Reactivity Umpolung of the C═N Bond in Quinoxaline Scaffold Enabling Direct Nucleophilic Attack of Alkyl Grignard Reagents at the N-Terminus.

The reactivity umpolung of the C═N bond in the quinoxaline scaffold has been successfully realized for the first time by introduction of a formyl or an acyl group adjacent to the C-position of the C═N moiety. The reversed reactivity of the C═N bond thus enabled direct nucleophilic attack of alkyl Grignard reagents at the N-terminus rather than the C-terminus, thereby providing an unprecedented and efficient method for the synthesis of quinoxalin-2(1 H )-one derivatives involving a tandem N-alkylation/C─C bond cleavage process.