Catalytic use of selenium electrophiles in cyclizations

Article abstract of DOI:10.1021/ol071223y

A new and convenient one-pot method for a catalytic addition-elimination reaction using selenium electrophiles has been developed. In the presence of 5 mol % diphenyl diselenide, [bis(trifluoroacetoxy)iodo]benzene in acetonitrile converted a range of (E)-3-butenoic acids into the corresponding butenolides in good yields.

Full text of DOI:10.1021/ol071223y

ORGANIC
LETTERS
2007
Vol. 9, No. 16
3169-3171
Catalytic Use of Selenium Electrophiles
in Cyclizations
Danielle M. Browne, Osamu Niyomura, and Thomas Wirth*
School of Chemistry, Cardiff UniVersity, Cardiff CF10 3AT, U.K.
wirth@cf.ac.uk
Received May 29, 2007
ABSTRACT
A new and convenient one-pot method for a catalytic addition−elimination reaction using selenium electrophiles has been developed. In the
presence of 5 mol % diphenyl diselenide, [bis(trifluoroacetoxy)iodo]benzene in acetonitrile converted a range of (E)-3-butenoic acids into the
corresponding butenolides in good yields.
Organic selenium compounds are frequently used as con-
venient reagents for introducing various functional groups
to carbon-carbon double bonds and for constructing het-
erocyclic compounds via ring-closure processes. The mild
reaction conditions usually associated with these reagents
led to frequent use in organic chemistry. Some of these
reactions suffer the drawback that the selenium reagent must
be used in stoichiometric quantities and that the preparation
of more advanced reagents requires several synthetic steps.1
We2 and other research groups have reported the use of
peroxydisulfates as oxidants in addition - elimination
sequences,3 but the turnover numbers are still small and the
amount of catalyst is relatively high. Recently, we reported
on an electrochemically induced selenenylation-deselene-
nylation sequence.4 The use of hypervalent iodine compounds
as oxidants to form selenium electrophiles from diselenides
has been reported previously but has not yet been applied to
catalytic reaction conditions.5 Herein, we describe a conve-
nient way to cyclize a range of â,γ-butenoic acids to the
corresponding butenolides with catalytic amounts of selenium
reagents. As butenolides are a class of biologically active
compounds, different methodologies for their synthesis have
been developed.6
Initial studies have been carried out using (E)-4-phenylbut-
3-enoic acid 1a, which is converted to 5-phenylfuran-2(5H)-
one 2a. A similar sequence has been described by Tiecco et
al. using 10 mol % of diselenide and 3 equiv of peroxydi-
sulfate as oxidant leading to the corresponding lactones in
good yields.3b Tiecco also found that using 2 equiv of
(diacetoxyiodo)benzene with diphenyl diselenide in aceto-
nitrile gave cleanly the corresponding lactone.7 The same
transformation has been investigated recently by Denmark
in great detail.8 Thus, the reaction of acid 1a with 1.05 equiv
of different hypervalent iodine reagents in the presence of 5
mol % of diphenyl diselenide in acetonitrile was performed.
The results are shown in Table 1. It was found that [bis-
(1) (a) Wirth, T. Angew. Chem. 2000, 112, 3890-3900, Angew. Chem.,
Int. Ed. 2000, 39, 3742-3751. (b) Wirth, T., Ed. Top. Curr. Chem. 2000,
208. (c) Browne, D. M.; Wirth, T. Curr. Org. Chem. 2006, 10, 1893-
1903. (d) Wirth, T. In ComprehensiVe Organometallic Chemistry III;
Crabtree, R. H., Mingos, D. M. P., eds.; Elsevier: Oxford, 2006; Vol. 9,
pp 457-500.
(2) Wirth, T.; Ha¨uptli, S.; Leuenberger, M. Tetrahedron: Asymmetry
1998, 9, 547-550.
(3) (a) Iwaoka, M.; Tomoda, S. J. Chem. Soc., Chem. Commun. 1992,
1165-1166. (b) Tiecco, M.; Testaferri, L.; Tingoli, M.; Bagnoli, L.; Santi,
C. Synlett 1993, 798-800. (c) Fujita, K.; Iwaoka, M.; Tomoda, S. Chem.
Lett. 1994, 923-926. (d) Fukuzawa, S.; Takahashi, K.; Kato, H.; Yamazaki,
H. J. Org. Chem. 1997, 62, 7711-7716. (e) Tiecco, M.; Testaferri, L.; Santi,
C. Eur. J. Org. Chem. 1999, 797-803. (f) Tiecco, M.; Testaferri, L.; Santi,
C.; Tomassini, C.; Marini, F.; Bagnoli, L.; Temperini, A. Tetrahedron:
Asymmetry 2000, 11, 4645-4650. (g) Nishibayashi, Y.; Uemura, S. Top.
Curr. Chem. 2000, 208, 201-233. (h) Tiecco, M.; Testaferri, L.; Santi, C.;
Tomassini, C.; Marini, F.; Bagnoli, L.; Temperini, A. Chem. Eur. J. 2002,
8, 1118-1124.
(4) Niyomura, O.; Cox, M.; Wirth, T. Synlett 2006, 251-254.
(5) (a) Tingoli, M.; Tiecco, M.; Chianelli, D.; Balducci, R.; Temperini,
A. J. Org. Chem. 1991, 56, 6809-6813. (b) Tingoli, M.; Tiecco, M.;
Testaferri, L.; Balducci, R. Synlett 1993, 211-212.
(6) (a) Knight, D. W. Contemp. Org. Synth. 1994, 1, 287-315. (b)
Bru¨ckner, R. Curr. Org. Chem. 2001, 5, 679-718.
(7) Tingoli, M.; Tiecco, M.; Testaferri, L.; Temperini, A. Synth. Commun.
1998, 28, 1769-1778.
(8) Denmark, S. E.; Edwards, M. G. J. Org. Chem. 2006, 71, 7293-
7306.
10.1021/ol071223y CCC: $37.00
© 2007 American Chemical Society
Published on Web 07/04/2007

Table 1. Catalytic Cyclization of (E)-4-Phenylbut-3-enoic Acid
1a
Table 3. Catalytic Cyclization of (E)-â,γ-Unsaturated
Carboxylic Acids 1 to Butenolides 2
entry
hypervalent iodine oxidant
2a, yield (%)
entry
R
2, yield (%)
1
2
3
4
5
6
PhI(OAc)2
PhI(OCOCF3)2
C6F5I(OCOCF3)2
IBA a
27
70
59
traces
50
1
2
3
4
5
6
7
8
9
1a, Ph
1b, CH2Ph
70
59
57
54
60
65
65
65
49
96
1c, 4-MeC6H4
1d, 4-BrC6H4
1e, 2-naphthyl
1f, 1-(2-methylnaphthyl)
1g, n-C3H7
1h, n-C4H9
1i, n-C5H11
1j, n-C10H21
FIBA b
IBX c
0
a 1-Hydroxy-1,2-benziodoxol-3-(1H)-one. b 5,6,7,8-Tetrafluoro-1-hydroxy-
1,2-benziodoxol-3-(1H)-one 1-oxide. c 1-Hydroxy-1,2-benziodoxol-3-(1H)-
one 1-oxide.
10
(trifluoroacetoxy)iodo]benzene produced butenolide 2a in
70% yield, while the less reactive (diacetoxyiodo)benzene
only gave 27% yield. The fluorinated and more soluble
reagent [bis(trifluoroacetoxy)iodo]pentafluorobenzene9 re-
sulted in only 59% yield, whereas the cyclic derivative IBA
as well as the iodine(v) reagent IBX10 did not activate the
diselenide sufficiently, and starting material was recovered.
Only the more reactive cyclic FIBA11 led to a 50% yield of
2a.
The starting materials required for these reactions were
obtained either from a Stille cross-coupling reaction with a
stannyl ester12 and an aryl halide or by a modified Knoev-
enagel condensation13 using a range of aldehydes and
malonic acid. As highest yields have been observed using
[bis(trifluoroacetoxy)iodo]benzene 3 in acetonitrile, these
conditions were used in all experiments.
The successful conversion of these butenoic acids into the
corresponding butenolides prompted experiments to identify
the active catalytic species responsible for their formation.
The 1H, 13C, and 19F NMR spectra of a mixture of diphenyl
diselenide and [bis(trifluoroacetoxy)iodo]benzene 3 (1:1, in
The optimization of the solvent used in the catalytic
reaction is summarized in Table 2. Complete conversion was
1
CDCl3) were recorded. The H and 13C NMR indicated a
Table 2. Optimization of Solvents
clear formation of iodobenzene. The 19F NMR showed a
chemical shift of δ ) -75 ppm, which can be assigned to
phenylselenenyl trifluoroacetate 4. Compound 4 was inde-
pendently prepared from phenylselenenyl chloride and silver
trifluoroacetate, and NMR experiments confirmed the results
suggesting that phenylselenenyl trifluoroacetate 4 is the active
catalytic selenenylating species in this reaction.
entry
solvent
2a, yield (%)
1
2
3
4
5
6
CH3CN
toluene
CH2Cl2
Et2O
MeOH
THF
70
68
66
64
20a
15a
The reaction is initiated by the oxidation of diphenyl
diselenide by the hypervalent iodine reagent 3 to form
phenylselenenyl trifluoroacetate 4 (Scheme 1). Reagent 4
then reacts with the â,γ-unsaturated carboxylic acid 1 in a
cyclization reaction to yield compound 5. The selenide in
lactone 5 can then be activated for elimination either by [bis-
(trifluoroacetoxy)iodo]benzene 3 or by phenylselenenyl tri-
fluoroacetate 4. Treatment of independently synthesized 5
(R ) Ph)14 with 3 and 4 revealed that a fast elimination
proceeded only with [bis(trifluoroacetoxy)iodo]benzene 3,
although some elimination product 2 was found also in the
stoichiomeric reaction of 5 and 4. We propose that the
1
a Conversion by H NMR.
observed in acetonitrile, toluene, and dichloromethane after
a reaction time of 3 h; in the other solvents, starting material
1a remained after the same reaction time. The scope was
further investigated by using different substituted â,γ-
unsaturated carboxylic acids in this catalytic reaction (Table
3).
(9) (a) Moriarty, R. M.; Penmasta, R.; Prakash, I. Tetrahedron Lett. 1987,
28, 877-880. (b) Harayama, Y.; Yoshida, M.; Kamimura, D.; Wada, Y.;
Kita, Y. Chem. Eur. J. 2006, 12, 4893-4899.
(10) (a) Wirth, T. Angew. Chem. 2001, 113, 2893-2895; Angew. Chem.,
Int. Ed. 2001, 40, 2812-2814. (b) Wirth, T. In Organic Synthesis Highlights
V; Schmalz, H.-G., Wirth, T., Eds.; Wiley-VCH: Weinheim, 2003; pp 144-
150.
(11) Richardson, R. D.; Zayed, J. M.; Altermann, S.; Smith, D.; Wirth,
T., Angew. Chem. 2007, 119, in press; Angew. Chem. Int. Ed. 2007, 46, in
press.
(12) Thibonnet, J.; Abarbri, M.; Parrain, J.-L.; Ducheˆne, A. Tetrahedron
2003, 59, 4433-4441.
(13) Kumar, H. M. S.; Reddy, B. V. S.; Reddy, E. J.; Yadav, J. S.
Tetrahedron Lett. 1999, 40, 2401-2404.
(14) Tiecco, M.; Testaferri, L.; Temperini, A.; Bagnoli, L.; Marini, F.;
Santi, C. Synlett 2001, 1767-1771.
3170
Org. Lett., Vol. 9, No. 16, 2007

Scheme 1. Proposed Catalytic Cycle
Scheme 2. Use of Enantiomerically Pure Diselenides 8
It was found that longer reaction times were required, lower
yields were observed, and the enantioselectivity was low.
The use of diselenides 8b and 8c resulted in almost racemic
product 2j, whereas with 8a the butenolide 2j was obtained
with an enantiomeric ratio (er) of 57:43 (84% yield).
Diselenide 8d led to 61:39 er (46% yield) of 2j in the
catalytic reaction.16 In a stoichiometric reaction, performed
at -100 °C, the lactone 2a was obtained in a enantiomeric
ratio of 86:14,17 this ratio changed to 63:37 when the reaction
was performed at room temperature. Further work is required
to scan a broader range of diselenides and substrates for the
asymmetric catalytic reaction. Sulfur-containing diselenides3h
and a camphor-based compound18 have been used for the
peroxydisulfate-promoted reaction to butenolides and up to
78:22 er have been obtained.
catalytic cycle proceeds mainly via the intermediate 6 to the
butenolide 2 in an elimination process while regenerating
the selenium electrophile 4.
When only 2 mol % of the catalyst was used in this
reaction, the yield of 2a was reduced to 32% together with
a side product 7 (Figure 1). The formation of 7 was increased
We have developed a novel method for the synthesis of
butenolides 2 from butenoic acids 1 using catalytic amounts
of diphenyl diselenide. [Bis(trifluoroacetoxy)iodo]benzene
3 as stoichiometric oxidant in acetonitrile gave the highest
yields. Using 5 mol % of the catalyst is critical since lower
catalytic loadings resulted in a side product. Further work is
required to achieve higher enantioselectivities in this reaction.
Figure 1. Side product 7 obtained without catalyst.
to 43% when the reaction was performed without diphenyl
diselenide as catalyst. It seems that the hypervalent iodine
compound reacted as an electrophile, and after cyclization,
a phenyl migration took place and the resulting carbocation
was captured by acetonitrile. Such phenyl migrations in
cyclization reactions of substituted styrene derivatives with
hypervalent iodine reagents have already been observed.15
The development of organoselenium reagents for asym-
metric synthesis has produced a range of chiral diselenides,
which are efficient in the transfer of chiral information.1a,c
Catalytic quantities of several enantiomerically pure dis-
elenides were used in place of diphenyl diselenide with
identical reaction conditions (Scheme 2). Substrate 1j was
chosen as it gave the highest yields in the range of examples.
Acknowledgment. We thank Dr. Robert D. Richardson,
Cardiff University, for helpful discussions. We thank The
Royal Society for a fellowship (O.N.), EPSRC for support,
and the National Mass Spectrometry Service Centre, Swansea,
for mass spectrometric data.
Supporting Information Available: Experimental pro-
cedures and spectral data for new compounds. This material
is available free of charge via the Internet at http://pubs.acs.org.
OL071223Y
(16) Slow racemization was observed under the reaction conditions.
(17) Fragale, G.; Wirth, T. Eur. J. Org. Chem. 1998, 1361-1369.
(18) Tiecco, M.; Testaferri, L.; Marini, F.; Santi, C.; Bagnoli, L.;
Temperini, A. Tetrahedron: Asymmetry 1999, 10, 747-757.
(15) Boye, A. C.; Meyer, D.; Ingison, C. K.; French, A. N.; Wirth, T.
Org. Lett. 2003, 5, 2157-2159.
Org. Lett., Vol. 9, No. 16, 2007
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