General synthesis of tetrasubstituted alkenyl-1,3,4-oxadiazoles

Tetrasubstituted alkenyl-1,3,4-oxadiazoles were synthesized in moderate to excellent yield, under mild conditions and in the presence of sensitive functional groups, via the cyclization of diacylhydrazides using PPh3 and hexachloroethane in the presence of Hünig’s base. An efficient one-pot acylation/cyclization approach for the conversion of acylhydrazides to 1,3,4-oxadiazoles is also described. The complexity of our substrate as well as the wide range of functional groups incorporated substantially broadens the scope of this methodology.