A new strategy for the synthesis of cinnoline derivatives
Abstract
Readily accessible 3-amino-5-hydroxy-4-(2-nitroaryl)pyrazoles undergo efficient base-catalysed cyclisation to afford 7-substituted 1-hydroxy-3H-pyrazolo[3,4-c]cinnoline 5-N-oxides, hypochlorite oxidation of which provides a viable synthetic route to hitherto inaccessible cinnoline-4-carboxylic acid 1-N-oxides.