photoepoxidation of α,β-unsaturated ketones driven by visible light in the presence of tetramethylguanidine (3b), tetraphenylporphine (H2TPP), and molecular oxygen under mild conditions was revealed. The corresponding α,β-epoxy ketones were obtained in yields of up to 94% in 96 h. The reaction time was shortened to 4.6 h by flow synthesis. The mechanism related to singlet oxygen was supported by experiments
Cascade annulation reaction (CAR): highly diastereoselective synthesis of pyranopyrazole scaffolds
作者:Manickam Bakthadoss、Manickam Surendar
DOI:10.1039/d0ra03400b
日期:——
An unprecedented domino protocol for the novel synthesis of highly diverse and functionalized tetrahydro pyranopyrazole scaffolds using chalcone epoxide has been reported for the first time. This synthetic protocol generates three consecutive stereogenic centres in a highlydiastereoselective manner with the formation of vicinal diol and a quaternary carbon centre. A wide range of substrates were utilized
Visible-light-induced epoxidation of α,β-unsaturatedketones is a kind of important chemical transformations, which could be applied for the synthesis of epoxypropane derivatives. Here, an efficient aerobic photoepoxidation protocol was reported. Through decatungstate-mediated photocatalysis, the aerobic Epoxidations of α,β-unsaturatedketones proceed well, furnishing the desired product in moderate
Visible-Light-Promoted Photoredox Syntheses of α,β-Epoxy Ketones from Styrenes and Benzaldehydes under Alkaline Conditions
作者:Jing Li、David Zhigang Wang
DOI:10.1021/acs.orglett.5b02629
日期:2015.11.6
A range of styrenes and benzaldehydes were smoothly combined to form alpha,beta-epoxy ketones under the synergistic actions of photocatalyst Ru(bpy)(3)Cl-2, tert-butyl hydroperoxide (t-BuOOH), cesium carbonate (Cs2CO3), and visible light irradiation. The process likely proceeds through visible-light-enabled photocatalytic generations of acyl radicals as key intermediates.