Metal-Free Iodoperfluoroalkylation: Photocatalysis versus Frustrated Lewis Pair Catalysis

Article abstract of DOI:10.1055/s-0040-1707232

A comparison of two catalytic, metal-free iodoperfluoroalkylation protocols is presented. Frustrated Lewis pairs [ ^tBu ₃P/B(C ₆F ₅) ₃] or phosphines/phosphites under visible light irradiation efficiently mediate the functionalization of non-activated alkenes and alkynes. A comprehensive account of the corresponding substrate scopes as well as insights into the mechanistic details of both reaction pathways are provided.

Full text of DOI:10.1055/s-0040-1707232

SYNTHESIS
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© Georg Thieme Verlag Stuttgart · New York
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L. Helmecke et al.
Feature
Synthesis
Metal-Free Iodoperfluoroalkylation: Photocatalysis versus
Frustrated Lewis Pair Catalysis
Lucas Helmecke
Michael Spittler
Bernd M. Schmidt
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Constantin Czekelius*
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Institute for Organic Chemistry and Macromolecular Chemistry,
Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1,
40225 Düsseldorf, Germany
constantin.czekelius@hhu.de
In memoriam Professor Rolf Huisgen
Received: 11.05.2020
Accepted after revision: 30.06.2020
Published online: 12.08.2020
tBu3P (10 mol%) 1
B(C6F5)3 (10 mol%) 2
R1
R2
R3
I
RF
R3
RF
I
+
R1
CH2Cl2, r.t.
DOI: 10.1055/s-0040-1707232; Art ID: ss-2020-z0252-fa
R2
Scheme 1 FLP-catalyzed iodoperfluoroalkylation of alkenes using tBu3P
(1) (10 mol%) and B(C6F5)3 (2) (10 mol%) as catalysts14,15
Abstract A comparison of two catalytic, metal-free iodoperfluoro-
alkylation protocols is presented. Frustrated Lewis pairs [tBu3P/B(C6F5)3]
or phosphines/phosphites under visible light irradiation efficiently me-
diate the functionalization of non-activated alkenes and alkynes. A
comprehensive account of the corresponding substrate scopes as well
as insights into the mechanistic details of both reaction pathways are
provided.
As this FLP-mediated iodoperfluoroalkylation showed
some peculiar characteristics, we investigated the mecha-
nism of this reaction more thoroughly.15 While activation of
the iodoperfluoroalkane by the Lewis base was indicated by
NMR spectroscopy, kinetic studies revealed strong evidence
for an additional photomediated process. Lewis base medi-
ated photochemical perfluoroalkylations have been docu-
mented earlier.17,18 Chen and co-workers17 used N,N,N′,N′-
tetraethylethylene diamine (TEEDA) to activate the iodoper-
fluoroalkane by forming an electron donor–acceptor (EDA)
complex. Moreno-Mañas18b as well as Huang and Zhang18a
reported that triphenylphosphine and related phospho-
rus(III) compounds can catalyze iodoperfluoroalkylations.
However, a photomediated process was not considered in
these publications. An electron donor–acceptor complex
formed from an electron-deficient perfluoroalkyl iodide
and an electron-rich phosphine can absorb light of lower
energy than the individual components. This can lead to
homolytic bond cleavage and radical formation.19 Develop-
ing this concept further, we presented the photomediated
iodoperfluoroalkylation of alkenes in the presence of tBu3P
(1) (Scheme 2).20
Key words iodoperfluoroalkylation, frustrated Lewis pair, electron
donor–acceptor complex, halogenations, radicals
The introduction of fluorine or large perfluoroalkyl
groups can significantly alter the electronic properties, li-
pophilicity, and metabolic stability of an organic molecule.1
In particular, the fine chemical industry,2 pharmaceutical
research3 and materials sciences4 strive for new methods
for the introduction of fluorinated functional groups.5 Over
the last few years, the portfolio of synthetic methodology
has changed and a plethora of new methods have been de-
veloped.6 Tailor-made fluorinating reagents,7 transition-
metal catalysts8 and metal-free methods9 have been devel-
oped, providing milder reaction conditions compared to es-
tablished transformations such as UV-light-mediated10 re-
actions. Transition-metal complexes11 (based on rutheni-
um, iridium, copper) or organic dyes12 (eosin Y, rose bengal,
riboflavin) are nowadays popular catalysts for photochemi-
cal reactions.9a,13
tBu3P (10 mol%) 1
R1
R2
R3
In 2016, we reported the frustrated Lewis pair (FLP)-
catalyzed iodoperfluoroalkylation of unsaturated hydrocar-
bons,14 which was followed by further mechanistic studies
in 2019 (Scheme 1).15 For these transformations, we used
the popular FLP consisting of tris(pentafluorophenyl)-
borane (2) (often abbreviated as BCF) and tri-tert-butyl-
phosphine (1).16
I
RF
R3
RF
I
+
R1
CH2Cl2, 30 °C, 1–6 h
461 nm
R2
Scheme 2 Photomediated iodoperfluoroalkylation of alkenes using
tBu3P (1) (10 mol%) as the catalyst20
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, A–L
Georg Thieme Verlag KG, Rüdigerstraße 14, 70469 Stuttgart, Germany

B
L. Helmecke et al.
Feature
Synthesis
Other research groups have also recently reported the
effective use of phosphorus compounds as catalysts for
similar transformations. Zhao, Li and He developed a difluo-
roalkylation of alkenes by using organophosphine reagents
(DPPM) at higher temperature.21 Zhang and co-workers
presented the phosphine-catalyzed difluoroalkylation of
arenes and heterocycles by using visible light.22 The group
of Dilman successfully developed the iododifluoromethyla-
tion of alkenes by utilizing (phosphonio)-difluoromethyl
radical cations.23 Furthermore, phenols,24 amines25 and
even acetone26 as a solvent were investigated as Lewis base
mediators in this context.
When we started our investigation on the FLP-catalyzed
reaction, one of the first observations was the formation of
t
[tBu3PI][FB(C6F5)3] (3) upon mixing Bu3P and B(C6F5)3 with
various perfluoroalkyl iodides (Scheme 3).14 The formation
Biographical Sketches
Lucas Helmecke was born in
1992 in Germany. He studied
chemistry at Heinrich-Heine-
Universität Düsseldorf and grad-
uated in 2017 with a master´s
degree in chemistry. He is cur-
rently a Ph.D. student under the
investigation of metal-free iodo-
perfluoroalkylation reactions
supervision
of
Constantin
and the activation of perfluoro-
alkyl iodides with phosphorus
compounds.
Czekelius. His work is mainly fo-
cused on the development and
Michael Spittler was born in
1988 in Germany. After under-
graduate studies at Krefeld,
where he studied chemistry and
biotechnology in combination
studies in chemistry at Heinrich-
Heine-Universität in 2015. He
earned his Ph.D. under the su-
pervision of Constantin Czeke-
lius for his work in the field of
asymmetric gold catalysis and
the investigation of frustrated
Lewis pair (FLP)-catalyzed io-
doperfluoroalkylation reactions.
Together with Lucas Helmecke,
he has started to develop the
activation of perfluoroalkyl io-
dides with phosphorus com-
pounds.
with an apprenticeship as
a
chemical laboratory assistant at
Evonik, he finished his master’s
Bernd M. Schmidt researches
responsive and functional su-
pramolecular systems. Born and
raised in Berlin, Germany, he
performed his Ph.D. with Dieter
Lentz at the Freie Universität
Berlin and with Hidehiro Sakurai
at the IMS in Okazaki, Japan,
working on bowl-shaped aro-
matic hydrocarbons (corannu-
lene and sumanene). Bernd
undertook postdoctoral studies
with Makoto Fujita at the Uni-
versity of Tokyo, Japan and with
Stefan Hecht at the Humboldt
University of Berlin, Germany,
to learn more about supramo-
lecular chemistry, physical–or-
ganic chemistry and molecular
photoswitches. Since February
2018, he has been an indepen-
dent research group leader at
Heinrich-Heine-Universität Düs-
seldorf, Germany.
Constantin Czekelius was
born in Germany in 1974. After
After postdoctoral studies in the
group of Richard R. Schrock at
MIT, he joined the Freie Univer-
sität Berlin as an independent
research group leader. Since
2013, he has been a chemistry
professor at Heinrich-Heine-
Universität Düsseldorf. His inter-
ests include enantioselective
catalytic methods for the facile
preparation of synthetically in-
teresting building blocks, the
synthesis of halogenated com-
pounds, and research on medic-
inal chemistry.
undergraduate
studies
at
Freiburg and Würzburg, he ob-
tained a diploma in chemistry at
the ETH Zurich in 2000. Under
the supervision of Erick M. Car-
reira he earned a Ph.D. in 2004.
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, A–L

C
L. Helmecke et al.
Feature
Synthesis
of this iodophosphonium fluoroborate salt suggested that
the Lewis pair was capable of activating the C–I bond. It was
proposed that upon its cleavage, either -fluoro- or -fluoro
elimination leads to the ion pair. It is noteworthy that the
salt is completely unreactive towards alkenes and neither
the fluoride nor the iodonium ion are transferred to cyclo-
hexene or hex-1-ene.
Non-functionalized internal and terminal alkenes as
well as cyclic alkenes were successfully transformed. Other
halides (12 and 13) and silanes (11) were also tolerated in
this iodoperfluoroalkylation. However, further investiga-
tions of the functional group tolerance showed that many
polar substituents were not compatible with this catalyst
system.
For example, alcohols were unsuitable as starting mate-
rials, presumably due to interaction with the empty orbital
of the borane. In contrast, substrates with aliphatic as well
as aromatic esters, phenol ethers or phthalimides were suc-
cessfully iodoperfluoroalkylated (Scheme 5), but some-
times slow conversions and low yields were observed. Due
to demethylation and concomitant deactivation of the bo-
rane, 4-allylanisole proved to be a challenging substrate as
well.
RF
I
[tBu3PI] [(C6F5)3BF]
tBu3P
+
B(C6F5)3
CH2Cl2, r.t.
1
2
3
Scheme 3 Formation of iodophosphonium fluoroborate salt 3 from io-
doperfluoroalkanes14
t
In contrast to this observation, when employing Bu3P
and B(C6F5)3 as an FLP together with nonafluoro-1-iodobu-
tane (4) in the presence of different alkenes, the corre-
sponding iodoperfluoroalkylated products were isolated
(Scheme 4).14 Herein, iodine was always regioselectively in-
corporated at the higher substituted carbon. When using
(Z)-3-hexene it was shown that the reaction was not diaste-
reoselective and that a mixture of isomers was isolated.
This implies that ring opening of a putative epi-iodonium
intermediate by nucleophilic substitution was less likely. In
contrast, when (E)-3-hexene was tested, no reaction was
observed over the period of 24 hours. Neither a reaction nor
polymerization were observed when styrene was used as
the starting material.14 Styrene even quenches the FLP-cata-
lyzed iodoperfluoroalkylation of other substrates.15 More-
no-Mañas et al. reported a similar behavior and ascribed it
to the high stability of potentially formed benzylic radi-
cals.18b
tBu3P (10 mol%) 1
B(C6F5)3 (10 mol%) 2
I
R2
RF
R2
RFI
+
R1
R1
CH2Cl2, r.t., 24 h to 35 d
I
O
C4F9
C4F9
4
I
MeO
Br
15, 28%, 6 d
16, 80%, 24 h
O
I
O
O
O
C4F9
C6F13
I
17, 76%, 35 d
18, 25%, 35 d
O
I
C4F9
O
O
3
C4F9
N
4
I
Cl
O
19, 87%, 24 h
20, 58%, 24 h
tBu3P (10 mol%) 1
B(C6F5)3 (10 mol%) 2
R2
Scheme 5 FLP-catalyzed iodoperfluoroalkylation of alkenes incorpo-
rating polar substituents
I
R2
C4F9I
+
R1
R1
C4F9
CH2Cl2, r.t., 12–40 h
4
I
I
C4F9
When changing to non-functionalized, terminal or in-
ternal alkynes as substrates using B(C5F6)3 (2) as the Lewis
acid, the corresponding monoaddition products for termi-
nal and internal alkynes were isolated in 10% yield after
long reaction times of up to 23 d (Table 1). Dureen and
C4F9
5, 73%
6, 95%
I
I
C4F9
C4F9
7, from cis-3-hexene: 33%, 62:38 d.r.
t
Stephan reported boron alkynylide formation from Bu3P,
8, 55%, 53:47 d.r.
B(C6F5)3 and phenylacetylene.27 We assumed that this for-
mation of a stable [tBu3PH][PhC≡CB(C6F5)] intermediate
might be a faster and more efficient process than the io-
doperfluoroalkylation of the alkyne. To overcome this prob-
lem of potential catalyst deactivation and potentially im-
proving tolerance towards heteroatoms, electronically
tuned boranes such as tris(2,6-difluorophenyl)borane (21)
and the more water-stable (2,3,6-trichlorophenyl)bis(2,3,6-
trifluorophenyl)borane (22) were investigated (Table 1 and
Table 2). However, the transformation of demanding
alkenes or terminal alkynes was not substantially im-
proved.
I
C4F9
I
I
C4F9
Me3Si
11, 81%
C4F9
9, 54%
10, 37%
I
I
Br
C4F9
C4F9
I
12, 56%
13, 84%
I
C4F9
14, 56%
Scheme 4 FLP-catalyzed iodoperfluoroalkylation of alkenes14
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, A–L

D
L. Helmecke et al.
Feature
Synthesis
Table 1 FLP-Catalyzed Iodoperfluoroalkylation of Non-Functionalized
Alkynes Using Different Boranes
the reaction rate, presumably by coordination of the Lewis
acid to the double bond as mentioned earlier in the case of
an alkyne.15
borane (10 mol%)
R2
R2
While we investigated the FLP-catalyzed reaction, we
obtained more and more evidence for a very efficient com-
peting photocatalytic process involving the perfluoroalkyl
I
tBu3P (10 mol%) 1
C4F9I
+
R1
R1
C4F9
CH2Cl2, r.t.
4
t
iodide and the used phosphine Bu3P. Therefore, we exam-
Entry
Substrate
Borane
Yield (%)
E/Z
ined this catalytic reaction in more detail. We started by
visible light irradiation of a mixture of 1-octene and C4F9I
1814
E-isomer
t
1
2
B(C6F5)3 (2)
with or without added Bu3P under similar conditions as
those of the FLP-catalyzed reaction.20 Surprisingly, we ob-
tained a yield of 89% after a reaction time of 1 hour in the
44
70:30
B(2,6-F2C6H3)3 (21)
5
t
presence of Bu3P (10 mol%). Without the phosphine, no
10
E-isomer
conversion was detected after 72 hours and only 32% after
3
4
B(C6F5)3 (2)
49 days.20
20
E-isomer
B(2,6-F2C6H3)3 (21)
Starting from this observation, we aimed at providing a
solution for issues described above, such as functional
group tolerance or poor alkyne transformation. Screening
of different phosphorus compounds showed that other
phosphines or phosphites were also capable of catalyzing
the reaction, although electron-rich and sterically demand-
5
B(2,6-F2C6H3)3 (21)
–
t
ing Bu3P (1) remained as the most efficient catalyst. Di-
Table 2 FLP-Catalyzed Iodoperfluoroalkylation Using Electronically
chloromethane was the best solvent in this case having the
additional positive side effect that it can be easily removed
from the volatile products.
Modified Boranes
borane (10 mol%)
I
R2
R2
tBu3P (10 mol%) 1
C4F9I
+
R1
Reactions at higher wavelengths (531 nm, 29%; 630 nm,
10%) did not lead to complete conversion. Only at 461 nm
full conversion was detected after 1 hour. At even lower
wavelengths (405 nm), an increasing occurrence of C4F9H in
the 1H and 19F NMR spectra could be detected.20 In contrast
to the FLP-catalyzed reaction, various terminal or internal
alkenes, carrying polar functional groups, such as alcohols,
ethers, esters, and amides, as well as halides, were cleanly
transformed in the photocatalytic iodoperfluoroalkylation
and good to excellent yields were obtained (Scheme 6).20
Moreover, alkenes incorporating E-configured double bonds
were now also suitable substrates. An exception was an
azide-functionalized alkene giving a low yield, which was
due to the difficulty in the purification process. The poten-
tially expected Staudinger product could not be observed in
this reaction. Electron-deficient alkenes still represent diffi-
cult substrates as no product could be isolated when ethyl
acrylate or related substrates were used (see the Supporting
Information).20
With these promising results in hand, we next investi-
gated the substrate scope by further extending it towards
alkynes (Scheme 7). Using 1-octyne as a model alkyne, we
were able to isolate the corresponding addition products as
efficiently as for the reactions with alkenes. Terminal, inter-
nal and phenylacetylenes gave the corresponding products
in 50–98% yield as isomeric mixtures with the E-iodoalkene
as the major product. In the case of 1-phenyl-1-propyne the
configuration was confirmed by crystal structure analysis
(see Figure 14 in the Supporting Information,). The carba-
mate product 48 was obtained in low yield and only the E-
CH2Cl2, r.t.
R1
C4F9
4
Entry Substrate
Borane
Yield (%)
–
OH
1
2
B(2,6-F2C6H3)3 (21)
B(2,6-F2C6H3)3 (21)
8
–
–
MeO
O
3
4
B(2,6-F2C6H3)3 (21)
O
O
B(2,3,6-Cl3C6H2)(2,3,6-F3C6H2)2
(22)
13
O
3
Cl
Only in the case of phenylacetylene (Table 1, entry 4) a
better yield was obtained by by changing the Lewis acid
from B(C6F5)3 (2) to B(2,6-F2C6H3)3 (21). With respect to the
phosphine catalyst partner, we found that only Bu3P (1)
t
promoted the reaction efficiently.15 Kinetic experiments on
the FLP-catalyzed reaction showed a first-order dependen-
cy with respect to the perfluoroalkyl iodide. In the catalytic
cycle the phosphine most likely coordinates to the perfluo-
roalkyl iodide and is involved in a fast-starting reaction, but
then conversion slows down rapidly. This initial coordina-
tion and interaction can be detected by 19F and 31P NMR
spectroscopy. Only a moderate rate increase could be ob-
served when using higher concentrations of the Lewis acid.
In contrast, higher concentrations of the alkene slow down
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, A–L

E
L. Helmecke et al.
Feature
Synthesis
R3
I
R3
RF
R2
I
R2
RF
tBu3P (10 mol%) 1
tBu3P (10 mol%) 1
R1
+
RFI
RF
+
I
R1
R1
CH2Cl2, 30 °C, 1–6 h
461 nm
R2
R1
CH2Cl2, 30 °C, 1–3 h
460 nm
R2
I
I
I
I
RF
5
C4F9
C4F9
R =
H 38, 81%; E/Z 95:5
= CF3 23, 76%
= C4F9 24, 89%
= C6F13 25, 97%
= C8F17 26, 67%
I
RF
RF
R
7 from cis-3-hexene: 62%, d.r. 65:35
from trans-3-hexene: 71%, d.r. 53:47
RF
=
CF3 34, 50%; E/Z 81:19
C4F9 35, 95%; E/Z 88:12
C6F13 36, 84%; E/Z 85:15
C8F17 37, 98%; E/Z 85:15
Me 39, 82%; E/Z 95:5
MeO 40, 84%; E/Z 92:8
tBu 41, 69%; E/Z 95:5
C4F9
C4F9
C4F9
I
I
14, 74%
Br 42, 62%; E/Z 94:6
I
I
6, 87%
9, 42%
I
I
C4F9
HO
I
C4F9
Br
C4F9
C4F9
C4F9
8
4
I
8, 89%
d.r. 55:45
27, 77%
28, 87%
43, 83%, E-isomer only
44, 64%; E/Z 70:30
I
I
I
TsO
C4F9
N3
C4F9
8
4
Me3Si
29, 71%
30, 20%
C8F17
C4F9
I
O
O
I
45, 52%, E-isomer only
46, 92%; E/Z 63:37
H2N
O
C4F9
C6F13
C4F9
17, 90%
31, 86%
O
MeO
I
I
N
C4F9
I
N
O
C4F9
C4F9
I
O
O
32, 96%
15, 95%
O
47, 70%; E/Z 69:31
48, 44%, E-isomer only
O
I
O
C4F9
4
O
C4F9
Scheme 7 Photocatalytic iodoperfluoroalkylation of alkynes using tri-
tert-butylphosphine
4
I
Cl
Br
Cl
16, 96%
19, 88%
O
I
I
the nitrile in this context, competition of the more abun-
dant solvent with the phosphine is likely to result in slower
conversion. While the reaction rate substantially increased
in acetonitrile in the presence of sodium iodide (entry 3),
the more soluble TBAI additive led to a higher conversion in
dichloromethane (entry 6).
H
N
C4F9
20, 86%
N
C4F9
4
33, 88%
O
O
Scheme 6 Photocatalytic iodoperfluoroalkylation of alkenes20
isomer was isolated. The Z-alkene was not isolated but only
1
detected in the H and 19F NMR spectra. Overall, the reac-
Table 3 Reactions of 1-Octene with C4F9I and PPh3 in the Presence of
Iodide Salts
tion times were quite similar to those for the transforma-
tions of alkenes (1–3 h).
PPh3 (10 mol%)
I
Employing the optimized reaction conditions, we tested
the scalability of the reaction and effectively prepared the
perfluoroalkylated product of 1-octene (49) with C4F9I (4)
in a quantity of 8.90 g (19.5 mmol, 98%).20 Similarly, 1-oc-
tyne (52) was transformed into 8.48 g of the corresponding
product 35 (18.6 mmol, 93%) (see the Supporting Informa-
tion).
In 2019, Fu et al. published the photocatalytic decarbox-
ylative alkylation with sodium iodide (1.5 equiv) as additive
and triphenylphosphine (20 mol%) as the catalyst.28 We re-
acted 1-octene (49) with C4F9I (4) under these standard
conditions and added sodium iodide (NaI) or tetrabutylam-
monium iodide (TBAI) in MeCN or CH2Cl2, respectively (Ta-
ble 3). Without an additive, the conversion in CH2Cl2 (entry
2) was higher than that in MeCN (entry 1). In theoretical
studies (vide infra), we found evidence for a Lewis pair in-
teraction between the perfluoroalkyl iodide and solvent
molecules.29a Given the more pronounced donor ability of
additive (1.5 equiv)
C4F9
C4F9I
+
solvent, 30 °C, 1 h
461 nm
5
5
49
4
24
Entry
Solvent
Additive
Conversion (%)
1
2
3
4
5
6
MeCN
CH2Cl2
MeCN
CH2Cl2
MeCN
CH2Cl2
–
26
45
68
56
36
66
–
NaI
NaI
TBAI
TBAI
In 2019, Zhao, Li, and He presented the phosphine-cata-
lyzed difluoroalkylation of alkenes.21 For the reaction with
ethyl 2,2-difluoro-1-iodoacetate they used bis(diphenyl-
phosphino)methane (DPPM) as the catalyst (10 mol%) and
1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, A–L

F
L. Helmecke et al.
Feature
Synthesis
(DMPU) as the additive to reduce the formation of
HCF2COOEt. They conducted this reaction at 80–90 °C in
THF for 20–30 hours. It is noteworthy that we were able to
perform the addition of ethyl 2,2-difluoro-1-iodoacetate
(50) to 1-octene (49) or 1-octyne (52) using Bu3P as the
catalyst in our setup over 3 hours at room temperature
(Scheme 8).
ducted to demonstrate the requirement of continuous light
irradiation (Figure 1). Once a solution of 1-octene (49) and
C4F9I (4) together with the catalyst had been irradiated for 1
minute, rapid conversion was detected after the first sam-
ple withdrawal. The solution was then stirred in the dark
for 20 minutes and only a minor increase in conversion was
detected. Next, irradiation was continued in increasing in-
tervals (as depicted) during which complete conversion was
observed after 3 hours.
t
O
I
I
50
OEt
5
F
F
CF2CO2Et
51, 90%
5
tBu3P (10 mol%) 1
49
CH2Cl2, 30 °C, 3 h
461 nm
I
5
5
52
CF2CO2Et
53, 97%, E/Z 84:16
Scheme 8 Phosphine-catalyzed reactions of 1-octene (49) and 1-oc-
tyne (52) with ethyl 2,2-difluoro-1-iodoacetate (50)
Mechanistic experiments confirmed the assumption of
a radical mechanism. When 2,2,6,6-tetramethylpiperidin-
1-yl-oxyl (54) (TEMPO) was added as radical scavenger to
the reaction mixture the corresponding TEMPO-C4F9 prod-
uct 55 was detected (Scheme 9).
C4F9
O
N
O
N
tBu3P (0.48 equiv) 1
[tBu3PI]
X
+
F9I
C4
+
CH2Cl2, 30 °C, 24 h
461 nm
54
4
55
56
I
C4F9
Figure 1 Interval irradiation of the reaction of 1-octene (49) with C4F9I
(4)
tBu3P (9.93 equiv) 1
+
C4F9I
CH2Cl2, 30 °C, 24 h
461 nm
EtO2C
CO2Et
EtO2C
CO2Et
57
4
58, 94%, d.r. 90:10
To exclude the possibility that C4F9I is thermally activat-
ed by the LEDs, we heated a solution of 1-octene (49) and
C4F9I (4) for 1 hour at 30 °C under best possible light exclu-
sion conditions (Scheme 10). After 1 hour at 30 °C, we mon-
itored 29% conversion, and after further heating to reflux
for another hour, 34% conversion was observed. This indi-
cates that thermal activation is negligible in this range.
I
I
tBu3P (10.5 equiv) 1
C6F13
I
+
+
CH2Cl2, 30 °C, 3 h
461 nm
C6F13
C6F13
62, 31%
59
60
61, 69%, E/Z 82:18
Scheme 9 Radical scavenger and radical clock experiments20
By using diethyl 2,2-diallylmalonate (57) as the starting
material for the iodoperfluoroalkylation, the functionalized
cyclopentane derivative 58, most likely formed via a radical
5-exo-trig-ring closure, was isolated (Scheme 9). As a sec-
ond radical clock, we tested ethynylcyclopropane (59) and
isolated the perfluoroalkylated vinylcyclopropane product
61 together with the ring-opened allene 62 (Scheme 9). Test
reactions showed that the addition of nonafluoro-1-io-
dobutane (4) to 1-octene (49) was very slow in the absence
of the phosphine (32% conversion after 49 d) or without
light irradiation (12% conversion after 1 h).20 We attributed
the latter observation to the fact that light could not be
completely excluded during the reaction setup or sample
withdrawal. An interval irradiation experiment was con-
I
tBu3P (9.63 mol%) 1
C4F9I
+
C4F9
5
CH2Cl2, 30 to 40 °C
5
49
4
24
hν
Scheme 10 Reaction at elevated temperatures and under exclusion of
light
As is known in the literature, perfluoroalkyl iodides can
form a halogen bond (XB) with a Lewis base (LB) such as
amines and phosphines.19a,29 We have already shown that
the interaction between C4F9I (4) and tBu3P (1) is observable
in the 19F and 31P NMR spectra of such a mixture.15 When
we screened various phosphorus(III) compounds as poten-
t
tial catalysts, we observed the best conversions for Bu3P
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, A–L

G
L. Helmecke et al.
Feature
Synthesis
(1 h, ≥99%) followed by (MeO)3P (6 h, 94%) and Ph3P (2 h,
possible for a small fraction of reactive conformers result-
ing in strong spectral tailing. In contrast, conformationally
locked phosphites (tBuO)3P or MeC(CH2O)3P are both unre-
active.
n
88%).20 Noteworthy, Bu3P was almost inactive. Using a 19F
NMR spectroscopy titration method, we determined the as-
sociation constants (Ka) for tBu3P (14.15 M–1), PPh3 (0.96 M–1),
and (MeO)3P (0.46 M–1), respectively. Taylor et al. showed
that the binding constant differs substantially in various
solvents.30 For this reason, we determined the binding con-
stant in CH2Cl2 and used an internal standard as a reference
(see the Supporting Information).
During the mechanistic investigations of the photocata-
lyzed reaction the nature of the light absorption process
caught our interest. Interestingly, the reaction solutions
containing different phosphine or phosphite catalysts ap-
pear completely colorless. Additionally, their UV–vis spec-
tra showed almost no overlap with the blue LED irradiation
profile (Figure 2).29a
In summary, two metal-free, mild and catalytic (10
mol%) iodoperfluoroalkylations have been compared: One
using a frustrated Lewis pair (BC6F5/tBu3P) as the catalyst,
and the other a photomediated process catalyzed by just a
Lewis base (tBu3P). It has been shown that FLPs can activate
perfluoroalkyl iodides for their reaction with unfunctional-
ized alkenes.14 In the presence of functionalized substrates
bearing polar substituents or in the transformation of
alkynes the original catalyst system is deactivated, presum-
ably by competitive interaction with the highly electron-
deficient borane. Reactivity is restored to some extent
when employing a modified catalyst system based on par-
t
tially fluorinated aryl boranes. When Bu3P as a Lewis base
is used as the sole catalyst and the reaction medium is irra-
diated by blue light, the restriction in substrate scope is
overcome rendering the process more efficient and opera-
tionally simple. By forming an electron donor–acceptor
(EDA) complex between the Lewis base and the perfluoro-
alkyl iodide, light-induced radical formation takes place.
Various alkenes or alkynes with different polar functional
groups are efficiently transformed in good to very good
yields. By switching from perfluoroalkylated iodides to eth-
yl 2,2-difluoro-1-iodoacetate, the corresponding addition
products could be obtained as well. Mechanistic investiga-
tions using radical clocks or radical scavengers support the
assumption of a radical mechanism. Apart from the Lewis
acid mediated or photochemically induced activation of the
EDA complex, its thermal activation has also been investi-
gated, but this process is not competitive in terms of reac-
tion rate. The association constants for the EDA complexes
of different phosphines and phosphites were determined.
These studies provide a basis for correlation with theoreti-
cal calculations, which have shown the intricacy of the
photocatalytic mode of action of phosphorus(III) com-
pounds. It was found that seemingly small variations of the
electronic properties and conformational flexibility result
in stark differences in the excitation and relaxation profiles.
These findings should also contribute to a deeper under-
standing of related photocatalytic processes involving EDA
complexes in general.
Figure 2 UV–vis absorption spectra of the reaction solutions and the
blue LED irradiation profile29a Int. = intensity. Intensitiy of the used LED
was normalized to 1.
In contrast to sensitizer-mediated processes, for exam-
ple involving transition-metal photocatalysts, binding of
the iodoperfluoroalkane to the phosphine does not result in
a red-shift of the absorption maximum. Instead, a signifi-
cant increase in the absorption coefficient with concomi-
tant broader tailing into the visible light region was found.
This could be rationalized by relativistic density functional
theory and multireference configuration interaction meth-
ods. This detailed study also allowed addressing the seem-
ingly puzzling observation that both tBu3P and P(OMe)3 are
active catalysts, but that closely related nBu3P is not. In the
Reagents and solvents were purchased from Acros, Sigma-Aldrich, ab-
cr, TCI, J&K Scientific or Avantor. Solvents were dried with a MP-SPS
800 solvent purification system from M. Braun and degassed by
freeze-pump-thaw cycles. Reactions were monitored by thin-layer
chromatography (TLC) using Macherey-Nagel silica gel plates (ALU-
GRAM® XtraSIL G/UV254, 0.20 mm thickness). Melting points were re-
corded on a Büchi B-540 instrument. IR spectra were recorded as
films on a NaCl single crystal using a Jasco FT/IR-6200 spectropho-
tometer. 1H,11B, 13C and 19F NMR spectra were recorded on Bruker
Avance III 300 and 600 spectrometers. Chemical shifts are reported in
t
case of the electron-rich and bulky Bu3P, the high Lewis
base donor ability drives the formation of the biradical trip-
let state. However, the adducts of tri-n-butylphosphine
show larger coordinate displacements for the ground and
the excited state leading to inefficient vibrational wave
function overlap. In contrast, phosphites are much less elec-
tron-rich but seem to allow for oxygen lone pair participa-
tion in the HOMO. In the flexible trimethyl phosphite this is
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, A–L

H
L. Helmecke et al.
Feature
Synthesis
parts per million (ppm) and referenced to the corresponding solvent;
mc = complex multiplet; E and Z refer to the assigned isomers. High-
resolution mass spectrometry (HRMS) was performed with a Bruker
Daltonics UHR-QTOF maXis 4G spectrometer. Elemental analyses
were recorded on an Elementar Vario Micro Cube.
Yield: 333 mg (76%); colorless liquid.
IR (film): 2962, 1747, 1433, 1366, 1237, 1042, 845, 812, 733, 699, 657,
606, 553, 530 cm–1
1H NMR (600 MHz, CDCl3):  = 4.45–4.36 (m, 1 H, –CH2CO2–), 4.35–
4.27 (m, 1 H, –CHI–), 4.21–4.10 (m, 1 H, –CH2CO2–), 3.03–2.90 (m, 1 H,
RFCH2–), 2.90–2.76 (m, 1 H, RFCH2–), 2.22–2.14 (m, 1 H, –CH2CH2–),
2.14–2.07 (m, 1 H, –CH2CH2–), 2.08–2.02 (m, 3 H, –CH3).
13C NMR (75.5 MHz, CDCl3):  = 170.8, 119.7–108.7 (m, CF2, CF3), 64.2,
42.0 (t, 2JCF = 20.8 Hz, –H2CCF2RF), 39.0, 20.9, 15.3.
19F NMR (282 MHz, CDCl3):  = –80.8 (tt, J = 10.1, 2.6 Hz, 3 F), –110.9
to –115.1 (m, 2 F), –121.6 to –122.0 (m, 2 F), –122.7 to –123.1 (m, 2 F),
–123.5 to –123.9 (m, 2 F), –126.0 to –126.4 (m, 2 F).
.
FLP-Catalyzed Iodoperfluoroalkylation; General Procedure A (GP-
A)
t
Using a glovebox (N2 atmosphere), Bu3P (10 mol%) and the borane
(10 mol%) were weighed into an amber glass screw-top vial, dissolved
in CH2Cl2 (2.1 mL) and a Teflon stir bar was added. The alkene or
alkyne substrate and the corresponding perfluoroalkyl iodide (1.10
mmol) were added. The reaction vial was sealed and the contents
stirred for the indicated reaction time. The solvent was evaporated
under a stream of nitrogen. Purification was conducted by silica gel
column chromatography.
HRMS (ESI): m/z [M + H]+ calcd for C12H11F13IO2: 560.9591; found:
560.9593.
4,4,5,5,6,6,7,7,7-Nonafluoro-2-iodoheptyl Acetate (18)
The title compound was prepared following GP-A.
Yield: 92.2 mg (25%); colorless liquid.
Photomediated Iodoperfluoroalkylation; General Procedure B
(GP-B)
Using a glovebox (N2 atmosphere), tBu3P (10 mol%) and the alkene or
alkyne substrate were weighed into an aluminum-foil-wrapped reac-
tion glass. CH2Cl2 (2 mL) and a Teflon stir bar were added. Under red
light conditions the corresponding perfluoroalkyl iodide (1.10 mmol)
was added. The reaction vial was sealed, transferred into a photoreac-
tor20 and was irradiated for the indicated time. After the stated
reaction time, irradiation was stopped and the solvent was evaporat-
ed under a stream of nitrogen. Purification was conducted by silica
gel column chromatography.
IR (film): 2958, 1750, 1432, 1382, 1356, 1233, 1135, 1043, 1026, 881,
739, 725 cm–1
.
1H NMR (600 MHz, CDCl3):  = 3.98–3.79 (m, 3 H, –CHI–, RFCH2–),
2.57–2.22 (m, 2 H, –CH2CO2–), 1.56 (s, 3 H, –CH3).
13C NMR (75.5 MHz, CDCl3):  = 169.1, 121.2–110.5 (m, CF2, CF3), 68.4,
37.9 (t, 2JCF = 21.2 Hz, –H2CCF2RF,), 20.0, 12.0.
19F NMR (282 MHz, CDCl3):  = –81.0 to –81.3 (m, 3 F), –112.4 to
–114.8 (m, 2 F), –124.2 to –124.5 (m, 2 F), –125.7 to –126.1 (m, 2 F).
HRMS (ESI): m/z [M + Na]+ calcd for C9H8F9INaO2: 468.9318; found:
468.9316.
1-Methoxy-4-(4,4,5,5,6,6,7,7,7-nonafluoro-2-iodoheptyl)benzene
(15)
The title compound was prepared following GP-A.
Yield: 114 mg (28%); colorless liquid.
6,6,7,7,8,8,9,9,9-Nonafluoro-4-iodononyl 4-Chlorobenzoate (19)17
The title compound was prepared following GP-A.
Yield: 364 mg (87%); colorless oil.
1H NMR (300 MHz, CDCl3):  = 8.00–7.93 (m, 2 H), 7.47–7.38 (m, 2 H),
4.46–4.32 (m, 3 H), 3.09–2.69 (m, 2 H), 2.14–1.84 (m, 4 H).
19F NMR (282 MHz, CDCl3):  = –81.1 (tt, J = 9.7, 3.3 Hz), –111.1 to
–112.4 (m), –114.4 to –115.5 (m), –124.4 to –124.8 (m), –125.7 to
–126.2 (m).
IR (film): 2838, 1613, 1585, 1514, 1467, 1442, 1351, 1246, 1135,
1037, 881, 832, 726, 518 cm–1
.
1H NMR (300 MHz, CDCl3):  = 7.18–7.07 (m, 2 H, Ar–H), 6.94–6.82
(m, 2 H, Ar–H), 4.43 (dq, J = 8.4, 6.4 Hz, 1 H, –CHI–), 3.81 (s, 3 H,
–OMe), 3.28–3.08 (m, 2 H, Ar–CH2–), 3.01–2.73 (m, 2 H, –CH2–RF).
13C NMR (75.5 MHz, CDCl3):  = 159.0, 130.8, 130.2, 114.1, 121.3–
110.3 (m, CF2, CF3), 55.4, 46.4, 40.6 (t, 2JCF = 20.9 Hz, –H2CCF2RF), 20.3.
19F NMR (282 MHz, CDCl3):  = –81.1 (tt, J = 9.7, 3.2 Hz, 3 F), –111.6 to
–114.7 (m, 2 F), –124.5 to –124.7 (m, 2 F), –125.8 to –126.0 (m, 2 F).
HRMS (ESI): m/z [M + H]+ calcd for C14H13F9IO: 494.9862; found:
494.9857.
2-(7,7,8,8,9,9,10,10,10-Nonafluoro-5-iododecyl)isoindoline-1,3-
dione (20)17
The title compound was prepared following GP-A; yield: 135 mg
(58%); light brown oil
1H NMR (300 MHz, CDCl3):  = 7.90–7.77 (m, 2 H), 7.77–7.67 (m, 2 H),
4.30 (tt, J = 8.1, 5.3 Hz, 1 H), 3.71 (t, J = 7.1 Hz, 2 H), 3.06–2.64 (m, 2
H), 1.93–1.57 (m, 5 H), 1.53–1.40 (m, 1 H).
19F NMR (282 MHz, CDCl3):  = –81.01 (tt, J = 9.7, 3.3 Hz), –111.01 to
–112.75 (m), –114.04 to –115.89 (m), –124.23 to –124.79 (m),
–125.40 to –126.64 (m).
1-Bromo-4-[(7,7,8,8,9,9,10,10,10-nonafluoro-5-iodo-
decyl)oxy]benzene (16)17
The title compound was prepared following GP-A.
Yield: 349 mg (80%); light yellow oil.
1H NMR (300 MHz, CDCl3):  = 7.42–7.33 (m, 2 H), 6.81–6.73 (m, 2 H),
4.35 (tt, J = 8.2, 5.3 Hz, 1 H), 3.95 (t, J = 6.0 Hz, 2 H), 3.07–2.66 (m, 2
H), 1.98–1.68 (m, 5 H), 1.68–1.54 (m, 1 H).
1,1,1-Trifluoro-3-iodonon-2-ene (34)31a
19F NMR (282 MHz, CDCl3):  = –81.0 (tt, J = 9.6, 3.3 Hz), –111.2 to
–113.0 (m), –113.6 to –116.1 (m), –124.3 to –124.8 (m), –125.7 to
–126.1 (m).
1,1,1-Trifluoro-3-iodonon-2-ene (34) was synthesized using a proce-
dure similar to GP-B. Bu3P (1) and 1-octene (49) were dissolved in
this case before a balloon with CF3I was connected.
t
Yield: 79.5 mg (50%, E/Z = 81:19); colorless liquid.
5,5,6,6,7,7,8,8,9,9,10,10,10-Tridecafluoro-3-iododecyl Acetate (17)
The title compound was prepared following GP-A.
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, A–L

I
L. Helmecke et al.
Feature
Synthesis
1H NMR (600 MHz, CDCl3):  = 6.39 (q, J = 7.7 Hz, 1 H, CICH, E), 6.29
(qt, J = 7.2, 1.4 Hz, 1 H, CICH, Z), 2.63–2.57 (m, 2 H, CH2CICH), 1.60–
1.53 (m, 2 H, CH2CH2CICH), 1.34–1.27 [m, 6 H, CH3(CH2)3CH2CICH],
0.90 (t, J = 6.7 Hz, 3 H, CH3).
19F NMR (565 MHz, CDCl3):  = –80.89 to –80.99 (m, 3 F, CF3, Z),
–81.05 (t, J = 9.6 Hz, 3 F, CF3, E), –105.44 (t, J = 12.6 Hz, 2 F, CF2, E),
–109.08 to –109.26 (m, 2 F, CF2, Z), –123.60 to –123.97 (m, 2 F, CF2),
–125.56 to –125.76 (m, 2 F, CF2, Z), –125.76 to –125.99 (m, 2 F, CF2, E).
19F NMR (282 MHz, CDCl3):  = –57.81 (s, CF3, E), –60.00 (s, CF3, Z).
1-Methyl-4-(3,3,4,4,5,5,6,6,6-nonafluoro-1-iodohex-1-en-1-
yl)benzene (39)31a
1,1,1,2,2,3,3,4,4-Nonafluoro-6-iodododec-5-ene (35)31
1-Methyl-4-(3,3,4,4,5,5,6,6,6-nonafluoro-1-iodohex-1-en-1-yl)ben-
zene (39) was synthesized using a procedure similar to GP-B. tBu3P (1)
was dissolved in this case before addition of 1-ethynyl-4-methylben-
zene and C4F9I (4) under a stream of nitrogen and with the best possi-
ble light exclusion outside the glovebox.
Following GP-A: Yield: 158.9 mg (44%, E/Z = 1.0:0.42); colorless liquid.
Following GP-B: Yield: 243 mg (95%, E/Z = 89:11); colorless liquid.
1H NMR (300 MHz, CDCl3):  = 6.32 (t, J = 14.5 Hz, 1 H, CICH, E), 6.24
(t, J = 13.1 Hz, 1 H, CICH, Z), 2.67 (t, J = 7.2 Hz, 2 H, CH2CICH, Z), 2.63 (t,
J = 7.5 Hz, 2 H, CH2CICH, E), 1.61–1.55 (m, 2 H, CH2CH2CICH), 1.36–
1.27 [m, 6 H, CH3(CH2)3CH2CICH], 0.90 (t, J = 6.9 Hz, 3 H, CH3).
19F NMR (282 MHz, CDCl3):  = –80.92 to –81.13 (m, 3 F, CF3), –105.55
to –105.67 (m, 2 F, CF2, E), –108.65 to –108.76 (m, 2 F, CF2, Z), –123.85
to –123.99 (m, 2 F, CF2, Z), –124.11 to –124.31 (m, 2 F, CF2, E), –125.71
to –125.92 (m, 2 F, CF2).
Yield: 201.6 mg (82%, E/Z = 95:5); light yellow oil.
1H NMR (300 MHz, CDCl3):  = 7.38 (mc, 2 H, Ar–H, Z), 7.21 (d, J = 8.3
Hz, 2 H, Ar–H, E), 7.14 (d, J = 8.2 Hz, 2 H, Ar–H, E), 7.03 (mc, 2 H, Ar-H,
Z), 6.57 (t, J = 13.4 Hz, 1 H, –CH–RF, E), 6.47 (t, J = 1.2 Hz, 1 H, –CH–RF,
Z), 2.39 (s, 3 H, Ar–CH3, Z), 2.36 (s, 3 H, Ar–CH3, E).
19F NMR (282 MHz, CDCl3):  = –80.88 to –80.97 (m, 3 F, CF3, Z),
–80.98 to –81.12 (m, 3 F, CF3, E), –105.20 to –105.43 (m, 2 F, CF2, E),
–108.83 to –109.02 (m, 2 F, CF2, Z), –123.76 to –123.93 (m, 2 F, CF2, E),
–125.64 to –125.75 (m, 2 F, CF2, Z), –125.76 to –125.95 (m, 2 F, CF2, E).
1,1,1,2,2,3,3,4,4,5,5,6,6-Tridecafluoro-8-iodotetradec-7-ene (36)32
The title compound was prepared following GP-B.
Yield: 262 mg (84%, E/Z = 85:15); colorless liquid.
1H NMR (600 MHz, CDCl3):  = 6.32 (t, J = 14.4 Hz, 1 H, CICH, E), 6.24
(t, J = 13.2 Hz, 1 H, CICH, Z), 2.69–2.65 (m, 2 H, CH2CICH, Z), 2.65–2.60
(m, 2 H, CH2CICH, E), 1.62–1.55 (m, 2 H, CH2CICH), 1.35–1.26 [m, 6 H,
CH3(CH2)3CH2CICH], 0.93–0.87 (m, 3 H, CH3).
19F NMR (565 MHz, CDCl3):  = –80.75 to –80.89 (m, 3 F, CF3), –105.40
(t, J = 13.3 Hz, 2 F, CF2, E), –108.46 (t, J = 13.2 Hz, 2 F, CF2, Z), –121.50 to
–121.83 (m, 2 F, CF2), –122.70 to –122.92 (m, 2 F, CF2), –122.92 to
–123.06 (m, 2 F, CF2, Z), –123.21 to –123.38 (m, 2 F, CF2), –125.99 to
–126.25 (m, 2 F, CF2).
1-Methoxy-4-(3,3,4,4,5,5,6,6,6-nonafluoro-1-iodohex-1-en-1-
yl)benzene (40)
1-Methoxy-4-(3,3,4,4,5,5,6,6,6-nonafluoro-1-iodohex-1-en-1-yl)ben-
zene (40) was synthesized using a procedure similar to GP-B. tBu3P (1)
was dissolved in this case before addition of 4-methoxyphenylacety-
lene and C4F9I (4) under a stream of nitrogen and with the best possi-
ble light exclusion outside the glovebox.
Yield: 220 mg (84%, E/Z = 92:8); yellow liquid.
IR (film): 3064, 3007, 2960, 2938, 2910, 2841, 2548, 2318, 2241,
2055, 1977, 1891, 1634, 1604, 1575, 1508, 1466, 1442, 1415, 1352,
1294, 1237, 1134, 1110, 1054, 1033, 929, 905, 890, 872, 855, 832,
9,9,10,10,11,11,12,12,13,13,14,14,15,15,16,16,16-Heptadecafluoro-
7-iodohexadec-7-ene (37)31a
749, 722, 664, 631, 590, 569, 553, 530 cm–1
.
Yield: 343 mg (98%, E/Z = 85:15); colorless liquid.
1H NMR (300 MHz, CDCl3):  = 7.46 (mc, 2 H, Ar-H, Z), 7.27 (mc, 2 H,
Ar-H, E), 6.89 (mc, 2 H, Ar-H, Z), 6.85 (m, 2 H, Ar-H, E), 6.56 (t, J = 13.9
Hz, 1 H, -CH-RF, E), 6.43 (t, J = 13.4 Hz, 1 H, -CH-RF, Z), 3.85 (s, 3 H,
OCH3, Z), 3.83 (s, 3 H, OCH3, E).
9,9,10,10,11,11,12,12,13,13,14,14,15,15,16,16,16-Heptadecafluoro-7-
iodohexadec-7-ene (37) was synthesized using a procedure similar to
t
GP-B. Bu3P (1) and 1-octyne (52) were dissolved in this case before
addition of C8F17I under a stream of nitrogen and with the best possi-
ble light exclusion outside the glovebox.
1H NMR (600 MHz, CDCl3):  = 6.32 (t, J = 14.4 Hz, 1 H, CICH, E), 6.23
(t, J = 13.1 Hz, 1 H, CICH, Z), 2.68 (t, J = 6.9 Hz, 2 H, CH2CICH, Z), 2.63 (t,
J = 7.7 Hz, 2 H, CH2CICH, E), 1.60–1.55 (m, 2 H, CH2CH2CICH), 1.33–
1.27 [m, 6 H, CH3(CH2)3CH2CICH], 0.90 (t, J = 7.2 Hz, 3 H, CH3).
19F NMR (565 MHz, CDCl3):  = –80.80 (t, J = 9.9 Hz, 3 F, CF3), –105.40
(t, J = 13.4 Hz, 2 F, CF2, E), –108.46 (t, J = 13.3 Hz, 2 F, CF2, Z), –121.33
to –121.58 (m, 2 F, CF2), –121.75 to –122.07 (m, 5 F, CF2), –122.60 to
–122.83 (m, 3 F, CF2), –122.87 to –123.02 (m, 2 F, CF2, Z), –123.17 to
–123.35 (m, 2 F, CF2), –125.99 to –126.29 (m, 2 F, CF2).
13C NMR (75.5 MHz, CDCl3):  = 160.4, 133.8, 135.7 (m, CF2, CF3),
129.0 (t, J = 2.61 Hz), 123.2–115.5 (m, CF2, CF3), 126.4 (t, J = 21.8 Hz),
113.9, 113.7 (t, J = 6.0 Hz), 113.5, 55.4.
19F NMR (282 MHz, CDCl3):  = –80.94 (tt, J = 9.9, 3.1 Hz, 3 F, CF3, Z),
–81.04 (tt, J = 9.6, 3.2 Hz, 3 F, CF3, E), –105.00 to –105.18 (m, 2 F, E),
–108.52 to –108.69 (m, 2 F, Z), –123.67 to –123.77 (m, 2 F, E), –123.76
to –123.96 (m, 2 F, Z), –125.63 to –125.76 (m, 2 F, Z), –125.77 to
–125.96 (m, 2 F, E).
Anal. Calcd for C13H8F9IO: C, 32.66; H, 1.69. Found: C, 32.61; H, 1.73.
1-(tert-Butyl)-4-(3,3,4,4,5,5,6,6,6-nonafluoro-1-iodohex-1-en-1-
yl)benzene (41)
(3,3,4,4,5,5,6,6,6-Nonafluoro-1-iodohex-1-en-1-yl)benzene (38)33
The title compound was prepared following GP-B.
1-(tert-Butyl)-4-(3,3,4,4,5,5,6,6,6-nonafluoro-1-iodohex-1-en-1-
yl)benzene (41) was synthesized using a procedure similar to GP-B.
tBu3P (1) was dissolved in this case before addition of 4-tert-butyl-
phenylacetylene and C4F9I (4) under a stream of nitrogen and with the
best possible light exclusion outside the glovebox.
Yield: 202 mg (81%, E/Z = 95:5); colorless liquid.
1H NMR (600 MHz, CDCl3):  = 7.38–7.35 (m, 5 H, Ar–H, Z), 7.35–7.27
(m, 5 H, Ar–H, E), 6.59 (t, J = 13.3 Hz, 1 H, CICH, E), 6.54–6.46 (m, 1 H,
CICH, Z).
Yield: 192.7 mg (69%, E/Z = 95:5); light yellow oil.
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, A–L

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L. Helmecke et al.
Feature
Synthesis
IR (film): 3087, 3035, 2966, 2908, 2872, 2326, 1910, 1790, 1636,
1604, 1506, 1465, 1405, 1352, 1296, 1234, 1134, 1109, 1055, 1026,
Yield: 169.1 mg (64%, E/Z = 70:30); colorless liquid.
IR (film): 3088, 3067, 3029, 2933, 2866, 1617, 1496, 1456, 1426,
1353, 1315, 1237, 1137, 1103, 1063, 1032, 947, 935, 918, 878, 841,
930, 892, 874, 842, 750, 737, 694, 674, 591, 526 cm–1
.
1H NMR (300 MHz, CDCl3):  = 7.36-7.32 (mc, 2 H, Ar-H, E) 7.31-7.42
(mc, 2 H, Ar-H, Z), 7.32-7.14 (mc, 2 H, Ar-H, Z), 6.51 (t, J = 13.8 Hz, 1 H,
CHI, E), 6.43 (t, J = 13.4 Hz, 1 H, CHI, Z), 1.27 (s, 9 H, Z), 1.26 (s, 9 H, E).
13C NMR (75.5 MHz, CDCl3):  = 153.9, 152.8, 138.4, 128.2, 127.0 (t, J =
2.63 Hz), 126.5 (t, J = 22.08 Hz), 125.1, 113.8 (t, J = 2.63 Hz), 34.9, 31.3.
19F NMR (282 MHz, CDCl3):  = –80.92 to –81.00 (m, 3 F, CF3, Z),
–81.06 (tt, J = 9.3, 2.7 Hz, 3 F, CF3, E), –105.06 to –105.40 (m, 2 F, CF2,
E), –108.80 to –109.14 (m, 2 F, CF2, Z), –123.65 to –124.08 (m, 2 F, CF2),
–125.65 to –126.06 (m, 2 F, CF2).
824, 811, 736, 698, 643, 557, 529 cm–1
.
1H NMR (300 MHz, CDCl3):  = 7.35 (mc, 2 H, Ar–H, E), 7.26 (mc, 3 H,
Ar–H, E), 6.39 (t, J = 14.4 Hz, 1 H, –CH–RF, E), 2.95 (m, 4 H, Ar-CH2-
CH2-CI, E).
13C NMR (75.5 MHz, CDCl3):  = 139.5, 128.8, 128.7, 127.1 (t, J = 23.9
Hz), 126.7, 121.1 (t, J = 6.3 Hz), 119.8–113.8 (m, CF2, CF3), 43.6 (t,
J = 3.0 Hz), 36.4.
19F NMR (282 MHz, CDCl3):  = –81.04 (m, 3 F, CF3), –105.91 to
–106.17 (m, 2 F), –124.03 to –124.38 (m, 2 F), –125.63 to –125.97 (m,
2 F).
Anal. Calcd for C16H14F9I: C, 38.12; H, 2.80. Found: C, 38.19; H, 2.81.
Anal. Calcd for C14H10F9I: C, 35.32; H, 2.12. Found: C, 35.21; H, 2.07.
1-Bromo-4-(3,3,4,4,5,5,6,6,6-nonafluoro-1-iodohex-1-en-1-
yl)benzene (42)
(E)-6,6,7,7,8,8,9,9,9-Nonafluoro-4-iodo-5-propylnon-4-ene (45)14
The title compound was prepared following GP-B.
Yield: 125.2 mg (52%); colorless liquid.
The title compound was prepared following GP-B.
Yield: 173.4 mg (62%, E/Z = 94:6); light yellow oil.
IR (film): 3065, 1902, 1780, 1638, 1584, 1561, 1484, 1393, 1352,
1296, 1235, 1134, 1072, 1057, 1028, 1013, 923, 906, 891, 873, 816,
1H NMR (300 MHz, CDCl3):  = 2.69 (t, J = 7.6 Hz, 2 H, CICRFH2), 2.46–
2.23 (m, 2 H, H2CICRF), 1.79–1.46 [m, 4 H, (CH3(CH2))2], 0.95 [dt,
J = 12.7, 7.3 Hz, 6 H, (CH3(CH2))2].
19F NMR (565 MHz, CDCl3):  = –80.97 (t, J = 9.8 Hz, 3 F, CF3), –102.96
(t, J = 14.9 Hz, 2 F, CF2), –122.11 to –122.38 (m, 2 F, CF2), –125.95 to
–126.22 (m, 2 F, CF2).
761, 745, 713, 693, 668, 636, 590, 562, 529 cm–1
.
1H NMR (300 MHz, CDCl3):  = 7.53 (mc, 2 H, Ar–H, Z), 7.48 (mc, 2 H,
Ar–H, E), 7.35 (mc, 2 H, Ar–H, Z), 7.17 (mc, 2 H, Ar–H, E), 6.61 (t, J = 13.4
Hz, 1 H, –CH–RF, E), 6.50 (d, J = 12.8 Hz, 1 H, –CH–RF, Z).
13C NMR (75.5 MHz, CDCl3):  = 140.3, 131.5, 128.6 (t, J = 2.55 Hz),
127.2 (t, J = 22.21 Hz), 123.8, 119.74–113.37 (m, CF2, CF3), 111.1 (t,
J = 6.34 Hz).
(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-Heptadecafluoro-1-iododec-1-
en-1-yl)trimethylsilane (46)34
19F NMR (282 MHz, CDCl3):  = –80.98 to –81.16 (m), –105.47 (t,
J = 11.2 Hz), –109.40 (t, J = 12.2 Hz), –123.68 to –123.92 (m), –125.65
to –125.77 (m), –125.75 to –125.97 (m).
(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-Heptadecafluoro-1-iododec-1-en-
1-yl)trimethylsilane (46) was synthesized using a procedure similar
t
to GP-B. Bu3P (1) and trimethylsilylacetylene were dissolved in this
case before addition of perfluorooctyl iodide under a stream of nitro-
gen and with the best possible light exclusion outside the glovebox.
Anal. Calcd for C12H5BrF9I: C, 27.35; H, 0.96. Found: C, 27.60; H, 0.85.
Yield: 315.3 mg (92%, E/Z = 63:37); colorless liquid.
(E)-(3,3,4,4,5,5,6,6,6-Nonafluoro-1-iodo-2-methylhex-1-en-1-
yl)benzene (43)
IR (film): 2962, 2904, 2370, 2346, 1588, 1413, 1369, 1353, 1325,
1242, 1213, 1150, 1136, 1116, 1061, 984, 848, 776, 766, 745, 736,
The title compound was prepared following GP-B.
725, 705, 658, 618, 595, 559, 528 cm–1
.
Yield: 218.8 mg (83%); colorless crystals; mp 72.4–76.9 °C.
1H NMR (300 MHz, CDCl3):  = 7.53 (t, J = 15.7 Hz, 1 H, –CH–RF, E),
7.03 (t, J = 13.5 Hz, 1 H, –CH–RF, Z), 0.36 (t, J = 1.5 Hz, 9 H, –SiMe3, E),
0.30 (s, 5 H, 9 H, –SiMe3, Z).
13C NMR (75.5 MHz, CDCl3):  = 139.3 (t, J = 23.1 Hz), 131.9 (t, J = 23.0
Hz), 129.3, 123.8–107.7, 1.2, –1.8.
IR (film): 3081, 3061, 3019, 2973, 2934, 2869, 2548, 2433, 2401,
2337, 1959, 1891, 1809, 1767, 1633, 1594, 1575, 1489, 1443, 1389,
1350, 1300, 1244, 1216, 1198, 1173, 1137, 1106, 1073, 1013, 999,
919, 881, 872, 861, 833, 765, 740, 707, 698, 674, 648, 624, 602, 569,
553, 532 cm–1
.
1H NMR (600 MHz, CDCl3):  = 7.33–7.18 (m, 5 H, Ar–H), 2.30 (s, 3
H, –CH3).
13C NMR (75.5 MHz, CDCl3):  = 144.3, 130.1 (t, J = 20.80 Hz), 128.3,
127.8, 126.9, 119.4–110.5 (m, CF2, CF3), 115.0 (t, J = 4.50 Hz), 26.8.
19F NMR (282 MHz, CDCl3):  = –81.61 to –81.80 (m, 3 F), –106.03 to
–106.31 (m, 2 F), 109.44 to –109.61 (m, 2 F), –121.79 to –122.22 (m, 2
F), –122.17 to –122.64 (m, 4 F), –122.89 to –123.14 (m, 1 F), –123.14
to –123.47 (m, 3 F), –126.61 to –126.93 (m, 2 F).
19F NMR (565 MHz, CDCl3):  = –81.01 (t, J = 9.3 Hz, 3 F, CH3), –103.30
to –103.49 (m, 2 F, CF2), –120.39 to –120.60 (m, 2 F, CF2), –126.11
to –126.35 (m, 2 F, CF2).
2-(4,4,5,5,6,6,7,7,7-Nonafluoro-2-iodohept-2-en-1-yl)isoindoline-
1,3-dione (47)
The title compound was prepared following GP-B.
Anal. Calcd for C13H8F9I: C, 33.79; H, 1.75. Found: C, 33.95; H, 1.68.
Yield: 201.4 mg (70%, E/Z = 69:31); colorless crystals; mp 58.5–
59.5 °C.
(5,5,6,6,7,7,8,8,8-Nonafluoro-3-iodooct-3-en-1-yl)benzene (44)
IR (film): 3064, 2937, 2332, 1776, 1725, 1634, 1469, 1419, 1394,
1352, 1234, 1135, 1109, 1089, 1032, 1006, 985, 940, 919, 903, 879,
(5,5,6,6,7,7,8,8,8-Nonafluoro-3-iodooct-3-en-1-yl)benzene (44) was
synthesized using a procedure similar to GP-B. tBu3P (1) was dissolved
in this case before addition of 4-phenyl-1-butyne and C4F9I (4) under
a stream of nitrogen and with the best possible light exclusion outside
the glovebox.
793, 772, 743, 713, 694, 666, 588, 528 cm–1
.
1H NMR (300 MHz, CDCl3):  = 7.97–7.85 (m, 2 H, Ar–H), 7.83–7.72
(m, 2 H, Ar–H), 6.62 (t, J = 15.0 Hz, 1 H, –CH–RF), 4.72–4.64 (m, 2 H, N–
CH2–CI).
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, A–L

K
L. Helmecke et al.
Feature
Synthesis
13C NMR (75.5 MHz, CDCl3):  = 167.1, 134.6, 131.9, 128.6 (t, J = 24.5
Hz), 123.9, 119.8–110.3 (m, CF2, CF3), 116.9 (t, J = 5.8 Hz), 43.0.
19F NMR (565 MHz, CDCl3):  = –97.72 (s, 1 F, E), –97.89 (s, 1 F, Z).
19F NMR (282 MHz, CDCl3):  = –80.96 (tt, J = 9.2, 2.9 Hz, 3 F), –105.42
to –106.68 (m, 2 F), –123.41 to –124.25 (m, 2 F), –125.19 to –126.45
(m, 2 F).
(3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluoro-1-iodooct-1-en-1-yl)cyclo-
propane (61)32
The title compound was prepared following GP-B.
HRMS (ESI): m/z [M + NH4]+ calcd for C15H11F9IN2O2: 548.9721; found:
Yield 241 mg. In a mixture with product 62. (69%, E/Z = 82:18); color-
548.9715.
less liquid.
1H NMR (300 MHz, CDCl3):  = 6.39 (t, J = 14.8 Hz, 1 H, E), 6.37–6.27
(m, 1 H, Z), 1.76–1.64 (m, 1 H, Z), 1.57–1.45 (m, 1 H, E), 0.89–0.82 (m,
4 H).
tert-Butyl (4,4,5,5,6,6,7,7,7-Nonafluoro-2-iodohept-2-en-1-
yl)(phenyl)carbamate (48)
tert-Butyl (4,4,5,5,6,6,7,7,7-nonafluoro-2-iodohept-2-en-1-yl)(phe-
nyl)carbamate (48) was synthesized using a procedure similar to GP-
B. Bu3P (1) was dissolved in this case before addition of N-(tert-bu-
toxycarbonyl)-N-(prop-2-ynyl)aniline and C4F9I (4) under a stream of
nitrogen and with the best possible light exclusion outside the glove-
box.
19F NMR (565 MHz, CDCl3):  = –80.84 (t, J = 10.0 Hz, E), –104.51 (t,
J = 13.5 Hz, E), –107.29 (t, J = 13.4 Hz, Z), –121.40 to –122.05 (m, 2 F),
–122.64 to –123.08 (m, 2 F), –123.08 to –123.43 (m, 2 F), –125.99
to –126.37 (m, 2 F).
t
6,6,7,7,8,8,9,9,10,10,11,11,11-Tridecafluoro-1-iodoundeca-3,4-di-
ene (62)32
Yield: 135.7 mg (44%); colorless liquid.
IR (film): 3348, 3065, 3043, 2979, 2933, 1705, 1652, 1634, 1598,
1522, 1496, 1478, 1456, 1430, 1412, 1382, 1369, 1355, 1317, 1297,
1237, 1169, 1135, 1047, 1022, 936, 918, 881, 862, 831, 799, 758, 741,
The title compound was prepared following GP-B.
Yield 241 mg. In a mixture with product 61. (31%); colorless liquid.
1H NMR (300 MHz, CDCl3):  = 5.83–5.69 (m, 1 H), 5.56–5.40 (m, 1 H),
3.21 (td, J = 7.1, 1.1 Hz, 2 H), 2.70 (tdd, J = 7.0, 2.9 Hz, 2 H).
19F NMR (565 MHz, CDCl3):  = –80.84 (t, J = 10.0 Hz), –108.23 (t,
J = 13.2 Hz), –107.29 (t, J = 13.4 Hz), –121.40 to –122.05 (m, 2 F),
–122.64 to –123.08 (m, 2 F), –123.08 to –123.43 (m, 2 F), –125.99
to –126.37 (m, 2 F).
731, 696, 582, 526 cm–1
.
1H NMR (300 MHz, CDCl3):  = 7.29 (mc, 5 H, Ar–H), 6.43 (t, J = 15.2
Hz, 1 H, –CH–RF, E), 4.66 (s, 2 H, N–CH2–CI), 1.48 (s, 9 H, CH3).
13C NMR (75.5 MHz, CDCl3):  = 157.4, 154.3, 141.1, 128.9, 127.3,
126.8, 121.9–114.4 (m, CF2, CF3), 81.7, 77.4, 54.1, 28.4.
19F NMR (282 MHz, CDCl3):  = –81.06 (tt, J = 9.7, 2.9 Hz, 3 F), –105.65
to –106.14 (m, 2 F), –123.92 to –124.28 (m, 2 F), –125.65 to –126.07
(m, 2 F).
HRMS (ESI): m/z [M + NH4]+ calcd for C18H21F9IN2O2: 595.0504; found
595.0493.
(3,3,4,4,5,5,6,6,7,7,8,8,8-Tridecafluoro-1-iodooct-1-en-1-yl)ben-
zene (70)35
Following GP-A with B(C6F5)3: Yield: 48.5 mg (10%); colorless liquid.
Following GP-A with B(2,6-F2C6H3)3: Yield: 92.6 mg (20%); colorless
liquid.
1H NMR (600 MHz, CDCl3):  = 7.38–7.35 (m, 5 H, Ar–H, Z), 7.35–7.27
(m, 5 H, Ar–H, E), 6.59 (t, J = 13.3 Hz, 1 H, CICH, E), 6.54–6.46 (m, 1 H,
CICH, Z).
19F NMR (565 MHz, CDCl3):  = –80.89 to –80.99 (m, 3 F, CF3, Z),
–81.05 (t, J = 9.6 Hz, 3 F, CF3, E), –105.44 (t, J = 12.6 Hz, 2 F, CF2, E),
–109.08 to –109.26 (m, 2 F, CF2, Z), –123.60 to –123.97 (m, 2 F, CF2),
–125.56 to –125.76 (m, 2 F, CF2, Z), –125.76 to –125.99 (m, 2 F, CF2, E).
Ethyl 2,2-Difluoro-4-iododecanoate (51)21,24
Yield: 170.1 mg (90%); colorless liquid.
Ethyl 2,2-difluoro-4-iododecanoate (51) was synthesized using a pro-
cedure similar to GP-B. tBu3P (1) and 1-octene (49) were dissolved in
this case before addition of ethyl difluoroiodoacetate (50) under a
stream of nitrogen and with the best possible light exclusion outside
the glovebox.
1H NMR (300 MHz, CDCl3):  = 4.34 (q, J = 7.2 Hz, 2 H), 4.29–4.12 (m, 1
H), 3.02–2.79 (m, 1 H), 2.80–2.62 (m, 1 H), 1.89–1.64 (m, 2 H), 1.63–
1.40 (m, 1 H), 1.40–1.16 (m, 10 H), 0.93–0.82 (m, 3 H).
Funding Information
19F NMR (565 MHz, CDCl3):  = –101.32 to –102.71 (m, 1 F), –105.65
This research was funded by the Deutsche Forschungsgemeinschaft
(DFG, German Research Foundation) (Grant No. 396890929/GRK
2482). The generous support provided to M. Spittler through a fellow-
ship provided by the Studienstiftung des deutschen Volkes (Dokto-
to –107.62 (m, 1 F).
Ethyl 2,2-Difluoro-4-iododec-3-enoate (53)32
Ethyl 2,2-difluoro-4-iododec-3-enoate (53) was synthesized using a
procedure similar to GP-B. tBu3P (1) and 1-octyne (52) were dissolved
in this case before addition of ethyl difluoroiodoacetate (50) under a
stream of nitrogen and with the best possible light exclusion outside
the glovebox.
randenstipendium) is most gratefully acknowledged.
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Supporting Information
Supporting information for this article is available online at
Yield: 187 mg (97%, E/Z = 84:16); colorless liquid.
https://doi.org/10.1055/s-0040-1707232.
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1H NMR (300 MHz, CDCl3):  = 6.40 (t, J = 13.2 Hz, 1 H, E), 6.37–6.31
(m, 1 H, Z), 4.45–4.38 (m, 2 H, Z), 4.33 (q, J = 7.2 Hz, 2 H, E), 2.64–2.54
(m, 2 H, E), 1.56–1.51 (m, 2 H, E), 1.40–1.27 (m, 9 H, E), 0.94–0.84 (m,
3 H, E).
© 2020. Thieme. All rights reserved. Synthesis 2020, 52, A–L

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L. Helmecke et al.
Feature
Synthesis
References
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