Synthesis Of Polysubstituted Pyrazoles And Polysubstituted Xanthones

There are two parts in this thesis, one is the base-promoted selective synthesis of polysubstituted pyrazoles from the reactions of aryloxyenynes with hydrazines. The other is the base-promoted synthesis of polysubstituded xanthones from the reactions of alkynones with 1,3-dicarbonyl compounds. It was interesting to note that in the presence of palladium catalysts the selective formation of xanthones was successfully achieved, and no phenols were obtained in most cases.In part one, we have developed a convenient base-promoted procedure for the formation of polysubstituted pyrazoles. Twelve desired products were selectively synthesized in good yields under mild conditions. They were characterized by1H NMR,13C NMR and HRMS spectroscopy, one of which was confirmed by X-ray single crystal diffraction.In part two, a base-promoted one-pot synthesis of by the tandem reactions of alkynones with 1,3-dicarbonyl compounds was developed. It was realized by a selective Michael addition reaction and an interesting C-C bond cleavage of 1,3-dicarbonyl compound. Fourteen desired xanthones, ten phenols and two intermediates were synthesized. It is worth noting that in the presence of palladium catalyst only xanthones were formed, and phenols were not observed in most cases. All new compounds were characterized by1H NMR, 13C NMR and HRMS spectroscopy. The structure was confirmed by X-ray crystallographic analysis.