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)

Abstract

The recyclizations of 5‐amino‐ and 5‐hydrazine‐1,3‐oxazoles mainly with electron‐withdrawing group in 4th position are considered. The chemical behavior of these heterocycles is due to the presence of two hidden amide fragments; therefore, the recyclization processes include a stage of nucleophile attack on 2nd or 5th position of the oxazole cycle. When the nitrile group is present in 4th position, it is often involved in the recyclization forming α‐aminoazoles. 5‐Amino/hydrazine‐1,3‐oxazoles undergo recyclization both in nucleophilic (amines, hydrazine, thionating agents) and electrophilic medium ((trifluoro)acetic acid, other acylating agents). The numerous types of functionalized heterocycles can be easily obtained with the usage of these recyclizations, such as the derivatives of 3‐amino‐6,7‐dihydro‐5H‐pyrrolo[1,2–a]imidazole, imidazolidine‐2,4‐dione, 1H‐pyrazole‐3,4,5‐triamine, 5,6‐diamino‐2,3‐diphenylpyrimidin‐4(3H)‐one, 2‐(2‐R‐7‐oxo‐5‐(trifluoromethyl)oxazolo[5,4–d]pyrimidin‐6(7H)‐yl)acetic acid, 2‐R‐4‐(5‐R′‐1,3,4‐oxadiazol‐2‐yl)oxazol‐5‐amine, (amino(5‐amino‐1,3,4‐thiadiazol‐2‐yl)methyl)phosphonate.