Cooperative action between Iron(III) chloride and diorganyl dichalcogenides for the cyclization of N-(ortho-Alkynyl)aryl-pyrroles

Article abstract of DOI:10.1016/j.tet.2021.132188

We report the ability of iron(III) chloride and diorganyl dichalcogenides to promote de cyclization of N-(ortho-alkynyl)aryl-pyrroles leading to 5-(organochalcogenyl)pyrrolo[1,2-a]quinolines. The combination of diorganyl dichalcogenides and iron(III) chloride was crucial for the cyclization reaction to occur because neither the iron salt nor diorganyl diselenide alone were able to promote the cyclization. The effects of solvent, temperature, reaction time, and stoichiometry on the efficiency of cyclization reactions were investigated. The standard reaction conditions were compatible with many functional groups in the substrates, such as methyl, chlorine, and methoxy. In addition, under these conditions, not only diaryl, but also dialkyl dichalcogenides have been cyclized in moderate to good yields. The 5-(organochalcogenyl)pyrrolo[1,2-a]quinolines prepared underwent a Suzuki cross-coupling reaction with boronic acids under palladium catalyze to give the cross-coupled products in good yields.

Full text of DOI:10.1016/j.tet.2021.132188

Tetrahedron 90 (2021) 132188
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Tetrahedron
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Cooperative action between Iron(III) chloride and diorganyl
dichalcogenides for the cyclization of N-(ortho-Alkynyl)aryl-pyrroles
,
*
Ana Maria S. Recchi a, Davi F. Back b, Gilson Zeni a
a
ꢀ
~
ꢀ
ꢀ
^
Laboratorio de Síntese, Reatividade, Avaliaçao Farmacologica e Toxicologica de Organocalcogenios, CCNE, UFSM, Santa Maria, Rio Grande do Sul, 97105-
900, Brazil
b
ꢀ
^
Laboratorio de Materiais Inorganicos, CCNE, UFSM, Santa Maria, Rio Grande do Sul, 97105-900, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history:
We report the ability of iron(III) chloride and diorganyl dichalcogenides to promote de cyclization of N-
(ortho-alkynyl)aryl-pyrroles leading to 5-(organochalcogenyl)pyrrolo[1,2-a]quinolines. The combination
of diorganyl dichalcogenides and iron(III) chloride was crucial for the cyclization reaction to occur
because neither the iron salt nor diorganyl diselenide alone were able to promote the cyclization. The
effects of solvent, temperature, reaction time, and stoichiometry on the efficiency of cyclization reactions
were investigated. The standard reaction conditions were compatible with many functional groups in the
substrates, such as methyl, chlorine, and methoxy. In addition, under these conditions, not only diaryl,
but also dialkyl dichalcogenides have been cyclized in moderate to good yields. The 5-(organo-
chalcogenyl)pyrrolo[1,2-a]quinolines prepared underwent a Suzuki cross-coupling reaction with boronic
acids under palladium catalyze to give the cross-coupled products in good yields.
Received 1 March 2021
Received in revised form
20 April 2021
Accepted 23 April 2021
Available online 5 May 2021
Keywords:
Diselenides
Iron salt
Cyclization
Quinolones
Pyrroles
© 2021 Elsevier Ltd. All rights reserved.
1. Introduction
triple bond is observed giving the addition product without cycli-
zation taking place [7]. To prevent this drawback, the application of
Alkynes represent an important class of functional groups which
present in organic substrates give them a peculiar reactivity by
under its behaves both as an electrophile and as a nucleophile [1].
Despite these, both metal-free and metal-catalyzed cyclization re-
actions of alkynes have emerged as one of the best choices for the
preparation of carbocycles and heterocycles [2]. Among them, the
electrophile-promoted nucleophilic cyclization has become an
effective tool to promote the cyclization of alkynes [3]. The ad-
vantages of these methodologies is that an electrophilic source is
generally used to activate the carbon-carbon triple bond of alkyne
as well as to introduce new functionality in the structure of the final
product. The halogens are the most used electrophilic agents [4],
although the organoselenium compounds have emerged as a ver-
satile and convenient alternative source [5]. The application of an
electrophilic organoselenium species to active the alkynes has been
a useful tool for the synthesis of carbocycles or heterocycles con-
taining an organoselenim function [6]. However, in some cases in
the cyclization reactions in which an electrophilic organoselenium
species is the activator, only the reduction of the carbon-carbon
iron(III) chloride and diorganyl diselenides, as a tool to promote de
cyclization of unsaturated substrates, has recently attracted much
attention [8]. The preparation of organoselenium compounds has
stimulated intensive research because of the exclusive reactivity of
the carbon-selenium bond, which enables the chemioselective
formation of new compounds [9], as well as because of their
promising pharmacological applications as therapeutic agents in
the treatment of several diseases [10]. The use of iron reagents is a
rapidly growing area because of their high efficiency, relative sta-
bility, abundance, low toxicity, economic, and ecologic advantages
[11]. The wide range of application of the intramolecular hydro-
arylation reaction [12] and the high ability that the mixture dio-
rganyl diselenides and iron(III) chloride has in promoting the
concomitant cyclization and functionalization of unsaturated sub-
strates, avoiding the reduction product 3, prompted us to propose
the synthesis of 5-(organochalcogenyl)pyrrolo[1,2-a]quinolines 2
from N-(ortho-alkynyl)aryl-pyrroles (Scheme 1). Pyrrolo[1,2-a]
quinolines are an important class of N-heterocycles because they
present significant biological properties, such as antimicrobial,
antibacterial, and antitumor, activities [13]. Furthermore, pyrrolo
[1,2-a]quinolines also have been found to have optoelectronic
properties [14].
* Corresponding author.
E-mail address: gzeni@ufsm.br (G. Zeni).
https://doi.org/10.1016/j.tet.2021.132188
0040-4020/© 2021 Elsevier Ltd. All rights reserved.

A.M.S. Recchi, D.F. Back and G. Zeni
Tetrahedron 90 (2021) 132188
in high yield (Table 1, entry 24).
We then used the optimal reaction conditions (Table 1, entry 24)
to explore the synthetic utility of this protocol for the variation of
the N-(ortho-alkynyl)aryl-pyrroles and diorganyl dichalcogenides.
The experimental results from these studies are shown in Table 2.
N-(ortho-alkynyl)aryl-pyrrole having electron-neutral, electron-
rich, and electron-poor aryl groups directly bonded to alkyne
reacted very well under optimized reactions conditions, in a very
short reaction time, to give the corresponding 5-(phenylselanyl)
pyrrolo[1,2-a]quinolines in good yields (Table 2, 2a-f). The reaction
yield was reduced with an alkyl chain at the alkyne (Tables 2 and
Scheme 1. General scheme.
2. Results and discussion
The requisite N-(ortho-alkynyl)aryl-pyrrole precursors are
readily synthesized from the corresponding 1-(2-iodophenyl)-1H-
pyrroles [15] via Sonogashira cross-coupling with terminal alkynes
[16]. After that, to study the optimization of the reaction conditions
of the proposed procedure, the cyclization reaction of N-(ortho-
alkynyl)aryl-pyrrole 1a was tested by varying several reaction pa-
rameters. The results are shown in Table 1. Considering the nucle-
ophilic nature of the triple bond, we planned that the use of
phenylselanyl bromide (PhSeBr) would promote activation of the
carbon-carbon triple bond followed by cyclization upon a nucleo-
philic attack of the pyrrole ring, to give the 5-(phenylselanyl)pyr-
rolo[1,2-a]quinoline 2a. To this end, the addition of phenylselanyl
bromide (1.5 equiv) to a solution of N-(ortho-alkynyl)aryl-pyrrole
1a (0.2 mmol) in dichloroethane (3 mL), was carried out at room
temperature under a nitrogen atmosphere for 24 h. These condi-
tions led to the formation of 2a in 20% yields in a mixture of
reduced 3a (Table 1, entry 1). Further studies revealed that the
increase of PhSeBr amount to 2.0 equiv and the addition of base did
not improve the yield of 2a (Table 1, entries 2 and 3). As indicated in
the introduction, the use of diorganyl diselenides and iron salts may
overcome these unsatisfactory results. For this purpose, we pro-
moted the addition of N-(ortho-alkynyl)aryl-pyrrole 1a
(0.20 mmol), at room temperature, under nitrogen atmosphere, to a
solution of FeCl3$6H2O (2.0) and diphenyl diselenide (1.1 equiv) in
dichloromethane (3 mL), which was prepared 15 min before. The
reaction was stirred at room temperature for 24 h. However, there
was no significant improvement in the reaction yield (Table 1, entry
4). Other iron salts were examined revealing that FeCl3 was the
most effective giving the product 2a in 81% yield (Table 1, entries
5e7). No significant effect on the reaction yield was observed by
using diphenyl diselenide with other Lewis or Brønsted acids
instead of iron(III) chloride (Table 1, entries 8e12). The employ-
ment of 1.5 and 1.0 equiv or catalytic amount of iron(III) chloride
gave the product 2a in lower yields, even under heating and long
reaction time (Table 1, entries 13e16). The amount of diphenyl
diselenide had a pronounced effect on the cyclization reaction in
which the decrease to 0.85 or 0.6 equiv led to a significant reduc-
tion in the yield of 2a (Table 1, entries 17e19). Among the solvents
screened for the reaction, dichloroethane, nitromethane, and
acetonitrile gave the product 2a in inferior yields than dichloro-
methane, while dimethylformamide and tetrahydrofuran did not
give the product (Table 1, entries 20e24). We used TLC for
measuring the time for complete consumption of the starting
material and we found that 0.5 h was the time required for the
reaction to reach completion (Table 1, entries 25 and 26). We made
other changes in the reaction parameters such as the addition of
bases, heating, and concentration of the solution; however, none of
these changes had any positive effects on the reaction yields
(Table 1, entries 27e32). Once studied the variations of the reaction
parameters, we concluded that the addition of N-(ortho-alkynyl)
aryl-pyrrole 1a (0.2 mmol) to a mixture of diphenyl diselenide (1.1
equiv) and FeCl3 (2.0 equiv) in dichloromethane (3 mL), under an
argon atmosphere, at room temperature, for 0.5 h, was the ideal
condition to obtain the 5-(phenylselanyl)pyrrolo[1,2-a]quinoline 2a
2g). This poor yield is probably because of the absence of pi (p)
bonds next to the alkyne, which becomes the carbon-carbon triple
bond less reactive towards iron activation and nucleophilic attack
(see Scheme 2, mechanism proposal). We also studied the intro-
duction of heteroatoms on the alkyne terminus. The reaction of
silylacetylene with standard conditions gave a mixture of desired
product 2 h and the hydrogenated derivative 2h’ (Table 2, 2h and
2h′). In this case, the formation of 2h′ may be attributed to the
cleavage of the carbon-silicon bond on the starting material leading
to the in situ formation of a terminal alkyne, which cyclizes to give
the product 2h’. When we introduced an iodine atom on the alkyne
terminus, the product of the reduction of the carbon-carbon triple
bond was formed with the entry of the SePh groups into carbons 1
and 2, respectively. We believe that this product was formed
through the in situ formation of selenoacetylene, which is further
reduced to 2i (Tables 2 and 2i). Another limitation of our meth-
odology was observed when we extended the optimized conditions
to N-(ortho-alkynyl)aryl-pyrrole having a terminal alkyne. This
substrate gave the product 2j in 14% yield together with the starting
material even though by texting other reaction conditions (Tables 2
and 2j). Next, we evaluated the influence of groups directly bonded
to the aromatic ring. In this study, we observed that the presence of
a chlorine atom in the aromatic ring greatly reduced the reaction
yield demonstrating the influence of the electronic effect in this
process (Table 2, 2k and 2l). From the results obtained by using
substituted diaryl diselenides, it is apparent that the electronic
effect of these substitutes did not have a great influence, although
diselenides having a methoxy group did not provide the product
(Table 2, 2m-s). However, the product 2n was detected by GC-MS in
the crude reaction, but it was not stable during the purification
process. The reaction rate of mesityl diselenide is slower compared
to that with diphenyl diselenide showing a strong steric influence
of the substituents (Tables 2 and 2s). In further screening, it was
found that similar yields were obtained by changing diaryl dis-
elenides to dialkyl diselenides in which dibutyl diselenide lead to
the formation of the expected products in good yields (Table 2, 2t
and 2u). The optimized conditions were then extended to the di-
sulfide and ditelluride derivatives. The reaction with diphenyl di-
sulfide did not afford the quinoline 2v corresponding (Tables 2 and
2v). We suppose that the iron incorporation into disulfides was
blocked because the sulfur-sulfur bond of disulfides is stronger
than the selenium-selenium bond. The cyclization with diphenyl
ditelluride resulted in the quinoline 2w in 84% yield, while with
dibutyl ditellurides only a trace amount of 2x was obtained (Table 2,
2w and 2x). All the compounds were characterized by 1H and 13C
NMR spectroscopy. Furthermore, the 6-endo-dig cyclization
sequence was confirmed by X-ray analysis of the crystalline sample
(Supporting Information, Figures F1 and F2, CCDC 2054305 and
2054306 for compounds 2b and 2m, respectively) [17].
Based on the above results and the previous report [18], a
possible reaction mechanism is shown in Scheme 2. The reaction of
FeCl3 and diorganyl diselenide would give the iron-seleno complex,
in which the electrophilic portion of the selenium species co-
ordinates to the carbon-carbon bond of alkyne to generate the
2

A.M.S. Recchi, D.F. Back and G. Zeni
Tetrahedron 90 (2021) 132188
Table 1
Effects of different reaction parameters on the preparation of 5-(phenylselanyl)pyrrolo[1,2-a]quinoline 2a.a.
Entry
promoter (equiv)
(PhSe)2 (equiv)
solvent
reaction time (h)
Yields (%)b
1
2
3
4
5
6
7
8
PhSeBr (1.5)
PhSeBr (2.0)
PhSeBr (2.0)
FeCl3$6H2O (2.0)
Fe2O3 (2.0)
FeSO4$7H2O (2.0)
FeCl3 (2.0)
BF3$OEt2 (2.0)
TsOH$H2O (2.0)
AgCl2 (2.0)
AlCl3 (2.0)
CuCl2
FeCl3 (1.5)
FeCl3 (1.0)
FeCl3 (1.0)
FeCl3 (0.3)
FeCl3 (2.0)
FeCl3 (2.0)
FeCl3 (2.0)
FeCl3 (2.0)
FeCl3 (2.0)
FeCl3 (2.0)
FeCl3 (2.0)
FeCl3 (2.0)
FeCl3 (2.0)
FeCl3 (2.0)
FeCl3 (2.0)
FeCl3 (2.0)
FeCl3 (2.0)
FeCl3 (2.0)
FeCl3 (2.0)
FeCl3 (2.0)
e
DCE
DCE
DCE
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
24
0.5
24
24
0.5
1
24
24
24
1
0.5
0.5
0.5
0.5
24
0.5
24
20c
e
29c,d
N.D.c,e
33
e
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
0.85
0.6
0.6
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
1.1
e
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCE
MeNO2
MeCN
DMF
THF
DCM
DCM
DCM
DCM
DCM
DCM
DCM
DCM
N.D.e
N.D.e
81
19
9
N.D.e
33
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
N.D.e
N.D.e
64
39
46f
N.D.e
52
57
47g
59
65
40
N.D.e
N.D.e
93
91
70h
76i
52j
75k
25l
N.D.e,m
a
The reaction was performed by the addition of N-(ortho-alkynyl)aryl-pyrrole 1a (0.20 mmol), at room temperature, under argon atmosphere, to a solution of promoter and
diphenyl diselenide in solvent (3 mL), which was prepared 15 min before. The reaction was stirred at room temperature for the time indicated in Table 1.
b
Isolated yield after column chromatography.
c
3a (X ¼ Br) was also detected, however in an inseparable mixture.
d
NaHCO3 (2 equiv) was used.
e
N.D. ¼ not detected.
f
The reaction was heated at 40 ꢀC.
g
The reaction was carried out under air atmosphere in an open flask.
K2CO3 (2 equiv) was used.
K3PO4 (2 equiv) was used.
The N-(ortho-alkynyl)aryl-pyrrole 1a was added at 0 ꢀC.
DCM (1 mL) was used.
DCM (5 mL) was used.
The reaction was carried out in the absence of diphenyl diselenide.
h
i
j
k
l
m
intermediate I. The carbon-carbon triple bond is activated by the
iron-seleno complex forming the seleniranium ion II. The selective
intramolecular 6-endo-dig cyclization promoted by anti nucleo-
philic attack of the pyrrole ring gives the intermediate III. The
removal of the hydrogen by the selenolate anion, restores the ar-
omatic system affording the cyclized product. Because the cycli-
zation promoted by iron salts can also form radical species, the
hypothesis of this reaction following a classical radical pathway
cannot be ruled out.
compounds that exhibit Csp2-Se or Csp2-Te bonds in the structure
are useful substrates for the formation of new carbon-carbon bonds
including carbon-alkynyl, carbon-vinyl, carbon-aryl, and carbon-
heteroaryl bond formation [19]. Thus, the presence of an organo-
chalcogenyl group at the 5-position of the quinolines making them
potential substrates for further transformations. In this context, we
evaluated the use of quinoline 2w as the substrate in the reaction
with boronic acids in a Suzuki cross-coupling reaction [20]. A brief
optimization of this reaction condition revealed that the reaction of
quinoline 2w with phenylboronic acid and p-tolylboronic acid,
using palladium(0) as the catalyst in DMF at 100 ꢀC gave the cross-
coupled products 4a and 4b in 68% and 73% yields, respectively
Organochalcogen compounds have received considerable
attention in modern organic chemistry because of their chemo,
regio, and stereoselective reactions. In this context, organic
3

A.M.S. Recchi, D.F. Back and G. Zeni
Tetrahedron 90 (2021) 132188
Table 2
Preparation of 5-(phenylselanyl)pyrrolo[1,2-a]quinoline 2.[a]
.
Scheme 3. Application of quinoline 2w as the substrate in the Suzuki cross-coupling
reactions.
Scheme 2. Reaction mechanism for the formation of 5- (phenylselanyl) pyrrolo [1,2-a]
quinoline.
as precursors for the synthesis of more highly functionalized
quinolines through palladium-catalyzed cross-coupling reactions
with aryl boronic acid. The main advantages of this methodology
are based on the incorporation of the useful organochalcogen
functionalities in the structure and the high regioselectivity of the
intramolecular 6-endo-dig over the 5-exo-dig mode.
(Scheme 3).
3. Conclusion
In summary, we demonstrated that the cooperative action be-
tween diorganyl dichalcogenides and iron(III) chloride was very
efficient to promote de cyclization of N-(ortho-alkynyl)aryl-pyr-
roles leading to 5-(organochalcogenyl)pyrrolo[1,2-a]quinolines.
The reaction parameters were studied and the standard condition
works well with a wide range of substituents in both diorganyl
dichalcogenides and N-(ortho-alkynyl)aryl-pyrroles, resulting in
the formation of products in good yields, and proceed under rela-
tively mild conditions. The resulting products proved to be versatile
4. Experimental section
Proton nuclear magnetic resonance spectra (1H NMR) were
obtained at 200 MHz or at 400 MHz spectrometer. Spectra were
recorded in CDCl3 solutions. Carbon-13 nuclear magnetic resonance
spectra (13C NMR) were obtained either at 50 MHz or at 100 MHz
4

A.M.S. Recchi, D.F. Back and G. Zeni
Tetrahedron 90 (2021) 132188
spectrometer. Spectra were recorded in CDCl3 solutions. Mass
spectra were recorded on a spectrometer using EI at 70 eV. High
resolution mass spectra were recorded on a LC-MS-IT-TOF. Column
chromatography was performed using Silica Gel (230e400 mesh).
Thin layer chromatography (TLC) was performed using Silica Gel
GF254, 0.25 mm thickness. For visualization, TLC plates were either
placed under ultraviolet light, or stained with iodine vapor, or
acidic vanillin. Most reactions were monitored by TLC for disap-
pearance of starting material.
General procedure for the preparation of 5-(organochalcog-
enyl)pyrrolo[1,2-a]quinolines 2a-x: In a Schlenke flask, under argon
atmosphere, at room temperature N-(ortho-alkynyl)aryl-pyrroles
(0.25 mmol) was added to a solution of FeCl3 (2.0 equiv) and dio-
rganyl dichalcogenides (1.1 equiv) in DCM (3 mL), which was pre-
pared 15 min before. The reaction was stirred at room temperature
for the time indicated in Table 2. The mixture was diluted with
ethyl acetate and washed with concentrated NH4Cl solution. The
organic phase was dried with MgSO4, the solvent was removed
under reduced pressure. The residue was purified by column
chromatography.
2.9 Hz, 1H), 6.18 (dd, J ¼ 3.9, 1.4 Hz, 1H), 3.83 (s, 3H), 2.37 (s, 3H). 13
C
{1H} NMR (CDCl3, 100 MHz):
d 159.2, 140.5, 134.1, 133.7, 132.2, 132.1,
131.0, 130.7, 130.6, 129.2, 129.1, 129.0, 125.6, 124.9, 117.3, 114.0, 113.2,
113.1, 112.8, 106.2, 55.2, 21.1. 77Se NMR (77 MHz, in CDCl3 with
diphenyl diselenide as external reference) d(ppm) 294.3. HRMS
calcd for C26H22NOSe (ESI-TOF, [M þ Hþ]), 444.0867, found
444.0875.
4-(4-chlorophenyl)-7-methyl-5-(phenylselanyl)pyrrolo[1,2-a]qui-
nolone (2e). The product was isolated by column chromatography
(hexane as eluent) as a green solid. Yield: 0.070 g (63%); mp.
133e136 ꢀC. 1H NMR (CDCl3, 400 MHz):
d (ppm) 8.18e8.16 (m, 1H),
7.91 (dd, J ¼ 2.9, 1.5 Hz, 1H), 7.79 (d, J ¼ 8.4 Hz, 1H), 7.36e7.30 (m,
3H), 7.25e7.20 (m, 2H), 7.12e7.03 (m, 5H), 6.73 (dd, J ¼ 3.9, 2.8 Hz,
1H), 6.12 (dd, J ¼ 3.9, 1.4 Hz, 1H), 2.38 (s, 3H). 13C {1H} NMR (CDCl3,
100 MHz):
d 139.4, 138.0, 133.9, 133.8, 133.7, 131.5, 131.0, 130.7,
130.6, 129.6, 129.1, 129.0, 128.1, 125.7, 124.7, 117.4, 114.1, 113.3, 113.0,
106.0, 21.23. MS (EI, 70 eV; m/z (relative intensity)): 447 (48), 367
(100), 331 (27), 254 (21),158 (30). HRMS calcd for C25H19ClNSe (ESI-
TOF, [M þ Hþ]), 448.0371, found 448.0360.
7-methyl-4-(naphthalen-2-yl)-5-(phenylselanyl)pyrrolo[1,2-a]
quinolone (2f). The product was isolated by column chromatog-
raphy (hexane as eluent) as a yellow solid. Yield: 0.075 g (65%); mp.
7-methyl-4-phenyl-5-(phenylselanyl)pyrrolo[1,2-a]quinolone
(2a). The product was isolated by column chromatography (hexane
as eluent) as a brown solid. Yield: 0.075 g (91%); mp.104e108 ꢀC. 1H
117e121 ꢀC. 1H NMR (CDCl3, 400 MHz):
d (ppm) 8.24e8.18 (m, 1H),
NMR (CDCl3, 400 MHz):
d
(ppm) 8.20e8.14 (m, 1H), 7.91 (dd, J ¼ 2.9,
7.90 (dd, J ¼ 2.9, 1.5 Hz, 1H), 7.87e7.83 (m, 2H), 7.82e7.77 (m, 1H),
7.78e7.72 (m, 1H), 7.74e7.70 (m, 1H), 7.49e7.41 (m, 3H), 7.31 (ddd,
J ¼ 8.4, 2.0, 0.5 Hz, 1H), 7.12e7.07 (m, 2H), 7.06e7.01 (m, 3H), 6.70
1.5 Hz, 1H), 7.79 (d, J ¼ 8.5 Hz, 1H), 7.40-7.34 (m, 3H), 7.34-7.27 (m,
3H), 7.16e7.08 (m, 2H), 7.09e7.03 (m, 3H), 6.72 (dd, J ¼ 3.9, 2.8 Hz,
1H), 6.13 (dd, J ¼ 3.9, 1.5 Hz, 1H), 2.37 (s, 3H). 13C {1H} NMR (CDCl3,
(dd, J ¼ 3.9, 2.8 Hz, 1H), 6.14 (dd, J ¼ 3.9, 1.5 Hz, 1H), 2.38 (s, 3H). 13
C
100 MHz):
d
140.8,139.7, 134.0,133.7, 131.9, 131.1, 130.7, 129.3,129.3,
{1H} NMR (CDCl3, 100 MHz):
d 140.6, 137.2, 134.1, 133.8, 133.0, 132.0,
129.2,128.9,127.8,127.8,125.6,124.8,117.2, 114.2,113.2,112.9,106.2,
21.2. MS (EI, 70 eV; m/z (relative intensity)): 413 (50), 411 (25), 333
(100), 255 (17), 158 (12). HRMS calcd for C25H20NSe (ESI-TOF,
[M þ Hþ]), 414.0761, found 414.0772.
132.0, 131.1, 130.768, 129.4, 129.3, 128.9, 128.4, 128.2, 127.7, 127.6,
127.4, 126.1, 126.0, 125.7, 124.9, 117.5, 114.1, 113.2, 113.0, 106.3,21.2.
HRMS calcd for C29H22NSe (ESI-TOF, [M þ Hþ]), 464.0917, found
464.0908.
4-butyl-7-methyl-5-(phenylselanyl)pyrrolo[1,2-a]quinoline (2g).
The product was isolated by column chromatography (hexane as
eluent) as a black oil. Yield: 0.037 g (38%). 1H NMR (CDCl3,
7-methyl-5-(phenylselanyl)-4-(p-tolyl)pyrrolo[1,2-a]quinolone
(2b). The product was isolated by column chromatography (hexane
as eluent) as a yellow solid. Yield: 0.063 g (59%); mp.149e154 ꢀC. 1H
NMR (CDCl3, 400 MHz):
d
(ppm) 8.16e8.14 (m, 1H), 7.93e7.87 (m,
400 MHz):
d
8.13 (s, 1H), 7.85 (dd, J ¼ 2.8, 1.4 Hz, 1H), 7.72 (d,
1H), 7.79 (d, J ¼ 8.4 Hz, 1H), 7.30 (d, J ¼ 8.5 Hz, 1H), 7.25e7.16 (m,
4H), 7.16e7.10 (m, 2H), 7.10e7.03 (m, 3H), 6.71 (dd, J ¼ 3.8, 2.9 Hz,
1H), 6.16 (dd, J ¼ 3.9, 1.4 Hz, 1H), 2.40 (s, 3H), 2.37 (s, 3H). 13C {1H}
J ¼ 8.4 Hz, 1H), 7.23 (dd, J ¼ 8.6, 1.9 Hz, 1H), 7.20e7.15 (m, 2H),
7.12e7.05 (m, 3H), 6.79 (dd, J ¼ 3.8, 2.9 Hz, 1H), 6.67 (dd, J ¼ 3.9,
1.4 Hz, 1H), 3.22e3.16 (m, 2H), 2.35 (s, 3H), 1.64 (qt, J ¼ 7.4 Hz, 2H),
1.44 (sext, J ¼ 7.3 Hz, 2H), 0.92 (t, J ¼ 7.3 Hz, 3H). 13C {1H} NMR
NMR (CDCl3, 100 MHz): d 140.9137.5, 136.9, 134.1, 133.7, 132.1, 131.1,
130.8, 129.2, 129.2, 128.9, 128.6, 125.6, 124.9, 117.1, 114.0, 113.1, 112.9,
106.3, 21.34, 21.2. MS (EI, 70 eV; m/z (relative intensity)): 427 (43),
347 (100), 331 (13), 268 (12), 254 (13), 207 (08), 165 (12), 158 (11).
HRMS calcd for C26H22NSe (ESI-TOF, [M þ Hþ]), 428.0917, found
428.0926.
7-methyl-5-(phenylselanyl)-4-(m-tolyl)pyrrolo[1,2-a]quinolone
(2c). The product was isolated by column chromatography (hexane
as eluent) as a brown solid. Yield: 0.073 g (68%); mp.108e112 ꢀC. 1H
(CDCl3, 100 MHz): d 140.5, 133.6, 133.5, 131.1, 130.7, 130.2, 129.1,
128.7, 128.5, 125.6, 125.1, 116.6, 113.9, 112.9, 112.6, 103.6, 34.5, 32.4,
23.1, 21.2, 13.9. MS (EI, 70 eV; m/z (relative intensity)): 393 (78), 316
(74), 270 (63), 254 (17), 236 (100), 220 (18), 194 (73), 127 (15).
HRMS calcd for C23H24NSe (ESI-TOF, [M þ Hþ]), 394.1074, found
394.1050.
7-methyl-5-(phenylselanyl)pyrrolo[1,2-a]quinoline (2j). The prod-
uct was isolated by column chromatography (hexane as eluent) as a
black oil. Yield: 0.014 g (14%). H NMR (CDCl3, 400 MHz):
1
NMR (CDCl3, 400 MHz):
d
(ppm) 8.18 (d, J ¼ 1.5 Hz, 1H), 7.87 (dd,
d
(ppm)
J ¼ 2.9, 1.5 Hz, 1H), 7.75 (d, J ¼ 8.4 Hz, 1H), 7.29e7.25 (m, 2H),
7.19e7.15 (m, 1H), 7.14e7.09 (m, 3H), 7.09e7.06 (m, 2H), 7.06e7.02
(m, 3H), 6.70 (dd, J ¼ 3.9, 2.8 Hz, 1H), 6.14 (dd, J ¼ 3.9, 1.5 Hz, 1H),
7.96e7.90 (m, 1H), 7.85e7.79 (m, 1H), 7.78e7.72 (m, 2H), 7.39e7.35
(m, 2H), 7.30 (dd, J ¼ 8.3,1.8 Hz,1H), 7.22e7.16 (m, 3H), 6.78e6.74 (m,
1H), 6.50 (d, J ¼ 3.8 Hz, 1H), 2.40 (s, 3H). 13C {1H} NMR (CDCl3,
2.36 (s, 3H), 2.30 (s, 3H). 13C {1H} NMR (CDCl3, 100 MHz):
d
140.9,
100 MHz): d 133.6, 132.1, 131.5, 131.2, 130.7, 130.7, 129.5, 129.2, 128.3,
139.6, 137.3, 134.2, 133.6, 131.9, 131.0, 130.7, 130.0, 129.3, 129.2,
128.9, 128.5, 127.7, 126.3, 125.6, 124.9, 117.1, 114.0, 113.1, 112.8, 106.2,
21.4, 21.2. MS (EI, 70 eV; m/z (relative intensity)): 427 (13), 347
(100), 331 (12), 268 (15), 165 (09), 127. HRMS calcd for C26H22NSe
(ESI-TOF, [M þ Hþ]), 428.0917, found 428.0902.
126.6, 124.0, 117.9, 114.2, 112.9, 112.6, 103.7, 21.1. MS (EI, 70 eV; m/z
(relative intensity)): 337 (25), 257(100), 180 (19), 168 (24), 127 (14).
HRMS calcd for C19H16NSe (ESI-TOF, [M þ Hþ]), 338.0448, found
338.0445.
4-phenyl-5-(phenylselanyl)pyrrolo[1,2-a]quinoline (2k). The prod-
uct was isolated by column chromatography (hexane as eluent) as a
grey solid. Yield: 0.078 g (78%); mp. 103e104 ꢀC. 1H NMR (CDCl3,
4-(4-methoxyphenyl)-7-methyl-5-(phenylselanyl)pyrrolo[1,2-a]
quinoline (2d). The product was isolated by column chromatog-
raphy (hexane as eluent) as a brown solid. Yield: 0.075 g (68%); mp.
400 MHz):
d
(ppm) 8.35 (dd, J ¼ 8.2, 1.2 Hz, 1H), 7.93 (dd, J ¼ 2.9,
162e165 ꢀC. 1H NMR (CDCl3, 400 MHz):
d
(ppm) 8.16 (s, 1H), 7.90
1.5 Hz, 1H), 7.88 (dd, J ¼ 8.3, 1.0 Hz, 1H), 7.47 (ddd, J ¼ 8.4, 7.2, 1.4 Hz,
1H), 7.39e7.36 (m, 3H), 7.35e7.31 (m, 2H), 7.25 (ddd, J ¼ 8.3, 7.2,
1.2 Hz, 1H), 7.13e7.09 (m, 2H), 7.07e7.03 (m, 3H), 6.73 (dd, J ¼ 3.9,
2.9 Hz, 1H), 6.16 (dd, J ¼ 3.9, 1.5 Hz, 1H). 13C {1H} NMR (CDCl3,
(dd, J ¼ 2.8, 1.5 Hz, 1H), 7.78 (d, J ¼ 8.4 Hz, 1H), 7.30 (dd, J ¼ 8.5,
1.5 Hz, 1H), 7.26 (d, J ¼ 2.0 Hz, 1H), 7.23 (d, J ¼ 3.8 Hz, 1H), 7.14e7.10
(m, 2H), 7.10e7.04 (m, 3H), 6.90 (d, J ¼ 8.7 Hz, 2H), 6.72 (dd, J ¼ 3.8,
5

A.M.S. Recchi, D.F. Back and G. Zeni
Tetrahedron 90 (2021) 132188
100 MHz):
d
140.8,139.6,133.9, 133.0,132.0, 130.9, 129.3, 129.0, 129.0,
70 eV; m/z (relative intensity)): 431(48), 351 (100), 335 (17), 321
(08), 255(20), 241(11), 167(13). HRMS calcd for C25H19FNSe (ESI-
TOF, [M þ Hþ]),432.0667, found 432.0648.
128.1, 127.9, 127.8, 125.6, 124.8, 124.2, 117.1, 114.1, 113.4, 113.2, 106.5.
MS (EI, 70 eV; m/z (relative intensity)): 399 (42), 397 (22), 319 (100),
241 (34), 159(15). HRMS calcd for C24H18NSe (ESI-TOF, [M þ Hþ]),
400.0604, found 400.0611.
7-chloro-4-phenyl-5-(phenylselanyl)pyrrolo[1,2-a]quinoline (2l).
The product was isolated by column chromatography (hexane as
eluent) as a yellow solid. Yield: 0.041 g (38%); mp. 120e120 ꢀC. 1H
7-methyl-4-phenyl-5-((3-(trifluoromethyl)phenyl)selanyl)pyrrolo
[1,2-a]quinolone (2r). The product was isolated by column chro-
matography (hexane as eluent) as a brown oil solid. Yield: 0.034 g
(28%); 1H NMR (CDCl3, 400 MHz):
d (ppm) 8.12 (s, 1H), 7.94 (s, 1H),
7.83 (d, J ¼ 8.4 Hz,1H), 7.44e7.31 (m, 6H), 7.31e7.24 (m, 2H), 7.21 (d,
NMR (CDCl3, 400 MHz):
d
(ppm) 8.38 (d, J ¼ 2.3 Hz, 1H), 7.86 (dd,
J ¼ 7.8 Hz, 1H), 7.15 (t, J ¼ 7.7 Hz, 1H), 6.74 (t, J ¼ 3.2 Hz, 1H), 6.16 (d,
J ¼ 2.9, 1.4 Hz, 1H), 7.78 (d, J ¼ 8.8 Hz, 1H), 7.44e7.35 (m, 4H),
J ¼ 3.3 Hz, 1H), 2.40 (s, 3H). 13C {1H} NMR (CDCl3, 100 MHz):
d 141.0,
7.31e7.27 (m, 2H), 7.12e7.02 (m, 5H), 6.73 (dd, J ¼ 3.9, 2.9 Hz, 1H),
139.4, 135.1, 133.9, 132.5, 131.7, 131.1 (q, J ¼ 32.3 Hz), 131.1, 130.2,
129.6,129.2,129.21,128.0,127.9,126.0 (q, J ¼ 4.0 Hz),124.5,123.7 (q,
J ¼ 272.7 Hz), 122.5 (q, J ¼ 3.7 Hz), 116.4, 114.2, 113.4, 113.0, 106.5,
21.2. MS (EI, 70 eV; m/z (relative intensity)): 481 (46), 401 (100),
336 (17), 255 (30), 241 (16), 127 (11). HRMS calcd for C26H19F3NSe
(ESI-TOF, [M þ Hþ]), 482.0635, found 482.0612.
6.17 (dd, J ¼ 3.9, 1.4 Hz, 1H). 13C {1H} NMR (CDCl3, 100 MHz):
d 141.9,
139.2,133.2,131.8,131.5,130.2,129.7,129.4,129.2,129.1,128.1,128.0,
127.9, 126.6, 126.0, 116.3, 115.6, 113.6, 113.6, 107.1. MS (EI, 70 eV; m/z
(relative intensity)): 437 (03), 433 (51), 353 (100), 317 (27), 275
(15), 240 (21), 213 (08), 158 (20). HRMS calcd for C24H17ClNSe (ESI-
TOF, [M þ Hþ]), 434.0215, found 434.0203.
5-(mesitylselanyl)-7-methyl-4-phenylpyrrolo[1,2-a]quinolone
(2s). The product was isolated by column chromatography (hexane
as eluent) as a black oil. Yield: 0.042 g (37%); 1H NMR (CDCl3,
7-methyl-4-phenyl-5-(p-tolylselanyl)pyrrolo[1,2-a]quinolone
(2m). The product was isolated by column chromatography (hex-
ane as eluent) as a yellow solid. Yield: 0.068 g (64%). mp.
400 MHz):
d
(ppm) 7.98 (s, 1H), 7.81 (s, 1H), 7.73 (d, J ¼ 8.4 Hz, 1H),
144e146 ꢀC. 1H NMR (CDCl3, 400 MHz):
d
(ppm) 8.19 (s, 1H), 7.86
7.32 (d, J ¼ 7.0 Hz, 3H), 7.23 (d, J ¼ 9.1 Hz, 1H), 7.19 (d, J ¼ 7.1 Hz, 2H),
6.65 (d, J ¼ 10.8 Hz, 3H), 5.98e5.92 (m, 1H), 2.34 (s, 3H), 2.16 (s, 3H),
(dd, J ¼ 2.7, 1.4 Hz, 1H), 7.74 (d, J ¼ 8.4 Hz, 1H), 7.39e7.24 (m, 6H),
7.01 (d, J ¼ 8.2 Hz, 2H), 6.87 (d, J ¼ 7.9 Hz, 2H), 6.69 (dd, J ¼ 3.9,
2.11 (s, 6H). 13C {1H} NMR (CDCl3, 100 MHz):
d 141.2, 139.3, 137.2,
2.8 Hz, 1H), 6.12 (dd, J ¼ 3.8, 1.3 Hz, 1H), 2.36 (s, 3H), 2.19 (s, 3H). 13
C
137.0, 133.0, 132.4, 130.7, 130.2, 129.6, 129.2, 129.0, 128.6, 127.8,
127.5, 124.8, 119.6, 114.0, 112.5, 112.4, 104.3, 23.8, 21.1, 20.8. MS (EI,
70 eV; m/z (relative intensity)): 455 (23), 257 (100), 241 (09). HRMS
calcd for C28H26NSe (ESI-TOF, [M þ Hþ]), 456.1230, found 456.1223.
5-(butylselanyl)-7-methyl-4-phenylpyrrolo[1,2-a]quinoline (2t).
The product was isolated by column chromatography (hexane as
eluent) as a brown oil. Yield: 0.066 g (67%); 1H NMR (CDCl3,
{1H} NMR (CDCl3, 100 MHz):
d 140.6, 139.9, 135.5, 133.6, 132.0, 131.1,
130.9,130.1, 129.8,129.5, 129.4,129.3,127.8, 127.7, 125.0,117.6, 114.0,
113.1, 112.9, 106.1, 21.2, 20.9. MS (EI, 70 eV; m/z (relative intensity)):
427 (41), 347 (100), 331 (12), 255 (15), 165 (16). HRMS calcd for
C
26H22NSe (ESI-TOF, [M þ Hþ]), 428.0917, found 428.0915.
5-((4-chlorophenyl)selanyl)-7-methyl-4-phenylpyrrolo[1,2-a]
quinoline (2o). The product was isolated by column chromatog-
400 MHz):
d
(ppm) 8.36e8.34 (m, 1H), 7.83 (dd, J ¼ 2.8, 1.5 Hz, 1H),
raphy (hexane as eluent) as a yellow solid. Yield: 0.067 g (60%); mp.
7.75 (d, J ¼ 8.4 Hz, 1H), 7.47e7.41 (m, 3H), 7.41e7.37 (m, 2H),
7.33e7.29 (m, 1H), 6.66 (dd, J ¼ 3.8, 2.8 Hz, 1H), 6.06 (dd, J ¼ 3.8,
1.5 Hz, 1H), 2.54 (d, J ¼ 7.3 Hz, 2H), 2.50 (s, 3H), 1.41 (qt, J ¼ 7.3 Hz,
2H), 1.19 (sext, J ¼ 7.3 Hz, 2H), 0.75 (t, J ¼ 7.3 Hz, 3H). 13C {1H} NMR
141e143 ꢀC. 1H NMR (CDCl3, 400 MHz):
d (ppm) 8.12e8.10 (m, 1H),
7.89 (dd, J ¼ 2.9, 1.5 Hz, 1H), 7.78 (d, J ¼ 8.4 Hz, 1H), 7.40e7.35 (m,
3H), 7.32e7.26 (m, 3H), 7.02 (d, J ¼ 0.6 Hz, 4H), 6.71 (dd, J ¼ 3.9,
2.8 Hz, 1H), 6.14 (dd, J ¼ 3.9, 1.5 Hz, 1H), 2.38 (s, 3H). 13C {1H} NMR
(CDCl3, 100 MHz):
d 140.1, 139.7, 133.4, 132.0, 131.0, 130.7, 129.9,
(CDCl3, 100 MHz):
d
140.9, 139.6, 133.8, 132.2, 131.7, 131.6, 131.4,
129.0, 127.8, 127.6, 125.4, 118.0, 114.1, 112.7, 112.5, 105.2, 32.0, 29.1,
131.1, 130.4, 129.5, 129.2, 129.0, 127.9, 127.9, 124.6, 116.7, 114.1, 113.3,
22.7, 21.3, 13.4. 77Se NMR (77 MHz, in CDCl3 with diphenyl dis-
113.0, 106.4, 21.2. 77Se NMR (77 MHz, in CDCl3 with diphenyl dis-
elenide as external reference) d(ppm) 168.2. MS (EI, 70 eV; m/z
elenide as external reference)
d
(ppm) 295.8.MS (EI, 70 eV; m/z
(relative intensity)): 393(69), 390 (38), 335 (100), 332 (28), 320
(22), 257 (63), 254 (19) 241 (15). HRMS calcd for C23H24NSe (ESI-
TOF, [M þ Hþ]), 394.1074, found 394.1069.
(relative intensity)): 447 (51), 367 (100), 331 (24), 255 (28), 226
(06), 158 (27). HRMS calcd for C25H19ClNSe (ESI-TOF, [M þ Hþ]),
448.0371, found 448.0363.
5-(butylselanyl)-4-(4-methoxyphenyl)-7-methylpyrrolo[1,2-a]
quinoline (2u). The product was isolated by column chromatog-
raphy (hexane as eluent) as a brown oil. Yield: 0.084 g (79%). 1H
5-((4-chlorophenyl)selanyl)-7-methyl-4-(p-tolyl)pyrrolo[1,2-a]
quinolone (2p). The product was isolated by column chromatog-
raphy (hexane as eluent) as a brown solid. Yield: 0.072 g (62%); mp.
NMR (CDCl3, 400 MHz):
d
(ppm) 8.36e8.31 (m,1H), 7.81 (dd, J ¼ 2.8,
162e166 ꢀC. 1H NMR (CDCl3, 400 MHz):
d
(ppm) 8.10e8.07 (m, 1H),
1.5 Hz, 1H), 7.73 (d, J ¼ 8.4 Hz, 1H), 7.34e7.30 (m, 2H), 7.28 (dd,
J ¼ 8.4, 1.6 Hz, 1H), 7.00e6.96 (m, 2H), 6.66 (dd, J ¼ 3.8, 2.8 Hz, 1H),
6.10 (dd, J ¼ 3.8, 1.5 Hz, 1H), 3.85 (s, 3H), 2.53 (d, J ¼ 7.3 Hz, 2H), 2.49
(s, 3H), 1.39 (qt, J ¼ 7.3 Hz, 2H), 1.19 (sext, J ¼ 7.3 Hz, 2H), 0.75 (t,
7.90 (dd, J ¼ 2.7, 1.4 Hz, 1H), 7.78 (d, J ¼ 8.4 Hz, 1H), 7.30 (dd, J ¼ 8.5,
1.7 Hz,1H), 7.19 (s, 4H), 7.03 (s, 4H), 6.72 (dd, J ¼ 3.8, 2.9 Hz,1H), 6.17
(dd, J ¼ 3.9, 1.4 Hz, 1H), 2.40 (s, 3H), 2.37 (s, 3H). 13C {1H} NMR
(CDCl3, 100 MHz):
d
141.0, 137.6, 136.7, 133.8, 132.3, 131.9, 131.6,
J ¼ 7.3 Hz, 3H). 13C {1H}NMR (CDCl3, 100 MHz):
d 159.0, 139.2, 133.3,
131.1, 130.4, 130.3, 129.4, 129.1, 129.0, 128.6, 124.6, 116.6, 114.1, 113.3,
113.0, 106.5, 21.4, 21.2. MS (EI, 70 eV; m/z (relative intensity)): 461
(56), 383 (37), 381 (100), 345 (18), 268(14),165 (18). HRMS calcd for
132.5, 132.1, 131.0, 130.8, 130.6, 128.9, 125.3, 118.1, 114.1, 113.2, 112.6,
112.5, 105.1, 55.1, 31.9, 29.0, 22.7, 21.2, 13.4. MS (EI, 70 eV; m/z
(relative intensity)): 423 (74), 366 (100), 335 (10), 323 (24), 287
(52), 242 (36), 207 (10), 161 (07), 120 (07). HRMS calcd for
C
26H21ClNSe (ESI-TOF, [M þ Hþ]), 462.0528, found 462.0537.
5-((4-fluorophenyl)selanyl)-7-methyl-4-phenylpyrrolo[1,2-a]qui-
C
24H26NOSe (ESI-TOF, [M þ Hþ]), 424.1180, found 424.1187.
nolone (2q). The product was isolated by column chromatography
7-methyl-4-phenyl-5-(phenyltellanyl)pyrrolo[1,2-a]quinolone
(hexane as eluent) as a yellow oil. Yield: 0.069 g (64%). 1H NMR
(2w). The product was isolated by column chromatography (hexane
as eluent) as a green solid. Yield: 0.097 g (84%); mp. 98e102 ꢀC. 1H
NMR (CDCl3, 400 MHz): 8.18 (s, 1H), 7.88e7.85 (m, 1H), 7.73 (d,
J ¼ 8.4 Hz,1H), 7.38 (d, J ¼ 6.5 Hz, 3H), 7.32 (d, J ¼ 7.1 Hz, 2H), 7.27 (t,
J ¼ 6.4 Hz, 3H), 7.08 (t, J ¼ 7.2 Hz, 1H), 7.01 (t, J ¼ 7.3 Hz, 2H),
6.71e6.68 (m, 1H), 6.09e6.07 (m, 1H), 2.36 (s, 3H). 13C {1H} NMR
(CDCl3, 400 MHz):
d (ppm) d 8.17 (s, 1H), 7.87 (s, 1H), 7.76 (d,
J ¼ 8.4 Hz, 1H), 7.40e7.33 (m, 3H), 7.32e7.24 (m, 3H), 7.06 (dd,
J ¼ 8.2, 5.6 Hz, 2H), 6.76 (t, J ¼ 8.7 Hz, 2H), 6.70 (t, J ¼ 3.1 Hz, 1H),
6.12 (d, J ¼ 3.7 Hz, 1H), 2.38 (s, 3H). 13C {1H} NMR (CDCl3, 100 MHz):
161.6 (d, J ¼ 245.6 Hz), 140.6, 139.6, 133.7, 131.8, 131.4 (d, J ¼ 7.9 Hz),
131.1, 130.5, 129.4, 128.2, 128.3 (d, J ¼ 3.4 Hz), 127.9, 127.8, 124.7,
117.6, 116.0 (d, J ¼ 21.9 Hz), 114.1, 113.2, 113.0, 106.3, 21.2. MS (EI,
(CDCl3, 100 MHz):
d 143.6, 143.1, 135.4, 135.1, 133.7, 131.5, 131.3,
130.4, 129.3, 129.2, 127.9, 127.8, 126.7, 126.0, 117.3, 114.1, 112.9, 112.8,
6

A.M.S. Recchi, D.F. Back and G. Zeni
Tetrahedron 90 (2021) 132188
(c) P. Maity, B.C. Ranu, Adv. Synth. Catal. 359 (2017) 4369.
[5] (a) A. Gupta, B.L. Flynn, J. Org. Chem. 81 (2016) 4012;
109.4, 106.1, 21.1. MS (EI, 70 eV; m/z (relative intensity)): 463(37),
384(15), 333(100), 255(44), 241(32), 158(10). HRMS calcd for
ꢀ
~
(b) A. Monleon, G. Blay, L.R. Domingo, M.C. Munoz, J.R. Pedro, Eur. J. Org Chem.
2015 (2015) 1020;
(c) A.S. Dillon, B.L. Flynn, Org. Lett. 22 (2020) 2987;
(d) L. Xing, Y. Zhang, B. Li, Y. Du, Org. Lett. 21 (2019) 3620.
[6] (a) A.D. Sonawane, R. Sonawane, M. Ninomiya, M. Koketsu, Adv. Synth. Catal.
362 (2020) 3485;
C
25H20NTe (ESI-TOF, [M þ Hþ]), 464.0658, found 464.0655.
Declaration of competing interest
(b) K.M.N. Win, A.D. Sonawane, M. Koketsu, Org. Biomol. Chem. 17 (2019)
9039.
[7] X. Zhang, S. Sarkar, R.C. Larock, J. Org. Chem. 71 (2006) 236.
[8] (a) Z.J. Yang, B.L. Hu, C.L. Deng, X.G. Zhang, Adv. Synth. Catal. 356 (2014) 1962;
(b) H.A. Du, R.Y. Tang, C.L. Deng, Y. Liu, J.H. Li, X.G. Zhang, Adv. Synth. Catal.
353 (2011) 2739;
The authors declare that they have no known competing
financial interests or personal relationships that could have
appeared to influence the work reported in this paper.
Acknowledgments
(c) X.-H. Gao, P.-C. Qian, X.-G. Zhang, C.-L. Deng, Synlett 27 (2016) 1110;
(d) H.-Y. Tu, Y.-R. Liu, J.-J. Chu, B.-L. Hu, X.-G. Zhang, J. Org. Chem. 79 (2014)
9907;
We are grateful to FAPERGS, CAPES, and CNPq for financial
support. CNPq and CAPES are also acknowledged for the fellow-
ships (A. M. R. and G. Z.).
(e) A.D. Sonawane, Y. Kubota, M. Koketsu, J. Org. Chem. 84 (2019) 8602.
[9] (a) B. Banerjee, M. Koketsu, Coord. Chem. Rev. 339 (2017) 104;
(b) D.R. Garud, M. Koketsu, H. Ishihara, Molecules 12 (2007) 504;
(c) A.D. Sonawane, M. Koketsu, Curr. Org. Chem. 23 (2019) 3206;
(d) N. Taniguchi, Tetrahedron 72 (2016) 5818;
Supplementary data
(e) N. Taniguchi, J. Org. Chem. 80 (2015) 1764;
(f) N. Taniguchi, Tetrahedron 68 (2012) 10510;
(g) N. Taniguchi, Tetrahedron 65 (2009) 2782;
(h) N. Taniguchi, J. Org. Chem. 72 (2007) 1241;
Experimental procedures, characterization data, and copies of
the 1H NMR and 13C NMR spectra for the products are available.
Supplementary data associated with this article can be found in the
online version.
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