Allenyl Azide Cycloaddition Chemistry.
Photochemical Initiation and CuI
Mediation Leads to Improved
Regioselectivity
Ken S. Feldman,*D. Keith Hester II,Carlos Silva López, and
Olalla Nieto Faza
Department of Chemistry, The Pennsylvania State University, University Park,
Pennsylvania 16802, Departmento de Quimica Organica, Universidade de Vigo,
Lagoas Marcosende, 36200 Vigo, Galicia, Spain, and Department of Chemistry,
University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455-0431
ksf@chem.psu.edu
Received February 25, 2008
Abstract:
Irradiation of 2-(3-alkenyl)allenylphenyl azides in the presence of excess CuI 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 modest-to-nonexistent regioselectivity that attended thermal cyclization of these allenyl azide substrates.
and
