Diastereoselectivity in the OH insertion reactions of rhodium carbenoids derived from phenyldiazoacetates of homochiral alcohols
摘要:
Rhodium(II) acetate catalysed decomposition of the phenyldiazoacetates 3 in the presence of alcohols (methanol, propan-2-ol, tert-butanol) led to the O-II insertion products 4-6 in varying yields; the diastercomeric excess of the product ranged from 5-53%.
Diastereoselectivity in the O-H Insertion Reactions of Rhodium Carbenoids Derived from Phenyldiazoacetates of Chiral Alcohols. Preparation of .alpha.-Hydroxy and .alpha.-Alkoxy Esters
摘要:
A series of phenyldiazoacetates 3 derived from enantiomerically pure alcohols ((-)-borneol, (+)menthol, (-)-menthol, (-)-8-phenylmenthol, (-)-trans-2-phenylcyclohexanol, (+)-trans-2-phenyl-cyclohexanol, and (-)10-(dicyclohexylsulfamoyl)-D-isoborneol) were prepared from the corresponding alpha-keto esters 1 by way of the tosylhydrazones 2. Rhodium(II)-catalyzed decomposition of the diazoacetates 3 in the presence of water or alcohols resulted in carbenoid O-H insertion reactions to give the corresponding 2-hydroxy- or 2-alkoxyphenylacetates in good yield, but with varying degrees of diastereoselectivity. A range of rhodium(II) and other metal catalysts were investigated, with rhodium(II) acetate and rhodium(II) acetamide giving the best results. The stereochemistry of the major diastereomer was proved in most cases by independent synthesis from a mandelic acid derivative of known configuration. Possible mechanisms are discussed.
Investigation of chiral induction in photochemical oxetane formation
作者:H. Koch、J. Runsink、H.-D. Scharft
DOI:10.1016/s0040-4039(00)88139-3
日期:1983.1
The formation of oxetanes from photochemicaladdition of tetramethylethylene (TME) or diethylketeneacetal with phenylglyoxylic acid esters in the “concave” position leads to high diastereomeric excess (de).
The use of α-bromoacetophenone and alcohols as starting materials provides easy access to a variety of α-ketoesters, which are important buildingblocks in organic synthesis. Additionally, metal-free conditions make this methodology more cost-effective compared to traditional metal-catalyzed methods. The wide substrate scope of this methodology means that a variety of different a-ketoesters can be
Diastereoselectivity in the O-H Insertion Reactions of Rhodium Carbenoids Derived from Phenyldiazoacetates of Chiral Alcohols. Preparation of .alpha.-Hydroxy and .alpha.-Alkoxy Esters
作者:Enrique Aller、David S. Brown、Geoffrey G. Cox、David J. Miller、Christopher J. Moody
DOI:10.1021/jo00119a023
日期:1995.7
A series of phenyldiazoacetates 3 derived from enantiomerically pure alcohols ((-)-borneol, (+)menthol, (-)-menthol, (-)-8-phenylmenthol, (-)-trans-2-phenylcyclohexanol, (+)-trans-2-phenyl-cyclohexanol, and (-)10-(dicyclohexylsulfamoyl)-D-isoborneol) were prepared from the corresponding alpha-keto esters 1 by way of the tosylhydrazones 2. Rhodium(II)-catalyzed decomposition of the diazoacetates 3 in the presence of water or alcohols resulted in carbenoid O-H insertion reactions to give the corresponding 2-hydroxy- or 2-alkoxyphenylacetates in good yield, but with varying degrees of diastereoselectivity. A range of rhodium(II) and other metal catalysts were investigated, with rhodium(II) acetate and rhodium(II) acetamide giving the best results. The stereochemistry of the major diastereomer was proved in most cases by independent synthesis from a mandelic acid derivative of known configuration. Possible mechanisms are discussed.
Diastereoselectivity in the OH insertion reactions of rhodium carbenoids derived from phenyldiazoacetates of homochiral alcohols
作者:Enrique Aller、Geoffrey G. Cox、David J. Miller、Christopher J. Moody
DOI:10.1016/s0040-4039(00)78227-x
日期:1994.8
Rhodium(II) acetate catalysed decomposition of the phenyldiazoacetates 3 in the presence of alcohols (methanol, propan-2-ol, tert-butanol) led to the O-II insertion products 4-6 in varying yields; the diastercomeric excess of the product ranged from 5-53%.