Checked by John R. Berry and Richard E. Benson.
1. Procedure
A.
Bis(2-cyanoethyl)phenylphosphine. A
250-ml., three-necked flask is equipped with a
magnetic stirrer, a
thermometer, a
pressure-equalizing dropping funnel, and a
reflux condenser, with the entire system flushed with
nitrogen. To the flask is added under an atmosphere of
nitrogen 50.0 g. (0.454 mole) of phenylphosphine (Note
1),
50 ml. of acetonitrile, and
10 ml. of 10 N potassium hydroxide (Note
2). An
ice-water bath is prepared for immediate cooling of the reaction flask. To the reaction mixture is added dropwise
50.0 g. (0.943 mole) of acrylonitrile (Note
3) with stirring and cooling over a period of 45–60 minutes. The rate of addition is controlled so that the temperature of the solution never exceeds 35° (Note
4). After the addition is complete, the solution is stirred at room temperature for an additional 2.5 hours. The reaction mixture is diluted with
100 ml. of ethanol and chilled to 0°. The product starts to crystallize, and the mixture is allowed to stand until crystallization is complete. The heavy slurry is filtered, and the crystalline product is washed with
200 ml. of cold ethanol and dried at 60° (2 mm.), yielding
74–84 g. (
76–86%) of
bis(2-cyanoethyl)phenylphosphine, m.p.
71–74° (Note
5). An additional
5–9 g. of product may be recovered from the combined washings and filtrate by concentration of the solution with subsequent chilling, bringing the total yield to
79–91 g. (
80–93%).
2. Notes
1.
Phenylphosphine is available from Pressure Chemical Company and Strem Chemicals Inc., and best stored in a dry box under
nitrogen. The compound is extremely air sensitive and malodorous. The
container should be handled in the
hood while wearing rubber gloves. Satisfactory preparations of
phenylphosphine have been described.
2
3.
Practical grade acetonitrile, available from Eastman Organic Chemicals, is satisfactory.
4. The optimum reaction temperature is approximately 30°. A yellow product results at higher reaction temperatures, while lower reaction temperatures lead to an uncontrollable reaction resulting from the base-initiated polymerization of
acrylonitrile.
5. This product is of satisfactory purity for the next step. If a purer product is desired,
bis(2-cyanoethyl)phenylphosphine may be recrystallized from hot
ethanol or distilled, b.p.
215–223° (0.2 mm.).
3 The IR adsorption maxima (KBr), cm.
−1, occur at 3086, 2242, 1481, 1429, 1333, 750, 716, and 694.
1H NMR spectrum (CDCl
3) shows complex multiplets centered at δ 7.2 (8H) and 7.6 (5H). The
31P NMR spectrum (40.5 MHz, C
2H
5OH) has a signal at −21.4 p.p.m. relative to 85% phosphoric acid.
7.
Reagent grade toluene was dried by standing over
sodium ribbon.
8. The reaction mixture becomes quite viscous when the addition is about two-thirds complete.
9. The product, as isolated, is pure enough for conversion to
1-phenyl-4-phosphorinanone. If a higher degree of purity is desired, the product may be recrystallized from ethanol–water or chromatographed on alumina. IR absorption maxima (KBr), cm
−1 occur at 3401, 3344, 3236, 2874, 2169, 1642, 1603, 1399, 1323, 1188, 830, 781, 737, and 690. The
1H NMR spectrum (CDCl
3, containing a small amount of dimethylsulfoxide-
d6) shows peaks at δ 1.8–3.0 (m, 2H), 5.15 (broad s, 2H), and 7.4–7.8 (m, 5H).
10. A small amount of product can be recovered from the filtrate by extracting the water layer with
chloroform.
11. A white precipitate forms in the reaction medium after approximately 6 hours of reaction time. This precipitate may be the
hydrochloride salt of 1-phenyl-4-phosphorinanone, m.p.
>200°.
12. Rapid addition of base seems to result in higher yields than a more cautious addition, even though the temperature of the solution increases to about 40°. The solution must be strongly basic for efficient extraction.
13. Impure
1-phenyl-4-phosphorinanone may crystallize at this point. If crystallization occurs, the solid is recovered by filtration and washed thoroughly with two 20-ml. portions of water. The material is dried in a desiccator over
phosphorus pentoxide, giving a product of m.p.
42.5–44°. To obtain a product satisfactory for distillation, the checkers found it necessary to dissolve the material in
ether and wash it with water before distillation.
14. GC analysis of the product on a column containing 10% SE-30 on acid-washed Chromosorb U indicated one component, injected as a 20% solution in
ethanol at 230° and
helium flow of 15 ml. per minute with a retention time of 760 seconds. The
1H NMR spectrum (CDCl
3) shows multiplets centered at δ 2.4 (8H) and 7.4 (5H). IR absorption maxima (KBr), cm
−1, occur at 3077 (=CH), 2976 and 2924 (CH), 1704 (C=O), 1595 and 1486 (aromatic C=C), 1433 (P-phenyl), 754 and 701 (monosubstituted phenyl). The
31P NMR spectrum (40.5 MHz., CHCl
3) shows a signal at −39.3 p.p.m. relative to 85% phosphoric acid.
3. Discussion
Phosphorinanones have been utilized as substrates for the preparation of alkenes,
12 amines,
13 indoles,
5,14 and in the synthesis of a series of secondary and tertiary alcohols
via reduction,
10 and by reaction with Grignard
6,12 and Reformatsky
12,15 reagents. Phosphorinanones have also been used as precursors to a series of 1,4-disubstituted phosphorins.
16 The use of
4-amino-1,2,5,6-tetrahydro-1-phenylphosphorin-3-carbonitrile for the direct formation of phosphorino[4,3-
d] pyrimidines has been reported.
17 The
13C NMR spectra of 1-phenylphosphorinanone has been reported.
18
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