[combatwombat]

The synthetic step is shown below. I am feeling like the mechanism could go either of 2 ways:
1) Lone pair on -NH₂ attacks a proton, then H₂O attacks carbon #2 to displace NH3.

2) The double bond attacks a proton, resulting in carbon #1 being protonated while #2 becomes a carbocation. The LP from the nitrogen forms a double bond with carbon #2 to stabilize the charge, then H₂O attacks carbon #2. Proton transfer to get -NH₃⁺ and -OH, and then remove 1 more proton from -OH to form the carbonyl, which kicks off NH₃.

Looking back, it seems like mechanism #2 is more more feasible; but a few things don't quite add up. I have to wonder if carbon #1 would be the more likely carbon to become protonated from electrophillic attack by the double bond, since it is alpha to the nitrile and protons there should therefore be more acidic (i.e., protonation at carbon #2 might be more stable?). It kind of seems like the lone pair on the -NH₂ would just be more basic than the double bond... Am I looking at this the right way?

[macman104]

Enamine hydrolysis.

Check out the page here and read about the enamine formation.  Can you formulate a reverse pathway now?

http://www.cem.msu.edu/~reusch/VirtualText/aldket1.htm