Synthesis of arylselenide ethers by photoinduced reactions of selenobenzamide, selenourea and selenocyanate anions with aryl halides

Article abstract of DOI:10.1016/j.tetlet.2010.11.115

Selenobenzamide (^-SeCNH(Ph), 1), selenourea ( ^-SeCNH(NH₂), 2) and selenocyanate (^-SeCN, 3) anions afford areneselenolate ions (ArSe^-) under photostimulation in the presence of tert-butoxide or 2-naphthoxide ions as electron donors (entrainment conditions) in DMSO. In a 'one-pot' procedure, ArSe^- anions can be trapped by a subsequent aliphatic nucleophilic substitution giving aryl methyl selenides in good to excellent yields (67-100%). This simple approach is compatible with electron-donating and electron-withdrawing substituents, such as nitro and carbonyl groups.

Full text of DOI:10.1016/j.tetlet.2010.11.115

Tetrahedron Letters 52 (2011) 969–972
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
Synthesis of arylselenide ethers by photoinduced reactions of selenobenzamide,
selenourea and selenocyanate anions with aryl halides
⇑
⇑
Lydia M. Bouchet, Alicia B. Peñéñory , Juan E. Argüello
INFIQC, Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina
a r t i c l e i n f o
a b s t r a c t
Selenobenzamide (ꢀSeCNH(Ph), 1), selenourea (ꢀSeCNH(NH2), 2) and selenocyanate (ꢀSeCN, 3) anions
afford areneselenolate ions (ArSeꢀ) under photostimulation in the presence of tert-butoxide or 2-naphth-
oxide ions as electron donors (entrainment conditions) in DMSO. In a ‘one-pot’ procedure, ArSeꢀ anions
can be trapped by a subsequent aliphatic nucleophilic substitution giving aryl methyl selenides in good to
excellent yields (67–100%). This simple approach is compatible with electron-donating and electron-
withdrawing substituents, such as nitro and carbonyl groups.
Article history:
Received 2 November 2010
Revised 19 November 2010
Accepted 22 November 2010
Available online 26 November 2010
Keywords:
Selenides
Ó 2010 Elsevier Ltd. All rights reserved.
SRN1
Photochemistry
Electron transfer
Radical
1. Introduction
reaction with KSeCN. The selenocyanate derivatives can be con-
verted to selenols by reduction with NaBH4 or hydrolysis in basic
Organoselenium compounds have attracted considerable atten-
tion not only because of their versatility in organic synthetic proce-
dures1 but also as a result of their unique biological and medicinal
activities, especially in cancer chemoprevention and as an antiviral
or antioxidant in food and plants.2,3
media.12 Selenourea can also be used instead of KSeCN; however,
the yields are modest.13 There are few examples of the formation
of ArSeCN including the reaction of hydrocarbons with ꢀSeCN in
the presence of an oxidant such as bromide or CAN; for these elec-
trophilic substitutions, a strong activation of the aromatic ring is
required.14 Se2ꢀ ion generated by the reduction of grey selenium
with metallic sodium in liquid ammonia (ꢀ33 °C) or hydrazine in
DMF (120 °C) is a powerful nucleophile towards aryl and hetero
aryl halides, affording good yields of ArSeH or Ar2Se2.15 Since we
have successfully developed a procedure for the formation of
arenethiolate anions involving the photoinduced reaction between
thiourea and thioacetate ions with aryl halides,16 we have
considered extending this methodology to the selenium analogues.
We herein report our results on the synthesis of arylselenide com-
pounds by photoinduced reaction of selenium containing anions,
such as selenobenzamide (1) selenourea (2) and selenocyanate
(3) with aryl halides. Selenobenzamide was prepared by the
addition of in situ generated H2Se to benzonitrile.17 These anions
can be generated by acid–base reaction in DMSO as solvent and
would yield arene selenolate anions in the presence of aryl halides
under mild conditions. These anions would render substitution
products under photostimulation by the SRN1 mechanism, which
is a chain process, involving radicals and radical anions as interme-
diates. In these reactions, a compound bearing an adequate leaving
group is substituted by a nucleophile. A wide variety of nucleo-
philes can be used, making the SRN1 reaction a powerful synthetic
tool.18
Two main reactions are possible for the synthesis of organosel-
enides. One involves the use of electrophilic arylselenium halides
with carbon and milder nucleophiles like aryl boronic acids, aryl
siloxanes and aryl stannanes.4 The most common procedure em-
ploys organoselenium anions in nucleophilic addition to alkyl or
aryl halides. Due to their sensitivity to air oxidation, these powerful
nucleophiles are usually prepared in situ from diaryl diselenides by
reaction with reducing agents such as NaBH4,5 alkali metals,6 or the
expensive La, In, Yb, Sm and Zn in ionic liquid,7,8 from deprotona-
tion of arylselenols9 and from insertion of elemental selenium into
lithium or Grignard reagents.10 This last methodology is widely
used for the synthesis of organoselenium compounds. However, it
is not compatible with functional groups susceptible to reduction,
such as NO2 or carbonyl groups. For aryl halides bearing a ketone
or aldehyde group their ketal derivatization is required; then, their
protecting groups must be removed after the Grignard reaction.11
Another approach for introducing a selenium atom into an aryl
ring involves the diazotization of aromatic amines followed by
⇑
Corresponding authors. Tel.: +54 351 434170x134; fax: +54 351 4333030x151.
E-mail addresses: penenory@fcq.unc.edu.ar (A.B. Peñéñory), jea@fcq.unc.edu.ar
(J.E. Argüello).
0040-4039/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2010.11.115

970
L. M. Bouchet et al. / Tetrahedron Letters 52 (2011) 969–972
substitution mechanism (SRN1) for the reaction between anion 1
2. Results and discussion
and 1-naphthyl halides. This process involves an electron transfer
from tert-BuOK to naphthyl halide as the initiation step, affording
the corresponding radical anion. Subsequent fragmentation of the
radical anion thus formed affords 1-naphthyl radical (8) and halide
ions (Eq. 2). Coupling of radical 8 with anion 1 yields a new radical
anion 9 (Eq. 3), which after fragmentation gives 1-naphthalene sel-
enolate ion (10) (Eq. 4). Further reaction of selenide anion 10 with
1-naphthyl radical followed by electron transfer to 4 finally yields
the disubstitution product bis(1-naphthyl) selenide (7) (Eq. 5).
Hydrogen atom abstraction from the solvent by 1-naphthyl radi-
cals gives the reduction product naphthalene (5) (Eq. 6). After irra-
diation, the reaction mixture is quenched by MeI to afford methyl-
1-naphthyl selenide (6) (Eq. 7).
Assuming that the global efficiency of an SRN1 process is the
product of the initiation and the propagation efficiencies,20 and
considering that 20 mol % of TEMPO inhibited the reaction by just
30%, the low inhibiting effect of this radical trap can be attributed
to a low initiation by tert-butoxide ion, or a low or even non-exis-
tent chain reaction.
2.1. Reaction of selenide anions 1–3 with 1-bromonaphthalene
(4) in DMSO
We initiated our study with selenobenzamide anion (1) and
1-bromonaphthalene (4) as a model substrate.19 Although anion
1 was unreactive towards 4 after 3 h of irradiation, the presence
of 2.5 equiv of potassium tert-butoxide (tert-BuOK) triggered the
reaction giving a mixture of naphthalene (5, 25%), methyl-1-
naphthyl selenide (6, 54%) and bis(1-naphthyl) selenide (7,
17%), after quenching with MeI (Eq. 1). In this reaction tert-BuOꢀ
ion acted as an electron donor in the photoinduced electron
transfer reaction (PET) (entrainment reactive). Similar results
were found for the sulfur analogues thioacetate and thiobenzo-
ate anions.16d The use of 2-naphthoxide ion as an electron donor
improved the formation of aryl methyl selenide 6 up to 66%
yield (Table 1, entries 1–3).
Br
SeMe
1) tert-BuO-, hν
Se
R2
DMSO
Displaying a similar behaviour to anion 1, selenourea anion
(2) was not reactive towards 4 under irradiation; however, in
the presence of tert-BuOꢀ or 2-naphthoxide ions, it afforded
products 5 and 6. 2-Naphthoxide ion showed a better perfor-
mance compared to tert-BuOꢀ ion, improving the conversion
and yield of selenide 6, formed in 67% and 24% yield respectively
(Table 1, entries 8–10).
or SeCN
+
+
R1
1-2
2) MeI
3
4
5
6
ð1Þ
1, R1 = Ph, R2 = NH
2, R1 = NH2, R2 = NH
Se
+
7
The reactivity of thiourea anion with 1-bromonaphthalene was
previously studied. This anion is able to initiate and maintain the
catalytic cycle of an SRN1 reaction, completed in 15 min with 91%
of conversion.16a By contrast, entrainment was necessary for the
reaction with selenourea anion (2), even when the yield of selenide
6 is comparable to its sulfide analogue, the overall process is
slower, needing up to 3 h for a complete conversion. It was also
reported that the thiocyanate anion is unreactive both in the initi-
ation step as an electron donor and in addition to 1-naphthyl rad-
icals generated by a photostimulated entrainment reaction with
tert-BuOK.16b However, its selenium analogue, ꢀSeCN (3), in the
presence of 4 and tert-BuOK yielded a mixture of naphthalene
(5%), methyl-1-naphthyl selenide (61%) and bis(1-naphthyl) sele-
nide (27%) after 3 h of irradiation. This reaction did not occur in
the absence of tert-BuOK (Table 1, entries 11 and 12).
There was no reaction in the dark after 3 h and the photoin-
duced reaction was inhibited by the presence of the well-known
radical trap 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) (Table
1, entries 4 and 5). In order to evaluate the nature of the PET reac-
tion, electron acceptors better and worse than bromide 4, 1-iodo
and 1-chloronaphthalene respectively, were tested. As expected
for an ET process, the iodo derivative was more reactive than 4
with a 100% of conversion while chloronaphthalene was the least
reactive, with only a 46% consumption of the substrate. These
results are in agreement with a photoinduced electron transfer
reaction (Table 1, entries 6 and 7).
The lack of reaction between anion 1 and 4 under irradiation,
the entrainment reaction in the presence of tert-BuOꢀ or 2-naphth-
oxide ions under light catalysis, the inhibition by a radical trap, the
reactivity order iodo > bromo > chloronaphthalene and the pres-
ence of a variable amount of naphthalene suggest a radical chain
tert-BuO
+
Br
(Ar-X)
Ar-X
ð2Þ
hν, ET
4
8
Table 1
Reactions of selenium nucleophiles 1–3 with 1-halonaphthalene in DMSOa
Entry
RSe
ꢀ
ArX, condition, additive
Product yieldb (%)
ArSeMe (6)
Convn
ArH (5)
ArSeAr (7)
1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
2
2
2
3
3
1-BrC10H7, h
1-BrC10H7, h
1-BrC10H7, h
m
m
m
—
—
—
—
17
9
—
7
—
—
—
—
—
—
27
, tert-BuOK (2.5 equiv)
, 2-naphthoxide (2.5 equiv)
96
100
—
67
100
46
—
46
100
—
25
21
—
11
47
15
—
15
31
—
54
66
—
49
53
31
—
24
67
—
1-BrC10H7, dark, tert-BuOK (2.5 equiv)
1-BrC10H7, h , tert-BuOK (2.5 equiv), TEMPO (0.2 equiv)
1-IC10H7, h , tert-BuOK (2.5 equiv)
1-ClC10H7, h , tert-BuOK (2.5 equiv)
m
m
m
1-BrC10H7, h
1-BrC10H7, h
1-BrC10H7, h
1-BrC10H7, h
1-BrC10H7, h
m
m
m
m
m
, tert-BuOK (1.5 equiv)
, 2-naphthoxide (2.5 equiv)
10
11
12
, tert-BuOK (5 equiv)
91
4
61
a
1-XC10H7: 0.05 M, selenium-centred nucleophiles (RSeꢀ): 0.25 M, under N2 atmosphere, irradiation time: 3 h with a high-pressure Hg lamp. The reactions were quenched
by the addition of MeI.
B
Determined by GC using (PhSe)2 as internal standard, error 5%. The conversion (convn) was determined by quantification of the recovered substrate.

L. M. Bouchet et al. / Tetrahedron Letters 52 (2011) 969–972
971
NH
obtained by the SRN1 reaction were quenched by MeI to afford
aryl methyl selenide (ArSeMe) derivatives in good to excellent
yields (66–100%). Diaryl selenide (ArSeAr) was formed as a side
product and in most cases the ratio Ar2Se/ArSeMe was higher for
anion 3. This finding can be ascribed to a higher reactivity to-
wards aryl radicals of the arene selenide ion (ArSeꢀ) formed dur-
ing the course of the reaction, compared to ꢀSeCN. When halo
ketones were used as substrates, anion 3 was not reactive and
the mass balance was poor (results not shown). However, anion
1 gave very good to excellent yields of the corresponding ArSe-
Me products. This latter result is better than those provided by
the Grignard methodology, which needs protection of the
carbonyl moiety. Furthermore, our procedure was also successful
Se Ph
8
1
+
ð3Þ
9
Se
ð4Þ
ð5Þ
+
C(NH)Ph
9
10
Se
with aryl halides bearing
a nitro group; not requiring the
4
, ET
10
8
7
( )
4
( )
+
+
expensive or non-commercially available amines shows another
advantage of the present methodology. Finally, our results are
comparable with those obtained with Na2Se as nucleophile;
however, this anion must be formed in situ by the reduction
of metallic selenium in liquid ammonia as solvent (ꢀ33 °C).15a
In conclusion, we have developed a new approach to the prep-
aration of ArSeꢀ anions in DMSO by photoinduced reaction of the
acid–base generated anions 1 and 3 with a variety of aryl halides
and in the presence of tert-BuOK as an entrainment reagent. Subse-
quent substitution with MeI affords ArSeMe derivatives from good
to excellent yields. This simple methodology is compatible with
both electron-donating and electron-withdrawing groups, includ-
ing nitro and carbonyl groups.
7
DMSO
ð6Þ
ð7Þ
8
5
10
6
+ MeI
2.2. Synthesis of aryl methyl selenides by the photoinduced
reactions of selenide anions 1 and 3 with aryl halides in DMSO
The observed reactivity of selenobenzamide anion towards
1-bromonaphthalene under irradiation encouraged us to further
explore the potential of this anion in the synthesis of selenide com-
pounds. The selenourea anion was not considered due to its low
reactivity, high cost, low stability and its air sensitive nature. Quite
a few examples of the use of ꢀSeCN were also included because of
its air-stable and commercially available potassium salt. Table 2
summarizes the results obtained in the photoinduced reactions
of 1 and 3 with a variety of aryl halides.
Acknowledgements
This work was supported partly by Consejo Nacional de Investi-
gaciones Científicas y Técnicas (CONICET), SECYT-UNC and Fondo
para la Investigación Científica y Technológica (FONCYT), Argen-
tina. L.M.B. gratefully acknowledges the receipt of a fellowship
from CONICET.
From Table 2, it is possible to conclude that this methodology
is appropriate for substrates bearing electron-donating and elec-
tron-withdrawing groups. In these cases, the arene selenide ions
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tetlet.2010.11.115.
Table 2
Reactions of selenium nucleophiles 1 and 3 with aryl halides (ArX) in DMSOa
References and notes
1) hν
Se
or SeCN + ArX
ArH + ArSeMe + ArSeAr
1. (a) Organoselenium Chemistry—Modern Developments in Organic Synthesis;
Wirth, T., Ed.Topics in Current Chemistry 208; Springer: Heidelberg, 2000;
(b)Organoselenium Chemistry: A Practical Approach; Back, T. G., Ed.; Oxford
University Press: New York, 1999; (c) Paulmier, C. Selenium Reagents and
Intermediates in Organic Synthesis;; Pergamon Press: Oxford, 1986; (d)The
Chemistry of Organic Selenium and Tellurium Compounds; Patai, S., Rappoport, Z.,
Eds.; Wiley: New York, 1986; Vol. 1, (e) Freudendahl, D. M.; Shahzad, S. A.;
Wirth, T. Eur. J. Org. Chem. 2009, 1649–1664; (f) Freudendahl, D. M.; Santoro, S.;
Shahzad, S. A.; Santi, C.; Wirth, T. Angew. Chem., Int. Ed. 2009, 48, 8409–8411;
(h) Mukherjee, A. J.; Zade, S. S.; Singh, H. B.; Sunoj, R. B. Chem. Rev. 2010, 110,
4357–4416.
2. (a) El-Bayoumy, K. Nutr. Cancer 2001, 40, 45; (b) Ip, C.; Ganther, H. E.
Carcinogenesis 1992, 13, 1167–1170; (c) Ip, C. J. Am. Coll. Toxicol. 1987, 5, 7–20;
(d) Ip, C.; Lisk, D. J.; Ganther, H.; Thompson, H. J. Anticancer Res. 1997, 17, 3195–
3199; (e) Sarma, B. K.; Mugesh, G. Org. Biomol. Chem. 2008, 6, 965–974; (f) Ip, C.
J. Nutr. 1998, 128, 1845–1854.
3. (a) Organic Selenium Compounds: Their Chemistry and Biology; Klayman, D. L.,
Günther, W. H. H., Eds.; Wiley Interscience: New York, 1973; (b)Biochemistry of
Selenium; Shamberger, R. J., Ed.; Plenum Press: New York, 1983; (c)Selenium in
Natural Product Synthesis; Nicolaou, K. C., Petasis, N. A., Eds.; CIS: Philadelphia,
PA, 1984; (d) Mugesh, G.; Du Mont, W.-W.; Sies, H. Chem. Rev. 2001, 101, 2125–
2180; (e) Chasteen, T. G.; Bentley, R. Chem. Rev. 2003, 103, 1–26; (f) Nogueira, C.
W.; Zeni, G.; Rocha, J. B. T. Chem. Rev. 2004, 104, 6255–6286.
4. (a) Bhadra, S.; Saha, A.; Ranu, B. C. J. Org. Chem. 2010, 75, 4864–4867; (b)
Godoi, B.; Speranca, A.; Back, D. F.; Brandao, R.; Nogueira, C. W.; Zeni, G. J. Org.
Chem. 2009, 74, 3469–3477; (c) Tomoda, S.; Takeuchi, Y.; Nomura, Y. Chem.
Lett. 1982, 253–256; (d) Arase, A.; Masuda, Y. Chem. Lett. 1976, 785–788;
(e) Woodgate, P. D.; Lee, H. H.; Rutledge, P. S.; Cambie, R. C. Synthesis 1978,
152–154.
Ph
NH
2) MeI
1
3
Entry
RSeꢀ
ArX
Products yieldb (%)
Convn
ArH
ArSeMe
ArSeAr
1
2c
3
1
3
1
1
3
1
3
1
1
1
3
1-IC10H7
1-IC10H7
PhI
p-MeOC6H4I
p-MeOC6H4I
o-MeC6H4I
o-MeC6H4I
100
100
100
100
97
100
65
100
96
47
7
53
67
—
27
—
—
21
—
10
—
—
—
—
—
—
11
—
—
2
2
—
—
100
99
66
100
55
4
5c
6
7c
8d
9d
10
11c
p-BrC6H4COMe
p-BrC6H4COPh
p-NO2C6H4I
98
93e
20
100
100
p-NO2C6H4I
75
ArX: 0.05 M, selenium-centred nucleophiles (RSeꢀ): 0.25 M in the presence of
0.125 M of tert-BuOK unless otherwise indicated, under N2 atmosphere, irradiation
time: 3 h with high-pressure Hg lamp. The reactions were quenched by the addition
of MeI.
Determined by GC using (PhSe)2 as internal standard, error 5%. The conversion
(convn) was determined by quantification of the recovered substrate.
a
b
c
0.25 M of tert-BuOK.
ArX: 0.1 M, 1: 0.125 M.
Reference 21.
d
e

972
L. M. Bouchet et al. / Tetrahedron Letters 52 (2011) 969–972
5. (a) Miyashita, M.; Hoshino, M.; Yoshikoshi, A. Tetrahedron Lett. 1988, 29, 347–
16. (a) Argüello, J. E.; Schmidt, L. C.; Peñéñory, A. B. Org. Lett. 2003, 5, 4133–4136;
(b) Argüello, J. E.; Schmidt, L. C.; Peñéñory, A. B. Arkivoc 2003, 411–419; (c)
Schmidt, L. C.; Rey, V.; Peñéñory, A. B. Eur. J. Org. Chem. 2006, 2210–2214; (d)
Schmidt, L. C.; Argüello, J. E.; Peñéñory, A. B. J. Org. Chem. 2007, 72, 2936–2944.
17. (a) Geisler, K.; Pfeiffer, W.-D.; Künzler, A.; Below, H.; Bulka, E.; Langer, P. Synlett
2002, 1983–1986; (b) Geisler, K.; Pfeiffer, W.-D.; Künzler, A.; Below, H.; Bulka,
E.; Langer, P. Synthesis 2004, 875–884.
18. For reviews, see: (a) Peñéñory, A. B.; Argüello, J. E. In Handbook of Synthetic
Photochemistry; Albini, A., Fagnoni, M., Eds.; Wiley-VCH: Weinheim, 2010; pp
319–351. Chapter 10; (b) Rossi, R. A.; Pierini, A. B.; Peñéñory, A. B. Chem. Rev.
2003, 103, 71–167; (c) Rossi, R. A.; Peñéñory, A. B. In CRC Handbook of Organic
Photochemistry and Photobiology; Horspool, W. M., Lenci, F., Eds., 2nd ed.; CRC
Press Inc.: Boca Raton, 2003; pp 47-1–47-24. Chapter 47.
19. Representative experimental procedure: The photochemical reaction was carried
out in a three-necked, 10 mL Schlenk tube equipped with a nitrogen gas inlet
and a magnetic stirrer. The flask was dried under vacuum, filled with nitrogen
and then charged with 10 mL of dried DMSO. 3.75 mmol of tert-BuOK for
selenobenzamide (3.25 mmol for anion selenourea and 2.5 mmol for KSeCN)
was added to the degassed DMSO under nitrogen, then 2.5 mmol of the
nucleophile 1–3 and 0.5 mmol of ArX were added to the reaction mixture. After
3 h of irradiation with a high-pressure Hg lamp, the reaction was quenched by
the addition of MeI (6 equiv) in excess and 30 mL of water, and the mixture
was then extracted with dichloromethane (3 ꢁ 20 mL). The organic extract was
washed twice with water, dried and the products were quantified by GC with
diphenyl diselenide as internal standard. The identity of all the products was
confirmed by 1H and 13C NMR and MS spectrometry. All the aryl methyl
selenides are known, otherwise indicated, and their data are in agreement with
those reported.
20. Argüello, J. E.; Peñéñory, A. B.; Rossi, R. A. J. Org. Chem. 2000, 75, 7175–7182.
21. 4-Benzoylphenyl methyl selenide: isolated by radial chromatography technique
with petroleum ether/ethyl ether (95:5) as eluent from the crude product
reaction mixture of selenourea anion and p-bromobenzophenone in the
presence of 0.125 M tert-BuOK. White solid Mp 76–77 °C. 1H NMR
(400.16 MHz, CDCl3): d 2.42 (s, 3H); 7.46 (d, 2H, J = 8.0 Hz); 7.48 (d, 2H,
J = 8.0 Hz); 7.58 (t, 1H, J = 7.2 Hz); 7.70 (d, 2H, J = 8.8 Hz); 7.78 (d, 2H,
J = 6.8 Hz). 13C NMR (100.62 MHz, CDCl3): d 6.5; 128.3; 128.6; 129.9; 130.6;
132.3; 134.8; 137.7; 139.4; 196.0. 77Se NMR (76.32 MHz, CDCl3): 216.41.MS:
(EI, m/z) 278 (15); 276 (M+, 79); 274 (46); 201 (18); 199 (94); 197 (52); 105
(100); 77 (97). HRMS (EI) calcd for C13H9SeO [M]+: 276.0053; found: 276.0049.
350; (b) Miyashita, M.; Suzuki, T.; Hoshino, M.; Yoshikoshi, A. Tetrahedron
1997, 53, 12469–12486.
6. (a) Liotta, D.; Markiewicz, W.; Santiesteban, H. Tetrahedron Lett. 1977, 18,
4365–4367; (b) Krief, A.; Trabelsi, M.; Dumont, W. Synthesis 1992,
933.
7. (a) Hoye, T. R.; Caruso, A. J. Tetrahedron Lett. 1978, 19, 4611–4614; (b) Liotta, D.;
Sunay, U.; Santiesteban, H.; Markiewicz, W. J. Org. Chem. 1981, 46, 2605–2610;
(c) Yoshimatsu, M.; Sato, T.; Shimizu, H.; Hori, M.; Kataoka, T. J. Org. Chem.
1994, 59, 1011–1019; (d) Andreadou, I.; Menge, W. M. P. B.; Commandeur, J. N.
M.; Worthington, E. A.; Vermeulen, N. P. E. J. Med. Chem. 1996, 39, 2040–2046;
(e) Nishino, T.; Okada, M.; Kuroki, T.; Watanabe, T.; Nishiyama, Y.; Sonoda, N. J.
Org. Chem. 2002, 67, 8696–8698; (f) Ranu, B. C.; Mandal, T.; Samanta, S. Org.
Lett. 2003, 5, 1439–1441; (g) Ranu, B. C.; Mandal, T. J. Org. Chem. 2004, 69,
5793–5795; (h) Ouchi, A.; Liu, S.; Li, Z.; Kumar, S. A.; Suzuki, T.; Hyugano, T.;
Kitahara, H. J. Org. Chem. 2007, 72, 8700–8706.
8. (a) Dowsland, J.; McKerlie, F.; Procter, D. J. Tetrahedron Lett. 2000, 41, 4923–
4927; (b) Su, W.; Gao, N.; Zhang, Y. J. Chem. Res. Synop. 2002, 4, 168–169; (c)
Taniguchi, N.; Onami, T. J. Org. Chem. 2004, 69, 915–920; (d) Ajiki, K.; Hirano,
M.; Tanaka, K. Org. Lett. 2005, 7, 4193–4195; (e) Movassagh, B.; Shamsipoor, M.
Synlett 2005, 121–122; (f) Movassagh, B.; Shamsipoor, M. Synlett 2005, 1316–
1318; (g) Krief, A.; Derock, M.; Lacroix, D. Synlett 2005, 2832–2834; (h)
Movassagh, B.; Tatar, A. Synlett 2007, 1954–1956; (i) Santi, C.; Santoro, S.;
Battistelli, B.; Testaferri, L.; Tiecco, M. Eur. J. Org. Chem. 2008, 5387–5390; (j)
Narayanaperumal, S.; Alberto, E. E.; Gul, K.; Rodrigues, O. E. D.; Braga, A. L. J.
Org. Chem. 2010, 75, 3886–3889.
9. Cohen, R. J.; Fox, D. L.; Salvatore, R. N. J. Org. Chem. 2004, 69, 4265–4268.
10. (a) Gould, E. S.; McCullough, J. D. J. Am. Chem. Soc. 1951, 73, 1109; (b) Reich, H.
J.; Renga, J. M.; Reich, I. L. J. Am. Chem. Soc. 1975, 97, 5434.
11. Comasseto, J. V.; Omori, A. T.; Porto, A. L. M.; Andrade, L. H. Tetrahedron Lett.
2004, 45, 473–476.
12. (a) Schmid, G. H.; Garratt, D. G. J. Org. Chem. 1983, 48, 4169–4172; (b) Yavuz, S.;
Dioli, A.; Yildirir, Y.; Türker, L. Molecules 2005, 10, 1000–1004.
13. Ashaks, J.; Bankovsky, Y.; Zaruma, D.; Shestakova, I.; Domracheva, I.;
Nesterova, A.; Lukevics, E. Chem. Heterocycl. Compd. 2004, 40, 776–780.
14. (a) Agenäs, L.-B. Acta Chem. Scand. 1963, 17, 268–270; (b) Nair, V.; Augustine,
A.; Geroge, T. G. Eur. J. Org. Chem. 2002, 2363–2366.
15. (a) Rossi, R. A.; Peñéñory, A. B. J. Org. Chem. 1981, 46, 4580–4582; (b) Bhasin, K.
K.; Singh, J. J. Organomet. Chem. 2002, 658, 71–76.