Hypervalent Iodine Compounds with Tetrazole Ligands

Article abstract of DOI:10.1021/acs.joc.8b01715

Hypervalent iodine compounds with two I-N bonds, containing 5-substituted tetrazoles as the ligands PhI(N₄CR)₂ (R = CH₃, C₆H₅, and 4-CH₃C₆H₄), were synthesized from PhI(O₂CCF₃)₂ or PhICl₂ and the corresponding tetrazole potassium salts. Alternatively, PhIO was reacted with the free tetrazoles, and the reactions afforded either PhI(N₄CR)₂ or, in most cases, μ-oxo- or oligomeric compounds with several I and O atoms in the backbone and two terminal tetrazole groups. The isolated compounds were reasonably stable in the solid state as well as in solution at room temperature but explosive at elevated temperatures (135-180 °C depending on the structure). The crystal structure of one representative compound (an oligomer with three I atoms in the backbone and 5-phenyltetrazole end groups) was solved and refined from synchrotron powder X-ray diffraction. The novel compounds were characterized by cyclic voltammetry and were found to be strong oxidants. In addition, they proved to be useful reagents for the iodotetrazolylation of unsaturated compounds such as styrene and cyclohexene and for the transfer of tetrazole groups to N,N-dimethylaniline.

Full text of DOI:10.1021/acs.joc.8b01715

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Article
Hypervalent Iodine Compounds with Tetrazole Ligands
Rajesh Kumar, Avichal Vaish, Tomce Runcevski, and Nicolay Vasilev Tsarevsky
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.8b01715 • Publication Date (Web): 17 Sep 2018
Downloaded from http://pubs.acs.org on September 17, 2018
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Hypervalent Iodine Compounds with Tetrazole Ligands
Rajesh Kumar, Avichal Vaish, Tomče Runčevski, and Nicolay V. Tsarevsky*
Department of Chemistry, Southern Methodist University, Dallas, TX 75275 (USA)
Email: nvt@smu.edu
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I
O
H
x
C6H5
H
N
N
N
N
N
N
N
R
R
+
or
N
L
I
L
C6H5
R
CN4
C6H5
N4C
R
I
I
z
O
C6H5
K
R
N
N
N
N
K
N
N
N
N
L
I
L
R
+
C H
6
5
R = CH3, C6H5, 4-CH3-C6H4; L = Cl, CH3CO2, CH3CO2; z = 0, 1, >2
ABSTRACT
Hypervalent iodine compounds with two IꢀN bonds, containing 5ꢀsubstituted tetrazoles as the ligands
PhI(N CR) (R = CH , C H , and 4ꢀCH C H ), were synthesized from PhI(O CCF ) or PhICl and the
4
2
3
6
5
3
6
4
2
3 2
2
corresponding tetrazole potassium salts. Alternatively, PhIO was reacted with the free tetrazoles, and the
reactions afforded either the compounds PhI(N CR) or, in most cases, µꢀoxoꢀ or oligomeric compounds
4
2
with several I and O atoms in the backbone and two terminal tetrazole groups. The isolated compounds
were reasonably stable in the solid state as well as in solution at room temperature but explosive at
o
elevated temperatures (135ꢀ180 C depending on the structure). The crystal structure of one representative
compound (an oligomer with three I atoms in the backbone and 5ꢀphenyltetrazole end groups) was solved
and refined from synchrotron powder Xꢀray diffraction. The novel compounds were characterized by
cyclic voltammetry and were found to be strong oxidants. In addition, they were proved to be useful
reagents for the iodotetrazolylation of unsaturated compounds such as styrene and cyclohexene, and for
the transfer of tetrazole groups to N,Nꢀdimethylaniline.
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INTRODUCTION
The organic compounds of polyvalent iodine have been known since 1886 when several
1
(
dichloroiodo)arenes ArICl were prepared by Willgerodt by the reaction of iodoarenes ArI with
2
0
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chlorine. This discovery was followed, in a swift succession during the following decade, by other
2ꢀ4
organic compounds of iodine(III) such as iodosylarenes ArIO
2
and (diacyloxyiodo)arenes ArI(O CR)2
3
,5
(and other, e.g., nitric and chromic, acid derivatives), as well as some of iodine(V), notably iodylarenes
4ꢀ6
7
ArIO2. By 1914, when the first monograph summarizing the knowledge about organic polyvalent
iodine compounds was published, hundreds of them had been reported and studied. The nature of bonding
in the molecules of these and in many other compounds containing polyvalent (i.e., exceeding the valency
expected from the octet rule) main group elements was a subject of debate for several decades. In 1951,
8
9
Hach and Rundle, and Pimentel reasoned that in polyhalide anions (and, as it was soon realized, by
10
extension – in the molecules of many of the other aforementioned compounds ), delocalized 3ꢀcenterꢀ4ꢀ
electron bonds are formed exclusively with the participation of pꢀorbital(s) of the central polyvalent atom.
This idea was applied more broadly to describe theoretically the bonding in many molecules containing
11
polyvalent main group elements in 1969 by Musher who dubbed the bonds in question hypervalent
(HV). The molecules of ArIL compounds (L represents a ligand with electronegative atom(s), such as
2
carboxylate or (pseudo)halide), which are the subject of this work, are Tꢀshaped and contain the almost
linear LꢀIꢀL fragment. The presence of the relatively weak, compared to the “classical” covalent (2ꢀ
centerꢀ2ꢀelectron), and highly polar HV bonds IꢀL determines the rich reactivity of HV iodine
compounds, i.e., their ability to participate in various electron transfer, ionic (e.g., ligand exchange with
7,12ꢀ15
16ꢀ27
nucleophiles), and radical reactions. A number of monographs or edited books
and review papers
deal with all aspects of organic HV iodine compounds, including the methods of their preparation,
structures, spectral and other physical as well as chemical properties, and uses in synthetic chemistry and
materials science.
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HV iodine(III) reagents can serve as efficient electrophiles and have found numerous applications
in synthetic organic chemistry in this capacity, for instance in CꢀH bond functionalization reactions with
28
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30
trifluoromethyl, cyano, azido, and many other functional groups. Radical reactions involving HV
22,31,32
iodine(III) compounds have found synthetic utility as well.
Heterocyclic compounds with HV
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iodine(III) atoms as part of the ring, such as Zhdankin’s, Togni’s, and other related reagents have
gained significant popularity due to their increased stability, compared to their acyclic analogues, at
ambient conditions. Acyclic compounds of the type ArIL are easily prepared by ligand exchange
2
reactions between commercially available compounds such as PhI(O CCH ) or PhI(O CCF ) and either
2
3 2
2
3 2
ꢀ
sources of the anions L (salts) or the silicon compounds Me SiL. An alternative approach is to employ
3
the reaction between iodosylarenes ArIO and the acid HL or Me SiL. Some ArIL compounds are rather
3
2
unstable (e.g., when L = N ) and are prepared in situ to afford, upon decomposition, the monovalent
3
•
iodine compound ArI and the radicals L , which can functionalize substrates (e.g., unsaturated
compounds) or initiate radical polymerization, yielding endꢀ and in some cases backboneꢀfunctionalized
35,36
ꢀ
polymers.
In other words, ligand exchange reactions at HV iodine(III) centers with the nucleophiles L
followed by homolytic decomposition of the newlyꢀformed compound ArIL – a reaction that is formally
2
ꢀ
•
identical to oxidation of the anion L to the radical L – is a convenient route to functional radicals from
readily accessible precursors.
Out of many oxidative ligand transfer reactions, those that allow for the direct transformation of
CꢀH to CꢀN bonds are of great interest, as the products of these reactions are often the building blocks of
various pharmaceuticals and biologically active natural compounds. Such transformations are often
conveniently carried out using HV iodine(III) reagents with IꢀN bonds but unfortunately, these
compounds, especially the acyclic ones, are comparatively unstable and difficult to store, which limits the
range of synthetically useful reactions that can be developed. These compounds are also usually
hydrolytically unstable, which imposes a further restriction on their utility. The formation of acyclic HV
19
37
iodine(III) compounds with IꢀN bonds derived from cyclic imides or azoles was first reported by
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Varvoglis. Over the following years, several other structural classes were demonstrated including
33,34,38,39
40,41
heterocyclic and iodonium salts with IꢀN bonds. For instance, azidoiodanes,
benziodazoles,
42ꢀ46
and iminoiodanes
were investigated as efficient reagents for CꢀN bondꢀforming reactions. These
39,47ꢀ49
43,47,50ꢀ55
44,45
reagents have been used in direct azidation,
amination,
aziridination,
and CꢀH insertion
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reactions.
The discovery of reactions in which the HV iodine(III) reagents with IꢀN bonds were
50,57
formed in situ using iodoarenes (typically, iodobenzene) as catalysts,
was a major advancement due to
the relatively inexpensive setup and the markedly reduced negative environmental impact compared to Cꢀ
H to CꢀN transformations mediated by transition metal compounds. Nevertheless, the need remains to
isolate and characterize structurally and determine the reactivity of more, especially acyclic, HV
iodine(III) compounds with Nꢀbased ligands, both from fundamental and applied chemistry viewpoint.
Among the many Nꢀbased nucleophiles that can potentially serve as ligands in HV iodine
58ꢀ63
compounds, tetrazoles
are of interest, due to properties such as complexꢀformation ability, biological
64
activity, and especially their highly positive enthalpy of formation, which makes them attractive as
effective propellants and explosives producing molecular nitrogen as the dominating gaseous product of
decomposition. Cꢀ(5ꢀ)substituted tetrazoles RCN H resemble structurally carboxylic acids RCO H and
4
2
65
are often characterized by similar (typically, within an order of magnitude) values of K , which is why
a
they are often referred to as tetrazolic acids. For instance, pK of 5ꢀmethyltetrazole CH CN H is around
a
3
4
65
66
5.6, while pK of CH CO H is 4.8. Likewise, the pKa values of 5ꢀphenyltetrazole and benzoic acid are
a
3
2
6
5
66
respectively 4.8 and 4.2. It was therefore to be expected that tetrazoles or tetrazolate anions can be
used in the place of carboxylic acids or carboxylate anions to prepare the compounds ArI(N CR) , which
4
2
are formally analogues of the corresponding dicarboxylates ArI(O CR) . Herein, we report the formation,
2
2
isolation, structural characterization, and reactivity studies of acyclic compounds of the type ArI(N CR) ,
4
2
as well as some oligomers with IꢀO bonds in the backbone, derived from 5ꢀmethylꢀ, 5ꢀphenylꢀ, and 5ꢀ(pꢀ
tolyl)tetrazole.
RESULTS AND DISCUSSION
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Synthesis
The reactions between iodosylbenzene PhIO and trimethylsilyl halides TMSX, hydrogen halides
67ꢀ69
or carboxylic acids are convenient routes to various HV iodine(III) compounds such as PhIF2,
6
7,70
71,72
PhI(O CCH ) ,
PhI(O CCF ) ,
etc. In our initial efforts, PhIO (2.0 mmol in 2 mL solvent) was
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3 2
2
3 2
reacted with 2 eq. of 5ꢀmethyltetrazole 1a to afford compound 3a (Scheme 1) in high yield in various
solvents such as CH Cl , CHCl , and CH CN (Table 1, entries 1ꢀ3).
2
2
3
3
R
R
CN4
Ar
N C
R
R
CN4
N C R
4
4
I
I
I
I
z
Ar
O
O
Ar
Ar
R
R
I
O
L
x
- H O
5 a-c
4 a-c
2
H
Ar
N
N
N
N
H O
2
+
or
N
N
N N
- 2 LH
H
1 a-c
L
I
CN4
I
N C
4
R
( L = CH CO , CF CO )
3 2 3 2
Ar
a-c
Ar
+
2 LH
3
R
R
- KL ( L = Cl, CF3CO2)
N
N K+
-
N
N
L
I
L
+
+
-
N
N
N
N K
Ar
2
a-c
R = CH (a), C H (b), 4-CH -C H (c)
3
6
5
3
6 4
Scheme 1. Synthetic routes to HV iodine(III) compounds with tetrazole ligands.
Table 1. Synthesis of HV iodine(III) compounds with tetrazole ligands in different solvents at 25 ºC
Entry HV iodine(III) precursor R in RCN H (eq.)
Solvent
Time (h)
Yield (%)
4
1
2
3
4
5
6
7
8
9
PhIO
“
“
“
“
“
“
“
CH (2)
CH CN
DCM
CHCl3
0.5
“
“
2
20
2
20
2
20
0.5
“
70
85
82
3
3
„
„
a
4ꢀCH C H (2)
CH CN
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72
78
27
60
3
6
4
3
b
„
“
“
“
“
“
“
“
b
4ꢀCH C H (4)
3
6
4
b
„
a
C H (2)
6
5
b
“
„
1
0
1
PhI(O CCH )
CH (2)
12
25
2
3 2
3
1
PhI(O CCF )
„
2
3 2
a
Oligomeric product 5 was obtained.
The main product was µꢀoxo compound 4.
b
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As the reactions proceeded, PhIO dissolved and the reaction mixtures remained homogeneous.
Compound 3a was isolated after vacuum evaporation of the solvent as an oily substance, which turned
o
into a sticky solid upon drying under high vacuum; it was stable at low temperature (ca. ꢀ20 C) for
1
13
1
several weeks. Its chemical identity was confirmed by H and C{ H} NMR spectroscopy, HRMS and
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MALDIꢀToF.
The same reaction of PhIO was then conducted using 5ꢀphenyltetrazole (1b) and 5ꢀ(pꢀ
tolyl)tetrazole (1c). The reaction mixtures when using 2 eq. of the tetrazoles vs PhIO in MeCN were
heterogeneous, and the products, isolated by filtration, were obtained as offꢀwhite solids and were found
to be insoluble in most organic solvents with the notable exception of MeOH. The reaction between PhIO
and carboxylic acids such as CH CO H and CF CO H usually generates oligomeric HV iodine(III)
3
2
3
2
70
compounds with I and O atoms in the backbone. Similarly, it was ascertained that the compounds
obtained from the reactions of PhIO and tetrazoles 1b and 1c were oligomeric compounds – 5b and 5c,
respectively (instead of the expected compounds 3b and 3c). The structural data (vide infra) revealed that
5
b exists as oligomeric HV iodine(III) compound, containing three I atoms linked through two bridging O
atoms, and the N2ꢀatoms of 5ꢀphenyl tetrazole were coordinated to the two terminal HV iodine(III)
centers. The reason the reactions of PhIO with 1b and 1c afforded oligomers could plausibly be attributed
to the poor solubility of those oligomers, which, as soon as formed, precipitated, and were not accessible
to react with the still present unreacted tetrazole. In contrast, as mentioned, compound 3a is much more
soluble and is formed as the main product (possibly via the reaction of initially formed oligomers 5a (not
observed) with 1a). The contact time of PhIO and 1b or 1c (2 eq.) in CH CN was increased to 20 h in
3
order to allow the unreacted tetrazole to cleave the IꢀOꢀI bridges in the poorly soluble oligomers (Table 1,
entries 5, 7, and 9). The increased reaction time resulted in offꢀwhite solids in both cases and the products
1
were found to be soluble in polar solvents such as DMF. H NMR analysis in DMFꢀd revealed that both
7
products were ꢁꢀoxo compounds 4b and 4c. This suggested that by varying the reaction time between
PhIO and 1b or 1c (2 eq.) and/or the excess amount of tetrazole, the molecular weights of obtained HV
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iodine(III) species could be controlled to some degree. It was observed that compounds 4b and 4c, while
soluble in DMSO, reacted with it and oxidized it.
73
70,74,75
Symmetric HV iodine(III) compounds such as PhI(OMe)2,
PhI(O CCH ) ,
or
2
3 2
7
6
PhI(O CCF ) are often conveniently prepared in high yields (and without the formation of noticeable
2
3 2
1
1
1
1
1
1
1
1
1
1
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2
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amounts of oligomers) by the reaction of PhIO with methanol or the corresponding carboxylic acids but in
all these cases the reactants are liquids and are employed as the reaction solvents, i.e., in large excess
relative to PhIO. Likewise, if large excess of the 5ꢀaryltetrazoles relative to PhIO and longer reaction
times were used in the reactions described above, most likely the amount of µꢀoxo bridged compounds 4b
and 4c would decrease and eventually compounds 3b and 3c would form in larger yields, but due to the
need of using expensive reagents, this route was not pursued further.
Subsequently, alternative methods to prepare symmetric HV iodine(III) compounds containing 1b
and 1c as the ligands were explored to eliminate the necessity of using excess amounts of tetrazoles. To
achieve this goal, ligand exchange reactions between dicarboxylates such as PhI(O CCH ) with various
2
3 2
tetrazoles were studied (Scheme 1). Varvoglis and coworkers showed that various acidic Nꢀcontaining
37,77
ligands can participate in exchange reactions with PhI(O CCH ) .
The reaction of PhI(O CCH ) with
2 3 2
2
3 2
1a afforded 3a in 12 % yield (Table 1, entry 10). The yield did not increase even at longer reaction times,
most likely due to the establishment of an equilibrium characterized with a comparatively low equilibrium
1
constant. This observation encouraged us to perform a solution study by H NMR spectroscopy to
investigate the ability of 1a to replace the acetoxy groups in PhI(O CCH ) (Figure 1a).
2
3 2
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1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
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a)
b)
a
b
a
b + i
c
c
g
h
+ 4 eq. 1a
+
4 eq. CH CO H
3
2
d
+
2 eq. 1a
+ 2 eq. CH
3
CO
2
H
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
b + i
a
c
+
1 eq. CH CO H
3
2
g
+ 1 eq. 1a
h
d
*
a
b
h
c
g
i
PhI(O CCH )
PhI(N CCH )
3 2
2
3
2
4
8
.5
8.0
7.5
7.0
8
.5
8.0
7.5
7.0
δ
[ppm]
δ
[ppm]
1
Figure 1. H NMR spectra of equilibrated (5 h) reaction mixtures containing (a) PhI(O CCH ) (10 mM in
CD CN) and varying amounts of 1a, and (b) compound 3a (10 mM in CD CN) with varying amounts of
2
3 2
3
3
CH CO H.
3
2
Scheme 2. Exchange of the acetoxy groups in PhI(O CCH ) with 1a.
2
3 2
PhI(O CCH ) (10 mM in CD CN) was mixed with different amounts of 1a (1, 2, and 4 eq.) and
2
3 2
3
sufficient time (5 h) was allowed for an equilibrium to be reached. With 1 eq. of 1a vs PhI(O CCH ) , the
2
3 2
formation of 3a (21 mol % of all HV iodine(III) species) and asymmetric compound 3a’ (6 mol %) was
observed (Scheme 2). When 1a was mixed with PhI(O CCH ) (in a molar ratio of 2:1 or even 4:1), the
2
3 2
1
H NMR yields of compounds 3a and 3a’ did not change substantially, suggesting that, as expected (from
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the low reaction yields discussed above) the equilibrium constants Kex,1 and Kex,2 (Scheme 2) were
relatively low. Another set of experiments were carried out (Figure 1b) where the isolated compound 3a,
from the reaction of PhIO and 1a, was mixed with varying amounts of CH CO H (1, 2, and 4 eq.) in
3
2
CD CN. When 1 eq. of CH CO H was added, the formation of PhI(O CCH ) and mixed compound 3a’
3
3
2
2
3 2
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
was immediately evident with NMR yields (after equilibrium was established in 5 h) of 28 mol % and 6
mol %, respectively. When 2 eq. of CH CO H was mixed with the solution of 3a, the NMR yields of
3
2
PhI(O CCH ) and 3a’ were calculated to be 78 mol % and 7 mol %, respectively. Increasing the amount
2
3 2
of CH CO H to 4 eq. was sufficient to replace all the tetrazole ligands from the symmetric and the
3
2
1
asymmetric HV iodine(III) compounds. These H NMR solution studies further proved that, at least in
CD CN, acetate anions have more pronounced affinity to HV iodine(III) centers than tetrazolate anions.
3
The results also explained why the exchange of acetoxy groups in PhI(O CCH ) with 1a was not an
2
3 2
efficient way to synthesize compound 3a. Even at high concentrations, compound 1a was incapable of
replacing all the acetoxy groups of PhI(O CCH ) .
2
3 2
Table 2. Synthesis of PhI(N CR) compounds under different conditions at 25 °C in CH CN.
4
2
3
-
+
Entry
HV iodine(III) precursor
R in RCN K
Yield (%)
4
1
2
3
4
5
6
PhICl2
CH3
82
69
65
70
80
82
„
„
C H5
6
4ꢀCH C H
3
6
5
4
PhI(O CCF )
CH3
2
3 2
„
„
C H5
6
4ꢀCH C H
3
6
The goal to obtain symmetric HV iodine(III) species with tetrazole ligands using minimum
amount of reactants was yet to be accomplished. Instead of free tetrazoles, efforts were undertaken to
accomplish the exchange using tetrazolate anions, in the form of potassium salts (2a-c) of the studied
tetrazoles and HV iodine(III) precursors such as PhICl and PhI(O CCF ) . These attempts were inspired
2
2
3 2
by the known fact that symmetric HV iodine(III) compounds of the type ArIL are efficiently produced by
2
ꢀ
51ꢀ53
the reaction of ArICl and ArI(O CR) with a sodium or potassium salts with nucleophilic anions L .
2
2
2
78
First, PhICl was prepared by reacting PhI with sulfuryl chloride in CH CO H. The isolated crystalline
2
3
2
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2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
PhICl was then reacted with the potassium salts 2a-c (2 eq.) in dry CH CN for 15 h (Scheme 1),
2
3
affording the compounds 3a-c in very good to excellent yields (Table 2, entries 1ꢀ3). The identity of the
1
13
1
isolated compounds 3a-c was confirmed by H, C{ H} NMR, and mass spectroscopy. When the same
reactions were carried out in CH CN, which had not been dried prior to the synthetic procedures, the salt
3
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
a gave 3a in similar yields but the salts 2b or 2c afforded the ꢁꢀoxo bridged compounds 4b or 4c. To
1
further prove this, a solution study using H NMR spectroscopy was performed where 3c (40 mM, 1 eq.)
was dissolved in DMFꢀd (0.9 mL) and D O (100 eq.) was added. As shown in Figure S1, the formation
7
2
of 4c was evident after several hours. This suggested that the aryl tetrazoleꢀbased HV iodine(III)
compounds 3b and 3c are more hydrolytically unstable than the aliphatic derivative 3a.
Exchange reactions were also carried out with PhI(O CCF ) and the potassium salts 2a-c in dry
2
3 2
CH CN for 15 h. The advantage of the reaction involving PhI(O CCF ) is that the byproduct, potassium
3
2
3 2
trifluoroacetate, remains dissolved, while the reaction products precipitate, which makes the purification
less involved than in the case of reactions employing PhICl , in which the main product and the byproduct
2
(
KCl) are both insoluble and need to be separated. The two studied exchange reactions with potassium
salts of tetrazoles proved to be very suitable for the preparation of symmetric HV iodine(III) compounds
3a-c, with equimolar amounts of tetrazoles to HV iodine(III) precursors being sufficient to obtain the
desired products in high yields.
Characterization
After synthesis and isolation of three symmetric HV iodine(III) compounds 3a-c, they were
further characterized by cyclic voltammetry (CV) to examine their oxidizing ability. The CV
measurements were performed in dry and deoxygenated DMF (good solvent for all compounds 3a-c)
using glassy carbon electrode. In addition to that, the reduction potential of PhI(O CCH ) was measured
2
3 2
in the same solvent and it was found that PhI(O CCH ) was harder to reduce than the tetrazoleꢀbased HV
2
3 2
iodine(III) compounds. The cyclic voltammogram of PhI(O CCH ) showed an irreversible wave with
2
3 2
+
twoꢀelectron reduction peak ranging from ꢀ1.223 V to ꢀ1.360 V (vs. Fc /Fc), depending on the scan rates
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(
Table S1, entries 10ꢀ12 and Figure S4). Compounds 3a-c were better electronꢀacceptors with a less
negative reduction potential than PhI(O CCH ) at any scan rate (Figure 2a). Compound 3b had the least
2
3 2
+
negative reduction potential ranging from ꢀ0.316 V to ꢀ0.332 V (vs. Fc /Fc) at various scan rates (Table
S1, entries 1ꢀ3 and Figure S5). The oxidizing power of compounds 3a-c followed the expected trend
based on the electron donating ability of the R group in the tetrazole ligand, i.e., compound 3c was more
oxidizing than compound 3a but less than 3b with reduction potential from ꢀ0.444 V to ꢀ0.412 V (vs.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
+
Fc /Fc) at different scan rates (Table S1, entries 4ꢀ6 and Figure S6). The reduction potential of compound
+
3a varied from ꢀ0.500 V to ꢀ0.588 V (vs. Fc /Fc) upon altering the scan rates (Table S1, entries 7ꢀ9 and
Figure 2b). It was found that the electrolyte used in CV measurements, (nꢀBu) NPF , does not interact
4
6
with the HV iodine(III) compounds (Figure S2).
0.2
a)
2c
b)
-6
2b
4.0x10
0
.0
0.2
-0.4
0.6
0.8
-1.0
1.2
1.4
2a
PhI(O CCH )
-6
-
2
3 2
3.0x10
-6
2
.0x10
-
-6
1
.0x10
-
0
.0
-6
Scan Rate (V/s)
-
-1.0x10
0
0
.02
.04
-
-6
0.06
-2.0x10
0.02
0.03
0.04
0.05
0.06
0.5
0.0
-0.5
-1.0
-1.5
-2.0
Scan Rate (V/s)
Voltage (V vs AgNO |Ag)
3
Figure 2. a) Reduction potentials for 1 mM solutions of PhI(O CCH ) and tetrazoleꢀcontaining HV
iodine(III) compounds 3a-c (vs. Fc /Fc) in anhydrous DMF containing 0.1 M (nꢀBu) NPF , at various scan
rates using a glassy carbon electrode, b) Cyclic voltammograms of 1 mM solutions of compound 3a at
different scan rates.
2
3 2
+
4
6
Growing single crystals of the studied compounds, suitable for single crystal Xꢀray diffraction,
proved to be a challenging task. However, 5b was obtained as a polycrystalline powder with an excellent
crystallinity. Therefore, the crystal structure was analyzed using powder Xꢀray diffraction data, collected
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1
1
1
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2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
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3
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4
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5
5
5
5
5
6
with synchrotron radiation. The structure was solved using the Simulated Annealing algorithm, and refined
by the Rietveld method (more information in the SI). The molecule of 5b consists of three iodine atoms
(
Figure 3a), linked through bridging oxygen atoms, with I–O distances ranging between 1.95 and 2.08 Å.
The two terminal iodine atoms are coordinated by the nitrogen atoms (N2) of the 5ꢀphenyl tetrazole units,
with I–N bond distances of 2.443(1) Å and 2.401(1) Å, respectively. The N–I–O–I–O–I–N fragment of the
structure adopts a characteristic zigzag geometry, because of the almost linear (with maximum deviation
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
o
from linearity of 11 ) arrangement of the structural motif LꢀIꢀL, where L is either bridging O atom or the
o
N2 atom of the terminal tetrazole ligands, combined with the valent angles of about 131.7(1) and
o
79
1
20.7(1) in the IꢀOꢀI fragments. This geometry is similar to other HV iodine(III) compounds. As
mentioned, the N–I–O and O–I–O angles were refined to be close to linear. Each iodine atom is
coordinated to a phenyl group, with I–C bond distances ranging between 2.00 and 2.12 Å. The three
phenyl groups are positioned perpendicularly to the zigzag motif of the oligomer backbone, and aligned in
almost parallel fashion one to another, with an average π–π distance of 3.8 Å. The crystal packing of 5b is
made of infinite, oneꢀdimensional molecular chains, connected with relatively strong intermolecular I⋅⋅⋅N
bonds (2.99(1) Å and 3.12(1) Å), as shown in Figure 3b.
We noticed that the lone pair of N3 of the tetrazole groups was not directed exactly as one would
expected. However, all attempts to model the orientation resulted in worse fit to the Rietveld plot.
Considering that the orientation deviates by only few degrees (and the I…N is relatively weak bonding),
we decided to present the structure as freelyꢀrefined (as it is customary for solving crystal structures from
powder diffraction data). This observation might be a result from local disorder, i.e., it can be assumed that
the tetrazole ring is rotationally disordered and the presented structure is an average of all positions. Due to
severe limitations of the powder Xꢀray diffraction method, it is not possible to address this potential
disorder issue in much greater detail. Less likely, this observation might be due to steric effects in the solid
state, where the crystal packing “forces” the tetrazole ligand in a slightly deviated angle with respect to the
I atom. A close inspection of difference Fourier electron density map did not indicate the presence of
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solvent molecules. However, we cannot exclude the possibility of disordered solvent molecules in close
contacts with the 5b molecule in the solidꢀstate. Unfortunately, even if present, these solvent molecules
would be difficult to detect even with single crystal diffraction, due to (potentially) low occupancies and
disorder.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Figure 3. a) One molecule of 5b featuring three HV iodine (III) atoms, linked by bridging oxygen atoms
and terminal nitrogen (N2) atoms of the 5ꢀphenyltetrazole units in a zigzag motif. b) Intermolecular IꢀꢀꢀN
interactions between two neighbouring molecules in the crystal packing of 5b.
Reactivity
In the above discussion, the preparation of HV iodine(III) compounds with two tetrazole terminal
groups, containing only one HV iodine(III) atom (compounds 3a-c), two HV iodine(III) atoms connected
through an oxoꢀbridge (the µꢀoxo compounds 4a-c), and more than two iodine(III) atoms and several oxoꢀ
bridges (the oligomeric compounds 5a-c) was demonstrated. Tetrazoles are commonly used as propellants
and explosives and it was interesting to test and compare the thermal stability of a series of HV iodine(III)
compounds with two identical tetrazole ligands at both ends of molecules with different chain lengths.
Four compounds (several milligrams) were charged in four test tubes, namely 5ꢀ(pꢀtolyl)tetrazole (1c,
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1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
placed in test tube No. 1), and compounds with the general formula 4ꢀCH C H CN ꢀI(Ph)ꢀ[OꢀI(Ph)] ꢀ
3
6
4
4
n
N CC H (4ꢀ)CH with n = 0 (i.e., compound 3c in test tube No. 2), n = 1 (i.e., the µꢀoxo compound 4c in
4
6
4
3
test tube No. 3), and n = 2ꢀ3 (mixture of oligomers 5c in test tube No. 4). The test tubes were immersed in
an oil bath, the temperature of which was gradually increased and monitored. The lowest molecular
weight HV iodine(III) compound (in test tube No. 2), which contained the largest molar fraction of
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
o
tetrazole groups, decomposed explosively at ca. 135 C, and it was followed by the next higher molecular
o
o
weight (µꢀoxo) compound at ca. 145 C. Eventually, the oligomer exploded at ca. 178 C, at which point
the experiment was stopped. The parent tetrazole was stable up to the end of the heating (i.e., up to ca.
o
1
80 C). The experiment was recorded and can be found as a video file in the SI. It can be expected that
control over the degree of polymerization in oligomers of type 5 would allow for control over the
temperatures of explosive degradation. More detailed studies related to the thermal properties of tetrazoleꢀ
containing HV iodine(III) compounds are underway.
8
0,81
Suarez and coworkers
demonstrated the use of PhI(O CCH ) ꢀI in the acetoxylation of various
2 3 2 2
82
substrates, and the reaction was further implemented to the iodoacetoxylation of olefins. In this context,
compounds 3a-c were reacted with cyclohexene and styrene in the presence of I in different solvents,
2
leading to the formation to iodotetrazolylation (addition) products. All reactions were performed in dark
0
at 25 C for 1 h as shown in Table 3.
Table 3. Iodotetrazolylation reaction of cyclohexene in different solvents.
Entry
Reactant
Solvent
Yield (%)
1
2
3
4
5
3a
„
„
„
„
CH CN
75
70
69
80
82
3
DCM
CHCl3
DMF
MeOH
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10
3b
„
„
3c
„
„
CH CN
DCM
MeOH
85
82
3
a
90
80
75
CH CN
3
DCM
MeOH
DCM
DCM
a
11
12
13
89
82
72
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
4b
4c
a
The reaction proceeded with the formation of iodomethoxylation product
When the reactions with compounds 3b and 3c with cyclohexene were conducted in methanol
Table 3, entries 8 and 11), the product obtained in both cases was compound 7 (Scheme 3). This product
(
could be the result of an exchange reaction between 3b or 3c and methanol (yielding PhI(OCH ) ),
3
2
followed by reaction of the newly formed compound with iodine and eventually – with cyclohexene. The
1
reaction between 3c and increasing amounts of MeOH was examined by H NMR in DMSOꢀd and the
6
results suggested that the exchange reaction indeed occured (Figure S8). This product was not observed
when compound 3a (Table 3, entry 5) was reacted with cyclohexene in the presence of iodine in
methanol.
Scheme 3. Exchange reaction of compounds 3b and 3c with MeOH and further reaction with cyclohexene
in the presence of I2.
This reaction was extended to styrene. Under similar conditions, two isomers, 8 and 9, were
isolated and characterized spectroscopically, and the former was determined to be the major product
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1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(
Table 4). The structures of the isomers were ascertained by comparing their NMR spectra (SI) with the
spectra of similar compounds that were products of the reaction between styrene with
82
(
diazidoiodo)benzene (generated in situ) and iodine, which yielded a mixture of (1ꢀazidoꢀ2ꢀ
iodoethyl)benzene (similar to 8 and dominant) and (2ꢀazidoꢀ1ꢀiodoethyl)benzene (analogous to 9). The
higher yield of primary iodide was explained with the stability of the corresponding carbocation
intermediate.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Table 4. Iodotetrazolylation of styrene in different solvents.
Entry
R in PhI(N CR)
Solvent
Yield (%)
4
2
8
9
1
2
3
4
5
CH3
„
„
CH CN
75
70
82
85
80
20
15
10
16
12
3
DCM
MeOH
DCM
DCM
C H
6
5
4ꢀCH C H
3
6
5
N CCH
4
3
N CCH
3
Bulk
4
I
N
N
+
0
8
0 C, 12 h
N CCH
4
3
3a
10
o
Scheme 4. Oxidative radical tetrazolylation of N,Nꢀdimethylaniline at 80 C in CH CN.
3
In addition to these PhI(N CR) ꢀI ꢀmediated reactions, the possibility of radical reactions of
4
2
2
compound 3a in the absence of I was explored. The reaction between 3a and N,Nꢀdimethylaniline
2
0
(Scheme 4) was performed at 80 C in bulk for 12 h and the product 10 was isolated using preparative
TLC.
In conclusion, novel symmetric HV iodine(III) reagents containing different 5ꢀsubstituted tetrazoles
were prepared and were found to be reasonably stable under ambient conditions in both the solid and
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solution states. The compounds proved to be strong oxidants. An oligomer with IꢀOꢀbased backbone and
tetrazole end groups was characterized by Xꢀray diffraction. The use of these reagents allowed oxidative
iodotetrazolylation reactions of styrene and cyclohexene as well as radical transfer of tetrazole groups to
N,Nꢀdimethylaniline. Further investigations focused on expanding the utility of the HV iodine(III)
reagents is currently in progress.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
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5
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8
9
0
1
2
3
4
5
6
7
8
9
0
EXPERIMENTAL SECTION
Materials. 5ꢀMethylꢀ1Hꢀtetrazole (Alfa Aesar, 97 %), 5ꢀphenylꢀ1Hꢀtetrazole (Alfa Aesar, 99 %), 5ꢀ(pꢀ
tolyl)ꢀ1Hꢀtetrazole (TCI, 98 %), (diacetoxyiodo)benzene (PhI(O CCH ) , Acros, 98 %),
2
3 2
[
bis(trifluoroacetoxy)iodo]benzene (PhI(O CCF ) , Acros, 98 %), cyclohexene (SigmaꢀAldrich, 97+ %),
2 3 2
styrene (Acros, 99 %), transꢀ2ꢀ[3ꢀ(4ꢀtertꢀbutylphenyl)ꢀ2ꢀmethylꢀ2ꢀpropenylidene]malononitrile (DCTB,
TCI, 98 %), NaCl (SigmaꢀAldrich, 99.9 %), NaNO (SigmaꢀAldrich, 99.9 %), (nꢀBu) NPF (TCI, 98 %),
3
4
6
I (SigmaꢀAldrich, 99.8 %), Na S O (Acros, 99.8 %), CH CO H (SigmaꢀAldrich, 99 %), Na SO (Sigmaꢀ
2
2
2
3
3
2
2
4
Aldrich, 99.8 %), N,Nꢀdimethylaniline (SigmaꢀAldrich, 99 %) were used as received. Iodosylbenzene
83
(
PhIO) was synthesized using a procedure described in the literature, which is based on the hydrolysis of
PhI(O CCH ) with 3 M aqueous NaOH (pellets, 97+ %, SigmaꢀAldrich, were employed to prepare the
2
3 2
solution), followed by washing with chloroform (Acros, 99 % extra pure). Dichloroiodobenzene (PhICl2)
78
was synthesized using a procedure described in the literature. The solvents, including anhydrous
acetonitrile (Acros, 99.9 %), anhydrous dichloromethane (Acros, 99.9 %), 1,2ꢀdichloroethane (Acros,
9
9.8 %), diethyl ether (Acros, 99 %), nꢀhexane (Acros, 99.9 %), methanol (Acros, 99.8 %) were used as
received.. The deuterated solvents, DMSOꢀd (Acros, 99.8 % D), DMFꢀd (Alfa Aesar, 99.5 % D),
6
7
CD CN (Cambridge Isotope Laboratories, 99.8 % D), CDCl (Cambridge Isotope Laboratories, 99.8 %
3
3
D), and CD OD (Cambridge Isotope Laboratories, 99.8 % D), contained a small amount of
3
tetramethylsilane (TMS) as a chemical shift reference. All chemicals were used as recieved without
further purification.
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4
4
4
4
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5
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5
5
5
5
5
5
5
5
6
Analytical procedures. NMR spectra were recorded on a Bruker Avance DRX (400 MHz) spectrometer.
Compound 3b-c and 4b-c were characterized by MALDIꢀToF. MALDI mass spectra were aquired on a
Shimadzu Axima Performance MALDI TOFꢀTOF (Shimadzu Biotech) in both positive and negative ion
reflectron modes (100ꢀ1000 Da). For each compound, 100 profiles of 10 spectra/profile were collected at
repetition rates of either 10 or 50 Hz. Laser power was optimized for each sample based on the intensity
and resolution of the peaks in the spectra. Pulsed ion extraction voltages were optimized for the expected
molecular weight of each compound. The matrix used was DCTB dissolved in methanol (30 mg/mL) and
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
NaCl and NaNO were used as doping agents. All spectra were baseline subtracted and Gaussian filtered
3
for final analysis and compared with the matrix spectrum. The exact mass for compounds 3a, 6a-c, 8a-c,
9
a-c, and 10 was obtained using Shimadzu LCMSꢀITꢀToF. Standard conditions (electrospray ion source,
positiveꢀion acquisition mode, interface voltage of +4.50 kV, CDL temperature of 200 °C, and block
heater temperature of 200 °C) were used to identify all compounds except 3a. Due to the instability of 3a,
a small peak corresponding to a fragment could only be observed when the analysis conditions were
changed as follows: electrospray ion source, positiveꢀion acquisition mode, interface voltage of +1.00 kV,
CDL temperature of 100 °C, and block heater temperature of 100°C. However, the HRMS data for 4b and
3c could not be obtained due to fragmentation of the fragile hypervalent IꢀN bonds. Electrochemical
measurements were carried out in an electrochemical cell system controlled with a CHI620E
electrochemical station (CH Instruments, Inc., USA) with a Pt wire as the counter electrode, AgNO /Ag
3
as the reference and glassy carbon (GC) as working electrode while purging dry argon. All potential
values are referenced to AgNO /Ag in 0.1 M (nꢀBu) NPF with 0.01 M AgNO in DMF. Samples were
3
4
6
3
ꢀ5
prepared by dissolving 10 mol of the studied HV iodine(III) compounds in 10 mL of 0.1 M solution of
(
nꢀBu) NPF in dry and deoxygenated DMF. The sample (10 mL) was divided in 3 parts and CV
4
6
measurements were done on each part only once at a particular scan rate. For comparison, first, the redox
potential of 1 mM ferrocene solution in DMF was measured with respect to AgNO /Ag at the same scan
3
rates. All samples were prepared in glove box to avoid moisture or air. Xꢀray diffraction setup is
described in the SI.
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General procedure for the synthesis of HV iodine (III) compounds 3a, 4b, 4c, 5b, and 5c
In a 10 mL dry reaction tube, a magnetic stir bar was placed followed by PhIO (2.0 mmol, 1 eq.)
and 1a (4.0 mmol, 2 eq.). The tube was capped with a rubber septum and wrapped with aluminum foil to
prevent exposure of the contents to light. Then, dry solvent (2.0 mL) was injected, the tube was immersed
in a water bath at 25 °C, and the mixture was stirred until a clear solution was formed (ca. 30 min). The
solvent was then evaporated under reduced pressure and the desired product was isolated. Similar
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
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5
6
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8
9
0
1
2
3
4
5
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8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
experiments were performed in CH CN using tetrazoles 1b and 1c for two different time intervals: 2 h
3
and 20 h. When the reaction time between PhIO and 1b or 1c was 2 h, the products were 5b or 5c,
whereas, when contact time was increased to 20 h, mixture of oligomers 4b or 4c were obtained. Due to
the poor solubility of both 5b and 5c, the spectroscopic characterizations were not performed.
Bis(5ꢀmethyltetrazolyl)iodobenzene (3a). Following the general procedure, PhIO (0.44 g, 2.0
mmol) and 1a (0.34 g, 4.0 mmol) were added in a vial followed by the addition of anhydrous CH Cl (2.0
2
2
1
mL) and then removal of CH Cl in 30 min yielded 3a (0.63 g, 85 %) as a sticky solid; H NMR (400
2
2
MHz, CD CN): δ 2.43 (s, 6H), 7.28 (t, J = 7.9 Hz, 2H), 7.46 (t, J = 7.5 Hz, 1H), 7.86 (d, J = 7.9 Hz, 2H);
3
13
1
C{ H}NMR (100.578 MHz, CD CN): δ 9.3, 125.9, 132.0, 132.8, 134.4, 154.9 ppm; HRMS: calculated
3
+
+
m/z for C H IN [MꢀCH CN ] : 286.9788; found: 286.9756; MALDIꢀToF: calculated m/z for
8
8
4
3
4
+
+
C H IN Na [M+Na] : 393.0038; found: 392.9162.
10
11
8
ꢁ
ꢀOxoꢀbis(5ꢀphenyltetrazolyl)iodobenzene (4b). Following the general procedure, PhIO (0.44 g,
2
.0 mmol) and 1b (0.58 g, 4.0 mmol) were added in a vial followed by the addition of anhydrous CH CN
3
1
(
(
20.0 mL) and then removal of solvent in 20 h yielded 4b (0.80 g, 60 %) as an offꢀwhite solid; H NMR
13
1
400 MHz, DMFꢀd ): δ 8.00 (s, 8H), 7.47 (dd, J = 36.0, 29.6 Hz, 12H).; C{ H}NMR (100.578 MHz,
7
DMFꢀd ): δ 126.6, 127.0, 128.0, 130.0, 131.0, 131.1, 133.7, 137.7 ppm; MALDIꢀToF: calculated m/z for
7
+
+
C H I N O [MꢀN CC H ] : 568.9335; found: 568.8090.
19 15 2
4
4
6
5
ꢁ
ꢀOxoꢀbis(5ꢀpꢀtolyltetrazolyl)iodobenzene (4c). Following the general procedure, PhIO (0.44 g,
2.0 mmol) and 1c (0.64 g, 4.0 mmol) were added in a vial followed by the addition of anhydrous CH CN
3
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2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
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4
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4
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4
4
5
5
5
5
5
5
5
5
5
5
6
1
(
(
20.0 mL) and then removal of solvent in 20 h yielded 4c (0.83 g, 56 %) as an offꢀwhite solid; H NMR
400 MHz, DMFꢀd ): δ 2.35 (s, 6H), 7.31 (d, J = 7.75 Hz, 4H), 7.44 (t, J = 7.5 Hz, 4H), 7.55 (t, J = 7.9
7
13
1
Hz, 2H), 7.92 (d, J = 7.8 Hz, 4H), 8.03 (b, 4H); C{ H}NMR (100.578 MHz, DMFꢀd ): δ 140.30,
7
1
37.68, 133.80, 132.06, 131.22, 130.78, 130.60, 129.74, 127.99, 126.97, 126.66, 20.80 ppm; MALDIꢀ
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
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4
5
6
7
8
9
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1
2
3
4
5
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7
8
9
0
ꢀ
ꢀ
ToF: calculated m/z for C H I N O [MꢀH] : 741.0084; found: 740.9355.
2
8
23 2
8
General procedure for the synthesis of PhI(N CR) (R = CH , C H , and 4-CH C H )
4
2
3
6
5
3
6
4
In a 10 mL dry reaction vial, a magnetic stir bar was placed followed by PhICl (2.0 mmol) and
2
2a (4.0 mmol). The tube was capped with a septum and wrapped with aluminum foil and then dry CH CN
3
(
4.0 mL) was injected. The tube was immersed in a water bath at 25 °C and the mixture was stirred for 15
h. The white precipitate (KCl) was filtered off and washed with CH CN (5×2 mL). The combined solvent
3
was evaporated under reduced pressure to afford 3a as yellow oil. The oil was dried under high vacuum
for 15 h to obtain a sticky solid in 82 % yield. Similar experiments were performed with 2b and 2c (to
afford 3b and 3c, respectively). In these cases, solids were isolated by filtration and washed with a
minimum amount of water (2×2 mL) in order to remove the byproduct, KCl, followed by CH CN (5×10
3
mL) and finally with diethyl ether. The products were dried overnight under high vacuum to obtain the
pure products with yields indicated in Table 2. The experiments with PhI(O CCF ) and 2a-c were
2
3 2
performed under similar conditions but with the change in the purification steps. After the reaction
between PhI(O CCF ) and 2a, the CH CN was evaporated and the obtained sticky yellow solid was
2
3 2
3
dissolved in CH Cl . The CH Cl dissolves the desired product 3a, leaving behind the salt, KO CCF
3
2
2
2
2
2
which was then filtered and further washed with CH Cl (4×4 mL). The combined solvent was evaporated
2
2
under reduced pressure to afford 3a as yellow oil. The oil was dried under high vacuum for 15 h to obtain
a sticky solid in 70 % yield. Similar experiments were performed with 2b and 2c (to afford 3b and 3c,
respectively). In these cases, solids were isolated by filtration and washed with CH CN (5×5 mL) in order
3
to remove the byproduct, KO CCF , followed by diethyl ether and dried under vacuum.
2
3
Bis(5ꢀphenyltetrazolyl)iodobenzene (3b). PhICl (0.55 g, 2.0 mmol) and 2b (0.74 g, 4.0 mmol)
2
were added to a vial, followed by anhydrous CH CN (20.0 mL), and the general method yielded 3b (0.68
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1
g, 69 %); H NMR (100.578 MHz, DMSOꢀd ): δ 8.06 (d, J = 6.6 Hz, 6H), 7.59 (d, J = 7.5 Hz, 9H);
6
13
1
C{ H}NMR (400 MHz, DMSOꢀd ): δ 158.1, 134.1, 132.1, 131.4, 130.8, 129.7, 127.1, 126.5 ppm;
6
ꢀ
MALDIꢀToF: calculated m/z for C H IN Cl [MꢀPhCN +Cl] : 383.9644; found: 383.9654
1
3
10
4
4
Bis(5ꢀ(4ꢀtolyltetrazolyl))iodobenzene (3c). PhICl (0.55 g, 2.0 mmol) and 2c (0.79 g, 4.0 mmol)
2
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
were added to a vial, followed by anhydrous CH CN (20.0 mL), and the general method yielded 3c (0.68
3
1
g, 65%); H NMR (400 MHz, DMSOꢀd ): δ 8.08 (d, J = 7.7 Hz, 2H), 7.92 (d, J = 8.1 Hz, 4H), 7.62 (t, J =
6
13
1
7.4 Hz, 1H), 7.51 (t, J = 7.7 Hz, 2H), 7.38 (d, J = 8.1 Hz, 4H), 2.39 (s, 6H); C{ H}NMR (100.578 MHz,
DMSOꢀd ): δ 158.0, 140.7, 134.0, 132.1, 131.3, 130.2, 127.1, 125.1–124.5, 123.6, 21.3 ppm; MALDIꢀ
6
+
+
ToF: calculated m/z for C H IN [M+H] : 523.0856; found: 523.0084
2
2
20
8
1
H NMR studies of exchange reaction between acetoxy groups of PhI(O CCH ) with 1a in CD CN
2
3 2
3
ꢀ5
In a 10 mL glass tube, PhI(O CCH ) (9.6 mg, 3.0×10 mol, to reach final concentration of 10
2
3 2
mM) was added in CD CN (3 mL) followed by C H Cl (internal standard; 10 ꢁL) and 1a (2.5 mg,
3
2
4
2
ꢀ5
3
.0×10 mol, to reach final concentration of 10 mM) and the mixture was stirred to dissolve the
components. Then, 0.8 mL of this solution was taken in a dark NMR tube and spectra (8 scans) were
collected. The equilibrium was determined as the time, at which the ratio of the integrals of the C H Cl
2
2
4
protons and aromatic protons of PhI(O CCH ) remained constant. It took 5 h to reach equilibrium.
2
3 2
Similar experiments were performed where larger amounts of 1a (2 and 4 eq.) in CD CN were used to
3
replace acetoxy groups of PhI(O CCH ) .
2
3 2
Exchange of CH CN groups in PhI(N CCH ) with acetoxy groups
3
4
4
3 2
ꢀ5
In a 10 mL reaction tube, a stir bar was added followed by PhI(N CCH ) (11 mg, 3.0×10 mol;
4
3 2
to reach final concentration of 10 mM) and the tube was wrapped with aluminum foil to protect the
contents from light. CD CN (3.0 mL) was then added. The solution was stirred until it became
3
ꢀ5
homogeneous (30 min) at room temperature. Then, CH CO H (1.72 ꢁL, 3.0×10 mol, to reach final
3
2
concentration of 10 mM) was added followed by C H Cl (10 ꢁL, 0.13 mmol) and TMS vapors. Then, 0.8
2
4
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1
mL of the solution were transferred into a dark (ambered) NMR tube and H NMR spectra (8 scans) were
collected. It took 5 h to reach equilibrium. Similar experiments were performed with larger amounts of
CH CO H.
3
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0
1
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0
Reaction of PhI(N RC) and RCN -I(Ph)-[O-I(Ph)] -N CR with cyclohexene in the presence of I
2
4
2
4
n
4
In a 10 mL reaction tube, a stir bar was placed followed by 3a (0.37 g, 1.0 mmol) and the tube
was wrapped with aluminum foil to protect the contents from light. Then, anhydrous CH CN (2.0 mL)
3
was added and the tube was immersed in a water bath at 25 °C and stirred until the solution became clear
(
ca. 30 min). Then, I (0.26 g, 1.0 mmol) was added and clear solution turned turbid white. This
2
heterogeneous solution was stirred for another 5 min. and cyclohexene (0.11 mL, 1.0 mmol) was added
using a micropipette. It was noted that upon the addition of cyclohexene the color turned brown and the
solution remained heterogeneous. After 1 h, the reaction was quenched using 10 % Na S O and the
2
2
3
contents were extracted with CH Cl (5×10 mL). All the CH Cl layers were collected and washed with
2
2
2
2
distilled water (3×10 mL), dried over Na SO , and then the solvent was evaporated using rotovap to
2
4
obtain a yellow oil as the crude product. The crude product was dissolved in CH Cl (1.0 mL) and hexane
2
2
(20.0 mL) was added. Subsequently, the mixture was left at room temperature for about an hour to obtain
crystals of pure 6a (0.218 g, 74.8 % yield). Similar experiments were carried out with 3a in different
solvents and with 3b and 3c under the same conditions, as well as with 4b and 4c in DCM. In the later
case, the products were identical to those isolated from the reactions involving 3b and 3c.
1
ꢀ(2ꢀiodocyclohexyl)ꢀ5ꢀmethyltetrazole (6a). Following the above procedure, product 6a was
1
obtained as colorless crystaline compound (0.22 g, 75 %); H NMR (400 MHz, CDCl ): δ 4.57 (ddd, J =
3
1
4
6
6
2.5,10.9, 4.3 Hz, 1H), 4.27 (td, J = 11.2, 4.2 Hz, 1H), 2.82–2.64 (m, 1H), 2.64 (s, 3H), 2.27–1.93 (m,
13
1
H), 1.71 (dd, J = 7.1, 2.6 Hz, 1H), 1.68–1.41 (m, 2H); C{ H}NMR (100.578 MHz, CD CN): δ 152.7,
3
4.4, 40.4, 34.7, 33.9, 28.3, 25.1, 9.4 ppm; GCꢀMS: calculated m/z for C H IN : 292.12; found: 292.0.
8
13
4
8
4
a was reported by Hassner and coꢀworkers but no NMR spectrum was reported.
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ꢀ(2ꢀiodocyclohexyl)ꢀ5ꢀphenyltetrazole (6b). Following the above procedure, product 6b was
1
obtained as colorless crystalline compound (0.30 g, 85 %); H NMR (400 MHz, CD CN): δ 7.80–7.40 (m,
3
5
H), 4.70 (ddd, J = 12.4, 10.9, 4.2 Hz, 1H), 4.64–4.50 (m, 1H), 2.64–2.55 (m, 1H), 2.39–2.04 (m, 4H),
1
3
1
1
.75–1.12 (m, 3H); C{ H}NMR (100.578 MHz, CD CN): δ 155.6, 132.2, 130.3, 130.3, 125.1, 65.3,
3
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
4
0.2, 35.1, 33.9, 28.2, 25.0 ppm; GCꢀMS: calculated m/z for C H IN : 354.19; found: 354.0. H NMR
13
15
4
85
spectrum is in agreement with that reported for 6b.
1ꢀ(2ꢀiodocyclohexyl)ꢀ5ꢀ(pꢀtolyl)tetrazole (6c). Following the above procedure, product 6c was
1
obtained as colorless crystalline compound (0.29 g, 80 %); H NMR (400 MHz, CD CN + DMSOꢀd ): δ
3
6
7
.72 – 7.56 (m, 2H), 7.56 – 7.40 (m, 2H), 4.76 – 4.61 (m, 1H), 4.54 (td, J = 11.3, 4.1 Hz, 1H), 2.55 (ddd, J
12.8, 5.6, 2.1 Hz, 1H), 2.46 (s, 3H), 2.29 (ddd, J = 6.0, 4.9, 3.1 Hz, 1H), 2.16 – 2.00 (m, 2H), 2.01 –
=
13
1
1
.90 (m, 1H), 1.67 – 1.41 (m, 3H); C{ H}NMR (100.578 MHz, CD CN + DMSOꢀd ): δ 141.37, 129.55,
3 6
1
28.78, 120.47, 117.24, 63.83, 33.69, 32.71, 26.82, 23.59, 20.25; HRMS: calculated for C H IN
4
14
17
+
[
M+H] : 369.0566; found: 369.0571.
1
1
ꢀiodoꢀ2ꢀmethoxyꢀcyclohexane (7). H NMR (500 MHz, CD CN): δ 4.06 (dd, J = 7.6, 5.5 Hz,
3
1
H), 3.41 (s, 3H), 3.31 – 3.16 (m, 1H), 2.40 (d, J = 15.8 Hz, 1H), 2.21 (d, J = 3.3 Hz, 1H), 2.13 – 1.90 (m,
1H), 1.90 – 1.66 (m, 1H), 1.66 – 1.49 (m, 1H), 1.53 – 1.11 (m, 3H); GCꢀMS: calculated m/z for C H IO:
7
13
1
86
240.08; found: 240.00. The H NMR spectrum is in agreement with that reported for 7.
Reaction of PhI(N CR) with styrene in the presence of I
2
4
2
In a 10 mL reaction tube, a stir bar was added followed by 3a (0.37 g, 1.0 mmol) and the tube
was wrapped with aluminum foil. Anhydrous CH CN (2.0 mL) was added and the tube was immersed in
3
a water bath at 25 °C and stirred until the solution became clear (ca. 30 min). Then, I (0.26 g, 1.0 mmol)
2
was added and clear solution turned turbid white. This heterogeneous solution was stirred for another 5
min and then styrene (0.12 mL, 1.0 mmol) was added using a micropipette. After 1 h, the reaction was
quenched using 10 % Na S O and then the contents were extracted with CH Cl (5×10 mL). All the
2
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CH Cl layers were collected and washed with distilled water (3×10 mL), dried over Na SO , and the
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solvent was evaporated to afford a yellow oil as the crude product. The crude product (a mixture of
isomers) was dissolved in CH Cl (2.0 mL) and the isomers were separated using a preparative thinꢀ
2
2
layered chromatography. The separated isomers were dissolved in CH Cl (1.0 mL) and hexane (20.0 mL)
2
2
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
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4
5
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8
9
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7
8
9
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1
2
3
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5
6
7
8
9
0
was added. Subsequently, the mixtures were left at room temperature for about an hour to obtain crystals
of compounds 8a and 8b as the pure products. Similar experiments were carried out with 3a in different
solvents and with 3b and 3c under the same conditions.
1ꢀ(2ꢀiodoꢀ1ꢀphenylethyl)ꢀ5ꢀphenylꢀtetrazole (8a). Following the above procedure, product 8a was
1
obtained as colorless crystalline compound (0.24 g, 75 %); H NMR (400 MHz, CD CN): δ 7.44–7.37 (m,
3
5
H), 6.20 (dd, J = 10.5, 4.7 Hz, 1H), 4.20 (t, J = 10.6 Hz, 1H), 3.94 (dd, J = 10.7, 4.8 Hz, 1H), 2.48 (d, J
13
1
=
3.7 Hz, 3H); C{ H}NMR (100.578 MHz, CD CN): δ 164.1, 137.6, 130.3, 130.0, 129.9, 129.2, 128.7,
3
+
1
27.9, 126.9, 73.8, 69.9, 11.1 ppm; HRMS calculated for C H IN [M+H] : 315.0095; found: 315.0101.
10
11
4
1
ꢀ(2ꢀiodoꢀ1ꢀphenylethyl)ꢀ5ꢀphenylꢀtetrazole (9a). Following the above procedure, product 8a was
1
obtained as colorless crystalline compound (0.24 g, 75 %); H NMR (400 MHz, CD CN): δ 7.55–7.23 (m,
3
5
H), 5.63 (dd, J = 10.5, 4.7 Hz, 1H), 4.19 (t, J = 10.6 Hz, 1H), 3.85 (dd, J = 10.7, 4.8 Hz, 1H), 2.54 (d, J
1
3
1
= 3.7 Hz, 3H); C{ H}NMR (100.578 MHz, CD CN): δ 153.31, 137.4, 130.05, 129.14, 128.60, 127.95,
3
+
126.87, 73.73, 64.14, 6.57; HRMS calculated for C H IN [M+H] : 315.0099; found: 315.0101.
10
11
4
1ꢀ(2ꢀiodoꢀ2ꢀphenylethyl)ꢀ5ꢀphenylꢀtetrazole (8b). Following the above procedure, product 8b was
1
obtained as colorless crystalline compound (0.32 g, 85 %); H NMR (400 MHz, CD CN): δ 8.14–8.12 (s,
3
2
2
1
3
H), 7.55–7.54 (m, 5H), 7.54–7.41 (m, 3H), 6.31 (dd, J = 10.4, 5.3 Hz, 1H), 4.27 (t, J = 10.6 Hz, 1H),
13
1
.16 (dd, J = 10.8, 5.3 Hz, 1H); C{ H}NMR (100.578 MHz, CD CN): δ 165.1, 136.6, 130.6, 129.5,
3
+
29.2, 129.1, 127.3, 127.1, 126.6, 69.5, 4.4; HRMS calculated for C H IN [M+H] : 377.0261; found:
15
13
4
77.0258.
1
ꢀ(2ꢀiodoꢀ1ꢀphenylethyl)ꢀ5ꢀphenylꢀtetrazole (9b). Following the above procedure, product 9b was
1
obtained as white solid (60.2 mg, 16 %); H NMR (400 MHz, CDCl ): δ 7.69–7.50 (m, 5H), 7.48–7.36
3
(m, 5H), 5.62 (dd, J = 11.1, 4.4 Hz, 1H), 4.23 (t, J = 11.0 Hz, 1H), 3.77 (dd, J = 10.8, 4.4 Hz, 1H);
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C{ H}NMR (100.578 MHz, CDCl ): δ 155.5, 136.7, 131.6, 129.8, 129.7, 129.4, 126.8, 123.8, 65.2, 6.1
3
+
ppm; HRMS calculated for C H IN [M+H] : 377.0255; found: 377.0258.
1
5
13
4
1
ꢀ(2ꢀiodoꢀ2ꢀphenylethyl)ꢀ5ꢀtolylꢀtetrazole (8c). Following the above procedure, product 8c was
1
obtained as white solid (0.31 g, 80 %); H NMR (400 MHz, CDCl ): δ 8.15–7.99 (m, 2H), 7.53–7.42 (m,
3
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
1
H), 7.41–7.32 (m, 3H), 7.28 (dd, J = 8.5, 0.6 Hz, 2H), 6.15 (dd, J = 10.3, 5.3 Hz, 1H), 4.31–4.13 (m,
13
1
H), 3.87 (dd, J = 10.8, 5.3 Hz, 1H), 2.40 (s, 3H); C{ H}NMR (100.578 MHz, CDCl ): δ 165.4, 140.6,
3
+
136.2, 129.6, 129.6, 129.2, 126.9, 126.9, 124.5, 70.0, 21.6 ppm; HRMS calculated for C H IN [M+H] :
16
15
4
391.0414; found: 391.0414.
1
ꢀ(2ꢀiodoꢀ1ꢀphenylethyl)ꢀ5ꢀtolylꢀtetrazole (9c). Following the above procedure, product 9c was
1
obtained as white solid (50.0 mg, 12 %); H NMR (400 MHz, CD CN): δ 7.36–7.29 (m, 9H), 5.73–5.69
3
(
dt, J = 7.6, 3.8 Hz, 1H), 4.09 (td, J = 10.8, 6.6 Hz, 1H), 3.81 (dt, J = 20.8, 10.4 Hz, 1H), 2.33 (s, 3H);
13
1
C{ H}NMR (100.578 MHz, CD CN): δ 156.3, 143.0, 137.7, 130.9, 130.6, 130.3, 130.2, 130.1, 130.0,
3
+
1
3
29.9, 127.9, 127.8, 127.5, 65.0, 21.5 ppm; HRMS calculated for C H IN [M+H] : 391.0417; found:
16
15
4
91.0414.
Reaction of PhI(N CCH ) with N,N-dimethylaniline in CH CN
4
3 2
3
In a 10 mL reaction tube, a stir bar was added followed by 3a (5.84 g, 15.78 mmol) and the tube
was wrapped with aluminum foil in order to protect the contents from light. The tube was carefully
purged with nitrogent for 30 min and in a different vial, N,Nꢀdimethylaniline (20 mL) was added and
purged with nitrogen for 30 min. Then, N,Nꢀdimethylaniline (10 mL, 78.9 mmol) was withdrawn using a
nitrogen purged syringe and added to the tube containing 3a immediately turning into a dark solution. The
reaction tube was then immersed in an oil bath preheated to 80 °C and stirred there for 12 h. Then, the
reaction was quenched using 10 % Na S O (20 mL) and the contents were extracted with ethyl acetate
2
2
3
(
5×50 mL). All the ethyl acetate layers were collected and washed with distilled water (3×100 mL), dried
over Na SO and the solvent was evaporated to afford a dark brown oil as the crude product. The crude
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6
product was dissolved in ethyl acetate (10.0 mL) and the products were separated using a preparative
thinꢀlayered chromatography. The desired product was isolated as brown solid (0.17 g, 15%).
NꢀmethylꢀNꢀ((5ꢀmethylꢀ1Hꢀtetrazolꢀ1ꢀyl)methyl)aniline (10). Following the above procedure,
1
product 10 was obtained in the mixture; H NMR (400 MHz, CD CN): δ 7.14 (d, J = 8.8 Hz, 2H), 6.89ꢀ
3
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
13
1
6
.61 (m, 3H), 5.36 (s, 2H), 2.90 (s, 3H), 2.45 (s, 3H); C{ H}NMR (100.578 MHz, CD CN): δ 153.3,
3
+
1
37.4, 130.2, 130.0, 129.1, 127.9, 126.9, 73.7, 64.1; HRMS calculated for C H N [M+H] : 204.1243;
10 13
5
found: 204.1244.
AUTHOR INFORMATION
*
Corresponding Author nvt@smu.edu
ACKNOWLEDMENTS
The authors gratefully acknowledge financial support by the National Science Foundation
through a CAREER grant (CHEꢀ1455200) to NVT. Professor Isaac GarciaꢀBosch, Khashayar
Rajabimoghadam, and Rachel Trammell are acknowledged for helping with the electrochemical
measurements. Powder Xꢀray diffraction data were collected on the 17ꢀBM Beamline at the Advanced
Photon Source, a U.S. Department of Energy Office of Science User Facility operated by Argonne
National Laboratory.
SUPPORTING INFORMATION
Supporting information includes spectral studies of the hydrolysis of 3c, interaction between (nꢀBu) NPF6
4
1
and 3c, and ligand exchange of 3c with CH OH; CV data for compounds 3a-c and PhI(O CCH ) ; H and
3
2
3 2
13
1
C{ H} NMR spectra, mass spectra; crystallographic data for 5b (CIF); and a video comparing the
explosive decomposition of 3c, 4c and 5c.
REFERENCES
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3)
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Willgerodt, C. Zur Kenntniss Der Jodosoꢀ Und Jodoverbindungen. Chem. Ber. 1893, 26, 1307ꢀ
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Hartmann, C.; Meyer, V. Ueber Jodobensoesaeure. Chem. Ber. 1893, 26, 1727ꢀ1732.
Willgerodt, C. Die Organischen Verbindungen Mit Mehrwertigem Jod; Ferdinand Enke:
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Varvoglis, A. Organic Compounds of Polycoordinated Iodine; WileyꢀVCH: Weinheim, 1992.
Varvoglis, A. Hypervalent Iodine in Organic Synthesis; Academic Press: San Diego, 1997.
Wirth, T. Hypervalent Iodine Chemistry: Modern Developments in Organic Synthesis; Springer:
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15) Zhdankin, V. V. Hypervalent Iodine Chemistry: Preparation, Structure and Synthetic
Applications of Polyvalent Iodine Compounds; Wiley: Chichester, 2014.
(
(
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Sandin, R. B. Organic Compounds of Polyvalent Iodine. Chem. Rev. 1943, 32, 249ꢀ276.
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Koser, G. F. In Supplement D: The Chemistry of Halides, Pseudohalides and Azides, Part 1;
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Varvoglis, A. Polyvalent Iodine Compounds in Organic Synthesis. Synthesis 1984, 709ꢀ726.
Moriarty, R. M.; Prakash, O. Hypervalent Iodine in Organic Synthesis. Acc. Chem. Res. 1986, 19,
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44ꢀ250.
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Stang, P. J.; Zhdankin, V. V. Organic Polyvalent Iodine Compounds. Chem. Rev. 1996, 96, 1123ꢀ
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Muraki, T.; Togo, H.; Yokoyama, M. Hypervalent Iodine Compounds as Free Radical Precursors.
Rev. Heteroatom Chem. 1997, 17, 213ꢀ243.
23) Zhdankin, V. V.; Stang, P. J. Recent Developments in the Chemistry of Polyvalent Iodine
Compounds. Chem. Rev. 2002, 102, 2523ꢀ2584.
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Zhdankin, V. V.; Stang, P. J. Chemistry of Polyvalent Iodine. Chem. Rev. 2008, 108, 5299ꢀ5358.
Zhdankin, V. V.; Protasiewicz, J. D. Development of New Hypervalent Iodine Reagents with
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28) Eisenberger, P.; Gischig, S.; Togni, A. Novel 10‐ I‐ 3 Hypervalent Iodine‐ Based Compounds
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Togo, H.; Katohgi, M. Synthetic Uses of Organohypervalent Iodine Compounds through Radical
Pathways. Synlett 2001, 565ꢀ581.
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Wang, X.; Studer, A. Iodine(III) Reagents in Radical Chemistry. Acc. Chem. Res. 2017, 50, 1712ꢀ
1
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3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
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6
7
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0
1
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(
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(
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