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.
N–H insertion reactions of rhodium carbenoids. Part 1. Preparation of α-amino acid and α-aminophosphonic acid derivatives
作者:Enrique Aller、Richard T. Buck、Martin J. Drysdale、Leigh Ferris、David Haigh、Christopher J. Moody、Neil D. Pearson、J. Bobby Sanghera
DOI:10.1039/p19960002879
日期:——
Rhodium(II) acetate-catalyseddecomposition of diazophenylacetates 1 and 3 in the presence of a range of N–H compounds results in an N–H insertion reaction of the intermediate carbenoids and formation of N-substituted phenylglycine derivatives 2 and 4. The corresponding reactions of dimethyl α-diazobenzylphosphonate 5 constitute a simple route to aminophosphonates 6.
Skipped dienes are not only present in fatty acid primary metabolites and natural products but also serve as reactive intermediates in diverse chemical synthesis. Despite this, the regioselective and stereoselective synthesis of skipped dienes remains a challenging goal. Strain release in organic molecules is a powerful tool for creating chemical complexity under mild conditions. The reactivity of
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%.
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.
H–F bond insertions into α-diazo carbonyl compounds
作者:Laiéli S. Munaretto、Rafael D. C. Gallo、Luiz Paulo M. O. Leão、Igor D. Jurberg
DOI:10.1039/d2ob00400c
日期:——
A reaction for H–F bond insertion into α-diazo carbonylcompounds is reported. The protocol describes a simple reaction setup employing commercially available HF·pyr (Olah reagent) as the fluorine source. The method is rapid and practical, and allows access to a broad range of α-fluorinated carbonylcompounds in generally good yields.