Synthesis and relative thermal stabilities of diphenylamino- vs piperidinyl-substituted bithiophene chromophores for nonlinear optical materials

Full text of DOI:10.1021/jo9517555

2242
J . Org. Chem. 1996, 61, 2242-2246
Syn th esis a n d Rela tive Th er m a l Sta bilities
of Dip h en yla m in o- vs
P ip er id in yl-Su bstitu ted Bith iop h en e
Ch r om op h or es for Non lin ea r Op tica l
Ma ter ia ls
Peter V. Bedworth,*,1 Yongming Cai,2 Alex J en,2 and
Seth R. Marder*,1,3
The Beckman Institute, Mail Stop 139-74, California
Institute of Technology, Pasadena, California 91125,
The J et Propulsion Laboratory, 4800 Oak Grove Dr.,
California Institute of Technology, Pasadena, California
91109, and ROI Technologies, 2000 Cornwall Rd.,
Monmouth J unction, New J ersey 08852
Received September 26, 1995
Electrooptic poled polymers can be used in a variety
of photonic applications involving the switching or modu-
lation of light. These polymers contain second-order
nonlinear optical chromophores that have been aligned
by electric-field poling near the glass transition temper-
ature of the polymer host. Loss of poling-induced align-
ment of the chromophores results in a decay of the
macroscopic nonlinearity and presents an important
issue that must be addressed if these materials are to
have a commercial impact. Accordingly, researchers
have attempted to incorporate chromophores into poly-
mers with glass transition temperatures far in excess of
the anticipated operating temperatures, such that over
the lifetime of the devices the decay of chromophore
alignment is minimized. This has created a need for
chromophores that not only are very nonlinear but also
have adequate thermal stability to survive the poling
process which may occur at temperatures exceeding 200
°C. Accordingly, as part of our ongoing effort to develop
chromophores for nonlinear optical applications we syn-
thesized a series bithiophene-based chromophores (Fig-
ure 1) with the hope that they may have both high optical
nonlinearity and good thermal stability. The donor-
acceptor bithiophene chromophores have the advantage
of having moderate aromatic stabilization in the ground
state, making them more oxidatively stable than the
analogous polyene chromophores and more polarizable
than the analogous biphenyl chromophores.4 In addition,
several reports in the literature demonstrated that
protons R to the amine donor attenuate the thermal
stability of other nonlinear optical chromophores.5 There-
fore we examined the relative stability of compounds
substituted with either piperidinyl or diphenylamino
donors.
F igu r e 1. Bithiophene bridges, donors, and acceptors used
in the study. (* indicates point of attachment).
F igu r e 2. Synthesis of (top) 2-piperidinylthiophene and
(bottom) 2-(diphenylamino)thiophene.
F igu r e 3. Synthesis of the aminothiophene stannanes.
N-piperidinyl or N,N-diphenylamino donors and 1,1-
dicyanovinyl (DCV), 4-methylidene-3-phenylisoxazolone
(ISOX), or 4-methylidenediethylthiobarbituric acid (DETB)
acceptors across a conjugated π-bridge containing a
bithiophene moiety (Figure 1). The chromophores were
assembled in a convergent manner as outlined below. The
donor sides of the chromophores, 2-(N-piperidinyl)th-
iophene6 and 2-(N,N-diphenylamino)thiophene, were pre-
pared from 2-thiophenethiol7 and 2-iodothiophene, re-
spectively (Figure 2). The modified Ullman coupling8 to
form 2-(N,N-diphenylamino)thiophene required the use
of stochiometric copper iodide and a polar aprotic solvent
such as hexamethylphosphoramide or dimethylpropyle-
neurea. The use of catalytic copper salts and less polar
aprotic solvents yielded either an intractable polymeric
mixture from which no appreciable amount of the desired
product could be obtained or, under less forcing condi-
tions, no evidence of reaction. The aminothiophenes were
then lithiated with n-butyllithium and converted to 5-(tri-
n-butylstannyl)-2-aminothiophenes (Figure 3).
Resu lts a n d Discu ssion
Syn th esis of th e Ch r om op h or es. As noted above,
a series of chromophores was synthesized with either
(1) The Beckman Institute.
(2) ROI Technologies.
(3) The J et Propulsion Laboratory.
(4) Marder, S. R.; Beratan, D. N.; Cheng, L.-T. Science 1991, 252,
103. Prasad, P. N.; Williams, D. J . Introduction to Nonlinear Optical
Effects in Molecules and Polymers; Wiley: New York, 1991; pp 152-
160. Gilmour, S.; Montgomery, R. A.; Cheng, L.-T.; J en A, K.-Y.; Cai,
Y.; Perry, J . W.; Dalton, L. R. Chem. Mater. 1994, 6, 1603. J en, A.-Y.;
Rao, V. P.; Drost, K. J .; Cai, Y. M.; Minini, R. M.; Kenney, J . T.; Dalton,
L. R.; Marder, S. R. Proc. SPIE 1994, 2143, 30.
(5) Moylan, C. R.; Twieg, R. J .; Lee, V. Y.; Swanson, S. A.; Betterton,
K. M.; Miller, R. D. J . Am. Chem. Soc. 1993, 115, 12599. Moylan, C.
R.; Twieg, R. J .; Lee, V. Y.; Swanson, S. A.; Betterton, K. M.; Miller,
R. Volksen, W.; Thackara, J . I.; Walsh, C. A. Proc. SPIE 1994, 2285,
17. Twieg, R. J .; Burland, D. M.; Hedrick, J .; Lee, V. Y.; Miller, R. D.;
Moylan, C. R.; Seymour, C. M.; Volksen, C. A.; Walsh, C. A. Proc. SPIE
1994, 2143, 2.
The acceptor sides of the chromophores were prepared
from 2-bromothiophene which was treated with lithium
(6) Hartmann, H.; Scheithaurer, S. J . Prakt. Chim. 1969, Band 311,
836.
(7) J ones, E.; Moodie, I. M. Organic Syntheses; Wiley: New York,
1988; Collect. Vol. VI, p 979.
(8) Lindley, J . Tetrahedron 1984, 40, 1433.
0022-3263/96/1961-2242$12.00/0 © 1996 American Chemical Society

Notes
J . Org. Chem., Vol. 61, No. 6, 1996 2243
Ch a r t 1. F r a ction of Ch r om op h or e Th a t Su r vives
h ea tin g (bottom ) for 3.5 h a t 175 °C in Va cu u m a n d
(top ) 45 m in a t 175 °C in Air
F igu r e 4. Synthesis of the bromothiophene aldehydes.
F igu r e 5. Synthesis of the aminobithiophene aldehydes.
Ta ble 1. Absor p tion Ma xim a (λm a x) a n d µâ Va lu es
Deter m in ed by EF ISH in Ch lor ofor m a t 1.9 µm for th e
Ch r om op h or es(Estim a ted Er r or in th e µâ Va lu es is
(20%)
λmax (nm) (ligroin),
(CHCl3), (NMP)
compd
µâ/10-48 (esu)
4a.0
4b.0
4a.1
4b.1
5a.0
5b.0
5a.1
5b.1
6a.0
6b.0
6a.1
6b.1
414, 566, 572
516, 542, 552
534, 582, 584
522, 534, 558
574, 608, 650
574, 588, 606
insol, 632, 642
568, 580, 584
574, 632, 650
532, 580, 616
578, 676, 700
534, 578, 610
1150
550
740
960
725 (dioxane)
1780
1420 (dioxane)
1170
1780
3840
2200
diisopropylamide to give 2-bromo-5-lithiothiophene, in
situ. Addition of either dimethylformamide or (dimethy-
lamino)acrolien9 to the solution of 2-bromo-5-lithio-
thiophene gave, after aqueous acidic workup, 2-bro-
mothiophene-5-carboxaldehyde and 3-(2-bromothiophene-
5-yl)acrolein (Figure 4). The donor and acceptor precursors
were coupled using a Stille palladium-catalyzed cross-
coupling to give the precursor aldehydes (Figure 5),10 in
yields ranging from 70% to 90%. These precursor alde-
hydes were then converted to the desired chromophores
by Knoevenagel condensation11 (Figure 6) to give the
desired product in high yield. Typically it was necessary
to purify the product by recrystallization from ethanol
in order to obtain analytically pure materials.
Th er m a l a n d Op tica l P r op er ties of th e Ch r o-
m op h or es. All of the chromophores in this study have
a strong charge-transfer band in the visible region of the
spectrum. With increasing solvent polarity the position
of the absorption maximum shifts to lower energy,
indicative of an increase in the dipole moments upon
excitation. While designing the chromophores, one prob-
lem we envisioned was the attenuated donor strength of
the diphenylamino donor relative to the piperidinyl
donor. Synthetically, the reduced donor strength (related
to nucleophilicity) of diphenylamine manifested itself in
the difficulty of the synthesis of the structurally simple
(diphenylamino)thiophene, as noted above. We reasoned
that the reduced donor strength would result in attenu-
ated µâ (the dot product of the first hyperpolarizability
along the dipole axis and the dipole moment) values
compared to those of the dialkylamino chromophores.
Consistent with this speculation, in most cases the
diphenylamino donor yielded dyes whose absorption
maxima were blue shifted and had µâ values of about
half those of the analogous piperidinyl dyes. Nonetheless
the µâ values are still comparable to or larger than
commonly used chromophores, such as Disperse Red 1.4
In an effort to determine the thermal stability of the
chromophores, we initially used closed pan differential
scanning calorimetry (DSC) measurements.5 Unfortu-
nately, the Td (onset of decomposition) was close to Tm
(onset of melt) in all cases. We felt that in this case the
values obtained from DSC did not give a useful measure
of relative thermal stability for the ultimate host-guest
polymer system. Accordingly, we examined the chro-
mophore within a poly(methyl methacrylate) film. To do
this we fabricated 2% weight to weight dye in poly(methyl
methacrylate) solid solution films on glass substrates by
spin coating. The films were then heated in air or
vacuum in the dark. The change in optical density at
the absorption maximum of the visible spectrum (λmax),
as a function of time, at various temperatures was
determined, and the results are shown in Chart 1. In
all cases the diphenylamino chromophores were more
(9) J utz, C. Chem. Ber. 1953, 51, 1873.
(10) Bao, Z.; Chan, W.; Yu, L. Chem. Mater. 1993, 5, 2.
(11) March, J . Advanced Organic Chemistry: Reaction Mechanisms
and Structure., Vol. 1-835; Wiley Interscience: New York, 1985.

2244 J . Org. Chem., Vol. 61, No. 6, 1996
Notes
F igu r e 6. Synthesis of the donor-acceptor bithiophene by Knoevenagel condesation of aminobithiophene aldehydes with (top)
malononitrile, (midde) 3-phenyl-5-isoxazolone, and (bottom) 1,3-diethylthiobarbituric acid.
induced second harmonic generation)13 using 1.9 µm fundamen-
thermally stable than their piperidinyl analogs. We also
tal radiation in chloroform or dioxane. Thin films of dyes in
found that aerobic conditions drastically reduced the life
PMMA were prepared by dissolving 20 mg of dye in 10 mL of
10%w/v PMMA in chlorobenzene. Thus an excess of the solution
of the chromophores. Surprisingly, the data also suggests
that under aerobic conditions the n ) 1 chromophores
are more thermally stable than the n ) 0 chromophores.
was then applied to square microscope cover slides on
a
spincoater and spun at 1600 rpm for 90 s. These slides were
dried overnight in vacuum, in the dark, before thermal testing.
The absorbances were recorded using a glass slide as reference.
In summary, the results obtained here suggest that in
agreement with previous findings for systems in which
the thermal stability of (diarylamino)phenyl chromophores
were compared to the analogous (dialkylamino)phenyl
chromophores,5 the (diphenylamino)thiophenes are more
stable than the piperidinyl chromophores. In addition
in several cases optical nonlinearities significantly larger
than that of Disperse Red 1 were observed, suggesting
that these compounds may be attractive candidates for
poled polymer applications.
2-(N,N-Dip h en yla m in o)th iop h en e. To a slurry of hexane
washed potassium hydride (31 g, 35% in mineral oil, 275 mmol)
in dimethylpropyleneurea (50 mL) was added a solution of N,N-
diphenylamine (46 g, 275 mmol) dropwise over 1 h under
nitrogen. The resulting yellow slurry was stirred an additional
hour. To the yellow slurry was added freshly prepared anhy-
drous copper(I) iodide (52 g, 275 mmol), and the mixture was
stirred for 1 h by which time all the copper(I) iodide had
dissolved giving a dark green turbid solution. The solution was
then heated to 80 °C, and a solution of 2-iodothiophene (46 mL,
412 mmol) in dimethylpropyleneurea (75 to 125 mL) was added
dropwise over 3 h. The dark mixture was heated until most of
the diphenylamine was consumed (10% remained) as determined
by gas chromatography. The mixture was then cooled and
poured into ethyl acetate (1000 mL) and filtered, concentrated
ammonium hydroxide (100 mL), was added and the organic layer
was washed with 10% ammonium hydroxide until no blue color
was observed. The organic layer was dried over magnesium
sulfate and filtered and the solvent removed in vacuo to give a
thick brown oil. The oil was subsequently subjected to molecular
path distillation with the major fraction distilling at 135 °C,
0.005 mmHg. This material was then recrystallized from
ethanol to give 27 g (40%) of the title compound: 1H NMR (500
MHz, CDCl3) δ 7.38 (ddd, J ) 10.82, 7.33, 1.14 Hz, 4 H), 7.26
(ddd, J ) 10.82, 1.35, 1.14 Hz, 4 H), 7.14 (tt, J ) 7.36, 1.14 Hz,
2 H), 7.13 (dd, J ) 5.67, 1.35 Hz, 1 H), 7.01 (dd, J ) 5.67, 3.74
Hz, 1 H), 6.86 (dd, J ) 3.67, 1.30 Hz, 1 H). Anal. Calcd: C,
76.46; H, 5.21; N, 5.57. Found: C, 76.88; H, 5.84; N, 5.11.
Exp er im en ta l Section
Ultraviolet-visible electronic absorption spectra were re-
corded on a Hewlett-Packard 8452A diode array detector or a
Perkin-Elmer Lambda 9 spectrophotometer. 1H NMR spectra
were recorded at 300 MHz using a General Electric QE-300 or
at 500 MHz using a Bruker AM-500. Elemental analyses were
performed by Atlantic Microlabs. Chemical shifts were refer-
enced to the chemical shift of the residual protons of the solvent
relative to tetramethylsilane. All reactions were performed
under nitrogen. Tetrahydrofuran was distilled from sodium
benzophenone ketyl under nitrogen. Dimethylformamide and
dimethylpropyleneurea were distilled from calcium hydride
under reduced pressure. Copper iodide was prepared using the
method of Kauffman12 and then dried overnight at 100 °C under
vacuum. 2-(N-Piperidinyl)thiophene was prepared by the method
of Hartmann.6 Bis(triphenylphosphine)palladium(II) chloride,
butyllithium, chlorobenzene, (dimethylamino)acrolein, dieth-
ylthiobarbituric acid, diphenylamine, malononitrile, 3-phenyl-
5-isoxazolone, poly(methyl methacrylate) (PMMA), and tribu-
tylchlorostannane were purchased from Aldrich and used as
received. 2-Iodothiophene was purchased from Lancaster and
used as received. µâ was determined by EFISH (electric field
5-(N-P ip er id in yl)-2-(tr i-n -bu tylsta n n yl)th iop h en e. To a
solution of 2-(N-piperidinyl)thiophene (18 g, 100 mmol) in
tetrahydrofuran (300 mL) at -78 °C under nitrogen was added
n-butyllithium (82 mL, 130 mmol, 1.6 M in hexanes). The
solution was stirred for 5 min. then warmed to ambient
(13) Cheng, L.-T.; Tam, W.; Stevenson, S. H.; Meredith, G. R.;
Rikken, G.; Marder, S. R. J . Chem Phys. 1991, 95, 10631.
(12) Kaufmann, G. B.; Pinell, R. P. Inorg. Synth. 1963, 6, 3.

Notes
J . Org. Chem., Vol. 61, No. 6, 1996 2245
temperature. The solution was then cooled with an ice/water
bath, tri-n-butylchlorostannane (35 mL, 130 mmol) was added,
and the reaction was stirred overnight. The mixture was then
added to brine (200 mL). The aqueous layer was extracted with
methylene chloride (3 × 50 mL). The combined organic layers
were dried with magnesium sulfate, and the solvent was
removed in vacuo to give the product in quantitative yield
contaminated with tri-n-butylchlorostannane residue (about 5%).
The product was used without further purification: 1H NMR
(300 MHz, CDCl3) δ 6.84 (d, J ) 3.3 Hz, 1 H), 6.25 (d, J ) 3.3
Hz, 1 H), 3.2 (t, 7 Hz, 4 H), 2.0-1.0 (5 overlapping m, 33 H).
5-(N ,N -D ip h e n y ls m in o )-2-(t r i-n -b u t y ls t a n n y l)t h io -
p h en e was prepared by the above method with nearly quantita-
tive yield and used without further purification: 1H NMR (500
MHz, CDCl3) δ 7.21 (dt, J ) 10, 2 Hz, 4 H), 7.1 (dm, J ) 10 Hz,
4 H) , 6.97 (tt, J ) 7.32, 1.1 Hz, 2 H), 6.91 (d, J ) 3.45 Hz, 1 H),
6.77 (d, J ) 3.45 Hz, 1 H), 1.6-1.4 (m, 6 H), 1.4-1.2 (m, 12 H),
0.87 (t, J ) 5.8 Hz, 9 H).
3-(5-Br om oth iop h en e-2-yl)a cr olein . To a solution of di-
isopropylamine (21.5 mL, 148 mmol) in tetrahydrofuran (200
mL) at -78 C under nitrogen was added n-butyllithium (59.2
mL, 148 mmol, 2.5 M in hexanes). The solution was warmed to
0 °C using an ice/water bath and then cooled to -78 °C. To the
solution was added 2-bromothiophene (14.2 mL, 148 mmol). The
solution was stirred for 1 h at -78 °C, then 3-(dimethylamino)-
acrolein (15 mL, 150 mmol) was added, and the solution was
allowed to warm to ambient temperature. The mixture was
added to 3 N hydrochloric acid (1000 mL) and extracted with
methylene chloride (3 × 100 mL). The combined organic layers
were dried over magnesium sulfate, and the solvent was removed
in vacuo. The crude material was distilled (2 mmHg, 110-120
°C) to give 25 g (80% yield) of the title product: 1H NMR (300
MHz, CDCl3) δ 9.59 (d, J ) 7.59 Hz, 1 H), 7.5 (d, J ) 15.7 Hz,
1 H), 7.08 (ABq, ∆ν ) 0.03 ppm, J ) 4.4 Hz, 2 H), 6.38 (dd, J )
15.7, 7.6 Hz, 1 H); HRMS calcd m/ z ) 215.9231, found m/ z )
215.9244.
2′,5-bithiophene-2-carboxaldehyde (2.61 g, 10 mmol) in chloro-
form (10 mL) was added triethylamine (1 drop). The solution
was heated to reflux for 1 h, then cooled, and dried over
magnesium sulfate, and filtered and the solvent removed in
vacuo. The resulting purple solid was recrystallized from
ethanol to give 1.8 g (70 %) of the title product: 1H NMR (500
MHz, CDCl3) δ 7.57 (s, 1 H), 7.45 (d, J ) 4.14 Hz, 1 H), 7.20 (d,
J ) 4.25 Hz, 1 H), 6.92 (d, J ) 4.20 Hz, 1 H), 5.99 (d, J ) 4.30
Hz, 1 H), 3.25 (t, J ) 5.47, 4 H), 1.71 (pent, J ) 5.46, 4 H), 1.61
(pent, J ) 5.57 Hz, 2 H); 13C NMR (125 MHz, CDCl3) δ 163.27,
152.35, 149.05, 149.02, 141.04, 130.53, 129.53, 120.97, 118.90,
115.36, 114.46, 104.89, 71.34, 51.41, 24.93, 23.51; UV-vis (CH2-
Cl2) λmax 560 nm; (CCl4) λmax 536 nm; (petroleum ether) λmax 414
nm; (NMP) λmax 572 nm; (AcCN) λmax 440 nm; (NMP) λmax 448
nm; mp 169-172 °C; HRMS calcd m/ z ) 325.0698, found m/ z
) 325.0707. Anal. Calcd: C, 62.727; H, 4.655; N, 12.913; S,
19.706. Found: C, 62.67; H, 4.59; N, 12.94; S, 19.60.
2-N-P ip er id in yl-5′-(1,1-d icya n o-1,3-b u t a d ien -4-yl)-2′,5-
bith iop h en e. The above method was used (70% yield): 1H
NMR (500 MHz, CDCl3) δ 7.41 (d, J ) 11.8 Hz, 1 H), 7.25 (d, J
) 14.6 Hz, 1 H), 7.20 (d, J ) 4.1 Hz, 1 H), 7.07 (d, J ) 4.2 Hz,
1 H), 6.89 (d, J ) 4.0 Hz, 1 H), 6.77 (dd, J ) 14.5, 11.8 Hz, 1 H),
5.98 (d, J ) 4.1 Hz, 1 H), 3.21 (3 line m, 4 H), 1.76-1.65 (m, 4
H), 1.64-1.57 (m, 2 H); UV-vis (ligroin) λmax 534 nm; (CHCl3)
λ
max 582 nm; (NMP) λmax 584 nm; HRMS calcd m/ z ) 351.0858,
found m/ z ) 351.0864. Anal. Calcd: C, 64.93; H, 4.87; N,
9.11.96; S, 18.24. Found: C, 64.78; H, 4.97; N, 11.83; S, 18.93.
5′-(1,1-D i c y a n o v i n y l)-2-(N ,N -d i p h e n y la m i n o -2′,5-
bith iop h en e. The above method was used (75% yield): 1H NMR
(500 MHz, CDCl3) δ 7.65 (s, 1 H), 7.52 (d, J ) 4.19, 1 H), 7.32 (t,
J ) 7.9 Hz, 4 H), 7.2 (d, J ) 8.6 Hz, 4 H), 7.21 (d, J ) 4.19 Hz,
1 H), 7.14 (t, J ) 7.36 Hz, 2 H), 7.01 (d, J ) 4.17 Hz, 1 H), 6.48
(d, J ) 4.13 Hz, 1 H); UV-vis (ligroin) λmax 516 nm; (CHCl3)
λmax 552 nm; (NMP) λmax 542 nm. Anal. Calcd: C, 70.39; H,
3.69; N, 10.26; S, 15.66. Found: C, 70.10; H, 3.76; N, 10.03; S,
15.44.
5′-N-P ip er id in yl-2′,5-bith iop h en e-2-ca r boxa ld eh yd e. To
a degassed solution of 5-bromo-2-thiophenecarboxaldehyde (10.5
g, 55 mmol) and 2-(tri-n-butylstannyl)-5-N-piperidinylthiophene
(22.3 g, 55 mmol) in dimethylformamide (100 mL) was added
bis(triphenylphosphine)palladium(II) chloride (1.4 g, 2 mmol).
The mixture was heated to 80 °C for 10 min, then cooled to 40
°C, and stirred under nitrogen for 5 h. The solution was cooled
to 0 °C for 10 h and then filtered and washed with cold
dimethylformamide to give 10.44 g (80% yield) of the title
compound: 1H NMR (500 MHz, CDCl3) δ 9.74 (s, 1 H), 7.56 (d,
J ) 4.0 Hz, 1 H), 7.09 (d, J ) 4.05 Hz, 1 H), 6.95 (d, J ) 3.96,
1 H), 5.99 (d, J ) 4.07, 1 H), 3.19 (t, J ) 5.65 Hz, 4 H), 1.71
(pent, J ) 5.59 Hz, 4 H), 1.59 (pent, J ) 5.43 Hz, 2 H): 13C
NMR (125 MHz, CDCl3) δ 149.36, 137.91, 126.99, 120.98, 104.76,
51.83, 25.02, 23.61; UV-vis (CH2Cl2) λ max 444 nm; (CCl4) λ max
5′-(1,1-Dicyan o-1,3-bu tadien -4-yl))-2-(N,N-diph en ylam in o)-
2′,5-bith iop h en e. The above method was used (70% yield): 1H
NMR (300 MHz, CDCl3) δ 7.46 (d, J ) 11.7 Hz, 1 H), 7.4-7.1
(m, 13 H), 6.98 (d, J ) 4.2 Hz, 1 H), 6.86 (dd, J ) 14.7, 11.7 Hz,
1 H), 6.53 (d, J ) 4.2 Hz, 1 H); UV-vis (ligroin) λmax 522 nm;
(CHCl3) λmax 558 nm; (NMP) λmax 554 nm. Anal. Calcd: C,
71.70; H, 3.93; N, 9.65; S, 14.72. Found: C, 71.61; H, 3.85; N,
9.58; S, 14.62.
5′-N-P ip er id in yl-2-(3-p h en yl-5-oxo-4-isoxa zolyl)m et h -
ylid en e)-2′,5-bith iop h en e. To a solution of 3-phenyl-5-isox-
azolone (1 g, 6 mmol) and 5′-N-piperidinyl-2′,5-bithiophene-2-
carboxaldehyde (1.3 g, 5 mmol) in chloroform (10 mL) was added
triethylamine (1 drop), and the solution was heated to reflux
for 1 h, then cooled, dried over magnesium sulfate, and filtered
and the solvent removed in vacuo. The resulting purple solid
was recrystallized from ethanol to give 1.5 g (75 %) of the title
product: 1H NMR (500 MHz, CDCl3) δ 7.75 (br s, 1 H), 7.62-
7.58 (m, 2 H), 7.55-7.80 (m, 4 H), 7.31 (d, J ) 4.22 Hz, 1 H),
7.02 (d, J ) 4.24 Hz, 1 H), 6.04 (d, J ) 4.28 Hz, 1 H), 3.26 (br t,
J ) 5.62 Hz, 4 H), 1.71 (br pent, J ) 5.34 Hz, 4 H), 1.62 (br
sext, J ) 5.2 Hz, 2 H); UV-vis (ligroin) λmax 574 nm; (CHCl3)
430 nm; (EtOH) λ
548 nm; (DMSO) λ
450 nm; mp 143-
max
max
145 °C; HRMS calcd m/ z ) 277.0596, found m/ z ) 277.0595.
Anal. Calcd: C, 60.604; H, 5.461; N, 5.050; O 5.767; S, 23.119.
Found: C, 60.66; H, 5.53; N, 5.11; S, 23.05.
(5′-N-P ip er id in yl-2′,5-bith iop h en e-2-yl)a cr olein was pre-
pared using the above method (90% yield): 1H NMR (500 MHz,
CDCl3) δ 9.55 (d, J ) 7.74 Hz, 1 H), 7.76 (d, J ) 15.42 Hz, 1 H),
7.17 (d, J ) 4.02 Hz, 1 H), 6.99 (d, J ) 4.07 Hz, 1 H), 6.87 (d, J
) 4.02, 1 H), 6.33 (dd, J ) 15.41, 7.74 Hz, 1 H), 5.95 (d, J )
4.07 Hz, 1 H), 3.17 (dd, J ) 5.69, 5.69 Hz, 4 H), 1.70 (pent, J )
5.74 Hz, 4 H), 1.57 (pent, J ) 5.38 Hz, 2 H); HRMS calcd m/ z
) 303.0750, found m/ z ) 303.0752.
λ
max 608 nm; (NMP) λmax 650 nm; HRMS calcd m/ z ) 420.0978,
found m/ z ) 420.0966. Anal. Calcd: C, 65.69; H, 4.79; N, 6.66;
S, 15.25. Found: C, 65.79; H, 4.77; N, 6.7 ; S, 15.27.
5′-N-P ip er id in yl-2-(3-(3-p h en yl-5-oxo-4-isoxa zolylid en e)-
p r op en yl)-2′,5-bith iop h en e. The above method was used (75%
1
yield): H NMR (500 MHz, CDCl3) δ 7.97 (dd, J ) 14.02, 12.11
5′-(N,N-Dip h en yla m in o)-2′,5-bith iop h en e-2-ca r boxa ld e-
h yd e was prepared using the above method (80% yield): 1H
NMR (500 MHz, CDCl3) δ 9.78 (s, 1 H), 7.58 (d, J ) 4.1 Hz, 1
H), 7.28 (t, J ) 7.9 Hz, 4 H), 7.18 (d, J ) 7.63 Hz, 4 H), 7.12 (d,
J ) 4.01 Hz, 1 H), 7.09 (t, J ) 7.39 Hz, 2 H), 7.03 (d, J ) 4.01
Hz, 1 H), 6.53 (d, J ) 6.53 Hz, 1 H).
(5′-(N,N-Dip h en yl a m in o)-2′,5-bith iop h en e-2-yl)a cr olein
was prepared using the above method (80% yield): 1H NMR (300
MHz, CDCl3) δ 9.63 (d, J ) 7.8 Hz, 1 H), 7.53 (d, J ) 15.6 Hz,
1 H), 7.4-7.3 (m, 4 H), 7.3-7.2 (m, 4 H), 7.2-7.1 (m, 4 H), 7.01
(d, J ) 3.9 Hz, 1 H), 6.59 (d, J ) 3.9 Hz, 1 H), 6.44 (dd, J )
15.6, 7.8 Hz, 1 H); HRMS calcd m/ z ) 387.0752, found m/ z )
387.0742.
Hz, 1 H), 7.60-7.55 (m, 2 H), 7.55-7.45 (m, 3 H), 7.33 (d, J )
12.10 Hz, 1 H), 7.25 (d, J ) 14.57 Hz, 1 H), 7.19 (d, J ) 4.06 Hz,
1 H), 7.07 (d, J ) 4.15 Hz, 1 H), 6.88 (d, J ) 4.00 Hz, 1 H), 5.99
(d, J ) 4.12 Hz, 1 H), 3.21 (br t, J ) 5.54 Hz, 4 H), 1.70 (br
pent, J ) 5.45 Hz, 4 H), 1.65-1.55 (m, 2 H); UV-vis (CHCl3)
λ
max 632 nm; (NMP) λmax 542 nm; HRMS calcd m/ z ) 446.1108,
found m/ z ) 446.1123. Anal. Calcd: C, 67.24; H, 4.97; N, 6.24;
S, 14.29. Found: C, 67.14; H, 5.07; N, 6.19; S, 14.29.
2-((3-P h en yl-5-oxo-4-isoxa zolyl)m et h ylid en e)-5′-(N,N-
d ip h en yla m in o)-2′,5-bith iop h en e. The above method was
used (70% yield): 1H NMR (300 MHz, CDCl3) δ 7.75 (bd, J ) 3
Hz, 1 H), 7.7-7.5 (m, 5 H), 7.4-7.2 (m, 10 H), 7.16 (t, J ) 7.2
Hz, 2 H), 7.09 (d, J ) 4.2 Hz, 1 H), 6.51 (d, J ) 4.2 Hz, 1 H);
UV-vis (ligroin) λmax 574 nm; (CHCl3) λmax 588 nm; (NMP) λmax
606 nm; HRMS calcd m/ z ) 504.0959, found m/ z ) 504.0959.
5′-N-P iper idin yl-2-(1,1-dicyan ovin yl)-2′,5-bith ioph en e. To
a solution of malononitrile (0.8 g, 12 mmol) and 5′-N-piperidinyl-

2246 J . Org. Chem., Vol. 61, No. 6, 1996
Notes
2-(3-(3-P h en yl-5-oxo-4-isoxazolyliden e)pr open yl)-5′-(N,N-
d ip h en yla m in o)-2′,5-bith iop h en e. The above method was
used (70% yield): 1H NMR (300 MHz, CDCl3) δ 8.07 (dd, J ) 15,
12.3 Hz, 1 H), 7.7-7.5 (m, 5 H), 7.4-7.1 (m, 14 H), 6.97 (d, J )
3.9 Hz, 1 H), 6.54 (d, J ) 3.9 Hz, 1 H); UV-vis (ligroin) λmax 568
nm; (CHCl3) λmax 580 nm; (NMP) λmax 584 nm; HRMS calcd m/ z
) 530.1122, found m/ z ) 530.1099.
nm; (CHCl3) λmax 676 nm; (NMP) λmax 700 nm; HRMS calcd m/ z
) 485.1286, found m/ z ) 485.1265.
Dieth ylth ioba r bitu r ic Acid Ad d u ct of 5′-(N,N-Dip h en yl-
a m in o)-2′,5-b it h iop h en e-2-ca r b oxa ld eh yd e. The above
method was used (75% yield): 1H NMR (500 MHz, CDCl3) δ 8.54
(s, 1 H), 7.71 (d, J ) 4.26 Hz, 1 H), 7.36 (d, J ) 4.14 Hz, 1 H),
7.32 (t, J ) 7.82 Hz, 4 H), 7.24 (d, J ) 4.13 Hz, 1H), 7.23 (d, J
) 8.3 Hz, 4 H), 7.14 (t, J ) 8.1 Hz, 2 H), 6.49 (d, J ) 4.15 Hz,
1 H), 4.58 and 4.56 (overlapping q, J ) 7.06 and 7.03 Hz, 4 H),
1.32 and 1.28 (overlapping t, J ) 6.92 and 6.97 Hz, 6 H); UV-
vis (ligroin) λmax 532 nm; (CHCl3) λmax 580 nm; (NMP) λmax 616
nm. Anal. Calcd: C, 64.06; H, 4.63; N, 7.73; S, 17.69. Found:
C, 64.27; H, 4.64; N, 7.60; S, 17.54.
5′-N-P ip er id in yl-2-((N,N-d iet h ylt h iob a r b it u r yl)m et h -
ylid en e)-2′,5-bith iop h en e. A solution of 5′-N-piperidinyl-2′,5-
bithiophene-2-carboxaldehyde (1.3 g, 5 mmol) and N,N-dieth-
ylthiobarbituric acid (1.2 g, 6 mmol) in acetic anhydride (5 mL)
was heated to reflux for 30 min and then cooled to ambient
temperature. The resulting mixture was poured into chloroform
and washed with 5% ammonium chloride solution. The organic
layer was dried over magnesium sulfate and the solvent removed
in vacuo. The resulting purple solid was recrystallized from
ethanol to give 1.4 g (65%) of the title product: 1H NMR (500
MHz, CDCl3) δ 8.45 (s, 1 H), 7.66 (d, J ) 4.2 Hz, 1 H), 7.38 (d,
J ) 4.4 Hz, 1 H), 7.06 (d, J ) 4.4 Hz, 1 H), 6.03 (d, J ) 4.3 Hz,
1 H), 4.6-4.5 (m, 4 H), 3.28 (t, J ) 5.3 Hz, 4 H), 1.70 (br pent,
J ) 5.7 Hz, 4 H), 1.68-1.58 (m, 2 H), 1.32 (t, J ) 6.7 Hz, 3 H),
1.29 (t, J ) 7.0 Hz, 3 H); 13C NMR (125 MHz, CDCl3) δ 178.6,
164.12, 161.5, 160.2, 158.6, 148.7, 147.7, 133.7, 130.7, 122.2,
119.8, 106.2, 105.3, 51.4, 43.8, 42.9, 24.9, 23.5, 15.5, 12.4; UV-
vis (CCl4) λ max 598 nm; (DMSO) λ max 598 nm; (NMP) λ max 650
3-(5′-(N,N-Diph en ylam in o)2′,5-bith ioph en e-2-yl)acr olein -
N,N-Dieth yltioba r bitu r ic Acid Con d en sa tion P r od u ct. The
above method was used (80% yield): 1H NMR (300 MHz, CDCl3)
δ 8.29 (dd, J ) 14.4, 12.3 Hz, 1 H), 8.13 (d, J ) 12.3 Hz, 1 H),
7.51 (d, J ) 14.4 Hz, 1 H), 7.40-7.05 (m, 12 H), 6.70 (d, J ) 3.9
Hz, 1 H), 6.53 (d, J ) 3.9 Hz, 1 H), 4.6-4.5 (m, 4 H), 1.3-1.4
(m, 6 H); UV-vis (ligroin) λ
534 nm; (CHCl3) λ
578 nm;
max
max
(NMP) λ
610 nm. Anal. Calcd: C, 65.35; H, 4.78; N, 7.38;
max
S, 16.88. Found: C, 64.88; H, 4.90; N, 7.22.
Ack n ow led gm en t. The research described in this
paper was performed in part by The J et Propulsion
Laboratory, California Institute of Technology, as part
of its Center for Space Microelectronics Technology and
was supported by the Ballistic Missile Defense Initiative
Organization, Innovative Science and Technology Office,
through a contract with the National Aeronautics and
Space Administration (NASA). Support from the AFOSR
(Grant F49620-95-1-0178) is gratefully acknowledged.
P.V.B. thanks the J ames R. Irvine foundation for a
postdoctoral fellowship.
nm; (petroleum ether) λ
574 nm; 192-210 °C dec; HRMS
max
calcd m/ z ) 459.1101, found m/ z ) 459.1109. Anal. Calcd:
C, 57.48; H, 5.49; N, 9.14; Found: C, 57.21; H, 5.51; N, 9.24.
(5′-N-P ip er id in yl-2′,5-bith iop h en e-2-yl)a cr olein -N,N-Di-
eth ylth iobar bitu r ic Acid Con den sation P r odu ct. The above
method was used (75% yield): 1H NMR (500 MHz, CDCl3) δ 8.21
(dd, J ) 14.34, 12.41 Hz, 1 H), 8.08 (d, J ) 12.49 Hz, 1 H), 7.48
(d, J ) 14.35, 1 H), 7.27 (d, J ) 4.14 Hz, 1 H), 7.10 (d, J ) 6.14
Hz, 1 H), 6.91 (d, J ) 4.07 Hz, 1 H), 5.99 (d, J ) 4.13 Hz, 1 H),
4.53 (pent, J ) 7.63 Hz, 4 H), 3.22 (dd, J ) 5.5, 5.5 Hz, 4 H),
1.71 (pent, J ) 5.5 Hz, 4 H), 1.65-1.50 (m, 4 H), 1.31 (t, J )5.2
Hz, 3 H), 1.28 (t, J ) 6.96 Hz, 3 H); UV-vis (ligroin) λmax 578
J O9517555