Büchwald-Hartwig Reaction Applied to Synthesis of New Luminescent Liquid Crystal Triarylamines Derived from Isoxazoles

Article abstract of DOI:10.1080/15421406.2015.1030982

The present work describes the synthesis and characterization of novel series of triarylamines isoxazoles (TAA) addressed to the organic photovoltaic materials. Diarylisoxazoles were synthesized by sequential [3+2] 1,3-dipolar cycloaddition reaction betwe

Full text of DOI:10.1080/15421406.2015.1030982

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Büchwald-Hartwig Reaction Applied to
Synthesis of New Luminescent Liquid
Crystal Triarylamines Derived from
Isoxazoles
G. D. Vilelaab, T. H. M. Fernandesa, S. M. Kellyb & A. A. Merloa
a Chemistry Institute, Universidade Federal do Rio Grande do Sul,
Porto Alegre, Brazil
b Chemistry Department, University of Hull, Hull, England
Published online: 06 Jul 2015.
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To cite this article: G. D. Vilela, T. H. M. Fernandes, S. M. Kelly & A. A. Merlo (2015) Büchwald-
Hartwig Reaction Applied to Synthesis of New Luminescent Liquid Crystal Triarylamines
Derived from Isoxazoles, Molecular Crystals and Liquid Crystals, 612:1, 169-182, DOI:
10.1080/15421406.2015.1030982
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Mol. Cryst. Liq. Cryst., Vol. 612: pp. 169–182, 2015
Copyright © Taylor & Francis Group, LLC
ISSN: 1542-1406 print/1563-5287 online
DOI: 10.1080/15421406.2015.1030982
Bu¨chwald-Hartwig Reaction Applied to Synthesis of
New Luminescent Liquid Crystal Triarylamines
Derived from Isoxazoles
G. D. VILELA,1,2 T. H. M. FERNANDES,1 S. M. KELLY,2
AND A. A. MERLO1,∗
1Chemistry Institute, Universidade Federal do Rio Grande do Sul, Porto Alegre,
Brazil
2Chemistry Department, University of Hull, Hull, England
The present work describes the synthesis and characterization of novel series of triary-
lamines isoxazoles (TAA) addressed to the organic photovoltaic materials. Diarylisoxa-
zoles were synthesized by sequential [3+2] 1,3-dipolar cycloaddition reaction between
arylnitrile oxides and selected arylalkenes followed by MnO2-oxidation. Isoxazoles
were coupled to diarylamines by Bu¨chwald-Hartwig reaction to afford desired com-
pounds 6a–k. Some TAA display liquid-crystalline behaviour and UV-Vis absorption
and fluorescence emission were analysed for all samples of TAA 6a–k.
Keywords Isoxazoles; [3+2] 1, 3-dipolar cycloaddition; Bu¨chwald-Hartwig reaction;
fluorescence; liquid crystals.
1. Introduction
Exciton migration and processability are important concepts in the emerging technologies
of molecular [1] electronics and optoelectronic devices [2], including photovoltaic cells
[3] and organic light-emitting diodes (OLEDs) [4]. The first one is important to optimize
the energies of excited states and energy transfer processes, the second one is important to
evaluate how this materials will be applied in the devices. Bipolar molecules, which can
accept and transport both holes and electrons, are attractive candidates for optoelectronic
studies [5] because the same molecule has both parts of P-N junction; and liquid crystals
are widely used because of their physical properties as self-assembling and fluidity [6].
In this field of organic electronics, triarylamines (TAA) have been widely studied to
be applied in organic solar cells (OSC) and organic light-emitting diodes (OLED) [7], due
to their good electron-donating properties. The triarylamine moieties are known to favour
solid-state fluorescence intensity due to their tendency to be amorphous [8]. TAA may
be considered a pseudo-3D structure which show strong resistance to crystallization and
thus avoid or preventing tight π-stacking interactions. Due to the steric interaction repul-
sion among phenyl groups, TAA adopts a non-planar propeller shape and, this way, TAA
∗Address correspondence to Aloir A. Merlo, Chemistry Institute, UFRGS, Bento Gonalves
Avenue, 9500, Campus do Vale, Porto Alegre, RS, Brazil CEP 91501970. Email: aloir.merlo@ufrgs.br
Color versions of one or more of the figures in the article can be found online at
www.tandfonline.com/gmcl.
[635]/169

170/[636]
G. D. Vilela et al.
represents an intermediate situation between planar 2D systems and true 3D conjugated
systems [9]. Heterocycles, such as isoxazoles, are receiving attention from organic elec-
tronic materials (OEM) [10] field because isoxazoles are aromatic heterocycles that behave
as electro-acceptor group. To achieve a unique molecular architecture with intramolecular
P-N junction, where a hole-transport group (p-type) and an electron-transporting group
(n-type) are chemically connected, we chose the Bu¨chwald-Hartwig [11] reaction as fi-
nal synthetic step to prepare luminescent liquid crystals (LLCs) as bipolar compounds
according to Scheme 1.
Scheme 1. Bu¨chwald-Hartwig reaction between 3,5-isoxazoles and disubstituted amines reported
herein.
Bu¨chwald-Hartwig reaction is one of the most important methodology to prepare
triarylamines by coupling secondary amines and aryl halides, due tolerance to functional
groups, high yields and mild conditions [8,12].
2. Discussion, Synthesis and Liquid Crystal Behaviour
The synthesis of key intermediate isoxazoles 5a–b from isoxazolines 4a–b is outlined in
Scheme 2. To accomplish these transformation a [3+2] 1,3-dipolar cycloaddition between
nitrile oxide derived from oxime [13] 2a and 2b and styrenes 3a–b followed by oxidation
mediated by MnO2. The isoxazolines 4a–b[10] are obtained in medium yields (44 and
27% respectively) and 5a–b [14] were obtained in good yields (95 and 87% respectively)
[10,15]. Products were confirmed by H NMR and 3C NMR spectroscopy.
Isoxazole 5a containing the labile tert-butyl group is the prime ticket to enter a precursor
phenol which can be transformed into the final key isoxazoles. Thus, tert-butyl group from
5a was removed by acid hydrolysis [16] to give free phenol 5c and then subjected to the
alkylation reaction with linear n-decyl and branched 2-ethylhexyl bromide to give 5d–e
[17].
Finally, the Buchwald-Hartwig (B-H) [12] cross-coupling reaction was performed
using 1% mol of Pd(OAc)2, 1% mol of BINAP, a large excess of Cs2CO3, diarylisoxazoles

¨
LLC Triarylamines from Buchwald-Hartwig Reaction
[637]/171
Scheme 2. Synthesis of 3,5-disubstituted isoxazoles.
5b, 5d and 5e and secondary amines, as describe in Scheme 1. Four amines such as
piperidine, morpholine, diphenylamine and phenothiazine were selected to participate to
the B-H reaction. The final products containing the isoxazoles and tertiary amines moieties
6a–k, as outlined in Figure 1, were obtained in good yields giving the desired compounds,
as showed in Table 1.
The thermal data for all trisubstituted amines is presented in Table 1. As we can see
compounds having linear alkyl chain displayed mesomorphic behaviour while for branched
amines no mesophase was observed. Among triarylamines synthesized, compounds 6e–g
have shown mesomorphic behaviour whereas 6h did not. Precursor 5d also have displayed
smectogenic behaviour, as reported previously [15]. Only nematic mesophase was found for
the piperidine derivative 6e (Figure 2a). However, as we expected, linear alkyl chain favours
the appearance of smectic mesophase as exemplified by 5d and 6f–g. These compounds
exhibit typical focal-conic texture, as depicted in Figure 2b-d. Compound 6g also exhibited
a second strucutured smectic phase, CrE phase above 78◦C. The crystallization process to
Scheme 3. Hydrolysis of isoxazole 5a and follow alkylation of phenol 5c.

172/[638]
G. D. Vilela et al.
Figure 1. Structure of isoxazoles 6a–k.
this sample occurs slowly after a long period of time where the CrE texture freeze into the
crystal phase, Figure 2c.
Nematic phase observed to 6e may be attributed to the flexibility of non-aromatic
piperidine group. Compound 6h did not show mesophase due to steric hindrance of phe-
nothiazine group that prevents orientational or lamellar arrangement. In general, the results
in Table 1 provide the idea that mesomorphic behaviour is a balance between flexibility

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LLC Triarylamines from Buchwald-Hartwig Reaction
[639]/173
Table 1. Thermal data (◦C) and yield (%) for the Isoxazoles 5a and 6a–k
LC
X
Y
Thermal Behaviour
Yield (%)
5d
6a
6b
6c
6d
6e
6f
6g
6h
6i
Br
n-Decyloxy
Piperidine
Morpholine
Diphenylamine
Phenotiazine
n-Decyloxy
n-Decyloxy
n-Decyloxy
Cr 90 CrE 115 SmA 191 I
207
259
216
95
87
61
63
60
55
64
56
84
42
43
42
NO2
NO2
NO2
NO2
218
Piperidine
Cr 127 N 134 I
Cr 142 SmA 156 I
CrE 78 SmA 145 I
121
136
87
Morpholine
Diphenylamine
Phenotiazine
Morpholine
Diphenylamine
Phenotiazine
n-Decyloxy
2-Ethyl-1-hexyloxy
2-Ethyl-1-hexyloxy
2-Ethyl-1-hexyloxy
6j
6k
97
afforded by alkyl chain and segregation effects between two regions - the rigid core and
the less polar alkyl chain. For non liquid crystals TAA listed on Table 1 the melting point
tendency observed for 6a–d and 6i–k depends on the nature of terminal groups X and Y.
TAA from morpholine 6b and 6i have the highest melting point which group of molecules.
Figure 2. (a) Nematic textures observed by POM at cooling of compound 6e at 130◦C, (b) SmA
texture for compound 6f at 147◦C, (c) CrE texture for compound 6g at 75◦C and (d) SmA texture for
compound 6g at 135◦C.

174/[640]
G. D. Vilela et al.
Figure 3. Compounds 6a–k excited under UV light at 365 nm.
Of course, nature of X and Y group has a great impact on melting point. π-Stacking in-
teraction is strong for derivatives having the nitro group and less efficient for derivatives
containing branched alkyl group.
2.1. Photophysical properties
A photophysical study of TAA amines 6a-k was performed to evaluate their absorption and
emission spectrum in solution of dichloromethane (CH2Cl2, DCM). A preliminary analysis
of absorption and emission data of these TAA was evaluated from dichloromethane solutions
of compounds 6a-k under UV irradiation at 365 nm. Sample solutions of compounds 6a-d
which bear the NO2 group did not show fluorescence emission. Fluorescence emission
of derivatives containing dipolar nitro group is deeply influenced by different decay ways
present in this group [18]. Generally the main pathway for polar groups with formal charge is
associated with charge transfer in the excited state. On the other hand, compounds 6e-k have
shown interesting fluorescence behaviour while under UV irradiation, the effect of coupled
amines in the fluorescence behaviour is remarkable. 6h and 6k which have phenothiazine
group exhibit a red-shifted emission compared to the others as seen in Figure 1. Another
remarkable observation was the intense shine of compounds bearing diphenylamine group.
In fluorescence phenomenon, the molecule is excited to a singlet state of higher energy,
followed by return to its ground state by different pathways, charge transfer, fluorescence,
phosphorescence or vibrational relaxation, as described in the well known Jablonski’s
diagram. Stokes shift and quantum efficiency are mainly determined by the way of that
molecules return to ground state.
The absorption and emission behavior of TAA structures in dichloromethane (DCM)
solution were analyzed by UV-vis and photoluminescence (PL) measurements as shown in
Figure 2, Figure 3 and Table 2. These materials exhibited absorption bands of 250–340 nm
assigned to π–π∗ transitions of the diarylisoxazole moiety.
Absorption spectra of compounds 6e–k showed in Figure 3 are divided in three groups
when analysing their absorption spectra. First group is formed by compounds 6e, 6f and 6i,
which were coupled with non aromatic piperidine and morpholine (Figure 3a). They show
λmax of absorption near 290 nm. Second group is formed by compounds 6g ad 6j, which
were coupled with diphenylamine (Figure 3b) show λmax at 336 nm and another intense
absorption band at 290 nm. Finally, a third group is formed by compounds 6h and 6k,
which were coupled with phenothiazine (Figure 3c) with λmax of absorption is also near

¨
LLC Triarylamines from Buchwald-Hartwig Reaction
[641]/175
Table 2. Photophysical data for TAA 6e–k
abs
max
em
max
λ
λ
ꢀλST ꢀEHOMO- ꢁPL,
Compound
X
Y
(nm) (nm) (nm)
a (eV) (%)
LUMO
6e
6f
6g
6h
6i
Piperidine
Morpholine
Diphenylamine n-Decyloxy
Phenothiazine n-Decyloxy
Morpholine
n-Decyloxy
n-Decyloxy
298 425 127
294 409 115
2,93
2,97
1,2
0,3
24,5
0,2
0,3
50
336 419
83
2,60
3,02
3,02
2,59
3,02
289 513 224
2-Ethyl-1-hexyloxy 289 408 119
84
6j
6k
Diphenylamine 2-Ethyl-1-hexyloxy 337 421
Phenothiazine 2-Ethyl-1-hexyloxy 289 524 235
0,1
abs
max
(a) Calculated by λ
.
290 nm accompanied by another higher intense transition at 257 nm. For comparison of the
absorption spectra behaviour 6i, 6j and 6k were grouped in Figure 3d. They have the same
linear n-decyl chain and morpholine for 6i, diphenylamine for 6j and phenothiazine for 6k.
Absorption λmax at 337 nm of 6j containing the diphenyl group is red-shifted whereas 6k
is blue-shifted with λmax at 289 nm.
Absorption band at 290 nm can be associated to the excitation of the basic rigid
core, because this value appears in all samples - 3,5-diphenyl-isoxazole shows absorption
maxima (λmax) at 263 mn [19], slightly red-shifted by the electro-donating alkyl groups
[18], as seen in Figure 3d. Compounds 6e, 6f and 6l have only the absorption maxima
(λmax) at 290 nm because piperidine and morpholine are non aromatic and they do not
affect the π−conjugation. Compounds 6h and 6k showed absorption maxima (λmax) at
289 nm as less intense transition, suggesting that the main excitation way do not include
the phenothiazine core. It is possible if the nitrogen turns to a sp3 configuration, breaking
both, conjugation and planarity. The absence of planarity can also explain the absence of
mesomorphic behaviour in compound 6h (Table 1). On the other hand, compounds 6g
and 6j show as less energetic absorption band λmax at 337 nm, indicating that two phenyl
rings of coupled amine are taking place in conjugation promoting a decreasing in the gap
between HOMO and LUMO, as expected to an interaction between a donator group and
an acceptor group.
Figure 4 displays the fluorescence emission spectra that were acquire in dichromethane
solution. Two different groups of chromophores can be seen with blue-shifted and red-
shifted of λmax of emission. Emission at λmax at 408–425 nm belongs to chromophores 6e,
6f, 6g, 6i and 6j. TAA with emission at λmax 513 and 524 nm belong to chromophores 6h
and 6k containing the phenothiazine group. Red-shifted behaviour for 6h and 6k can be
attributed to influence of internal conversions of different configurations of phenothiazine
group leading to non-radiative relaxation of molecules in the excited state.
Table 2 displays the photophysical data for compounds 6e–k. Absorption and emission
data were acquired in dichloromethane solutions. Quinine sulphate in 0.5 M H2SO4 solution
[20] was used as standard to obtain the fluorescence quantum yield calculation.
Spectral UV-vis and fluorescence data can explained by analyzing chemical structure
of TAA synthesized in this work. Compounds with piperidine and morpholine groups (6e,
6f and 6i) have some vibrational freedom that allow relaxation of excited state before
emission, this relaxation causes significant decreasing on quantum yield, however absence

176/[642]
G. D. Vilela et al.
Figure 4. UV-Vis absorption spectra of compounds 6e–k. (a) Spectra of compounds bearing piperi-
dine and morpholine groups. (b) Spectra of compounds bearing diphenylamine group. (c) Spectra
of compounds bearing phenothiazine group. (d) Comparison among compounds bearing the same
branched alkyl chain, but with different coupled amines.
Figure 5. Fluorescence emission spectra of compounds 6e–k in dichloromethane solution. Signal in
582 nm is due to re-absorption of sample.

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LLC Triarylamines from Buchwald-Hartwig Reaction
[643]/177
of internal conversions lead to a narrow Stokes shift. Compounds bearing diphenylamine
group 6g and 6j have a rigid and conjugated aromatic core and display a shorter energy gap
between HOMO and LUMO. The high quantum yields and small Stokes shift for 6g and
6j can be explained by the absence of other preferential ways to decay from excited state
of fluorescence. In compounds containing phenothiazine group 6h and 6k, the resonance
between two forms is necessary to allow aromaticity in phenothiazine; according Hu¨ckel’s
law, an aromatic core has 4n + 2 electrons π involved in the conjugated core, phenothiazine
receives twelve electrons from both benzene rings, allowing just more two electrons to be
inserted into the conjugation, these two electrons are from sulphur or nitrogen, never from
both at same time, as seen in Figure 5. Interconversion between two different excited states
generates a large energetic relaxation and probably causes a large Stokes shifts and low
quantum yields.
3. Conclusions
A collection of eleven TAA 6a–k derived from 3,5-diaryl-isoxazole core were synthe-
sized using the Bu¨chwald-Hartwig cross-coupling reaction. Compounds 6a–d did not show
fluorescence, because of nitro group. TAA 6e–k have shown distinct liquid crystals and
fluorescence behaviour. Comparison between two alkyl chains showed that linear alkyl
chain induced mesomorphic behaviour in compounds 6e–g, however branched alkyl chain
inhibited mesophase formation. Effect of branch enhances solubility for compounds 6i–k.
UV-vis and emission data for amines having non-aromatic amines (piperidine and mor-
pholine) are unaffected by these group. However, changes in their absorption and emission
spectra were observed for diphenilamine 6g/6j and phenothiazine 6h/6k.
TAA with diphenilamine group displayed a short Stokes shift (between 83–84 nm)
and an good quantum yield (24% in 6g, and 50% in 6j), probably related to their rigidity
and larger conjugation over all rigid core which allow photon emission as low energetic
path from excited state to the ground state. On the other hand, phenothiazine group decays
from excited state by interconversion of two different aromatic conformers, this energy loss
induce large Stokes shift (between 224–235 nm) and low quantum yields (0.1% in 6h and
0.2% in 6k).
4. Experimental Section
1H NMR and 13C NMR spectra in CDCl3 were obtained using Bruker-400 MHz spec-
trometer using TMS as an internal standard. The thermal transitions and the textures were
determined using an Olympus BX43 polarizing microscope in conjunction with a Mettler
FP90 controller and HT84 heating stage and TA Instruments Q20 Serie differential scanning
calorimeter. The rate of heating or cooling was 10◦C min−1
.
The reagents hydroxylamine chloridrate, 4-hydroxybenzaldehyde, pyridine, 11-
bromoundecan-1-ol, methacrylic acid, acrylic acid, N-chlorosuccinimide (NCS) were used
as received from Aldrich Co. Analytical thin layer chromatography (TLC) was conducted
on Merck aluminium plates with 0.2mm of s´ılica gel 60F–254. Anhydrous sodium sulfate
was used to dry all organic extracts. Toluene and THF were first heated at reflux over
sodium and then distilled under argon. AIBN was freshly recrystallised from methanol.
Purification by column chromatography was carried out on 70–230 mesh Merck silica gel
60. All other solvents and reagents were used without previous purification.

178/[644]
G. D. Vilela et al.
4.1. Syntheses
4.1.1. Synthesis of oximes 2a–b. Representative procedure for compound 2a. In a round
bottom flask p-bromobenzaldehyde (0.9 g, 25.0 mmol) and hydroxylamine hydrocloride
(4.9 g, 62.5 mmol) were dissolved in ethanol (100 mL), then was added sodium acetate
(8.2 g, 100 mmol) dissolved in water (50.0 mL). The reaction mixture was stirred at reflux
(78◦C) for an hour, followed by remotion of solvent under reduced pressure and cooled
down to room temperature. The crude material was recrystallized in ethanol. Data for 2a:
White solid, yield 95%, m.p. 112◦C. 1H NMR (CDCl3, 300 MHz): 7.29 (s, 1H, CHNOH,
Z isomer), 7.47 (d, 2H, Ar, J = 8.4 Hz), 7.57 (m, 4H, Ar, Z and E isomers), 7.85 (d, 2H,
Ar, Z isomer, J = 8.4 Hz), 8.12 (s, 1H, CHNOH, E isomer).
Data for 2b: Yellow solid, yield 91%, m.p. 128◦C. 1H NMR (CDCl3, 300 MHz): 7.76
(d, 2H, Ar, J = 9.0 Hz), 8.11 (s, 1H, OH), 8.21 (s,1H, CHNOH), 8.25 (d, 2H, Ar, J =
9.0 Hz).
4.1.2. Cicloaddition [3 + 2] 1,3-Dipolar - Synthesis of Isoxazolines 4a–b.. Representative
procedure for compound 4a. In a round bottom flask, were added 4-bromobenzaldehyde
oxime (2a) (1.0 g, 5.0 mmol), N-chlorossuccinimide (0.8 g, 6.0 mmol), dichloromethane
(35.0 mL) and a drop of HCl (conc.), the mixture was stirred for 4 hours to form the oximoyl
chloride. After the formation of the intermediate the mixture was cooled in ice bath, and
to the solution were added 4-tert-butoxystyrene (3a) (1.0 g, 5.5 mmol) and triethylamine
(2.0 mL, 15.0 mmol) dropwise, then the mixture was stirred at room temperature for
24 hours. The reaction mixture was washed with 1M HCl (2 × 20 mL), water (2 × 20 mL)
and brine (30 mL), the organic layer was dried over Na2SO4. Solvent was removed under
reduced pressure giving the crude material. The product was purified by recrystallization in
ethanol. Data for 4a: White solid, yield 44%, m.p. = 122◦C; 1H NMR (CDCl3, 300 MHz):
1.34 (s, 9H, C(CH3)3), 3.31 (dd, 1H, Jcis = 8.4 Hz, Jgem = 16.5 Hz), 3.71 (dd, 1H, Jtrans
=
10.8 Hz, Jgem = 16.5 Hz), 5.70 (dd, 1H, Jcis = 8.7 Hz, Jtrans = 10.8 Hz), 6.99 (d, 2H, Ar, J
= 8.4 Hz), 7.27 (d, 2H, Ar, J = 8.4 Hz), 7.55 (s, 4H, Ar); 13C RMN (CDCl3, 75.5 MHz):
28.8, 42.7, 78.7, 82.7, 126.6, 126.7, 128.1, 128.5, 131.9, 135.1, 155.4, 155.5.
1
Data for 4b: Yellow solid, yield 27%, m.p. = 132◦C; H NMR (CDCl3, 300 MHz):
3.33 (dd, 1H, Jcis = 8.1 Hz, Jgem = 16.8 Hz), 3.83 (dd, 1H, Jtrans = 11.1 Hz, Jgem = 16.8 Hz),
5.81 (Jcis = 8.1 Hz, Jtrans = 11.1 Hz), 7.27 (d, 2H, Ar, J = 8.4 Hz), 7.53 (d, 2H, Ar, J =
8.4 Hz), 7.85 (d, 2H, Ar, J = 9.0 Hz), 8.27 (d, 2H, Ar, J = 9.0 Hz); 13C RMN (CDCl3,
75.5 MHz): 42.5, 82.8, 122.4, 124.0, 127.4, 127.5, 132.0, 135.2, 139.2, 148.5, 154.6.
4.2. Synthesis of Isoxazoles 5a–b. (Oxidation Reaction)
Representative procedure for 5a. In a round bottom flask were added isoxazoline 4a (2.4 g,
6.4 mmol), benzene (120 mL) and MnO2 (12.0 g), the reaction was carried under azeotropic
reflux for 24 hours. After consumption of starting material (followed by TLC) the mixture
was cooled down and filtered over a plug of celite. The solvent was removed under reduced
1
pressure giving the crude product. Data for 5a: White solid, yield 95%, m.p. 158◦C; H
NMR (CDCl3, 300 MHz): 1.40 (s, 9H, C(CH3)3), 6.69 (s, 1H, isoxazole ring), 7.08 (d, 2H,
Ar, J = 8.7 Hz), 7.59 (d, 2H, Ar, J = 8.4 Hz), 7.71 (d, 2H, Ar, J = 8.4 Hz), 7.72 (d, 2H,
Ar, J = 8.4 Hz); 3C NMR (CDCl3, 75.5 MHz): 28.9, 79.4, 96.3, 122.0, 123.9, 124.2, 126.7,
126.8, 128.2, 132.1, 157.6, 161.9, 170.6.
Data for 5b: Yellow solid, yield 87%, m.p. 225◦C; H NMR (CDCl3, 300 MHz): 7.03
(s, 1H, isoxazole ring), 7.67 (d, 2H, Ar, J = 8.4 Hz), 7.75 (d, 2H, Ar, J = 8.7 Hz), 8.08

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LLC Triarylamines from Buchwald-Hartwig Reaction
[645]/179
(d, 2H, Ar, J = 9.0 Hz), 8.36 (d, 2H, Ar, J = 8.7 Hz); 3C NMR (CDCl3, 75.5 MHz): 97.8,
124.1, 124.9, 125.6, 127.1, 127.5, 132.2, 134.8, 148.5, 161.1, 170.1.
4.3. Synthesis of Phenol 5c. (hydrolysis)
A solution of isoxazole 5a (2.2 g, 5.9 mmol), methanol (180 mL), acetic acid (8.9 mL),
HBr (conc.) (4.5 mL) was stirred under reflux for 6 hours. After the consumption of starting
material (followed by TLC) the mixture was cooled to room temperature and neutralized
to pH 6 with saturated solution of NaHCO3, the product was precipitated and filtered off,
giving a white solid. Yield: 95%, m.p. = 206◦C; H NMR (CDCl3, 300 MHz): 2.82 (ws,
water), 6.68 (s, 1H, isoxazol ring), 6.95 (d, 2H, Ar, J = 8.1 Hz), 7.60 (d, 2H, Ar, J =
8.4 Hz), 7.67 (d, 2H, Ar, J = 8.4 Hz), 7.73 (d, 2H, Ar, J = 8.1 Hz), 9.48 (s, 1H, OH); 3C
NMR (CDCl3, 75.5 MHz): 95.0, 115.8, 118.2, 123.6, 127.1, 127.9, 131.7, 158.2, 161.5,
170.7.
4.4. Synthesis of Isoxazoles 5d–e. (Alkylation Reaction)
Representative procedure for compound 5d. In a round bottom flask were added isoxazole
5c (0.8 g, 2.5 mmol), acetone (30.0 mL), potassium carbonate (0.4 g, 3.0 mmol) and 1-
Bromodecane (0.6 mL, 2.8 mmol), the reaction mixture was stirred under reflux for 24 hours
(followed by TLC) then mixture was filtered and the solvent was removed under reduced
pressure. The crude material was recrystallized in ethanol. Data for 5d: White solid; yield
95%; m.p. K 90.4◦C SmE 115.0◦C SmA 190.8◦C I; H NMR (CDCl3, 300 MHz): 0.88 (t,
3H, CH3, J = 6.44 Hz), 1.28 (m, 12H, alkyl chain), 1.47 (ws, 2H), 1.81 (m, 2H, OCH2CH2),
4.00 (t, 2H, OCH2, J = 6.59 Hz), 6.66 (s, 1H, isoxazole ring), 6.98 (d, 2H, Ar, J = 8.79 Hz),
7.60 (d, 2H, Ar, J = 8.50 Hz), 7.70 (d, 2H, Ar, J = 8.5 Hz), 7.76 (d, 2H, Ar, J = 8.5 Hz);
3C NMR (CDCl3, 75.5 MHz):.
Data for 5e: White solid; yield 92%; m.p. 134.8◦C; H NMR (CDCl3, 300 MHz):
0.93 (2 t, 6H, CH3, J = 7.5 Hz), 1.33 (m, 4H, CH2CH2CH2CH3), 1.48 (m, 4H,
OCH2CH(CH2CH3)CH2), 1.75 (m, 1H, OCH2CHR2), 3.90 (d, 2H, OCH2CH, J = 5.7 Hz),
6.66 (s, 1H, isoxazole ring), 6.99 (d, 2H, Ar, J = 9.0 Hz), 7.60 (d, 2H, Ar, J = 8.4 Hz),
7.73 (d, 2H, Ar, J = 8.4 Hz), 7.74 (d, 2H, Ar, J = 8.7 Hz); 3C NMR (CDCl3, 75.5 MHz):
11.1, 14.1, 23.0, 23.8, 29.1, 30.5, 39.3, 70.7, 95.8, 114.9, 119.7, 124.2, 127.4, 128.3, 129.1,
132.1, 161.1, 162.0, 170.8.
4.5. Synthesis of Triarylamines 6a–k. Buchwald-Hartwig Reaction
Representative procedure for compound 6a. In a Schlenck flask, under inert atmosphere,
degassed toluene (15.0 mL), Pd(OAc)2 (4 mg, 1% mol) and BINAP (11 mg, 1% mol) were
added and stirred for some minutes to form the complex Pd(BINAP); then the isoxazole
5a (0.6 g, 1.7 mmol), piperidine (0.2 mL, 2.1 mmol) and Cs2CO3 (2.8 g, 8.7 mmol) were
added to the flask. The flask was sealed and the reaction mixture was stirred under reflux
for 48 hours; after this time the mixture was filtered over celite and the filtrate was washed
with 1M HCl, water and brine; the organic layer was dried over Na2SO4 and the solvent
removed under reduced pressure. General procedure of purification was recrystallization
from ethanol, but sometimes column chromatography in hexane/dichloromethane was nec-
1
essary to purify the products. Data for 6a: Yield 87%; m.p. 207◦C; H NMR (CDCl3,
300 MHz): 1.68 (m, 6H, piperidine ring), 3.32 (t, 4H, piperidine ring, J = 4.5 Hz), 6.71 (s,
1H, isoxazole ring), 6.97 (d, 2H, Ar, J = 8.7 Hz), 7.71 (d, 2H, Ar, J = 8.4 Hz), 8.04 (d,

180/[646]
G. D. Vilela et al.
2H, Ar, J = 8.4 Hz), 8.34 (d, 2H, Ar, J = 8.1 Hz); 3C NMR (CDCl3, 75.5 MHz): 8.1, 24.3,
25.5, 49.2, 95.1, 115.0, 115.8, 124.2, 127.2, 127.6, 135.7, 148.6, 151.4, 161.0, 172.0.
Data for 6b: Yield 61%; m.p. 259◦C; 1H NMR (CDCl3, 300 MHz): 1.53 (ws, water),
3.22 (t, 4H, N(CH2)2, J = 4.99 Hz), 3.82 (t, 4H, O(CH2)2, J = 4.99 Hz), 6.67 (s, 1H,
isoxazole ring), 6.93 (d, 2H, Ar, J = 8.8 Hz), 7.69 (d, 2H, Ar, J = 8.8 Hz), 7.97 (d, 2H, Ar,
J = 8.8 Hz), 8.27 (d, 2H, Ar, J = 8.8 Hz); 3C NMR (CDCl3, 75.5 MHz): 47.2, 65.6, 94.6,
113.9, 119.5, 123.2, 126.2, 126.6, 134.5, 147.6, 151.4, 160.0, 170.6.
1
Data for 6c: Yield 63%; m.p. 216◦C; H NMR (CDCl3, 300 MHz): 6.67 (s, 1H,
isoxazole ring), 7.07 (m (3 d), 8H, Ar), 7.24 (t, 4H, Ar, J = 7.63 Hz), .58 (d, 2H, Ar, J
= 8.8 Hz), 7.96 (d, 2H, Ar, J = 8.8 Hz), 8,26 (d, 2H, Ar, J = 8.8 Hz); 3C NMR (CDCl3,
75.5 MHz): 95.9, 119.6, 121.6, 124.2, 125.5, 126.9, 127.7, 129.6, 135.5, 146.8, 148.6,
150.1, 161.1, 171.5.
Data for 6d: Yield 60%; m.p. 218◦C; 1H NMR (CDCl3, 300 MHz): 6.72 (d, 2H, Ar, J
= 8.4 Hz), 6.89 (s, 1H, isoxazole ring), 7.04 (m, 4H, Ar), 7.22 (d, 2H, Ar, J = 7.5 Hz), 7.39
(d, 2H, Ar, J = 8.7 Hz), 7.93 (d, 2H, Ar, J = 8.7 Hz), 8.06 (d, 2H, Ar, J = 8.4 Hz), 8.36
3
(d, 2H, Ar, J = 8.4 Hz); C NMR (CDCl3, 75.5 MHz): 97.2, 120.3, 123.9, 124.1, 124.2,
125.5, 125.9, 127.0, 127.6, 27.7, 127.8, 135.2, 142.8, 145.0, 148.7, 161.2, 170.9.
1
Data for 6e: Yield 55%; m.p. K 127 N 134 I; H NMR (CDCl3, 300 MHz): 0.80 (t,
3H, CH3, J = 6.4 Hz), 1.28 (m, 14H, alkyl chain), 1.47 (m, 2H, OCH2CH2), 1.78 (m, 6H,
piperidine ring), 3.26 (t, 4H, N(CH2)2, J = 5.3 Hz), 4.00 (t, 2H, OCH2, J = 6.4 Hz), 6.63
(s, 1H, isoxazole ring), 6.98 (m, 4H, Ar), 7.74 (m, 4H, Ar); 3C NMR (CDCl3, 75.5 MHz):
14.2, 22.7, 24.3, 25.5, 26.0, 29.2, 29.3, 29.4, 29.5, 29.6, 31.9, 49.8, 68.2, 95.7, 114.8, 115.7,
120.3, 127.3, 127.7, 160.6, 162.7, 165.0, 169.9.
Data for 6f: Yield 64%; m.p. K 142 SmA 156 I; 1H NMR (CDCl3, 300 MHz): 0.88 (t,
3H, CH3, J = 6.59 Hz), 1.28 (m, 14H, alkyl chain), 1.47 (m, 2H), 1.8 (m, 2H, OCH2CH2),
3.24 (t, 4H, N(CH2)2, J = 6.59 Hz), 3.88 (t, 4H, O(CH2)2, J = 4.84 Hz), 4.00 (t, 2H, OCH2,
J = 6.44 Hz), 6.64 (s, 1H, isoxazole ring), 6.97 (d, 4H, Ar, J = 8.79 Hz), 7.75 (d, 2H, Ar,
J = 8.7 Hz), 7.77 (d, 2H, Ar, J = 8.7 Hz); 3C NMR (CDCl3, 75.5 MHz): 14.2, 22.7, 26.0,
29.2, 29.3, 29.4, 29.5, 29.6, 31.9, 48.7, 66.7, 68.2, 95.7, 114.9, 115.2, 120.2, 127.4, 127.8,
152.1, 160.7, 162.6, 165.0, 170.1.
Data for 6g: Yield 56%; m.p. K 78 SmA 145 I; 1H NMR (CDCl3, 300 MHz): 0.88 (t,
3H, CH3, J = 6.7 Hz), 1.28 (ws, 14H, alkyl chain), 1.47 (m, 2H, alkyl chain), 1.81 (m, 2H,
OCH2CH2), 4.01 (t, 2H, OCH2, J = 6.6 Hz), 6.67 (s, 1H, isoxazole ring), 6.98 (m, 4H,
Ar), 7.10 (m, 6H, Ar), 7.27 (d, 2H, Ar, J = 8.8 Hz), 7.60 (d, 2H, Ar, J = 8.6 Hz), 7.73
(d, 2H, Ar, J = 8.6 Hz), 7.75 (d, 2H, ar, J = 8.9 Hz); 3C NMR (CDCl3, 75.5 MHz): 14.1,
22.7, 26.0, 29.1, 29.3, 29.4, 29.5, 29.6, 31.9, 68.2, 95.8, 114.9, 119.8, 122.6, 123.5, 124.1,
125.0, 127.4, 127.6, 128.0, 128.2, 129.4, 132.1, 147.2, 160.1, 170.8.
Data for 6h: Yield 81%; m.p. 121◦C; 1H NMR (CDCl3, 300 MHz): 0.89 (t, 3H, CH3, J
= 5.4 Hz), 1.28 (ws, 12H, alkyl chain), 1.48 (m, 2H, alkyl chain), 1.81 (m, 2H, OCH2CH2),
4.02 (t, 2H, OCH2, J = 6.6 Hz), 6.42 (d, 2H, Ar, J = 7.8 Hz), 6.74 (s, 1H, isoxazole ring),
6.90 (m, 4H, Ar), 7.00 (d, 2H, Ar, J = 9.0 Hz), 7.09 (d, 2H, Ar, J = 7.2 Hz), 7.46 (d, 2H,
3
Ar, J = 8.4 Hz), 7.78 (d, 2H, Ar, J = 8.4 Hz), 8.04 (d, 2H, Ar, J = 8.1 Hz); C NMR
(CDCl3, 75.5 MHz): 14.2, 22.7, 26.1, 29.2, 29.3, 29.4, 29.5, 29.6, 31.9, 68.3, 96.0, 115.0,
117.6, 119.9, 122.3, 123.2, 127.0, 127.1, 127.5, 128.3, 129.1, 129.4, 143.2, 143.7, 160.9,
162.2, 170.8.
1
Data for 6i: Yield 42%; m.p. 136◦C; H NMR (CDCl3, 300 MHz): 0.94 (2 t, 6H,
CH3-, J = 7.2 Hz), 1.33 (m, 4H, alkyl chain), 1.47 (m, 4H, alkyl chain), 1.75 (m, 1H,
OCH2CHR2), 3.25 (t, 4H, N(CH2)2, J = 4.8 Hz), 3.88 (m, 6H, OCH2 + O(CH2)2), 6.65

¨
LLC Triarylamines from Buchwald-Hartwig Reaction
[647]/181
(s, 1H, isoxazole ring), 6.97 (d, 2H, Ar, J = 9.0 Hz), 6.98 (d, 2H, Ar, J = 9.0 Hz), 7.75
(d, 2H, Ar, J = 8.7 Hz), 7.77 (d, 2H, Ar, J = 8.7 Hz); 3C NMR (CDCl3, 75.5 MHz): 11.2,
14.1, 23.1, 23.9, 29.1, 30.5, 39.4, 48.6, 66.8, 70.7, 95.7, 114.9, 115.1, 120.2, 120.4, 127.4,
127.8, 152.3, 160.9, 162.6, 170.1.
Data for 6j: Yield 93%; m.p. 87◦C; 1H NMR (CDCl3, 300 MHz): 0.83 (2 t, 6H, CH3),
1.24 (m, 4H, alkyl chain), 1.38 (m, 4H, alkyl chain), 1.66 (m, 1H, OCH2CR2), 3.80 (d, 2H,
OCH2, J = 6.0 Hz), 6.54 (s, 1H, isoxazole ring), 6.88 (d, 2H, Ar, J = 8.7 Hz), 7.00 (m,
8H, Ar), 7.19 (m, 4H, Ar), 7.61 (d, 2H, Ar, J = 8.7 Hz), 7.65 (d, 2H, Ar, J = 8.4 Hz); 3C
NMR (CDCl3, 75.5 MHz): 11.2, 14.2, 23.1, 23.9, 29.1, 30.5, 39.4, 70.7, 95.8, 115.0, 120.1,
122.6, 122.7, 123.6, 125.0, 127.4, 127.7, 129.5, 147.3, 149.4, 161.0, 162.5, 170.3.
Data for 6k: Yield 42%; m.p. 97◦C; 1H NMR (CDCl3, 300 MHz): 0.93 (m, 6H, CH3),
1.33 (m, 4H, alkyl chain), 1.47 (m, 4H, alkyl chain), 1.76 (m, 1H, OCH2CHR2), 3.91 (d,
2H, OCH2, J = 5.7 Hz), 6.42 (d, 2H, Ar, J = 8.1 Hz), 6.74 (s, 1H, isoxazole ring), 6.91
(m, 4H, Ar), 7.01 (d, 2H, Ar, J = 8.8 Hz), 7.09 (d, 2H, Ar, J = 7.3 Hz), 7.46 (d, 2H, Ar, J
= 8.4 Hz), 7.78 (d, 2H, Ar, J = 8.8 Hz), 8.04 (d, 2H, Ar, J = 8.5 Hz); 3C NMR (CDCl3,
75.5 MHz): 11.1, 14.1, 23.0, 23.8, 29.0, 30.4, 39.3, 70.6, 95.9, 114.9, 117.5, 119.8, 122.2,
123.1, 126.9, 127.4, 128.2, 129.0, 129.6, 143.4, 161.0, 162.2, 170.8.
Acknowledgments
The authors gratefully acknowledge the INCT-Cata´lise, Fapergs-Edital PqG 2012 and
Edital 01/12-PPG-Qu´ımica-UFRGS. G. D. Vilela thanks Capes agency for his fellowship
and CNPq agency for financial assistance during his stage at University of Hull under
supervision of Prof. S. M. Kelly. T. H. M. Fernandes is an undergraduate student and
thanks PROBIC-Fapergs for her fellowship.
References
[1] Maruccio, G., & Cingolani, R., Rinaldi, R. (2004). J. Mater. Chem., 14, 542.
[2] Forest, S. R., Thompson, M. E. (2007) Chem. Rev., 107, 923.
[3] Gust, D.; Moore, T. A., & Moore, A. L. (2001) Acc. Chem. Res., 34, 40.
[4] (a)Mu¨llen, K.; & Scherf, U. (2006). Organic Light-Emitting Devices, Wiley-VCH: Weinheim.
(b) Sun, Y., Giebink, N. C., Kanno, H., Ma, B., Thompson, M. E.; & Forrest, S. R. (2006).
Nature, 440, 908. (c) Grimsdale, A. C., Chan, K. L., Martin, R. E., Jokisz, P. G., & Holmes, A.
B. (2009). Chem. Rev., 109, 897.
[5] (a)Hancock, J. M., Gifford, A. P., Zhu, Y., Lou, Y., & Jenekhe, S. A. (2006). Chem. Mater., 18,
4924. (b) Zhu, Y., Kulkarni, A. P., Wu, P.-T., & Jenekhe, S. A. (2008). Chem. Mater., 20, 4200.
(c) Kulkarni, A. P., Zhu, Y., Babel, A., Wu, P. T., & Jenekhe, S. A. (2008). Chem. Mater., 20,
4212. (d) Takizawa, S., Montes, V. A., & Anzenbacher, P., Jr. (2009). Chem. Mater., 21, 2452.
(e) Zeng, L. C., Lee, T. Y. H., Merkel, P. B., & Chen, S. H. (2009). J. Mater. Chem., 19, 8772.
(f) Estrada, L. A., & Neckers, D. C. (2009). J. Org. Chem., 74, 8484. (g) Duan, L., Qiao, J.,
Sun, Y., & Qiu, Y. (2011). Adv. Mater., 23,1137.
[6] (a)Kelly SM, O’Neill M (2000). In Handbook of Advanced Electronic and Photonic Materials
and Devices; Nalwa H. S. (Eds). Liquid Crystals, Display and Laser Materials, Vol. 7, Academic
Press: Los Angeles, CA. (b) Fukuda, A., & Kawamura, I. (2006). Liq. Cryst., 33, 1339.
[7] (a)Zheng, Y., Batsanov, A. S., Jankus, V., Dias, F. B., Bryce, M. R., & Monkman, A. P. (2011).
J. Org. Chem., 76, 8300. (b) Patel, D. G., Feng, F., Ohnishi, Y.-Y., Abboud, K. A., Hirata, S.,
Schanze, K. S., & Reynolds, J. R. (2012). J. Am. Chem. Soc., 134, 2599.
[8] Shirota, Y. (2000). J. Mater. Chem., 10, 1.
[9] Roncali, J., Leriche, P., & Cravino, A. (2007). Adv. Mater., 19, 2045.

182/[648]
G. D. Vilela et al.
[10] (a)Tavares, A., Schneider, P. H., & Merlo, A. A. (2009). Eur. J. Org. Chem., 889. (b) Tavares,
A., Livotto, P. R., Gonc¸alves, P. F. B., & Merlo, A. A. (2009). J. Braz. Chem. Soc., 20, 1742.
(c) Tavares, A., Ritter, O. M. S., Vasconcelos, U. B., Arruda, B. C., Schrader, A., Schneider, P.
H., & Merlo, A. A. (2010). Liq. Cryst., 37, 159. (d) Passo, J. A., Vilela, G. D., Schneider, P. H.,
Ritter, O. M. S., & Merlo, A. A. (2008). Liq. Cryst., 35, 833. (e) Ritter, O. M. S., Giacomelli,
F. C., Passo, J. A., Silveira, N. P., & Merlo A. A. (2006). Polym. Bull., 56, 549.
[11] (a)Hartwig, J. F. (1999). IUPAC, Pure Appl. Chem., 71, 1417. (b) Paul, F., Platt, J., & Hartwig,
J. F. (1994). J. Am. Chem. Soc., 116, 5969. (c) Muci, A. R., & Buchwald, S. L. (2002). Top.
Curr. Chem., 219, 131. (d) Buchwald, S. L. (1996). J. Am. Chem. Soc., 118, 7215.
[12] (a)Shirota, Y. J. (2005). Mater. Chem., 15, 75. (b) Ning, Z., & Tien, H. (2009). Chem. Commun.,
5483. (c) Duan, L., Hou, L., Lee, T.-W., Qiao, J., Zhang, D., Dong, G., Wang, L., & Qiu, Y.
(2010). J. Mater. Chem., 20, 6392.
[13] Kateley, L. J., Martin, W. B., Wiser, D. C., & Brummond, C. A. (2002). J. Chem. Educ., 79,
225.
[14] (a)Barco, A., Benetti, S., Pollini, P. (1977). Synthesis, 12, 837. (b) Fatiadi, A. J. (1976). Synthesis,
65, 133. (c) Kovganko, V. N., & Kovganko, N. N. (2006). Rus. J. Org. Chem., 42, No. 02, 243.
[15] Vilela, G. D., da Rosa, R. R., Schneider, P. H., Bechtold, I. H., Eccher, J., & Merlo, A. A. (2011).
Tetrahedron Lett., 52, 6569.
[16] McOmie, J. F. W. (1973). Protective Groups in Organic Chemistry, Plenum Press: London and
New York.
[17] Meyer, E., Zucco, C., & Gallardo, H. (1998). J. Mater. Chem., 8(6), 1351
[18] Skoog, D. A., et al. (2007). Principles of Instrumental Analysis 6th Edition, Thomson
Brooks/Cole. (b) Harris, D. C., & Bertolucci, M. D. (1989). Symmetry and Spectroscopy, An
Introduction to Vibrational and Eletronic Spertroscopy, Dover Publications, Inc., New York.
[19] Demas, J. N., & Crosby, G. A. (1971). J. Phys. Chem., 75, 991.