Approaches to 1H-Cyclopropa[l]phenanthrenes. Eliminations with 1a,9b-Dihydro-1H-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 1H-cyclopropal]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 .