Cyclization of arylhydrazones of cross-conjugated enynones: synthesis of luminescent styryl-1<i>H</i>-pyrazoles and propenyl-1<i>H</i>-pyrazoles
作者:Radik N. Itakhunov、Ivan S. Odin、Dmitry M. Gusev、Stanislav A. Grabovskiy、Kareem V. Gordon、Anna V. Vologzhanina、Sergey A. Sokov、Ilya M. Sosnin、Alexander A. Golovanov
DOI:10.1039/d2ob01427k
日期:——
5-disubstituted pent-1-en-4-yn-1-ones with arylhydrazines in acidified alcohol results mainly in the formation of the corresponding arylhydrazones with traces of the side products of cyclization at the double bond – 1,5-diaryl-3-(arylethynyl)-4,5-dihydro-1H-pyrazoles (pyrazolines). Arylhydrazones are cyclized only by refluxing in high-boiling polar solvents (DMF and ethylene glycol), with the selective formation
1,5-二取代的 pent-1-en-4-yn-1-ones 与芳基肼在酸化酒精中的缩合主要导致相应的芳基腙的形成,在双键处有痕量的环化副产物 – 1,5 -二芳基-3-(芳基乙炔基)-4,5-二氢-1 H-pyrazoles (pyrazolines). Arylhydrazones are cyclized only by refluxing in high-boiling polar solvents (DMF and ethylene glycol), with the selective formation of 1,5-disubstituted 3-styrylpyrazoles in up to 77–95% yields. Thermodynamically, the cyclization of arylhydrazones at the triple bond is the