Evaluation of Amino Nitriles and an Amino Imidate as Organo­catalysts in Aldol Reactions

The efficiency of l -valine and l -proline nitriles and a tert-butyl­ l -proline imidate as organocatalysts for the aldol reaction have been evaluated. l -Valine nitrile was found to be a syn-selective catalyst, while l -proline nitrile was found to be anti-selective, and gave products in modest to good enantioselectivities. tert-Butyl l -proline imidate was found to be a very efficient catalyst in terms of conversion of starting reagents to products, and gave good anti-selectivity. The enantioselectivity of the tert-butyl l -proline imidate was found to be good to excellent, with products being formed in up to 94% enantiomeric excess.