A facile one-step synthesis of aromatic indolizines by 1,3-dipolar cycloaddition of pyridinium and related heteroaromatic ylides with alkenes in the presence of TPCD [Copy4(HCrO4)2]

A facile and general one-step method is presented for the synthesis of aromatic indolizine compounds 3a–n in moderate to high yields (53–99%) by reaction of the pyridinium N-ylides 1a–e, the quinolinium N-ylide 1f and the isoquinolinium N-ylide 1g with various olefinic dipolarophiles, such as acrylonitrile 2a, methyl acrylate 2b, acrylamide 2c, diethyl maleate 2d and methyl crotonate 2e, respectively, in the presence of a new oxidant TPCD [Copy4(HCrO4)2, tetrapyridinecobalt(II) dichromate] at 90 °C for 2 h in DMF.