Microwave irradiation 1,2,4-oxadiazole synthesis

Bentiss, F., Lagrenee, M. and Barbry, D., Rapid synthesis of 2,5-disubstituted 1,3,4-oxadiazoles under microwave irradiation, Synth. Commun., 2001, 31, 935-938. 

Scheme 32 One-step synthesis of 1,3,4-oxadiazoles under microwave irradiation...

An efficient solvent-free synthesis of 1,2,4-oxadiazoles 235 was described using microwave irradiation by reaction of acyl chlorides with amidoximes <03H(60)2287>. The same kind of condensation was used for the synthesis of unnatural p and a-amino acids, 237 and 239 respectively, with an oxadiazole nucleus, using different derivatives of aspartic acid... 

Li et al. [30] gave the solvent free synthesis of 2-aryl-5-(coumarin-3 -yl)-l,3,4-oxadiazoles (xxv) in high yields by reacting the coumarin-3-carboxylic acid (xxiii) with (un)substituted benzoic acid hydrazides (xxiv) in presence of PEG supported dichlorophosphate under microwave irradiation. 

A single pot synthetic protocol for the synthesis of 2-sulphonamide-l,3,4-oxadiazoles from 1,2-diacylhydrazine (xxix) under microwave irradiation using PS-BEMP (xxxi) and corresponding sulfonyl chloride (xxx) is reported by Baxendale et al. [33]. 

Rostamizadeh S, Ghaieni HR et al (2010) Clean one-pot synthesis of 1,2,4-oxadiazoles under solvent-free conditions using microwave irradiation and potassium fluoride as catalyst and solid support. Tetrahedron 66 494-497... 

In related work, rapid synthesis of 1,2,4-oxadiazoles was achieved on polymer-supported reagents [109]. Two independent pathways were used to prepare these heterocycles from carboxylic acids and amidoximes under the action of microwave irradiation. In accordance with the conventional method using HBTU and N,N-diisopropylethylamine (DIEA) for synthesis of this heterocycle, a method utilizing polymer-supported bases was employed. The use of PS-BEMP in the presence of HBTU proved to be beneficial in the microwave procedure. Heating for 15 min in acetonitrile at 160 °C furnished high yields for a series of substrates. 1,2,4-Oxadiazoles can also be synthesized from carboxylic acid chlorides. Because these... 

Montazeri, N. and Rad-Moghadam, K. 2008. An expeditious and one-pot synthesis of unsym-metrical 2,5-disubstituted-l,3,4-oxadiazoles under microwave irradiation and solvent-free conditions. Chin. Chem. Lett. 19(10) 1143-1146. 

Brain et al. [86] suggested the synthesis of 1,3,4-oxadiazoles using a polymer-supported Buigess reagent (Scheme 11.33). Reactant 1,2-diacylhydiazines were taken and the product was purified by filtration through siUca gel. The product was obtained with up to 96% yield under microwave irradiation within 2-10 min. Kidwai et al. [87] reported iV-alkylation with 71-79% yield of the product under microwave irradiation (Scheme 11.34). 

The conventional synthesis of oxadiazoles takes about 90 min while this time is reduced to 5-10 min under microwave irradiation and sidewise, the yield is also improved. 

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