2-Methyl Substituent Effects in the Antihomoaromatic Cyclopropinden-1-yl Cation

Article abstract of DOI:10.1021/jo00172a024

The rates and products of hydrolysis of the endo- and exo-2-methylcycloprop<2,3>inden-1-yl 3,5-dinitrobenzoates in 80percent aqueous acetone have been determined.These are compared with similar data for the corresponding unsubstituted esters and for the 1-methyl-substituted and unsubstituted endo- and exo-2-bicyclo<3.1.0>hexyl 3,5-dinitrobenzoate model systems.This was done in connection with reports that toward acid-catalyzed epimerization in 50percent aqueous dioxane at 80 deg C 2-methyl substitution caused a 250-fold rate deceleration in the endo-cycloprop<2,3>inden-1-ol system.For the endo 3,5-dinitrobenzoates the 2-methyl substituent did produce a rate decrease; however, this was only by a factor of about 1.2 at 80 deg C.In the 2-bicyclo<3.1.0>hexyl model system, the corresponding 1-methyl substitution caused approximately a 2-fold rate increase.