Approaches to 1H‐Cyclopropa[l]phenanthrenes. Eliminations with 1a,9b‐Dihydro‐1H‐cyclopropa[l]phenanthrene Derivatives

Base‐induced elimination of the sulfonium salt2iin the presence of furan affords the addition products7and8, derived from 1H‐cyclopropa[l]phenanthrene (1) and the isomeric cyclopropene5a(Scheme 3). Upon oxidation, the selenide2cyields phenanthrene‐9‐methanol (9), presumablyvia1. No evidence for the intermediate1is obtained from sulfoxide pyrolysis with2e, which leads to products formed by radical pathways(Scheme 5). Reductive elimination of the disulfone3bgives half‐reduction to monosulfone2gand complete reduction to cyclopropane2as well as 9‐methylphenanthrene (15), but no evidence for the intermediate1.