Download full text in PDF Opens in a new window. Article suggestions will be shown in a dialog on return to ScienceDirect. ... Please enable JavaScript to use all the features on this page. ... Photogenerated 1,1-diarylspiropentane cation radicals competitively rearranged to the more thermodynamically stable 1-(diarylmethylene)cyclobutanes and the less stable 2,2-diaryl-1-methylenecyclobutanes in a concerted and stepwise manner, respectively.