Conversion of tetrazoles into hydrazonoyl chlorides. Novel donor-dithiazolium interactions

Article abstract of DOI:10.1039/b202211g

5-Substituted tetrazoles 13, readily prepared from RCN and aluminium azide, react rapidly with Appel salt 1 at room temperature to give hydrazonoyl chlorides 16 in high yield. 5-Aminotetrazole 4 reacts further to give the extended bis(iminodithiazole) 6 and a minor product 7. Mechanisms are proposed for these reactions (except for the formation of 7) which are supported by the smooth conversion of 5-amino-2-substituted tetrazoles 11, but not 5-amino-1-substituted tetrazoles, into the normal iminodithiazoles 12. The red bis(imine)6 rearranges to the yellow 1,3,4-thiadiazole 19 in warm DMSO. The structures of 1,6,7 and 19 are proved by X-ray crystallography which also reveals the presence in each case of a strong intermolecular 3-centre interaction between the adjacent dithiazole ring sulfur atoms and either oxygen, nitrogen or chlorine donors.

Full text of DOI:10.1039/b202211g

View Online / Journal Homepage / Table of Contents for this issue
Conversion of tetrazoles into hydrazonoyl chlorides.
Novel donor–dithiazolium interactions
Charles W. Rees,* Sivaprasad Sivadasan, Andrew J. P. White and David J. Williams
1
Department of Chemistry, Imperial College of Science, Technology and Medicine, London,
UK SW7 2AY
Received (in Cambridge, UK) 4th March 2002, Accepted 1st May 2002
First published as an Advance Article on the web 24th May 2002
5-Substituted tetrazoles 13, readily prepared from RCN and aluminium azide, react rapidly with Appel salt 1 at
room temperature to give hydrazonoyl chlorides 16 in high yield. 5-Aminotetrazole 4 reacts further to give the
extended bis(iminodithiazole) 6 and a minor product 7. Mechanisms are proposed for these reactions (except for
the formation of 7) which are supported by the smooth conversion of 5-amino-2-substituted tetrazoles 11, but not
5-amino-1-substituted tetrazoles, into the normal iminodithiazoles 12. The red bis(imine) 6 rearranges to the yellow
1,3,4-thiadiazole 19 in warm DMSO. The structures of 1, 6, 7 and 19 are proved by X-ray crystallography which
also reveals the presence in each case of a strong intermolecular 3-centre interaction between the adjacent dithiazole
ring sulfur atoms and either oxygen, nitrogen or chlorine donors.
Introduction
5-Arylimino-4-chloro-1,2,3-dithiazoles
2 are stable yellow
crystalline solids reliably prepared in high yields from primary
aromatic amines and 4,5-dichloro-1,2,3-dithiazolium chloride 1
(“Appel salt”) which itself is readily available in large quantities
from chloroacetonitrile and disulfur dichloride.1 Formation of
iminodithiazoles 2 is a general reaction which has been
extended to a wide range of aromatic and heteroaromatic
amines because of their synthetic versatility.2 This versatility
derives from their reactivity towards inter- and intra-molecular
nucleophilic attack at S-1, S-2 and C-5 of the dithiazole ring,
largely driven by regeneration of the latent cyano group.3 Some
of these reactions involve the dithiazole ring only, such as
treatment with triphenylphosphine in DCM at room temper-
ature to give cyanothioformanilides 3 in high yield,4 whilst
others involve cyclisation onto the adjacent aromatic ring.2
Scheme 1
derived from one equiv. of tetrazole 4 and two equiv of salt 1,
with loss of N2 and 3 HCl; with two to three equiv. of 1 the
yields of 6 and 7 rose to 20 and 3% respectively but were not
increased further with more Appel salt. The structure of
maroon product 7 was more difficult to solve. All the carbons
in C6ClN3OS3 were in different environments; the ultra-violet
maxima at 344 and 376 nm, the infra-red signal at 2220 cmϪ1 for
a conjugated cyanide, and mechanistic considerations did not
lead to an unambiguous structure. Suitable crystals for X-ray
crystallography could not be obtained from either ethyl acetate,
ether, ethanol, DCM, chloroform, methanol or pentane, all of
which gave powders. Crystals were finally obtained from
DMSO, though these, when left in air at room temperature for
about 16 hours, reverted to a powder (vide infra).
Results and discussion
Reaction of 5-aminotetrazoles with Appel salt5 1
We were interested in extending these reactions to amino-
tetrazoles because of the potential for the extrusion of
dinitrogen from the products to generate reactive inter-
mediates.6 Treatment of 5-aminotetrazole monohydrate 4 with
Appel salt (1.1 equiv.) under our standard conditions in DCM
at room temperature with pyridine as base, took an entirely
different course from that observed with other primary amines,
giving none of the corresponding imine 5 (C3HClN6S2). Upon
mixing 4 and 1 in DCM, nitrogen was evolved from the
(complex) reaction mixture from which minor amounts (8 and
1% respectively) of two unexpected products were isolated:
6 (C5Cl3N5S4) as long red needles and 7 (C6ClN3OS3) as a
maroon powder. The structure of 6 was deduced from analysis,
spectroscopy and mechanistic considerations (Scheme 1) and
was confirmed by X-ray crystallography. This product was
DOI: 10.1039/b202211g
J. Chem. Soc., Perkin Trans. 1, 2002, 1535–1542
This journal is © The Royal Society of Chemistry 2002
1535

View Online
Table 1 Synthesis of tetrazoles 13 and hydrazonoyl chlorides 16
It is possible that the red compound 6 was formed from 1 and
4 via the “normal” iminodithiazole 5, but this seems unlikely
since (i) extensive conjugation in 4 renders the exocyclic amino
group less nucleophilic than the ring nitrogens and (ii) several
other 5-substituted tetrazoles 11, with substituents inert to the
Appel salt, reacted entirely analogously with the salt at N-2
(vide infra). We propose therefore (Scheme 1) that 1 and 4 give
the 2,5-disubstituted tetrazole 8 which then reacts with
more Appel salt to give the 2 : 1-adduct 9. The strongly
electron withdrawing dithiazolium group at N-2 will induce
equilibration of 9 with the stabilised diazonium tautomer 10
which with ClϪ would give the isolated covalent trichloro
compound 6.
The central “imidoyl” chloride function of 6 was not readily
hydrolysed; heating 6 with aqueous silver nitrate did not give
a precipitate of silver chloride. Bimolecular displacement of
the chloride would be disfavoured by the electron releasing
dithiazole rings, and the structure of 6 does not allow effective
stabilisation of the unimolecularly dissociated “nitrilium”
chloride by the dithiazole rings.
R
13
Yield (%)
16
Yield (%)
C6H5–
13a
13b
13c
13d
13e
13f
85
77
82
88
86
83
22
90
65
—
16a
16b
16c
16d
16e
16f
16g
16h
16i
87
2-MeOC6H4–
3-MeOC6H4–
4-MeOC6H4–
2-FC6H4–
2-ClC6H4–
C6H5O–
ClCH2CH2–
CH2᎐᎐CH–
4-O2NC6H4–
64a
83a
78a
87
73a
56a
75
80
80
13g
13h
13i
13jb
16j
a With pyridine added. b Commercial product.
The conversion of 1 and 4 into 6 as shown in Scheme 1,
requires initial nucleophilic attack on 1 by 4 through N-2 of the
tetrazole ring to give intermediate 8. N-2 is the normal site of
electrophilic attack on tetrazoles, as in the Huisgen reaction,7
but with 5-aminotetrazole the regiochemistry is more finely
balanced and attack at N-1 is not uncommon.6 In the present
reaction attack by the Appel salt at N-1 analogous to the
(87%) was isolated and purified by chromatography. For some
of the tetrazoles the addition of pyridine could be omitted if
the reaction mixture was stirred for a longer time (12 to 16
hours) at room temperature, these reactions being both cleaner
and higher yielding. Analysis and spectroscopy showed that
the product, C9H5Cl2N3S2, from 5-phenyltetrazole retained the
phenyl ring and two chlorine atoms. By analogy with the
reaction of Scheme 1 and the structure 6, which was proved
by X-ray diffraction, we assigned the hydrazonoyl chloride
structure 16a to this product, and analogous structures to all
the products in Table 1. Except for the phenyl 16a, vinyl 16i and
p-nitrophenyl 16j compounds, they are very soluble in organic
solvents, and show two absorption maxima in their UV spectra
at 280–300 and 420–450 nm. They are all stable except for
the chloroethyl derivative 16h which decomposed rapidly in the
solid state and the phenoxy derivative 16g which decomposed
slowly.
conversion 8
9
10 (Scheme 1) would lead to an unstable
N-diazonium chloride, or isomeric chloroazide. This could have
occurred in the present complex reaction, though it is sterically
disfavoured and could not obviously lead to stable covalent
products which would survive chromatography.
We investigated this aspect of the proposed mechanism of
Scheme 1 by separately blocking the N-1 and N-2 positions of
5-aminotetrazole by N-methylation with iodomethane8 and by
N-ethoxycarbonylmethylation with ethyl bromoacetate.9 The
5-amino-2-alkylated tetrazoles 11a,b with N-2 of the ring
blocked, reacted with the Appel salt as expected for primary
heteroaromatic amines to give the imino-adducts 12a,b in high
yield. By contrast, the 5-amino-1-alkylated tetrazoles with
Appel salt gave complex reactions with several very minor
products only, from which the normal imines, isomeric with
12a,b, could not be isolated. This observation suggests that
reaction is probably again occurring at N-2 as well as at the
primary amino group, to give N-alkylated quaternary salts that
are not isolated by column chromatography.
A mechanism for the conversion of the tetrazoles and Appel
salt 1 into the hydrazonoyl chlorides 16 is shown in Scheme 2.
Reaction of 5-substituted tetrazoles with Appel salt 1
Scheme 2
To extend the scope of this new tetrazole reaction and to
support the mechanism of Scheme 1, we investigated the
reaction of a series of tetrazoles 13 in which the amino group
is replaced by aryl, alkyl, vinyl and phenoxy substituents, all of
which are inert to the Appel salt. The tetrazoles (Table 1) were
all prepared by azide addition to the appropriate cyanide.6 The
best method involved in situ generation of aluminium triazide
from aluminium trichloride and sodium azide;10 these reactions
were fast and high-yielding. 5-Phenoxytetrazole was prepared
from phenyl cyanate11 and sodium azide.12
The reaction of 5-phenyltetrazole 13a with Appel salt 1 was
typical. A suspension of 13a in DCM at room temperature was
stirred with 1 (1.1 equiv.) for 30 minutes; addition of pyridine
(1 equiv.) then gave a clear solution with the evolution of
nitrogen and some hydrogen chloride. The yellow product 16a
By analogy with the 5-aminotetrazole reactions (Scheme 1) the
1 : 1-adducts 14 should be formed; since, in the absence of
the 5-amino group, these cannot react further with 1 they could
equilibrate directly with the stabilised diazonium chlorides
15 and hence give the isolated products 16, analogous to 6. In
the Huisgen reaction with neutral rather than positively
charged electron withdrawing groups (e.g. benzoyl) on N-2 of
the 2,5-disubstituted tetrazole, the dinitrogen is lost in a
concerted manner to generate a nitrilimine which then cyclises
(e.g. to a 1,3,4-oxadiazole). It is also possible that the analogous
nitrilimine 17 is formed here and then intercepted by chloride.
Similarly a related nitrilimine could be formed by concerted
loss of dinitrogen from intermediate 9 in Scheme 1. It has
been shown13 that treatment of 5-phenyltetrazole with tri-
1536
J. Chem. Soc., Perkin Trans. 1, 2002, 1535–1542

View Online
Table 2 Bond lengths (Å) and angles (Њ) for 1
only marginally longer than that reported for the corresponding
separation [2.023 Å] in a fully delocalised dithiole ring,15
though a shorter distance of 2.007 Å has also been observed.16
In a fully delocalised dithiadiazole ring an S–S separation of
2.055 Å has been observed.17 In a recently reported closely
related compound 4-chloro-5-perfluorophenyl-1,2,3-dithiazol-
2-ium chloride,18 where the 5-chloride substituent in 1 has
been replaced by a C6F5 ring, the bonding within the dithiazole
ring is essentially identical to that seen in 1. Perhaps a more
interesting feature of dithiole salts and related compounds is
their behaviour “beyond the molecule”. In 1, there is a short
triangular and almost in plane approach [2.932(2) Å to S(1) and
2.974(2) Å to S(2), a and b in Fig. 1 respectively] of the chloride
anion to the two sulfur centres of the dithiazole ring (the
chloride lies 0.34 Å out of the ring plane). Approaches of this
type by halides are relatively commonplace and have been
commented on in a number of early studies of dithiole contain-
ing salts by Hordvik et al.19a who invoked a degree of partial
bonding between the halide and the two ring sulfur atoms
involving weak triangular three-centre two-electron bonds. In
addition to this interaction, in 1 there is also a near-linear
side-on approach (c) of the chloride anion to the S–S bond,
the chloride ion also being positioned over the centre of the
dithiazole ring of an adjacent molecule (d) at a distance com-
patible with an electrostatic interaction. Cl ؒ ؒ ؒ ring centroid
approaches of this type have also been commented on by
Andreasen et al.19b Interestingly, all three of the aforementioned
interactions are also present in the structure of 4-chloro-5-
perfluorophenyl-1,2,3-dithiazol-2-ium chloride.18 In 1, there is
also a short non-bonded Cl ؒ ؒ ؒ Cl contact of 3.163(2) Å (e)
that is not present in the C6F5 analogue.
S(1)–C(5)
S(2)–N(3)
C(4)–C(5)
C(5)–Cl(5)
1.673(4)
1.615(4)
1.405(7)
1.683(5)
S(1)–S(2)
N(3)–C(4)
C(4)–Cl(4)
2.034(2)
1.319(7)
1.709(4)
C(5)–S(1)–S(2)
C(4)–N(3)–S(2)
N(3)–C(4)–Cl(4)
C(4)–C(5)–S(1)
S(1)–C(5)–Cl(5)
92.9(2)
115.7(3)
119.2(4)
115.0(3)
119.9(3)
N(3)–S(2)–S(1)
N(3)–C(4)–C(5)
C(5)–C(4)–Cl(4)
C(4)–C(5)–Cl(5)
97.9(2)
118.5(4)
122.3(4)
125.1(4)
phenylphosphine in tetrachloromethane at room temperature
gives the intriguing product 18 which is probably formed by an
analogous mechanism initiated by similar electrophilic attack
of the tetrazole at N-2 by Ph3PϩClϪ.
Treatment of the red compound 6 with warm DMSO
converted it into a new yellow crystalline compound 19 whose
crystal packing provides another example of the interaction
between a donor atom of one molecule and the two dithiazole
sulfur atoms of another (vide infra). The mechanism of this
transformation and some of its ramifications such as the rapid,
high-yielding conversion of the hydrazonoyl chlorides 16 into
simpler 1,3,4-thiadiazoles will be reported later.
A single crystal structure analysis shows 6 to have a planar
structure (Fig. 2), all of the atoms being required to lie within
X-Ray crystallography
As a prelude to our studies of a series of related dithiazole-
containing species, we thought that it would be interesting
to look at the structure of the simple dithiazole 4,5-dichloro-
1,2,3-dithiazolium chloride (1),14 often referred to as the Appel
salt.1 The X-ray analysis of 1 reveals a pattern of bonding
within the dithiazole ring (Table 2) that indicates delocalisation
that extends around the ring from one sulfur atom to the other
(Fig. 1), and indeed there is also evidence for a shortening of
the S–S bond length [2.034(2) Å] compared with that normally
associated with an S–S single bond. The distance seen here is
Fig. 2 The molecular structure of 6 showing the intramolecular
S ؒ ؒ ؒ N contacts and the linear approach of one of these to the S–S
bond, a 2.597(2), b 2.835(2) Å; the non-bonded S ؒ ؒ ؒ S separation c is
3.353(1) Å.
a crystallographic mirror plane. The two dithiazole rings have
essentially identical geometries (Table 3), but a pattern of
bonding that differs markedly from that seen in 1. Here, with
the exception of the C᎐N linkages [1.276(3) and 1.278(4) Å]
᎐
which have pronounced double bond character, all of the bonds
are noticeably lengthened compared to their values in 1, being
more consistent with conventional single bonds. The bonds
linking the two ring systems show a clear pattern of alternating
double or single bond character, though with evidence for
a modest degree of delocalisation. A feature of this linking
backbone is a substantial contraction of the C(5)–N(6)–N(7)
bond angle to 111.9(2)Њ—and to a lesser degree that for C(8)–
N(9)–C(10) [118.6(2)Њ]—though this is partially compensated
for by an enlargement of the N(7)–C(8)–N(9) and a contraction
of the N(6)–N(7)–C(8) angles, thereby avoiding too short
a contact between S(1) and S(11). The planar molecular
geometry results in a short intramolecular contact of 2.597(2)
Å between N(7) and S(11) (a in Fig. 2), the N(7) ؒ ؒ ؒ S(11)–
S(12) angle being 166.70(6)Њ; a short S(1) ؒ ؒ ؒ S(11) approach
is further prevented by enlargements of the S(1)–C(5)–N(6) and
Fig. 1 The packing of molecules of 1 showing the short non-bonded
intermolecular contacts (Å) a 2.932(2), b 2.974(2), c 3.173(2), d 3.355(2)
and e 3.163(2).
J. Chem. Soc., Perkin Trans. 1, 2002, 1535–1542
1537

View Online
Table 3 Bond lengths (Å) and angles (Њ) for 6
Table 4 Bond lengths (Å) and angles (Њ) for 7
S(1)–C(5)
1.741(2)
1.644(3)
1.464(3)
1.296(3)
1.291(3)
1.732(3)
1.452(3)
S(1)–S(2)
2.0852(11)
1.276(3)
1.709(3)
1.377(3)
1.354(3)
1.302(3)
1.733(2)
1.633(3)
1.718(3)
S(1)–C(5)
1.712(3)
1.619(3)
1.442(5)
1.395(5)
1.432(5)
1.436(5)
1.782(3)
1.136(5)
1.765(5)
S(1)–S(2)
2.0570(14)
S(2)–N(3)
C(4)–C(5)
C(5)–N(6)
N(7)–C(8)
C(8)–Cl(8)
C(10)–C(14)
S(11)–S(12)
N(13)–C(14)
N(3)–C(4)
C(4)–Cl(4)
N(6)–N(7)
C(8)–N(9)
N(9)–C(10)
C(10)–S(11)
S(2)–N(3)
C(4)–C(5)
C(5)–C(6)
C(6)–C(10)
C(8)–C(11)
S(9)–C(10)
C(11)–N(11)
S(20)–C(21)
N(3)–C(4)
C(4)–Cl(4)
C(6)–N(7)
N(7)–C(8)
C(8)–S(9)
C(10)–O(10)
S(20)–O(20)
S(20)–C(22)
1.290(5)
1.706(3)
1.384(4)
1.287(4)
1.733(4)
1.220(4)
1.495(3)
1.767(5)
2.0818(10) S(12)–N(13)
1.278(4)
C(14)–Cl(14)
C(5)–S(1)–S(2)
92.62(8)
116.2(2)
119.8(2)
122.3(2)
111.8(2)
116.8(2)
123.2(2)
118.6(2)
128.1(2)
93.01(8)
115.8(2)
N(3)–S(2)–S(1)
97.87(9)
121.5(2)
118.7(2)
125.9(2)
111.9(2)
123.3(2)
113.5(2)
120.8(2)
111.1(2)
97.71(9)
122.4(2)
C(5)–S(1)–S(2)
93.61(12) N(3)–S(2)–S(1)
97.27(11)
120.4(3)
122.3(3)
119.5(2)
124.9(3)
119.6(3)
121.3(3)
119.5(3)
127.1(3)
107.9(2)
105.9(2)
97.3(2)
C(4)–N(3)–S(2)
N(3)–C(4)–Cl(4)
N(6)–C(5)–C(4)
C(4)–C(5)–S(1)
C(8)–N(7)–N(6)
N(7)–C(8)–Cl(8)
C(10)–N(9)–C(8)
N(9)–C(10)–S(11)
C(10)–S(11)–S(12)
C(14)–N(13)–S(12)
N(3)–C(4)–C(5)
C(5)–C(4)–Cl(4)
N(6)–C(5)–S(1)
C(5)–N(6)–N(7)
N(7)–C(8)–N(9)
N(9)–C(8)–Cl(8)
N(9)–C(10)–C(14)
C(14)–C(10)–S(11)
N(13)–S(12)–S(11)
N(13)–C(14)–C(10)
C(4)–N(3)–S(2)
N(3)–C(4)–Cl(4)
C(6)–C(5)–C(4)
C(4)–C(5)–S(1)
N(7)–C(6)–C(10)
C(8)–N(7)–C(6)
N(7)–C(8)–S(9)
C(8)–S(9)–C(10)
O(10)–C(10)–S(9)
N(11)–C(11)–C(8)
O(20)–S(20)–C(22)
116.8(2)
117.2(3)
128.6(3)
111.8(2)
115.5(3)
109.7(3)
119.1(3)
87.7(2)
N(3)–C(4)–C(5)
C(5)–C(4)–Cl(4)
C(6)–C(5)–S(1)
N(7)–C(6)–C(5)
C(5)–C(6)–C(10)
N(7)–C(8)–C(11)
C(11)–C(8)–S(9)
O(10)–C(10)–C(6)
C(6)–C(10)–S(9)
O(20)–S(20)–C(21)
C(21)–S(20)–C(22)
124.9(3)
178.8(4)
106.0(2)
N(13)–C(14)–Cl(14) 118.6(2)
C(10)–C(14)–Cl(14) 119.0(2)
other with head-to-tail partial overlap of the dithiazole ring
systems; the interplanar separation is 3.36 Å.
In the solid state, 7 is seen to have an almost planar structure
(maximum deviation from planarity of 0.06 Å), with the
dithiazole ring having a pattern of bonding that is intermediate
between that seen in 1 and the essentially localised pattern
observed for these rings in 6. There is a noticeable lengthening
of the C᎐C double bond [1.395(5) Å] linking the dithiazole and
᎐
1,3-thiazole ring systems, having a value typical of a C–C
aromatic bond and indicating a degree of delocalisation that
extends from one ring to the other (Table 4). The C–C and C–S
bonds in the 1,3-thiazole ring have lengths typical of single
bonds whereas the C᎐N bond has retained its double bond
᎐
character. Perhaps of greater interest is the packing of the
molecules with respect to the included dimethyl sulfoxide
solvent. These assemble in dimeric units wherein the oxygen
atoms of a pair of dimethyl sulfoxide molecules form both
near-linear (d) and triangular (b and c) O ؒ ؒ ؒ S–S arrange-
ments (Fig. 4) where all of the S ؒ ؒ ؒ O distances are less than
3 Å, and the oxygen atom O(20) lies only 0.18 Å out of the
S(1)-containing dithiazole ring plane. This motif can also be
considered to include the short non-bonded intramolecular
Fig. 3 Part of one of the tapes present in the structure of 6, and the
short intermolecular contacts d 3.035(2), e 3.437(7), f 3.239(4), 3.286(8),
g 3.500(1) and h 3.565(2) Å.
N(9)–C(10)–S(11) angles relative to their “exterior” counter-
parts. Centrosymmetrically related pairs of molecules are
linked by short S ؒ ؒ ؒ N interactions [3.035(2) Å, d in Fig. 3].
This intermolecular S ؒ ؒ ؒ N contact also forms a near linear
arrangement with the S(11)–S(12) bond [N ؒ ؒ ؒ S–S angle
172.84(6)Њ] which extends to include the intramolecular S ؒ ؒ ؒ N
contact to N(7) (vide supra) thus producing an approximately
linear N ؒ ؒ ؒ S–S ؒ ؒ ؒ N geometry. Directly analogous centro-
symmetric pairs of linear intermolecular S–S ؒ ؒ ؒ N patterns,
with comparable S ؒ ؒ ؒ N distances, are also present in
the structures of 4,4Ј,4Љ-(1,3,5-triazine-2,4,6-triyl)tris(1,2,3,5-
dithiadiazole)20
and
tris(naphtho[2,1-d:6,5-dЈ]bis([1,2,3]-
dithiazole)) bis(tetrafluoroborate),21 but were not commented
upon by the authors. The dichloromethane molecules included
in the crystals of 6, although partially disordered about the
crystallographic C2 axis (and the mirror plane), still play a
significant role in cementing the S ؒ ؒ ؒ N linked “dimers” to
form the tapes depicted in Fig. 3. The chlorine atoms form a
roughly triangular arrangement (e and f in Fig. 3) with respect
to the sulfur atoms of one of the dithiazole rings [based on
S(11)], a geometry directly analogous to that seen in 1. The
chlorine atom Cl(8) in one bis(dithiazole) molecule is
positioned linearly with respect to the S(1)–S(2) bond of
another, though the distance (g) is only ca. 0.15 Å shorter than
the sum of the van der Waals radii (the intermolecular
S(2) ؒ ؒ ؒ Cl(14) contact (h) is only ca. 0.10 Å shorter than the
sum of the van der Waals radii). Combinations of linear and
triangular approaches of chloride ions to S–S bonds have been
discussed previously by Hordvik.22 Adjacent tapes overlay each
Fig. 4 The solid-state structure of 7 showing the short intra-molecular
contact, a 2.614(3) Å, and the intermolecular contacts between
centrosymmetrically-related molecules and the DMSO solvent, b
2.839(3), c 2.711(3), and d 2.948(3) Å.
1538
J. Chem. Soc., Perkin Trans. 1, 2002, 1535–1542

View Online
Table 5 Bond lengths (Å) and angles (Њ) for 19
S(1)–C(5)
S(2)–N(3)
C(4)–C(5)
C(5)–N(6)
C(7)–N(11)
S(8)–C(9)
C(9)–C(12)
C(12)–N(12)
1.7331(14)
1.640(2)
1.459(2)
1.306(2)
1.312(2)
1.710(2)
1.430(2)
1.139(2)
S(1)–S(2)
2.0767(7)
1.280(2)
1.708(2)
1.359(2)
1.7308(14)
1.308(2)
1.359(2)
N(3)–C(4)
C(4)–Cl(4)
N(6)–C(7)
C(7)–S(8)
C(9)–N(10)
N(10)–N(11)
C(5)–S(1)–S(2)
92.86(5)
N(3)–S(2)–S(1)
N(3)–C(4)–C(5)
C(5)–C(4)–Cl(4)
N(6)–C(5)–S(1)
C(5)–N(6)–C(7)
N(11)–C(7)–S(8)
C(9)–S(8)–C(7)
N(10)–C(9)–S(8)
C(9)–N(10)–N(11)
N(12)–C(12)–C(9)
98.13(5)
122.03(13)
118.12(11)
127.99(11)
117.78(12)
113.55(11)
86.37(7)
115.42(11)
111.54(12)
179.2(2)
C(4)–N(3)–S(2)
N(3)–C(4)–Cl(4)
N(6)–C(5)–C(4)
C(4)–C(5)–S(1)
N(11)–C(7)–N(6)
N(6)–C(7)–S(8)
N(10)–C(9)–C(12)
C(12)–C(9)–S(8)
C(7)–N(11)–N(10)
115.51(11)
119.84(11)
120.55(12)
111.46(10)
125.74(13)
120.69(10)
120.86(13)
123.72(12)
113.12(12)
S(1) ؒ ؒ ؒ O(10) contact (a), thus giving an O ؒ ؒ ؒ S–S ؒ ؒ ؒ O
pattern similar to the N ؒ ؒ ؒ S–S ؒ ؒ ؒ N arrangement seen in 6.
Triangular S–S ؒ ؒ ؒ O approaches are relatively commonplace
and have been considered to represent partial bonding15
analogous to that seen for halogens. The S ؒ ؒ ؒ O distances seen
here [2.711(3) and 2.839(3) Å for c and b respectively] are at the
short end of such interactions, although even shorter contacts
of 2.600 and 2.624 Å have been observed in the structure of
a related trisulfur-dinitrido salt.23 Simultaneous end-on and
triangular approaches are, however, comparatively rare, with
only four examples having been identified,24 one of which is the
above mentioned trisulfur-dinitrido salt. Centrosymmetrically
related pairs of molecules stack head-to-tail with partial
overlap of the thiazole and dithiazole ring systems with a mean
interplanar separation of ca. 3.40 Å. These pairs of molecules
then stack with their counterparts across an independent
inversion centre with the thiazole ring in one pair partially
overlaying its counterpart in the next; here the mean interplanar
separation is ca. 3.46 Å.
Fig.
5
The approach of centrosymmetrically-related pairs of
molecules in the structure of 19. The non-bonded contacts are a
2.625(1), b 3.018(2) and c 3.001(2) Å.
benzene28 and p-bis(1,2,3,5-dithiadiazolium-4-yl)benzene.29
These “dimer pairs” form continuous stacks with partial
dithiazole–thiadiazole overlap with a mean interplanar separ-
ation of ca. 3.42 Å. Adjacent stacks pack to give a chevron-like
pattern (Fig. 6) with the cyano nitrogen atoms N(12) in one
stack being directed approximately orthogonally into the C(4)
carbon atoms of the next; the N ؒ ؒ ؒ C distance is 3.111(2) Å.
The X-ray structure analysis shows 19 to also have an
essentially planar structure with a maximum deviation from
planarity of 0.09 Å, the small out-of-plane deviation being
a consequence of a ca. 2Њ torsional twist about C(5)᎐N(6). The
᎐
bond lengths in the dithiazole ring (Table 5) are the same as
those observed in 6, though the N(3)᎐C(4) linkage is longer, and
᎐
the S(2)–N(3) bond shorter, than is observed in 5-benzoyl-
oxyimino-4-chloro-5H-1,2,3-dithiazole.25 The C(5)᎐N(6) and
᎐
N(6)–C(7) bonds that link the two ring systems are longer and
shorter respectively than those associated with localised double
and single bonds, thus indicating some delocalisation extending
between the two ring systems. The thiadiazole ring exhibits a
greater degree of delocalisation than is seen in related systems,26
and is most noticeable for the N(10)–N(11) bond of 1.359(2) Å,
cf. a normal single bond distance of ca. 1.39 Å. One of the
thiadiazole nitrogen atoms N(11) makes a fairly short intra-
molecular, and approximately linear, approach of 2.625(1) Å to
the S(1)–S(2) bond (a in Fig. 5). Centrosymmetrically related
pairs of molecules abut such that one of the nitrogen atoms of
the thiadiazole ring [N(10)] in one molecule is positioned in a
triangular relationship with respect to the two sulfur atoms of
the dithiazole ring of the other and vice versa, the N ؒ ؒ ؒ S
distances being (b) 3.018(2) Å to S(1) and (c) 3.001(2) Å to S(2);
the nitrogen atom N(10A) lies 0.38 Å out of the plane of the
S(1)-containing dithiazole. This geometry, which is directly
analogous to those seen between the S–S bond and chlorine and
oxygen in the structures discussed above, has also been com-
mented on by Hordvik and Kjoge,27 where the two N ؒ ؒ ؒ S
distances are both 2.867 Å. Other examples of similar short
N ؒ ؒ ؒ S–S contacts are seen in the structures of the cations
1-(1,3,2,4-dithiadiazolium-5-yl)-4-(1,2,3,5-dithiadiazolium-4-yl)-
Fig. 6 The chevron-like pattern produced by adjacent stacked pairs of
molecules of 19. The N(12) ؒ ؒ ؒ C(4) separation is 3.111(2) Å.
Experimental
Solvents were purified and dried by standard procedures. Light
petroleum refers to the fraction boiling between 60 and 80 ЊC.
Flash chromatography was on Merck Kieselgel 60 H. Infra-red
absorptions are quoted for medium–strong and strong peaks
only. Melting points were measured on a Kofler hot-stage
microscope and are uncorrected. Organic layers were dried over
Na2SO4.
J. Chem. Soc., Perkin Trans. 1, 2002, 1535–1542
1539

View Online
4,5-Dichloro-1,2,3-dithiazolium chloride 1
5-(4-Chloro-5H-1,2,3-dithiazol-5-ylimino)-2-methyltetrazole 12a
4,5-Dichloro-1,2,3-dithiazolium chloride
following the literature method.1
1
was prepared
To a solution of 5-amino-2-methyltetrazole 11a (300 mg, 3.03
mmol) in dichloromethane (40 ml) was added 4,5-dichloro-
1,2,3-dithiazolium chloride 1 (809 mg, 3.88 mmol). The mixture
was stirred at room temperature for 30 minutes and then
pyridine (0.57 ml, 7.06 mmol) was added. The mixture was
stirred for a further 15 minutes and filtered through silica gel
(25 mesh), eluting with dichloromethane. The product was
purified by flash chromatography on silica gel eluting with
dichloromethane to give the title compound 12a (632 mg, 89%)
as yellow needles, mp 226–228 ЊC (Found: C, 20.7; H, 1.2; N,
35.7; C4H3ClN6S2 requires C, 20.5; H, 1.3; N, 35.9%); νmax
(Nujol)/cmϪ1 1552, 1496, 1174, 1026, 883, 784, 758 and 722;
δH (270 MHz, CDCl3) 4.45 (3H, s, N–CH3); δC (68 MHz,
(CD3)2SO) 159.8, 157.4, 141.1 and 40.4 (N–CH3); m/z 234 (Mϩ,
8%), 206 (3, Mϩ Ϫ N2), 163 (6, Mϩ Ϫ CH3N4), 137 (10), 102
(21), 93 (4), 79 (3), 76 (6), 70 (18), 64 (8, Sϩ2), 58 (4) and 46 (4).
Crystal data for 1†. [C2NS2Cl2][Cl], M = 208.5, orthorhombic,
P212121 (no. 19), a = 5.947(1), b = 10.228(1), c = 10.985(1) Å, V =
668.23(7) Å3, Z = 4, Dc = 2.072 g cmϪ3, µ(Cu-Kα) = 17.4 mmϪ1
,
T = 173 K, dark brown prisms; 680 independent measured
reflections, F 2 refinement, R1 = 0.029, wR2 = 0.068, 638
independent observed absorption corrected reflections [|Fo| >
4σ(|Fo|), 2θ ≤ 130Њ], 75 parameters. Though it has crystallised in
a chiral space group, R-factor tests [R1ϩ = 0.0296, R1Ϫ = 0.0304]
and the Flack parameter [xϩ = ϩ0.40(7), xϪ = ϩ0.60(7)] indicate
that 1 is a ca. 60 : 40 racemic twin. CCDC 180848.
3-Chloro-1,4-bis(4-chloro-5H-1,2,3-dithiazol-5-ylidene)-1,2,4-
triazabut-2-ene 6 and 4- (4-chloro-5H-1,2,3-dithiazol-5-ylidene)-
2-cyano-4H-thiazol-5-one 7
Ethyl 5-(4-chloro-5H-1,2,3-dithiazol-5-ylimino)tetrazol-2-yl-
To a suspension of 5-aminotetrazole monohydrate 4 (0.50 g,
4.85 mmol) in dichloromethane (30 ml) was added 4,5-dichloro-
1,2,3-dithiazolium chloride 1 (3.04 g, 14.5 mmol). The reaction
mixture was stirred at room temperature for 5 hours and then
pyridine (1.17 ml, 14.55 mmol) was added. A gas was evolved
from the reaction mixture, which was stirred until gas evolution
ceased. The red slurry was filtered through a short pad of silica
gel (C25 mesh), eluting with dichloromethane. The products
were purified by flash chromatography on silica gel, eluting with
dichloromethane–light petroleum (1 : 2) to give, firstly, the red
compound 6 (0.35 g, 20%) as needles, mp 218–220 ЊC (Found: C,
16.6; H, 0; N, 19.2; C5Cl3N5S4 requires C, 16.4; H, 0; N, 19.2%);
νmax (Nujol)/cmϪ1 1526, 1492, 1422, 1263, 1246, 1158, 1070, 909,
797, 757, 723 and 704; λmax (EtOH)/nm 234 (ε/dm3 molϪ1 cmϪ1
17230), 276 (12430), 358 (7870), 469 (9450) and 489 (9710);
δC (68 MHz, (CD3)2SO) 162.6, 162.2, 151.5, 148.1 and 143.3;
m/z 363 (Mϩ, 40%), 328 (7, Mϩ Ϫ Cl), 293 (5, Mϩ Ϫ Cl2), 261
acetate 12b
To a solution of ethyl (5-aminotetrazol-2-yl)acetate 11b (0.25 g,
1.46 mmol) in dichloromethane (35 ml) was added 4,5-dichloro-
1,2,3-dithiazolium chloride 1 (0.37 g, 1.77 mmol). The mixture
was stirred at room temperature for 1 hour and then pyridine
(0.24 ml, 2.92 mmol) was added. The mixture was stirred for a
further 15 minutes and filtered through silica gel (C25 mesh),
eluting with dichloromethane. The product was purified by
flash chromatography on silica gel eluting with dichlorometh-
ane to give the title compound 12b (0.32 g, 75%) as canary
yellow needles, mp 183 ЊC (Found: C, 27.4; H, 2.4; N, 27.2;
C7H7ClN6O2S2 requires C, 27.45; H, 2.3; N, 27.45%); νmax
.
(Nujol)/cmϪ1 1744 (CO), 1564, 1467, 1376, 1241, 1172, 1022
and 881; λmax (EtOH)/nm 234 (ε/dm3 molϪ1 cmϪ1 16540), 370 sh,
383 (26780) and 399 sh; δH (270 MHz, (CD3)2SO) 5.90 (2H, s,
N–CH2–O) and 4.23 (2H, q, J 7 Hz, CH2CH3) and 1.23 (3H, t,
J 7 Hz, CH2CH3); δC (68 MHz, (CD3)2SO) 166.6, 165.8, 164.6,
147.6, 62.1, 54.1 and 13.9 (CH2CH3); m/z 306 (Mϩ, 2%), 278
(4, Mϩ Ϫ N2), 205 (11, Mϩ Ϫ C3H5N2O2), 178 (7), 162 (27), 139
(18), 137 (39), 112 (29), 102 (34), 88(3), 87 (55), 85 (36), 76 (10),
71 (26), 64 (21, Sϩ2), 59 (100), 53 (5) and 44 (16, CSϩ).
(51, Mϩ
Ϫ Ϫ ClSCl2), 168 (73,
SCl2), 226 (91, Mϩ
Mϩ Ϫ CCl3NS2), 102 (29, C2NS2ϩ), 70 (38), 64 (100, S2ϩ),
44 (19, CSϩ) and 32 (35, Sϩ) and, secondly, the maroon com-
pound 7 (38 mg, 3%), mp 252–254 ЊC (Found: C, 27.6; H, 0;
N, 15.7; S, 36.9; C6ClN3OS3 requires C, 27.6; H, 0; N, 16.1;
S, 36.8%); νmax (Nujol)/cmϪ1 2220 (conj. CN), 1587, 1462,
1402, 1378, 1276, 1159, 1128, 1067, 901, 841, 773, 725, 685,
646 and 561; λmax (EtOH)/nm 344 (ε/dm3 molϪ1 cmϪ1 16260) and
476 (3710); δC (68 MHz, (CD3)2SO) 185.6 (CO), 155.0, 147.5,
135.0, 123.4 and 113.7 (CN); m/z 261 (Mϩ, 35%), 162 (4,
Mϩ Ϫ S2Cl), 102 (26, C2NS2ϩ), 70 (72, C2NSϩ), 64 (15, S2ϩ) and
32 (28, Sϩ).
3-Chloro-1-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)-3-phenyl-
1,2,-diazaprop-2-ene 16a
To a suspension of 5-phenyltetrazole 13a (5.0 g, 34 mmol)
in dichloromethane (300 ml) was added 4,5-dichloro-1,2,3-
dithiazolium chloride 1 (7.85 g, 37 mmol). The mixture
was stirred at room temperature for 12 h. The resulting solution
was filtered through silica gel (C25 mesh), eluting with
dichloromethane–light petroleum (1 : 3) to give the title
compound 16a (8.6 g, 87%) as yellow cubes, mp 145 ЊC (Found:
C, 37.2; H, 1.7; N, 14.4; C9H5Cl2N3S2 requires C, 37.25; H, 1.7;
N, 14.5%); νmax. (Nujol)/cmϪ1 1619, 1587, 1568, 1465, 1466,
1258, 791 and 684; λmax (EtOH)/nm 280 (ε/dm3 molϪ1 cmϪ1
13,290) and 418 (9960); δH (270 MHz, (CD3)2SO) 8.12–8.18
(2H, dd, Ar–H) and 7.21–7.58 (3H, m, Ar–H); δC (68 MHz,
(CD3)2SO) 166.0, 147.6, 142.4, 132.6, 132.3, 128.8 and 128.1;
m/z 289 (Mϩ, 34%), 254 (45, Mϩ Ϫ Cl), 187 (89, Mϩ Ϫ SCl2),
151 (21, C2N2ClS2ϩ), 135, 103 and 77.
Crystal data for 6†. C5N5S4Cl3ؒ0.5CH2Cl2, M = 407.2, mono-
clinic, C2/m (no. 12), a = 21.140(5), b = 6.724(2), c = 10.004(3)
Å, β = 103.22(2)Њ, V = 1384.4(6) Å3, Z = 4 (Cs symmetry),
Dc = 1.953 g cmϪ3, µ(Mo-Kα) = 1.45 mmϪ1, T = 293 K,
yellow needles; 2410 independent measured reflections, F 2
refinement, R1 = 0.042, wR2 = 0.106, 1942 independent observed
reflections [|Fo| > 4σ(|Fo|), 2θ ≤ 120Њ], 130 parameters. CCDC
180850.
Crystal data for 7†. C6N3OS3ClؒMe2SO, M = 339.9, triclinic,
¯
P1 (no. 2), a = 8.314(2), b = 9.068(3), c = 9.915(3) Å,
α = 112.17(2), β = 97.07(2), γ = 100.08(2)Њ, V = 666.8(3) Å3, Z =
2, Dc = 1.693 g cmϪ3, µ(Cu-Kα) = 8.39 mmϪ1, T = 293 K, red
blocks; 1774 independent measured reflections, F 2 refinement,
R1 = 0.038, wR2 = 0.102, 1609 independent observed absorption
corrected reflections [|Fo| > 4σ(|Fo|), 2θ ≤ 113Њ], 164 parameters.
CCDC 180851.
3-Chloro-1-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)-3-
(2-methoxyphenyl)-1,2-diazaprop-2-ene 16b
To a suspension of 5-(2-methoxyphenyl)tetrazole 13b (80 mg,
0.46 mmol) in dichloromethane (20 ml) was added 4,5-dichloro-
1,2,3-dithiazolium chloride 1 (137 mg, 0.66 mmol). The mixture
was stirred at room temperature for 3 hours and then pyridine
(0.07 ml, 0.91 mmol) was added to the green slurry. The mixture
was stirred for a further 30 minutes and filtered through silica
gel (C25 mesh) eluting with dichloromethane. The product was
† CCDC reference numbers 180848–180851. See http://www.rsc.org/
suppdata/p1/b2/b202211g/ for crystallographic files in .cif or other
electronic format.
1540
J. Chem. Soc., Perkin Trans. 1, 2002, 1535–1542

View Online
purified by flash chromatography on silica gel eluting with
dichloromethane–light petroleum (1 : 2) to give the title com-
pound 16b (93 mg, 64%) as an orange solid, mp 92 ЊC (Found:
318.9378; C10H7Cl2N3OS2 requires 318.9379); δH (270 MHz,
CDCl3) 7.63 (1H, dd, J 2 and 6 Hz, Ar–H), 7.50 (1H, t, J 6 Hz,
Ar–H), 7.04 (2H, m, Ar–H) and 3.92 (3H, s, Ar–OCH3); m/z
319 (Mϩ, 8%), 284 (16, Mϩ Ϫ Cl), 217 (66, Mϩ Ϫ SCl2), 188
(18), 90 (80), 84 (14), 64 (81, S2ϩ) and 44 (35, CSϩ).
dichloromethane–light petroleum (1 : 2) to give the title
compound 16e (0.94 g, 87%) as yellow needles, mp 128 ЊC
(Found: C, 35.65; H, 1.1; N, 13.55; C9H4Cl2FN3S2 requires C,
35.2; H, 1.3; N, 13.7%. Found: 306.9208, calculated 306.9208);
νmax (Nujol)/cmϪ1 1612, 1588, 1572, 1554, 1536, 1512, 1282,
1250, 1219, 1188, 1160, 1108, 1031, 942, 894, 812, 792 and 754;
δH (270 MHz, CDCl3) 7.85 (1H, t, J 4 Hz, Ar–H), 7.50 (1H, m,
Ar–H) and 7.22 (2H, m, Ar–H); δC (68 MHz, CDCl3) 166.3,
[161.4 and 159.3 (d, J 260 Hz)], 144.9 (d. J 7 Hz), 144.2, 133.2
(d, J 9 Hz), 131.6, 124.2 (d, J 3 Hz), 122.5 (d, J 9 Hz) and 116.5
(d, J 22 Hz); m/z 307 (Mϩ, 8%), 272 (12, Mϩ Ϫ Cl), 205 (14, Mϩ
Ϫ SCl2), 156 (6), 153 (15), 139 (7), 107 (13), 95 (20, C6H4Fϩ), 64
(35, Sϩ2) and 44 (73, CSϩ).
3-Chloro-1-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)-3-
(3-methoxyphenyl)-1,2-diazaprop-2-ene 16c
To a suspension of 5-(3-methoxyphenyl)tetrazole 13c (0.50 g,
2.84 mmol) in dichloromethane (35 ml) was added 4,5-dichloro-
1,2,3-dithiazolium chloride 1 (0.65 g, 3.12 mmol). The mixture
was stirred at room temperature for 1 hour and then pyridine
(0.46 ml, 5.68 mmol) was added to the green slurry. The mixture
was stirred for a further 30 minutes and filtered through silica
gel (25 mesh), eluting with dichloromethane. The product was
purified by flash chromatography on silica gel eluting with
dichloromethane–light petroleum (1 : 2) to give the title
compound 16c (0.75 g, 83%) as a yellow solid, mp 131 ЊC
(Found: C, 37.5; H, 2.3; N, 13.0; C10H7Cl2N3OS2 requires C,
37.6; H, 2.2; N, 13.2%); νmax (Nujol)/cmϪ1 1604, 1566, 1465,
1378, 1262, 1163, 1051, 1038, 965, 894, 867, 788 and 680; λmax
(EtOH)/nm 279 (ε/dm3 molϪ1 cmϪ1 14750); δH (270 MHz,
CDCl3) 7.72 (1H, d, J 8 Hz, Ar–H), 7.65 (1H, t, J 3 Hz, Ar–H),
7.38 (1H, t, J 8 Hz, Ar–H), 7.10 (1H, dd, J 3 and 8 Hz, Ar–H)
and 3.89 (3H, s, Ar–OCH3); δC (68 MHz, CD3(SO3)2) 165.7,
159.6, 150.2, 144.3, 134.7, 129.7, 121.5, 118.3, 113.9 and 55.5
(Ar–OCH3); m/z 319 (Mϩ, 44%), 284 (70, Mϩ Ϫ Cl), 217 (79,
3-Chloro-1-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)-3-
(2-chlorophenyl)-1,2-diazaprop-2-ene 16f
To a suspension of 5-(2-chlorophenyl)tetrazole 13f (0.50 g, 2.78
mmol) in dichloromethane (35 ml) was added 4,5-dichloro-
1,2,3-dithiazolium chloride 1 (0.83 g, 3.99 mmol). The mixture
was stirred at room temperature for 30 minutes and then
pyridine (0.59 ml, 7.2 mmol) was added. The mixture was
stirred for a further 30 minutes and filtered through silica gel
(C25 mesh), eluting with dichloromethane. The product was
purified by flash chromatography on silica gel eluting with
dichloromethane–light petroleum (1 : 2) to give the title
compound 16f (0.65 g, 73%) as yellow platelets, mp 143–144 ЊC
(Found: C, 33.6; H, 1.2; N, 12.9; C9H4Cl3N3S2 requires C, 33.4;
H, 1.2; N, 13.0%); νmax(Nujol)/cmϪ1 1606, 1587, 1518, 1472,
1435, 1287, 1240, 1193, 1067, 904, 899 and 791; δH (270 MHz,
CDCl3) 7.67 (1H, dd, J 2, and 4 Hz, Ar–H) and 7.40 (3H, m,
Ar–H); δC (68 MHz, CDCl3) 166.0, 146.6, 144.2, 133.8, 132.7,
131.7, 131.2, 130.7 and 126.8; m/z 323 (Mϩ, 2%), 288 (20, Mϩ Ϫ
Cl), 221 (32, Mϩ Ϫ SCl2), 169 (30), 137 (100, C6H4ClCNϩ), 125
(6), 123 (13), 111 (19), 102 (30), 97 (3), 75 (33), 64 (64, Sϩ2) and
44 (51, CSϩ).
M
ϩ Ϫ SCl2), 133 (100, CH3OC6H4CNϩ), 119 (15), 107 (24), 90
(28), 78 (6), 77 (34), 64 (23, Sϩ2), 50 (13) and 39 (14).
3-Chloro-1-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)-3-
(4-methoxyphenyl)-1,2-diazaprop-2-ene 16d
To a suspension of 5-(4-methoxyphenyl)tetrazole 13d (0.50 g,
2.84 mmol) in dichloromethane (30 ml) was added 4,5-dichloro-
1,2,3-dithiazolium chloride 1 (0.71 g, 3.41 mmol). The mixture
was stirred at room temperature for 1 hour and then pyridine
(0.46 ml, 5.7 mmol) was added to the slurry. The mixture was
stirred for a further 30 minutes and filtered through silica gel
(C25 mesh), eluting with dichloromethane–light petroleum (1 :
1). The product was purified by flash chromatography on silica
gel eluting with dichloromethane–light petroleum (1 : 2) to give
the title compound 16d (0.85 g, 78%) as yellow solid, mp 177 ЊC
(Found: C, 37.6; H, 2.4; N, 13.05; C10H7Cl2N3OS2 requires C,
37.6; H, 2.2; N, 13.2%); νmax (Nujol)/cmϪ1 1603, 1585, 1569,
1505, 1464, 1378, 1307, 1267, 1255, 1198, 1173, 1019, 901, 829,
785, 722, 673 and 627; λmax (EtOH)/nm 304 (ε/dm3 molϪ1 cmϪ1
14070), 410 inf, 425 sh and 446 (8470); δH (270 MHz, CDCl3)
8.10 (2H, d, J 9 Hz, Ar–H), 6.93 (2H, d, J 9, Ar–H) and 3.90
(3H, s, Ar–OCH3); δC (68 MHz, CD3(SO3)2) 165.8, 162.9, 148.0,
142.7, 130.1, 114.5, 125.0 and 55.7 (Ar–CH3); m/z 319 (Mϩ,
28%), 284 (39, Mϩ Ϫ Cl), 217 (77, Mϩ Ϫ SCl2), 191 (3), 159 (3),
154 (10), 151 (17), 150 (4), 134 (10), 133 (100, MeOC6H4CNϩ),
128 (5), 119 (11), 107 (6), 103 (13), 92 (7), 90 (19), 77 (12), 76 (9),
70 (4), 64 (11, Sϩ2) and 32 (7, Sϩ).
3-Chloro-1-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)-3-phenoxy-
1,2-diazaprop-2-ene 16g
To a suspension of 5-phenoxytetrazole 13g (200 mg, 1.23
mmol) in dichloromethane (20 ml) was added 4,5-dichloro-
1,2,3-dithiazolium chloride 1 (309 mg, 1.48 mmol). The mixture
was stirred at room temperature for 6 hours and then pyridine
(0.20 ml, 2.46 mmol) was added. The mixture was stirred for a
further 30 minutes and filtered through silica gel (C25 mesh),
eluting with dichloromethane. The product was purified
by flash chromatography on silica gel eluting with
dichloromethane–light petroleum (1 : 3) to give the title com-
pound 16g (210 mg, 56%) as a yellow solid, mp 80–82 ЊC
(Found: 306.9222, calculated 306.9222); νmax (Nujol)/cmϪ1
1608, 1578, 1378, 1172, 1148, 1062, 1024, 962, 906, 898, 814,
774, 732 and 682; δH (270 MHz, CDCl3) 7.43 (2H, m, Ar–H)
and 7.29 (3H, m, Ar–H); δC (68 MHz, CDCl3) 163.8, 153.4,
152.3, 143.8, 129.7, 126.5 and 120.6; m/z 305 (Mϩ, 16%), 270
(39, Mϩ Ϫ Cl), 228 (18, Mϩ Ϫ Ph), 212 (24, Mϩ Ϫ OPh), 206
(Mϩ Ϫ S2Cl), 203 (18), 151 (22), 91 (29), 77 (100, Phϩ), 65 (22),
51 (43) and 39 (17).
3,5-Dichloro-1-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)-1,2-
diazapent-2-ene 16h
3-Chloro-1-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)-3-
(2-fluorophenyl)-1,2-diazaprop-2-ene 16e
To a solution of 5-(2-chloroethyl)tetrazole 13h (0.50 g, 3.79
mmol) in distilled dichloromethane (35 ml), under nitrogen,
was added 4.5-dichloro-1,2,3-dithiazolium chloride 1 (0.87 g,
4.17 mmol). The mixture was stirred at room temperature for
12 hours. The resulting solution was filtered through silica gel
(C25 mesh), eluting with dichloromethane. The product was
purified by flash chromatography on silica gel eluting with
dichloromethane–light petroleum (1 : 1) to give the title
To a suspension of 5-(2-fluorophenyl)tetrazole 13e (0.50 g, 3.05
mmol) in dichloromethane (35 ml) was added 4,5-dichloro-
1,2,3-dithiazolium chloride 1 (0.95 g, 4.55 mmol). The mixture
was stirred at room temperature for 2 hours and then pyridine
(0.67 ml, 8.26 mmol) was added. The mixture was stirred
for a further 15 minutes and filtered through silica gel (C25
mesh), eluting with dichloromethane. This product was
purified by flash chromatography on silica gel eluting with
compound 16h (0.78 g, 75%) as
a
yellow solid which
J. Chem. Soc., Perkin Trans. 1, 2002, 1535–1542
1541

View Online
2 T. Besson, J. Guillard and C. W. Rees, Tetrahedron Lett., 2000, 41,
1027 and references cited therein; K. Kim, Sulfur Reports, 1998, 21,
147.
3 T. Besson, M.-J. Dozias, J. Guillard, P. Jacquault, M.-D. Legoy and
C. W. Rees, Tetrahedron Lett., 1998, 54, 6475.
decomposed rapidly; δH (270 MHz, CDCl3) 3.89 (2H, t, J 7 Hz,
–CH2–CH2–Cl) and 3.20 (2H, t, J 7 Hz, –CH2–CH2–Cl); δC (68
MHz, CDCl3) 165.1, 149.2, 144.0, 42.4 (–CH2–CH2–Cl) and
40.0 (–CH2–CH2–Cl).
4 T. Besson, K. Emayan and C. W. Rees, J. Chem. Soc., Perkin Trans.
1, 1995, 2097.
3-Chloro-1-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)-1,2-
5 For a preliminary account of some of this work, see V.-D. Le,
C. W. Rees and S. Sivadasan, Tetrahedron Lett., 2000, 41, 9407.
6 R. N. Butler, in Comprehensive Heterocyclic Chemistry, eds.
A. R. Katritzky and C. W. Rees, Pergamon, Oxford, 1984, vol. 5,
p. 791; R. N. Butler, in Comprehensive Heterocyclic Chemistry II, eds.
A. R. Katritzky, C. W. Rees and E. F. V. Scriven, Pergamon, Oxford,
1996, vol. 4, p. 621; R. N. Butler, Adv. Heterocycl. Chem., 1977, 21,
323.
7 R. Huisgen, J. Sauer and M. Seidel, Chem. Ber., 1960, 93, 2885;
R. Huisgen, H. J. Sturm and M. Seidel, Chem. Ber., 1961, 94,
1555; R. Huisgen, C. Axen and H. Seidl, Chem. Ber., 1965, 98,
2966.
diazapenta-2,4-diene 16i
To a suspension of 5-vinyltetrazole 13i (0.50 g, 5.21 mmol) in
dichloromethane (35 ml) was added 4,5-dichloro-1,2,3-
dithiazolium chloride 1 (1.30 g, 6.24 mmol). The mixture was
stirred at room temperature for 24 hours. The resulting solution
was filtered through silica gel (25 mesh), eluting with dichloro-
methane. The product was purified by flash chromatography on
silica gel eluting with dichloromethane–light petroleum (1 : 1)
to give the title compound 16i (1.00 g, 80%) as bronze platelets,
mp 105 ЊC (Found: 238.9150, C5H3Cl2N3S2 requires 238.9145);
νmax (Nujol)/cmϪ1 1680, 1606, 1564, 1378, 1288, 1216, 1180, 980,
936, 892, 822, 784, 710 and 694; δH (270 MHz, CDCl3) 6.20 (1H,
8 R. J. Spear, Aust. J. Chem., 1984, 37, 2453.
9 R. Raap and J. Howard, Can. J. Chem., 1969, 47, 813.
10 C. Arnold and D. N. Thatcher, J. Org. Chem., 1969, 34, 1141.
11 R. E. Murray and G. Zweifel, Synthesis, 1980, 150.
12 D. Martin and A. Weise, Chem. Ber., 1966, 99, 317.
13 I. N. Zhmurova, V. G. Yurchenko and A. M. Pinchuk, Zh. Obshch.
Khim., 1981, 51, 2462 (Chem. Abstr., 1982, 96, 162824).
14 During this work, an independent study of the crystal structure of 1
was reported (S. Rabe and U. Müller, Z. Kristallogr., 1999, 214, 68).
There are no statistically significant differences in the metric
parameters obtained in our study compared with those in the
literature work, though we do not concur with their interpretation
of the degree of delocalisation within the ring system. They do not
discuss any intermolecular interactions other than noting the
triangular Cl ؒ ؒ ؒ S2 approach.
dd, J 7 and 10 Hz, CH᎐CH ), 6.35 (1H, d, J 7 Hz, CH᎐CH H )
᎐
᎐
2
a
b
and 5.90 (1H, d, J 10 Hz, CH᎐CH CH ); m/z 239 (Mϩ, 22%),
᎐
a
b
204 (100, Mϩ Ϫ Cl), 151 (16, Mϩ Ϫ C3H3ClN), 143 (11), 139 (3),
137 (7, Mϩ Ϫ SCl2), 125 (4), 115 (5), 102 (11), 85 (5), 70 (9), 64
(70, Sϩ2) and 58 (7, SCNϩ).
3-Chloro-1-(4-chloro-5H-1,2,3-dithiazol-5–ylidene)-3-
(4-nitrophenyl)-1,2-diazaprop-2-ene 16j
To a suspension of 5-(4-nitrophenyl)tetrazole 13j (100 mg, 0.52
mmol) in dichloromethane (20 ml) was added 4,5-dichloro-
1,2,3-dithiazolium chloride 1 (126 mg, 0.60 mmol). The mixture
was stirred at room temperature for 12 hours. The resulting
solution was filtered through silica gel (C25 mesh), eluting with
dichloromethane. The product was purified by flash chrom-
atography on silica gel eluting with dichloromethane–light
petroleum (1 : 3) to give the title compound 16j (140 mg, 80%) as
orange needles, mp 225–226 ЊC (Found: C, 32.3; H, 1.3; N, 16.6;
15 A. Hordvik, K. Jynge and I. Pedersen, Acta Chem. Scand., Ser. A,
1981, 35, 607.
16 J. R. Cannon, K. T. Potts, C. L. Raston, A. F. Sierakowski and
A. H. White, Aust. J. Chem., 1978, 31, 297.
17 A. J. Banister, M. I. Hansford, Z. V. Hauptman, A. W. Luke,
S. T. Wait, W. Clegg and K. A. Jorgensen, J. Chem. Soc., Dalton
Trans., 1990, 2793.
18 T. M. Barclay, L. Beer, A. W. Cordes, R. T. Oakley, K. E. Preuss,
N. J. Taylor and R. W. Reed, Chem Commun., 1999, 531.
19 See, for example (a) A. Hordvik and E. Sletten, Acta Chem. Scand.,
1966, 20, 1874; (b) O. Andreasen, A. C. Hazell and R. Grønbæk
Hazell, Acta Crystallogr., Sect. B, 1977, 33, 1109.
20 A. W. Cordes, R. C. Haddon, R. G. Hicks, D. K. Kennepohl,
R. T. Oakley, L. F. Schneemeyer and J. V. Waszczak, Inorg. Chem.,
1993, 32, 1554.
21 T. M. Barclay, I. J. Burgess, A. W. Cordes, R. T. Oakley and
R. W. Reed, Chem Commun., 1998, 1939.
C9H4Cl2N4O2S2 requires C, 32.3; H, 1.2; N, 16.7%); νmax
.
(Nujol)/cmϪ1 1573, 1558, 1515, 1475, 1376, 1339, 1256, 1041,
892, 860 and 851; λmax (EtOH)/nm 283 (ε/dm3 molϪ1 cmϪ1
12110) and 433 (11690); δH (270 MHz, (CD3)2SO) 8.61 (2H, dd,
J 1 and 5 Hz, Ar–H) and 8.43 (2H, dd, J 1 and 5 Hz); m/z 334
(Mϩ, 14%), 299 (14, Mϩ Ϫ Cl), 248 (2, Mϩ Ϫ C2NOS), 244 (2),
232 (2), 214 (3, Mϩ Ϫ NOCNS2), 202 (15, Mϩ Ϫ NOC2NS2),
118 (12), 102 (25, C2NS2ϩ) and 64 (100, Sϩ2).
22 A. Hordvik, Rep. Sulfur Chem., 1970, 5, 21.
23 B. Krebs, G. Henkel, S. Pohl and H. Roesky, Chem. Ber., 1980, 113,
226.
Crystal data for 19†. C5N5S3Cl, M = 261.7, monoclinic, P21/c
(no. 14), a = 10.947(3), b = 6.065(2), c = 14.001(4) Å, β =
90.48(2)Њ, V = 929.6(4) Å3, Z = 4, Dc = 1.870 g cmϪ3, µ(Mo-Kα)
= 1.05 mmϪ1, T = 293 K, yellow plates; 2716 independent
measured reflections, F 2 refinement, R1 = 0.029, wR2 = 0.076,
2365 independent observed absorption corrected reflections
[|Fo| > 4σ(|Fo|), 2θ ≤ 60Њ], 128 parameters. CCDC 180849.
24 (a) M.-K. Jeon and K. Kim, Tetrahedron, 1999, 55, 9651; (b)
A. Hordvik and E. Sletten, Acta Chem Scand., 1966, 20, 2043; (c)
B. Ayres, A. J. Banister, P. D. Coates, M. I. Hansford, J. M. Rawson,
C. E. F. Rickard, M. B. Hursthouse, K. M. A. Malik and
M. Motevalli, J. Chem. Soc., Dalton Trans., 1992, 3097.
25 L. S. Konstantinova, O. A. Rakitin, C. W. Rees, T. Torroba,
A. J. P. White and D. J. Williams, J. Chem. Soc., Perkin Trans. 1,
1999, 2243–2248.
26 See, for example (a) K. Wermann, M. Walther, W. Gunther, H. Gorls
and E. Anders, J. Org. Chem., 2001, 66, 720; (b) E. Anders,
K. Wermann, B. Wiedel, W. Gunther and H. Gorls, Eur. J. Org.
Chem., 1998, 2923; (c) R. W. Janes, Acta Crystallogr., Sect. C, 2000,
56, 508; (d ) G. Kornis, P. J. Marks and C. G. Chidester, J. Org.
Chem., 1980, 45, 4860.
Acknowledgements
We thank the SERC and MDL Information Systems UK Ltd
for financial support, the Wolfson foundation for establishing
the Wolfson Centre for Organic Chemistry in Medical Science
at Imperial College and Professor R. N. Butler for valuable
discussions on tetrazoles.
27 A. Hordvik and H. M. Kjoge, Acta Chem. Scand., 1969, 23,
1367.
28 A. J. Bannister, I. Lavender, J. M. Rawson, W. Clegg,
B. K. Tanner and R. J. Whitehead, J. Chem. Soc., Dalton Trans.,
1993, 1421.
29 S. W. Liblong, R. T. Oakley and A. W. Cordes, Acta Crystallogr.,
Sect. C, 1990, 46, 140.
References
1 R. Appel, H. Janssen, M. Siray and F. Knoch, Chem. Ber., 1985, 118,
1632.
1542
J. Chem. Soc., Perkin Trans. 1, 2002, 1535–1542