A Sydnone-Based Route to Indazolo[2,3-a]quinoxaline Derivatives

Abstract

A new synthetic route to indazolo[2,3-a]quinoxaline derivatives is described. The strategy is based on the 1,3-dipolar cycloaddition of arynes and quinoxaline-sydnone derivatives, as a key step. These polyaromatic sydnones were prepared through a copper-promoted intramolecular cyclisation of the C-4 position of sydnones on imines.

Synthesis of pyrazino[1,2-b]indazoles via cascade cyclization of indazole aldehydes with propargylic amines

“…The key step of the strategy involves utilizing the 1,3-dipolar cycloaddition reaction between arynes and quinoxaline-sydnone derivatives. 13 One major drawback of above strategies is the use of dangerous aryl azide derivatives as starting materials. The Jamison group solved this problem by developing a visible-light-induced iridium-catalyzed decarboxylative radical cyclization of ortho -substituted arylisocyanides with radicals generated by phenyliodine( iii ) dicarboxylate reagents (Scheme 2b-5).…”