Tonight’s problem comes once again from Harvard’s challenging organic problems website.
In the early 1980’s, Robert Stevens’s group at UCLA studied nucleophilic additions to and reductions of tetrahydropyridiniums, which could potentially yield alkaloid products. Actually getting to these cyclic imines and iminium ions in the first place can be an interesting exercise in arrow-pushing. It certainly was in the case of makomakine, which the Stevens group made from beta-pinene in only two steps! Barret Valentine would be proud.
Mercuric ion, being a Lewis acid, does interesting things with that double bond to start things off. From there, the arrows get crazy! See if you can draw a mechanism for the transformations below and come up with the intermediate X. One million EXP if you can!