Reaction of 3,4-Dihydro-β-Carbolines with 4-Fluorophenyl-Nitrile Oxide

The reaction of 3,4-dihydro-β-carboline 5a with the nitrile oxide generated from 4-fluoro-N-hydroxybenzenecarboximidoyl chloride (6) gave novel adduct 7a that on standing at 26 °C in CDCl3 was isomerized to species 8. As an extension, the reaction of the dihydro-β-carbolines substituted on C(1) (5b-e) afforded the analogous adducts (7b-e). In case of using two equivalents of reagent 6, the corresponding 1,2,4-triazole-2-oxide (10b-e) was also formed beside the adduct (7b-e).