2
Heteroatom Chemistry
R
2. Materials and Methods
R
.(2
.(2
N
S
a
b, c
2.1. Materials and Physical Measurements. All the reagents
and solvents were of analytical grade and used as obtained
from commercial suppliers (Sigma Aldrich and Merck).
CHNS analyses were determined on Elementar Analysensys-
teme varioMICRO V1.6.2. One- and two-dimensional NMR
spectra (1H, 13C, DEPT135, COSY, HMBC, and HSQC)
.(2
S
#(3
R
a: KSCN, Bromine, Acetic acid
b: KOH, (2O
c: EtOH, MeI, KOtBu
R = -OC(3, -C(3, -Cl, Br
were obtained in CDCl on a Bruker Avance 400 MHz
3
Scheme 1: Synthesis scheme for substituted 6-(methylthio)anilines.
NMR spectrometer. Chemical shifs were recorded in ppm
with reference to the residual solvent proton relative to
tetramethylsilane. Infrared spectra of the compounds were
determined in the region 4000–400 cm–1 on PerkinElmer
Spectrum 100 ATR-FTIR spectrometer. Far-infrared spectra
for the complexes in the region 700–30 cm–1 were obtained
as mulls held between polyethylene discs and recorded on
Perkin Elmer Spectrum 400 FTIR/FIR spectrometer. Te
UV/Vis electronic spectra (250–1100 nm) were determined
in DMF on a PerkinElmer Lambda 25 UV/VIS Spectrometer.
Te molar conductance was measured in DMF at room
temperature on AZ5 86555 pH/mV/Cond./TDS/Temp at
10–3 M. Magnetic susceptibility measurements were taken
on a Sherwood magnetic susceptibility balance Mark 1.
A Galenkemp melting point apparatus was used to deter-
mine the melting points (uncorrected). Te powder electron
paramagnetic resonance (EPR) spectra were recorded on a
Bruker ESP 300E X-band EPR spectrometer with 100 kHz
feld modulation. Other experimental parameters: 9.762 GHz,
16.05 G modulation amplitude, 20 mW power, 1.25 ms time
constant, and 100 s sweep time.
in vacuo. Te residue was dissolved in water, neutralized
to pH 7 with concentrated HCl and the product extracted
with dichloromethane. Removal of the solvent under pres-
sure yielded crude 2-methoxy-2-(methylthio)aniline. Tis
was purifed by column chromatography on silica gel using
hexane/ether (6:1 vol/vol) as eluent to aford the pure oil.
Yield: 55%, mp 68-70∘C. Colour: Brown. Anal. Calc. for
C H NS (Mr 169.2): C, 62.70; H, 7.24; N, 9.14; S, 20.92. Found:
8
11
C, 61.97; H, 7.44; N, 9.02; S, 20.64%. FTIR (cm−1): 3383, 3293
Vasy/sym(NH ), 1620 ꢀ(NH ), 1269 v(C–N). UV ꢁ
(DMF,
max
2
2
nm (ꢂ, M–1 cm–1): 284sh, 308 (12240).
Other 2-(methylthio)anilines were similarly prepared
from their starting ortho-substituted anilines.
2.2.2. 2-Methyl-6-(methylthio)aniline (L2). Yield 24%, brown
oil. Anal. Calc. for C H NS (Mr 153.3): C, 62.70; H, 7.24; N,
8
11
9.14; S, 20.92. Found: C, 62.03; H, 7.99; N, 9.01; S, 20.91%. FTIR
(cm–1): 3452, 3355 Vasy/sym(NH ), 1619 ꢀ(NH ), 1279 v(C–N).
2
2
2.2. Synthesis of Substituted 2-(Methylthio)anilines. Ortho-
substituted-2-(methylthio)anilines were prepared in a two-
pot reaction involving the conversion of o-anisidine, o-
toluidine, o-chloroaniline, and o-bromoaniline to the corre-
sponding aminobenzothiazoles [7, 8] which were hydrolyzed
and methylated to yield the crude products (Scheme 1) [6].
UV ꢁmax (DMF, nm (ꢂ, M–1 cm–1): 286sh, 309 (11960).
2.2.3. 2-Chloro-6-(methylthio)aniline (L3). Yield 29%, brown
oil. Anal. Calc. for C H ClNS (Mr 173.7): C, 48.41; H, 4.64;
7
8
N, 8.07; S, 18.46. Found: C, 48.80; H, 4.81; N, 8.02; S, 18.39%.
FTIR (cm–1): 3459, 3358 Vasy/sym(NH ), 1615 ꢀ(NH ), 1292
2
2
v(C–N). UV ꢁmax (DMF, nm (ꢂ, M–1 cm–1): 285sh, 317 (9975).
2.2.1. 2-Methoxy-6-(methylthio)aniline (L1). o-Anisidine (1.00 g,
8.11 mmol) and potassium thiocyanate (3.16 g, 32.50 mmol)
were rapidly stirred in glacial acetic acid (16 mL) and bromine
liquid (1.30 g, 8.11 mmol) was added dropwise. Te mixture
was stirred for 10 h keeping the temperature below 35∘C,
during which a precipitate was formed. Tis mixture was
fltered and the precipitate washed with water. Te combined
fltrate was neutralized to pH 7 with aqueous ammonia
solution during which a shiny brown precipitate formed
and the mixture was fltered and dried (2.00 g). Te crude
6-methoxy-2-aminobenzothiazole (0.54 g, 3.00 mmol) was
slowly added to potassium hydroxide (1.54 g, 27.40 mmol) in
2 mL water. Te mixture was slowly heated to 135∘C allowing
the water to evaporate. Te temperature was then increased
to 165∘C and held there for 2 h. Te reaction mixture was
allowed to cool to room temperature and quenched with 2 mL
of water. Te mixture was fltered to remove the unreacted 2-
aminobenzothiazole. Te fltrate was collected and the water
removed under vacuum. Iodomethane (0.19 mL, 3.00 mmol)
and 4 mL ethanol were each added to the residue and the
slurry was stirred for 16 h afer which ethanol was removed
2.2.4. 2-Bromo-6-(methylthio)aniline (L4). Yield 22%, light
yellow oil. Anal. Cald. for C H BrNS (Mr 218.1): C, 38.55; H,
7
8
3.70; N, 6.42; S, 14.70. Found: C, 39.54; H, 3.71; N, 6.36; S,
14.76%. FTIR (cm–1): 3455, 3354 Vasy/sym(NH ), 1611 ꢀ(NH ),
2
2
1290 v(C–N). ꢁmax (DMF, nm (ꢂ, M–1 cm–1): 285sh, 317 (9975).
2.2.5. Synthesis of [Cu(L1)Cl2]. 2-Methoxy-6-(methylthio)an-
iline, L1 (0.14 g, 0.80 mmol) in 3 mL ethanol was stirred
at room temperature and ethanol solution of CuCl .2H O
2
2
(0.14 g, 0.80 mmol) was added dropwise. Te mixture was
stirred for 3 h. Te deep brown precipitate was obtained
by fltration, washed with ethanol, and dried (0.08 g, 32%),
mp >200∘C. Anal. Calc. for C H Cl CuNOS (Mr 303.7): C,
8
11
2
31.64; H, 3.65; N, 4.61; S, 10.56. Found: C, 31.72; H, 4.15; N,
4.50; S, 10.33%. FTIR-ATR (cm−1): 3251, 3171 Vasy/sym(NH ),
2
1585 ꢀ(NH ), 1245 v(C–N), 414 v(Cu–N), 314 v(Cu–Cl), 280
2
v(Cu–S). UV-Vis ꢁ
(DMF, nm (ꢂ, M–1 cm–1): 275sh, 315
(5805), 335 (3664), m4a5x4 (3400). ꢃ (BM) = 1.8. Λ (Ω cm2
–1
ef
mol–1) = 33.4.