Synthesis of alkylcarbazole aminoderivatives

Article abstract of DOI:10.1002/hc.20742

New alkylcarbazole aminoderivatives were prepared with various alkyl chain lengths. Syntheses were evaluated and procedures simplified. Producing alkylcarbazole aminoderivatives is a two-step process, wherea-in the first step-alkycarbazol is obtained in the alkyl chain substitution reaction and the appropriate aminoderivative of alkylcarbazole is synthesized in direct amination of aromatic compounds as the second step. The products were verified with nuclear magnetic resonance analysis, and general thermal properties were determined by thermogravimetric analysis. Alkylcarbazole aminoderivatives are amphiphilic molecules, therefore expanding the list of known surfactants, compatibilizing agents, and other surface modifiers.

Full text of DOI:10.1002/hc.20742

Heteroatom Chemistry
Volume 23, Number 1, 2012
Synthesis of Alkylcarbazole Aminoderivatives
Krzysztof Garman, Ewa Olewnik, and Wojciech Czerwinski
Chair of Physical Chemistry and Physicochemistry of Polymers, Faculty of Chemistry, Nicolaus
Copernicus University, 87-100 Torun, Poland
Received 7 November 2008; revised 2 June 2011
phiphilic, so they broaden the spectrum of surface
ABSTRACT: New alkylcarbazole aminoderivatives
and structure modifying molecules.
were prepared with various alkyl chain lengths. Syn-
Alkylcarbazole aminoderivatives are noncom-
theses were evaluated and procedures simplified. Pro-
mercial compounds, so it was necessary to con-
ducing alkylcarbazole aminoderivatives is a two-step
duct their synthesis. In alkylcarbazole aminoderiva-
process, where—in the first step—alkycarbazol is ob-
tives, the molecules’ hydrophilic parts are the amino
tained in the alkyl chain substitution reaction and the
groups (aromatic rings of carbazole are substituted
appropriate aminoderivative of alkylcarbazole is syn-
with) and organophilic parts are the alkyl chains (ni-
thesized in direct amination of aromatic compounds
trogen atoms of carbazole molecules are substituted
as the second step. The products were verified with
with).
nuclear magnetic resonance analysis, and general ther-
In a two-step process, we have synthesized
mal properties were determined by thermogravimet-
from carbazole 9-buthyl-9H-carbazole (denoted
ric analysis. Alkylcarbazole aminoderivatives are am-
as NBUK), 9-penthyl-9H-carbazole (denoted as
phiphilic molecules, therefore expanding the list of
NPEK), 9-hepthyl-9H-carbazole (denoted as NHEK)
known surfactants, compatibilizing agents, and other
and 9-butyl-9H-carbazole-3,6-diamine (denoted as
ꢀ
C
surface modifiers.
2011 Wiley Periodicals, Inc. Het-
DANBUK), 9-pentyl-9H-carbazole-3,6-diamine (de-
noted as DANPEK), 9-heptyl-9H-carbazole-3,6-
diamine (denoted as DANHEK), respectively.
eroatom Chem 23:1–4, 2012; View this article online at
wileyonlinelibrary.com. DOI 10.1002/hc.20742
According to previous papers from 1960s
concerning direct amination of aromatic com-
pounds, this method is appropriate for rather small
molecules like benzene, toluene, xylene, and mesity-
lene [1,2]. Since then this method of amination has
evolved and currently has different forms as well as
different applications [3–7]. In this paper, the direct
amination method relies on electrophilic substitu-
INTRODUCTION
Nowadays surface and structure studies have be-
come a necessity; for example, aiming to produce
polymer nanocomposites, it is usually necessary to
modify clay and other nanofillers with compatibiliz-
ing agents. There is a constant need for synthesis
and application of new surfactant molecules. These
compatibilizing agents need to be amphiphilic—
have hydrophilic and organophilic sections in their
structures. Alkylcarbazole aminoderivatives are am-
+
+
=
=
≡
tion of the onium ion (NH N NH or N N NH2),
which is a protonated form of hydrazoic acid. Re-
action is conducted in concentrated sulphuric acid,
which plays both the part of a solvent and a catalyst
as Broensted acid. The mentioned method allows for
the amination of the compound in one step, contrary
to common two-step methods (with nitration and re-
duction stages) [8,9]. Direct amination as one of the
electrophilic substitution reactions is determined
by the direct substitution effect. If we assume no
Correspondence to: Krzysztof Garman; e-mail: kgarman@
doktorant.umk.pl.
c
ꢀ
2011 Wiley Periodicals, Inc.
1

2
Garman, Olewnik, and Czerwinski
FIGURE 1 General synthesis of alkylcarbazole aminoderivatives.
C4a C4b bond, which leads to diphenylamine struc-
ture, the onium ion will be substituted in preferred
para-position, that is in 3 and 6 positions of
carbazole. However, this leads also to ortho-
substitution, carried in carbazole in 1 and 8 po-
sitions (positions 4a and 4b are blocked with
C C bond). If we assume no N9 C9a bond, which
suggests biphenyl-2-amine structure, the substi-
tution of the onium ion will also take place
in a preferred para- position, that is, 2 and 7
positions in carbazole. Less likely is the ortho-
substitution in that structure, which goes in 4
and 5 carbazole positions (positions 8a and 9a
are blocked with C N bond). In experiments,
the onium ion is substituted in 3 and 6 positions
of carbazole, thanks to preferable para-substitution
to N,N-dibenzeneamine-like molecules [10].
carried out for 24 h in ambient temperature, stirring
rapidly, protected from outer air and moisture with a
drying agent. The reaction was quenched by adding
methanol, until mixture foaming ended and an ecru
precipitate appeared. The solvent was removed un-
der reduced pressure at a temperature of 170◦C. A vi-
olet product was dissolved in 100 mL of chloroform,
poured to the separatory funnel and extracted with
200 mL of 2M hydrochloric acid aqueous solution,
using portions of 200 mL of 2M hydrochloric acid
aqueous solution and 100 mL of distilled water. A
chloroform fraction was collected, dried over anhy-
drous magnesium sulfate for 24 h, and recrystallized
in ambient atmosphere. The violet-brown residue in
the crystallizer was melted and rapidly cooled below
0◦C to recrystallization and gaining beige color.
EXPERIMENTAL
Synthesis of NPEK
Syntheses of alkylcarbazole aminoderivatives were
prepared on the grounds of known reactions
but with our own modifications and in unique
compilation [1,2,11] (Fig. 1, where R C4H9 for
NBUK and DANBUK, R C5H11 for NPEK and
21.18 g of carbazole, 32 mL of 1-bromopentane,
140 mL of N,N-dimethylformamide, and 4.8 g of
sodium hydride in methylcyclohexane suspension
were used to synthesize 9-penthyl-9H-carbazole, in a
reactor equipped with an air cooler, a thermometer,
and a magnetic stirrer. All procedures were main-
tained so that the reaction proceeded in a known
way and all characteristic effects were as the previ-
ously observed ones.
=
=
=
DANPEK, R C7H15 for NHEK and DANHEK). The
main novelty in the procedures was the applica-
tion of N,N-dimethylformamide instead of N,N-
dimethylformamide-tetrahydrofurane (1/3, v/v) so-
lution, as aprotic and anhydrous solvent in reaction
conditions. This also allows saving the sodium hy-
dride that enters a reaction with water. However,
THF is eliminated from the THF-DMF solution; no
negative aspects of the reaction (its mechanism,
yield, etc.) were noted.
Synthesis of NHEK
The next compound was synthesized strictly accord-
ing to the prepared procedure. For this synthesis
4.98 g of carbazole, 6.5 mL of 1-bromoheptane,
35 mL of N,N-dimethylformamide, and 1.2 g of
sodium hydride in methylcyclohexane suspension
were used. The whole process was conducted ac-
cording to the known procedure; observed reaction
effects and features of compounds were as expected.
Synthesis of NBUK
5.33 g of carbazole, 7 mL of 1-bromobutane, 35 mL
of N,N-dimethylformamide, and 1.8 g of sodium hy-
dride in methylcyclohexane suspension were added
to a reactor equipped with an air cooler, a ther-
mometer, and a magnetic stirrer. The reaction was
Heteroatom Chemistry DOI 10.1002/hc

Synthesis of Alkylcarbazole Aminoderivatives
3
7.50 (m, 2,3,4,5,6,7-CHAR), 8.10–8.13 (d, J = 9, 1,8-
CHAR).
Synthesis of DANBUK
8.01 g of sodium azide was dissolved in 100 mL of
concentrated sulfuric acid in a reactor equipped with
a cooler, a dropping funnel, a thermometer, and a
magnetic stirrer. After heating to 60◦C, the concen-
trated solution of NBUK (13.37 g) in chloroform
was added drop by drop into the mixture, stirring
rapidly. Another 8.01 g of sodium azide was added
and the reaction was carried out for 1 h in 65◦C
temperature, stirring rapidly. The dark blue mixture
changed color to dark green after it was poured onto
500 mL of crumbled ice. After stirring intensively, a
dark green precipitate appeared, which was filtered,
washed with water, dried for 24 h at the temperature
of 80◦C, and recrystallized from methanol.
NBUK13C NMR (CDCl3, δ = 76.57–77.42 ppm)
13.86 (CH3), 20.55 (γ-CH2), 31.10 (β-CH2), 42.79
(α-CH2), 106.62 (1,8-CAR), 118.66 (3,6-CAR), 120.31
(4,5-CAR), 122.79 (4a,4b-CAR), 125.52 (2,5-CAR),
140.42 (8a,9a-CAR).
NPEK 1H NMR (CDCl3, δ = 7.26 ppm) 0.85–0.89
(t, J = 4, CH3), 1.37–1.38 (m, γ, δ-CH2), 1.85–1.92 (q,
=
J = 4.6, β-CH2), 4.27–4.34 (t, J 7, α-CH2), 7.19–7.52
=
(m, 2,3,4,5,6,7-CHAR), 8.09–8.14 (d, J 10, 1,8-CHAR).
NPEK 13C NMR (CDCl3, δ = 76.30–77.56 ppm)
13.86 (CH3), 22.39 (δ-CH2), 28.57 (γ-CH2), 29.32 (β-
CH2), 42.91 (α-CH2), 108.54 (1,8-CAR), 118.58 (3,6-
CAR), 120.22 (4,5-CAR), 122.71 (4a,4b-CAR), 125.45
(2,5-CAR), 140.33 (8a,9a-CAR).
NHEK 1H NMR (CDCl3, δ = 7.26 ppm) 0.85–0.91
(t, J = 6, CH3), 1.27–1.39 (m, γ, δ, ε, ζ-CH2), 1.82–
1.98 (m, β-CH2), 4.27–4.35 (t, J = 8, α-CH2), 7.20–
7.52 (m, 2,3,4,5,6,7-CHAR), 8.10–8.15 (d, J = 10, 1,8-
CHAR).
Synthesis of DANPEK
Analogically to DANBUK synthesis DANPEK was
synthesized, using 10.0 g of NPEK, 2 × 8.00 g of
sodium azide and 100 mL of concentrated sulfuric
acid. The reaction occurred without any complica-
tions, analogically to DANBUK synthesis, and a dark
green product was obtained. DANPEK became insol-
uble in simple protic solvents, for example, water,
methanol, and ethanol.
NHEK13C NMR (CDCl3, δ = 76.37–77.64 ppm)
14.02 (CH3), 22.56 (ζ-CH2), 27.25 (ε-CH2), 28.95–
29.06 (γ, δ-CH2), 31.70 (β-CH2), 43.02 (α-CH2),
108.61 (1,8-CAR), 118.64 (3,6-CAR), 120.29 (4,5-CAR),
122.79 (4a,4b-CAR), 125.51 (2,5-CAR), 140.40 (8a,9a-
CAR).
DANBUK 1H NMR (DMSO-d6, δ = 2.49 ppm)
0.89 (CH3), 1.32 (γ-CH2), 1.81 (β-CH2), 4.43 (NH2),
4.68 (α-CH2), 7.56–7.95 (m, 2,4,5,7-CHAR), 8.55–8.97
(m, 1,8-CHAR).
Synthesis of DANHEK
Aiming to synthesize DANHEK 5.0 g of NHEK,
2 × 4.00 g of sodium azide, and 50 mL of concen-
trated sulfuric acid were used and procedures used
in previous synthesis were applied as well. The reac-
tion proceeded properly, as in the previous one, but
the product that resulted was a dark green blob, in-
soluble in water, methanol, and other simple protic
solvents.
DANBUK 13C NMR (DMSO-d6, δ = 37.93–41.09
ppm) 13.77 (CH3), 19.86 (γ-CH2), 30.90 (β-CH2),
42.27 (α-CH2), 109.12 (4,5-CAR), 118.12 (1,8-CAR),
121.28 (2,7-CAR), 123.98 (4a,4b-CAR), 131.90 (8a,9a-
CAR), 139.48 (3,6-CAR).
DANPEK 1H NMR (DMSO-d6, δ = 2.49 ppm)
0.82 (CH3), 1.29 (γ, δ-CH2), 1.82 (β-CH2), 3.91 (NH2),
4.44 (α-CH2), 7.56–8.15 (m, 2,4,5,7-CHAR), 8.56–8.80
(m, 1,8-CHAR).
RESULTS
The obtained products were protected against mois-
ture; to ensure that the reactions were carried
out correctly, the 1H nuclear magnetic resonance
(1H NMR) analysis and 13C nuclear magnetic reso-
nance (13C NMR) analysis (on spectrometers Bruker
AVANCE 300 and Varian Gemini 200) were done.
Thermal properties of these compounds were de-
termined according to thermogravimetric analysis
(TGA) done with derivatograph OD102 by MOM
Budapest.
DANPEK 13C NMR (DMSO-d6, δ = 37.93–41.09
ppm) 13.89 (CH3), 21.95 (δ-CH2), 28.56 (β, γ-CH2),
42.56 (α-CH2), 109.00 (4,5-CAR), 118.13 (1,8-CAR),
120.73 (2,7-CAR), 124.02 (4a,4b-CAR), 132.14 (8a,9a-
CAR), 139.46 (3,6-CAR).
DANHEK 1H NMR (DMSO-d6, δ = 2.49 ppm)
0.82 (CH3), 1.24 (γ, δ, ε, ζ-CH2), 1.79 (β-CH2), 4.22
(NH2), 4.36 (α-CH2), 7.10–7.93 (m, 2,4,5,7-CHAR),
8.29–8.79 (m, 1,8-CHAR).
DANHEK13C NMR (DMSO-d6, δ = 38.69–40.36
ppm) 13.93 (CH3), 18.59 (ζ-CH2), 22.04 (ε-CH2),
26.51 (δ-CH2), 28.52 (γ-CH2), 31.20 (β-CH2), 42.51
(α-CH2), 109.15 (4,5-CAR), 118.02 (1,8-CAR), 121.02
(2,7-CAR), 124.08 (4a,4b-CAR), 132.16 (8a,9a-CAR),
139.5 (3,6-CAR).
The Results of NMR Analysis
1
NBUK H NMR (CDCl3, δ = 7.26 ppm) 0.94–0.98 (t,
J = 6, CH3), 1.41–1.43 (q, J = 1.9, γ-CH2), 1.85–1.92
(q, J = 6.9, β-CH2), 4.30–4.34 (t, J = 6, α-CH2), 7.22–
Heteroatom Chemistry DOI 10.1002/hc

4
Garman, Olewnik, and Czerwinski
compounds’ state from solids with short chains to
liquids with longer chains.
The Results of TGA Analysis
The temperatures of decomposition of synthesized
new alkylcarbazole aminoderivatives are 209◦C,
207◦C, and 197◦C, respectively, for DANBUK,
DANPEK, and DANHEK.
Different alkylcarbazole aminoderivatives’ chain
length corresponds with changes in compound sol-
ubility. The longer the chain in a molecule, the
more a nonpolar solvent needs to be involved to
dissolve the molecule; for example, DANBUK is a
water/methanol soluble substance and DANHEK is
in DMSO.
DISCUSSION AND CONCLUSIONS
The procedures presented in this paper are used
to synthesize alkylcarbazole aminoderivatives ho-
mologous compounds, for example, 9-butyl-9H-
carbazole-3,6-diamine.
Elimination of THF from the THF-DMF solution
allows the reaction of alkyl-substitution in aprotic
and anhydrous solvent. This also allows saving the
sodium hydride that enters the reaction with water.
However, THF is eliminated from the THF-DMF so-
lution; no negative aspects of the reaction (its mech-
anism, yield, etc.) were observed.
Reactions of direct amination with hydrazoic
acid become simpler and faster than common meth-
ods, like two-step amination with nitration and re-
duction.
The alkylcarbazole aminoderivatives are am-
phiphilic compounds and may be applied, for ex-
ample, as surfactants, surface modifiers for polymer
nanocomposites fillers, monomers for new conduct-
ing polymers, or have many other applications.
Elongation of alkyl chain in alkylcarbazole
aminoderivatives leads to diversification of these
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Heteroatom Chemistry DOI 10.1002/hc