Preparation and X-ray structure of 4-BrC6H4CNSC(Cl)N

Article abstract of DOI:10.1515/znb-1997-0503

The title compound was obtained in 82% yield by the intramolecular cyclization of 4-BrC₆H₄C(NSCCl₃)[N(SiMe₃) ₂] in CH₂Cl₂ at 23°C. It crystallizes in the triclinic system, space group P1?, a = 7.957(3) A?, b = 10.864(5) A?, c = 5.625(1) A?, α = 95.94(3)°, β = 97.79(2)°, γ = 100.72(3)°, V = 469.2(3) A?3, and Z = 2. The bond lengths of the planar C₂N₂S ring indicate partial π-delocalization.

Full text of DOI:10.1515/znb-1997-0503

Preparation and X-Ray Structure of 4-BrC6H4CNSC(Cl)N
Tristram Chivers*, Masood Parvez, Peter Zoricak
Department of Chemistry, The University of Calgary, Calgary, Alberta, Canada T2N 1N4
Z. Naturforsch. 52 b, 557-559 (1997); received September 5, 1996
Crystal Structure, 1,2,4-Thiadiazole, Intramolecular Cyclization
The title compound was obtained in 82% yield by the intramolecular cyclization of 4-
BrC6H4C(NSCCl3)[N(SiMe3)2] in CH2CI2 at 23°C. It crystallizes in the triclinic system, space
group PI, a = 7.957(3) Ä, b = 10.864(5) A, c = 5.625(1) A, a = 95.94(3)°, ß = 97.79(2)°, 7
= 100.72(3)°, V = 469.2(3) A3, and Z - 2. The bond lengths of the planar C2N2S ring indicate
partial 7r-delocalization.
Introduction
A variety of synthetic approaches to the 1,2,4-
thiadiazole ring system is available [1], For ex-
ample, the cyclocondensation of carbamidines
RC(NH2)(NH2)+Cl~ with CI3CSCI produces
RCNSC(C1)N [1]. In this note we report the syn-
thesis and X-ray structure of 3-p -bromophenyl-
5-chloro-l,2,4-thiadiazole (2 ), which was obtained
by the spontaneous intramolecular cyclization of
4 -BrC6H4C(NSCCl3)[N(SiMe3)2] (1 ), according to
eq. (1 ).
for 2.
thiadiazoles [5-10], the heterocyclic ring in 2 is es-
sentially planar and the bond lengths indicate some
7r-delocalization. Thus the S-N distance of 1.650(6)
A is significantly shorter than the predicted single
bond value of 1.73 A [11] and the sequence of C-
N bond lengths is 1.331(7), 1.380(8) and 1.302(7)
A (cf. single and double bond values of ca. 1.29
and 1.47 A, respectively [12]). The 4-BrC6H4 sub-
stituent is coplanar with the heterocyclic ring and
there are no significant intermolecular interactions.
The synthetic route represented by eq. (1) repre-
sents an alternative to the use ofcarbamidines [2] for
the synthesis of 1,2,4-thiadiazoles containing a 5-C1
substituent that can be subsequently functionalized.
Results and Discussion
The monothiolated benzamidine 1 was pre-
pared from 4 -BrC6H4CN2(SiMe3)3 [2,3] and
CCI3SCI (1:1 molar ratio) c f synthesis of
PhC(SCCl3)[N(SiMe3)2] [4], The lU NMR spec-
trum of 1 showed resonances for 4-BrC6H4 (an
AA’XX’ pattern centred at 6 8.80 and 7.56) and
SiMe3 groups (6 0.30) in the intensity ratio 4:18.
In addition, a second weak AA’XX’ pattern (6
8.15 and 7.65) attributed to 2 was evident. A so-
lution of 1 in CH9CI2 was kept for 72 h at 23 °C
and, after subsequent work-up, the heterocycle 2
was obtained in 82% yield. A small amount of 4-
BrC6H4C(NH)(NH2), the hydrolysis product of 1 ,
was also isolated.
Experimental Section
Preparation of 4-BrC6H4CNSC(Cl)N (2)
The structure of 2 was determined by X-ray
crystallography (see Fig. 1). The pertinent bond
lengths, bond angles and torsion angles are sum-
marized in Table I. In common with other 1,2,4-
A solution of CI3CSCI (0.60 g, 3.22 mmol) in 25 ml of
CH2CI2 was added dropwise to 4-BrC6H4CN2(SiMe3)3,
(1.37 g, 3.30 mmol) in 25 ml of CH2C12 at 23°C under
an atmosphere of N2. The reaction mixture was stirred
for 72h and then solvent and Me3SiCl were removed by
vacuum transfer to give a viscous yellow oil containing a
small amount of white powder. The oil was dissolved
* Reprint requests to Tristram Chivers.
K
0939-5075/97/0500-0557 $ 06.00
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1997 Verlag der Zeitschrift für Naturforschung. All rights reserved.
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558
Br-
T. Chivers et al. • Preparation and X-Ray Structure of 4-BrC6H4CNSC(Cl)N
NSCCl
N— S
CH2C12, 72h, 23°C
-2Me,SiCl
ßr—(f
V
/
( 1)
\
N(SiMe,),
N = C
CI
Table I. Selected bond lengths (A) and bond angles (deg) Table II. Crystal data for 4-BrC6H4CNSC(Cl)N 2.
for 2.
C8H4N.SBrCl
275.55
Formula
Fw.
Bond lengths
Bond angles
triclinic
Crystal System
Space Group
a [A]
b [A]
c [A]
a [deg]
ß [deg]
7 [deg]
V [A r]
S-N(2)
S-C(l)
N( 1)-C( 1)
C(2)-N(l)
N(2)-C(2)
Cl-C(l)
1.650(6)
1.709(7)
1.302(7)
1.380(8)
1.331(7)
1.706(7)
1.467(8)
91.8(3)
107.9(5)
108.4(5)
122.8(4)
123.5(5)
113.6(5)
118.3(6)
N(2)-S-C(l)
Pi (No. 2)
7.957(3)
10.864(5)
5.625(1)
95.94(3)
97.79(2)
100.72(3)
469.2(3)
2
C(l)-N(l)-C(2)
S-N(2)-C(2)
Cl-C(l)-S
Cl-C(l)-N(l)
S-C(l)-N(l)
N(l)-C(2)-N(2)
C(2)-C(3)
Torsion angles
Z
1.950
0.50 x 0.40 x 0.20
25
18.50-29.97
A= 0.71069
170(1)
d c a lc [g cm“ 3]
Crystallogr. Dim. [mm]
Cell detn, refls
Cell detn, 26 range,Jdeg]
Radiation, MoKQ [A]
Temperature [K]
Scan type
Cl-C(l)-S-N(2)
-178.8(4)
Cl-C(l)-N(l)-C(2) 178.8(4)
S-N(2)-C(2)-N(l)
S-N(2)-C(2)-C(3)
S-C(l)-N(l)-C(2)
C(l)-S-N(2)-C(2)
0.0(7)
179.8(4)
-0.6(6)
u>-26
-0.3(5)
16.0
Scan rate [deg min-1]
Scan width [deg]
26 max [deg]
1.57 + 0.34 tan 6
50.1
48.48
empirical
0.32- 1.00
1797
1666
1149
118
0.042
0.041
2.54
0.00
0.53, -1.22
in CH2Cl2:diethyl ether and the insoluble white solid
was removed by filtration. Solvent was removed from
the filtrate. Slow evaporation of a diethyl ether solution
of the residue gave pale yellow rectangular crystals of
4-BrC6H4CNSC(Cl)N (0.73 g, 82%). M.p. 85°C.
/j [cm-1]
Absorption correction
Absorption, range
Total reflections
Unique reflections
Data with I > 3<j (I)
Parameters refined
R
Analysis for CsH+BrCl^S
Calcd C 34.87 H 1.46 N 10.17%,
Found C 35.39 H 1.50 N 9.33%.
Rw
GOF
'H NMR (in CDCI3): 6 8.15 and 7.65 (4-BrC6H4,
AA'XX’ pattern). 13C NMR (in CDC13): 6 173.3 and
171.2 (NC(S)Cl and CN2), 132.1, 130.8, 129.6 and
125.6 (CöH4). The white solid was identified as 4-
BrC6H4C(NH)(NH2) (0.10 g, 16%) by EI-MS (m/z = 198
and 200, M+).
Largest A la
Final diff. map [e A-3]
F(000)
268
anisotropically. Hydrogen atoms were included at ge-
ometrically idealized positions. Scattering factors were
taken from Cromer and Waber [15] and allowance was
made for anomalous dispersion [16]. All calculations
were performed using teXsan [17].
X-ray analysis
The crystal structure of 2 was determined by using a
Rigaku AFC6S diffractometer. Experimental details are
summarized in Table II*. The structure was solved by
the heavy atom method [13] and expanded using Fourier
techniques [14], The non-hydrogen atoms were refined
Acknowledgments
We thank the Natural Sciences and Engineering Re-
search Council of Canada for financial support and Igna-
cio Vargas-Baca for recording the l3C NMR spectrum.
*Furthercrystal structure data may be obtained from the Fach-
informationszentrum Karlsruhe, D-76344 Eggenstein-Leopolds-
hafen. by quoting the Registry No. CSD-406259.
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T. Chivers et al. • Preparation and X-Ray Structure of 4-BrC6H4CNSC(Cl)N
559
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