A new thiatriazine isomer: Synthesis, tautomerism, and molecular structure of 3,6-diphenyl-4H-1,2,4,5-thiatriazine as a precursor to the 1,2,4,5-thiatriazinyl radical

Article abstract of DOI:10.1021/jo991126l

The diphenyl derivative of 4H-1,2,4,5-thiatriazine (5) was prepared by oxidative cyclization of 9. The molecular structure of 5, obtained by X-ray diffraction [orthorhombic, Pna2₁, a = 9.7746(13) A, b = 21.692(2) A, c = 5.6580(8) A, compares favorably with that predicted with ab initio calculations. The thiatriazine 5 was used as a precursor to the 3,6-diphenyl- 1,2,4,5-thiatriazinyl radical (4) through either oxidation with PbO₂, or conversion to and reduction of sulfiminyl chloride 6 with Ph₃Sb. The weak ESR quintet (a(N) = 1.03 mT, g = 2.0103) observed in the latter case correlates well with the molecular structure of 4, but the results of DFT calculations are ambiguous. Ab initio calculations show that 4H-1,2,4,5- thiatriazine (I-4H) is the most stable tautomer and is the second most stable isomer among the six possible thiatriazines. All isomeric thiatriazinyl radicals exhibit similar spin distribution patterns. 1,2,4,5-Thiatriazinyl radical (I-R) is calculated to be 23.1 kcal/mol less stable than the most stable 1,2,4,6 isomer II-R.

Full text of DOI:10.1021/jo991126l

VOLUME 65, NUMBER 4
FEBRUARY 25, 2000
© Copyright 2000 by the American Chemical Society
Articles
A New Th ia tr ia zin e Isom er : Syn th esis, Ta u tom er ism , a n d
Molecu la r Str u ctu r e of 3,6-Dip h en yl-4H-1,2,4,5-th ia tr ia zin e a s a
P r ecu r sor to th e 1,2,4,5-Th ia tr ia zin yl Ra d ica l
J ohn M. Farrar, Mahesh K. Patel, and Piotr Kaszynski*
Organic Materials Research Group, Department of Chemistry, Vanderbilt University,
Nashville, Tennessee 37235
Victor G. Young, J r.
X-ray Crystallographic Laboratory, Department of Chemistry, University of Minnesota,
Minneapolis, Minnesota 55455
Received J uly 14, 1999
The diphenyl derivative of 4H-1,2,4,5-thiatriazine (5) was prepared by oxidative cyclization of 9.
The molecular structure of 5, obtained by X-ray diffraction [orthorhombic, Pna21, a ) 9.7746(13)
Å, b ) 21.692(2) Å, c ) 5.6580(8) Å], compares favorably with that predicted with ab initio
calculations. The thiatriazine 5 was used as a precursor to the 3,6-diphenyl-1,2,4,5-thiatriazinyl
radical (4) through either oxidation with PbO2, or conversion to and reduction of sulfiminyl chloride
6 with Ph3Sb. The weak ESR quintet (aN ) 1.03 mT, g ) 2.0103) observed in the latter case correlates
well with the molecular structure of 4, but the results of DFT calculations are ambiguous. Ab initio
calculations show that 4H-1,2,4,5-thiatriazine (I-4H) is the most stable tautomer and is the second
most stable isomer among the six possible thiatriazines. All isomeric thiatriazinyl radicals exhibit
similar spin distribution patterns. 1,2,4,5-Thiatriazinyl radical (I-R) is calculated to be 23.1 kcal/
mol less stable than the most stable 1,2,4,6 isomer II-R.
In tr od u ction
whose properly 3,6-disubstituted (“para”) derivatives
satisfy the geometric requirements of calamitic liquid
crystals.3,4
A literature search shows that thiatriazines II-VI are
known ring systems and the derivatives of 1,2,4,6-
thiatriazine (II) are the most abundant.5,6 The majority
of the known thiatriazine derivatives are cyclic sulfon-
Liquid crystalline radicals are rare, and those with a
π-delocalized neutral spin are still unknown.1 We have
focused on the -N-S- fragment as a spin source and
designed new sulfur-nitrogen heterocyclic rings which
are potential structural elements for this class of materi-
als.2 1,2,4,5-Thiatriazine (I in Figure 1) is one such ring
* To whom correspondence should be addressed. Phone/fax: (615)
322-3458. E-mail: PIOTR@ctrvax.vanderbilt.edu.
(1) Kaszynski, P. In Magnetic Properties of Organic Materials; Lahti,
P. M., Ed.; Marcel Dekker: New York, 1999; pp 305-324.
(2) Patel, M. K.; Huang, J .; Kaszynski, P. Mol. Cryst. Liq. Cryst.
1995, 272, 87.
(3) Toyne, K. J . In Thermotropic Liquid Crystals; Gray, G. W., Ed.;
Wiley & Sons: New York, 1987; pp 28-63.
(4) Demus, D. Mol. Cryst. Liq. Cryst. 1988, 165, 45.
(5) Fischer, E. Sulfur Rep. 1992, 11, 257.
(6) Fischer, E. In Hetarene IV; Schaumann, E., Ed.; Georg Thieme
Verlag: New York, 1998; Vol. E9c, p 803.
10.1021/jo991126l CCC: $19.00 © 2000 American Chemical Society
Published on Web 01/26/2000

932 J . Org. Chem., Vol. 65, No. 4, 2000
Farrar et al.
Sch em e 1
F igu r e 1. Six thiatriazine ring systems with carbon atoms
in the para, meta, and ortho positions.
amides and parts of fused ring systems. Single-ring
thiatriazines containing a two-coordinated sulfur atom
are rather rare, and those with six, seven, or eight π
electrons in the six-atom heterocyclic structure are
scarce. For instance, there are only a few examples of
such π systems with II,7 III,8,9 and V10 skeletons in
addition to our recently reported derivative of I.2
Although all thiatriazines I-VI can, in principle, form
seven π electron radicals, only derivatives of II have been
studied in this context.11 3,5-Disubstituted 1,2,4,6-thia-
triazinyls, and among them the diphenyl derivative 1,12
are persistent and thermally stable radicals. They have
been obtained by one-electron reduction of the cyclic
sulfinimidoyl chlorides such as 2, which can be prepared
from the corresponding sulfenamide 3.7
F igu r e 2. Possible intermediates for routes to I shown in
Scheme 1.
the results of ab initio calculations, which assess the
stability of the tautomeric forms for 5 and compare its
thermodynamic stability with the five other regioisomers.
We also investigate the formation of the chloride 6 and
the generation of radical 4. We compare the experimental
ESR spectra with those calculated and discuss the
relative stabilities of 1 and 4 in the context of the
remaining members of the thiatriazine series.
To assess the usefulness of thiatriazinyl I as a struc-
tural element for liquid crystals, we set out to study 3,6-
diphenyl-1,2,4,5-thiatriazinyl (4), the para isomer of 1,
which, in principle, could be accessed from the corre-
sponding 4H-1,2,4,5-thiatriazine 5 or chloride 6.
Resu lts a n d Discu ssion
Retr osyn th etic An a lysis for th e 1,2,4,5-Th ia tr ia z-
in e Rin g Closu r e. Scheme 1 shows a retrosynthetic
analysis of I with five indicated possible routes, and
Figure 2 presents likely intermediates for each approach.
The critical N-S bond can be formed at different stages
of the ring construction, but due to its sensitivity, it is
preferably formed at the last step in either a bimolecular
reaction (path a and path b) or a intramolecular cycliza-
tion reaction (path c and path d).
The formation of the thiatriazine ring in path a follows
the preparation of other ring systems,13,14 the heterocyclic
ring of 6 could be formed through a condensation reaction
of 1-amino-1,4-diphenyl-2,3-diaza-1,3-butadiene15 (7) with
SCl2, in which the initially formed sulfinimide inserts into
the iminyl dCsH bond. Alternatively, the sulfur center
may act as a nucleophile and react with 1-chloro-4-(N-
chloroamino)-1,4-diphenyl-2,3-diaza-1,3-butadiene (8) to
form 5, according to path b.
Here we describe the methodology for construction of
the 1,2,4,5-thiatriazine ring and report the synthesis and
molecular and crystal structures of its 3,6-diphenyl
derivative 5. The experimental data are compared with
(7) Boere´, R. T.; Cordes, A. W.; Hayes, P. J .; Oakley, R. T.; Reed, R.
W.; Pennington, W. T. Inorg. Chem. 1986, 25, 2445.
(8) Butler, R. N.; Evans, A. M.; McNeela, E. M.; O’Halloran, G. A.;
O’Shea, P. D.; Cunningham, D.; McArdle, P. J . Chem. Soc., Perkin
Trans. 1 1990, 2527.
(9) Hassan, A. A.; Ibrahim, Y. R.; Semida, A. A.; Mourad, A.-F. E.
Liebigs Ann. Chem. 1994, 989.
In path c the N-S bond of 5 can be formed from
thiobenzoyl derivative 916 via the corresponding sulfenyl
halide, which cyclizes to form the thiatriazine. Another
(10) Spasov, A.; Chemishev, B. Dokl. Bolg. Akad. Nauk 1970, 23,
791; Chem. Abstr. 1970, 73, 120593z.
(11) Boere´, R. T.; Oakley, R. T.; Reed, R. W.; Westwood, N. P. C. J .
Am. Chem. Soc. 1989, 111, 1180.
(13) Levchenko, E. S.; Borovikova, G. S.; Borovik, E. I.; Kalinin, V.
N. J . Org. Chem. USSR 1984, 20, 176.
(14) Markovskii, L. N.; Darmokhval, E. A.; Levchenko, E. S. J . Org.
Chem. USSR 1973, 9, 2055.
(12) Hayes, P. J .; Oakley, R. T.; Cordes, A. W.; Pennington, W. T.
J . Am. Chem. Soc. 1985, 107, 1346.
(15) van der Burg, W. J . Recl. Trav. Chim. Pays-Bas 1955, 74, 257.
(16) Doyle, K. M.; Kurzer, F. Tetrahedron 1976, 32, 1031.

A New Thiatriazine Isomer
Sch em e 2
J . Org. Chem., Vol. 65, No. 4, 2000 933
Sch em e 3
Sch em e 4
possibility for thiatriazine ring closure of I and prepara-
tion of 5 arises from decomposition of azide 10 and the
intramolecular nitrene reaction with the sulfur function-
ality and elimination of an alkene (path d).
Alternatively, the insertion of a nitrogen atom (path
e) to form the N-C bond can be envisioned using sulfenyl
azide 11 (obtained from the corresponding sulfenyl halide
and an azide) in an way analogous to that of a similar
ring closure reaction.17 The intermediate sulfenyl nitrene
should insert into the iminyl dCsH bond in the final
step.
All five approaches were investigated in some detail,
but only path c led to the efficient preparation of I as
4H-1,2,4,5-thiatriazine 5. Attempts at generation of I
along path d led to unexpected results described else-
where.18
Syn th esis of 5. N-Thiobenzoylbenzamidrazone16 (9),
an intermediate to 5 in path c, was obtained in 76% yield
from thiobenzhydrazide19 (12) and benzonitrile in the
presence of 2 equiv of trimethylaluminum. This new
preparation of 9 represents a successful extension of the
original method20 developed for benzhydrazide and benz-
amidrazone to their sulfur analogue thiobenzhydrazide
(12).
Treatment of benzamidrazone 9 with bromine in the
presence of pyridine gave 3,6-diphenyl-4H-1,2,4,5-thia-
triazine (5) along with 2,5-diphenyl-1,3,4-thiadiazole (13)
as shown in Scheme 2. The ratio of 5:13 is sensitive to
the reaction conditions. The highest yields of thiatriazine
5 (up to 70%) with less than 10% of the byproduct 13
were obtained at 0 °C and using a large excess of
pyridine. However, the most reliable results and yields
up to 50% were obtained using 0.5 equiv of bromine.
When stoichiometric amounts of pyridine and bromine
were used, the yields significantly varied from run to run
and ranged from 10% to 45%.
a few similar examples for the six-membered rings.23-25
Other oxidants and bases were ineffective in the
generation of thiatriazine 5. In the case of NCS, t-BuOCl,
and I2/pyridine as oxidants, the predominant product was
thiadiazole 13, and only traces of the desired 5 were
detected at best. An attempt to obtain 5 by initial
deprotonation of 9 with NaH followed by treatment with
iodine or SO2Cl2 as oxidants resulted in the preferential
formation of 13 (43% yield), while the desired product
was isolated in less than 7% yield. The exclusive forma-
tion of 13 was observed when 9 was treated with pyridine
or under acidic conditions.16 We have found that about
80% of 9 was converted into 13 upon storage at room
temperature for over a year. Thiatriazine 5 also shows
contamination with thiadiazole 13 after prolonged stor-
age.
The formation of the thiadiazole ring of 13 can be
rationalized by intramolecular attack of the thiolate
anion on the amidinyl carbon atom and loss of ammonia
after proton transfer (Scheme 3). Running the reaction
under neutral or weakly acidic conditions disfavors the
formation of the five-membered ring, and 5 becomes the
major product.
Another approach to 5 through disulfide 14 was briefly
investigated (path e). The disulfide 14 was envisioned to
react with bromine followed by treatment with trimeth-
ylsilyl or sodium azide to yield sulfenyl azide 11, which
via a nitrene insertion into the carbon-hydrogen bond
would form 5 (Scheme 4).
Treatment of 14 with 0.5 equiv of Br2 in CCl4 produced
a mixture characterized by a complex NMR spectrum,
which was much simplified when 1 equiv of Br2 was used.
In both spectra, the resonance at 8.32 ppm assigned to
the NdCsH proton was absent and the multiplet corre-
sponding to the ortho hydrogens was shifted downfield
from about 7.7 to about 8.1 ppm. Such a shift may
indicate that upon bromination an intramolecular cy-
clization occurs and the thiadiazole ring of 13 is formed.
This is not an unexpected result considering a great
tendency of divalent sulfur-containing species to close
The cyclization reaction is considered to proceed through
a sulfenyl halide intermediate. There are numerous
examples of such oxidative N-S bond formation reported
for the five-membered heterocycles,21,22 but there are only
(17) Wolmersha¨user, G.; Schnauber, M.; Wilhelm, T. J . Chem. Soc.,
Chem. Commun. 1984, 573.
(18) Kaszynski, P.; Young, V. G., J r. J . Am. Chem. Soc., in press.
(19) Singh, N. K.; Sharma, U. Synth. React. Inorg. Met.-Org. Chem.
1989, 19, 235.
(20) Kauffmann, T.; Ban, L.; Kuhlmann, D. Chem. Ber. 1981, 114,
3684.
(21) Schulze, B. In Hetarene III; Schaumann, E., Ed.; Georg Thieme
Verlag: New York, 1993; Vol. E8a, Part 1, p 668.
(22) Dietz, J . In Hetarene III; Schaumann, E., Ed.; Georg Thieme
Verlag: New York, 1994; Vol. E8d, Part 4, p 105.
(23) J imonet, P.; Audiau, F.; Barreau, M.; Mignani, S. Heterocycles
1993, 36, 2745.
(24) Vasudeva, S. K.; Mahajan, M. P.; Ralhan, N. K. J . Indian Chem.
Soc. 1974, 51, 631.
(25) Yadav, L. D. S.; Sharma, S. Indian J . Chem., Sect. B 1993, 32,
882 and references therein.

934 J . Org. Chem., Vol. 65, No. 4, 2000
Farrar et al.
Sch em e 5
F igu r e 3. Thermal ellipsoid diagram of 5. Ellipsoids are
drawn at 50% probability, and hydrogen atoms are given
arbitrary radii.
general procedure.31 Alternatively, a suspension of an-
hydrous Li2S in THF was prepared from (TMS)2S and
MeLi32 and reacted with dichloride 8. No traces of
thiatriazine 5 nor starting 8 were observed in either
reaction. A similar negative result was obtained when 8
and (TMS)2S were refluxed in dry benzene for several
hours. These reactions were not investigated further.
Dichloride 8 was obtained in 22% yield by chlorination
of amidrazone 7 with tert-butyl hypochlorite in methylene
chloride (Scheme 6). Although the formation of the N,N-
dichloro isomer is also possible, the spectroscopic data
are fully consistent with the structure of 8. The IR
spectrum of 8 exhibits a single peak at 3287 cm-1
characteristic of a secondary amine. The N-H proton
peak appears in the 1H NMR spectrum as a broad singlet
at 9.64 ppm, while the imine peak in the starting 7 at
8.57 ppm is absent. The position of the peak of the
benzylidene carbon atom in 7 (155 ppm)33 is substantially
shifted upfield in 8 to 132 ppm, while the chemical shift
of the amidrazonyl carbon in 7 (159 ppm)33 is less affected
by the chlorination of the nitrogen atom and is shifted
downfield by 4 ppm.
Sch em e 6
five-membered rings such as thiadiazole.26 This attempt
was not investigated any further.
The synthesis of 14 was accomplished via modification
of the procedure described by Holmberg27 (Scheme 5). The
structure of the disulfide was confirmed by NMR analy-
sis, which showed a sharp peak at 8.32 ppm character-
istic of the NdCsH proton and two carbon resonances
at 160.2 and 166.5 ppm, which can be ascribed to the
iminyl NdCsH and thioimidyl NdCsS groups, respec-
tively. These NMR absorptions are absent in 15, the
precursor to 14, whose spectra are consistent with the
1,3,4-thiadiazoline tautomeric form 15-c rather than with
the hydrazide 15-o.28,29
N-Benzylidenobenzamidrazone (7) was conveniently
prepared in 53% yield using an adaptation of a literature
procedure in which benzaldehyde was used instead of
acylamino R-ketoester.34 The acyclic structure of 7 was
confirmed by NMR analysis.33
It has been reported that oxidation of 15 under acidic
or neutral conditions leads to the exclusive formation of
1,3,4-thiadiazole (13),27,30 while the conversion to 14
requires the presence of a base.27 NMR analysis of the
crude reaction product obtained under the latter condi-
tions indicated the presence of significant amounts of 13.
As was demonstrated before,29,30 base shifts the tauto-
meric equilibrium to the open form anion 15-o-, which
then apparently undergoes a persulfate oxidation to 14.
Molecu la r a n d Cr ysta l Str u ctu r es for 5. X-ray
analysis35 of a single crystal of 5 confirmed its anticipated
molecular structure and revealed the 4H tautomer of the
puckered 1,2,4,5-thiatriazine ring (Figure 3). The experi-
mental details are collected in Table 1, and a summary
of the bond lengths and angles for 5 is given in Table 2.
The thiatriazine ring in 5 adopts a boatlike or “open
book” conformation characteristic of eight-π-electron six-
atom heterocyclic 1,4-dienes.7,8,36,37 The ring is folded
along the S(1)‚‚‚N(2) axis by about 45°, and the two
halves of the open book are nearly coplanar with torsional
angle values of 6.2(6)° for the S(1)-N(1)-C(2)-N(2) and
3.2(6)° for the S(1)-C(1)-N(3)-N(2) fragments. The S(1)
and the N(2) atoms are displaced from the plane of the
remaining ring atoms by about 0.62 and 0.47 Å, respec-
tively.
Finally, the synthesis of thiatriazine 5 was attempted
using dichloride 8 and (TMS)2S as a source of S2- as
shown in Scheme 6 (path b in Figure 1). The sulfide anion
was generated in situ by treating a mixture of dichloride
8 and (TMS)2S with Bu4NF (1 M in THF) according to a
(32) Steliou, K.; Salama, P.; Corriveau, J . J . Org. Chem. 1985, 50,
4969.
(26) Flowers, W. T.; Robinson, J . F.; Taylor, D. R.; Tipping, A. E. J .
Chem. Soc., Perkin Trans. 1 1981, 356.
(27) Holmberg, B. Ark. Kemi 1956, 9, 65.
(28) Evans, D. M.; Taylor, D. R. J . Chem. Soc., Chem. Comunn. 1982,
188.
(29) Evans, D. M.; Hill, L.; Taylor, D. R.; Myers, M. J . Chem. Soc.,
Perkin Trans. 1 1986, 1499.
(33) Zelenin, K. N.; Khrustalev, V. A.; Sergutina, V. P. J . Org. Chem.
USSR 1980, 16, 822.
(34) Charles, I.; Latham, D. W. S.; Hartley, D.; Oxford, A. W.; Scopes,
D. I. C. J . Chem. Soc., Perkin Trans. 1 1980, 1139.
(35) Preliminary results are presented in ref 2.
(36) Daley, S. T. A. K.; Rees, C. W.; Williams, D. J . J . Chem. Soc.,
Chem. Commun. 1984, 57.
(30) Mayer, K. H.; Lauerer, D. Liebigs Ann. Chem. 1970, 731, 142.
(31) Hu, J .; Fox, M. A. J . Org. Chem. 1999, 64, 4959.
(37) Sundermeyer, J .; Roesky, H. W.; Noltemeyer, M. Angew. Chem.,
Int. Ed. Engl. 1989, 28, 609.

A New Thiatriazine Isomer
J . Org. Chem., Vol. 65, No. 4, 2000 935
Ta ble 1. Cr ysta l Da ta a n d Su m m a r y of Da ta Collection for 5
empirical formula
fw
cryst habit, color
cryst dimens
space group
cell dimens (Å)
C
14H11N3S
θ for data collectn (deg)
index ranges
total no. of reflns
no. of independent reflns
refinement method
abs correctn
1.88 e θ e 25.06
253.32
0 e h e 11, 0 e k e 25, -6 e l e 6
prism, yellow
0.22 × 0.05 × 0.05 mm
Pna21 (no. 33)
a ) 9.7746(13)
b ) 21.692(2)
c ) 5.6580(8)
1199.7(3)
4
6251
2123 (Rint ) 0.0596)
full-matrix least-squares on F
SADABS (Sheldrick, 1996)
1.00 and 0.414
0.1(2)
2
max and min transitn
abs structure param
no. of data/restraints/params
R indices (I > 2σ(I) ) 1506)
R indices (all data)
V (Å3)
2121/2/167
Z
R1 ) 0.0679, Rw2 ) 0.1608
R1 ) 0.0900, Rw2 ) 0.1722
0.952
calcd density (g/cm3)
1.403
0.253
528
abs coeff (mm-1
)
goodness-of-fit on F2
max/min peak in final diff map (e-/Å3)
F(000)
0.879/-0.619
Ta ble 2. Selected Exp er im en ta l a n d Ca lcu la ted Bon d Len gth s (Å) a n d An gles (d eg) for 5
distance
exptl
calcda
angle
exptl
calcda
99.7
116.7
123.1
119.3
120.8
29, 37
40
152 (0.53)
144.5 (0.41)
S(1)-N(1)
N(1)-C(2)
C(2)-N(2)
N(2)-N(3)
N(3)-C(1)
C(1)-S(1)
C(1)-CPh
C(2)-CPh
S(1)‚‚‚N(2)
1.705(5)
1.308(6)
1.371(6)
1.434(6)
1.282(6)
1.754(6)
1.480(7)
1.496(7)
2.77
1.710
1.262
1.384
1.389
1.256
1.775
1.487
1.490
2.812
C(1)-S(1)-N(1)
S(1)-N(1)-C(2)
N(1)-C(2)-N(2)
C(2)-N(2)-N(3)
S(1)-C(1)-N(3)
φ(1), φ(2)b
100.0(2)
114.1(3)
122.0(4)
118.2(4)
120.7(4)
8, 30
Rc
45
S(1): θd (te)
146 (0.62)
139 (0.47)
N(2): θd (te)
a
b
Gas-phase calculation (HF/6-31G*) at the C1 symmetry. Angles between the planes of three-atom fragments S(1)-C(1)-N(3) and
N(1)-C(2)-N(2) and the planes of phenyl rings attached to them. c Ring puckering angle defined as an average angle between the S(1)-
d
N(1)-C(2)-N(2) and S(1)-C(1)-N(3)-N(2) planes. The X-*-* angle in which asterisks are the midpoints between the C(1)‚‚‚N(1) and
C(2)‚‚‚N(3) atoms. e Approximate distance of the atom from the C(1)-N(3)-C(2)-N(1) plane.
The intraring bond lengths correspond to SsC, SsN,
CsN, and NsN single bonds and CdN double bonds and
are consistent with the structure of the 4H tautomer. For
instance, the S(1)sC(1) and S(1)sN(1) distances (1.754-
(6) and 1.705(5) Å) in 5 are close to the values of 1.770-
tively, which corresponds to 89% and 102% of the van
der Waals separation.39
The gas-phase ab initio geometry for 5 matches the
experimental solid-state results well, and the comparison
is shown in Table 2. The calculations predict a boatlike
conformation for the heterocycle with similar puckering
angles R and θ. The calculated distances are generally
larger on average by 0.010 Å. The noticeable differences
are observed for the N(1)-C(2) and N(2)-N(3) distances.
The smaller experimental dihedral angles φ are presum-
ably due to their compression in the crystal as compared
to the gas-phase environment used in the calculations.
In both cases, however, the angle between the phenyl ring
and the three-atom fragment centered on C(2), φ2, is large
and reflects the H(12)‚‚‚Ph steric interactions.
A comparison of the calculated geometries for the
parent ring with its diphenyl derivative 5 shows that the
introduction of the phenyl substituents has relatively
little effect on the ring geometry. The most affected are
the two carbon atoms, C(1) and C(2), whose bonding
distances to the neighboring atoms are slightly expanded
by about 0.01 Å, and the intraring angles centered on
the carbon atoms are contracted by about 3°. The
dihedral angle between the two halves of the open book
conformation is expanded by about 4°.
2
(3) and 1.689(2) Å observed for the analogous SsC(sp ) and
2
SsN(sp ) bonds in an acyclic N-sulfenyl ketimine.38 Simi-
larly, the imine CdN bond length of the N-sulfenyl
ketimine38 is consistent with those for CdN double bonds
found in 5.
The ring internal angles are within expectation. The
angle centered on the sulfur atom (100.0(2)°) is typical
for organic sulfides and consistent with that of 98.2(1)°
2
2
found for the analogous acyclic fragment C(sp )-S-N(sp )
in acyclic N-sulfenyl ketimine.38 The ring carbon atoms
and their three substituents are coplanar within experi-
mental error, confirming their sp2 hybridization.
The proton of the N(2) atom was refined positionally,
but it refined to about 0.75 Å instead of the usual 0.90 Å
length. This was fixed at 0.90(2) Å, still allowing the
proton to find its best position.
The phenyl rings are rotated relative to the planes
defined by the adjacent thioiminyl and amidinyl frag-
ments by 8° and 30°, respectively. The higher torsional
angle observed for the ring attached to the C(2) carbon
may reflect the steric interactions of the phenyl ring with
the N(2) hydrogen atom.
The crystal structure appears to be composed of infinite
chains of hydrogen-bonded groups through the ring
nitrogen atom, N(2). The proton points close to the
midpoint between the S(1) and N(2) atoms weighted for
the van der Waals radii, forming 80° and 100° angles,
respectively. The distances from the proton to the neigh-
boring N(2) and S(1) atoms are 2.45 and 2.98 Å, respec-
Attem p ted Gen er a tion of Ra d ica l 4 fr om 5 a n d
7. Treatment of the 4H-thiatriazine 5 with lead dioxide/
potassium carbonate40,41 or thianthrenium perchlorate/
pyridine2 failed to generate radical 4 (Scheme 7), and the
starting material was recovered. Negative results were
also obtained by initial deprotonation of 5 with NaH
followed by reaction of the resulting anion with iodine
or silver triflate. No ESR signal was observed.
(39) Rowland, R. S.; Taylor, R. J . Phys. Chem. 1996, 100, 7384.
(40) Miura, Y.; Yamano, E.; Tanaka, A.; Yamauchi, J . J . Org. Chem.
1994, 59, 3294.
(41) Markovskii, L. N.; Talanov, V. S.; Polumbrik, O. M.; Shermolov-
ich, Y. G. J . Org. Chem. USSR 1981, 17, 2338.
(38) Pirozhenko, V. V.; Chernega, A. N.; Boldeskul, I. E.; Yufit, D.
S.; Antipin, M. Y.; Struchkov, Y. T.; Talanov, V. S.; Shermovich, Y. G.
J . Gen. Chem. USSR 1983, 53, 325.

936 J . Org. Chem., Vol. 65, No. 4, 2000
Farrar et al.
Sch em e 7
F igu r e 5. Calculated (B3LYP/6-31G*) total spin density maps
for 1 and 4.
formed, and the expected7,14,42 adduct 16 could not be
isolated.
The radical generated from thiatriazine 5 was obtained
in about 1% yield based on ESR signal integration. It
persists for several hours in solution and shows little
sensitivity to oxygen but is immediately quenched upon
filtration through a silica gel, alumina, or Florisil plug
under a nitrogen atmosphere.
F igu r e 4. ESR spectrum of a radical obtained from 5 (see
the text).
Sch em e 8
The ESR signal of the radical consists of five well-
defined lines43 with a hyperfine coupling (hfc) of aN
)
1.03 mT and a relatively large g ) 2.0103 (Figure 4) and
is consistent with the structure of 4. The latter value
compares to g ) 2.0059 measured for radical 1,12 an
isomer of 4. The two g values, however, do not correlate
well with the calculated spin concentrations on the sulfur
atom in 4 and 1, which are 0.27 and 0.37, respectively.
The assignment of the ESR spectrum to the cyclic
structure of 4 was aided with DFT calculations, which
were found to be well suited for analysis of cyclic
thioaminyl radicals such as 1 and 4.44 The distributions
of spin densities in heterocyclic rings 1 and 4 are similar.
Atoms 3 and 5 (positions meta to sulfur) are at nodal
positions and have only small negative values (Figure
5). This results in only two nitrogen atoms with signifi-
cant spin densities in 4, and a quintet pattern for the
ESR spectrum is expected.
The results of the hfc calculation for 4 turned out to
be rather ambiguous. Analysis of scaled Fermi contact
values for 1 at the planar C2v ground state shows that
the two types of nitrogen atoms, N(2,6) and N(4), exhibit
close hfc’s of 12.75 and 13.16 MHz, which yield an
average value of 12.96 MHz.44 This compares reasonably
well with the experimental hfc value of 11.15 MHz for
the septet, and the geometry is in agreement with the
planar molecular structure of the radical 1 in its dimer.12
The calculations show low sensitivity to conformational
changes, and the hfc values obtained for the staggered
orientation of the phenyl rings are slightly higher by 0.6
MHz. Similar values were obtained for the radical when
the UHF/6-31G* geometry was used in the Fermi con-
stant calculations (B3LYP/6-31G*//UHF/6-31G* level of
theory).
Since the direct oxidation of 5 was unsuccessful, it was
hoped that radical 4 could be generated by reduction of
the chloride 6 with triphenylantimony, according to a
general procedure.12 The synthesis of chloride 6 was
envisioned from 4H-thiatriazine 5 by treatment with
sulfuryl chloride, conditions described for preparation of
the analogous chloride 2 from 3,7 or amidrazone 7 in
reaction with sulfur dichloride (path a in Figure 1) under
general conditions.13,14
Addition of SO2Cl2 to a solution of 5 in acetonitrile
resulted in the immediate appearance of an orange color,
presumably 6, which bleached within a few seconds at
ambient temperature. The orange color is characteristic
of cyclic sulfinimidoyl chlorides, which are thermally
unstable species that readily decompose in solution
unless excess chlorine or SCl2 is present.13,14 The bleach-
ing was slower at -40 °C and still slower in methylene
chloride at -78 °C. Treatment of the latter reaction
mixture with triphenylantimony caused a color change
to dark green and the appearance of a weak ESR signal
(Figure 4).
Amidrazone 7 was treated with 2 equiv of sulfur
dichloride in methylene chloride containing a stoichio-
metric amount of pyridine at -78 °C. Upon addition of
SCl2 the solution became dark orange and changed to
pale yellow when treated with Ph3Sb. No ESR signal was
obtained.
In contrast to 1, hfc values calculated for radical 4 are
sensitive to changes in the molecular geometry. Geometry
optimization performed at the UHF/6-31G* level yields
a planar structure of 3,6-diphenyl-1,2,4,5-thiatriazinyl
In an attempt to demonstrate the presence of chloride
6 in the reaction mixture obtained from 5, the orange
solution was treated with either N-trimethylsilylmor-
pholine or N,N-dimethyl-N-trimethylsilylamine (Scheme
8). In both cases a complex mixture of products was
(42) Kornuta, P. P.; Derii, L. I.; Markovskii, L. N. J . Org. Chem.
USSR 1980, 16, 1130.
(43) Alternatively, the spectrum may be interpreted as a septet if
the weak features on the edges of the spectrum are included. This
would require three nitrogen atoms with similar hfc’s.
(44) Kaszynski, P. Submitted for publication.

A New Thiatriazine Isomer
J . Org. Chem., Vol. 65, No. 4, 2000 937
boat conformation. This is certainly consistent with
tautomeric preferences for other eight-π-electron six-
membered heterocyclic 1,4-dienes, which all form boatlike
conformations, avoiding the ring planarity and the
unfavorable electronic conjugation of eight π electrons.
The planarization energies for the thiatriazine tautomers
are not high, and the ∆SCF for the planar and boat I-4H
is 3.1 kcal/mol, while the same energy difference calcu-
lated for the 2H tautomer is 4.1 kcal/mol.
A comparison of the relative SCF energies of the 4H-
1,2,4,5-thiatriazine with other isomeric 4H tautomers45
shown in Figure 8 indicates that the 4H-1,2,4,6-thiatri-
azine II-4H is the most stable and the 1,2,4,5 isomer I-4H
is the next most stable in the series. In general, the
relative stability of the thiatriazines roughly correlates
with the ring folding angle R (Figure 8) and also
decreases as the S-N bond length increases. Among the
thiatriazines the least stable is 4H-1,2,3,4-thiatriazine
(VI-4H).
Ra d ica ls. Calculations at the B3LYP/6-31G* level of
theory predict that the 1,2,4,5-thiatriazinyl (I-R) is less
stable by 23 kcal/mol than the most thermodynamically
stable thiatriazinyl radicals II-R (Figure 9). Other radi-
cals, except for VI-R, show similar low stability relative
to that of II-R, and the 1,2,3,5-thiatriazinyl (IV-R)
appears to be the second most stable among the thiatri-
azinyls. No minimum on the potential energy surface
corresponding to the 1,2,3,4-thiatriazinyl (VI-R) was
found, and instead the radical undergoes loss of an N2
molecule. Radical IV-R shows a significantly elongated
S-N bond (2.03 Å), and it can be considered to be an
intramolecular adduct of a thiyl radical to the diazo
group. Similarly, the S(1)-N(2) bond in V-R is longer by
about 0.1 Å as compared to the typical value of 1.69 Å.
F igu r e 6. Simulated ESR spectra for 4 based on hfc values
obtained from (a) B3LYP/6-31G* (aN ) 15.58, 22.03, 10.17
MHz), and (b) B3LYP/6-31G*//UHF/6-31G* (aN ) 16.69, 18.49,
0.8 MHz) calculations. Line width 0.5 G, g ) 2.0059.
(4), while the same optimization on the B3LYP/6-31G*
level of theory predicts a puckered thiatriazinyl ring
along the S(1)‚‚‚N(4) line (24°) and the C(6)-Ph dihedral
angle of 17°. Spin densities (Figure 5) calculated for both
geometries at the B3LYP/6-31G* method are similar and
within 10%, while the Fermi constants differ signifi-
cantly. The largest difference is observed for the N(5)
atom, which has a low Fermi contact value (0.84 MHz)
for the planar UHF geometry, while in the puckered
B3LYP geometry this value is an order of magnitude
larger (10.17 MHz). The average hfc values for the N(2)
and N(4) atoms are 0.67 and 0.62 mT for the two
geometries. This large difference in the hfc values for the
N(5) atom results in two significantly different ESR
spectra as is shown in Figure 6.
Radicals II-R and V-R are planar according to normal-
mode analysis, while the remaining radicals are signifi-
cantly puckered. The planar structure of I-R represents
a conformational maximum between two puckered minima
with the calculated interconversion energy barrier ∆G
of 1.93 kcal/mol.
The pattern of the weak ESR signal generated from 5
is similar to the quintet shown in Figure 6b, but the hfc’s
are significantly different. While the experimental spec-
The results of geometry optimization obtained with the
DFT methods differ for some radicals from those obtained
at the UHF/6-31G* level of theory. Radicals IV-R-VI-R
show much less tendency toward ring opening, and the
largest elongation of the S-N bond by 0.1 Å is calculated
for VI-R, which now represents an intramolecular adduct
of a thiyl radical to the azido group. The UHF calcula-
tions predict that only III-R and VI-R adopt a boat
conformation while the remaining radicals, including I-R,
are planar.
trum shows aN ) 1.03 mT, the predicted value is aN
)
0.67 mT, which is in line with the hfc observed in 1 (aN
) 0.397 mT). Thus, considering the concentration of the
radical and the hfc, the evidence for the assignment of
the spectrum to radical 4 is weak at best.
Hydrogen atoms of the phenyl rings in 1 and 4 show
only small spin concentrations, and the largest hfc values
(aH > 0.07 mT) are predicted for the ortho and para
hydrogens. No hydrogen splitting is observed in the
spectrum of 1.12
Com p a r ison of 4 a n d 5 w ith Oth er Th ia tr ia zin es.
A comparison of isomeric thiatriazines provides useful
information and serves as a predictive tool for future
exploration of this class of compounds.
Ta u tom er s. The thermodynamic stability of the I-4H
tautomer was compared with those for the remaining 2H
and 6H tautomers, and their optimized geometries and
relative energies are shown in Figure 7. The 4H tautomer
appears to be most stable, presumably by allowing for
the low-energy distortion from planarity and forming the
The distributions of spin densities in the radicals are
similar in all five isomers, showing positive spin popula-
tions on the sulfur and in the 2,4,6 position and small
negative spin densities on the atoms meta to sulfur.
Except for II-R, all radicals have one or two carbon atoms
bearing positive spin densities. This is expected to be
energetically unfavorable and may be one of the reasons
(45) For the purpose of this comparison it has been assumed that
the 4H tautomer is the most stable for all isomeric heterocycles. The
actual solid-state experimental evidence is available for only three of
them.

938 J . Org. Chem., Vol. 65, No. 4, 2000
Farrar et al.
F igu r e 7. Ab initio (HF/6-31G*) optimized geometries and the relative SCF energies for three tautomers of 1,2,4,5-thiatriazine.
roughly parallels that of the stabilities of the 4H-
thiatriazines.
Con clu sion s
Oxidative cyclization of thiohydrazide 9 proved to be
an effective way to prepare 3,6-diphenyl-4H-1,2,4,5-
thiatriazine (5), an example of the last unknown isomer
of thiatriazine. Other methods for construction of the
1,2,4,5-thiatriazine ring have been investigated with less
success.
The attempts at generation of the 1,2,4,5-thiatriazinyl
radical 4 from 5 or from acyclic precursor 7 are mostly
discouraging, although a weak ESR signal was observed
F igu r e 8. Relative SCF (HF/6-31G*) energies and dihedral
in the former experiment. Correlation of the signal with
the structure of 4 was attempted with the aid of DFT
calculations, but the results were inconclusive. The
calculated hfc’s show significant sensitivity to conforma-
tional changes, which results in qualitatively different
ESR spectral patterns. It is possible that the radical 4
and the intermediate chloride 6 are much less stable than
the analogous 1 and 2, which are the only known radicals
and chlorides among the thiatriazines.
angles R for isomeric thiatriazine 4H tautomers.
On the basis of quantum-mechanical calculations, it
appears that the 1,2,4,6-thiatriazine is unique among the
isomeric thiatriazines. Both the radical II-R and the
thiatriazine II-4H are at least 14 kcal/mol more stable
than the next member of the family of isomers, radical
IV-R and thiatriazine I-4H. The 1,2,4,5-thiatriazinyl (I-
R) is predicted to be less stable than the known 1,2,4,6-
thiatriazinyl by about 23 kcal/mol, which may explain
the difficulty with experimental observation of 4.
F igu r e 9. Calculated (B3LYP/6-31G*) spin distribution maps
in isomeric thiatriazinyls with indicated relative SCF energies
and molecular symmetries other than C1. Circles represent
relative total positive (full circles) and negative (open circles)
spin densities.
The lack of a convenient method for generation of the
radical 4 and its seemingly low stability cast serious
doubt on 1,2,4,5-thiatriazinyl being used as a structural
element for liquid crystals. Fortunately, other heterocy-
clic radicals were found to be suitable for this purpose.
For instance a liquid-crystal-like molecule containing the
for their calculated lower thermodynamic stabilities
relative to that of the II-R isomer.
The stability order for the radicals, excluding III,

A New Thiatriazine Isomer
J . Org. Chem., Vol. 65, No. 4, 2000 939
ideal positions and refined as riding atoms with relative
isotropic displacement parameters. For the amine proton, see
the text.
benzothiadiazenyl has been demonstrated to easily form
highly stable radicals.46
Attem p ted Gen er a tion of 3,6-Dip h en yl-1,2,4,5-th ia tr i-
a zin yl (4). Meth od A. Thiatriazine 5 (5 mg, 0.02 mmol) was
dissolved in degassed benzene (1 mL) and stirred over PbO2
(4.7 mg, 0.02 mmol) and K2CO3 (2.7 mg, 0.02 mmol) for 0.5 h.
The solution changed to a darker yellow.
Meth od B. Thiatriazine 5 (5 mg, 0.0198 mmol) and pyridine
(3 mg) were dissolved in dry CH2Cl2 (5 mL), degassed, and
cooled to -77 °C. Distilled sulfuryl chloride (3 µL) was added,
and the solution immediately became orange. The solution was
filtered through a coarse frit onto solid Ph3Sb (8 mg, 0.023
mmol). The solution became green-black and was transferred
to a flame-dried ESR tube. The solution was degassed twice
more before the ESR spectrum was taken.
Com p u ta tion a l Meth od s
Quantum mechanical calculations were carried out at the
HF/6-31G* and B3LYP/6-31G* levels of theory using the
Gaussian 94 package47 on an SGI R8000 workstation. Geom-
etry constraints were used in geometry optimizations as
specified. The ground-state conformations and transition states
were verified by analysis of normal modes. Thermodynamic
parameters were calculated using scaling factors of 0.9135 and
0.9804 for HF and B3LYP methods, respectively.48 The cal-
culated Fermi contact values were expressed in megahertz and
scaled by 1.046.44 Simulation of ESR spectra was done using
the Calleo ESR 1.2 program.
Meth od C. Thiatriazine 5 (1 mg, 0.004 mmol) was dissolved
in CH2Cl2 (1 mL). Chlorine (18 µL, 0.215 M in CCl4) was added
via syringe. After overnight stirring, the starting material was
recovered.
Exp er im en ta l Section
Melting points were determined in open capillaries and are
uncorrected. NMR spectra were measured at 300 MHz (1H
spectra) and 100 MHz (13C) in CDCl3 and referenced to TMS
(1H) or the solvent (13C), unless specified otherwise. Coupling
constants were calculated from chemical shifts. IR spectra
were recorded in KBr. Mass spectrometry was performed using
a GC-MS instrument. Elemental analysis was provided by
Atlantic Microlab, Norcross, GA.
X-band ESR spectra were taken on a Bruker 300E in
distilled dichloromethane or benzene. Solvents were degassed
by the freeze/pump/thaw method repeated three times. Spin
concentration was calculated by integration of the signal
intensity of the sample versus a measured amount of 2,2-
diphenyl-1-picrylhydrazyl hydrate radical purchased from
Aldrich and assumed to be 100%. Samples were referenced
using strong pitch with g ) 2.0028.
Meth od D. Amidrazone 7 (5.64 mg, 0.025 mmol) was
dissolved in CH2Cl2 (2 mL) containing pyridine (3 mg) and
cooled to -77 °C. SCl2 in CH2Cl2 (0.90 mL, 0.06 M) was added
dropwise. The resulting orange solution was placed over Ph3-
Sb (0.1 g). The reaction time with SCl2 was varied from 10
min to 1 h before reaction with Ph3Sb and measurement of
ESR signal.
3,6-Dip h en yl-4H-1,2,4,5-th ia tr ia zin e (5). A solution of
bromine (0.10 mL, 2.0 mmol) and dry pyridine (2 mL) was
added dropwise to 9 (1.00 g, 3.9 mmol) dissolved in dry THF
(20 mL) over 2 min at 0 °C under nitrogen. The reaction
mixture was gradually warmed to room temperature with
stirring over 2 h and passed through a silica gel plug using
methylene chloride. The orange filtrate was evaporated, and
the resulting red solid was purified on Chromatotron (silica,
CH2Cl2/hexanes, 1:1). Collecting the red lead band with CH2-
Cl2 elution gives the desired product of 0.530 g (54% yield) as
a red solid which can be further purified by recrystallization
from a CH2Cl2/pentane mixture to give golden needles or by
sublimation: mp 126.5-127 °C; 1H NMR (CD2Cl2) δ 7.39-7.57
(m, 6H), 7.76 (d, J ) 7.28 Hz, 2H), 7.82 (d, J ) 7.03 Hz, 2H),
8.76 (s, 1H); 13C NMR δ 126.98, 127.12, 128.68, 128.89, 130.88,
131.57, 131.71, 132.52, 148.90, 160.22; IR 3326, 3311, 1298,
693 cm-1. Anal. Calcd for C14H11N3S: C, 66.40; H, 4.35; N,
16.60; S, 12.65. Found: C, 66.43; H, 4.41; N, 16.65; S, 12.58.
The second fraction from chromatographic separation (CH2-
Cl2) was identified as 2,5-diphenyl-1,3,4-thiadiazole (13): mp
140-141 °C (lit.26 mp 141-142 °C); 1H NMR (CD2Cl2) δ 7.51-
7.54 (m, 6H), 8.00-8.03 (m, 4H); 13C NMR (CD2Cl2) δ 128.18,
129.53, 130.63, 131.42, 168.45. Anal. Calcd for C14H10N2S: C,
70.59; H, 4.20; N, 11.77; S, 13.45. Found: C, 70.44; H, 4.17;
N, 11.70; S, 13.40.
All reagents were used as received except as noted. Tet-
rahydrofuran was distilled from Na/benzophenone ketyl. Ben-
zene, dichloromethane, and pyridine were distilled from CaH2.
Acetonitrile was distilled from phosphorus pentoxide. Benzene-
d6 was kept over Na.
X-r a y Cr yst a llogr a p h y for 3,6-Dip h en yl-4H -1,2,4,5-
th ia tr ia zin e (5). A crystal of the compound grown from a
methylene chloride/pentane mixture was attached to a glass
fiber and mounted onto the Siemens SMART Platform CCD
system for data collection at 173(2) K and a wavelength of λ
) 0.710 73 Å. An initial set of cell constants was calculated
from reflections harvested from 3 sets of 20 frames. These
initial sets of frames are oriented such that orthogonal wedges
of reciprocal space were surveyed. This produces orientation
matrixes determined from 42 reflections. Final cell constants
are calculated from a set of 1983 strong reflections from the
actual data collection. Please refer to Table 1 for additional
crystal and refinement information.
All crystals appeared to twin in a manner similar to that of
branching in trees. The specimen used for data collection was
freed from most, but not all, twins. The specimen appears to
be enantiomerically pure in the solid state. Some methods for
modeling twins were attempted, but none improved the model
significantly.
1-Am in o-1,4-diph en yl-2,3-diaza-1,3-bu tadien e15 (7). Benz-
amidine hydrochloride hydrate (8.73 g, 50 mmol) was dissolved
in ethanol (50 mL), and a solution of hydrazine hydrate (2.50
g, 50 mmol) in ethanol (10 mL) was added. The mixture was
stirred at ambient temperature for 30 min (while a precipitate
formed), and benzaldehyde (5.30 g, 50 mmol) in ethanol (10
mL) was added. The resulting yellow mixture was stirred for
3 h, the precipitate was filtered off, and the solution was
evaporated to leave a yellow crystalline product. The crude
product was dissolved in benzene and passed through an
alumina plug and the solvent removed. The remaining solid
(7.66 g) was recrystallized twice from a toluene/isooctane
mixture to give 6.47 g (53% yield) of yellow crystals: mp 133-
134 °C (lit.33 133-134 °C); 1H NMR (400 MHz) δ 5.75 (br, 2H),
7.41-7.49 (m, 6H), 7.79-7.82 (m, 2H), 7.84-7.87 (m, 2H), 8.57
(s, 1H).
1-Ch lor o-4-(N-ch lor oa m in o)-1,4-d ip h en yl-2,3-d ia za -1,3-
bu ta d ien e (8). A solution of tert-butyl hypochlorite (2.30 g,
21 mmol) in dry methylene chloride (20 mL) was added
dropwise to amidrazone 7 (2.23 g, 10 mmol) dissolved in dry
CH2Cl2 (25 mL) at 0 °C. The mixture was stirred for 1.5 h,
and the solvents were evaporated. The resulting crude product
was dissolved in a small amount of CH2Cl2 deposited on a silica
All non-hydrogen atoms were refined with anisotropic
displacement parameters. All hydrogen atoms were placed in
(46) Farrar, J . M.; Huang, J .; Kaszynski, P. Submitted for publica-
tion.
(47) Gaussian 94, Revision E.1: Frisch, M. J .; Trucks, G. W.;
Schlegel, H. B.; Gill, P. M.; J ohnson, B. G.; Robb, M. A.; Cheeseman,
J . R.; Keith, T.; Petersson, G. A.; Montgomery, J . A.; Raghavachari,
K.; Al-Laham, M. A.; Zakrzewski, V. G.; Ortiz, J . V.; Foresman, J . B.;
Cioslowski, J .; Stefanov, B. B.; Nanayakkara, A.; Challacombe, M.;
Peng, C. Y.; Ayala, P. Y.; Chen, W.; Wong, M. W.; Andres, J . L.;
Replogle, E. S.; Gomperts, R.; Martin, R. L.; Fox, D. J .; Binkley, J . S.;
Defrees, D. J .; Baker, J .; Stewart, J . P.; Head-Gordon, M.; Gonzalez,
C.; Pople, J . A., Gaussian, Inc., Pittsburgh, PA, 1995.
(48) Foresman, J . B.; Frisch, A. Exploring Chemistry with Electronic
Structure Methods; Gaussian, Inc.: Pittsburgh, PA, 1996.

940 J . Org. Chem., Vol. 65, No. 4, 2000
Farrar et al.
1
gel plug and eluted with CH2Cl2, keeping the yellow band on
the gel. The filtrate was evaporated, yielding 1.38 g of yellow
oil which was recrystallized twice from hexanes to give 0.65 g
(22% yield) of the dichloride as long colorless needles: mp 118-
mp 133.5-134.5 °C (lit.27 mp 134-136 °C); H NMR δ 7.30-
7.48 (m, 16H), 7.72 (dd, J 1 ) 7.7 Hz, J 2 ) 1.4 Hz, 4H), 8.32 (s,
2H); 13C NMR δ 127.89, 128.25, 128.66 (2C), 129.30, 130.09,
131.54, 133.77, 160.17, 166.52. Anal. Calcd for C28H22N4S2: C,
70.29; H, 4.60; N, 11.72; S, 13.39. Found: C, 70.17; H, 4.54;
N, 11.77; S, 13.32.
1
124 °C dec; H NMR (400 MHz) δ 7.34-7.43 (m, 3H), 7.45-
7.53 (m, 3H), 7.66-7.73 (m, 4H), 9.65 (br s, 1H); 13C NMR δ
127.09, 127.99, 128.52, 129.38, 130.71, 130.83, 130.96, 131.25,
132.92, 162.98; IR 3287, 3065, 1588, 1565, 1385, 1257, 933,
708 cm-1. Anal. Calcd for C14H11N3Cl2: C, 57.55; H, 3.79; N,
14.38; Cl, 24.27. Found: C, 57.62; H, 3.86; N, 14.39; Cl, 24.17.
Ben zen eca r both ioic Acid 2-(Im in op h en ylm eth yl)h y-
d r a zid e (9).16 To thiobenzoic hydrazide19,49 (12; 2.50 g, 16.45
mmol) partially dissolved in dry benzene (20 mL) was added
dropwise 2 M Me3Al in toluene (17.3 mL, 34.55 mmol) over 10
min. To the resulting green, homogeneous solution was added
benzonitrile (2.03 g, 19.74 mmol) dissolved in benzene (2.5 mL).
The mixture was heated to reflux under nitrogen for 6 h. Water
(11 mL) was then very slowly added to the mixture, and the
resulting yellow-green product was filtered and quickly washed
with MeOH. Evaporation of the solvent gave 2.54 g (76% yield)
of bright yellow needles: mp 151.5-152.5 °C (lit.16 mp 154-
156 °C); 1H NMR (acetone-d6) δ 2.88 (s, 1H), 2.92 (s, 2H), 7.29-
7.33 (m, 3H), 7.67-7.80 (m, 3H), 7.97 (m, 2H), 8.32 (m, 2H);
13C NMR (acetone-d6) δ 127.93, 128.02, 128.48, 128.84, 129.73,
130.59, 134.27, 142.62, 155.99, 183.99. Anal. Calcd for
2,5-Dip h en yl-∆2-1,3,4-th ia d ia zolin e (15)50 was obtained
in 94% yield according to the literature procedure:29 mp 76-
78 °C (lit.29 mp 78-80 °C); 1H NMR δ 6.37 (s, 1H), 7.35-7.40
(m, 4H), 7.47-7.51 (m, 4H), 7.67-7.70 (m, 1H), 8.00-8.03 (m,
2H); (C6D6) δ 5.81 (br s, 1H), 5.87 (s, 1H), 6.99-7.07 (m, 6H),
7.18-7.22 (m, 2H), 7.80-7.82 (m, 2H); 13C NMR δ 74.64 (br),
126.48, 127.02, 127.05, 128.53, 128.95, 129.09, 129.66, 131.17,
140.68.
Ack n ow led gm en t . This project has been sup-
ported by the NSF (Grant CHE-9528029) and
Vanderbilt University. We are in debt to Prof. Timothy
Hanusa for assistance with X-ray crystallography. We
thank Ms. Monika Sienkowska and Mr. Wolfgang
Fendrich, a visiting student from Prof. Volkmar Vill’s
group at Hamburg University, for their technical as-
sistance.
C
14H13N3S: C, 65.88; H, 5.10; N, 16.47; S, 12.55. Found: C,
Su p p or tin g In for m a tion Ava ila ble: Text describing data
collection and structure solution and refinement and tables
giving crystal data, atomic coordinates, isotropic and aniso-
tropic displacement parameters, bond distances and angles,
and torsion angles for 5 and spin distribution in isomeric
thiatriazinyls. This material is available free of charge via the
Internet at http://pubs.acs.org.
65.95; H, 5.11; N, 16.42; S, 12.47.
N-P h en ylm eth ylen eben zen eca r boh yd r a zon yl Disu l-
fid e (14).27 To 15 (1.50 g, 6.25 mmol) suspended in 1 N NaOH
(12.5 mL, 12.5 mmol) was added dropwise K2S2O8 (1.69 g, 6.25
mmol) dissolved in water (38 mL) at 0 °C. A yellow solid
gradually began to accumulate. Stirring was continued for 2
days at room temperature, and then the solid was collected
by filtration, washed with water, dried, and recrystallized from
ethanol (65 mL) to afford 0.74 g (50% yield) of yellow needles:
J O991126L
(49) Holmberg, B. Ark. Kemi, Mineral. Geol. 1944, 17A (23), 1.
(50) Holmberg, B. Ark. Kemi, Mineral. Geol. 1948, 25A (18), 1.