Chemistry

V. L. Foss, V. V. Kudinova, G. B. Postnikova, I. F. Lutsenko

Derivatives of β-Ketophosphinic Acids

(Presented by Academician A. N. Nesmeyanov, May 10, 1962)

The reduction, proposed by Uollesh, Beck, and Woodstock \((^1)\), of the products of addition of phosphorus pentachloride to unsaturated compounds to the acid chlorides of phosphinic acids by means of white phosphorus was used by us for the synthesis of previously inaccessible derivatives—β-ketophosphinic acids.

First of all, the reduction of adducts of phosphorus pentachloride with enol esters was studied. The primary addition products, as had earlier been established by one of us and M. Kirillov, are stable only at low temperatures \((^2)\). This compelled us to carry out the reduction at temperatures excluding the possibility of rearrangement—at \(5\text{–}6^\circ\) for the adduct from phosphorus pentachloride and vinyl acetate, and at \(-20^\circ\) for the adduct from phosphorus pentachloride and isopropenyl acetate. In the first case, β-acetoxy-β-chloroethyl dichlorophosphine was obtained in 70% yield; in the second case, acetonyl dichlorophosphine was obtained

\[ \mathrm{CH_3—C—CH_2PCl_4 \cdot PCl_5} \ \xrightarrow[\ ]{P_{\text{white}}}\ \left[\mathrm{CH_3—C—CH_2PCl_2}\right] \ \xrightarrow[-\mathrm{CH_3COCl}]{}\ \mathrm{CH_3COCH_2PCl_2} \]

\[ \begin{array}{cc} \mathrm{\ \ \ \ |} & \mathrm{\ \ \ \ |} \\ \mathrm{Cl\ \ OCOCH_3} & \mathrm{Cl\ \ OCOCH_3} \end{array} \]

Elimination of acetyl chloride occurs on heating the reduction product to \(65\text{–}75^\circ\). Since reduction at \(-20\text{–}23^\circ\) proceeds extremely slowly (in some experiments for more than 3 days), the temperature had to be raised to \(-10\text{–}12^\circ\). Under these conditions two reactions proceed in parallel—reduction and rearrangement; on vacuum distillation, acetonyl dichlorophosphine (53.2–20.4%) and the previously described \((^3)\) acid chloride of α-acetyl-β-chloropropenylphosphinic acid (11.3–42.7%) were obtained. Acetonyl dichlorophosphine rapidly resinifies on storage.

We also extensively investigated another route of access to derivatives of β-ketophosphinic acids, namely the reduction by white phosphorus of adducts of phosphorus pentachloride with simple vinyl ethers:

\[ \mathrm{CH_2{=}CHOR} \qquad (\mathrm{R=C_2H_5,\ iso\text{-}C_3H_7,\ C_4H_9,\ C_6H_5}), \]

\[ \mathrm{CH_2{=}C(OC_4H_9)R} \qquad (\mathrm{R=CH_3,\ C_2H_5,\ C_3H_7}), \]

\[ \mathrm{CH_2{=}C(OC_2H_5)C_2H_5} \]

By the time the experiment had been completed, a paper by K. N. Anisimov and N. E. Kolobova \((^4)\) had appeared, the results of which coincide with ours in several points. Since we were able to clarify the course of the reaction in greater detail and obtained higher yields, we present our data also for these coinciding compounds.

Reduction by white phosphorus of the addition product of phosphorus pentachloride to vinyl butyl ether at room temperature leads to the formation of two products—β-butoxyvinyldichlorophosphane (30%) and a lower-boiling product—α-chloroethyl butyl ether (36%,

b.p. 64–65°/70 mm; \(n_D^{20}\) 1.4136; \(d_4^{20}\) 0.9340). Literature data (5): b.p. 34–35°/7 mm; \(n_D^{20}\) 1.4126; \(d_4^{20}\) 0.9339.

Found, %: C 52.87; H 9.64; Cl 25.63
\( \mathrm{C_6H_{13}OCl} \). Calculated, %: C 52.76; H 9.59; Cl 25.97

However, if the addition is carried out at \(-10\)–\(12^\circ\), the yield of the low-boiling product drops sharply, while the yield of the dichloroanhydride of β-butoxyvinylphosphinic acid increases to 71.6%. This proved to be true also in the case of the other vinyl ethers investigated.

Data on the synthesized chloroanhydrides and esters of phosphinic acids, obtained by the usual methods from chloroanhydrides, are given in Table 1.

Table 1

* Literature data (4): b.p. 64–69°/5 mm, \(n_D^{20}\) 1.5234, \(d_4^{20}\) 1.2471.
* M.p. 16–17°.
** Literature data (4): b.p. 113°/2 mm, \(n_D^{20}\) 1.4570, \(d_4^{20}\) 0.9764.

Experimental Part

β-Butoxyvinyldichlorophosphine. To a solution of 83.2 g (0.4 mole) of phosphorus pentachloride in 800 ml of dry carbon tetrachloride, with stirring, 20 g (0.2 mole) of n-butyl vinyl ether is added dropwise at a temperature of \(-10\)–\(12^\circ\). After stirring for 5 hours at the same temperature, 0.3 g of iodine is added to the suspension of the addition product obtained, and a solution of 8 g (0.258 mole) of white phosphorus in 4 ml of carbon disulfide* is rapidly poured in. The mixture is stirred for another 3.5 hours at a temperature of \(-10\)–\(12^\circ\) until the crystalline precipitate has completely dissolved; then the solvent, phosphorus trichloride, and α-chloroethyl butyl ether are distilled off under the vacuum of a water-jet pump with slight heating (bath temperature \(+30^\circ\)). After distillation of the residue, 27.5 g (71.6% of theory) of a substance is obtained with b.p. 99–100°/9 mm; \(n_D^{20}\) 1.5127; \(d_4^{20}\) 1.1675.

Found, %: C 36.15; H 5.75; P 15.45
\( \mathrm{C_6H_{11}OPCl_2} \). Calculated, %: C 35.84; H 5.51; P 15.40

β-Ethoxy-β-ethylvinyldichlorophosphine. To a solution, cooled to \(-15^\circ\), of 171.5 g (0.8 mole) of phosphorus pentachloride in 800 ml of carbon tetrachloride, 40 g (0.4 mole) of α-ethylvinyl ethyl ether is added with stirring. The mixture is stirred at the same temperature for 5 hours, and then a solution of 16.6 g (0.54 mole) of white phosphorus in 10 ml of carbon disulfide and 0.6–0.8 g of iodine, dissolved

* Reduction with white phosphorus, esterification, and all distillations are carried out in an atmosphere of dry nitrogen.

in 15 ml of carbon tetrachloride. Reduction at −10–15° takes 2–3 hr. After removal of the solvent, the residue is distilled to give 40.3 g (50% of theory) of a substance with b.p. 86–86°/7 mm; \(n_D^{20}\) 1.5140; \(d_4^{20}\) 1.1614.

\[ \begin{aligned} \mathrm{C_6H_{11}OPCl_2}. \quad &\text{Found, \%: } &&\mathrm{C}\ 35.90; \quad \mathrm{H}\ 5.75; \quad \mathrm{P}\ 15.31 \\ &\text{Calculated, \%: } &&\mathrm{C}\ 35.84; \quad \mathrm{H}\ 5.51; \quad \mathrm{P}\ 15.40 \end{aligned} \]

β-Acetoxy-β-chloroethyldichlorophosphine. To the adduct from 205 g (1 mole) of phosphorus pentachloride and 56 g (0.5 mole) of vinyl acetate in 800 ml of carbon tetrachloride, at 2–3° there is added a solution of 22 g of white phosphorus in 4 ml of carbon disulfide, and 0.5 g of iodine is added. The mixture is stirred for 4–5 hr at 2–6°. After the precipitate has disappeared, carbon tetrachloride and \(\mathrm{PCl_3}\) are distilled off in vacuo. The residue is filtered from the precipitate and distilled in a nitrogen atmosphere. Yield 78 g (70% of theory); b.p. 76–77°/3 mm; \(n_D^{20}\) 1.5052; \(d_4^{20}\) 1.4263; \(MR\) found 46.50, calculated 46.40.

\[ \begin{aligned} \mathrm{C_4H_6O_2PCl_3}. \quad &\text{Found, \%: } &&\mathrm{C}\ 21.56;\ 21.51; \quad \mathrm{H}\ 2.66;\ 2.61; \quad \mathrm{P}\ 13.82;\ 13.98 \\ &\text{Calculated, \%: } &&\mathrm{C}\ 21.50; \quad \mathrm{H}\ 2.71; \quad \mathrm{P}\ 13.87 \end{aligned} \]

Acetonyldichlorophosphine. For reduction of the adduct obtained at −23–25° from 83.2 g (0.4 mole) of phosphorus pentachloride and 22 g (0.2 mole) of isopropenyl acetate in 800 ml of carbon tetrachloride, a solution of 7.4 g (0.239 mole) of white phosphorus in 4 ml of carbon disulfide is added, and 0.6 g of iodine is added. The mixture is stirred for 4 hr at −20–22°, and then the temperature is raised to −10–12°. Stirring is continued until the precipitate has completely dissolved. The subsequent treatment is analogous to that described above. Nine grams of substance are obtained (32% of theory). On redistillation, acetonyldichlorophosphine is isolated with b.p. 73–74°/10 mm; \(n_D^{20}\) 1.5105; \(d_4^{20}\) 1.3452; \(MR\) found 35.36, calculated 35.31.

\[ \begin{aligned} \mathrm{C_3H_5OPCl_2}. \quad &\text{Found, \%: } &&\mathrm{C}\ 22.94;\ 22.69; \quad \mathrm{H}\ 3.04;\ 3.32; \quad \mathrm{P}\ 19.04;\ 19.19 \\ &\text{Calculated, \%: } &&\mathrm{C}\ 22.68; \quad \mathrm{H}\ 3.17; \quad \mathrm{P}\ 19.49 \end{aligned} \]

From the higher-boiling fraction there was obtained the acid chloride of α-acetyl-β-chloropropenylphosphinic acid (20.1 g, 42.7% of theory), with b.p. 113–114°/2 mm; \(n_D^{20}\) 1.5235; \(d_4^{20}\) 1.4416. Literature data (3): b.p. 112°/1.5 mm; \(n_D^{20}\) 1.5240; \(d_4^{20}\) 1.4413.

Received
10 V 1962

REFERENCES CITED

1. E. N. Walsh, T. M. Beck, W. H. Woodstock, J. Am. Chem. Soc., 77, 929 (1955).
2. И. Ф. Луценко, М. Кирилов, DAN, 132, No. 4, 842 (1960).
3. И. Ф. Луценко, М. Кирилов, DAN, 128, No. 1, 89 (1959).
4. К. Н. Анисимов, Н. Е. Колобова, Izv. AN SSSR, OKhN, 1962, No. 3, 442.
5. М. Ф. Шостаковский, Simple Vinyl Ethers, Moscow, 1952, p. 131.