Organocatalytic vinyl and Friedel-Crafts alkylations with trifluoroborate salts.

Over the last 8 years, our laboratory has developed the concept of iminium catalysis, a mode of LUMO-lowering activation that has enabled the invention of a large number of enantioselective organocatalytic transformations including Diels-Alder cycloadditions, Friedel-Crafts alkylations, Mukaiyama-Michael additions, hydrogenations, and heteroconjugate additions.1 Central to the utility of this technology has been the discovery that a wide variety of π-rich aromatics, such as indoles, pyrroles, furans, and aniline rings, readily participate in iminium-catalyzed 1,4-addition with enals, a Friedel-Crafts mechanism that ensures highly rigid regiocontrol with respect to ring functionalization (e.g., indole selective for 3-position, pyrrole 2-position, etc.).2