Thermal rearrangements of tropolone ethers. Part 4

Abstract

The Claisen rearrangements of prop-2-ynyl ethers of 3-chloro- and 3-phenyl-tropolone are described. Products arising from an apparent [3,7] sigmatropic shift predominate in the thermolysis of 3-chloro-2-(prop-2-ynyloxy)-tropone, but the corresponding 3-phenyltropolone ether rearranges largely via the normal [3,3] shift. The occurrence of a novel [1,9] sigmatropic inter-oxygen alky migration in thermolyses of benzyl and cyclopropyl methyl ethers of tropolones is described, together with silatropic shifts in tropolone trimethylsilyl ethers.