Regioselective addition of Grignard reagents to N-acylpyrazinium salts: synthesis of substituted 1,2-dihydropyrazines and Δ5-2-oxopiperazines (Beilstein Journal of Organic Chemistry)

Abstract The regioselective addition of Grignard reagents to mono- and disubstituted N-acylpyrazinium salts affording substituted 1,2-dihydropyrazines in modest to excellent yields (45–100%) is described. Under acidic conditions, these 1,2-dihydropyrazines can be converted to substituted Δ5-2-oxopiperazines providing a simple and efficient approach towards their preparation. Beilstein J. Org. Chem. 2019, 15, 72–78. doi:10.3762/bjoc.15.8