One-pot relay reduction–isomerization of β-trifluoromethylated-α,β-unsaturated ketones to chiral β-trifluoromethylated saturated ketones over combined catalysts in aqueous medium
Synthesis of trifluoromethyl-/cyclopropyl-substituted 2-isoxazolines by DBU-promoted domino reaction
作者:Xiao-Dong Liu、Hai-Yan Ma、Chun-Hui Xing、Long Lu
DOI:10.1016/j.cclet.2017.03.031
日期:2017.8
cyclopropyl substituted 2-isoxazolines were synthesized via a DBU-promoted domino reaction of β-trifluoromethyl-/β-cyclopropyl-substituted enones with hydroxylamine. The domino reaction consists of a Michael addition and the followed cyclization. A wide range of 3-substituted 5-cyclopropyl-5- trifluoromethyl-2-isoxazolines were obtained in good to excellent yields under mild reaction conditions. The method
Diastereoselective and Enantioselective Epoxidation of Acyclic β-Trifluoromethyl-β,β-Disubstituted Enones by Hydrogen Peroxide with a Pentafluorinated Quinidine-Derived Phase-Transfer Catalyst
efficient catalytic asymmetric epoxidation of β‐trifluoromethyl‐β,β‐disubstituted unsaturated ketones has been achieved by a pentafluorine‐substituted phase‐transfer catalyst with hydrogenperoxide (30%). Thus, the β‐trifluoromethyl‐α,β‐epoxy ketones with a quaternary carbon centre were obtained in excellent diastereoselectivities (up to 100:1 dr) and excellent enantioselectivities (up to 99.7% ee). Low catalyst
Efficient Access to Trifluoromethyl Diarylpyrrolines and their N-Oxides through Enantioselective Conjugate Addition of Nitromethane to β,β-Disubstituted Enones
The cupreidinium salt 1 catalyzes the highlyenantioselectiveconjugateaddition of nitromethane to β‐aryl‐β‐trifluoromethyl aryl enones (2). The biologically important chiral pyrrolines 4 and N‐oxide 5, having a trifluoromethylated all‐carbon quaternary chiral center, were easily synthesized from the key intermediate (R)‐3 in high to excellent yields. M.S.=molecular sieves.
An efficient transition-metal-free hydrodefluorination reaction of trifluoromethyl alkenes for accessing gem-difluoroalkenes is developed. It was surprising to find that the phosphoryl anion is able to mediate the defluorination.
Enantioselective Synthesis of Epoxides Having a Tetrasubstituted Trifluoromethylated Carbon Center: Methylhydrazine-Induced Aerobic Epoxidation of β,β-Disubstituted Enones
unprecedented title reaction is catalyzed by a methylhydrazine/base/organocatalyst (1) system. Biologically attractive epoxides (2) having a tetrasubstituted trifluoromethylated carboncenter were obtained with excellent enantioselectivity for the first time. 18O‐labeling experiments suggest a mechanism involving the activation of molecular oxygen. MTBE=methyl tert‐butyl ether.