Arylative Methylation of 2,3-Dihydropyrazines and Pyrazinones Using Dimethyl Sulfoxide as a C1 Source

Divergent synthesis of alpha-C-H methylated pyrazines and pyrazinones using dimethyl sulfoxide as a nonconventional methylating agent under metal-free conditions was reported. Dimethyl sulfoxide-coordinated bromine cation pools generated from the treatment of dimethyl sulfoxide and 1,2-dibromoethane undergo Pummerer-type fragmentation to afford an electrophilic methyl(methylene)sulfonium ion for reaction with a carbon nucleophile followed by aromatization to afford alpha-methylated pyrazines and pyrazinones.

Automated summary

A divergent synthesis of alpha-C-H methylated pyrazines and pyrazinones was achieved using dimethyl sulfoxide as a nonconventional methylating agent under metal-free conditions. The dimethyl sulfoxide-coordinated bromine cation pools generated from the treatment of dimethyl sulfoxide and 1,2-dibromoethane underwent Pummerer-type fragmentation, leading to the formation of an electrophilic methyl(methylene)sulfonium ion. This ion reacted with a carbon nucleophile and subsequent aromatization afforded alpha-methylated pyrazines and pyrazinones.