Direct synthesis of 2,4,5-trisubstituted imidazoles and di/tri-substituted pyrimidines via cycloadditions of α,β-unsaturated ketones/aldehydes and N′-hydroxyl imidamides
作者:Ping Wu、Xueguo Zhang、Baohua Chen
DOI:10.1016/j.tetlet.2019.03.025
日期:2019.4
di/trisubstituted pyrimidines via iron-catalyzed cross-dehydrogenative coupling (CDC), with excellent tolerance and yields, has been developed. In this report, α,β-unsaturatedaldehydes/ketones and N′-hydroxyl imidamides undergo [3+2] and [3+3] cycloadditions in two processes, involving iron-mediated Michael reaction, Robinson Annulation and 1,5-electrocyclization.
1‐Arylvinyl formates as a kind of new CO surrogate have been explored for the first time. Most of the known CO precursors usually produce undesired residuals, which have to be removed. In this strategy, after CO release, the in situ generated acetophenones from 1‐arylvinyl formates can be successfully applied as a good ketone source in the synthesis of chalcones with benzaldehydes via a palladium‐catalyzed
Synthesis of Functionalized Pyrazolo[1,5-a]pyridines: [3+2] Cycloaddition of N-Aminopyridines and α,β-Unsaturated Carbonyl Compounds/Alkenes at Room Temperature
through oxidative [3+2] cycloaddition of N-aminopyridines with α,β-unsaturatedcarbonylcompounds or electron-withdrawing olefins is described. The reactions proceed in N-methylpyrrolidone as the solvent under metal-free conditions at room temperature. The synthesis of functionalized pyrazolo[1,5-a]pyridines through oxidative [3+2] cycloaddition of N-aminopyridines with α,β-unsaturatedcarbonyl compounds
摘要 描述了通过N-氨基吡啶与α,β-不饱和羰基化合物或吸电子烯烃的氧化[3 + 2]环加成反应,合成官能化的吡唑并[1,5- a ]吡啶。反应在室温下在无金属条件下在N-甲基吡咯烷酮作为溶剂中进行。 描述了通过N-氨基吡啶与α,β-不饱和羰基化合物或吸电子烯烃的氧化[3 + 2]环加成反应,合成官能化的吡唑并[1,5- a ]吡啶。反应在室温下在无金属条件下在N-甲基吡咯烷酮作为溶剂中进行。
Iron(III)/Iodine-Catalyzed C(<i>sp</i><sup>2</sup>)H Activation of α,β-Unsaturated Aldehydes/Ketones with Amidines: Synthesis of 1,2,4,5-Tetrasubstituted Imidazoles
An efficient methodology to access a library of 1,2,4,5-tetrasubstitutedimidazoles from a broad range of amidines and α,β-unsaturatedaldehydes/ketones via a C(sp2)H amination has been developed. This method represents a new and simple way to prepare highly substituted imidazoles from easily available starting materials, inexpensive catalysts, and with good functional group tolerance in good to excellent
A transition metal-free iodinecatalyzedsynthesis of indolizine derivatives through [3+2] cyclization of 2-pyridylesters and chalcones has been described. The method is efficient to synthesize a variety of substituted indolizines including hetero aromatic indolizines. Mechanistic studies reveal that, the reaction follows the radical pathway.