Reactions of benzeneselenenyl fluoride generated by XeF2-(PhSe)2 system with electron-deficient alkenes

Article abstract of DOI:10.1016/S0022-1139(99)00282-1

Fluoro-benzeneselenenylation of electron-deficient alkenes with benzeneselenenyl fluoride [PhSeF] generated in situ by the reaction of diphenyl diselenide and xenon difluoride proceeded smoothly in dichloromethane. The product yields increased remarkably

Full text of DOI:10.1016/S0022-1139(99)00282-1

Journal of Fluorine Chemistry 102 (2000) 215±218
Reactions of benzeneselenenyl ¯uoride generated by XeF2-(PhSe)2
system with electron-de®cient alkenes
Kenji Uneyama*, Shigemoto Hiraoka, Hideki Amii
Department of Applied Chemistry, Faculty of Engineering, Okayama University, Tsushimanaka, Okayama 700-8530, Japan
Received 29 June 1999; received in revised form 19 July 1999; accepted 12 August 1999
Dedicated to Professor Paul Tarrant on the occasion of his 85th birthday
Abstract
Fluoro-benzeneselenenylation of electron-de®cient alkenes with benzeneselenenyl ¯uoride [PhSeF] generated in situ by the reaction of
diphenyl diselenide and xenon di¯uoride proceeded smoothly in dichloromethane. The product yields increased remarkably in higher
concentration of the seleno-reagent. The reactive seleno-reagent PhSeF may be stabilized in the higher concentration presumably by the
favorable association of the reagent. # 2000 Elsevier Science S.A. All rights reserved.
Keywords: Benzeneselenenyl ¯uoride; Fluoro-selenenylation; Organoselenium compound; 1,2-addition; b-¯uorinated selenides
1. Introduction
has been reported by Tomoda [18]. We have demonstrated
that XeF2-(PhSe)2 in CH2Cl2 can generate a benzenesele-
nenyl ¯uoride equivalent which undergoes a facile ¯uoro-
selenenylation of electron-rich alkenes [19]. Likewise, sub-
stituted acetylenes and phosphaalkynes were also converted
to 2-¯uoroalkenylselenides [20] and vicinal bis(phenylsele-
nenyl)phosphaalkenes [21], respectively, by this system. On
the other hand, PhSeF3 or PhSeF5 generated in situ with an
excess of XeF2 gave mainly di¯uorinated alkenes [22].
In the (PhSe)2-XeF2 system, the electron rich alkenes
reacted very fast, mostly within a minute to give 1,2-adducts
in good yields. But, electron de®cient alkenes reacted slowly
to afford the adducts in very poor yields [19]. Here, we
describe a method which facilitates the effective ¯uoro-
selenenylation of electron-de®cient alkenes. It appears that
benzeneselenenyl ¯uoride decomposes before completion of
the desired reaction with electron-de®cient alkenes (2 h at
08C). After surveying the reaction conditions, we have found
that the concentration of the seleno-reagent was critical. The
higher concentration of the reagent remarkably improved
the yields of ¯uoro-selenenyl compounds (Scheme 1).
Recently, the ef®cient methods for mono¯uorination have
been extensively studied [1±8]. Fluoro-selenenylation of
alkenes is one of the attractive methods for introduction
of ¯uorine atom into a molecule because the selenenium
moiety of the ¯uorinated selenides are versatile for the
further chemical modi®cations [9].
Other electrophilic selenenylating reagents have been
reported and the organoselenium compounds can be used
for further synthetic transformation by photolysis, chemical-
and electrochemical oxidation and reduction and other
chemical modi®cations [10±12]. Generally, when the elec-
tronegativity of X in benzeneselenenyl reagents (PhSeX;
X ˆ Cl, Br, CN, OH, OAc, OTf, NR2, etc.) becomes stron-
ger, the electrophilicity of the phenylseleno group increases.
Since ¯uorine is the most electronegative element, it is
expected to strongly activate the seleno-moiety of the ben-
zeneselenenyl ¯uoride. Several ¯uoroselenenylation sys-
tems such as PhSeNR2-PyÁHF/CH2Cl2 [13], PhSeBr-AgF/
CH2Cl2 [14], PhSeNR2-AgF/CH3CN [15], PhSeNR2-
PyÁ9HF/CH2Cl2 [16], (PhSe)2-Et3NÁ3HF/CH2Cl2/electroox-
idation [17] have been studied. Fluoroselenenylation of a-
diazoketones and a-diazoesters affording the a-¯uoro-a,b-
unsaturated ketones and esters using a PhSeBr-AgF system
* Corresponding author. Tel.: ‡81-86-251-8075; fax: ‡81-86-257-8075.
E-mail address: uneyamak@cc.okayama-u.ac.jp (K. Uneyama).
Scheme 1
0022-1139/00/$ ± see front matter # 2000 Elsevier Science S.A. All rights reserved.
PII: S 0 0 2 2 - 1 1 3 9 ( 9 9 ) 0 0 2 8 2 - 1

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K. Uneyama et al. / Journal of Fluorine Chemistry 102 (2000) 215±218
Table 1
Fluoroselenenylation of electron-deficient alkenes
1 a
)
1
Entry
Substrate 1
(0.2 mol l
1.0 mol l
2 ‡ 3 yield (%)b
Ratio (2 : 3)
2 ‡ 3 yield (%)
Ratio (2 : 3)
a
b
c
1a
1b
1c
49
24
50
(20 : 80)
(0 : 100)
(0 : 100)
58
44
75
(30 : 70)
(0 : 100)
(0 : 100)
d
e
1d
1e
34
24
(80 : 20)
(0 : 100)
57
79
(70 : 30)
(0 : 100)
a The concentration of [PhSeF] in dichloromethane.
b All yields are determined by 19F NMR.
2. Results and discussion
octene proceeded very fast at the temperature within 10 min
and was not affected by the concentration of the seleno-
reagent.
A survey of the data in Table 1 shows that ¯uoroselene-
nylation of electron-de®cient alkenes gave moderate yields
of the ¯uoroselenenylated products at higher concentration.
Because of the instability of the products, the yields were
determined by 19F NMR integration (Table 1).
The benzeneselenenyl ¯uoride was generated at 208C
and allowed to react with alkenes in the temperature range
between 20 and 08C. The addition reaction was mostly
completed at the temperature within 2 h. The higher con-
centration of [PhSeF] equivalent was found to be more
effective to the reaction of [PhSeF] with electron de®cient
alkenes as shown in Fig. 1. Interestingly, the reaction with 1-
Unfortunately, much higher concentration of the reagent
was not achieved because of the low solubility of diphenyl
diselenide in dichloromethane at lower temperatures. The
effect of the concentration is not clear at this moment, but it
might be plausible that benzeneselenenyl ¯uoride [PhSeF]
was stabilized in the higher concentration due to the pos-
sible association of the reagent which made the lifetime of
the reagent longer and the desired reaction effective. Cal-
culation of heats of formation of [PhSeF] as a monomer and
its dimer by PM3 of Mac Spartan Plus revealed that the
dimer is more stable by 18 kcal/mol than the monomer.
Regioselectivity was highly dependent on the substituent
of the a,b-unsaturated carbonyl compounds. Carbomethoxy
group retarded the reaction rate and induced electrophilic
selenenylation at the a-carbon of methyl acrylate as a major
reaction pathway. On the other hand, substitution of b-
methyl and b-phenyl groups resulted in exclusive selene-
nylation at the a-carbon atom (entries 1, 2, and 5). The
regiochemistry may arise from the stabilization of the
inspient carbocation by the electron donating b-substituents.
Meanwhile, the a-methyl group (entry 4) made b-selene-
nylation slightly favorable presumably due to electronic and
steric effects of the a-methyl group.
3. Experimental
1H NMR (200 MHz), 13C NMR (50 MHz), and 19F NMR
(188 MHz) were recorded in CDCl3 on a Varian Gemini-200
1
and VXR-200. Chemical shifts for H and 13C NMR are
reported in ppm down®eld from TMS. 19F NMR spectra
were obtained using C6F6 as an internal standard
( 162.3 ppm), but are reported as chemical shifts up®eld
Fig. 1. Effect of concentration of [PhSeF] ( 20 ! 08C).

K. Uneyama et al. / Journal of Fluorine Chemistry 102 (2000) 215±218
217
from CFCl3. Yields of the 1,2-adducts shown in Table 1 are
3.4. Methyl 3-fluoro-3-phenyl-2-(phenylseleno)
propanoate (3c)
calculated by the relative integral of the crude product
obtained by a simple extraction of the reaction mixture to
the internal standard 1,3-bistri¯uoromethylbenzene added
to the mixture, because of the partial hydrolysis of the 1,2-
addition products during the separation by a column chro-
matography.
All reactions were performed under N2 atmosphere. Two-
necked ¯ask of 30 ml equipped with a septum cap, and a
Te¯on-coated magnetic stirring bar was charged with XeF2
1
IR(neat): 1736 cm 1. H NMR (200 MHz, CDCl3): d
3
3
3.69 (s, 3H), 4.03 (dd, 1H, JHF ˆ 8.7, JHH ˆ 10.5 Hz),
2
3
5.77 (dd, 1H, JHF ˆ 46.4, JHH ˆ 10.5 Hz), 7.2 ꢀ 7.3 (m,
3H), 7.5 ꢀ 7.6 (m, 2H). 19F NMR (188 MHz, CDCl3): d
154.9 (dd, 1 F, J ˆ 46.4, 8.7 Hz); Anal. Calc. for
C11H13FO2Se: C, 45.99; H, 4.25; Found: C, 46.05.; H,
4.14%.
(67.7 mg, 0.4 mmol). At
208C, diphenyldiselenide
(125 mg, 0.4 mmol) dissolved in CH2Cl2 was added. After
the solution was stirred for about 15 min, ole®ns (0.8 mmol)
dissolved in CH2Cl2 was added. The mixture was stirred for
2 h. The mixture was washed with saturated aqueous
NaHCO3 and brine, dried (MgSO4) and then concentrated
to give the crude product as an oil. The product was puri®ed
by a silica gel chromatography.
3.5. Methyl 2-fluoro-2-methyl-3-(phenylseleno)
propanoate (2d)
1
IR(neat): 1766 cm 1. H NMR (200 MHz, CDCl3): d
1.65 (d, 3H, 3JHF ˆ 21.0 Hz), 3.37 (d, 1H, 3JHF ˆ 18.0 Hz),
3
18.0 Hz), 3.40 (dd, 1H, JHF ˆ 24.4 Hz), 3.68 (s, 3H),
7.2 ꢀ 7.3 (m, 3H), 7.5 ꢀ 7.6 (m, 2H). 13C NMR
2
(50 MHz, CDCl3): d 23.8 (d, JCF ˆ 24 Hz), 35.3 (d,
1
3.1. Methyl 2-fluoro-3-(phenylseleno) propanoate (2a)
2JCF ˆ 24.7 Hz), 52.5, 94.7 (d, JCF ˆ 185 Hz), 127.5,
129.1, 129.6, 133.4, 170.9 (d, JCF ˆ 25.4 Hz). 19F NMR
2
1
IR(neat): 1760 cm 1. H NMR (200 MHz, CDCl3): d
(188 MHz, CDCl3): d 151.2 ꢀ 150.5 (m, 1 F); Anal.
Calc. for C11H13FO2Se: C, 48.01; H, 4.76; Found: C, 48.00;
H, 5.16%.
3.1 ꢀ 3.5 (m, 2H), 3.72 (s, 3H), 5.10 (ddd, 1H,
3
2JHF ˆ 47.0, JHH ˆ 6.5, 5.2 Hz), 7.2 ꢀ 7.3 (m, 3H),
7.5 ꢀ 7.7 (m, 2H). 13C NMR (50 MHz, CDCl3): d 28.6
2
1
(d, JCF ˆ 22 Hz), 52.5, 88.0 (d, JCF ˆ 186 Hz), 127.8,
3.6. Methyl 3-fluoro-2-methyl-2-(phenylseleno)
propanoate (3d)
128.6, 129.2, 133.8, 136.0, 168.7 (d, JCF ˆ 24 Hz). 19F
2
NMR (188 MHz, CDCl3): d 185.4 ꢀ 184.9 (m, 1H);
Anal. Calc. for C10H11FO2Se: C, 45.99; H, 4.25; Found:
C, 45.68; H, 4.54%.
1
IR(neat): 1734 cm 1. H NMR (200 MHz, CDCl3): d
2
1.52 (s, 3H), 3.53 (s, 3H), 4.40 (dd, 1H, JHF ˆ 47.8,
2JHH ˆ 9.0 Hz), 4.70 (dd, 1H, 2JHF ˆ 47.4, 2JHH ˆ 9.0 Hz),
3.2. Methyl 3-fluoro-2-(phenylseleno) propanoate (3a)
9.0 Hz), 7.2 ꢀ 7.4 (m, 3H), 7.5 ꢀ 7.6 (m, 2H). 13C NMR
3
(50 MHz, CDCl3): d 20.2 (d, JCF ˆ 3.0 Hz), 48.5 (d,
1
IR(neat): 1730 cm 1. H NMR (200 MHz, CDCl3): d
2JCF ˆ 18 Hz), 52.8, 86.7 (d, JCF ˆ 180 Hz), 125.9,
1
3.72 (s, 3H), 3.87 (ddd, 1H, JHF ˆ 10.3, JHH ˆ 5.2,
129.5, 130.3, 138.6, 172.4 (d, JCF ˆ 2.0 Hz). 19F NMR
3
3
3
2
2
5.2 Hz), 4.65 (ddd, 1H, JHF ˆ 47.0, JHH ˆ 10.3,
(188 MHz, CDCl3): d 209.8 ꢀ 209.4 (m, 1 F); Anal.
Calc. for C11H13FO2Se: C, 48.01; H, 4.76; Found: C, 48.28;
H, 4.81%.
2
2
3JHH ˆ 5.2 Hz), 4.74 (ddd, 1H, JHF ˆ 47.0, JHH ˆ 10.3,
3JHH ˆ 5.2 Hz), 7.26 ꢀ 7.40 (m, 3H), 7.6 ꢀ 7.7 (m, 2H).
13C NMR (50 MHz, CDCl3): d 41.3 (d, 2JCF ˆ 19 Hz), 52.5,
81.9 (d, 1JCF ˆ 177 Hz), 126.0, 129.2, 129.3, 136.0, 170.6.
3.7. 4-Fluoro-4-methyl-3-(phenylseleno)-2-pentanone (3e)
19F NMR (188 MHz, CDCl3): d
204.9 (ddd, 1F,
1
IR(neat): 1706 cm 1. H NMR (200 MHz, CDCl3): d
3
2JHF ˆ 47.0, 47.0, JHF ˆ 10.3 Hz); Anal. Calc. for
C10H11FO2Se: C, 45.99; H, 4.25; Found: C, 45.66; H,
4.62%.
3
3
1.47 (d, 3H, JHF ˆ 7.3 Hz), 1.58 (d, 3H, JHF ˆ 7.0 Hz),
3
2.27 (s, 3H), 3.75 (d, 1H, JHF ˆ 17.2 Hz), 7.2 ꢀ 7.3 (m,
3H), 7.5 ꢀ 7.6 (m, 2H). 13C NMR (50 MHz, CDCl3): d 25.5
2
2
3.3. Methyl 3-fluoro-2-(phenylseleno) butanoate (3b)
(d, JCF ˆ 4.5 Hz), 26.1 (d, JCF ˆ 3.5 Hz), 29.2, 63.1 (d,
2JCF ˆ 23 Hz), 95.1 (d, JCF ˆ 171 Hz), 128.4, 129.2,
1
IR(neat): 1736 cm 1. H NMR (200 MHz, CDCl3): d
129.4, 134.4, 203.4. 19F NMR (188 MHz, CDCl3): d
135.6 ꢀ 134.7 (m, 1 F); Anal. Calc. for C12H15FOSe:
C, 52.76; H, 5.53; Found: C, 52.64; H, 5.90%.
1
3
3
1.50 (dd, 3H, JHF ˆ 24.1, JHH ˆ 6.2 Hz), 3.58 (s, 3H),
3.5 ꢀ 3.6 (m, 1H), 4.94 (ddq, 1H, 2JHF ˆ 47.2, 3JHH ˆ 6.9,
6.2 Hz), 7.2 ꢀ 7.4 (m, 3H), 7.5 ꢀ 7.6 (m, 2H). 13C NMR
2
(50 MHz, CDCl3): d 18.9 (d, JCF ˆ 23 Hz), 48.2 (d,
1
2JCF ˆ 21 Hz), 52.2, 89.8 (d, JCF ˆ 173 Hz), 126.8,
Acknowledgements
129.0, 129.2, 135.6, 170.7. 19F NMR (188 MHz, CDCl3):
d 165.1 ꢀ 164.4 (m, 1 F); Anal. Calc. for C11H13FO2Se:
C, 48.01; H, 4.76; Found: C, 47.82; H, 4.45%.
We are grateful to the Ministry of Education, Culture,
Sports and Science of Japan for the ®nancial support (Grand

218
K. Uneyama et al. / Journal of Fluorine Chemistry 102 (2000) 215±218
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