The Isomeric Enol Acetates of Acetylacetone. Evidence for an Unusual Stabilizing Interaction between cis Acetyl and Acetoxy Groups

Abstract

The configuration and conformation of the isomeric enol acetates of acetylacetone have been elucidated. P.m.r. shift data obtained by the use of tris(1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedionato)europium(III) (Eu(fod)3) allow assignment of the (S)-cis conformation to both isomers. The remarkable stability of the isomer having acetyl cis to acetoxy is attributed to neighboring group interaction, a rationale consistent with p.m.r. spectroscopic data.