Synthesis of γ-carboline N-oxide under gold(I)-catalysis and C-1 amino and fluoro γ-carboline

Abstract Intramolecular gold (I)-catalyzed cyclization of 2-alkynylindole-3-carbaldehyde oximes enabled direct construction of the unknown γ-carboline N-oxide scaffold at ambient temperature. This reaction proceeded through an interesting 6-endo-dig mechanism and afforded the desired products with satisfactory to high yields. The scope and limitations of the methodology were evaluated and the final compounds fully characterized. From the 3-phenyl-N-oxide derivative, fluorination assays were achieved in two steps including the design of several C-1 ammonium salts and their nucleophilic displacements by fluorine to yield 1-fluoro-γ-carboline.