Full text of DOI:10.1002/jhet.5570390225

Mar-Apr 2002
Synthesis of Some Benzimidazole-, Benzothiazole- and Pyridine-
Derived Chelating Agents
399
Jayakumar G. Gilbert [a], Anthony W. Addison* [a], Mallayan Palaniandavar [b],
and Raymond J. Butcher [c]
[a] Department of Chemistry, Drexel University, Philadelphia, PA 19104-2875, USA.
[b] Department of Chemistry, Bharathidasan University, Tiruchirapalli-620024, India.
[c] Department of Chemistry, Howard University, Washington, D.C. 20059, USA.
Received August 9, 2001
Procedures are given for the preparation of new linear bidentate, tetradentate and tripodal heptadentate
ligands incorporating benzimidazole, benzothiazole and pyridyl groups. The compounds were characterized
by their nmr, uv and mass spectra. The crystal and molecular structure is reported for a chiral benzothiazole
derived from camphoric acid.
J. Heterocyclic Chem., 39, 399 (2002).
in aqueous hydrochloric acid (Phillips' method [8]).
However, insolubility of the acid in aqueous HCl, or its
thermal decarboxylation are also determinative factors.
Introduction.
We have been interested in the synthesis and properties
of mulitidentate ligands containing benzimidazole, ben-
zothiazole and pyridine groups for some time [1-4]. As an
extension of our earlier work [5-7], we report the syntheses
of new heterocycles which are potential ligands for transi-
tion metals, Figure 1.
Discussion.
For benzimidazole synthesis in polyphosphoric acid,
N-phosphorylation usually ensues, and the resulting phos-
1
2
5 R = 2'-benzylimidazolyl
6 R = 2'-pyridyl
4
3
7 n = 2 8 n = 2 9 n = 2
10 R = 2'-pyridyl
11 R = 2'-benzylimidazolyl
Figure 1. The ligands synthesized.
Benzimidazoles and benzothiazoles are generally
preparable by condensation of the carboxylic acid or ester
with o-phenylenediamines or o-aminothiophenols in acid
medium [8-12], the choice of the medium determining the
reaction time. In polyphosphoric acid the reaction may be
achieved in a few hours at the higher accessible tempera-
tures, while it may take days for completion of the reaction
phoramide must be hydrolyzed with a strong base to obtain
the free azole; this was the case with 1 and 2.
Most of the pyridine thioethers 6-10 were synthesized in
very good yields in one step, by the addition of the appro-
priate thiol across the exocyclic double bond of 2-vinyl-
pyridine, Scheme 1. This addition, which follows
Markovnikov's rule, can be carried out either by refluxing

400
J. G. Gilbert, A. W. Addison, M. Palaniandavar and R. J. Butcher
Vol. 39
Table 1
Crystal Data for (1R,3S)-(+)-cis-1,3-Bis(benzothiazol-2'-yl)-
1,2,2-trimethylcyclopentane (3).
Formula
fw
C H N S
22 22 2 2
378.54
Cryst system
Cryst size, mm
Space group
a, Å
Orthorhombic
0.26 × 0.72 × 0.24
P2 2 2
1 1 1
6.664 (2)
19.028 (5)
30.229 (8)
3833 (2)
8
b, Å
c, Å
V, Å
3
Z
–3
D
, g cm
1.312
1600
0.286
calc
F(000)
–1
µ, mm
(Mo-Kα), Å
T, K
0.71073
293 (2)
0.0712; 0.1372
a
b
R;
R
w
2
2 1/2
R = Σ||F | − |F || / Σ|F |. R = [Σw(|F | − |F |) / Σw(F ) ]
.
o
c
o
w
o
c
o
confirmed by X-ray analysis (Table 1). This crystal struc-
ture of 3 (with atomic numbering scheme) is shown in
Figure 2, while selected bond lengths and bond angles are
given in Table 2. This bis-benzothiazole has four each of
two inequivalent molecules in the asymmetric unit cell,
one of these two molecule types being disordered with
respect to the 4,5-positions (C16, C17) of the cyclopentane
moiety. In all the molecules, the benzothiazole groups
flank the putative camphoryl unit on each side. Due to the
configuration of the cyclopentane ring, the benzothiazole
General procedures followed in the synthesis of the ligands. Method a: ligands 1
and 3; method b: ligand 3; method c: ligands 4,5 and 11; method d: ligands 6 to 10.
Figure 2. ORTEP diagram of (1R,3S)-(+)-cis-1,3-bis(benzothiazol-2'-yl)-1,2,2-trimethylcyclopentane (3), showing atom labeling scheme.
the reactants in ethanol, or by simply stirring the liquid
reactants together in the absence of a solvent for a few
hours. The ligands 3, 4 and 11 were prepared by nucle-
ophilic displacement of the halide by the thiolates [13].
The chiral benzothiazole 3 is derived from (1R,3S)-(+)-
camphoric acid, and its structure was unambiguously
ring nitrogen atoms are oriented well away from one
another. Consequently, use of the compound as a ligand
for preparing mononuclear metal complexes is restricted.
However, 3 may be capable of acting as a bridging group;
such potentially binuclear nickel complexes are currently
under investigation. The average C-C bond length in the

Mar-Apr 2002
Some Benzimidazole-, Benzothiazole- and Pyridine- Derived Chelating Agents
401
Table 2
Selected Bond Distances and Angles for (1R,3S)-(+)-cis-1,3-Bis(benzothiazol-2'-yl)-1,2,2-trimethylcyclopentane (3)
Bond distances [Å]
S(1A)-C(11A)
1.744(11)
1.709(11)
1.270(12)
1.389(13)
1.394(15)
S(1B)-C(11B)
S(1B)-C(17B)
N(1B)-C(11B)
N(1B)-C(12B)
C(12B)-C(17B)
1.749(11)
1.712(11)
1.304(11)
1.383(13)
1.424(16)
S(1A)-C(17A)
N(lA)-C(11A)
N(lA)-C(12A)
C(12A)-C(17A)
Bond Angles [ ° ]
C(17A)-S(1A)-C(11A)
C(11A)-N(1A)-C(12A)
N(1A)-C(11A)-S(1A)
N(1A)-C(12A)-C(17A)
N(1A)-C(12A)-C(13A) 125.2(14)
89.4(6)
C(17B)-S(1B)-C(11B)
C(11B)-N(1B)-C(12B)
N(1B)-C(11B)-S(1B)
N(1B)-C(12B)-C(17B)
N(1B)-C(12B)-C(13B)
90.0(6)
111.2(11)
115.5(8)
114.5(11)
109.5(10)
115.9(8)
116.2(10)
126.8(14)
aromatic ring is 1.382 Å; the C(12B)-C(17B) bond devi-
ates the most from this, at 1.424(16) Å. Within a given
molecule, the C-N bond lengths of the two symmetry-
inequivalent benzothiazole units are not identical. For
example C(11A)-N(1A) and C(11B)-N(1B) bonds differ
by 0.113(12) Å. All the bond distances nonetheless agree
closely with previously reported values [14-16].
The CD spectrum of 3 shows a distinct positive Cotton
effect around 260 nm (Figure 3b), with two sharper nega-
tive bands between 230 and 240 nm. The sign appears
consistent with the (+)-designation of the reactant acid
being carried through to the product. Normalization of the
rotational strength in the spectrum with respect to the asso-
ciated absorption yields the optical (Kuhn) anistropy spec-
trum in Figure 3c. This shows that the greatest anisotropy
is associated with the transition(s) around 260-270 nm. In
the optical spectra of benzothiazoles, the longer-wave-
length transitions are assigned as n––>π* and the shorter-
wavelength ones as π––>π*, the demarcation being con-
sidered 270 nm [5-7]. As π––>π* transitions are normally
magnetic-dipole forbidden, but n––>π* ones magnetically
allowed, it is apparent that the absorption manifold around
265 nm is n––>π* rather than π––>π* in origin. We note
also, that the magnitude of the optical anisotropy and the
absence of any indication of a negative Cotton effect com-
ponent suggest that the two benzothiazoles respond with
the same sign for ∆ε, to their vicinal chiral carbons in the
molecule.
EXPERIMENTAL
2-Vinylpyridine, polyphosphoric acid (PPA), ethyl 4-methyl-
5-imidazole carboxylate, 2-picolyl chloride hydrochloride, 1,4-
butanedithiol, 1,2-bis(mercaptomethyl)benzene, 1,5-pen-
tanedithiol, 1,6-hexanedithiol, 1,2-diaminobenzene, α ',α '-
dichloro-o-xylene, 2-aminothiophenol, potassium hydroxide,
sodium hydroxide, sodium borohydride and sodium were from
Aldrich Chemical Co., Inc. Tris(2'-mercaptoethyl)amine [17],
2-(2'-mercaptoethyl)benzimidazole [18], tris(2'-chloroethyl)-
amine hydrochloride [19] and 2-(2'-pyridyl)-1,3-dichloropropane
Figure 3. Spectral of (1R,3S)-(+)-cis-1,3-bis(benzothiazol-2'-yl)-1,2,2-
trimethylcyclopentane (3) in methanol. (a) Electronic spectrum. (b) CD
Spectrum. (c) Kuhn anisotropy spectrum. Wavelength scale in nm,
-1 -1
while the ε and ∆ε axes are in units of M cm
.

402
J. G. Gilbert, A. W. Addison, M. Palaniandavar and R. J. Butcher
Vol. 39
[20] were prepared by published procedures. Elemental micro-
analyses were performed by Robertson Microanalytical
Laboratories (Madison, NJ) or by the Microanalytical Laboratory
of the University of Pennsylvania. All reactions involving thiols
were carried out under a nitrogen atmosphere. The compounds
1-5 and 11, which were obtained as solids were dried overnight in
a desiccator over sulfuric acid, while the compounds 6-10 were
Anal. Calcd. for C H N S: C, 61.4; H, 4.21; N, 19.5. Found:
11 9 3
C, 61.0; H, 4.17; N, 19.4.
(1R,3S)-(+)-cis-1,3-Bis(benzothiazol-2'-yl)-1,2,2-trimethyl-
cyclopentane (3).
To o-aminothiophenol (8.8 g, 70 mmol) in 30 ml of polyphos-
phoric acid at 130 °C was added 7.0 g (35 mmol) of (1R,3S)-(+)-
camphoric acid. The reaction mixture was stirred at 110-140 °C
for 5 hours and allowed to cool to ca. 70 °C. It was then poured
slowly into 500 ml of vigorously stirred ice-cold 4 M potassium
hydroxide solution. After the suspension had cooled, the product
was isolated by filtration, washed with water, recrystallised from
1
13
obtained as colorless oily liquids. The H nmr and C nmr spec-
tra were recorded on a Bruker AC250 spectrometer using CDCl
3
(deuteriochloroform) or DMSO-d (deuterio-dimethyl sulfoxide)
6
as solvent, with TMS (tetramethylsilane) as internal standard.
Infrared spectra were recorded on a Perkin-Elmer 1610 FT-IR.
Electronic spectra were obtained on a Perkin-Elmer Lambda-2
UV-visible spectrophotometer. Mass spectra are from a VG-
ZABHF high resolution double-focusing mass spectrometer
operating in the FAB mode and using 2-nitrobenzyl alcohol as the
sample matrix. Circular dichroism (CD) spectra were recorded
on an Aviv Associates 60DS spectrophotometer and the optical
rotation was measured in a Perkin Elmer 341 Digital Polarimeter.
acetonitrile (charcoal), and dried in vacuo over sulfuric acid to
1
give 4.7 g (12.5 mmol, 35%) of effloresced cream powder.
H
nmr (DMSO-d ): δ 0.43 (s, 3H, -CH ); 1.42 (s, 3H, -CH ); 1.58
6
3
3
(s, 3H, -CH ); 1.95-2.05 (m, 1H, -CH-); 2.32-2.48 (m, 1H, -CH-);
3
2.55-2.69 (m, 1H, -CH-); 2.96-3.09 (m, 1H, -CH-); 3.93 (t, J =
9.5 Hz, -CH-); 7.42.-7.53 (m, 4H, aro); 7.99-8.02 (m, 2H, aro);
13
8.08 (d, J = 7.5 Hz, 2H, aro). C nmr (DMSO-d ): δ 20.9, 22.1,
6
25.5, 26.2, 35.3, 48.6, 52.1, 54.8, 121.9, 122.3, 122.5, 124.8,
4-Methyl-5-(benzimidazol-2'-yl)imidazole (1).
124.9, 126.1, 134.1, 134.2, 152.5, 152.7, 175.1. FAB-MS m/z:
-1
481 [M+Na] (29%), 379 [M+H] (100%). IR (KBr): ν
cm
To 70 ml of polyphosphoric acid stirring at 100 °C was added
a powdered mixture of ethyl 4-methyl-5-imidazole carboxylate
(7.7 g, 50 mmol) and o-phenylenediamine (5.41 g, 50 mmol).
The temperature was slowly raised and kept at 175 °C for 7
hours. The green reaction mixture was cooled to 80 °C, and
poured slowly into 200 ml of vigorously stirred ice-cold concen-
trated sodium hydroxide solution. After stirring overnight, the
pale brown precipitate obtained was isolated by filtration and
recrystallized from methanol as colorless needles. Yield 6.9 g
max
3444 w and 3350 w (N-H stretching), 3073 m (C-H aromatic
stretching), 2930 m (C-H aliphatic stretching), 1605 s (C=C ring
stretching), 1456 and 1477 s (C=N ring stretching). UV
(methanol): 294 (3350), 283 (4950), 255 (20800), 220 (48900);
20
mp 115-116 °C. [α]
= + 9.4 (0.5, MeOH).
D
Anal. Calcd. for C H N S : C, 69.8; H, 5.86; N, 7.40; S,
22 22
2 2
16.9. Found, C, 69.3; H, 5.82; N, 7.41. When a hot butyronitrile
solution of 3 was allowed to cool and stand for 2 days, colourless
prisms suitable for X-ray diffraction were obtained.
1
(35 mmol, 70%). H nmr (DMSO-d ): δ 1.78 (s, 3H, -CH );
6
3
6.19-6.26 (m, 2H, aro); 6.53-6.56 (m, 1H, aro); 6.67-6.70 (m, 1H,
1,9-Bis(benzimidazol-2'-yl)-5-(2''-pyridyl)-3,7-dithianonane (4).
13
aro); 6.84 (s, 1H, aro).
C nmr (DMSO-d ): δ 10.8, 110.8,
6
118.0, 121.1, 127.5, 127.7, 133.9, 134.5, 149.5. FAB-MS m/z:
To 10.7 g (60 mmol) of 2-(2'-mercaptoethyl)benzimidazole in
ethanol were added firstly 0.5 g of sodium borohydride and then
3.36 g (60 mmol) of potassium hydroxide. To this solution 6.79
g (30 mmol) of 2-(2'-pyridyl)-1,3-dichloropropane hydrochloride
in ethanol was added. It was stirred overnight and then heated on
a steam bath for 30 minutes. After treatment with Norit-A decol-
orizing carbon, the solvent was removed at reduced pressure and
the resulting yellow powder was isolated by filtration, recrystal-
+
+
-1
221 [M+Na] (36%), 199 [M+H] (100%). IR (KBr): ν
cm
max
3460 w (N-H stretching), 3040 m (C-H aromatic stretching),
2942 m (C-H aliphatic stretching), 1625 s (C=C ring stretching),
1547 s (C=N ring stretching). UV (methanol): 307 (17400), 295
(23100), 261 (8700), 237 (15200), 203 (28600); mp > 295 °C
(decomp).
Anal. Calcd. for C H N : C, 66.6; H, 5.09; N, 28.3. Found:
11 10
4
lized from methanol to yield a white solid. Yield 5.7 g (12 mmol,
C, 66.2; H, 5.23; N, 27.9.
1
40%). H nmr (DMSO-d ): δ 2.95 (t, J = 6.9 Hz, 4H, -CH -);
6
2
4-Methyl-5-(benzothiazol-2'-yl)imidazole (2).
3.10 (t, J = 6.9 Hz, 4H, -CH -); 3.23-3.56 (m, 5H, -CH- and
2
-CH -); 7.11-7.14 (m, 5H, aro); 7.29 (d, J = 7.7 Hz, 2H, aro);
A mixture of 3.4 g (22 mmol) of ethyl 4-methyl-5-imidazole
carboxylate and 2.76 g (22 mmol) of 2-aminothiophenol was
heated in 60 ml of polyphosphoric acid at 180 °C for 4.5 hours.
The reaction mixture was cooled to 80 °C, poured into 200 ml of
ice-cold concentrated potassium hydroxide solution and allowed
to stir for 1 hour. The resulting grey precipitate was isolated by
2
13
7.43-7.48 (m, 4H, aro); 7.72 (t, J = 7.7 Hz, 1H, aro).
C nmr
(DMSO-d ): δ 28.9, 29.0, 36.7, 121.1, 121.2, 137.6, 153.5, 158.1.
6
+
+
FAB-MS m/z: 238 [M+Na] (100%), 216 [M+H] (38%), 199
(17%). IR (KBr): ν
-1
cm 3342 w (N-H stretching), 3048 m
max
(C-H aromatic stretching), 2946 m and 2840 m (C-H aliphatic
stretching), 1618 s and 1589 (C=C ring stretching), 1541 s (C=N
ring stretching). UV (methanol): 281 (21700); 274 (21700);
251(14300); 244 (15300); mp 167-168 °C.
filtration and recrystallized from methanol (charcoal), giving 2.9
1
g (13.5 mmol, 60%) of pale yellow flakes. H nmr (DMSO-d ):
6
δ 2.68 (s, 3H, -CH ); 7.32-7.38 (m, 1H, aro); 7.43-7.49 (m, 1H);
3
Anal. Calcd. for C H N S : C, 65.9; H, 5.75; N, 14.8.
Found: C, 65.6; H, 5.54; N, 14.8.
7.73 (s, 1H); 7.93 (d, J = 8.1 Hz, 1H, aro); 8.05 (d, J = 7.8 Hz,
26 27
5 2
13
1H, aro).
C nmr (DMSO-d ): δ 10.9, 121.8, 124.2, 125.9,
6
128.0, 130.5, 133.6, 135.2, 154.2, 165.1. FAB-MS m/z: 238
Tris[5-(benzimidazol-2'-yl)-3-thiapentyl]amine (5).
+
+
[M+Na] (100%), 216 [M+H] (35%), 199 (16%). IR (KBr):
-1
This compound was prepared in a manner similar to that of 4,
using 6.02 g (25 mmol) of tris(2-chloroethyl)amine hydrochloride
and 13.4 g (75 mmol) of 2-(2'-mercaptoethyl)benzimidazole. The
ν
cm 3342 w (N-H stretching), 3070 m (C-H aromatic
max
stretching), 2956 m (C-H aliphatic stretching), 1603 s (C=C ring
stretching), 1547 s (C=N ring stretching). UV (methanol): 307
(19800); 255 (7100); 247 (7400); 209 (22000); mp 168-170 °C.
1
yield of white solid was 7.07 g (11.2 mmol, 45%). H nmr (DMSO-

Mar-Apr 2002
Some Benzimidazole-, Benzothiazole- and Pyridine- Derived Chelating Agents
403
+
[M+H] (100%), 256 (7%), 240 (23%), 208 (12%), 167 (8%). IR
d ): δ 2.51-2.61 (m, 12H, -CH -); 2.98 (t, J = 6.1 Hz, 6H, -CH -);
6
2
2
-1
(neat): ν
cm 3064 m and 3006 m (C-H aromatic stretching),
3.06-3.08 (m, 6H, -CH -); 7.09-7.13 (m, 6H, aro); 7.45-7.49 (m,
max
2
13
2925 s and 2852 s (C-H aliphatic stretching), 1592 s and 1568 s
(C=C ring stretching), 1473 s and 1435 s (C=N ring stretching).
UV (methanol): 268 (8700), 262 (10500), 256 (9200), 204
(25600).
Anal. Calcd. for C H N S •0.5C H OH: C, 65.0; H, 7.91;
N, 7.58. Found: C, 65.0; H, 7.77; N, 7.93.
6H, aro). C nmr (DMSO-d ): 29.2, 29.6, 53.4, 56.2, 114.6, 121.4,
138.7, 153.7. FAB-MS m/z: 652 [M+Na] (100%), 630 [M+H]
(28%), 474 (25%), 452 (28%). IR (KBr): ν
6
+
+
-1
cm 3376 w (N-H
max
stretching), 3078 m (C-H aromatic stretching), 2918 m and 2846 m
(C-H aliphatic stretching), 1623 m (C=C ring stretching), 1455 s
and 1467 s (C=N ring stretching). UV (methanol): 281 (24500),
274 (23400), 244 (18900); mp 103-104 °C.
19 26
2
2
2 5
1,12-Bis(2'-pyridyl)-3,10-dithiadodecane (9).
Anal. Calcd. for C H N S •2H O: C, 59.5; H, 6.51; N,
33 39
7
3
2
14.7. Found: C, 59.5; H, 6.61; N, 14.6.
The reaction of 2.98 g (19.8 mmol) of 1,2-hexanedithiol and
4.17 g (39.6 mmol) of 2-vinylpyridine produced 6.02 g (16.7
Tris[5-(2'-pyridyl)-3-thiapentyl]amine (6).
1
mmol, 84%) of 9 as a colorless oil. H nmr (CDCl ): δ 1.33-1.39
3
Tris(2'-mercaptoethyl)amine, 4.5 g (22.6 mmol) and 7.1 g
(67.9 mmol) of 2-vinylpyridine were refluxed in 100 mL anhy-
drous ethanol for two days. The reaction mixture was treated
with Norit-A decolorizing carbon and the solvent was removed at
reduced pressure, leaving 10.5 g of yellow oil. Chromatography
on silica gel with a hexane/acetonitrile/ethanol mixture gave 8.15
(m, 4H, -CH -); 1.55-1.61 (m, 4H, -CH -); 2.52 (t, J = 7.3 Hz,
2
2
4H, -CH -); 2.89-2.96 (m, 4H, -CH -); 3.02-3.09 (m, 4H, -CH -);
2
2
2
7.1-7.20 (m, 4H, aro); 7.61 (td J = 1.8 Hz, 7.7 Hz, 2H, aro); 8.53-
13
8.56 (m, 2H, aro).
C nmr (CDCl ): δ 28.1, 29.2, 31.4, 31.9,
3
38.3, 121.2, 122.9, 136.1, 149.1, 159.8. FAB-MS m/z: 361
-1
[M+H] (100%), 256 (40%), 222 (13%). IR (neat): ν
cm
max
1
g (15.9 mmol, 70%) of colorless oil. H nmr (CDCl ): δ 2.54-
3064 m and 3007 m (C-H aromatic stretching), 2924 s and 2853 s
(C-H aliphatic stretching), 1591 s and 1568 s (C=C ring stretch-
ing), 1473 s and 1435 s (C=N ring stretching). UV (methanol):
268 (7900), 262 (9600), 255 (8200), 203 (24000).
3
2.62 (m, 6H, -CH -); 2.65-2.72 (m, 6H, -CH -); 2.91-2.97 (m,
2
2
6H, -CH -); 3.02-3.08 (m, 6H, -CH -); 7.10-7.19 (m, 6H, aro);
2
2
13
7.56-7.63 (m, 3H, aro); 8.52-8.54 (m, 3H, aro).
C nmr
(CDCl ): 30.0, 31.9, 38.5, 53.9, 121.4, 123.1, 136.3, 149.3,
Anal. Calcd. for C H N S •0.5C H OH: C, 65.7; H, 8.15;
3
20 28
2
2
2 5
+
159.8. FAB-MS m/z: 513 [M+H] (100%), 408 (14%), 391
N, 7.30. Found: C, 65.6; H, 8.26; N, 7.48.
(12%), 374 (38%), 360 (65%), 269 (35%), 195 (56%), 166
1,2-Bis[4-(2'-pyridyl)-2-thiabutyl]benzene (10).
-1
(59%). IR (neat): ν
cm 3064 m and 3007 m (C-H aromatic
max
stretching), 2960 s and 2919 s (C-H aliphatic stretching), 1592 s
and 1569 s (C=C ring stretching), 1473 s and 1435 s (C=N ring
stretching). UV (methanol): 268 (9900), 262 (12000), 255
(10500), 243 (9000), 234 (9100), 202 (28400).
By reaction of 3.48 g (20.4 mmol) of 1,2-bis(mercap-
tomethyl)benzene and 4.3 g (40.9 mmol) of 2-vinylpyridine, 6.07
g (15.9 mml, 78%) of 10 was obtained as a colorless oil. H nmr
1
(CDCl ): δ 2.85-2.92 (m, 4H, -CH -); 3.01-3.07 (m, 4H, -CH -);
3
2
2
Anal. Calcd. for C H N S •0.25CH CN•0.5CH OH: C,
3.87 (s, 4H, -CH -); 7.1-7.24 (m, 8H, aro); 7.59 (td J = 1.8 Hz,
7.4 Hz, 2H, aro); 8.53 (dd, J = 1.6 Hz, 5.3 Hz, 2H, aro). C nmr
27 36
4
3
3
3
2
13
62.4; H, 7.25; N, 11.0. Found: C, 62.6; H, 7.45; N, 11.1.
The compounds 7-10 were prepared and purified by adopting a
procedure similar to that used for the preparation of 6, in all
instances ethanol being used as the solvent.
(CDCl ): δ 31.5, 33.7, 38.1, 121.4, 123.1, 127.2, 130.5, 136.3,
3
+
+
149.3, 159.8. FAB-MS m/z: 403[M+Na] , (100%); 381[M+H]
(87%), 349 (21%), 305 (19%), 278 (15%), 261 (15%), 242
-1
(15%). IR (neat): ν
cm 3063 m and 3008 m (C-H aromatic
max
1,10-Bis(2'-pyridyl)-3,8-dithiadecane (7).
stretching), 2921 s and 2855 s (C-H aliphatic stretching), 1591 s
and 1568 s (C=C ring stretching), 1473 s and 1435 s (C=N ring
stretching). UV (methanol): 268 (7600), 262 (9700), 255
(8600), 207 (28600).
This compound was prepared from 2.8 g (23 mmol) of 1,4-
butanedithiol and 4.7 g (46 mmol) of 2-vinylpyridine, as a color-
1
less oil in 69% yield. H nmr (CDCl ): δ 1.63-1.69 (m, 4H,
3
-CH -); 2.50-2.55 (m, 4H, -CH -); 2.88-2.95 (m, 4H, -CH -);
Anal. Calcd. for C H N S •0.25H O: C, 68.6; H, 6.41; N,
7.28. Found: C, 68.7; H, 6.54; N, 6.90.
2
2
2
22 24
2
2
2
3.02-3.09 (m, 4H, -CH -); 7.11-7.19 (m, 4H, aro); 7.61 (td J = 1.8
2
Hz, 7.6 Hz, 2H, aro); 8.54 (d, J = 4.6 Hz, 2H, aro). FAB-MS m/z:
1,2-Bis[4-(benzimidazol-2'-yl)-2-thiabutyl]benzene (11).
+
333 [M+H] (100%), 226 (28%), 194 (19%). IR (neat): ν
max
-1
cm 3063 m and 3007 m (C-H aromatic stretching), 2922 s and
2853 s (C-H aliphatic stretching), 1592 s and 1568 s (C=C ring
stretching), 1474 s and 1435 s (C=N ring stretching). UV
(methanol): 268 (6600), 262 (8400), 255 (7100), 202 (18000).
To 4.76 g (26.7 mmol) of 2-(2'-mercaptoethyl)benzimidazole in
50 ml of ethanol was added 0.61 g (26.7 mmol) of metallic sodium.
After the sodium had dissolved, an ethanolic solution of 2.34 g
(13.4 mmol) of α,α'-dichloro-o-xylene was added dropwise. After
the mixture had been stirred overnight, heated on the steambath for
0.5 hour and the sodium chloride was filtered off, the solvent was
removed by rotary evaporation. The brown solid obtained was
Anal. Calcd. for C H N S : C, 65.0; H, 7.28; N, 8.42.
18 24
2 2
Found: C, 65.0; H, 7.36; N, 7.98.
1,11-Bis(2'-pyridyl)-3,9-dithiaundecane (8).
The reaction of 3.91 g (28.6 mmol) of 1,5-pentanedithiol with
recrystallized from aqueous ethanol (charcoal) to give 3.9 g (8.2
1
mmol, 61%) of white flakes. H nmr (DMSO-d ): δ 2.93 (t, J = 7.3
6
6.01 g (57.2 mmol) of 2-vinylpyridine gave 7.8 g (23 mmol,
Hz, 4H, -CH -); 3.12 (t, J = 7.2 Hz, 4H, -CH -); 3.89 (s, 4H, -CH -);
7.09-7.12 (m, 4H, aro); 7.13-7.21 (m, 2H, aro); 7.22-7.31(m, 2H,
2 2 2
1
79%) of the product. H nmr (CDCl ): δ 1.40-1.50 (m, 2H,
3
13
-CH -); 1.59 (q, J = 7.3 Hz, 4H, -CH -); 2.52 (t, J = 7.2 Hz, 4H,
aro); 7.35-7.52 (m, 4H, aro). C nmr (DMSO-d ): δ 29.1, 29.5,
2
2
6
+
-CH -); 2.89-2.96 (m, 4H, -CH -); 3.02-3.09 (m, 4H, -CH -);
32.5, 127.2, 130.4, 136.3, 153.4. FAB-MS m/z: 481 [M+Na]
(87%), 459 [M+H] (43%), 433 (18%), 393 (27%), 261 (51%),
217 (37%), 199(100%). IR (KBr): ν
2
2
2
+
7.12-7.20 (m, 4H, aro); 7.61 (td J = 1.8 Hz, 7.7 Hz, 2H, aro); 8.55
13
-1
(d, J = 4.0 Hz, 2H, aro). C nmr (CDCl ): δ 27.9, 29.0, 31.5,
cm 3384 w (N-H
3
max
31.9, 38.4, 121.3, 122.9, 136.2, 149.2, 159.9. FAB-MS m/z: 347
stretching), 3048 m (C-H aromatic stretching), 2917 m and 2840 m

404
J. G. Gilbert, A. W. Addison, M. Palaniandavar and R. J. Butcher
Vol. 39
[2] A. W. Addison, T. N. Rao, J. Reedijk, J. van Rijn and G. C.
Verschoor, J. Chem. Soc., Dalton Trans., 1349 (1984).
[3] V. V. Pavlishchuk, S. V. Kolotilov, E. Sinn, M. J. Prushan
and A. W. Addison, Inorg. Chim. Acta., 278, 217 (1998).
[4] J. G. Gilbert, A. W. Addison and R. J. Butcher, Inorg.
Chim. Acta., 308, 22 (2000).
(C-H aliphatic stretching), 1621 m and 1589 m (C=C ring stretch-
ing), 1455 s and 1435 s (C=N ring stretching). UV (methanol):
281 (18700), 274 (18000), 244 (156001); mp >226 °C (decomp.).
.
Anal. Calcd. for C H N S H O: C, 65.5; H, 5.92; N, 11.8.
26 26
4
2
2
Found: C, 65.8; H, 5.50; N, 11.5.
[5] A. W. Addison and P. J. Burke, J. Heterocyclic Chem., 18,
803 (1981).
[6] A. W. Addison, T. N. Rao and C. G. Wahlgren, J.
Heterocyclic Chem., 20, 1481 (1983).
[7] C. G. Wahlgren and A. W. Addison, J. Heterocyclic
Chem., 26, 541 (1989).
[8] M. A. Phillips, J. Chem. Soc., 2393 (1928).
[9] L. L-Y. Wang and M. M. Joullié, J. Am. Chem. Soc., 79,
5706 (1957).
[10] P. C. Vyas, C. K. Oza and A. K. Goyal, Chem. Ind.
(London), 287 (1980).
[11] C. Rai and J. B. Braunwarth, J. Org. Chem., 26, 3434
(1961).
[12] D. W. Hein, R. J. Alheim and J. J. Leavitt, J. Am. Chem.
Soc., 79, 427 (1957).
[13] R. P. F. Kanters, R. Yu and A. W. Addison, Inorg. Chim.
Acta., 196, 97 (1992).
[14] Y. Feng, W. Zhang, L. Chen, J. Froelich, K. Meretter and
F. Sauter, J. Heterocyclic Chem., 36, 1307 (1999).
[15] T. Zimmermann and U. Abram, J. Heterocyclic Chem., 36,
1223 (1999).
[16] C. Mitsos, J. Petrou, O. I. Markopoulou and J.
Markopoulos, J. Heterocyclic Chem., 36, 881 (1999).
[17] P. Barbaro, C. Bianchini, G. Scapacci, D. Masi and P.
Zanello, Inorg. Chem., 33, 3180 (1994).
[18] A. Benzekri, P. Dubourdeaux, J. M. Latour, J. Laugier and
P. Rey, Inorg. Chem., 27, 3710 (1988).
[19] J. P. Manson and D. J. Gasch, J. Am. Chem. Soc., 60, 2816
(1938).
Structure Analysis.
For X-ray diffraction, a suitable crystal of 3 was mounted on a
glass fiber with epoxy cement and attached to the goniometer head
in a Siemens P4S diffractometer employing graphite–monochro-
mated Mo-Kα radiation (λ= 0.7103 Å). Cell constants and orien-
tation matrices were obtained by least-squares refinement of set-
ting angles of 25 randomly selected reflections. SHELXA as
found in the SHELXTL package was used to provide an empirical
absorption correction [21]. The structure was solved by a combi-
nation of the Patterson and direct methods and refined by full-
matrix least-squares on F . A total of 3599 reflections was col-
lected (0 ≤ h ≤ 18, -26 ≤ k ≤ 0, -14 ≤ 1 ≤ 12) in the range of 2.16°
to 27.50°, with 3469 being unique (R = 0.0292). The empirically
derived transmission coefficient ranged from 0.623 to 0.524.
Hydrogens were included in structure factor calculations in
calculated positions and refined using a riding model. Thermal
ellipsoids are displayed at 20% probability level for clarity, and
hydrogen atoms are shown as spheres of arbitrary size [22].
2
int
Conclusion.
The oligodentate ligands reported here were prepared in good
yields by straightforward procedures. The electronic spectra of
these compounds show intense absorption in 230-280 nm region.
For the benzothiazoles, the π →π* transition is observed below
250nm and the weak absorption above 250nm is attributed to the
n → π* transition [23]. The proton nmr spectra were consistent
with the expected structures. The metal complexes of these lig-
ands are presently under investigation.
[20] A. R. Katritzky, W. Fan and Q. Li, Youji Huaxue, 8, 53
(1988); Chem. Abstr., 109, 109196h (1988).
[21] SHELXTL, Version 5.030; Siemens Analytical X-ray
Instruments; Madison, WI, 1994.
Acknowledgements.
We thank J. K. Murray and Prof. R. F. Pasternack for assis-
tance with nmr and CD spectroscopies, respectively, and V.
Srirajan for measuring the optical rotation and Drexel University
for support.
[22] Crystallographic data for the structure reported in this
paper have been deposited with the Cambridge Crystallographic Data
Centre. Copies of the data can be obtained, free of charge, on appli-
cation to the Director, CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK (fax: +44-(0)1223-336033 or e-mail: deposit@ccdc.cam.ac.uk)
quoting the deposit number CCDC 175590.
[23] J. V. Metzger, Comprehensive Heterocyclic Chemistry-
Structure, Reactions, Synthesis and Uses of Heterocyclic
Compounds, Vol 6, Part 4B, A. R. Katritzky, C. W. Rees, K. T. Potts,
eds, Pergamon Press, Oxford, 1984, p236.
REFERENCES AND NOTES
[1] A. W. Addison, P. J. Burke, K. Henrick, T. N. Rao and E.
Sinn, Inorg. Chem., 22, 3645 (1983).