u/Extra_Key_980

Trying to figure out to what degree the dialkylation of tryptamine will happen yield-wise versus cyclization. Can anyone speak to why this tryptamine + formaldehyde + formic acid reaction, as well as other imine/iminium intermediate reductive aminations like this with borohydrides/acetic acid, wouldn’t just close into a ring?

Link for reference: https://en.wikipedia.org/wiki/Pictet–Spengler\_reaction