POLYFLUOROARALKYLAMINES - AN IMPROVED SYNTHESIS OF 4,5,6,7-TETRAFLUOROINDOLE

Tetrafluoroindole (5), a precursor for potential biologically-active c ompounds, 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 amou nt of a secondary amine, which, like 3, undergoes cyclization to an in doline and subsequent dehydrogenation to a new indole 8. The side-reac tion in the reduction of 2 to 3 is obviated by the use of LiAIH(4)/AlC l3 (1:1). The final aromatization to yield 5 is vastly improved by rep lacing MnO2 with DDQ.