Cyclopentadienone oxime dimers as precursors to cyclone equivalents

Monomerisation (110–150 °C) of the stereoisomeric mixture of the dioxime 6a, or its ethers or esters, 6b–e, gives the oximes 7 which can be trapped by a wide range of dienophiles to give good yields of the adducts 8–12; deoximation of these to the ketones can be effected by catalytic hydrogen transfer (Pd/C, cyclohexadiene) as a mild alternative to acid hydrolysis.