Dedicated to the memory of Professor Jean Normant
Abstract
In situ generated 2-phenyl-azetidinium ylides react with boronic esters to form acyclic
γ-dimethylamino tertiary boronic esters. The transformation is believed to involve
the formation of a zwitterionic boronate, which subsequently undergoes ring-opening
1,2-migration, which is promoted by the relief of ring strain. Owing to the configurational
instability of the initially formed ylides, which appear to be in equilibrium with
the open-chain carbene form, the reaction is not stereospecific. The C–B bond of the
γ-dimethylamino tertiary boronic esters can be transformed into a variety of functional
groups (C–OH, C–vinyl, C–H, C–BF3), thus giving a diverse selection of 3-aryl-1-aminopropanes, which represent a privileged
motif among drug molecules.
Key words
3-aryl-1-aminopropanes - azetidinium ion - lithiation - borylation - ring-opening
- boronic esters