Studies on phosphoroheterocycle chemistry I: A facile synthesis of new tricyclic phosphoroheterocycles 1,3,2-oxazaphospholidino(or oxazaphosphorino)[3,2-a][1,3,2]benzodiazaphosphorines

Article abstract of DOI:10.1055/s-2001-16754

Reaction procedures have been developed for the preparation of structurally different phosphoroheterocyclic compounds. Firstly, the treatment of PCl₃ with functionalized compound N-ethyl-2-(β-hydroxyethyl)aminobenzamide gave chlorinated phosphoroheterocycle, 1-(2-chloroethyl)-3-ethyl-2,3-dihydro-1,3,2-benzodiazaphosphorin-4(1H)-one 2-oxide. Secondly, novel tricyclic phosphoroheterocycles, 1,3,2-oxazaphospholidino(or oxazaphosphorino)[3,2-a][1,3,2]benzodiazaphosphorines, have been conveniently synthesized by cyclization of tris(diethylamino)phosphine with 2-(N-(β or γ-hydroxyalkyl)aminobenzamides. Finally, the reaction of 2-(N-ethoxycarbonylmethyl)amino-N-(2′-hydroxyethyl)benzamide with P(NEt₂)₃ afforded five-membered phosphoroheterocycle, 3-(2′-N-ethoxycarbonylmethylamino)benzoyl-2-diethylamino-1,3,2- oxazaphospholidine-2-sulfide. Additionally, the preliminary bioassays showed that several title compounds possessed herbicidal activity to some extent.

Full text of DOI:10.1055/s-2001-16754

PAPER
1631
Studies on Phosphoroheterocycle Chemistry I: A Facile Synthesis of New
Tricyclic Phosphoroheterocycles 1,3,2-Oxazaphospholidino(or
Oxazaphosphorino)[3,2-a][1,3,2]benzodiazaphosphorines
Synthesis of
N
h
ew Phospho
e
roheterocyc
n
les g Lou Deng,*a Dong Zhi Liu,a Jun Min Huang,b Ru Yu Chenb
a
School of Chemical Engineering, Tianjin University, Tianjin 300072, P. R. China
E-mail: shengloudeng@eyou.com
b
Institute of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, P. R. China
Received 19 February 2001; revised 7 May 2001
Abstract: Reaction procedures have been developed for the prepa-
ration of structurally different phosphoroheterocyclic compounds.
Firstly, the treatment of PCl3 with functionalized compound N-eth-
yl-2-( -hydroxyethyl)aminobenzamide gave chlorinated phospho-
roheterocycle, 1-(2-chloroethyl)-3-ethyl-2,3-dihydro-1,3,2-benzo-
diazaphosphorin-4(1H)-one 2-oxide. Secondly, novel tricyclic
phosphoroheterocycles, 1,3,2-oxazaphospholidino(or oxazaphos-
phorino)[3,2-a][1,3,2]benzodiazaphosphorines, have been conve-
niently synthesized by cyclization of tris(diethylamino)phosphine
with 2-(N-( or -hydroxyalkyl)aminobenzamides. Finally, the re-
action of 2-(N-ethoxycarbonylmethyl)amino-N-(2’-hydroxyethyl)-
benzamide with P(NEt2)3 afforded five-membered phosphoro-
Scheme 1
improving the reaction yields. These materials 2a–f could
be readily prepared in large amounts and gave satisfactory
analytical data (Table 1).
heterocycle, 3-(2’-N-ethoxycarbonylmethylamino)benzoyl-2-di-
Cyclization reactions for the preparation of the desired tri-
cyclic compounds were initially attempted by using PCl3.
Treatment of compound 2b with PCl3 in anhydrous ben-
zene under reflux conditions gave the chlorinated bicyclic
heterocycle, 1-(2-chloroethyl)-3-ethyl-2,3-dihydro-1,3,2-
benzodiazaphosphorin-4(1H)-one 2-oxide. It is possible
that the desired tricyclic phosphoroheterocycle was ini-
tially formed and subsequently underwent Arbuzov rear-
rangement under hydrochloride atmosphere to give
chlorinated product (Scheme 2). These results suggested
the use of alternative reagents, which should not release
nucleophilic chloride ions.
ethylamino-1,3,2-oxazaphospholidine-2-sulfide. Additionally, the
preliminary bioassays showed that several title compounds pos-
sessed herbicidal activity to some extent.
Key words: multifunctional compounds, cyclization, facile synthe-
sis, tricyclic phosphoroheterocycles, herbicidal activity
In past decades, there has been considerably growing in-
terest in the use of tris(diethylamino)phosphine [P(NEt2)3]
for the synthesis of pharmaceutically or agriculturally im-
portant phosphoroheterocyclic compounds.1–4 As an use-
ful reagent, P(NEt2)3 exhibited altered reactivity for a
variety of cyclizing reactions in the preparation of cyclic
products.5,6 However, the use of P(NEt2)3 as a
cyclocondensation reagent for the multifunctional com-
pounds 2-(N-( or -hydroxyalkyl)aminobenzamides has
not been reported. Usually, the fused phosphoroheterocy-
cles were prepared step by step in the ring closure,7,8 while
in this paper, we are interested in developing cyclocon-
densation methods for one-pot synthesis of fused-ring
phosphoroheterocyclic compounds by utilizing P(NEt2)3
for the conversion of multifunctional compounds 2a–f
into the corresponding tricyclic heterocycles 3a–h and Scheme 2
4a–c.
P(NEt2)3 may promote the desired sequential cyclizations
Starting materials of amides 2a–f were routinely obtained
by the reaction of 2-aminobenzamides 1a–d with 2-bro-
moethanol or 3-chloropropanol in refluxing toluene
(Scheme 1). It was found that triethylamine and 2-bromo-
ethanol or 3-chloropropanol could be used in excess for
for the synthesis of tricyclic products. The sizes of N-alkyl
groups in the starting materials determined the reaction
conditions and methods for the conversion of substrates
2a–f into the corresponding tricyclic products
(Scheme 3). For small substituents such as methyl or ethyl
group, reactions could readily take place in anhydrous
benzene in the presence of catalytic amount of iodine
(Method A). The reaction progress could be monitored by
thin layer chromatography and the yields of 3a–h were
Synthesis 2001, No. 11, 28 08 2001. Article Identifier:
1437-210X,E;2001,0,11,1631,1634,ftx,en;F01701SS.pdf.
© Georg Thieme Verlag Stuttgart · New York
ISSN 0039-7881

1632
S. L. Deng et al.
PAPER
Table 1 Compounds 2a–f Prepared
Prod-
ucta
R
n
1
1
1
Yield Mp
1H NMR (CDCl3/TMS)
, J (Hz)
(%)b
(°C)
2a
2b
2c
Me
Et
69
96–98
2.80 (d, 3 H, 3JH-H = 5.20, CH3), 3.24 (t, 2 H, 3JH-H = 7.24, NHCH2CH2OH), 3.69 (t, 2 H,
3JH-H = 7.24, NHCH2CH2OH), 5.40 (br, 1 H, NH), 6.60–7.78 (m, 4 Harom
)
53
51
70–72
97–99
1.21 (t, 3 H, 3JH-H = 7.24, NHCH2CH3), 3.30–3.50 (m, 4 H, NHCH2CH3 + NHCH2CH2OH),
3.79 (t, 2 H, 3JH-H = 7.36, NHCH2CH2OH), 6.20 (br, 1 H, NH), 6.55 –7.55 (m, 4 Harom
)
i-Pr
1.25 (d, 6 H, 3JH-H=7.32, 2 CH3), 3.40 (t, 2 H, 3JH-H = 7.20, NHCH2CH2OH), 3.83 (t, 2 H,
3JH-H = 7.20, NHCH2CH2OH), 4.16–4.40 (d, 1 H, 3JH-H = 7.32, CH), 4.85 (br, 1 H, OH), 6.00
(br, 1 H, NH), 6.60–7.44 (m, 4 Harom
)
2d
2e
Bn
1
2
53
69
134–136 3.24 (t, 2 H, 3JH-H = 7.24, NCH2CH2OH), 3.70 (t, 2 H, 3JH-H = 7.24, NCH2CH2OH), 4.08 (br,
1 H, NH), 4.52 (d, 2 H, 3JH-H = 5.40, NHCH2Ph), 6.60–8.01 (m, 9 Harom
)
Me
97–98
68–70
1.63–1.89 (m, 2 H, NCH2CH2CH2OH), 2.81 (d, 3 H, 3JH-H = 4.80, CH3), 3.21 (t, 2 H, 3JH-H
=
7.26, NCH2CH2CH2OH), 3.61 (t, 2 H, 3JH-H = 7.20, NCH2CH2CH2OH), 4.56 (br, 1 H, NH),
6.48–7.62 (m, 4 Harom), 8.15 (br, 1 H, CONH)
2f
Et
2
51
1.30 (t, 3 H, 3JH-H = 7.28, CH3), 1.64–1.86 (m, 2 H, NCH2CH2CH2O), 3.10–3.34 (m, 4 Harom
NCH2CH2CH2O + NCH2CH3), 3.60 (t, 2 H, 3JH-H = 7.24, NCH2CH2CH2OH), 4.24 (br, 1 H,
NH), 6.50–7.65 (m, 4 Harom), 8.08 (br, 1 H, CONH)
a Satisfactory microanalyses obtained: C, H, N 0.4.
b Yields of isolated products.
improve the yield in both the methods. The title com-
pounds were characterized by spectroscopy and elemental
analyses (Table 2), and the molecular structure of com-
pound 3c was further confirmed by X-ray diffraction de-
termination.9
For the purpose of synthesizing another type of tricyclic
phosphoroheterocycle 7 by similar methods, reacting
P(NEt2)3 with multifunctional compound 5 was carried
out. Although the target product 7 was not produced
(Scheme 4), a five-membered phosphoroheterocycle 6
was generated with moderate yields (33% by Method A,
48% by Method B). The different results from compound
5 will be explained after further studies by the use of a va-
riety of other substrates.
The preliminary bioassays showed that several com-
pounds had herbicidal activity against Brassica campes-
tris. Under the concentration of 100mg/L, the compounds
3a, 3c and 6 showed inhibition against Brassica campes-
tris of 32.4%, 23.7% and 47.6%, respectively.
Scheme 3
generally in the range of 18–47%. For several other
groups such as isopropyl and benzyl in the substrates,
Method A appeared to be unsatisfactory for ring-closure
due to the steric effect of N-alkyl groups. Alternatively,
Method B, which was to heat the compounds 2c–d direct-
ly with P(NEt2)3, became effective in affording the target
products 4a–c. Reaction temperatures should be con-
trolled in the range of 110–120 °C. Whereas, higher tem-
perature (>150 °C) usually led to the formation of
polymers, lower temperature (<90 °C) gave poor yields of
4a–c. In addition, a slight excess of P(NEt2)3 was found to
Scheme 4
Synthesis 2001, No. 11, 1631–1634 ISSN 0039-7881 © Thieme Stuttgart · New York

PAPER
Synthesis of New Phosphoroheterocycles
1633
Table 2 Compounds 3a–h and 4a–c Prepared
Producta Yield
(%)b
Mp(°C)
31P NMR
72.38
–
1H NMR (CDCl3/TMS)
, J (Hz)
3a
3b
3c
3d
3e
3f
24
19
47
25
31
22
41
25
25
15
16
108–110
114–116
130–132
132–134
178–180
182–184
186–188
193–195
157–159
162–164
148–150
3.22 (d, 3 H, 3JP-H = 9.35, CH3), 3.70–3.85 (m, 1 H, NCHaHbCH2), 4.31–4.68 (m, 3 H,
NCHaHbCH2O), 7.05–8.15 (m, 4 Harom
)
3.22 (d, 3 H, 3JP-H = 9.43, CH3), 3.70–3.85 (m, 1 H, NCHaHb), 4.29–4.66 (m, 3 H,
NCHaHbCH2O), 7.10–8.14 (m, 4 Harom
)
71.94
–
1.33 (t, 3 H, 3JH-H = 7.07, CH3), 3.74–3.95 (m, 3 H, NCHaHbCH2O + CH2CH3), 4.28–4.75
(m, 3 H, NCHaHbCH2O), 7.04–8.09 (m, 4 Harom
)
1.33 (t, 3 H, 3JH-H = 7.02, CH3), 3.72–3.85 (m, 3 H, NCHaHbCH2O + CH2CH3), 4.30–4.73
(m, 3 H, NCHaHbCH2O), 7.06–8.10 (m, 4 Harom
)
65.42
–
2.14–2.40 (m, 2 H, NCH2CH2CH2O), 3.21 (d, 3 H, 3JP-H = 8.04, NCH3), 3.83–3.90 (m, 2
H, NCH2CH2CH2O), 4.24–4.80 (m, 2 H, NCH2CH2CH2O), 6.89– 8.14 (m, 4 Harom
)
2.03–2.42 (m, 2 H, NCH2CH2CH2O), 3.19 (d, 3 H, 3JP-H = 10.11, NCH3), 3.75–3.85 (m,
2 H, NCH2CH2CH2O), 4.28–4.83 (m, 2 H, NCH2CH2CH2O), 6.87–8.14 (m, 4 Harom
)
3g
3h
4a
4b
4c
65.44
66.95
70.49
67.77
–
1.35 (t, 3 H, 3JH-H = 7.12, CH2CH3), 2.02–2.40 (m, 2 H, NCH2CH2CH2O), 3.72–4.84 (m,
6 H, NCH2CH2CH2O + CH2CH3), 6.88–8.13 (m, 4 Harom
)
1.33 (t, 3 H, 3JH-H = 7.24, CH3), 2.05–2.40 (m, 2 H, NCH2CH2CH2O), 3.70–4.83 (m, 6 H,
NCH2CH2CH2O + CH2CH3), 6.65–8.13 (m, 4 Harom
)
1.54–1.58 (q, 6 H, 4JP-H = 3.27, 3JH-H = 4.74, 2 CH3), 3.65–3.73 (m, 1 H, NCHaHbCH2O),
4.21–4.63 (m, 4 H, NCHaHbCH2O + NCH), 6.99–8.08 (m, 4 Harom
)
1.56–1.63 (t, 6 H, 4JP-H = 6.87, 3JH-H = 7.06, 2 CH3), 3.66–3.70 (m, 1 H, NCHaHbCH2O),
4.25–4.66 (m, 4 H, NCHaHbCH2O + NCH), 7.03–8.11 (m, 4 Harom
)
3.62–4.01 (m, 2 H, NCH2CH2O), 4.22–4.52 (m, 2 H, NCH2CH2O), 4.60– 5.36 (qq, 2 H,
2JH-H = 14.56, 3JP-H = 10.25, NCH2Ph), 7.04–8.17 (m, 9 Harom
)
a Satisfactory microanalyses obtained: C, H, N 0.4.
b Yields of isolated pure products.
°C; 1d: R = Bn; Yield: 85%; mp 120–121 °C (Lit.10 mp123–123.5
In summary, we have studied the reaction of P(NEt2)3
with multifunctional compounds and found con-
venient methods for generating interesting tricyclic
phosphoroheterocyclic compounds such as 1,3,2-oxaza-
phospholidino(or oxazaphosphorino)[3,2-a][1,3,2] ben-
zodiazaphosphorines, which, to some extent, exhibited
herbicidal activity.
°C). -Chloropropanol was prepared according to Lit.11.
2-( - or -Hydroxyalkyl)aminobenzamides 2a–f; General
Procedure
To a 100 mL three-necked flask containing a mixture of compound
1a–d (0.037 mol), anhyd toluene (35 mL) and Et3N (5.65g, 0.056
mol) was added 2-bromoethanol (or -chloropropanol) (0.074 mol)
at r.t. The mixture was heated to reflux for 10 h, and then cooled to
r.t. After the removal of precipitate, the filtrate was concentrated un-
der reduced pressure to give a sticky oil, which was purified on a sil-
ica gel column (100 4.5 cm, 250–300 mesh) using petroleum
ether–EtOAc (1:1 v/v) as eluent. Products 2a–f were obtained and
recrystallized from EtOAc–EtOH (4:1 v/v).
1H NMR and 31P NMR spectra were recorded with a Bruker AC-P
200 Spectrometer (CDCl3 as solvent, TMS as internal, 85% H3PO4
as external standard) with exception of the compounds 2a–f (re-
corded on a Jeol-FX-90Q Spectrometer). Melting Points were deter-
mined using Thomashoover melting point apparatus and are
uncorrected. Elemental analyses were carried out with Yanaco
CHN CORDER MT-3 autoanalysis apparatus. EI-MS spectra were
recorded on a VG-7070E spectrometer. X-ray analysis was per-
formed on a Bruker Smart 1000 diffractometer with graphite
monochromated MoK radiation ( = 0.71073 Å) and –2 scan
mode. 2-Bromoethanol and P(NEt2)3 were purchased from Aldrich
(Germany). P(NEt2)3 and PCl3 were distilled before use. Benzene
was dried over sodium. Petroleum ether used had the boiling range
30–60 °C.
1-(2-Chloroethyl)-3-ethyl-2,3-dihydro-1,3,2-benzodiaza-
phosphorin-4(1H)-one 2-Oxide
A suspension of 2b (2.08g, 0.01mol) in anhydrous benzene (100
mL) in a 500 mL three-necked flask was heated with stirring until
the mixture became transparent. PCl3 (1 equiv) was added dropwise
within 30 min under N2 and the resulting solution was refluxed for
another 5 h. The mixture was then concentrated and the crude prod-
uct was purified by flash chromatography using EtOAc–petroleum
ether (1:3 v/v) as eluent. Recrystallization from Et2O–petroleum
ether (1:5 v/v) gave a solid (1.67 g, 62%; mp 99–101 °C).
Compounds 1a–d were prepared according to Lit.10 1a: R = Me;
Yield: ~100%; mp 128–130 °C; 1b: R = Et; Yield: 91%; mp 100–
101 °C (Lit.10 mp 102–103 °C); 1c: R = i-Pr; Yield: 93%; mp 148
Anal. Calcd for C11H14ClN2O2P (272.5): C, 48.44; H, 5.14; N,
10.28. Found: C, 48.52; H, 5.08; N, 10.54.
Synthesis 2001, No. 11, 1631–1634 ISSN 0039-7881 © Thieme Stuttgart · New York

1634
S. L. Deng et al.
PAPER
1H NMR: =1.32 (t, 3 H, 3JH-H = 7.07 Hz, CH3), 3.60–4.10 (m, 6 H,
CH2), 7.87 (d, 1 H 1JP-H = 642.03 Hz, PH), 6.9–8.2 (m, 4 Harom).
3-(2’-N-Ethoxycarbonylmethylamino)benzoyl-2-diethylamino-
1,3,2-oxazaphospholidine-2-sulfide (6)
3
To a solution of P(NEt2)3 (0.74 g, 3 mmol) and anhyd benzene (30
mL), kept in a 100 mL three-necked flask, was added I2 (0.076 g,
0.3 mmol) under N2. The reaction mixture was subsequently
warmed up to 70 °C and stirred for 15 min. After cooling to r.t.,
compound 5 (0.79 g, 3 mmol) was added to the solution. The reac-
tion mixture was kept at 75 °C for another 2.5 h. and then S8 (0.1 g,
3.1 mmol) was added. After heating the solution at reflux for anoth-
er 1.5 h, the solvent was evaporated under reduced pressure to give
a yellow oil, which was purified on a silica gel column (100 3.5,
250–300 mesh) using petroleum ether–EtOAc (3:1 v/v) as eluent.
The obtained crude product 6 was further purified by recrystalliza-
tion from a mixture of CHCl3 and petroleum ether (1:5 v/v) to afford
0.39 g (33%) of a colorless product; mp 92 °C.
EIMS: m/z (%) = 272 (M+, 22.7) 274 (M+ + 2, 7.6).
1,3,2-Oxazaphospholidino-(or Oxazaphosphorino)-[3,2-
a][1,3,2]benzodiazaphosphorines 3a–h; General Procedure
Method A: To a solution of P(NEt2)3 ( 0.55g, 2.2 mmol) and anhyd
benzene (30 mL) in a 100 mL three-necked flask was added I2
(0.051 g, 0.2 mmol) under N2 at r.t. The reaction mixture was heated
at 70 °C for 15 min, and then cooled to r.t. After the addition of cor-
responding 2a,b,e,f (2 mmol), the mixture was subsequently heated
at 75 °C for another 2.5 h. After cooling to r.t., S8 or Se (2 mmol, 1
equiv) was added and the mixture was then heated to reflux for an-
other 1.5 h. After the solvent was removed under reduced pressure,
the desired product was isolated by flash chromatography with
EtOAc–petroleum ether (1:1 v/v) as eluent and further purified by
recrystallization from a mixture of CHCl3 and petroleum ether (1:5
v/v).
Anal. Calcd for C17H26N3O4PS (399.5): C, 51.13; H, 6.52; N, 10.53.
Found: C, 50.81; H, 6.51; N, 10.21.
3
1H NMR (CDCl3/TMS)
= 0.97 [t, 6 H, JH-H = 7.13 Hz,
N(CH2CH3)2], 1.27 (t, 3 H, 3JH-H = 7.14 Hz, OCH2CH3), 2.92–3.02
[m, 4 H, N(CH2CH3)2], 3.95–4.15 (m, 4 H, NCH2CH2O +
NCH2C=O), 4.21–4.49 (m, 4 H, NCH2CH2O + OCH2CH3), 5.82
(br, 1 H, NH), 6.89–7.89 (m, 4 Harom).
1,3,2-Oxazaphospholidino-(or Oxazaphosphorino)-[3,2-
a][1,3,2]benzodiazaphosphorines 4a–c; General Procedure
(Method B)
A mixture of 2c or 2d (2 mmol) and P(NEt2)3 (0.5 g, 2 mmol) was
heated under N2 in a 25 mL two-necked flask at 110–120 °C for 2.5–
3 h. After the solution was cooled to r.t., a solution of a slight excess
of S8 or Se (2.2 mmol) in anhyd benzene (15 mL) was added. The
mixture was heated at 75 °C for 1.5–2 h and the solvent was evap-
orated under reduced pressure. The product was purified by chro-
matography on a silica gel (100 3.5, 250–300 mesh) using a
mixture of petroleum ether and EtOAc (3:1 v/v) as eluent to give
solid materials, which were recrystallized from a mixture of CHCl3
and petroleum ether (1:5 v/v).
31P NMR (CDCl3/85% H3PO4): =76.32.
References
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a pale solid material. Colorless crystals (1.26 g, 95%) were obtained
after recrystallization of the crude product from a mixture of CHCl3
and EtOAc (1:1 v/v); mp 95–97 °C.
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Anal. Calcd for C13H18N2O4 (266.3): C, 58.65; H, 6.77; N, 10.53.
Found: C, 58.82; H, 6.53; N, 10.77.
3
1H NMR (CDCl3/TMS): = 1.30 (t, 3 H, JH-H = 7.20 Hz, CH3),
3.45–3.70 (m, 2 H, NCH2CH2O), 3.75–3.92 (m, 2 H, NCH2CH2O),
4.01 (s, 2 H, NCH2C=O), 4.18–4.40 (q, 2 H, OCH2CH3), 5.32 (br, 1
H, NH), 6.60–7.59 (m, 4 Harom).
Synthesis 2001, No. 11, 1631–1634 ISSN 0039-7881 © Thieme Stuttgart · New York