Copper-Catalyzed Allenylation-Isomerization Sequence of Penta-1,4-diyn-3-yl Acetates with P(O)H Compounds: Facile Synthesis of 1-Phosphonyl 2,4-Diynes

The copper-catalyzed reaction of 5-substituted penta-1,4-diyn-3-yl acetates with P(O)H compounds to efficiently give a new class of phosphonyl diynes is reported. The reaction may take place through a regioselective nucleophilic attack of phosphorus nucleophiles on Cu-allenylidene intermediates to form allenyl intermediates followed by a rapid allene-alkyne isomerization process. The synthetic utility of the obtained products is demonstrated. (Figure presented.).