Asian Journal of Research in Chemistry

An efficient and inexpensive approach to the synthesis of 2-substituted 1, 3, 4-oxadiazoles from arylhydrazides and orthoester is reported using catalytic PTSA. The optimized reaction is performed using catalytic PTSA in EtOH and is complete within 1 h for non aromatic orthoesters and 2–30 h for aromatic orthoesters. The reaction permits both electron releasing and electron withdrawing groups on the arylhydrazide substrate. Most products formed in high yield and require only minimal purification. The reaction proceeded smoothly and cleanly under mild reaction conditions and no side reactions were observed. The structures of the products were confirmed by IR, 1H NMR, 13C NMR, mass spectroscopy, and elemental analysis. Compared with early reports, the current reactions proceed in shorter time and require less of the orthoester.