Polyfluoroaralkylamines: an improved synthesis of 4,5,6,7-tetrafluoroindole

Article abstract of DOI:10.1016/0022-1139(94)03202-B

Tetrafluoroindole (5), a precursor for potential biologically-active compounds, was prepared previously in a four-step synthesis from C6F6.However, catalytic reduction of pentafluorophenylacetonitrile (2) to 2-pentafluorophenylethyl amine (3) is accompanied by a significant amount of a secondary amine, which, like 3, undergoes cyclization to an indoline and subsequent dehydrogenation to a new indole 8.The side-reaction in the reduction of 2 to 3 is obviated by the use of LiAlH4/AlCl3 (1:1).The final aromatization to yield 5 is vastly improved by replacing MnO2 with DDQ. - Keywords: Polyfluoroaralkylamines; Synthesis; Tetrafluoroindole; NMR spectroscopy; IR spectroscopy