Highly Efficient One‐Pot Solvent‐Free Synthesis of 2,5‐Disubstituted‐1,3,4‐Oxadiazole via BTI ‐mediated Oxidation of N‐Acylhydrazone from Hydrazide and Aldehyde

2,5‐Disubstituted‐1,3,4‐oxadiazoles are prepared in excellent yields (up to 97%) under totally solvent‐free conditions by the quantitative formation of N‐acylhydrazone from the reaction of a hydrazide with an aldehyde using a ball‐mill for 10 min at room temperature followed by oxidation with BTI at 80°C for 1h.