Hydroxyacetonitrile diphosphonic acid, a process for its production, and its use

A process for the preparation of a hydroxyacetonitrile diphosphonic acid or salt thereof corresponding to the following general formula ##STR15## in which each M independently is H or an alkali metal cation or the ammonium cation R.sup.5 R.sup.6 R.sup.7 R.sup.8 N.sup.+ in which R.sup.5, R.sup.6, R.sup.7 and R.sup.8 independently of one another are hydrogen or a branched or unbranched C.sub.1 -C.sub.12 alkyl radical, comprising the steps of

• A. reacting a 3-R.sup.2 -3-oxo-1-aminopropane-1,1-diphosphonic acid of the formula ##STR16## in which R.sup.1 represents a tertiary alkyl group having the general formula --(R.sup.2)C(R.sup.3)(R.sup.4), where R.sup.2 and R.sup.3 independently of one another represent a C.sub.1 -C.sub.3 alkyl group, and R.sup.4 is a C.sub.1 -C.sub.10 alkyl group,
• a cycloalkyl group which can be substituted by a methyl or ethyl group, or
• an aryl or heteroaryl group which can be substituted by halogen, C.sub.1 -C.sub.5 alkoxy, di-C.sub.1 -C.sub.5 alkylamino or C.sub.1 -C.sub.5 alkyl,
• with nitrous acid, wherein the molar ratio of nitrous acid to the compound of formula IV being in the range of from about 1:1 to about 6:1, at a temperature of from about 20.degree. to about 75.degree. C. to form a reaction mixture containing a compound of formula III;
• and
• B. isolating the compound of formula III from the reaction mixture.

A process for the preparation of a hydroxyacetonitrile diphosphonic acid or salt thereof corresponding to the following general formula ##STR17## in which each M is H or an alkali metal cation or the ammonium cation R.sup.5 R.sup.6 R.sup.7 R.sup.8 N.sup.+ in which R.sup.5, R.sup.6, R.sup.7 and R.sup.8 independently of one another are hydrogen or a branched or unbranched C.sub.1 -C.sub.12 alkyl radical, comprising the steps of:

• A. reacting a 3-R.sup.1 -3-oxo-1-aminopropane-1,1 diphosphonic acid or the formula ##STR18## in which R.sup.1 represents a tertiary alkyl group having the general formula --(R.sup.2)C(R.sup.3)(R.sup.4), where R.sup.2 and R.sup.3 independently of one another represent a C.sub.1 -C.sub.3 alkyl group, and R.sup.4 is a C.sub.1 -C.sub.10 alkyl group,
• a cycloalkyl group which can be substituted by a methyl or ethyl group, or
• an aryl or heteroaryl group which can be substituted by halogen, C.sub.1 -C.sub.5 alkoxy, di-C.sub.1 -C.sub.5 -alkylamino or C.sub.1 -C.sub.5 alkyl,
• with nitrous acid prepared in situ from an alkali metal nitrite and a dilute mineral acid wherein the molar ratio of nitrous acid to the compound of formula IV being in the range of from about 1:1 to about 6:1, at a temperature of from about 20.degree. C. to about 75.degree. C. to form a reaction mixture containing a compound of formula III;
• B. treating the reaction mixture with an acidic reagent to form a compound of formula III wherein all M groups are hydrogen;
• and, where the M groups of formula III are other than hydrogen,
• C. treating the compound of formula III where the M groups are hydrogen with a basic reagent of the formula M.sup.+ OH, where M.sup.+ is an alkali metal or ammonium cation R.sup.5 R.sup.6 R.sup.7 R.sup.8 N.sup.+, where R.sup.5, R.sup.6, R.sup.7 and R.sup.8 have the meaning given above, to form a compound of formula III in which M is an alkali metal or ammonium cation.