Sodium Bicarbonate-Catalyzed Stereoselective Isomerizations of Electron-Deficient Propargylic Alcohols to (<i>Z</i>)-Enones
作者:John P. Sonye、Kazunori Koide
DOI:10.1021/jo0623944
日期:2007.3.1
Redoxisomerization is a synthetically important process because it creates two new functional groups in the product, among which is the isomerization of propargylic alcohols to conjugated enones. Although E-enones have been prepared by this approach, Z-enones could not be accessed. We previously reported DABCO-catalyzed E-selective isomerization of electron-deficient propargylic alcohols to enones
Base-Catalyzed Stereoselective Isomerization of Electron-Deficient Propargylic Alcohols to <i>E</i>-Enones
作者:John P. Sonye、Kazunori Koide
DOI:10.1021/jo060304p
日期:2006.8.1
stereoselective methods to isomerize electron-deficient propargylic alcohols to E-enones under mild conditions (EWG = electron-withdrawing group). Among weak bases we screened, catalytic (10−20 mol %) 1,4-diazabicyclo[2.2.2]octane (DABCO) was found to be effective in most cases. When the substrate is conjugated with an amide, the addition of sodium acetate catalyzed the isomerization.
Synthesis of γ-Acetoxy β-Keto Esters Through Regioselective Hydration of γ-Acetoxy-α,β-alkynoates
作者:Tapas R. Pradhan、Kishor L. Mendhekar、Debendra K. Mohapatra
DOI:10.1021/acs.joc.5b00400
日期:2015.6.5
The At(I)-catalyzed regioselective hydration of gamma-acetoxy-alpha,beta-acetylinic ester by the assistance of a neighboring carbonyl group has beets developed. Varieties of simple primary, secondary, and tertiary gamma-acetoxy-alpha,beta-acetylinic esters, even those bearing sensitive functional group in the remote reaction sites, are selectively hydrated to the corresponding beta-keto esters. The reaction' tolerates a wide variety of other carboxylates, such as benzoates, propionates, acrylates, and pivalates, including chiral carboxylates with retention of the configuration. The broad substrate scope, including the derivatization of complex natural products and neutral and open air conditions, makes this atom economical approach very practical. O-18 labeling experiments disclose that the oxygen transposition occurs from the carboxylate group to the triple bond, not from water.