title: Cascade radical-mediated cyclisations with conjugated ynone electrophores. An approach to the synthesis of steroids and other novel ring-fused polycyclic carbocycles.
abstract: A cascade radical-mediated Diels-Alder reaction with the iododienynone 16b produced the tricyclic ketone 17 (22%). By contrast, treatment of the substituted furans 36 and 47 with Bu(3)SnH-AIBN, instead led to the tetracycles 44 and 58 respectively, rather than the anticipated oestranes, i.e. 38 and 48. In a separate study, attempted cascade radical-mediated cyclisations from the ortho-aryl substituted iododienynones 72 and 73, leading to the ring-D aromatic steroid 7, instead gave the macrocyclic ketone 76 or the novel bridged tricycles 77/82, respectively, depending on whether benzene or heptane was used as solvent in the reactions.
authors.affiliation: School of Chemistry, The University of Nottingham, University Park, Nottingham, England, UK NG7 2RD. gp@nottingham.ac.uk
authors.forename: Gerald
authors.initials: G
authors.lastname: Pattenden
authors.forename: Davey A
authors.initials: DA
authors.lastname: Stoker
authors.forename: Nicholas M
authors.initials: NM
authors.lastname: Thomson