Synthesis of new heterocyclic system of 4,5,7,8-tetrahydroimidazo[1,2-c][1, 3]thiazolo [4,5-e][1,3,2]diazaphosphinine starting from 2-aroylamino-3,3- dichloroacrylonitrile

Article abstract of DOI:10.1002/hc.20638

Easily accessible 2-aroylamino-3,3-dichloroacrylonitriles, when treated successively with ethylenediamine, phosphorus pentasulfide, water, and methyl and benzyl halides, furnish the corresponding derivatives of 4,5,7,8-tetrahydroimidazo[1,2-c][1,3]thiazolo[4,5-e][1,3,2]diazaphosphinine, a novel-fused heterocycle. The structure of the compounds obtained is unequivocally confirmed by the spectroscopic method and X-ray diffraction analysis.

Full text of DOI:10.1002/hc.20638

Heteroatom Chemistry
Volume 21, Number 7, 2010
Synthesis of New Heterocyclic System of
4,5,7,8-Tetrahydroimidazo[1,2-c][1,3]thiazolo
[4,5-e][1,3,2]diazaphosphinine Starting from
2-Aroylamino-3,3-dichloroacrylonitrile
Alexander P. Kozachenko,1 Oleg V. Shablykin,1 Andrei A. Gakh,2
Eduard B. Rusanov,3 and Vladimir S. Brovarets1
1Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine,
Kyiv, Ukraine
2Oak Ridge National Laboratory, Oak Ridge, TN 37831-6242
3Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Kyiv, Ukraine
Received 17 March 2010
starting materials to obtain a hitherto unknown
ABSTRACT: Easily accessible 2-aroylamino-3,3-
heterocyclic system, 4,5,7,8-tetrahydroimidazo[1,2-
c][1,3]thiazolo[4,5-e][1,3,2]diazaphosphinine.
dichloroacrylonitriles, when treated successively with
ethylenediamine, phosphorus pentasulfide, water, and
methyl and benzyl halides, furnish the correspond-
ing derivatives of 4,5,7,8-tetrahydroimidazo[1,2-c]
[1,3]thiazolo[4,5-e][1,3,2]diazaphosphinine, a novel-
fused heterocycle. The structure of the compounds ob-
tained is unequivocally confirmed by the spectroscopic
RESULTS AND DISCUSSION
2-Aroylamino-3,3-dichloroacrylonitriles react with
N-nucleophiles (primary aliphatic and aromatic
amines) to yield, as a rule, 5-amino-4-cyanooxazole
derivatives [3–10]. Interestingly, the reaction with
1,4-N,N-dinucleophiles, for example, ethylenedi-
amine, proceeds in quite a different way: Instead of
cyclization to 5-aminooxazole derivatives, two chlo-
rine atoms in reagents 1a–c are substituted by the
ethylenediamine residue thus affording the imida-
zolidine ring as in products 2a–c (Scheme 1 and
Table 1).
ꢀ
C
method and X-ray diffraction analysis.
2010 Wi-
ley Periodicals, Inc. Heteroatom Chem 21:492–498, 2010;
View this article online at wileyonlinelibrary.com. DOI
10.1002/hc.20638
INTRODUCTION
2-Aroylamino-3,3-dichloroacrylonitriles that are
readily prepared from easily accessible chloral
adducts of carboxamides [1–4] have been exten-
sively utilized in heterocyclic synthesis [3–18].
The present study offers their new application as
The IR spectra of compounds 2a–c show the va-
lence vibration bands of the carbonyl and cyano
groups in the respective regions 1652–1657 and
1
2155–2177 cm−1 (Table 2). H NMR absorption is
represented by two singlets of the imidazolidine
NH groups at 6.56–6.85 ppm and the signals of the
amide NH group at 8.66–8.92 ppm as well as the
resonances of aliphatic and aromatic protons, with
Correspondence
brovarets@bpci.kiev.ua.
2010 Wiley Periodicals, Inc.
to:
Vladimir
S.
Brovarets;
e-mail:
c
ꢀ
492

Synthesis of New Heterocyclic System of 4,5,7,8-Tetrahydroimidazo[1,2-c][1,3]thiazolo[4,5-e][1,3,2]diazaphosphinine 493
S
P
%
(
(aClcd)
onud
F
,
N
H
C
Aanlyis
Eemntal
ihgt)
e
W
(
ual
m
r
o
F
Meocular
%)
(
edl
i
Y
C
(
.
Mp.
(rPoduct)
Cpmound
Heteroatom Chemistry DOI 10.1002/hc

494 Kozachenko et al.
TABLE 2 Spectroscopic Data of Compounds 2–7
31P NMR
(ppm)
Mass-Spectrum:
m/z, [M]+
Compound
IR (KBr) (cm−1
)
1H NMR (DMSO/TMS), δ
2a
3300–3100, 2177, 1652a 3.42 (m, 4H, 2CH2), 6.56 (s, 1H, NH), 6.65 (s,
1H, NH), 7.39–7.92 (m, 5H, arom), 8.74 (s,
1H, NH)
–
–
–
–
228
242
262
262
2b
2c
3a
3450–3200, 2171, 1655a 2.37 (s, 3H, CH3), 3.41 (m, 4H, 2CH2), 6.56 (s,
1H, NH), 6.61 (s, 1H, NH), 7.20–7.80 (m, 4H,
Harom.), 8.66 (s, 1H, NH)
3540–3130, 2155, 1657a 3.36 (m, 4H, 2CH2), 6.66 (s, 1H, NH), 6.85 (s,
1H, NH), 7.52–7.93 (m, 4H, Harom.), 8.92 (s,
1H, NH)
3469, 3337, 3221, 3171,
3.43 (m, 2H, CH2), 3.70 (m, 2H, CH2), 6.30 (br
s, 2H, NH2), 6.86 (s, 1H, NH), 7.39–7.98 (m,
5H, arom), 8.77 (s, 1H, CONH), 10.20 (s, 1H,
NH)
1656, 1590a
3b
3c
3466, 3364, 3272, 3198,
1665, 1570a
2.35 (s, 3H, CH3), 3.39 (m, 2H, CH2), 3.66 (m,
2H, CH2), 6.35 (br s, 2H, NH2), 6.85 (s, 1H,
NH), 7.23–7.88 (m, 4H, arom), 8.72 (s, 1H,
CONH), 10.19 (s, 1H, NH)
3.39 (m, 2H, CH2), 3.66 (m, 2H, CH2), 6.45 (br
s, 2H, NH2), 6.92 (s, 1H, NH), 7.50–7.99 (m,
4H, arom), 8.85 (s, 1H, CONH), 10.19 (s, 1H,
NH)
–
–
276
296
3416, 3315, 3258, 3190,
1643, 1578a
4a
4b
4c
3058, 1617, 1541a
3129, 1614,1542a
3115, 1614, 1539a
3.89 (m, 2H, CH2), 4.15 (m, 2H, CH2),
7.50–7.85 (m, 5H, arom), 10.29 (br s, 2H,
SH + NH)
80.6
81.2
80.1
338
352
372
2.36 (s, 3H, CH3), 3.87 (m, 2H, CH2), 4.15 (m,
2H, CH2), 7.58–7.84 (m, 4H, arom), 9.81 (br.
s, 2H, SH + NH)
3.90 (m, 2H, CH2), 4.16 (m, 2H, CH2),
7.60–7.86 (m, 4H, arom), 10.52 (br s, 2H,
SH + NH)
5a
5b
6a
3331, 1622a, 1530a
3329, 1618a, 1534a
1613, 1530,1507
3.62–4.00 (m, 6H, 3CH2), 7.16–7.83 (m, 10H,
arom), 9.67 (br s, 1H, NH)
60.1
59.3
65.6
428
442
366
2.36 (s, 3H, CH3), 3.30–3.95 (m, 6H, 3CH2),
7.15–7.72 (m, 9H, arom), 9.66 (br. s, 1H, NH)
2.10 (d, 3H, CH3), 3.63 (s, 3H, CH3), 3.93 (m,
2H, CH2), 4.07 (m, 2H, CH2), 7.46–7.77 (m,
5H, arom)
2.11 (d, 3H, CH3), 2.34 (s, 3H, CH3), 3.62 (s,
3H, CH3), 3.92 (m, 2H, CH2), 4.08 (m, 2H,
CH2), 7.27–7.66 (m, 4H, arom)
2.10 (d, 3H, CH3), 3.62 (s, 3H, CH3), 3.93 (m,
2H, CH2), 4.07 (m, 2H, CH2), 7.54–7.78 (m,
4H, arom)
3.22–3.91 (m, 6H, 3CH2), 5.02–5.49 (dd, 2H,
CH2), 7.14–7.78 (m, 15H, arom)
2.34 (s, 3H, CH3), 3.24–3.92 (m, 6H, 3CH2),
5.11–5.44 (dd, 2H, CH2), 7.15–7.64 (m, 14H,
arom)
3.24–3.94 (m, 6H, 3CH2), 5.07–5.43 (dd, 2H,
CH2), 7.15–7.80 (m, 14H, arom)
3.22–3.56 (m, 2H, CH2), 3.47 (s, 3H, CH3),
3.70–4.03 (m, 4H, 2CH2), 7.14–7.84 (m,
10H, arom)
2.38 (s, 3H, CH3), 3.21–3.54 (m, 2H, CH2),
3.47 (s, 3H, CH3), 3.68–4.02 (m, 4H, 2CH2),
7.13–7.75 (m, 9H, arom)
6b
6c
1613, 1511a
63.3
62.7
380
400
1614, 1533, 1508
6d
6e
1592a, 1508a
1596a, 1515a
60.1
60.9
518
532
6f
1600a, 1529a
1598a, 1527a
60.7
61.1
553
442
7a
7b
1601a, 1530a
61.2
456
aA band with a shoulder.
Heteroatom Chemistry DOI 10.1002/hc

Synthesis of New Heterocyclic System of 4,5,7,8-Tetrahydroimidazo[1,2-c][1,3]thiazolo[4,5-e][1,3,2]diazaphosphinine 495
Cl
HN
H
N
H
N
Ar
Ar
H2NCH2CH2NH2 (excess)
Cl
N
H
O
C
N
O
C
N
1a–c
2a–c
H2S (excess), Py
2 P2S5, Py
N
N
HN
H
N
N
Ar
2 P2S5, Py
N
H
Ar
S
P
O
S
N
H
SH
S
NH2
3a–c
4a–c
PhCH2Cl, EtONa
2AlkHlg, 2EtONa
Alk
N
N
N
N
N
N
P
Ar
S
S
Ar
S
P
S
S
N
N
Ph
SAlk
H
5a,b
6a–f
5
a
b
6
a
b
c
d
e
f
Ph
—
4-MeC6H4
—
Ph
4-MeC6H4
Me
4-ClC6H4
Me
Ph
4-MeC6H4
PhCH2
4-ClC6H4
PhCH2
Ar
Alk
Ar
Me
PhCH2
Alk
1–4 a = Ph, b = 4-MeC6H4, c = 4-ClC6H4
SCHEME 1
the expected integral intensity ratio. Moreover, the
structure of products 2a–c is unambiguously evi-
denced by the characterization data for their pre-
viously reported analogue, N-[cyano(imidazolidin-2-
ylidene)methyl]acetamide [5].
On reacting with hydrogen sulfide in pyridine,
nitriles 2a–c were converted almost quantitatively
to corresponding thioamides 3, which were then
treated with 2 equiv of P2S5 in pyridine by the
known procedure [17–20] to furnish substituted
tive alkylating agent such as benzyl chloride, it was
possible to isolate both S-monosubstituted and N,S-
disubstituted benzyl derivatives (compounds 5a,b
and 6d–f, respectively) depending on the reagent ra-
tio. At the same time, alkylation with a more reactive
methyl iodide, even if used in an equimolar amount,
provided exclusively N,S-dimethyl derivatives (com-
pounds 6a–c).
To prepare dialkyl derivatives 7a,b analogous to
6 but containing different alkyl groups at the N and S
atoms, we treated S-monosubstituted benzyl deriva-
tives 5a,b with methyl iodide.
derivatives
4
of 4,5,7,8-tetrahydroimidazo[1,2-
c][1,3]thiazolo[4,5-e][1,3,2]diazaphosphinine,
a
novel-fused heterocyclic system. As found, com-
pounds 4 are also obtainable directly from 2 by
treating with phosphorus pentasulfide. However,
the reaction course is complicated in this case,
leading to much lower yields of products 4a–c than
in the conversion 2→3→4.
Me
N
N
S
MeI, EtONa
N
P
5a,b
Ar
S
S
N
Ph
By substituting two exchangeable hydrogen
atoms in compounds 4a–c, we obtained their benzyl
and methyl derivatives 5–7. With a moderately reac-
7a,b
7a Ar = Ph, 7b Ar = 4-MeC6H4
Heteroatom Chemistry DOI 10.1002/hc

496 Kozachenko et al.
N-[Cyano(imidazolidin-2-ylidene)methyl]
carboxamides 2a–c
To a suspension of 1a–c (50 mmol) obtained by
the known procedure [3,4] in propan-2-ol (100 mL),
ethylenediamine (250 mmol) was added. The mix-
ture was allowed to stand at room temperature (r.t.)
for 5 min. The resulting precipitate was filtered off
and washed with H2O. The product was purified by
recrystallization from EtOH.
N-(2-Amino-1-imidazolidin-2-ylidene-2-
thioxoethyl) Carboxamides 3a–c
FIGURE 1 Perspective view and labeling scheme for
molecule 6C. Selected bond lengths (A) and angles (de-
˚
grees) for 6C: P1–S2 2.0823(10), P1–S3 1.9276(10), N3–P1
1.706(2), N4–P1 1.618(2), C2–N4 1.326(3), C2–C3 1.403(3),
C3–C4 1.407(3), C4–N3 1.361(3), C4–N2 1.322(3), C5–N2
1.454(3), C5–C6 1.523(4), C6–N3 1.462(3), C2–S1 1.750(3),
C1–S1 1.764(2), C1–N1 1.293(3), C3–N1 1.377(3); N4–P1–
N3 104.48(10), N4–P1–S3 119.95(9), N3–P1–S3 111.58(9),
N4–P1–S2 108.63(10), N3–P1–S2 103.46(8), S3–P1–S2
107.51(5).
To 2a–c (4 mmol), pyridine (10 mL) and triethy-
lamine (1 mL) were added, and dry hydrogen sulfide
was bubbled through the mixture for 1.5–2 h (until
a solution was formed). The mixture was allowed to
stand at r.t. for 12 h. The resulting precipitate was
filtered off and washed with EtOH. The product was
purified by recrystallization from EtOH.
The identity of all compounds was verified by
IR, NMR, and mass spectra, and 6c was struc-
turally determined by X-ray diffraction analysis,
thus clearly indicating the presence of a new
heterocyclic system, 4,5,7,8-tetrahydroimidazo[1,2-
c][1,3]thiazolo[4,5-e][1,3,2]diazahosphinine.
The main geometrical parameters (bond lengths
and angles) of the central tricyclic core of structure
6c are shown in Fig. 1. The bond lengths of P1–S2
and P1–S3 are in the normal range for such bonds.
The bond P1–N3 is longer than P1–N4, whereas the
other structural parameters of the tricyclic core are
typical of π-delocalized systems. The central core is
planar (deviations of atoms from the least-squares
plane do not exceed 0.021 Å), and the phenyl ring is
practically coplanar with it (the dihedral angle S1–
C1–C9–C14 is 1.07(9)◦).
2-Aryl-5-mercapto-5-thioxo-4,5,7,8-
tetrahydroimidazo[1,2-c][1,3]thiazolo[4,5-e]
[1,3,2]diazaphosphinine 4a–c
A mixture of 3a–c (2 mmol) and P2S5 (4 mmol) in
anhydrous pyridine was refluxed for 4 h. Then it was
treated with water (100 mL), filtered, washed with
EtOH, and purified by recrystallization from DMF-
H2O (5:1) to give 4a–c.
Compounds 4a–c were also obtained by boil-
ing 2a–c (2 mmol) in pyridine (10 mL) with P2S5
(4 mmol) for 4 h. The products were isolated as de-
scribed above. Yields were 35–42%. The samples of
compounds 4a–c obtained from 2 and 3 exhibited
identical IR spectra.
EXPERIMENTAL
2-Aryl-5-benzylthio-5-thioxo-4,5,7,8-
tetrahydroimidazo[1,2-c][1,3]thiazolo[4,5-e]
[1,3,2]diazaphosphinine 5a,b
NMR spectra were recorded on a Varian Gemini 300
spectrometer at 300 (1H) and 80.95 MHz (31P). H
1
NMR chemical shifts are given in δ (ppm) relative
to Me4Si as an internal standard. 31P NMR spectra
were recorded relative to 85% H3PO4 as an external
standard. IR spectra were measured on a Specord
M-80 spectrometer for KBr disks. Mass spectra were
measured on a Surveyor MSQ instrument (Thermo
Finnigan) using the atmospheric pressure chemical
ionization (APCI) method and 0.1% aqueous solu-
tion of formic acid and acetonitrile as solvents.
To a suspension of 4a,b (1 mmol) in anhydrous
EtOH (5 mL), a solution of EtONa (1 mmol) in
EtOH (5 mL) and a solution of benzyl chloride
(1 mmol) in EtOH (5 mL) were added. The reac-
tion mixture was heated under reflux for 1 min and
then cooled. After filtering off NaCl, the solvent was
evaporated in vacuo and the residue was treated with
H2O, filtered off, dried, and purified by recrystalliza-
tion from DMF–EtOH (1:1).
Heteroatom Chemistry DOI 10.1002/hc

Synthesis of New Heterocyclic System of 4,5,7,8-Tetrahydroimidazo[1,2-c][1,3]thiazolo[4,5-e][1,3,2]diazaphosphinine 497
anisotropic approximation for non-hydrogen atoms
using the SHELXS97 and SHELXL97 programs
[21,22]. All hydrogen atoms were placed at calcu-
lated positions and refined with a riding model. In
the refinement, 3459 reflections including 2540 those
with I ≥ 2σ(I) were used. Convergence was obtained
at R1 = 0.0388, wR2 = 0.0983 for all reflections
and R1 = 0.0613, wR2 = 0.1123, GOF = 1.003 for
those observed (253 parameters; obs/variabl. 10.0;
the largest and smallest peaks in the final difference
map 0.29 and −0.33 e/Å3). The weighting scheme is
9-Alkyl-5-alkylthio-2-aryl-5-thioxo-5,7,8,9-
tetrahydroimidazo[1,2-c][1,3]thiazolo[4,5-e]
[1,3,2]diazaphosphinine 6a–f
To a suspension of 4a–c (1 mmol) in anhydrous
EtOH (10 mL), a solution of EtONa (2 mmol) in
EtOH (10 mL) and a solution of methyl iodide or
benzyl chloride (2 mmol) in EtOH (10 mL) were
added. The reaction mixture was heated under re-
flux for 1 min, cooled, and allowed to stand at r.t.
for 12 h. The resulting precipitate was filtered off,
washed with H2O, dried, and purified by recrystal-
lization from EtOH.
Compounds 6d,e were also obtained by reacting
5a,b (1 mmol) with benzyl chloride (1 mmol) and
EtONa (1 mmol) in EtOH (20 mL). Yields were 88–
92%. The samples of compounds 6d,e obtained from
4a,b and 5a,b exhibited identical IR spectra.
2
as follows: ω = 1/[σ2(Fo ) + (0.0602 P)2 + 0.5161 P],
2
2
where P = (Fo + 2Fc )/3. Full crystallographic de-
tails have been deposited at the Cambridge Crystal-
lographic Data Centre (CCDC). Any request to the
CCDC for this material should quote the full lit-
erature citation and the reference number CCDC
768486.
2-Aryl-5-benzylthio-9-methyl-5-thioxo-5,7,8,9-
tetrahydroimidazo[1,2-c][1,3]thiazolo[4,5-e]
[1,3,2]diazaphosphinine 7a,b
ACKNOWLEDGMENTS
This research was supported by the Global IPP pro-
gram through the Science and Technology Center in
Ukraine. Oak Ridge National Laboratory is managed
and operated by UT-Battelle, LLC, under U.S. De-
partment of Energy contract DE-AC05-00OR22725.
This paper is a contribution from the Discovery
Chemistry Project.
To a solution of 5a,b (1 mmol) in anhydrous EtOH
(20 mL), a solution of EtONa (1 mmol) in EtOH (5
mL) and a solution of methyl iodide (1 mmol) in
EtOH (5 mL) were added. The mixture was allowed
to stand at room temperature for 12 h. The resulting
precipitate was filtered off, washed with H2O, dried
in vacuo over P2O5, and purified by recrystallization
from EtOH.
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Heteroatom Chemistry DOI 10.1002/hc