Light-induced iodoperfluoroalkylation reactions of carbon-carbon multiple bonds in water

Article abstract of DOI:10.1016/j.jfluchem.2011.10.002

In this work we have undertaken the radical-induced addition of 1-iodo-n-perfluorobutane onto electron-rich alkenes, alkenes with electron withdrawing groups, and alkynes in water, initiated photochemically. The lack of hydrogen donor (i.e.: (Me₃Si)₃SiH) in our reaction medium facilitates a Halogen Atom-transfer reaction (HAT), affording the respective perfluorobutylated alkyl and alkenyl halides (iodides) in good yields in water. We have also found that water exerts a relevant solvent effect on the rates of perfluoroalkyl radical additions onto double and triple bonds. The stereoselectivity of the radical addition reaction of alkynes is studied. The novelty of this work relies on the photochemical generation of fluorinated radicals in water, and the Halogen Atom-transfer addition reactions of iodoperfluoroalkanes onto carbon-carbon unsaturated bonds in water induced by light.

Full text of DOI:10.1016/j.jfluchem.2011.10.002

Journal of Fluorine Chemistry 135 (2012) 137–143
Contents lists available at SciVerse ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Light-induced iodoperfluoroalkylation reactions of carbon–carbon
multiple bonds in water
a
b
b
b
a,
*
´
M. Slodowicz , S. Barata-Vallejo , A. Vazquez , N. Sbarbati Nudelman , A. Postigo
a Faculty of Science-University of Belgrano-Villanueva 1324 CP 1428-Buenos Aires, Argentina
b
´
´
Departamento de Quı´mica Organica-Facultad de Ciencias Exactas y Naturales-Universidad de Buenos Aires-Pabellon II,
3er piso-Ciudad Universitaria-CP 1428-Buenos Aires, Argentina
A R T I C L E I N F O
A B S T R A C T
Article history:
In this work we have undertaken the radical-induced addition of 1-iodo-n-perfluorobutane onto
electron-rich alkenes, alkenes with electron withdrawing groups, and alkynes in water, initiated
photochemically. The lack of hydrogen donor (i.e.: (Me3Si)3SiH) in our reaction medium facilitates a
Halogen Atom-transfer reaction (HAT), affording the respective perfluorobutylated alkyl and alkenyl
halides (iodides) in good yields in water. We have also found that water exerts a relevant solvent effect on
the rates of perfluoroalkyl radical additions onto double and triple bonds. The stereoselectivity of the
radical addition reaction of alkynes is studied. The novelty of this work relies on the photochemical
generation of fluorinated radicals in water, and the Halogen Atom-transfer addition reactions of
iodoperfluoroalkanes onto carbon–carbon unsaturated bonds in water induced by light.
ß 2011 Elsevier B.V. All rights reserved.
Received 27 July 2011
Received in revised form 8 September 2011
Accepted 1 October 2011
Available online 6 October 2011
Keywords:
Radical perfluoroalkylation in water
Halogen atom transfer
Perfluoroalkyl-substituted compounds
1. Introduction
with perfluoroalkyl moieties is through the SRN1 mechanism,
which involves radicals and radical ions as intermediates [10,11].
Halogen Atom-transfer (HAT) reactions have been extensively
studied and widely used in organic synthesis. The addition of a
carbon–halogen bond across a double bond was pioneered by
Kharasch [1a] (Scheme 1) and provides new carbon–carbon and
carbon–halogen bonds in a single operation. The choice of the
halogen that transfers in the reaction determines the success of
atom-transfer additions. More recently, HAT reactions have been
studied and reviewed in water [1b].
On the other hand, perfluoroalkyl-substituted compounds are
regarded as important components of fluorophors and for the
introduction of fluorous tags into organic substrates [2]. In
medicine, fluorocarbons and perfluoroalkyl-substituted alkanes
serve as vascular implants [3], inhalation anesthetics [4] aerosol
propellants [5], breathing liquids for immature or damaged lungs,
and components in blood substitutes [6]. Biotechnology employs
fluorocarbon liquids to transport respiratory gases in cell culture
systems [7]. Their syntheses in organic solvents are achieved
through different methods, among which, the addition of
perfluoroalkyl radicals to unsaturated bonds represents a conve-
nient choice [8,9]. Another route to the synthesis of compounds
Perfluoroalkyl iodides and bromides are convenient perfluor-
oalkyl radical precursors in the presence of radical initiators [12].
Because perfluoroalkyl iodides exhibit their absorption in UV and
near-UV regions, the photoinitiation based on the homolytic
dissociation of the Rf–I bond is also applicable for the radical
iodoperfluoroalkylation of unsaturated compounds with RfI [13].
Ogawa et al. undertook a photochemically induced radical
iodoperfluoroalkylation reaction of unsaturated carbon–carbon
double and triple bonds in benzotrifluoride as solvent [13]. These
authors also utilized non-conjugated dienes, conjugated dienes,
allenes, vinylcyclopropanes, and isocyanides as radical-acceptor
substrates for the radical iodoperfluoroalkylation reactions in
benzotrifluoride, affording good yields of the corresponding
iodoperfluoroalkylated derivatives. In the past, these reactions
have been attempted as neat liquids [14a].
The work of Huang and collaborators on sulfinatodehalogena-
tion reactions has contributed significantly to the development of
perfluoroalkylation reactions of unsaturated systems [15–19]. For
example, radical reactions of alkenes, alkynes, isocyanides, etc.
with RfI initiated by sodium dithionate in aqueous systems lead to
addition perfluoroalkylated products in high yields. Their work
triggered intensive research on this area [20–22].
The need to resort to more environmentally friendly solvents
opened the scope of radical carbon–carbon bond formation
reactions in water, and other aqueous mixtures. Atom transfer
intermolecular carbon–carbon bond formation reactions in water
have been investigated in detail by many authors [23]. Oshima
´
´
* Corresponding author at: Departamento de Quımica Organica-Facultad de
Farmacia y Bioquı´mica. Junı´n 956-CP 1113-Buenos Aires-ARGENTINA.
Tel.: +54 11 4964 8252; fax: +54 11 4964 8252.
E-mail address: apostigo@ffyb.uba.ar (A. Postigo).
0022-1139/$ – see front matter ß 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2011.10.002

138
M. Slodowicz et al. / Journal of Fluorine Chemistry 135 (2012) 137–143
R´
3. Results
When we subject alkenes 1a–d (10 mM) to reaction with 1-iodo-
R´
R
R
perfluorobutane (11 mM) in water (3 mL) under irradiation
(254 nm, 2 h, quartz, vigorous stirring), we obtain iodo-perfluor-
obutyl alkanes 2a–d in yields ranging from 58 to 84% (Eq. (2) and
Table 1). Both electron-rich (entries 1 and 2, Table 1) and electron-
deficient (entries 3 and 4, Table 1) alkenes react efficiently in water
(entries 1–4, Table 1). Organic solvent-soluble alkenes 1b–d (entries
2–4, Table 1) as well as water-soluble (allyl alcohol 1a, entry 1, Table
1) alkenes react with 1-iodoperfluorobutane in water (Eq. (2)).
Acrylonitrile 1c affords two HAT products, i.e.: 2ci and 2cii (Table
1, entry 3)in a 88:12 ratio (isolated combined yield 66%). Product 2ci
prevails in the mixture, as arising from a cyano-substituted,
resonance stabilized secondary alkyl radical adduct (see Section 4).
Interestingly, crotononitrile1d (entry 4, Table 1) also affords
two iodoperfluoroalkylated products, 3,3,4,4,5,5,6,6,6-nonafluoro-
2-(1-iodoethyl)hexanenitrile 2di and 4,4,5,5,6,6,7,7,7-nonafluoro-
2-iodo-3-methylheptanenitrile 2dii in 3 and 97% relative yields,
respectively (isolated 58%). Clearly, product 2dii is favored over
product 2di, as the cyano-substituted radical adduct is resonance-
stabilized as opposed to the inductively stabilized alkyl-substitut-
ed radical adduct intermediate (vide infra, Section 4).
R´
R´
R
R
+
RX
+
R
X
Scheme 1. Mechanism for carbon–carbon bond formation with Halogen Atom-
transfer.
et al. [24] reported the intermolecular carbon–carbon bond
formation reaction in water from ethyl bromoacetate and 1-
octene affording ethyl 4-bromodecanoate in 80% yield when the
reaction is initiated by triethylborane (Et3B)/air.
O
Et3B/air
O
Br
n-C6H13
C2H5O
C2H5O
water
(1)
+
Br
80%
nC6H13
Other types of intermolecular radical carbon–carbon bond
formation reactions in water have been lately reported, describing
radical additions to radical acceptors such as imines and their
derivatives [25–27]. These latter consecutive radical reactions are
also initiated by Et3B/air.
When we subject alkynes 3a–d (12 mM) to reaction with 1-
iodo-perfluorobutane (10 mM) in water (3 mL) under irradiation
(254 nm, 2 h, quartz) and vigorous stirring, we obtain iodo-
perfluorobutyl-substituted alkenes 4a–d (Eq. (3)) in yields ranging
from 67 to 98% (Table 2). The stereoselectivity of the iodo-
perfluorobutyl-substituted alkenes obtained is shown in column 4,
Table 2. Both organic-solvent soluble (3b,c) and water-soluble
Dolbier et al. [28] have found that perfluorinated radicals were
much more reactive than their hydrocarbon counterparts in
addition to normal, electron rich alkenes such as 1-hexene (40,000
times more reactive) in organic solvents. Thus the authors
(3a,d) alkynes react efficiently in water (Table 2).
determined that kadd has
a
value of 7.9 ꢀ 106 Mꢁ1 sꢁ1 in
I
hυ, 254 nm
benzene-d6 at 298 K, and the rate value of H-transfer from the
silicon hydride (Me3Si)3SiH (kH) is ca. 50 ꢀ 106 Mꢁ1 sꢁ1 in
benzene-d6 at 303 K.
´R
´R
C4F9I
+
R
R
H2O
C4F9
(2)
Barata-Vallejo and Postigo [29] have undertaken the consecu-
tive radical perfluoroalkylation addition reaction of alkenes in
water, mediated by (Me3Si)3SiH as hydrogen donor, initiated either
through the decomposition of azo compounds or dioxygen
initiation. Thus, the authors obtained perfluoroalkylated alkanes
in fairly good yields in water, either from electron-rich and
electron-deficient alkenes. The mechanism of the (Me3Si)3SiH-
mediated intermolecular perfluoroalkylation of alkenes in water
has been investigated in detail [29], with reasonable evidence for
the presence of silyl and perfluoroalkyl radical intermediates. The
same authors found that the rates of perfluoroalkylation reactions
of olefins seemed to be increased in water with respect to organic
solvents.
Given the known rate acceleration effects of radical reactions in
water, it becomes challenging at this time to attempt to explore the
iodoperfluoroalkylation reactions of multiple-bonded substrates
in this medium (HAT), through photochemical initiation, as a
potential entry route for the generation of fluorinated radicals in
water.
1a R = CH2OH, R´= H
2a
2b
2ci
2di
1b
1c
1d
CH2Cl, R´= H
CN,
CN,
R´=H
R´= CH3
Table 1
Photochemical-induced (254 nm, 60 W, 2 h) radical perfluoro-n-butylation of
alkenes 1a–d (10 mM) with C4F9I (11 mM) in Ar-deoxygenated water (3 mL) under
˚
vigorous stirring at 25 C.
Entry
1
Substrate
Product, %
Allylic alcohol, 1a
Allylic chloride, 1b
Acrylonitrile, 1c
I
OH
C4F9
2a, 84
2
3
4
I
Cl
C4F9
2. Materials and methods
2b, 75
I
C4F9
I
C4F9
2.1. Method of radical initiation in water
CN
CN
The photoinduced homolysis (254 nm, 2 ꢀ 40 W UV lamps,
I
˚
25 C, quartz vessel) of the C–I bond from C4F9I was used at room
2ci + 2cii, 66
temperature in water as a means of radical initiation. The reactions
(2 h) proceeded in quartz cells provided with stir bars, and rubber
septa. The vessels contain 3 mL of Ar-deoxygenated (15 min) milli-
Q water, 10–12 mM of substrate, and ca. 12 mM C4F9I, introduced
as neat liquids with microsyringe through the septa. The solutions
were vigorously stirred throughout the irradiation.
Crotononitrile, 1d
C4F9
N
C4F9
N
I
2di + 2dii, 58

M. Slodowicz et al. / Journal of Fluorine Chemistry 135 (2012) 137–143
139
addition of Rfꢂ radicals onto alkenes correlate with the alkene IP
(which reflects the HOMO energies) [32]. Indeed, the major
transition state orbital interaction for the addition of the highly
electrophilic Rfꢂ radical to an alkene is that between the SOMO of
the radical and the HOMO of the alkene. Thus, the rates of Rfꢂ radical
addition to electron deficient alkenes are slower than those to
electron rich alkenes (as observed in organic solvents) [33]. From
our results, however, it becomes apparent, that in water the
reactivity for both electron rich and electron deficient alkenes
towards Rfꢂ radical addition could be comparable. This trend has
also been found in the consecutive radical perfluoroalkylation
addition reaction of alkenes in water mediated by (Me3Si)3SiH [29].
We suspect that kinetic solvent effects (KSE) are somewhat
responsible for this leveling of reactivity (vide infra). Perhaps, some
amphiphilic character of Rf radicals can be invoked to account for
these indirect kinetic solvent effects.
In previous reports, we have observed that the radical
hydrosilylation reactions in water of water-soluble substrates
took place efficiently with the aid of amphiphilic 2-mercaptoetha-
nol, as chain carrier [34]. This is because silyl radicals being
hydrophobic need the assistance of amphiphilic thiyl radicals (i.e.:
ꢂSCH2CH2OH) to carry on the chain reaction into the aqueous
environment, where the water-soluble substrate is dissolved.
Interestingly, both organic solvent-soluble substrates and water-
soluble substrates undergo radical pefluoroalkylation reactions in
water without the assistance of a chain carrier. This observation
could be better interpreted in light of the distinct reactivity of Rf
radicals in water rather than to a difference in hydrophobicity of Rf
radicals in comparison to silyl radicals. Perhaps, some distinct
amphiphilic character of Rf radicals can be invoked in this case.
Ogawa and collaborators have shown that the perfluoroalky-
lated radical adduct formed upon addition of Rf radicals to alkenes
or alkynes is followed by addition of an iodine atom to afford the
iodo-perfluoroalkylated compound. For a chain reaction to take
place, it is likely that a mechanism such as that illustrated in
Scheme 2 takes place. The radical adduct (in this case an alkenyl-
substituted adduct) abstracts iodine atom from C4F9I, rendering
the end addition product (i.e. 4a–e) and C4F9 radical, which carries
on the chain reaction. The E end-alkene is favored over the Z
isomer, as accounted in Scheme 2, and Table 2. The radical adduct
formed upon addition of Rf radical onto the alkyne, which can
equilibrate between the E and Z stereoisomers, will abstract iodine
atom from the less hindered/congested radical adduct in the Z
configuration than the E configuration, rendering the E alkene end-
product (Scheme 2).
Table 2
Photochemical-induced (254 nm, 2 h) radical perfluoro-n-butylation of alkynes
(12 mM) with C4F9I (10 mM) in Ar-deoxygenated water (3 mL) under vigorous
˚
stirring at 25 C.
Entry
1
Alkyne
Product, yield%
E:Z ratio
Propargyl alcohol [14a], 3a
Propargyl chloride [14a], 3b
1-hexyne [32], 3c
70:30a
I
OH
C4F9
4a, 84
2
45:55a
I
Cl
C4F9
4b, 94
3
93:7a
I
C4H9
C4F9
4c, 98
4
N,N-dimethylpropargyl amine, 3d
67:33a
I
N
C4F9
4d, 67
a
Non-optimized isomer ratio obtained after 2 h-irradiation.
I
h
υ
, 254 nm
C4F9I
R
+
R
H2O
C4F
9 4a
4b
4c
4d
(3)
3a R = OH
3b R = Cl
3c R = C3H9
3d R = N(CH3)2
4. Discussion
The electrophilicity of Rfꢂ radicals are the dominant factor
giving rise to their high reactivity. The stronger carbon–carbon
bond which forms when Rfꢂ versus Rꢂ radicals add to an alkene is a
driving force for the radical addition (the greater exothermicity of
the Rfꢂ radical addition is expected to lower the activation energy)
[30,31]. It has been observed, in organic solvents, that the rates of
The prevalence of the Z stereoisomer from propargyl chloride
3b radical addition reaction, i.e.: products 4b, is due to a post-
isomerization process of the initially formed 4b (E) isomer, as
confirmed by analyzing aliquots at shorter photolysis times, where
the mixture is enriched in the E-isomer. Data in Table 2 are given at
Scheme 2. Proposed mechanism for the formation of perfluoroalkyl-substituted E-alkenes in water.

140
M. Slodowicz et al. / Journal of Fluorine Chemistry 135 (2012) 137–143
C4F9
CN
C4F9
CN
C4F9I
2di
I
C4F9
Bi
CN
I
C4F9I
CN
CN
2dii
C4F9
C4F9
Bii
Scheme 3. Formation of products 2di and 2dii from crotononitrile.
2 h-irradiation time. The same applies to N,N-dimethylpropargyl
amine 3d. In the original work reported by Keese and collaborators
[14b], alkyne substrates (3c among them) render a mixture of the Z
and E diastereomers (see Scheme 2).
The finding of products 2ci and 2cii from the radical
iodoperfluorobutylation reaction of 1c in water (entry 3, Table 1
and Fig. 1) is significant in terms of the reaction pathways
accounting for both products, as depicted in Fig. 1.
The observation of the two iodo-perfluoroalkylated products
2di and 2dii (entry 4, Table 1) obtained from the radical
iodoperfluoroalkylation of crotononitrile 1d in water is notorious.
It is well known that internal alkenes are far less reactive than
terminal alkenes in radical alkylation and hydrosilylation reac-
tions, both in organic solvents and in water [20].
The ratio of products 2ci and2cii (Table 1, entry 3) obtained
(88:12) is in agreement with both the stability of the radicals
involved (secondary alkyl radicals i being better-stabilized than
primary alkyl radical ii, Fig. 1) and in accordance with the terminal
sp2 carbon of acrylonitrile being less impeded for attack from the Rf
radical than the central sp2 carbon (vide infra). However, at this
point it is not yet clear why neither substrates 1a or 1b undergo
attack of the Rf radical at the central sp2 carbon atom, unless some
Intermediates Bi and Bii (Scheme 3) are able to abstract iodine
atom from C4F9I to render products 2di and 2dii, respectively. This
difference could be due to a combination of factors, such as the
enhanced reactivity of Rf radicals in water; the smaller size of
fluorinated radicals in comparison to (Me3Si)3Si radicals or other
radicals; the enthalpy effect involved, which precludes reversibili-
ty of the radical-adduct formation, the effect of water in radical
reactivity as opposed to organic solvents, and the distinct
stabilization of the radical intermediates formed [34]. The ratio
of products 2di and 2dii (29:71) should also reflect on the ratio of
radical intermediates Bi and Bii, being the methyl-substituted
secondary alkyl radical intermediate Bi two-and-a-half fold less
stable than the cyano-substituted resonance-stabilized secondary
alkyl radical intermediate Bii. This behavior has been reported
neither in organic solvents nor in neat liquid [13,14a].
effect of resonance stabilization of the cyano group at the
position of the radical intermediate ii (Fig. 1) could be invoked
(intermediate i is resonance-stabilized by the -CN group). Hence,
if this is the case, a resonance stabilization of the cyano group at the
position of radical intermediate ii should outweigh or compen-
b
a
b
sate steric effects in the approximation of the Rf radical.
The enhanced reactivity of Rf radicals in addition reactions (vide
supra) as opposed to alkyl radicals, has been explained in terms of
the substantial bending (14–158 from planarity) apparently
required in the transition state for alkyl radical addition to
alkenes, i.e.: non-planar perfluoroalkyl radicals might therefore be
expected to have an inherent energetic advantage over a (planar)
alkyl radicals in addition reactions. It is also presumed that the
polar effect is playing a role in the iodine transfer, being the
incipient electrophilic C4F9-substituted radical adduct and the I
atom involved in a polar state, as in Fig. 2.
Inthe case for substrate 1c, an analogous resonance stabiliza-
tion of the cyano group could be invoked as well in accounting for
the prevalence of product 2ci.
Since the rate constant (kc) for cyclization of 5-hexenyl radical
is 2.0 ꢀ 105 sꢁ1 [35,36], it was estimated that the rate constant for
the iodine abstraction by radical intermediates from nC10F21I is
roughly 2.6 ꢀ 105 Mꢁ1 sꢁ1 [13]. This radical capturing ability is
lower compared with those of nBu3SnH or (PhSe)2 and similar than
those of (Me3Si)3SiH or nBu3GeH [29,37].
CN
C4F9
The fact that n-perfluoroalkyl radicals react with acrylonitrile
even faster than primary alkyl radicals [9] (2.2 ꢀ 106
and 5.3 ꢀ 105 Mꢁ1 sꢁ1for n-C8F17 and primary alkyl radical,
ꢂ
C4F9
CN
CN
ii
i
C4F9
seconday alkyl radical
primary alkyl radical
C4F9I
I
C4F9
CN
12 : 88
CN
I
C4F9
2cii
2ci
Fig. 1. Primary and secondary alkyl radicals from 1c.
Fig. 2. Transition state for the HAT to the perfluoroalkyl-substituted radical adduct.

M. Slodowicz et al. / Journal of Fluorine Chemistry 135 (2012) 137–143
141
respectively, at 25 8C and in organic solvents [38]) means that the
deactivating polar effect of the cyano group is more than balanced
by the activating enthalpic effect, and the same would apply to 1d.
It is also interesting to point out that the photoinduced-
iodoperfluoroalkylation reaction of acrylonitrile in benzotrifluor-
ide as solvent only led to oligomerization product [13]. It is likely
that the rate of the reaction of perfluoroalkyl radicals in water is
enhanced with respect to organic solvent, as it has been suggested
recently [29]. It has also to be pointed out, that the photoinduced-
iodoperfluorobutylation in neat liquid (absence of solvent) is less
efficient than the methodology presented in this paper in water as
sole solvent [14a].
predicted that the KSE should be dependent on the ability of XOH
to participate as a hydrogen bond donor to HBA solvents but should
be independent of the reactivity or nature of the radical which does
the hydrogen atom abstraction. This prediction, which is the first
new and unifying principle for organic free radical chemistry to
have been proposed in the last forty years, has been confirmed for
hydrogen abstraction from phenol by the highly reactive
cumyloxyl radical, PhCMe2Oꢃ [43,44], and by the very unreactive
diphenylpicryl hydrazyl radical, DPPH, Ph, NꢃNC6H(NO) [45].
5. Conclusions
Quite remarkable is the finding of products 2a,b and 4a, derived
from allylic alcohol, allyl chloride, and propargyl alcohol, respec-
tively. In the case of alcohols, R–OH, the carbon radicals (Rf) can
abstract H atoms from either the O–H functionality or one of the
hydrogen atoms of the R group. The former abstraction is few kcal/
mol more endothermic than the latter because of the relative bond
strengthsoftheO–HandC–Hbonds. WecouldexpectthatRf radicals
would abstract hydrogen from the allylic position of substrates 1a
and 1b to render allyl radical intermediates that react with C4F9I.
However, no substitution products were observed in the reaction
Radical atom transfers reactions (such as those studied here)
are classical examples of atom efficiency in Organic synthesis
devoted to waste minimization. The lack of hydrogen donor (i.e.:
(Me3Si)3SiH) in our reaction medium facilitates a Halogen Atom-
transfer reaction (HAT), affording the respective perfluoroalky-
lated alkyl and alkenyl iodides in good yields.
Interestingly is the fact that both organic solvent-soluble and
water-soluble substrates react well with C4F9I in water, not
necessitating the aid of a chain carrier such as 2-mercaptoethanol.
We have shown that the iodoperfluorobutylation of alkynes in
water render the thermodynamically favored E isomers in higher
yields than the previously reported Z isomers.
Our account provides a versatile and convenient method to
achieve perfluoroalkylation reactions of alkenes and alkynes in
water to render perfluoroalkylated haloalkanes and alkenes as key
intermediates in the synthesis of fluorophors and other fluorinated
materials. This is the first report where iodoperfluoroalkyl-
substituted alkanes and alkenes are synthesized through intermo-
lecular radical carbon–carbon bond formation reactions in water
alone, induced by light. We also found that water exerts a relevant
solvent effect on the rates of perfluoroalkyl radical additions onto
double bonds.
mixtures. No
b-elimination–substitution product (chlorine atom
elimination) derived from allyl chloride 1b were neither observed
(i.e.: 4,4,5,5,6,6,7,7,7-nonafluorohept-1-ene). This is quite interesting,
since the same substrate, 1b, upon reaction with (Me3Si)3Si radicals
in water affords a
b-elimination (chlorine atom)–substitution
product as well as the radical addition product [22].
This subtle point among the peculiar distinct behavior of
(Me3Si)3Si and Rf radicals in water towards the same substrate (1b)
is a telltale sign of the enhanced reactivity of Rf radicals in water.
Presumably, the rate constant for formation of the substitution
product that would derive from substrate 1b (b-elimination of the
Cl atom and substitution product i.e.: 4,4,5,5,6,6,7,7,7-nonafluor-
ohept-1-ene) is much lower, and is not competing with the rate
constant for Rf radical addition onto the double bond of substrate
1b to form product 2b.
6. Experimental part
H-abstraction from the OH functionality of alcohols 1a and 3a is
neither observed. The apparent relative rate constant for H
abstraction of carbon-centered (Rf) radicals from H-donors
((Me3Si)3SiH) in organic solvents is higher than the rate constant
for addition onto carbon–carbon multiple bonds when both H-
donors and alkenes are present [28b]. However Ingold and co-
workers, found that rate constants for hydrogen atom abstractions
from phenols were reduced in solvents where the phenol was
stabilized by hydrogen bonding [39]. In this case, it was the
reactivity of the substrate (i.e.: 3a), not the radical, that was
diminished as a result of a solute/solvent interaction. In the last
few years, solvent effects have been extensively investigated by
Ingold and co-workers [40]. This work can be summarized briefly
as follows:
6.1. General
The internal standard method was employed for quantitative
GC analysis with use of authentic samples when available, and one
of the following capillary columns was employed: HP-5
(30 m ꢀ 0.28 mm i.d.) or HP-1 (30 m ꢀ 0.32 mm i.d.). Oven
program: starting at 50 8C for 5 min, followed by an increase of
5 8/min up to 250 8C. NMR spectra were recorded at 500 MHz (for
1H) or 125.77 MHz (for 13C) or at 400 MHz (for 1H) or 100.6 MHz
(for 13C) and 376.17 MHz (for 19F) in CDCl3 as deuterated solvent
and referenced with the residual solvent peak at 7.26 ppm in the
1H NMR spectra and 77.0 ppm (CDCl3) in the 13C NMR spectra, and
the internal spectrometer reference for 19F NMR. Materials. Alkene
and alkyne substrates were also commercially available and used
as received from the supplier, except for acrylonitrile, crotononi-
trile, 1-hexyne, N,N-dimethylpropargylamine, which were previ-
ously distilled at atmospheric pressure and stored over molecular
(i) There are generally no solvent effects on the rates of hydrogen
atom abstraction from a C-H bond.
˚
(ii) There may be solvent effects on the rates of unimolecular
radical scission reactions (i.e.; Rf–I) but these are generally
fairly small.
sieves (4 A) prior to use.
6.2. Isolation, purification and characterization of compounds
(iii) There are large solvent effects on the rates of hydrogen atom
abstraction from O–H bonds (and to a lesser extend from N–H
bonds) [41–44].
The reactions were monitored by TLC analysis, at regular
photolysis intervals. Compounds were isolated by extraction into
pentane or ethyl ether (3ꢀ), the organic layers gathered, dried over
sodium sulfate, evaporated, checked by TLC for purity, and when
necessary, column-chromatographed on silica gel with hexane:
ethyl acetate (9:1 or 8:2).
Point (i) means that radical reactivities, insofar as hydrogen
abstraction (and addition) reactions are concerned, are not
influenced by the solvent. Point (iii) means that O–H containing
substrates (e.g., phenols, hydroperoxides, etc.) have their reactiv-
ities towards radicals influenced by the solvent. Therefore, it was
Sometimes the mixtures were sufficiently pure to conduct
compound characterization. Characterization of compounds was

142
M. Slodowicz et al. / Journal of Fluorine Chemistry 135 (2012) 137–143
achieved by regular spectroscopic techniques, such as NMR, MS,
and HRMS analyses. E and Z isomers were identified in the mixture,
by high resolution NMR and HSQC experiments.
(2Z)-1-chloro-4,4,5,5,6,6,7,7,7-nonafluoro-2-iodohept-2-ene
4b (Z) [14a]: (oil) 1H NMR (400 MHz, CHLOROFORM-D)
ppm 6.45
(t, J = 14.5 Hz, 1H,55CHRf). MS, EI, 70 eV, m/z (%): 422 (27), 420 (75),
d
Unequivocal assignment of 1H and 13C resonances was obtained
from HSQC experiments for compounds 2c, and 2d. Some NMR
spectral connectivity data were confirmed by 1H–13C HSQC for the
other compounds. Products from Eqs. (2), (3) and Tables 1 and 2
were characterized by standard spectroscopic techniques and
compared with spectral data from the literature when available.
Spectral characterization of compounds 4a–c, have been
previously reported [14], but some spectroscopic data informed
do not match with those found in this work, which were re-
confirmed by high field NMR experiments, especially for the E and
Z isomers (for 4b,c) and are presented below:
274 (26), 253 (33), 251 (100), 124 (80), 89 (76).
(5E)-1,1,1,2,2,3,3,4,4-nonafluoro-6-iododec-5-ene
[14a,b]: (oil) 1H NMR (400 MHz, CHLOROFORM-D)
(t, J = 8 Hz, 3H, CH3), 1.35 (m, 2H, H8, H80), 1.57 (m, 2H, H7, H70),
2.63 (m, 2H, H6, H60), 6.31 (t, J = 14.5 Hz, 1H, = CHRf, H3). 19F NMR
4c
(E)
d ppm 0.94
(376.17 MHz, CHLOROFORM-D)
d
ppm ꢁ81.55, ꢁ106.01, ꢁ124.66,
ꢁ126.28. 13C NMR (125.77 MHz CHLOROFORM-D)
d ppm 13.8
(CH3), 21.6 (CH2CH3), 32.1 (CH2CH2CH2), 40.9 (CH2–C(I)55), 126.3
(C(I)55C), 126.5 (HRfC55C). MS, EI, 70 eV, m/z (%): 428 (6), 386 (100),
301 (64), 259 (90), 213 (33), 195 (29), 139 (20), 127 (10), 103 (50).
(5Z)-1,1,1,2,2,3,3,4,4-nonafluoro-6-iododec-5-ene
4c
(Z)
4,4,5,5,6,6,7,7,7-Nonafluoro-2-iodoheptan-1-ol 2a: (oil) 1H
[14a,b]: (oil) 1H NMR (400 MHz, CHLOROFORM-D)
d ppm 6.31
NMR (400 MHz, CHLOROFORM-D)
d
ppm 2.81 (td, J = 6.3 Hz,
(t, J = 14.5 Hz, 1H, 55CHRf). 13C NMR (125.77 MHz CHLOROFORM-
1.5 Hz, 1H, H5), 3.01 (td, J = 6.3 Hz, 1.5 Hz, 1H, H50), 3.78 (broad
D) d ppm 14.1 (CH3), 21.2 (CH2CH3), 29.7 (CH2CH2CH2), 48.1 (CH2–
C(I)55), 123.1 (C(I)55C), 123.0 (HRfC55C). MS, EI, 70 eV, m/z (%):428
(5), 386 (100), 301 (33), 259 (41), 127 (10).
s, 2H, H2, H20), 4.4 (m, 9 lines, 1H, H3). 19F NMR (376.17 MHz,
CHLOROFORM-D)
d
ppm ꢁ81.48, ꢁ114.49, ꢁ124.90, ꢁ126.34. MS,
EI, 70 eV, m/z (%): 404 (M+, 1), 278 (10), 277 (100), 189 (76), 127
(51), 69 (79). EI-HRMS anal. calc. for C7H6F9I: 403.9319. Found:
403.9325.
(2E)-4,4,5,5,6,6,7,7,7-nonafluoro-2-iodo-N,N-dimethylhept-2-
en-1-amine 4d (E): (oil) 1H NMR (400 MHz, CHLOROFORM-D)
d
ppm 2.28 (s, 6H), 3.12 (broad s, 2H), 6.54 (t, J = 14.5 Hz, 1H). 19
F
7-Chloro-1,1,1,2,2,3,3,4,4-nonafluoro-6-iodoheptane 2b: (oil)
NMR (376.17 nMHz, CHLOROFORM-D)
d
ppm ꢁ81.42, ꢁ114.30,
1H NMR (400 MHz, CHLOROFORM-D)
d
ppm 2.71 (m, 1H, H5), 3.15
ꢁ124.67, ꢁ126,11. MS, EI, 70 eV, m/z (%): 429 (34), 302 (20), 164
(22), 69 (43), 58 (100). EI-HRMS anal. calc. for C9H9F9IN: 428.9636.
Found: 428.9639.
(2Z)-4,4,5,5,6,6,7,7,7-nonafluoro-2-iodo-N,N-dimethylhept-2-
en-1-amine 4d (Z): (oil) 1H NMR (400 MHz, CHLOROFORM-D)
(m, 1H, H50), 3.82 (dd, J = 12 Hz, 8.5 Hz, 1H, H3), 4.01 (dd,
J = 11.7 Hz, 4.4 Hz, 1H, H30), 4.43 (ddd, J = 12.6 Hz, 8.2 Hz, 4.5 Hz,
1H, H2). 19F NMR (376.17 MHz, CHLOROFORM-D)
d
ppm ꢁ81.42,
ꢁ114.30, ꢁ124.96, ꢁ126.30. 13CNMR (100.54 MHz CHLOROFORM-
D)
d
ppm 29.7 (CH2Rf), 37.9 (CHI), 50.3 (CH2Cl). MS, EI, 70 eV, m/z
d ppm 2.30 (s, 6H), 3.31 (br s, 2H), 6.79 (t, J = 14.5 Hz, 1H). MS, EI,
(%): 422 (M+, 1), 297 (26), 295 (72), 259 (100), 189 (45), 127 (51), 69
(87). EI-HRMS anal. calc. for C7H5ClF9I: 421.8981. Found:
421.8975.
70 eV, m/z (%): 429 (5), 302 (5), 164 (12), 127 (10), 69 (28), 58
(100). EI-HRMS anal. calc. for C9H9F9IN: 428.9636. Found:
428.9630.
4,4,5,5,6,6,7,7,7-Nonafluoro-2-iodoheptanenitrile 2ci: (oil) 1H
NMR (500 MHz, CHLOROFORM-D)
d ppm 2.87 (complex m, 1H,
Acknowledgements
H5), 3.09 (complex m, 1H, H50), 4.49 (dd, 1H, H3). MS, EI, 70 eV, m/z
(%): 399 (M+, 50), 231 (45), 203 (100), 175 (21), 119 (22), 69 (60).
EI-HRMS anal. calc. for C7H3F9IN: 398.9166. Found: 398.9145.
3,3,4,4,5,5,6,6,6-Nonafluoro-2-(iodomethyl)hexanenitrile 2cii:
´
Thanks are given to Conicet and AgenciaNacional de Promocion
´
´
Cientıfica y Tecnica. We would also like to thank Professor Roberto
Rossi for kindly supplying us with C4F9I.
(oil) 1H NMR (500 MHz, CHLOROFORM-D)
d ppm 3.26 (complex m,
2H, H2, H20), 4.46 (m, 1H, H3). MS, EI, 70 eV, m/z (%): 399 (M+, 45),
231 (35), 203 (100), 175 (26), 119 (21), 69 (60). EI-HRMS anal. calc.
for C7H3F9IN: 398.9166. Found: 398.9125.
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