

PREPARATION OF 1,3,4-OXADIAZOLES AND 1,3,4-THIADIAZOLES VIA CHEMOSELECTIVE СYCLOCONDENSATION OF ELECTROPHILICALLY ACTIVATED NITROALKANES TO (THIO)SEMICARBAZIDES OR THIOHYDRAZIDES

Abstract
Unusual reaction proceeding via the electrophilic activation of nitroalkanes in the presence of polyphosphoric acid has been discovered. Subsequent nucleophilic attack with semicarbazides or thiosemicarbazides allows to access 2-amino-1,3,4-oxadiazoles and 2-amino-1,3,4-thiadiazoles, respectively.
Keywords
nitroalkanes; 1,3,4-oxadiazoles; semicarbazides; 1,3,4-thiadiazoles; thiosemicarbazides; Brønsted acid catalysis; cascade reaction; nucleophilic cycloadition.
Latvian Institute of Organic Synthesis - Aizkraukles iela, 21, Riga, LV-1006, Latvia - hgs@osi.lv