A Facile Route to Diastereomeric Phosphorus Ylides. Chemoselective Synthesis of Dialkyl ( E)-2-[1-(2-Oxocyclopentylidene)ethyl]-2-butenedioates

Abstract

2-Acetylcyclopentanone undergoes a smooth reaction with triphenylphosphine and dialkyl acetylenedicarboxylates to produce dialkyl 2-(1-acetyl-2-oxocyclopentyl)-3-(1,1,1-triphenyl-λ ⁵-phosphanylidene)succinates. These compounds undergo intra-molecular Wittig reactions in boiling benzene to produce highly strained spirocyclobutene derivatives, which spontaneously undergo ring-opening reactions to produce dialkyl ( E)-2-[1-(2-oxocyclopentyliden)ethyl]-2-butenedioates.