TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The compound (A) is ammonium bromide, or ammonium iodide. The base of the step (E) is an alkali metal hydroxide (preferably sodium hydroxide, potassium hydroxide; especially sodium hydroxide). The acid in the step (F) is hydrochloric acid, or sulfuric acid (preferably hydrochloric acid).    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The organic solvent of the step (A) is N,N-dimethylformamide, and/or N,N-dimethylacetamide. The organic solvent of the step (C) is methylene chloride. The alcoholic solvent of the step (H) is methanol. Preferred Method: The pH of the reaction mixture in the step (F) is adjusted below 2. All the steps are performed at -10 degrees C to reflux temperature of the solvent used. EXAMPLE - 7-Phenylacetamido-3-chloromethyl-3-cephem-4-carboxylic acid-para-methoxybenzyl ester (100 g) was dissolved in N,N dimethylformamide (150 ml) at room temperature, triphenylphosphine (55 g) and ammonium bromide (19.46 g) were added under stirring, and the temperature was raised slightly to facilitate the reaction. After the completion of reaction in 2.5 hours, methylene chloride (500 ml) was added and the reaction mixture was cooled to 12-14 degrees C. The reaction mixture was then filtered and washed with methylene chloride (100 ml). After 10 minutes of stirring, 36% aqueous formaldehyde solution (108 g) and sodium hydroxide solution (10 g/100 ml) were added. After 40 minutes of further stirring of the reaction mixture, water (800 ml) and hydrochloric acid (5 ml, 36%) were added to this, so that the pH became less than 2. The organic layer was separated and aqueous layer was extracted with methylene chloride (2x 100 ml). The mixed organic layer was concentrated by distilling out methylene chloride. Methanol (1200 ml) was added to the concentrated mass and stirred for 1 hour to complete the precipitation. Remaining methylene chloride was distilled out and water (350 ml) was added. The reaction mixture was then cooled down to 10 degrees C, stirred for 1 hour, the solid was filtered, washed with aqueous methanol, and dried at 37 degrees C to yield 7-phenylacetamido-3-vinyl cephalosporanic acid-para-methoxy benzyl ester (78 g; chemical purity = more than 96.46% by HPLC).