Mn(III)-mediated reactions of cyclopropanols with vinyl azides: Synthesis of pyridine and 2-azabicyclo[3.3.1]non-2-en-1-ol derivatives

(Chemical Equation Presented) A Mn(III)-mediated divergent synthesis of substituted pyridines and 2-azabicyclo[3.3.1]non-2-en-1-ol derivatives was exploited using readily available vinyl azides and cyclopropanols with a wide range of substituents. In short, the reactions of vinyl azides with monocyclic cyclopropanol provided pyridines in the presence of Mn(acac)₃ (1.7 equiv), whereas those with bicyclic cyclopropanols led to the formation of 2-azabicyclo[3.3.1]non-2-en-1-ol derivatives using a catalytic amount of Mn(acac)₃. These reactions may be initiated by a radical addition of β-keto radicals, generated by the one-electron oxidation of cyclopropanols, to vinyl azides to give iminyl radicals, which would cyclize with the intramolecular carbonyl groups. In addition, versatile transformations of 2-azabicyclo[3.3.1] non-2-en-1-ol to 2-azabicyclo[3.3.1]nonane or -non-2-nen frameworks were developed.