Abstract. The reaction of 2-substituted 4-methallylthiosemicarbazides 1 with carbonyl compounds ca-talyzed by weak acids gives thiosemicarbazones 2 and 1, 2, 4-triazolidine-3- thiones 3. By contrast under strong acidic conditions the reaction occurs by electrophilic cyclisation with participation of the methallyl and thiono groups, and 4, 5-dihydro-l, 3- thiazoles 5 are formed after neutralisation. The electrophilic cyclisation of N-methallyl ...
