When forming acetal from a C=O group with alcohol, the alcohol will act as a nucleophile and attack twice as the carbon is made very electrophilic twice.
I wonder in the last intermediate before forming the enamine, is it able for the 2' amine to act as a nucleophile and attack the carbon bonded to a highly electronegative N with a positive formal charge? (like the attack from the alcohol when forming acetal) Then with the help with 1 proton transfer, forming a product that has 2 RR'N?
My thought is that it may be too sterically hindered compared to the alcohol when attacking. But is it valid?