Fluorinations of α-seleno carboxylic acid derivatives with hypervalent (difluoroiodo)toluene

Article abstract of DOI:10.1002/ejoc.200400659

A very efficient synthesis of (difluoroiodo)toluene avoiding the use of elemental chlorine and elemental fluorine is described. We have fluorinated a series of α-acceptor substituted selenides using (difluoroiodo)toluene. The reactions are usually very clean and under the reaction conditions no further oxidized products are observed. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.

Full text of DOI:10.1002/ejoc.200400659

FULL PAPER
Fluorinations of α-Seleno Carboxylic Acid Derivatives with Hypervalent
(Difluoroiodo)toluene
Maria A. Arrica[a] and Thomas Wirth*[a]
Dedicated to Dedicated to Professor Yasuyuki Kita on the occasion of his 60th birthday
Keywords: Fluorination / Hypervalent iodine / Selenides
A very efficient synthesis of (difluoroiodo)toluene avoiding
the use of elemental chlorine and elemental fluorine is de-
scribed. We have fluorinated a series of α-acceptor substi-
tuted selenides using (difluoroiodo)toluene. The reactions
are usually very clean and under the reaction conditions no
further oxidized products are observed.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2005)
nucleophile. But also electrophilic fluorinations have be-
come useful methods for the introduction of fluorine atoms
and are based on reagents with the fluorine atom bound to
a powerful leaving group. Reagents such as molecular fluor-
ine itself (F2), acetyl hypofluorites, and several reagents
with a nitrogen–fluorine bond belong to this category, the
most important of them being Selectfluor,[2] from which
stereoselective fluorinations have been developed.[3]
The use of iodine(iii) compounds as reagents in organic
synthesis is valuable and rich.[4] Numerous transformations
with these reagents have been developed and include oxi-
dations, additions, cyclizations, and rearrangements. It
should come as no surprise, given the breadth of reactivity
of these compounds, that fluorinating reagents would be
among them. (Difluoroiodo)toluene has, for example, be-
come a very useful reagent in the transfer of fluorine to
several organic substrates.[5,6] The use of (difluoroiodo)tolu-
ene avoids harmful reagents such as molecular fluorine,
toxic fluoride salts or DAST. Double bonds, α-positions of
carbonyl compounds, or triple bonds are among the func-
tionalities, which react with (difluoroiodo)toluene, allowing
the synthesis of important fluorinated compounds.
Introduction
The fluorination of organic molecules has been of in-
creasing interest to organic and medicinal chemists for the
past 50 years.[1] The substitution of a hydrogen atom with
an isosteric fluorine atom allows chemists to probe reactiv-
ities and to synthesize compounds with important physical
and biological properties of high value. The fluorinated
products do not present appreciable steric differences
towards the corresponding hydrogen compounds, but at the
same time their electronic structures change, sometimes in
a dramatic way. The elevated stability of the carbon–fluor-
ine bond compared with the carbon–hydrogen bond implies
that these substrates can be employed in studies of meta-
bolic transformations and in many cases they have been
used as enzymatic inhibitors exploiting biomimetic effects.
Therefore, the judicious placement of fluorine atoms on
pharmaceutical target molecules allows a change of various
properties. Additionally, positron emission tomography
(PET) uses the isotope fluorine-18 as a nuclide probe for
medicine and methods for a clean incorporation into or-
ganic molecules are therefore highly sought after.
The unique and useful characteristics of fluorine-con-
taining compounds, although sometimes unpredictable, are
united with numerous applications in a variety of areas.
Therefore different approaches to their synthesis have been
developed. The most straightforward method is a substitu-
Results and Discussion
The reactivity of sulfur-containing substrates towards
tion reaction whereby a fluoride ion from HF, from fluoride (difluoroiodo)toluene was demonstrated already by
salts or from (diethylamino)sulfur trifluoride (DAST) is dis- Motherwell et al.[5] α-Fluoro sulfides have been obtained
placing a leaving group. A disadvantage of these methods as main reaction products through a Fluoro-Pummerer re-
is that the fluoride anion can react as a base instead as a action. By this procedure the fluoride is incorporated into
the sulfur-containing molecule allowing for the synthesis of
[a]
Department of Chemistry, Cardiff University
monofluorides and difluorides. Depending on reaction con-
ditions, fluoro-sulfoxides can be formed as well. Very little
attention has been paid to the analogous organoselenium
P. O. Box 912, Cardiff CF10 3TB, United Kingdom
Fax: (internat.) +44-2920-876968
E-mail: wirth@cf.ac.uk
Eur. J. Org. Chem. 2005, 395–403
DOI: 10.1002/ejoc.200400659
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395

M. A. Arrica, T. Wirth
FULL PAPER
compounds. As we have already done research in hyperval- source (as LiF, NaF, etc) of fluorine failed. It is worth men-
ent iodine chemistry and in organoselenium chemistry, we tioning that acidic fluorination of (diacetoxyiodo)toluene
were particularly interested in the reactivity of organoselen- with aqueous HF produced (difluoroiodo)toluene (4) along
ium compounds towards (difluoroiodo)toluene. Sulfur and with some side products and therefore in lower overall yi-
selenium have similar chemical reactivity, but differ in size elds.
and electronegativity, and thus, in nucleophilicity. Sulfur
During our studies, an alternative synthesis was pub-
seems to exhibit a particular affinity to the iodine atom in lished which involved the preparation of (dichloroiodo)tol-
(difluoroiodo)toluene. We were interested in determining if uene.[14] In the synthesis described above we avoid the syn-
that affinity is similar in reactions with analogous selenium- thesis of the dichloride, which is notoriously unstable as
containing compounds which would play an important role well as light and heat-sensitive. On the other hand, (diacet-
in the reactivity of selenium substrates toward (difluoro- oxyiodo)toluene (2) is a stable crystalline compound which
iodo)toluene. It is well known that fluorosulfides are useful can be stored for long periods of time. The overall yield of
synthetic intermediates.[7] The synthesis of fluoroselenides 4 reported by Hara and co-workers is around 80 % starting
will lead also to potential building blocks and allow for the from the (dichloroiodo)toluene. In our procedure, (di-
synthesis of fluoroalkenes under milder conditions (lower fluoroiodo)toluene (4) can be obtained in overall yield of
temperatures) than the corresponding sulfides.[8] Fluorosel- up to 97 % starting from (diacetoxyiodo)toluene (2).
enides bearing acceptor substituents can also be synthesized
by other reactions like deprotonation and reaction with an
electrophilic fluorinating agent.[8a,8c] The selenenyl substitu-
ent as an easily removable group can be used in subsequent
synthetic steps.
Preparation of Organoselenium Substrates
Organoselenium substrates were easily prepared by α-se-
lenenylation of commercially available α-chloro esters 5
using (PhSe)2/NaBH4 as shown in Scheme 4. Subsequent
hydrolysis to the corresponding carboxylic acid 7 and reac-
tion with the appropriate alcohol or amine after activation
with DMAP and EDCI gave a range of organoselenium
substrates 8 for the investigation of fluorinations with (di-
fluoroiodo)toluene (Scheme 2).
Synthesis of (Difluoroiodo)toluene
Hypervalent iodine(iii) difluorides have been synthesized
first in 1901 by Stille[9] and several methods for their prepa-
ration are known.[10] The methods commonly used for the
synthesis of (difluoroiodo)toluene are those developed by
Carpenter[11] and Pollak-Zupan[12] using chlorine and mer-
cury oxide or xenon difluoride, respectively. We have devel-
oped an alternative synthesis avoiding the use of these haz-
ardous reagents which involves three steps, perborate oxi-
Fluorinations with (Difluoroiodo)toluene
The reaction of selenide 8a with (difluoroiodo)toluene
dation, basic hydrolysis and reaction with aqueous HF as (4) is believed to proceed in a similar way as the corre-
shown in Scheme 1. sponding sulfides via a Seleno-Pummerer reaction. An in-
The oxidation of iodotoluene (1) with perborate proceeds teraction of the hypervalent iodine with the selenium atom
smoothly.[13] The diacetoxy derivative 2 is hydrolysed by leads to a ligand exchange on the iodine with loss of a fluo-
treatment with aqueous sodium hydroxide to iodosyltol- ride and generate the cationic selenium intermediate 9 as
uene (3), which is then fluorinated using 40 % aqueous hy- shown in Scheme 3. Elimination to 10 and subsequent fluo-
drogen fluoride to give (difluoroiodo)toluene (4) in good rination leads to the monofluorinated selanyl ester 11a. An
overall yield. Attempts to accomplish a direct ligand ex- alternative reaction path is the displacement of the selanyl
change of (diacetoxyiodo)toluene using a nucleophilic group by a nucleophile after activation by the hypervalent
Scheme 1. Synthesis of (difluoroiodo)toluene (4)
Scheme 2. Synthesis of α-selanylesters and α-selanylamides 8
396
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Org. Chem. 2005, 395–403

Fluorinations of α-Seleno Carboxylic Acid Derivatives
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Scheme 3. Fluoro-Pummerer reaction of substrates 8 with (difluoroiodo)toluene (4)
iodine compound. The carbon–selenium bond is much HPLC. Unlike the fluorinated esters, the corresponding flu-
weaker than the carbon–sulfur bond. Additionally, the orinated amides were easily separated from their starting
PhSe–ITol(F)+ group exhibits hypernucleofugicity. These materials by column chromatography.
characteristics could lead to the substitution of the phe-
In Table 1 the yields of the monofluoro esters 11 using an
nylselanyl group either by a fluoride or by another nucleo- excess of (difluoroiodo)toluene (2 equivalents) are reported.
phile, especially because activation of selenides by electro- The results illustrate the formation of monofluorinated acy-
philes is a known mechanism.[15] Such reaction products clic compounds with yields ranging from 20 to 65 %. A typ-
have, however, not been identified in the reactions described ical aqueous work-up with extraction with an organic sol-
here, but these reaction pathways might result in the forma- vent resulted in a significant loss of material. The presence
tion of volatile side-products.
of hydrofluoric acid in the reaction might result in the hy-
Before embarking on the reaction of different substrates drolysis of the ester. No loss of compound was observed by
8, we initially followed the reaction of some selected sub- work-up just by evaporation of the solvent. Additionally,
strates and analysed their behaviour under different reac- decomposition of the product was detected in some cases
tion conditions. Various temperatures (0 °C Ǟ 25 °C, during chromatography, while in other substrates the pres-
40 °C) and different ratios of (difluoroiodo)toluene:sub- ence of monofluorinated phenylselanyl acetic acid was no-
strate were investigated.
ticed.
Reactions employing a 1:1 molar ratio of 4:8 (either at
0 °C or at 40 °C) showed, after a reaction time of 16 hours,
still significant amounts of starting material. For shorter
reaction times (4 h), again with a 1:1 ratio of reagent:sub-
strate at 0 °C, the starting material was found to be the
major component of the reaction mixture. Increasing the
temperature and the reaction time until 16 hours and using
an excess (2 equivalents) of (difluoroiodo)toluene, increases
the yield of the monofluorinated product. Several solvents
differing in polarity and boiling points were also investi-
gated. An increase in reaction temperature affected posi-
tively the ratio between the monofluorinated product and
the starting material, but even working at 100 °C (e.g. tolu-
ene), a complete conversion was not observed with a 1:1
ratio of reagent to substrate.
Table 1. Fluorination of esters 8 with (difluoroiodo)toluene (4)
Entry
Substrate
X
Yield
11a: 62 %
1
2
3
4
5
6
7
8
8a
8b
8c
8d
8e
8f
OEt
OPh
11b: 46 %
11c: 41 %
11d: 65 %
11e: 45 %
11f: 20 %
11g: 34 %
11h: 38 %
OCH2CH=CH2
OCH2CH=C(CH3)2
(E)-OCH2CH=CHPh
OCH2CH2C(CH3) = CH2
OCH2CϵCH
8g
8h
OCH2CH2OH
The reactivity of α-seleno esters did not change even
when more than 2 equivalents of (difluoroiodo)toluene
were used. The same was observed for the corresponding
amides, these results are summarized in Table 2.
The formation of the mono-fluorinated selenides 11 is
clearly visible by the 1H NMR signal and integration of the Table 2. Fluorination of amides 8 with (difluoroiodo)toluene 4
α-protons. The α-protons of 8a appears at δ = 3.51 ppm,
Entry
Substrate
X
Yield
11i: 31 %
11j: 42 %
11k: 31 %
11l: 40 %
11m: 53 %
while the α-proton of 11a appears at δ = 6.34 ppm as a
1
2
3
4
5
8i
8j
8k
8l
8m
NHCH3
N(CH3)2
NHPh
N(CH3)Ph
NHCH2Ph
1
doublet with a typical coupling constant JHF = 51.7 Hz.
The absence of difluorinated products can be seen by the
19F NMR of the crude reaction mixture, which shows only
a doublet due to the fluorine-hydrogen coupling. This is
obviously different to the corresponding sulfides, where the
incorporation of two fluorine atoms was observed.[5] The
Even with large excess of (difluoroiodo)toluene, we have
monofluorinated selenides are more difficult to deprotonate never observed any difluorinated products and it seems that
than the sulfur analogues and do not undergo a second a second fluorination reaction does not take place at all.
seleno-Pummerer reaction.
This is probably due to the presence of the α-fluorine atom,
The mixtures of α-fluoro α-phenylselanyl esters 11, and which decreases the nucleophilicity of the selenium atom
their starting materials 8 are almost impossible to separate towards a second electrophilic attack by the iodine atom of
by flash chromatography. They displayed identical behav- (difluoroiodo)toluene.
iour in all solvent systems investigated. Even the use of flu-
We thought that the hypernucleofugicity of the PhSe–
orinated solvents or MPLC failed to separate the mixtures. ITol(F)+ moiety could lead to the formation of fluoroesters
Separation of these mixtures could only be achieved with or, in the presence of an internal nucleophile as in substrate
Eur. J. Org. Chem. 2005, 395–403
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397

M. A. Arrica, T. Wirth
FULL PAPER
8h, the formation of lactone products. In all substrates there
was, however, no evidence for the formation of fluorinated
products with loss of selenium. Additionally, reaction of es-
ters containing a multiple bond showed no reaction with
the hypervalent iodine compound and no evidence of lac-
tone formation. Obviously groups such as double bonds,
triple bonds or hydroxyl groups are not nucleophilic enough Scheme 4. Synthesis of α-selenonitriles
to carry out an attack on the activated selenium moiety.
The construction of quaternary carbon atoms using (di-
Reaction of nitriles 15 with (difluoroiodo)toluene under
the reaction conditions described above led to the forma-
tion of the α-fluoro-substituted compounds. As with esters
and amides 8 and 12, only the unsubstituted α-phenylselan-
ylacetonitrile (15a) could be fluorinated, the α-methylated
compound 15c was unreactive. The low yields observed in
the fluorination of nitrile 15b are probably due to the high
volatility of the fluorinated product. The results are sum-
marized in Table 4.
fluoroiodo)toluene was also investigated (Table 3). Reaction
of ethyl α-phenylselanylpropionate (12a) failed to generate
any fluorinated products and starting material was reco-
vered. To investigate the steric and electronic contribution
of the phenylselanyl moiety on the fluorination reaction, α-
methylselanyl derivatives 12b and 12c were also synthesized.
Higher reactivity of these substrates was expected with (di-
fluoroiodo)toluene due to the greater localised positive
charge of the selenium cation and due to the presence of
the methyl group as a less sterically demanding moiety. The
experimental results support this hypothesis. In contrast to
12a, which did not react with (difluoroiodo)toluene, the
corresponding (methylselanyl)propanoate 12c was fluori-
nated to generate product 13c with a quaternary carbon
atom, although the conversion was not complete and unre-
acted starting material contaminated the product. The cor-
responding amide derivatives 12d and 12e did not react at
all shown in Table 3 (Entries 4 and 5).
Table 4. Fluorination of nitriles with (difluoroiodo)toluene (4)
Table 3. Fluorination of α-methylated substrates 12 with (difluoro-
iodo)toluene (4)
Conclusion
We have developed a very efficient synthesis of (difluoro-
iodo)toluene avoiding the use of elemental chlorine and ele-
mental fluorine. A series of α-acceptor-substituted selenides
have been fluorinated using (difluoroiodo)toluene. Al-
though the yields are only moderate, the reactions are usu-
ally very clean and, under the reaction conditions used, no
further oxidized products are observed.
Experimental Section
1
General Remarks: H NMR and 13C NMR spectra were recorded
on a Bruker DPX-400 MHz. CDCl3 was used as solvent and as
internal reference (δ = 7.26/77.0) in all the spectra; coupling con-
stants J are given in Hertz. IR spectra were obtained with a Perkin–
Elmer 1600 series FTIR as a liquid film.
19F NMR spectra were recorded on a Jeol ECLIPSE+300 FT
NMR (282.8 MHz) using BF3 •2EtOH as external reference. 77Se
NMR spectra were recorded on the same instrument using di-
phenyl diselenide as external reference.
[a] Product is very volatile and an accurate determination of the
isolated yield is difficult.
Mass spectroscopy analyses were performed either by atmospheric
pressure chemical ionisation (APCI) over fisons VG platform II or
by GC-MS over adb5 column. In this latter case (GC-MS), the
following temperature conditions were used: from 70 to 200 °C for
In order to compare the reactivities of acceptor-substi-
tuted α-seleno derivatives, we synthesized the corresponding
α-selenonitriles as shown in Scheme 4.
398
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Fluorinations of α-Seleno Carboxylic Acid Derivatives
FULL PAPER
36 minutes, from 200 to 250 °C for 4 minutes and 250 °C for 5
minutes; in this case electronical ionization (EI) were used as an
ionization method. Accurate high resolution mass spectroscopic
data were recorded by National Mass Spectrometry Service Centre
at University of Swansea. All reagents were purchased as ACS
grade and used without any further purification. CH2Cl2 was dis-
tilled immediately prior the use from CaH2.
1687, 1450, 1377, 1329, 1298, 1243, 1162, 1078, 737, 667 cm–1; MS
(EI): m/z (%) = 230 (32), 185 (16), 157 (73), 105 (54), 77 (100),
51 (65), 45 (94). HRMS for [M + NH4] C9H10O2Se+NH4+: calcd.
248.0184, found 248.0184.
Esterification of 2-(Phenylselanyl)acetic Acid: To a solution of phe-
nylselanylacetic acid (1.5 g, 7 mmol) in CH2Cl2 (40 mL) was added
the alcohol (10 mmol), DMPA (0.98 g, 8 mmol) and EDCI (1.50 g,
8 mmol). The mixture was stirred at room temperature overnight.
The organic solution was washed with 1 m NaOH to eliminate any
traces of acid, dried and concentrated. The crude oil was then puri-
fied by flash chromatography (petroleum ether: EtOAc (9:1) when
not specified).
(Diacetoxyiodo)toluene (2): (Diacetoxyiodo)toluene was prepared
according to the procedure described by McKillop.[13]
4-Iodosotoluene (3): (Diacetoxyiodo)toluene (2) (3 g, 9 mmol) was
stirred in 5 m NaOH (10 mL) for 2 h at room temperature. The
yellow solid was collected by suction and washed with water
(500 mL) and then with CHCl3 (100 mL). The collect solid was
dried by suction and immediately used in the next reaction.
Phenyl 2-(Phenylselanyl)acetate (8b): Obtained in 75 % yield as a
1
pale yellow solid. M.p. 44–46 °C. H NMR (400 MHz, CDCl3): δ
= 3.63 (s, 2 H), 6.89–6.95 (m, 2 H), 7.12–7.33 (m, 6 H), 7.57–7.63
(Difluoroiodo)toluene (4): In a round-bottomed flask made of Tef-
lon, a slurry of iodosyltoluene (3) (2 g, 8.6 mmol) in CH2Cl2
(30 mL) was prepared. Hydrofluoric acid 40 % was added (16 ×
9 mmol) and the reaction mixture was allowed to stir for 30 min.
The mixture was extracted with CH2Cl2 (2 × 10 mL). The com-
bined extracts were washed several times with small portions of
water, dried with molecular sieves, and the solvent was removed at
atmospheric pressure through nitrogen flow to obtain a pale yellow
solid, which was used without further purification. Yield was up to
97 % (2.14 g, 8.35 mmol). 1H NMR (400 MHz, CDCl3): δ = 2.49
(s, 3 H), 7.40 (d, J = 8.5 Hz, 2 H, Ar), 7.84 (d, J = 8.5 Hz, 2 H,
Ar). 13C NMR (100 MHz, CDCl3): δ = 21.2, 120.8, 130.2, 132.1,
142.3. 19F NMR (282.8 MHz, CDCl3): δ = –177.33 (ref.[16]: δ =
–147.30; ref.[10d]: δ = –174.3 ppm).
(m, 2 H). 13C NMR (100 MHz, CDCl3): δ = 27.4, 121.3, 125.9,
128.2, 128.7, 129.3, 129.4, 133.9, 150.6, 169.5. IR (nujol): ν = 2922,
˜
1738, 1590, 1458, 1377, 1246, 1195, 1163, 1096, 934, 735, 688 cm–1.
MS (APCI): m/z (%) = 292 (13), 198 (36), 170 (100), 123 (8), 83
(12), 71 (50). HRMS for [M + NH4+] C14H12O2Se+NH4+: calcd.
310.0341, found 310.0343.
Allyl 2-(Phenylselanyl)acetate (8c): Obtained in 72 % yield. 1H
NMR (400 MHz, CDCl3): δ = 3.56 (s, 2 H), 4.59 (d, J = 5.5 Hz, 2
H), 5.24 (dd, 3Jcis = 10.5, 2J = 2.4 Hz, 1 H), 5.31 (dd, 3Jtrans = 17.0,
2J = 1.0 Hz, 1 H), 5.85 (m, 1 H), 7.30 (m, 3 H), 7.58–7.63 (m, 2
H). 13C NMR (100 MHz, CDCl3): δ = 27.4, 65.8, 118.4, 127.9,
129.1, 129.1, 131.6, 133.4, 170.5. IR: ν = 3057, 2935, 1730, 1648,
˜
1578, 1478, 1438, 1410, 1261, 1107, 989, 931, 690 cm–1. MS
(APCI): m/z (%) = 256 (58), 196 (30), 170 (40), 122 (25), 83 (41),
70 (100). HRMS for [M + NH4] C11H12O2Se+NH4: calcd.
274.0341, found 274.0339.
General Procedure for the Synthesis of Ethyl α-Phenylselanyl Esters
6: To a solution of diphenyl diselenide (1.252 g, 4 mmol) in EtOH
(30 mL), NaBH4 (454 mg, 12 mmol) was added portionwise at
0 °C. When the solution becomes clear, a solution of ethyl 2-chloro-
ester 5 (10 mmol) in EtOH was added. The mixture was stirred at
0 °C for 1 h and allowed to warm to room temperature. Water and
diethyl ether were added. The organic layer was separated, washed
with water, dried with brine and MgSO4, filtered, and concentrated.
3-Methyl-2-butenyl 2-(Phenylselanyl)acetate (8d): Obtained in 70 %
yield. 1H NMR (400 MHz, CDCl3): δ = 1.60 (s, 3 H), 1.70 (s, 3 H),
3.45 (s, 2 H), 4.50 (d, J = 7.2 Hz, 2 H), 5.20 (m, 1 H), 7.20 (m, 3
H), 7.50 (m, 2 H). 13C NMR (100 MHz, CDCl3): δ = 17.9, 25.7,
27.5, 27.9, 62.3, 118.1, 127.7, 129.1, 133.3, 139.5, 170.8. IR (film):
ν = 3005, 2969, 1726, 1578, 1478, 1438, 1260, 1105, 962, 736,
˜
[17]
690 cm–1. MS (APCI): m/z (%) = 285 (9), 216 (17), 198 (16), 170
(9), 69 (100). HRMS for [M + H] C13H16O2Se+H: calcd. 285.0388,
found 285.0388.
Ethyl 2-(Phenylselanyl)acetate (6, R = H) (= 8a):
Obtained in
1
92 % yield. H NMR (400 MHz, CDCl3): δ = 1.19 (t, J = 7.0 Hz,
3 H), 3.51 (s, 2 H), 4.13 (q, J = 7.0 Hz, 2 H), 7.26 (m, 3 H), 7.57–
7.61 (m, 2 H). 77Se NMR (57.3 MHz, CDCl3): δ = 333.25.
1
Cinnamyl 2-(Phenylselanyl)acetate (8e): Obtained in 76 % yield. H
[17]
Ethyl 2-(Phenylselanyl)propanoate (6, R = Me) (= 12a):
Ob-
NMR (400 MHz, CDCl3): δ = 3.49 (s, 2 H), 4.65 (d, J = 6.5 Hz, 2
H), 6.10 (dt, J = 15.8, J = 6.5 Hz, 1 H), 6.50 (d, J = 15.9 Hz, 1 H),
7.18–7.31 (m, 8 H), 7.51 (m, 2 H). 13C NMR (100 MHz, CDCl3):
δ = 27.5, 65.8, 122.6, 126.6, 127.9, 128.1, 128.6, 128.9, 129.2, 133.6,
1
tained with 70 % yield. H NMR (400 MHz, CDCl3): δ = 1.17 (t,
J = 7.1 Hz, 3 H), 1.54 (d, J = 7.0 Hz, 2 H), 3.77 (q, J = 7.0 Hz, 1
H), 4.09 (q, J = 7.1 Hz, 2 H), 7.27–7.36 (m, 3 H), 7.57–7.63 (m, 2
H).
134.4, 136.1, 170.7. IR (film): ν = 3056, 2956, 1729, 1573, 1473,
˜
1443, 1257, 1106, 966, 740, 690 cm–1. MS (EI): m/z (%) = 332 (8),
171 (12), 131 (12), 117 (100), 91 (29), 77 (12), 51 (16). HRMS for
C17H16O2Se: calcd. 332.0310, found 332.0315.
[18]
Phenylselanylacetic Acid (7, R = H):
To a solution of ethyl 2-
phenylselanylacetate (6, R = H) (410 mg, 1.69 mmol) in EtOH
(10 mL) was added a solution of 30 % aq. KOH (10 mL). The mix-
ture was stirred until completion. Water and diethyl ether were
added. The basic layer was acidified with conc. HCl and extracted
with diethyl ether. The combined organic layers were washed with
water, dried with MgSO4 and the solvent was evaporated. The pro-
duct was obtained in 95 % yield as pale yellow liquid. 1H NMR
(400 MHz, CDCl3): δ = 3.52 (s, 2 H), 7.28 (m, 3 H), 7.58–7.64 (m,
2 H).
3-Methyl-3-butenyl 2-(Phenylselanyl)acetate (8f): Obtained in 70 %
1
yield. H NMR (400 MHz, CDCl3): δ = 1.69 (s, 3 H), 2.19 (t, J =
6.8 Hz, 2 H), 3.40 (s, 2 H), 4.10 (t, J = 6.9 Hz, 2 H), 4.62 (s, 1 H),
4.71 (s, 1 H), 7.2 (m, 3 H), 7.5 (m, 2 H). 13C NMR (100 MHz,
CDCl3): δ = 22.4, 27.4, 36.3, 63.4, 112.3, 127.7, 129.1, 129.2, 133.3,
141.2, 170.8. IR: ν = 735, 891, 1106, 1262, 1473, 1579, 1649, 1724,
˜
2955, 3066 cm–1. MS (APCI): m/z (%) = 284 (45), 216 (12), 145
(38), 122 (18), 108 (18), 82 (30), 71 (100). HRMS for [M +
NH4]:C13H16O2Se+NH4: calcd. 302.0654, found 302.0655.
2-(Phenylselanyl)propionic Acid (7, R = Me): Obtained in 97 %
1
yield. H NMR (400 MHz, CDCl3): δ = 1.57 (d, J = 7.2 Hz, 3 H),
3.77 (q, J = 7.2 Hz, 1 H), 7.30–7.40 (m, 3 H, Ar), 7.65 (d, J = 7.8,
Propargyl 2-(Phenylselanyl)acetate (8g): Obtained in 76 % yield. 1H
NMR (400 MHz, CDCl3): δ = 2.41 (s, 1 H), 3.46 (s, 2 H), 4.55 (s,
2 H), 7.20 (m, 2 H), 7.53 (m, 3 H). 13C NMR (100 MHz, CDCl3):
J = 1.6 Hz, 2 H, Ar). 13C NMR (100 MHz, CDCl3): δ = 17.4, 36.9,
127.4, 128.8, 129.1, 135.8, 135.8, 179.8. IR (nujol): ν = 2923, 2852,
˜
Eur. J. Org. Chem. 2005, 395–403
www.eurjoc.org
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
399

M. A. Arrica, T. Wirth
FULL PAPER
δ = 26.9, 52.5, 75.1, 127.9, 128.6, 129.0, 133.5, 169.9. IR: ν = 3287,
(m, 10 H, Ph), 8.02 (1 H, s broad, PhNH). The spectroscopic data
˜
3056, 2935, 2122, 1734, 1573, 1473, 1438, 1247, 1096, 1021, 996,
730, 695 cm–1. MS (APCI): m/z (%) = 255 (17), 199 (31), 171 (42),
145 (18), 123 (26), 105 (29), 83 (25), 71 (100). HRMS for [M +
NH4] C11H14O2Se+NH4: calcd. 272.0184, found 272.0180.
are in agreement with those in literature.[9]
N-Methyl-N-phenyl-2-(phenylselanyl)acetamide (8l): Obtained in
45 % yield as pale yellow solid after purification by flash chroma-
tography with petroleum ether/EtOAc (7:3). Rf = 0.4; m.p.: 75–
77 °C. 1H NMR (400 MHz, CDCl3): δ = 3.22 (s, 3 H, CH3N), 3.40
(s, 2 H, CH2Se), 7.02 (d, 2 H, Ph), 7.14 (m, 3 H, Ph), 7.20–7.30
(m, 3 H, Ph), 7.38 (m, 2 H, Ph). 13C NMR (100 MHz, CDCl3): δ
= 28.7, 37.8, 127.3, 127.5, 128.0, 129.0, 129.7, 129.8, 133.3, 143.6,
2-Hydroxyethyl 2-(Phenylselanyl)acetate (8h): Obtained in 47 %
yield as pale yellow liquid after purification by flash chromatogra-
phy with petroleum ether/EtOAc (1:1). Rf = 0.31. 1H NMR
(400 MHz, CDCl3): δ = 1.59 (s, broad, 1 H, OH), 3.48 (s, 2 H,
CH2Se), 3.65 (t, J = 4.0 Hz, 2 H, CH2OH), 4.11 (t, J = 4.0 Hz, 2 H, 169.9. IR (nujol): ν = 2923, 1644, 1594, 1568, 1462, 1376, 1113,
˜
CH2O), 7.25 (m, 3 H, Ph), 7.54 (m, 2 H, Ph). 13C NMR (100 MHz,
722, 738, 694 cm–1. GC (DB5) retention time: 30.26 min. MS (EI):
m/z (%) 305 (54), 107 (100). HRMS for [M
H+]
C15H15NOSe+H+: calcd. 306.0392, found 306.0392.
CDCl3): δ = 27.3, 61.0, 66.8, 128.1, 129.0, 129.3, 133.6, 171.1. 77Se
=
+
NMR (57.3 MHz, CDCl ): δ = 340.9. IR: ν = 3385 (br), 3030,
˜
3
2957, 1725, 1578, 1478, 1438, 1410, 1264, 1110, 1074, 1022, 960,
886, 739, 690 cm–1. GC (DB5) retention time: 23.27 min. MS (EI):
m/z (%) = 260 (100), 243 (10), 216 (20), 171 (45), 157 (35), 91 (90),
77 (43), 51 (50). HRMS for C10H12O3Se: calcd. 259.9946, found
259.9944.
N-Benzyl-2-(phenylselanyl)acetamide (8m): Obtained in 83 % yield
as white solid after purification by flash chromatography with pe-
troleum ether/EtOAc (7:3). Rf = 0.2; m.p.: 70–71 °C. 1H NMR
(400 MHz, CDCl3): δ = 3.54 (s, 2 H, CH2Se), 4.43 (d, J = 5.8 Hz,
2 H, CH2NH), 6.65 (s broad, 1 H, CH2NH), 7.03–7.40 (m, 10 H,
Ph). 13C NMR (100 MHz, CDCl3): δ = 30.2, 44.0, 127.5, 127.6,
2-(2-Phenylselanylacetoxy)ethyl 2-(Phenylselanyl)acetate: Obtained
as side product of the reaction to 2-hydroxyethyl phenylselanylacet-
ate as a pale yellow liquid in 10 % yield. Purification by flash chro-
matography with petroleum ether/EtOAc (1:1). Rf = 0.79. 1H NMR
(400 MHz, CDCl3): δ = 3.40 (s, 4 H, CH2Se), 4.10 (s, 4 H, CH2O),
127.7, 128.7, 128.8, 129.5, 132.2, 137.7, 168.3. IR (nujol): ν = 2921,
˜
2852, 1639, 1461, 1377, 1262, 743 cm–1. GC (DB5) retention time:
32.02 min. MS (EI): m/z (%) = 306 (30), 224 (10), 148 (100), 107
(25), 91 (24), 77 (8), 65 (8), 51 (8). HRMS for C15H15NOSe: calcd.
7.25 (m, 6 H), 7.45 (m, 4 H). 13C NMR (100 MHz, CDCl3): δ = 305.0313, found 305.0316.
27.1, 62.7, 127.9, 129.0, 129.2, 133.4, 170.6. IR: ν = 3030, 2959,
˜
General Procedure to Synthesize α-Fluoroselenides: To a solution of
(difluoroiodo)toluene 4 (51 mg, 0.2 mmol) in CH2Cl2 (2 mL) in a
Teflon round-bottomed flask was added at 40 °C the chosen sub-
strate (0.1 mmol) in CH2Cl2 (1 mL). The mixture was stirred over-
night at 40 °C. The solvent was evaporated and the crude residue
was purified by column chromatography.
1731, 1578, 1477, 1437, 1248, 1102, 1022, 972, 911, 735, 689 cm–1;
MS (APCI): m/z (%) = 457 (8), 243 (100). HRMS for C18H18O4Se2:
calcd. 457.9530, found 457.9523.
Amides from 2-(Phenylselanyl)acetic Acid and 2-(Phenylselanyl)pro-
pionic Acid: To a solution of phenylselanyl acetic acid or 2-(phe-
nylselanyl)propionic acid (7 mmol) in CH2Cl2 (40 mL) was added
the amine (10 mmol), DMPA (0.98 g, 8 mmol), and EDCI (1.50 g,
8 mmol). The mixture was stirred at room temperature overnight.
The organic solution was washed with 1 m NaOH to eliminate any
traces of acid, with 1 m HCl to eliminate any unreacted bases, dried,
and concentrated. The crude reaction mixture was then purified by
flash chromatography or crystallisation.
Ethyl 2-Fluoro-2-(phenylselanyl)acetate (11a): Obtained in 62 %
yield as yellow oil after purification by flash chromatography with
petroleum ether/EtOAc (9:1). Rf = 0.4. 1H NMR (400 MHz,
CDCl3): δ = 1.09 (t, J = 7.0 Hz, 3 H, CH ), 4.01 (q, J = 7.0 Hz, 2
3
H, CH2 ), 6.34 (d, JHF = 51.7 Hz, 1 H, CHF), 7.30 (m, 3 H, Ph),
7.63 (dd, J = 7.9, J = 1.2 Hz, 2 H). 13C NMR (100 MHz, CDCl3):
1
δ = 13.9, 62.1, 88.9 (d, JCF = 244 Hz, CFHSeC=O), 125.6, 129.3,
3
N-Methyl-2-(phenylselanyl)acetamide (8i): Obtained in 66 % yield
129.4, 135.9, 166.5 (d, JCF = 26.8 Hz, CFHSeC=O). 19F NMR
as pale yellow solid after purification by flash chromatography with
petroleum ether/EtOAc (1:1). Rf = 0.4; m.p.: 27–30 °C. H NMR
(282.8 MHz, CDCl3): δ = –166.50 (d, JHF = 55.64 Hz, 1 F,
CFHSeC=O). 77Se NMR (57.3 MHz, CDCl3): δ = 510.0. IR
1
(400 MHz, CDCl3): δ = 2.70 (d, J = 4.9 Hz, 3 H, CH3NH), 3.52
(s, 2 H, CH2Se), 6.40 (s broad, 1 H, CH3NH), 7.21 (m, 3 H, Ph),
(nujol): ν = 2975, 1744, 1579, 1473, 1433, 1363, 1327, 1267, 1227,
˜
1157, 1051, 1016, 855, 735, 695 cm–1. MS (EI): m/z (%) = 262
7.40 (m, 2 H, Ph). 13C NMR (100 MHz, CDCl3): δ = 26.8, 30.2, (37), 188(12), 156 (34), 109 (100), 77 (45), 51 (30). HRMS for
127.6, 129.1, 129.4, 131.9, 169.0. IR: ν = 3347, 3066, 2935, 1644,
[M + NH4+] C10H11O2SeF+NH4+: calcd. 280.0247, found 280.0247.
˜
1584, 1478, 1408, 1307, 1162, 1021, 740 cm–1. GC (DB5) retention
time: 13.03 min. MS (EI): m/z (%) = 229 (100), 224 (10), 107 (53),
91 (10), 77 (5). HRMS for C9H11NOSe: calcd. 229.0000, found
229.0004.
Phenyl 2-Fluoro-2-(phenylselanyl)acetate (11b): Obtained in 46 %
yield as red solid after purification by flash chromatography with
1
petroleum ether/EtOAc (9:1). Rf = 0.26; m.p.: 72–76 °C. H NMR
2
(400 MHz, CDCl3): δ = 6.54 (d, JHF = 51.2 Hz, 1 H, CHF), 6.78
N,N-Dimethyl-2-(phenylselanyl)acetamide (8j): Obtained in 80 %
yield as a pale yellow oil. H NMR (400 MHz, CDCl3): δ = 2.81
(d, J = 8.5 Hz, 2 H, Ar), 7.10–7.40 (m, 6 H, Ar), 7.66 (d, J = 7 z,
1
2 H, Ar). 13C NMR (100 MHz, CDCl3): δ = 88.3 (d, 1JCF = 283 Hz,
(s, 3 H, CH3N), 2.82 (s, 3 H, CH3N), 4.61 (s, 2 H, CH2Se), 7.21 CFHSeC=O), 120.9, 125.1, 126.3, 129.5, 129.6, 136.2, 136.2, 149.8,
3
(m, 3 H, Ph), 7.52 (m, 2 H, Ph). 13C NMR (100 MHz, CDCl3): δ
165.0 (d, JCF = 28.2 Hz, CFHSeC=O). 19F NMR (282.8 MHz,
= 28.2, 35.6, 37.9, 127.9, 129.2, 131.3, 133.2, 169.3. IR: ν = 3066,
CDCl3): δ = –166.8 (d, JHF = 52.19 Hz, 1 F, CFHSeC=O). IR
˜
2925, 1639, 1579, 1473, 1433, 1388, 1262, 735 cm–1; Gc (DB5) re-
tention time: 23.27 minutes [70/200 (5m); 200/250 (13m); 250 (5m)];
MS (EI): m/z (%) = 243 (100), 121 (24), 72 (55), 58 (40). HRMS
for [M + H+] C10H13NOSe+H+: calcd. 244.0235, found 244.0236.
(KBr): ν = 3045, 2955, 1739, 1649, 1579, 1493, 1438, 1237, 1026,
˜
931, 840, 735, 685 cm–1. MS (EI): m/z (%) = 310 (42), 156 (25), 109
+
(48), 77 (91), 65 (59), 51 (46), 39 (100). HRMS for [M + NH4
]
C14H11O2SeF+NH4+: calcd. 328.0247, found 328.0252.
[19]
N-Phenyl-2-(phenylselanyl)acetamide (8k):
Obtained in 64 %
Allyl 2-Fluoro-2-(phenylselanyl)acetate (11c): Obtained in 41 %
yield as yellow oil after purification by flash chromatography with
petroleum ether/EtOAc (9:1). Rf = 0.6. 1H NMR (400 MHz,
yield as pale yellow solid after purification by flash chromatogra-
phy with petroleum ether/EtOAc (8:2). Rf = 0.2; m.p.: 73–75 °C.
1H NMR (400 MHz, CDCl3): δ = 3.60 (s, 2 H, CH2Se), 6.90–7.50 CDCl3): δ = 4.45 (qt, J = 1.3, J = 11.3 Hz, 1 H), 4.47 (qt, J =
2
3
2
400
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Org. Chem. 2005, 395–403

Fluorinations of α-Seleno Carboxylic Acid Derivatives
FULL PAPER
1.3, 3 J = 11.3 Hz, 1 H), 5.17 (dq, 2J = 1.3, 3Jcis = 10, 4 J = 1.0 Hz, 76.3, 88.4 (d, JCF = 243 Hz, CFHSeC=O), 125.2, 129.4, 129.6,
1
2
3
4
3
1 H), 5.23 (dq, J = 1.4, Jtrans = 17, J = 1.4 Hz, 1 H), 5.71 (m, 136.1, 165.8 (d, JCF
=
28.9 Hz, CFHSeC=O). 19F NMR
(282.8 MHz, CDCl3): δ = –167.40 (d, JHF = 55.19 Hz, 1 F,
CFHSeC=O), IR (film): ν = 3293, 3056, 2935, 2360, 1760, 1476,
3
1 H), 6.34 (d, JHF = 51.2 Hz, 1 H, CHF), 7.25–7.40 (m, 3 H, Ph),
7.57 (dd, J = 8.5, J = 1.5 Hz, 2 H, Ph). 13C NMR (100 MHz,
˜
1
CDCl3): δ = 66.4, 88.9 (d, JCF = 242 Hz, CFHSeC=O), 119.4,
1438, 1220, 1153, 1050, 740 cm–1. GC (DB5) retention time: 18.56
minutes [70–200 (26m)/200–250 (4m)/250 (5m)], MS (EI): m/z (%)
= 272 (30), 189 (13), 157 (23), 109 (100), 77 (35), 51 (27). HRMS for
[M + NH4+] C11H9O2SeF+NH4+: calcd. 290.0090, found 290.0089.
3
125.5, 129.3, 129.4, 130.9, 135.9, 165.8 (d, JCF = 26.3 Hz,
CFHSeC=O). 19F NMR (282.8 MHz, CDCl3): δ = –166.59 (d, JHF
= 55.17 Hz, 1 F, CFHSeC=O). IR (film): ν = 3059, 2950, 1754,
˜
1648, 1578, 1477, 1439, 1272, 1226, 1156, 1049, 740, 691 cm–1. GC
2-Hydroxyethyl 2-Fluoro-2-(phenylselanyl)acetate (11h): Obtained
in 38 % yield as pale yellow oil after purification by flash chroma-
tography with petroleum ether/EtOAc (1:1). Rf = 0.26. 1H NMR
(400 MHz, CDCl3): δ = 1.46 (s broad, 1 H, OH), 3.62 (m, 2 H),
4.08 (m, 2 H), 6.37 (d, JHF = 51.0 Hz, 1 H, CFHSeC=O), 7.20–
7.30 (m, 3 H, Ar), 7.59 (dd, J = 7.0, J = 1.0 Hz, 2 H, Ar). 13C
(DB5) retention time: 18.36 min. MS (EI): m/z (%) = 274 (19), 189
+
(12), 157 (19), 109 (100), 77 (25). HRMS for [M + NH4
]
C11H11O2SeF+NH4+: calcd. 292.0247, found 292.0250.
3-Methylbut-2-enyl 2-(Fluorophenylselanyl)acetate (11d): Obtained
in 65 % yield as yellow oil after purification by flash chromatogra-
phy with petroleum ether/EtOAc (9:1). Rf = 0.4. 1H NMR
1
NMR (100 MHz, CDCl3): δ = 60.6, 67.4, 88.5 (d, JCF = 244 Hz,
3
(400 MHz, CDCl3): δ = 1.60 (s, 3 H, CH3 ), 1.67 (s, 3 H, CH3 ), CFHSeC=O), 125.3, 129.4, 129.6, 136.1, 167.7 (d, JCF = 27.2 Hz,
4.46 (m, 2 H), 5.14 (m, 1 H), 6.35 (d, J = 53.2 Hz, 1 H, CHF), CFHSeC=O). 19F NMR (282.8 MHz, CDCl3): δ = –167.975 (d,
7.25–7.40 (m, 3 H, Ph), 7.58 (d, J = 7.6 Hz, 2 H, Ph). 13C NMR
JHF = 55.2 Hz, 1 F, CFHSeC=O). 77Se NMR (57.3 MHz, CDCl3):
1
(100 MHz, CDCl3): δ = 18.0, 25.8, 62.8, 88.9 (d, JCF = 243 Hz,
δ = 512.5. IR (film): ν = 3427 (br), 3056, 2945, 1744, 1579, 1473,
˜
CFHSeC=O), 117.4, 125.6, 129.3, 129.4, 135.9, 140.4, 166.5 (d,
1433, 1373, 1327, 1277, 1232, 1162, 1051, 740, 685 cm–1. MS (EI):
3JCF = 27.2 Hz, CFHSeC=O). 19F NMR (282.8 MHz, CDCl3): δ m/z (%) = 296 (100), 140 (73), 135 (69), 122 (54), 77 (47). HRMS
= –166.26 (d, JHF = 58.94 Hz, 1 F, CFHSeC=O), IR (liquid film):
for [M + NH4+] C10H11FO3Se+NH4+: calcd. 296.0196, found
ν = 2915, 1744, 1645, 1599, 1579, 1438, 1262, 1222, 1152, 1041, 296.0199.
˜
740 cm–1. MS (EI): m/z (%) = 302 (4), 234 (10), 157 (11), 109 (25),
N-Methyl-2-fluoro-2-(phenylselanyl)acetamide (11i): Obtained in
+
77 (27), 69 (100), 41 (72). HRMS for [M
+
NH4 ]
31 % yield as brown solid after purification by flash chromatogra-
phy with petroleum ether/EtOAc (1:1). Rf = 0.4; m.p.: 60–64 °C.
1H NMR (400 MHz, CDCl3): δ = 2.59 (d, J = 4.9 Hz, 3 H,
CH3NH), 5.89 (s broad, 1 H, NH), 6.39 (d, JHF = 52.3 Hz, 1 H,
C13H15O2SeF+NH4+: calcd. 320.0560, found 320.0563.
Cinnamyl 2-Fluoro-2-(phenylselanyl)acetate (11e): Obtained in 45 %
yield as yellow oil after purification by flash chromatography with
petroleum ether/EtOAc (9:1). Rf = 0.6. 1H NMR (400 MHz,
CDCl3): δ = 4.60 (dd, J = 6.5, J = 1 Hz, 1 H), 4.63 (dd, J = 7, J (100 MHz, CDCl3):
= 1 Hz, 1 H), 6.04 (dt, J = 16, J = 7.1 Hz, 1 H), 6.35 (d, J = CFHSeC=O), 125.4, 129.2, 129.4, 136.3, 167.0 (d, JCF = 22.4 Hz,
CFHSeC=O), 7.20–7.40 (m, 3 H, Ph), 7.59 (m, 2 H, Ph). 13C NMR
1
δ
=
25.9, 92.9 (d, JCF
=
245.9 Hz,
3
52.3 Hz, 1 H, CHF), 6.54 (d, J = 16 Hz, 1 H), 7.20–7.30 (m, 8 H,
CFHSeC=O). 19F NMR (282.8 MHz, CDCl3): δ = –163.5 (d, JHF
Ar), 7.57 (dd, J = 8.5, J = 1.5 Hz, 2 H, Ar). 13C NMR (100 MHz, = 55.2 Hz, 1 F, CFHSeC=O). IR: ν = 3447, 2925, 2855, 1664, 1458,
˜
1
CDCl3): δ = 66.5, 88.7 (d, JCF = 242 Hz, CFHSeC=O), 121.7,
1376, 1263, 743 cm–1. GC (DB5) retention time: 12.06 min. MS
(EI): m/z (%) = 247 (100), 157 (25), 109 (81), 77 (33), 58 (58), 42
(19). HRMS for [M + H+] C9H10NOFSe+H+: calcd. 246.9906,
found 246.9904.
126.7, 128.3, 128.6, 128.7, 129.2, 129.4, 135.4, 135.8, 136.1, 166.3
3
(d, JCF = 25.3 Hz, CFHSeC=O). 19F NMR (282.8 MHz, CDCl3):
δ = –166.59 (1 F, d, JHF = 51.51 Hz, CFHSeC=O). IR (liquid film):
ν = 3030, 1753, 1653, 1438, 1263, 1225, 1156, 966, 740 cm–1. MS
˜
N,N-Dimethyl-2-fluoro-2-(phenylselanyl)acetamide (11j): Obtained
in 42 % yield as yellow oil after purification by flash chromatogra-
phy with petroleum ether/EtOAc (1:1). Rf = 0.4. 1H NMR
(400 MHz, CDCl3): δ = 2.88 (s, 3 H, CH3), 2.98 (s, 3 H, CH3), 6.51
(d, JHF = 54.5 Hz, 1 H, CFHSeC=O), 7.20–7.30 (m, 3 H, Ph), 7.60
(m, 2 H, Ph), 13C NMR (100 MHz, CDCl3): δ = 36.2, 37.1, 92.9
(EI): m/z (%) = 350 (3), 157 (22), 117 (100), 109 (65), 91 (53), 77
(63), 51 (41). HRMS for [M +] C17H15O2SeF+: calcd. 350.0216,
found 350.0224.
3-Methylbut-3-enyl 2-Fluoro-2-(phenylselanyl)acetate (11f): Ob-
tained in 20 % yield as yellow oil after purification by flash chroma-
tography with petroleum ether/EtOAc (9:1). Rf = 0.6. 1H NMR
1
(d, JCF = 241 Hz, CFHSeC=O), 127.3, 129.1, 129.4, 135.1, 165.8
(400 MHz, CDCl3): δ = 1.65 (s, 3 H), 2.18 (t, J = 6.9 Hz, 2 H), (d, JCF = 21.4 Hz, CFHSeC=O). 19F NMR (282.8 MHz, CDCl3):
3
4.09 (dt, J = 6.9, J = 2.2 Hz, 2 H), 4.64 (s, 1 H), 4.74 (s, 1 H), 6.33
(d, J = 51.8 Hz, 1 H, CHF), 7.23–7.38 (m, 3 H, Ar), 7.59 (dd, J =
δ = –160.8 (d, JHF = 58.9 Hz, 1 F, CFHSeC=O). IR: ν = 3057,
˜
2936, 1657, 1576, 1479, 1399, 1262, 1130, 1027, 741, 678 cm–1. GC
8.0, J = 1.2 Hz, 2 H). 13C NMR (100 MHz, CDCl3): δ = 22.5, 36.3, (DB5) retention time: 13.17 min. MS (EI): m/z (%) = 261 (75), 214
1
64.2, 88.9 (d, JCF = 244 Hz, CFHSeC=O), 112.7, 125.7, 129.3,
(22), 104 (23), 72 (100), 42 (11). HRMS for [M +
H+]
3
129.4, 135.9, 140.9, 166.5 (d, JCF = 27.3 Hz, CFHSeC=O). 19F C10H12NOFSe+H+: calcd. 261.0063, found 261.0059.
NMR (282.8 MHz, CDCl3): δ = –166.48 (d, JHF = 51.48 Hz, 1 F,
2-Fluoro-N-phenyl-2-(phenylselanyl)acetamide (11k): Obtained in
31 % yield as brown-red solid after purification by flash chromatog-
raphy with petroleum ether/EtOAc (7:3). Rf = 0.7; m.p.: 99–104 °C.
1H NMR (400 MHz, CDCl3): δ = 6.47 (d, JHF = 51.7 Hz, 1 H,
CFHSeC=O), 7.06 (m, 1 H, Ar), 7.20–7.30 (m, 7 H, Ar), 7.42 (s
broad, 1 H, NH), 7.60 (dd, J = 1.6, J = 7.0 Hz, 2 H, Ar). 13C NMR
CFHSeC=O). IR (liquid film): ν = 3075, 2966, 1753, 1651, 1578,
˜
1477, 1439, 1377, 1329, 1269, 1229, 1158, 1051, 895, 740, 690 cm–1.
MS (EI): m/z (%) = 302 (8), 234 (26), 157 (28), 109 (53), 77 (61),
51 (44), 41 (100).
Propargyl 2-Fluoro-2-(phenylselanyl)acetate (11g): Obtained in
1
34 % yield as yellow oil after purification by flash chromatography
(100 MHz, CDCl3): δ = 92.6 (d, JCF = 248 Hz, CFHSeC=O),
1
with petroleum ether/EtOAc (9:1). Rf = 0.4. H NMR (400 MHz,
120.1, 124.8, 125.2, 128.9, 129.3, 129.6, 136.1, 136.5, 164.0 (d, 3JCF
CDCl3): δ = 2.43 (t, J = 2.6 Hz, 1 H), 4.53 (dd, J = 23.7, J =
2.5 Hz, 1 H), 4.58 (dd, J = 23.7, J = 2.5 Hz, 1 H), 6.35 (d, J =
51.7 Hz, 1 H, CHF), 7.20–7.40 (m, 3 H, Ph), 7.59 (dd, J = 8.5, J
= 1.5 Hz, 2 H, Ph). 13C NMR (100 MHz, CDCl3): δ = 53.1, 75.9,
= 21.4 Hz, CFHSeC=O). 19F NMR (282.8 MHz, CDCl3): δ = –
162.2 (d, JHF = 55.8 Hz, 1 F, CFHSeC=O). IR: ν = 3200, 1664,
˜
1599, 1523, 1006, 730 cm–1. GC (DB5) retention time: 29.18 min.
MS (EI): m/z (%) = 309 (100), 208 (10), 132 (20), 109 (50), 93 (16),
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M. A. Arrica, T. Wirth
77 (10). HRMS for [M + H+] C14H12NOFSe+H+: calcd. 310.0141, 1.58 (d, J = 7.1 Hz, 3 H, CH3 CH), 3.76 (q, J = 7.1 Hz, 1 H,
FULL PAPER
found 310.0146.
CH3CH), 7.02 (m, 1 H, Ph), 7.20–7.30 (m, 7 H, Ph), 7.52 (d, J =
7.1, 2 H, Ph), 7.63 (s broad, 1 H, NH). 13C NMR (100 MHz,
CDCl3): δ = 18.0, 41.4, 119.7, 124.4, 127.8, 128.7, 128.9, 129.5,
2-Fluoro-N-methyl-N-phenyl-2-(phenylselanyl)acetamide (11l): Ob-
tained in 40 % yield as brown solid after purification by flash chro-
matography with petroleum ether/EtOAc (7:3). Rf = 0.6; m.p.: 75–
77 °C. 1H NMR (400 MHz, CDCl3): δ = 3.24 (s, 3 H, CH 3N), 6.11
(d, J = 54.1 Hz, 1 H, CHFSe), 7.03–7.42 (m, 10 H, Ar). 13C NMR
(100 MHz, CDCl3): δ = 37.9, 92.1 (d, 1JCF = 245 Hz, CFHSeC=O),
127.4, 127.5, 128.6, 128.7, 128.9, 129.9, 134.7, 141.8, 165.6 (d, 3JCF
= 21.5 Hz, CFHSeC=O). 19F NMR (282.8 MHz, CDCl3): δ = –
135.2, 137.6, 170.5. IR (nujol): ν = 3437, 1639, 1458, 1378,
˜
720 cm–1. GC (DB5) retention time: 30.31 min (50–250/250 10m).
MS (EI): m/z (%) = 305 (67), 212 (30), 185 (20), 169 (24), 157 (27),
120 (70), 105 (81), 93 (100), 77 (71), 65 (46), 51 (39). HRMS for
[M + H+] C15H15NOSe+H+: calcd. 306.0392, found 306.0392.
N-Methyl-N-phenyl-2-(phenylselanyl)propionamide (12e): Obtained
in 82 % yield as white solid after purification by flash chromatogra-
phy with petroleum ether/EtOAc (6:4). Rf = 0.75; m.p.: 64–66 °C.
1H NMR (400 MHz, CDCl3): δ = 1.46 (d, J = 6.5 Hz, 3 H, CH3
CH), 3.18 (s, CH3N), 3.66 (q, J = 6.6 Hz, 1 H, CH3CH), 7.01 (d,
J = 6 Hz, 2 H, Ph), 7.10–7.30 (m, 8 H, Ph). 13C NMR (100 MHz,
CDCl3): δ = 18.9, 37.3, 37.7, 127.2, 127.9, 128.2, 128.3, 128.8,
162.9 (d, JHF = 55.8 Hz, 1 F, CFHSeC=O). IR: ν = 3206, 3056,
˜
2985, 1664, 1594, 1493, 1413, 1267, 725 cm–1. GC (DB5) retention
time: 20.10 min. MS (EI): m/z (%) = 323 (94), 146 (93), 134 (100),
109 (84), 77 (32), 51 (21). HRMS for [M + H+] C15H14NOFSe+H+:
calcd. 324.0297, found 324.0300.
N-Benzyl-2-fluoro-2-(phenylselanyl)acetamide (11m): Obtained in
53 % yield as brown solid after purification by flash chromatogra-
phy with petroleum ether/EtOAc (7:3). Rf = 0.5; m.p: 57–61 °C. 1H
NMR (400 MHz, CDCl3): δ = 4.19 (dd, J = 14.5, J = 6.5 Hz, 1 H,
PhCH2 NH), 4.20 (dd, J = 14.5, J = 6.5 Hz, 1 H, PhCH2 NH),
6.08 (s broad, 1 H, NH), 6.37 (d, JHF = 51.7 Hz, 1 H, CFHSeC=O),
6.92 (m, 2 H, Ph), 7.20–7.40 (m, 6 H, Ph), 7.59 (dd, J = 1, J =
8 Hz, 2 H, Ph). 13C NMR (100 MHz, CDCl3): δ = 43.5, 92.6 (d,
1JCF = 245 Hz, CFHSeC=O), 125.1, 127.7, 127.8, 128.7, 129.3,
129.7, 135.6, 143.5, 172.8. IR (nujol): ν = 2925, 1644, 1589, 1458,
˜
1378, 1112, 625 cm–1. GC (DB5) retention time: 29.54 min (50–
250/250 10m). MS (EI): m/z (%) = 319 (59), 162 (54), 134 (46), 107
(100), 77 (55), 65 (100), 51 (25). HRMS for [M
+
H+]
C16H17NOSe+H+: calcd. 320.0548, found 320.0549.
Ethyl 2-Fluoro-2-(methylselanyl)acetate (13b): Obtained in 25 %
yield as yellow oil after purification by preparative TLC with petro-
1
leum ether/EtOAc (9:1). H NMR (400 MHz, CDCl3): δ = 1.26 (t,
3
129.4, 136.5, 136.8, 166.4 (d, JCF = 22.3 Hz, CFHSeC=O). 19F
J = 7.2 Hz, 3 H, CH 3CH2), 2.14 (s, 3 H, CH Se), 4.24 (m, J =
3
7.1, J = 2.9 Hz, 2 H, CH3 CH2 ), 6.15 (d, JHF = 47.69 Hz, 1 H,
NMR (282.8 MHz, CDCl3): δ = –163.7 (d, JHF = 55.8 Hz, 1 F,
CHFSe). 13C NMR (100 MHz, CDCl3): δ = 3.3, 14.1, 62.1, 84.4
CFHSeC=O). IR: ν = 3337, 1664, 1518, 1453, 1378, 1262,
˜
1
3
735 cm–1. GC (DB5) retention time: 30.51 min. MS (EI): m/z (%)
= 309 (100), 288 (10), 208 (10), 132 (20), 109 (50), 104 (31), 93
(17), 63 (11). HRMS for C15H14NOFSe+: calcd. 323.0219, found
323.0216.
(d, JCF = 239 Hz, CFHSeC=O), 167.1 (d, JCF = 28.1 Hz,
CFHSeC=O). 19F NMR (282.8 MHz, CDCl3): δ = –173.82 (d, JHF
= 51.5 Hz, 1 F, CFHSeC=O). 77Se NMR (57.3 MHz, CDCl3): δ =
291.9. IR: ν = 2983, 1747, 1446, 1370, 1329, 1268, 1234, 1161, 1049,
˜
912, 733 cm–1. MS (EI): m/z (%) = 200 (62), 127 (93), 106 (100), 78
Synthesis of α-Methylselanyl Esters: To a solution of dimethyl di-
selenide (600 mg, 3 mmol) in EtOH (24 mL), NaBH4 (363 mg,
10 mmol) was added at 0 °C. When the solution becomes clear, a
solution of ethyl 2-chloroester (8 mmol) in EtOH was added. The
mixture was stirred at 0 °C for 1 h and allowed to warm up to room
temperature. Water and diethyl ether were added. The organic layer
was separated, washed with water, dried with brine and MgSO4,
filtered and concentrated.
(36). HRMS for C5H9O2FSe: calcd. 199.9746, found 199.9748.
Ethyl 2-Fluoromethylselanylpropanoate (13c): Obtained in about
40 % yield which could not be purified from starting material. H
NMR (400 MHz, CDCl3): δ = 1.20 (t, J = 7.1 Hz, 3 H), 1.90 (d, J
1
= 19.2 Hz, 3 H, CH CF), 2.10 (s, 3 H, CH3 Se), 4.20 (dq, J = 2,
3
J = 7.1 Hz, 2 H). 19F NMR (282.8 MHz, CDCl3): δ = –137.44 (q,
JHF = 18.5 Hz, 1 F, CFHSeC=O).
Procedure for the Synthesis of 15a and 15b: To a solution of di-
phenyl diselenide (1.252 g, 4 mmol) or dimethyl diselenide in EtOH
(30 mL), NaBH4 (454 mg, 12 mmol) was added portionwise at
0 °C. When the solution becomes clear, a solution of chloroacetoni-
trile 14 (754 mg, 10 mmol) in EtOH was added. The mixture was
stirred at 0 °C for 1 h and then allowed to warm up to room tem-
perature. Water and diethyl ether were added. The organic layer
was separated, washed with water, dried with brine and MgSO4,
filtered and concentrated.
Ethyl 2-(Methylselanyl)acetate (12b): Obtained in 98 % yield as
colourless liquid. 1H NMR (400 MHz, CDCl3): δ = 1.30 (t, J =
7.1 Hz, 3 H, CH3CH2), 2.19 (s, 3 H, CH3Se), 3.15 (s, 2 H, CH2Se),
4.19 (q, J = 7.1 Hz, 2 H, CH3CH2). 13C NMR (100 MHz, CDCl3):
δ = 5.9, 14.1, 23.7, 61.2, 171.5. 77Se NMR (57.3 MHz, CDCl3): δ
= 135.9. IR (liquid film): ν = 2927, 2853, 1727, 1458, 1419, 1365,
˜
1263, 1109, 1031, 935, 737, 668 cm–1. MS (EI): m/z (%) = 182 (57),
109 (100), 88 (71). HRMS for C5H10O2Se: calcd. 181.9841, found
181.9842.
[20]
(Phenylselanyl)acetonitrile (15a):
Obtained in 90–94 % yield as
Ethyl 2-(Methylselanyl)propanoate (12c): Obtained as colourless li-
1
a colorless liquid. H NMR (400 MHz, CDCl3): δ = 3.30 (s, 2 H,
CH2 ), 7.30 (m, 3 H, Ph), 7.60 (m, 2 H, Ph). The spectroscopic
data are in agreement with those in literature.
1
quid in 92 % yield. H NMR (400 MHz, CDCl3): δ = 1.22 (t, J =
7.0 Hz, 3 H, CH3 CH2), 1.46 (d, J = 7.0 Hz, 3 H, CH3 CH), 2.05
(s, 3 H, CH3 Se), 3.36 (q, J = 7.0 Hz, 1 H, CHSe), 4.12 (q, J =
7.0 Hz, 2 H, CH3 CH2 ). 13C NMR (100 MHz, CDCl3): δ = 3.9,
(Methylselanyl)acetonitrile (15b): Obtained in 67 % yield as pale
yellow liquid. 1H NMR (400 MHz, CDCl3): δ = 2.30 (s, 3 H, CH3),
3.20 (s, 2 H, CH2Se). 13C NMR (100 MHz, CDCl3): δ = 6.1, 30.9,
117.1. IR: 2985, 2928, 2245, 1421, 1401, 1281, 1189, 923 cm–1. GC
(DB5) retention time: 3.14 min. MS (EI): m/z (%) = 135 (70), 84
(100), 45 (70). HRMS for [M + H+] C3H5NSe+H+: calcd. 134.9582,
found 134.9585.
14.2, 17.0, 32.1, 60.9, 173.7. IR (liquid film): ν = 2985, 1722, 1450,
˜
1368, 1326, 1257, 1208, 1147 cm–1. GC (DB5) retention time:
5.45 min. MS (EI): m/z (%) = 196 (80), 123 (100), 102 (51), 74 (11),
55 (22), 41 (70). HRMS for C6H12O2Se: calcd. 195.9997, found
195.9994.
N-Phenyl-2-(phenylselanyl)propionamide (12d): Obtained in 79 %
yield as white solid after crystallisation from CH2Cl2 and petro-
[21]
2-(Phenylselanyl)propionitrile (15c):
A solution of 15a (5 mmol,
leum ether. m.p.: 121–124 °C. 1H NMR (400 MHz, CDCl3): δ = 974 mg) in THF (10 mL) was added at –78 °C under inert and an-
402
© 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Eur. J. Org. Chem. 2005, 395–403

Fluorinations of α-Seleno Carboxylic Acid Derivatives
FULL PAPER
[2] Selectfluor [1-Chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]-
octane bis(tetrafluoroborate)]: R. P. Singh, J. M. Shreeve, Acc.
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hydrous atmosphere to a solution freshly prepared LDA (0.5 m).
This mixture was stirred for about 30 minutes and methyl iodide
(6 mmol, 851 mg) was added. The resulting solution was kept at
–78 °C for 1 h and warmed up to room temperature slowly. The
solution was poured into sat. aq. NH4Cl and extracted three times
with CH2Cl2. The organic layer was dried with MgSO4 and concen-
trated under vacuum. The residue was purified by flash chromatog-
raphy (petroleum ether/EtOAc (9:1)) and the product obtained in
54 % yield as pale yellow liquid. Rf = 0.4. 1H NMR (400 MHz,
CDCl3): δ = 1.60 (d, J = 7.0 Hz, 3 H, CH3 CH), 3.70 (q, J = 7.0 Hz,
CH3 CH, 1 H), 7.30 (m, 3 H, Ph), 7.6 (m, 2 H, Ph). 13C NMR
(100 MHz, CDCl3): δ = 19.2, 19.5, 120.8, 125.8, 129.5, 129.7, 136.5.
IR: ν = 3045, 2985, 2925, 2222, 1579, 1478, 1438, 1338, 1302, 1162,
˜
1086, 1016, 976, 730, 700 cm–1. MS (EI): m/z (%) = 210 (38), 157
+
(100), 116 (18), 77 (88), 51 (72). HRMS for [M + NH4
]
C9H9NSe+NH4+: calcd. 229.0238, found 229.0241.
2-Methyl-2-(phenylselanyl)propionitrile[22] was obtained as side pro-
duct during the synthesis of 15c in 28 % yield. Purified by flash
chromatography with petroleum ether/EtOAc (9:1). Rf = 0.5. 1H
NMR (400 MHz, CDCl3): δ = 1.60 (s, 6 H, CH3 CCH3 ), 7.30 (m,
3 H, Ph), 7.70 (m, 2 H, Ph). The spectroscopic data are in agree-
ment with those in literature.
Chem. Soc., Perkin Trans.
1 2002, 2809–2815; f) W. B.
Motherwell, M. F. Greaney, D. A. Tocher, J. Chem. Soc., Per-
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3801; b) M. Inoue, S. Yamashita, M. Hirama, Tetrahedron Lett.
2004, 45, 2053–2056.
[23]
2-Fluoro-2-(phenylselanyl)acetonitrile (16a):
Obtained in 50 %
yield after purification by flash chromatography. 1H NMR
(400 MHz, CDCl3): δ = 6.40 (d, JHF = 50.2 Hz, 1 H, CHF), 7.40
(m, 3 H, Ph), 7.60 (m, 2 H, Ph). 13C NMR (100 MHz, CDCl3): δ
= 76.3 (d, JCF = 253.6 Hz, CHF), 113.8 (d, JCF = 36.1 Hz, CHF),
124.6, 129.8, 130.5, 136.4. 19F NMR (282.8 MHz, CDCl3): δ =
[8] a) A. Thenappan, D. J. Burton, J. Org. Chem. 1990, 55, 4639–
4642; b) T. Fuchigami, T. Hayashi, A. Konno, Tetrahedron
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164.42 (d, JHF = 52.2 MHz, 1 F). IR: ν = 3056, 2955, 2353, 1573,
˜
1478, 1438, 1302, 1011, 926, 740, 680, 660 cm–1. MS (EI): m/z (%)
= 215 (80), 157 (100), 116 (17), 77 (78), 51 (43). HRMS for [M+]
C8H6NFSe+: calcd. 214.9644, found 214.9645.
2-Fluoro-2-(methylselanyl)acetonitrile (16b): Obtained in 26 % yield
as pale yellow liquid by preparative TLC. 1H NMR (400 MHz,
CDCl3): δ = 2.39 (s, 3 H, CH3 Se); 6.32 (d, JHF = 49.8 Hz, 1 H,
CHF). 13C NMR (100 MHz, CDCl3): δ = 53.4, 72.8 (d, JCF
=
235.2 Hz, CHF), 113.9 (d, JCF = 39.8 Hz, CHF). 19F NMR
[13] A. McKillop, D. Kemp, Tetrahedron 1989, 45, 3299–3306.
[14] M. Sawaguchi, S. Ayuba, S. Hara, Synthesis 2002, 1802–1803.
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(Ed.: T. Wirth), Springer, Heidelberg.
(282.8 MHz, CDCl3): δ = 168.61 (d, JHF = 52 Hz, 1 F). IR: ν =
˜
2984, 2359, 1374, 1248, 1045, 908 cm–1. MS (EI): m/z (%) = 153
(61), 95 (100), 58 (19).
[16] M. Sawaguchi, S. Hara, Y. Nakamura, S. Ayuba, T. Fukuhara,
N. Yoneda, Tetrahedron 2001, 57, 3315–3319.
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Funding was provided by the Department of Chemistry, Cardiff
University and by EPSRC grant no. GR/S25456 (NMR). We thank
the EPSRC National Mass Spectrometry Service Centre, Swansea,
for high resolution mass spectrometric data.
[22] Z. Janousek, S. Piettre, F. Gorissen-Hervens, H. G. Viehe, J.
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Received September 21, 2004
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