A radical coupling reaction of diverse vinylsulfones and epoxides was mediated by Cp2TiCl (Cp = cyclopentadienyl) to provide a straightforward synthetic pathway to hydroxy sulfones. The reaction was successfully achieved by using either an excess or a catalytic amount of the TiIII reagent. The scope of the reaction was studied for several different functionalized and substituted epoxides and vinyl
Reaction of oxiranes with alkali metals in aprotic solvents yields a variety of products depending on the nature of the metal and the structure of the oxirane. Deoxygenation to olefins is the major reaction in case of lithium. Rearrangement to carbonyl compounds, reduction to alcohols and formation of dimeric products occur when oxiranes are treated with sodium. All the reactions could be rationalised
Control of Homocoupling Versus Reduction in Titanium(III)-Mediated Radical Opening of Styrene Oxides
作者:José A. González-Delgado、Jesús F. Arteaga
DOI:10.1002/ejoc.201901625
日期:2019.12.31
Titanocene monochloride mediates the homolytic opening of styrene oxides in a chemoselectively controlled manner, leading either to homocoupling products or to phenethyl alcohol derivatives. Remarkably this protocol encompasses the diverse reactivity pattern of styrene oxides towards the desired products, thereby adding value to this interesting building block.
Diastereocontrol in Asymmetric Allyl–Allyl Cross-Coupling: Stereocontrolled Reaction of Prochiral Allylboronates with Prochiral Allyl Chlorides
作者:Laura A. Brozek、Michael J. Ardolino、James P. Morken
DOI:10.1021/ja2075967
日期:2011.10.26
Palladium-catalyzed allyl-ally cross-coupling was investigated with substituted prochiral allylic boronates. These reactions deliver products bearing adjacent stereocenters, and the issue of diastereocontrol is therefore paramount. Under appropriately modified conditions, this allyl allyl coupling strategy was found to apply to a range of substrates, generally occurring with high enantioselectivity (92:8 to >99:1 er) and good diastereoselection (4:1 to 14:1 dr).
Titanocene-Promoted Intermolecular Couplings of Epoxides with Nitriles. An Easy Access to β-Hydroxyketones
Radical couplings of epoxides and nitriles mediated by Cp2TiCl provide a diastereoselective route to the synthesis of beta-hydroxyketones. The conditions of this "aldol-like" reaction are mild enough to avoid the dehydration of the beta-hydroxyketone. The scope of the coupling reaction with functionalized and tetrasubstituted epoxides has been studied. The radical character of the coupling reactions is demonstrated.