XIV xv phoric acid produced tetrahydrofluorene XV in reasonable yield. The structure of XV was established by dehydrogenation to the known l-methylfluorene. To ascertain the effect of the carbethoxyl group on the cyclization, X was treated with polyphosphoric acid directly and after hydrogenation of the double bond. In contrast to the cyclization of XII, X was converted to XVI in good yield; however, XVI was so readily aromatized to XVII that the ...
