A series of dialkyl 2-amino-5-substituted-4-thiazolyl phosphonates I (R = CO2Et, cyano, (un)substituted Ph; R1 = Et, Me2CH) have been synthesized by the reaction of the substituted acetyl phosphonates II with formamidine disulfide dihydrobromide (III). However, the reaction between BzCH2P(O)(OEt)2 and III was carried out under similar condition, affording the expected product 2-amino-4-substituted-5-thiazolyl phosphonate IV only with low yield. The effects of the substituent in thiazole ring through bonding and nonbonding interactions are indicated by studying 1H and 31P NMR of the compounds I and IV. A series of substituted acetyl phosphonates II were prepared as synthetic intermediate. The keto-enol tautomerism of compound II was studied by 1H and 31P NMR.

Key words: THIAZOLE P, BIOLOGICAL ACTIVITY, REACTION MECHANISM, PHOSPHONIC ACID ESTER, AMINO GROUP, BACTERICIDAL AGENTS