Preparation of some phosphonic acids

Abstract

Β-Aminoethyl, α-aminopropyl-, [symbol]-aminopropyl-, α-aminoisopropyl, α-aminobutyl-, α-aminoisobutyl, α-aminopentyl-, α-aminoheptyl-, and α-aminohendecylphosphonic acids were synthesized utilizing the procedure devised by J. R. Chambers.¹ This procedure involves the Curtius degradation of the ester of a phosphonocarboxylic acid. Five of these amino acids, α-aminobutyl-, α-aminoisobutyl-, α-aminopentyl-, α-aminoheptyl-, α-aminohendecylphosphonic acids, were new compounds. Benzoyl derivatives of all nine of the amino phosphonic acids were prepared, and all of them were new compounds.Three of the amino phosphonic acids synthesized are analogs of naturally occurring amino carboxylic acids. Β-Aminoethylphosphonic acid is analogous to the Β-amino carboxylic acid, Β-alanine, α-aminoisobutylphosphonic acid is the phosphorus analog of valine, and y-aminopropylphosphonic acid is the analog of y-aminobutyric acid. Approximate pK values for B-aminoethyl-, α-aminopropyl-, [symbol]-aminopropyl-, α-aminoisopropyl, α-aminobutyl-, α-aminoisobutyl, α-aminopentylphosphonic acids were determined from potentiometric titrations of these compounds. Seven esters of phosphonocarboxylic acids were synthesized. Two of these compounds, triethyl α-phosphono valerate and triethyl α-phosphonoisovalerate, were new compounds. Several unsuccessful attempts were made to prepare trifluoromethylphosphonic acid. During these experiments, it was observed that potassium fluoride dehydrate acted upon diethyl trichloromethylphosphonate with the apparent cleavage of the carbon to phosphorus bond. The products which were tentatively identified were chloroform and triethyl phosphate. Anhydrous Potassium fluoride similarly cleaved the carbon to phosphorus bond with the formation of diethyl phosphonofluoridate and unidentified products.