Chromium-catalyzed olefination of arylaldehydes with haloforms assisted by 2,3,5,6-tetramethyl- N , N '-bis(trimethylsilyl)-1,4-dihydropyrazine.

Chromium-catalyzed olefination of arylaldehydes with haloforms was achieved using 2,3,5,6-tetramethyl- N , N '-bis(trimethylsilyl)-1,4-dihydropyrazine (1a) as an organic reducing agent, giving β-halostyrene derivatives in a trans -selective manner. The reaction required no metal powders, such as zinc and manganese, as reductants, thereby minimizing metal-based reaction waste.