An unprecedented route for the preparation of fused tetracyclic
N-heterocycles is presented through the palladium-catalyzed cyclization
of isocyanides with alkyne-tethered aryl iodides. In this transformation,
a novel amino-to-alkyl 1,5-palladium migration/intramolecular C(sp3)–C(sp2) coupling sequence was observed
first. More importantly, isocyanide exhibited three roles, serving
simultaneously as a C1 synthon, a C1N1 synthon, and the donor of C(sp3) for C(sp3)–C(sp2) coupling,
and the reaction was the sole successful example that achieved C(sp3)–H activation of isocyanide.