Synthesis of 2-Cyano-1,1,2,2-tetraphenylethyl Cation and Silver Ion Assisted Solvolysis of sym-Tetraphenylethylene Dichloride

Article abstract of DOI:10.1021/jo00123a032

The reaction of 3-chloro-2,2,3,3-tetraphenylpropanenitrile (2) with AgSbF6 or SbCl5 below -55 deg C in methylene chloride produces the stable, long-lived cation 2-cyano-1,1,2,2-tetraphenylethyl cation (5).Treatment of 5 with TMSCN affords a 98percent yield of 2,2,3,3-tetraphenylsuccinonitrile.It was also found that cation 5 generated with AlCl3 at 0 deg C can undergo intramolecular aromatic substitution to give 9-(cyanodiphenylmethyl)fluorene (8).In the reactions of sym-tetraphenylethylene dichloride (1) with CF3COOAg in the presence of methanol, it was found that tetraphenylethanone dimethyl ketal (9) can be synthesized in 91percent yield.Because rearrangement occured, 1-methoxy-1,2,2,2-tetraphenylethyl cation (15) is proposed as a reaction intermediate.In contrast, treatment of dichloride 1 with CF3CO2Ag in the presence of phenol or isopropyl or allyl alcohol did not produce the corresponding ketals but the 1,3-dioxolane ortho esters 19, 20, or 21 (2-alkoxy-2-trifluoromethyl)-4,4,5,5-tetraphenyl-1,3-dioxolanes).