# Predict the major product of the following reaction with mechanism [closed]

I started to do the problem by coordinating H+ with the lone pair of oxygen then after that I can't proceed .please send the solution by show the detailed mechanism.

• Are you sure the carbonyl will be protonated when there's an imine group around? – William R. Ebenezer Apr 28 '19 at 17:47
• I think answer is (C), which is impossible to achieve under given conditions. – Mathew Mahindaratne Apr 28 '19 at 20:37

There are two equally important path for the given reaction: (i) Via protonation of imine $$\ce{N}$$; and (ii) Via protonation of keto $$\ce{O}$$.

(i) Protonation of imine $$\ce{N}$$ would end up with 1,4-addition to give structure (A), which rearranges to structure (B) via keto-enol tautomerism.

(ii) It is also possible that Protonation can be undergone through keto $$\ce{O}$$, which would end up with 1,4-addition followed by keto-enol tautomerism to give structure (D). See the depicted arrow-pushing mechanism below:

To get structure (C), it need to have 1,6-addition, which is impossible. Therefore, the answer is (C).

• Did you mean, therefore the answer is (B)? – user55119 Apr 30 '19 at 1:47
• @user55119: I meant answer is (C). Asking is "which is X cannot be?"! – Mathew Mahindaratne Apr 30 '19 at 15:42