Synthesis of secondary and tertiary aminothiophenes via palladium-catalyzed amination

Full text of DOI:10.1021/jo016195q

J . Org. Chem. 2001, 66, 9067-9070
9067
Ta ble 1. P d -Ca ta lyzed Am in a tion of 3-Br om oth iop h en e
Syn th esis of Secon d a r y a n d Ter tia r y
Am in oth iop h en es via P a lla d iu m -Ca ta lyzed
Am in a tion
Katsu Ogawa, Karla R. Radke, Scott D. Rothstein, and
Seth C. Rasmussen*
Department of Chemistry, North Dakota State University,
Fargo, North Dakota 58105
entry
amine
product (%)a
product (%)a
1
2
3
4
5
6
7
NH2C6H13
NH2C8H17
NH2C10H21
NH2C(CH3)3
1a (37)
2a (36)
3a (44)
4a (54)
5 (24)
1b (20)
2b (29)
3b (44)
4b (19)
seth.rasmussen@ndsu.nodak.edu
Received October 12, 2001
NH(C6H13
)
2
p-NH2ArC6H13
6a (75)
6b (18)
2b (83)
2a
In tr od u ction
a
Isolated yields based on 3-bromothiophene.
Functionalized thiophenes are useful precursors for
natural products,1 pharmaceuticals,2 conjugated poly-
mers,3 and other related materials.4 While a wide variety
of functionalized thiophenes have been synthesized for
these applications, no broadly applicable methodology
really exists for the synthesis of aminothiophenes. The
Gewald reaction is the most well-established route but
is limited to the production of primary 2-aminothiophenes
containing electron-withdrawing groups in the 3-posi-
tion.2a,5 The analogous 3-aminothiophene has been made
by a number of methods,6 and Paulmier and co-workers
have investigated its N-alkylation, but with only a small
number of functional groups.6b
Reported examples of the direct amination of thiophenes
are even more limited. Certain halothiophenes undergo
nucleophilic aromatic substitution with amines, but this
reaction is restricted to very electron deficient systems.7
More recently, however, Buchwald8 and Hartwig’s9 work
on the palladium-catalyzed amination of arylhalides has
been applied to halothiophenes. The first Pd-catalyzed
amination of a halothiophene was reported by Watanabe
and co-workers, who showed that mono- and dibro-
mothiophenes could be successfully coupled with diaryl-
amines using a Pd(OAc)2/P(tBu)3 catalyst system.4 Fol-
lowing up on this work, Luker and co-workers reported
an alternate catalytic system that could be used under
milder conditions but was limited to the coupling of
halothiophenes containing electron-withdrawing groups
in conjugation with the halogen (2,3- or 2,5-isomers).2b
Due to our interest in the production of functionalized
polyaminothiophenes, we needed a convenient and gen-
eral approach to the production of 3-(N-alkyl)- and 3-(N-
aryl)-aminothiophenes while leaving the thiophene R-po-
sitions free for subsequent polymerization. Working
toward this goal, we have applied Watanabe’s reaction
conditions to the alkylamination of bromothiophenes and,
in the process, have carefully studied the working
boundaries of the various reaction conditions.
Resu lts a n d Discu ssion
Application of the Pd(OAc)2/P(tBu)3 catalyst system to
the amination of 3-bromothiophene successfully produced
the desired 3-(N-alkyl)- and 3-(N,N-dialkyl)-amino-
thiophenes as shown in Table 1 (entries 1-5). The
isolated yields in these cases, however, were much lower
than the analogous reactions using arylamines (Table 1,
entries 6 and 7), and in all cases, the use of primary
amines resulted in a significant amount of diarylation
byproduct (1b-4b, 6b). In all cases, catalyst concentra-
tions could be reduced to 1 mol % without a reduction in
yields.
A proposed catalytic cycle based on the previous
mechanistic studies of haloaryl aminations is shown in
Scheme 1.8,9 The lower yields resulting from the use of
alkylamines is at least partially due to a â-elimination
pathway that competes with the desired reductive elimi-
nation step (i.e., formation of complex VI). The presence
of this pathway is evidenced by the isolation of small
amounts of alkylimines in these reactions. In addition,
when the possibility of â-elimination is removed as in
entry 4, a significant increase is observed in the isolated
yield. Likewise, the use of dialkylamines increases the
potential for â-elimination and results in lowered yields
(entry 5).
(1) (a) Bohlmann, F.; Zdero, C. In Thiophene and its Derivatives;
Gronowitz, S., Ed.; J ohn Wiley & Sons: New York, 1985; Part 1, pp
261-323. (b) Koike, K.; J ia, Z.; Nikaido, T.; Liu, Y.; Zhao, Y.; Guo, D.
Org. Lett. 1999, 1, 197.
(2) (a) Pinto, I. L.; J arvest, R. L.; Serafinowska, H. T. Tetrahedron
Lett. 2000, 41, 1597. (b) Luker, T. J .; Beaton, H. G.; Whiting, M.; Mete,
A.; Cheshire, D. R. Tetrahedron Lett. 2000, 41, 7731.
(3) (a) Conjugated Conducting Polymers; Kiess, H., Ed.; Springer
Series in Solid State Sciences, Vol. 102; Springer-Verlag: New York,
1992. (b) Roncali, J . Chem. Rev. 1992, 92, 711. (c) Schopf, G.; Kossmehl,
G. Adv. Polym. Sci. 1997, 129, 1. (d) Rasmussen, S. C.; Straw, B. D.;
Hutchison, J . E. In Semiconducting Polymers: Applications, Synthesis,
and Properties; Hsieh, B. R., Wei, W., Galvin, M., Eds.; ACS Sympo-
sium Series 735; American Chemical Society: Washington, DC, 1999;
pp 347-366.
(4) Watanabe, M.; Yamamoto, T.; Nishiyama, M. Chem. Commun.
2000, 133.
(5) Gronowitz, S. In Thiophene and its Derivatives; Gronowitz, S.,
Ed.; J ohn Wiley & Sons: New York, 1985; Part 1, pp 42-59.
(6) (a) Grehn, L. J . Heterocycl. Chem. 1978, 15, 81. (b) Outurquin,
F.; Lerouge, P.; Paulmier, C. Bull. Soc. Chim. Fr. 1986, 259. (c) Barker,
J . M.; Huddleston, P. R.; Wood, M. L. Synth. Commun. 1995, 25, 3729.
(7) Prim, D.; Kirsch, G.; Nicoud, J .-F. Synlett 1998, 383.
(8) (a) Buchwald, S. L.; Marcoux, J .-F.; Wagaw, S.; Wolfe, J . P. Acc.
Chem. Res. 1998, 31, 805. (b) Yang, B. H.; Buchwald, S. L. J .
Organomet. Chem. 1999, 576, 125. (c) Wolfe, J . P.; Buchwald, S. L. J .
Org. Chem. 2000, 65, 1144. (d) Wolfe, J . P.; Tomori, H.; Sadighi, J . P.;
Yin, J .; Buchwald, S. L. J . Org. Chem. 2000, 65, 1158.
In an attempt to reduce possible side products in the
reactions of the primary alkylamines, a variety of condi-
tions were investigated, including temperature, solvent,
stoichiometry, palladium source, and the ligand used.
(9) (a) Hartwig, J . F. Angew. Chem., Int. Ed. Engl. 1998, 37, 2046.
(b) Hartwig, J . F. Acc. Chem. Res. 1998, 31, 852. (c) Hartwig, J . F.;
Kawatsura, M.; Hauck, S. I.; Shaughnessy, K. H.; Alcazar-Roman, L.
M. J . Org. Chem. 1999, 64, 5575.
10.1021/jo016195q CCC: $20.00 © 2001 American Chemical Society
Published on Web 12/04/2001

9068 J . Org. Chem., Vol. 66, No. 26, 2001
Notes
Ta ble 2. Com p a r a tive Stu d ies Utilizin g Va r iou s Ca ta lyst
P r ecu r sor sa
Sch em e 1. P r op osed Ca ta lytic Cycle for
Th iop h en e Am in a tion
entry
Pd compound
1a yielda
1b yielda
1
2
3
4
Pd(OAc)2
Pd2(dba)3
PdCl2
37
14
13
25
20
7
21
24
[Pd(π-C3H5)Cl]2
a
Isolated yields based on 3-bromothiophene.
Ta ble 3. Com p a r a tive Stu d ies Utilizin g Va r iou s P R3
Liga n d sa
entry
R
cone angleb 1a yielda 1b yielda bithiophenea
1
2
3
4
5
6
7
8
cyclohexyl
tBu2iPr
neopentyl
tBu
t-pentyl
C6F5
170
175
180
12
64
18
182
37
trace
20
∼186c
12
184
o-tolyl
mesityl
194
212
16
22
a
b
Isolated yields based on 3-bromothiophene. From ref 13.
c Estimated from space-filling model.
3-bromothiophene with the various palladium precursors
are shown in Table 2. All cases successfully produce
amination products, but the alternate sources (Table 2,
entries 2-4) give lower yields than the intial Pd(OAc)2
(entry 1). Changes in the palladium precursor do seem
to have a minor influence on product distributions, but
no real selectivity is observed. In the case of PdCl2 (Table
2, entry 3), however, the distribution does shift to favor
the diarylation product over the desired secondary ami-
nation product.
In addition to the tri-tert-butylphosphine ligand, we
have also investigated a number of other phosphines,
varying both the cone angle13 and electronic parameters
of the ligand used. The results of this study are shown
in Table 3. For comparison purposes, all reactions in
entries 1-8 were carried out utilizing hexylamine as the
primary amine.
With the exception of the original conditions (Table 3,
entry 4) and the tri-tert-pentylphosphine ligand (entry
5), which gave trace amounts of the desired product, all
other ligands gave no aminothiophene products and no
trends could be established on the basis of the cone angles
of the ligands used. In most cases, large amounts of
1-hexanimine were isolated resulting from a competing
â-elimination pathway. The only major thiophene product
in the failed attempts was 3,3′-bithiophene.
The use of the pentafluorophenyl ligand (entry 6)
resulted in no reaction of any kind, possibly suggesting
that the initial oxidative addition step failed in this
example. Finally, to investigate the potential of chelating
phosphines, the bidentate ligand 1,1′-bis(diphenylphos-
phino)ferrocene was also investigated, but again the only
products isolated were 1-hexanimine and 3,3′-bithiophene.
A proposed mechanism for the formation of isolated
3,3′-bithiophene is shown in Scheme 2 on the basis of
analogous catalytic processes resulting in the production
of biaryls.14 This proposed mechanism is additionally
supported by the detection of R-brominated thiophenes
in some reaction mixtures. Such brominated products
would be readily formed in the presence of the Br2 and
HBr produced as shown in Scheme 2.
Temperatures of 110 °C or greater had very little effect
on the product yield or distribution. The formation of
amination product was seen at temperatures as low as
60 °C, but the lower temperatures resulted in reduced
product yields. It has been previously explained that the
high reaction temperature is needed to overcome the
formation of the very stable amide dimer (complex IV)
produced after deprotonation of the coordinated amine
by the NaOtBu as shown in Scheme 1.10 This restriction
in temperature thus limits potential solvents. Although
toluene and THF solvent systems both successfully gave
amination products, they did so with reduced yields that
scale with the reduced temperatures. DMF was also
investigated as a polar, high-boiling solvent, but amina-
tion was not observed under these conditions.
Variations in the ratio of bromothiophene to amine
used had only minor effects on the distribution of
secondary to tertiary products. For this reason, it is
believed that the aminothiophene product must remain
coordinated to the palladium center after reductive
elimination (Scheme 1, complex VI). Such coordination
has been previously proposed by Hartwig.11 Formation
of the tertiary diarylation product would then be con-
trolled by competition between bromothiophene oxidative
addition (i.e., path B of Scheme 1) and product displace-
ment rather than the competitive binding of different
amines. It was found, however, that large excesses of
amine (10-fold or greater) resulted in the production of
only trace amounts of the diarylation byproduct. Unfor-
tunately, these conditions also significantly reduced the
yield of the desired amination product as well. The high
amine concentration should enhance product displace-
ment but also has a greater likelihood of poisoning the
catalyst.
As the palladium catalyst precursor has been previ-
ously shown to affect the amination product yields,12
PdCl2, Pd2(dba)3, (Pd(π-allyl)Cl)2 were investigated as
alternate sources of palladium for the catalyst mixture.
Comparative yields for the coupling of hexylamine and
(10) Villanueva, L. A.; Abboud, K. A.; Boncella, J . M. Organo-
metallics 1994, 13, 3921.
(11) Hartwig, J . F.; Paul, F. J . Am. Chem. Soc. 1995, 117, 5373.
(12) Wolfe, J . P.; Rennels, R. A.; Buchwald, S. L. Tetrehedron 1996,
52, 7525.
(13) Tolman, C. A. Chem. Rev. 1977, 77, 313.
(14) Ozawa, F.; Hidaka, T.; Yamamoto, T.; Yamamoto, A. J . Orga-
nomet. Chem. 1987, 330, 253.

Notes
J . Org. Chem., Vol. 66, No. 26, 2001 9069
mmol, 0.4 mL of 50 mg/mL solution in o-xylene) were mixed in
40 mL of o-xylene and refluxed at 120 °C for 4 h. After the
mixture was cooled, water was added and the organic layer
separated. The remaining aqueous layer was then extracted with
hexanes (2 × 50 mL), and the combined organic fractions were
dried with Na2SO4 and concentrated in vacuo. The crude product
was then purified by chromatography over silica gel (2.5%
EtOAc/hexanes).
Sch em e 2. P r op osed Ca ta lytic Cycle for
Bith iop h en e F or m a tion
N-Hexyl-3-a m in oth iop h en e (1a ). 1H NMR (CDCl3): δ 7.16
(dd, J ) 3.0, 5.4 Hz, 1H), 6.62 (dd, J ) 1.8, 5.4 Hz, 1H), 5.95
(dd, J ) 1.8, 3.0 Hz, 1H), 3.56 (br, 1H), 3.07 (t, J ) 7.1 Hz, 2H),
1.63 (m, 2H), 1.36 (m, 6H), 0.92 (t, J ) 6.9 Hz, 3H). 13C NMR
(CDCl3): δ 149.1, 125.3, 120.2, 95.5, 46.6, 31.9, 29.8, 27.2, 22.9,
14.3. Anal. Calcd for C10H17NS: C, 65.52; H, 9.35; N, 7.64.
Found: C, 65.40; H, 9.36; N, 7.27.
1
N-Hexyl-N-(3′-th ien yl)-3-a m in oth iop h en e (1b). H NMR
(CDCl3): δ 7.21 (dd, J ) 3.0, 5.4 Hz, 2H), 6.90 (dd, J ) 1.8, 5.4
Hz, 2H), 6.49 (dd, J ) 1.8, 3.0 Hz, 2H), 3.60 (t, J ) 7.7 Hz, 2H),
1.67 (m, 2H), 1.32 (m, 6H), 0.91 (t, J ) 6.6 Hz, 3H). 13C NMR
(CDCl3): δ 148.2, 124.9, 123.0, 105.9, 54.5, 31.9, 27.5, 27.1, 23.0,
14.4. Anal. Calcd for C14H19NS2: C, 63.35; H, 7.22; N, 5.28.
Found: C, 63.16; H, 7.03; N, 4.88.
To investigate the versatility of the coupling reaction,
we also studied the amination of 4-bromo-2,2′-bithio-
phene15 and 2-bromothiophene. Amination of 4-bromo-
2,2′-bithiophene produced the desired 4-(N-octylamino)-
2,2′-bithiophene in yields of 20%.16 As with the previous
amination of 3-bromothiophene, a diarylation byproduct
was also isolated from this reaction in yields of 20%. In
contrast to the successful aminations of 2-bromothiophenes
with diarylamines,4 we have found that analogous reac-
tions with either monoarylamines or alkylamines were
unsuccessful. Repeating Watanabe’s amination of 2-bro-
mothiophene with diphenylamine, we were able to suc-
cessfully isolate the amination product in 54% yield (lit.
36%).4 In addition, we have had some success with
reactions between 2-bromothiophene and 5a and are
continuing to investigate the selectivity of the R-bromides
under these reaction conditions.
1
N-Octyl-3-a m in oth iop h en e (2a ). H NMR (CDCl3): δ 7.15
(dd, J ) 3.0, 5.4 Hz, 1H), 6.62 (dd, J ) 1.8, 5.4 Hz, 1H), 5.95
(dd, J ) 1.8, 3.0 Hz, 1H), 3.58 (br, 1H), 3.07 (t, J ) 6.9 Hz, 2H),
1.62 (m, 2H), 1.30 (m, 10H), 0.90 (t, J ) 7.2 Hz, 3H). 13C NMR
(CDCl3): δ 149.1, 125.3, 120.2, 95.5, 46.6, 32.1, 29.9, 29.7, 29.5,
27.5, 22.9, 14.4. Anal. Calcd for C12H21NS: C, 68.19; H, 10.01;
N, 6.63. Found: C, 68.54; H, 9.73; N, 6.29.
N-Octyl-N-(3′-th ien yl)-3-a m in oth iop h en e (2b). 1H NMR
(CDCl3): δ 7.23 (dd, J ) 3.0, 5.4 Hz, 2H), 6.94 (dd, J ) 1.8, 5.4
Hz, 2H), 6.54 (dd, J ) 1.8, 3.0 Hz, 2H), 3.65 (t, J ) 7.7 Hz, 2H),
1.73 (m, 2H), 1.35 (m, 10H), 0.97 (t, J ) 7.2 Hz, 3H). 13C NMR
(CDCl3): δ 148.3, 125.0, 123.0, 105.9, 54.5, 32.2, 29.8, 29.7, 27.6,
27.5, 23.0, 14.5. Anal. Calcd for C16H23NS2: C, 65.48; H, 7.90;
N, 4.77. Found: C, 65.36; H, 7.77; N, 4.74.
N-Decyl-3-a m in oth iop h en e (3a ). 1H NMR (CDCl3): δ 7.16
(dd, J ) 3.0, 5.4 Hz, 1H), 6.62 (dd, J ) 1.8, 5.4 Hz, 1H), 5.96
(dd, J ) 1.8, 3.0 Hz, 1H), 3.58 (br, 1H), 3.08 (t, J ) 7.1 Hz, 2H),
1.64 (m, 2H), 1.30 (m, 14H), 0.92 (t, J ) 7.2 Hz, 3H). 13C NMR
(CDCl3): δ 149.1, 125.3, 120.2, 95.4, 46.7, 32.2, 29.9, 29.9, 29.8,
29.6, 27.5, 27.2, 23.0, 14.4. Anal. Calcd for C14H25NS: C, 70.23;
H, 10.53; N, 5.85. Found: C, 70.23; H, 10.13; N, 5.55.
Further investigations into the optimization of these
catalytic aminations are underway. As with the il-
lustrated successes of haloaryl aminations,8,9 a greater
amount of control may be possible through the additional
utilization of various chelating ligands.
1
N-Decyl-N-(3′-th ien yl)-3-a m in oth iop h en e (3b). H NMR
(CDCl3): δ 7.23 (dd, J ) 3.0, 5.4 Hz, 2H), 6.93 (dd, J ) 1.8, 5.4
Hz, 2H), 6.52 (dd, J ) 1.8, 3.0 Hz, 2H), 3.63 (t, J ) 7.7 Hz, 2H),
1.71 (m, 2H), 1.33 (m, 14H), 0.96 (t, J ) 6.9 Hz, 3H). 13C NMR
(CDCl3): δ 148.2, 124.9, 123.0, 105.9, 54.5, 32.2, 30.0, 29.9, 29.8,
29.7, 27.6, 27.5, 23.0, 14.5. Anal. Calcd for C18H27NS2: C, 67.24;
H, 8.46; N, 4.36. Found: C, 67.57; H, 8.41; N, 4.61.
Exp er im en ta l Section
Gen er a l. Unless noted, all materials were reagent grade,
purchased from Sigma-Aldrich, and used without further puri-
fication. Xylene was distilled from sodium and benzophenone
prior to use. Isopropyldi-tert-butylphosphine,17 trineopentylphos-
phine,18 and tri-tert-pentylphosphine19 were prepared as de-
scribed in the literature. Chromatography was performed using
EM Science silica gel (230-400 mesh). All glassware was oven-
dried, assembled hot, and cooled under a dry nitrogen stream
before use. All reactions were performed under nitrogen. 1H and
13C NMR spectra were obtained in CDCl3 on a Varian 300 MHz
spectrometer and referenced to the chloroform signal. Elemental
analyses were performed in house on a Perkin-Elmer Series II
CHNS/O Analyzer 2400.
N-ter t-Bu tyl-3-a m in oth iop h en e (4a ). 1H NMR (CDCl3): δ
7.04 (dd, J ) 3.0, 5.1 Hz, 1H), 6.57 (dd, J ) 1.5, 5.1 Hz, 1H),
6.15 (dd, J ) 1.5, 3.0 Hz, 1H), 1.20 (s, 9H). 13C NMR (CDCl3):
δ 145.6, 124.3, 124.1, 103.1, 52.1, 29.8. Anal. Calcd for C8H13
-
NS: C, 61.89; H, 8.44; N, 9.02. Found: C, 62.00; H, 8.54; N,
8.83.
N-ter t-Bu tyl-N-(3′-th ien yl)-3-a m in oth iop h en e (4b). 1H
NMR (CDCl3): δ 7.12 (dd, J ) 3.3, 5.1 Hz, 2H), 6.70 (dd, J )
1.2, 5.1 Hz, 2H), 6.66 (dd, J ) 1.2, 3.3 Hz, 2H), 1.37 (s, 9H). 13C
NMR (CDCl3): δ 147.7, 127.7, 123.5, 113.3, 56.2, 29.2. Anal.
Calcd for C12H15NS2: C, 60.72; H, 6.37; N, 5.90. Found: C, 60.58;
H, 6.20; N, 5.92.
Gen er a l Am in a tion P r oced u r e. 3-Bromothiophene (10
mmol), amine (10 mmol), sodium tert-butoxide (11 mmol),
palladium acetate (0.1 mmol), and tri-tert-butylphosphine (0.1
N-(p-Hexylp h en yl)-3-a m in oth iop h en e (5a ). 1H NMR (CD-
Cl3): δ 7.25 (dd, J ) 3.0, 5.4 Hz, 1H), 7.08 (d, J ) 6.6 Hz, 2H),
6.93 (d, J ) 6.6 Hz, 2H), 6.90 (dd, J ) 1.8, 5.4 Hz, 1H), 6.68 (dd,
J ) 1.8, 3.0 Hz, 1H), 5.65 (br, 1H), 2.55 (t, J ) 7.8 Hz, 2H), 1.60
(m, 2H), 1.32 (m, 6H), 0.91 (t, J ) 7.2 Hz, 3H). 13C NMR
(CDCl3): δ 142.4, 135.0, 129.4, 125.3, 122.8, 116.3, 105.3, 35.4,
32.0, 32.0, 29.3, 22.9, 14.4. Anal. Calcd for C16H21NS: C, 74.08;
H, 8.16; N, 5.40. Found: C, 73.90; H, 8.15; N, 5.12.
(15) Rasmussen, S. C.; Pickens, J . C.; Hutchison, J . E. J . Heterocycl.
Chem. 1997, 34, 285.
(16) Crude yields as determined by 1H NMR prior to separation were
higher. However, due to the increased conjugation of this compound,
it is very susceptible to oxidation and thus not very stable. This
instability makes its purification challenging and results in losses due
to decomposition.
(17) Bottomley, A. R. H.; Crocker, C.; Shaw, B. L. J . Organomet.
Chem. 1983, 250, 617.
(18) King, R. B.; Cloyd, J . C., J r.; Reimann, R. H. J . Org. Chem.
1976, 41, 972.
(19) Gilheany, D. G.; Mitchell, C. M. Preparation of Phosphines. In
The Chemistry of Organophosphorus Compounds; Hartley, Frank R.,
Ed.; Wiley & Sons: Chichester, England, 1990; Vol. 1, pp 151-190.
N-(p-Hexylph en yl)-N-(3′-th ien yl)-3-am in oth ioph en e (5b).
1H NMR (CDCl3): δ 7.21 (dd, J ) 3.0, 5.4 Hz, 2H), 7.06 (m, 4H),
6.89 (d, J ) 5.4 Hz, 2H), 6.63 (poorly resolved doublet 2H), 2.57
(t, J ) 7.9 Hz, 2H), 1.61 (m, 2H), 1.33 (m, 6H), 0.90 (t, J ) 6.9
Hz, 3H). 13C NMR (CDCl3): δ 147.2, 145.8, 138.0, 129.3, 125.0,
124.4, 122.9, 110.9, 35.6, 32.0, 31.8, 29.3, 22.9, 14.4. Anal. Calcd

9070 J . Org. Chem., Vol. 66, No. 26, 2001
Notes
for C20H23NS2: C, 70.33; H, 6.79; N, 4.10. Found: C, 70.29; H,
6.89; N, 3.82.
American Chemical Society, for partial support of this
research. Additional support was provided by North
Dakota EPSCoR and North Dakota State University.
N,N-Dih exyl-3-a m in oth iop h en e (6). 1H NMR (CDCl3): δ
7.19 (dd, J ) 3.0, 5.4 Hz, 1H), 6.74 (dd, J ) 1.2, 5.4 Hz, 1H),
5.81 (dd, J ) 1.2, 3.0 Hz, 1H), 3.16 (t, J ) 7.7 Hz, 4H), 1.56 (m,
4H), 1.31 (m, 12H), 0.91 (t, J ) 6.6 Hz, 6H). 13C NMR (CDCl3):
δ 150.7, 124.9, 119.1, 94.6, 52.8, 32.0, 27.5, 27.2, 23.0, 14.3. Anal.
Calcd for C16H29NS: C, 71.85; H, 10.93; N, 5.24. Found: C, 71.45;
H, 11.09; N, 5.31.
Su p p or tin g In for m a tion Ava ila ble: IR and Rf data for
compounds 1-6 and reaction conditions, spectroscopic data,
and elemental analysis for 4-(N-octylamino)-2,2′-bithiophene
and its diarylation byproduct. This material is available free
of charge via the Internet at http://pubs.acs.org.
Ack n ow led gm en t. The authors thank the donors
of the Petroleum Research Fund, administered by the
J O016195Q