Regioselective nucleophilic substitution of 5-bromo-2-methoxytropone

Article abstract of DOI:10.1002/hc.21201

The reaction of 5-bromo-2-methoxytropone with O- and N-nucleophiles, such as ethanol/potassium carbonate, sodium hydroxide, diethylamine, propylamine, p-chloroaniline/triethylamine, and p-phenylenediamine/triethylamine, gave corresponding 2-O- and 2-N-substituted troponoids. Alkyl diamines reacted with the substrate to produce bis(2-aminotropone)s. In the case of S-nucleophiles as 1-propanethiol, thiophenol, and 4-aminothiophenol with a base, the regioselective substitution at the 5-position occurred. Halogenation reagents, triphenyldibromophosphorane and its dichloro analogue, furnished 2,5-dibromo- and 2,5-dichlorotropones, respectively.

Full text of DOI:10.1002/hc.21201

Heteroatom Chemistry
Volume 25, Number 6, 2014
Regioselective Nucleophilic Substitution of
5-Bromo-2-methoxytropone
Ohki Sato, Ai Nitta, and Ami Yamamoto
Department of Chemistry, Graduate School of Science and Engineering, Saitama University,
Saitama 338-8570, Japan
Received 31 March 2014; revised 28 May 2014
troponoid system were reported. For further devel-
ABSTRACT:
The
reaction
of
5-bromo-2-
opment of this category, a wide variety of polysub-
stituted troponoids should be presented. It is known
that 2-substituted troponoids could be prepared by
the reaction of activated tropones (1b-e, Fig. 1) and
their alkyl/aryl substituted analogues, which have a
leaving group at their 2-position, with reagents hav-
ing a nucleophilic oxygen atom or a nitrogen atom
(O- or N-nucleophiles) [5]. However, substitution
of activated troponoids with plural leaving groups
has been rarely studied. As part of construction of
polysubstituted troponoids, especially disubstituted
ones, we focused on 5-bromo-2-methoxytropone (2)
as shown in Fig. 1. Compound (2) has two different
kinds of leaving groups, and its reactivity toward
various nucleophiles is of interest. A few reaction
of 2 with dimethyl- and diethylamines [6] and aryl
cross-coupling one with palladium catalysts [7]
were reported, whereas there is no systematic and
comprehensive investigation. We report herein the
reaction of 2 with some kinds of nucleophiles,
resulting in the regioselective substitution on the
basis of the nucleophilic atoms in the reagents.
methoxytropone with O- and N-nucleophiles, such
as ethanol/potassium carbonate, sodium hydroxide,
diethylamine, propylamine, p-chloroaniline/triethyl-
amine,
and
p-phenylenediamine/triethylamine,
gave corresponding 2-O- and 2-N-substituted tro-
ponoids. Alkyl diamines reacted with the substrate
to produce bis(2-aminotropone)s. In the case of
S-nucleophiles as 1-propanethiol, thiophenol, and
4-aminothiophenol with a base, the regioselective
substitution at the 5-position occurred. Halogena-
tion reagents, triphenyldibromophosphorane and
its dichloro analogue, furnished 2,5-dibromo- and
ꢀC
2,5-dichlorotropones, respectively. 2014 Wiley Pe-
riodicals, Inc. Heteroatom Chem. 25:644–650, 2014;
View this article online at wileyonlinelibrary.com.
DOI 10.1002/hc.21201
INTRODUCTION
Tropolone (1a) and its analogous troponoids have
unique properties as formation of tropylium cations
with acids and complexes with various metal
ions [1]. Functional troponoids with their charac-
teristics are the interesting class of compounds;
however, their construction has not been much in-
vestigated. Liquid crystals [2], catalysts for polymer-
ization [3], and light-emitting materials [4] having
RESULTS AND DISCUSSION
It is known that activated troponoids (1c) and (1e)
reacted with thiourea to generate 2-S-substituted
compounds (3) as HX salts (X = OTs and Cl). A ther-
mal intramolecular cyclization of 3 and successive
dehydration gave iminium salts (4a), which were hy-
drolyzed to furnish 2H-cyclohepta[d]thiazol-2-one
(4b) [8, 9]. Compound (4b) has a unique reactivity
and could be transformed into a novel heptafulvene
as shown in Scheme 1 [9].
Correspondence to: Ohki Sato; e-mail: ohkisato@chem.saitama-
u.ac.jp
This paper is dedicated to Professor Renji Okazaki on the occa-
sion of his 77th birthday.
ꢀC
2014 Wiley Periodicals, Inc.
644

Regioselective Nucleophilic Substitution of 5-Bromo-2-methoxytropone 645
[6b], (11), and (12), respectively. From the products
analysis, it is found that 5-substitution of 2 and
further one of the products (8–12) with the O- and
N-nucleophiles did not proceed in these conditions.
Next, we examined the reaction with S-
nucleophiles in expectation of the 5-selective sub-
stitution (Scheme 4, left). The treatment of 2 with
1-propanethiol in the presence of potassium carbon-
ate furnished the desired 5-substituted compound, 2-
methoxy-5-propylthiotropone (13). Thiophenol with
triethylamine gave a 5-substitute (14). Substitution
with the thiolates at room temperature occurred
only at the 5-position of 2, and 2-substituted and/or
2,5-disubstituted products were not formed at all.
Triphenyldibromophosphorane and its dichloro
analogue could convert ethers and esters into cor-
responding alkyl/aryl halides and acid halides, re-
spectively [11]. We attempted the reaction of 2 with
these reagents as halide nucleophiles (Scheme 4,
right). The treatment with the former afforded 2,5-
dibromotropone (15). In the case with 2 mol equiv of
the latter reagent afforded only 2,5-dichlorotropone
(16), whereas with 1 mol equiv of the latter reagent
gave a trace amount of 5-chloro-2-methoxytropone
together with 16 and recovery of 2. These results
suggest that the first attack of the nucleophile would
occur at the 5-position of 2.
FIGURE 1 Tropolone and activated troponoids.
In expectation of conversion into a 5-bromo
derivative (5b), we tried treatment of 2 with thiourea
(Scheme 2). As a result, surprisingly, neither a 2-S-
substitute (6) nor its cyclized imine (5a) was formed
at all, and the product was a hydrobromide of 5-
substituted compound (7) replacing a bromine atom
of 2 with a sulfur atom of thiourea. This result indi-
cates that compound (2) has an ability to be substi-
tuted at the 5-position. If the reactivity at the 2- and
5-positions could be controlled by reaction condi-
tions, 2 would be a useful precursor for construction
of various 2,5-disubstituted tropones. Therefore, we
decided that the reaction of 2 with other kinds of
nucleophiles is worth trying.
According to the anticipation, we first at-
tempted the reaction with O-nucleophiles (Scheme
3, left). The treatment of 2 in boiling ethanol with
potassium carbonate as a base furnished a single
component of 5-bromo-2-ethoxytropone (8). The
reaction with sodium hydroxide proceeded only at
the 2-position to give a known product (9) [10].
Phenol did not react in spite of the presence of
potassium carbonate or sodium hydride. In the case
with N-nucleophiles, the same 2-selectivety was
shown regardless of alkyl or aryl amines (Scheme
3, right). That is, diethylamine, propylamine, and
p-chloroaniline/triethylamine reacted with 2 under
boiling conditions to give 2-aminotropones (10)
In this manner, the different reactivity at 2-
and 5-positions of 2 was revealed according to the
type of nucleophilic atoms in the reagents. The
reason remains unknown; however, a tendency of
the reactivity might be explained by using the Hard
and Soft Acids and Bases (HSAB) concept [12]. That
is, S-nucleophiles regarded as relatively soft bases
would prefer to attack at the 5-position of 2, whereas
SCHEME 1
SCHEME 2
Heteroatom Chemistry DOI 10.1002/hc

646 Sato, Nitta, and Yamamoto
SCHEME 3
SCHEME 4
O- and N-nucleophiles regarded as relatively hard
bases would prefer to attack at the 2-position.
amine under boiling conditions, aminotroponimine
(21) was produced together with 17. Compound (21)
would arise from a thermal intramolecular cycliza-
tion of a one-to-one substitute of 2 and ethylenedi-
amine and successive dehydration. This is a rare case
because of the difficulty of imination in troponoids
under basic conditions.
On the other hand, aryl N,N- and N,S-
nucleophiles such as p-phenylenediamine and 4-
aminothiophenol produced one-to-one substitutes
of 2 and the nucleophiles (Scheme 6). The same
Reagents having two nucleophilic atoms would
supply two-to-one substitutes, which have two tro-
pone nuclei bridged by a nucleophile moiety. The
reaction of 2 with 0.5 mol equiv of alkyl diamines,
such as ethylenediamine, 1,3-propanediamine, 2,2-
dimethyl-1,3-propanediamine, and cystamine, at
room temperature afforded corresponding bis(2-
aminotropone)s (17), (18), (19), and (20) as ex-
pected (Scheme 5). In the only case with ethylenedi-
SCHEME 5
Heteroatom Chemistry DOI 10.1002/hc

Regioselective Nucleophilic Substitution of 5-Bromo-2-methoxytropone 647
1H), 7.39 (dd, J = 12.7, 1.8 Hz, 1H), 7.65 (dd,
J = 10.3, 1.8 Hz, 1H), 8.93–9.08 (br, 4H); IR (KBr):
ν 3016, 1660, 1622, 1567; MS (FAB, NBA): m/z
211 ([M – Br]+). Anal. calcd for C9H11BrN2O2S: C,
37.13; H, 3.81; N, 9.62. Found: C, 37.43; H, 3.75; N,
9.49.
The Reaction of 2 with Ethanol/Potassium
Carbonate
An absolute ethanol (2.0 mL) solution of 2 (65 mg,
0.30 mmol) with potassium carbonate (0.30 mmol)
was boiled for 24 h under argon. The solvent was
SCHEME 6
regioselectivety mentioned above was shown, and
the products were 2-N- and 5-S-substitutes (22)
and (23), respectively. A 2-N-substitute with 4-
aminothiophenol was not formed at all. Further sub-
stitution of 22 and 23 did not proceed even if using
an excess amount of 2 or the nucleophiles.
In conclusion, we have found the regios-
elective nucleophilic substitution of 5-bromo-2-
methoxytropone (2) according to the type of nucle-
ophilic atoms in the reagents. Further work, aimed
at elucidation of the regioselectivity using computa-
tional chemistry and in the construction of various
troponoids with two different substituents at 2- and
5-positions, is in progress.
removed in vacuo, and the residue was purified
by silica gel column chromatography to give 8 (55
1
mg, 79%); yellow needles; mp 124–125°C; H NMR
(300 MHz, CDCl3): δ 1.53 (t, J = 7.0 Hz, 3H), 4.11
(q, J = 7.0 Hz, 2H), 6.48 (d, J = 10.9 Hz, 1H), 7.01
(d, J = 13.2 Hz, 1H), 7.38 (dd, J = 10.9, 2.0 Hz, 1H),
7.41 (dd, J = 13.2, 2.0 Hz, 1H); IR (KBr): ν 1614,
1574; MS (FAB, NBA): m/z 229 (MH+), 231 ([MH
+ 2]+). Anal. calcd for C9H9BrO2: C, 47.19; H, 3.96.
Found: C, 47.34; H, 3.84.
The Reaction of 2 with Sodium Hydroxide
To an absolute methanol (1.5 mL) solution of 2
(65 mg, 0.30 mmol), 0.60 M sodium hydroxide
(0.60 mmol) was added under argon and boiled for
13 h. The reaction mixture was quenched with 1.0 M
hydrochloric acid, and the aqueous layer was ex-
tracted with diethyl ether. The organic layer was
dried over magnesium sulfate, and the solvent was
removed under reduced pressure. The residue was
purified by silica gel column chromatography to give
9 [10] (56 mg, 92%); yellow solids; mp 150–151°C;
1H NMR (300 MHz, CDCl3): δ 7.11 (d, J = 11.8 Hz,
2H), 7.67 (d, J = 11.8 Hz, 1H); IR (KBr): ν 3114,
1605, 1566; MS (FAB, NBA): m/z 201 (MH+), 203
([MH + 2]+). Anal calcd for C7H5BrO2: C, 41.82; H,
2.51. Found: C, 41.57; H, 2.70.
EXPERIMENTAL
Melting points were determined with a laboratory
devices MEL-TEMP apparatus and are uncorrected.
1H and 13C NMR spectra (SiMe4 as the internal
standard) were obtained with Bruker AV500, AV
400, AV300, and AC300 spectrometers. IR spectra
were obtained with a Perkin–Elmer System 2000 FT
instrument. MS spectra were obtained with JEOL
JMS700AM and Bruker AutoflexIII spectrometers.
Unless otherwise stated, the spectra were taken in
the following solvents/media: IR, KBr; H and 13C
NMR, CDCl3, and DMSO-d6; MS spectra were taken
at FAB and MALDI-TOF methods. The progress of
reactions was followed by thin-layer chromatogra-
1
The Reaction of 2 with Alkyl Amines
phy method using a Merck Silica gel 60F254
.
A solution of 2 with alkyl amines (diethylamine and
propylamine; 4.0 mol equiv) in absolute ethanol
(0.15 mM) was boiled for 24 h under argon. After
removal of the solvent in vacuo, the residue was
purified by silica gel column chromatography to
give 10 [6b] (98%) and 11 (97%), respectively.
5-Bromo-2-(diethylamino)tropone (10). Yellow-
ish brown crystals; mp 183–185°C; 1H NMR (300
MHz, CDCl3): δ 1.22 (t, J = 7.0 Hz, 6H), 3.53 (q, J =
7.0 Hz, 4H), 6.22 (d, J = 11.4 Hz, 1H), 6.62 (d, J =
12.5 Hz, 1H), 7.21 (dd, J = 11.4, 2.4 Hz, 1H), 7.27
The Reaction of 5-Bromo-2-methoxytropone (2)
with Thiourea
A solution of 2 (431 mg, 2.0 mmol) and thiourea
(2.0 mmol) in absolute ethanol (10 mL) was boiled
for 13 h under argon. The resulting precipitate
was filtered and washed with ethanol to give 7
(479 mg, 82%); pale yellow solids; mp 220–221°C;
1H NMR (300 MHz, DMSO-d6): δ 3.91 (s, 3H),
6.94 (d, J = 10.3 Hz, 1H), 6.98 (d, J = 12.7 Hz,
Heteroatom Chemistry DOI 10.1002/hc

648 Sato, Nitta, and Yamamoto
(dd, J = 12.5, 2.4 Hz, 1H); IR (KBr): ν 1614, 1563;
MS (FAB, NBA): m/z 256 (MH+), 258 ([MH + 2]+).
Anal. calcd for C11H14BrNO: C, 51.58; H, 5.51; N,
5.47. Found: C, 51.66; H, 5.41; N, 5.39.
lute methanol (1.5 mL) was stirred for 24 h at room
temperature under argon. After removal of the sol-
vent in vacuo, the residue was purified by silica gel
column chromatography to give 14 (67 mg, 91%);
1
5-Bromo-2-(propylamino)tropone (11). Yellow-
pale yellow needles; mp 198–199°C; H NMR (300
1
ish brown plates; mp 85–86°C; H NMR (300 MHz,
MHz, CDCl3): δ 3.92 (s, 3H), 6.63 (d, J = 10.7 Hz,
1H), 7.06 (d, J = 12.5 Hz, 1H), 7.07 (dd, J = 10.7, 2.0
Hz, 1H), 7.19 (dd, J = 12.5, 2.0 Hz, 1H), 7.35–7.42
(m, 5H); IR (KBr): ν 1618, 1580; MS (FAB, NBA):
m/z 245 (MH+). Anal. calcd for C14H12O2S: C, 68.83;
H, 4.95. Found: C, 68.82; H, 4.87.
CDCl3): δ 1.05 (t, J = 7.3 Hz, 3H), 1.70–1.82 (m, 2H),
3.26 (q like, J = 7.3 Hz, 2H), 6.29 (d, J = 11.4 Hz,
1H), 6.92 (d, J = 12.5 Hz, 1H), 7.29 (br, 1H), 7.44–
7.50 (m, 2H); IR (KBr): ν 3249, 1585, 1512; MS (FAB,
NBA): m/z 242 (MH+), 244 ([MH + 2]+). Anal. calcd
for C10H12BrNO: C, 49.61; H, 5.00; N, 5.79. Found:
C, 49.64; H, 4.91; N, 5.51.
The Reaction of 2 with Halogenation Reagents
The Reaction of 2 with p-Chloroaniline/
A solution of 2 with halogenation reagents (triph-
enyldibromophosphorane: 1.0 mol equiv; triph-
enyldichlorophosphorane: 2.0 mol equiv) in dry
dichloromethane (0.15 mM) was stirred for 24 h at
room temperature under argon. After removal of the
solvent in vacuo, the residue was purified by silica
gel column chromatography to give 15 (73%) and 16
(77%), respectively.
2,5-Dibromotropone (15). Pale yellow needles;
mp 84–85°C; 1H NMR (300 MHz, CDCl3): δ 6.96 (d, J
= 12.9 Hz, 1H), 7.21 (dd, J = 10.4, 2.2 Hz, 1H), 7.38
(dd, J = 12.9, 2.2 Hz, 1H), 7.80 (d, J = 10.4 Hz, 1H); IR
(KBr): ν 1609, 1583; MS (FAB, NBA): m/z 263 (MH+),
265 ([MH + 2]+), 267 ([MH + 4]+). Anal. calcd for
C7H4Br2O: C, 31.86; H, 1.53. Found: C, 32.16; H,
1.82.
2,5-Dichlorotropone (16). Pale yellow needles;
mp 87–88°C; 1H NMR (300 MHz, CDCl3): δ 7.09 (dd,
J = 10.3, 2.2 Hz, 1H), 7.12 (d, J = 12.9 Hz, 1H),
7.28 (dd, J = 12.9, 2.2 Hz, 1H), 7.63 (d, J = 10.3
Hz, 1H); IR (KBr): ν 1621, 1580; MS (FAB, NBA):
m/z 175 (MH+), 177 ([MH + 2]+), 179 ([MH + 4]+).
Anal. calcd for C7H4Cl2O: C, 48.04; H, 2.30. Found:
C, 48.36; H, 2.61.
Triethylamine
A solution of 2 (65 mg, 0.30 mmol) with p-
chloroaniline (0.93 mmol) and triethylamine (0.93
mmol) in absolute ethanol (1.5 mL) was boiled for
24 h under argon. After removal of the solvent in
vacuo, the residue was purified by silica gel column
chromatography to give 12 (76 mg, 81%); yellow
crystals; mp 175–177°C; 1H NMR (300 MHz, CDCl3):
δ 6.85 (d, J = 11.2 Hz, 1H), 7.06 (d, J = 12.5 Hz, 1H),
7.22 (d, J = 8.6 Hz, 2H), 7.41 (d, J = 8.6 Hz, 2H), 7.43
(dd, J = 11.2, 2.2 Hz, 1H), 7.57 (dd, J = 12.5, 2.2 Hz,
1H), 8.65 (br, 1H); IR (KBr): ν 3208, 1589, 1548; MS
(FAB, NBA): m/z 310 (MH+), 312 ([MH + 2]+), 314
([MH + 4]+). Anal. calcd for C13H9BrClNO: C, 50.27;
H, 2.92; N, 4.51. Found: C, 50.36; H, 2.85; N, 4.50.
The Reaction of 2 with 1-Propanethiol/
Potassium Carbonate
An absolute methanol (1.5 mL) solution of 2 (65 mg,
0.30 mmol) and 1-propanethiol (0.30 mmol) with
potassium carbonate (0.30 mmol) was stirred for
12 h at room temperature under argon. The solvent
was removed in vacuo, and the residue was puri-
fied by silica gel column chromatography to give 13
(43 mg, 68%); yellow needles; mp 54–55°C; 1H NMR
(300 MHz, CDCl3): δ 1.50 (t, J = 7.2 Hz, 3H), 1.70
(sext, J = 7.2 Hz, 2H), 2.89 (t, J = 7.2 Hz, 2H), 3.92
(s, 3H), 6.66 (d, J = 10.5 Hz, 1H), 7.01 (dd, J = 10.5,
1.8 Hz, 1H), 7.11 (d, J = 12.5 Hz, 1H), 7.24 (dd, J =
12.5, 1.8 Hz, 1H); IR (KBr): ν 1614, 1557; MS (FAB,
NBA): m/z 211 (MH+). Anal. calcd for C11H14O2S: C,
62.83; H, 6.71. Found: C, 63.00; H, 6.54.
The Reaction of 2 with Alkyl Diamines
A solution of 2 with alkyl diamines (ethylene-
diamine, 1,3-propanediamine, 2,2-dimethyl-1,3-
propanediamine, and cystamine dihydrochloride;
0.5 mol equiv) and triethylamine (1.1 mol equiv;
only in the case of cystamine dihydrochloride: 2.6
mol equiv) in absolute methanol (0.10 mM) was
stirred for 24 h at room temperature under argon.
After removal of the solvent in vacuo, the residue
was purified by aluminum oxide (active V) column
chromatography to give 17 (63%), 18 (49%), 19
(61%), and 20 (71%), respectively. Ethylenediamine
(0.5 mol equiv) in the presence of triethylamine
(1.1 mol equiv) reacted with 2 in absolute methanol
The Reaction of 2 with Thiophenol/
Triethylamine
A solution of 2 (65 mg, 0.30 mmol) with thiophenol
(0.60 mmol) and triethylamine (2.4 mmol) in abso-
Heteroatom Chemistry DOI 10.1002/hc

Regioselective Nucleophilic Substitution of 5-Bromo-2-methoxytropone 649
(0.10 mM) under boiling conditions for 24 h to give
21 (33%) together with 17 (45%).
The Reaction of 2 with p-Phenylenediamine/
Triethylamine
Bis(2-aminotropone) (17). Ocher solids; mp
280°C (dec.); 1H NMR (500 MHz, CDCl3): δ 3.68 (m,
4H), 6.31 (d, J = 11.0 Hz, 2H), 6.94 (d, J = 13.0
Hz, 2H), 7.50–7.53 (m, 6H); 13C NMR (100 MHz,
DMSO-d6): δ 40.9 (2C), 108.2 (2C), 114.2 (2C), 127.5
(2C), 138.6 (2C), 139.6 (2C), 155.6 (2C), 175.8 (2C);
IR (KBr): ν 3308, 1594; MS (MALDI-TOF, dithranol):
m/z 425 (MH+), 427 ([MH + 2]+), 429 ([MH + 4]+).
Anal. calcd for C16H14Br2N2O2: C, 45.10; H, 3.31; N,
6.57. Found: C, 44.80; H, 3.30; N, 6.41.
Bis(2-aminotropone) (18). Ocher plates; mp
167–168°C; 1H NMR (500 MHz, CDCl3): δ 2.19
(quint, J = 6.5 Hz, 2H), 3.45 (q like, J = 6.5 Hz,
4H), 6.27 (d, J = 11.0 Hz, 2H), 6.95 (d, J = 12.0 Hz,
2H), 7.22 (br, 2H), 7.49 (dd, J = 11.0, 2.0 Hz, 2H),
7.52 (dd, J = 12.0, 2.0 Hz, 2H); IR (KBr): ν 3254,
1591; MS (MALDI-TOF, dithranol): m/z 439 (MH+),
441 ([MH + 2]+), 443 ([MH + 4]+). Anal. calcd for
C17H16Br2N2O2: C, 46.39; H, 3.66; N, 6.36. Found:
C, 46.14; H, 3.60; N, 6.12.
A solution of 2 (50 mg, 0.23 mmol) with p-
phenylenediamine (0.35 mmol) and triethylamine
(0.72 mmol) in absolute methanol (1.2 mL) was
boiled for 24 h under argon. After removal of the
solvent in vacuo, the residue was purified by sil-
ica gel column chromatography to give 22 (63 mg,
93%); red plates; mp 188–189°C; 1H NMR (300 MHz,
CDCl3): δ 3.78 (br, 2H), 6.71 (d, J = 11.2 Hz, 1H), 6.74
(d, J = 8.5 Hz, 2H), 7.01 (d, J = 12.3 Hz, 1H), 7.04
(d, J = 8.5 Hz, 2H), 7.39 (dd, J = 11.2, 2.2 Hz, 1H),
7.53 (dd, J = 12.3, 2.2 Hz, 1H), 8.59 (br, 1H); IR
(KBr): ν 3335, 3244, 3208, 1589; MS (FAB, NBA):
m/z 291 (MH+), 293 ([MH + 2]+). Anal. calcd for
C13H11BrN2O: C, 53.63; H, 3.81; N, 9.62. Found: C,
53.57; H, 3.57; N, 9.56.
The Reaction of 2 with 4-Aminothiophenol/
Triethylamine
Bis(2-aminotropone) (19). Ocher powder; mp
154–155°C; 1H NMR (500 MHz, CDCl3): δ 1.21
(s, 6H), 3.21 (d like, J = 6.5 Hz, 4H), 6.24 (d, J =
11.0 Hz, 2H), 6.94 (d, J = 12.5 Hz, 2H), 7.36 (dd,
J = 11.0, 2.5 Hz, 2H), 7.39 (br, 2H), 7.50 (dd, J =
12.5, 2.5 Hz, 2H); 13C NMR (125 MHz, CDCl3): δ
24.1 (2C), 36.7, 50.1 (2C), 108.0 (2C), 116.3 (2C),
127.8 (2C), 138.3 (2C), 140.4 (2C), 154.9 (2C), 175.9
(2C); IR (KBr): ν 3260, 1594; MS (MALDI-TOF,
dithranol): m/z 467 (MH+), 469 ([MH + 2]+), 471
([MH + 4]+). Anal. calcd for C19H20Br2N2O2: C,
48.74; H, 4.31; N, 5.98. Found: C, 48.42; H, 4.17; N,
5.75.
A solution of 2 (101 mg, 0.47 mmol) with 4-
aminothiophenol (0.71 mmol) and triethylamine
(1.86 mmol) in absolute methanol (4.0 mL) was
stirred for 20 h at room temperature under argon.
After removal of the solvent in vacuo, the residue
was purified by silica gel column chromatography
to give 23 (85 mg, 70%); yellow powder; mp 164–
1
165°C; H NMR (300 MHz, CDCl3): δ 3.95 (s, 3H),
4.09 (br, 2H), 6.57 (d, J = 10.8 Hz, 1H), 6.71 (d, J =
8.8 Hz, 2H), 6.74 (dd, J = 10.8, 1.8 Hz, 1H), 7.07 (d, J
= 12.4 Hz, 1H), 7.12 (dd, J = 12.4, 1.8 Hz, 1H), 7.29
(d, J = 8.8 Hz, 2H); IR (KBr): ν 3339, 3222, 1633,
1556; MS (FAB, NBA): m/z 260 (MH+). Anal. calcd
for C14H13NO2S: C, 64.84; H, 5.05; N, 5.40. Found:
C, 65.05; H, 4.90; N, 5.24.
Bis(2-aminotropone) (20). Yellow solids; mp
1
200°C (dec.); H NMR (500 MHz, CDCl3): δ 2.97 (t,
J = 6.5 Hz, 4H), 3.65 (q like, J = 6.5 Hz, 4H), 6.31
(d, J = 11.0 Hz, 2H), 6.94 (d, J = 13.0 Hz, 2H), 7.42
(br, 2H), 7.47–7.52 (m, 4H); 13C NMR (125 MHz,
CDCl3): δ 35.4 (2C), 41.2 (2C), 107.7 (2C), 113.9 (2C),
127.1 (2C), 138.2 (2C), 139.2 (2C), 154.7 (2C), 175.1
(2C); IR (KBr): ν 3245, 1589; MS (MALDI-TOF,
dithranol): m/z 517 (MH+), 519 ([MH + 2]+), 521
([MH + 4]+). Anal. calcd for C18H18Br2N2O2S2: C,
41.71; H, 3.50; N, 5.41. Found: C, 41.42; H, 3.34; N,
5.21.
REFERENCES
[1] (a) Nozoe, T. Bull Chem Soc Jpn 1936, 11, 295; (b)
Doering, W. v. E.; Knox, L. H. J Am Chem Soc 1951,
73, 828; (c) Nozoe, T.; Seto, S.; Mukai, T.; Yamane,
K.; Matsukuma, A. Proc Jpn Acad 1951, 27, 224; (d)
Cook, J. W.; Gibb, A. R.; Raphael, R. A.; Somerville, A.
R. J Chem Soc 1951, 503; (e) Bryant, B. E.; Fernelius,
W. C.; Douglas, B. E. J Am Chem Soc 1953, 75, 3784.
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Soc Jpn 2002, 75, 1353; (b) Mori, A.; Mori, R.; Take-
moto, M.; Yamamoto, S.; Kribayashi, D.; Uno, K.;
Kubo, K.; Ujiie, S. J Mater Chem 2005, 15, 3005.
[3] Hicks, F. A.; Jenkins, J. C.; Brookhart, M.
Organometallics 2003, 22, 3533.
Aminotroponimine (21). Orange powder; mp
1
140°C (dec.); H NMR (500 MHz, CDCl3): δ 3.56 (s,
4H), 6.20 (d, J = 11.3 Hz, 2H), 6.87 (d, J = 11.3
Hz, 2H); IR (KBr): ν 3220; MS (MALDI-TOF, dithra-
nol): m/z 225 (MH+), 227 ([MH + 2]+). Anal. calcd
for C9H9BrN2: C, 48.02; H, 4.03; N, 12.45. Found: C,
48.30; H, 3.88; N, 12.18.
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236.
Heteroatom Chemistry DOI 10.1002/hc

650 Sato, Nitta, and Yamamoto
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Heteroatom Chemistry DOI 10.1002/hc