Chalcogenoalkynes: Precursors for the regioselective preparation of 2-chalcogeno-1-halonaphthalenes through [4+2] cycloaddition

Article abstract of DOI:10.1002/ejoc.201200482

Chalcogenoalkynes and o-alkynylbenzaldehydes reacted in the presence of copper(II) salt to give the [4+2] cycloadducts 2-chalcogeno-1-halonaphthalenes in good yields (46-89 %) and high regioselectivities. The methodology was carried out by using CuCl₂ or CuCl₂/LiBr in 1,2-dichloroethane (DCE) at 80 °C. The potential and generality of this system was evaluated by using a variety of chalcogenoalkynes including aromatic, substituted aromatic, and aliphatic substrates having both sulfur and selenium atoms. In this sequence, due to the ability of the chalcogen atoms to stabilize charges, these substituents exert regiocontrol that guides the selectivity. Chalcogeoalkynes and o-alkynylbenzaldehydes reacted in the presence of CuCl ₂ to furnish the [4+2] cycloadducts 2-chalcogeno-1-halonaphthalenes in good yields (46-89 %) and high regioselectivities. The methodology was carried out by using CuCl₂ or CuCl₂/LiBr in dichloroethane (DCE) at 80 °C. Copyright

Full text of DOI:10.1002/ejoc.201200482

Job/Unit: O20482
/KAP1
Date: 10-07-12 16:42:05
Pages: 7
FULL PAPER
DOI: 10.1002/ejoc.201200482
Chalcogenoalkynes: Precursors for the Regioselective Preparation of
2-Chalcogeno-1-halonaphthalenes through [4+2] Cycloaddition
Anderson C. Mantovani,[a] Davi F. Back,[b] and Gilson Zeni*[a]
Keywords: Alkynes / Selenium / Sulfur / Regioselectivity / Cycloaddition
Chalcogenoalkynes and o-alkynylbenzaldehydes reacted in
the presence of copper(II) salt to give the [4+2] cycloadducts
2-chalcogeno-1-halonaphthalenes in good yields (46–89%)
and high regioselectivities. The methodology was carried out
by using CuCl2 or CuCl2/LiBr in 1,2-dichloroethane (DCE) at
80 °C. The potential and generality of this system was evalu-
ated by using a variety of chalcogenoalkynes including aro-
matic, substituted aromatic, and aliphatic substrates having
both sulfur and selenium atoms. In this sequence, due to the
ability of the chalcogen atoms to stabilize charges, these sub-
stituents exert regiocontrol that guides the selectivity.
that can be used to access halogenated naphthalenes are
rare. The transition-metal-catalyzed annulation strategy has
Introduction
Polycyclic aromatic compounds with fused benzene rings been shown to be a versatile approach to the regioselective
have received much attention because of their interesting construction of such compounds.[5] However, the prepara-
physical and chemical properties.[1] In particular, polycyclic tion of naphthalene derivatives in which C-1 and C-2 con-
π-conjugated structures have recently become increasingly tain a halogen and chalcogen atom, respectively, has, to the
important in the area of organic electronics.[2] The con- best of our knowledge, not been reported in the literature.
struction of a fused benzene ring can be achieved by In addition, the introduction of chalcogen groups into or-
derivatization of naphthalenes through electrophilic or nu- ganic molecules has found wide utility because of their ef-
cleophilic substitution or by functional-group transforma- fects on an extraordinary number of very different reac-
tion and annulation methods from open-chain precursors. tions.[6] There are several reasons for this: (i) they have a
The annulation approach has significant advantages over widely varied synthetic organochemical potential, (ii) the
conventional linear substitution reactions, in particular for chalcogen atom exercises a stabilizing effect on neighboring
the preparation of highly substituted naphthalenes.[3] One positive as well as negative charges, (iii) the latter effect
advantage is that annulation reactions generally avoid the makes the carbon atom directly bonded to the chalcogen
regioselectivity problems, the restricted scope, and the low atom responsive towards both nucleophilic and electrophilic
yields associated with aromatic substitution reactions.[4] attack, which can allow control of regioselectivity. Con-
Likewise, in contrast to naphthalenes, preparative methods sidering that the chemical behavior of the halogen atom is
Scheme 1. Copper(II)-mediated cyclization of o-alkynylbenzaldehydes 1 and chalcogenoalkynes 2.
distinctly different to that of a chalcogen atom, this class of
compounds has become valuable in synthesis, particularly
when one considers that there are many ways to transform
the resulting halogen and chalcogen functionalities into
other substituents. Keeping in mind the capacity of chal-
cogen atoms to stabilize positive as well as negative charges,
we decided to study the influence of such atoms in the re-
[a] Laboratório de Síntese, Reatividade, Avaliação Farmacológica
e Toxicológica de Organochalcogênios, CCNE, UFSM,
Santa Maria, Rio Grande do Sul, CEP 97105-900, Brazil
E-mail: gzeni@pq.cnpq.br
[b] Laboratório de Materiais Inorgânicos, CCNE, UFSM, Santa
Maria,
Rio Grande do Sul, 97105-900, Brazil
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201200482.
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1

Job/Unit: O20482
/KAP1
Date: 10-07-12 16:42:05
Pages: 7
A. C. Mantovani, D. F. Back, G. Zeni
FULL PAPER
gioselectivity of the cycloaddition reactions of chalcog-
enoalkynes towards o-alkynylbenzaldehydes in the prepara-
tion of 2-chalcogeno-1-halonaphthalenes (Scheme 1).
Scheme 2. Retrosynthetic analysis.
Results and Discussion
Table 1. Optimization of cyclization conditions.[a]
The retrosynthetic analysis of this cyclization suggested
the use of 2-bromobenzaldehyde, terminal alkynes, and
chalcogenoalkynes as the starting materials and copper
salts as cyclizing agents (Scheme 2). The required precur-
sors o-alkynylbenzaldehydes 1a–c were synthesized in good
yields by the reaction of appropriate 2-bromobenzaldehydes
with terminal alkynes under Sonogashira conditions.[7] For
the preparation of chalcogenoalkynes, we first generated the
lithium acetylide intermediate by reaction of terminal al-
kynes with 1 equiv. of nBuLi, in tetrahydrofuran (THF) at
–78 °C for 1 h, then treated the lithiated intermediate with
an electrophilic chalcogen species.[8] Based on our recent
report on the cyclization of (Z)-chalcogenoenynes to afford
3-halochalcogenophenes mediated by copper(II) salts,[9] the
cyclization reaction was initially investigated by treating o-
alkynylbenzaldehyde 1a (1 equiv.), chalcogenoalkyne 2a
(1 equiv.), and CuCl2 (2 equiv.) in 1,2-dichloroethane
(DCE) (3 mL) under argon at room temperature for 12 h.
The use of these reaction conditions, however, did not gen-
erate the desired product 3a in an acceptable yield (Table 1,
Entry 1). In view of this disappointing result, we further
investigated the reaction with different solvents, tempera-
tures and amounts of copper salt, aiming to improve the
protocol. The outcome of these studies and an investigation
Entry
Solvent
Temperature
[°C]
CuCl2
[equiv.]
Yield
[%][b]
1
2
3
4
5
6
7
8
9
10
11
12
13[c]
14[d]
DCE
DCE
DCE
DCE
DCE
DCE
DCE
dioxane
MeCN
MeNO2
CH2Cl2
THF
25
50
reflux
80
80
80
80
80
80
80
2
2
2
2
1
1.5
2.5
2
2
2
2
2
2
2
30
76
63
82
49
55
60
31
33
44
69
24
68
54
reflux
reflux
80
DCE
DCE
80
[a] Reaction conditions: 1a (0.25 mmol), 2a (0.25 mmol), solvent
(3 mL). [b] GC yield. [c] Reaction performed by using 0.3 mmol of
2a. [d] Reaction performed by using 0.2 mmol of 2a.
of other reaction parameters is summarized in Table 1. As The results indicated that the reaction seems to be sensitive
listed in Table 1, by increasing the temperature to either to electronic effects of the substituents in the aromatic ring
50 °C or to reflux temperature, we observed a significant directly bonded to the alkyne. For example, chalcogeno-
improvement in the reaction, and the product was formed alkynes with –F and –Cl groups gave lower yields than
in good yields (Table 1, Entries 2 and 3). However, the best those with a methyl group (Table 2, Entries 2–4). The re-
result was obtained at 80 °C, which gave the desired product sults demonstrated that the cyclization efficiency was also
3a in 82% yield (Table 1, Entry 4). Next, the amount of significantly influenced by the steric effects of the alkyl
CuCl2 was investigated (from 1.0 to 2.5 equiv.); however, no group bonded to the selenium atom in the chalcogeno-
improvement in the yield was observed (Table 1, Entries 5– alkynes, because the cyclization reaction gave lower yields
7). We assume that the use of 2.0 equiv. CuCl2 is necessary with a butyl group than with a methyl or ethyl group
in this reaction, because CuCl2 acts not only as a triple- (Table 2, Entries 5–8). Cyclization with chalcogenoalkynes
bond activator but also as a chlorine source and as a Cu0 containing a substituted aromatic ring directly bonded to
oxidizing reagent (see Scheme 4). Regarding the influence the selenium atom smoothly gave the expected cyclized
of the solvent, the best results were achieved by using DCE products in good yields (Table 2, Entries 9 and 10). Com-
as solvent. We observed that dioxane, MeCN, MeNO2, pared with the selenium derivatives, the reaction employing
CH2Cl2 and THF were less effective, because the product sulfur was similar, giving the cyclized products equally in
3a was obtained in poor yields with these solvents (Table 1, good yields (Table 2, Entries 12–16). It should be noted that
Entries 8–12). Poor yields of 3a were found when the reac- the yield for substituted o-alkynylbenzaldehydes 1b and 1c
tion was performed in DCE at 80 °C by using either larger (Table 2, Entries 17–19) was lower than for unsubstituted o-
amounts of o-alkynylbenzaldehyde (3.0 mmol) or lower alkynylbenzaldehyde 1a. This is probably due to the slower
amounts (0.2 mmol) of chalcogenoalkyne (Table 1, En- copper triple-bond activation step (Scheme 4, Step 1) in the
tries 13 and 14).
reaction course, resulting in a decrease in the alkyne electro-
To examine the effect on the yield of the substituents on philicity. Meanwhile, to evaluate the possibility of introduc-
the chalcogen alkynes, we next tested the optimized reac- ing further functionality at C-1 of the naphthalene ring, we
tion conditions summarized in Table 1, Entry 4 [Method: 1 tested the behavior of this cyclization reaction using CuBr2
(0.25 mmol),
2 (0.25 mmol), CuCl2 (0.5 mmol), DCE as a bromine source. Unfortunately, all conditions tested
(3 mL), 80 °C] with other o-alkynylbenzaldehydes (Table 2). were found to be ineffective, and CuBr2 did not produce
2
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O20482
/KAP1
Date: 10-07-12 16:42:05
Pages: 7
2-Chalcogeno-1-halonaphthalenes
the desired cyclized product. Rudrawar reported that a mix- reaction conditions described in Table 1 (Entry 4) gave 1-
ture of copper(II) bromide and LiBr provides quantitative bromo-2-chalcogenonaphthalenes 4a and 4b in 44 and 40%
access to nucleophilic bromine species.[10] Gratifyingly, we yield, respectively (Scheme 3).
found that the addition of LiBr (1 equiv.) to the optimized
The [4+2] benzannulation of o-alkynylbenzaldehydes and
unsymmetrical alkynes promoted by Lewis acids could gave
a mixture of regioisomers.[11] The results have shown that
the regiochemical outcome of the reaction is strongly de-
pendent on the electronic (relative nucleophilicity of the
functional groups, polarization of the carbon–carbon triple
bond, and cationic nature of the intermediate) and steric
effects (hindrance and geometrical alignment of the func-
tional groups), as well as on the nature of the transition-
metal source. In this context, our cyclization methodology
showed high regioselectivity, providing the desired 2-chalco-
geno-1-halonaphthalenes 3 as unique regioisomers; this re-
sult was confirmed by X-ray diffraction analysis (Figure 1).
This high selectivity is probably due to the presence of the
chalcogen atom directly bonded to the carbon atom of the
triple bond. The selenium atom exerts a significant stabili-
zation of the positive charge at C-1 of the selenonium inter-
mediate d (Scheme 2), forcing subsequent attack at this car-
bon atom. Considering that the chalcogenoalkynes used are
unsymmetrical alkynes, which could give a mixture of re-
gioisomers, and based on an understanding that the chal-
cogen atom exerts a high stabilization of the positive charge
at the α-position, we propose a plausible mechanism to sup-
port the current CuII cyclization, as illustrated in Scheme 4.
Thus, (i) coordination of the carbon–carbon triple bond to
the CuII species generates intermediate a; (ii) anti attack of
the carbonyl group on the activated triple bond of interme-
diate a produces salt b, and (iii) copper reductive elimi-
nation provides heterodiene c and Cu0. The formed Cu0 can
be oxidized by CuCl2 to produce CuCl, which makes sense
given the need for 2 equiv. of CuCl2 for this reaction;[12] (iv)
the [4+2] cycloaddition between c and the chalcogenoal-
kyne results in the creation of cycloadduct e, via intermedi-
ates d. There is a stabilization of a positive charge on C-1
of the intermediary d, which is attacked by π-electrons from
the double bond to give e, and (iv) chlorine attack on the
carbonyl group followed by a retro-Diels–Alder reasction
Table 2. CuCl2-promoted cycloaddition of 2-alkynylbenzaldehydes
and chalcogenoalkynes.[a]
Entry Aldehyde
R3
R4
Y
Product Yield
[%][b]
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1c
1a
1b
1b
1c
Ph
p-MeC6H4
p-FC6H4
p-ClC6H4
Ph
nBu
nBu
nBu
nBu
Ph
p-ClC6H4
Ph
p-FC6H4
Ph
nBu
nBu
nBu
nBu
Me
Se
Se
Se
Se
Se
Se
Se
Se
Se
Se
Se
S
S
S
S
S
Se
S
Se
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
3q
3r
3s
75
89
66
78
76
82
60
56
62
72
78
74
66
84
63
63
68
46
56
Me
Et
nBu
Ph
p-MeC6H4
Et
Me
nBu
Ph
nBu
nBu
Et
nBu
Et
Ph
nBu
nBu
Ph
nBu
[a] Reaction conditions: 1 (0.25 mmol), 2 (0.25 mmol), CuCl2
(0.5 mmol), DCE (3 mL), 80 °C. [b] Isolated yield.
Scheme 3. Preparation of 1-bromo-2-chalcogenonaphthalenes 4.
Scheme 4. Proposed mechanism for the copper(II)-mediated cyclization of o-alkynylbenzaldehydes 1 and chalcogenoalkynes 2.
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3

Job/Unit: O20482
/KAP1
Date: 10-07-12 16:42:05
Pages: 7
A. C. Mantovani, D. F. Back, G. Zeni
FULL PAPER
corded with a Shimadzu GC–MS-2010P. Elemental analyses were
performed with a Vario EL III elemental analysis instrument. HR
mass spectra were recorded with a Shimadzu LC-MS-IT-TOF spec-
trometer.
produces the desired naphthalenes as product and benzoyl
chloride as side-product.
General Procedure for the CuCl2-Mediated Cycloaddition: Into a
two-necked round-bottomed flask equipped with a reflux con-
denser, under argon, containing a solution of CuCl2 (0.067 g,
0.5 mmol) in 1,2-dichloroethane (3 mL), was added 2-(phenylethy-
nyl)benzaldehyde (0.051 g, 0.25 mmol) and the alkynyl chalcogen-
ide (0.25 mmol). The reaction mixture was stirred at 80 °C for 12 h,
then the mixture was diluted with dichloromethane (20 mL) and
washed with saturated NH4Cl (20 mL). The organic phase was sep-
arated, dried with MgSO4, and concentrated under vacuum. The
residue was purified by flash chromatography and eluted with hex-
ane.
2-(Butylseleno)-1-chloro-3-phenylnaphthalene (3a): 1H NMR
(CDCl3, 200 MHz): δ = 8.37–8.32 (m, 1 H, ArH), 7.83–7.78 (m, 1
H, ArH), 7.68 (s, 1 H, ArH), 7.64–7.49 (m, 2 H, ArH), 7.46–7.48
(m, 5 H, ArH), 2.58 (t, J = 7.4 Hz, 2 H, CH2CH2), 1.44–1.09 [m,
4 H, 2ϫ (CH2CH2CH3)], 0.74 (t, J = 7.3 Hz, 3 H, CH3) ppm. 13C
NMR (CDCl3, 100 MHz): δ = 144.4, 142.8, 137.8, 133.4, 130.4,
130.5, 129.5, 128.4, 128.0, 127.6, 127.6, 127.4, 127.3, 127.1, 125.3,
32.0, 29.1, 22.6, 13.3 ppm. MS (EI, 70 eV): m/z (%) = 374 (76), 318
(62), 282 (69), 238 (100), 202 (63), 57 (7). C20H19ClSe (373.78):
calcd. C 64.27, H 5.12; found C 64.40, H 5.19.
Figure 1. ORTEP representation of the molecular structure of 3e.
Conclusions
The presented work allowed us to study the reactivity of
readily available chalcogenoalkynes and o-alkynylbenzalde-
hydes toward 2-chalcogeno-1-halonaphthalenes. As a result,
we have found that the [4+2] cycloaddition reactions of
chalcogenoalkynes and o-alkynylbenzaldehydes promoted
by CuCl2 led to the exclusive formation of 2-chalcogeno-1-
halonaphthalenes in good yields. It has been shown that the
protocol is not only a facile method but is also applicable
to a large substrate range; both electron-rich and electron-
poor chalcogenoalkynes, having a sulfur or selenium atom,
cyclized with o-alkynylbenzaldehydes in the presence of
CuCl2. Another feature of this protocol is that the organo-
chalcogen used as substrate serves as a regiocontrolling
agent that guides the selectivity. Our process could, there-
fore, provide an efficient protocol for the preparation of
molecules that have two independent reactive centers. It
should prove quite useful in synthesis, particularly when
one considers that there are many ways to transform the
resulting halogen and chalcogen functionalities into other
substituents. It is also important to point out that both
chalcogenoalkynes and 2-chalcogenonaphthalenes are
either solids or oils, they are completely odorless, very
stable, and can be purified and stored in the laboratory in
a simple flask for more than 1 month.
2-(Butylseleno)-1-chloro-3-(p-tolyl)naphthalene (3b): 1H NMR
(CDCl3, 400 MHz): δ = 8.33 (d, J = 8.6 Hz, 1 H, ArH), 7.78 (d, J
= 7.3 Hz, 1 H, ArH), 7.66 (s, 1 H, ArH), 6.61 (quint, J = 7.6 Hz,
2 H, ArH), 7.33 (d, J = 8.0 Hz, 2 H, ArH), 7.23 (d, J = 7.9 Hz, 2
H, ArH), 2.61 (t, J = 7.4 Hz, 2 H, CH2CH2), 2.43 (s, 3 H, CH3),
1.44–1.10 [m, 4 H, 2ϫ (CH2CH2CH3)], 0.74 (t, J = 7.2 Hz, 3
H,CH2CH3) ppm. 13C NMR (CDCl3, 100 MHz): δ = 144.7, 140.0,
137.7, 137.0, 133.4, 130.4, 129.4, 128.4, 127.9, 127.6, 127.2, 127.0,
125.3, 32.0, 29.2, 22.7, 21.2, 13.3 ppm. MS (EI, 70 eV): m/z (%) =
332 (67), 296 (78), 252 (100), 215 (70), 189 (11), 73 (11). HRMS:
calcd. for C21H21ClSe 388.0497; found: 388.0518.
2-(Butylseleno)-1-chloro-3-(4-fluorophenyl)naphthalene (3c): 1H
NMR (CDCl3, 400 MHz): δ = 8.33 (d, J = 8.3 Hz, 1 H, ArH), 7.79
(d, J = 8.3 Hz, 1 H, ArH), 7.65 (s, 1 H, ArH), 7.64–7.50 (m, 2 H,
ArH), 7.46–7.36 (m, 2 H, ArH), 7.10 (t, J = 8.8 Hz, 2 H, ArH),
2.60 (t, J = 7.0 Hz, 2 H, CH2CH2), 1.45–1.11 [m, 4 H, 2ϫ
(CH2CH2CH3)], 0.75 (t, J = 7.2 Hz, 3 H, CH3) ppm. 13C NMR
(CDCl3, 100 MHz): δ = 162.2 (d, J = 246 Hz), 143.6, 138.8, 137.6
(d, J = 3.6 Hz), 133.4, 131.6, 131.4 (d, J = 8.0 Hz), 130.6, 128.0,
127.7, 127.5, 127.2, 125.4, 114.6 (d, J = 22 Hz), 32.0, 29.2, 22.6,
13.3 ppm. MS (EI, 70 eV): m/z (%) = 392 (53), 336 (49), 300 (43),
256 (100), 220 (47), 207 (19), 57 (10). HRMS: calcd. for
C20H18ClFSe 392.0246; found 392.0253.
2-(Butylseleno)-1-chloro-3-(4-chlorophenyl)naphthalene (3d): 1H
NMR (CDCl3, 400 MHz): δ = 8.32 (d, J = 8.3 Hz, 1 H, ArH), 7.77
(d, J = 8.3 Hz, 1 H, ArH), 7.63 (s, 1 H, ArH), 7.59–7.47 (m, 2 H,
ArH), 7.37 (s, 4 H, ArH), 2.61 (t, J = 7.3 Hz, 2 H, CH2CH2), 1.39
(quint, J = 7.2 Hz, 2 H, CH2CH2CH2), 1.20 (sext, J = 7.0 Hz, 2
H, CH2CH2CH3), 0.75 (t, J = 7.0 Hz, 3 H, CH3) ppm. 13C NMR
(CDCl3, 100 MHz): δ = 143.6, 141.3, 138.3, 133.5, 131.0, 130.8,
128.3, 128.0, 127.9, 127.6, 127.2, 125.5, 32.0, 29.4, 22.6, 13.3 ppm.
MS (EI, 70 eV): m/z (%) = 408 (80), 352 (77), 316 (72), 272 (100),
200 (44), 73 (18), 57 (22). HRMS: calcd. for C20H18Cl2Se 407.9951;
found 407.9946.
Experimental Section
General Remarks: 1H NMR spectra were obtained at 200 MHz
with a DPX-200 NMR spectrometer or at 400 MHz with a DPX-
400 NMR spectrometer; spectra were recorded in CDCl3 solutions.
13C NMR spectra were obtained either at 50 MHz with a DPX-
200 NMR spectrometer or at 100 MHz with a DPX-400 NMR
spectrometer; spectra were recorded in CDCl3 solutions. Column
chromatography was performed by using Merck silica gel (230–
400 mesh). Thin layer chromatography (TLC) was performed by
using Merck silica gel GF254 (0.25 mm thickness); for visualiza-
tion, TLC plates were either placed under UV light, or stained with
iodine vapor, or acidic vanillin. Most reactions were monitored by
TLC for disappearance of starting material. Mass spectra were re-
1-Chloro-3-phenyl-2-(methylseleno)naphthalene (3e): 1H NMR
(CDCl3, 200 MHz): δ = 8.33 (d, J = 8.2 Hz, 1 H, ArH), 7.80 (d, J
4
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O20482
/KAP1
Date: 10-07-12 16:42:05
Pages: 7
2-Chalcogeno-1-halonaphthalenes
= 7.3 Hz, 1 H, ArH), 7.68 (s, 1 H, ArH), 7.63–7.24 (m, 7 H, ArH), J = 7.4 Hz, 2 H, CH2CH3), 1.14 (t, J = 7.4 Hz, 3 H, CH2CH3)
2.04 (s, 3 H, CH3) ppm. 13C NMR (CDCl3, 100 MHz): δ = 144.1, ppm. 13C NMR (CDCl3, 100 MHz): δ = 143.6, 141.3, 138.3, 133.5,
142.6, 137.1, 133.3, 130.5, 129.4, 128.0, 127.8, 127.7, 127.4, 127.4,
133.4, 130.9, 130.7, 128.0, 127.9, 127.7, 127.6, 127.6, 127.3, 125.4,
127.1, 125.1, 10.0 ppm. MS (EI, 70 eV): m/z (%) = 331(0.15), 283 23.1, 15.2 ppm. MS (EI, 70 eV): m/z (%) = 380 (57), 341 (31), 316
(83), 233 (100), 189 (16), 94 (8). C17H13ClSe (331.70): calcd. C (93), 281 (51), 207 (100), 73 (73). HRMS: calcd. for C18H14Cl2NaSe
61.56, H 3.95; found C 61.68, H 4.01.
402.9535; found 402.9581.
3-Butyl-1-chloro-2-(methylseleno)naphthalene (3f): 1H NMR 1-Chloro-2-(methylthio)-3-phenylnaphthalene (3l): 1H NMR
(CDCl3, 200 MHz): δ = 8.30–8.25 (m, 1 H, ArH), 7.77–7.72 (m, 1 (CDCl3, 200 MHz): δ = 8.33 (d, J = 8.4 Hz, 1 H, ArH), 7.78 (d, J
H, ArH), 7.60 (s, 1 H, ArH), 7.55–7.45 (m, 2 H, ArH), 3.07 (t, J = 7.7 Hz, 1 H, ArH), 7.68 (s, 1 H, ArH), 7.60–7.37 (m, 7 H, ArH),
= 7.3 Hz, 2 H, CH2CH2), 2.35 (s, 3 H, CH3), 1.71–1.60 (m, 2 H, 2.15 (s, 3 H, CH3) ppm. 13C NMR (CDCl3, 100 MHz): δ = 143.7,
CH2CH2CH2), 1.43 (sext, J = 7.44 Hz, 2 H, CH2CH2CH3), 0.97 (t,
J = 7.2 Hz, 3 H, CH2CH3) ppm. 13C NMR (CDCl3, 50 MHz): δ =
144.4, 134.0, 129.9, 127.4, 127.0, 126.5, 126.0, 125.3, 38.3, 34.1,
22.5, 14.0, 9.7 ppm. MS (EI, 70 eV): m/z (%) = 311 (51), 309 (25),
270 (23), 175 (100), 152 (23), 139 (24). HRMS: calcd. for
C15H17ClSe 312.0184; found 312.0194.
141.5, 137.5, 133.3, 132.7, 130.7, 129.4, 128.2, 127.9, 127.8, 127.4,
127.3, 127.2, 125.1, 18.9 ppm. MS (EI, 70 eV): m/z (%) = 284 (93),
234 (100), 202 (15), 189 (16), 117 (35), 104 (4), 94 (8). C17H13ClSe
(331.70): calcd. C 61.56, H 3.95; found C 61.68, H 4.01.
2-(Butylthio)-1-chloro-3-(4-fluorophenyl)naphthalene
(3m):
1H
NMR (CDCl3, 200 MHz): δ = 8.33 (d, J = 8.3 Hz, 1 H, ArH), 7.79
3-Butyl-1-chloro-2-(ethylseleno)naphthalene (3g): 1H NMR (CDCl3, (d, J = 8.3 Hz, 1 H, ArH), 7.66 (s, 1 H, ArH), 7.64–7.50 (m, 2 H,
200 MHz): δ = 8.31–8.26 (m, 1 H, ArH), 7.77–7.72 (m, 1 H, ArH),
7.61 (s, 1 H, ArH), 7.55–4.45 (m, 2 H, ArH), 3.11–2.94 [m, 4 H,
ArH), 7.48–7.38 (m, 2 H, ArH), 7.11 (t, J = 8.6 Hz, 2 H, ArH),
2.35 (t, J = 7.0 Hz, 2 H, CH2CH2), 1.36–1.08 [m, 4 H, 2ϫ
2ϫ (CH2CH2)], 1.71–1.59 (m, 2 H, CH2CH2CH2), 1.52–1.41 (m, 2 (CH2CH2CH3)], 0.73 (t, J = 7.2 Hz, 3 H, CH3) ppm. 13C NMR
H, CH2CH2CH3), 1.33 (t, J = 7.4 Hz, 3 H, CH2CH3), 0.96 (t, J = (CDCl3, 100 MHz): δ = 162.3 (d, J = 246 Hz), 143.3, 138.2, 137.6
7.2 Hz, 3 H, CH2CH3) ppm. 13C NMR (CDCl3, 50 MHz): δ = (d, J = 3.6 Hz), 133.4, 131.6, 131.4 (d, J = 8.0 Hz), 130.9, 128.1,
144.9, 138.7, 129.0, 129.9, 129.4, 127.4, 126.9, 126.5, 125.9, 125.4,
38.3, 33.9, 23.0, 22.5, 15.4, 14.0 ppm. MS (EI, 70 eV): m/z (%) =
326 (76), 220 (29), 201 (11), 175 (100), 165 (36), 139 (39), 55 (4).
C16H19ClSe (325.74): calcd. C 59.00, H 5.88; found C 59.21, H
5.91.
128.0, 127.4, 127.3, 125.4, 114.6 (d, J = 22 Hz), 35.4, 31.4, 21.6,
13.3 ppm. MS (EI, 70 eV): m/z (%) = 344 (72), 288 (100), 252 (91),
233 (20), 220 (20), 207 (36), 73 (13). C20H18ClFS (344.87): calcd.
C 69.65, H 5.26; found C 69.77, H 5.31.
1-Chloro-3-phenyl-2-(phenylthio)naphthalene (3n): 1H NMR
3-Butyl-2-(butylseleno)-1-chloronaphthalene (3h): 1H NMR (CDCl3, (CDCl3, 200 MHz): δ = 8.36 (d, J = 8.5 Hz, 1 H, ArH), 7.84 (m, 1
200 MHz): δ = 8.30–8.25 (m, 1 H, ArH), 7.76–7.71 (m, 1 H, ArH),
7.60 (s, 1 H, ArH), 7.54–7.44 (m, 2 H, ArH), 3.07 (t, J = 7.4 Hz,
2 H, CH2CH2), 2.97 (t, J = 7.2 Hz, 2 H, CH2CH2), 1.71–1.25 [m,
8 H, 4ϫ (CH2CH2CH3)], 0.96 (t, J = 7.2 Hz, 3 H, CH3), 0.86 (t, J
H, ArH), 7.76 (s, 1 H, ArH), 7.61 (m, 2 H, ArH), 7.28 (s, 5 H,
ArH), 7.13–7.02 (m, 3 H, ArH), 6.90–6.85 (m, 2 H, ArH) ppm. 13
C
NMR (CDCl3, 100 MHz): δ = 144.4, 141.1, 138.9, 137.2, 133.9,
130.8, 129.5, 129.3, 128.6, 128.1, 127.8, 127.5, 127.2, 125.6,
= 7.2 Hz, 3 H, CH3) ppm. 13C NMR (CDCl3, 100 MHz): δ = 144.8, 125.3 ppm. MS (EI, 70 eV): m/z (%) = 346 (73), 311 (100), 234 (30),
138.6, 164.0, 129.9, 127.4, 126.9, 126.4, 125.9, 125.3, 38.3, 34.0,
32.3, 29.4, 22.9, 22.5, 14.0, 13.5 ppm. MS (EI, 70 eV): m/z (%) =
354 (100), 300 (30), 218 (49), 177 (41), 175 (98), 139 (22), 57 (17).
C18H23ClSe (353.79): calcd. C 6.11, H 6.55; found C 61.27, H 6.59.
207 (23), 190 (10), 73 (15). C22H15ClS (346.87): calcd. C 76.18, H
4.36; found C 76.37, H 4.41.
6-(Butylthio)-5-chloro-7-phenylnaphtho[2,3-d][1,3]dioxole (3o): 1H
NMR (CDCl3, 200 MHz): δ = 7.92 (d, J = 9.0 Hz, 1 H, ArH), 7.66
(s, 1 H, ArH), 7.50–7.37 (m, 5 H, ArH), 7.27–7.23 (m, 1 H, ArH),
3-Butyl-1-chloro-2-(phenylseleno)naphthalene (3i): 1H NMR
(CDCl3, 200 MHz): δ = 8.32–8.26 (m, 1 H, ArH), 7.84–7.79 (m, 1 6.16 (s, 2 H, ArH), 2.50 (t, J = 7.0 Hz, 2 H, CH2CH2), 1.34–1.07
H, ArH), 7.69 (s, 1 H, ArH), 7.63–7.52 (m, 2 H, ArH), 7.16 (s, 5 [m, 4 H, 2ϫ (CH2CH2CH2)], 0.72 (t, J = 7.2 Hz, 3 H, CH2CH3)
H, ArH), 3.01 (t, J = 7.4 Hz, 2 H, CH2CH2), 1.68–1.53 (m, 2 H,
CH2CH2CH2), 1.46–1.21 (m, 2 H, CH2CH2CH3), 0.90 (t, J =
7.3 Hz, 3 H, CH3) ppm. 13C NMR (CDCl3, 100 MHz): δ = 144.8,
139.5, 134.6, 133.0, 131.5, 130.1, 129.2, 129.1, 127.7, 127.5, 127.4,
126.7, 126.6, 126.0, 125.9, 38.0, 33.7, 22.5, 13.9 ppm. MS (EI,
ppm. 13C NMR (CDCl3, 100 MHz): δ = 144.7, 144.4, 141.6, 141.5,
138.7, 129.6, 129.3, 127.6, 127.3, 127.0, 119.8, 119.7, 119.6, 111.3,
102.2, 35.3, 31.3, 21.6, 13.4 ppm. MS (EI, 70 eV): m/z (%) = 370
(60), 314 (47), 281 (46), 253 (31), 207 (100), 147 (21), 73 (67).
C21H19ClO2S (370.89): calcd. C 68.00, H 5.16; found C 68.20, H
70 eV): m/z (%) = 374 (100), 283 (35), 215 (93), 177 (32), 139 (32), 5.19.
91 (71). C22H15ClSe (393.77): calcd. C 67.10, H 3.84; found C
67.33, H 3.90.
3-Butyl-2-(butylthio)-1-chloronaphthalene (3p): 1H NMR (CDCl3,
200 MHz): δ = 8.30–8.25 (m, 1 H, ArH), 7.75–7.71 (m, 1 H, ArH),
1-Chloro-3-phenyl-2-(p-tolylseleno)naphthalene (3j): 1H NMR 7.59 (s, 1 H, ArH), 7.54–7.44 (m, 2 H, ArH), 3.06 (t, J = 7.4 Hz,
(CDCl3, 200 MHz): δ = 8.34 (d, J = 8.3 Hz, 1 H, ArH), 7.87–7.82 2 H, CH2CH2), 2.91 (t, J = 7.3 Hz, 2 H, CH2CH2), 1.74–1.32 [m,
(m, 1 H, ArH), 8.74 (s, 1 H, ArH), 7.64–7.44 (m, 2 H, ArH), 7.31– 8 H, 4ϫ (CH2CH2CH3)], 0.97 (t, J = 7.2 Hz, 3 H, CH3), 0.88 (t, J
7.20 (m, 5 H, ArH), 7.94–7.83 (m, 4 H, ArH), 2.23 (s, 3 H, CH3) = 7.2 Hz, 3 H, CH3) ppm. 13C NMR (CDCl3, 100 MHz): δ = 144.5,
ppm. 13C (CDCl3, 100 MHz): δ = 144.9, 142.6, 138.4, 136.3, 136.1, 138.4, 133.9, 132.6, 130.2, 127.4, 126.9, 126.4, 126.3, 125.1, 35.9,
133.8, 130.9, 130.6, 129.6, 129.3, 129.0, 128.3, 128.1, 128.0, 127.5,
33.7, 31.7, 22.6, 22.0, 13.9, 13.6 ppm. MS (EI, 70 eV): m/z (%) =
127.4, 127.1, 125.7, 21.0. MS (EI, 70 eV): m/z (%) = 408 (100), 372
306 (94), 250 (66), 207 (100), 172 (75), 139 (15), 73 (12). HRMS:
(33), 357 (21), 292 (53), 278 (30), 202 (57), 91 (213). C23H17ClSe calcd. for C18H23ClS 306.1209; found 306.1215.
(407.80): calcd. C 67.74, H 4.20; found C 67.92, H 4.37.
1
3-Butyl-1-chloro-6-fluoro-2-(ethylseleno)naphthalene (3q): H NMR
1-Chloro-3-(4-chlorophenyl)-2-(ethylseleno)naphthalene (3k): 1H (CDCl3, 400 MHz): δ = 8.31–8.24 (m, 1 H, ArH), 7.53 (s, 1 H,
NMR (CDCl3, 200 MHz): δ = 8.33 (d, J = 9.0 Hz, 1 H, ArH),
7.82–7.77 (m, 1 H, ArH), 7.65 (s, 1 H, ArH ), 7.61–7.50 (m, 2 H,
ArH), 7.38 (s, 4 H, ArH), 7.63 (q, J = 7.4 Hz, 2 H, ArH), 2.63 (q,
ArH), 7.28–7.31 (m, 2 H, ArH), 3.09 [m, 4 H, 2ϫ (CH2CH2)],
1.70–1.41 [m, 4 H, 2ϫ (CH2CH2CH3)], 1.33 (t, J = 7.3 Hz, 3 H,
CH3), 0.96 (t, J = 7.3 Hz, 3 H, CH3) ppm. 13C NMR (CDCl3,
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5

Job/Unit: O20482
/KAP1
Date: 10-07-12 16:42:05
Pages: 7
A. C. Mantovani, D. F. Back, G. Zeni
FULL PAPER
100 MHz): δ = 161.4 (d, J = 248.8 Hz), 146.4, 139.0, 135.1 (d, J =
erfeiçoamento de Pessoal de Nível Superior (SAUX) and Fundação
9.1 Hz), 128.9, 128.4 (d, J = 8.7 Hz), 127.2, 125.3 (d, J = 5.1 Hz), de Amparo à Pesquisa do Estado do Rio Grande do Sul
116.7 (d, J = 24.8 Hz), 110.4 (d, J = 20.4 Hz), 38.3, 33.8, 23.1,
22.5 ppm. MS (EI, 70 eV): m/z (%) = 344 (84), 238 (29), 193 (100),
183 (31), 170 (33), 157 (40), 55 (5). HRMS: calcd. for C20H18ClFSe
392.0246; found 392.0253.
(PRONEX-10/0005-1), for the fellowship and financial support
(A. C. M. and G. Z.).
2-(Butylthio)-1-chloro-6-fluoro-3-phenylnaphthalene (3r): 1H NMR
(CDCl3, 200 MHz): δ = 8.38–8.31 (m, 1 H, ArH), 7.62 (s, 1 H,
ArH), 7.47–7.30 (m, 7 H, ArH), 2.51 (t, J = 7.20 Hz, 2 H,
CH2CH2), 1.36–1.07 [m, 4H 2ϫ (CH2CH2)], 0.73 (t, J = 7.35 Hz,
3 H, CH2CH3) ppm. 13C NMR (CDCl3, 100 MHz): δ = 161.59 (d,
J = 249.55 Hz), 145.67, 141.43, 138.24, 134.45 (d, J = 9.51 Hz),
129.69, 128.38 (d, J = 8.78 Hz), 128.01, 127.178, 127.52, 127.38 (d,
J = 5.12 Hz), 117.57 (d, J = 25.61 Hz), 111.13 (d, J = 20.49 Hz),
35.46, 31.46, 21.64, 13.39 ppm. MS (EI, 70 eV): m/z (%) = 344 (89),
287 (100), 251 (80), 223 (18), 206 (13). C20H18ClFS (344.87): calcd.
C 69.65, H 5.26; found C 69.80, H 5.30.
7-Butyl-5-chloro-6-(ethylseleno)naphtho[2,3-d][1,3]dioxole (3s): 1H
NMR (CDCl3, 400 MHz): δ = 7.88 (d, J = 8.9 Hz, 1 H, ArH), 7.57
(s, 1 H, ArH), 7.20 (t, J = 8.9 Hz, 1 H, ArH), 6.17 (s, 2 H, ArH),
3.09–2.91 [m, 4 H, 2ϫ (CH2CH2)], 1.71–1.41 [m, 4 H, 2ϫ
(CH2CH2CH2)], 1.33 (t, J = 7.3 Hz, 3 H, CH2CH3), 0.96 (t, J =
7.3 Hz, 3 H, CH2CH3) ppm. 13C NMR (CDCl3, 100 MHz): δ =
145.3, 144.3, 140.8, 139.5, 127.5, 126.4, 120.4, 119.9, 117.3, 110.5,
102.0, 38.5, 33.7, 23.1, 22.5, 15.3, 13.9 ppm. MS (EI, 70 eV): m/z
(%) = 370 (42), 341 (33), 253 (29), 208 (22), 207 (100), 147 (20), 73
(68). C17H19ClO2Se (369.75): calcd. C 55.22, H 5.18; found C
55.34, H 5.22.
[1]
a) L. Chen, S. Revel, K. Morris, L. C. Serpell, D. J. Adams,
Langmuir 2010, 26, 13466; b) Y. M. Pu, Y. Y. Ku, T. Grieme,
L. A. Black, A. V. Bhatia, M. Cowart, Org. Process Res. Dev.
2007, 11, 1004; c) S. Kawasaki, M. Yamada, K. Kobori, F. Jin,
Y. Kondo, H. Hayashi, Y. Suzuki, T. Takata, Macromolecules
2007, 40, 5284.
a) C. B. de Koning, A. L. Rousseau, W. A. L. van Otterlo, Tet-
rahedron 2003, 59, 7; b) Modern Arene Chemistry (Ed.: D. As-
truc), Wiley-VCH, Weinheim, 2002; c) M. D. Watson, A. Fech-
tenkotter, K. Müllen, Chem. Rev. 2001, 101, 1267.
a) Y. Lin, L. Wu, X. Huang, Eur. J. Org. Chem. 2011, 2993; b)
Y. Isogai, Menggenbateer, F. N. Khan, N. Asao, Tetrahedron
2009, 65, 9575; c) N. Asao, K. Sato, Org. Lett. 2006, 8, 5361;
d) N. Asao, T. Nogami, S. Lee, Y. Yamamoto, J. Am. Chem.
Soc. 2003, 125, 10921; e) N. Asao, K. Takahashi, S. Lee, T.
Kasahara, Y. Yamamoto, J. Am. Chem. Soc. 2002, 124, 12650.
a) N. Asao, Synlett 2006, 1645; b) N. Asao, H. Aikawa, Y.
Yamamoto, J. Am. Chem. Soc. 2004, 126, 7458.
a) J. F. Brazeau, S. Zhang, I. Colomer, B. K. Corkey, F. D. To-
ste, J. Am. Chem. Soc. 2012, 134, 2742; b) N. Joseph, J. John, R.
Rajan, S. Thulasi, A. Mohan, E. Suresh, K. V. Radhakrishnan,
Tetrahedron 2011, 67, 4905; c) M. Rubin, A. W. Sromek, V.
Gevorgyan, Synlett 2003, 2265.
[2]
[3]
[4]
[5]
[6]
a) A. F. Cozzolino, P. J. W. Elder, I. Vargas-Baca, Coord. Chem.
Rev. 2011, 1426; b) C. Santi, S. Santoro, B. Battistelli, Curr.
Org. Chem. 2010, 14, 2442; c) S. Santoro, B. Battistelli, L. Tes-
taferri, M. Tiecco, C. Santi, Eur. J. Org. Chem. 2009, 4921; d)
S. Flemer Jr., Molecules 2011, 3232; e) S. Flemer Jr., Mini-Rev.
Org. Chem. 2009, 196; f) G. Zeni, P. H. Menezes, “Vinylic Tel-
lurides”, in Patai’s Chemistry of Functional Groups (Ed.: Z.
Rappport), John Wiley & Sons, New York, 2012, DOI:
10.1002/9780470682531.pat0569; g) P. H. Menezes, G. Zeni,
“Vinylic Selenides”, in Patai’s Chemistry of Functional Groups
(Ed.: Z. Rappport), John Wiley & Sons, New York, 2012, DOI:
10.1002/9780470682531.pat0568; h) G. Zeni, A. L. Braga,
H. A. Stefani, Acc. Chem. Res. 2003, 36, 731; i) G. Zeni, D. S.
Lüdtke, R. B. Panatieri, A. L. Braga, Chem. Rev. 2006, 106,
1032; j) N. Taniguchi, J. Org. Chem. 2007, 72, 1241; k) M.
Wang, K. Ren, L. Wanga, Adv. Synth. Catal. 2009, 351, 1586; l)
D. Alves, C. G. Santos, M. W. Paixão, L. C. Soares, D. Souza,
O. E. D. Rodrigues, A. L. Braga, Tetrahedron Lett. 2009, 50,
6635.
General Procedure for the CuCl2/LiBr-Mediated Cycloaddition: Into
a two-necked round-bottomed flask equipped with a reflux con-
denser, under argon, containing a solution of CuCl2 (0.067 g,
0.5 mmol) and LiBr (0.087 g, 1 mmol) in 1,2-dichloroethane
(3 mL), was added 2-(2-phenylethynyl)benzaldehyde (0.051 g,
0.25 mmol) and the alkynyl chalcogenide (0.25 mmol). The reac-
tion mixture was stirred for the desired time at 80 °C, then the
mixture was diluted with dichloromethane (20 mL) and washed
with saturated aqueous NH4Cl solution (20 mL). The organic
phase was separated, dried with MgSO4, and concentrated under
vacuum. The residue was purified by flash chromatography and
eluted with hexane.
1-Bromo-2-(butylseleno)-3-phenylnaphthalene (4a): 1H NMR
(CDCl3, 200 MHz): δ = 8.37–8.33 (m, 1 H, ArH), 7.78 (t, J =
8.4 Hz, 1 H, ArH), 7.69 (d, J = 12.8 Hz, 1 H, ArH), 7.61–7.50 (m,
2 H, ArH), 7.46–7.37 (m, 5 H, ArH), 2.60–2.53 (m, 2 H, CH2CH2),
[7] B. Gabriele, L. Veltri, V. Maltese, R. Spina, R. Mancuso, G.
Salerno, Eur. J. Org. Chem. 2011, 5626.
[8] J. V. Comasseto, P. H. Menezes, H. A. Stefani, G. Zeni, A. L.
Braga, Tetrahedron 1996, 52, 9687.
[9] D. A. Barancelli, R. F. Schumacher, M. R. Leite, G. Zeni, Eur.
J. Org. Chem. 2011, 6713.
[10] S. Rudrawar, Synlett 2005, 1197.
[11] a) Y. Isogai, Menggenbateer, F. N. Khan, N. Asao, Tetrahedron
2009, 65, 9575; b) N. Asao, T. Nogami, S. Lee, Y. Yamamoto,
J. Am. Chem. Soc. 2003, 125, 10921; c) N. Asao, K. Takahashi,
S. Lee, T. Kasahara, Y. Yamamoto, J. Am. Chem. Soc. 2002,
124, 12650.
[12] a) A.-Y. Peng, F. Hao, B. Li, Z. Wang, Y. J. Du, J. Org. Chem.
2008, 73, 9012; b) J. K. Kochi, J. Am. Chem. Soc. 1955, 77,
5274.
1.47–1.33 (m,
2
H, CH2CH2CH2), 1.24–1.14 (m,
2 H,
CH2CH2CH3), 0.74 (t, J = 7.3 Hz, 3 H, CH2CH3) ppm. 13C NMR
(CDCl3, 100 MHz): δ = 144.8, 143.1, 137.8, 133.4, 132.2, 131.5,
130.5, 129.5, 128.6, 127.9, 127.6, 127.2, 127.0, 125.3, 32.0, 29.1,
22.6, 13.3 ppm. MS (EI, 70 eV): m/z (%) = 419 (42), 417 (52), 361
(37), 281 (100), 279 (46), 202 (63), 57 (6). HRMS: calcd. for
C20H20BrSe 417.9835; found 417.9846.
Supporting Information (see footnote on the first page of this arti-
cle): Experimental procedures, additional experimental details for
the preparation of all compounds and 1H and 13C NMR spectra
for all reaction products.
Acknowledgments
Received: April 14, 2012
Published Online: ᭿
We are grateful to Conselho Nacional de Desenvolvimento Ci-
entífico e Tecnológico (CNPq/INCT-catalise), Coordenação de Ap-
6
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O20482
/KAP1
Date: 10-07-12 16:42:05
Pages: 7
2-Chalcogeno-1-halonaphthalenes
Cycloaddition Reactions
A. C. Mantovani, D. F. Back,
G. Zeni* ............................................ 1–7
Chalcogenoalkynes: Precursors for the Re-
gioselective Preparation of 2-Chalcogeno-
1-halonaphthalenes through [4+2] Cyclo-
addition
Chalcogeoalkynes and o-alkynylbenzalde-
hydes reacted in the presence of CuCl2 to
furnish the [4+2] cycloadducts 2-chalcog-
eno-1-halonaphthalenes in good yields (46–
89%) and high regioselectivities. The meth-
odology was carried out by using CuCl2 or
CuCl2/LiBr in dichloroethane (DCE) at
80 °C.
Keywords: Alkynes / Selenium / Sulfur / Re-
gioselectivity / Cycloaddition
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
7