On the Reaction of Indole with Sodium Borohydride in Triflueoacetatic Acid

Abstract

The reaction of indole (1) wlth sodlum borohydride in trifluoroacetic acid gives, successively, indoline (3), N-(2.2.2-trifluoroethyl) indoline (4).and 1,1,l-trifluoro-2, -2-bisI5-(N--(2,2,2-tr~fluoroethyll imblinyll lethan (51, whose structure is established by chemical and spectral means.Similar reactions are observed wlth N-methylaniline ( 8 ) and anisole, but not with dibenzazepines 11 and -15, which give only F-trifluoroethylat~on.2Several years ago we reported that sodium borohydride (NaBH4) In carboxylic acid media effects the reduction and alkylation of indoles to give N-alkylindolines, l*L, but that sodium cyanoborohydride (NaBH3CN) in acetic acid at room temperature brings about reduction of the lndole double bond without N-alkylation.1-3.3'4