Synthesis of annulated 10-methyloctalones by epoxyolefin cyclisation
Abstract
Boron trifluoride–ether catalysed cyclisation of 2-[2-(cyclohex-1-enyl)ethyl]-1,2-epoxy-4,4-ethylenedioxy-1-methylcyclohexane (4) yields, after hydrolysis, a mixture of ketols (12) which probably have steroid geometry at C-9 and C-10. Cyclisation of 5,10-epoxy-3,3-ethylenedioxy-18-nor-9,10-secoandrost-8-ene (4a) yields some 18-norsteroid products (12a) but is complicated by (4a) being a mixture of isomers.