Novel Carbazole (Cbz)-Based Carboxylated Functional Monomers: Design, Synthesis, and Characterization

Article abstract of DOI:10.1002/open.201500059

A series of novel functional carbazole (Cbz)-based carboxylated monomers were synthesized and characterized. A Clauson-Kaas procedure, a deprotection step, amide coupling, and hydrolysis were utilized as key chemical reactions towards the multistep synthesis of monomers in good to excellent isolated yields. The design strategy was further extended to complex carbazole-COOH monomers incorporated arylazo groups as photoreactive moieties. In addition, photoreactive hybrid carbazole (Cbz)-pyrrole (Pyr)-based carboxylated monomers, comprising a pyrrole core linking a carbazole and a photoreactive phenylazide or benzophenone moiety through an amide spacer in the molecular structure, were also synthesized. The latter can be utilized for surface modification of polymeric films in their monomeric form or as polymeric microparticles (MPs). Functional monomers: Novel functional carbazole-based carboxylated monomers were accessed using a Clauson-Kaas procedure, a deprotection step, amide coupling, and hydrolysis in a multistep synthesis. The design strategy was extended to complex carbazole-COOH monomers incorporating arylazo and phenylazide or benzophenone as photoreactive moieties, which can be utilized for functionalization/decoration of various polymeric and non-polymeric surfaces, matrices, and non-functional nanomaterials in their monomeric states or as polymeric microparticles (MPs).

Full text of DOI:10.1002/open.201500059

DOI: 10.1002/open.201500059
Novel Carbazole (Cbz)-Based Carboxylated Functional
Monomers: Design, Synthesis, and Characterization
Ejabul Mondal,* Jean-Paul Lellouche,* and Maria Naddaka[a]
A series of novel functional carbazole (Cbz)-based carboxylated
monomers were synthesized and characterized. A Clauson-
Kaas procedure, a deprotection step, amide coupling, and hy-
drolysis were utilized as key chemical reactions towards the
multistep synthesis of monomers in good to excellent isolated
yields. The design strategy was further extended to complex
carbazole-COOH monomers incorporated arylazo groups as
photoreactive moieties. In addition, photoreactive hybrid car-
bazole (Cbz)-pyrrole (Pyr)-based carboxylated monomers, com-
prising a pyrrole core linking a carbazole and a photoreactive
phenylazide or benzophenone moiety through an amide
spacer in the molecular structure, were also synthesized. The
latter can be utilized for surface modification of polymeric
films in their monomeric form or as polymeric microparticles
(MPs).
Introduction
The development of nanomaterials has gained tremendous re-
search interest in recent years due to their potential applica-
tions in the various fields, such as biomedical, imaging, sens-
ing, drug delivery, therapy systems, and so forth.[1] In this
regard, the design and fabrication of polymeric nanoparticles/
microparticles (NPs/MPs) have attracted considerable attention
because of the availability of a wide range of polymerization
methods, of monomeric source materials, and of tunable NP/
MP surface functionalities, which make these particles attrac-
tive for numerous applications.[2] Conducting polymer (CP)-
based nanomaterials such as polyaniline (PANI), polypyrrole
(polypyr), and polythiophene (polyTh) have been already ex-
tensively investigated and well documented.[3] In contrast, pol-
ycarbazole-based particles are less reported.[4–7] This can be at-
tributed to higher oxidation potentials of carbazole-based ma-
terials, making them less prone to oxidation and causing inef-
fective oxidative electrochemical/chemical polymerizations. An-
other reason for the lack of research into this class of material
is that carbazole-based monomers are not easy to synthesize.
Carbazole-based materials have emerged as new and attrac-
tive advanced materials having been used in organic light-
emitting diodes (OLEDs),[8] organic solar cells (OSCs),[9] chemical
sensors,[10] photoconductive materials,[11] and electrochromic
materials.[12] In addition, carbazole derivatives are potential al-
kaloids.[13] Polycarbazole polymers as conducting materials
have several advantageous properties since the carbazole het-
erocycle is chemically stable and can be easily modified at the
C3, C6, and 9 positions that can improve thermal stability and
impart good electrooptical properties on the resulting poly-
mers. Furthermore, the moderate oxidation potential of carba-
zole-containing compounds makes them promising hole trans-
porting materials in optoelectronic applications. Usually, carba-
zole-based materials are designed through p-conjugation den-
drimers, oligomers or polymers. Along this line, carbazole-
based small molecules are also emerging as promising materi-
als for use in OSCs,[14] solution processed/thermal evaporation-
based OLEDs,[15,16] and thermally activated delay fluorescence
(TADF) materials.[17]
Recently, we reported a novel strategy for designing new
carbazole-based materials and the formation of the corre-
sponding well-shaped spherical poly-carbazole (polyCbz)-
based MPs using an oxidative liquid-phase polymerization
method.[18] These earlier studies revealed that various aromatic
functionalities can be introduced into polyCbz-based MPs in-
cluding phenyl bromide and carbazole heterocycle. We special-
ly designed a number of photoreactive molecules by extend-
ing our previous protocol and investigated their reactivity to-
wards highly chemically stable poly(2-chloro-paraxylelene) (Par-
ylene C) films.[19] Our efforts continue towards the design and
development of new Cbz-based monomers/polymeric nano-
materials with tailored physical, chemical and biological prop-
erties.
[a] Dr. E. Mondal, Prof. J.-P. Lellouche, Dr. M. Naddaka
Laboratory of Nanoscale Materials & System, Department of Chemistry
Nanomaterial Research Center, Institute of Nanotechnology & Advanced
Materials, Bar-Ilan University, Ramat-Gan 5290002 (Israel)
E-mail: ejabuliitg@gmail.com
lellouj@biu.ac.il
Herein, we report the design, synthesis, and full characteriza-
tion of a novel class of Cbz-and Cbz-pyrrole (Pyr)-based hybrid
oxidizable monomers following multistep synthetic strategies.
By replacing aromatic components at the w-position of (S)-
methyl 6-amino-2-carbazol-9-yl-hexanoate, we synthesized vari-
ous monomers incorporating arylazo- and photoreactive moi-
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/open.201500059.
ꢀ 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
This is an open access article under the terms of the Creative Commons
Attribution-NonCommercial License, which permits use, distribution and
reproduction in any medium, provided the original work is properly
cited and is not used for commercial purposes.
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eties and systematically characterized them. This versatile mo-
lecular design can lead to several advantageous properties:
1) nanostructures having chirality since those starting materials
are derived from chiral amino acid lysine, which has been ex-
tensively studied as a precursor for self-assembling nanostruc-
tures; 2) functionalization of the active sites at C3 and C6 posi-
tions of the carbazole unit can provide ready access to new
materials with interesting properties. Furthermore, monomers
M7–M12 could reveal potential UV-mediated photo-responsive
properties upon UV irradiation.
Results and Discussion
The chemical structures of monomers M1–M6 are shown in
Figure 1. Schemes 1–4 depict the synthetic routes for mono-
mers M1–6. The preparation of Cbz-based monomers M1–M6
was carried out according to our previously reported proce-
dure.[20,21] Interestingly, monomers M1–M4 were specially de-
signed to investigate the morphology of the resultant MPs in
order to compare with our earlier findings.[18] The key starting
material, (S)-methyl 6-(benzyloxycarbonylamino)-2-(9H-carba-
zol-9-yl)hexanoate (3) was synthesized by treatment of w-NHZ-
lysine methyl ester and 2,5-dimethoxy-tetrahydrofuran (DMT;
2) in mixtures of 1,4-dioxane/acetic acid/12m HCl at reflux for
2–4 hours.[18] Then, key amine 4[18] was obtained by catalytic
hydrogenation of 3 with 10% palladium on carbon in a mixed
solvent of tetrahydrofuran (THF)/isopropanol at room tempera-
ture. Amidation of the acid chloride of 2-carboxythiophene 5
with amine 4 in the presence of triethylamine at room temper-
ature afforded compound 6 in 95% yield. On the other hand,
compounds 8 and 10 were obtained by reacting amine build-
ing block 4 with pyrrole-2-carboxylic acid 7 and 2-(thiophen-3-
yl) acetic acid 9, respectively, using standard amide coupling
reagents N,N’-dicyclohexylcarbodiimide (DCC), 1-hydroxyben-
zotriazole (HOBt) and triethylamine at room temperature in
83% yield.
Figure 1. Chemical structures of Cbz-based oxidizable carboxylated mono-
mers M1–6.
laboratory.[21] Compound 12 was then coupled with amine 4
using a similar amide coupling strategy to afford 13 in 82%
yield. Monomer M4 was obtained in 95% yield in a two-step
procedure as shown in Scheme 3. To generalize the synthetic
variant towards more complex monomers design, we synthe-
Hydrolysis of the methyl ester of compounds 6, 8 and 10
gave the desired carboxylated monomers, M1, M2 and M3
with 85–86% isolated yields (Schemes 1 and 2). Next, we syn-
thesized compound 12 using previously reported work in our
Scheme 1. Synthesis of monomer M1. Reagents and conditions: a) AcOH, dioxane, 75–1108C, 2–3 h, rt, 5–6 h; b) 10% PdÀC, H2, isopropanol/THF (1:1), rt, 4 h;
c) Et3N, CH2Cl2, rt, 2 h, 95%; d) alc. KOH, 608C, 5 h, then H3O+, 08C, 30 min, 85%.
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Scheme 2. Synthesis of monomers M2–M3. Reagents and conditions: a) 1. DCC, HOBt, Et3N, CH2Cl2, 15 min, rt; 2. amine 4, CH2Cl2, rt, 30 min, 83%; b) alc. KOH,
608C, 5 h, then H3O+, 08C, 30 min, 86%.
Scheme 3. Synthesis of monomer M4. Reagents and conditions: a) 1. NaOAc, H2O, AcOH, rt–75 8C, 30 min, 2. 2, 758C, 2 h, 90%; b) 1. DCC, HOBt, Et3N, CH2Cl2,
30 min, rt; 2. amine 4, CH2Cl2, rt, 30 min, 82%; c) 10% PdÀC, H2, isopropanol/THF (1:1), rt, 5 h, 88%; d) alc. KOH, 608C, 90 min, then H3O+, 08C, 30 min, 95%.
sized two C2-symmetric monomers M5 and M6 by incorporat-
ing the peptide bonds in Cbz-COOH monomers based on 1,3
and 1,4 linkers in our earlier report.[18] Compounds containing
the 1,3 (M5) and 1,4 (M6) linkers were synthesized by straight-
forward coupling of intermediate 4 with N-benzoyloxy glycine
15 employing the same amidation procedure as previously de-
scribed to obtain intermediate 16, followed by catalytic hydro-
genation (10% Pd/C), acid chloride amidation with isophthalo-
yl dichloride (1,3) or terephthaloyl dichloride (1,4) and finally
basic hydrolysis (Scheme 4). All of the monomers (M1–M6) and
intermediates were characterized by NMR (1H, 13C) and IR spec-
troscopy, and mass spectrometry. Detailed synthetic proce-
dures and complete characterization data are given in the Ex-
perimental Section and Supporting Information.
and at positions 2,5 (M3) of the thiophene moiety. Further-
more, these monomers can be functionalized post-polymeri-
zation at these positions. Interestingly, among the three mono-
mers, M3 produces MPs with a smooth spherical morphology,
thus we assume that the polymerization not only takes place
at the 3,6 positions of the carbazole moiety but also at the
2,5 positions of the thiophene unit.
Next, we extend our synthetic strategies for the synthesis of
a novel class of UV-photoreactive monomers. We designed
two types of monomers: azo-based Cbz-COOH monomers
(M7–M9) and phenylazide and benzophenone-based hybrid
Cbz-Pyr monomers (M10–M12) containing a pyrrole core linker
between carbazole and phenylazide units or a benzophenone
moiety as shown in Figures 2 and 3. Scheme 5 illustrates the
route for the synthesis of monomers M7 and M8. Our strategy
for designing monomers M7–M9 was to study properties due
to cis–trans isomerization in monomers as well as in their parti-
cle state upon photo-irradiation. Monomers M7 and M8 were
synthesized starting from (E)-4,4’-(diazene-1,2-diyl)dibenzoic
acid, accessed from 4-nitrobenzoic acid by conversion to acid
chloride 22 upon treatment with phosphorus pentachloride at
508C for 45 minutes with an isolated yield of 90%.[22] Interest-
We believe that well-shaped spherical polyCbz-MPs can be
formed from monomers M1–M6 (Figure 1) using an oxidative
liquid-phase polymerization, and studies to this end are ongo-
ing.[18] Monomers M1–M6 have some advantages in terms of
the shape/morphology of the resultant MPs. First, these mono-
mers contain active sites at C3 and C6 positions on the carba-
zole moiety offering potential polymerization. In addition,
monomers M1 and M3 contain reactive sites at position 5 (M1)
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Scheme 4. Synthesis of monomer M5–M6. Reagents and conditions: a) 1. DCC, HOBt, N-methylmorpholine (NMM), CH2Cl2, rt, 30 min; 2. amine 4, CH2Cl2, rt, 1 h,
82%; b) 10% Pd/C, H2, isopropanol/THF (1:1), rt, 5 h, 97%; c) isophthaloyl dichloride (1,3; to give M5) or terephthaloyl dichloride (1,4; to give M6) Et3N,
CH2Cl2, rt, 2 h, 68–70%; d) alc. KOH, 608C, 5 h, then H3O+, 08C, 30 min, 88–95%.
On the other hand, the synthetic route for monomer M9
was started from 4-aminobenzoic acid. Compounds 25d and
25e were synthesized following a literature procedure.[23,24]
The complete synthetic route for M9 is provided in Scheme 6.
Monomers M7–M9 were obtained in 90–93% yield after basic
hydrolysis, as used for previous monomers syntheses, of the
methyl ester precursors (23, 24, and 25).
To study the liquid-phase chemical polymerization of hybrid
Cbz-Pyr-based carboxylated monomers, we designed and syn-
thesized new photoreactive monomers M10–M12 (Figure 3).
Monomers M10–M12 are new synthetic variants of our previ-
ously reported Cbz-based photoreactive monomers.[19] We as-
sumed that the addition of a pyrrole core connecting the car-
bazole and photoreactive moieties would improve the shape
and size of MPs for better reactivity and improved conductivity
on the polymeric surfaces as compared with our previously re-
ported materials during UV irradiation. First, we synthesized
mono-tert-butyloxycarbonyl (BOC)-protected diamines 28 and
29, which were then coupling with the appropriate acid (30
Figure 2. New oxidizable carbazole azo-based carboxylated monomers M7–
9.
and 33) employing our standard amidation protocol (for de-
tails, see the Experimental Section), and finally w-NH2 free
building blocks 35–37 using trifluoroacetic acid (TFA) at room
temperature with 68–97% isolated yields. Amidation coupling
reaction employing 1-ethyl-3-(3-dimethylaminopropyl)carbodii-
mide (EDC)/HOBt was used to obtain compounds 38, 39 and
40 in 65–70 isolated yields (for experimental procedures, see
the Supporting Information). The Cbz-Pyr hybrids 38, 39 and
40 were hydrolyzed employing a previous protocol to obtain
the final Cbz-Pyr hybrid photoreactive monomers M10–M12
(Schemes 7 and 8).
ingly, (E)-4,4’-(diazene-1,2-diyl)dibenzoic acid is poorly soluble
in almost polar solvents but acid chloride derivative 22 is
highly soluble in chloroform. Finally, acid chloride 22 was treat-
ed with amine 4 in the presence of triethylamine to afford
methyl ester derivatives 23 and 24, precursors of monomers
M7 and M8, respectively, depending upon the amount of
amine 4 used at room temperature or under ice-cold condi-
tions.
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monomers can give interesting
opportunities for the functionali-
zation/decoration of various
polymeric and non-polymeric
surfaces, matrices, and nonfunc-
tional nanomaterials in their
monomeric states or as polymer-
ic MPs. The oxidative fabrication
of corresponding MPs arising
from these monomers is in prog-
ress.
Experimental Section
General remarks: Reactions were
performed under nitrogen and
were magnetically stirred. Solvents
were distilled from appropriate
dying agent prior to use. All re-
agents were obtained commercial-
ly from Sigma–Aldrich and used as
received without any further purifi-
cation unless otherwise noted.
Chromatographic purification of
products were accomplished using
Figure 3. New oxidizable hybrid photoreactive carbazole-pyrrole-based carboxylate monomers M10–12.
Conclusions
flash chromatography on Merck silica gel 60 (0.040–0.063) 230–
400 mesh ASTM. Room temperature (RT) refers to 20–228C. All re-
actions were monitored by TLC with Macherey–Nagel pre-coated
aluminum foil sheets (0.20 mm with fluorescent indicator UV254).
Compounds were visualized with UV light at 254 nm and 365 nm.
Melting points were measured on a Fargo MP-1D and are uncor-
rected. Fourier transformed infrared (FTIR) spectra were recorded
on a Bruker TENSOR 27 spectrometer at a resolution better than
1.0 cmÀ1 for the indicated wavelength spectral window (400–
4000 cmÀ1).
A series of novel Cbz-based monomers M1–M12 were de-
signed, synthesized and characterized. Monomers M1–M4 con-
tain additional reactive sites for potential oxidative polymeri-
zation, which can produce good morphology of the resultant
MPs after polymerization. Monomers M5–M12 were synthe-
sized following multistep synthetic routes in good to high iso-
lated yields. Due to their dual conducting carbazole or carba-
zole/thiophene/pyrrole and COOH functionalities, these novel
Scheme 5. Synthesis of monomer M7–M8. Reagents and conditions: a) 1. amine 4 (1.0 mmol), acid chloride (2.0 mmol), Et3N, CH2Cl2, 08C, 2 h, 61%; 2) amine 4
(2.0 mmol), acid chloride (1.0 mmol), Et3N, CH2Cl2, 08C!rt, 30 min, 85%; c) alc. KOH, CH3OH/toluene (2:1), 60–708C, 2–3 h, then H3O+, 08C, 30 min, 90–93%.
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Scheme 6. Synthesis of monomer M9. Reagents and conditions: a) EtOH, H2SO4, reflux, 4 h; b) 1. NANO2, 1m aq HCl, 08C, 30 min; 2. 25c, NaHCO3, 08C, 1 h,
81%; c) alc. KOH, EtOH, reflux, 4 h, then H3O+, 93%; d) pyridine, Ac2O, rt, 2 h, 92%; e) 1. PCl5, CHCl3, rt, 2 h; 2. amine 4, Et3N, CH2Cl2, rt, 12 h, 65%, two steps;
f) K2CO3, CH3OH, rt, 30 min, 99%; g) alc. KOH, CH3OH/toluene (2:1), 608C, 4 h, then H3O+, 08C, 30 min, 93%.
1H and 13C NMR spectra were re-
corded on a Bruker DRX spectro-
meter (300 MHz and 75.5 MHz for
1H and 13C, respectively). Nuclear
displacements are referenced inter-
nally (TMS or solvent references).
Data for 1H NMR are reported as
follows: chemical shift (d in ppm),
multiplicity (s, singlet; br, broad
signal; d, doublet; t, triplet; q,
quartet; m, multiplet), coupling
constant (Hz), and integration.
Data for 13C NMR are reported in
terms of chemical shift (d in ppm).
Mass spectra (MS) analyses were
performed on a Waters VG-Fison
AutoSpec Premier high resolution
spectrometer. MALDI-TOF analyses
were performed on a Bruker Auto-
flex mass spectrometer.
Abbreviations: carbazole (Cbz);
N,N’-dicyclohexylcarbodiimide
(DCC); 1-ethyl-3-(3-dimethylamino-
propyl)carbodiimide (EDC); N-hy-
droxybenzotriazole (HOBt); N-
methylmorpholine (NMM); pyrrole
(Pyr).
General procedure 1. Amide cou-
Scheme 7. Synthesis of amine 35, 36 and 37. Reagents and conditions: a) BOC2O, CHCl3, 08C!rt, 12 h; b) 1. PCl5,
pling of acid chloride and amine
in the presence of base: To
a stirred solution of amine, (S)-
CHCl3, 08C, 45 min; 2. amine 28, Et3N, CHCl3, rt, 30 min, 94%; c) 1. EDC, Et3N, CH2Cl2, 15 min, rt; 2. amine 29, Et3N,
CH2Cl2, rt, 6 h, 85%; d) 1. PCl5, CHCl3, 08C, 45 min; 2. amine 28, Et3N, CHCl3, rt, 30 min, 78%, two steps; e) TFA,
CHCl3, rt, 12–20 h, 95–97%.
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Scheme 8. Synthesis of monomer M10–M12. Reagents and conditions: a) 1. EDC, HOBt, Et3N, CH2Cl2, 30 min, rt, 5–12 h; 2. amine 37 (for 38/M10) or 35 (for 39/
M11) or 36 (for 40/M12), CH2Cl2, rt, 6–12 h, 65–70%; b) 1. alc. KOH, 50–608C, 3–7 h; 2. H3O+, 08C, 30 min, 72–91%.
methyl 6-amino-2-carbazol-9-yl-hexanoate
4
(1.0 mmol) in dry
General procedure 3. Amide coupling of acid and amine in the
presence of EDC, HOBt and N-methyl morpholine/Et3N: To
a stirred solution of acid (1.0 mmol) in CH2Cl2 (10 mL) was added
EDC (1.0 mmol), HOBt (1.0 mmol) and Et3N (1.5–2.0 mmol, excess)
successively at RT under nitrogen atmosphere to give a clear solu-
tion. Amine (1.0 mmol) in CH2Cl2 (5 mL) was added to this solution,
which turned from clear to turbid. The reaction was kept stirring
overnight at RT. The reaction mixture was diluted with CH2Cl2
(50 mL) and washed with brine (2”20 mL). After drying and evapo-
ration, the crude residue was purified by flash column chromatog-
raphy (CH2Cl2/CH3OH, 9.9:0.1!9.8:0.2) to afford a solid.
CH2Cl2 (10 mL) was added dry Et3N (0.5 mL) at 08C under nitrogen
atmosphere. Acid chloride (1.0 mmol) in dry CH2Cl2 was then
added dropwise to the reaction mixture. The reaction mixture was
brought to RT and stirred for 2–3 h. Evaporation of the volatiles
under reduced pressure gave a thick oily residue, which was puri-
fied by flash chromatography on silica gel (230–400 mesh) using
CH2Cl2/MeOH (98:2) as eluent to obtain a solid.
General procedure 2. Amide coupling of acid and amine in the
presence of DCC, HOBt and N-methyl morpholine/Et3N: A mix-
ture of acid (1.0 mmol), HOBt (1.10 mmol), DCC (1.10 mmol) and N-
methyl morpholine/Et3N (2.4 mmol) in dry CH2Cl2 (10 mL) was
stirred at RT under nitrogen atmosphere for 15–30 min. Then a so-
lution of amine 4 (1.0 mmol) in dry CH2Cl2 (5 mL) was added drop-
wise into the reaction mixture. A thick gelatinous precipitate was
observed once the addition was completed. The reaction mixture
was allowed to stir under same condition for 30 min. After comple-
tion of the reaction (TLC), the precipitated solid was filtered, and
the filtrate was washed successively with ice-cold dil. HCl (5.0 mL),
saturated aq NaHCO3 (5 mL), and brine (2”10 mL). The organic
phase was dried over anhydrous Na2SO4, filtered and concentrated
under reduced pressure provided gummy residue, which was puri-
fied by flash column chromatography on silica gel (230–400 mesh)
using CH2Cl2/MeOH (99:1!98:2) to furnish a solid.
General procedure 4. Hydrolysis of ester to the corresponding
acid: To a solution of methyl ester (1.0 mmol) in CH3OH (10 mL)/
toluene (5 mL) was added methanolic KOH (2–3 mmol) at RT. The
reaction mixture was heated at 60–808C for 5 h. After cooling to
08C, 1m aq HCl was added dropwise for acidification to pH 3–4,
and the mixture was extracted with EtOAc (2”30 mL). The com-
bined organic extracts were washed with water (2”20 mL), dried
over anhydrous Na2SO4, and filtered. Removal of solvent under re-
duced pressure provided.
(S)-2-(9H-Carbazol-9-yl)-6-(thiophene-2-carboxamido)hexanoic
acid (M1): To a solution of (S)-2-carbazol-9-yl-6-[(thiophene-2-car-
bonyl)-amino]-hexanoic acid methyl ester (5) (0.370 g, 0.880 mmol)
in CH3OH (10 mL)/toluene (5 mL) was added methanolic KOH
(0.099 g, 1.77 mmol) at RT. The reaction mixture was heated at
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608C for 5 h. After cooling to 08C, 1m aq HCl was added dropwise
for acidification to pH 3–4, and the mixture was extracted with
EtOAc (2”30 mL). The combined organic extracts were washed
with water (2”20 mL), dried over anhydrous Na2SO4, and filtered.
Removal of solvent under reduced pressure provided M1 as
a white solid (0.305 g, 85%).
Keywords: arylazo monomers
syntheses · photoreactive monomers · pyrroles · thiophenes
·
carbazoles
·
multistep
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(S)-2-(9H-Carbazol-9-yl)-6-(2-(thiophen-3-yl)acetamido)hexanoic
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(S)-6-(4-((E)-(4-((S)-5-(9H-Carbazol-9-yl)-6-methoxy-6-oxohexylcar-
bamoyl)phenyl)diazenyl)benzamido)-2-(9H-carbazol-9-yl)hexano-
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(S,E)-2-(9H-Carbazol-9-yl)-6-(4-(4-hydroxyphenyl)diazenyl)benza-
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(S)-6-{(S)-4-(2-(4-Azidobenzamido)ethylamino)-4-oxo-3-(1H-
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Supporting Information: Complete details of all synthetic proce-
dures together with characterization data (IR, 1H, 13C NMR, and
HRMS/MS) for all intermediate and final compounds is available as
Supporting
Information
under
http://dx.doi.org/10.1002/
open.201500059.
Acknowledgements
Funding by the 6th Famework European STREP project MULTIPOL
(contract no FP6-2004-TI-STREP 033201) is gratefully acknowl-
edged.
Received: March 2, 2015
Published online on April 30, 2015
ChemistryOpen 2015, 4, 489 – 496
www.chemistryopen.org
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ꢀ 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim