Reaction of selenoamide dianions with thio- and selenoformamides leading to the formation of 5-aminoselenazoles: Photophysical and electrochemical properties

Article abstract of DOI:10.1021/jo500499g

5-Amino-2-selenazolines were synthesized by reacting selenoamide dianions generated from secondary selenoamides and BuLi with tertiary thio- and selenoformamides followed by treatment with iodine. The resulting 5-amino-2-selenazolines were further oxidize

Full text of DOI:10.1021/jo500499g

Article
pubs.acs.org/joc
Reaction of Selenoamide Dianions with Thio- and Selenoformamides
Leading to the Formation of 5‑Aminoselenazoles: Photophysical and
Electrochemical Properties
Toshiaki Murai,*,†,‡ Kirara Yamaguchi,† Fumihiko Hori,† and Toshifumi Maruyama†
†Department of Chemistry and Biomolecular Science, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193, Japan
‡JST, ACT-C, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
S
* Supporting Information
ABSTRACT: 5-Amino-2-selenazolines were synthesized by react-
ing selenoamide dianions generated from secondary selenoamides
and BuLi with tertiary thio- and selenoformamides followed by
treatment with iodine. The resulting 5-amino-2-selenazolines were
further oxidized with iodine to give 5-aminoselenazoles in moderate
to good yields. The general tendencies in the 77Se NMR spectra of
the starting selenoamides, 5-amino-2-selenazolines, and 5-amino-
selenazoles were determined. The chemical shifts of these
compounds were highly influenced by the skeletons involving the
selenium atom as well as the substituents on the carbon atoms of
each skeleton. The molecular structures of 5-aminoselenazoles were
clarified by X-ray analyses, and their electronic structures were elucidated by DFT calculations. Finally, UV−vis and fluorescence
spectroscopy and cyclic voltammetry (CV) of 5-aminoselenazoles were performed, and their properties are discussed in relation
to the substituents on the selenazole rings.
pared for the first time in our studies on chalcogenocarbonyl13
INTRODUCTION
■
and chalcogenophosphoryl compounds.14 In this reaction,
2-Selenazolines1 and selenazoles2,3 are an interesting class of
thioamide dianions were generated from secondary thioamides
and treated with thioformamides (Scheme 1).
selenium- and nitrogen-containing heterocycles in view of their
unique properties, although they have received less attention
than other selenium-containing heterocycles4 such as seleno-
phenes5 and ebselen.6 It is partly due to the lack of the diversity
Scheme 1. Synthesis of 5-Aminothiazoles
of the substitution patterns in the known derivatives. In fact,
selenazole cores possess three carbon atoms, to which a wide
range of substituents can be introduced. For example,
compounds with amino groups at the 2-positions of selenazoles
I have been studied to some extent7 (Chart 1).
Chart 1. A Range of Aminoselenazoles
Notably, 5-N,N-diarylaminothiazoles have been shown to
possess strong fluorescence properties and are considered to be
candidates for use in thiazole-based organic light-emitting
diodes (OLED) and fluorescent chemosensors.15 In contrast, to
the best of our knowledge, only metal complexes have been
In contrast, little is known about those aminoselenazoles with
amino groups at the 4- and 5-positions of general structures II8
examined in studies on fluorescence properties of selenazole-
and III. In particular, to the best of our knowledge, only one
containing compounds.16 Our synthetic studies on selenoa-
example of a 5-N,N-disubstituted aminoselenazole has been
mides have shown that selenoamide dianions17 similar to
thioamide dianions can be generated. We report here the
reactions of selenoamide dianions with thio- and selenoforma-
reported.9,10 One method that is frequently used for the
synthesis of selenazoles is the condensation reaction of primary
selenoureas and selenoamides with α-halo carbonyl com-
pounds.11 However, with these methods, amino groups cannot
be introduced at the 5-positions of selenazoles. Very recently,
sulfur isologues12 of 5-N,N-diarylaminoselenazoles were pre-
Received: March 3, 2014
Published: April 28, 2014
© 2014 American Chemical Society
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a
Table 1. Synthesis of 5-Amino-2-selenazolines 4−9
a
The reaction was carried out as follows, unless otherwise noted: To a solution of selenoamide 1 (1.0 equiv) in THF (2.0 mL) was slowly added n-
BuLi (2.0 equiv), and the mixture was stirred. To this was added thio- or selenoformamide 3 (1.0 equiv), and the mixture was stirred. To this was
b
added iodine (1.0 or 2.0 equiv), and the mixture was stirred. Isolated yields.
mides leading to the formation of unprecedented 5-amino-
selenazoles. The photophysical and electrochemical properties
of the obtained compounds are also described along with the
results of computational studies.
observed. The trans stereochemistry of 4−6 was determined by
comparing their 1H NMR spectra with those of the
corresponding 2-thiazolines.12 Additionally, the J3 coupling
constants (J3 = 1.4−4.5 Hz) between the protons on two
carbon atoms adjacent to NR2 and NC groups supported the
trans configuration. N,N-Diphenyl thioformamide (3b) was
then treated with selenoamide dianion 2a, but the reaction gave
a complex mixture that included the 2-selenazoline and 2-
thiazoline (entry 4). Instead, the reaction of selenoamide
dianion 2a with N,N-diphenyl selenoformamide (3c) was
carried out to successfully give the desired 2-seleanazoline 7
with high purity in moderate yield (entry 5). The introduction
of 2-pyridyl and biphenyl groups at the 2-position of the 2-
selenazoline ring was achieved with the use of the
corresponding secondary selenoamides 1d and 1e (entries 6
and 7). In all cases, the formation of cis isomers was not
observed probably because of the steric hindrance of the
substituents at the 4- and 5-positions.
RESULTS AND DISCUSSION
■
Synthesis. Initially, N-benzyl aromatic selenoamides were
prepared by the selenation reaction of the corresponding
amides with Woollins reagent18 and/or the combination of
HSiCl3/Se/amines developed by us19 in moderate to high
yields. N-Benzyl selenobenzamide (1a) was then treated with
BuLi at 0 °C for 10 min (Table 1). The reaction mixture turned
deep purple, which was indicative of the formation of
selenoamide dianion 2a. To the reaction mixture was added
N,N-dimethyl thioformamide (3a), and the mixture was stirred
at the same temperature for 1 h. Iodine was added to the
reaction mixture, and stirring was continued for 2 h to give the
first example of 5-amino-2-selenazoline 4 in 91% yield (entry
1). A similar reaction was carried out with secondary
selenoamides 1b and 1c to give the corresponding 2-
selenazolines 5 and 6 in moderate yields (entries 2 and 3).
In all cases, products that contained a sulfur atom were not
Further oxidation of the resulting 2-selenazolines 4−9 with
iodine was carried out to give the corresponding selenazoles
10−15 in low to good yields (Table 2). The completion of the
reaction was monitored by TLC, and the use of 2 equiv of I2
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a
Table 2. Synthesis of 5-Aminoselenazoles 10−15
Figure 2. Structures of selenazoyl and thiazoly moieties of 13 and 16.
To further compare the structures of the 5-aminoselenazoles,
DFT calculations of selenazoles 10 and 13 were carried out
with the B3LYP/6-31G(d) basis set.20 The calculated molecular
structures are shown in Figure 3. For 10, almost no deviation
a
The reaction was carried out as follows, unless otherwise noted: To a
solution of selenazoline 4−9 (1.0 equiv) in THF was added iodine,
b
and the mixture was stirred. Isolated yields.
facilitated the reaction. In all cases, when the starting 2-
selenazolines were completely consumed, the reaction mixtures
were subjected to aqueous workup. In some cases, during this
procedure, the products partially decomposed, and the isolated
yields of the products were highly dependent on the
substituents. Nevertheless, once they were isolated, they
could be stored at least within 1 month in a refrigerator.
Molecular Structures. The structures of 5-aminoselena-
zoles were unequivocally determined by X-ray structure
analyses. An ORTEP drawing of 13 is shown in Figure 1.
Figure 3. Molecular structures of 10 and 13 derived from DFT
calculations (B3LYP/6-31G(d)).
was observed for the two phenyl groups at the 2- and 4-
positions and the selenazole ring. Although the calculated
dihedral angle for Se−C1−N1−C2 of 13 did not match the
results of X-ray analyses, the deviation of diphenylamino group
was confirmed. Likewise, even for 10, the amino group at the 5-
position was deviated, with the dihedral angle of 65.4° for Se−
C1−N1−C2.
77Se NMR Spectroscopy. The 77Se nucleus is NMR active.
Indeed, it is three times more sensitive than the 13C nucleus,
and the chemical shifts are highly influenced by the
fundamental skeletons of organoselenium compounds and the
substituents close to the selenium atom.21 These data for the
starting selenoamides, 2-selenazolines, and 5-aminoselenazoles
are listed in Chart 2. The signals of selenoamides 1 were
observed in the region from 517 to 638 ppm, and replacement
of the phenyl group with a 2-pyridyl group at the 2-position
shielded the signal by 120 ppm (see 1a and 1d). The signals of
5-amino-2-selenazolines are found from 346 to 541 ppm,
whereas those of 5-aminoselenazoles range from 629 to 707
ppm. Unlike the effect of the 2-pyridyl group in selenoamide
1d, introduction of a 2-pyridyl group at the 2 positions in 2-
selenazolyl and selenazole rings deshielded the signals (see 1d,
8, and 14). The signals of 5-amino-2-selenazolines and 5-
aminoselenazoles with an N,N-dimethylamino group are in
higher field regions than those with an N,N-diphenylamino
Figure 1. ORTEP drawing of 5-aminoselenazole 13.
Phenyl groups at the 2- and 4-positions are located within
nearly the same plane as the selenazole ring, with dihedral
angles of −22.85° and 18.54° for C7−C2−C1−Se1 and N1−
C21−C27−C26, respectively, although they are more deviated
than those in the corresponding thiazole 16. In contrast, the
diphenylamino group and selenazole ring are highly deviated,
with a dihedral angle of 60.86° for Se1−C8−N2−C9. Figure 2
shows a comparison of the bond lengths and bond angles of the
selenazoyl moiety of 13 and those of its sulfur isologue 16. Due
to the longer ionic radius of the selenium atom, the bond
lengths of the C−Se bonds in 13 are ca. 1.09 times longer than
the C−S bonds in the corresponding thiazole 16. The bond
angle of C−Se−C in 13 was more acute than that of C−S−C in
16.
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Chart 2. 77Se NMR Spectra of Selenoamides, 2-Selenazolines, and Selenazoles
group, and the signals for 5-amino-2-selenazolines are highly
sensitive to the substituents on the nitrogen atom.
The coupling constants between the carbon and selenium
atoms are also informative. Those of selenoamides, selenazo-
lines, and selenazoles (Chart 3) were mainly dependent on the
12 were only slightly fluorescent. In contrast, the introduction
of phenyl groups to the nitrogen atom at the 5-position
enhanced the fluorescence quantum yields of selenazoles 13−
15. Replacement of the selenium atom in 14 with a sulfur atom
as in 17 shifted the absorption and emission spectra to shorter
wavelengths by ca. 10 nm, and thiazole 17 was more
fluorescent.
Chart 3. J1 Coupling Constants of CSe and C−Se Bonds
of Selenoamides, 2-Selenazolines, and Selenazoles
Theoretical Calculations. To gain further insights into the
electronic properties, DFT and time-dependent (TD) DFT
calculations were carried out for compounds 10−15 and 17.
The results at the TD-B3LYP/6-31G(d)//B3LYP/6-31(d)
level of theory with the ground-state geometries are shown in
Tables 3 and 4 and Figure 5. The HOMOs of N,N-
dimethylaminoselenazoles 10−12 are delocalized mainly at
the aromatic ring at the 4-positions and selenazole rings,
whereas those of N,N-diphenylaminoselenazoles 13−15 are
localized on the N,N-diphenyl amino groups. In contrast, the
LUMOs of all the selenazoles are delocalized on the selenazole
rings and the aromatic rings at the 2-positions. The calculated
λmax values of 10−12 are close to the observed values. In
contrast, those of 13−15 were red-shifted by 20−32 nm
compared with the observed values, although the general
tendencies of the absorption wavelengths for the observed and
calculated values were identical. The absorption maxima in the
low-energy region of all the selenazoles 10−15 were attributed
to the transitions from the HOMO to the LUMO.
molecular skeletons to which the selenium atom was
introduced. For selenoamides, J1
values were ca. 210 Hz,
CSe
whereas in 2-selenazolines and selenazoles, J1
ranged from 125 to 131 Hz.
values
NC−Se
Electronic Absorption and Fluorescence Spectrosco-
py. The photophysical properties of selenazoles 10−15 and
thiazole 17 are summarized in Table 3. The absorption spectra
and fluorescence spectra of 13−15 and 17 are shown in Figure
4. In the UV−visible spectra, the longest wavelengths of
compounds 10 and 11 were observed at around 333 nm,
whereas those of 12−15 were shifted to longer wavelengths.
Those of 5-aminoselenazoles 13−15 appeared at 395 11 nm.
These results implied that the substituents at not only the 2-
positions of selenazoles but also on the nitrogen atom at the 5-
position strongly influenced the absorption spectra. In a series
of N,N-diphenylaminoselenazoles 13−15, bathochromic shifts
of the longest wavelengths and absorption onset (λonset) were
observed when the phenyl group at the 2-position in 13 was
replaced with a 2-pyridyl group as in 14. The fluorescence
spectra were also dependent on the substituents and were
observed from 438 to 498 nm. N,N-Dimethyl selenazoles 10−
Cyclic Voltammograms. To experimentally estimate
energy levels of HOMO, electrochemical measurements were
carried out on selenazoles 13−15 and thiazole 17. In all cases,
reversible one-electron oxidation waves were observed at
around E1/2 = +0.59 eV (vs Fc/Fc+([nBu4N]ClO4/MeCN).
ox
Replacement of the sulfur atom in 17 with a selenium atom
slightly reduced the oxidation potential (14 vs 17).
Finally, the energy levels of HOMO and LUMO derived
from absorption and fluorescence spectroscopy, cyclic
voltammetry, and DFT calculations are compared in Table 4.
The experimental values of HOMO−LUMO band gaps derived
from λonset and of the energy levels of HOMO derived from
cyclic voltammograms were comparable to those obtained from
TD-DFT and DFT calculations.
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Table 3. Photophysical Properties and DFT Calculation of Selenazoles 10−15 and Thiazole 17
a
b
In CHCl3, excited at 350 nm, c = 10−5 M. TD-DFT (TD/B3LYP/6-31G(d)) calculations were carried out with the use of optimized structures at
B3LYP/6-31G(d).
aminoselenazoles. On the basis of X-ray analyses and DFT
calculations, the 5-amino groups on 5-aminoselenazoles were
found to be highly deviated from the plane of the selenazolyl
ring. The photophysical properties of 5-aminoselenazoles were
elucidated by UV−visible and fluorescence spectroscopy. In the
cyclic voltammograms of 5-N,N-diphenylaminoselenazoles,
reversible one-electron oxidation was observed. The exper-
imental and calculated values of the HOMO−LUMO band
gaps and the energy levels of HOMO are self-consistent.
Further studies on the reactivity of chalcogenoamide dianions
and the properties of 5-aminochalcogenazoles and the
application of their fluorescent properties are in progress.
EXPERIMENTAL SECTION
■
General Remarks. All reagents and solvents were purchased from
commercial sources and were used without purification. 1H NMR and
13C NMR spectra were measured with tetramethylsilane and CDCl3 as
an internal standard, respectively. 77Se NMR spectra were measured
with Me2Se as an external standard. All experiments were carried out
under an argon atmosphere in dried glassware.
Figure 4. UV and fluorescent spectra of 13−15 and 17.
CONCLUSION
■
N,N-Disubstituted selenazoles were synthesized, and their
properties were demonstrated. The addition reaction of
selenoamide dianions to thio- and selenoformamides followed
by treatment with iodine gave 5-amino-2-selenazolines. Their
further oxidation with iodine gave the corresponding 5-
N-(Phenylmethyl)benzenecarboselenoamide (1a).22 To a solution
of N-phenylmethyl phenylamide (1.06 g, 5.0 mmol) in toluene (5.0
mL) were added elemental selenium (0.43 g, 5.5 mmol), dibenzyl-
amine (1.06 mL, 5.5 mmol), and trichlorosilane (0.52 mL, 5.5 mmol),
and the mixture was stirred for 3 h at 115 °C. The combined organic
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Table 4. Electrochemical Properties and HOMO−LUMO Energy Gaps of Selenazoles 13−15 and Thiazole 17
a
b
λonset are taken as the intersection of spectrum baseline and a tangent line to edge of the absorption band. HOMO−LUMO energy gaps calculated
c
d
from λonset. HOMO−LUMO energy gaps calculated from TD-DFT (TD/B3LYP/6-31G(d)) calculations. V vs Fc/Fc+ in acetonitrile containing
tetrabutylammonium perchlorate (Bu4NClO4, 0.1 M) as supporting electrolyte at a scan rate of 100 mV/s. Counter and working electrodes were
e
f
made of Pt. Halfwave oxidation potentials are shown. EHOMO (eV) = −4.8 − E1/2ox, ref 23. EHOMO (eV) calculated from DFT calculations (B3LYP/
6-31G(d)).
phase was washed with a saturated aqueous solution of NaOH and
NaCl, dried over MgSO4, and concentrated under reduced pressure.
The crude material was purified by column chromatography (SiO2,
hexane:EtOAc = 10:1) to give 1a (0.52 g, 85%). 1H NMR (400 MHz,
CDCl3) δ 4.99 (d, J = 5.4 Hz, 2H), 7.33−7.48 (m, 8H), 7.73−7.76 (m,
2H), 8.20 (br, 1H).
CDCl3) δ 517.9; MS (EI) m/z 276 (M+); HRMS (EI) Calcd for
C13H12N2Se: 276.0166; found: 276.0164.
N-(Phenylmethyl)[1,1′-biphenyl]-4-carboselenoamide (1e). Ac-
cording to the synthetic procedure of 1c, compound 1e was prepared.
The crude material was purified by column chromatography (SiO2,
dichlorometane) to give 1e (0.26 g, 75%) as an orange solid (mp
174−177 °C): IR (KBr) 3276, 3026, 2923, 1601, 1528, 1512, 1483,
4-Methoxy-N-(phenylmethyl)benzenecarboselenoamide (1b).22
According to the synthetic procedure of 1a, compound 1b was
prepared, and the crude material was purified by column
chromatography (SiO2, hexane:EtOAc = 10:1) to give 1b (0.52 g,
85%) as an orange liquid. 1H NMR (400 MHz, CDCl3) δ 5.00 (d, J =
4.9 Hz, 2H), 6.84 (d, J = 8.8 Hz, 2H), 7.25−7.40 (m, 8H), 7.77 (d, J =
8.8 Hz, 2H), 8.14 (br, 1H).
1
1403, 1321, 1194, 1063, 911, 891, 841, 767, 752, 696, 687 cm−1; H
NMR (400 MHz, CDCl3) δ 5.02 (d, J = 5.4 Hz, 2H), 7.36−7.47 (m,
8H), 7.57−7.60 (m, 4H), 7.85 (d, J = 8.8 Hz, 2H), 8.20 (br, 1H); 13C
NMR (100 MHz, CDCl3) δ 54.7, 127.0, 127.1, 127.2, 128.0, 128.4,
128.5, 128.9, 129.1, 135.4, 139.8, 143.2, 143.9, 203.7; 77Se NMR (76
MHz, CDCl3) δ 637.3; MS (EI) m/z 351 (M+); HRMS (EI) Calcd for
C20H17NSe: 351.0526; found: 351.0523.
General Procedure for the Preparation of 2-Selenazolines. To a
solution of selenoamide (1 equiv) in THF was added slowly 1.25 M
solution of n-butyllithium in n-hexane (2 equiv) at 0 °C, and the
mixture was stirred for 10 min at this temperature. To this was added
thio- or selenoformamide (1 equiv) at 0 °C, and the mixture was
stirred for 0.5−1.3 h at this temperature. To this was added iodine (1−
2 equiv) at 0 °C, and the mixture was stirred for 2 h at 0 °C. The
resulting mixture was poured into a saturated aqueous solution of
Na2S2O3 and extracted with Et2O. The organic layer was dried over
MgSO4 and concentrated in vacuo. The residue was purified by
column chromatography (SiO2) to give the corresponding 2-
selenazolines.
(4R*,5S*)-4,5-Dihydro-N,N-dimethyl-2,4-diphenyl-5-selenazol-
amine (4). According to the general procedure for selenazolines,
compound 4 was prepared. The crude material was purified by column
chromatography (SiO2, hexane:EtOAc:Et3N = 7:1:0.01) to give 4
(0.15 g, 91%) as an orange solid (mp 97−98 °C): IR (KBr) 2952,
2823, 1599, 1448 cm−1; 1H NMR (400 MHz, CDCl3) δ 2.11 (s, 6H),
5.61 (d, J = 2.0 Hz, 1H), 5.67 (d, J = 2.0 Hz, 1H), 7.16−7.27 (m, 5H),
7.31−7.40 (m, 3H), 7.89 (d, J = 6.8 Hz, 2H); 13C NMR (100 MHz,
CDCl3) δ 41.4, 86.5, 95.9, 126.3, 127.6, 128.5, 128.6, 129.1, 131.1,
136.1, 139.2, 168.3; 77Se NMR (76 MHz, CDCl3) δ 291.2; MS (EI)
m/z 330 (M+); HRMS (EI) Calcd for C17H18N2Se (M+) 330.0635,
found: 330.0631.
4-Chloro-N-(phenylmethyl)benzenecarboselenoamide (1c). To a
solution of Woollins reagent (0.09 g, 0.17 mmol) in toluene (0.5 mL)
was added N-phenylmethyl 4-chlorobenzamide (0.07 g, 0.27 mmol),
and the mixture was stirred for 2 h at 130 °C. The resulting mixture
was concentrated in vacuo. The crude material was purified by column
chromatography (SiO2, dichloromethane) to give 1c (0.06 g, 71%) as
an orange liquid. IR (KBr) 3084, 3061, 3025, 2920, 2836, 1949, 1877,
1811, 1602, 1495, 1453, 1254, 1174, 1027, 834, 747, 735, 699 cm−1;
1H NMR (400 MHz, CDCl3) δ 4.90 (d, J = 5.4 Hz, 2H), 7.11−7.35
(m, 7H), 7.62 (d, J = 8.8 Hz, 1H), 7.74−7.76 (m, 1H), 8.07 (br, 1H);
13C NMR (100 MHz, CDCl3) δ 52.9, 113.4, 126.7, 127.9, 128.2, 128.3,
128.6, 128.7, 140.0, 202.8; 77Se NMR (76 MHz, CDCl3) δ 578.7; MS
(EI) m/z 308 (M+); HRMS (EI) Calcd for C14H12ClNSe: 308.9823;
found: 308.9843.
N-(Phenylmethyl)-2-pyridinecarboselenoamide (1d). According
to the synthetic procedure of 1c, compound 1d was prepared. The
crude material was purified by column chromatography (SiO2,
dichloromethane) to give 1d (0.09 g, 61%) as an orange solid. (mp
59−61 °C); IR (KBr) 3217, 3065, 3044, 3024, 2924, 1519, 1454, 1434,
1373, 1329, 1053, 1044, 913, 743, 733, 695, 686 cm−1; 1H NMR (400
MHz, CDCl3) δ 5.04 (d, J = 5.4 Hz, 2H), 7.35−7.47 (m, 6H), 7.82−
7.86 (m, 1H), 8.43 (d, J = 4.4 Hz, 1H), 8.82 (d, J = 7.8 Hz, 1H), 10.97
(br, 1H); 13C NMR (100 MHz, CDCl3) δ 53.4, 126.1, 127.7, 128.2,
128.4, 128.9, 135.6, 137.3, 146.9, 153.0, 195.4; 77Se NMR (76 MHz,
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Figure 5. Molecular orbital plots and energy levels of HOMOs and LUMOs of 10−15 and 17.
(4R*,5S*)-4,5-Dihydro-N,N-dimethyl-2-(4-methoxyphenyl)-4-
phenyl-5-selenazolamine (5). According to the general procedure for
selenazolines, compound 5 was prepared. The crude material was
purified by column chromatography (SiO2, hexane:EtOAc:Et3N =
5:1:0.01) to give 5 (0.09 g, 51%) as an orange solid (mp 97−100 °C):
IR (KBr) 1598, 1508, 1447, 1301 cm−1; 1H NMR (400 MHz, CDCl3)
δ 2.19 (s, 6H), 3.85 (s, 3H), 5.66 (d, J = 1.5 Hz, 1H), 5.72 (d, J = 1.4
Hz, 1H), 6.92−6.95 (m, 2H), 7.25−7.34 (m, 5H), 7.89−7.92 (m, 2H);
13C NMR (100 MHz, CDCl3) δ 41.4, 55.4, 86.5, 95.8, 113.8, 126.4,
(d, J = 8.3 Hz, 2H), 7.82 (d, J = 8.3 Hz, 2H); 13C NMR (100 MHz,
CDCl3) δ 41.5, 86.5, 96.7, 126.3, 127.8, 128.6, 128.7, 130.3, 134.7,
137.2, 139.0, 167.0; 77Se NMR (76 MHz, CDCl3) δ 356.0; MS (EI)
m/z 364 (M+); HRMS (EI) Calcd for C17H17ClN2Se: 364.0245;
found: 364.0223.
(4R*,5S*)-4,5-Dihydro-N,N,2,4-tetraphenyl-5-selenazolamine (7).
According to the general procedure for selenazolines, compound 7 was
prepared. The crude material was purified by column chromatography
(SiO2, hexane:EtOAc:Et3N = 30:1:0.01) to give 7 (0.213 g, 47%) as a
yellow solid (mp 157−158 °C): IR (KBr) 3437, 1492, 1229, 1032
127.6, 128.6, 128.9, 130.8, 139.5, 162.0, 167.4; 77Se NMR (76 MHz,
CDCl3) δ 346.4; MS (EI) m/z 360 (M+); HRMS (EI) Calcd for
C18H20N2OSe: 360.0741; found: 360.0736.
1
cm−1; H NMR (400 MHz, CDCl3) δ 5.98 (d, J = 3.9 Hz, 1H), 6.57
(d, J = 3.9 Hz, 1H), 6.98−7.04 (m, 6H), 7.18−7.24 (m, 5H), 7.25−
7.29 (m, 4H), 7.31 (t, J = 7.3 Hz, 2H), 7.38 (t, J = 7.3 Hz, 1H), 7.67
(d, J = 6.8 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ 83.4, 84.3, 123.2,
123.8, 126.5, 127.8, 128.4, 128.7, 128.8, 129.3, 131.0, 136.1, 139.6,
145.7, 167.8; 77Se NMR (76 MHz, CDCl3) δ −114.0; MS (EI) m/z
454 (M+); HRMS (EI) Calcd for C27H22N2Se (M+) 454.0948, found:
454.0971.
(4R*,5S*)-4,5-Dihydro-N,N-dimethyl-2-(4-chlorophenyl)-4-phe-
nyl-5-selenazolamine (6). According to the general procedure for
selenazolines, compound 6 was prepared. The crude material was
purified by column chromatography (SiO2, hexane:EtOAc = 10:1) to
give 6 (0.085 g, 47%) as an orange oil: IR (KBr) 3082, 3060, 3027,
2949, 2861, 2930, 2788, 1601, 1485 cm−1; 1H NMR (400 MHz,
CDCl3) δ 2.15 (s, 6H), 5.63−5.69 (m, 2H), 7.19−7.25 (m, 5H), 7.34
4936
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127.9, 128.2, 128.8, 129.1, 129.3, 129.6, 136.5, 145.8, 149.2, 161.7; MS
(EI) m/z 407(M+); HRMS (EI) Calcd for C26H21N3S: 407.1456,
found: 407.1431.
General Procedure for Preparation of Selenazoles. To a solution
of selenazoline (1 equiv) in THF was added iodine (2 equiv) at room
temperature, and the mixture was stirred for 2 h at this temperature.
The resulting mixture was poured into a saturated aqueous solution of
Na2S2O3 and extracted with Et2O. The organic layer was dried over
MgSO4 and concentrated in vacuo. The residue was purified by
column chromatography (SiO2) to give the corresponding selenazoles.
N,N-Dimethyl-2,4-diphenyl-5-selenazolamine (10). According to
the general procedure of selenazoles, compound 10 was prepared. The
crude material was purified by column chromatography (SiO2,
hexane:EtOAc:Et3N = 10:1:0.01) to give 10 (0.09 g, 46%) as a
1
yellow oil: IR (KBr) 3487, 2943, 2859, 1530, 1489 cm−1; H NMR
(400 MHz, CDCl3) δ 2.63 (s, 6H), 7.17−7.39 (m, 6H), 7.74−7.88 (m,
2H), 8.04−8.10 (m, 2H); 13C NMR (100 MHz, CDCl3) δ 48.1, 125.7,
126.5, 126.9, 128.3, 128.8, 129.5, 135.6, 137.2, 143.3, 160.2, 164.3; 77Se
NMR (76 MHz, CDCl3) δ 654.6; MS (EI) m/z 328 (M+); HRMS
(EI) Calcd for C17H16N2Se: 328.0479; found: 328.0466.
N,N-Dimethyl-2-(4-methoxyphenyl)-4-phenyl-5-selenazolamine
(11). According to the general procedure of selenazoles, compound 11
was prepared. The crude material was purified by column
chromatography (SiO2, hexane:EtOAc = 25:1) to give 11 (0.02 g,
22%) as a pale yellow solid (mp 82−86 °C): IR (KBr) 3046, 3013,
2983, 2938, 2856, 2834, 2782, 1605, 1519, 1492 cm−1; 1H NMR (400
MHz, CDCl3) δ 2.71 (s, 6H), 3.85 (s, 3H), 6.90−6.92 (m, 2H), 7.25−
7.29 (m, 1H), 7.38−7.42 (m, 2H), 7.82−7.84 (m, 2H), 8.17−8.19 (m,
2H); 13C NMR (100 MHz, CDCl3) δ 48.1, 55.4, 113.8, 114.1, 114.7,
127.1, 128.2, 129.0, 129.3, 129.7, 134.0, 134.7, 161.2; 77Se NMR (76
MHz, CDCl3) δ 629.2; MS (EI) m/z 358 (M+); HRMS (EI) Calcd for
C18H18N2OSe: 358.0584; found: 358.0560.
Figure 6. Cyclic voltammogram of 13−15 and 17.
(4R*,5S*)-4,5-Dihydro-2-(2-pyridyl)-N,N,4-triphenyl-5-selenazol-
amine (8). According to the general procedure for selenazolines,
compound 8 was prepared. The crude material was purified by column
chromatography (SiO2, hexane:EtOAc = 8:1) to give 8 (0.14 g, 61%)
as a brown oil: IR (KBr) 3058, 2923, 2854, 1687, 1588, 1493 cm−1; 1H
NMR (400 MHz, CDCl3) δ 6.06 (d, J = 4.4 Hz, 1H), 6.59 (d, J = 4.4
Hz, 1H), 7.05−7.07 (m, 5H), 7.17 (d, J = 7.8 Hz, 1H), 7.27−7.34 (m,
10H), 7.69−7.73 (m, 1H), 7.92 (d, J = 7.8 Hz, 1H), 8.67 (s, 1H); 13C
NMR (100 MHz, CDCl3) δ 80.5, 84.9, 120.7, 121.9, 123.4, 123.7,
125.4, 126.6, 127.1, 127.9, 128.8, 129.0, 129.3, 130.3, 136.4, 139.8,
146.0, 149.4, 153.2, 171.2; 77Se NMR (76 MHz, CDCl3) δ 540.9; MS
(EI) m/z 455 (M+); HRMS (EI) Calcd for C26H21N3Se: 455.0901;
found: 455.0913.
N,N-Dimethyl-2-(4-chlorophenyl)-4-phenyl-5-selenazolamine
(12). According to the general procedure of selenazoles, compound 12
was prepared. The crude material was purified by column
chromatography (SiO2, hexane:EtOAc = 30:1) to give 12 (0.03 g,
41%) as a yellow oil: IR (KBr) 3051, 2987, 2944, 2795, 1527, 1487
1
cm−1; H NMR (400 MHz, CDCl3) δ 2.73 (s, 6H), 7.25−7.28 (m,
1H), 7.34−7.42 (m, 4H), 7.81 (d, J = 8.3 Hz, 2H), 8.13 (d, J = 7.8 Hz,
2H); 13C NMR (100 MHz, CDCl3) δ 47.8, 48.3, 126.7, 127.2, 127.4,
127.7, 127.9, 128.6, 129.3, 135.3, 135.4, 143.2, 162.5; 77Se NMR (76
MHz, CDCl3) δ 643.6; MS (EI) m/z 362 (M+); HRMS (EI) Calcd for
C17H15ClN2 Se: 362.0089; found: 362.0079.
(4R*,5S*)-2-[1,1′-Biphenyl]-4-yl-4,5-dihydro--N,N,4-triphenyl-5-
selenazolamine (9). According to the general procedure for
selenazolines. The crude material was purified by column chromatog-
raphy (SiO2, hexane:EtOAc = 25:1) to give 9 (0.12 g, 44%) as a brown
1
oil: IR (KBr) 3055, 3026, 1600, 1490 cm−1; H NMR (400 MHz,
N,N,2,4-Tetraphenyl-5-selenazolamine (13). According to the
general procedure of selenazoles, compound 13 was prepared. The
crude material was purified by column chromatography (SiO2,
hexane:EtOAc:Et3N = 10:1:0.01) to give 13 (0.16 g, 84%) as an
orange yellow solid (mp 118−119 °C): IR (KBr) 2962, 1587, 1487,
CDCl3) δ 6.07 (d, J = 4.4 Hz, 1H), 6.66 (d, J = 4.4 Hz, 1H), 7.07−7.08
(m, 6H), 7.27−7.38 (m, 10H), 7.44−7.46 (m, 2H), 7.61 (d, J = 7.8
Hz, 4H), 7.82 (d, J = 8.3 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ
83.5, 84.4, 123.3, 123.9, 125.7, 126.5, 126.6, 126.9, 127.1, 127.8, 127.9,
128.7, 128.8, 129.3, 135.0, 139.6, 140.1, 143.9, 145.8; 77Se NMR (76
MHz, CDCl3) δ 530.6; MS (EI) m/z 530 (M+); HRMS (EI) Calcd for
C33H26N2Se: 530.1261; found: 530.1274.
1
1287 cm−1; H NMR (400 MHz, CDCl3) δ 6.87 (t, J = 6.8 Hz, 2H),
7.04−7.15 (m, 12H), 7.28 (d, J = 2.0 Hz, 1H), 7.29 (d, J = 2.0 Hz,
1H), 7.80 (d, J = 6.3 Hz, 4H); 13C NMR (100 MHz, CDCl3) δ 121.6,
123.1, 126.7, 127.7, 127.8, 128.1, 128.8, 129.1, 130.1, 134.1, 136.8,
146.8, 147.6, 150.3, 170.0; 77Se NMR (76 MHz, CDCl3) δ 692.5; MS
(EI) m/z 452 (M+); HRMS (EI) Calcd for C27H20N2Se (M+)
452.0792, found: 452.0816.
Preparation of (4R*,5S*)-4,5-Dihydro-2-(2-pyridyl)-N,N,4-tri-
phenyl-5-thiazolamine. To a solution of N-phenylmethyl-2-pyridine-
carbothioamide (0.23 g, 1.0 mmol) in THF (3.0 mL) was added
slowly a 1.25 M solution of n-butyllithium in n-hexane (1.28 mL, 2.0
mmol) at 0 °C, and the mixture was stirred for 10 min at this
temperature. To this was added N,N-diphenylthioformamide (0.21 g,
1.0 mmol) at 0 °C, and the mixture was stirred for 20 min at this
temperature. To this was added iodine (0.76 g, 3.0 mmol) at 0 °C, and
the mixture was stirred for 3 h at room temperature. The resulting
mixture was poured into a saturated aqueous solution of Na2S2O3 and
extracted with Et2O. The organic layer was dried over MgSO4 and
concentrated in vacuo. The crude material was purified by column
chromatography (SiO2, hexane:EtOAc:Et3N = 30:1:0.01) to give
thiazoline (0.27 g, 66%) as a brown liquid: IR (KBr) 3060, 2956, 2930,
2-(2-Pyridyl)-N,N,4-triphenyl-5-selenazolamine (14). According to
the general procedure of selenazoles, compound 14 was prepared. The
crude material was purified by column chromatography (SiO2,
hexane:EtOAc = 15:1) to give 14 (0.043 g, 46%) as a yellow solid
1
(mp 85−88 °C): IR (KBr) 3049, 1583, 1485, 1472 cm−1; H NMR
(400 MHz, CDCl3) δ 6.96−6.99 (m, 2H), 7.14−7.22 (m, 11H), 7.32−
7.33 (m, 1H), 7.76−7.84 (m, 3H), 8.22 (d, J = 7.8 Hz, 1H), 8.54 (d, J
= 4.4 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 118.5, 121.9, 123.1,
124.4, 127.6, 127.7, 128.0, 129.0, 129.3, 134.4, 136.8, 147.0, 149.5,
150.7, 153.5, 170.9; 77Se NMR (76 MHz, CDCl3) δ 706.3; MS (EI)
m/z 453 (M+); HRMS (EI) Calcd for C26H19N3Se: 453.0744; found:
453.0727.
1
2871, 2246, 1950, 1874, 1686, 1591 cm−1; H NMR (CDCl3) δ 6.02
(d, J = 4.4 Hz, 1H), 6.30 (d, J = 4.4 Hz, 1H), 7.02−7.06 (m, 6H),
7.23−7.34 (m, 10H), 7.69 (ddd, J = 1.7 Hz, J = 1.7 Hz, J = 1.7 Hz,
1H), 7.97 (d, J = 7.0 Hz, 1H), 8.65−8.67 (m, 1H); 13C NMR (CDCl3)
δ 80.1, 82.9, 121.4, 123.6, 123.7, 125.0, 126.0, 126.4, 126.8, 126.9,
2-[1,1′-Biphenyl]-4-yl-N,N,4-triphenyl-5-selenazolamine (15). Ac-
cording to the general procedure of selenazoles, compound 15 was
prepared. The crude material was purified by column chromatography
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(SiO2, hexane:EtOAc = 15:1) to give 15 (0.043 g, 46%) as a yellow
4679. (i) Ramesh, P.; Bhaskar, K. Pharma Chem. 2013, 5, 191.
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L.; Thomae, D. Curr. Org. Synth. 2010, 7, 44. (b) Ninomiya, M.;
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Organomet. Chem. 2012, 26, 655. (b) Mugesh, G. Curr. Chem. Biol.
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Silicon 2011, 186, 1650. (b) Kuarm, B. S.; Madhav, J. V.; Rajitha, B.
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1
solid (mp 148−152 °C): IR (KBr) 3024, 2920, 1589, 1487 cm−1; H
NMR (400 MHz, CDCl3) δ 7.05−7.07 (m, 2H), 7.22−7.30 (m, 12H),
7.43−7.53 (m, 2H), 7.69−7.71 (m, 4H), 7.96 (d, J = 7.8 Hz, 2H), 8.03
(d, J = 8.3 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ 121.1, 121.7,
123.2, 123.5, 127.0, 127.2, 127.5, 127.8, 127.9, 128.1, 128.5, 128.9,
129.1, 129.5, 140.2, 142.9, 146.9, 147.6, 188.8; 77Se NMR (76 MHz,
CDCl3) δ 678.1; MS (EI) m/z 528 (M+); HRMS (EI) Calcd for
C33H24N2Se: 528.1105; found: 528.1122.
2-(2-Pyridyl)-N,N,4-triphenyl-5-thiazolamine (17). To a solution
of 2-(2-pyridyl)-4-phenyl-5-diphenylaminothiazoline (0.38 g, 0.94
mmol) in THF (8.0 mL) was added iodine (0.48 g, 1.88 mmol) at
room temperature, and the mixture was stirred for 2 h under reflux.
The resulting mixture was poured into a saturated aqueous solution of
Na2S2O3 and extracted with Et2O. The organic layer was dried over
MgSO4 and concentrated in vacuo. The residue was purified by
column chromatography (SiO2, hexane:EtOAc = 30:1) to give 17
(0.18 g, 48%) as a yellow solid (mp 92−97 °C): IR (KBr) 3050, 1586,
1565, 1523, 1488 cm−1; 1H NMR (400 MHz, CDCl3) δ 6.98 (t, J = 7.3
Hz, 2H), 7.12−7.14 (m, 4H), 7.19−7.31 (m, 8H), 7.80 (ddd, J = 2.0
Hz, J = 2.0 Hz, J = 1.5 Hz, 1H), 7.91−7.94 (m, 2H), 8.28 (d, J = 7.8
Hz, 1H), 8.56 (d, J = 4.9 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ
119.3, 121.7, 123.1, 124.4, 127.3, 127.9, 128.1, 129.2, 133.4, 136.9,
142.6, 146.5, 148.9, 149.3, 151.4, 163.8; MS (EI) m/z 405 (M+);
HRMS (EI) Calcd for C26H19N3S: 405.1300, found: 405.1320.
ASSOCIATED CONTENT
■
S
* Supporting Information
X-ray data including a cif file, theoretical data, and H and 13C
1
(8) Thomae, D.; Perspicace, E.; Xu, Z.; Henryon, D.; Schneider, S.;
NMR spectra of all new compounds. This material is available
free of charge via the Internet at http://pubs.acs.org.
Hesse, S.; Kirsch, G.; Seck, P. Tetrahedron 2009, 65, 2982.
(9) Schaumann, E.; Nimmesgern, H.; Adiwidjaja, G.; Carlsen, L.
Chem. Ber. 1982, 115, 2516.
(10) For an example of 5-secondary aminoselenazoles, see: Maeda,
H.; Kambe, N.; Sonoda, N.; Fujiwara, S.; Shin-Ike, T. Tetrahedron
1997, 53, 13667.
AUTHOR INFORMATION
Corresponding Author
*E-mail: mtoshi@gifu-u.ac.jp.
Notes
■
(11) Narender, M.; Reddy, M. S.; Kumar, V. P.; Reddy, V. P.;
Nageswar, Y. V. D.; Rao, K. R. J. Org. Chem. 2007, 72, 1849.
(12) Murai, T.; Hori, F.; Maruyama, T. Org. Lett. 2011, 13, 1718.
(13) For recent examples, see: (a) Murai, T.; Mutoh, Y. Chem. Lett.
2012, 41, 2. (b) Murai, T.; Nonoyama, T. Tetrahedron 2012, 68,
10489. (c) Murai, T.; Ezaka, T.; Kato, S. Synthesis 2012, 44, 3179.
(d) Murai, T.; Shibahara, F.; Maruyama, T. Org. Biomol. Chem. 2012,
10, 4943. (e) Shibahara, F.; Kobayashi, S.; Maruyama, T.; Murai, T.
Chem.Eur. J. 2013, 19, 304. (f) Murai, T.; Nagaya, E.; Miyahara, K.;
Shibahara, F.; Maruyama, T. Chem. Lett. 2013, 42, 828. (g) Murai, T.;
Morikawa, K.; Maruyama, T. Chem.Eur. J. 2013, 19, 13112.
(14) For a recent example, see: Murai, T.; Maekawa, Y.; Monzaki, M.;
Ando, T.; Maruyama, T. Chem. Commun. 2013, 49, 9675.
(15) For recent examples, see: (a) Wakamiya, A.; Taniguchi, T.;
Yamaguchi, S. Angew. Chem., Int. Ed. 2006, 45, 3170. (b) Traven, V. F.;
Bochkov, A. Y.; Krayushkin, M. M.; Yarovenko, V. N.; Nabatov, B. V.;
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2008, 10, 1319. (c) Helal, A.; Kim, H.-S. Tetrahedron Lett. 2009, 50,
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The authors declare no competing financial interest.
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