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

Base‐induced elimination of the sulfonium salt 2i in the presence of furan affords the addition products 7 and 8 , derived from 1 H ‐cyclopropa[ l ]phenanthrene ( 1 ) and the isomeric cyclopropene 5a (Scheme 3) . Upon oxidation, the selenide 2c yields phenanthrene‐9‐methanol ( 9 ), presumably via 1 . No evidence for the intermediate 1 is obtained from sulfoxide pyrolysis with 2e , which leads to products formed by radical pathways (Scheme 5) . Reductive elimination of the disulfone 3b gives half‐reduction to monosulfone 2g and complete reduction to cyclopropane 2 as well as 9‐methylphenanthrene ( 15 ), but no evidence for the intermediate 1 .