The rapid assembly of molecular complexity continues to be at the forefront of novel reaction development. In the pursuit of that goal, we herein report a novel Sc(OTf)3 -catalyzed, one-pot multicomponent reaction that furnishes complex multicyclic 2-pyrrolines with excellent overall yields and perfect diastereocontrol. This process is based on our previously established (2+2+1)-cycloannulation of in situ generated 1-azaallyl cations, 1,3-dicarbonyls and primary amines. The newly formed and highly reactive aminal moiety is readily substituted with indoles and pyrroles both as external and internal π-nucleophiles to provide densely functionalized N-heterocycles with four new σ-bonds and two vicinal quaternary stereogenic centers. In addition, DFT calculations have been conducted to further characterize the intermediate 1-azaallyl cations.
Keywords: 1-azaallyl cations; Lewis acid catalysis; aza-Friedel-Crafts reaction; multicomponent reactions; tertiary alcohols.
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