DBU‐Promoted 6π‐Azaelectrocyclization and Hydrogen‐Migration to Prepare 6‐Alkyl Pyridine N‐Oxides from N‐Vinyl‐α,β‐Unsaturated Nitrones

Abstract We describe a DBU‐controlled 6π‐azaelectrocyclization of dibenzylideneacetone‐derived N ‐vinyl‐ α , β ‐unsaturated nitrones to prepare 6‐alkyl pyridine N ‐oxides in 24–82% yields. Mechanistic studies revealed that DBU had a great impact on the formation of 6‐alkyl pyridine N ‐oxides and served as a base and the carrier of hydrogen sources to in situ reduce C=C bonds. The 6‐alkyl pyridine N ‐oxide was prepared at gram‐scales and converted to estrone‐derived pyridine and pyrido[2,3‐c]carbazole 4‐oxide in 46% and 52% yields in two steps, respectively. magnified image