Desymmetrization of 1,4-Dien-3-ols and Related Compounds via Ueno−Stork Radical Cyclizations
作者:Félix Villar、Olivier Equey、Philippe Renaud
DOI:10.1021/ol005613v
日期:2000.4.1
text] Desymmetrization of 1,4-dien-3-ols and related compounds via Ueno-Stork radicalcyclizations is reported. The stereochemistry of the cyclization is controlled by the acetal center. Excellent stereocontrol at C(4) and C(5) of the newly formed tetrahydrofuran rings is observed. Use of a chiral auxiliary allows the preparation of enantiomerically pure material. The utility of this method has been demonstrated
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
Polarity Reversal Catalysis in Radical Reductions of Halides by N-Heterocyclic Carbene Boranes
作者:Xiangcheng Pan、Emmanuel Lacôte、Jacques Lalevée、Dennis P. Curran
DOI:10.1021/ja300416f
日期:2012.3.28
ineffective radicalreductions of alkyl and aryl halides by N-heterocyclic carbene boranes (NHC-boranes) are catalyzed by thiols. Reductions and reductive cyclizations with readily available 1,3-dimethylimidazol-2-ylidene borane and a water-soluble triazole relative are catalyzed by thiophenol and tert-dodecanethiol [C(9)H(19)C(CH(3))(2)SH]. Rate constants for reaction of the phenylthiyl (PhS•) radical with
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