Dearomatizing conversion of pyrazines to 1,4-dihydropyrazine derivatives via transition-metal-free diboration, silaboration, and hydroboration

Pyrazines and substituted pyrazines undergo addition of boron reagents having B-B, Si-B, and H-B bonds under transition-metal-free conditions, leading to high-yield synthesis of N-borylated 1,4-dihydropyrazines and 1,2,3,4-tetrahydropyrazine.