Bimolecular elimination reactions of cyclopentyl compounds

Syntheses and eliminations of cyclopentyl derivatives

“…Similarly, it has been reported (94) that synthesis of 1-iso-propylcyclopentanol in this manner proceeds in Hydroboration of 3-t-butylcyclopentene yielded a 65:35 ratio of 2-tbutylcyclopentanol and 3-Jt-butylcyclopentanol. This ratio of alcohols is exactly the same as Smith (32) observed in the hydroboration of 3-phenylcyclopentene, and is quite different from Brown's result (97) of the hydroboration of 3-methylcyclopentene which gave 55% of the 3-alcohol.…”

“…This is slightly higher than the value (1.90 x 10"^) determined by Smith (32). The two batches of base prepared gave rate constants for a number of compounds which were consistent and reproducible.…”

“…The relative rate ratios of the different halogen derivatives were shown to be constant from the beta-phenylethyl and cyclopentyl systems (81,32), whereas the relative rate of the £-toluenesulfonate group was dependent upon the system studied. The large difference observed in the bromide/£-toluenesulfonate rate ratio (Table 11) indicates the transition state of an elimination reaction is undoubtedly important in determining this ratio.…”

“…Also from the product ratios in these systems it appears that the ease of heterolysis of the C-0 bond in the transition state is more sensitive to electronic influences of the leaving group than to the acidifying effect on the 0-hydrogens (75). Data for numerous E2 reactions have been correlated by the above mentioned criteria to determine the relative extents and timing of C-H and C-X bond breaking and C=C bond formation in the transition state (77,32,50). Recently the ratios of product olefins were used in the 2-substltuted butyl and pentyl systems to substantiate the predicted effects resulting from changes in the leaving group (78) and changes in the base/ solvent system (79, 80) on the E2 transition state.…”

“…Smith (32) reported in the hydroboration of 3-phenylcyclopentene that the 2-alcohols formed consisted of 90% of the trans-isomer and the 3-alcohol contained 60% of the trans-isomer. Brown and Zweifel (97) reported the hydroboration of 3-methylcyclohexene gave 49% of the 2-alcohol and 51% of the 3-alcohol.…”