Reactions of 1-Bromo-2-(p-Tolyl)Cyclopropane with Nucleophiles in the Presence of Crown Ether

Reactions of 1-bromo-2-(p-tolyl)cyclopropane with potassium acetate in the presence of crown ether in various solvents (DMSO, t-butanol, and toluene) have been examined. No cyclopropyl products were observed, only ring-opened p-methylsinnamyl acetates. The trans 1-bromo-2-(p-tolyl)cyclopropane isomer reacts about 3.8 times faster than the cis isomer in DMSO, but only about 1.5 times faster in t-butanol, seemingly related to solvation factors in the transition state. Although stability studies indicated that p-methylcinnamyl bromide might be an intermediate, the rate of formation of this compound in the absence of potassium acetate was much lower than rate of product formation even in the presence of potassium perchlorate to maintain high ionic strength. A Hammett treatment of reaction rate data for 1-bromo-2-(p-tolyl)cyclopropane and 1-bromo-2-phenylcyclopropane reacting with potassium acetate gave a ρ value of -1.18

Reactions of 1-Bromo-2-(p-Tolyl)Cyclopropane with Nucleophiles in the Presence of Crown Ether

Reactions of 1-bromo-2-(p-tolyl)cyclopropane with potassium acetate in the presence of crown ether in various solvents (DMSO, t-butanol, and toluene) have been examined. No cyclopropyl products were observed, only ring-opened p-methylsinnamyl acetates. The trans 1-bromo-2-(p-tolyl)cyclopropane isomer reacts about 3.8 times faster than the cis isomer in DMSO, but only about 1.5 times faster in t-butanol, seemingly related to solvation factors in the transition state. Although stability studies indicated that p-methylcinnamyl bromide might be an intermediate, the rate of formation of this compound in the absence of potassium acetate was much lower than rate of product formation even in the presence of potassium perchlorate to maintain high ionic strength. A Hammett treatment of reaction rate data for 1-bromo-2-(p-tolyl)cyclopropane and 1-bromo-2-phenylcyclopropane reacting with potassium acetate gave a ρ value of -1.18