Allenyl azide cycloaddition chemistry.: Photochemical initiation and Cul mediation leads to improved regioselectivity

Irradiation of 2-(3-alkenyl)allenylphenyl azides in the presence of excess Cul furnished functionalized 2,3-cyclopentenylindoles in good yield with only trace amounts of competitive C-N-bonded regioisomeric products. These results represent a significant departure from the modestto-nonexistent regioselectivity that attended thermal cyclization of these allenyl azide substrates.