Reaction of 1, 1-diphenylethylene (1) with (p-BrC 6 H 4) 3 N\ overset+· SbCl 6− produced indan dimer 2 in dried solvents and gave a butadiene derivative 7 and a tetrahydrofuran derivative 8 in wet solvents whereas the dimerization of the derivatives of 1 afforded cyclobutane type dimers and butadiene type dimers.
