Hot water as a mild Bronsted acid catalyst in ring opening reactions of epoxides
Ring opening of extremely hydrophobic epoxides with water, amines, sodium azide and thiophenol was realized in the mixture solvent of water and 1, 4-dioxane under reflux condition. Hot water was believed to act as a mild Bronsted acid catalyst in the epoxide-opening reactions.
Xu, Zhaobing,Qu, Jin
experimental part
p. 1718 - 1725
(2012/04/18)
Anionic Zirconaoxiranes as Nucleophilic Aldehyde Equivalents. Application to Intermolecular Pinacol Cross Coupling
Selective intermolecular pinacol cross coupling is achieved by reaction of anionic zirconaoxiranes with aromatic aldehydes and ketones, thereby providing an efficient route to unsymmetrical vicinal diols.
Askham, Fredric R.,Carroll, Kevin M.
p. 7328 - 7329
(2007/10/02)
Diastereomerically Pure 3-(Silyloxy)oxetanes by a Selective Paterno-Buechi Reaction
Diastereomerically pure 3-oxetanes 3 were prepared in moderate to good yields (45-72percent) by the Paterno-Buechi reaction of silyl enol ethers 2 with benzaldehyde.The phorocycloaddition exhibits a high degree of regio- and diastereoselectivity.The substituents R in the silyl enol ether have been varied , and it was found that steric bulk is mainly responsible for enhanced selectivity (diastereoselectivity from 70:30 up to 95:5).The regiochemical control is perfect (regioselectivity > 95:5) except for silyl enol ether 2a (R = Me) in the case of which a 90:10 ratio of regioisomers was observed.Irradiation of the reaction mixture at lower temperature (-25 deg C) led to a further improvement of diastereoselectivity.The relative configuration of the products obtained was elucidated both by 1H-NMR spectroscopy and by chemical degradation.As a mechanistic hypothesis to explain the high observed diastereoselectivity we propose that the steric environment in the intermediate diradical 11 determines the stereoselectivity according to two possible reaction pathways, i.e. bond formation and retrocleavage. - Key Words: Paterno-Buechi reaction / Oxetanes / Diastereoselectivity / Enol silyl ethers / Photocycloaddition
Bach, Thorsten,Joedicke, Kai
p. 2457 - 2466
(2007/10/02)
Stereoselektivitaet und relative Reaktivitaet bei der Reaktion von Organotitan- und -zirconium-Agentien mit Carbonylverbindungen
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Reetz, Manfred T.,Steinbach, Rainer,Westermann, Juergen,Urz, Ralf,Wenderoth, Bernd,Peter, Roland
p. 133 - 134
(2007/10/02)
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