Organocatalytic diboration involving "reductive addition" of a boron-boron σ-bond to 4,4'-bipyridine.

A 4,4'-bipyridine-based catalyst system for diboration of pyrazine derivatives was established. The catalyst cycle consists of the following two steps: (1) reductive addition of the boron-boron bond of bis(pinacolato)diboron to 4,4'-bipyridine to form N,N'-diboryl-4,4'-bipyridinylidene and (2) oxidative boryl transfer from the intermediate to pyrazine to give N,N'-diboryl-1,4-dihydropyrazine with regeneration of 4,4'-bipyridine.