Dibromo[2-(4-methoxyphenyl)cyclopent-1-enyl]phosphine and its derivatives

Article abstract of DOI:10.1023/A:1020836014685

Direct phosphorylation of 4-(1-cyclopent-1-enyl)anisole with PBr ₃ was carried out. The resulting compound initially exists in two tautomeric forms. Isolation of the dibromophosphine and its further transformations lead to formation of a single

Full text of DOI:10.1023/A:1020836014685

Russian Journal of General Chemistry, Vol. 72, No. 8, 2002, pp. 1254 1255. Translated from Zhurnal Obshchei Khimii, Vol. 72, No. 8, 2002,
pp. 1336 1337.
Original Russian Text Copyright
2002 by Tolmachev, Mitrokhin, Kharchenko.
Dibromo[2-(4-methoxyphenyl)cyclopent-1-enyl]phosphine
and Its Derivatives
A. A. Tolmachev, A. Yu. Mitrokhin, and A. V. Kharchenko
Ukrainian State University of Chemical Technology, Dnepropetrovsk, Ukraine
Institute of Organic Chemistry, National Academy of Sciences of Ukraine, Kiev, Ukraine
Received October 31, 2000
Abstract Direct phosphorylation of 4-(1-cyclopent-1-enyl)anisole with PBr3 was carried out. The resulting
compound initially exists in two tautomeric forms. Isolation of the dibromophosphine and its further trans-
formations lead to formation of a single tautomer.
It is known that anisole, unlike 1-ethoxynaphtha-
lene and 1,3-dimethoxybenzene, fails to react under
mild conditions with phosphorus tribromide, while
under rigid conditions an O-phosphorylation product
is preferentially formed [1]. We found that the reac-
tion of 4-(1-cyclopent-1-enyl)anisole with PBr3 in the
presence of triethylamine occurs quickly and under
mild conditions to give dibromophosphine I. The
product was isolated and characterized in the form of
amides IIa and IIb, thiophosphonate IIIb, and phos-
phonium halide IVa.
PhOCH3-p
PR2
S
S
PhOCH3-p
PhOCH3-p
PhOCH3-p
HR
IIIb
PBr3, NEt3
NEt3 HBr
PBr2
PR2
HR HBr
+
PhOCH3-p
CH3I
I
IIa, IIb
I
PR2
CH3
IVa
R = N(CH2CH2)2O (a), N(CH2CH2)2CH2 (b).
In the 31P NMR spectrum of the reaction mixture
containing dibromophosphine I we unexpectedly
found two signals with a 3:7 intensity ratio. This fact
led us to propose that this compound initially exists
atom is located downfield as compared to that of the
phosphorus atom at an sp2-carbon atom. This fact
allows easy identification of the structures. Analogous
partial or complete double-bond migration in 2-phos-
phorylated 1-morpholinocyclopentenes and -cyclo-
hexenes was earlier observed in [2, 3]. This tasuto-
merism permitted two phosphorus-containing groups
to be introduced in 1-morpholinocyclopentenes and
-cyclohexenes [4]. But when 4-(1-cyclopent-1-enyl)-
anisole was phosphorylated with a twofold or higher
excess of phosphorus tribromide, no signals of the
expected bisphosphorylated product were observed in
the 31P NMR spectra.
as a mixture of two tautomeric forms IA (
P
132.13 ppm) and IB ( 153.53 ppm).
P
PhOCH3-p
1
PhOCH3-p
1
2 PBr2
3
2 PBr2
3
5
5
4
4
IA
IB
The signal of the phosphorus atom at an sp3-carbon
1070-3632/02/7208-1254$27.00 2002 MAIK Nauka/Interperiodica

DIBROMO[2-(4-METHOXYPHENYL)CYCLOPENT-1-ENYL)PHOSPHINE
1255
As would be expected, attempted isolation of the
dibromophosphine and its further transformations lead
to formation of a single tautomer A. In the H NMR
[2-(4-Methoxyphenyl)cyclopent-1-enyl]phos-
phonic dipiperidide (IIb) was prepared and isolated
analogously to compound Ia, using piperidine instead
of morpholine. Yield 58%, mp 125 C, colorless
1
spectra of diamides IIa and IIb, the third methylene
unit of cyclopentene appears as a multiplet at 1.78
1.82 ppm. In the spectra of sulfide IIIb and phos-
phonium halide IVa, this multiplet is located at
1.92 1.96 and 2.08 2.14 ppm, respectively. The
olefin proton signal, which in the spectrum of the
starting compound appears as a multiplet at 6.04 ppm,
is absent from the spectra of all the products. The 31P
NMR spectra provide further evidence to show that
compounds IIa, III, and IV exists as a single tauto-
1
crystals. H NMR spectrum (CD3CN), , ppm: 1.35
1.43 m (12H, 6CH2), 1.78 1.82 m (2H, CH32), 2.83
2.86 m [8H, N(CH2)2], 2.87 2.89 m (4H, 2CH42,5),
3.85 s (3H, O CH3), 6.88 m (2H, C6H4), 7.35 m (2H,
C6H4). 31P NMR spectrum (CHCl3), P, ppm: 83.8 d.
[2-(4-Methoxyphenyl)cyclopent-1-enyl]thiophos-
phonic dipiperidide (IIIb). To a solution of 1 mmol
of compound IIb in 15 ml of dry benzene, 1 mmol of
finely powdered sulfur was added. The reaction mix-
ture was stirred for 12 h. The solvent was removed,
and the residue was crystallized from octane. Yield
mer ( 82.5, 65.8, and 50.3 ppm, respectively).
P
EXPERIMENTAL
1
73%, mp 154 C, yellow crystals. H NMR spectrum
(CDCl3), , ppm: 1.32 1.45 m (12H, 6CH2), 1.92
1.96 m (2H, CH32), 2.80 2.90 m [8H,2N(CH2)2],
2.86 2.90 m (4H, 2CH42,5), 3.82 s (3H, OCH3),
6.85 m (2H, C6H4), 7.41 m (2H, C6H4). 31P NMR
The NMR spectra were measured on Gemini-200
1
(200 MHz, H) and Bruker-200 (81.03 MHz, 31P)
spectrometers against internal TMS (1H) and external
85% H3PO4 (31P NMR). The elemental analyses
agree with calculation.
spectrum (CHCl3):
65.8 ppm.
P
[2-(4-Methoxyphenyl)cyclopent-1-enyl](methyl)-
dimorpholinophosphonium iodide (IVa). To a solu-
tion of 1 mmol of compound IIb in 15 ml of dry
pentene, 1 ml of methyl iodide was added. The reac-
tion mixture was kept for 30 h. The product that
precipitated was filtered off and washed with pentane
(3 5 ml). Yield 82%, mp 142 C, colorless crystals.
1H NMR spectrum (CDCl3), , ppm: 2.08 2.14 m (2H,
CH32), 2.28 d (3H, P CH3, JHH 14.0 Hz), 3.10
3.20 m [8H, 2N(CH2)2], 3.00 3.25 m (4H, 2CH42,5),
3.69 3.72 m [8H, 2O(CH2)2], 3.85 s (2H, CH2),
6.96 m (2H, C6H4), 7.18 m (2H, C6H4). 31P NMR
[2-(4-Methoxyphenyl)cyclopent-1-enyl]phos-
phonic dimorpholide. To a solution of 0.1 mol of
4-(1-cyclopent-1-enyl)-anisole and 0.11 mol of tri-
ethylamine in 20 ml of dry pyridine, a solution of
0.1 mol of phosphorus tribromide in 30 ml of dry
hexane was added with stirring and cooling at 5 10 C.
The resulting mixture was stirred with cooling for an
additional 2 h and then left to stand for a day. The
reaction completion was detected by the disappearance
of the signal of PBr3 from the 31P NMR spectrum.
The mixture was diluted with 20 ml of hexane. The
precipitate of pyridine hydrobromide was filtered off
with protection from air moisture. The resulting solu-
tion of dibromo[2-(4-methoxyphenyl)cyclopent-1-
spectrum (CHCl3):
50.3 ppm.
P
REFERENCES
enyl)phosphine (
132.13 and 153.53 ppm) was
P
added with vigorous stirring and cooling to a solution
of 0.4 mol of dry morpholine in 50 ml of dry hexane.
The reaction mixture was stirred for 2 h, morpholine
hydrobromide was filtered off, the filtrate was evapo-
rated, and the residue was treated with dry hexane
(3 10 ml) and crystallized from octane. Yield 56%,
mp 115 C, colorless crystals. 1H NMR spectrum
(C6D6), , ppm: 1.78 1.82 m (2H, CH32); 2.83
2.88 m [8H, 2N(CH2)2]; 2.80 2.94 m (4H, 2CH42,5);
3.44 s (3H, OCH3); 3.46 3.51 m [8H, 2O(CH2)2];
6.85 m (1H, C6H4); 7.08 m (1H, C6H4); 7.12 m (1H,
C6H4); 7.39 m (1H, C6H4). 31P NMR spectrum
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Kozlov, E.S., Zh. Obshch. Khim., 1989, vol. 59, no. 5,
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Lampeka, R.D., Kozlov, E.S., and Pinchuk, A.M., Zh.
Obshch. Khim., 1991, vol. 61, no. 7, pp. 1607 1617.
3. Tolmachev, A.A., Morozova, L.N., Kostyuk, A.N.,
Lampeka, P.D., Kozlov, E.S., and Pinchuk, A.M., Zh.
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Obshch. Khim., 1991, vol. 61, no. 8, pp. 1912 1913.
(CHCl3):
82.5 ppm.
P
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 72 No. 8 2002