Metal-Free Oxidative [5+1] Cyclization of 1,5-Enynes for the Synthesis of Pyrazine 1-Oxide

A chemo-selective nitrosylation of 1,5-enynesviaa sequence of NO radical incorporation and intramolecular radical cyclization was reported. The formation of two C-N bonds and one C-O bond make this [5+1] cycloaddition reaction an efficient approach to synthesize pyrazine 1-oxides in moderate to good yields. Metal-free, short reaction time and mild conditions render this strategy more practical, eco-friendly and convenient. Synthetic utility of this protocol is highlighted by scaffolds diversification.