A New Chemoselective Base-Mediated Protection/Deprotection Method for Aldehydes
作者:Darren J. Dixon、Mark S. Scott、Chris A. Luckhurst
DOI:10.1055/s-2003-42470
日期:——
wide range of aldehydes was efficiently protected as pyrrole carbinol derivatives by direct addition of lithium pyrrolate in THF at -78 °C. The protection is chemoselective towards aldehydes over ketones and the O-lithiated, O-protonated or O-silylated carbinols may be used to block the aldehyde from nucleophilic and basic reagents at low temperatures. Mild, basic deprotection using DBU, NaOMe or TBAF
A stereocontrolled approach to electrophilic epoxides
作者:Otto Meth-Cohn、Clive Moore、Heinrich C. Taljaard
DOI:10.1039/p19880002663
日期:——
Lithium t-butyl hydroperoxide (easily generated by addition of an alkyl-lithium to anhydrous t-butyl hydroperoxide in THF solution) is a powerful reagent for the epoxidation of electrophilic alkenes at –20 to 0 °C under full stereocontrol.
Highly (<i>E</i>)-Selective Wadsworth−Emmons Reactions Promoted by Methylmagnesium Bromide
作者:Timothy D. W. Claridge、Stephen G. Davies、James A. Lee、Rebecca L. Nicholson、Paul M. Roberts、Angela J. Russell、Andrew D. Smith、Steven M. Toms
DOI:10.1021/ol802212e
日期:2008.12.4
An experimentally simple protocol for the very highly (E)-selective Wadsworth-Emmonsreaction [(E):(Z) selectivities in excess of 180:1 in some cases] of a range of straight-chain and branched aliphatic, substituted aromatic, and base-sensitive aldehydes via reaction with an alkyl diethylphosphonoacetate and MeMgBr is reported.
Homochiral lithium amides for the asymmetric synthesis of β-amino acids
作者:Stephen G. Davies、Narciso M. Garrido、Dennis Kruchinin、Osamu Ichihara、Luke J. Kotchie、Paul D. Price、Anne J. Price Mortimer、Angela J. Russell、Andrew D. Smith
DOI:10.1016/j.tetasy.2006.05.008
日期:2006.7
Secondary homochiral lithium amides derived from α-methylbenzylamine undergo highly diastereoselective conjugate additions to a range of α,β-unsaturated esters. The corresponding β-aminoacids are readily liberated by successive N-debenzylation and ester hydrolysis, furnishing (R)-β-amino butyric acid, (R)-β-amino pentanoic acid, (S)-β-leucine, (R)-β-amino octanoic acid, (S)-β-phenylalanine, (S)-β-tyrosine
作者:Denisa Hidasová、Martin Janák、Emanuela Jahn、Ivana Císařová、Peter G. Jones、Ullrich Jahn
DOI:10.1002/ejoc.201801139
日期:2018.10.9
With a single jump anti‐β‐amino‐α‐hydroxy esters or amides are obtained by merging polar aza‐Michael additions of chiral 1‐phenylethylamides to α,β‐unsaturated carboxylic acid derivatives and diastereoselective radical coupling with persistent free radical TEMPO.