5-Butyl-3,5-diaryl-4,5-dihydro-1,2,4-oxadiazoles, and a One-Step Synthesis of 4,4-Dibutyl-2-phenylbenzo-1,3-oxazine

Synthesis of Benzoxazines, Quinazolines and 4H-Benzo[e][1,3]thiazine by ANRORC Rearrangements of 1,2,4-Oxadiazoles

“…Compounds 6a, 6b, 7a and 7b were prepared by applying Srivastava's procedure. 6 As reported, 6 addition of n-butyllithium (1 equiv) to 3,5-diphenyl-1,2,4-oxadiazole (3a) at…”

“…It is known that n-butyllithium adds to C-5 of a 1,2,4oxadiazole ring (the most electrophilic site) initiating a cascade of ring opening/ring closing rearrangements (ANRORC type). 6 We have now studied two-step rearrangements of 1,2,4-oxadiazoles using n-butyllithium (2 to 4 equiv) as an external nucleophile, and potential O, S, and N nucleophiles attached to position-5. We also examined the behavior of the 1,2,4-oxadiazole ring in the presence of Grignard reagents as external nucleophiles.…”

Synthesis of Novel 3‐Aryl‐5‐dichloromethyl‐Δ2‐1,2,4‐oxadiazolines

“…1,3‐Dipolar cycloadditions between nitrile oxides and imines (Scheme b) have proved to be highly useful. Conversions of 1,2,4‐oxadiazoles to Δ 2 ‐1,2,4‐oxadiazolines have also been reported (Scheme c ; Scheme d ).…”

1,2,4- and 1,3,4-Oxadiazoles as Scaffolds in the Development of Antiparasitic Agents

“…For example, 1,2,4-oxadiazoles can react with strong nucleophiles such as n-butyllithium in THF (tetrahydrofuran) at -78 °C, via a nucleophilic addition, to form the derivatives depicted below (Figure 8). 36 However, 1,3,4-oxadiazoles do not react under the same reaction condition due to the fact they are much less electrophilic. It is certainly linked to the aromaticity of the 1,3,4-oxadiazolic core, which favors substitution in place of addition reactions.…”

“…In a recently published work, Karad et al 46 described the synthesis of 1,2,4-oxadiazoles as antimicrobial and antifungal agents. The properly substituted amidoximes (36) were obtained from the respective 2-morpholinoquinoline-3-carbonitriles (37). O-Acylation and cyclization steps were conducted in a one-pot reaction with the benzoic acids (38) in the presence of coupling reagent ethyl-(N',N'-dimethylamino)-propyl-carbodiimide hydrochloride (EDC.HCl).…”