ORIGINAL ARTICLES
ethoxy ethanol (3.8 g, 0.03 mol) were added to N,N-dimethylformamide
ployed for isolation of impurities. The mobile phase consisted of (A)
0.1 M ammonium acetate solution and (B) acetonitrile. Flow rate was set
at 20 ml/min and UV detection was carried out at 225 nm. The gradient
program was as follows, time(min)/A(v/v) : B(v/v); T0.01/98 : 2, T20.0/90 : 10,
(25 ml) at room temperature. The reaction mass was heated to ꢃ100 ꢂC
and stirred for 8 h while monitoring the process by HPLC. There after, the
reaction mass was cooled to room temperature and poured into water
(200 ml). The product was extracted with ethyl acetate (2 ꢁ 75 ml) and the
organic extract was washed with water (2 ꢁ 80 ml). The organic layer was
concentrated completely under the reduced pressure at 50–55 ꢂC. The resi-
due contains ꢃ5% of this impurity which was isolated by preparative
HPLC.
T
35.0/80 : 20, T50.0/70 : 30, T60.0/60 : 40, T75.0/50 : 50, T90.0/25 : 75.
3.4. LC-MS/MS analysis
LC-MS/MS analysis was carried out using a Perkin Elmer triple quadru-
pole mass spectrometer (API 2000, PE SCIEX) coupled with a Shimadzu
HPLC equipped with SPD 10 AT VP UV-VIS detector and LC 10 AT VP
pumps. Analyst software was used for data acquisition and data processing.
The turbo ion spray voltage was maintained at 5.5 kv and temperature was
set at 375 ꢂC. The auxillary gas and curtain gas used was high pure nitro-
gen. Zero air was used as nebulizer gas. LC-MS spectra were acquired from
m/z 100–1000 in 0.1 amu steps with 2.0 s dwell time. The analysis was
carried out using Hypersil BDS C18, 150 ꢁ 4.6 mm column with 5 mm par-
ticle dia. Mobile phase consisted of (A) 0.01 M ammonium acetate and (B)
1 : 1 mixture of acetonitrile and methanol. UV detection was carried out at
225 nm and flow rate was kept at 1.5 ml/min. Data acquisition time was
50 min. The gradient program was as follows, Time (min)/ A(v/v) : B(v/v);
T0.01/75 : 25, T5.0/75 : 25, T35.0/50 : 50, T40.0/15 : 85, T50.0/15 : 85.
3.1.3. Impurity III, quetiapine carboxylate
Impurity III was isolated from mother liquors obtained during the prepara-
tion of compound 1.
3.1.4. Synthesis of impurity IV, N-ethyl-11-piperazinyl thiazepine
11-Piperazinyl thiazepine dihydrochloride (5 g, 0.0136 mol) reacted with
ethyl bromide (2.4 g, 0.020 mol) in the presence of sodium carbonate
(8.7 g, 0.0821 mol) and dimethylformamide (15 ml) at room temperature
for 2 h and the reaction was monitored by TLC. The reaction mass was
poured into water (200 ml) and extracted with ethylacetate (2 ꢁ 80 ml).
The organic layer was washed with water (2 ꢁ 50 ml) and concentrated
completely under reduced pressure at 50–55 ꢂC. The resulting residue was
dissolved in ethanol (40 ml) and treated with ethanolic HCl (10 ml, 20%
w/w) at pH 2.0. Isopropylether (20 ml) was added dropwise to isolate the
product. The product was stirred at room temperature for 1 h. The product
was filtered, washed with isopropylether (5.0 ml) and dried at 55–60 ꢂC to
yield 4.2 g of title compound.
3.5. NMR Spectroscopy
The 1H NMR, 13C NMR (proton decoupled) and DEPT spectra were re-
corded on Bruker 300 MHz spectrometer using DMSO-d6 as solvent and
tetramethylsilane (TMS) as internal standard.
3.6. Mass spectrometry
3.1.5. Impurity V, synthesis of ethyl quetiapine
Mass spectra were recorded on a Perkin Elmer PE SCIEX-API 2000 mass
spectrometer equipped with a Turboionspray interface at 375 ꢂC. Detection
of ions was performed in electrospray ionisation, positive ion mode.
Ethyl bromide (5.3 g, 0.0486 mol) was added dropwise to a mixture of
quetiapine fumarate (10 g) and sodium hydroxide (2.9 g, 0.073 mol) in
dimethylformamide (50 ml) at 15–17 ꢂC. The reaction mass was stirred
at 15–20 ꢂC for 8 h and the reaction mass was monitored by HPLC until
completion. Water (250 ml) was added to the reaction mass and extracted
with methylene chloride (2 ꢁ 100 ml). The organic layer was washed
with water (2 ꢁ 50 ml) and concentrated under reduced pressure. The re-
sidue was dissolved in ethanol (50 ml) and ethanolic HCl (20 ml, ꢃ20%
w/w) was added dropwise. The precipitated product was stirred for 1 h.
The product was filtered, washed with ethanol (5 ml) and dried at 40–
45 ꢂC to yield 6 g of product containing ꢃ91% of the desired product by
HPLC.
3.7. FT-IR Spectroscopy
FT-IR spectra were recorded as KBr pellet on a Perkin-Elmer instrument
model –– spectrum one.
3.8. Isolation of impurities by preparative HPLC
All impurities were isolated by preparative HPLC from crude samples by
using the conditions described above. Fractions collected were analyzed by
analytical HPLC as per the conditions mentioned above. Fractions of
>90% were pooled together, concentrated on Rotavapor to remove acetoni-
trile. The concentrated fractions were passed through the preparative col-
umn using water:acetonitrile (50 : 50) as mobile phase to remove the buf-
fers used for isolation. Again the eluate was concentrated in a Rotavapor
to remove acetonitrile. The aqueous solutions were lyophilized using freeze
dryer (Virtis advantage 2XL).
3.1.6. Impurity VI, synthesis of bis(dibenzo)thiazepine
11-Chloro-dibenzo[b,f ][1,4]thiazepine (20.5 g, 0.0835 mol) was added in
small portions to a stirred mixture of piperazine (14.4 g, 0.167 mol) in to-
luene (160 ml) at ꢃ50 ꢂC. The reaction was heated to ꢃ100 ꢂC, stirred for
4 h and the reaction was monitored by HPLC until disappearance of start-
ing material. The reaction mass was cooled to ꢃ20 ꢂC and filtered the
salts. The toluene filtrate was washed with water (4 ꢁ 100 ml). The organic
layer was concentrated completely under reduced pressure at 50–55 ꢂC.
The residue contains ꢃ12% of bis(dibenzo)thiazepine impurity which was
isolated by preparative HPLC.
Acknowledgements: The authors gratefully acknowledge the management
of Aurobindo Pharma Limited, for allowing us to carry out the present
work. The authors are also thankful to the colleagues of Analytical Re-
search Department (ARD) and Chemical Research Department (CRD) for
their co-operation.
3.2. High performance liquid chromatography
A Waters Alliance 2695 separation module equipped with 2996 photodiode
array detector with Empower pro data handling system [Waters corpora-
tion, MILFORD, MA 01757, USA] was used. The analysis was carried
out on YMC Pack-C8, 150 mm long, 4.6 mm i.d., 5 mm particle diameter
column. Mobile phase A was a mixture of phosphate buffer and acetonitrile
in the ratio of 90 : 10 v/v, adjusted to pH 6.7 ꢅ 0.05 with dilute orthopho-
sphoric acid solution (phosphate buffer was prepared by dissolving 0.77 g
of disodium hydrogen orthophosphate (anhydrous) and 0.57 g of potassium
dihydrogen orthophosphate in 1000 ml of water). Mobile phase B was
acetonitrile. UV detection was carried out at 225 nm and flow rate was
kept at 1.5 ml/min. Column oven temperature was set at 45 ꢂC and data
acquired for 45 min. Pump mode was gradient and the program was as
follows, Time (min)/A(v/v) : B(v/v); T0.01/80 : 20, T15.0/70 : 30, T25.0/60 : 40,
T30.0/35 : 65, T35.0/30 : 70, T45.0/25 : 75, T50.0/80 : 20, T60.0/80 : 20.
References
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3.3. Preparative liquid chromatography
A Shimadzu LC-8A preparative liquid chromatograph equipped with SPD-
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