Regioselective Fluorination of 7-Oxo-1,2,4-benzotriazines Using Selectfluor.

7-Oxo-1,2,4-benzotriazines (benzo[1,2,4]triazin-7-ones) are reversible thioredoxin reductase inhibitors that exhibit very strong correlations to pleurotin. In this article, we provide the first synthesis of fluorinated derivatives. Fluorination using Selectfluor of benzo[1,2,4]triazin-7-ones occurs regioselectively and in high yield at the enamine-activated position. This electron N-lone pair activation overrides the activation/deactivation effects of some other substituents. The reaction time was significantly reduced with the use of microwave irradiation at 120 °C and 7 bar. The cytotoxicity and cyclic voltammetry measurements for 8-fluoro-1,3-diphenylbenzo[e][1,2,4]triazin-7(1H)-one (2) are presented and compared with its synthetic precursor, 1,3-diphenylbenzo[e][1,2,4]triazin-7(1H)-one (1a).