Two efficient, scalable routes to bis-1,2,4-oxadiazole have been developed by tandem Staudinger/aza-Wittig reaction from the same starting material diaziglyoxime, isocyanates and triphenylphosphonium in good yields.Background:Two convenient and efficient routes for synthesizing diamino derivatives of bis-1,2,4-oxadiazoles were described.Objective:This study provides a simple protocol for the synthesis of bis-1,2,4-oxadiazoles.Methods:The two procedures were based on a tandem Staudinger/aza-Wittig reaction from the same starting material of diaziglyoxime, isocyanates and triphenylphosphonium.Results:In synthesis method I, diaziglyoxime1was treated with various aromatic or aliphatic isocyanates to give diazioxalimides2a high yield. Diazioxalimides2reacted with Ph3P to produce the iminophosphoranes4; the reaction was directly heated from room temperature to 115°C to get the desired diamino derivatives of bis-1,2,4-oxadiazole4in 72-92% yields. In synthesis method II, the same target compounds4were synthesized in a one-pot reaction by Ph3P and aromatic or aliphatic isocyanates in toluene for 10 h under 115 °C in 53-71% yields.Conclusion:The two procedures provide proficient methods of making nitrogen-containing heterocyclic rings. The structures of target compounds 4 were identified by IR,1HNMR,13CNMR and HRMS.