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Third, arylphosphonic acid derivatives have been made by or-ganometallic reactions, such as the reaction of C6H5MgBr with (C^HsObPOCl or of phcnyllithium with phosphorodipiperididic chloride 9c 11
Fourth, the present procedure bears a resemblance to the photochemical reaction of aryl iodides with trialkyl phosphites, by means of which several dialkyl arylphosphonates have been prepared.13 However, prolonged irradiation (>24 hours) in quartz vessels was employed.
1. Board of Studies in Chemistry, University of California, Santa Cruz, California 95064.
2. J. Ę Bunnett and X. Creary, J. Org. Chem., 39, 3612 (1974).
3. J. F. Bunnett and R. P. Traber, J. Org. Chem., 43, 1867 (1978).
4. J. K. Kim and J. F. Bunnett, J. Amer. Chem. Soc., 92, 7463, 7464 (1970).
5. R. A. Rossi and J. F. Bunnett, J. Amer. Chem. Soc., 94, 683 (1972); J. Org. Chem., 38, 1407 (1973); J. F. Bunnett and J. E. Sundberg, Chem. Pharm. Bull. (Jap.), 23, 2620 (1975); J. F. Bunnett and J. E. Sundberg, J. Org. Chem., 41, 1702 (1976).
6. X. Creary, unpublished work.
7. J. F. Bunnett and B. F. Gloor, J. Org. Chem., 39, 382 (1974).
8. J. F. Bunnett and X. Creary, J. Org. Chem., 39, 3173 (1974).
9. K. Sasse, “Methoden der Organischen Chemie” (Houben-Weyl), 4th ed., Band XII/1, Georg Thieme, Stuttgart, 1963, (a) p. 314; (b) p. 352; (c) p. 372; (d) p. 392.
10. Ň. H. Siddall, III, and C. A. Prohaska, J. Amer. Chem. Soc., 84, 3467 (1962).
11. G. M. Kosolapoff, Org. React., 6, 273 (1951).
12. t D. Freedman and G. O. Doak, Chem. Rev., 57, 479 (1957).
13. J. B. Plumb, R. Obrycki, and Ń. E. Griffin, J. Org. Chem., 31, 2455 (1966); Ń. E. Griffin, R. B. Davison, and M. Gordon, Tetrahedron, 22, 561 (1966); R. Obrycki and C.
E. Griffin, J. Org. Chem., 33, 632 (1968).
Chemical Abstracts Nomenclature (Collective Index Number; Registry Numbers)
Diethyl phenylphosphonate: Phosphonic acid, phenyl-, diethyl ester (8,9); (1754-49-0)
ORGANIC SYNTHESES—VOL. 58
Diethyl phosphonate: Phosphonic acid, diethyl ester (8,9); (762-04-9)
Benzene, iodo- (8,9); (591-50-4)
Acetone (8); 2-Propanone (9); (67-64-1)
Ammonium nitrate: Nitric acid, ammonium salt (8,9); (6484-52-2) Ethyl ether (8); Ethane, l,l'-oxybis- (9); (60-29-7)
Potassium diethyl phosphite: Phosphorous acid, diethyl ester, potassium salt (8,9); (54058-00-3)
Benzene, bromo- (8,9); (108-86-1)
C6H5MgBr: Magnesium, bromo phenyl (8,9); (100-58-3) (C2H50)2P0C1: Phosphorochloridic acid, diethyl ester (8,9); (814-
Lithium, phenyl- (8,9); (591-51-5)
Phosphorodipiperididic chloride: Phosphonic dichloride, piperi-dino- (8,9); (1498-56-2)
SULFIDE SYNTHESIS: BENZYL SULFIDE (Benzene, l,l-[thiobis(methylene) Ibis-)
(C6H5CH2)2S2 + [(CH3)2N]3P (C6H5CH2)2S + [(CH3)2N]3PS
Submitted by David N. Harpp and Roger A. Smith1 Cheeked by Susan A. Vladuchick and William A. Sheppard
Caution! See benzene warning, p. 168. (Note 1).
A 100-ml., one-necked, round-bottomed flask is equipped with a magnetic stirring bar and an efficient reflux condenser topped with a drying tube. The flask is charged with 3.92 g. (0.024 mole) of freshly-distilled hexamethylphosphorous triamide (Note 2), 15 ml. of dry benzene (Note 3), and 4.93 g. (0.020 mole) of benzyl disulfide (Note 4). The mixture is then refluxed for 1 hour (Notes 5 and 6), during which time it may develop a slight yellow color. After cooling to room temperature, the solution is concentrated on a rotary evaporator (Note 7), and the residue is chromatographed
SULFIDE SYNTHESIS: BENZYL SULFIDE
over 75 g. of silica gel (Note 8). After eluting with hexane-chloroform (8:2 v/v) at 3-4 ml. per minute (Note 9) and monitoring the eluant by gas chromatography (Note 10), an initial fraction containing no product is collected (typically 100 ml.)- Successive fractions (ca. 1.45 1.) contain the product. These are combined and evaporated (Note 11), 20 ml. of absolute ethanol is added to the residue, and the mixture is heated on a steam bath for ca. 30 seconds to form a homogeneous solution. The solution is filtered hot through a Buchner funnel (medium-porosity fritted disk) and washed three times with 3-ml. portions of absolute ethanol. The solvent is then removed to constant weight of residue by rotary evaporation to yield 4.15-4.27 g. (96.7-99.5%) of benzyl sulfide as a white solid or as a colorless oil that crystallizes on standing (cooling on dry ice for ca. 1 minute may be required), m.p. 46.5-47.5°. This product is of sufficient purity for most purposes (Note 12). Further elution of the column with 1.1 1. of chloroform (same flow rate as above) and removal of solvent by rotary evaporation afford 3.94-4.06 g. (101-104%) of crude (ca. 95% pure) tris(dimethylamino)phosphine sulfide (Note 13).
1. To avoid benzene, dry toluene or acetonitrile can be used as solvents following the same procedure.
2. The hexamethylphosphorus triamide is obtained from the Eastman Kodak Company. It is distilled under reduced pressure (water aspirator) to yield a clear, colorless oil, b.p. 46-48° (7 mm.). It is then stored under nitrogen (rubber septums should be avoided as they tend to deteriorate on prolonged contact with phosphine vapors). Hexamethylphosphorus triamide that has not been freshly distilled often requires much longer reaction times. Since this chemical is an irritant, all operations with it should be performed in a well-ventilated hood. Hexamethylphosphoramide is a classified carcinogen; see Org. Syn., 55, 103 (1976). It should not be confused with hexamethylphosphorus triamide used in this preparation.