Reactants ratio effect on direction of the cyclocondensation of hydrazine with 1,5-diarylpent-1-en-4-yn-3-ones: synthesis of the 4,5-dihydro-1H-pyrazole derivativesстатья
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Дата последнего поиска статьи во внешних источниках: 13 августа 2025 г.
Аннотация:The direction of the cyclocondensation of hydrazine with (E)-1,5-diaryl-substituted pent-1-en-4-yn-3-ones (cross-conjugated enynones) was determined by the reactants ratio in the reaction mixture. At the nearly equimolar ratio of enynone to hydrazine, 5-aryl-3-arylethynyl-4,5-dihydro-1H-pyrazoles were formed (in 46–92 % yields). With a fold excess of hydrazine, cyclocondensation occurred with the participation of the ketoethynyl fragment of enynone, and resulting in the formation of 3-(2-hydrazinylethyl)-1H-pyrazoles (yields 79–84 %). A mechanism explaining the effect of the reactants ratio on the cyclocondensation direction was proposed and confirmed using NMR spectroscopy experiments.