Structure and Reactivity of N-Heterocyclic Alkynyl Hypervalent Iodine Reagents

Article abstract of DOI:10.1002/chem.202101475

Ethynylbenziodoxol(on)e (EBX) cyclic hypervalent iodine reagents have become popular reagents for the alkynylation of radicals and nucleophiles, but only offer limited possibilities for further structure and reactivity fine-tuning. Herein, the synthesis o

Full text of DOI:10.1002/chem.202101475

Accepted Article
Accepted Article
Title: Structure and Reactivity of N-Heterocyclic Alkynyl Hypervalent
Iodine Reagents
Authors: Eliott Le Du, Thibaut Duhail, Matthew D. Wodrich, Rosario
Scopelliti, Farzaneh Fadaei-Tirani, Elsa Anselmi, Emmanuel
Magnier, and Jerome Waser
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To be cited as: Chem. Eur. J. 10.1002/chem.202101475
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Structure and Reactivity of N-Heterocyclic Alkynyl Hypervalent
Iodine Reagents
Eliott Le Du,[a] Thibaut Duhail,[b] Matthew D. Wodrich,[a] Rosario Scopelliti,[c] Farzaneh Fadaei-Tirani,[c]
Elsa Anselmi,[b,d] Emmanuel Magnier,[b] and Jerome Waser*[a]
Dedicated to Prof. Antonio Togni on the occasion of his retirement and as a tribute to his immense contribution to the chemistry of hypervalent
iodine.
Abstract: Ethynylbenziodoxol(on)e (EBX) cyclic hypervalent iodine
reagents have become popular reagents for the alkynylation of
radicals and nucleophiles, but only offer limited possibilities for further
structure and reactivity fine-tuning. Herein, we report the synthesis of
new N-heterocyclic hypervalent iodine reagents with increased
structural flexibility based on amide, amidine and sulfoximine
scaffolds. Solid state structures of the reagents are reported and the
analysis of the I-Calkyne bond lengths allowed assessing the trans-
effect of the different substituents. Molecular electrostatic potential
(MEP) maps of the reagents, derived from DFT computations,
revealed less pronounced σ-hole regions for sulfonamide-based
compounds. Most reagents reacted well in the alkynylation of β-
ketoesters. The alkynylation of thiols afforded more variable yields,
with compounds with a stronger σ-hole reacting better. In metal-
mediated transformations, the N-heterocyclic hypervalent iodine
reagents gave inferior results when compared to the O-based EBX
reagents.
(Togni’s reagent),[6] (hetero)Ar-BX,[7] EBX (R = alkynyl),[8] and
VBX (R = alkene)[9] have found their main applications in
functional group transfer reactions. Despite their success, these
reagents offer only limited options for fine-tuning their reactivity by
structural modification, as the oxygen in the heterocycle can have
only one substituent. The replacement of the oxygen by a nitrogen
atom in the iodoheterocycle was therefore considered by several
researchers.[10] The benziodazol(on)e (BZ) class of reagent was
discovered in the late 60’s and most reports focused on the
determination and the study of their X-ray structure (Figure 1A).[11]
The first synthetic application of this type of HIR was reported only
recently with a radical dehydrogenative olefination of C(sp3)-H
bonds using an alanine derived BZ reagent.[12] Later our group
reported the first synthesis of EBZ (R = alkyne) reagents and
studied their reactivity towards nucleophiles and in the
oxyalkynylation of diazo compounds.[13] Interestingly, although it
had been computed that the benziodoxole-based SCF3-reagent
would not be stable,[14] Zhang and coworkers reported in 2020 the
synthesis of SCF3-BZ reagents and employed them for the
trifluoromethylthiolation of various nucleophiles.[15]
Introduction
In the last decades, hypervalent iodine reagents (HIR) have been
established as versatile and environmentally benign oxidants and
mainstream reagents for functional group transfer in organic
chemistry.[1] Among them, cyclic HIRs bearing a benzene ring and
incorporating the iodine atom in a heterocycle exhibit higher
stability. The most studied cyclic HIRs belong to the
benziodoxol(on)e (BX) class of reagents characterized by an I-O
bond in the iodoheterocycle (Figure 1A).[2] Iodine(V) reagents,
such as the Dess-Martin Periodinane (R = (OAc)3, Y = O), have
found widespread application as mild and stable oxidants.[3] In
contrast, iodine(III) reagents, such as CN-BX,[4] N3-BX,[5] CF3-BX
[a]
[b]
Eliott Le Du, Dr. Matthew D. Wodrich and Prof. Dr. Jerome Waser
Laboratory of Catalysis and Organic Synthesis
Ecole Polytechnique Fédérale de Lausanne
EPFL SB ISIC LCSO, BCH 4306, 1015 Lausanne, CH
E-mail: jerome.waser@epfl.ch @LcsoLab @EPFL_CHEM_Tweet
Thibaut Duhail, Dr. Elsa Anselmi and Dr. Emmanuel Magnier
Institut Lavoisier de Versailles
Université Paris-Saclay, UVSQ, CNRS, UMR 8180
7800 Versailles (France)
E-mail: emmanuel.magnier@uvsq.fr @EmmanuelMagnier
Dr. Rosario Scopelliti, Dr. Farzaneh Fadaei Tirani
Institute of Chemical Sciences and Engineering
Ecole Polytechnique Fédérale de Lausanne
EPFL SB ISIC GE, BCH 2111, 1015 Lausanne, CH
Dr. Elsa Anselmi
[c]
[d]
Figure 1. A) Established BX reagents and BZ reagents. B) Other examples of
nitrogen-stabilized HIR. C) New alkynyl reagents synthesized in this work.
Université de Tours, Faculté des Sciences et Techniques, 37200
Tours (France)
Supporting information for this article is given via a link at the end of
the document.
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Moreover, other types of nitrogen-stabilized (pseudo)-cyclic HIR
have been reported in the literature (Figure 1B). The groups of
Zhdankin,[16] Nachtsheim[17] and Tsarevsky[18] studied the
synthesis, the stability and the reactivity of (pseudo)cyclic N-
heterocycle hypervalent iodine compounds in oxidative
transformations. Compound 1[19] and benziodathiazole reagents
(Y = O)[20] were also reported in the literature but their reactivity
was not investigated. More recently, the Magnier and Togni
groups disclosed the synthesis of sulfoximine based reagents (Y
=
CF3) and studied their reactivity in trifluoromethylation
reactions.[21] Finally, Braddock and coworkers speculated on the
formation of an amidine-derived bromoiodinane reagent 2 when
performing the bromolactonization of alkenes.[22]
Scheme 1. Synthesis of precursors 8, 9 and 10 from 2-iodobenzonitrile (7).
Our initial goal when designing the first EBZ reagents was to
develop an atom-economical aminoalkynylation of diazo
compounds that would have led to α-amino acid derivatives.[13]
Unfortunately only oxyalkynylation products were obtained
through the reaction of the oxygen atom on the amide. Removing
the nucleophilic amide oxygen appeared therefore as a promising
strategy and reagents bearing amidine, amine and sulfoximine
core structures were envisioned. More generally, access to these
unprecedented reagents was expected to further increase our
understanding on the structure-reactivity relationship of cyclic
alkynyl hypervalent iodine reagents. Herein, we report the first
The sulfoximine precursor 12 was synthesized on multigram scale
from benzene (11), in 52% yield over 4 steps according to our
previous methodology (Scheme 2. A, see Supporting Information
for details).[21a,27] Finally, ortho-iodination afforded racemic
sulfoximine precursor 13 in 94% yield. Both enantiomers of the
iodosulfoximine 13 could be separated by preparative chiral
HPLC and were configurationally stable (see Supporting
Information for details). Four other ortho-iodinated sulfoximines
were synthetized from the corresponding sulfides 14 and 16a-16c
in good yields (Scheme 2. B and C respectively, see Supporting
Information for the preparation of sulfides).[28] With both alkyl
substituted sulfoximine 15 and aryl-substituted sulfoximines 17a-
17c in hand, the influence of the group linked to the sulfur atom
was then investigated.
synthesis of ethynylbenziodazolimine (EBZI,
3
and 4),
ethynylbenziodazole (EBz, 5) and ethynylbenziodosulfoximine
(EBS, 6) (Figure 1C).[23] Their structures as well as their reactivity
in standard reactions were compared to already reported EBX
and EBZ reagents. Although these reagents did not allow to
develop the desired aminoalkynylation of diazo compounds, they
were competent alkyne-transfer reagents towards several
nucleophiles.
Results and Discussion
Synthesis of the precursors
In order to access the amidine-based and the benziodazole
reagents, iodine(I) precursors 8, 9 and 10 were obtained from
commercially available 2-iodobenzonitrile (7) (Scheme 1).
Nucleophilic addition of LiHMDS onto the nitrile group followed by
hydrolysis and tosyl protection afforded 8 in 66% yield over two
steps.[24] A second tosyl protection led to compound 9 in 83% yield.
A stepwise protection procedure was favored as it would allow to
finely tune the properties of the amidine-based reagents by
adding two different electron-withdrawing groups. Reducing the
electron-density on the nitrogen atom bound to the iodine was
expected to be essential to obtain stable reagents.[11l,25] Other
protecting groups such as benzoyl or Boc were introduced using
similar conditions. However they were not tolerated under the
reaction conditions required to form hypervalent iodine reagents
and only hydrolysis of the amidine was observed in most cases.
Tosyl-protected 2-iodobenzylamine (10) could be obtained in 59%
yield in two steps via borane-reduction according to a reported
procedure,[26] followed by tosylation.
Scheme 2. Synthesis of A) Trifluoromethyl-substituted sulfoximine 13, B)
Methyl-substituted sulfoximine 15, and C) Aryl-substituted sulfoximines 17a-17c.
Synthesis and structure of the new reagents
We started our investigation on the synthesis of amidine-based
hypervalent iodine reagents by attempting the one-pot oxidation-
alkynylation protocol reported to convert 2-iodobenzamides into
EBZs.[13] Unfortunately, only degradation and hydrolysis of
amidines 8 and 9 was observed under these conditions. Hence,
we decided to follow a stepwise oxidation, ligand exchange
strategy.[8b,11i] Acetoxylation of monoprotected amidine 8 followed
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by ligand exchange after activation with trimethylsilyl triflate led to
the formation of TIPS-H,Ts-EBZI (3) in 27% yield over the two
steps (Scheme 3).
The structure of 4 was determined by X-ray diffraction (Figure
3).[29] The presence of a potential secondary interaction between
the iodine atom and an oxygen atom from a tosyl protecting group
might help to stabilize the hypervalent iodine reagent.
Scheme 3. Synthesis of TIPS-H,Ts-EBZI (3).
Figure 3. Structure of TIPS-Ts-EBZI (4) (see Table 1 for structural properties).
The structure of 3 was unambiguously established by X-ray
analysis (Figure 2).[29] Similarly to what was observed by Zhdankin
and coworkers with benziodazolone reagents, the isomer with the
endocyclic free nitrogen atom was formed.[11i] Moreover, the
presence of a hydrogen-bond between one of the oxygen of the
sulfonyl group and the hydrogen on the endocyclic nitrogen might
enhance the donating ability of the nitrogen.
H atoms are omitted for clarity; thermal ellipsoids given at 50% probability.
To our delight, EthynylBenziodazole (EBz) reagent (5) and
EthynylBenziodoSulfoximine (6) (EBS) could be obtained
following a one-pot two steps procedure in 49% and 75% yield
respectively (Scheme 5).[13] Moreover, starting from enantiopure
sulfoximine precursor 13, a chiral alkynyl hypervalent iodine
reagent was obtained in good yield and high enantiopurity. Only
few chiral alkynyl hypervalent iodine reagents have been reported
so far.[30] Despite our efforts, no other HIR with a sulfoximine motif
was obtained starting from 15 or 17a-17c, highlighting the
essential role of the CF3 group of 13 for successful synthesis.
Figure 2. Structure of TIPS-H,Ts-EBZI (3) (see Table 1 for structural properties).
H atoms (except H1) are omitted for clarity; thermal ellipsoids given at 50%
probability.
Unfortunately, bis-tosylated amidine 9 was degraded in a
peracetic acid-acetic acid solution and no hypervalent iodine
reagent was detected. However, a sequence of chlorination
followed by two ligand exchanges afforded TIPS-Ts-EBZI (4) in
67% yield over three steps (Scheme 4).
Scheme 5. A) Synthesis of TIPS-Ts-EBz (5) B) Synthesis of TIPS-CF3-EBS (6).
The structure of both reagents 5 and 6 was also established by
X-ray analysis (Figure 4).[29] As previously observed in reagent 4
a potential secondary interaction between an oxygen atom and
the iodine atom might stabilize 5.
Scheme 4. Synthesis of TIPS-Ts-EBZI (4).
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values, we can conclude that the monoprotected amidine 3 and
the sulfonamide 5 are the ligands having the higher trans
influence of the studied substituents (entries 1 and 2). The
sulfoximine ligand in 6 has a slightly lower influence (entry 3, I1-
C8 = 2.089(3) Å vs 2.102(3) and 2.100(3) for 3 and 5). The
benziodazolone and benziodoxolone moieties have similar trans
effect (I1-C8 = 2.060(9) Å and 2.054(2) for 22 and 21 respectively,
entries 4 and 5). Finally the diprotected amidine has the lower
trans influence (I1-C8 = 2.046(2) Å for 4, entry 6). The iodine-
heteroatom bond length is similar for EBz (5), EBS (6) and EBX
(21) (2.333(3), 2.337(2), 2.338(1) Å respectively, entries 2, 3 and
5). On the other hand, for the TIPS-Ts-EBZI (4) reagent, this bond
is significantly longer (2.443(1) Å, entry 6), probably due to higher
steric hindrance. As observed in TIPS-EBX (21) and TIPS-Ts-
EBZ (22) (entries 5 and 4), the hypervalent bond in the new
reagents was close to linearity with X1-I1-C8 angle ranging from
164.74(9)° for 3 (entry 1) to 171.23(1)° for 6 (entry 3). The C1-I1-
C8 angles between the alkyne and the benzene range from
90.0(1)° for 3 (entry 1) to 93.03(6)° for 4 (entry 6). These angles
are fully coherent with the T-shape structure expected for
hypervalent iodine reagents. The torsion angle (C8-I1-C1-C2)
showed that in most cases the alkynyl bond is in the plane of the
aromatic ring from -8.33(2)° for 21 (entry 5) to 3.44(2)° in 3 (entry
1). In the case of TIPS-Ts-EBZI (4) the torsion angle is relatively
high -16.56(1)° (entry 6). Finally, in reagents 5, 22 and 4 the short
distance between one oxygen atom of the tosyl protecting group
and the iodine center (3.246(3) Å for 5, 3.285(5) Å for 22, 3.319(1)
Å for 4, entries 2, 4 and 6) indicated a possible interaction.
Figure 4. A) Structure of TIPS-Ts-EBz (5) B) Structure of TIPS-CF3-EBS (6)
(see Table 1 for structural properties). H atoms are omitted for clarity; thermal
ellipsoids given at 50% probability.
The structural features of the newly obtained hypervalent iodine
reagents were compared to that of the reported TIPS-EBX (21)
and TIPS-Ts-EBZ (22) (Table 1).[13] The comparison of the I1-C8
bond lengths between the different species allows to assess the
relative trans effects of the substituents.[11l,25] This parameter
plays an important role in the stability of hypervalent iodine
species and is usually related to the donating ability of the ligands
along the 3c-4e- bond. The longer the I1-C8 bond, the higher the
trans influence of the corresponding ligand. From the measured
Table 1. Comparison of bond lengths and bond angles in alkynyl hypervalent iodine reagents obtained from single crystal X-ray diffraction. X = O or N. The torsion
angle corresponds to C8-I1-C1-C2.
Entry
1
Reagent
I1-C8 (Å)
2.102(3)
2.100(3)
2.089(3)
2.060(9)
2.054(2)
2.046(2)
I1-X1 (Å)
2.317(2)
2.333(3)
2.337(2)
2.387(6)
2.338(1)
2.443(1)
X1-I1-C8 (°)
164.74(9)
165.99(1)
171.23(1)
165.79(3)
166.11(6)
165.51(5)
C1-I1-C8 (°)
90.0(1)
Torsion (°)
3.44(2)
I-Osulfonyl (Å)
TIPS-H,Ts-EBZI (3)
TIPS-Ts-EBz (5)
TIPS-CF3-EBS (6)
TIPS-Ts-EBZ (22)
TIPS-EBX (21)
-
2
90.77(1)
90.31(1)
92.08(3)
91.37(7)
93.03(6)
-0.49(3)
2.85(2)
3.246(3)
3
-
4[a]
5[a]
6
-6.63(7)
-8.33(2)
-16.56(1)
3.285(5)
-
TIPS-Ts-EBZI (4)
3.319(1)
[a]Data taken from the literature.[13]
In order to get a deeper understanding on the electronic effects of
the different substituents next to the iodine atom, molecular
electrostatic potential (MEP) maps were generated (Figure 5, see
Supporting Information for details). A strong polarization towards
the ligand is observed in almost all the reagents. The calculated
molecular dipole moment is higher for 21 (8.30 D) followed by 22
(8.03 D). The new reagents have lower calculated dipole moment,
7.97 D for monoprotected amidine 3, 7.17 D for the sulfoximine 6,
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6.03 D for the diprotected amidine 4 and finally 5.82 D for the
benziodazole 5. The MEPs allowed also to visualize the σ-hole
regions of the reagents. These regions of positive charge at the
iodine atom play an important role on the strength and the
directionality of reagent-solvent or -substrate interactions.[31] The
most extended positive regions are observed for TIPS-EBX (21),
TIPS-EBS (6) and TIPS-H,Ts-EBZI (3), while the reagents having
a tosyl group on the heteroatom bound to the iodine atom (TIPS-
Ts-EBz (5), TIPS-Ts-EBZ (22) and TIPS-Ts-EBZI (4)) have a less
extended σ-hole region. As observed in the X-ray structures of
these reagents, the secondary interaction between one of the
oxygen of the tosyl group and the iodine atom might weaken the
have an impact on the spatial extension of the σ-hole region, but
not on the potential maximum on the iodine. While the oxygen
atom bound to iodine from TIPS-EBX (21) and the nitrogen atom
bound to iodine from 6 have a significant negative electron-
density, the nitrogen bound to iodine in the other reagents is
almost neutral. The negative charge seems in fact transferred to
the oxygen of the sulfonamide for TIPS-Ts-EBz (5) and TIPS-Ts-
EBZI (4) or on the other heteroatom present in the
iodoheterocycle for TIPS-H,Ts-EBZI (3) and TIPS-Ts-EBZ (22).
The higher electron-density on the oxygen in TIPS-Ts-EBZ (22)
reagent might explain why only oxyalkynylation was observed
with diazo compounds and not the targeted aminoalkynylation.[13]
Overall, these observations might indicate that the major
resonance structures for these reagents are not the one drawn,
but instead ionic structures with a positively charged iodine atom
and a negative charge on the oxygen atoms.
σ-hole. From the MEPs plots, local potential maximum (Vx,max
)
around the atoms can also be extracted. In all the reagents the
potential maximum around the C(sp) bound to the iodine atom
(Vc,max) and around the iodine (VI,max) are similar (between - 0.002
and + 0.005 and + 0.032 and + 0.052 au respectively, see
Supporting Information). The iodoheterocycle structure seems to
Figure 5. Molecular electrostatic potential (MEP) maps computed at the M06/def2-SVP level. MEPs were mapped onto the 0.001 au isodensity surface. VX
represents the potential maximum around the atom X and is given in au (see Supporting Information for details).
(Scheme 6).[32] In the case of the monoprotected amidine-based
reagent 3, only degradation of the reagent was observed. In the
case of reagent 5, alkyne-transfer was observed, but the side
product ortho-iodobenzylamine could not be separated from the
Comparison of the reactivity of the new reagents
With the new reagents in hand, we investigated their reactivity in
electrophilic alkynylations and compared them to the already
existing reagents TIPS-EBX (21) and TIPS-Ts-EBZ (22). First we
focused our attention on the alkynylation of β-ketoester 23
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desired product 24. The sulfoximine-based reagent 6 afforded 24
in 90% yield. Unfortunately, when using enantiopure sulfoximine
reagent 6, only racemic alkyne 24 was obtained. Probably, the
chiral center in the reagent is too far from the reactive site to
induce any selectivity. Finally reagents 22, 21 and 4 afforded 24
in quantitative yield.
Scheme 8. Photoredox-catalyzed decarboxylative-alkynylation of Cbz-proline
27.
Finally, the gold-catalyzed alkynylation of indole (29)[36] was
studied using the newly developed reagents, but no C3-
alkynylated indole 30 was isolated (Scheme 9. A). Likewise, all
attempts to employ these reagents in the atom-economical
aminoalkynylation of diazo compounds under the conditions
developed for oxyalkynylation[13,37] did not afford promising results
(Scheme 9. B). The lack of reactivity could be linked to the lack of
nitrogen nucleophilicity observed on the MEP maps.
Scheme 6. Alkynylation of keto ester 23. [a]The desired product could not be
separated from side-products, CH2Br2 was used as internal standard. [b]No
stereoinduction was observed when enantiopure reagent 6 was employed.
Next we studied the thioalkynylation of ortho-bromothiophenol
(25) following our reported procedure (Scheme 7).[32] When using
the monoprotected amidine based reagent 3, the desired product
was not detected and only degradation of the reagent was
observed. Alkynylated product 26 could be obtained in low yield
from TIPS-Ts-EBz (5). Reagents with more pronounced σ-hole
regions TIPS-CF3-EBS (6), TIPS-Ts-EBZ (22)[13] and TIPS-EBX
(21)[33] afforded 26 in good to excellent yields. Finally, TIPS-Ts-
EBZI (4) led to the formation of 26 in 46% yield. Computations
suggested that the accessibility of the σ-hole was key for success
in this transformation.[34] The lower yields often observed with
tosylated reagents (with the exception of 22) with a smaller σ-hole
region is in accordance with this hypothesis.
Scheme 9. Unsuccessful A) Alkynylation of indole (29) and B)
Aminoalkynylation of diazo compounds.
Conclusions
In summary, we have synthesized four new N-heterocyclic alkynyl
hypervalent iodine reagents and elucidated their solid-sate
structures via X-ray crystallography. We demonstrated the
possibility to modulate the iodine-alkyne bond length by modifying
the iodoheterocycle and fine-tuning the trans effect. The
modification of the iodoheterocycle had also a clear impact on the
distribution of the electron density on the reagents. Computed
MEP maps showed a transfer of electron-density away from the
nitrogen bound to the iodine, and a diminished σ-hole region in
the case of tosylated reagents. Finally, the reactivity of the new
hypervalent compounds was compared to the already established
EBX and EBZ reagents. The alkynylation of β-ketoester was
successful with all new reagents, except for the unstable reagent
3 bearing an unprotected amidine group. On the other hand, only
reagents with more pronounced σ-hole regions reacted well in the
thioalkynylation reaction. Transfer to radical intermediates was
possible in low yield for the benzylamine and sulfoximine based
Scheme 7. Alkynylation of thiol 25.
The photoredox-catalyzed decarboxylative alkynylation of
carboxylic acids was then investigated (Scheme 8).[35] The
procedure developed for EBX reagents afforded alkynylated
proline 28 in 90% yield with TIPS-EBX (21). Unfortunately, these
conditions were not suitable for the amidine based reagents as
only degradation was observed with 3 and 4. When benzylamine
or sulfoximine based reagents 5 and 6 were submitted to the
reaction conditions, around 10% of the desired alkynylated proline
28 was obtained.
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reagents
alkynylation of proline.
in
the
photoredox-catalyzed
decarboxylative
Acknowledgements
[9]
We thank the Swiss National Science Foundation (Grant No.
200020_182798), EPFL and the Agence Nationale de la
Recherche (ANR) with PRCI funding (ANR-17-CE07-0048-01) for
financial support. MDW acknowledges Prof. C. Corminboeuf and
the Laboratory for Computational Molecular Design for providing
computational resources.
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Keywords: hypervalent iodine, sulfoximine, alkynyl transfer
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Reagents Nomenclature: TIPS-H,Ts-EBZI (3) = substituent on alkyne-
substituent on the nitrogen linked to the iodine, substituent on the other
nitrogen-EthynylBenziodazoIImine; TIPS-Ts-EBZI (4) = substituent on
alkyne-substituent on both nitrogen-EthynylBenziodazoIImine; TIPS-
Ts-EBz (5) = substituent on alkyne-substituent on the nitrogen linked to
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alkyne-substituent on the sulfoximine-EthynylBenziodoSulfoximine.
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This article is protected by copyright. All rights reserved.

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Chemistry - A European Journal
FULL PAPER
Cambridge Crystallographic Data Centre and Fachinformationszentrum
Karlsruhe Access Structures service www.ccdc.cam.ac.uk/structures.
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This article is protected by copyright. All rights reserved.

10.1002/chem.202101475
Chemistry - A European Journal
FULL PAPER
FULL PAPER
Eliott Le Du, Thibaut Duhail, Matthew D.
Wodrich, Rosario Scopelliti, Farzaneh
Fadaei-Tirani, Elsa Anselmi, Emmanuel
Magnier and Jerome Waser*
Page No. – Page No.
Four new N-heterocyclic alkynyl hypervalent iodine reagents have been synthesized.
Their structures and reactivity are described and compared to already reported cyclic
hypervalent iodine reagents, showing less extended  holes for tosylated reagents.
Good alkyne transfer properties towards strong nucleophiles were observed, but
applications in radical and metal-catalyzed processes were more limited.
Structure and Reactivity of N-
Heterocyclic Alkynyl Hypervalent
Iodine Reagents
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