Divergent Synthesis of 3-(Indol-2-yl)quinoxalin-2-ones and 4-(Benzimidazol-2-yl)-3-methyl(aryl)cinnolines via Polyphosphoric Acid (PPA)-Mediated Intramolecular Rearrangements of 3-(Methyl/aryl(2-phenylhydrazono)methyl)quinoxalin-2-ones.

Herein, we report a polyphosphoric acid (PPA)-mediated divergent metal-free operation to access a diverse collection of 3-(indol-2-yl)quinoxalin-2-ones and 4-(benzimidazol-2-yl)-3-methylcinnolines in moderate to excellent overall yields. The described process involves two distinct, and competing rearrangements of 3-(methyl(2-phenylhydrazono)methyl)quinoxalin-2-ones, namely [3,3]-sigmatropic Fischer rearrangement with the formation of an indole ring to produce 3-(indol-2-yl)-quinoxalin-2-ones, and Mamedov rearrangement with simultaneous construction of benzimidazole and cinnoline rings to form the new biheterocyclic system─4-(benzimidazol-2-yl)-3-methylcinnolines. The reaction mechanism of both rearrangement channels is explored by extensive dispersion-corrected DFT calculations.

Bromine-Promoted One-Pot Furo[]annulation and α-C(sp)-Thiomethylation Cascade of ()-3-Styrylquinoxalin-2(1)-ones with Dimethyl Sulfoxide.

A new process has been developed for the bromine-promoted sequential (sp)C = (sp)C bond functionalization of ()-3-styrylquinoxalin-2(1)-ones and furo[]annulation via the 5-cyclization in dimethyl sulfoxide (DMSO). The reaction represents a novel strategy for the synthesis of 2-aryl-3-(methylthio)furo[2,3-]quinoxalines and involves 3-(1,2-dibromo-2-arylethyl)quinoxalin-2(1)-ones and 2-arylfuro[2,3-]quinoxalines as key intermediates. Furthermore, DMSO was converted to dimethyl sulfide in situ, which served as the methylthiolation reagent in the reaction.