Can grignard reagent contain secondary amino group? Is there any reason why this grignard reagent wouldn't work? My best guess is that perhaps the nitrogen could act as a second nucleophilic "head", thereby not giving a good yield on the intended product. Or maybe this isn't stable enough?
I guess it wouldn't even exist. Grignard's reagent is basic enough to easily take off an imine proton, so as soon as you try to make such a thing, it will turn upon itself.

Probably they have a suitable protecting group for this, but here I'm stepping outside my expertise.