Advanced Synthesis and Catalysis
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The formal [3+2] dipolar cycloaddition (or annulation) of donor-acceptor cyclopropanoate esters with pyridines and 5-nitroquinoline is reported. Electron-deficient pyridine dipolarophiles (R=CN, CO2Et, COMe) participate in the annulation whereas electron rich species do not. The product 2,3-dihydroindolizines undergo rapid autooxidation, and the X-ray structures for two of the aromatic products are reported.