3
46
R. Patil et al. / Journal of Molecular Structure 1075 (2014) 345–351
was synthesized by Liu et al. using molecular iodine under
ultrasonic irradiation [6]. Screening of 2-(n-alkylamino)-1,4-naph-
thoquinone as antifilarial agent has been evaluated by Mathew
et al. [7].
Our interest is to study the molecular structures of amino-
naphthoquinones by single crystal X-ray crystallography; such
studies will reveal the association of these molecules in solid
state, which can be correlated to the biological activities. We
have studied the antiproliferative [8] and antifungal activities
of 2-(n-alkylamino)-3-chloro-1,4-naphthoquione derivatives [9].
In present investigation 2-(n-alkylamino)-1,4-naphthoquinones
package was used for solution and artwork of the structures, Shel-
XL97 [13] was used for the refinement. All non-hydrogen atoms
were anisotropically refined and hydrogen atoms were placed at
calculated positions and refined as riding atoms with isotropic dis-
placement parameters. Crystallographic data of the compounds are
listed in Table 1.
Synthesis
General procedure for synthesis LH-1–LH-7
1 g of 1,4-naphthoquinone was dissolved in about 30 ml of
dichloromethane and the solution were stirred for 15 min. To this
solution primary amines were added drop wise (methyl: LH-1
(0.345 mL), ethyl: LH-2 (0.590 mL), propyl: LH-3 (0.591 mL), butyl:
LH-4 (0.462 mL), pentyl: LH-5 (0.732 mL), hexyl: LH-6 (0.835 mL),
heptyl: LH-7 (0.937 mL)) have been added drop wise. The reaction
mixtures were stirred for 24 h at room temperature (26 °C) and
were kept in refrigerator at 4 °C for about 12 h. The crude product
was purified by column chromatography using toluene: methanol
(
where n-alkyl: methyl; LH-1, ethyl; LH-2, propyl; LH-3, butyl;
LH-4, pentyl; LH-5, hexyl; LH-6 and heptyl; LH-7) have been
synthesized and characterised. These reactions are spontaneous
reactions and take place at laboratory temperatures (26 °C)
(Scheme 1). The present investigation also reports the single crys-
tal X-ray structures of ethyl (LH-2) and hexyl (LH-6) derivatives.
Experimental section
(
9:1) as eluent. X-ray quality crystals of LH-2 and LH-6 were
obtained by evaporation of the dark red band of eluted fraction
of the column.
General materials and methods
The materials used viz 1,4-naphthoquinone, methyl amine solu-
tion (40%), ethyl amine solution (70%), propyl, butyl, pentyl, hexyl,
and heptyl amine and were purchased from Sigma–Aldrich and
used as received. The solvents used such as dichloromethane, tol-
uene, methanol are of analytical grade were purchased from Merck
Chemicals, India. Solvents were distilled by standard methods [10]
and dried wherever necessary. Melting points of LH-1–LH-7 were
determined using melting point apparatus (Make-METTLER) and
were corrected using DSC (Differential Scanning Calorimetry) tech-
nique (Make-TA Q2000) (Fig. S1 in ESI ). The FT-IR spectra of the
Analytical data
Analytical data for LH-1 to LH-4 are represented in Supplemen-
tary material.
Characterization of 2-pentylamino-1,4-naphthoquinone
LH-5: Red crystals, Yield: 0.860 g (55.1%). M.P. 106 °C. Anal. data
calcd. for C15
H17NO
2
: C, 74.05; H, 7.04; N, 5.76. Found C, 74.21; H,
ꢃ1
7
1
1
1
.24; N, 5.49. FT-IR (KBr,
670, 1624, 1615, 1592, 1564, 1509, 1465, 1354, 1332, 1305, 1273,
256, 1238, 1211, 1120, 1091, 1081, 1048, 1031, 1012, 973, 834,
80, 769, 723, 671. H NMR (500 MHz, DMSO-d
v
max/cm ): 3339, 3063, 2945, 2926, 2865,
ꢃ1
compounds were recorded between 4000 and 400 cm as KBr pel-
1
lets on BRUKER Tensor 37 Spectrometer (Fig. S2 in ESI ) and H,
1
6
, d (ppm): 0.85
1
3
C, DEPT, HSQC, COSY NMR of compounds were recorded
Figs. S3–S9 and Tables S1–S8 in ESI ) in DMSO-d , on Varian
00 MHz NMR instrument. TMS (tetramethylsilane) was used as
(
3H, t, J = 6.7), 1.27 (2H, m), 1.55 (2H, p, J = 7.1 Hz), 3.14 (2H, q,
(
5
6
J = 7.0 Hz), 5.63 (1H, s), 7.52 (1H, br. t, D O ex.), 7.68 (1H, t,
J = 7.3 Hz), 7.79 (1H, t, J = 7 Hz), 7.90 (2H, d, J = 7.5 Hz), 7.93 (2H,
d, J = 7.5 Hz). UV–Vis; (kmax/nm, DMSO): 272, 329, 459. GC–MS
2
the reference. Elemental analysis was performed on Thermo Finn-
igan EA 1112 Flash series Elemental Analyzer at SAIF, IIT Mumbai,
India. Mass of LH-1 to LH-7 was determined on GC–MS 2010-eV
+
(
EI); m/z: 243 (M + H).
(
Make SHIMADZU).
Characterization of 2-hexylamino-1,4-naphthoquinone
LH-6: Red crystals, Yield: 0.874 g (53.0%). M.P.115 °C. Anal. data
X-ray crystallographic data collection and refinement of the structures
calcd. for C16H19NO : C, 74.68; H, 7.44; N, 5.44. Found C, 74.17; H,
2
ꢃ1
7
.66; N, 5.99. FT-IR (KBr,
v
max/cm ): 3340, 3060, 2958, 2943, 2918,
Single crystals of compounds LH-2 and LH-6 were coated with
perfluoropolyether, picked up with nylon loops and were mounted
in the nitrogen cold stream of the diffractometers. Monochromated
2865, 2854, 1676, 1621, 1594, 1568, 1514, 1466, 1392, 1353, 1326,
1307, 1293, 1274, 1250, 1233, 1211, 1153, 1121, 1094, 1080, 1053,
1
1041, 1030, 1005, 967, 893, 839, 812, 776, 749, 721, 670. H NMR
Mo Ka
radiation (Bruker-AXS Kappa Mach3 with Incoatec Helios
(500 MHz, DMSO-d , d (ppm): 0.84 (3H, t, J = 6.7), 1.26 (6H, m),
6
mirror, k = 0.71073 Å) from a Mo-target rotating-anode X-ray
source was used for LH-2 and LH-6. Final cell constants were
obtained from least squares fits of several thousand strong reflec-
tions. Intensity data were corrected for absorption using intensities
of redundant reflections with the program SADABS [11]. The struc-
tures were readily solved by direct methods and subsequent differ-
ence Fourier techniques. The Siemens ShelXTL [12] software
1.55 (2H, p, J = 7.1 Hz), 3.15 (2H, q, J = 7.0 Hz), 5.64 (1H, s), 7.51
(1H, br. t, D O ex.), 7.69 (1H, t, J = 7.3 Hz), 7.80 (1H, t, J = 7.3 Hz),
2
7.91 (2H,d, J = 6.5 Hz), 7.95(2H, d, J = 7.5 Hz). UV–Vis; (kmax/nm,
+
DMSO): 272, 331, 459. GC–MS (EI); m/z: 257 (M + H).
Characterization of 2-heptylamino-1,4-naphthoquinone
LH-7: Red crystals, Yield: 0.853 g (49.0%). M.P.105 °C. Anal. data
calcd. for C17
H
21NO
2
: C, 74.69; H, 8.48; N, 5.12. Found C, 74.14; H,
ꢃ1
7
.89; N, 4.89. FT-IR (KBr,
v
max/cm ): 3340, 3064, 2944, 2916, 2866,
O
where,
8
2848, 1674, 1621, 1595, 1569, 1513, 1466, 1392, 1354, 1333, 1306,
9
1
NH
1275, 1247, 1210, 1154, 1121, 1094, 1081, 1020, 968, 890, 845,
7
6
3
LH-1: R=H ; LH-2: R=CH ;
CH R
1
2
2
820, 812, 772, 750, 720, 671. H NMR (500 MHz, DMSO-d
6
, d
2 5 3 7
LH-3:R=C H , LH-4: R=C H
3
(ppm): 0.83 (3H, t, J = 7.0), 1.27 (8H, m), 1.55 (2H, p, J = 6.8 Hz),
3.15 (2H, q, J = 6.7 Hz), 5.64 (1H, s), 7.51 (1H, br. t, D O ex.), 7.68
1H, t, J = 7.3 Hz), 7.80 (1H, t, J = 7.3 Hz), 7.90 (2H, d, J = 8.0 Hz),
1
0
5
4
LH-5: R=C H ; LH-6: R=C H
4
9
5
11;
2
O
(
LH-7: R=C
6
H
13
7
.93 (2H, d, J = 8.0 Hz). UV–Vis; (kmax/nm, DMSO): 272, 331, 459.
+
Scheme 1. Molecular formula of LH-1–LH-7.
GC–MS (EI); m/z: 271 (M + H).