Julien Doyon

Acetylide anions exert complete control over aldolization during the direct conversion of squarate esters into polyquinanes

Abstract The sequential condensation of diisopropyl squarate with a vinyl anion and a lithium acetylide triggers a cascade of mechanistic events that eventuates in formation of highly functionalized unsaturated diquinanes.

Sequenced reactions involving squarate esters. The first suggestion that helical equilibration within the advanced octatetraene intermediate is responsible for stereochemical control

When a chiral (racemic or nonracemic) alkenyl anion is added to a squarate ester, an approximate 1:1 mixture of diastereomers results. Further reaction with a second alkenyl anion leads only to a single product, a finding compatible with helical equilibration at the 1,3,5,7-octatetraene stage of the cascade.

Reaction cascades based on squarate esters. 1,3-Dioxolane as a chaperone functional group for lithium ions

Abstract The consequences of adding enantiomerically pure 1-lithiocyclohexene-5,6-diol acetonide and 1-cyclopentenyllithium seriatim to diisopropyl squarate has been studied. The first-stage addition leads to a chromatographically separable mixture of diastereomeric keto alcohols, which are formed in a ratio approximating 1:1. Separate reaction of these intermediates with the second cycloalkenyl anion initiates a cascade of chemical steps. The consequences of the second-stage stereoselectivity are profound in dictating the manner in which the polycyclic end products are formed.