Synthesis of 1,3,4-thiazaphosphole by the reaction of O-phenyl (chloromethyl)isothiocyanatidophosphonothioate with R-(+)-(1-phenylethyl)amine

Full text of DOI:10.1007/s11176-008-2023-9

ISSN 1070-3632, Russian Journal of General Chemistry, 2008, Vol. 78, No. 2, pp. 315 316.
Pleiades Publishing, Ltd., 2008.
Original Russian Text M.A. Pudovik, R.Kh. Bagautdinova, L.K. Kibardina, V.A. Al’fonsov, 2008, published in Zhurnal Obshchei Khimii, 2008, Vol. 78,
No. 2, pp. 330 331.
LETTERS
TO THE EDITOR
Synthesis of 1,3,4-Thiazaphosphole by the Reaction
of O-Phenyl (Chloromethyl)isothiocyanatidophosphonothioate
with R-(+)-(1-Phenylethyl)amine
M. A. Pudovik, R. Kh. Bagautdinova, L. K. Kibardina, and V. A. Al’fonsov
Arbuzov Institute of Organic and Physical Chemistry, Kazan Research Center,
Russian Academy of Sciences, ul. Akad. Arbuzova 8, Kazan, Tatarstan, 420088 Russia
e-mail: pudovic@iopc.knc.ru
Received July 17, 2007
DOI: 10.1134/S1070363208020230
Earlier we showed that the reaction of O-phenyl
(chloromethyl)isothiocyanatidophosphonothioate (I)
with a racemic and an optically pure (1-phenylethyl)-
amine proceeded with a fairly high stereoselectivity
and provides a mixture of diastereomeric 1,3,4-thiaza-
phospholes [1]. We explored the possibility for pre-
paring analogous phosphorus-containing cyclic struc-
tures by the reaction of isothiocyanate I with derivat-
ives of R-(+)-(1-phenylethyl)amine: optically pure
hydrochloride III and N-trimethylsilyl(1-phenylethyl)-
amine IV. Simple methods of synthesis of (phenyl-
ethyl)amine hydrochloride have not been reported. As
a rule, this compound is prepared via decomposition
of structurally more complex compounds [2 6]. Our
attempt to prepare hydrochloride III by bubbling HCl
through a benzene or an ether solution of amine II
was unsuccessful, and the yield of hydrochloride III
did not exceed 10%. We found that both target start-
ing compounds III and IV can be prepared by the
reaction of chlorotrimethylsilane with R-(+)-(1-phenyl-
ethyl)amine (II) in a 1:2 ratio.
and gave a mixture of diastereomeric thiazaphos-
pholes VI ( 119.60 and 119.98 ppm) in a percent
ratio of 32:6P8 (1H and 31P NMR data) [1]. It is im-
portant to note that the intermediate phosphorylated
thiourea is not detected, which provides evidence for
its rapid cyclization.
Ph
*
S
S
ClCH2
PhO
ClCH2
PhO
Et3N
PNCS + III
PNHC(S)NHCHMe
Et3N HCl
I
V
S
Ph
N
Et3N
PhO P
*
C NHCH Me
Et3N HCl
S
VI
The reaction of isothiocyanate I with silylated
amine IV is effected in an ether solution at 20 C. In
this case, the reaction is slightly more selective, and
diastereomeric thiazaphospholes VIa and VIb (
P
120.09 and 119.85 ppm) are formed in a 24:76
percent ratio.
*
2R-(+)-MeCHNH2 + MeSiCl
Ph
S
II
PhO
*
*
P N C(S) NHCH(Ph)Me
SiMe3
I + IV
2R-(+)-MeCHNH2 HCl + R-(+)-MeCHNHSiMe3 .
Ph Ph
III IV
ClCH2
Me
Me
C C
S
N
S
S
+
C NH C
P
P
Me3SiCl
Ph
Ph
Isothiocyanate I did not react with hydrochloride
III, but in the presence of 2 equiv of triethylamine
the reaction smoothly occurred at room temperature
PhO
PhO
S
N
H
H
VIa RCRP
VIb RCSP
315

316
PUDOVIK et al.
The prevailing diastereomer RCSP-VIb was isolated
(31%) of compound VIb, mp 161.5 163 C. [ ]2D0 +290
1
by fractional crystallization from the solution. Earlier
the structure of thiazaphosphole VIb prepared from
isothiocyanate I and the free amine and having the
(c 2.44, CH3CN). H NMR spectrum [(CD3)2CO)],
, ppm (J, Hz): 1.54 d (3H, CH3C, 2JHH 7.0), 3.49 d.d
2
2
(1H, PCHA, JHP 3.6, JHH 13.3), 3.81 d.d (1H, PCHB,
same rotation angle, melting point, and
lished by X-ray diffraction [1].
was estab-
2JHP = 2JHH = 13.3), 5.23 d.q (1H, CHN, 3JHH = 3JHP
=
P
7.0), 6.79 7.40 m (10H, 2Ph), 8.28 s (1H, NH). 31P
NMR spectrum (benzene), P, ppm: 120.67. IR spec-
Reaction of chlorotrimethylsilane with (R)-(+)-
(1-phenylethyl)amine. To a solution of 2.53 g of
amine II in 20 ml of benzene, 1.13 g of chlorotri-
methylsilane was added with stirring and cooling to
5 C. After one day, a precipitate formed and was
separated and washed with two portions of benzene
to obtain 1.68 g (83%) of hydrochloride III, mp
169 171 C. [ ]2D0 +6.4 (c 4.25, C2H5OH) [3]. The
liquid reaction mixture was reduced and distilled in a
vacuum to obtain 0.81 g (40%) of silylamine IV, bp
1
trum, , cm : 684 (P=S), 1210 (POPh), 1570 (C=N),
1590 (Ph), 3275 (NH). Found, %: C 55.58; H 4.88; N
8.16; P 9.12. C16H17N2OPS2. Calculated, %: C 55.14;
H 4.93; N 8.04; P 8.82.
The IR spectra were recorded on a UR-20 spec-
1
trometer in the range 400 3600 cm in mineral oil.
1
The H NMR spectra were registered on a Bruker
WM-250 instrument at 250.132 MHz, internal re-
ference TMS. The 31P NMR spectra were measured
on a Bruker MSL-400 NMR Fourier spectrometer
at 162.0 MHz.
83 84 C (12 mm Hg), n2D0 1.4918. [ ]2D0 +36.2 (c 1.4,
1
C6H6). H NMR spectrum [(CD3)2CO)], , ppm (J,
3
Hz): 0.10 s (9H, Me3Si), 4.17 q (1H, CH, JHH 7.1),
3
1.44 d (3H, MeC, JHH 7.1), 7.36 m (5H, Ph). Found,
ACKNOWLEDGMENTS
%: C 68.38; H 9.70; N 7.34. C11H19NSi. Calculated,
%: C 68.39; H 9.84; N 7.25.
The work was financially supported by the Russian
Foundation for Basic Research (project no. 06-03-
32085).
2-(1-Phenylethyl)amino-4-phenoxy-4,5-dihydro-
5
1,3,4 -thiazaphosphole 4-sulfide VI. a. A solution
of 0.89 g of hydrochloride III, 1.49 g of isothio-
cyanate I, and 1.14 g of triethylamine in 20 ml of
methylene chloride was kept at 20 C for 3 days.
Benzene, 40 ml, was then added to the reaction mix-
ture, triethylamine hydrochloride was filtered off, the
solution was evaporated, and the crystals that formed
were separated and washed with three portions of
benzene to obtain 0.99 g (51%) of product VIa + VIb,
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RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 2 2008