3-bromo-2-pyrone: an easily prepared chameleon diene and a synthetic equivalent of 2-pyrone in thermal diels-alder cycloadditions

3-Bromo-2-pyrone, a stable solid prepared by a new route (eq. 1), has been found to undergo smooth and regiospecific 2+4-cycloadditions between 78-90°C with both electron-rich and electron-deficient dienophiles; subsequent high-yield reductive debrominations produced halogen-free cycloadducts thus showing 3-bromo-2-pyrone to be a practical and effective synthetic equivalent of 2-pyrone in thermal Diels-Alder cycloadditions.