Degenerate Rearrangement of 9-Isopropenyl-9,10-dimethyl-phenanthren-9-yl and 9,10-Dimethyl-9-(trans-1-methylprop-1-en-1-yl)phenanthren-9-yl Cations

摘要

~1H NMR study has shown that long-lived 9-R-9,10-dimethylphenanthren-9-yl cations(R=iso-propenyl,trans-1-methylprop-1-en-1-yl)generated in the system HSO_3F-SO_2ClF-CD_2Cl_2 at-130 deg C undergo degenerate rearrangement via 1,2-vinyl shifts(DELTA G~(not=)=37 and 39 kJ/mol,respectively,at-88 deg C).Analysis of the geometric parameters of the initial structures and transition states calculated by the DFT method indicates that unfavorable steric factors are responsible for the sharp deceleration of 1,2-shifts of the isopropenyl and trans-1-methylprop-1-en-1-yl groups as compared to vinyl and cis-1-methylprop-1-en-1-yl groups,respectively.