N-Heterocyclic Carbene-Catalyzed Intramolecular Nucleophilic Substitution: Enantioselective Construction of All-Carbon Quaternary Stereocenters.

Abstract

An efficient enantioselective N-heterocyclic carbene (NHC)-catalyzed intramolecular SN 2' nucleophilic substitution of aldehydes with (E/Z)-trisubstituted allylic bromides was accomplished. A range of enantioenriched chromanones bearing an all-carbon quaternary stereocenter at the C3 position were prepared with up to 97 % yield and 98 % enantiomeric excess. The resulting vinyl and carbonyl groups in these products can be transformed into a variety of synthetically important building blocks.