Pyridine Radicals in Synthesis. Part 3: Cyclopentannulation of Pyridine via the 3-Pyridyl Radical and a Formal Synthesis of (±)-Oxerine

The allylation and propargylation of 3-bromo-4-formylpyridine under zinc-mediated Barbier conditions is described. The homoallylic alcohols produced are cyclised via the derived 3-pyridyl radical to give cyclopentannulated pyridines. One of these bicyclic compounds is converted into an advanced intermediate in a previous synthesis of the monoterpene alkaloid (±)-oxerine.