Total syntheses of trisphaeridine (3)
and norchelerythrine (4), fully
aromatized phenanthridine and benzo[c]phenanthridine alkaloids, were
accomplished via the internal arylâaryl coupling reaction of
halo amides protected by a methoxymethyl group with the palladium reagent,
followed by reduction with lithium aluminium hydride and treatment with hydrochloric
acid.
A palladium reagent prepared from Pd (OAc)(2) (0.2 eq) and n-Bu3P (0.6 eq) catalyzed an aryl-aryl coupling reaction. This procedure is effective for coupling reactions of aryl triflate possessing no oxygen groups with arene, and of aryl iodide with arene.