A systematic investigation of radical haloacetal cyclizations (Ueno-Stork reaction) where the acetal center is the unique stereogenic element is reported. This highly diastereoselective reaction can be used for the preparation of polysubstituted tetrahydrofurans and gamma-lactones. We report herein the full experimental details of reactions where up to three new chiral centers are created. To demonstrate
Disulfides and Boryl Sulfides Serve as both Initiators and Precatalysts in Radical Reductions of Halides by an N‐Heterocyclic Carbene⋅Borane
作者:Xiangcheng Pan、Jacques Lalevée、Emmanuel Lacôte、Dennis P. Curran
DOI:10.1002/adsc.201300752
日期:2013.12.16
AbstractDiphenyl disulfide (PhSSPh), a typical boryl monosulfide (diiPr‐Imd‐BH2SPh) and a typical boryl bis‐sulfide [diMe‐Imd‐BH(SPh)2] all serve as both initiators and precatalysts in the reduction of alkyl and aryl halides by readily available 1,3‐dimethylimidazol‐2‐ylidene⋅borane (diMe‐Imd‐BH3). The reactions are suggested to occur by a polarity reverse catalysis mechanism where in situ generated thiophenol is the active catalyst.magnified image