1,3,3-Trimethyl-1,2,3,4-tetra­hydro­pyrido[1,2-a]benzimidazol-1-ol

Mehdi, S.H.; Hashim, R.; Ghalib, R.M.; Yeap, C.S.; Fun, H.-K.

doi:10.1107/S1600536810024487

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 66| Part 7| July 2010| Page o1832

doi:10.1107/S1600536810024487

Open

access

1,3,3-Trimethyl-1,2,3,4-tetrahydropyrido[1,2-a]benzimidazol-1-ol

Sayed Hasan Mehdi,^a Rokiah Hashim,^a Raza Murad Ghalib,^a Chin Sing Yeap ^b ‡ and Hoong-Kun Fun ^b ^*§

^aSchool of Industrial Technology, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia, and ^bX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia
^*Correspondence e-mail: hkfun@usm.my

(Received 18 June 2010; accepted 23 June 2010; online 26 June 2010)

In the title compound, C₁₄H₁₈N₂O, the benzimidazole grouping is close to planar, with a maximum deviation of 0.042 Å; the six-membered non-aromatic ring adopts an envelope conformation. In the crystal structure, molecules are linked into infinite sheets lying parallel to the bc plane by O—H⋯N and C—H⋯O hydrogen bonds.

Related literature

For applications of benzimidazole derivatives, see: Horton et al. (2003 ); Insuasty et al. (2008a ,b ). For the preparation of the title compound, see: Grech et al. (1994 ). For ring conformations, see Cremer & Pople (1975 ). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986 ).

Experimental

Crystal data

C₁₄H₁₈N₂O
M_r = 230.30
Monoclinic, P 2₁ /c
a = 9.615 (5) Å
b = 8.194 (4) Å
c = 15.965 (8) Å
β = 99.601 (12)°
V = 1240.2 (11) Å³
Z = 4
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 100 K
0.38 × 0.12 × 0.07 mm

Data collection

Bruker APEXII DUO CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ) T_min = 0.971, T_max = 0.995
13460 measured reflections
3597 independent reflections
2612 reflections with I > 2σ(I)
R_int = 0.052

Refinement

R[F² > 2σ(F²)] = 0.046
wR(F²) = 0.117
S = 1.02
3597 reflections
226 parameters
All H-atom parameters refined
Δρ_max = 0.33 e Å⁻³
Δρ_min = −0.25 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1O1⋯N1ⁱ	0.97 (2)	1.84 (2)	2.803 (2)	174 (2)
C5—H5A⋯O1ⁱⁱ	0.962 (15)	2.499 (15)	3.216 (2)	131.3 (11)
Symmetry codes: (i) $[-x+1, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (ii) -x+1, -y+1, -z.

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536810024487/hb5508sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536810024487/hb5508Isup2.hkl

checkCIF report

Comment top

Benzimidazole derivatives are an important class of bioactive molecules and are well known due to their wide range of pharmacological activities as an anti-ulcers, anti-hypertensive, anti-viral, anti-fungal, anti-cancer, and anti-histaminic (Horton et al., 2003; Insuasty et al., 2008a, b) agents. Here we report the synthesis and the crystal structure of title compound.

In the title compound (Fig. 1), the benzimidazole group is essentially coplanar (N1/C1–C6/N2/C11) with the maximum deviation of 0.042 Å at atom C6. The N2/C7–C11 ring adopts an envelope conformation with Q=0.4933 (14) Å, θ=52.81 (15)° and ϕ=182.3 (2)° (Cremer & Pople, 1975).

In the crystal structure, the molecules are linked into infinite two-dimensional planes parallel to bc plane by the intermolecular O1—H1O1···N1 and C5—H5A···O1 hydrogen bonds (Fig. 2, Table 1).

Related literature top

For applications of benzimidazoles derivatives, see: Horton et al. (2003); Insuasty et al. (2008a,b). For the preparation of the title compound, see: Grech et al. (1994). For ring conformations, see Cremer & Pople (1975). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986).

Experimental top

A mixture of o-phenylenediamine (0.108 g m) and dimedone (0.140 g m) in molar ratio 1:1 was refluxed in a mixture of acetic acid-ethanol (1:1 v/v) for 3 h (Grech et al., 1994). The reaction mixture was dried on rotavapor at low pressure and further fractionated successively with diethyl ether, chloroform and ethanol. The ethanol fraction was dried on rotavapor and the dry mass so obtained was crystallized in methanol:chloroform (1:1) mixture to give yellow needles of (I) (55%, m.p. 451 K).

Computing details top

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top

	Fig. 1. The molecular structure of (I) with 50% probability ellipsoids for non-H atoms.
	Fig. 2. The crystal packing of (I), viewed down the b axis, showing the molecules linked into sheets lying parallel to bc. Intermolecular hydrogen bonds are shown as dashed lines.

1,3,3-Trimethyl-1,2,3,4-tetrahydropyrido[1,2-a]benzimidazol-1-ol top

Crystal data top

C₁₄H₁₈N₂O	F(000) = 496
M_r = 230.30	D_x = 1.233 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 2162 reflections
a = 9.615 (5) Å	θ = 3.1–29.6°
b = 8.194 (4) Å	µ = 0.08 mm⁻¹
c = 15.965 (8) Å	T = 100 K
β = 99.601 (12)°	Needle, yellow
V = 1240.2 (11) Å³	0.38 × 0.12 × 0.07 mm
Z = 4

Data collection top

Bruker APEXII DUO CCD diffractometer	3597 independent reflections
Radiation source: fine-focus sealed tube	2612 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.052
ϕ and ω scans	θ_max = 30.0°, θ_min = 2.6°
Absorption correction: multi-scan (SADABS; Bruker, 2009)	h = −13→13
T_min = 0.971, T_max = 0.995	k = −11→10
13460 measured reflections	l = −22→18

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.046	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.117	All H-atom parameters refined
S = 1.02	w = 1/[σ²(F_o²) + (0.0528P)² + 0.2357P] where P = (F_o² + 2F_c²)/3
3597 reflections	(Δ/σ)_max < 0.001
226 parameters	Δρ_max = 0.33 e Å⁻³
0 restraints	Δρ_min = −0.25 e Å⁻³

Crystal data top

C₁₄H₁₈N₂O	V = 1240.2 (11) Å³
M_r = 230.30	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 9.615 (5) Å	µ = 0.08 mm⁻¹
b = 8.194 (4) Å	T = 100 K
c = 15.965 (8) Å	0.38 × 0.12 × 0.07 mm
β = 99.601 (12)°

Data collection top

Bruker APEXII DUO CCD diffractometer	3597 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2009)	2612 reflections with I > 2σ(I)
T_min = 0.971, T_max = 0.995	R_int = 0.052
13460 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.046	0 restraints
wR(F²) = 0.117	All H-atom parameters refined
S = 1.02	Δρ_max = 0.33 e Å⁻³
3597 reflections	Δρ_min = −0.25 e Å⁻³
226 parameters

Special details top

Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
O1	0.65445 (9)	0.44319 (11)	0.12156 (6)	0.0178 (2)
N1	0.40305 (10)	0.05504 (14)	0.22183 (7)	0.0176 (2)
N2	0.54560 (10)	0.19700 (13)	0.15038 (6)	0.0148 (2)
C1	0.32424 (12)	0.11377 (16)	0.14618 (8)	0.0160 (3)
C2	0.17999 (13)	0.09810 (17)	0.11474 (9)	0.0199 (3)
C3	0.12707 (13)	0.17745 (18)	0.03945 (9)	0.0215 (3)
C4	0.21420 (13)	0.27314 (18)	−0.00320 (8)	0.0199 (3)
C5	0.35783 (13)	0.28830 (17)	0.02639 (8)	0.0179 (3)
C6	0.41136 (12)	0.20479 (15)	0.10110 (8)	0.0152 (2)
C7	0.67647 (12)	0.27365 (16)	0.13019 (8)	0.0153 (3)
C8	0.79944 (12)	0.23815 (16)	0.20337 (8)	0.0164 (3)
C9	0.79390 (12)	0.07980 (16)	0.25468 (8)	0.0165 (3)
C10	0.65512 (13)	0.08393 (18)	0.29055 (8)	0.0186 (3)
C11	0.53240 (12)	0.10891 (16)	0.22157 (8)	0.0157 (3)
C12	0.70543 (14)	0.21133 (19)	0.04460 (9)	0.0208 (3)
C13	0.80018 (14)	−0.07437 (18)	0.20160 (9)	0.0218 (3)
C14	0.91813 (13)	0.08019 (19)	0.32872 (9)	0.0224 (3)
H1A	0.0269 (15)	0.1672 (18)	0.0155 (9)	0.020 (4)*
H2A	0.1203 (16)	0.033 (2)	0.1467 (10)	0.026 (4)*
H4A	0.1727 (15)	0.3345 (18)	−0.0553 (9)	0.016 (4)*
H5A	0.4140 (15)	0.3569 (19)	−0.0037 (9)	0.017 (4)*
H8A	0.8923 (16)	0.241 (2)	0.1794 (10)	0.025 (4)*
H8B	0.8028 (15)	0.334 (2)	0.2438 (10)	0.025 (4)*
H10A	0.6384 (15)	−0.0185 (19)	0.3209 (9)	0.018 (4)*
H10B	0.6583 (16)	0.177 (2)	0.3319 (10)	0.024 (4)*
H12A	0.7260 (17)	0.095 (2)	0.0457 (11)	0.030 (4)*
H12B	0.7853 (17)	0.279 (2)	0.0300 (11)	0.032 (4)*
H12C	0.6228 (18)	0.233 (2)	−0.0008 (11)	0.034 (5)*
H13A	0.7168 (16)	−0.0878 (19)	0.1571 (10)	0.024 (4)*
H13B	0.8059 (15)	−0.171 (2)	0.2371 (10)	0.024 (4)*
H13C	0.8856 (17)	−0.074 (2)	0.1725 (11)	0.032 (4)*
H14A	0.9187 (16)	0.180 (2)	0.3648 (10)	0.028 (4)*
H14B	0.9107 (17)	−0.017 (2)	0.3658 (11)	0.034 (5)*
H14C	1.0108 (18)	0.082 (2)	0.3068 (11)	0.036 (5)*
H1O1	0.640 (2)	0.487 (3)	0.1756 (13)	0.050 (6)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0215 (4)	0.0149 (5)	0.0175 (5)	0.0005 (3)	0.0047 (3)	0.0024 (4)
N1	0.0167 (5)	0.0195 (6)	0.0166 (5)	−0.0010 (4)	0.0028 (4)	0.0018 (4)
N2	0.0138 (4)	0.0170 (5)	0.0130 (5)	−0.0010 (4)	0.0009 (4)	0.0014 (4)
C1	0.0169 (5)	0.0153 (6)	0.0158 (6)	0.0004 (4)	0.0024 (4)	−0.0007 (5)
C2	0.0155 (5)	0.0206 (7)	0.0232 (7)	−0.0010 (5)	0.0020 (5)	−0.0017 (6)
C3	0.0171 (6)	0.0229 (7)	0.0229 (7)	0.0009 (5)	−0.0014 (5)	−0.0041 (6)
C4	0.0208 (6)	0.0210 (7)	0.0164 (6)	0.0036 (5)	−0.0018 (5)	−0.0009 (5)
C5	0.0202 (6)	0.0173 (7)	0.0157 (6)	0.0013 (5)	0.0014 (5)	0.0001 (5)
C6	0.0148 (5)	0.0160 (6)	0.0144 (6)	0.0001 (4)	0.0010 (4)	−0.0019 (5)
C7	0.0154 (5)	0.0150 (6)	0.0157 (6)	−0.0013 (4)	0.0036 (4)	0.0021 (5)
C8	0.0157 (5)	0.0162 (6)	0.0167 (6)	−0.0007 (4)	0.0007 (4)	0.0004 (5)
C9	0.0145 (5)	0.0169 (6)	0.0170 (6)	0.0002 (4)	0.0000 (4)	0.0018 (5)
C10	0.0176 (5)	0.0229 (7)	0.0147 (6)	−0.0007 (5)	0.0012 (4)	0.0041 (6)
C11	0.0168 (5)	0.0153 (6)	0.0150 (6)	0.0006 (4)	0.0030 (4)	0.0017 (5)
C12	0.0223 (6)	0.0249 (8)	0.0164 (6)	0.0014 (5)	0.0067 (5)	−0.0008 (6)
C13	0.0230 (6)	0.0177 (7)	0.0241 (7)	0.0018 (5)	0.0017 (5)	0.0002 (6)
C14	0.0185 (6)	0.0244 (8)	0.0220 (7)	0.0007 (5)	−0.0030 (5)	0.0038 (6)

Geometric parameters (Å, º) top

O1—C7	1.4085 (17)	C8—C9	1.5400 (19)
O1—H1O1	0.96 (2)	C8—H8A	1.029 (15)
N1—C11	1.3203 (16)	C8—H8B	1.012 (16)
N1—C1	1.3997 (17)	C9—C13	1.528 (2)
N2—C11	1.3700 (17)	C9—C14	1.5340 (18)
N2—C6	1.3965 (16)	C9—C10	1.5378 (18)
N2—C7	1.4890 (16)	C10—C11	1.4878 (18)
C1—C2	1.4000 (18)	C10—H10A	0.995 (16)
C1—C6	1.4060 (18)	C10—H10B	1.004 (16)
C2—C3	1.387 (2)	C12—H12A	0.976 (18)
C2—H2A	0.988 (16)	C12—H12B	1.006 (17)
C3—C4	1.404 (2)	C12—H12C	0.998 (17)
C3—H1A	0.979 (14)	C13—H13A	0.984 (16)
C4—C5	1.3886 (18)	C13—H13B	0.967 (17)
C4—H4A	0.997 (15)	C13—H13C	1.009 (17)
C5—C6	1.3968 (18)	C14—H14A	1.000 (17)
C5—H5A	0.961 (15)	C14—H14B	1.001 (18)
C7—C12	1.5271 (19)	C14—H14C	1.010 (17)
C7—C8	1.5450 (18)

C7—O1—H1O1	108.6 (12)	H8A—C8—H8B	106.5 (12)
C11—N1—C1	104.90 (11)	C13—C9—C14	109.35 (11)
C11—N2—C6	106.65 (10)	C13—C9—C10	109.98 (11)
C11—N2—C7	126.90 (10)	C14—C9—C10	109.00 (11)
C6—N2—C7	126.43 (10)	C13—C9—C8	113.17 (11)
N1—C1—C2	129.74 (12)	C14—C9—C8	108.46 (11)
N1—C1—C6	109.93 (11)	C10—C9—C8	106.78 (10)
C2—C1—C6	120.29 (12)	C11—C10—C9	110.96 (11)
C3—C2—C1	117.79 (12)	C11—C10—H10A	107.7 (8)
C3—C2—H2A	122.8 (9)	C9—C10—H10A	112.6 (8)
C1—C2—H2A	119.4 (9)	C11—C10—H10B	108.4 (9)
C2—C3—C4	121.33 (12)	C9—C10—H10B	109.2 (9)
C2—C3—H1A	119.5 (9)	H10A—C10—H10B	108.0 (12)
C4—C3—H1A	119.1 (9)	N1—C11—N2	113.35 (11)
C5—C4—C3	121.67 (13)	N1—C11—C10	125.66 (12)
C5—C4—H4A	118.4 (8)	N2—C11—C10	120.98 (11)
C3—C4—H4A	119.9 (8)	C7—C12—H12A	112.3 (10)
C4—C5—C6	116.79 (12)	C7—C12—H12B	106.4 (10)
C4—C5—H5A	119.5 (9)	H12A—C12—H12B	112.6 (14)
C6—C5—H5A	123.7 (9)	C7—C12—H12C	110.3 (10)
N2—C6—C5	132.67 (11)	H12A—C12—H12C	108.8 (14)
N2—C6—C1	105.13 (11)	H12B—C12—H12C	106.2 (14)
C5—C6—C1	122.06 (11)	C9—C13—H13A	112.9 (9)
O1—C7—N2	108.58 (10)	C9—C13—H13B	110.6 (9)
O1—C7—C12	106.80 (10)	H13A—C13—H13B	106.9 (13)
N2—C7—C12	109.84 (10)	C9—C13—H13C	111.5 (10)
O1—C7—C8	110.08 (10)	H13A—C13—H13C	107.1 (13)
N2—C7—C8	108.95 (10)	H13B—C13—H13C	107.4 (13)
C12—C7—C8	112.51 (11)	C9—C14—H14A	111.9 (9)
C9—C8—C7	118.09 (10)	C9—C14—H14B	109.3 (10)
C9—C8—H8A	108.9 (9)	H14A—C14—H14B	107.6 (13)
C7—C8—H8A	108.5 (9)	C9—C14—H14C	110.6 (10)
C9—C8—H8B	108.3 (9)	H14A—C14—H14C	105.5 (13)
C7—C8—H8B	106.0 (9)	H14B—C14—H14C	111.8 (14)

C11—N1—C1—C2	−177.80 (14)	C6—N2—C7—C12	−58.00 (16)
C11—N1—C1—C6	−0.14 (15)	C11—N2—C7—C8	0.12 (17)
N1—C1—C2—C3	176.20 (13)	C6—N2—C7—C8	178.34 (11)
C6—C1—C2—C3	−1.2 (2)	O1—C7—C8—C9	148.09 (11)
C1—C2—C3—C4	−1.3 (2)	N2—C7—C8—C9	29.14 (15)
C2—C3—C4—C5	2.2 (2)	C12—C7—C8—C9	−92.92 (14)
C3—C4—C5—C6	−0.5 (2)	C7—C8—C9—C13	64.20 (14)
C11—N2—C6—C5	173.80 (14)	C7—C8—C9—C14	−174.28 (11)
C7—N2—C6—C5	−4.7 (2)	C7—C8—C9—C10	−56.95 (15)
C11—N2—C6—C1	−1.75 (14)	C13—C9—C10—C11	−68.67 (15)
C7—N2—C6—C1	179.73 (11)	C14—C9—C10—C11	171.46 (11)
C4—C5—C6—N2	−176.96 (13)	C8—C9—C10—C11	54.49 (14)
C4—C5—C6—C1	−2.03 (19)	C1—N1—C11—N2	−1.04 (15)
N1—C1—C6—N2	1.20 (14)	C1—N1—C11—C10	177.57 (12)
C2—C1—C6—N2	179.11 (11)	C6—N2—C11—N1	1.82 (15)
N1—C1—C6—C5	−174.94 (11)	C7—N2—C11—N1	−179.67 (11)
C2—C1—C6—C5	3.0 (2)	C6—N2—C11—C10	−176.86 (12)
C11—N2—C7—O1	−119.77 (13)	C7—N2—C11—C10	1.64 (19)
C6—N2—C7—O1	58.45 (16)	C9—C10—C11—N1	150.69 (13)
C11—N2—C7—C12	123.78 (14)	C9—C10—C11—N2	−30.80 (17)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1O1···N1ⁱ	0.97 (2)	1.84 (2)	2.803 (2)	174 (2)
C5—H5A···O1ⁱⁱ	0.962 (15)	2.499 (15)	3.216 (2)	131.3 (11)

Symmetry codes: (i) −x+1, y+1/2, −z+1/2; (ii) −x+1, −y+1, −z.

Experimental details

Crystal data
Chemical formula	C₁₄H₁₈N₂O
M_r	230.30
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	100
a, b, c (Å)	9.615 (5), 8.194 (4), 15.965 (8)
β (°)	99.601 (12)
V (Å³)	1240.2 (11)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.08
Crystal size (mm)	0.38 × 0.12 × 0.07

Data collection
Diffractometer	Bruker APEXII DUO CCD diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2009)
T_min, T_max	0.971, 0.995
No. of measured, independent and observed [I > 2σ(I)] reflections	13460, 3597, 2612
R_int	0.052
(sin θ/λ)_max (Å⁻¹)	0.704

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.046, 0.117, 1.02
No. of reflections	3597
No. of parameters	226
H-atom treatment	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	0.33, −0.25

Computer programs: APEX2 (Bruker, 2009), SAINT (Bruker, 2009), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1O1···N1ⁱ	0.97 (2)	1.84 (2)	2.803 (2)	174 (2)
C5—H5A···O1ⁱⁱ	0.962 (15)	2.499 (15)	3.216 (2)	131.3 (11)

Symmetry codes: (i) −x+1, y+1/2, −z+1/2; (ii) −x+1, −y+1, −z.

Footnotes

‡Thomson Reuters ResearcherID: A-5523-2009.

§Thomson Reuters ResearcherID: A-3561-2009.

Acknowledgements

SHM and RMG thank Universiti Sains Malaysia (USM) for the University Grant (1001/PTEKIND/8140152). HKF and CSY thank USM for the Research University Golden Goose Grant (1001/PFIZIK/811012). CSY also thanks USM for the award of a USM Fellowship.

References

Bruker (2009). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Cosier, J. & Glazer, A. M. (1986). J. Appl. Cryst. 19, 105–107. CrossRef CAS Web of Science IUCr Journals Google Scholar
Cremer, D. & Pople, J. A. (1975). J. Am. Chem. Soc. 97, 1354–1358. CrossRef CAS Web of Science Google Scholar
Grech, O., Sakellariou, R. & Speziale, V. (1994). J. Heterocycl. Chem. 31, 509–511. Google Scholar
Horton, D. A., Bourne, G. T. & Smythe, M. L. (2003). Chem. Rev. 103, 893–930. Web of Science CrossRef PubMed CAS Google Scholar
Insuasty, B., Orozco, F., Lizarazo, C., Quiroga, J., Abonía, R., Hursthouse, M., Nogueras, M. & Cobo, J. (2008a). Bioorg. Med. Chem. 16, 8492–8500. Web of Science CSD CrossRef PubMed CAS Google Scholar
Insuasty, B., Orozco, F., Quiroga, J., Abonía, R., Nogueras, M. & Cobo, J. (2008b). Eur. J. Med. Chem. 43, 1955–1962. Web of Science CrossRef PubMed CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar