Synthesis and stille cross-coupling reactions of 2-(tributylstannyl)-and 2,5-bis(trimethylstannyl)tellurophene

Article abstract of DOI:10.1055/s-0029-1216958

Herein, we describe the synthesis and Stille cross-coupling reactions of 2-(tributylstannyl)-and 2,5-bis(trimethylstannyl) tellurophene. The reactions were most optimal when using aryl iodides as coupling partners, and a mixed catalyst system consisting o

Full text of DOI:10.1055/s-0029-1216958

3214
PAPER
Synthesis and Stille Cross-Coupling Reactions of 2-(Tributylstannyl)- and
2,5-Bis(trimethylstannyl)tellurophene
Stille
R
eactions of
a
2-(Tributyl
n
stannyl)
-
a
nd
i
2,5-B
e
is(trimethy
l
lstannyl)tellur
P
ophene . Sweat, Chad E. Stephens*
Department of Chemistry and Physics, Augusta State University, Augusta, GA 30904, USA
Fax +1(706)4345597; E-mail: cstephe7@aug.edu
Received 30 March 2009; revised 13 June 2009
Initially, we focused on the synthesis of 2-(tributylstan-
Abstract: Herein, we describe the synthesis and Stille cross-cou-
pling reactions of 2-(tributylstannyl)- and 2,5-bis(trimethylstan-
nyl)tellurophene. The reactions were most optimal when using aryl
iodides as coupling partners, and a mixed catalyst system consisting
nyl)tellurophene (1). Similar to furan and thiophene,8
standard monolithiation of tellurophene using butyllithi-
um (1.1 equiv) in diethyl ether for 30 minutes at room
of tetrakis(triphenylphosphine)palladium(0) and copper(I) iodide, temperature, followed by quenching with tributyltin chlo-
together with cesium fluoride as additive, in N,N-dimethylform-
ride, gave the desired mono-tin tellurophene 1 in 57%
amide. This is the first reported synthesis and use of stannylated tel-
yield as a pale-yellow liquid after vacuum distillation
lurophenes for cross-coupling reactions.
(Scheme 1). The use of N,N,N’,N’-tetramethylethylenedi-
amine (TMEDA) in the monolithiation did not improve
Key words: tellurophene, Stille reaction, cross-coupling, palladi-
um, heterocyclic
the yield.
Next, we turned our attention to the synthesis of the di-tin
tellurophene. In this case, we elected to prepare the bis(tri-
Transition-metal catalyzed cross-coupling reactions are
methylstannyl) analogue (2), as this was expected to form
highly utilized in organic synthesis for the construction of
a crystalline solid, considering the corresponding
carbon–carbon bonds.1,2 Of the various types of aryl–aryl
thiophene11 and selenophene13 are solids. Our initial at-
cross-coupling reactions, the Stille reaction is one of the
tempts at dilithiation using butyllithium (2.1 equiv) and
most used due to the stability and wide functional-group
TMEDA in diethyl ether at room temperature gave a poor
compatibility of arylstannanes.3 As a result, the synthesis
yield of the di-stannyl tellurophene 2 (<20% yield), with
of numerous aryl and heteroaryl stannanes and their sub-
a significant amount of the mono-stannyl product being
sequent use in cross-coupling reactions have now been de-
isolated (27% yield) after quenching with trimeththyltin
scribed in the literature.1–3
chloride. However, upon performing the dilithiation using
sec-butyllithium and TMEDA11 and heating in hexanes
for 45 minutes before quenching, we were able to obtain
a 42% yield of 2 as a colorless crystalline solid after re-
crystallization from methanol. Both the mono- and di-
stannyl tellurophenes appear to be very stable compounds,
with no visual evidence of decomposition upon prolonged
storage at 0 °C. In contrast, tellurophene itself is prone to
decomposition upon similar storage.
As part of an ongoing project involving the synthesis of
di-cationic diarylchalcogenophenes,4,5 we were in recent
need of an efficient synthesis of various 2,5-diaryltel-
lurophenes. The most common route to such compounds,
involving the cyclization of 1,4-diaryl-1,3-butadiynes to
2,5-diaryltellurophenes with sodium telluride (Na2Te),6
was not sufficient in our hands. We thus considered the
use of the Stille cross-coupling reactions of a distannylat-
ed tellurophene with an aryl halide. A literature review re-
vealed that Stille reactions using stannylated
tellurophenes have not been previously described, al-
though reactions employing stannylated furans,7
thiophenes1b and even selenophenes8 are known. Further-
more, although there have been recent examples of cross-
coupling reactions involving halogenated tellurophenes as
coupling partners,9 there have been no reports of cross-
coupling reactions involving a metallated tellurophene as
a coupling partner.10 We thus set out to develop this chem-
istry. As a result, we now describe the synthesis and cross-
coupling reactions of 2-(tributylstannyl)tellurophene and
2,5-bis(trimethylstannyl)tellurophene for the convenient
synthesis of 2-aryl- and 2,5-diaryltellurophenes.
1. n-BuLi ( 1 equiv), Et2O, r.t.
2. (n-Bu)3SnCl (1 equiv)
Te
Sn(n-Bu)3
1 (57%)
Te
1. s-BuLi (2 equiv), TMEDA,
hexanes, Δ
Me3Sn
Te
2 (42%)
SnMe3
2. Me3SnCl (2 equiv)
Scheme 1 Synthesis of mono- and di-stannyltellurophenes
With the mono- and di-stannyl tellurophenes in hand, we
turned to the Stille cross-coupling reactions. Our first cou-
pling involved the reaction of mono-tin tellurophene 1
with 4-bromobenzonitrile (1 equiv) in the presence of tet-
SYNTHESIS 2009, No. 19, pp 3214–3218
Advanced online publication: 21.08.2009
DOI: 10.1055/s-0029-1216958; Art ID: M01409SS
© Georg Thieme Verlag Stuttgart · New York
x
x.
x
x
.
2
0
0
9

PAPER
Stille Reactions of 2-(Tributylstannyl)- and 2,5-Bis(trimethylstannyl)tellurophene
3215
rakis(triphenylphosphine)palladium(0) (2–3 mol%) in night (16 h) at just 60 °C, with a 64% yield of coupling
toluene, which are typical conditions3 for a Stille coupling product 3a being obtained after purification. Satisfied
(Scheme 2). This reaction proved sluggish, and after heat- with this result, we explored the use of other aryl iodides
ing for two days at near reflux, the yield of 2-(4-cy- in this reaction. Table 1 shows the results obtained from
anophenyl)tellurophene (3a) was only 36% following the synthesis of a number of 2-aryltellurophenes that were
purification. In our previous work, these standard condi- prepared in this manner, with purified yields ranging from
tions gave much higher yields when the analogous mono- 61–88%.
stannyl furan,7 thiophene12 and even selenophene4 were
coupled with 4-bromobenzonitrile, with no noticeable dif-
Table 1 Yields for Various 2-Aryltellurophenes Prepared by Stille
Coupling
ferences in reactivity observed within the series. On the
other hand, Tierney and co-workers13 have recently ob-
I
served a lower reactivity of a stannylated selenophene
R
compared to the analogous thiophene. In the end, our re-
sults here suggest a relatively low reactivity for stannylat-
ed tellurophene 1 in Stille couplings.
Te
Te
Sn(n-Bu)3
R
Pd(PPh3)4, CuI, CsF
DMF, 60 °C, ~16 h
3a–e
1
Entry
Compd
R
Yield (%)
Mp (°C)
65–66
45–46
47–48
102
Br
1
2
3
4
5
3a
3b
3c
3d
3e
CN
H
64
61
62
88
63
CN
Pd(PPh3)4, PhMe, 110 °C
2 d, 36%
Me
NO2
OMe
Te
Sn(n-Bu)3
Te
3a
106–107
I
1
CN
CN
The mixed catalyst conditions were next applied to cross-
coupling reactions with of di-stannyl tellurophene 2. Here
again, aryl iodides were used as coupling partners. As
shown in Table 2, the yields obtained for the symmetrical
2,5-diaryltellurophenes ranged from moderate to excel-
lent (42–88%), with yields being highest for those prod-
ucts containing an electron-withdrawing group (entries 1
and 4). The lower yields for the other products may partly
be a consequence of our purification method (recrystalli-
zation), although the electronic nature of the substituents
could have affected the coupling reaction. Ultimately, this
Stille approach has allowed us to prepare these 2,5-diaryl-
tellurophenes in a very convenient manner, where the tra-
ditional tellurophene ring-forming approach had
generally failed in our hands.
Pd(PPh3)4, CuI, CsF
DMF, 60 °C
16 h, 64%
Scheme 2 Stille coupling of mono-stannyl tellurophene 1 with
4-bromo- or 4-iodobenzonitrile
In an attempt to improve the yield of the coupling reac-
tion, we explored the use of an aryl iodide as coupling
partner, instead of the aryl bromide. We also included
copper(I) iodide as co-catalyst and cesium fluoride as ad-
ditive, and changed the solvent to N,N-dimethylform-
amide, conditions which have been shown to improve
certain Stille couplings.14 Under these conditions
(Scheme 2), the reaction was complete after heating over-
Table 2 Yields for Various 2,5-Diaryltellurophenes Prepared by Stille Coupling
I
(2 equiv)
R
Te
Me3Sn
Te
SnMe3
Pd(PPh3)4, CuI, CsF
DMF, 60 °C, ~16 h
R
R
4a–e
2
Entry
Compd
4a
R
Yield (%)
Mp (°C)
231–232
224–225
239–240
271–272
278
1
2
3
4
5
CN
H
88
42
47
67
42
4b
4c
Me
NO2
OMe
4d
4e
Synthesis 2009, No. 19, 3214–3218 © Thieme Stuttgart · New York

3216
D. P. Sweat, C. E. Stephens
PAPER
CuSO4 until no more precipitate appeared. The extract was filtered
over Celite, washed with H2O (2 × 50 mL), dried over Na2SO4 and
concentrated to approximately 50 mL on a rotary evaporator. After
chilling on ice, crystals (6.8 g) were collected by suction. Concen-
tration of the filtrate and trituration with MeOH gave a second crop
of crystals (1.2 g). Both sets of crystals were combined and recrys-
tallized from MeOH.
In summary, novel mono- and di-stannyl tellurophenes
have been prepared and used for the convenient prepara-
tion of 2-aryl- and 2,5-diaryltellurophenes by Stille cou-
pling with aryl iodides. The mixed copper–palladium
catalyst system, with cesium fluoride as additive, was
found to give moderate to excellent yields of the coupling
products and appears to perform better than the standard
Stille conditions that employ a palladium catalyst alone.
This chemistry, which is the first example of the use of
stannylated tellurophenes for coupling reactions, has al-
Yield: 7.1 g (42%); colorless crystals; mp 120 °C (MeOH).
1H NMR (300 MHz, CDCl3): d = 8.31 (s, 2 H), 0.26 (s, 18 H).
13C NMR (75 MHz, CDCl3): d = 147.3, 146.0, –7.3.
lowed the preparation of arylated derivatives that were not Anal. Calcd for C10H20Sn2Te: C, 23.77; H, 3.99. Found: C, 23.86;
H, 4.01.
readily available by other methods.
Synthesis of 2-Aryltellurophenes by Stille Coupling; Typical
Procedure
Tellurophene was prepared according to our published procedure.15
Et2O was distilled from a sodium/benzophenone still prior to use.
Hexanes was dried over CaH2 and distilled prior to use. Anhydrous
DMF was purchased and used as received. 1H NMR spectra were re-
corded on a Bruker Avance spectrometer at 300 MHz using the re-
sidual solvent peak as an internal standard (d = 7.26 ppm for CDCl3,
2.49 ppm for DMSO-d6). 13C NMR spectra were recorded at 75
MHz using the residual solvent peak as an internal standard (d =
77.5 ppm for CDCl3; 39.5 ppm for DMSO-d6). Melting points were
obtained using a Mel-Temp 1201D apparatus and are uncorrected.
Elemental analyses were performed by Atlantic Microlab, Inc. High
resolution mass spectra were provided by the Mass Spectrometry
Laboratory at the University of Alabama. IR was performed with a
Perkin–Elmer Spectrum 100 FT-IR spectrometer using ATR.
2-(4-Cyanophenyl)tellurophene (3a)
To a 25 mL round-bottom flask was added 4-iodobenzonitrile
(0.192 g, 0.84 mmol), Pd(PPh3)4 (0.048 g, 42 mmol), CsF (0.255 g,
1.68 mmol), CuI (0.016 g, 84 mmol), and then DMF (2 mL). After
purging with nitrogen, tellurophene 1 (0.436 g, 0.93 mmol) was
added and the mixture was heated at 50–60 °C overnight. After this
time, TLC (hexanes–EtOAc, 3:1) showed the disappearance of 4-
iodobenzonitrile. The reaction was then extracted with CH2Cl2 and
washed with H2O (3 × 10 mL). The extract was dried over Na2SO4
and concentrated on a rotary evaporator. The yellow solid was then
recrystallized from hexanes (30 mL) to give the product 3a.
Yield: 0.15 g (64%); fine yellow solid; mp 63 °C.
IR: 3093, 3027, 2919, 2847, 2226, 1598, 1439, 1255, 825, 676 cm–1.
2-(Tributylstannyl)tellurophene (1)
1H NMR (300 MHz, DMSO-d6): d = 9.01 (dd, J = 1.0, 6.7 Hz, 1 H),
8.20 (dd, J = 1.0, 4.1 Hz, 1 H), 7.88 (dd, J = 4.1, 6.7 Hz, 1 H), 7.79
(d, J = 8.5 Hz, 2 H), 7.72 (d, J = 8.5 Hz, 2 H).
13C NMR (75 MHz, DMSO-d6): d = 147.3, 144.3, 138.6, 136.2,
133.0, 131.7, 172.2, 119.0, 109.3.
To a three-neck, round-bottom flask (100 mL) was added tel-
lurophene (3.58 g, 20 mmol) and anhyd Et2O (50 mL). An addition
funnel loaded with (n-Bu)3SnCl (7.16 g, 22 mmol) was placed on
the flask. At r.t. and under nitrogen, BuLi (13.75 mL, 1.6 M in hex-
anes, 22 mmol) was added slowly by syringe to the tellurophene so-
lution, and the resulting tan-colored mixture was stirred at r.t. for 45
min. The mixture was then chilled in a salt-water–ice bath, and the
(n-Bu)3SnCl was slowly added. After stirring overnight (~18 h), a
small amount of EtOH was added and the mixture was washed with
H2O (3 × 50 mL). The dark-red organic layer was dried over
Na2SO4 and concentrated by rotary evaporation to give a thin oil.
Vacuum distillation (8 cm vigreux fractionating column at ~1 Torr)
gave the product 1, which was pure by GC/MS.
Anal. Calcd for C7H11NTe: C, 47.05; H, 2.51; N, 4.99. Found: C,
46.82; H, 2.45; N, 4.90.
2-Phenyltellurophene (3b)
Yield: 0.130 g (61%); golden sheets; mp 45–46 °C (MeOH–H2O).
IR: 3071, 3045, 3009, 1592, 1483, 1444, 1256, 1209, 1071, 1033,
843, 752, 679 cm–1.
1H NMR (300 MHz, CDCl3): d = 8.81 (dd, J = 3.7, 4.4 Hz, 1 H),
7.82 (d, J = 4.2 Hz, 1 H), 7.51–7.48 (m, 1 H), 7.35–7.26 (m, 5 H).
13C NMR (75 MHz, CDCl3): d = 150.2, 140.6, 139.2, 133.8, 129.4,
128.0, 127.6, 126.0.
Yield: 5.3 g (57%); pale-yellow liquid; bp 160 °C.
1H NMR (300 MHz, CDCl3): d = 9.28 (d, J = 6.4 Hz, 1 H), 8.15 (d,
J = 3.6 Hz, 1 H), 8.02 (d, J = 6.4 Hz, 1 H), 1.60–1.40 (m, 6 H),
1.38–1.33 (m, 6 H), 1.14–1.08 (m, 6 H), 0.95–0.90 (m, 9 H).
13C NMR (75 MHz, CDCl3): d = 146.0, 140.4, 140.2, 130.5, 29.5,
27.8, 14.2, 12.1.
HRMS (EI): m/z calcd for C10H8Te: 253.9659 (126Te), 255.9671
(
(
128Te), 257.9688 (130Te). Found: 253.9655 (126Te), 255.9677
128Te), 257.9685 (130Te).
HRMS (EI): m/z [M+] calcd for C16H30118Sn130Te: 470.0275; found:
470.0289.
2-(4-Methylphenyl)tellurophene (3c)
Yield: 0.115 g (62%); yellow solid; mp 47–48 °C (MeOH–H2O).
2,5-Bis(trimethylstannyl)tellurophene (2)
IR: 3081, 3056, 3017, 2917, 2860, 1725, 1603, 1535, 1504, 1445,
1256, 1120, 807, 746, 706, 688 cm–1.
1H NMR (300 MHz, CDCl3): d = 8.76 (dd, J = 1.5, 6.6 Hz, 1 H),
7.78 (m, 2 H), 7.38 (d, J = 8.1 Hz, 2 H), 7.14 (m, 2 H), 2.36 (s, 3 H).
13C NMR (75 MHz, CDCl3): d = 150.3, 139.1, 138.1, 136.8, 133.2,
130.1, 127.4, 125.2, 21.6.
To a three-neck, round-bottom flask (500 mL) was added tel-
lurophene (6.1 g, 34 mmol), TMEDA (8.33 g, 71.6 mmol) and hex-
anes (100 mL). Under nitrogen, the mixture was chilled in an ice–
water bath and s-BuLi (51.1 mL, 1.4 M in cyclohexane) was added
dropwise by addition funnel. The resulting light colored suspension
was then heated to near reflux for 45 min. The dark-brown mixture
was then chilled in an ice-bath again and Me3SnCl (71.6 mL, 1.0 M
in hexanes) was slowly added by addition funnel. After stirring
overnight at r.t., sat. aq NH4Cl (80 mL) was added to the reaction.
The layers were separated and the organic layer was washed with aq
HRMS (EI): m/z calcd for C11H10Te: 267.9816 (130Te), 269.9827
(
(
128Te), 271.9845 (126Te). Found: 267.9816 (130Te), 269.9828
128Te), 271.9848 (126Te).
Synthesis 2009, No. 19, 3214–3218 © Thieme Stuttgart · New York

PAPER
Stille Reactions of 2-(Tributylstannyl)- and 2,5-Bis(trimethylstannyl)tellurophene
3217
2-(4-Nitrophenyl)tellurophene (3d)
Yield: 0.220 g (88%); yellow-orange crystals; mp 102 °C (hex-
anes).
13C NMR (75 MHz, DMSO-d6): d = 148.1, 139.7, 134.9, 129.6,
128.3, 126.9.
2,5-Bis(4-methylphenyl)tellurophene (4c)
Yield: 0.158 g (47%); grey sheets; mp 239–240 °C (CH2Cl2–hex-
anes).
IR: 3097, 3071, 1584, 1522, 1500, 1430, 1370, 1317, 1260, 1207,
1184, 1113, 850, 828, 749, 686, 679 cm–1.
1H NMR (300 MHz, CDCl3): d = 9.02 (dd, J = 1.2, 6.8 Hz, 1 H),
8.20 (d, J = 8.8 Hz, 2 H), 7.98 (dd, J = 1.2, 4.1 Hz, 1 H), 7.88 (dd,
J = 4.0, 6.5 Hz, 1 H), 7.60 (d, J = 8.8 Hz, 2 H).
13C NMR (75 MHz, CDCl3): d = 147.2, 146.9, 139.5, 136.6, 132.1,
130.0, 127.8, 124.9.
IR: 3014, 2911, 2855, 2722, 1893, 1545, 1497, 1462, 1287, 1122,
893, 796 cm–1.
1H NMR (300 MHz, DMSO-d6): d = 7.92 (s, 2 H), 7.42 (d, J = 7.8
Hz, 4 H), 7.16 (d, J = 7.8 Hz, 4 H), 2.29 (s, 6 H).
13C NMR (75 MHz, DMSO-d6): d = 147.8, 138.1, 137.4, 134.6,
130.5, 127.1, 21.6.
Anal. Calcd for C10H7NO2Te: C, 39.93; H, 2.35; N, 4.66. Found: C,
40.00; H, 2.24; N, 4.61.
Anal. Calcd for C18H16Te: C, 60.07; H, 4.48. Found: C, 59.79; H,
4.51.
2-(4-Methoxyphenyl)tellurophene (3e)
Yield: 0.150 g (63%); golden sheets; mp 106–107 °C (hexanes)
(Lit.16 111–112 °C).
2,5-Bis(4-nitrophenyl)tellurophene (4d)
Yield: 0.261 g (67%); dark-red solid; mp 271–272 °C (CH2Cl2–
hexanes).
IR: 3083, 3019, 2968, 2936, 2913, 2840, 1600, 1571, 1554, 1533,
1501, 1442, 1415, 1307, 1283, 1257, 1241, 1178, 1022, 824, 812,
793, 686 cm–1.
1H NMR (300 MHz, CDCl3): d = 8.72 (dd, J = 6.8, 1.2 Hz, 1 H),
7.77 (dd, J = 6.8, 4.0 Hz, 1 H), 7.68 (d, J = 1.2, 4.0 Hz, 1 H), 7.42
(dd, J = 6.7, 2.2 Hz, 2 H), 6.87 (dd, J = 6.7, 2.2 Hz, 2 H), 3.83 (s,
3 H).
IR: 3109, 3063, 2911, 1581, 1539, 1495, 1446, 1322, 1294, 1276,
1109, 841, 796, 725, 683 cm–1.
1H NMR (300 MHz, CDCl3): d = 8.24 (d, J = 9.4 Hz, 4 H), 8.05 (s,
2 H), 7.61 (d, J = 9.4 Hz, 4 H).
13C NMR (75 MHz, CDCl3): d = 148.9, 147.5, 146.0, 137.2, 127.6,
125.0.
13C NMR (75 MHz, CDCl3): d = 159.8, 149.9, 139.1, 133.5, 132.7,
128.6, 124.7, 114.8, 55.9.
Anal. Calcd for C16H10N2O4Te: C, 45.55; H, 2.39; N, 6.64. Found:
C, 45.43; H, 2.38; N, 6.65.
Anal. Calcd for C11H10OTe: C, 46.23; H, 3.53. Found: C, 46.17; H,
3.49.
2,5-Bis(4-methoxyphenyl)tellurophene (4e)
Yield: 0.154 g (42%); golden sheets; mp 278 °C (acetone).
2,5-Diaryltellurophenes by Stille Coupling; Typical Procedure
2,5-Bis(4-cyanophenyl)tellurophene (4a)
IR: 3016, 2949, 2836, 1600, 1567, 1544, 1498, 1466, 1439, 1411,
1273, 1240, 1178, 1113, 1028, 1006, 831, 822, 799, 790 cm–1.
1H NMR (300 MHz, CDCl3): d = 7.66 (s, 2 H), 7.40 (d, J = 6.7 Hz,
4 H), 6.87 (d, J = 6.7 Hz, 4 H), 3.83 (s, 6 H).
13C NMR (75 MHz, CDCl3): d = 159.3, 146.7, 133.0, 132.8, 127.8,
114.3, 55.4.
To a 25 mL round-bottom flask was added 4-iodobenzonitrile
(0.498 g, 2 mmol), Pd(PPh3)4 (0.107 g, 93 mmol), CsF (0.565 g, 3.72
mmol), CuI (0.035 g, 186 mmol) and then DMF (4 mL). After purg-
ing with nitrogen, 2,5-bis(trimethylstannyl)tellurophene (2; 0.467
g, 0.93 mmol) was added and the mixture was heated at 50–60 °C
overnight (~16 h). The reaction was then diluted with MeOH and
the resulting precipitate was collected by suction. This precipitate
was dissolved in CH2Cl2 and gravity filtered to remove Pd catalyst.
The filtrate was then partially concentrated on a rotary evaporator
(to about half volume) and diluted with hexanes (about equal vol-
ume). The solution was then further concentrated until nearly all the
CH2Cl2 had evaporated. The resulting solid (0.302 g, 88%) was col-
lected by suction and recrystallized from MeOH (~130 mL) to give
the product 4a.
Anal. Calcd for C18H16O2Te: C, 55.16; H, 4.11. Found: C, 55.09; H,
4.16.
Acknowledgment
This work was supported by the Bill and Melinda Gates Foundation
through collaborations with Georgia State University and the Uni-
versity of North Carolina at Chapel Hill. Support from our Depart-
ment and University is also gratefully acknowledged.
Yield: 0.302 g (88%); fibrous golden-red crystals; mp 231–232 °C.
IR: 3025, 2220, 1920, 1680, 1595, 1547, 1537, 1491, 1456, 1408,
1201, 1174, 898, 837, 797 cm–1.
References
1H NMR (300 MHz, DMSO-d6): d = 8.30 (s, 2 H), 7.89 (d, J = 8.0
Hz, 4 H), 7.75 (d, J = 8.0 Hz, 4 H).
(1) (a) Corbet, J.-P.; Mignani, G. Chem. Rev. 2006, 106, 2651.
(b) Li, J. J.; Gribble, G. W. Palladium in Heterocyclic
Chemistry, 2nd ed; Elsevier Ltd.: Amsterdam, 2007.
(2) (a) Cross-Coupling Reactions: A Practical Guide; Miyaura,
N., Ed.; Springer-Verlag: Berlin / Heidelberg, 2002.
(b) Nicolaou, K. C.; Bulger, P. G.; Sarlah, D. Angew. Chem.
Int. Ed. 2005, 44, 4442.
(3) Farina, V.; Krishnamurthy, V.; Scott, W. J. Organic
Reactions, Vol. 50; Paquette, L., Ed.; Wiley: New York,
1997.
(4) Liu, Y.; Collar, C. J.; Kumar, A.; Stephens, C. E.; Boykin,
D. W.; Wilson, W. D. J. Phys. Chem. B 2008, 112, 11809.
(5) (a) Rosypal, A. C.; Werbovetz, K. A.; Salem, M.; Stephens,
C. E.; Kumar, A.; Boykin, D. W.; Hall, J. E.; Tidwell, R. R.
J. Parasitol. 2008, 94, 743. (b) Silva, C. F.; Batista, M. M.;
13C NMR (75 MHz, CDCl3): d = 148.3, 143.4, 137.3, 133.0, 127.3,
118.9, 109.9.
Anal. Calcd for C18H10N2Te: C, 56.61; H, 2.64; N, 7.34. Found: C,
56.74; H, 2.64; N, 7.36.
2,5-Diphenyltellurophene (4b)
Yield: 0.130 g (42%); light-yellow sheets; mp 224–225 °C (CHCl3–
MeOH) (Lit.17 220–224 °C).
IR: 3052, 3008, 1592, 1481, 1461, 1439, 887, 809, 743, 683 cm–1.
1H NMR (300 MHz, DMSO-d6): d = 8.02 (s, 2 H), 7.57–7.54 (m,
4 H), 7.39–7.29 (m, 6 H).
Synthesis 2009, No. 19, 3214–3218 © Thieme Stuttgart · New York

3218
D. P. Sweat, C. E. Stephens
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Synthesis 2009, No. 19, 3214–3218 © Thieme Stuttgart · New York