Bromineless bromine as an efficient desulfurizing agent for the preparation of cyanamides and 2-aminothiazoles from dithiocarbamate salts

Article abstract of DOI:10.1080/00397911003642658

In a one-pot procedure, bromineless brominating reagent 1,1'-(ethane-1,2-diyl)dipyridinium bistribromide (EDPBT) has been used as a desulfurizing agent in the preparation of organic cyanamides and substituted thiazoles starting from dithiocarbamic acid salts. In this approach, alkyl/aryl isothiocyantes were first obtained by the desulfurization of dithiocarbamic acid salts with EDPBT. The in situ-generated isothiocyanates reacts with an aqueous ammonia, forming alkyl or aryl thioureas, which on subsequent oxidative desulfurization with EDPBT led to the formation of corresponding cyanamides in good yields. Alternatively, an efficient one-pot synthesis of substituted thiazoles has been achieved by the condensation of the in situ-generated 1-aryl thioureas with the in situ-generated -bromoketones from ketones, again using EDPBT. The reagent EDPBT can be easily prepared from the readily available reagents. Desulfurizing ability dominates over its brominating ability for substrates amenable to bromination.

Full text of DOI:10.1080/00397911003642658

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Bromineless Bromine as an Efficient
Desulfurizing Agent for the Preparation
of Cyanamides and 2-Aminothiazoles
from Dithiocarbamate Salts
Ramesh Yella a , Veerababurao Kavala a & Bhisma K. Patel a
a Department of Chemistry, Indian Institute of Technology Guwahati,
Guwahati, Assam, India
Version of record first published: 25 Feb 2011.
To cite this article: Ramesh Yella, Veerababurao Kavala & Bhisma K. Patel (2011): Bromineless
Bromine as an Efficient Desulfurizing Agent for the Preparation of Cyanamides and 2-Aminothiazoles
from Dithiocarbamate Salts, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 41:6, 792-805
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Synthetic Communications1, 41: 792–805, 2011
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911003642658
BROMINELESS BROMINE AS AN EFFICIENT
DESULFURIZING AGENT FOR THE PREPARATION OF
CYANAMIDES AND 2-AMINOTHIAZOLES FROM
DITHIOCARBAMATE SALTS
Ramesh Yella, Veerababurao Kavala, and Bhisma K. Patel
Department of Chemistry, Indian Institute of Technology Guwahati,
Guwahati, Assam, India
GRAPHICAL ABSTRACT
Abstract In a one-pot procedure, bromineless brominating reagent 1,10-(ethane-1,2-diyl)
dipyridinium bistribromide (EDPBT) has been used as a desulfurizing agent in the
preparation of organic cyanamides and substituted thiazoles starting from dithiocarbamic
acid salts. In this approach, alkyl/aryl isothiocyantes were first obtained by the desulfuriza-
tion of dithiocarbamic acid salts with EDPBT. The in situ–generated isothiocyanates reacts
with an aqueous ammonia, forming alkyl or aryl thioureas, which on subsequent oxidative
desulfurization with EDPBT led to the formation of corresponding cyanamides in good
yields. Alternatively, an efficient one-pot synthesis of substituted thiazoles has been
achieved by the condensation of the in situ–generated 1-aryl thioureas with the in situ–
generated a-bromoketones from ketones, again using EDPBT. The reagent EDPBT can
be easily prepared from the readily available reagents. Desulfurizing ability dominates over
its brominating ability for substrates amenable to bromination.
Keywords Cyanamide; desulfurizing agent; dithiocarbamate; ditribromide; thiazole
INTRODUCTION
Recently we have taken advantage of the desulfurizing ability of a hypervalent
iodine reagent, diacetoxyiodobenzene (DIB), for the oxidative N-acylation of
Received August 7, 2009.
Address correspondence to Bhisma K. Patel, Department of Chemistry, Indian Institute of
Technology Guwahati, Guwahati 781039, Assam, India. E-mail: patel@iitg.ernet.in
792

ONE-POT PREPARATION OF CYANAMIDE AND THIAZOLE
793
1,3-disubstituted thiourea,[1] in the preparation of isothiocyanates and for the
construction of heterocycles[2a] and cyanamides,[2b] from dithiocarbamate salts.
However, methods using a hypervalent iodine reagent are efficient but not economi-
cally viable when applied to large-scale reactions. In yet another related work, we
have demonstrated that the hypervalency of iodine is not really essential, particularly
for the transformation of dithiocarbamate to isothiocyanate[2a] and cyanamide,[2b]
and at times molecular iodine[2c,d] and bromine equivalent 1,10-(ethane-1,2-diyl)
dipyridinium bistribromide (EDPBT)[3a,b] were found to be equally efficient.[3c]
The advantage of the reagent EDPBT over conventional organic ammonium tribro-
mides[4] has been reflected by a series of interesting organic transformations carried
out in the past few years.[5a] Very recently, we have revealed its desulfurizing ability
in the preparation of isothiocyanate from the corresponding dithiocarbamate salt.[3c]
In this article, we demonstrate its utility in the construction of yet another useful
organic functional group, cyanamide, and extending it further to an efficient one-pot
synthesis of substituted thiazoles by using EDPBT as a key reagent.
RESULTS AND DISCUSSION
In this strategy, alkyl=aryl thioureas were prepared directly from dithiocraba-
mate salts and EDPBT in an aqueous ammonia (Scheme 1). The use of aqueous
ammonia serves a dual purpose as a base in the first step to generate isothiocyanate
from dithiocarbamate salt and as a nucleophile to form alkyl=aryl thioureas from the
in situ–generated isothiocyanates.
However, when EDPBT was used instead of hypervalent iodine, ammonia was
not that effective as a base in the second step and had to be replaced with a relatively
stronger base, triethylamine. This in part may be due to the lesser thiophilicity of
bromine as compared to the hypervalent iodine, DIB. Further, the relative acidity
of the NH proton of dithiocarbamate salt is greater compared to NH protons of
alkyl=aryl thiourea; hence, a stronger base is required for the latter. After completion
of the reaction, precipitated spent reagent was filtered and washed with acetonitrile.
Acetonitrile was removed and mixed with water (10 mL), and the product extracted
with ethylacetate and purified over a short column of silica gel. The aqueous layer
Scheme 1. Proposed mechanism for the formation of cyanamide with in situ–generated isothiocyanate and
alkyl=aryl thiourea.

794
R. YELLA, V. KAVALA, AND B. K. PATEL
containing the spent reagent 1,10-(ethane-1,2-diyl)dipyridinium dibromide
(EDPDB), along with the Et3N ꢀ HBr and NH4Br, were combined with the precipi-
tated spent reagent obtained by filtration, and the ditribromide reagent (EDPBT)
was regenerated using appropriate amounts of KBr and Oxone.[3] By employing this
one-pot strategy, several aromatic cyanamides (1a–10a) could be successfully pre-
pared from their dithiocarbamate salts (1–10) (Table 1). Although the overall iso-
lated yields look moderate, considering the multistep process leading to the
products, they should be considered good to excellent.
As can be seen from Table 1, this strategy was successful even when an
electron-withdrawing substituent such as the -NO2 group (Table 1, entry 5) was
attached to the aromatic ring. Substrates amenable to ring bromination (7, 8) and
a-bromination (9) gave their corresponding cyanamides without undergoing bro-
mination. This method also worked well for the preparation of hindered and
disubstituted substrate (10a) starting from corresponding dithiocarbamate (10).
Cyanamides of aliphatic amines (11 and 12) and benzylic amines (13 and 14) were
obtained from their dithiocarbamate salts in one pot.
Dithiocarbamate salts derived from chiral amines (15 and 16) yielded their cya-
namides 15a and 16a respectively in excellent yields with retention of optical activity
as shown in Scheme 2. Surprisingly, the magnitudes of the specific rotation of both
amines and cyanamides were found to be identical. Finally, cyanamide of homover-
atrylamine (17a) was obtained successfully in good yield from its dithiocarbamate
salt (17).
After successfully preparing a series of cyanamides, we thought of exploiting
the in situ–generated 1-arylthiourea for the construction of substituted thiazoles
by treating it with the in situ–generated a-haloketones. Thiazole skeleton is present
in several naturally occurring compounds such as peniciline and vitamin B1 (thia-
min). Of late, thiazole derivatives have attracted interest because of their biological
activities. Among these, the 2-aminothiazole ring system is a useful structural motif
in medicinal chemistry, having application in drug development for the treatment of
allergies,[8] hypertension,[9] inflammation,[10] schizophrenia,[11] bacterial infec-
tions,[12] and HIV.[13] These are also known to be ligands of estrogen receptors,[14]
adenosine receptor antagonists,[15] and neuropeptide Y5 receptor.[16]
The most commonly adopted method for the synthesis of 2-amino thiazoles is
the reaction of thiourea or thioamide with a-bromo ketones.[17] These reactions have
been further improved using catalysts such as ammonium-I2-molybdophosphate
(AMP)[18] and b-cyclodextrin in water,[19] conventional heating, and the use of
microwaves in an alcoholic media[20] at ambient temperature or in an aqueous
medium.[21]
Although some of the methods for preparation of thiazoles are effective, the
drawback associated with most of the procedures reported is separate preparation
of precursors, namely, a-bromoketone and thiourea. In our strategy, both these pre-
cursors can be synthesized from readily available substrates using a single recyclable
reagent, EDPBT, which in turn can be prepared from commercially available start-
ing materials. The reaction at ambient temperature and the use of aqueous medium
associated with the one-pot procedure adds to the synthetic potential of this method.
When phenyldithiocarbamate salt (1) was treated with EDPBT in the presence
of aqueous ammonia, 1-phenylthiourea (18) was obtained directly. While EDPBT

ONE-POT PREPARATION OF CYANAMIDE AND THIAZOLE
795
Table 1. Preparation of cyanamides from dithiocarbamates and EDPBTa
Substrate
Productb
Yield (%)c[Ref.]
74[2b]
65
68[2b]
70[2b]
63[2b]
60[2b]
70[2b]
72[6a]
75[2b]
63
60[2b]
(Continued )

796
R. YELLA, V. KAVALA, AND B. K. PATEL
Table 1. Continued
Substrate
Productb
Yield (%)c[Ref.]
72[2b]
73[2b]
74[2b]
69[6b]
69[7]
65
aReactions were monitored by TLC.
bConfirmed by IR, 1H NMR, and 13C NMR.
cIsolated yield.
acts as a desulfurizing agent,[3c] the aqueous ammonia acts as a base in the forma-
tion of the intermediate isothiocyanate and as a nucleophile in the formation of
1-phenylthiourea (Scheme 1). Since EDPBT used here is 0.5 equivalent (being a ditri-
bromide reagent, the bromine content is 1 equivalent), the reaction stops at the thio-
urea stage and does not lead to cyanamide. In another flask, a-bromoketone was
prepared using EDPBT according to our recently reported procedure,[3a,b] which
was then added to the flask after getting rid of the excess ammonia. The thiourea
(being an S-based nucleophile particularly toward softer electrophiles[5d–f]) attacks
the bromomethyl carbon, forming S-alkylated product (X). Intramolecular attack
of the NH2 group of the intermediate on the carbonyl group would give the inter-
mediate tertiary alcohol (Y), which undergoes acid-catalyzed E1 elimination in
water, as has been proved by us.[5f] Thus the removal of the excess ammonia is essen-
tial in the previous step to facilitate an acid-mediated E1 process.
Starting from 1-phenyl thiourea (18), several thiazoles derivatives (18a–c) were
prepared successfully as shown in Table 1. The presence of a thiazole skeleton has
been confirmed by x-ray crystallography, as shown in Fig. 1.

ONE-POT PREPARATION OF CYANAMIDE AND THIAZOLE
797
Table 2. One-pot preparation of 2-aminothiazolesa
a-Haloketone=alkyl
halide
Yield
(%)c[Ref.]
Thiourea
Productb
72[21a]
76[21a]
73
55
55
60
61[21b]
69[21c]
65
aReactions were monitored by TLC.
bConfirmed by IR, 1H NMR, and 13C NMR.
cIsolated yield.

798
R. YELLA, V. KAVALA, AND B. K. PATEL
Scheme 2. Specific rotations of chiral amines and their cyanamides.
Scheme 3. Proposed mechanism for the formation of thiazole.
Unsymmetrical ketones such as ethylmethyl ketone (d) gave two different pro-
ducts (18d and 18e) depending on the reaction condition. This is because when bro-
mination is allowed to continue for a longer period of time, dibrominated product
(d) is obtained, giving the major thiazole product (18d). However, kinetically con-
trolled bromination of ethylmethylketone gave the brominated product (e) leading
to the thiazole (18e). Similarly, the thermodynamically stable brominated product
(f)[22] of ethylacetoacetate gave exclusively thiazole derivative (18f). This type of iso-
merization or formation of thermodynamic stable brominated product is well docu-
mented in the literature.[22] Cyclic diketone gave exclusively the brominated product
flanked by two carbonyl groups (i.e., kinetically stable product and the enol
form),[23] which led to the formation of product (18g). Other in situ–generated
thioureas such as 19 and 20 reacted with phenacyl bromide (a), giving thiazole deri-
vatives 19a and 20a respectively in modest yield. The presence of the thiazole
Figure 1. ORTEP view of 18c with the atomic numbering scheme.

ONE-POT PREPARATION OF CYANAMIDE AND THIAZOLE
799
Figure 2. ORTEP view of 20a with the atomic numbering scheme.
skeleton and the structure of 20a has been further confirmed by x-ray crystallogra-
phy as shown in Fig. 2.
CONCLUSION
In summary, bromineless brominating reagent has been used as a thiophilic
reagent for the preparation of alkyl and aryl cyanamides from their dithio-
carbamates in one pot. Subsequently, 2-amino thiazoles were synthesized by the
condensation of the in situ–generated bromoketones and thioureas from their dithio-
carbamates. Advantages of this protocol include ease of preparation of this reagent,
facile isolation of products, and recyclability of the spent reagent, which make these
methods environmentally acceptable. Although at first glance the product yields
seem to be moderate, because these are actually three-step reactions in one pot,
the yield can be considered very good.
EXPERIMENTAL
All the reagents were of commercial grade and purified according to the estab-
lished procedures. Organic extracts were dried over anhydrous sodium sulfate. Sol-
vents were removed in a rotary evaporator under reduced pressure. Silica gel (60–120
mesh) was used for the column chromatography. Reactions were monitored by thin
layer chromatography (TLC) on silica gel 60 F254 (0.25 mm). NMR spectra were
recorded in CDCl3 or dimethyl sulfoxide (DMSO-d6) with tetramethylsilane
(TMS) as the internal standard for 1H NMR (400 MHz) and in CDCl3 or DMSO-d6
solvent as the internal standard for 13C NMR (100 MHz). Mass spectra were
recorded using Waters MS system, Q-TOF premier, and data analyzed using Mass
Lynx 4.1. Specific rotations were recorded on a Perkin-Elmer model 343 polarimeter.
Elemental analysis was performed with a Perkin-Elmer 2400 elemental analyzer.
Melting points were recorded on a Buchi B-545 melting-point apparatus and are
uncorrected. Infrared (IR) spectra were recorded in KBr or neat on a Nicolet Impact
410 spectrophotometer.
Crystallographic Description
Crystal data were collected with Bruker Smart Apex-II CCD diffractometer
˚
using graphite monochromated MoKa radiation (k ¼ 0.71073 A) at 298 K. Cell

800
R. YELLA, V. KAVALA, AND B. K. PATEL
parameters were retrieved using SMART[24] software and refined with SAINT[24] on
all observed reflections. Data reduction was performed with the SAINT software
and corrected for Lorentz and polarization effects. Absorption corrections were
applied with the program SADABS.[25] The structure was solved by direct methods
implemented in the SHELX-97[26] program and refined by full-matrix least-squares
methods on F2. All nonhydrogen atomic positions were located in difference Fourier
maps and refined anisotropically. The hydrogen atoms were placed in their geome-
trically generated positions. Light yellow crystals were isolated in rectangular shape
from ethylacetate and hexane at room temperature.
General Experimental Procedure for the Preparation of Cyanamide
Ice-cooled aqueous ammonia (25%, 2 mL) was added to a stirred, ice-cold sol-
ution of dithiocarbamate salt 1 (0.542 g, 2 mmol) in acetonitrile (8 mL). EDPBT
(0.666 g, 1 mmol) was added in pinches over a period of 10 min. The reaction mixture
was stirred at room temperature for 30–40 min, and complete conversion to corre-
sponding 1-phenyl thiourea was observed as judged from thin-layer chromatography
(TLC). Excess ammonia was removed by heating the reaction mixture on a
hot-water bath (60 ꢁC) for 10 min. Triethylamine (1.1 mL, 8 mmol) was added fol-
lowed by pinchwise addition of EDPBT (0.666 g, 1 mmol) at room temperature over
a period of 10 min. The conversion of intermediate 1-phenylthiourea to correspond-
ing cyanamide (1a) was observed within 10 min of complete addition of EDPBT.
After completion of the reaction, some of the spent reagent was filtered and washed
with acetonitrile. Acetonitrile was evaporated and mixed with water (10 mL), and the
product was extracted with ethylacetate (2 ꢂ 10 mL), which was then dried over
anhydrous Na2SO4, concentrated under reduced pressure, and purified over a short
column of silica gel (hexane–ethylacetate, 8:2) to give 175 mg (74% yield) of 1b.[2b]
General Experimental Procedure for the Preparation of Thiazole
Ice-cooled aqueous ammonia (25%, 2 mL) was added to a stirred, ice-cold sus-
pension of dithiocarbamate 1 (540 mg, 2 mmol) in water (6 mL). EDPBT (666 mg,
1 mmol) was added in CH3CN (4 mL) dropwise over a period of 15 min. After
complete addition of EDPBT, the reaction mixture was allowed to stirred at room
temperature for 30–40 min, and complete conversion to corresponding 1-phenyl
thiourea was observed as judged from TLC. Excess ammonia was removed by a
rotary evaporator, during which CH3CN also was evaporated, leaving behind some
in an aqueous layer.
Acetophenone (0.264 g, 2.2 mmol) was added to a solution of EDPBT (666 mg,
1 mmol) in acetonitrile (4 mL), and stirring continued for 45 min. During this period,
the bromination of acetophenone (a) was complete as judged from the disappearance
of the orange color of EDPBT. The supernatant containing the bromoketone was
then directly filtered into a solution of the in situ–generated phenyl thiourea 18 in
water (obtained previously) and stirred at room temperature. The reaction was com-
pleted within 1 h, as judged from TLC. After completion of the reaction, solvent
(CH3CN) was evaporated and extracted with ethyl acetate (2 ꢂ 20 mL). The ethyl
acetate layer was washed with a saturated solution of NaHCO3 (5 mL), dried over

ONE-POT PREPARATION OF CYANAMIDE AND THIAZOLE
801
anhydrous Na2SO4, concentrated under reduced pressure, and purified over a
silica-gel column (hexane–EtOAc, 9:1:) to give 182 mg (74% yield) of 18a.[21a]
Spectral Data
The new compounds were fully characterized by IR, NMR (1H, 13C), mass,
and elemental analysis.
2-Fluoro-phenyl cyanamide (2a). White solid; mp 95 ꢁC; 1H NMR
(400 MHz, CDCl3): 6.87 (brs, 1H), 6.90–7.45 (m, 4H). 13C NMR (100 MHz, CDCl3):
110.9, 115.7, 115.9, 116.8, 124.1, 124.1 125.09, 125.12, 125.6, 125.8, 150.1, 152.5. IR
(KBr, cmꢃ1): 3068, 2037, 1606, 1587, 1495, 1265, 1212, 1104, 941, 808, 752.
C7H5FN2 (136.13) calcd.: C, 61.76; H, 3.70; N, 20.58. Found: C, 61.80; H, 3.73;
N, 20.53.
2-Iodo-4-methyl-phenyl cyanamide (10a). White solid; mp 144 ꢁC; 1H
NMR (400 MHz, CDCl3): 2.29 (s, 3H), 6.17 (brs, 1H), 7.17 (dd, 2H, J ¼ 8.2 Hz),
7.56 (s, 1H). 13C NMR (100 MHz, CDCl3): 20.4, 84.2, 110.7, 115.4, 130.9, 135.4,
139.6. IR (KBr, cmꢃ1): 3229, 2919, 2217, 1603, 1573, 1502, 1420, 1383, 1283,
1032, 866, 805. C8H7N2 (258.06) calcd.: C, 37.23; H, 2.73; N, 10.86. Found: C.
37.27; H, 2.75; N, 10.84.
3,4-Dimethoxyphenylethyl cyanamide (17a). Gummy; 1H NMR
(400 MHz, CDCl3): 2.84 (t, 2H, J ¼ 7.2 Hz), 3.28 (q, 2H, J ¼ 7.2 Hz), 3.83 (s, 3H),
3.84 (s, 3H), 4.37 (brs, 1H), 6.76 (m, 3H). 13C NMR (100 MHz, CDCl3): 35.5,
47.5, 55.92, 55.95, 111.4, 111.9, 116.5, 120.9, 130.0, 147.8, 148.9. IR (KBr, cmꢃ1):
3274, 2937, 2219, 1592, 1517, 1464, 1262, 1236, 1156, 1142, 1026, 913.
C11H14N2O2(206.24) calcd.: C, 64.06; H, 6.84; N, 13.58. Found: C, 64.12; H, 6.80;
N, 13.54.
4-(4-Bromophenyl)-n-phenylthiazol-2-amine (18c). White Solid; mp
156–158 ꢁC; 1H NMR (400 MHz, CDCl3): 6.81 (s, 1H), 7.08 (m, 1H), 7.36 (m,
4H), 7.51 (d, 2H, J ¼ 8.4 Hz), 7.71 (d, 2H, J ¼ 8.4 Hz). 13C NMR (100 MHz, CDCl3):
102.4, 118.6, 121.9, 123.4, 127.9, 129.7, 131.9, 133.6, 140.4, 150.4, 165.2. IR (KBr,
cmꢃ1): 3382, 3113, 1601, 1594, 1556, 1497, 1471, 1458, 1406, 1397, 1341, 1311,
1270, 1194, 1103, 1070, 1052, 1007, 914, 849, 829, 746, 726. HRMS (ESI): MHþ
found 330.9901; C15H11BrN2S requires 330.9905.
1
[4-(1-Bromo-ethyl)-thiazol-2-yl]-phenyl-amine (18d). Gummy; H NMR
(400 MHz, CDCl3): 1.53 (s, 3H), 4.83 (q, 1H, J ¼ 6.4 Hz), 6.40 (s, 1H), 7.05 (m,
1H), 7.24–7.34 (m, 4H). 13C NMR (100 MHz, CDCl3): 22.4, 66.3, 101.5, 118.6,
123.4, 129.7, 140.4, 156.2, 166.1. IR (KBr, cmꢃ1): 3274, 3130, 2975, 1602, 1542,
1498, 1459, 1312, 1260, 1139, 1095, 1027, 964, 885, 749. C11H11BrN2S (283.19)
calcd.: C, 46.65; H, 3.92; N, 9.89; S, 11.32. Found: C, 46.69; H, 3.88; N, 9.81; S,
11.21.
4,5-Dimethyl-n-phenylthiazol-2-amine
(18e). Yellow
solid;
mp
1
112–114 ꢁC; H NMR (400 MHz, CDCl3): 2.18 (s, 3H), 2.32 (s, 3H), 7.02 (t, 1H,
J ¼ 6.8 Hz), 7.25–7.34 (m, 4H). 13C NMR (100 MHz, CDCl3): 11.2, 14.7, 114.3,
118.3, 122.6, 129.5, 141.1, 142.9, 161.8. IR (KBr, cmꢃ1): 3241, 3194, 3138, 3068,

802
R. YELLA, V. KAVALA, AND B. K. PATEL
2916, 1605, 1569, 1499, 1458, 1424, 1376, 1328, 1297, 1222, 1195, 991, 874, 846, 746,
713, 685. C11H12N2S (204.29) calcd.: C, 64.67; H, 5.92; N, 13.71; S, 15.70. Found: C,
64.73; H, 5.96; N, 13.63; S, 15.73.
Ethyl-2-(2-(phenylamino)thiazol-4-yl)acetate (18f). Gummy; 1H NMR
(400 MHz, CDCl3): 1.26 (t, 3H, J ¼ 7.2 Hz), 3.64 (s, 2H), 4.17 (q, 2H, J ¼ 7.2 Hz),
6.44 (s, 1H), 7.04 (m, 1H), 7.79–7.32 (m, 4H). 13C NMR (100 MHz, CDCl3): 14.3,
37.4, 61.2, 104.6, 118.6, 123.2, 129.6, 140.5, 144.7, 165.4, 170.7. IR (KBr, cmꢃ1):
3337, 3064, 2981, 1731, 1603, 1526, 1497, 1459, 1445, 1370, 1311, 1246, 1178,
1030, 994, 939, 851, 751. C13H14N2O2S (262.33): calcd. C, 59.52; H, 5.38; N,
10.68; S, 12.22. Found: C, 59.48; H, 6.40; N, 10.54; S, 12.34.
4-Bromo-phenyl-(4-phenyl-thiazol-2-yl)-amine (20a). White solid; mp
1
147–148 ꢁC; H NMR (400 MHz, CDCl3): 6.83, (s, 1H), 7.24 (d, 2H, J ¼ 8.0 Hz),
7.30 (m, 1H), 7.38 (m, 4H), 7.82 (d, 2H, J ¼ 8.0 Hz), 8.00 (brs, 1H). 13C NMR
(100 MHz, CDCl3): 102.3, 115.3, 119.8, 126.4, 128.2, 128.9, 132.4, 134.6, 139.6,
151.7, 164.3. IR (KBr, cmꢃ1): 3378, 3110, 2925, 1584, 1557, 1481, 1442, 1416, 1382,
1325, 1295, 1277, 1213, 1071, 1055, 1009, 915, 817, 770, 707. C15H11BrN2S (331.23)
calcd. : C, 54.39; H, 3.35; N, 8.46; S, 9.68. Found: C, 54.33; H, 3.39; N, 8.52; S, 9.78.
Crystallographic Description of 18c
Crystal dimension (mm): 0.48 ꢂ 0.28 ꢂ 0.19; C15H11BrN2S, Mr ¼ 331.23;
˚
˚
orthorhombic, space group Pbca; a ¼ 14.7566(9) A, b ¼ 5.7446(4) A, c ¼ 31.925(2)
A; a ¼ b ¼ c ¼ 90, V ¼ 2706.3(3) A ; Z ¼ 8; qcal ¼ 1.626 mg=m3; m (mmꢃ1) ¼ 3.178;
F (000) ¼ 1328; reflection collected=unique ¼ 41573=4573; refinement method ¼
full-matrix least-squares on F2; final R indices [I > 2rl] R1 ¼ 0.0431, wR2 ¼ 0.1312,
R indices (all data) R1 ¼ 0.1126; wR2 ¼ 0.1700, goodness of fit ¼ 0.975. CCDC No.
739036.
3
˚
˚
Crystallographic Description of 20a
Crystal dimension (mm): 0.45 ꢂ 0.28 ꢂ 0.23; C15H11BrN2S, Mr ¼ 331.23; tricli-
˚
˚
˚
nic, space group P-1; a ¼ 5.7775(5) A, b ¼ 14.8715(12) A, c ¼ 16.3074(12) A; a ¼
92.837(4), b ¼ 100.20, c ¼ 90.01; V ¼ 1377.23(19) (A3); Z ¼ 4; qcal ¼ 1.597 mg=m3;
m (mmꢃ1) ¼ 3.127; F (000) ¼ 664; reflection collected=unique ¼ 13454=4279; refine-
ment method ¼ full-matrix least-squares on F2; final
R
indices [I > 2rl]
R1 ¼ 0.1261, wR2 ¼ 0.3114, R indices (all data) R1 ¼ 0.1604; wR2 ¼ 0.3183, goodness
of fit ¼ 1.842. CCDC No. 739035.
ACKNOWLEDGMENTS
B. K. P. acknowledges support of this research from the Department of Science
and Technology (DST), New Delhi (SR=S1=OC-15=2006), and the Council of
Scientific and Industrial Research (CSIR), 01(2270)=08=EMR-II. R. Y. thanks the
CSIR for the fellowship. Thanks are due to CIF IIT Guwahati for NMR spectra
and DST Funding for Infrastructure in Science and Technology (FIST) for the
X-ray diffraction facility.

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803
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