MþH]þ found 419.1711, C17H24O4I requires 419.1719.
4.2.3.9. 2-Iodoxybenzoic acid (2R)-endo-fenchylester 2h. Accord-
ing to GP 2 1h (73.7 mg, 192
DMDO in acetone (53.9 mM, 3.6 mL, 192
room temperature. Yield: 99% (79.3 mg, 190
m
mol) was stirred in a solution of
mol, 1 equiv) for 8 h at
mol), colorless solid.
): 3439.5 (m),
m
3. IBX and DMP tend to be explosive due to impact or heating over 200 ꢀC Plumb,
J. B.; Harper, D. J. Chem. Eng. News 1990, 68, 3.
4. Willgerodt, C.; Howells, V. A. Chem. Ber. 1900, 33, 841e851.
5. Sharefkin, J. G.; Saltzman, H. Org. Synth. 1963, 43, 65e67.
6. Katritzky, A. R.; Savage, G. P.; Gallos, J. K.; Durst, H. D. Org. Prep. Proced. Int. 1989,
21, 157e162.
7. (a) Gakovic, Z.; Morgan, K. J. J. Chem. Soc. B 1967, 416e418; (b) Bamberger, E.;
Hill, A. Ber. Dtsch. Chem. Ges. 1900, 33, 533e536; (c) Kennedy, R. J.; Stock, A. M.
J. Org. Chem. 1960, 25, 1901e1906.
8. Arbusov, I. T. Kazansk. Chim. Techn. Inst. 1936, 1, 201e202.
9. (a) Dess, D. B.; Martin, J. B. J. Am. Chem. Soc. 1991, 113, 7277e7287; (b) Dess, D. B.;
Martin, J. B. J. Org. Chem. 1983, 48, 4155e4156.
10. (a) Stang, P. J.; Zhdankin, V. V. Chem. Rev.1996, 96,1123e1178; (b) Katritzky, A. R.;
Savage, G. P.; Palenic, G. J.; Quian, K.; Zhang, Z.; Durst, H. D. J. Chem. Soc., Perkin
Trans. 2 1990, 1657e1661; (c) Dess, D. B.; Wilson, S. R.; Martin, J. C. J. Am. Chem.
Soc. 1993, 115, 2488e2495; (d) Katritzky, A. R.; Savage, G. P.; Gallos, J. K.;
Durst, H. D. J. Chem. Soc., Perkin Trans. 2 1990, 1515e1518; (e) Weclas-Henderson,
L.; Nguyen, T. T.; Hayes, R. A.; Martin, J. C. J. Org. Chem. 1991, 56, 6565e6573.
11. Zhdankin, V. V.; Litvinov, D. N.; Koposov, A. Y.; Luu, T.; Ferguson, M. J.; McDo-
nald, R.; Tykwinski, R. R. Chem. Commun. 2004, 106e107.
m
25
Mp 163 ꢀC. [
a
]
þ24.0 (c 0.20, DMSO). IR (KBr) (
n
D
3064.0 (w), 2954.9 (s), 2871.5 (m), 2363.5 (w), 2322.6 (w), 1725.4
(m), 1681.8 (s), 1583.7 (m), 1458.3 (m), 1365.7 (m), 1340.0 (s),
1300.3 (s), 1136.8 (s), 1109.5 (s), 1033.2 (m), 984.1 (m), 967.8 (m),
771.6 (s), 738.9 (s), 640.8 (m), 613.5 (m) cmꢁ1. 1H NMR (500 MHz,
CDCl3):
d
¼0.84 (s, 3H, 8-CH3), 1.12 (s, 3H, 10-CH3), 1.20 (s, 3H, 100-
CH3), 1.20e1.28 (m, 1H, fenchyl), 1.30 (dd, 1H, J¼10.5, 1.4 Hz,
fenchyl), 1.51e1.58 (m, 1H, fenchyl), 1.66e1.71 (m, 1H, fenchyl),
1.74e1.82 (m, 2H, fenchyl), 1.85e1.91 (m, 1H, fenchyl), 4.70 (d, 1H,
J¼1.1 Hz, 2-CH), 7.74 (td, 1H, J¼7.5, 1.0 Hz, 14-CH), 7.98 (td, 1H,
J¼7.8, 1.3 Hz, 13-CH), 8.15 (dd, 1H, J¼7.6, 1.3 Hz, 12-CH), 8.51
(dd, 1H, J¼7.9, 0.8 Hz, 15-CH) ppm. 13C NMR (125 MHz, CDCl3):
d
¼19.8 (8-C), 20.5, 26.0, 27.1, 29.9, 40.4, 41.7, 48.5, 49.1, 90.7 (2-C),
125.2, 127.1, 130.6, 133.3, 135.5 (11-C), 146.3 (16-C), 168.7 (1-C)
ppm. m/z (ESI)¼480.1 (100), 417.1 (19), 384.9 (9), 343.9 (47), 321.9
(46), 305.9 (20), 264.9 (19), 247.9 (13), 165.1 (2). HRMS (ESI):
[MþH]þ found 417.0553, C17H22O4I requires 417.0563.
12. Zhdankin, V. V.; Koposov, A. Y.; Netzel, B. C.; Yashin, N. V.; Rempel, B. P.; Fer-
guson, M. J.; Tykwinski, R. R. Angew. Chem. 2003, 115, 2244e2246; Angew.
Chem., Int. Ed. 2003, 42, 2194e2196.
13. Zhdankin, V. V.; Koposov, A. Y.; Litvinov, D. N.; Ferguson, M. J.; McDonald, R.;
Luu, T.; Tykwinski, R. R. J. Org. Chem. 2005, 70, 6484e6491.
14. Tohma, H.; Takizawa, S.; Maegawa, T.; Kita, Y. Angew. Chem. 2000, 112,
1362e1364; Angew. Chem., Int. Ed. 2000, 39, 1306e1308.
15. (a) Varvoglis, A. Hypervalent Iodine in Organic Synthesis; Academic: London,
1997; (b) Zhdankin, V. V.; Stang, P. J. Chem. Rev. 2002, 102, 2523e2584;
(c) Tohma, H.; Kita, Y. Top. Curr. Chem. 2003, 224, 209e248.
16. Quideau, S.; Lyvinec, G.; Marguerit, M.; Bathany, K.; Ozanne-Beaudenon, A.;
Buffeteau, T.; Cavagnat, D.; Chénedé, A. Angew. Chem. 2009, 121, 4675e4679;
Angew. Chem., Int. Ed. 2009, 48, 4605e4609.
17. Kazmierczak, P.; Skulski, L.; Kraszkiewicz, L. Molecules 2001, 6, 881e891.
18. Banerjee, A.; Banerjee, G. C.; Bhattacharya, S.; Banerjee, S.; Samaddar, H. J.
Indian Chem. Soc. 1981, 58, 605e607.
19. Fragerio, M.; Santagostino, M.; Sputore, S. J. Org. Chem. 1999, 64, 4537e4538.
20. Bravo, A.; Fontana, F.; Fronza, G.; Minisci, F.; Serri, A. Tetrahedron Lett. 1995, 36,
6945e6948.
21. (a) Meprathu, B. V.; Justik, M. W.; Protasiewicz, J. D. Tetrahedron Lett. 2005, 46,
5187e5190; (b) Macikenas, D.; Skrzypczak-Jankun, E.; Protasiewicz, J. D. Angew.
Chem. 2000, 112, 2063e2066; Angew. Chem., Int. Ed. 2000, 39, 2007e2010.
22. Yusubov, M. S.; Chi, K.-W.; Park, J. Y.; Karimov, R.; Zhdankin, V. V. Tetrahedron
Lett. 2006, 47, 6305e6308.
4.2.3.10. 2-Iodoxybenzoic acid propylester 2i. According to GP 3
1j (58.0 mg, 200
m
mol) was stirredtogether with NaOCl (2.0 mL) and
L) in CH2Cl2 (8 mL) at room temperature for 3 days.
mol), colorless solid. Decomposition
): 3417.5 (w) (H2O), 2965.6 (w),1679.4 (m),1584.0
(w), 1463.5 (w), 1393.2 (w), 1302.8 (m), 1142.1 (w), 1112.0 (w), 750.4
(m) cmꢁ1.1H NMR (500 MHz, CDCl3):
acetic acid (200
m
Yield: 60% (38.8 mg, 120
m
point: 186 ꢀC. IR (
n
d¼1.02 (t, 3H, J¼7.4 Hz,1-CH3),
1.82 (sex, 2H, J¼7.1 Hz, 2-CH2), 4.33 (t, 2H, J¼6.7 Hz, 3-CH2), 7.66 (t,
1H, J¼7.5 Hz, 7- or 8-CH), 7.92 (t, 1H, J¼7.4 Hz, 7- or 8-CH), 8.09 (d,
1H, J¼7.2 Hz, 6-CH), 8.43 (d, 1H, J¼7.9 Hz, 9-CH) ppm. 13C NMR
(125 MHz, CDCl3):
d
¼10.7 (1-C), 22.1 (2-C), 69.0 (3-C), 125.2, 126.8,
130.6, 132.2, 135.3 (5-C), 149.9 (10-C), 168.4 (4-C) ppm. m/z (ESI)¼
322.9 (100), 321.9 (26), 305.9 (12), 280.9 (9), 264.9 (6), 202.1 (3).
HRMS (ESI): [MþH]þ found 322.9776, C10H12O4I requires 322.9780.
23. Compounds 1ae1c, 1e, and 1fe1h were fully characterized earlier: Altermann,
S. M.; Richardson, R. D.; Page, T. K.; Schmidt, R. K.; Holland, E.; Mohammed, U.;
Paradine, S. M.; French, A. N.; Richter, C.; Bahar, A. M.; Witulski, B.; Wirth, T. Eur.
J. Org. Chem. 2008, 5315e5328 Commercially available 1j was used.
24. Murray, R. W.; Singh, M. Org. Synth. 1997, Coll. Vol. 74, 91e100.
25. The concentration of the solution of DMDO in acetone was determined by the
reaction of 1 mL of the DMDO solution with 30 mg trans-stilbene; from the
conversion determined from the 1H NMR spectrum of the reaction mixture,
the concentration of the DMDO was calculated.
Acknowledgements
We thank the EPSRC National Mass Spectrometry Service Cen-
tre, Swansea, for mass spectrometric data and EPSRC for funding
this project (S.M.A.). This work was also supported by the Deutsche
Forschungsgemeinschaft (DFG) (S.S.).
26. CCDC-769051 (2d) contains the supplementary crystallographic data for this
paper. These data can be obtained free of charge from The Cambridge Crys-
tallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
27. Richardson, R. D.; Zayed, J. M.; Altermann, S.; Smith, D.; Wirth, T. Angew. Chem.
2007, 119, 6649e6652; Angew. Chem., Int. Ed. 2007, 46, 6529e6532.
28. Frigerio, M.; Santagostino, M. Tetrahedron Lett. 1994, 35, 8019e8022.
29. Ladziata, U.; Carlson, J.; Zhdankin, V. V. Tetrahedron Lett. 2006, 47, 6301e6304.
References and notes
1. (a) Varvoglis, A. The Organic Chemistry of Polycoordinated Iodine; VCH: New
York, NY, 1992; (b) Wirth, T. In Organic Synthesis Highlights V; Schmalz, H.-G.,
Wirth, T., Eds.; Wiley-VCH: Weinheim, 2003; pp 144e150; (c) Zhdankin, V. V.;
Stang, P. J. Chem. Rev. 2008, 108, 5299e5358; (d) Topics in Current Chemistry: