Realization of Complete Regiochemical Control during the Conversion of Squarate Esters into Complex Linear and Angular Polyquinanes. The Consequences of Incorporating a Leaving Group into One of the Alkenyllithium Reactants
作者:Leo A. Paquette、Julien Doyon
DOI:10.1021/jo962181m
日期:1997.3.1
A useful method is presented for controlling whether linear or angular triquinanes are formed during a reaction cascade initiated by the 2-fold addition of alkenyl anions to diisopropyl squarate, The key feature of the process involves the incorporation of a leaving group into one of the original nucleophilic reagents. Placement of the nucleofuge within a cyclic anion leads ultimately to formation of a linear product. Extracyclic and intracyclic options are possible, with preference given to the better leaving group when a competitive situation exists, When the leaving group is incorporated into an acyclic component, angular triquinanes result instead. Several other aspects of this impressive scaffolding scheme are detailed.