An alternative facile preparation of telluro- and selenochromones from o-bromophenyl ethynyl ketones

Article abstract of DOI:10.1055/s-1998-2062

Treatment of o-bromophenyl ethynyl ketones 2 with sodium hydrogen telluride and selenide gave telluro- 3A and selenochromones 3B, respectively, in one pot via the presumed intermediates 4.

Full text of DOI:10.1055/s-1998-2062

May 1998
SYNTHESIS
745
An Alternative Facile Preparation of Telluro- and Selenochromones from
o-Bromophenyl Ethynyl Ketones1
Haruki Sashida
Faculty of Pharmaceutical Sciences, Hokuriku University, Kanagawa-machi, Kanazawa 920-1181, Japan
Fax +81(76)2292781
Received 13 October 1997; revised 20 November 1997
Abstract: Treatment of o-bromophenyl ethynyl ketones 2 with
sodium hydrogen telluride and selenide gave telluro- 3A and sele-
nochromones 3B, respectively, in one pot via the presumed inter-
mediates 4.
did not proceed, and only the homo-coupling product of
trimethylsilylacetylene was obtained. Therefore, the ben-
zylchlorobis(triphenylphosphine)palladium(II)-induced
coupling reaction of benzoyl chloride with organotin re-
agents as reported by Stille and co-workers8 was applied.
This palladium-catalyzed coupling reaction of 1 with
tributyl[(trimethylsilyl)ethynyl]stannane9 afforded the
desired compound 2g in 45% yield.
Key words: tellurochromones, selenochromones, o-bromophenyl
ethynyl ketones, intramolecular cyclization
The chemistry of six-membered tellurium- or selenium-con-
taining heterocyclic compounds2 has recently been devel-
oped for their displays of certain characteristic elucidations
of structures and reactions.Among these compounds, there
are a few known heterocycles of the chromone type.3–5
The intramolecular Friedel–Crafts cyclization4 of b-(ar-
ylseleno)cinnamic acids or the corresponding acid chlo-
rides gives selenochromones, and this method is also
useful for the preparation of the corresponding thio ana-
logs.4a But, with respect to the synthesis of the corre-
sponding tellurochromones, the Friedel–Crafts reaction of
b-(aryltelluro)cinnamoyl chlorides is less effective.4b The
reason is that this ring-closure reaction can proceed to
give the chromones only in the case of the presence of a
strong electron-donating group in positions 5 and (or) 7 on
the benzene ring.4c
Scheme 1
Renson and co-workers5 have reported the synthesis of
tellurochromones using the intramolecular cyclization of
b-(o-bromotelluroaroyl) enamines5a under the action of
hypophosphoric acid, and furthermore, the preparation of
selenochromones5b by the hydrobromic acid induced ring
closure of ethynyl o-(methylseleno)phenyl ketones. How-
ever, these procedures4,5 for the preparation of seleno-
and tellurochromones have limited success and generali-
ty, not only at the position and the variety of the substitu-
ents on the aromatic ring, but also for the kind of
chalcogen element.
For the preparation of the telluro- 3A and seleno-
chromones 3B, we first examined the conversion to the
phenylchalcogenols 4 from alkynyl phenyl ketones 2. The
method10 presented by Liu and co-workers was used for
this purpose. Treatment of 2 with sodium hydrogen tellu-
ride and selenide generated in situ from tellurium (seleni-
um) powder and sodium borohydride in DMF resulted in
a direct ring closure to afford the tellurochromones 3A
On the other hand, we have previously6 presented synthet-
ic methods for the preparation of chalcogen-containing
heterocycles via the intramolecular ring closure of a -SeH
or -TeH moiety to a triple bond. In this paper, the exten-
sion of our synthetic methodology for the preparation of
the title compounds is described.
The key starting materials, o-bromophenyl ethynyl ke-
tones 2, were readily prepared from o-bromobenzoyl
chloride (1) as shown in Scheme 1. Compound 1 was cou-
pled with various 1-substituted acetylenes in the presence
of a catalytic amount of dichlorobis(triphenylphos-
phine)palladium(II) and copper(I) iodide to give the cor-
responding product 2 in good yields.7 In the case of
trimethylsilyl derivatives, this hetero-coupling reaction Scheme 2

746
Papers
SYNTHESIS
Table. Tellurochromones 3A and Selenochromones 3B
Prod-
uct
M
R
Yield Appearance
(%)
Formula
HRMS
Calcd
IR
n
1H NMR (60 MHz) d, J (Hz)
C=O (cm–1)
3-H
5-H
Ar-H
(6-, 7-,
8-H)
R-H
(Found)
3Aa
3Ab
Te
Te
Me
28
48
pale-yellow prisms C10H8OTe
1600
1608
listed in ref 5a
R = Me
mp 98–99°C
273.9637
(273.9645)
(Lit.5a 99–100°C)
n-Bu
orange oil
C13H14OTe
316.0107
7.20
(s)
8.6–8.8
(m)
7.3–7.7
(3H, m)
0.90, 1.1–1.8, 2.72
(3H, t, J = 6, 4H,
m, 2H, t, J = 6);
R = n-Bu
(316.0101)
3Ac
3Ad
Te
Te
t-Bu
63
orange oil
orange oil
C13H14OTe
316.0107
(316.0114)
1608
1608
7.31
(s)
8.6–8.8
(m)
7.3–7.7
(3H, m)
1.27 (9H, s);
R = t-Bu
n-Hexa 39
n-Octh 43
C15H18OTe
344.0420
(344.0417)
7.20
(br s)
8.6–8.8
(m)
7.3–7.8
(3H, m)
0.87, 1.0–1.8, 2.72
(3H, t, J = 5, 8H,
m, 2H, t, J = 7); R =
n-Hexa
3Ae
Te
orange oil
C17H22OTe
372.0733
(372.0743)
1608
7.18
(s)
8.6–8.8
(m)
7.3–7.7
(3H, m)
0.87, 1.1–2.0, 2.77
(3H, t, J = 5, 12H,
m, 2H, t, J = 7); R =
n-Octb
3Af
3Ah
3Ba
3Bb
Te
Te
Se
Se
Ph
48
5
yellow prisms
mp 114–116°C
C15H10OTe
335.9794
(335.9790)
1610
1574
1616
1620
7.23
(s)
8.7–8.9
(m)
7.3–7.7
(8H, m)
R = Ph
H
yellow prims
mp126–l28°C
(Lit.5a 130°C)
C9H6OTe
259.9481
(289.9488)
listed in ref 11
R = H
Me
n-Bu
48
90
pale-yellow prisms C10H8OSe
7.00
(d, J = 1)
8.5–8.7
(m)
7.4–7.7
(3H, m)
2.50 (3H, d, J = 1);
R = Me
mp 97–98°C
223.9741
(223.9743)
(Lit.5a 96–98°C)
yellow oil
C13H14OSe
266.0210
(266.0213)
7.00
(br s)
8.5–8.7
(m)
7.2–7.6
(3H, m)
0.93, 1.1–2.0, 2.70
(3H, t, J = 6, 4H,
m, 2H, br t, J = 7);
R = n-Bu
3Bc
3Bd
Se
Se
t-Bu
93
pale-yellow prisms C13H14OSe
1620
1622
7.08
(s)
8.5–8.7
(m)
7.3–7.6
(3H, m)
1.33 (9H, s); R = t-
Bu
mp 89–91°C
266.0210
(266.0209)
n-Hexa 79
n-Octb 86
ellow oil
C15H18OSe
294.0523
7.00
(br s)
8.5–8.7
(m)
7.3–7.7
(3H, m)
0.90, 1.1–2.0, 2.67
(3H, t, J = 5, 8H,
m, 2H, br t, J = 7);
R = n-Hexa
(294.0526)
3Be
Se
yellow oil
C17H22OSe
322.0837
1624
6.98
(s)
8.5–8.7
(m)
7.5–7.7
(3H, m)
0.87, 1.1–2.0, 2.67
(3H, t, J = 5, 12H,
m, 2H, t, J = 7); R =
n-Octb
(322.0842)
3Bf
Se
Se
Ph
H
84
59
pale-yellow prisms C15H10OSe
1612
1610
listed in ref 4a
listed in ref 11
R = Ph
mp133–l34°C
285.9897
(285.9899)
(Lit.5c 133°C)
3Bh
pale-yellow prisms C9H6OSe
R = H
mp 90–92°C
209.9584
(209.9588)
(Lit.5c 93–94°C)
a n-Hexyl.
b n-Octyl.

May 1998
SYNTHESIS
747
1H NMR (60 MHz): d = 1.33 (9H, s, t-Bu), 7.3–7.7 and 8.0–8.2 (3H,
m and 1H, m, Ar-H).
and selenochromones 3B, respectively, as the sole product
in moderate to good yields except for 3Ah. The TMS de-
rivative 2g gave the 2-unsubstituted telluro- 3Ah and se-
lenochromone 3Bh with reductive removal of the TMS
group under these reaction conditions. No five-membered
cyclization products 5 were obtained.
HRMS m/z: M+ Calcd for C13H13OBr: 264.0150, 266.0130. Found:
264.0150, 266.0351.
2d (R = n-Hex): yellow oil; yield: 20.51 g (70%).
IR: n = 2204 (CC), 1660 cm–1 (C=O).
1H NMR (60 MHz): d = 0.90, 1.0–2.0 and 2.46 (3H, t, J = 6 Hz, 8H,
m and 2H, t, J = 6 Hz, n-Hex), 7.4–7.9 and 8.0–8.3 (3H, m, and 1H,
m, Ar-H).
These results for the formation of 3 clearly indicate the
following two points: (1) the essential intermediates 4 are
probably generated in situ by replacement of the bromo
anion with the hydrotelluro or hydroseleno group because
of an enhancement of the reactivity due to the presence of
a carbonyl group as an electron-withdrawing group;10 and
(2) the intramolecular regioselective Michael-type addi-
tion in 4 proceeds via path a to afford the six-membered
ring heterocycles 3. The results and the spectral data of the
products 3 are summarized in the Table.
HRMS m/z: M+ Calcd for C15H17OBr: 292.0463, 294.0444. Found:
292.0070, 294.0036.
2e (R = n-Oct): yellow oil; yield: 22.79 g (7l%).
IR: n = 2208 (CC), 1660 cm–1(C=O).
1H NMR (60 MHz): d = 0.87, 1.0–1.8 and 2.43 (3H, t, J = 6 Hz, 12H,
m and 2H, t, J = 6 Hz, n-Oct), 7.3–7.7 and 7.9–8.1 (3H, m and 1H, m,
Ar-H).
HRMS m/z: M+ Calcd for C17H21OBr: 320.0776, 322.0757. Found:
320.0783, 322.0743.
In conclusion, the present results provide a new synthetic
route for preparing telluro- and selenochromones. Studies
on the utility of these compounds and their applications to
other synthetic strategies are in progress.
2f (R = Ph): yellow oil; yield: 22.96 g (89%).
IR: n = 2196 (CC), 1652 cm–1(C=O).
1H NMR (60 MHz): d = 7.3–7.8 and 8.0–8.2 (8H, m and 1H, m, Ar-
H).
HRMS m/z: M+ Calcd for C15H9OBr: 283.9837, 285.9818. Found:
283.9836, 285.9818.
Mps were measured on a Yanagimoto micro melting point hot stage
apparatus and are uncorrected. IR spectra were determined with a Hi-
tachi 270-30 spectrometer. MS and HRMS were recorded on a JEOL
JMS-DX300 instrument.1H NMR spectra were determined with a
JEOL PMX-60SI (60 MHz) spectrometer in CDCl3 using TMS as in-
ternal standard. Although o-bromobenzoyl chloride (1) is commer-
cially available, it is easily prepared from o-bromobenzoic acid and
thionyl chloride almost quantitatively.
o-Bromophenyl Trimethylsilylethynyl Ketone (2g):
Amixture of benzoyl chloride 1 (10.98 g, 50 mmol), tributyl[(trimeth-
ylsilyl)ethynyl]stannane (20.18 g, 52 mmol) and benzylchloro-
bis(triphenylphosphine)palladium(II) (200 mg) in CHCl3 (50 mL)
was heated at 60°C with stirring for 6 h. The mixture was cooled, di-
luted with Et2O (200 mL), and filtered through a Celite pad to remove
the palladium precipitate. After evaporation oforganic solvent, the re-
sulting residue was purified by chromatography (silica gel, n-hexane)
to give 2g; pale-yellow oil; yield: 6.32 g (45%).
o-Bromophenyl Ethynyl Ketones 2; Typical Procedure:
To a mixture of a 1-alkyne (0.1 mol) and o-bromobenzoyl chloride (1)
(21.95 g, 0.1 mol) in Et3N (160 mL) and benzene (40 mL) were added
PdCl2[Ph3P]2 (100 mg) and Cul (100 mg). The mixture was stirred at
r.t. under argon for 12–15 h. After addition of MeOH (10 mL), the
solvent was removed under reduced pressure. Benzene (300 mL) and
water (200 mL) were added to the residue and the aqueous layer was
extracted with benzene (2´200 mL). The combined organic extract
was washed with water (5´200 mL), 5% H2SO4 (3 ´ 200 mL), sat.
NaHCO3 (2´200 mL) and brine (2´200 mL), and then dried
(MgSO4). Benzene was removed in vacuo. The red residual oil was
purified by chromatography (silica gel, n-hexane) to give pure 2. In
the case of 2a, a slow stream of methylacetylene, which was prepared
from 1,2-dibromopropane and KOH in refluxing BuOH, was imme-
diately passed through the mixture without isolation.
IR: n = 2156 (CC), 1660 cm–1(C=O).
1H NMR (60 MHz): d = 0.35 (9H, s, TMS), 7.3–7.8 and 8.0–8.2 (3H,
m and 1H, m, Ar-H).
HRMS m/z: M+ Calcd for C12H13OBrSi: 279.9919, 281.9899. Found:
279.9886, 281.9869.
Preparation of Tellurochromones 3A; Typical Procedure:
A solution of o-bromophenyl ethynyl ketone 2 (10 mmol) in DMF
(20 mL) was slowly added to a stirred solution of NaHTe (12 mmol),
which was prepared from tellurium powder (1.54 g) and NaBH4
(0.54 g) in DMF (40 mL), at about 100°C for 1 h under argon. The
mixture was stirred under these conditions for 2–5 h. After the addi-
tion of water (100 mL), the mixture was filtered. The filtrate was ex-
tracted with benzene (3 ´ 100 mL). The combined organic extracts
were washed with water (3 ´ 200 mL) and brine (2 ´ 200 mL), dried
(MgSO4), and concentrated. The resulting residue was purified by
chromatography (silica gel, n-hexane/acetone 50:1) to give 3A. Crys-
talline products were recrystallized from n-hexane/acetone.
2a (R = Me): yellow oil; yield: 7.36 g (33%).
IR: n = 2212 (CC), 1658 cm–1(C=O).
1H NMR (60 MHz): d = 2.12 (3H, s, Me), 7.3–7.8 and 8.0–8.2 (3H,
m and 1H, m, Ar-H).
HRMS m/z: M+ Calcd for C10H7OBr: 221.9680, 223.9660. Found:
221.9677, 223.9696.
Preparation of Selenochromones 3B; Typical Procedure:
A solution of 2 (10 mmol) in EtOH (20 mL) was treated with NaHSe
(12 mmol), prepared from selenium powder (0.95 g) and NaBH4
(0.54 g), as described above. Similar workup gave 3B.
2b (R = n-Bu): yellow oil; yield: 18.82 g (71%).
IR: n = 2204 (CC), 1658 cm–1(C=O).
1H NMR (60 MHz): d = 0.93, 1.2–1.8 and 2.47 (3H, t, J = 7 Hz, 4H,
m and 2H, t, J = 6 Hz, n-Bu), 7.3–7.8 and 8.0–8.2 (3H, m and 1H, m,
Ar-H).
HRMS m/z: M+ Calcd for C13H13OBr: 264.0150, 266.0130. Found:
264.0150, 266.0121.
(1) Studies on Tellurium-Containing Heterocycles part 5. For part
4, see ref 6d.
(2) Sadekov, I. D.; Minkin, V. Adv. Heterocycl. Chem. 1995, 63, 1.
(3) Bossert, F. Angew. Chem., Int. Ed. Engl. 1965, 4, 879.
2c (R = t-Bu): yellow oil; yield: 18.82 g (71%).
IR: n = 2212 (CC), 1662 cm–1(C=O).

748
Papers
SYNTHESIS
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