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Russian Journal of General Chemistry,Vol. 72, No. 8,2002, pp. 125431255. Translated from Zhurnal ObshcheiKhimii, Vol. 72, No. 8,2002,pp. 133631337.Original Russian Text CopyrightC 2002 by Tolmachev,Mitrokhin, Kharchenko.

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Dibromo[2-(4-methoxyphenyl)cyclopent-1-enyl]phosphineand 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 resultingcompound 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 undermild conditions with phosphorus tribromide, whileunder rigid conditions anO-phosphorylation productis preferentially formed [1]. We found that the reac-tion of 4-(1-cyclopent-1-enyl)anisole with PBr3 in the

ÄÄÄÄÄÄÄÄÄÄÄÄ

presence of triethylamine occurs quickly and undermild conditions to give dibromophosphineI . Theproduct was isolated and characterized in the form ofamidesIIa and IIb , thiophosphonateIIIb , and phos-phonium halideIVa .

NUgPhOCH3-p

NUgPhOCH3-p

7776PBr3, NEt33NEt3.HBrjPBr2

I IIa, IIb

77763HR.HBr

HR

NUgPhOCH3-p

jPR2

NUgPhOCH3-p

jPR2oS

IIIb

NUgPhOCH3-p

jPR2gCH3

99

99

99

99

3

3

99

99

99

99

3

3

+

I3

99

9999

9999

99

776

776

7

IVa

S

CH3I

R = N(CH2CH2)2O (a), N(CH2CH2)2CH2 (b).ÄÄÄÄÄÄÄÄÄÄÄÄ

In the 31P NMR spectrum of the reaction mixturecontaining dibromophosphineI we unexpectedlyfound two signals with a 3 :7 intensity ratio. This factled us to propose that this compound initially existsas a mixture of two tautomeric formsIA (dP132.13 ppm) andIB (dP 153.53 ppm).

NUgPhOCH3-p

jPBr25

4 32

17647 NgPhOCH3-p

jPBr25

4 32

1

XIA IB

The signal of the phosphorus atom at ansp3-carbon

atom is located downfield as compared to that of thephosphorus atom at ansp2-carbon atom. This factallows easy identification of the structures. Analogouspartial 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 groupsto be introduced in 1-morpholinocyclopentenes and-cyclohexenes [4]. But when 4-(1-cyclopent-1-enyl)-anisole was phosphorylated with a twofold or higherexcess of phosphorus tribromide, no signals of theexpected bisphosphorylated product were observed inthe 31P NMR spectra.

RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 72 No. 8 2002

DIBROMO[2-(4-METHOXYPHENYL)CYCLOPENT-1-ENYL)PHOSPHINE 1255

As would be expected, attempted isolation of thedibromophosphine and its further transformations leadto formation of a single tautomerA. In the 1H NMRspectra of diamidesIIa and IIb , the third methyleneunit of cyclopentene appears as a multiplet at 1.783

1.82 ppm. In the spectra of sulfideIIIb and phos-phonium halide IVa , this multiplet is located at1.9231.96 and 2.0832.14 ppm, respectively. Theolefin proton signal, which in the spectrum of thestarting compound appears as a multiplet at 6.04 ppm,is absent from the spectra of all the products. The31PNMR spectra provide further evidence to show thatcompoundsIIa , III , and IV exists as a single tauto-mer (dP 82.5, 65.8, and 50.3 ppm, respectively).

EXPERIMENTAL

The NMR spectra were measured on Gemini-200(200 MHz, 1H) and Bruker-200 (81.03 MHz,31P)spectrometers against internal TMS (1H) and external85% H3PO4 (31P NMR). The elemental analysesagree with calculation.

[2-(4-Methoxyphenyl)cyclopent-1-enyl]phos-phonic dimorpholide. To a solution of 0.1 mol of4-(1-cyclopent-1-enyl)-anisole and 0.11 mol of tri-ethylamine in 20 ml of dry pyridine, a solution of0.1 mol of phosphorus tribromide in 30 ml of dryhexane was added with stirring and cooling at 5310oC.The resulting mixture was stirred with cooling for anadditional 2 h and then left to stand for a day. Thereaction completion was detected by the disappearanceof the signal of PBr3 from the 31P NMR spectrum.The mixture was diluted with 20 ml of hexane. Theprecipitate of pyridine hydrobromide was filtered offwith protection from air moisture. The resulting solu-tion of dibromo[2-(4-methoxyphenyl)cyclopent-1-enyl)phosphine (dP 132.13 and 153.53 ppm) wasadded with vigorous stirring and cooling to a solutionof 0.4 mol of dry morpholine in 50 ml of dry hexane.The reaction mixture was stirred for 2 h, morpholinehydrobromide was filtered off, the filtrate was evapo-rated, and the residue was treated with dry hexane(3010 ml) and crystallized from octane. Yield 56%,mp 115oC, colorless crystals.1H NMR spectrum(C6D6), d, ppm: 1.7831.82 m (2H, CH2

3); 2.8332.88 m [8H, 2N(CH2)2]; 2.8032.94 m (4H, 2CH2

4,5);3.44 s (3H, OCH3); 3.4633.51 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(CHCl3): dP 82.5 ppm.

[2-(4-Methoxyphenyl)cyclopent-1-enyl]phos-phonic dipiperidide (IIb) was prepared and isolatedanalogously to compoundIa, using piperidine insteadof morpholine. Yield 58%, mp 125oC, colorlesscrystals.1H NMR spectrum (CD3CN), d, ppm: 1.3531.43 m (12H, 6CH2), 1.7831.82 m (2H, CH2

3), 2.8332.86 m [8H, N(CH2)2], 2.8732.89 m (4H, 2CH2

4,5),3.85 s (3H, O3CH3), 6.88 m (2H, C6H4), 7.35 m (2H,C6H4).

31P NMR spectrum (CHCl3), dP, ppm: 83.8 d.

[2-(4-Methoxyphenyl)cyclopent-1-enyl]thiophos-phonic dipiperidide (IIIb). To a solution of 1 mmolof compoundIIb in 15 ml of dry benzene, 1 mmol offinely powdered sulfur was added. The reaction mix-ture was stirred for 12 h. The solvent was removed,and the residue was crystallized from octane. Yield73%, mp 154oC, yellow crystals.1H NMR spectrum(CDCl3), d, ppm: 1.3231.45 m (12H, 6CH2), 1.9231.96 m (2H, CH2

3), 2.8032.90 m [8H,2N(CH2)2],2.8632.90 m (4H, 2CH2

4,5), 3.82 s (3H, OCH3),6.85 m (2H, C6H4), 7.41 m (2H, C6H4).

31P NMRspectrum (CHCl3): dP 65.8 ppm.

[2-(4-Methoxyphenyl)cyclopent-1-enyl](methyl)-dimorpholinophosphonium iodide (IVa). To a solu-tion of 1 mmol of compoundIIb in 15 ml of drypentene, 1 ml of methyl iodide was added. The reac-tion mixture was kept for 30 h. The product thatprecipitated was filtered off and washed with pentane(305 ml). Yield 82%, mp 142oC, colorless crystals.1H NMR spectrum (CDCl3), d, ppm: 2.0832.14 m (2H,CH2

3), 2.28 d (3H, P3CH3, JHH 14.0 Hz), 3.1033.20 m [8H, 2N(CH2)2], 3.0033.25 m (4H, 2CH2

4,5),3.6933.72 m [8H, 2O(CH2)2], 3.85 s (2H, CH2),6.96 m (2H, C6H4), 7.18 m (2H, C6H4).

31P NMRspectrum (CHCl3): dP 50.3 ppm.

REFERENCES

1. Tolmachev, A.A., Ivonin, S.P., Kharchenko, A.V., andKozlov, E.S.,Zh. Obshch. Khim.,1989, vol. 59, no. 5,pp. 119331194.

2. Tolmachev, A.A., Kostyuk, A.N., Morozova, L.N.,Lampeka, R.D., Kozlov, E.S., and Pinchuk, A.M.,Zh.Obshch. Khim.,1991, vol. 61, no. 7, pp. 160731617.

3. Tolmachev, A.A., Morozova, L.N., Kostyuk, A.N.,Lampeka, P.D., Kozlov, E.S., and Pinchuk, A.M.,Zh.Obshch. Khim.,1989, vol. 59, no. 10, pp. 238832389.

4. Tolmachev, A.A., Kostyuk, A.N., and Kozlov, E.S.,Zh.Obshch. Khim.,1991, vol. 61, no. 8, pp. 191231913.