Substituted 1,3,2,4-benzodithiadiazines: Novel derivatives, by-products, and intermediates

Article abstract of DOI:10.1002/hc.1087

The synthesis of the title compounds 1 by 1:1 condensation of Ar-N=S=N=SiMe₃2 with SCl₂ followed by intramolecular ortho-cyclization of each [Ar-N=S=N-S-Cl] intermediate is complicated by further reaction of 1 with SCl₂ to give Herz salts 3. With the 2:SCl₂ ratio of 2:1, the formation of by-products 3 is reduced and novel compounds 1 are accessible. With ortho-I containing starting material 2j, the parent compound 1s is obtained as the result of an unexpected I, not H, substitution. The rate of the 1 + SCl₂ reaction depends upon a substituent's position, and the minor 8-R isomers 1l,p (R=Br, I) are isolated for the first time from mixtures with the major 6-R isomers due to reduced reactivity toward SCl₂. The synthesized compounds 1-3 are characterized by multinuclear (including nitrogen) NMR and X-ray crystallography. According to the X-ray diffraction data, 1j (6-Br) and 1k (7-Br) derivatives are planar, whereas 1i (5-Br) and 11 (8-Br) are bent along the S1···N4 line by ～5° and ～4°, respectively, and the 1r (7-OCH₃) derivative is planar in contrast to the known 5-OCH₃ isomer, which possesses a significantly folded heterocycle. The distortion of the planar geometry of some compounds 1 is interpreted in terms of a pseudo-Jahn-Teller effect as the result of π-highest occupied molecular orbital (HOMO) - σ*-(LUMO) lowest unoccupied molecular orbital + 1 mixing in a planar conformation. The 2p compound is the first structurally defined Ar-N=S=N-SiMe₃ azathiene. The compound Ar-N=S=N-S-NH-Ar 6 modeling the aforementioned intermediate has been isolated and structurally characterized. We describe the attempts to synthesize compounds 1 from 2-aminobenzenethiols and (SN)₄ and from salts 3 and Me₃SiN₃, and we discuss the reaction pathways.

Full text of DOI:10.1002/hc.1087

Heteroatom Chemistry
Volume 12, Number 7, 2001
Substituted 1,3,2,4-Benzodithiadiazines: Novel
Derivatives, By-Products, and Intermediates*
Alexander Yu. Makarov, Irina Yu. Bagryanskaya, Yuri V. Gatilov,
Tatiana V. Mikhalina, Makhmut M. Shakirov,
Lyudmila N. Shchegoleva, and Andrey V. Zibarev
Institute of Organic Chemistry, Russian Academy of Sciences, 630090 Novosibirsk, Russia
Received 6 September 2000; revised 19 January 2001
cycle. The distortion of the planar geometry of some
ABSTRACT: The synthesis of the title compounds 1
compounds 1 is interpreted in terms of a pseudo-Jahn-
Teller effect as the result of -highest occupied molec-
ular orbital (HOMO) *-(LUMO) lowest unoccu-
by1:1condensationof Ar N
followed by intramolecular ortho-cyclization of each
[Ar N N S Cl] intermediate is complicated by
S N SiMe3 2withSCl2
S
pied molecular orbital + 1 mixing in a planar
conformation. The 2p compound is the first structur-
ally defined Ar–N = S = N–SiMe3 azathiene. The
compound Ar–N = S = N–S–NH-Ar 6 modeling the
aforementioned intermediate has been isolated and
structurally characterized. We describe the attempts to
synthesize compounds 1 from 2-aminobenzenethiols
and (SN)4 and from salts 3 and Me3SiN3, and we dis-
further reaction of 1 with SCl2 to give Herz salts 3. With
the 2:SCl2 ratio of 2:1, the formation of by-products 3
is reduced and novel compounds 1 are accessible. With
ortho-I containing starting material 2j, the parent
compound 1s is obtained as the result of an unex-
pected I, not H, substitution. The rate of the 1 + SCl2
reaction depends upon a substituent’s position, and
the minor 8-R isomers 1l,p (R = Br, I) are isolated
for the first time from mixtures with the major 6-R
isomers due to reduced reactivity toward SCl2. The
synthesized compounds 1–3 are characterized by mul-
tinuclear (including nitrogen) NMR and X-ray crys-
tallography. According to the X-ray diffraction data, 1j
(6-Br) and 1k (7-Br) derivatives are planar, whereas 1i
(5-Br) and 1l (8-Br) are bent along the S1 N4 line
by 5 and 4 , respectively, and the 1r (7-OCH3) de-
rivative is planar in contrast to the known 5-OCH3
isomer, which possesses a significantly folded hetero-
C
cuss the reaction pathways. 2001 John Wiley & Sons,
Inc. Heteroatom Chem 12:563–576, 2001
INTRODUCTION
Recently, various 5-R, 6-R and 7-R substituted
1,3,2,4-benzodithiadiazines (1) (Scheme 1) were syn-
thesized by 1:1 condensation of RC6H4
N
S
N
SiMe3 (2) with SCl2 followed by intramolecular elec-
trophilic ortho-cyclization [3]. These heterocycles
reveal some formal features of antiaromaticity [4]
along with high and varied, essentially unpredict-
able, heteroatom reactivity [1,3,5,6] thus provoking
keen interest. However, their chemistry has been
only briefly investigated. In particular, it was found
that mild thermolysis of 1 in dilute hydrocarbon so-
lutions resulted in practically quantitative yields of
stable 1,2,3-benzodithiazolyl -radicals [1], interest-
ing as potential building blocks in the design and
*Part XV of the series “Cyclic Aryleneazachalcogenenes”; part
XIV: Ref. [1], part XIII: Ref. [2].
Correspondence to: Andrey V. Zibarev. E-mail: zibarev@
nioch.nsc.ru
Contract Grant Sponsor: Russian Foundation for Basic Re-
search.
Contract Grant Number: 99-03-33115.
Contract Grant Number: 96-03-40001.
Contract Grant Number: 96-07-89187.
c
2001 John Wiley & Sons, Inc.
563

564 Makarov et al.
synthesis of organic molecules with high-spin
ground states (molecular magnets) [7, and references
there-in]. On the whole, it is believed that many new
reactions will be observed and many new structural
types will be found among the reaction products
of 1.
In some cases the preparations of compounds 1
from 2 [3] were unsuccessful, especially with para-
substituted starting materials (precursors of 7-R iso-
mers of 1), independent of the character of each sub-
stituent R. The 8-R substituted compounds 1, minor
products of regioselective cyclizations of meta-sub-
stituted starting materials leading predominantly to
6-R isomers, were characterized only spectroscopi-
cally without isolation [3].
Improved Cyclization
The synthesis of 1 by a 1:1 reaction of 2 with SCl2 is
complicated by formation of Herz salts (3) (1,2,3-
arenodithiazolium chlorides [12]). In some cases
they are even the major products. Control experi-
ments (see Cyclic By-Products) indicate that the salts
3 come from further reaction of 1 with SCl2. It fol-
lows that the 2:SCl2 ratio should be changed in favor
of 2 to suppress this side-process while preparing 1.
Indeed, with the 2:SCl2 ratio of 2:1 it is possible to
The present article deals with the improved
synthesis of 7-R and some other derivatives of 1
including the first-ever isolation of minor 8-R iso-
mers, as well as with the by-products and interme-
diates of the cyclization. Attempts to synthesize 1
by different approaches to the ring closure are also
described.
RESULTS AND DISCUSSION
Precursors
SCHEME 2 Compounds 2:
I/R
2
3
4
Me2N
(a)
b
(c)
NO2
d
(e)
f
Br
g
h
i
I
j
k
l
F
OCH3
The starting materials 2 bearing a strong donor
(Me2N) or a strong acceptor (NO2) substituent R, as
well as an I substituent, were of special interest [8].
The novel compounds 2 were synthesized from
m
n
3,5-Br2: 2o, 4-(40-IC6H4): 2p
Parentheses indicate that corresponding compound was not
synthesized by this way.
LiN(SiMe3)2 and corresponding RC6H4
(cf. [3,9]) or RC6H4
SCl2 (R = NO2) (Scheme 2).
Surprisingly, both approaches were not effectual
N
S
O
N
with R
3-NO2 and the first one with R
2-Me2N
or 4-Me2N.
The 2p compound (Figure 1) is the first struc-
turally defined Ar N N SiMe3 azathiene [2p:
S
Ar 4-(40-IC6H4)C6H4]. In the crystal, 2p adopts the
Z,E configuration with a dihedral angle between the
NSN plane and the adjacent ring of 14.3(2) , and
between the rings of 29.9(1) . The S1N2 bond dis-
tance (Figure 1) is rather short but corresponds to
those found in the related (Z,E)Ph3Si N
SiPh3 compound (1.506 and 1.508 A) [10]. Other
bond lengths and bond angles are typical [11].
S
N-
˚
FIGURE 1 Structure of molecule 2p in the crystal. Selected
1
1
bond lengths (A) and bond angles ( ): N S 1,513(3); S1N2
1.508(3); N1C1 1.417(5); N2Si1 1.740(3); I1C10 2.096(4);
C1N1S1 130.3(2); N1S1N2 119.0(2); S1N2Si1 127.7(2).
˚
SCHEME 1

Substituted 1,3,2,4-Benzodithiadiazines: Novel Derivatives, By-Products, and Intermediates 565
obtain 7-R derivatives of 1 from the cyclizations pre-
viously unsuccessful [3] with the 1:1 ratio (i.e., 1q,r;
F, OCH3) as well as to prepare several novel
derivatives (Scheme 3).
With 4–RC6H4
erocycle formation proceeds also with R
IC6H4. On the other hand, with R NO2 or CF3 the
tion is highly regioselective, leading predomi-nantly
to 6-R substituted compounds 1, with the preferred
direction of ring closure being consistent with the
thermodynamics of the corresponding ␴-complexes
as well as the factors of kinetic control for orbital-
controlled El-Nu interaction. In this work, for R
Br, the ratio of the major 6-Br (1j) isomer to the mi-
R
N
S
N–SiMe3, the target het-
Br, I, 4-
expected compounds are not obtained under the im-
proved reaction conditions (cf. Ref. [3]).
nor 8-Br (1l) one was found to be 80:20. For R
however, the ratio of 6-I (1n) and 8-I (1p) isomers
was only 60:40.
The observed ratio of isomers would be affected
by their further reaction with SCl2 at different rates.
Control experiments on available mixtures of 6-R
I,
In the case of 2-RC6H4
clization readily occurs with R Br. With starting
material 2j (R I) the parent 1,3,2,4-benzodithia-
N S N SiMe3 the cy-
diazine 1s was isolated from the reaction mixture
instead of the expected 5-I derivative 1m. One can
think that in this case the ring closure is mediated
by the bipolar ion (Scheme 3) [13] originated from
initial electrophilic attack on iodine, rather than on
carbon [14]. The postulated (Scheme 3) ICl by-prod-
uct should react further with both 2j and 1s. At
any rate, control experiments have shown that Cl2 is
highly reactive toward 1 to give a complex mixture
and 8-R isomers (R
Br, I) have shown that the 6-
R isomer reacts with SCl2 much more rapidly than
the 8-R isomer, which makes possible the eventual
isolation of 8-Br and 8-I derivatives. Thus, the cycli-
zation itself seems to be more regioselective than it
appears from the observed ratios of isomers in the
reaction mixtures presented in [3] and this work.
With R
failed.
Me2N (2b) or CF3 the cyclization
of unidentified products. With R
zation failed.
NO2, the cycli-
Earlier [3], it was discovered that for 3-RC6H4
S N SiMe3 (R CH3, OCH3, F, Cl) the cycliza-
Molecular Structures
N
According to the previous data of X-ray crystallog-
raphy, the parent compound 1s [6] and its 5-CF3 and
6-F derivatives [3] are planar, whereas 5-OCH3, 6-
CH3 [3], and 5,6,7,8-F4 [15] derivatives are bent along
the S1 N4 line by 11 , 7 , and 5.5 , respectively.
The MP2/6-31G** calculations do not reproduce this
intriguing structural dichotomy with 1s, its 5-OCH3
and 5,6,7,8-F4 derivatives, and the model 1,3,2,4-di-
thiadiazine (11) being found to be bent along the
S1 N4 line by 38 , 39 , 34 , and 45 respec-
tively. On the other hand, B3LYP/6-31G* calculations
[2] predict a bent (26 ) conformation for a free mol-
ecule of 1s, but a perfectly planar conformation for
its 5,6,7,8-F4 derivative.
In the present work, both types of molecular ge-
ometry were observed again in the crystal (Figure 2,
Table 1). For example, among 1i–l isomers, 1j (6-Br)
and 1k (7-Br) are planar, whereas 1i (5-Br) and 1l
(8-Br) are bent along the S1 N4 line by 5.3(3) and
3.8(3) , respectively (throughout this work the term
planar conventionally means that the angle above
is smaller than 3 ). Furthermore, for two crystal-
lographically independent molecules of 1j, one is
perfectly planar, whereas another is bent by 3.1(2) ,
which directly indicates the importance of pack-
ing effects. The 1r (7-OCH3) derivative (Figure 2,
Table 1) is planar, in contrast to the significantly
folded 5-OCH3 isomer (see previous paragraph).
Thus, the type of the molecular geometry of the title
compound in the crystal, planar or bent, depends
SCHEME 3 Heterocycles 1:
n/R
5
6
Me2N
(a)
(b)
NO2
(e)
(f)
Br
i
j
k
l
I
(m)
n
o
7
8
(c)
(d)
(g)
(h)
p
R
7-F, 1q; 7-OCH3, 1r; H, 1s; 6,8-Br2, 1t; 7-(4-IC6H4), 1u
Parentheses indicate that corresponding heterocycle was not
synthesized by this way.

566 Makarov et al.
FIGURE 2 Structure of molecules 1i-l,r in the crystal. For selected bond lengths and bond angles, see Table 1.
not only on the substituent character, but also on its
position.
The bond lengths and bond angles of 1i–l,r are
typical [3,11]. Within experimental accuracy they are
molecular orbital (MO) model, one can identify
orbital interactions capable of reducing molecular
symmetry of the compounds under consideration
from Cs to C1. With Cs symmetry the molecular
1
the same for all molecules (Table 1). In the N
S
N
ground state is (
2), namely, A0. It follows from
fragment the bond lengths differ except for 1l
(Table 1).
the calculations (Table 2) that for both 1s and 11
the Cs structure is the TS of the molecular bend-
ing. The transition to C1 symmetry is possible by
It can be assumed that the distortion of the pla-
nar Cs geometry in the calculations reflects the ten-
dency of the molecules to minimize thermodynamic
destabilization associated with antiaromaticity via a
pseudo-Jahn-Teller effect [16]. With a simplifying
1
vibronic interaction with excited A00. states achiev-
able by
→
and
→
excitations. For 1s the
lowest-energy excitation of these types is 6a00 → 20a0.
The mixing of 6a00 ( -highest occupied molecular

Substituted 1,3,2,4-Benzodithiadiazines: Novel Derivatives, By-Products, and Intermediates 567
a
˚
TABLE 1 Selected Bond Lengths (A ) and Bond Angles ( ) in Molecules 1i-1,r
1i
1j (two independent molecules)
1k
1l
1r
S1N2
1.674(8)
1.547(8)
1.526(4)
1.413(7)
1.779(6)
1.413(8)
106.5(3)
122.9(3)
119.2(3)
123.3(4)
124.4(5)
123.2(4)
1.684(5), 1.679(5)
1.543(4), 1.548(5)
1.527(4), 1.533(4)
1.425(5), 1.417(5)
1.785(4), 1.787(4)
1.401(6), 1.400(6)
105.6(2), 106.0(2)
123.5(2), 123.3(3)
119.3(2), 119.2(2)
123.0(3), 122.9(3)
124.2(4), 124.9(4)
124.2(3), 123.7(3)
1.664(4)
1.546(4)
1.524(4)
1.406(5)
1.787(3)
1.408(5)
105.8(2)
123.8(2)
118.8(2)
123.7(3)
124.2(3)
123.7(3)
1.684(5)
1.538(5)
1.533(3)
1.426(7)
1.788(4)
1.405(6)
105.7(2)
123.8(3)
118.9(2)
123.3(3)
124.1(4)
123.9(4)
1.678(3)
1.538(3)
1.528(3)
1.421(4)
1.785(3)
1.402(4)
106.1(2)
123.1(2)
119.3(2)
123.5(2)
123.8(3)
124.0(2)
N2S3
S3N4
N4C10
S1C9
C9C10
C9S1N2
S1N2S3
N2S3N4
S3N4C10
N4C10C9
C10C9S1
aFor atom numbering, see Figure 1.
TABLE 2 Quantum Chemical Calculations Data for Molecules 1s and 11
RHF/6-31G* Etot
(PES point)a (a.u.)
MP2/6 -31G* Etot
(PES point)a (a.u.)
1
1
Compound (symmetry)
11 (Cs)
Erel (kcal mol
)
Erel (kcal mol
)
980.664074
(TS)
980.665451
(min)
0.86
0
11 (C1)
1s (Cs)
1133.337707
(TS)
1133.338154
(min)
0.28
0
1134.702832
(TS)
1134.706710
(min)
2.43
0
1s (C1)
aThe types of stationary PES points were determined by the Hessian calculations.
orbital (HOMO)) with 20a0 (the lowest virtual *-MO,
which is next to the 7a00 -lowest unoccupied molec-
ular orbital (LUMO), i.e., LUMO + 1) (Figure 3)
causes the molecule to fold along the S1 N4 line
in accordance with the results of MP2/6-31G** cal-
culations and the data of X-ray crystallography for
5-OCH3,5-Br, 6-CH3, 8-Br, and 5,6,7,8-F4 derivatives.
According to the atomic orbital (AO) contributions
to the 6a00 and 20a0 MOs (Figure 3), the density of
the corresponding one-electron transition is local-
ized mainly on S1. The energy gain on going from
1
Cs to C1 sym-metry is smaller by 1 kcal mol at the
RHF level of theory becoming about nine-fold higher
(for 1s) at the MP2 level (Table 2).
Spectral Properties
In accordance with previous data [3], in 15N NMR
spectra of the title compounds, 15N values lie inside
a narrow range, 280–250 ppm, demonstrating
weak dependence upon position and character of a
carbocyclic substituent (for details, see Table 6 in
FIGURE 3 The 6a00 -HOMO and 20a0 *-LUMO + 1 (see
text) of Cs-1s and the corresponding MOs of Cs-11 (RHF/6-
31G*).
1
Experimental). In the 15N{ H} spectrum of the parent
compound 1s, the signal at 263.1 ppm (Table 3) is a

568 Makarov et al.
TABLE 3 Assignment of 1H, 13C, and 15N NMR Spectra of
1sa
(J, Hz)
N2 269.2 (s)
(J, Hz)
C8a 115.3 (tdd, 8.5, 1.7, 0.8)
C4a 138.5 (tt, 9.3, 2.1)
N4 263.1 (d, 2.3)
H5 5.90 (dd, 7.8, 1.3) C5 123.0 (ddt, 163.2, 8.5, 1.3)
H6 6.63 (tm, 7.8)
H7 6.79 (tm, 7.6)
C6 133.2 (ddm, 164.8, 8.5)
C7 130.5 (ddm, 164.5, 7.2)
H8 5.79 (dd, 7.5, 1.2) C8 124.0 (ddddd, 161.5, 8.9, 2.1, 1.3)
aFor atom numbering, see Scheme 1.
doublet under selective decoupling with H8, but a sin-
glet under selective decoupling with H5, thus prov-
ing the empirical assignment given in [3]. Table
1
3 provides also the complete assignment of the H
and 13C NMR spectra of 1s based on double reso-
nance, COLOC, and off-resonance techniques.
The long-wave absorption maxima in the UV–vis
spectra of the title compounds are found in the range
of 610–635 nm (cf. [3]), again with weak depen-
dence upon the position and character of the sub-
stituent R (for details, see Table 6).
SCHEME 4 Salts 3: R H (a), 4-OCH3 (b), 6-OCH3 (c),
5-Br (d), 5-CH3 -6-Cl (e), 5-I (f)
probably proceed in a similar way. Formation of
1,2,3-benzodithiazolyls by thermolysis of 1 [1] is very
likely mediated by 5 as well [17a].
Me3SiCl is inert toward 1 under conditions of the
cyclization, in contrast to its reaction with the re-
lated 1,3,5,2,4-benzotrithiadiazepine, leading to
1,3,2-benzodithiazolium chloride (4) [23], isomeric
with 3a.
Cyclic By-Products
The Herz salts 3, are cyclic by-products. Special pre-
parative experiments as well as 14N NMR identifica-
tion of thiazyl chloride NSCl in the reaction mixtures
suggest that it is possible to explain the formation of
3 by further reaction of 1 with SCl2 (Scheme 4). One
can postulate singlet 1,2,3-benzodithiazol-2-ylni-
trene (5, an isomer of 1) to be the key intermediate
of the reaction of 1 with SCl2. Then, the reaction
seems to be an oxidative imination of SCl2 with 5 fol-
lowed by an elimination of NSCl from the product
to give the final salt 3 (Scheme 4) [17]. Previously,
similar elimination of NSCl has been observed dur-
ing thermal decomposition of PhSO2N SCl2 [18]
(Scheme 4). It follows from control experiments that
NSCl (taken as its trimer) also reacts with 1 to give
Herz salts.
A thermodynamic gain of transformation of an
antiaromatic system into an aromatic system seems
to be a driving force of the reaction of 1 with SCl2.
With planar geometry [19] and 10␲-electrons, the
cations of 3 possess aromaticity, although reduced
as compared with the symmetric isomer 4 [20,21a].
Previously described 1:1 addition of 1 to PPh3
that afforded a derivative of (1,2,3-benzodithiazol-2-
yl)iminophosphorane (Scheme 4) [5] can also be in-
terpreted as an oxidative imination of the phosphine
with nitrene 5. Thus, the reactions of 1 with formal
both an electrophile (SCl2 ) and a nucleophile (PPh3)
A Model for the Cyclization Intermediate
Compound
(6), actually isolated from a reaction of 4-FC6H4
N SiMe3 (2m) with salt 3a, can formally be
considered as a [4-FC6H4 N S Cl] interme-
4-FC6H4
N
S
N S NH C6H4F-4
N
S
N
S
diate in the synthesis of 1q (Scheme 3), trapped by
the parent amine 4-FC6H4NH2. According to the data
of X-ray crystallography (Figure 4), in the crystal this
model compound adopts the E,Z configuration (cf.
Z,E configuration of Ar N
S N SiMe3 2p, Figure
1). As the cyclization requires a Z,Z configuration,
one can conclude that the model belongs to the early
stages of the process. The compound 6 features
considerable nonplanarity. The molecule consists
of three planar fragments: ring C1-C6 (A plane,
˚
standard deviation 0.005 A), chain NSNSN (B plane,
˚
standard deviation 0.74 A), and ring C7-C12 (C
˚
plane, standard deviation 0.003 A) with dihedral
angles A-B, B-C, and A-C of 101.4 , 30.7 and 71.6 ,
respectively. The bond lengths and bond angles of

Substituted 1,3,2,4-Benzodithiadiazines: Novel Derivatives, By-Products, and Intermediates 569
SCHEME 5
respectively, with standards tetramethylsilane (TMS)
and NH3 (liq.); the 19F NMR spectra were taken on
a Bruker AC-200 machine at a frequency of 188.28
FIGURE 4 Structure of molecule 6 in the crystal. Selected
MHz with C6F6 as the standard. The mass spectra (EI,
70 eV) were collected on a Finnigan MAT MS-8200
instrument, and the UV–vis spectra were recorded
on Specord M40 and HP 8453 spectrophotometers.
The X-ray structure determinations (Table 4)
were carried out on a Syntex P21 diffractometer us-
ing Cu K␣ radiation (compounds 1k,r, 6) and on
a Bruker P4 diffractometer using Mo K␣ radiation
(compounds 1i,j,l, 2p), with a graphite monochro-
mator. Corrections for absorption by crystal habit
were used for 1i-l and 6. The structures were solved
by direct methods using the SHELX-86 (1j,k,r, 6),
SHELXS-97 (2p), and XS-SHELXTL (1i,l) programs
and refined by the least-squares method in the
full-matrix anisotropic (isotropic for H atoms) ap-
proximation using the SHELXL-93 and SHELXL-
97 (1j,k,l,r,2p, 6) and XL-SHELXTL (1i) programs.
Hydrogen atoms were located on difference Fourier
maps (1j,l,r, 2p) or geometrically (1i,k, 6).
The ESR spectra were recorded on a Bruker
EMX spectrometer (MW power, 0.64 mW; modu-
lation frequency, 100 KHz; modulation amplitude,
0.1 G).
The RHF/6-31G*, MP2/6-31G*, MP2/6-31G**,
and the PM3 calculations were performed using the
GAMESS program [28] and the MNDO-92 program
[29], respectively.
1
1
˚
bond lengths (A) and bond bond angles ( ): N S 1.639(4);
S1N2 1.690(3); N2S2 1.549(3); S2N3 1.551(3); C1N1
1.402(5); C7N3 1.415(4); C1N1S1 125.2(3); N1S1N2 101.2(2);
S1N2S2 118.5(2); N2S2N3 110.0(2); S2N3C7 119.4(3).
the sulfur-nitrogen fragment of 6 are typical (cf. the
nearest analog Ph N
S N S Ph [24]).
Attempted Approaches to the Ring Closure
An attempt was made to synthesize 1 by reaction of
2-aminobenzenethiols with (SN)4 as a source of the
sulfur-nitrogen fragment necessary to the ring clo-
sure. However, the reaction proceeded only as ox-
idation of the thiol to the corresponding disulfide
(Scheme 5).
Another approach tried was based on the reac-
tion of a Herz salt 3 with Me3SiN3. It was believed
that the reaction will lead via the corresponding co-
valent azide to a singlet nitrene 5 capable of isom-
erization into a compound 1 (cf. singlet nitrenes Ar
N: [25] and Ar S N: [26,27]). However, only persis-
tent 1,2,3-benzodithiazolyl radicals 8 [1] were iden-
tified as reaction products (Scheme 5; cf. [27]). It
should be noted that formation of a Herz-type ionic
azide is also possible in this system followed by a
redox process directly leading to an 8 radical [21b].
Compounds 1s [6], 2f,m,n [3,9], 3a–c [12], and
7 [30] were known previously.
The syntheses described subsequently were per-
formed in an argon atmosphere in absolute solvents
with stirring. The reagents were added dropwise, and
the solvents were distilled off at reduced pressure.
Tables 5 and 6 list the physical and analytical data
for the compounds synthesized.
EXPERIMENTAL
1
The H, 13C, 14N, and 15N NMR spectra were mea-
sured on a Bruker DRX-500 spectrometer at fre-
quencies of 500.13, 125.76, 36.13, and 50.68 MHz,

570 Makarov et al.
TABLE 4 Crystal and Refinement Data of Compounds 1i–1r, 2p, and 6a
1i
1j
1k
Formula
M
C6H3BrN2S2
247.13
C6H3BrN2S2
247.13
C6H3BrN2S2
247.13
Crystal system
Space group
Orthorhombic
Fdd 2
Triclinic
P-1
Triclinic
P-1
˚
a (A)
13.094(2)
31.286(5)
7.741(1)
3.9933(5)
10.903(1)
18.428(2)
97.532(7)
91.743(9)
95.351(8)
791.21(15)
4
2.075
6.067(2)
7.444(2)
8.784(2)
85.00(2)
84.42(2)
86.84(2)
392.9(2)
2
2.089
˚
b (A)
˚
c (A)
( )
( )
( )
V (A3)
3171.1(8)
16
2.071
5.638
1920
Z
3
Dc (g cm
(mm
F (000)
)
1
)
5.649
480
11.518
240
Crystal size (mm)
Scan mode
0.09 0.50 0.90
–2
<55
0.01 0.14 1.7
–2
<50
0.09 0.40 1.20
–2
<140
2
range ( )
Reflections measured
1103
1016
0.13–0.60
0.0346
0.0957
1.064
2587
2075
0.47–0.84
0.0340
0.0884
1.038
1490
1381
0.04–0.38
0.0405
0.1134
1.093
ObservedF0 > 4
Transmission
R (observed)
wR2 (all data)
Goodness of fit
F
1l
1r
2p
6
Formula
M
C6H3BrN2S2
247.13
C7H6N2OS2
198.26
C15H17IN2SSi
412.36
C12H9F2N3S2
297.34
Crystal system
Space group
Monoclinic
P21/c
Monoclinic
P21/n
Triclinic
P-1
Monoclinic
P21/n
˚
a (A)
13.6916(17)
3.9952(4)
14.393(2)
6.052(1)
10.554(2)
12.938(2)
6.2520(4)
11.8804(8)
12.463(3)
4.652(1)
23.276(6)
˚
b (A)
˚
c (A)
12.2049(7)
96.821(5)
101.336(5)
93.620(5)
879.1(1)
2
( )
( )
( )
V (A3)
95.79(1)
97.49(2)
102.86(2)
783.28(16)
4
2.096
819.3(2)
4
1.607
1315.6(5)
4
1.501
Z
3
Dc (g cm
(mm
)
1.558
2.001
1
)
5.709
5.479
3.812
F (000)
Crystal size (mm)
Scan mode
480
408
402
608
0.025 0.4 0.84
–2
0.12 0.17 1.40
–2
0.06 0.47 1.30
–2
0.12 0.16 1.60
2
range ( )
<50
1340
1101
0.19–0.89
0.0391
0.1045
1.084
<130
1390
1086
<50
3079
2595
0.39–0.85
0.0334
0.0957
1.057
<140
2328
1436
0.38–0.70
0.0542
0.1395
1.020
Reflections measured
Observed F0 > 4
Transmission
R (observed)
wR2 (all data)
Goodness of fit
F
0.0476
0.1277
1.110
aAtomic coordinates, thermal parameters, bond lengths, and bond angles have been deposited at the Cambridge Crystallographic Data Centre.

Substituted 1,3,2,4-Benzodithiadiazines: Novel Derivatives, By-Products, and Intermediates 571
TABLE 5 Characterization of the Compounds
TABLE 5 (Continued ) Characterization of the Compounds
MS M + (m/z)
Measured
(calculated,
35Cl, 79Br)
MS M + (m/z)
Measured
(calculated,
35Cl, 79Br)
Com-
m.p. ( C),
Yield
Com- m.p. ( C), Yield
pound b.p. ( C/mm) (%)
pound b.p. ( C/mm) (%)
Formula
Formula
1i
103–105
92–93
18 C6H3BrN2S2
15 C6H3BrN2S2
3 C6H3BrN2S2
3 C6H3BrN2S2
1 C6H3IN2S2
245.8925
(245.8922)
245.8925
(245.8922)
245.8932
(245.8922)
245.8922
(245.8922)
293.8780
(293.8784)
293.8786
(293.8784)
293.8771
(293.8784)
185.9720
(185.9722)
197.9920
(197.9922)
323.8032
(323.8027)
369.9096
(369.9097)
253.1077
(253.1069)
7
109–110c
107–108/1
55–56
82 C12H10Cl2N2S2
47 C8H10N2OS
95 C6H3Br2NOS
315.9665
(315.9662)
182.0510
(182.0514)
294.8303
(294.8308)
340.9372
(340.9373)
182.0514
(182.0514)
1j
10a
10b
10c
10d
1k
1l
118–120
95–97
131–132
120–122/4
90
C12H8INSO
1n
1o
1p
1q
1r
1t
130–130.5
137–138
124–126
88–89
92 C8H10N2OS
1 C6H3IN2S2
aElemental analysis, found (calculated), %: 1t: C, 22.21 (22.09); H,
0.51 (0.61); Br, 48.90 (49.08); N, 8.47 (8.59); S, 19.86 (19.63).
b(M + Cl) peak.
8 C6H3IN2S2
cCorresponds to Ref. [30].
3 C6H3FN2S2
18 C7H6N2OS2
10 C6H2Br2N2Sa2
2 C12H7IN2S2
37 C11H19N3SSi
109–110
152–153
108–110
105–107/1
105–107/1
1u
2b
2d
2f
1-Aryl-3-trimethylsilyl-1,3-diaza-2-thiaallenes
(2b,d,f,g–k,o,p)
67 C9H13N3O2SSi 255.0494
(255.0498)
A solution of 0.06 mol of the corresponding ArNSO
in 25 mL of hexane was added to a suspension of
10.0 g (0.06 mol) of LiN(SiMe3)2 in 50 mL of hexane
at 30 C. During 2 hours, the temperature was
raised to 20 C, and 6.6 g (0.06 mol) of Me3SiCl in 10
mL of hexane was added. The precipitate was filtered
off, the solvent was distilled off, and the residue (ex-
cept for 2p) was distilled in vacuum. Compounds
2b,g–k,o were obtained as orange oils (2i solidified
to orange-yellow crystals upon standing), and 2p was
obtained as yellow crystals (from hexane). With Ar
2-Me2NC6H4, 4-Me2NC6H4, only ArNHSiMe3 (45
and 60%, respectively) and (ArN )2S were isolated.
With Ar = 3-O2NC6H4, in both hexane and Et2O (see
[3,9]) only the corresponding (ArN )2S [31] was ob-
tained in high yield. For previously described 3-
CF3C6H4NSNSiMe3, the yield in hexane was 82%
compared to 30% in Et2O [3].
To a suspension of 4.01 g (0.024 mol) of
LiN(SiMe3)2 in 50 mL of Et2O at 60 C, 5.73 g (0.024
mol) of n-O2NC6H4N SCl2 (n = 2–4) [32] was added
in small portions during 15 minutes. During 2 hours,
the temperature was raised to 20 C, the precipitate
was filtered off, and the residue distilled in vacuum.
With n = 2, 4, compounds 2d,f were isolated as yel-
low oils (2f solidified upon standing). With n = 3, a
mixture of ArNSNSiMe3 (2e) and ArNHSiMe3 along
with (ArN )2S was obtained.
144–145/1, 52-53 54 C9H13N3O2SSi 255.0507
(255.0498)
2g
2h
2i
126–128/1
62 C9H13BrN2SSi 287.9723
(287.9753)
60 C9H13BrN2SSi 287.9761
(287.9753)
124–126/1
28–29,125–126/3 48 C9H13BrN2SSi 287.9731
(287.9753)
141–143/1
134–135/1
121–123/0.4
2j
30 C9H13IN2SSi
65 C9H13IN2SSi
20 C9H13IN2SSi
335.9618
(335.9615)
335.9618
(335.9615)
335.9621
(335.9615)
2k
2l
2o
2p
125–126/1
75–76
60 C9H12Br2N2SSi 366 (366)
17 C15H17IN2SSi
411.9926
(411.9928)
153.9775
3a
3b
3c
3d
3e
3f
194–196 (dec.) 54 C6H4ClNS2
154–158 (dec.) 74 C7H6ClNOS2
170–174 (dec.) 79 C7H6ClNOS2
193–197 (dec.) 60 C6H3BrClNS2
185–190 (dec.) 58 C7H3Cl2NS2
180–185 (dec.) 54 C6H3ClIN2S
(153.9785)b
183.9887
(183.9891)b
183.9896
(183.9891)b
231.8874
(231.8891)b
201.9512
(201.9552)b
279.8750
(279.8754)b
297.0221
6
126–127
C12H9F2N3S2
(297.0221)

572 Makarov et al.
TABLE 6 Spectral Data of the Compounds
NMRa
13C
Compound
1H
15N (J, Hz)
UV/Visb
(nm) (log ε)
max
1i
6.85, 6.59, 5.69 137.1, 134.8, 133.3, 276.9 (s), 256.4 (s) 635 (2.67), 391 (3.18), 303 (4.18), 296 (4.18)
122.9, 119.5, 117.6
1j
6.92, 6.06, 5.66 139.4, 135.3, 125.9, 273.0 (s), 259.4 (d, 633 (2.57), 377 (3.02), 290 (4.33)
125.0, 123.4, 114.4 2.3)
1k
1l
6.73, 5.92, 5.75 137.5, 133.0, 126.7, 266.2 (s), 260.3 (d, 629 (2.52), 376 (2.92), 365 (2.93), 298
125.7, 124.1, 117.2 2.4)
(4.06), 290 (4.66)
6.78, 6.39, 5.69 139.6, 136.1, 130.9, 264.7 (s), 252.3 (d, 624 (2.65), 386 (3.16), 298 (4.20)
122.0, 119.6, 116.9 2.8)
1n
7.14, 6.24, 5.53 141.5, 139.0, 131.2, 272.3 (s), 259.2 (d) 629 (2.37), 379 (3.01), 289 (4.25)
125.2, 115.4, 94.2
626 (2.66), 402 (3.09, sh), 379 (3.23), 291
(4.20)
7.02, 6.27, 5.72 142.1, 140.6, 131.6, 269.2 (s), 254.7 (d) 624 (2.61), 393 (3.11), 288 (3.99)
122.9, 120.0, 95.2
6.25, 5.90, 5.59 165.2, 134.5, 124.6, 260.7 (s), 256.5 (s) 608 (2.63), 296 (4.24), 288 (4.23)
117.5, 115.4, 112.3
6.06, 5.89, 5.41, 163.4, 131.8, 124.6, 263.4 (d, 2.5), 249.1 626 (2.84), 378 (3.39), 357 (3.09), 303 (4.23)
1o
1p
1qc
1r
6.98, 6.10, 5.61 139.5, 138.3, 132.2, 264d
124.3, 117.0, 96.7
3.63
116.5, 112.0, 111.5, (s)
55.3
1t
6.90, 5.77
140.7, 137.6, 125.2, 270d, 251d
123.4, 119.7, 116.7
632 (2.38), 390 (2.82), 303 (4.01), 294 (4.00)
626 (2.77), 380 (3.38, sh), 311 (4.35)
1u
2b
2d
2g
2h
7.60, 7.00, 6.68,
5.86, 5.83
7.07, 6.91, 6.48,
2.90, 0.21
7.91, 7.55, 7.36,
7.23, 0.16
7.69, 7.63, 7.34,
6.88, 0.27
401 (3.40, sh), 342 (3.97), 281 (3.97), 248
(4.12)
344 (3.75), 266 (4.05)
351 (3.47), 270 (3.53), 267 (3.56)
342 (3.67), 245 (3.59)
7.80, 7.48, 7.23,
7.12, 0.22
2i
2j
7.85, 7.34, 0.37
7.84, 7.34, 7.23,
6.79, 0.16
352 (3.94)
350 (3.15), 263 (3.54), 257 (3.56)
2k
7.98, 7.51, 7.44,
6.99, 0.22
342 (3.74), 255 (3.51), 225 (3.82)
2l
2o
2p
7.58, 7.42, 0.24
7.78, 7.51, 0.30
7.84, 7.77, 7.54,
7.35, 0.34
358 (3.57), 245 (3.44)
340 (3.78)
367 (4.28), 270 (4.22)
3ac
3b
9.09, 9.00, 8.65, 164.0, 156.2, 139.1, 406d
426 (3.25), 347 (4.38)g
551 (3.54), 344 (4.05)
8.46f
8.60, 8.39, 7.62, 159.8, 158.1, 157.8, 378d
133.9, 128.1, 123.4
4.42
145.6, 115.7, 111.8,
58.1
3c
8.79, 8.29, 7.76, 173.5, 163.9, 161.8, 389d
439 (3.87), 368 (3.77)
4.39f
131.9, 130.8, 105.2,
59.7
3d
3e
9.22, 8.84, 8.61 166.3, 156.7, 143.6, 406d
131.7, 131.3, 125.0
8.99, 8.90, 2.95 165.5, 157.2, 154.9, 400d
148.6, 129.8, 125.3,
440 (3.43, sh), 378 (4.21)
414 (4.00)
21.6
3f
6c
9.49, 8.77, 8.72 167.2, 158.3, 149.7, 401.7 (d, 1.4)
139.2, 125.9, 103.1
7.04–6.98, 5.79 160.6, 158.7, 142.0, 298d,h
140.6, 116.0, 115.8

Substituted 1,3,2,4-Benzodithiadiazines: Novel Derivatives, By-Products, and Intermediates 573
TABLE 6 (Continued ) Spectral Data of the Compounds
NMRa
Compound
1H
13C
15N (J, Hz)
UV/Visb
(nm) (log ε)
max
7
7.12–7.04, 6.55,
4.21
10a
7.14–7.09, 6.62,
2.90
436 (3.20)
10b
10c
7.90, 7.68
7.93, 7.78, 7.59,
7.33
313 (3.70)
354 (4.32)
10d
8.35, 7.10, 6.75,
6.70, 2.87
392 (2.00)
aIn CDCl3; 7, 10a, b, CCl4; 3a–d, CF3COOH; 2d, neat liquid.
bIn CHCl3; 2b,d,g–i, o, 6, 10c, heptane; 3a–f, CF3COOH.
c
19F: 1q, 55.5; 6, 45.1, 39.9.
d14N
ecf. 1,3,2-benzodithiazolium chloride (4) [23]: 1H: 9.09, 8.22; 13C: 163.3, 132.6, 122.8; 14N: 378;
(log ε) 398 (3.38).
max
f cf. Ref. [45]
gcf. Ref. [46]
hUnresolved asymmetric broad line.
Substituted 1,3,2,4-Benzodithiadiazines (1i-l,n–
r,t,u)
Reactions of Compounds 1 with SCl2. 1,2,3-
Benzodithiazolium Chloride (3a) and Its
4-Methoxy- (3b), 6-Methoxy- (3c),
5-Bromo- (3d), 5-Methyl-6-chloro- (3e), and
5-Iodo (3f) Derivatives, and 14N NMR Detection
of Thiazyl Chloride NSCl
Solutions of 0.01 mol of Ar N
S N SiMe3 (2, this
work and [3]) and 0.51 g (0.5 mol) of SCl2 (0.0075
mol in the case of 2g,h,k), each in 30 mL of CH2Cl2,
were mixed by adding them to 300 mL of CH2Cl2 at
20 C, over a period of 1 hour. After an additional 1
hour, the reaction mixture was filtered, the solvent
was distilled off, and the residue was sublimed in
vacuum and recrystallized from hexane. Com-
pounds 1j,l,o,q,r,u were obtained as black crystals,
1i,k were obtained as shiny black-green prisms, and
1t was obtained as lustrous dark-green crystals.
A mother liquor from recrystallization of 1j was
evaporated to dryness. The residue (which consisted
of a mixture of 60% of 1l and 40% of 1j according
to the 1H NMR data) was treated with an amount of
SCl2 equimolar to 1j under conditions described be-
low (Reactions of compounds 1 with SCl2). Com-
pound 1l was isolated as black crystals.
The compounds 1n,p (38%) were obtained by
sublimation of reaction residue as a 3:2 mixture (1H
NMR). Fractional crystallization from hexane af-
forded pure 1n as black needles. A sample of pure
1p was prepared by reaction of the 1n,p mixture
with SCl2 (see below Reactions of compounds 1 with
SCl2).
At 20 C, a solution of 0.003 mol of the corresponding
1 (this work and [3]) in 10 mL of CH2Cl2 was added
during 45 minutes to a solution of 0.31 g (0.003 mol)
of SCl2 in 10 mL of the same solvent. After 15 min-
utes, the precipitate was filtered off, dried in
vacuum, and, in the case of 3a–c, recrystallized from
SOCl2:CCl4 (3:1). Salts 3a–e [12] were obtained as
crystalline solids (in the case of 3e,d chlorination of
a carbocycle occurred during reaction or recrystal-
lization, respectively).
To detect NSCl, the interaction was performed
in CCl4 with more concentrated ( 0.6 M) solutions,
and the 14N NMR spectrum of the reaction mix-
ture was measured periodically during the reaction.
The 14N NMR identification of NSCl ( 14N: 730) was
based on previously reported data [33] and on con-
trol measurements with an authentic sample pre-
pared [33] by heating a solution of (NSCl)3 [34] in
CCl4. At the same time, (NSCl)3 [33,35] was not found
in the reaction mixtures in accordance with the con-
clusion that trimerization of NSCl is very ki-netically
hindered [33].
At 20 C, to a solution of 0.247 g (0.001 mol) of a
1:1 mixture of 6-Br (1j) and 8-Br (1l) derivatives of
1 in 5 mL of CH2Cl2 was added during 15 minutes to
a solution of 0.051 g (0.0005 mol) of SCl2 in 5 mL of
1,3,2,4-Benzodithiadiazine (1s)
Under the conditions described previously, com-
pound 1s [6] was obtained from 2j in 9% yield.

574 Makarov et al.
the same solvent. The precipitate was filtered off. Salt
3d (0.081 g; 60%) was obtained as a yellow pow-
der. Its purity was checked by 1H NMR spectroscopy.
No traces of the 7-Br isomer have been found. The
filtered solution was evaporated to dryness, and the
residue was sublimed in vacuum. A 10:1 (1H NMR)
mixture (0.121 g) of 1l and 1j was obtained. Recrys-
tallization from hexane gave pure 1l (0.060 g).
In a similar way, 3f (light brown powder) and 1p
(black crystals) were prepared from the 3:2 mixture
of 1n and 1p.
Cyclotetra(azathiene) (SN)4
At 20 C, solutions of 4.12
g (0.02 mol) of
(Me3SiN )2 S [37] and 2.06 g (0.02 mol) of SCl2, each
in 30 mL of CH2Cl2, were mixed by adding them to
100 mL of CH2Cl2 over a period of 1 hour. After an
additional 2 hours, the mixture was filtered, the sol-
vent was distilled off, and the residue was recrys-
tallized from toluene. (SN)4 [38] (1.57 g; 85%) was
obtained as orange-yellow needles, m.p. (decompo-
sition) 185–186 C (cf. [38]).
Reaction of 5,6,7,8-tetrafluoro-1,3,2,4-benzodi-
thiadiazine [15] with SCl2 provided only unidentified
products without any evidence of the formation of
the polyfluorinated analog of 3a.
Reaction of 1-(4-fluorophenyl)-3-trimethylsilyl-
1,3-diaza-2-thiaallene (2m) with
1,2,3-benzodithiazolium chloride (3a)
At 20 C, to a suspension of 0.40 g (0.0021 mol) of 3a
(this work and Ref. [12]) in 5 mL of CH2Cl2 was
added, during 20 minutes, a solution of 0.48 g
(0.0021 mol) of 2m [3] in 5 mL of the same solvent.
The mixture was stirred overnight, the solution was
filtered off, the solvent was distilled off, and the res-
idue was recrystallized twice from hexane. Com-
pound 6 was obtained in 0.01 g yield as small orange
needles.
Reaction of 1,3,2,4-Benzodithiadiazine (1s)
with (NSCl)3 and Cl2
At 20 C, to a solution of 0.17 g (0.0007 mol) of
(NSCl)3 [34] in 2 mL of CCl4 was added a solution of
0.34 g (0.002 mol) of 1s [6] in 2 mL of the same sol-
vent. The crude salt 3a (0.38 g; 80%) was obtained
as a brown precipitate.
At 20 C, an excess of Cl2 was passed through a
solution of 0.34 g (0.002 mol) of 1s in 10 mL of CCl4.
A slightly exothermic fast reaction afforded a com-
plex mixture (1H NMR, MS) of unidentified
products.
N-Sulfinylanilines. RC6H4NSO (10) was pre-
pared by the Michaelis reaction [39] from the
corresponding amines and SOCl2 [40] except for the
Me2N-substituted derivatives synthesized from
ArNH2 and PhSO2 NSO [40] or ArNH2 and dipyrid-2-
yl sulfite [47]. Most compounds were known earlier
[40], except for those in which R = 3-Me2N (10a,
dark red oil), 3,5-Br2 (10b, pale yellow crystals), 4-
(40-IC6H4) (10c, bright yellow crystals) and 2-Me2N
(10d, dark red oil) derivatives.
Attempted Preparation of 1 from 2-
Aminobenzenethiols
Reaction of 5-Chloro-2-aminobenzenethiol (9)
with (SN)4 A mixture of 0.80 g (0.005 mol) of 9 [30],
0.46 g (0.0025 mol) of (SN)4 (see below), and 50 mL
of MeCN was boiled until NH3 evolution ceased ( 1
hour). The mixture was filtered, the solvent was dis-
tilled off, and the residue was recrystallized from tol-
uene. Compound 7 was obtained as yellow crystals.
4-Iodo-40-aminobiphenyl [41]. 70%, Colorless
plates, m.p. 165–165.5 C (hexane/toluene) for prep-
aration of 10c was obtained by SnCl2/HCl reduction
of 4-iodo-40-nitrobiphenyl synthesized in one step
from biphenyl under the Tronov–Novikov conditions
[42] by a known procedure [43] [37%, colorless crys-
tals, m.p. 217–218 C (toluene) (212 C [43])]. Both
compounds were purified by column chromatogra-
phy on silica followed by recrystallization. Warning:
the compounds needed to be treated with caution
because they are potential carcinogens [44].
Attempted Preparation of 1 from Herz Salts
Reaction of 1,2,3-Benzodithiazolium Chloride
(3a) with Trimethylsilyl Azide, and ESR Detection of
1,2,3-benzodithiazolyl (8) A mixture of 0.115 mg
6
6
(10 mol) of Me3SiN3 [36], 0.190 mg (10 mol) of
3a, and 1 mL of hexane, outgassed by three freeze-
pump-thaw cycles, was heated in an ESR valve-
equipped quartz capillary tube to 50 C. The ESR
spectrum of the solution was identical to that of 8
[1]. Experiments on a preparative scale (in both hex-
ane and MeCN) were accompanied by gas evolution
and, after usual work-up, gave unidentified red tar.
Similar results were obtained with salts 3b,c.
ACKNOWLEDGMENTS
The authors are grateful to Mr. Ivan V. Vlasyuk
for ESR measurements and Mr. Yuri V. Pavlov for
assistance in some preparations.

Substituted 1,3,2,4-Benzodithiadiazines: Novel Derivatives, By-Products, and Intermediates 575
leva, L. N. Molecular Distortions in Ionic and Excited
States; CRC Press: Boca Raton, FL, 1995.
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