SYNTHESIS AND MOLECULAR-STRUCTURE OF CARBOXYALKENYLPHOSPHONIC, AND ALKENYLBISPHOSPHONIC DERIVATIVES

A series of carboxyalkenyl-, aminocarbonylalkenylphosphonic, and alken ylbisphosphonic derivatives has been synthesized. The synthesis of 2-e thoxycarbonylvinylphosphonates has been improved with a yield of 73% a nd an E/Z isomer ratio of 57/43. The separation of both isomers and th eir hydrolysis to the corresponding phosphonic acids have been studied . The synthesis of 2-ethoxycarbonyl-1-propenylphosphonates has been in vestigated, obtaining a global yield three times higher than that prev iously reported, and both E/Z isomers have been separated with a yield of 97.5%. Total and selective hydrolysis to the corresponding phospho nic acids have also been studied. By the appropriate choice of reactio n conditions the 2-cyanovinylphosphonate esters can be selectively and partially hydrolyzed to the 2-aminocarbonylvinylphosphonic acids. UV, IR, Raman, and H-1, C-13 and P-31 NMR spectroscopic studies have been performed in these compounds. Dipole moments and C=C/P=O conformation al populations have been calculated theoretically by ab initio methods . The effect of solvent polarity on the conformational population has been observed by IR spectroscopy, disclosing two C=C/P=O conformers. I ntramolecular hydrogen bonds have been found in (Z)-2-carboxy-1-propen yl and (Z)-2-carboxyvinylphosphonic acids. Experimental and theoretica l results have been compared and show very good agreement.