DBU‐Promoted 6π‐Azaelectrocyclization and Hydrogen‐Migration to Prepare 6‐Alkyl Pyridine <i>N</i>‐Oxides from <i>N</i>‐Vinyl‐<i>α</i>,<i>β</i>‐Unsaturated Nitrones
Ning Zou, Zhang‐Wei Liu, Gong‐Gui Yan, Ying‐Chun Wang, Cui Liang, Dong‐Liang Mo
Abstract
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
Topics & Concepts
ChemistryPyridineAlkylPyridine-N-oxidePolymer chemistryOxideCarbazoleMedicinal chemistryHydrogen bondHydrogenOrganic chemistryMoleculeCatalytic C–H Functionalization MethodsSynthesis and Biological EvaluationCyclopropane Reaction Mechanisms