Catalyst-Controlled Enantioselective and Regiodivergent Addition of Aryl Boron Nucleophiles to N‑Alkyl Nicotinate Salts

Dihydropyridines are versatile building
blocks for the synthesis
of pyridines, tetrahydropyridines, and piperidines. Addition of nucleophiles
to activated pyridinium salts allows synthesis of 1,2-, 1,4-, or 1,6-dihydropyridines;
however, this process often leads to a mixture of constitutional isomers.
Catalyst-controlled regioselective addition of nucleophiles to pyridiniums
has the potential to solve this problem. Herein, we report that the
regioselective addition of boron-based nucleophiles to pyridinium
salts can be accomplished by the choice of a Rh catalyst.