Urea-hydrogen peroxide complex: A selective oxidant in the synthesis of 2-phenylselenyl-1,3-butadienes

Article abstract of DOI:10.1080/00397910802109224

2-Phenylselenyl-1,3-butadienes were synthesized via the selective oxidation of 2,4-diphenylselenyl-1-butenes with urea-hydrogen peroxide followed by the selenoxide elimination. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397910802109224

This article was downloaded by: [Pennsylvania State University]
On: 31 May 2012, At: 04:52
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954
Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH,
UK
Synthetic Communications: An
International Journal for Rapid
Communication of Synthetic
Organic Chemistry
Publication details, including instructions for
authors and subscription information:
http://www.tandfonline.com/loi/lsyc20
Urea–Hydrogen Peroxide
Complex: A Selective
Oxidant in the Synthesis of 2-
Phenylselenyl-1,3-butadienes
Lei Yu a , Bo Meng a & Xian Huang a b
a Department of Chemistry, Zhejiang University,
Campus Xixi, Hangzhou, China
b State Key Laboratory of Organometallic Chemistry,
Shanghai Institute of Organic Chemistry, Chinese
Academy of Sciences, Shanghai, China
Available online: 09 Sep 2008
To cite this article: Lei Yu, Bo Meng & Xian Huang (2008): Urea–Hydrogen Peroxide
Complex: A Selective Oxidant in the Synthesis of 2-Phenylselenyl-1,3-butadienes,
Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 38:18, 3142-3150
To link to this article: http://dx.doi.org/10.1080/00397910802109224
PLEASE SCROLL DOWN FOR ARTICLE
Full terms and conditions of use: http://www.tandfonline.com/page/terms-
and-conditions

This article may be used for research, teaching, and private study purposes.
Any substantial or systematic reproduction, redistribution, reselling, loan,
sub-licensing, systematic supply, or distribution in any form to anyone is
expressly forbidden.
The publisher does not give any warranty express or implied or make any
representation that the contents will be complete or accurate or up to
date. The accuracy of any instructions, formulae, and drug doses should be
independently verified with primary sources. The publisher shall not be liable
for any loss, actions, claims, proceedings, demand, or costs or damages
whatsoever or howsoever caused arising directly or indirectly in connection
with or arising out of the use of this material.

Synthetic Communications1, 38: 3142–3150, 2008
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print/1532-2432 online
DOI: 10.1080/00397910802109224
Urea–Hydrogen Peroxide Complex: A Selective
Oxidant in the Synthesis of 2-Phenylselenyl-1,3-
butadienes
Lei Yu,1 Bo Meng,1 and Xian Huang1,2
1Department of Chemistry, Zhejiang University, Campus Xixi, Hangzhou, China
2State Key Laboratory of Organometallic Chemistry, Shanghai Institute of
Organic Chemistry, Chinese Academy of Sciences, Shanghai, China
Abstract: 2-Phenylselenyl-1,3-butadienes were synthesized via the selective
oxidation of 2,4-diphenylselenyl-1-butenes with urea–hydrogen peroxide followed
by the selenoxide elimination.
Keywords: 1,3-Butadiene, methylenecyclopropane, oxidation, selenium, urea–
hydrogen peroxide
For a long period, selenium compounds have attracted the attention of
chemists because of their synthetic applications and biological activities
including antitumor and antibacterial activities and other properties.[1]
In the selenium methodology, the selenylated group could be easily intro-
duced, transformed, and eliminated from the organic substrate to allow
selective reactions under mild conditions. Conjugated dienes, which are
also a kind of traditional building blocks in organic synthesis, have been
widely investigated for decades.[2] The Diels–Alder reactions of conju-
gated dienes would help to build ring-contained organic molecules
efficiently and conveniently. Therefore, 2-phenylselenyl-1,3-butadienes,
containing both a selenium atom and a conjugated diene structure unit,
may also play important roles in organic methodology research.[3]
In our previous investigations, we developed a method for the
synthesis of 2-phenylselenyl-1,3-butadienes via the reaction of diaryl
Received December 25, 2007.
Address correspondence to Xian Huang, Department of Chemistry, Zhejiang
University, Campus Xixi, Hangzhou 310028, China. E-mail: huangx@-
mail.hz.zj.cn
3142

Urea–Hydrogen Peroxide Complex
3143
Scheme 1. Synthesis of acetic acid (4-bromo-phenyl)-(1-phenylselenyl-cyclopropyl)-
methyl ester 5.
substituted methylenecyclopropanes (MCPs) with diphenyl diselenide in
the presence of copper(II) acetate.[4] However, when alkyl substituted
MCPs were employed, the corresponding 2-phenylselenyl-1,3-butadienes
could not be obtained. This was probably because of the b-elimination of
the organocopper intermediate with the adjacent hydrogen atom linked
on the alkyl group. Thus, we tried to develop some other synthetic
method that could be tolerant of the alkyl-substituted MCPs.
The selenoxide elimination has emerged as one of the synthetically
most useful olefin-forming reactions.[1a] Hence, 2,4-diphenylselenyl-1-
butenes 1, which could be prepared via the free radical addition of MCPs
with diphenyl diselenide[5] (Scheme 1), might be the possible material
for the synthesis of 2-phenylselenyl-1,3-butadienes if the 4-position
phenylselenyl group could be selectively oxidized. However, the literature
has reported that when 2,4-diphenylselenyl-1-butenes were oxidized with 5
equivalents of hydrogen peroxide, both of their phenylselenyl groups were
oxidized and 3-phenylselenyl-2,5-dihydrofurans 2 were obtained instead
of the expected 2-phenylselenyl-1,3-butadienes[5a] (Scheme 2). This was
probably due to the strong oxidation ability of hydrogen peroxide.
Hydrogen-bonded urea–hydrogen peroxide complex [CO(N-
H2)2 ꢀ H2O2, UHP], which is obtained by recrystallization of urea from
commercially available 33% aqueous hydrogen peroxide, is a cheap
and commercially available white crystalline solid (mp 84–86 ꢁC, dec.)
and can be accurately measured.[6] Compared with hydrogen peroxide,
it is a much milder oxidant. Hence, we presumed whether the 4-position
Scheme 2. Oxidation of 2,4-diphenylselenyl-1-butenes by hydrogen peroxide.

3144
L. Yu B. Meng, and X. Huang
Scheme 3. Selective oxidation of 2,4-diphenylselenyl-1-butenes by UHP.
phenylselenyl group of 2,4-diphenylselenyl-1-butenes could be selectively
oxidized with 1 equivalent of UHP followed by the selenoxide elimination
with the adjacent hydrogen atom to provide the corresponding 2-phenyl-
selenyl-1,3-butadienes (Scheme 3).
Initially, we stirred 0.1 mmol of 1,1-diphenyl-2,4-diphenylselenyl-1-
butene (1a) and 0.1 mmol of UHP in acetone at room temperature. After
24 h, the expected product 1,1-diphenyl-2-phenylselenyl-1,3-butadiene
(3a) was obtained in 43% yield, and 12% of 1a was recovered (Table 1,
entry 1). Further screening demonstrated that the reaction finished
completely if 10% excess of UHP was employed, and the yield of 3a
Table 1. Reactions of 1,1-diphenyl-2,4-diphenylselenyl-1-butene (2a) and UHP
under different conditionsa
Entry
Solvent
T (ꢁC)
Time (h)b
Yield of 3a (%)c
1
2
3
4
5
6
7
Acetone
Acetone
C2H5OH
CH2Cl2
THF
20
20
20
20
20
40
60
24
16
24
9
5
5
43
51
14
56
62
73
51
THF
THF
4
a1a (0.1 mmol) and solvent (2 mL) were employed. In entry 1, 0.1 mmol of UHP
was employed whereas in entries 2–7, 0.11 mmol of UHP was employed.
bThe reaction was monitored by TLC (eluent: petroleum ether).
cIsolated yields.

Urea–Hydrogen Peroxide Complex
3145
Table 2. Synthesis of 2-phenylselenyl-1,3-butadienesa
Entry
R, R
Yield of 3 (%)b
1
2
3
4
5
6
7
8
C6H5, C6H5 (1a)
73 (3a)
60 (3b)
43 (3c)
62 (3d)
55 (3e)
52 (3f)
34 (3g)
50 (3h)
p-CH3C6H4, p-CH3C6H4 (1b)
p-CH3OC6H4, p-CH3OC6H4 (1c)
p-FC6H4, p-FC6H4 (1d)
p-ClC6H4, p-ClC6H4 (1e)
ꢂCH2CH2CH(C6H5)CH2CH2ꢂ (1f)
ꢂ(CH2)5ꢂ (1g)
ꢂ(CH2)7ꢂ (1h)
a1 (0.1 mmol), UHP (0.11 mmol), and THF (2 mL) were employed.
bIsolated yields.
was enhanced to 51% (Table 1, entry 2). It is obviously that THF was a
better solvent (Table 1, entries 1–5). This was probably because of the
better solubility of UHP in THF. The yield of 3a was enhanced when
the reaction was carried out at 40 ꢁC (Table 1, entry 6).
With these results in hand, a series of 2,4-diphenylselenyl-1-butenes were
employed, and the corresponding 2-phenylselenyl-1,3-butadienes were synthe-
sized under these conditions (Table 2). In this method, both aryl (Table 2,
entries 1–5) and alkyl (Table 2, entries 6–8) substituted MCPs could be trans-
formed to the corresponding 2-phenylselenyl-1,3-butadienes smoothly.
Previously, we disclosed that when mono aryl substituted MCP 4 and
diphenyl dieslenide were irradiated under visible light in the presence of
copper(II) acetate with acetate acid as solvent, acetic acid (4-bromo-phenyl)-
(1-phenylselanyl-cyclopropyl)-methyl ester 5 was obtained[4] (Scheme 4).
Scheme 4. Synthesis of acetic acid (4-bromo-phenyl)-(1-phenylselenyl-cyclopropyl)-
methyl ester 5.

3146
L. Yu B. Meng, and X. Huang
Scheme 5. Oxidation of 5 by UHP.
In the molecule of 5, there is a hydrogen atom adjacent to the
phenylselenyl group. Hence, we wondered whether 5 could be oxidized
=
by UHP, followed by selenoxide elimination to produce the C C
double-bond-functionalized MCP 7 . The experimental results showed
that when 5 was oxidized with UHP at room temperature, 6 could be
separated in 90% yield instead of the expected product 7 . When 6 was
heated in THF at 60 ꢁC for 6 h, 7 could be obtained in 24% yield while
more than 60% of 6 was recovered (Scheme 5). The selenoxide elimin-
ation of 6 was not easy.
In conclusion, we disclosed that UHP could oxidize the 4-position
phenylselenyl group of 2,4-diphenylselenyl-1-butenes selectively and
further selenoxide elimination would give 2-phenyselenyl-1,3-butadienes.
Compared with our previous work, this methodology is much more tol-
erant of the substituted group on the starting material of MCPs, and
alkyl substituted 2-phenylselenyl-1,3-butadienes could also be prepared
in this method. The synthetic applications of this methodology are under
further investigations in our laboratory.
EXPERIMENTAL
1H NMR spectra were recorded on a Bruker Avance 400-MHz spec-
trometer in CDCl3 with TMS as the internal standard.13C NMR spectra
were recorded on a Bruker AC-400 (100-MHz) spectrometer in CDCl3.
IR spectra were recorded on a Shimadzu IR-408 spectrometer. EIMS
were run on a HP 5989B mass spectrometer.
Typical Procedure for Preparation of 3
A solution of 1,1-diphenyl-2,4-diphenylselenyl-1-butene (1a, 0.052 g,
0.1 mmol) and UHP (0.010 g, 0.11 mmol) was stirred in 2 mL of THF
at room temperature for 1 h. Then the mixture was stirred at 40 ꢁC for
an extra 4 h. When the reaction was completed, the solvent was evapo-
rated under vacuum, and the residue was subjected to preparative TLC

Urea–Hydrogen Peroxide Complex
3147
(eluent: petroleum ether) to afford 3a in 73% yield. The spectrum data
were consistent with literature.[4]
Typical Procedure for Preparation of 6
Under a nitrogen atmosphere, UHP (0.030 g, 0.33 mmol) was added to
the solution of 5 (0.127g, 0.3 mmol) in THF (2 mL). The mixture was
stirred at room temperature for 3 h. Then, the solvent was evaporated
under vacuum, and the residue was separated by preparative TLC
(eluent: petroleum ether–EtOAc 1:1) to give 6 in 90% yield.
Typical procedure for Preparation of 7
Under a nitrogen atmosphere, 6 (0.044 g, 0.1 mmol) was heated in THF
(2 mL) at 60 ꢁC. After 6 h, the solvent was evaporated under vacuum,
and the residue was separated by TLC (eluent: petroleum ether–EtOAc
8:1), and 7 was obtained in 24% yield. Compound 6 could be recovered
in 60% yield.
Data
1
Compound 3a: Oil. H NMR (400 Hz, CDCl3): d 7.14–7.34 (m, 15H),
6.56–6.63 (m, 1H), 5.81–5.85 (m, 1H), 5.22–5.25 (m, 1H). 13C NMR
(100 Hz, CDCl3): d 120.9, 125.8, 127.3, 127.7, 128.1, 128.9, 129.4,
130.0, 130.1, 130.2, 133.0, 135.4, 141.6, 144.1, 151.6. IR (film, cmꢂ1):
3054, 1576, 1477, 1440, 737, 697. MS (70 eV, EI) m=z: 362 (Mþ , 30),
281 (15), 205 (100). HRMS (EI) calcd. for C22H18Se (Mþ ): 362.0574;
found: 362.0567.
Compound 3b: Oil. 1H NMR (400 Hz, CDCl3, d, ppm): 7.08–7.35 (m,
13H), 6.59–6.66 (m, 1H), 5.77–5.81 (m, 1H), 5.19–5.22 (m, 1H), 2.39 (s,
3H), 2.34 (s, 3H); 13C NMR (100 Hz, CDCl3, d, ppm): 21.2 (d), 120.3,
125.6, 128.3, 128.6, 128.7, 128.8, 129.3, 129.9, 130.1, 133.2, 135.5,
137.1, 137.5, 138.8, 141.4, 151.9; IR (film, n, cmꢂ1): 2921, 1507, 1022,
735; MS (70 eV, EI) m=z: 390 (Mþ , 47), 233 (77), 218 (100).
Compound 3c: Oil. 1H NMR (400 Hz, CDCl3, d, ppm): 6.75–7.32 (m,
13H), 6.58–6.62 (m, 1H), 5.75–5.79 (m, 1H), 5.18–5.21 (m, 1H), 3.83 (s,
3H), 3.78 (s, 3H); 13C NMR (100 Hz, CDCl3, d, ppm): 55.1, 55.2,
112.9, 113.3, 119.9, 125.6, 128.1, 128.8, 129.9, 131.0, 131.8, 133.3,
134.2, 135.8, 136.9, 151.2, 158.9, 159.2; IR (film, n, cmꢂ1): 2924, 1603,
1507, 1248, 1029; MS (70 eV, EI) m=z: 422 (Mþ , 80), 341 (34), 265 (100).

3148
L. Yu B. Meng, and X. Huang
1
Compound 3d: Oil. H NMR (400 Hz, CDCl3, d, ppm): 6.87–7.26
(m, 13H), 6.49–6.52 (m, 1H), 5.83–5.88 (m, 1H), 5.26–5.29 (m, 1H);
13C NMR (100 Hz, CDCl3, d, ppm): 114.6, 114.8, 115.0, 115.3, 121.4,
126.1, 128.9, 129.0, 130.5, 131.2, 131.3, 131.9, 132.0, 132.6, 135.4,
148.6; IR (film, n, cmꢂ1): 2924, 1504, 1227, 835; MS (70 eV, EI) m=z:
398 (Mþ , 48), 241 (76), 220 (100).
1
Compound 3e: Oil. H NMR (400 Hz, CDCl3, d, ppm): 7.03–7.60
(m, 13H), 6.47–6.50 (m, 1H), 5.85–5.89 (m, 1H), 5.28–5.31 (m, 1H);
13C NMR (100 Hz, CDCl3, d, ppm): 121.9, 126.2, 128.0, 128.4, 128.8,
129.0, 129.2, 129.3, 129.6, 130.1, 130.6, 130.9, 131.5, 132.4, 135.3,
139.6; IR (film, n, cmꢂ1): 2921, 1738, 1244, 735; MS (70 eV, EI) m=z:
430 (Mþ , 37), 238 (100).
Compound 3f: Oil. 1H NMR (400 Hz, CDCl3, d, ppm): 7.15–7.34 (m,
10H), 6.75–6.82 (m, 1H), 5.68–5.72 (m, 1H), 5.18–5.21 (m, 1H), 3.58–3.62
(m, 1H), 3.24–3.29 (m, 1H), 2.77–2.83 (m, 1H), 2.19–2.27 (m, 2H), 1.98–
2.18 (m, 2H), 1.49–1.63 (m, 2H); 13C NMR (100 Hz, CDCl3, d, ppm):
31.5, 35.3, 35.4, 37.1, 44.5, 119.3, 123.3, 125.6, 126.1, 126.8, 128.4,
128.9, 129.6, 132.9, 133.4, 146.1, 151.2; IR (film, n, cmꢂ1): 2924, 2853,
1606, 1474, 735, 696; MS (70 eV, EI) m=z: 354 (Mþ , 77), 197 (20), 91
(100).
1
Compound 3g: Oil. H NMR (400 Hz, CDCl3, d, ppm): 7.12–7.29
(m, 5H), 6.75–6.82 (m, 1H), 5.62–5.66 (m, 1H), 5.12–5.15 (m, 1H),
2.71–2.74 (m, 2H), 2.55–2.58 (m, 2H), 1.55–1.62 (m, 4H), 0.86–0.88
(m, 2H); 13C NMR (100 Hz, CDCl3, d, ppm): 26.7, 28.4, 29.7, 31.9,
37.5, 118.7, 122.4, 125.4, 128.9, 129.5, 133.0, 133.4, 152.9; IR (film, n,
cmꢂ1): 2925, 2853, 1608, 1473, 1095, 733; MS (70 eV, EI) m=z: 278
(Mþ , 5), 157 (33), 55 (100).
1
Compound 3h : Oil. H NMR (400 Hz, CDCl3, d, ppm): 7.14–7.30
(m, 5H), 6.78–6.82 (m, 1H), 5.64–5.68 (m, 1H), 5.12–5.15 (m, 1H),
2.74–2.77 (m, 2H), 2.61–2.64 (m, 2H), 1.72–1.84 (m, 4H), 1.46–1.56
(m, 6H); 13C NMR (100 Hz, CDCl3, d, ppm): 25.9, 26.3, 26.7, 27.5,
27.7, 32.0, 37.9, 118.0, 124.6, 125.4, 128.8, 129.5, 133.0, 133.7, 155.1;
IR (film, n, cmꢂ1): 2923, 2853, 1474, 1096, 734; MS (70 eV, EI) m=z:
306 (Mþ , 100), 155 (20).
1
Compound 6 : Oil. H NMR (400 Hz, CDCl3): d 6.99–7.26 (m, 9H),
5.96 (s, 1H), 2.04 (s, 3H), 1.20–1.24 (m, 2H), 0.90–0.94 (m, 2H). 13C NMR
(100 Hz, CDCl3): d 169.7, 139.7, 136.0, 134.9, 131.7, 129.4, 128.2, 126.6,
122.6, 74.8, 20.7, 6.3, 5.6. IR (film, cmꢂ1): 1720, 1242, 1003, 740. MS
(70 eV, EI) m=z: 441 (Mþ þ 1, 21), 440 (Mþ , 4), 145 (100). HRMS (EI)
calcd. for C18H17BrO3Se (Mþ ): 439.9526; found: 439.9520.
1
Compound 7 : Oil. H NMR (400 Hz, CDCl3): d 7.44–7.46 (m, 4H),
2.31 (s, 3H), 1.65 (t, J ¼ 7.2 Hz, 2H), 1.29 (t, J ¼ 7.2 Hz, 2H). 13C NMR
(100 Hz, CDCl3): d 168.9, 135.9, 133.6, 131.4, 125.9, 122.0, 112.0, 20.8,

Urea–Hydrogen Peroxide Complex
3149
5.5, 2.6. IR (film, cmꢂ1): 3743, 1747, 1210, 1137, 1008, 827. MS (70 eV,
EI) m=z: 266 (Mþ , 9), 145 (100). HRMS (EI) calcd. for C12H11BrO2
(Mþ ): 265.9942; found: 265.9954.
ACKNOWLEDGMENT
This work was supported by the National Natural Science Foundation of
China (20332060, 20472072) and Academic Foundation of Zhejiang
Province.
REFERENCES
1. For the applications of selenium-containing compounds, see (a) Back, T. G.
Organoselenium Chemistry: A Practical Approach; Oxford University Press:
Oxford, UK, 1999; (b) Zeni, G.; Stracke, M. P.; Nogueira, C. W.; Braga, A.
L.; Menezes, P. H.; Stefani, H. A. Hydroselenation of alkynes by lithium
butylselenolate: An approach in the synthesis of vinylic selenides. Org. Lett.
2004, 6, 1135–1138; (c) Prediger, P.; Moro, A. V.; Nogueira, C. W.; Saveg-
nago, L.; Menezes, P. H.; Rocha, J. B. T.; Zeni, G. Palladium-catalyzed suzuki
cross-coupling of 2-haloselenophenes: synthesis of 2-arylselenophenes, 2,5-dia-
rylselenophenes, and 2-arylselenophenyl ketones. J. Org. Chem. 2006, 71,
3786–3792; (d) Soares do Rego Barros, O.; Nogueira, C. W.; Stangherlin, E.
C.; Menezes, P. H.; Zeni, G. Copper-promoted carbon-nitrogen bond forma-
tion with 2-iodo-selenophene and amides. J. Org. Chem. 2006, 71, 1552–1557;
(e) Shafiee, A.; Mazloumi, A.; Cohen, V. I. Synthesis of pyrrolo [3,3-d] selena-
zole and pyrrolo [3,2-d] thiazole: Two novel heterocycles. J. Heterocycl. Chem.
1979, 16, 1563–1566; (f) Shafiee, A.; Shafaati, A.; Khamench, B. H. Selenium
heterocycles, XXXIX (1): Synthesis of thieno [3,4-d] thiazole, thieno [3,4-d]
selenazole, selenolo [3,4-d] thiazole, and seleno [3,4-d] selenazole. J. Hetero-
cycl. Chem. 1989, 26, 709–711.
2. Selected recent articles about 1,3-butadienes: (a) Shi, M.; Wang, B.; Huang, J.
Palladium-catalyzed isomerization of methylenecyclopropanes in acetic acid. J.
Org. Chem. 2005, 70, 5606–5610; (b) Wang, K.-T.; Hung, Y.-Y. A convenient
one-pot synthesis of homoallylic halides and 1,3-butadienes. Tetrahedron Lett.
2003, 44, 8033–8036; (c) Itazaki, M.; Nishihara, Y.; Osakada, K. Platinum
complex-catalyzed hydrosilylation and isomerization of methylenecyclopro-
pane derivatives: effect of structures of the substrate and catalyst. J. Org.
Chem. 2002, 67, 6889–6895; (d) Nakamura, I.; Siriwardana, A.; Saito, S.;
Yamamoto, Y. Addition of heteroaromatics to alkylidenecyclopropanes
catalyzed by palladium. J. Org. Chem. 2002, 67, 3445–3449.
3. (a) Roversi, E.; Vogel, P. Competition between Hetero–Diels–Alder and che-
letropic additions of sulfur dioxide to 2-substituted buta-1,3-dienes: Synthesis
of 2-(1-Naphthyl)- and 2-(2-Naphthyl)buta-1,3-diene. Helv. Chim. Acta. 2002,
85, 761–771; (b) Roversi, E.; Monnat, F.; Vogel, P.; Schenk, K.; Roversi, P.

3150
L. Yu B. Meng, and X. Huang
Substituent effect on the competition between Hetero–Diels–Alder and chele-
tropic additions of sulfur dioxide to 1-substituted buta-1,3-dienes. Helv. Chim.
Acta. 2002, 85, 733–760; (c) Bates, G. S.; Fryzuk. M. D.; Stone, C. Convenient
synthesis and cycloaddition reactions of 2-phenylseleno-1,3-butadienes and
2-trialkylstannyl-1,3-butadienes. Can. J. Chem. 1987, 65, 2612–2617; (d)
Liotta, C. L.; Verbicky, J. W. J. The effect of sulfur and selenium substitutents
on the regiochemistry of Diels–Alder reactions. Tetrahedron Lett. 1985, 26,
1395–1398; (e) Redon, S.; Berkaoui, A.-L. B.; Pannecoucke, X.; Outurquin,
F. Selenylated dienes: Synthesis, stereochemical studies by 77Se NMR, and
transformation into functionalized allenes. Tetrahedron 2007, 63, 3707–3717.
4. Yu, L.; Huang, X. Copper(II) Acetate mediated reactions of methylenecyclo-
propane and diphenyl diselenide. Synlett 2007, 1371–1374.
5. Liu, L.; Shi, M. Ring-opening reactions of methylenecyclopropanes with
diphenyl diselenide upon heating: Formation of 3-phenylselenyl-2,5-dihydro-
furan derivatives. Chem. Comm. 2004, 2878–2879; (b) Yu, L.; Huang, X. Reac-
tion of methylenecyclopropanes and diphenyl diselenide under visible-light
irradiation. Synlett 2006, 2136–2138.
6. For the preparation and application of UHP, see: Taliansky, S. Urea–
hydrogen peroxide complex. Synlett 2005, 1962–1963, and references therein.