Sciencemadness Discussion Board

Stereoselective N-alkylation of ketimines

dean stark - 11-4-2011 at 03:27

Possibly an odd question, but...

It's pretty common to see enantiopure alpha-methylbenzylamine being used in amination reactions where the imine is hydrogenated e.g. by trichlorosilane*.

I'm just wondering if there is any evidence of N-alkylation as in Klute's example to yield the corresponding secondary amine after hydrolysis with any degree stereoselectivity? Does that even makes sense?

Thanks in advance...

* This is a cool paper. DMF is used as a ligand for the reduction of said imines via trichlorosilane, with high yield and very high ee. (Hint: if someone with access to Synthesis feels like slinging me this paper, feel free =)

Nicodem - 11-4-2011 at 07:10

You might want to clarify what you are talking about. N-Alkylation of enantiopure alpha-methylbenzylamine derived imines can not give enantiomeric excess of secondary amines, because secondary amines don't have a stereogenic N-atom (see nitrogen inversion), while other atoms are not affected or prochiral. Only C-alkylation of imines at the alpha position can give enantiomeric excesses, but it does not appears that you are talking about that.

dean stark - 11-4-2011 at 14:39

That makes sense. I guess I figured that since adding hydrogen across the double bond (to both C and N) is stereoselective, that adding an alkyl (to the N) might be as well.

Thanks for the explanation.