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 convenient one-pot synthesis of 3,5-diarylisoxazoles via oxidative cyclisation using catalytic CuBr2 and oxone
作者:Ashish Bhatt、Rajesh K. Singh、Ravi Kant
DOI:10.1016/j.tetlet.2019.03.044
日期:2019.4
A facile one-pot synthesis of 3,5-diarylisoxazoles from α,β-unsaturated ketones and hydroxylamine hydrochloride is reported. The reaction is efficiently promoted by catalytic CuBr2 and Oxone to afford the desired products mostly in high yields and in relatively short time. The mild nature of the synthesis and short reaction time are notable advantages of the developed protocol. This protocol is effective
Copper-catalyzed aerobic oxidative C–O bond formation for the synthesis of 3,5-disubstituted isoxazoles from enone oximes
作者:Yadong Sun、Ablimit Abdukader、Haiyan Zhang、Wanle Yang、Chenjiang Liu
DOI:10.1039/c7ra11436b
日期:——
oxidative coupling reaction of enone oximes using a catalytic quantity of Cu(OAc)2. This method features an inexpensive metal catalyst, molecular oxygen as a green oxidant, good functional group tolerance and readily available starting materials. This attractive method for the synthesis of isoxazole derivatives is of great significance due to the product's versatile reactivity for further transformations.
3,5-Diarylisoxazoles 2 a-i were prepared in moderate to high yields (51-94%) by oxidation of chalcone oximes with a new metal complex oxidant, tetrakis(pyridine)cobalt(II) dichromate (TPCD).