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276 CHAPTER 8 
 
Based on this, a possible mechanism is illustrated below. Protonation of the tertiary alcohol, followed by loss of water, 
gives the stable tertiary benzylic carbocation (at C2). Markovnikov attack by the terminal alkene (C6 and C8) at the 
tertiary benzylic carbocation affords a tertiary carbocation at C6. This carbocation is then attacked by the phenolic 
oxygen to afford the final product after removal of the acidic proton. 
 
 
 
 
8.96. 
The first step involves formation of a bromonium ion, which requires three curved arrows (See Mechanism 8.5), 
followed by an intramolecular nucleophilic attack in which the OH group functions as a nucleophilic center and attacks 
the bromonium ion. Deprotonation then affords a cyclic ether. In the last step, a methoxide ion functions as a base and 
removes a proton, which leads to expulsion of bromide in an E2 process. 
 
 
 
You might be wondering about the stereochemistry of the last step (the E2 process). In general, E2 processes occur 
more rapidly when the H and the leaving group are anti-periplanar in the transition state. However, it is possible for an 
E2 process to occur via a transition state in which the H and leaving group are syn-periplanar. In general, this is not 
favored (the transition state is high in energy because all groups are eclipsed rather than staggered), but in this case, the 
rigid geometry of the polycyclic structure essentially locks the H and the leaving group into a syn-periplanar 
arrangement, where the H and the leaving group are eclipsing each other. As such, the reaction can occur, because the 
minimum requirement of periplanarity is still met. 
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