Josiphos-Catalyzed Asymmetric Homodimerization of Ketoketenes
作者:Ahmad A. Ibrahim、Pei-Hsun Wei、Gero D. Harzmann、Nessan J. Kerrigan
DOI:10.1021/jo101867m
日期:2010.11.19
phosphine-catalyzed homodimerization of ketoketenes that provides access to a variety of highlysubstitutedketoketenedimerβ-lactones (11 examples) is reported. The Josiphos catalytic system displays good to excellent enantioselectivity (up to 96% ee). Ring-opening reactions of the enantioenriched ketoketenedimers were also carried out to access 1,3-diketones, enolesters, and β-hydroxyketones with good
Copper(I)‐catalyzed [2+2] cycloadditions of various ketenes with 2‐nitrosopyridine to afford synthetically highly valuable 1,2‐oxazetidine‐3‐ones are shown to occur with good enantioselectivities. The thermal uncatalyzed process furnishes the unstable regioisomeric oxazetidinone. Density function theory (DFT) calculations give evidence that the reaction occurs via a concerted [2+2] cycloaddtion pathway
作者:Ahmad A. Ibrahim、Gero D. Harzmann、Nessan J. Kerrigan
DOI:10.1021/jo8024785
日期:2009.2.20
A general method for the catalytic dimerization of ketoketenes is described. Tri-n-butylphosphine was found to be the optimal organocatalyst for the racemic reaction. When lithium iodide was used as an additive, the reaction was rendered selective for dimer formation (dimer/trimer >= 16:1). Ring-opening reactions of the ketoketene dimers as well as preliminary studies toward the development of an asymmetric variant are also reported.