Synthesis of novel fused thienodiazaphosphorine derivatives from 2-amino-3-cyanothiophenes and Lawesson's reagent

Article abstract of DOI:10.1080/17415993.2011.639021

In a simple one-pot procedure, treatment of 2-amino-3-cyanothiophenes with Lawesson's reagent (LR) leads to the new thieno[2,3-d][1,3,2]diazaphosphorine-6- thione-2-sulfides in good to excellent yields. A possible reaction mechanism, involving a Dimroth-type rearrangement, is proposed. The structure of obtained products was confirmed by NMR (1H, 31P, and 13C) and IR spectroscopies and by mass spectrometry.

Full text of DOI:10.1080/17415993.2011.639021

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Synthesis of novel fused
thienodiazaphosphorine derivatives
from 2-amino-3-cyanothiophenes and
Lawesson's reagent
Khaoula Khalladi a & Soufiane Touil a
a Laboratory of Heteroatom Organic Chemistry, Department of
Chemistry, Faculty of Sciences of Bizerta, University of Carthage,
7021-Jarzouna, Tunisia
Published online: 05 Dec 2011.
To cite this article: Khaoula Khalladi & Soufiane Touil (2012): Synthesis of novel fused
thienodiazaphosphorine derivatives from 2-amino-3-cyanothiophenes and Lawesson's reagent,
Journal of Sulfur Chemistry, 33:1, 27-32
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Journal of Sulfur Chemistry
Vol. 33, No. 1, February 2012, 27–32
Synthesis of novel fused thienodiazaphosphorine derivatives
from 2-amino-3-cyanothiophenes and Lawesson’s reagent
Khaoula Khalladi and Soufiane Touil*
Laboratory of Heteroatom Organic Chemistry, Department of Chemistry, Faculty of Sciences of Bizerta,
University of Carthage, 7021-Jarzouna, Tunisia
(Received 3 September 2011; final version received 27 October 2011)
In a simple one-pot procedure, treatment of 2-amino-3-cyanothiophenes with Lawesson’s reagent (LR)
leads to the new thieno[2,3-d][1,3,2]diazaphosphorine-6-thione-2-sulfides in good to excellent yields.
A possible reaction mechanism, involving a Dimroth-type rearrangement, is proposed. The structure
of obtained products was confirmed by NMR (1H, 31P, and 13C) and IR spectroscopies and by mass
spectrometry.
S
R1
H
S
R1
CN
N
(0.5 eq)
LR
Ar
P
2
Toluene/80°C
24-48 h
2
R
R
N
S
NH2
S
H
1
2
70-96 %
S
Ar
S
S
S
,
P
P
Ar:
OMe
LR:
Ar
Keywords: thiophenes; diazaphosphorines; Lawesson’s reagent; thienodiazaphosphorines; fused hetero-
cycles; Dimroth rearrangement
1. Introduction
Thiophene derivatives and their fused heterocyclic ring systems are associated with a wide range of
biological properties including antimicrobial (1,2), antiviral (3), analgesic (4), anti-inflammatory
(1,5), and anticancer (6,7) activities.
On the other hand, compounds bearing 1,3,2-diazaphosphorine ring are known to exhibit
antimicrobial (8), antiviral (9), and antitumor (10,11) activities.
*Corresponding author. Email: soufiane.touil@fsb.rnu.tn
ISSN 1741-5993 print/ISSN 1741-6000 online
© 2012 Taylor & Francis
http://dx.doi.org/10.1080/17415993.2011.639021
http://www.tandfonline.com

28 K. Khalladi and S. Touil
In view of the above, and in continuation of our research program concerning the prepa-
ration of new heterocycles with possible biological properties (12–18), we report here the
synthesis of the new thieno[2,3-d][1,3,2]diazaphosphorine-6-thione-2-sulfides which might show
enhanced biological activity due to the presence of fused thiophene and diazaphosphorine ring
systems.
These compounds were obtained, in a simple one-pot protocol, from easily made 2-amino-3-
cyanothiophenes and commercially available Lawesson’s reagent (LR), as starting materials.
2. Results and discussion
The starting 2-amino-3-cyanothiophenes 1 were easily prepared according to the reported Gewald
synthetic procedure (19). It was found that reaction of compounds 1 with a stoichiometric
amount of LR (0.5 equiv.), performed in toluene, at 80◦C, for 24–48 h, led to thieno[2,3-
d][1,3,2]diazaphosphorine-6-thione-2-sulfides 2 in 70–96% yield (Scheme 1). It is important
to note here that the use of excess LR (1 equiv. instead of 0.5) did not enhance the reaction rate
but made purification of the products more difficult.
A plausible mechanism for the formation of compounds 2 is depicted in Scheme 2. The trans-
formation is believed to proceed via a nucleophilic attack of the NH2 group on LR giving rise
S
R1
H
S
R1
CN
(0.5 eq)
LR
N
Ar
P
2
2
R
Toluene/80°C
R
N
S
NH2
S
H
1
2
S
Ar
S
S
S
,
P
P
Ar:
OMe
LR:
Ar
2a
2b
(CH2)3
70
2c
Ph
H
2d
2e
R1
R2
CH3
CH3
87
Ph-CH2
Ph
(CH2)4
96
Yield(%)
73
95
2f
2g
2h
2i
CH3
Ph
R1
CH3
CH3
H
CH3
Ph-CH2
92
R2
(CH3)2CH
85
Yield(%)
76
82
Scheme 1. Synthesis of thieno[2,3-d][1,3,2]diazaphosphorine-6-thione-2-sulfides (2).

Journal of Sulfur Chemistry 29
S
S
S
S
S
Ar
S
2
Ar P
P
P
LR:
Ar
S
S
R1
CN
Ar
P
R1
R2
C
N
_
SH
_
NH2
R2
N
P
S
Ar
S
S
H
1
I1
S
HN
R1
R2
NH2
P
R1
R2
S
Ar
Ar
P
N
N
S
S
S
S
H
I2
S
H
S
R1
N
Ar
P
R2
N
S
H
2
Scheme 2. Reaction mechanism for the synthesis of compounds 2.
to the intermediate I1. A subsequent intramolecular cyclization, through the nucleophilic attack
of the sulfur atom at the nitrile group, leads to the cyclic intermediate I2. The latter under-
goes a Dimroth-typerearrangement (20) that consists in a translocation of endocyclic sulfur
and exocyclic nitrogen atoms through a ring-opening–ring-closure sequence, leading to the final
products 2.
This proposed mechanism is consistent with some literature data that report similar rearrange-
ments in reactions of LR with some nitrile derivatives (21–23).
The stability of the product is the driving force of the rearrangement; indeed, theoretical
RHF/6-31G calculation performed with the Gaussian 03 program showed a stabilization of about
15 kcal/mol in favor of the rearranged product 2.
The structures of thienodiazaphosphorines 2 were established through IR, NMR (1H, 31P, and
13C) and mass spectral data. The IR spectra of compounds 2 showed a characteristic absorption
band around 1100 cm−1 attributable to the C S group. We observed, on the other hand, a broad
=
band in the region 3070–3450 cm−1 corresponding to the N H vibrators.Another band ascribable
−
−1
=
to the P S group is present at nearly 700 cm
.
The 1H NMR spectra showed, in particular, the presence of broad singlets at 10.0–10.5 ppm,
corresponding to the protons of NH groups. We observed also a singlet at 3.8 ppm attributable to
the OCH3 protons.
Other evidence for the structure of compound 2 is provided by 13C NMR. Indeed, we find
the signals of all carbons and particularly those corresponding to the heterocyclic ring. Of
=
particular interest is the C S carbon which resonates as a doublet at 185–207 ppm. Such a
doublet is characteristic of the coupling with phosphorus with a JCP coupling constant of
2
about 9 Hz.

30 K. Khalladi and S. Touil
3. Experimental
1H, 31P and 13C NMR spectra were recorded with CDCl3 as the solvent, on a Bruker-300 spec-
trometer. The chemical shifts are reported in ppm relative to TMS (internal reference) for 1H and
13C NMR and relative to 85% H3PO4 (external reference) for 31P NMR. The couplingconstants
are reported in Hz. For the 1H NMR, the multiplicities of signals are indicated by the following
abbreviations: s: singlet, d: doublet, t: triplet, q: quartet, sept: septuplet, m: multiplet.
Mass spectra were determined on an Agilent 5975B spectrometer, under electronic impact
(EI) conditions. IR spectra were recorded on a Perkin Elmer Paragon 1000 PC spectrometer.
The progress of the reactions was monitored by TLC. Purification of products was performed by
column chromatography using silica gel 60 (Fluka).
3.1. Synthesis of 2-amino-3-cyanothiophenes (1)
The starting 2-amino-3-cyanothiophenes 1 were prepared according to the reported
procedure (19).
3.2. Synthesis of thieno[2,3-d][1,3,2]diazaphosphorine-6-thione-2-sulfides (2)
A mixture of 2-amino-3-cyanothiophene 1 (0.01 mol), LR (0.005 mol), and dry toluene (30 ml)
was heated at 80◦C with stirring for the reaction time (RT) (the reaction was monitored by TLC).
The reaction mixture was then concentrated in vacuo. The residue obtained was chromatographed
on a silica gel column using a mixture of ether and hexane 3:1 as the eluent.
2a: Light brown solid; m.p. = 236◦C; r.t. = 24 h; 31P NMR (121.5 MHz, CDCl3): δ = 50.1 ppm;
1H NMR (300 MHz, CDCl3): δ = 1.69–3.21 (m, 8H, cyclic H), 3.77 (s, 3H, CH3–O), 6.88–
7.81 (m, 4H, arom-H), 10.10 (broad s, 2H, 2NH); 13C NMR (75.5 MHz, CDCl3): δ (JCP):
−
− = −
−
−
− = −
− = −
22.1 (CH2 CH2 C C S), 22.2 (CH2 CH2 CH2 C C S), 24.4 (CH2 C C S), 28.7
−
− = − = −
−
(CH2 (CH2)3 C C S), 55.1 (CH3 O), 113.4 (d, 16.6 Hz, C C P), 118.9 (d, 4.5 Hz,
− = − − = − − = − =
C C C P), 122.9 (CH2 C C S), 126.2 (d, 132.1 Hz, C P S), 132.9 (d, 14.3 Hz, C C S),
− −
− −
− −
133.4 (CH2 C S), 149.8 (d, 2.3 Hz, N C S), 162.6 (d, 3.0 Hz, C O CH3), 187.6 (d, 9.1 Hz,
= 702 cm−1, νC = 1111 cm−1, νNH =3076–3469 cm−1; EI-HRMS:
=
C S); IR (KBr): νP
=
=
S
S
calculated for C16H17N2OPS3, 380.0241 (M+); found: 380.0243.
2b: Light brown solid; m.p. = 159◦C; r.t. = 24 h;31P NMR (121.5 MHz, CDCl3): δ = 50.6 ppm;
1H NMR (300 MHz, CDCl3): δ = 1.69–3.21 (m, 6H, cyclic H), 3.82 (s, 3H, CH3 O), 6.77–
−
7.73 (m, 4H, arom-H), 10.17 (broad s, 2H, 2NH); 13C NMR (75.5 MHz, CDCl3): δ (JCP): 15.3
−
− = −
− = −
−
− = −
−
(CH2 CH2 C C S), 21.4 (CH2 C C S), 29.7 (CH2 (CH2)2 C C S), 55.9 (CH3 O),
= − − = − − = −
113.7 (d, 16.3 Hz, C C P), 118.7 (d, 4.7 Hz, C C C P), 125.3 (CH2 C C S), 126.7
− =
− =
− −
(d, 113.2 Hz, C P S), 129.2 (d, 14.1 Hz, C C S), 137.9 (CH2 C S), 151.0 (d, 3.0 Hz,
N C S), 161.5 (d, 3.0 Hz, C O CH3), 185.2 (d, 9.8 Hz, C S); IR (KBr): νP
=703 cm−1
,
− −
− −
=
=
S
νC =1115 cm−1, νNH =3072–3350 cm−1; EI-HRMS: calculated for C15H19N2OPS3, 370.0397
=
(M+S); found: 370.0395.
2c: Light brown solid; m.p. = 136◦C; r.t. = 48 h;31P NMR (121.5 MHz, CDCl3): δ = 67.5 ppm;
1H NMR (300 MHz, CDCl3): δ = 3.77 (s, 3H, CH3 O), 6.80–8.29 (m, 10H, arom-H), 10.37
−
(broad s, 2H, 2NH); 13C NMR (75.5 MHz, CDCl3): δ (JCP): 55.2 (CH3 O), 113.5 (d, 15.0 Hz,
−
= −
− = −
− = −
− =
C C P), 122.9 (d, 5.9 Hz, C C C P), 124.9 (Ph C C S), 128.2 (d, 126.8 Hz, C P S),
− =
− = −
− −
128.9 (d, 12.8 Hz, C C S), 133.4 (Ph C C S), 146.0 (d, 2.3 Hz, N C S), 162.2 (d,
− −
=
3.0 Hz, C O CH3), 207.5 (d, 9.0 Hz, C S); Phenyl carbons: 114.0, 127.8, 128.2, 130.6; IR
(KBr): νP
= 702 cm−1, νC = 1111 cm−1, νNH = 3195–3497 cm−1; EI-HRMS: calculated
=
=
S
S
for C18H15N2OPS3, 402.0084 (M+); found: 402.0031.

Journal of Sulfur Chemistry 31
2d: Light brown solid; m.p. = 174◦C; r.t. = 48 h; 31P NMR (121.5 MHz, CDCl3): δ =
48.8 ppm;1H NMR (300 MHz, CDCl3): δ = 2.21 (s, 3H, CH3 C C S), 2.52 (s, 3H,
− − −
CH3 C S), 3.82 (s, 3H, CH3 O), 6.85–7.82 (m, 4H, arom-H), 10.23 (broad s, 2H, 2NH); 13C
− −
−
− − −
− −
−
NMR (75.5 MHz, CDCl3): δ (JCP): 12.6 (CH3 C C S), 16.4 (CH3 C S), 55.2 (CH3 O),
= − − = − − = −
113.8 (d, 15.8 Hz, C C P), 120.0 (d, 7.5 Hz, C C C P), 124.4 (CH3 C C S), 130.3
− =
− =
− −
(d, 141.9 Hz, C P S), 132.5 (d, 12.6 Hz, C C S), 132.8 (CH3 C S), 157.5 (d, 3.0 Hz,
− −
− −
=
N C S), 162.0 (d, 3.0 Hz, C O CH3), 206.9 (d, 9.1 Hz, C S); IR (KBr): νP
= 703 cm−1
,
=
S
νC = 1111 cm−1, νNH = 3154–3428 cm1; EI-HRMS: calculated for C14H13N2OPS3, 351.9928
=
(M+S); found: 351.9926.
2e:Lightbrownsolid;m.p. = 182◦C;r.t. = 48 h;31PNMR(121.5 MHz, CDCl3):δ = 48.7 ppm;1H
−
NMR (300 MHz, CDCl3): δ = 3.79 (s, 3H, CH3 O), 4.46 (s, 2H, CH2), 6.90–7.80 (m, 14H,
arom-H), 10.07 (broad s, 2H, 2NH); 13C NMR (75.5 MHz, CDCl3): δ (JCP): 33.9 (Ph CH2), 55.4
−
−
= −
− = −
− = −
(CH3 O), 113.8 (d, 16.6 Hz, C C P), 120.3 (d, 5.3 Hz, C C C P), 125.2 (CH2 C C S),
− =
− =
− −
126.5 (d, 123.0 Hz, C P S), 132.7 (d, 9.8 Hz, C C S), 134.1 (Ph C S), 152.1 (d, 3.0 Hz,
− −
− −
=
N C S), 162.9 (d, 3.0 Hz, C O CH3), 188.5 (d, 9.8 Hz, C S); Phenyl carbons: 113.3, 127.8,
128.0, 128.4, 128.6, 128.7, 129.4, 132.8; IR (KBr): νP
= 702 cm−1, νC = 1111 cm−1, νNH
=
=
=
S
S
3043–3448 cm−1; EI-HRMS: calculated for C25H21N2OPS3, 492.0554 (M+); found: 492.0574.
2f: Light brown solid; m.p. = 122◦C; r.t. = 24 h;31P NMR (121.5 MHz, CDCl3): δ = 49.6 ppm; 1H
NMR(300 MHz, CDCl3):δ = 1.19(d, 6H,3JH−H = 6.0 Hz, (CH3)2CH), 2.52(s, 3H, CH3 C C),
− =
3
−
2.72 (sept, 1H, JH−H = 6.0 Hz, (CH3)2CH), 3.81 (s, 3H, CH3 O), 6.17–7.82 (m, 4H, arom-
H), 10.16 (broad s, 2H, 2NH); 13C NMR (75.5 MHz, CDCl3): δ (JCP): 15.3 ((CH3)2CH), 22.4
− =
−
= −
(CH3 C C), 28.0 ((CH3)2CH), 55.2 (CH3 O), 110.4 (d, 15.8 Hz, C C P), 114.1 (d, 4.5 Hz,
− = − − = − − = − =
C C C P), 124.3 (CH3 C C S), 123.2 (d, 113.2 Hz, C P S), 132.9 (d, 15.1 Hz, C C S),
− = −
− −
− −
133.1 (CH3 C C S), 151.4 (d, 3.0 Hz, N C S), 162.8 (d, 3.0 Hz, C O CH3), 188.7 (d,
9.0 Hz, C S); IR (KBr): νP
= 702 cm−1, νC = 1119 cm−1, νNH = 3150–3321 cm−1; EI-
=
=
=
S
S
HRMS: calculated for C16H19N2OPS3, 382.0397 (M+); found: 382.0404.
2g: Light brown solid; m.p. = 162◦C; r.t. = 48 h; 31P NMR (121.5 MHz, CDCl3): δ = 50.4 ppm;
1H NMR (300 MHz, CDCl3): δ = 2.31 (s, 3H, CH3 C C), 3.82 (s, 3H, CH3 O), 6.75–7.78
− =
−
(m, 5H, arom-H), 10.26 (broad s, 2H, 2NH); 13C NMR (75.5 MHz, CDCl3): δ (JCP): 15.2
− =
−
= −
− = −
(CH3 C C), 55.2 (CH3 O), 114.1 (d, 16.6 Hz, C C P), 120.4 (d, 5.2 Hz, C C C P),
− = − − = − =
125.3 (CH3 C C S), 125.4 (d, 132.1 Hz, C P S), 133.1 (d, 15.1 Hz, C C S), 138.6
− = −
− −
− −
(CH3 C C S), 151.1 (d, 2.3 Hz, N C S), 162.3 (d, 3.2 Hz, C O CH3), 188.4 (d, 9.0 Hz,
= 702 cm−1, νC
cm−1, νNH = 3071–3415 cm−1; EI-HRMS: calcu-
=
=
C S); IR (KBr): νP
=
=
S
S
lated for C13H13N2OPS3, 339.9928 (M+); found: 339.9924.
2h: Light brown solid; m.p. = 141◦C; r.t. = 24 h; 31P NMR (121.5 MHz, CDCl3): δ = 49.8 ppm;
1H NMR (300 MHz, CDCl3): δ = 2.31 (s, 3H, CH3 C C), 2.55 (s, 2H, CH2 Ph), 3.77 (s,
− =
−
3H, CH3 O), 6.88–7.85 (m, 9H, arom-H), 10.35 (broad s, 2H, 2NH); 13C NMR (75.5 MHz,
−
− =
−
−
CDCl3): δ (JCP): 17.0 (CH3 C C), 33.0 (Ph CH2), 55.4 (CH3 O), 113.7 (d, 15.8 Hz,
= −
− = −
− = −
− =
C C P), 119.9 (d, 4.8 Hz, C C C P), 125.1 (CH3 C C S), 126.3 (d, 102.6 Hz, C P S),
− = − − − −
132.4 (d, 12.1 Hz, C C S), 133.3 (CH2 C S), 150.8 (d, 2.6 Hz, N C S), 162.9 (d,
− −
=
3.1 Hz, C O CH3), 188.4 (d, 9.0 Hz, C S); Phenyl carbons:120.7, 125.3, 128.2, 128.9; IR
(KBr): νP
= 702 cm−1; νC = 1111 cm−1, νNH = 3080–3328 cm−1; EI-HRMS: calculated
=
=
S
S
for C20H19N2OPS3, 430.0397 (M+); found: 430.0396.
2i: Light brown solid; m.p. = 102◦C; r.t. = 24 h;31P NMR (121.5 MHz, CDCl3): δ = 49.6 ppm;
1
=
− =
−
H NMR (300 MHz, CDCl3): δ 2.37 (s, 3H, CH3 C C), 3.73 (s, 3H, CH3 O), 6.78–
7.88 (m, 9H, arom-H), 10.30 (broad s, 2H, 2NH); 13C NMR (75.5 MHz, CDCl3):
− =
−
= −
δ (JCP): 15.2 (CH3 C C), 55.2 (CH3 O), 113.6 (d, 16.6 Hz, C C P), 122.2 (d,

32 K. Khalladi and S. Touil
− = −
− = −
− =
4.6 Hz, C C C P), 125.3 (CH3 C C S), 127.1 (d, 119.2 Hz, C P S), 133.0 (d,
− =
− = −
− −
12.1 Hz, C C S), 133.5 (CH3 C C S), 152.5 (d, 3.0 Hz, N C S), 162.4 (d, 3.1 Hz,
− −
=
C O CH3), 188.1 (d, 9.4 Hz, C S); Phenyl carbons: 128.2, 128.5, 129.0, 129.4; IR
(KBr): νP
= 702 cm−1, νC =1111 cm−1, νNH = 3072–3357 cm−1; EI-HRMS: calculated
=
=
S
S
for C19H17N2OPS3, 416.0241 (M+); found: 416.0244.
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