Reaction of diethyl 5-hydrazino-2-(4-methylphenyl)-1,3-oxazol-4-ylphosphonate with acyl isothiocyanates

Recyclization of 5‐Amino‐ oxazoles as a Route to new Functionalized Heterocycles (Developments of V.P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry of the NAS of Ukraine)

“…Under these conditions, hydrolysis of the phosphonate group of compounds 58 didn't occur; the hydrolysis of this group happened when thiosemicarbazides 57 recyclization was employed in hot acetic acid. [28] Also, phosphonate acids 59 were obtained by acid hydrolysis of the corresponding esters 58, which confirmed the sameness of substrates 56 recyclization under different conditions.…”

“…Due to the interaction of hydrazine 56 and acylisothiocyanate, it was possible to isolate thiosemicarbazides 57 : they were obtained under mild conditions in 5 min (Scheme 17), but subsequent boiling this reaction mixture in acetonitrile for 2 h led to oxazole recyclization and 1,3,4‐thiadiazoles 58 formation. Under these conditions, hydrolysis of the phosphonate group of compounds 58 didn't occur; the hydrolysis of this group happened when thiosemicarbazides 57 recyclization was employed in hot acetic acid [28] . Also, phosphonate acids 59 were obtained by acid hydrolysis of the corresponding esters 58 , which confirmed the sameness of substrates 56 recyclization under different conditions.…”