Pericyclic reactions of the enolate ions of 2,6,6-trimethylcyclohepta-2,4-dienone and 1,4,4-trimethylbicyclo[5.1.0]oct-5-en-2-one

Abstract

The rate at which the enolate ions of 2,6,6-trimethylcyclohepta-2,4-dienone (III), and 1,4,4-trimethylbicyclo-[5.1.0]oct-5-en-2-one (XII) undergo pericyclic reactions has been investigated by studying the n.m.r. spectra of the anions, and by methylation. In the case of (XII), Cope rearrangement of the enolate ion produces an isolable isomeric ketone. The thermal rearrangement of three 3-alkylcar-4-en-2-ones has been studied. Dehydration of 1,4,4-trimethylbicyclo[5.1.0]oct-5-en-2-ol (XX), and its 2-methyl homologue (XXII), using phosphorus pentaoxide–benzene or polyphosphoric acid, involves extensive, but stereospecific, structural changes producing di- and tri-methylisopropylbenzenes respectively.