METHYL-1-PHENYL-1-PHOSPHA-3-CYCLOPENTENE 1-OXIDE

1-Dichloro- l-phenyl-3-methyl-l-phospha-3-cyclopentene. A dry 1-1. suction flask (Note 1) is charged with 179 g. (1.00 mole) 

A suction flask provides a strong-walled reactor that is conveniently stored for the reaction period. 

Material obtained from the Victor Chemical Works is suitable after redistillation. 

Shell Chemical material (92% minimum purity) was used. It was noted by the checkers that redistilled isoprene gave slightly better yields. The excess isoprene serves both as a solvent and for mass action. Moreover, dichlorophenylphosphine tends to dissolve in the product, and excess isoprene, by extracting the solid, promotes completion of reaction. 

Ionol is a commercial antioxidant, 2,6-di-/cr/-butyl- -cresol, manufactured by Shell Chemical Corp. Inhibitors appear to minimize formation of polymeric side products, although with isoprene the effect is often small. 

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A soln. of phenyldichlorophosphine and commercial isoprene containing lonol (2,6-di-fert-butyl-p-cresol) as antioxidant allowed to stand 5-7 days at room temp, in a stoppered flask, the resulting 1,1-dichloro-1-phenyl-3-methyl-1-phospha-3-cyclopentene stirred into ice-water, and stirring continued until essentially all of it is dissolved 3-methyl-l-phenyl-l-phospha-3-cyclopentone 1-oxide. Y 57-63%.—This is a general reaction, and there can be a wide variety of alkyl, aryl, and halogeno substituents on the diene and phosphorus. W. B. McCormack, Org. Synth. 43, 73 (1963). 

Methyl-l-phenyl-l-phospha-3-cyclopentene 1-oxide has been prepared only as described here.2... 

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