Abstract
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, diaziglyoxime 1 was treated with various aromatic or aliphatic isocyanates to give diazioxalimides 2 a high yield. Diazioxalimides 2 reacted with Ph3P to produce the iminophosphoranes 4; the reaction was directly heated from room temperature to 115 ℃ to get the desired diamino derivatives of bis-1,2,4-oxadiazole 4 in 72-92% yields. In synthesis method II, the same target compounds 4 were synthesized in a one-pot reaction by Ph3P and aromatic or aliphatic isocyanates in toluene for 10 h under 115 ℃ 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.
Keywords: Diamino derivatives of bis-1, 2, 4-oxadiazole, Staudinger reaction, Aza-Wittig reaction, diaziglyoxime, diazioxalimides
Graphical Abstract
[http://dx.doi.org/10.2174/1570178616666190725090906]
[http://dx.doi.org/10.2174/1570180815666180627121006]
[http://dx.doi.org/10.1021/acsomega.1c06294] [PMID: 35252669]
[http://dx.doi.org/10.1021/acsmedchemlett.9b00379] [PMID: 32184964]
[http://dx.doi.org/10.2174/1389557514666140329200745] [PMID: 24678879]
[http://dx.doi.org/10.1021/acs.jafc.1c00236] [PMID: 34137594]
[http://dx.doi.org/10.1021/acsmedchemlett.0c00532] [PMID: 33738065]
[http://dx.doi.org/10.1002/anie.201600068] [PMID: 26822007]
[http://dx.doi.org/10.1021/acs.cgd.0c00016]
[http://dx.doi.org/10.1021/cr300333u] [PMID: 23305185]
[http://dx.doi.org/10.1002/cber.18840170230]
[http://dx.doi.org/10.1016/j.inoche.2007.04.020]
[http://dx.doi.org/10.1002/chem.201406436] [PMID: 25649720]
[http://dx.doi.org/10.1021/acs.joc.1c00216] [PMID: 33861599]
[http://dx.doi.org/10.1016/j.tet.2006.09.048]
[http://dx.doi.org/10.1039/C9CS00478E] [PMID: 32658233]
[http://dx.doi.org/10.3987/COM-21-14600]
[http://dx.doi.org/10.1016/j.dyepig.2016.12.040]
[http://dx.doi.org/10.1021/jo202588j] [PMID: 22332823]
[http://dx.doi.org/10.1055/s-0036-1588308]
[http://dx.doi.org/10.1016/j.tet.2012.07.002]
[http://dx.doi.org/10.1016/S0040-4020(99)00692-4]