Studies on the reactions of cyclopropylcarbinyl bromide and iodide with trimethylstannyl anionoids have been made with emphasis on counterion, solvent, and addend (teri-butylamine and dicyclohexylphosphine) effects. Both halides yield cyclopropylcarbinyl- and 3-butenyltrimethylstannanes as major products. Depending upon reaction parameters much or all of the latter is shown to be formed by a mechanism or mechanisms which do not involve kinetically free radical or ionic intermediates. With cyclopropylcarbinyl bromide no electron transfer (ET) (free radical) component is observed in THF or in THF-containing 18-crown-6. However, in 20% THF-80% benzene a small extent of the ET mechanism is observed in the presence of DCPH. The iodide reacts in THF via SN2 (or equivalent) and halogen-metal exchange (HME) mechanisms leading to the formation of both methylcyclopropane and 1-butene in the presence of the traps, indicating that the cyclopropylcarbinyl anion can undergo rearrangement to the 3-butenyl anion in competition with other processes. In the presence of 18-crown-6 and DCPH a small ET component is observed with the iodide.
All Science Journal Classification (ASJC) codes
- Organic Chemistry