Methylene chloride hydroxymethylene

In a 2-1. wide-necked Erlenmeyer flask are mixed 66.2 g. (0.525 mole) of 2-(hydroxymethylene)cyclohexanone (Note 1), 400 ml. of methylene chloride, and 106 g. (1.05 moles) of triethylamine (Note 2). The flask is cooled in an ice-salt bath at —12 to —15°, and 98.0 g. (0.500 mole) of p-toluenesulfonyl azide (Note 3) is added with vigorous mechanical stirring over a period of approximately 1 hour, at such a rate that the temperature of the reaction mixture does not rise above —5°. Stirring is continued for an additional 2 hours as the cooling bath melts. A solution of 30.8 g. (0.55 mole) of potassium hydroxide in 400 ml. of water is added, and the mixture is stirred for 15 minutes at room temperature. The resulting emulsion is placed in a 2-1. separatory funnel, the methylene chloride layer is separated after the emulsion has broken, and the aqueous alcoholic layer is... 

The active ingredients are diphosphonic acids - dicarboxypropane diphosphonic acid (DPD), hydroxymethylene diphosphonic acid (HDP or HMDP), hydroxyethylidene diphosphonic acid (EHDP), methylene diphosphonic acid (MDP) - or their sodium salts. As stabilizers are used N-(4-aminobenzoyl)-L-glutaminic acid, gentisic acid (2,5-dihydroxybenzoic acid), ascorbic acid, or carbamide. For reduction of Tc-pertechne-tate to lower oxidation states, tin(II) chloride and tin(II) fluoride are employed. 

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