Intramolecular P=S and P=N alkylation. General method for synthesizing 1,2-heteraphosphacyclanes

Article abstract of DOI:10.1023/A:1014815628426

Results have been generalized for investigations on the synthesis of 1,2-thiaphosphacyclanes by intramolecular P=S alkylation of ω-haloalkyl substituted compounds of four-coordinated phosphorus with a P=S bond. The method has been extended to nitrogen-con

Full text of DOI:10.1023/A:1014815628426

Chemistry of Heterocyclic Compounds, Vol. 38, No. 1, 2002
INTRAMOLECULAR P=S
AND P=N ALKYLATION. GENERAL
METHOD FOR SYNTHESIZING
1,2-HETERAPHOSPHACYCLANES*
I. M. Aladzheva, O. V. Bykhovskaya, D. I. Lobanov, P. V. Petrovskii, K. A. Lysenko,
and T. A. Mastryukova
Results have been generalized for investigations on the synthesis of 1,2-thiaphosphacyclanes by
intramolecular P=S alkylation of ω-haloalkyl substituted compounds of four-coordinated phosphorus
with a P=S bond. The method has been extended to nitrogen-containing analogs with a P=N bond. A
new general method is proposed for the synthesis of 1,2-thia- and 1,2-azaphosphacyclanes.
Keywords: 1,2-azaphosphacyclanes, 1,2-thiaphosphacyclanes, intramolecular alkylation, ring–chain
halotropic tautomerism.
Interest in the chemistry of phosphorus-containing heterocyclic compounds is linked with their
participation in many biochemical processes, with their use as therapeutic preparations and agents for plant
protection, with use in organic synthesis, metal-complex catalysis, and other areas. Unlike the
1,3,2-diheteraphosphacyclanes, which have been well investigated, the 1,2-heteraphosphacyclanes have been
little studied due to their lower availability. A most part of them were obtained by multistage syntheses,
frequently under rigid conditions [1-4].
In recent years we have developed
a
new general approach to the synthesis of
1,2-heteraphosphacyclanes based on the intramolecular alkylation of ω-haloalkyl substituted compounds of
four-coordinated phosphorus with a P=E bond (E = S, N). The aim of the present work was to correlate our
investigations on the synthesis and study of the properties of 1,2-thiaphosphacyclanes [5-10] and to supplement
them with new data on the development of methods of synthesizing 1,2-azaphosphacyclanes.
Intramolecular P=E alkylation (E=S) was used for the first time for the synthesis of 2,2-diphenyl-1,2λ4-
thiaphospholanium iodide and 2,2-diphenyl-1,2λ4-thiaphosphorinanium iodide (1), which were obtained on
refluxing ω-chloroalkyldiphenylphosphine sulfides 2 with NaI in acetone [5] (Scheme 1). Reaction occurs
through the intermediate formation of the ω-iodoalkyl-substituted derivatives 3, revealed on the base of 31P and
1H NMR spectra. The ω-bromoalkyl-substituted phosphine sulfides 4 are smoothly converted on short-term
heating at 100°C in the absence of solvent into the cyclic bromides 5 [6,8], from which the perchlorates 6 and
tetrafluoroborate 7b are obtained by anion exchange reaction [7].
_______
* Dear Mikhail Grigorievich! Accept our congratulations on your anniversary. We acknowledge profoundly
your enormous creative powers.
__________________________________________________________________________________________
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Moscow
119991; e-mail: fos@ineos.ac.ru. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 105-116,
January, 2002. Original article submitted June 8, 2001.
0009-3122/02/3801-0095$27.00©2002 Plenum Publishing Corporation
95

Scheme 1
NaI
acetone
Ph2P(S)(CH2)nI
Ph2P(S)(CH2)nCl
∆
2a,b
3a,b
PBr3, ∆
benzene
Ph2P(S)(CH2)nBr
Ph2P(S)(CH2)nOH
4a,b
CH2
S
+
CH2
S
–
+
NaX, 20 °C
CH3CN
–
Hal
X
Ph2P
CH2
Ph2P
(CH2)n–2
(CH2)n–2
CH2
1a,b, 5a,b
6a,b, 7b
1 Hal = I, 5 Hal = Br, 6 X = ClO4, 7 X = BF4, a n = 3, b n = 4
The 1,2-thiaphosphacyclanium salts 1, 5-7 are stable crystalline compounds, which structures were
1
confirmed by data of IR, and 31P and H NMR spectra (Table 1), and also by data of X-ray structural
investigations for iodides 1a,b, bromides 5a,b, and for perchlorate 6a. An intense absorption band was observed
in the IR spectra of the cyclic salts at 570 cm-1, assigned to the vibrations of the P–S–CH2 ring fragment. The
position of the δP signal in the 31P NMR spectra depends on the ring size. It was shifted by 35 ppm towards low
field in 1,2-thiaphospholanium salts compared with 1,2-thiaphosphorinanium salts, which is in agreement with
the data of [11].
According to the data of X-ray structural investigations [5-7] the five-membered phosphorus-containing
rings in compounds 1a, 5a, and 6a are characterized by an envelope conformation with the average deviation of
one of the carbon atoms from the plane of the remaining coplanar atoms by 0.6 Å. The six-membered
phosphorus-containing rings in 1,2-thiaphosphorinanium salts 1b and 5b have the conformation of a slightly
distorted chair. In all the structures investigated the phosphorus atom is characterized by a slightly distorted
tetrahedral configuration with a reduction in the endocyclic angle to 100.3(2)° and 108.1(2)° in the
1,2-thiaphospholanium and 1,2-thiaphosphorinanium rings respectively. Unexpectedly shortened P+S···Hal-
interionic contacts were detected for the halide salts. 1,2-Thiaphosphacyclanes have not been investigated by
X-ray structural analysis previously.
TABLE 1. Physicochemical and Spectral Characteristics of Compounds 1, 5-7
IR spectrum (KBr), 31P NMR spectrum
Com-
pound
mp, °C (solvent)
Yield, %
Ref.
ν, (P–S–CH2), cm -1 (in CH2Cl2), δ, ppm
203-204
572
565
572
567
570
570
572
72.2
37.6
72.6
38.0
72.6
37.6
37.4
77
65
[5]
[5]
[6]
[8]
[7]
[7]
[7]
1a
1b
5a
5b
6a
6b
7b
(CH3CN–EtOAc)
204-205
(CH3CN–EtOAc)
163-164
77
(CHCl3–EtOAc)
161-162
78
(CHCl3–EtOAc)
152-153.5
81
(CHCl3–ether)
182-184
67
(CH2Cl2–ether)
186-188
Quant.
(CH2Cl2–ether)
96

The behavior of 1,2-thiaphosphacyclanium salts 1 and 5 and ω-haloalkylphosphine sulfides 2 and 4 in
solution proved to be very interesting. It was found that a tautomeric equilibrium was established in solution
between the cyclic and linear forms, which belongs to a new type of ring–chain anionotropic tautomerism,
comparatively rarely met in organic chemistry and little investigated [12]. We studied the ring–chain
tautomerism of 1,2-thiaphosphacyclanium salts using bromides as an example, for which both the linear 4a,b
and cyclic 5a,b isomers were successfully isolated as individual compounds [6,8]. The equilibrium for bromide
5a and its linear isomer 4a in CH2Cl2 was established after 1 day. In the case of bromide 5b with a
six-membered ring (or its linear isomer 4b) about 25 days were required to establish equilibrium in CH2Cl2 at
20°C. The dependence of the position of tautomeric equilibrium on temperature was studied using bromide 4a
as example by 31P NMR spectroscopy. On increasing the temperature the content of the linear form in the
equilibrium mixture increased, i.e. the conversion of the cyclic into the linear form, as in other ring–chain
tautomeric systems, is an endothermal process. Certain thermodynamic parameters of the equilibrium have been
calculated [6].
.
.
Kinetic investigations of the tautomeric interconversions 5a 4a and 5b 4b were carried out by
31P NMR spectroscopy in CH2Cl2 at 20°C. Both the cyclic and linear isomers were used as starting materials.
The rate constants k1 and k2 for the mutual interconversion of isomers were calculated [7].
A study of the various factors on the position of equilibrium in solutions of the cyclic salts and their
linear isomers showed (Table 2) [7] that the content of the cyclic form in the equilibrium mixture increased on
going from the 1,2-thiaphospholane ring to the 1,2-thiaphosphorinane, from chlorides to bromides, and further
to iodides and salts with complex anions. The content of the cyclic form is also increased on reducing the
temperature and increasing the polarity of the solvent.
The intramolecular P=S alkylation reaction was also investigated for other classes of ω-haloalkyl-
substituted compounds with a P=S group to synthesize new types of 1,2-thiaphosphacyclanes [10].
It was established that esters of ω-chloroalkylphosphonic and thiophosphinic acids (8-11), with an
alkoxy substituent at the phosphorus atom, undergo an intramolecular thione–thiol rearrangement on refluxing
with an excess of NaI in acetone or acetonitrile with the formation of 2-substituted 2-oxo-1,2-
thiaphosphacyclanes (so-called thiolphostones) 12-15.
Scheme 2
R
R
NaI
P(S)(CH2)nCl
P(S)(CH2)nI
EtO
EtO
CH3CN (acetone)
8a,b – 11a,b
∆
∆
CH2
S
R
+
P
–
Hal
(CH2)n–2
EtO
CH2
16a,b
CH2
CH2
S
CH2
(CH2)n–2
S
NaClO4
– NaCl
Et
R
+
P
–
ClO4
P
– EtI
CH2
CH2
EtO
O
12a,b – 14a,b, 15a
17a
8, 12 R = EtO, 9, 13 R = Ph, 10, 14 R = Et, 11, 15 R = Et2N, Hal = Cl, I, a n = 3, b n = 4
The compounds synthesized (with the exception of the crystalline thiolphostones 13a,b) were
undistillable oily liquids, which were purified by column chromatography. The structures of the compounds
obtained were confirmed by IR, 31P NMR (Table 3) and 1H NMR spectra, and for compounds 13a,b by data of
13C NMR spectra as well [10].
97

TABLE 2. Content of the Cyclic Form (%) in Solutions of Compounds 1, 2,
and 4-6 (according to 31P NMR spectra) [7]
Chlorides
Bromides
Iodides
Perchlorates
Solvent
n = 3
n = 4
n = 3
n = 4
n = 3
n = 4
n = 3
n = 4
CH2Cl2
CHCl3
CH3CN
0
0
9*
0
0
38
65
82
48
85
82
70
87
100
85
92
100
100
100
—
100
100
—
3*2
_______
*After 6 months.
*2 System did not achieve an equilibrium state.
TABLE 3. Physicochemical and Spectral Characteristics of Compounds
12-15 and 17 [7, 10]
IR spectrum (KBr),
31P NMR spectrum
ν, cm-1
Compound
mp, °С (solvent)
Yield*, %
(in CH2Cl2), δ, ppm
P–S–CH2
P=O
Oil*2
Oil*2
555
543
555
548
555
553
535
565
1212, 1232
1218, 1248
1190
83.0
46.8
73.4
90
65
95
96
82
86
83
27
12a
12b
102-103 (hexane)
77-78.5 (hexane)
Oil*2
13a
13b
1190
1190
1190
39.5
14a·0.4NaI
14b·0.5NaI
15a
92.9 br. s
56.5 br. s
76.4
Oil*2
Oil*2
1200, 1230
—
93-95 (MeCN–EtOAc)
138.8
17a
_______
* From 31P NMR spectra of the reaction mixture.
*2 Purified by column chromatography.
The structure of the 2-phenyl substituted thiaphosphorinane 13b was investigated by X-ray structural
analysis. It was found that the 1,2-thiaphosphorinane ring has a slightly distorted chair conformation with the
oxygen atom of the P=O group in the axial position. The bond lengths were close to the corresponding values
for the 1,2-thiaphosphacyclanium salts investigated previously [7].
It was estimated that the rate of rearrangement of esters of ω-haloalkyl substituted phosphorus thioacids
was influenced by the length of the alkyl chain in the ω-haloalkyl residue (1,2-thiaphospholane cycles are
formed more readily), the polarity of the solvent, the temperature, and the nature of the substituent R at the
phosphorus atom. Reaction occurs through the intermediate formation of products of P=S alkylation, the
quasiphosphonium salts 16 (Scheme 2), the dealkylation of which under the reaction conditions leads to the
final thiolphostones 12-15. We succeeded, by substituting the nucleophilic halogen anion by perchlorate anion
in the case of 16a (R = Et), in obtaining the crystalline perchlorate 17a (Scheme 2, Table 3), the first isolated
intermediate of the thiol-thiol rearrangement of esters of phosphorus thioacids proceeding under the action of
alkyl halides.
The intramolecular P=E alkylation method has been further extended to ω-haloalkyl-substituted
iminophosphoryl compounds. It is known that the P=N group exceeds significantly the P=S group in relative
reactivity in nucleophilic substitution reactions. Consequently it might have been expected that alkylation of
iminophosphoryl compounds will take place under milder conditions. To synthesize ω-haloalkyl-substituted
iminophosphoryl compounds by the interaction of ω-chloroalkyldiphenylphosphines 18a,b with phenyl azide
the iminophosphoranes 19a,b were synthesized.
98

Two methods were used to obtain phosphines 18a,b. These were the alkylation of Ph2PNa(Li) with
α,ω-bromochloroalkanes in toluene (classical method) [13-15], and the alkylation of Ph2PH with
α,ω-bromochloroalkanes under phase-transfer catalysis (PTC) conditions in the two-phase system of solid
KOH/CH3CN in the presence of triethylbenzylammonium chloride (TEBA) as catalyst. The latter method was
significantly more simple experimentally.
Phosphine 18b was obtained in low yield, which is explained by its partial cyclization under the
conditions of the reaction leading to 1,1-diphenylphospholanium chloride. The latter is hydrolyzed under PTC
conditions with the formation of 1-oxo-1-phenylphospholane 20 (see Experimental).
Scheme 3
Br(CH2)nCl, –65 °C (– 20 °C)
Ph2PNa(Li)
toluene
PhN3
Ph2P(CH2)nCl
Br(CH2)nCl, ∆
solid KOH, CH3CN, TEBA
Ph
Et2O
18a,b
Ph2PH
Ph
N
CH2
CH2
N
NaX, 20 °C
CH3CN
∆
+
+
–
–
X
Cl
(CH2)n–2
Ph2P(CH2)nCl
Ph2P
Ph2P
(CH2)n–2
CH3CN
CH2
CH2
NPh
19a,b
21a,b
22a,b, 23b
21 X = I, 22 X = ClO4, a n = 3, b n = 4
TABLE 4. Physicochemical Characteristics of Compounds 19, 21-23
Found, %
——————
Com-
pound
Empirical
formula
mp, °С
Yield, %
Calculated, %
(solvent)
С
Н
Hal
N
P
C21H21ClNP
C22H23ClNP
71.20 6.17
71.28 5.98
—
—
—
3.84
3.96
—
—*
15.0
19a
(86)*2
71.81 6.35
3.70
8.42
8.44
—
81-83
30.0
19b
(hexane)
(87)* 2
71.84 6.26
3.81
21a*3
C21H21ClNP·Н2О 67.63 6.36
3.53
3.77
—*4
85
(70)*5
67.87 6.23
C22H23ClNP
C21H21INP
72.09 6.23
71.84 6.26
9.60
9.66
3.71
3.81
8.30
8.44
226-230
(decomp.)
quant.
21b
22a
22b
23b
(96)*5
(CH2Cl2–ЕtOAc)
57.00 4.97 29.15
56.64 4.75 28.50
—
—
6.86
6.96
232-234
92
80
82
(decomp.)
(CH2Cl2–EtOAc)
C22H23INP
57.60 5.18 27.81
57.53 5.05 27.63
6.71
6.74
191-193
(decomp.)
(CH2Cl2–EtOAc)
C22H23ClNO4P
61.20 5.38
61.19 5.37
8.97
8.21
3.24
3.22
7.34
7.17
213-215
(decomp.)
(CH2Cl2–EtOAc)
_______
* Undergoes cyclization on determining mp.
*2 According to data of 31P NMR spectra of the reaction mixture.
*3 Crystallizes with a molecule of water.
*4 Decomposes on determining mp.
*5 Yield from phosphine 18.
99

TABLE 5. Spectral Characteristics of Compounds 19 (in C6D6) and 21-23 (in CDCl3)
31P NMR spectrum,
Com-
13C NMR spectrum, δ, ppm, coupling constant J (Hz)*2
1H NMR spectrum, δ, ppm, coupling constant J (Hz)
pound*
δ, ppm
2.78
3.77
1.84-1.94 (2H, m, CH2CH2P); 2.34-2.44 (2H, m, CH2P);
19a
19b
3.08 (2H, t, 3JHH = 6.2, CH2Cl); 6.87-7.78 (15H, m, Harom
)
19.47 (CH2CH2P, d, 2JPC = 3.2); 27.17 (CH2P, d,1JPC = 69.5);
33.33 (CH2CH2Cl, d, 3JPC = 13.5); 43.97 (CH2Cl, br. s)
1.41 (2H, dt, 3JHH = 7.2,CH2CH2Cl);
1.55-1.66 (2H, m, CH2CH2P); 2.06-2.15 (2H, m, CH2P);
2.90 (2H, t, 3JHH = 6.8, CH2Cl); 6.87-7.82 (15H, m, Harom
)
54.6
21.68 (CH2CH2P, s); 28.27 (CH2P, d, 1JPC = 63.4);
52.99 (CH2N, d, 2JPC = 16.5)
2.46 (2H, s, H2O); 2.49-2.54 (2H, m, CH2CH2P);
22a
3.68 (2H, dt, 3JHH = 7.2, 3JPH = 7.2, CH2N);
4.32 (2H, dt, 3JHH = 6.0, 2JPH = 8.4, CH2P); 6.76-8.00 (15H, m, Harom
)
42.5
53.9
19.44 (CH2CH2P, s); 22.48 (CH2P, d, 1JPC = 61.0);
2.11-2.28 (4H, m, CH2CH2CH2P); 3.37-3.45 (2H, m, CH2N);
22b
23a
25.04 (CH2CH2N, d, 3JPC = 5.4); 54.11 (CH2N, d, 2JPC = 1.7)
3.78-3.88 (2H, m, CH2P); 6.93-7.85 (15H, m, Harom)
21.31 (CH2CH2P, s); 28.45 (CH2P, d, 1JPC = 64.5);
52.87 (CH2N, d, 2JPC = 16.5)
2.66 (2H, m, CH2CH2P); 3.64 (2H, dt, 3JHH = 7.2, 3JPH = 7.6, CH2N);
4.38 (2H, dt, 3JHH = 6.4, 2JPH = 8.4, CH2P);
6.89-8.04 (15H, m, Harom
)
42.0
41.7
19.38 (CH2CH2P, d, 2JPC = 7.1); 23.06 (CH2P, d, 1JPC = 61.9);
25.07 (CH2CH2N, d, 3JPC = 5.3); 54.17 (CH2N, br. s)
2.13-2.32 (4H, m, CH2CH2CH2P); 3.23-3.31(2H, m, CH2N);
3.85-3.93 (2H, m, CH2P); 7.04-7.84 (15H, m, Harom
2.14-2.28 (4H, m, CH2CH2CH2P); 2.98-3.07 (2H, m, CH2N);
3.91 (2H, dt, 3JHH = 5.6, 3JPH = 8.8, CH2P); 7.00-7.78 (15H, m, Harom
23b
24
)
19.38 (CH2CH2P, d, 2JPC = 7.1); 22.42 (CH2P, d, 1JPC = 62.6);
25.09 (CH2CH2N, d, 3JPC = 4.3); 54.16 (CH2N, br. s)
)
_______
* IR spectrum (KBr): νP=N 1346 (19a) and 1340 cm-1 (19b).
*2 Chemical shifts of benzene ring carbon atoms are not given.

The interaction of phosphines 18a,b with phenyl azide in ether solution proceeds to iminophosphoranes
31
19a,b in high yield, according to data of P NMR spectra of the reaction mixture. However isolation of the
crystalline readily hydrolysable compounds 19a,b succeeded with significantly lower yields (see [16]). This is
attributed preferably to iminophosphorane 19a, for which an intramolecular P=N alkylation partially occurs
during its isolation with the formation of 1,2,2-triphenyl-1,2λ4-azaphospholanium chloride (21a). The
composition and structure of iminophosphoranes 19a,b were confirmed by data of elemental analysis, IR
spectra, and 1H, 31P, and 13C NMR spectra (Tables 4, 5).
An intense absorption band was present in the IR spectra of the compounds at 1300 cm-1 for the
stretching vibrations of the P=N group. The chemical shift of the δP signal in the 31P NMR spectra was found in
the region of iminophosphorane signals (about 0 ppm) [11]. In the 1H NMR spectra a characteristic triplet signal
was observed near 3.0 ppm for the protons of the (CH2)CH2Cl group with a coupling constant of about 6 Hz in
addition to multiplet signals for the protons of the CH2 groups and the phenyl rings.
Further investigations showed that iminophosphoranes 19a,b readily entered into an intramolecular
alkylation reaction with the formation of 1,2,2-triphenyl-1,2λ4-azaphospholanium salt 21a and
azaphosphorinanium salt 21b. The rate of cyclization depended significantly on the length of the alkyl chain. In
benzene iminophosphorane 19a was completely converted into chloride 21a on heating for 40 min at 50°C,
while iminophosphorane 19b was cyclized to only 30% on refluxing in benzene for 3 h. In the more polar
CH3CN the cyclization of iminophosphorane 19b was completed after 2 h at 80°C. To increase the yield,
chlorides 21a,b were also obtained directly from phosphines 18a,b without isolating the intermediate
iminophosphoranes 19a,b. The yields in this case were 70 and 96% calculated on the initial phosphine. It was
established [7] that in difference to the iminophosphoranes 19a,b, the phosphine sulfides 2a,b with an
ω-chloroalkyl substituent on the phosphorus atom did not participate in the intramolecular alkylation reaction
even under rigid conditions.
The synthesized compounds 21a,b are high-melting crystalline substances. The iodides 22a,b and a
perchlorate 23b were obtained by anion exchange from the chlorides (Table 4). The structures of compounds
21-23 were confirmed by data of NMR spectra (1H, 31P, 13C) (Table 5). The
signal low-field shift was
δP
observed in the 31P NMR spectra of the 1,2-azaphospholanium salts 21a, 22a compared with the
(Δ
1,2-azaphosphorinanium salts 21b, 22b
12 ppm).
δ
The structures of iodides 22a,b were investigated by X-ray structural analysis (Figs. 1 and 2).
Fig. 1. General view and numbering of atoms in the cation of iodide 22a.
101

Fig. 2. General view and numbering of atoms in the cation of iodide 22b.
The main geometric parameters, with the exception of the endocyclic angle N(1)P(1)C(4) do not in fact
depend on the size of the ring (Table 6). The 1,2-azaphospholane ring is characterized by an envelope
conformation with deviation of the C(3) atom from the plane of C(1)N(1)P(1)C(4) by 0.54 Å, but the
1,2-azaphosphorinane ring has the conformation of a slightly distorted chair. The bonds at the nitrogen atom in
both structures lie in a plane (sum of valence angles at N(1) is 359.6° on average). The mutual dispositions of the
N(1)–P(1) bond and the phenyl group at the nitrogen atom in cations 22a and 22b are different. In 22a the torsion
angle N(1)–P(1)–C(17)–C(22) is equal to 13° while in 22b it is 45°, which probably causes the differences in the
N(1)–C(11) distance. The iodine anions in both structures participate in the formation of weak C–H···I contacts
(the H···I distances are in the range 2.9-3.1 Å).
Unlike the 1,2-thiaphosphacyclanium salts 1, 5 no ring–chain halotropic tautomerism was detected in
solutions of 1,2-azaphosphacyclanium chlorides and iodides 21 and 22 according to data of 31P NMR spectra. In
this case due to the higher nucleophilicity of the nitrogen atom of the P=N group the equilibrium is completely
displaced to the cyclic isomer.
TABLE 6. Bond Lengths and Valence Angles in Compounds 22a,b
d, Å
ω, deg
Bond
Angle
22a*
22b
22a*
22b
P(1)–N(1)
1.644(4)
1.788(5)
1.787(5)
1.796(4)
1.492(6)
1.421(6)
1.641(5)
1.794(6)
1.779(5)
1.793(5)
1.494(7)
1.437(7)
N(1)–P(1)–C(4)
N(1)–P(1)–C(5)
N(1)–P(1)–C(11)
C(4)–P(1)–C(5)
C(4)–P(1)–C(11)
C(5)–P(1)–C(11)
P(1)–N(1)–C(17)
P(1)–N(1)–C(1)
C(1)–N(1)–C(17)
96.8(2)
111.3(2)
113.3(2)
110.9(3)
112.5(2)
111.3(2)
126.2(3)
112.0(3)
121.4(4)
105.3(3)
112.0(2)
109.2(3)
110.7(3)
109.3(3)
110.1(2)
127.7(4)
113.9(4)
118.4(4)
P(1)–C(4)
P(1)–C(5)
P(1)–C(11)
N(1)–C(1)
N(1)–C(17)
_______
* Mean values for the two independent molecules are given for compound 22a.
102

TABLE 7. Main Crystallographic Parameters and Refinement
Characteristics of Compounds 22a and 22b
Parameter
C21H21INP (23a)
C22H23INP (23b)
M
445.26
1776
17.33
1.522
P21/с
Siemens P3/PC
θ/2θ
459.28
460
16.83
1.523
P21
F(000)
µ (MoKα), cm-1
d
calc, g·cm-3
Space group
Diffractometer
Scanning type
Smart 1K CCD
ω with 0.3° step in ω and
10 sec exposure for each frame
T, K
298
110
a, Å
13.570(2)
14.285(2)
20.554(2)
102.82(1)
3885.0(7)
8
8.1818(4)
10.3687(6)
12.1005(7)
102.755(1)
1001.2(1)
2
b, Å
c, Å
β, deg
V, Å3
Z
2θmax, deg
50
55
Reflections measured
Independent reflections
6464
6157 (Rint = 0.0232)
0.0856
6860
3576 (Rint = 0.0235)
0.0932
wR2 calculated on F2
for each reflection
R1 calculated on F
0.0378 (4554 ref.)
0.989
0.0376 (3335 ref.)
1.020
for reflections with I > 2 σ(I)
GOF
In conclusion it must be said that the P=E intramolecular alkylation method may also be used for the
synthesis of 1,2-heteraphosphacyclanes containing various functional substituents in the ring. For example the
method was successfully applied to the synthesis of 3-cyano-substituted 1,2-thiaphosphacyclanes [17,18].
EXPERIMENTAL
Reactions were carried out in an atmosphere of argon using absolute solvents. The IR spectra were taken
on a UR 20 instrument (KBr). The NMR spectra were recorded on Bruker WP 200SY (operating frequency
1
31
1
200.13 MHz for H and 81.01 MHz for P) and Bruker AMX 400 (operating frequency 400.13 MHz for H,
161.98 MHz for 31P, and 100.61 MHz for 13C) instruments. Internal standard was TMS (1H, 13C), external
standard was 85% H3PO4 (31P).
(3-Chloropropyl)diphenylphosphine (18a). Powdered KOH (1.12 g, 20 mmol) was added at 20°C
with vigorous stirring to a solution of Ph2PH (1.50 g, 8.0 mmol), 1,3-bromochloropropane (1.88 g, 12 mmol),
and TEBA (0.20 g, 0.9 mmol) in CH3CN (10 ml). The reaction mixture was heated at 70°C for 1.5 h, then
benzene (20 ml) and ice-water (20 ml) were added on cooling. The benzene layer was separated, washed with
water (2 × 10 ml), and dried over Na2SO4. The benzene was removed in vacuum, the residue was extracted with
boiling hexane, and the extract left for 1 day in the refrigerator. The hexane solution was decanted from the
crystalline residue, the solvent and the excess of 1,3-bromochloropropane were removed by heating in vacuum.
Phosphine 18a was obtained as a viscous oil. Yield 1.56 g (74%). 31P NMR (hexane): -16.9 ppm (lit. [13]:
δP -17.5 ppm).
(4-Chlorobutyl)diphenylphosphine (18b) was obtained analogously to 18a from Ph2PH (2.0 g,
11 mmol), 1,4-bromochlorobutane (3.77 g, 22 mmol), KOH (1.50 g, 26 mmol), and TEBA (0.24 g, 1.1 mmol) in
CH3CN (15 ml). The mixture was heated at 55-60°C for 1.5 h, then treated as in the previous experiment at a
103

temperature below 40°C. Compound 18b (1.30 g, 43%) was obtained as a viscous oil. 31P NMR spectrum
(hexane): -16.4 ppm {lit. [14]: δP -17.1 ppm (CHCl3)}.
(3-Chloropropyl)diphenylphenyliminophosphorane (19a). Phenyl azide (0.78 g, 6.5 mmol) in ether
(9 ml) was added dropwise to a solution of compound 18a (1.56 g, 5.9 mmol) in ether (10 ml). Evolution of
nitrogen was observed and the reaction mixture warmed to 26°C. The reaction mixture was stirred for 1 h at
20°C and then for 1 h on refluxing. The ether was removed, the residue was maintained in vacuum (1 mm Hg) at
a temperature no greater than 40°C, and then extracted with hot hexane. The crystalline solid precipitated from
the hexane solution was filtered off, and iminophosphorane 19a (0.31 g, 15%) was obtained (Tables 4, 5).
(4-Dhlorobutyl)diphenylphenyliminophosphorane (19b) was obtained analogously to compound 19a
from phosphine 18b (1.3 g, 4.7 mmol) and PhN3 (0.8 g, 6.7 mmol) in ether. The yield of compound 19b 0.5 g
(30%) (Tables 4, 5).
4
1,2,2-Triphenyl-1,2 -azaphospholanium Chloride (21a). A. Synthesis from iminophosphorane 19a.
λ
A solution of compound 19a (0.12 g, 0.34 mmol) in benzene (2 ml) was heated at 50°C for 40 min, the
precipitated solid was filtered off, washed with benzene, and chloride 21a (0.10 g, 85%) was isolated
(Tables 4, 5).
B. Synthesis from phosphine 18a. Phenyl azide (0.76 g, 6.4 mmol) in benzene (5 ml) was added
dropwise with stirring to a solution of compound 18a (1.41 g, 5.4 mmol) in benzene (10 ml). The reaction
mixture was maintained at 20°C for 1 h, then at 50°C for 40 min, and processed as in method A. Yield 1.34 g
(70%).
4
1,2,2-Triphenyl-1,2 -azaphosphorinanium Chloride (21b). A. Synthesis from iminophosphorane
λ
19b. A solution of compound 19b (0.30 g, 0.82 mmol) in CH3CN (8 ml) was refluxed for 2 h, and the solvent
removed in vacuum. Benzene (10 ml) was added to the residue, the mixture refluxed for 10 min, the precipitated
solid was filtered off, and washed with benzene. Chloride 21b (0.30 g, quantitative yield) was obtained
(Tables 4, 5).
B. Synthesis from phosphine 18b. Phenyl azide (0.50 g, 4.0 mmol) in ether (5 ml) was added to a
solution of compound 18b (1.41 g, 5.4 mmol) in ether (5 ml) at 20°C. The reaction mixture was refluxed for 1 h,
then CH3CN (10 ml) added, the mixture refluxed for 2.5 h, and processed as in method A. Yield 0.95 g (96%).
4
1,2,2-Triphenyl-1,2 -azaphospholanium Iodide (22a). A solution of NaI (0.13 g, 0.87 mmol) in
λ
CH3CN (2 ml) was added at 20°C to a solution of chloride 21a (0.20 g, 0.56 mmol) in CH3CN (2 ml). After 1 h
the precipitate of NaCl was filtered off, the solvent removed in vacuum, and the residue dissolved in CHCl3 with
heating. The excess of NaI was filtered off, and after removing the solvent, the residue was crystallized from
CH2Cl2–EtOAc. Yield 0.26 g (92%) (Tables 4, 5).
4
1,2,2-Triphenyl-1,2 -azaphosphorinanium Iodide (22b) was obtained analogously to compound 22a
λ
from chloride 21b (0.12 g, 0.33 mmol) and NaI (0.15 g, 1.0 mmol) in CH3CN (7 ml). Yield 0.12 g (80%)
(Tables 4, 5).
4
1,2,2-Triphenyl-1,2 -azaphosphorinanium Perchlorate (23b) was obtained analogously to
λ
compound 23a from chloride 21b (0.20 g, 0.54 mmol) and NaClO4 (0.20 g, 1.63 mmol) in CH3CN (15 ml).
Yield 0.19 g (82%) (Tables 4, 5).
1-Oxo-1-phenylphospholane (20). The aqueous solution obtained in the synthesis of phosphine 18b
(see above) was evaporated to dryness in vacuum. The residue was extracted with benzene. After removing the
benzene the waxy product 20 (0.4 g) was obtained. IR spectrum (CHCl3):
1175 cm-1 (lit. [19]:
δ
νP=O
νP=O 1180 cm-1). 31P NMR spectrum (CDCl3): δP 60.8 ppm. 1H NMR spectrum (CDCl3), , ppm: 1.77-2.15 [8H,
m, (CH2CH2)2P]; 7.35-7.68 (5H, m, C6H5) {lit. [20]: 1H NMR spectrum, , ppm: 1.95 (8H, m); 7.71 (5H, m)}.
δ
X-ray Structural Investigation. The main crystallographic data and refinement characteristics of
compounds 22a and 22b are given in Table 7. Estimation of the absorption was carried out from azimuthal
scanning for (22a) and empirically as the equivalent for (22b). The structures were solved by the direct method
and refined with an anisotropic–isotropic full matrix approach on F2. The hydrogen atoms were revealed
104

in difference syntheses of electron density and inserted in the final refinement in an isotropic approach. The
absolute configuration of structure 22b was determined based on the Flack parameter [0.02(3)]. All calculations
were carried out using the SHELXTL PLUS Ver. 5.0 set of programs on a personal computer.
The work was carried out with the support of the Russian Fund for Fundamental Investigations (grants
99-03-33014a, 00-15-97386).
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