The Convergent Synthesis of Pyrazinyl and Quinoxalinyl Phenylmethanones from 2-Lithio Pyrazines and Quinoxalines.
John S. Ward and Leander Merritt. J. Heterocyclic Chem. 28, 765 (1991)
Pyrazines and quinoxalines bearing 2-substituents that direct ortho metalation reacted with lithium 2,2,6,6-tetramethylpiperidide to produce 2-substituted-3-lithiopyrazines and quinoxalines. These lithio reagents reacted with N-methoxy-N-methylbenzamide to give good to moderate yields of 3-substituted pyrazinyl or quinoxalinylphenylmethanones. The 3-methylthio substituents of some ketone products were oxidized to methylsulfonyl groups that were susceptible to nucleophilic displacement.