Ag-Catalyzed Intramolecular Sequential Vicinal Diamination of Alkynes with Isocyanates: Synthesis of Fused Indole-Cyclic Urea Derivatives

A formal intramolecular
vicinal 1,2-diamination of alkynes is achieved
for the synthesis of indole-cyclic urea fused derivatives through
a double cyclization process from readily available aminophenyl propargyl
alcohols. This sequential triple C–N bond construction event
was possible using isocyanate as urea precursor and Ag­(I) catalyst
as alkyne activating agent. Control experiments reveal that the cyclization,
followed by 1,3-allylic amino dehydroxylation, is preceded by urea
formation.