Unexpected formation of 4-alkyl-5-(4-alkylthiosemicarbazido)-4,5-dihydro-1,2,4-triazine-3(2H)-thiones from 1,3-dialkyl-4,5-bis-(4-alkylthiosemicarbazido)imidazolidin-2-ones in acidic medium

4-Alkyl-5-(4-alkylthiosemicarbazido)-4,5-dihydro-1,2,4-triazine-3(2H)-thiones are obtained either by heating 1,3-dialkyl-4,5-bis-(4-alkylthiosemicarbazido)imidazolidin-2-ones in acidic medium or the reaction of 1,3-dialkyl-4,5-dihydroxyimidazolidin-2-ones with 4-methylthiosemicarbazide.