Chalcogen-Bonding Catalysis with Telluronium Cations

Article abstract of DOI:10.1002/anie.202105482

Chalcogen bonding results from non-covalent interactions occurring between electrodeficient chalcogen atoms and Lewis bases. Among the chalcogens, tellurium is the strongest Lewis acid, but Te-based compounds are scarcely used as organocatalysts. For the first time, telluronium cations demonstrated impressive catalytic properties at low loadings in three benchmark reactions: the Friedel–Crafts bromination of anisole, the bromolactonization of ω-unsaturated carboxylic acids and the aza-Diels–Alder between Danishefsky's diene and imines. The ability of telluronium cations to interact with a Lewis base through chalcogen bonding was demonstrated on the basis of multi-nuclear (¹⁷O, ³¹P, and ¹²⁵Te) NMR analysis and DFT calculations.

Full text of DOI:10.1002/anie.202105482

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How to cite:
International Edition: doi.org/10.1002/anie.202105482
German Edition: doi.org/10.1002/ange.202105482
Organocatalysis
Chalcogen-Bonding Catalysis with Telluronium Cations
Robin Weiss, Emmanuel Aubert, Patrick Pale,* and Victor Mamane*
Abstract: Chalcogen bonding results from non-covalent
interactions occurring between electrodeficient chalcogen
atoms and Lewis bases. Among the chalcogens, tellurium is
the strongest Lewis acid, but Te-based compounds are scarcely
used as organocatalysts. For the first time, telluronium cations
demonstrated impressive catalytic properties at low loadings in
three benchmark reactions: the Friedel–Crafts bromination of
anisole, the bromolactonization of w-unsaturated carboxylic
acids and the aza-Diels–Alder between Danishefskyꢀs diene
and imines. The ability of telluronium cations to interact with
a Lewis base through chalcogen bonding was demonstrated on
the basis of multi-nuclear (17O, 31P, and 125Te) NMR analysis
and DFT calculations.
A
lthough known since 1783, tellurium only slowly gained
interest.[1] It is employed in some alloys, solar panels and
semiconductors. Its implication in organic chemistry is more
diverse, owing to the special properties of this element.[2]
Tellurium is the last stable element of the chalcogen group,[3]
and as such, the largest[4] and the less electronegative,[5] that is
the more polarizable and ionizable in this series. For these
reasons, tellurium species exhibit the strongest non-covalent
interaction with electron-rich atom through the so-called
chalcogen bond (ChB), compared to their sulfur and selenium
analogs.[6,7] ChBs are defined in analogy with halogen bonds
(XB) as the interaction of an electron donor (Lewis base)
with the electropositive region (s-hole) located at the outer-
most end of a s-bond including a chalcogen atom.[8]
Scheme 1. Te-based organocatalysis: The two sole examples known
and those described here.
in Michael reactions with indoles (Scheme 1, middle).[15]
While working on this manuscript, Gabbaꢀ very recently
demonstrated that telluronium species can bind chloride and
even act as chloride transporter.[16]
ChB has been sparingly investigated in the last few
decades and mostly in solid state.[9] Following the develop-
ment of XB applications in biology[10] and organic chemis-
try,[11] ChBs have very recently raised increasing interest in
organic chemistry, especially in anion recognition and trans-
port as well as in organocatalysis.[12] In the latter growing area,
mostly S and Se derivatives have so far been investigated.[13]
Nevertheless, in 2018, Matile studied perfluorophenylselenide
and telluride as ChB donors in chloride-binding catalysis
(Scheme 1, up)[14] and more recently, Huber used a bidentate
triazolium-based tellurium catalyst in the same reaction and
Engaged in XB and ChB study for applications in
organocatalysis, we have recently designed new chiral cata-
lysts.[17] To further explore this area and take benefit of the
tellurium enhanced ChB property, we are currently designing
tellurium-based catalysts. Inspired by the works of Lenar-
d¼o[18] and Yeung[19] who demonstrated that selenonium could
act as organic Lewis acid and promote reaction, we designed
new telluronium salts and studied them, and we report here
their ChB ability and for the first time the high efficiency of
these telluronium species as organocatalysts in typical reac-
tions (Scheme 1, bottom).
To tune the expected ChB intensity, a series of telluro-
nium derivatives carrying electron-rich or electron-poor
substituent was prepared by alkylation of diaryltellurides.
Addition of methyl triflate to diaryltellurides provided
telluronium triflates but in modest yields (10–20%), while
methyl iodide addition delivered unstable telluronium io-
dides. Adding silver triflate, tetrafluoroborate, nitrate, or
hexafluoroantimonate together with methyl iodide readily
gave the corresponding telluroniums 1a,b, 2a,b, 3a,b, 3d,e
[*] R. Weiss, Prof. P. Pale, Dr. V. Mamane
LASYROC, UMR 7177, University of Strasbourg
1 Rue Blaise Pascal, 67000 Strasbourg (France)
E-mail: ppale@unistra.fr
vmamane@unistra.fr
Dr. E. Aubert
CRM2, University of Lorraine, BP 70239
Boulevard des Aiguillettes, 54506 Vandoeuvre-lꢀs-Nancy (France)
Supporting information and the ORCID identification number(s) for
the author(s) of this article can be found under:
https://doi.org/10.1002/anie.202105482.
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surface potential (ESP) around the tellurium centre (Fig-
ure 1b). The corresponding Vs,max values perfectly reflect the
electron-withdrawing or donating properties of the substitu-
ent (Table S23), and as expected, the CF3 group induces
a significant increase (Vs,max (kcalmolÀ1): 130.3 (3+) vs. 113.0
(1+) vs. 103.2 (2+)) deepening the s-holes. The Vs,max values of
the two Te-Ar s-holes are almost identical to one another
whatever the telluronium, while the Te-Me s-holes are always
slightly lower. Superimpositions of the molecular packing
around telluronium cations in 3a and of the positions of the
ESP extrema (Figure 1a and S16-S17) show that the position
of the anions is governed by the electrostatic interaction with
the cation, guided through the three s-holes that are
responsible for the VS,max observed on the molecular surface.
Encouraged by these positive structural results, we further
studied the telluronium ChB in solution. For that, 17O-
labelled Ph3PO[21] was used as a probe in NMR, expecting that
direct 17O and 125Te NMR monitoring of the interacting atoms
would give key information on the interaction between the
basic Ph3PO oxygen atom and the Te s-holes. Using
a phosphine oxide as ChB acceptor could further allow
31P NMR monitoring.[22] Once added to a telluronium di-
chloromethane-d2 solution, Ph3PO induced significant shifts
of the 17O, 31P and 125Te NMR signals (Table 1).
Scheme 2. Synthesis of the telluronium ChB donors.
and 4a,b with excellent yields (Scheme 2). The tetrakis[3,5-
bis(trifluoromethyl)phenyl]borate (BArF) telluroniums 1c,
2c, 3c, 4c and tetrakis(pentafluorophenyl)borate telluronium
3 f were quantitatively obtained by anion metathesis from the
corresponding triflates. They proved stable at room temper-
ature for months as solids, except for 3d, as well as in solution,
except for 3e, which slowly evolved to the starting diary-
ltelluride.[20] Among them, 3a and 3e provided suitable
crystals for X-ray analysis, confirming the structures of these
new telluronium salts.
In the solid state, 3a and 3e both crystallize with two
independent cations in the asymmetric unit, all four mole-
cules exhibiting a similar conformation (Figure S9-S11 in
Supporting Information). In each structure, the telluronium
cations exhibit close interaction with three neighbouring
Expected to be driven by Te s-holes deepness, the
equilibrium occurring upon Ph3PO addition should be
affected by the electronic effect of the telluronium aryl
substituent, but also by the ability of the anion to act as
a Lewis base and thus to compete with the added OPPh3. Such
competition may be responsible for the variable peak broad-
anions, one in each direction opposite to the CAr-Te and CMe
-
Table 1: 125Te, 17O and 31P NMR chemical shift differences from telluro-
nium salts 1–4 in the presence of Ph3PO.[a]
Te bonds, almost aligned with the Te s-holes (Figure 1a).
With anion-Te distances ranging from 2.831 to 3.048 ꢁ, well
below the sum of the van der Waals radii of the two elements
(O 1.52 ꢁ, Te 2.06 ꢁ) and with a nearly linear arrangement of
À
the TfO/NO3··Te C bonds (166 to 1758; Figure S12-S15, S16-
S17 and Table S10), these structures revealed the presence of
ChB between each Te-C s-hole and the non-bonding
electrons of the triflate or nitrate oxygen atom (Figure 1b).
DFT calculations performed on the isolated telluronium
cation 3+ confirmed the presence of three s-holes along the
Entry
Telluronium (R, X)
125Te Dd[b]
17O Dd[c]
31P Dd[d]
1
2
3
4
5
6
7
8
1a (H, OTf)
1b (H, BF4)
2.08
4.13
31.64
4.16
4.10
29.90
-3.13
-4.26
11.62
-4.65
6.33
0.57
4.96
10.37
4.69
5.03
9.69
4.47
8.41
21.10
7.25
2.21
9.45
1.81
2.09
5.04
6.71
1.89
3.07
4.45
1.65
3.78
0.98
2.27
6.83
3.17
0.70
3.22
0.55
0.66
2.41
1c (H, BArF )
4
À
three Te C bonds, as shown by the positive electrostatic
2a (OMe, OTf)
2b (OMe, BF4)
2c (OMe, BArF )
4
3a (CF3, OTf)
3b (CF3, BF4)
9
3c (CF3, BArF )
4
10
11
12
13
14
15
3d (CF3, SbF6)
3e (CF3, NO3)
3 f (CF3, B(C6F5)4)
4a (t-Bu, OTf)
4b (t-Bu, BF4)
0.06
0.78
1.50
24.48
4c (t-Bu, BArF )
4
[a] Conditions: 1:1 mixture (20 mM) of telluronium salts and Ph3PO in
CD2Cl2 at 258C; [b] dTe of the telluronium salts before and after addition
of Ph3PO are given in S.I. (Table S1) as well as NMR incertitudes
(Table S2); [c] dO in the presence of 1–4 (given in S.I. (Table S1) as well as
NMR incertitudes (Table S4)) compared to dO of free Ph3PO
(47.41 ppm); [d] dP in the presence of 1–4 (given in Supporting
Information (Table S1) as well as NMR incertitudes (Table S3)) com-
pared to dP of free Ph3PO (27.45 ppm).
Figure 1. a) Molecular packing about tellurium Te1 in telluronium
triflate 3a (intermolecular Te···O bond distances in ꢂ) and its super-
position with the location of the ESP extrema (VS,max, magenta dots;
O···Te···VS,max angles are indicated in 8); b) ESP map for the telluronium
3+ on DFT 1=0.001 a.u. isodensity surface. Location of the three most
positive extrema of ESP (VS,max points) are indicated with black arrows.
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ening observed in some spectra for certain telluronium-
OPPh3 complexes.
between the calculated chemical shielding and the measured
dTe for the telluronium-OPPh3 adducts (Figure S20). This was
expected because the measured dTe in solution corresponded
to an equilibrium process whereas the chemical shielding
were calculated for the adducts only.
It is interesting to note that the measured and calculated
chemical shift values of the telluroniums reported here nicely
fit with those recently reported (Figure S19).[24e]
To further probe this Ph3PO··Te interaction and to assess
the formation of a monoadduct Ph3PO–Te+, we performed
NOESY experiment (Figure S7) on the solution containing
Ph3PO and 3c, the most effective salt for such complex
formation (see above). This experiment clearly established
the spatial proximity of ortho protons of Ph3PO with the ortho
protons of the 3,5-di(trifluoromethyl)phenyl group of the
telluronium entity (Figure 2a). Furthermore, nOe was also
Therefore, electronic effect should best be detectable if no
competition for Te s-holes occurs. The telluronium series 1c,
2c, 3c and 4c, carrying the less coordinating anion BArF, was
designed and prepared for these reasons in order to maximize
Ph3PO··Te interaction. Rewardingly, these BArF derivatives
exhibited the largest NMR shifts (entries 3, 6, 9 and 15),
whatever the measured nucleus. Furthermore, good correla-
tions between Dd and s Hammett constants were obtained in
17O and 31P NMR (R2 = 0.9375 and 0.9846 respectively; see
Figure S4). The latter clearly confirms the formation of
Ph3PO··Te complexes, and the role electronic effects played
in this formation: the most effectively formed was obtained
with the more electrodeficient telluronium 3+, the one having
the largest s-holes (see Vs,max values above), inducing the
largest 17O and 31P NMR shifts.
Alternatively, the anion effect could be best evaluated
within the telluronium series which exhibits the largest s-
holes (see Table S21), that is, the 3+ derivatives. Interestingly,
the a index proposed by Alvarez to define the coordination
ability of anions toward transition metal ions[23a] allowed to
rationalize the observed Dd variations. Remarkable correla-
tions were indeed achieved with 17O and 31P NMR shifts for
the 3a-3 f telluronium salt series (entries 7–12; see Figure S5,
R2 = 0.9607 and R2 = 0.9420 respectively). These results
confirm that coordination of the telluronium counterions
compete with Ph3PO for the formation of Ph3PO··Te com-
plexes.
It is worth noticing that, although a values were reported
for transition metals, lanthanides, and s-block metals,[23] the
present correlations suggest that they are also well suited for
telluronium cations.
Figure 2. a) Representation of the interactions between OPPh3 and the
telluronium protons of 3c as suggested from 17O, 31P and 125Te NMR
and NOESY experiment (only one single hydrogen was highlighted for
clarity); b) B3LYP-D3/Def2TZVPP calculations of the 3+-Ph3PO com-
plex; c) mass spectrum of the 3+-Ph3PO complex.
In contrast to DdO and DdP, only moderate to poor
correlations could be achieved with DdTe, both for electronic
and anion effects (see Figure S6). This was expected because
125Te NMR spectroscopy is highly sensitive to electronic and
geometry changes in the tellurium environment.[24] Never-
theless, the correlation profile between DdTe and a for the
telluronium salt series 3+XÀ showed that DdTe is differently
influenced if the anion is well or poorly coordinating. Thus, by
considering only low (BArF and B(C6F5)4) and medium (SbF6
and BF4) coordinating anions, a very good correlation (R2 =
0.9931) was obtained between DdTe and a. With the more
coordinating anions (NO3 and TfO), the effect of Ph3PO
addition is balanced by other parameters, probably related to
their competition for interaction with the telluronium and
may be some modifications of the telluronium geometry if
both the anion and Ph3PO interact with.
detected between the ortho-protons of Ph3PO and the methyl
group of the telluronium. Interestingly, calculations per-
formed on a complex Ph3PO-3+ also highlighted the proximity
of these protons (Figure 2b and S25), with a very short
distance between Te and O (2.570 ꢁ), in line with the
strongest 17O NMR shift (Dd 21.1 ppm) observed with this
complex. Its formation was further confirmed by in situ mass
spectrometry, which allowed to detect the species present in
the corresponding solution with a mass peak at 849.0448
within a set of peaks typical for the isotopic distribution of
a 1:1 adduct between 3c and Ph3PO (Figure 2c and S8).
Overall, these effects established the presence of a ChB
between Te and O of Ph3PO through interaction of the latter
with the aryl-Te s-hole located between the telluronium
methyl and the other aryl group, as schematically shown in
Figure 2a.
A complementary analysis of 125Te chemical shifts was
performed by calculating the chemical shielding of the
tellurium in telluronium cations 1+-4+ (see S. I., section
VII). Interestingly, the good linear correlation between the
chemical shifts of telluroniums 1c–4c measured in solution
and the calculated chemical shielding of 1+-4+ showed that the
dTe trend in this series can be well reproduced by DFT
calculations (R2 = 0.9076, Figure S18). This result confirmed
that dTe in telluroniums 1c–4c is mostly influenced by
electronic parameters. However, no correlation was observed
As these observations clearly showed the Lewis acidity of
the cationic chalcogen and its ability to activate a carbonyl-
type derivative, it was worth evaluating their propensity to act
as catalyst in some reactions. The bromination of anisole with
N-bromosuccimide (NBS) was first used as benchmark
reaction with catalysts 1–3 (Table 2). Interaction of the NBS
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Table 2: Bromination of anisole catalyzed by telluroniums.
nisole in high yields and no significant difference was noted
between TfO and BF4 anions. As expected from the preceding
studies, the BArF telluroniums 1c, 2c and 3c provided the
best results, giving within 5 min the brominated product in
high yields and almost quantitatively with 3c as catalyst
(entries 4, 7 and 10). Based on these results and on the higher
Vs,max values (Table S23), catalyst 3c was used for further
catalytic tests (entries 11–15) and for other reactions (Ta-
bles 3 and 4). Increasing or decreasing the catalyst amount did
not change the catalyst efficiency (entries 11, 12 vs. 10), and
interestingly, as low as 0.5 mol% of catalyst still very
efficiently promoted this reaction within 5 min. (entry 13).
The catalyst 3c was then evaluated in competition with
chloride, known to strongly interact with Te species.[7a,15a,16,25]
Accordingly, the catalytic activity of 3c was suppressed in the
presence of an equivalent amount of tetrabutylammonium
chloride (entry 14). The possibility of hidden Brønsted
catalysis was ruled out by adding potassium carbonate which
did not modify the reaction course and its yield (entry 15). It
is worth to mention that this reaction could be performed at
mmol scale without significant change (entry 10f). The
catalyst stability was also attested by NMR monitoring of
the reaction; 1H and 19F NMR confirmed the structural
integrity of the catalyst after reaction (see S.I. p 31–33).
As NBS was efficiently activated by the telluronium
catalyst in the aryl bromination described above, it seemed
worth to examine another classical reaction induced by NBS,
the bromolactonization reaction. A series of w-unsaturated
carboxylic acids was submitted to NBS in the presence of
telluronium catalyst 3c (Table 3). Rewardingly, the expected
bromolactones were obtained within 30 min in good to
Entry[a]
1
Catalyst
None
loading
Yield (%)[b]
0
2
3
4
1a
1b
1c
5 mol%
5 mol%
5 mol%
79[c]
86
89
5
6
7
2a
2b
2c
5 mol%
5 mol%
5 mol%
84
81
87
8
3a
3b
3c
5 mol%
5 mol%
5 mol%
82
Table 3: Bromolactonisation catalyzed by telluronium.
9
87
10
96 (94)[f]
11
12
3c
3c
3c
3c
3c
10 mol%
1 mol%
0.5 mol%
1 mol%
1 mol%
96
97
97
0
Entry[a]
Alkene
x
Lactone
Yield[b,c]
13
14[d]
15[e]
1
2
3
4
5
6
0
1
5
10
1
0
29 (26)
70
77 (68)
100 (98)
99 (92)[d]
98
n=1
[a] Reactions were carried out with anisole (0.054 mmol), catalyst and
NBS (0.056 mmol) in CD2Cl2 at rt for 5 min.; [b] Determined by 1H NMR
(see SI for details, NMR yield incertitude: Æ5%); [c] The same yield was
obtained with 1a synthesized directly from MeOTf, thus ruling out
catalysis by silver salts; [d] In the presence of 1 mol% of nBu4NCl after
24 h; [e] In the presence of 10 mol% of K2CO3 after 5 min; [f] Isolated
yield in brackets for a reaction performed at 1 mmol scale.
n=2
n=3
5
7
8
5
10
62
82
9
n=4
n=8
5
5
32
29
carbonyl with the Te s-hole should lower the N-Br bond
LUMO and favour its attack by the electron-rich aromatic
moiety of anisole.
At room temperature, no reaction occurred without
telluronium (entry 1), but in the presence of catalytic amount
of it (5 mol%), anisole bromination was achieved within
5 min. All the telluronium salts gave the expected 4-bromoa-
10
[a] Reactions were carried out with w-unsaturated carboxylic acid
(0.23 mmol), catalyst and NBS (0.23 mmol) in CH2Cl2 at rt for 30 min.;
[b] Determined by 1H NMR (see SI for details, NMR yield incertitude:
Æ5%); [c] Isolated yield in bracket; [d] reaction performed at 1 mmol
scale.
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quantitative yields for 4 to 6-membered rings (entries 1–8),
but in lower yields for larger rings (entries 9–10), while no
reaction occurred without catalyst (entry 1). The catalyst
remained stable during the reaction (see S.I. p 31–33),
excluding the possible role Lewis bases could play in bromo-
and iodolactonisation.[26] The g-lactone was quantitatively
formed (entries 5–6), even with only 1 mol% of catalyst
(entry 5) but higher catalyst loading proved necessary for
efficiently producing the b- or d-lactones (entries 3–4 and 7–8
vs. entry 5). For each case, the observed regioselectivity
corresponds to what is expected from Baldwin ꢂrulesꢃ.[27]
In order to further illustrate the s-hole catalytic property
of telluronium species, we evaluated the ability of the
telluronium 3c to catalyze aza-Diels–Alder-type reaction.
As an archetypal reaction, the Danishefskyꢃs diene conden-
sation with various imines was investigated (Table 4). Such
reaction is known to follow a step-wise mechanism with soft
Lewis acids or in protic solvents, driven by N-coordination or
protonation.[28] Therefore, the soft telluronium 3c should here
similarly activate the imine and induce Mannich-type addi-
tion of the Danishefskyꢃs diene. All the examined imines
readily afforded the expected N-phenyl 2,3-dihydro-4-pyridi-
nones in good to high yields with only 1 mol% of catalyst
within 2 h at room temperature (entries 1, 3, 7). As expected,
higher catalyst loading further improved the catalysis effi-
ciency (entry 5 vs. 4) and up to 91% of adducts could be
obtained with 10 mol% of catalyst (entry 6 vs. 4). Longer
reaction times did not much improve yields (entries 2 vs. 1, 4
vs. 3 and 8 vs. 7). A slight electronic effect was observed, with
electron-poor imine being less reactive (entries 7,8) as
expected from the envisaged mechanism.
telluronium and their importance in solution as indicated by
Ph3PO binding studies through 17O, 31P and 125Te NMR. The
enhanced properties of these telluronium salts could be
readily translated for the first time into high catalytic
performance. These telluronium salts, especially the BArF
telluronium carrying electron-withdrawing groups (3c), were
able to efficiently catalyze various reactions, even at low
loading. Quantitative reactions were thus achieved in the
bromination of aromatic and in bromolactonization with only
0.5 mol% of catalyst. Aza-Diels–Alder-type reactions were
also very effective (up to 90%) with 5 mol% of catalyst. The
versatility of telluronium salts in their applications uncovered
here opens up new routes/strategies in organic syntheses.
Further works in those area are underway in our group.
Acknowledgements
This research was funded by the International Center of
Frontier Research in Chemistry (icFRC), the LabEx CSC
(ANR-10-LABX-0026 CSC). RB thanks the LabEx CSC,
Strasbourg, for a PhD fellowship. The EXPLOR mesocenter
is thanked for providing access to their computing facility
(project 2019CPMXX0984/wbg13).
Conflict of Interest
The authors declare no conflict of interest.
Keywords: chalcogen bonding · Lewis acids ·
non-covalent interactions · organocatalysis · tellurium
Table 4: Telluronium-catalyzed condensation of imines with the Dani-
shefsky’s diene.
[1] a) J. Ibers, Nat. Chem. 2009, 1, 508; b) J. V. Comasseto, J. Braz.
Chem. Soc. 2010, 21, 2027 – 2031.
[2] N. Petragnani, H. A. Stefani, Tellurium in Organic Synthesis 2nd
Ed., Academic Press-Elsevier, Londres-Amsterdam, 2007.
[3] The latest element of this series, polonium, is radioactive, with
a half-live of 138 days for the a-emitting 210Po isotope and 128
years for the 209Po isotope. Nevertheless, tellurium also contains
2 radioactive isotopes with very long half-life (> 9 1016 years).
[4] Atomic radius of this series (ꢁ): O 0.66, S 1.04, Se 1.17, Te 1.37.
[5] Pauling electronegativity: O 3.5, S 2.5, Se 2.4, Te 2.1.
[6] T. Chivers, R. S. Laitinen, Chem. Soc. Rev. 2015, 44, 1725 – 1739.
[7] For recent examples, see: a) E. Navarro-Garcia, B. Galmꢄs,
M. D. Velasco, A. Frontera, A. Caballero, Chem. Eur. J. 2020, 26,
4706 – 4713; b) S. Mehrparvar, C. Wçlper, R. Gleiter, G.
Haberhauer, Angew. Chem. Int. Ed. 2020, 59, 17154 – 17161;
Angew. Chem. 2020, 132, 17303 – 17311.
Entry[a]
1
Imine
Catalyst loading
1 mol%
Time
2 h
Yield[b,c]
R=H
87 (84)
(76)[d]
87
73
78 (73)
87
91 (88)
60
64 (56)
2
3
4
5
6
7
8
“
1 mol%
1 mol%
1 mol%
5 mol%
10 mol%
1 mol%
1 mol%
24 h
2 h
24 h
24 h
24 h
2 h
R=OMe
“
“
“
R=NO2
“
24 h
[8] C. B. Aakerçy, D. L. Bryce, G. R. Desiraju, A. Frontera, A. C.
Legon, F. Nicotra, K. Rissanen, S. Scheiner, G. Terraneo, P.
Metrangolo, G. Resnati, Pure Appl. Chem. 2019, 91, 1889 – 1892.
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Manuscript received: April 22, 2021
Revised manuscript received: June 4, 2021
Accepted manuscript online: June 24, 2021
Version of record online: && &&
,
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&&&&
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Angewandte
Research Articles
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Research Articles
Organocatalysis
New telluronium salts exhibit enhanced
properties due to the presence of 3 s-
holes. This is highlighted in solution by
Ph3PO-binding studies through 17O, 31P,
and 125Te NMR as well as mass spec-
trometry and NOESY NMR. The
enhanced chalcogen-bonding properties
translated into high catalytic perfor-
mance, with low loadings (0.5–5 mol%),
short reaction times (5 min–2 h), and
high yields.
R. Weiss, E. Aubert, P. Pale,*
V. Mamane*
&&&& — &&&&
Chalcogen-Bonding Catalysis with
Telluronium Cations
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ꢁ 2021 Wiley-VCH GmbH
Angew. Chem. Int. Ed. 2021, 60, 2 – 8
These are not the final page numbers!