Electrophilic chemistry (protonation, nitration, bromination) of crowded (Z)-2,2,5,5-tetramethyl-3,4-diphenylhex-3-ene; formation of phenanthrenium ions by facial ring protonation/transannular cyclization in superacid media; p,p-dinitration and p,p-dibromination with NO<sub>2</sub><sup>+</sup>BF<sub>4</sub><sup>–</sup>and Br<sub>2</sub>–SO<sub>2</sub>
作者:Kenneth K. Laali、James E. Gano、Charles W. Gundlach、Dieter Lenoir
DOI:10.1039/p29940002169
日期:——
4-diphenylhex-3-ene 1 is ring protonated in FSO3H·SbF5(1 : 1)-SO2ClF or in FSO3H·SbF5(4:1 )–SO2ClF superacid media and undergoes a rapid transannular cyclization eventually leading to mixtures of persistent phenanthrenium mono- and dications. The cofacial relationship of the phenyl groups is required for phenanthrenium ion formation. Low-temperature protonation of the corresponding (E)-stilbene 2gives But+ as