Unsymmetrical diaryliodonium phenyltrifluoroborate salts: Synthesis, structure and fluorination

Article abstract of DOI:10.1016/j.jfluchem.2019.04.004

The unprecedented reaction of organotrifluoroborates salts of unsymmetrical diaryliodoniums to give aryl fluorides is presented. This preliminary report describes the first synthesis of unsymmetrical diaryliodonium phenyltrifluoroborates along with an exe

Full text of DOI:10.1016/j.jfluchem.2019.04.004

Accepted Manuscript
Title: Unsymmetrical Diaryliodonium Phenyltrifluoroborate
Salts: Synthesis, Structure and Fluorination
Authors: Omar Sadek, David M. Perrin, Emmanuel Gras
PII:
S0022-1139(19)30066-1
DOI:
Reference:
https://doi.org/10.1016/j.jfluchem.2019.04.004
FLUOR 9307
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Received date:
Revised date:
Accepted date:
20 February 2019
3 April 2019
4 April 2019
Please cite this article as: Sadek O, Perrin DM, Gras E, Unsymmetrical Diaryliodonium
Phenyltrifluoroborate Salts: Synthesis, Structure and Fluorination, Journal of Fluorine
Chemistry (2019), https://doi.org/10.1016/j.jfluchem.2019.04.004
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Unsymmetrical Diaryliodonium Phenyltrifluoroborate Salts: Synthesis, Structure
and Fluorination
Omar Sadek, David M. Perrin*, Emmanuel Gras*
*David M Perrin
dperrin@chem.ubc.ca
Chemistry Department
2
036 Main Mall
UBC
Vancouver, BC, V6T1Z1
*Emmanuel Gras
emmanuel.gras@lcc-toulouse.fr
LCC UPR 8241
CNRS
Université de Toulouse
2
3
05 Route de Narbonne
1077 Toulouse Cedex 4,
France
and
ITAV USR 3505
Université de Toulouse, CNRS
1
3
place Pierre Potier
1106 Toulouse Cedex 1
France

Graphical Abstract
Highlights:
This is the first report of fluoride transfer from an aryltrifluoroborate to an aryl

cation generated from an aryliodonium salt that favors the more electron-rich
aryl cation.
Abstract
The unprecedented reaction of organotrifluoroborates salts of unsymmetrical
diaryliodoniums to give aryl fluorides is presented. This preliminary report describes the
first synthesis of unsymmetrical diaryliodonium phenyltrifluoroborates along with an
exemplary x-ray crystal structure, and explores their reactivity regarding the fluorination
of the diaryliodonium cation. Fluorination was found to be chemoselective, providing
exclusively hindered aryl fluoride products in moderate to good yields (up to 89%).

1
Introduction
Hypervalent iodine compounds are immensely useful reagents; specifically,
3
unsymmetrical diaryl-λ -iodanes (diaryliodonium salts) have received considerable
attention owing to their efficient functionalization of aryl groups with a variety of
nucleophiles under both metal-free and metal-mediated conditions.[1, 2] Of particular
interest is the utility of these reagents as aryl fluoride precursors when reacted with a
-
source of fluoride anion (F ).[3, 4] This methodology has been extended to solid-
supported systems[5] and metal catalysed processes.[6] Importantly, these reagents
have been used to afford fluoroaromatic compounds and 18F-labelled
radiopharmaceuticals.[7-20]
Given the potential of this methodology, considerable attention has focused on the
mechanism underlying these transformations along with an ensuing optimisation of
reaction parameters including solvent selection to limit ligand exchange,[21, 22] the
inhibition of radical decomposition pathways,[23] critical mechanistic insights that govern
the selectivity of aryl ring fluorination,[24-28] and the design of auxiliary “dummy” ligands
to enhance the regioselectivity of aryl fluorination.[10, 17, 25, 29] Despite the large
number of publications on the direct fluorination of diaryliodonium salts, most reports have
relied on alkali metal fluorides (KF and CsF). Less commonly, tetramethylammonium
4
fluoride (TMAF) and potassium tetrafluoroborate (KBF ) have found use as sources of
anionic fluoride.
We have recently explored the potential of organotrifluoroborates as sources of anionic
fluoride[30] in the fluoro-dediazoniation of in-situ-generated aryl diazonium salts in the

Balz-Schiemann reaction in which an arenium cation is implicated.[31] Although
fragmentation to an arenium cation is also possible in the case of diaryliodonium cations,
typically a concerted addition-elimination mechanism has prevailed. Hence, we wished to
explore the potential for organotrifluoroborates to transfer fluoride from boron–to–carbon
in the case of iodonium salts. Remarkably, such a transfer is unprecedented despite an
extensive body of literature that has addressed the reaction of organotrifluoroborates and
diaryliodonium salts in palladium-catalysed C-C bond formation,[32, 33] and more
recently in terms of bifunctional reagents, comprising an iodonium and trifluoroborate on
the same arene.[34]
As no report has described the formation of aryl fluorides as products of reactions
involving organotrifluoroborates and diaryliodonium salts, we decided to explore this
reactivity by applying organotrifluoroborates towards the fluorination of these substrates,
as this might appear as an unexpected reaction path in reaction featuring both reagents.
Hence, we synthesised and characterised seven unsymmetrical diaryliodonium
phenyltrifluoroborate salts in a preliminary exploration of their chemical reactivity to give
aryl fluoride products.
2
2
Results and Discussion
.1 Synthesis of Unsymmetrical Diaryliodonium Phenyltrifluoroborate Salts
A series of unsymmetrical diaryliodonium tetrafluoroborates (BF -
using BF OEt as a Lewis acid in CH Cl (Scheme 1). Variations of steric demand were
achieved by reacting iodomesitylene diacetate (MesI(OAc) ) and phenyliodine(III)
diacetate (PIDA), while aryl boronic acids were used to introduce electronic and steric
) was first synthesised
4
3
2
2
2
2

variations on the second aryl fragment. In addition, a diaryliodonium salt with either a
methoxy or a nitrile at the para-positions was synthesized to address the respective
effects of electron-releasing and electron-withdrawing substituents. Synthesis of the
unsymmetrical diaryliodonium phenyltrifluoroborate salts was achieved via facile anion
exchange. Indeed, following overnight stirring in MeCN, precipitated KBF
from the reaction mixture. The salts were purified by Et O-induced precipitation from
concentrated CH Cl solutions to furnish the desired salts in moderate to excellent yields
over two steps (Scheme 1). Anion exchange gave nearly quantitative conversion while
4
was filtered
2
2
2
1
19
the purity of all diaryliodonium phenyltrifluoroborate salts was confirmed by H-, F-, and
11B-NMR spectroscopy along with elemental analysis and high-resolution mass
spectrometry.

Scheme 1 Scope of unsymmetrical diaryliodonium salts synthesised (isolated yields). a, (i) BF
0 minutes, (ii) MesI(OAc) or PIDA, 0 C then room temperature, 18 hours. b, potassium phenyltrifluoroborate,
MeCN, room temperature, 18 hours. Reported yields are over two synthetic steps.
3 2 2 2
·OEt , CH Cl , 0 C,
1
2
2
.2 Structure of Diaryliodonium Phenyltrifluoroborate Salts
Single crystals, suitable for X-ray analysis, of 1 were obtained by slow solvent
evaporation; the salt crystallised in the orthorhombic Pbca space group (Figure 1). Carbon-
Iodine bond lengths, for both mesityl and phenyl rings are essentially identical at 2.114(2)
and 2.115(2) Å, respectively. The iodonium cation adopts T-shaped geometry, as
3
expected for a  -iodane,[2] evidenced by a C-I-C angle of 95.46(8). Additionally, the
aryl fragments are almost perpendicular with an angle of 87.7 between the planes of
both rings. An interaction between the phenyltrifluoroborate anion and diaryliodonium
cation is evidenced by a short contact interaction (2.856(2) Å) between one F-atom on
the trifluoroborate and the electrophilic I(III) centre. Notably, such a short distance, in the

solid state, between the F-atom on the phenyltrifluoroborate and the I(III) centre of the
diaryliodonium appears highly favourable for the desired fluoride transfer.
Figure 1 X-ray crystal structure of 1 with selected angles () and short contact interaction (Å). Carbon in grey, iodine
in purple, boron in pink, fluorine in green/yellow. Hydrogen atoms are omitted for clarity.
2
.3 Fluorination Studies
We began by studying the decomposition of 1 in various solvents at different
temperatures to determine if any fluorinated products could be detected (Table 1, for full
solvent screen please refer to ESI). Based on the above observation in the solid state,
we focused on poorly dissociating solvents. Generally, low boiling solvents resulted in no
conversion of 1 (Table 1, entries 1 and 2) however, trace yields of 2-fluoro-1,3,5-
trimethylbenzene (8) were observed in CHCl
3
and THF (Table 1, entries 3 and 4);
otherwise, unreacted and/or deborylated 1 were observed by 19F-NMR spectroscopy
(signals observed corresponding to phenyltrifluoroborate and/or tetrafluoroborate,
respectively). Higher boiling solvents such as benzene, MeCN and DMF, which have
been extensively used in the decomposition of diaryliodonium fluorides and

tetrafluoroborates,[3, 35] did not result in any fluorinated products (Table 1, entries 5, 6
and 7, respectively). However, yields could be increased by employing high-boiling, non-
polar solvents such as toluene, xylenes and in particular 1,2-dichlorobenzene, which
provided 8 in 22% yield (Table 1, entries 8-10). The use of non-polar, high-boiling,
solvents is consistent with previous reports of improved yields.[3, 22]
3
Given well-established reactivity and selectivity rules for  -iodane intermediates with
nucleophiles, we expected the major product to be 8 due to electronic and the so-called
“ortho” effects.[1, 26, 27, 36] Radical scavengers, such as 2,2,6,6-tetramethyl-1-
piperidinyloxy (TEMPO), have successfully increased fluorination yields by suppressing
the propagation of in situ generated aryl radicals that arise through homolytic cleavage of
the aryl-I bond.[23] However, under our reaction conditions, the addition of TEMPO did
not improve reaction efficiencies (Table 1, entries 11 and 12), corroborating heterolysis.

Table 1 Solvent optimisation for the decomposition of 1
Product distribution (%)a
Entry
1b
Solvent
Et
CH
Temperature (°C)
8
9
2
O
80
-
-
2b
80
-
-
2
Cl
2
3b
CHCl
80
trace
-
3
4b,c
5b
THF
80
trace
-
Benzene
100
100
140
140
140
140
140
140
-
-
6b
MeCN
-
-
7b,c
8b
DMF
-
-
Toluene
8
-
9b,c
Xylenes
8
trace
1
1
1
0b,c
1c,d
2c,e
1,2-dichlorobenzene
1,2-dichlorobenzene
1,2-dichlorobenzene
22
15
21
trace
-
-
Reaction conditions: 1 (0.05 mmol), solvent (1.0 mL) in pressure vial with Teflon lined cap,
a
19
heated at indicated temperature for 2 hours. Yields determined by F-NMR using 2,2,2-
b
19
c
trifluoroethanol as an internal standard. unreacted 1 observed by F-NMR. deborylation
observed by F-NMR. 0.2 eq. TEMPO added to reaction mixture. 1.0 eq. TEMPO added to
reaction mixture.
19
d
e

Having determined 1,2-dichlorobenzene as the optimal solvent we investigated the
decomposition of salts 2-7 (Table 2). Salt 2 decomposed selectively provided 8 in 16%
yield (Table 2, entry 1), while 4-fluoroanisole went undetected despite predictions to the
contrary as both aryl rings are electron-rich. Salt 3 decomposed selectively to furnish 8
as the sole product in good yield (62%) (Table 2, entry 2); this is surprising as the
expected product should be 4-fluorobenzonitrile since this would arise from the most
electron-deficient arene and should therefore be preferentially fluorinated according to
the well-accepted mechanism. Similarly, 4 provided 8 as the only product in excellent
yields (89%) contrary to the prediction that 1,2,3-trifluorobenzene would have resulted
based on both electronic and “ortho” effects (Table 2, entry 3). More surprisingly, 5, which
was expected to selectively decompose to 1,2,3-trifluorobenzene, provided
fluorobenzene (9) as the sole product, albeit in only 13% yield (Table 2, entry 4). The
decomposition of 6 and 7 delivered only trace amounts (<2%) of the expected product 9;
no traces 4-fluoroanisole or 2-fluorothiophene were detected (Table 2, entries 5 and 6,
respectively), perhaps due to the energetic availability of lower lying radical
decomposition pathways. Considering the decomposition of salts 1-4, one appreciates an
emergent trend of increasing yields of 2-fluoro-1,3,5-trimethylbenzene. The increase in
yields correlates with increasing electron-deficiency of the second aryl fragment in the
order 4-OMe < H < 4-CN < 2,6-di-F.

Table 2 Product distribution from the decomposition of salts 2-7
Entry
1
Compound
Product distribution (%)a
1
6
8
6
2
9
2
3
1
3
4
5b
trace
trace
6b
Reaction conditions: precursor (0.05 mmol), 1,2-dichlorobenzene (1.0 mL) in pressure vial with Teflon
a
19
lined cap, heated at 140 °C for 2 hours, X = phenyltrifluoroborate. Yields determined by F-NMR using
b
11
19
-
2
,4-dinitrofluorobenzene as an internal standard. Deborylation observed by B and F-NMR (BF
4
peak
detected).

The reactivity and selectivity observed in the decomposition of diaryliodonium salts 1-7
seem to implicate a mechanism that differs from the accepted one for the fluorination of
-
diaryliodonium fluorides.[24, 27] Generally, fluorination of diaryliodonium salts with F is
thought to proceed under Curtin-Hammett control whereby the ratio of fluorinated
products is dependent on the difference in the free energies of transition states derived
3
from the two conformers of the  -iodane intermediate (Scheme 2).
Given that such selectivity is not observed for the decomposition of 3, 4 and 5, our findings
suggest that the product distribution is determined by irreversible fragmentation of the
iodonium cation to give the more stable aryl cation, by analogy to fluorodediazoniation.
Indeed if unsymmetrical diaryliodonium phenyltrifluoroborate salts were undergoing
fluorination following the accepted mechanism for fluorination of iodonium salts depicted
in Scheme 2, we would expect to detect the formation of both aryl fluoride products
(Scheme 2, PI and PII) and those distributions should be comparable to previously
reported examples, [6] as the transition states would be identical irrespective of the
-
source of F . As the observed distributions are not consistent with past reports, the
-
phenyltrifluoroborate cannot be transferring F to one of two rapidly exchanging
conformers.

Scheme 2 Accepted mechanism for the fluorination of diaryliodonium salts with F-
Instead, based on our recent report on the reaction of a range of diazonium salts, we
propose a mechanism whereby thermolysis of the diaryliodonium salt results in the
heterolytic cleavage of the I-Ar bond, forming an aryl iodide and the aryl cation. This is
1
directly analogous to dediazoniation that occurs upon aryl diazonium salt decomposition
in the Balz-Schiemann reaction wherein the mesityldiazonium gave the highest yields.
Hence, fluorination of the aryl cation likely occurs within the tight ion pair I such that
fluoride transfer proceeds directly from phenyltrifluoroborate (Scheme 3). This may
account for the trend of increasing yields with more electron-deficient aryl ligands; Indeed
+
within the diaryliodonium, Ar
2
–I –Ar
1
, I-Ar becomes an increasingly activated leaving
1
group leading to more efficient fluorination. This mechanism may explain the considerably

higher yields of fluoromesitylene that arise from fluorination of the sterically hindered and
kinetically more stable aryl cation; such reactivity parallels our findings in the fluorination
of sterically hindered anilines using organotrifluoroborates in a Balz-Schiemann type
transformation.[31]
Scheme 3 Proposed mechanism for the fluorination of diaryliodonium salts with phenyltrifluoroborate
This mechanism would also be consistent with the results observed for the decomposition
of unsymmetrical diaryliodonium tetrafluoroborates 3a and 4a which displayed identical
selectivity and yields as their corresponding phenyltrifluoroborate salts (Table 3, entries
1
and 2). Surprisingly, we did not observe any conversion to aryl fluorides when using
tetrafluoroborate salt 5a (Table 3, entry 3) in contrast to its corresponding
phenyltrifluoroborate salt 5 (Table 2, entry 4). This result suggests that
phenyltrifluoroborate may serve a unique role as a fluorinating agent compared to BF
-.
4

Table 3 Product distribution for the decomposition of salts 3a – 5a
Entry
1
Compound
Product distribution (%)a
6
8
2
9
2
3
no conversion
Reaction conditions: precursor (0.05 mmol), 1,2-dichlorobenzene (1.0 mL) in pressure vial with Teflon
a
19
lined cap, heated at 140 °C for 2 hours. Yields determined by F-NMR using 2,4-dinitrofluorobenzene
as an internal standard.
3
Conclusions
In summary, we have described the synthesis and full characterisation of an abbreviated
series of unsymmetrical diaryliodonium phenyltrifluoroborate salts. The fluorination of
these salts was investigated by thermal decomposition in various solvents and was found
to be most efficient at high temperatures in non-polar solvents. Fluorination of all salts
was observed to be completely chemoselective, providing a single aryl fluoride in low to
excellent yields. The observed selectivity contrasts with that observed in the
decomposition of diaryliodonium fluorides; these differences suggest that fluorination
occurs via fluoride transfer to an aryl cation that forms in situ, as seen similarly in the
fluorination of aryl diazonium salts. These preliminary results expand the repertoire of

organotrifluoroborates as new, versatile, and intriguing sources of nucleophilic fluorine
18
with potential for use in the context of F-labeled organotrifluoroborates.[37]
We believe that this work uncovers an unexpected reactivity of organotrifluoroborates
with diaryliodonium salts thus highlighting potential reactivity when both reagents are
mixed. Although yields are low, we expect that these preliminary findings may prompt
further investigations of this reaction. Moreover, we suggest that these results paves the
way for future developments as demonstrated by recent work of Hu and coworkers;[38]
hence it is expected that suitable additives including oxidants or catalytic metals may
enhance yields substantially.

4
Experimental
All chemicals were purchased from commercial sources and used as received unless
otherwise noted. Solvents, MeCN and CH Cl , were dried and distilled using standard
methods (MeCN dried over activated 3A molecular sieves, CH Cl obtained from a
2
2
2
2
PureSolv solvent purification system). All reactions were performed in oven-dried
glassware under argon atmosphere unless otherwise stated. Deuterated solvents for
NMR spectroscopic analysis were purchased from Euriso-top. NMR spectroscopy
1
13
11
experiments were performed in deuterated solvents. H NMR, C NMR, B NMR and
1
9F spectra were recorded on 300 Avance (300 MHz), 400 Avance (400 MHz) and 400
AvanceIII (400 MHz) Bruker spectrometers. All spectra were recorded at ambient
temperature (298 K). Chemical shifts (δ) are reported in parts per million (ppm) relative
1
13
to the residual protium in the solvents ( H) or the solvent carbon ( C) as internal
standards. 19F spectra of aryl fluorides were referenced to 2,4-dinitrofluorobenzene or
2
,2,2-trifluoroethanol as internal standards (1 equivalent). Multiplicity of signals is
indicated using the following abbreviations: s (singlet), b (broad), d (doublet), t (triplet), q
11
(
quartet), q (1:1:1:1 of peaks arising from coupling to B with S=3/2, midpoint of signal
B
reported), dd (doublet of doublets), dt (doublet of triplet), ddt (doublet of doublet of triplet),
dddt (doublet of doublet of doublet of triplet), tt (triplet of triplet) and m (multiplet). 13C
signals arising from the quaternary carbon bearing the trifluoroborate group were not
always observed and therefore were not always listed. Reactions were monitored using
Merck Silica gel 60 F254 glass backed plates. TLC plates were visualized by UV
fluorescence (λ= 254 nm) and one of the following stains: KMNO or HBQ. Flash column
4
chromatography was performed using VWR Chemicals Silica gel 60 – 200 µm. IR spectra
were recorded on a PerkinElmer Frontier FT-IR spectrometer with frequencies expressed
-1
in cm . High-resolution mass spectra (HRMS) were recorded using either electrospray
ionization (ESI) or desorption chemical ionization (DCI) using a Waters GCT Premier or
Sciex QTRAP 4500 AB or Thermo Fisher Scientific DSQ II spectrometers. X-ray
crystallography was performed on single crystal diffractometers: Agilent Gemini, Bruker
Nonius and Bruker Kappa Apex II. Crystal and refinement data are collected in the ESI.
Crystallographic data has been deposited to the Cambridge Crystallographic Data Centre
as CCDC 1879815.
General procedure for the synthesis of unsymmetrical diaryliodonium
tetrafluoroborates:

A round-bottom flask was charged with a stir bar, arylboronic acid (1 eq.) and CH
M), the reaction mixture was stirred and cooled to 0 °C in an ice-water bath and then
BF ·OEt (3 eq.) was added, this solution was stirred at 0 °C for 10 minutes. In a separate
flask MesI(OAc) or PIDA (1.1 eq) was dissolved in CH Cl (0.37 M) and added dropwise
2
Cl (0.1
2
3
2
2
2
2
to the reaction mixture at 0 °C. The resulting solution was allowed to warm to room
temperature and stirred overnight. The reaction mixture was then transferred directly onto
a plug of Silica gel and washed with CH
CH Cl /MeOH (9.5:0.5). Collected fractions were concentrated under reduced pressure
then dropped on Et O to precipitate the product which was collected by filtration and
further washed with Et O.
2
Cl , the product was then eluted with
2
2
2
2
2
(2,4,6-trimethylphenyl)(phenyl)iodonium tetrafluoroborate (1a)
-1
Isolated as a white fluffy powder (408.6 mg, 99%). IR νmax/cm (neat film): 2989, 2970,
1
2
–
901, 1473, 1445, 1057, 736. H NMR (400 MHz, DMSO-d
6
) δ 8.00 – 7.94 (m, 2H), 7.67
13
7.60 (m, 1H), 7.54 – 7.47 (m, 2H), 7.22 (s, 2H), 2.60 (s, 6H), 2.30 (s, 3H). C NMR (101
MHz, DMSO-d
6
) δ 143.1 (C
q
), 141.6 (C
q
), 134.5 (CH), 131.9 (CH), 131.8 (CH), 129.8
19
(CH), 122.5 (C
q
), 115.0 (C ), 26.2 (CH
q
3
), 20.5 (CH
3
). F NMR (376 MHz, DMSO-d
6
) δ -
11
1
45.58 – -150.82 (m). B NMR (128 MHz, DMSO-d
6
) δ -1.29 (s). HRMS-ESI (m/z): found
+
16I+ requires 323.0297.
[
M] 323.0295, calc’d C15
H
(4-methoxyphenyl)(2,4,6-trimethylphenyl)iodonium tetrafluoroborate (2a)
-1
Isolated as a grey powder (262.8 mg, 59%). IR νmax/cm (neat film): 2989, 2973, 2901,
1
1
582, 1569, 1486, 1302, 1259, 1051, 1027, 827. H NMR (400 MHz, DMSO-d
6
) δ 7.95 –
7
.89 (m, 2H), 7.19 (s, 2H), 7.06 – 7.01 (m, 2H), 3.78 (s, 3H), 2.60 (s, 6H), 2.29 (s, 3H).
) δ 161.7 (C ), 142.9 (C ), 141.3 (C ), 136.6 (CH), 129.7
), 117.50 (CH), 103.3 (C ), 55.7 (CH ), 26.2 (CH ), 20.5 (CH
376 MHz, DMSO-d ) δ -146.91 – -149.49 (m). B NMR (128 MHz, DMSO-d ) δ -1.30 (s).
1
3C NMR (101 MHz, DMSO-d
6
q
q
q
1
9
(CH), 123.0 (C
q
q
3
3
3
). F NMR
11
(
6
6
+
+
HRMS-ESI (m/z): found [M] 353.0402, calc’d C16
H18IO requires 353.0402.
(4-cyanophenyl)(2,4,6-trimethylphenyl)iodonium tetrafluoroborate (3a)

-1
Isolated as a beige powder (208.9 mg, 48%). IR νmax/cm (neat film): 2989, 2970, 2901,
1
2
237, 1482, 1066, 832. H NMR (400 MHz, DMSO-d
6
) δ 8.11 (d, J = 8.7 Hz, 2H), 7.96 (d,
13
J = 8.7 Hz, 2H), 7.25 (s, 2H), 2.58 (s, 6H), 2.31 (s, 3H). C NMR (101 MHz, DMSO-d
6
) δ
), 117.4
) δ -146.91 – -
) δ -1.30 (s). HRMS-ESI (m/z): found [M]+
1
43.5 (C
q
), 141.8 (C
q
), 135.1 (CH), 134.9 (CH), 130.0 (CH), 122.6 (C
), 26.3 (CH
49.84 (m). 1 B NMR (128 MHz, DMSO-d
q
), 119.4 (C
q
19
(C
q
), 114.4 (C
q
3
), 20.6 (CH
3
). F NMR (376 MHz, DMSO-d
6
1
1
3
6
+
48.0254, calc’d C16
H
15IN requires 348.0249.
(2,6-difluorophenyl)(2,4,6-trimethylphenyl)iodonium tetrafluoroborate (4a)
-1
Isolated as a white powder (780.4 mg, 88%). IR νmax/cm (neat film): 3090, 3028, 2960,
1
) δ 7.81 (tt, 3JHH
2
8
2
918, 1592, 1469, 1241, 1015, 994, 792. H NMR (400 MHz, DMSO-d
6
=
.4, 4JHF = 6.7 Hz, 1H), 7.45 (dd, JHH = 8.4, 3JHF = 7.3 Hz, 2H), 7.23 (s, 2H), 2.61 (s, 6H),
3
.29 (s, 3H). 13C NMR (101 MHz, DMSO-d
), 143.5 (C ), 141.6 (C
), 137.0 (t, 3JCF = 10.1 Hz) (CH), 129.9 (CH), 122.8 (C
113.1 (m) (CH), 91.7 (t, 2JCF = 28.1 Hz) (C ), 25.9 (t, 6JCF = 1.8 Hz) (CH
), 20.5 (CH
) δ 160.6 (dd, 1JCF = 250.6, 3JCF = 5.9 Hz)
), 113.48
).
6
(C
q
q
q
q
–
q
3
3
1
9F NMR (377 MHz, DMSO-d
6
) δ -95.82 (t, JHF = 7.0 Hz, 2F), -147.71 – -149.04 (m, 4F).
) δ -1.29 (s). HRMS-ESI (m/z): found [M] 359.0110, calc’d
11B NMR (128 MHz, DMSO-d
I+ requires 359.0108.
+
6
C
15 14 2
H F
(2,6-difluorophenyl)(phenyl)iodonium tetrafluoroborate (5a)
-1
Isolated as a white powder (267.4 mg, 66%). IR νmax/cm (neat film): 3096, 3058, 1591,
1
1
=
2
467, 1447, 1241, 1054, 995, 987, 788, 744. H NMR (400 MHz, DMSO-d
6
) δ 8.20 (d, J
7.6 Hz, 2H), 7.80 (tt, JHH = 8.4, 4JHF = 6.7 Hz, 1H), 7.70 (t, J = 7.4 Hz, 1H), 7.55 (m,
3
H), 7.46 (dd, 3JHH = 8.5, 3JHF = 7.0 Hz, 2H). C NMR (101 MHz, DMSO-d
) δ 160.1 (dd,
13
6
1JCF = 251.0, 3JCF = 5.5 Hz) (C
32.2 (CH), 117.1 (C
377 MHz, DMSO-d
128 MHz, DMSO-d
), 137.2 (t, 3JCF = 9.9 Hz) (CH), 135.2 (CH), 132.5 (CH),
), 113.3 – 112.9 (m) (CH), 94.3 (t, 2JCF = 28.2 Hz) (C
). F NMR
) δ -96.40 (t, JHF = 7.0 Hz, 2F), -147.60 – -149.53 (m, 4F). B NMR
) δ -1.29 (s). HRMS-ESI (m/z): found [M] 316.9647, calc’d C12
q
19
1
(
(
q
q
11
6
+
F
I+
6
H
8
2
requires 316.9639.
(4-methoxyphenyl)(phenyl)iodonium tetrafluoroborate (6a)
-1
Isolated as a grey powder (199.3 mg, 51%). IR νmax/cm (neat film): 3196, 3097, 2951,
1
2
846, 1573, 1489, 1302, 1260, 1181, 1047, 1013, 988, 830, 744. H NMR (400 MHz,
DMSO-d ) δ 8.19 (t, J = 9.3 Hz, 4H), 7.64 (t, J = 7.4 Hz, 1H), 7.52 (t, J = 7.6 Hz, 2H), 7.07
6
1
3
(
1
d, J = 8.5 Hz, 2H), 3.79 (s, 3H). C NMR (101 MHz, DMSO-d
6
) δ 162.0 (C
q
), 137.3 (CH),
19
34.8 (CH), 131.9 (CH), 131.7 (CH), 117.5 (CH), 117.0 (C
q
), 105.4 (C
q
), 55.7 (CH ). F
3

1
1
NMR (376 MHz, DMSO-d
1
6
) δ -148.05 – -148.35 (m). B NMR (128 MHz, DMSO-d
6
) δ -
+
127
+
.23 (s). HRMS-ESI (m/z): found [M] 310.9935, calc’d C13
H12 IO requires 310.9933.
(2-thienyl)(phenyl)iodonium tetrafluoroborate (7a)
-1
Isolated as a burgundy powder (467.5 mg, 62%). IR νmax/cm (neat film): 3092, 1559,
1
1
470, 1443, 1386, 1227, 1049, 1031, 1007, 988, 846, 739, 726. H NMR (400 MHz,
DMSO-d
.5 Hz, 1H), 7.53 (t, J = 7.0 Hz, 2H), 7.24 – 7.13 (m, 1H). C NMR (101 MHz, DMSO-d
δ 140.4 (CH), 137.4 (CH), 134.6 (CH), 132.1 (CH), 131.7 (CH), 129.7 (CH), 119.3 (C
6
) δ 8.25 (d, J = 7.5 Hz, 2H), 8.07 (s, 1H), 7.97 (d, J = 4.5 Hz, 1H), 7.66 (t, J =
13
7
6
)
q
),
19
11
1
00.7 (C
DMSO-d
86.9391.
q
). F NMR (376 MHz, DMSO-d
6
) δ -147.95 – -148.54 (m). B NMR (128 MHz,
+
127
+
6
) δ -1.27 (s). HRMS-ESI (m/z): found [M] 286.9393, calc’d C10
H
8
IS requires
2
General procedure for the synthesis of unsymmetrical diaryliodonium
aryltrifluoroborates:
A round-bottom flask was charged with a stir bar, diaryliodonium tetrafluoroborate (1 eq.)
and MeCN (0.1 M); to the stirring reaction mixture potassium phenyltrifluoroborate (1 eq.)
was added in one portion and the mixture stirred at room temperature for 18 hours. The
reaction mixture was passed through a 0.2 µm PTFE filter to remove insoluble impurities,
and the filter washed with MeCN. The filtrate was then concentrated to dryness under
reduced pressure, and then left under high vacuum for 6 hours. The remaining residue
was triturated with CH
insoluble impurities. The filtrate was then concentrated to saturation and then dropped
onto Et O to precipitate the product, which was collected by filtration and further washed
with Et O.
2
Cl and the solution passed through 0.2 µm PTFE filter to remove
2
2
2

(2,4,6-trimethylphenyl)(phenyl)iodonium phenyltrifluoroborate (1)
Isolated as an off-white powder (54.7 mg, >99%). Colourless, single crystals suitable for
X-ray analysis were grown by slow evaporation of a CHCl solution. Mp: 114 – 127. IR
3
-
1
ν
max/cm (neat film): 3071, 3049, 3009, 2984, 1441, 1200, 1005, 986, 937, 906, 752, 743,
1
7
7
0
d
07. H NMR (400 MHz, DMSO-d
.46 (m, 2H), 7.32 (d, J = 6.6 Hz, 2H), 7.23 – 7.19 (m, 2H), 7.07 (dddt, J = 7.3, 5.9, 1.4,
6
) δ 7.99 – 7.95 (m, 2H), 7.65 – 7.60 (m, 1H), 7.53 –
13
.7 Hz, 2H), 7.04 – 6.97 (m, 1H), 2.60 (s, 6H), 2.29 (s, 3H). C NMR (101 MHz, DMSO-
) δ 143.1 (C ), 141.6 (C
), 134.5 (CH), 131.9 (CH), 131.8 (CH), 131.3 (q, 3JCF = 1.7 Hz)
), 114.5 (C ), 26.3 (CH ), 20.5 (CH ).
). B NMR (128 MHz, DMSO-d ) δ 3.15 (q,
1JBF = 52.0 Hz). HRMS-ESI (m/z): found [M-C ]+ 323.0293, calc’d C15 16I+ requires
BF
22.0297, found [M-C15 requires 144.0473. Anal. calc’d
16I]- 144.0474, calc’d C BF -
for C21 I: C, 53.88; H, 4.52; N, 0.00. Found C, 52.85; H, 4.32; N, 0.02.
6
q
q
(
1
CH), 129.8 (CH), 126.2 (CH), 124.9 (CH), 122.6 (C
q
q
3
3
9F NMR (376 MHz, DMSO-d
) δ -139.06 (q
11
6
B
6
H
6 5
3
H
3
H
H
6 5
3
H
21BF
3
(4-methoxyphenyl)(2,4,6-trimethylphenyl)iodonium phenyltrifluoroborate (2)
-1
Isolated as a grey powder (234.1 mg, 80%). Mp: 120-127. IR νmax/cm (neat film): 3085,
1
2
970, 2845, 1571, 1486, 1253, 1195, 1020, 951, 941, 831, 754, 707. H NMR (400 MHz,
DMSO-d ) δ 7.95 – 7.89 (m, 2H), 7.31 (d, J = 6.8 Hz, 2H), 7.19 (s, 2H), 7.10 – 6.97 (m,
6
1
3
5
1
1
H), 3.78 (s, 3H), 2.60 (s, 6H), 2.28 (s, 3H). C NMR (101 MHz, DMSO-d
42.9 (C ), 141.3 (C
), 136.6 (CH), 131.3 (q, 3JCF = 1.9 Hz) (CH), 129.7 (CH), 126.2 (CH),
24.8 (CH), 123.0 (C
6
) δ 161.7 (C ),
q
q
q
19
q
), 117.5 (CH), 103.3 (C
q
), 55.7 (CH
). B NMR (128 MHz, DMSO-d
53.1 Hz). HRMS-ESI (m/z): found [M-C BF
]+ 353.0397, calc’d C16
18IO] 144.0477, calc’d C requires 144.0473. Anal. calc’d
BF -
IO: C, 53.05; H, 4.65; N, 0.00. Found C, 53.21; H, 4.60; N, 0.03.
3
), 26.2 (CH
3
), 20.5 (CH
3
). F
1
1
1
NMR (376 MHz, DMSO-d
=
3
6
) δ -139.13 (q
B
6
) δ 3.11 (q, JBF
H18IO requires
+
6
H
5
3
-
53.0402, found [M-C16
H
6
H
5
3
for C22
H23BF
3
(4-cyanophenyl)(2,4,6-trimethylphenyl)iodonium phenyltrifluoroborate (3)
-1
Isolated as a white powder (206.2 mg, 91%). Mp: 135 – 143. IR νmax/cm (neat film):
1
3
097, 3047, 3020, 3005, 2231, 1580, 1475, 1203, 948, 827, 751, 701. H NMR (400 MHz,
DMSO-d
.25 (s, 2H), 7.07 (t, J = 7.1 Hz, 2H), 7.03 – 6.97 (m, 1H), 2.58 (s, 6H), 2.31 (s, 3H). C
NMR (101 MHz, DMSO-d ) δ 143.5 (C ), 141.8 (C ), 135.0 (CH), 134.9 (CH), 131.3 (q,
3JCF = 1.9 Hz) (CH), 130.0 (CH), 126.2 (CH), 124.8 (CH), 122.7 (C
), 119.4 (C ), 117.4
) δ -139.12 (q ).
6
) δ 8.10 (d, J = 8.7 Hz, 2H), 7.95 (d, J = 8.7 Hz, 2H), 7.31 (d, J = 6.7 Hz, 2H),
13
7
6
q
q
q
q
1
9
(
C
q
), 114.4 (C
q
), 26.3 (CH
B NMR (128 MHz, DMSO-d
BF
]+ 348.0250, calc’d C16
3
), 20.5 (CH
3
). F NMR (376 MHz, DMSO-d
6
B
1
1
1
6
) δ 3.12 (q, JBF = 51.5 Hz). HRMS-ESI (m/z): found [M-
+
-
C
6
H
5
3
H
15IN requires 348.0249, found [M-C16
H
15IN] 144.0477,

-
calc’d C
H BF
6 5 3
requires 144.0473. Anal. calc’d for C22
H
20BF IN: C, 53.59; H, 4.09; N,
3
2
.84. Found C, 53.30; H, 3.84; N, 2.82.
(2,6-difluorophenyl)(2,4,6-trimethylphenyl)iodonium phenyltrifluoroborate (4)
-1
Isolated as a white powder (520 mg, 92%). Mp: 158 – 167. IR νmax/cm (neat film): 3067,
1
3
046, 3022, 3004, 2924, 1593, 1468, 1239, 1205, 1016, 995, 942, 925, 901, 892, 749. H
NMR (400 MHz, DMSO-d
6
) δ 7.80 (tt, 3JHH = 8.4, 4JHF = 6.7 Hz, 1H), 7.44 (dd, 3JHH = 8.4,
3JHF = 7.3 Hz, 2H), 7.31 (d, J = 6.7 Hz, 2H), 7.22 (s, 2H), 7.07 (t, J = 7.3 Hz, 2H), 7.03 –
13
) δ 160.6 (dd, 1JCF
6
=
.97 (m, 1H), 2.61 (s, 6H), 2.28 (s, 3H). C NMR (101 MHz, DMSO-d
250.7, 3JCF = 6.0 Hz) (C ), 137.0 (t, 3JCF = 10.1 Hz) (CH), 131.3
), 143.5 (C ), 141.6 (C
6
q
q
q
(
(
(
q, 3JCF = 1.7 Hz) (CH), 129.9 (CH), 126.2 (CH), 124.9 (CH), 122.9 (C
m) (CH), 91.7 (t, 2JCF = 28.1 Hz) (C ), 25.9 (t, 6JCF = 2.1 Hz) (CH
376 MHz, DMSO-d ) δ -95.84 (t, JHF = 7.0 Hz, 2F), -139.10 (q , 3F). B NMR (128 MHz,
q
), 113.52 – 113.03
19
q
3
), 20.5 (CH ). F NMR
3
1
1
6
B
DMSO-d
calc’d C15
6
) δ 3.13 (q, 1JBF = 52.8 Hz). HRMS-ESI (m/z): found [M-C
H BF
6 5 3
]+ 359.0112,
BF -
-
H F
14 2
I+ requires 359.0108, found [M-C15
14 2
H F I] 144.0473, calc’d C
H
6 5
3
requires 144.0473. Anal. calc’d for C21
H
19BF I: C, 50.04; H, 3.80; N, 0.00. Found C, 49.97;
5
H, 3.43; N, 0.04.
(2,6-difluorophenyl)(phenyl)iodonium phenyltrifluoroborate (5)
-1
Isolated as a white powder (132.9 mg, 77%). Mp: 142 – 153. IR νmax/cm (neat film):
1
3
080, 3066, 3049, 3007, 1593, 1467, 1242, 1206, 998, 946, 898, 788, 753, 706. H NMR
(
400 MHz, DMSO-d
6
) δ 8.20 (d, J = 7.7 Hz, 2H), 7.80 (tt, 4JHF = 8.5, 3JHH = 6.7 Hz, 1H),
.70 (t, J = 7.4 Hz, 1H), 7.55 (t, J = 7.8 Hz, 2H), 7.49 – 7.43 (m, 2H), 7.31 (d, J = 6.9 Hz,
7
2
1
1
13
H), 7.07 (t, J = 7.2 Hz, 2H), 7.00 (t, J = 7.1 Hz, 1H). C NMR (101 MHz, DMSO-d
6
) δ
60.1 (dd, 1JCF = 251.0, 3JCF = 5.5 Hz) (C
), 137.2 (t, 3JCF = 9.9 Hz) (CH), 135.2 (CH),
q
32.5 (CH), 132.2 (CH), 131.3 (q, 3JCF = 1.8 Hz) (CH), 126.2 (CH), 124.8 (CH), 117.1
), 113.1 (dd, 2JCF = 22.9, 4JCF = 2.8 Hz) (CH), 94.4 (t, 2JCF = 28.1 Hz) (C
). F NMR
19
(C
q
q
11
(377 MHz, DMSO-d
6
) δ -96.41 (t, JHF = 7.0 Hz, 2F), -139.12 (q , 3F). B NMR (128 MHz,
B
DMSO-d
calc’d C12
6
) δ 3.12 (q, 1JBF = 50.6 Hz). HRMS-ESI (m/z): found [M-C
6
H
5
BF
3
]+ 316.9644,
BF -
I+ requires 316.9639, found [M-C12
H F
8 2
I] 144.0474, calc’d C
-
H
H F
8 2
6
5
3
requires 144.0473. Anal. calc’d for C18
H
13BF I: C, 46.80; H, 2.84; N, 0.00. Found C, 46.41;
5
H, 2.25; N, 0.19.
(4-methoxyphenyl)(phenyl)iodonium phenyltrifluoroborate (6)
-1
Isolated as a light grey powder (93.9 mg, 81%). IR νmax/cm (neat film): 3070, 3009, 2971,
936, 2840, 1581, 1571, 1488, 1442, 1300, 1255, 1200, 1179, 1009, 990, 951, 904, 754.
2

1H NMR (400 MHz, DMSO-d
H), 7.31 (d, J = 6.5 Hz, 2H), 7.11 – 7.04 (m, 4H), 7.03 – 6.97 (m, 1H), 3.79 (s, 3H). C
NMR (101 MHz, DMSO-d ) δ 162.0 (C ), 137.2 (CH), 134.8 (CH), 131.8 (CH), 131.6 (CH),
31.3 (q, 4JC-F = 1.7 Hz) (CH), 126.1 (CH), 124.8 (CH), 117.5 (CH), 117.0 (C
), 105.3 (C ),
). B NMR (128 MHz, DMSO-
) δ 8.22 – 8.13 (m, 4H), 7.68 – 7.62 (m, 1H), 7.56 – 7.49 (m,
6
13
2
6
q
1
5
d
q
q
1
9
11
5.7 (CH
) δ 3.10 (q, 1JBF = 52.9 Hz). HRMS-ESI (m/z): found [M] 310.9929, calc’d C13
10BF -
requires 144.0473. Anal.
IO: C, 50.04; H, 3.76; N, 0.00. Found C, 49.91; H, 3.18; N, 0.06.
3
). F NMR (376 MHz, DMSO-d
6
) δ -139.14 (q
B
+
H
12127IO+
6
requires 310.9933, found [M]— 144.0456, calc’d C
calc’d for C19
H
6 5
3
H
17BF
3
(2-thienyl)(phenyl)iodonium phenyltrifluoroborate (7)
-1
Isolated as a light pink powder (318.7 mg, 92%). Mp: 110 – 115. IR νmax/cm (neat film):
1
3
096, 3006, 1470, 1442, 1435, 1383, 1199, 1014, 1007, 988, 970, 890, 758, 736, 707. H
NMR (400 MHz, DMSO-d
dd, J = 5.3, 1.3 Hz, 1H), 7.67 (ddt, J = 8.5, 7.0, 1.1 Hz, 1H), 7.54 (ddt, J = 8.2, 7.3, 1.3
Hz, 2H), 7.35 – 7.28 (m, 2H), 7.18 (dd, J = 5.3, 3.8 Hz, 1H), 7.07 (dddt, J = 7.4, 5.9, 1.4,
6
) δ 8.28 – 8.22 (m, 2H), 8.06 (dd, J = 3.8, 1.3 Hz, 1H), 7.97
(
1
3
0
(
1
.7 Hz, 2H), 7.04 – 6.98 (m, 1H). C NMR (101 MHz, DMSO-d
6
) δ 140.4 (CH), 137.4
3
CH), 134.6 (CH), 132.1 (CH), 131.7 (CH), 131.3 (q, JCF = 1.7 Hz) (CH), 129.7 (CH),
19
26.2 (CH), 124.8 (CH), 119.3 (C
q
), 100.7 (C
q
). F NMR (376 MHz, DMSO-d ) δ -139.11
6
11
) δ 3.09 (q, 1JBF = 52.6 Hz). HRMS-ESI (m/z): found
(q
B
). B NMR (128 MHz, DMSO-d
6
+
127
+
-
[
M] 286.9396, calc’d C10
H
8
IS requires 286.9391, found [M] 144.0475, calc’d
IS: C, 44.48; H, 3.03; N, 0.00.
C
H
6 5
10BF
3
-
requires 144.0473. Anal. calc’d for C16
H13BF
3
Found C, 44.16; H, 2.32; N, 0.00.
General procedure for the fluorination of unsymmetrical diaryliodonium
phenyltrifluoroborates salts:

A 10 mL microwave vial was charged with the diaryliodonium phenyltrifluoroborate salt
0.05 mmol) and solvent (1 mL), the vial was capped and sealed with a crimper. The vial
(
was placed in an oil bath at the specified temperature and stirred at the designated
temperature for 2 hours. After cooling to room temperature, an internal standard was
6
added to the crude reaction mixture followed by d -DMSO (0.5 mL) and the yield was
19
determined by F NMR spectroscopy.
Conflict of interest
There are no conflicts to declare.
Acknowledgments
Support from the U. Paul Sabatier and the French Canadian Research Fund is
acknowledged.

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