Synthesis and crystal structure analysis of 9-phenyl-β-carboline

Article abstract of DOI:10.1080/15421406.2014.882699

An efficient method is described for the synthesis of 9-phenyl-9H-pyrido[3,4-b]indole and 9-(4-chlorophenyl)-9H-pyrido[3,4-b]indole by employing a catalytic amount of CuI (10 mole%) without any ligand. The single crystal of 9-phenyl-9H-pyrido[3,4-b]indole

Full text of DOI:10.1080/15421406.2014.882699

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Synthesis and Crystal Structure Analysis
of 9-Phenyl-β-carboline
a
a
a
Ramu Meesala , Mohd Nizam Mordi , Sharif Mahsufi Mansor & Mohd
b
Mustaqim Rosli
a
Centre For Drug Research, Universiti Sains Malaysia, Minden,
Penang, Malaysia
b
X-ray Crystallography Unit, School of Physics, Universiti Sains
Malaysia, Penang, Malaysia
Published online: 15 Dec 2014.
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To cite this article: Ramu Meesala, Mohd Nizam Mordi, Sharif Mahsufi Mansor & Mohd Mustaqim Rosli
2014) Synthesis and Crystal Structure Analysis of 9-Phenyl-β-carboline, Molecular Crystals and Liquid
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Crystals, 605:1, 125-134, DOI: 10.1080/15421406.2014.882699
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Mol. Cryst. and Liq. Cryst., Vol. 605: pp. 125–134, 2014
Copyright © Taylor & Francis Group, LLC
ISSN: 1542-1406 print/1563-5287 online
DOI: 10.1080/15421406.2014.882699
Synthesis and Crystal Structure Analysis
of 9-Phenyl-β-carboline
1
,∗
1
RAMU MEESALA, MOHD NIZAM MORDI, SHARIF
1
2
MAHSUFI MANSOR, AND MOHD MUSTAQIM ROSLI
1Centre For Drug Research, Universiti Sains Malaysia, Minden, Penang,
Malaysia
2
X-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia,
Penang, Malaysia
An efficient method is described for the synthesis of 9-phenyl-9H-pyrido[3,4-b]indole
and 9-(4-chlorophenyl)-9H-pyrido[3,4-b]indole by employing a catalytic amount of
CuI (10 mole%) without any ligand. The single crystal of 9-phenyl-9H-pyrido[3,4-
b]indole was produced by crystallization from hexane and ethyl acetate mixture that was
investigated by single X-ray diffraction (XRD). The compound crystallizes in monoclinic
P21/c space group with unit cell dimensions a = 11.3132(5) Å, b = 12.0061(5) Å,
◦
◦
◦
1
13
c = 9.2498(4) Å, α = 90 , β = 103.187(3) , γ = 90 . H and C NMR, IR, and mass
spectroscopic methods of the compounds are also discussed.
Keywords β-Carboline; copper iodide; single crystal; tetrahydro-β-carboline-3-
carboxylic acid; X-ray diffraction
Introduction
β-Carbolines are one of the most interesting structural frameworks, which are extensively
investigated because of their large existence in biological and medicinal applications [1,
2]. The compounds containing β-carboline moiety exhibit a wide range of biological
activities, such as antimalarial [3–5], antitumor [6–8], and anti-HIV [9–11]. The β-carboline
moiety also exhibits potent binding affinities toward benzodiazepine receptors in the central
nervous system, thereby acting as diazepam antagonists [12–14]. As a part of our ongoing
studies on novel β-carboline derivatives of potential pharmacological interest, we report in
this communication the synthesis of 9-phenyl-β-carboline derivatives from tetrahydro-β-
carboline-3-carboxylic acids by sequential decarboxylation, aromatization, and C N bond
coupling.
Received September 12, 2013; in final form November 15, 2013.
∗
Address correspondence to Ramu Meesala, Centre For Drug Research, Universiti Sains
Malaysia, Minden, 11800 Penang, Malaysia. Tel.: +604-6533888 Ext. 2145; Fax: +604-6568669;
E-mail: cu ram@yahoo.co.in
Color versions of one or more of the figures in the article can be found online at
www.tandfonline.com/gmcl.
125

126
R. Meesala et al.
Experimental
General Procedures and Materials
All reactions were carried out under nitrogen atmosphere. Melting points were determined
on a Stuart SMP 20 digital melting point apparatus and are uncorrected. All compounds
were routinely checked by thin layer chromatography (TLC), gas chromatography-mass
1
spectrometry (GC-MS), and H NMR. TLC was performed on aluminium-backed silica
gel plates (Merck DC, Alufolien Kieselgel 60F254) with spots visualized by UV light. All
chemicals and reagents were purchased from Aldrich Co. Ltd. (Sigma-Aldrich (M) Sdn
Bhd, Selangor Darul Ehsan, Malaysia).
1H and 13C NMR Spectroscopy
1H and 13C NMR spectra were determined in CDCl3 and DMSO-d6 solution using Bruker
AV 500 MHz spectrometer. Proton chemical shifts (δ) are relative to tetramethylsilane
(
δ = 0.0) as internal standard and expressed in parts per million. Spin multiplicities are
expressed as s (singlet), d (doublet), t (triplet), and m (multiplet). Coupling constants (J)
are given in hertz.
Infrared Spectroscopy
Nicolet 6700 Thermo Scientific infrared spectrophotometer was utilized to record the
infrared (IR) spectra of the samples. The spectra were recorded over the range of
−
1
4
000–500 cm .
Table 1. Crystal data and structure refinement for compound 2a
CCDC
958591
Formula
C17H12N2
244.29
100(1)
−1
Formula Weight (g·mole )
Temperature (K)
Wavelength (Å)
Crystal system
0.71073
Monoclinic
P21/c
Space group
◦
Unit cell (Å, )
a = 11.3132(5), b = 12.0061(5), c = 9.2498(4) β = 103.187(3)
3
Volume (Å )
1223.25(9)
4
Z
−3
Calculated density (g·cm )
1.327
0.079
512
0.09 × 0.20 × 0.57
2.5–30.1
−1
Absorption coefficient (mm )
F(000)
Crystal size (mm)
Theta min – max ( )
◦
Dataset
15 ≤ h ≤ 15; −16 ≤ k ≤ 16; −12 ≤ l ≤ 13
13918, 3564, 0.047
2524
Total/unique data/R(int)
Observed data [I > 2.0σ(I)]
Data/parameters
3564, 220
R/wR2/Goodness of fit
Largest diff. peak and hole e·Å−3
0.0530, 0.1143, 1.03
−0.23, 0.23

Synthesis and Crystal Structure
127
X-Ray Crystallography
X-ray diffraction (XRD) data for compound 2a were collected from single crystal by using
a Bruker APEX II CCD diffractometer with a graphite monochromatic Mo-Kα radiation at
a detector distance of 5 cm with APEX2 software [15]. The collected data had been reduced
by using SAINT program and the empirical absorption corrections were performed with the
SADABS program [15]. The structure of complex was solved by direct methods and was
2
refined using the full-matrix least-square method on F using the SHELXTL program [16].
All non-hydrogen atoms were refined anisotropically. All hydrogen atoms were located
from a difference Fourier maps and freely refined. The final refinement converged well.
Data for publication were prepared by using SHELXTL [16] and PLATON [17]. Crystal
structure and refinement data for the compound 2a are summarized in Table 1.
Results and Discussion
Outcome of the reactions are presented in Table 2.
Procedure [18] for the preparation of (S)-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole-
3-carboxylic acid (1). L-tryptophan (10 g, 0.05 mol) was added to the solution of NaOH
Table 2. Synthesis of 9-phenyl-β-carbolines
aisolated yields.

128
R. Meesala et al.
Table 3. Final coordinates and equivalent isotropic displacement parameters of the non-
hydrogen atoms for compound 2a
Atom
x
y
z
Ueq (Å2)
N1
N2
C1
C2
C3
C4
C5
C6
0.86996 (12)
0.71726 (10)
0.59977 (12)
0.52739 (13)
0.41304 (14)
0.37097 (15)
0.44127 (14)
0.55760 (13)
0.65336 (13)
0.66796 (15)
0.77605 (15)
0.85654 (13)
0.74997 (12)
0.79396 (12)
0.85376 (12)
0.93073 (13)
0.94560 (13)
0.88414 (13)
0.80883 (13)
0.60054 (11)
0.52223 (10)
0.55910 (11)
0.53703 (13)
0.58448 (14)
0.65190 (14)
0.67207 (13)
0.62545 (11)
0.62889 (11)
0.67864 (12)
0.66219 (13)
0.55206 (12)
0.56435 (11)
0.45955 (11)
0.36585 (12)
0.30724 (12)
0.34065 (13)
0.43343 (13)
0.49392 (12)
−0.09662 (13)
0.20532 (12)
0.20373 (15)
0.30374 (16)
0.27488 (18)
0.14983 (19)
0.04942 (18)
0.07663 (15)
−0.00272 (15)
−0.13436 (16)
−0.17507 (17)
0.03020 (15)
0.07933 (14)
0.32091 (14)
0.28597 (15)
0.39919 (16)
0.54615 (16)
0.58042 (16)
0.46804 (15)
0.0284 (3)
0.0195 (3)
0.0205 (3)
0.0243 (3)
0.0291 (3)
0.0325 (4)
0.0286 (4)
0.0225 (3)
0.0216 (3)
0.0279 (3)
0.0297 (4)
0.0227 (3)
0.0193 (3)
0.0183 (3)
0.0205 (3)
0.0240 (3)
0.0248 (3)
0.0250 (3)
0.0219 (3)
C7
C8
C9
C10
C11
C12
C13
C14
C15
C16
C17
Note: Ueq = 1/3 of the trace of the orthogonalized U tensor.
Table 4. Hydrogen atom positions and isotropic displacement parameters for
compound 2a
Atom
x
y
z
Uiso (Å2)
H2A
H3A
H4A
H5A
H8A
H9A
H10A
H13A
H14A
H15A
H16A
H17A
0.5550 (14)
0.3640 (16)
0.2892 (16)
0.4090 (15)
0.6013 (15)
0.7920 (15)
0.9255 (14)
0.8400 (14)
0.9733 (15)
1.0015 (14)
0.8973 (15)
0.7667 (15)
0.4887 (13)
0.5692 (14)
0.6856 (15)
0.7195 (14)
0.7226 (14)
0.6952 (14)
0.5083 (13)
0.3415 (13)
0.2406 (15)
0.2990 (14)
0.4581 (14)
0.5613 (14)
0.3871 (17)
0.3394 (19)
0.1336 (18)
−0.0414 (18)
−0.1972 (18)
−0.2687 (19)
0.0838 (16)
0.1834 (17)
0.3747 (18)
0.6261 (18)
0.6827 (18)
0.4919 (17)
0.025 (4)
0.035 (5)
0.039 (5)
0.032 (4)
0.034 (5)
0.037 (5)
0.024 (4)
0.025 (4)
0.032 (4)
0.030 (4)
0.031 (4)
0.029 (4)
ꢀ
ꢁ
2
Note: The temperature factor has the form of e−T, where T = 8π U
2
(sin)θ
λ
for isotropic atoms.

Synthesis and Crystal Structure
129
Table 5. Anistropic displacement parameters for compound 2a
U11
U22
U33
U12
U13
U23
N1
N2
C1
C2
C3
C4
C5
C6
C7
C8
C9
0.0330 (7) 0.0300 (7) 0.0230 (6) −0.0076 (6)
0.0080 (5) −0.0001 (5)
0.0184 (6) 0.0224 (6) 0.0181 (5)
0.0183 (7) 0.0204 (7) 0.0220 (7)
0.0020 (5)
0.0008 (5)
0.0050 (4) 0.0006 (4)
0.0030 (5) −0.0056 (5)
0.0059 (6) −0.0045 (6)
0.0100 (7) −0.0112 (7)
0.0021 (7) −0.0128 (7)
0.0228 (7) 0.0262 (8) 0.0242 (7) −0.0010 (6)
0.0215 (7) 0.0336 (9) 0.0341 (8) −0.0028 (6)
0.0224 (8) 0.0318 (9) 0.0409 (9)
0.0264 (8) 0.0241 (8) 0.0315 (8)
0.0239 (7) 0.0190 (7) 0.0223 (7)
0.0051 (7)
0.0044 (6) −0.0014 (6) −0.0063 (6)
0.0014 (5)
0.0004 (5) −0.0058 (5)
0.0009 (5) −0.0023 (5)
0.0266 (7) 0.0164 (7) 0.0197 (6) −0.0012 (5)
0.0376 (9) 0.0207 (7) 0.0222 (7) −0.0021 (6)
0.0407 (9) 0.0267 (8) 0.0219 (7) −0.0096 (7)
0.0005 (6)
0.0077 (7)
0.0015 (6)
0.0015 (6)
C10 0.0237 (7) 0.0234 (7) 0.0210 (7) −0.0026 (6)
C11 0.0224 (7) 0.0191 (7) 0.0162 (6) −0.0014 (5)
C12 0.0166 (6) 0.0207 (7) 0.0179 (6) −0.0028 (5)
C13 0.0212 (7) 0.0211 (7) 0.0197 (7) −0.0015 (5)
0.0052 (6) −0.0004 (5)
0.0037 (5) −0.0015 (5)
0.0042 (5)
0.0020 (5)
0.0058 (5) −0.0010 (5)
C14 0.0213 (7) 0.0227 (7) 0.0287 (8)
0.0017 (6)
0.0070 (6)
0.0042 (5)
0.0030 (6)
0.0079 (6)
C15 0.0205 (7) 0.0320 (8) 0.0216 (7) −0.0002 (6)
C16 0.0211 (7) 0.0364 (9) 0.0179 (7) −0.0023 (6)
C17 0.0194 (7) 0.0252 (7) 0.0220 (7) −0.0007 (6)
0.0053 (6) −0.0003 (6)
0.0067 (6) −0.0022 (5)
ꢂ
−T
2
∗ ∗
i j
Note: The temperature factor has the form of e , where T = 2π
i j
h h Uij a a for anisotropic.
ij
Table 6. Bond distances for compound 2a (Å)
Atoms
Length
Atoms
Length
N1–C10
N1–C9
N2–C11
N2–C1
N2–C12
C1–C2
C1–C6
C2–C3
C2–H2A
C3–C4
C3–H3A
C4–C5
1.3487 (18)
1.361 (2)
1.3955 (17)
1.3978 (17)
1.4280 (17)
1.394 (2)
1.4102 (19)
1.383 (2)
0.959 (16)
1.403 (2)
0.921 (18)
1.375 (2)
0.989 (18)
1.399 (2)
1.012 (16)
1.441 (2)
1.400 (2)
C7–C11
C8–C9
C8–H8A
1.4116 (19)
1.373 (2)
0.992 (16)
1.006 (17)
1.390 (2)
0.977 (15)
1.3883 (19)
1.3951 (19)
1.3908 (19)
0.971 (15)
1.390 (2)
0.986 (17)
1.388 (2)
0.991 (16)
1.389 (2)
0.970 (16)
0.989 (17)
C9–H9A
C10–C11
C10–H10A
C12–C13
C12–C17
C13–C14
C13–H13A
C14–C15
C14–H14A
C15–C16
C15–H15A
C16–C17
C16–H16A
C17–H17A
C4–H4A
C5–C6
C5–H5A
C6–C7
C7–C8

130
R. Meesala et al.
◦
Table 7. Bond angles ( ) for compound 2a
Atom
Angles
Atom
Angles
C10–N1–C9
C11–N2–C1
C11–N2–C12
C1–N2–C12
C2–C1–N2
C2–C1–C6
N2–C1–C6
C3–C2–C1
C3–C2–H2A
C1–C2–H2A
C2–C3–C4
C2–C3–H3A
C4–C3–H3A
C5–C4–C3
C5–C4–H4A
C3–C4–H4A
C4–C5–C6
C4–C5–H5A
C6–C5–H5A
C5–C6–C1
C5–C6–C7
C1–C6–C7
C8–C7–C11
C8–C7–C6
C11–C7–C6
C9–C8–C7
C9–C8–H8A
C7–C8–H8A
118.00 (14)
108.01 (11)
125.77 (12)
126.06 (12)
129.36 (13)
121.50 (13)
109.13 (12)
117.33 (14)
121.6 (10)
121.0 (9)
121.56 (16)
117.9 (11)
120.5 (11)
121.24 (15)
119.4 (10)
119.4 (10)
118.25 (15)
120.3 (10)
121.4 (10)
120.09 (14)
133.04 (14)
106.87 (12)
118.13 (14)
134.99 (13)
106.88 (12)
117.80 (14)
121.4 (10)
120.8 (10)
N1–C9–C8
N1–C9–H9A
C8–C9–H9A
124.59 (14)
113.7 (10)
121.7 (10)
121.11 (13)
116.0 (9)
N1–C10–C11
N1–C10–H10A
C11–C10–H10A
C10–C11–N2
C10–C11–C7
N2–C11–C7
C13–C12–C17
C13–C12–N2
C17–C12–N2
C12–C13–C14
C12–C13–H13A
C14–C13–H13A
C15–C14–C13
C15–C14–H14A
C13–C14–H14A
C16–C15–C14
C16–C15–H15A
C14–C15–H15A
C15–C16–C17
C15–C16–H16A
C17–C16–H16A
C16–C17–C12
C16–C17–H17A
C12–C17–H17A
122.9 (9)
130.52 (12)
120.36 (13)
109.12 (12)
120.67 (13)
119.86 (12)
119.47 (12)
119.29 (13)
119.6 (9)
121.1 (9)
120.37 (14)
120.2 (9)
119.4 (9)
119.99 (13)
120.1 (9)
119.9 (10)
120.17 (13)
119.7 (10)
120.1 (10)
119.49 (14)
120.3 (9)
120.2 (9)
(2 g, 0.05 mol) and H2O (20 mL) and stirred until clear. Formalin solution (30%; 5 g,
0.05 mol) was added to the reaction mixture. The mixture was stirred at room temperature
for 2 hr and then refluxed for 3 hr. The reaction mixture was neutralized (pH 5) with 6N
HCl (8 mL) and cooled. The precipitate was collected, washed well with H2O, MeOH, and
CH2Cl2, and dried. The compound was obtained as a white solid and the weight of the
product was 10 g.
Procedure for the preparation of 9-phenyl-9H-pyrido[3,4-b]indole (2a). A mixture of
compound 1 (0.21 g, 1 mmol), iodobenzene (0.2 g, 1 mmol), K2CO3 (0.14 g, 1 mmol), and
◦
CuI (18.5 mg, 0.1 mmol) in dimethylformamide (DMF, 12 mL) at 130 C was heated for 18
hr. Water (20 mL) was added and the aqueous solution was extracted with dichloromethane
(
DCM, 3 × 20 mL). DCM was dried over anhyd. Na2SO4 and evaporated under reduced
pressure. The crude product was purified by column chromatography by using silica gel.
◦
The pure product was obtained as a white solid (0.14 g, yield = 61%). M.p.: 128–130 C.
1
H NMR (500 MHz, CDCl3) δ: 8.8 (s, 1H), 8.47 (s, 1H), 8.13 (d, J = 7.5 Hz, 1H), 7.95
(d, J = 5 Hz, 1H), 7.58–7.55 (m, 3H), 7.52–7.50 (m, 3H), 7.47–7.46 (m, 1H), 7.29–7.26

Synthesis and Crystal Structure
131
◦
Table 8. Torsion angles ( ) for compound 2a
Atom
Angles
Atom
Angles
0.2 (2)
C11–N2–C1–C2
C12–N2–C1–C2
C11–N2–C1–C6
C12–N2–C1–C6
N2–C1–C2–C3
C6–C1–C2–C3
C1–C2–C3–C4
C2–C3–C4–C5
C3–C4–C5–C6
C4–C5–C6–C1
C4–C5–C6–C7
C2–C1–C6–C5
N2–C1–C6–C5
C2–C1–C6–C7
N2–C1–C6–C7
C5–C6–C7–C8
C1–C6–C7–C8
C5–C6–C7–C11
C1–C6–C7–C11
C11–C7–C8–C9
C6–C7–C8–C9
C10–N1–C9–C8
C7–C8–C9–N1
178.46 (14)
−5.8 (2)
C9–N1–C10–C11
N1–C10–C11–N2
N1–C10–C11–C7
C1–N2–C11–C10
C12–N2–C11–C10
C1–N2–C11–C7
C12–N2–C11–C7
C8–C7–C11–C10
C6–C7–C11–C10
C8–C7–C11–N2
−179.94 (13)
−0.29 (15)
175.41 (12)
−179.75 (13)
−1.1 (2)
−0.4 (2)
179.89 (14)
4.2 (2)
0.33 (15)
0.2 (2)
1.1 (2)
−175.39 (12)
0.6 (2)
−1.4 (2)
−179.85 (12)
−179.81 (12)
−0.24 (15)
−52.53 (19)
132.51 (14)
126.88 (15)
−48.07 (19)
−1.1 (2)
0.4 (2)
179.86 (15)
0.8 (2)
179.70 (12)
−178.73 (13)
0.14 (15)
0.0 (3)
C6–C7–C11–N2
C11–N2–C12–C13
C1–N2–C12–C13
C11–N2–C12–C17
C1–N2–C12–C17
C17–C12–C13–C14
N2–C12–C13–C14
C12–C13–C14–C15
C13–C14–C15–C16
C14–C15–C16–C17
C15–C16–C17–C12
C13–C12–C17–C16
N2–C12–C17–C16
179.53 (15)
−179.43 (15)
0.06 (15)
−0.5 (2)
178.29 (12)
1.4 (2)
−0.5 (2)
−0.8 (2)
−179.90 (15)
−0.1 (2)
1.1 (2)
−0.1 (2)
0.2 (2)
−179.53 (13)
(
1
1
m, 1H); 13C NMR (125 MHz, CDCl3) δ: 140.6, 138.8, 135.8, 132.1, 129.0, 127.9, 127.5,
27.0, 125.8, 120.7, 120.5, 119.6, 109.5; GC-MS: 244 (M); IR (ν, cm ): 1746, 1621,
596, 1501, 1464, 1433, 1362, 1324, 1230, 1026, 827, 746.
−1
Procedure for the preparation of 9-(4-chlorophenyl)-9H-pyrido[3,4-b]indole (2b). The
compound 2b was synthesized by following the same procedure like compound 2a with
compound 1 (0.21 g, 1.0 mmol), 1-chloro-4-iodobenzene (0.24 g, 1.0 mmol), K2CO3
(
0.14 g, 1 mmol), and CuI (18.5 mg, 0.1 mmol). The compound was obtained as a white
o
1
solid (0.13 g, 50%). M.p.: 93–95 C; H NMR (500 MHz, DMSO-d6) δ: 8.7 (s, 1H), 8.44
(
7
d, J = 5.5 Hz, 1H), 8.34 (d, J = 10 Hz, 1H), 8.22 (d, J = 10 Hz, 1H), 7.73–7.67 (m, 4H),
13
.61–7.58 (m, 1H), 7.46 (d, J = 8.0 Hz, 1H), 7.37 (t, J = 10 Hz, 1H); C NMR (125 MHz,
DMSO-d6) δ: 140.6, 139.7, 136.0, 134.8, 132.34, 132.3, 130.3, 129.1, 128.4, 128.3, 122.1,
Table 9. C H···π interaction in compound 2a (Å, ◦)
D–H···A
d(D–H)
d(H···A)
d(D···A)
<(DHA)
C8–H8A···Cg2
0.992 (16)
2.585 (17)
3.5274 (16)
158.6 (13)
Symmetry: x, 3/2−y, −1/2+z.

132
R. Meesala et al.
Figure 1. π–π and C–H···π interactions found in compound 2a. Cg1 is centroid for
N2/C1/C6–C7/C11 five member ring, Cg2 is centroid for C1–C6 six member ring.
−1
1
1
21.0, 120.9, 114.9, 110.2; GC-MS: 278 (M); IR (ν, cm ): 1626, 1592, 1561, 1494, 1451,
432, 1359, 1317, 1276, 1222, 1089, 1009, 817.
The atomic coordinates and its isotropic displacement parameters for compound 2a
are listed in Table 3 for non-hydrogen atoms and Table 4 for hydrogen atoms. The final
anisotropic displacement parameters are listed in Table 5.
Figure 2. The structure of compound 2a, showing 50% probability displacement ellipsoid.

Synthesis and Crystal Structure
133
Figure 3. The crystal packing of compound 2a viewed along the c-axis.
All bond lengths, angles, and torsion angles in compound 2a are within normal ranges
[19] as shown in Tables 6, 7, and 8, respectively, and comparable with the closely related
structure [20]. The β-carboline ring, N1–N2/C1–C11, is almost planar with the maximum
◦
deviation of −0.014(2) Å from atom C2. It make a dihedral angle of 50.37(5) with the
attached benzene ring C12–C17.
No hydrogen bonds were observed in the crystal packing. However, π–π interaction
was found in the crystal packing with Cg1···Cg2 distance of 3.559(1) Å [1−x, 1−y, −z],
where Cg1 is centroid for N2/C1/C6–C7/C11 five member ring, while Cg2 is centroid
for C1–C6 six member ring as shown in Fig. 1. The crystal structure is further stabilized
by C–H···π interaction (Table 9, Fig. 1). The ORTEP and crystal packing diagrams of
compound 2a were presented in Figs. 2 and 3, respectively.
Conclusions
In summary, we have developed a new method for the synthesis of 9-phenyl-9H-pyrido[3,4-
b]indole and 9-(4-chlorophenyl)-9H-pyrido[3,4-b]indole from (S)-2,3,4,9-tetrahydro-1H-
pyrido[3,4-b]indole-3-carboxylic acid by employing a catalytic amount (10 mole%) of
CuI. The molecular structure of the compound 2a was determined by single-crystal XRD
method.
Acknowledgment
The Research University Grant Scheme of Universiti Sains Malaysia (RUT-USM) is grate-
fully acknowledged by the authors for financial support.
Supplementary Data
Crystallographic data for the compound 2a have been deposited at the Cambridge Crystallo-
graphic Data Centre with CCDC number 958591. The data can be obtained free of charge via

134
R. Meesala et al.
www.ccdc.cam.ac.uk/data request/cif, or by E-mailing to data request@ccdc.cam.ac.uk,
or by contacting The Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK; fax:
+44(0)1223-336033.
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