ChemInform Abstract: The Witkop—Winterfeldt Oxidation Converts Tetrahydropyridoindoles into Pyrroloquinolones and Cinnolines by an Unprecedented Scaffold Rearrangement.

Abstract

Tosylated γ-carbolines (I) are converted into dihydroquinolones (II) by a one-pot reaction via ozone oxidation, reduction of the assumed intermediate ozonide by pyridine, and final cyclization of the formed keto-lactam in the presence of Et3N. Carboline (Ib) affords additionally the unprecedented cinnoline betaine (III). The deprotection of the tosyl group of quinolones (II) is easily achieved to give quinolones (IV), which are selectively brominated at the 3-position. -(MENTEL, M.; PETERS, M.; ALBERING, J.; BREINBAUER*, R.; Tetrahedron 67 (2011) 5, 965-970, http://dx.