Science of Synthesis

Hemming, K., Science of Synthesis, (2004) 13, 142.

The reaction of amidoximes ‌25‌ with acid chlorides gives O-acyl amidoximes ‌29‌ which, on heating, undergo ring closure to form 1,2,4-oxadiazoles (‌Table 4‌).[‌4‌,‌30‌,‌64‌,‌94‌,‌104‌–‌108‌] If the O-acylation is carried out at above 100°C, the 1,2,4-oxadiazole is formed directly. Recent modifications rely on the in situ formation of the O-acyl amidoxime in pyridine, followed by ring closure on heating in pyridine.[‌30‌,‌94‌] Functionalities such as chloromethyl,[‌108‌] trichloromethyl,[‌30‌] (acetoxy)(alkyl)methyl,[‌30‌] and carboxylate[‌107‌] on the acid chloride allow further manipulations of the 3-substituent on 1,2,4-oxadiazole, whereas the use of formyl fluoride allows access to monosubstituted 1,2,4-oxadiazoles[‌34‌] (‌9‌, R2 = H). Some examples are shown in ‌Table 4‌.

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M8	M8	Meeeeeeeee	Meeee (%)	Mee
8-MeM8M8MM8MM8	MM8Me	MMM, eeeeee, 8.8 e	88	[‌888‌]
	Me	8. Me8M ee MMMe8 8. eeeeeee eeeeeee	88	[‌888‌]
Me	Me	eeeeeeee, eeeeee, 88 eee	88	[‌88‌]
Me	Me	eeeeeeee, eeeeee, 88 eee	88	[‌88‌]
Me	8-MeMM8M8	eeeeeeee, eeeeee, 88 eee	88	[‌88‌]
	MMe8	Me8MMM8M, 88–88°M	88	[‌88‌]
	MM(M8)MMe	8. M8MM8 ee eeeeeee 8. 888°M	88–88	[‌88‌]

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8-Meeeee-8-eeeeee-8,8,8-eeeeeeeeee (‌8‌, M8 = Me; M8 = Me); Meeeeee Meeeeeeee:[‌88‌]

MeMe (8.8 eM) eee eeeee ee e eeeeeee eeeeeeeeee ee eeeeeeeeeeeee (‌88‌, M8 = Me; 8.8 e, 88.8 eeee) ee eeeeeeee (8 eM). Meee eeeeeeee, eee eeee eeeeee, eee eeeeeee eee eeeeeeeee eee 88 eee, eeeee eeeee eee eeeeeeeeeeeee eeeee eee ee eeeeeeee ee MMM. Mee eeee eee eeeeee ee ee, eeeeeee eeee M8M (88 eM), eee eeeeee ee e eeeeeeeeeeee eeeeeeeee. Mee eeeeeeeee eeeeeeeeeee eee eeeeeeeee ee eeeeeeeeee, eeeeee eeee M8M, eee eeeee; eeeee: 8.88 e (88%); ee 88–88°M.

References

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• 8.Meeeee-Meee, (8888) 8, 888.
• 8.Meeeee-Meee, (8888) M 8e, 888.
• 8.Meeeee-Meee, (8888) M 8e, 888.