Synthesis and structure of some 6,7-dihydro-thiazolo[4,5-d][1,3,2]diaza- λ5-phosphorines

Article abstract of DOI:10.1080/713744577

1,2,4-Thiadiazol-5(2H)-imines 1 react with malononitrile under ring cleavage cycloaddition and subsequent ring rearrangement. The products 2 incorporate the enaminonitrile fragment. Treatment of compounds 2 with phosphorus pentachloride results in thiazol

Full text of DOI:10.1080/713744577

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Synthesis and Structure of Some 6,7-Dihydro-
thiazolo[4,5- d ][1,3,2]diaza-λ 5 -phosphorines
Mikhail A. Rensky a , Vladimir S. Zyabrev a & Alexander N. Chernega a
a National Academy of Sciences of Ukraine, Keiv, Ukraine
Version of record first published: 27 Oct 2010.
To cite this article: Mikhail A. Rensky, Vladimir S. Zyabrev & Alexander N. Chernega (2003): Synthesis and Structure of Some
6,7-Dihydro-thiazolo[4,5- d ][1,3,2]diaza-λ 5 -phosphorines, Phosphorus, Sulfur, and Silicon and the Related Elements, 178:10,
2127-2135
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Phosphorus, Sulfur, and Silicon, 178:2127–2135, 2003
ꢀC
Copyright Taylor & Francis Inc.
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500390221591
SYNTHESIS AND STRUCTURE OF SOME
6,7-DIHYDRO-THIAZOLO[4,5-d][1,3,2]DIAZA-λ5-
PHOSPHORINES
Mikhail A. Rensky, Vladimir S. Zyabrev,
and Alexander N. Chernega
National Academy of Sciences of Ukraine, Keiv, Ukraine
(Received July 24, 2002; accepted March 4, 2003)
1,2,4-Thiadiazol-5(2H)-imines 1 react with malononitrile under ring
cleavage cycloaddition and subsequent ring rearrangement. The prod-
ucts 2 incorporate the enaminonitrile fragment. Treatment of com-
pounds 2 with phosphorus pentachloride results in thiazolo[4,5-
d][1,3,2]diaza-λ5-phosphorine derivatives 3 with a reactive chloro
substituent in position 2 and 4 which can be substituted by various
nucleophiles. The structure of the trimethoxy derivative 7c was deter-
mined by an X-ray structure analysis.
Keywords: Bicyclic heterocyclic compounds; cycloadditions; rearrange-
ments; substitution
The synthesis of 1,3,2-diaza-λ5-phosphorine derivatives has been re-
ported in 1963,1 and during the ensuing years their chemical, spec-
tral, and pesticidal properties have been intensively studied.2–8 Some
of them exhibited significant antimycotic activity.9 Nevertheless, fused
heterocycles containing the unsaturated 1,3,2-diaza-λ5-phosphorine
ring have not been reported up to now, whereas bicyclic nitrogen and
phosphorus containing compounds are actively screened to search for
antitumour agents.10
Herein, we describe the first representatives of the thiazolo[4,5-
d][1,3,2]diazaphosphorine series, which are conveniently prepared from
easily available 1,2,4-thiadiazol-5(2H)-imines 1 (Scheme 1). We recently
revealed that compounds 1 react with malononitrile under ring cleav-
age cycloaddition and subsequent rearrangement to yield the products
Address correspondence to V. S. Zyabrev, Institute of Bioorganic Chemistry and
Petrochemistry, National Academy of Sciences of Ukraine, 1 Murmanskaya St., 02094
Kiev, Ukraine. E-mail: users@bpci.kiev.ua
2127

2128
M. A. Rensky et al.
SCHEME 1 The synthesis of compounds 2–8.
2 which are suitable substrates for further heterocyclizations.11 One
interesting heterocyclization occurs when 2 is treated with phospho-
rus pentachloride. The reaction proceeds quite regioselectively with
participation of the amino and cyano groups as in the case of simple
enaminonitriles.12 The anellation products 3, containing three reac-
tive chlorine atoms, react differently with amines and alcoholates de-
pending on the nature of the nucleophile and the temperature. These
peculiarities of the compounds 3 were exploited with respect to the
synthesis of thiazolo[4,5-d][1,3,2]diaza-λ5-phosphorine derivatives 4–8
bearing various substituents at positions 2 and 4.
The structure of all compounds was verified by IR and 1H NMR
spectra, whereas the structure of 7c was determined by an x-ray
diffraction analysis (Figure 1, Table I). The P(1)S(1)N(1–3)C(1–3,7)
bicyclic system of this compound is almost planar. Deviations from
˚
the least-squares plane do not exceed 0.092 A, the dihedral angle
between the 5- and 6-membered ring is only 2.3◦. The bond system
C(7) N(4) C(20)[C(21)] N(15) C(14) is approximately coplanar to the

5
Synthesis of 6,7-Dihydro-thiazolo[4,5-d][1,3,2]diaza-λ -phosphorines
2129
FIGURE 1 Perspective view and labelling scheme for molecule 7c (hydrogen
atoms are omitted for clarity).
least-squares plane, the corresponding dihedral angle is 7.2◦. The ster-
ically unfavourable cisoid conformation of the diazadiene fragment
C(7)N(4)C(20)N(5) is probably due to packing forces in the solid state.
In a solution, however, 7c exists as a mixture of two stereoisomers, as
1
evidenced by the H NMR spectra (see Experimental section). These
stereoisomers or conformers can result from syn-anti isomerization at
N(4) and N(5), as well as from rotation around the N(4)-C(20) bond. At
90◦C, they are rapidly interconverting on the NMR time scale. Similar
1
conformation equilibriums were documented by the HNMR also for
compounds 4d and 7a.
EXPERIMENTAL
All reagents and solvents were commercial products and were used
as received unless otherwise indicated. Melting points were deter-
mined on a capillary tube apparatus and are uncorrected. IR spec-
tra were taken on a Specord 71IR spectrophotometer in a CH2Cl2
1
solution and on a UR 20 spectrophotometer in a KBr disk. H NMR
spectra were recorded on a Varian VXR 300 (300 MHz) and a Varian
Gemini 200 (200 MHz) spectrometer. TMS was used as the internal

2130
M. A. Rensky et al.
TABLE I Selected Bond Length and Angles in 7c
ω (◦)
˚
Bond
d (A)
Angle
S(1)-C(2)
S(1)-C(7)
P(1)-O(1)
P(1)-O(2)
P(1)-N(1)
P(1)-N(2)
N(1)-C(1)
N(2)-C(3)
N(3)-C(1)
N(3)-C(7)
N(4)-C(7)
N(4)-C(20)
N(5)-C(14)
N(5)-C(20)
C(1)-C(2)
C(2)-C(3)
C(20)-C(21)
1.758(5)
1.747(5)
1.541(4)
1.575(4)
1.607(4)
1.602(4)
1.339(6)
1.324(6)
1.375(6)
1.407(5)
1.284(6)
1.394(6)
1.412(6)
1.279(6)
1.384(6)
1.384(6)
1.485(6)
C(2)S(1)C(7)
O(1)P(1)O(2)
O(1)P(1)N(1)
O(2)P(1)N(1)
O(1)P(1)N(2)
O(2)P(1)N(2)
N(1)P(1)N(2)
P(1)N(1)C(1)
P(1)N(2)C(3)
C(1)N(3)C(7)
C(7)N(4)C(20)
C(14)N(5)C(20)
N(1)C(1)C(2)
N(3)C(1)C(2)
S(1)C(2)C(1)
C(1)C(2)C(3)
N(2)C(3)C(2)
S(1)C(7)N(3)
S(1)C(7)N(4)
N(4)C(20)N(5)
N(4)C(20)C(21)
N(5)C(20)C(21)
90.3(2)
101.6(2)
110.5(2)
112.1(2)
113.1(2)
104.2(2)
114.5(2)
114.1(4)
117.6(4)
115.0(4)
118.5(4)
124.8(4)
127.8(5)
111.9(4)
112.6(4)
120.1(5)
124.9(5)
110.2(3)
131.3(4)
119.4(4)
111.4(4)
129.1(4)
standard. Crystallographic measurements of compound 7c were per-
formed at 18◦C on an Enraf-Nonius CAD 4 diffractometer operating in
the ω-2ꢀ scan mode (the ratio of the scanning rates ω/2ꢀ = 1.2). In-
tensity data were collected within the range 2 < ꢀ < 60◦ (0 < h < 19,
0 < k < 13, −30 < 1 < 30) using graphite monochromated CuKα ra-
diation. The intensities of 4329 reflections (3954 unique reflections,
R = 0.023) were measured. Data were corrected for Lorentz and po-
larization effects. An empirical absorption correction based on azimutal
scan data was also applied.13 The structure was solved by direct method
and refined by full-matrix least-squares technique in an anisotropic
approximation usig the CRYSTALS program package.14 In the refine-
ment, 2579 reflections with I > 4σ(I) were used. All hydrogen atoms
were located in the difference Fourier maps and included in the fi-
nal refinement with fixed positional and thermal parameters. Conver-
gence was obtained at R = 0.056, Rw = 0.056, and GOF = 1.107 (343
refined parameters; obs/variabl. 7.5; the largest and minimal peaks in
3
˚
the final difference map, 0.51 and −0.37 e/A ). The weighting scheme
ω = l/(0.01F02 + 12σ(F02) + 1) was used.

5
Synthesis of 6,7-Dihydro-thiazolo[4,5-d][1,3,2]diaza-λ -phosphorines
2131
1,2,4-Thiadiazol-5(2H)-imine Hydrobromides 1a---d·HBr
To a stirred solution or a suspension of the appropriate N-imidoyl-
thiourea of the general formula PhN C(Ar)NHC(S)NHR∗ (50 mmol)
in CHCl3 (50 mL), pyridine (50 mmol) was added in one portion. Then
a solution of bromine (50 mmol) in CHCl3 (25 mL) was added dropwise
in 40 min. The mixture was stirred for 1 h and the precipitated salt
was filtered off and washed with MeOH. The filtrate was concentrated
in vacuo and the residue was washed with MeOH to give an additional
amount of the product.
Compound la · HBr: yield 90%, m.p. 217◦C dec. (AcOH) (lit. 207–
208◦C,16 230–232◦C17). Found: Br 19.05, N 10.06, S 7.76%. Calcd for
C20H15N3S · HBr. Br 19.47, N 10.24, S 7.81%.
Compound Ib · HBr: yield 91%, m.p. 216◦C dec. (AcOH). Found: Br
19.11, N 9.72, S 7.59%. Calcd for C21H17N3S · HBr: Br 18.83, N 9.90, S
7.56%.
Compound 1c · HBr: yield 95% m.p. 218◦C dec. (CICH2CH2Cl).
Found: Br 18.03, N 9.63, S 7.24%. Calcd for C21H17N3OS · HBr: Br 18.15,
N 9.54, S 7.28%.
Compound ld · HBr: yield 93% m.p. 206◦C dec. (EtOH). Found: Br
18.31, N 9.97, S 7.52%. Calcd for C21H17N3S · HBr: Br 18.83, N 9.90, S
7.56%.
Free 1,2,4-Thiadiazol-5(2H)-imines 1a---c
To a suspension of salt 1a–c · HBr (20 mmol) in EtOH (40 mL), triethy-
lamine (22 mmol) was added. The mixture was stirred for 4 h and the
product was filtered off.
Compound 1a: yield 88%, m.p. l38◦C (EtOH) (lit. 143–146◦C,17 142–
143◦C18). Found: N 12.86, S 9.78%. Calcd for C20H15N3S: N 12.76, S
9.73%.
Compound 1b: yield 94%, m.p. 148◦C (EtOH). Found: N 12.32, S
9.47%. Calcd for C21H17N3S: N 12.23, S 9.34%.
Compound 1c: yield 88%, m.p. 139◦C (EtOH). Found: N 11.60, S
8.94%. Calcd for C21H17N3OS: N 11.69, S 8.92%.
4-Amino-5-cyano-2,3-dihydro-2-imidoylimino-3-
phenylthiazoles 2a---c
A stirred mixture of 1a–c (20 mmol), malononitrile (20 mmol) and diox-
ane (10 mL) was heated under reflux for 3 h, cooled, and filtered to
∗N-Imidoylthioureas were prepared using the general procedure developed by J.
Goerdeler and coworkers.15

2132
M. A. Rensky et al.
separate the product which was washed with dioxane and dried at
100◦C.
Compound 2a: yield 88%, m.p. 208◦C dec. (MeCN). IR (CH2Cl2, cm−1
)
2190 (ν C N), 3380, 3460 (ν NH2). Found: C 70.08, H 4.65, N 17.53, S
8.02%. Calcd for C23H17N5S: C 69.85, H 4.33, N 17.71, S 8.11%.
Compound 2b: yield 76%, m.p. 215◦C dec. (MeCN). IR (KBr, cm−1
)
1
2200 (ν C N), 3220–3380 (ν NH2). H NMR (200 MHz, DMSO-D6) δ
3
2.18 (s, CH3), 6.69 (d, JHH = 11 Hz, 2 Har.), 6.84 (s, NH2), 6.92–7.05
(m, 5 Mar.), 7.21 (t, 3JHH = 11 Hz, 2 Har.), 7.47–7.60 (m, 5 Har.). Found:
C 71.48, H 4.80, N 17.41, S 7.87%. Calcd for C24H19N5S: C 70.39, H
4.68, N 17.10, S 7.83%.
Compound 2c: yield 75%, m.p. 219◦C dec. (dioxane). IR (KBr, cm−1
)
1
2200 (ν C N), 3220, 3270, 3340, 3460 (ν NH2). H NMR (200 MHz,
DMSO-D6) δ 3.66 (s, CH3), 6.67–6.73 (m, 4 Har.), 6.83 (s, NH2), 6.95–
7.27 (m, 5 Har.), 7.48–7.62 (m, 5 Har.). Found: C 66.91, 4.61, N 16.59, S
7.42%. Calcd for C24H19N5OS: C 67.74, H 4.50, N 16.46, S 7.54%.
4-Amino-3-benzyl-5-cyano-2,3-dihydro-2-
(N-phenylbenzimidoyl)iminothiazole 2d
To a stirred mixture of salt 1d · HBr (15 mmol) and malononitrile
(15 mmol) in CH2Cl2 (20 mL), a solution of triethylamine (15 mmol) in
CH2Cl2 (5 mL) was added dropwise. The reaction mixture was stirred
for 5 h and the precipitated product was filtered off and washed with
water; yield 75%, m.p. 210◦C dec. (MeCN). IR (CH2Cl2, cm−1) 2180 (ν
C N), 3280–3400 (ν NH2). Found: C 70.16, H 4.53, N 16.81, S 7.65%.
Calcd for C24H19N5S: C 70.39, H 4.68, N 17.10, S7.83%.
2,2,4-Trichloro-6,7-dihydro-6-imidoyliminothiazolo-
[4,5-d][1,3,2]diaza-λ5-phosphorine Hydrochlorides 3a---d
A stirred mixture of 2a–d (4 mmol) and PCl5 (4.2 mmol) in anhy-
drous chlorobenzene (6 mL) was heated at 100◦C for 1 h. After cool-
ing, the precipitate was separated and dried in vacuo to give the prod-
uct in quantitative yield. Only compound 3b was analytically pure;
m.p. 192◦C dec. Found: Cl 25.08, N 11.78, P 5.30, S 5.41%. Calcd for
C24H17Cl3N5PS · HCl: Cl 24.39, N 12.05, P 5.33, S 5.52%.
7-Benzyl-6,7-dihydro-2,2,4-tris(methylamino)-6-
(N-phenylbenzimidoyl)imino-thiazolo-
[4,5-d][1,3,2]diaza-λ5-phosphorine 4d
Through a suspension of 3d (1.6 mmol) in anhydrous benzene (10 mL),
methylamine was bubbled during 2 h. The resulting mixture was

5
Synthesis of 6,7-Dihydro-thiazolo[4,5-d][1,3,2]diaza-λ -phosphorines
2133
allowed to stand for a further 10 h then the precipitate was sepa-
rated and washed with water to obtain the pure product; yield 75%,
1
m.p. 182◦C dec. (MeCN). H NMR (300 MHz, DMSO-D6) δ 2.33 (dd,
3
3
3JHH = 13 Hz, JHH = 5 Hz, 2 CH3); 2.64, 2.76 (d, 1:5, JHH = 3 Hz,
CH3); 4.33 (br. s, 2 NH); 4.98, 5.35 (s, 1:5, CH2); 6.38–7.71 (m, 3 C6H5).
Found: N 21.08, P 5.72, S, 5.91%. Calcd for C27H29N8PS: N 21.20, P
5.86, S 6.06%.
2,2-Dichloro-6,7-dihydro-6-(4-methyl-N-
phenylbenzimidoyl)imino-4-morpholino-7-
phenylthiazolo[4,5-d][1,3,2]diaza-λ5-phosphorine 5b
To a suspension of 3b (1.5 mmol) in anhydrous benzene (8 mL), mor-
pholine (12 mmol) was added in one portion. The reaction mixture was
stirred for 2 h then the precipitate was filtered, washed with water, and
dried in vacuo over P205; yield 72%, m.p. 213◦C (MeCN). 1H NMR (300
MHz CDCl3) δ 2.24 (br. s, CH3), 3.76 (br. s, 2 CH2), 3.90 (br. s, 2 CH2),
6.80–7.74 (m, 2 C6H5, C6H4). Found: Cl 12.16, N 13.83, S 5.44%. Calcd
for C28H25Cl2N6OPS: Cl 11.91 N 14.11, S 5.38%.
6,7-Dihydro-6-(4-methyl-N-phenylbenzimidoyl)imino-
2,2,4-trimorpholino-7-phenylthiazolo[4,5-d][1,3,2]diaza-
λ5-phosphorine 6b
A stirred mixture of 3b (1.5 mmol) and morpholine (18 mmol) in an-
hydrous benzene (8 mL) was heated under reflux for 5 h, cooled, and
filtered. The filtrate was concentrated in vacuo and the residue was
treated with EtOH (10 mL) to crystallize the product; yield 79%, m.p.
174◦C (EtOH). 1H NMR (300 MHz, CDCl3) δ 2.23 (br. s, CH3), 3.01 (br.
s, 4 CH2), 3.58 (br. s, 4 CH2), 3.74 (br. s, 4 CH2), 6.79–7.80 (m, 2 C6H5,
C6H4). Found: C 61.47, H 6.00, N 16.32, P 4.41, S 4.63%. Caled for
C36H41N8O3PS: C 61.87, H 5.91, N 16.08, P 4.44, S 4.60%.
6,7-Dihydro-6-imidoylimino-2,2,4-trimethoxy-7-
phenylthiazolo[4,5-d][1,3,2]diaza-λ5-phosphorines 7a,c
To a suspension of 3a,c (2 mmol) in dioxane (5 mL), a solution of 4.3 M
MeONa/MeOH (1.9 mL) in dioxane (3 mL) was added dropwise. The
reaction mixture was stirred for 2 h and filtered. The filtrate was con-
centrated in vacuo and the residue was treated with MeOH to afford
the crystalline product.
1
Compound 7a: yield 53%, m.p. 171◦C (MeCN). H NMR (300 MHz,
3
CDCl3) δ 3.62 (d, JHH = 12 Hz, 2 CH3); 3.83, 3.96 (s, 1:2, CH3);

2134
M. A. Rensky et al.
6.79–7.89 (m, 3 C6H5). Found: N 13.36, P 5.78, S 6.23%. Calcd for
C26H24N5O3PS: N 13.53, P 5.98, S 6.20%.
Compound 7c: yield 77%, m.p. 186◦C (AcOMe). 1H NMR (300 MHz,
3
DMSO-D6, 19◦C) δ 3.57 (d, JHP = 12 Hz, 2 CH3); 3.67, 3.80 (s, 4:1,
1
CH3); 3.80, 3.91 (s, 1:4, CH3); 6.69–7.79 (m, 2 C6H5, C6H4). H NMR
3
(300 MHz, DMSO-D6, 90◦C) δ 3.57 (d, JHP = 12 Hz, 2 CH3), 3.72 (s,
CH3), 3.88 (s, CH3), 6.75–7.53 (m, 2 C6H5, C6H4). Found: N 13.03,
P 5.53, S 5.91%. Calcd for C27H26N5O4PS: N 12.79, P 5.66, S 5.86%.
A single crystal for x-ray analysis was prepared by crystallization
from MeCN: size 0.09 × 0.29 × 0.31 mm, monoclinic, space group C2/c,
◦
˚
Z = 8, a = 17.497(3), b = 12.174(3), c = 27.112(1) A, β = 112.26(1) ,
3
V = 5344.9 A , Dc = 1.36 g · cm−3, µ = 19.75 cm−1,∗
.
˚
2,2-Dibutoxy-6,7-dihydro-6-(4-methyl-N-
phenylbenzimidoyl)imino-4-morpholino-
7-phenylthiazolo[4,5-d][1,3,2]diaza-λ5-phosphorine 8b
To a suspension of 5b (0.4 mmol) in dioxane (5 mL), a solution of 1.9 M
BuONa/BuOH (0.6 mL) was added. The reaction mixture was refluxed
for 1.5 h. After cooling, the solvent was evaporated in vacuo and the
residue was treated with EtOH (5 mL) to afford the crystalline product;
1
yield 55%, m.p. 126◦C (EtOH). H NMR (300 MHz, CDCl3) δ 0.88 (m,
2 CH3), 1.36 (m, 2 CH2), 1.58 (m, 2 CH2), 2.23 (br. s, CH3) 3.79 (m, 6
CH2), 6.79–7.80 (m, 2 C6H5, C6H4). Found: C 64.41, H 6.62, N 12.82,
P 4.56, S 4.86%. Calcd for C36H43N6O3PS: C 64.45, H 6.46, N 12.53, P
4.62, S 4.78%.
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graphic Data Centre (CCDC 166902).

5
Synthesis of 6,7-Dihydro-thiazolo[4,5-d][1,3,2]diaza-λ -phosphorines
2135
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