Syntheses of Fluorinated 1,3-Oxazoles, 1,3,4-Oxadiazoles, 1,3,4-Thiadiazoles, and Oxazolo[4,5-d]pyrimidines

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)

“…The transformations similar to those shown in Scheme 15, 16 later were carried out on the substrates with fluorinated substituents, [27] and new 1,3,4‐oxadiazoles 55 (R 1 , R 2 – fluoroalkyl, fluoroaryl) were obtained in such way.…”

“…[26] Interestingly, after interaction of 2-R-5-hydrazinyl-4-cyano-1,3-oxazoles 52 with chloroanhydrides in pyridine, products 53 of simple acylation of hydrazine group were hardly isolated, because they ). [22] The transformations similar to those shown in Scheme 15, 16 later were carried out on the substrates with fluorinated substituents, [27] and new 1,3,4-oxadiazoles 55 (R 1 , R 2fluoroalkyl, fluoroaryl) were obtained in such way.…”

“…The conversion of thiosemicarbazides 69 (Scheme 20) containing nitrile group in 4 th position of oxazole cycle and fluorinated substituent in 2 nd position was similar to the previous scheme. After 1,3,4‐thiadiazole and new oxazole fragments were alternately formed, the heating in acetic acid caused the oxazole cycle opening and decarboxylation; [27] but in this case, interestingly, amide group formed with the participation of fluorine‐containing acid was stable.…”