Abstract
Vinylogous amides 1 and 11 are oxidized by dried Mn(OAc)(3) in benzene at 90 degrees C to pyridines 5 and 12, respectively, whereas the analogous N-trifluoroacetyl vinylogous amides 6 and 13 are oxidized by dried Mn(OAc)(3) in benzene at 120 degrees C to give acetates 7 and 14. The alpha'-oxo radicals that are generated in this oxidation cyclize to proximal double bonds to give tricylic alkenes such as 20.
