An Intramolecular Wittig Approach toward Heteroarenes: Synthesis of Pyrazoles, Isoxazoles, and Chromenone-oximes
作者:Pankaj V. Khairnar、Tsai-Hui Lung、Yi-Jung Lin、Chi-Yi Wu、Srinivasa Rao Koppolu、Athukuri Edukondalu、Praneeth Karanam、Wenwei Lin
DOI:10.1021/acs.orglett.9b01395
日期:2019.6.7
α-Halohydrazones/ketoximes are transformed into trisubstituted pyrazoles/disubstituted isoxazoles by treatment with phosphine, acyl chloride, and a base. Mechanistic investigations revealed the in situ formation of azo/nitroso olefin intermediates which underwent a tandem phospha-Michael/N- or O-acylation/intramolecular Wittig reaction to afford the heteroarenes in moderate to good yields. Further
A copper-mediatedsynthesis of 4-(trifluoromethyl)pyrazoles is described. In one step from readily accessible α,β-alkynic tosylhydrazones, a remarkable domino sequence of cyclization, trifluoromethylation, and detosylation takes place to furnish the 4-CF3N-H pyrazole cores with good functional group compatibility. The reaction conditions are mild and convenient, at room temperature in air, using the
描述了铜介导的4-(三氟甲基)吡唑的合成。从易于获得的α,β-炔基甲苯磺酰nes的一个步骤中,发生了显着的环化,三氟甲基化和脱甲苯基化的多米诺序列,为4-CF 3 N -H吡唑核提供了良好的官能团相容性。使用可商购的三氟甲基三甲基硅烷(TMSCF 3)作为CF 3源,在空气中于室温下,反应条件温和且方便。该方法可以应用于抗炎药塞来昔布的4-CF 3类似物的合成。
Efficient Copper-Catalyzed Synthesis of Substituted Pyrazoles at Room Temperature
method for the synthesis of pyrazoles through a copper-catalyzed condensation reaction has been developed. The new catalytic system not only maintained a broad substrate scope but was also active under acid-free reaction conditions, overcoming the conventional requirement for an acid-catalyzed system. Furthermore, the copper catalyst enabled this reaction to be performed at roomtemperature and in a short