In previous papers of this series,* it has been shown that the cyclization of certain 2-biphenyl- ylolefin oxides (I, one or both R groups = H) can lead to the formation of phenanthrene hydro- carbons (11) with substituents in the 9- or 9,lO- positions. ... I I1 As a means for the elucidation of the mechanism of this reaction, a study of oxides of the type illustrated (R = alkyl) seemed particularly promising. Should the cyclization of such an oxide be accomplished, the ...