Acrolein → 2H-1-Benzopyran-3-carboxaldehyde, 6-bromo-

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Reaction Steps

The starting material is prepared as follows: A mixture of 5-bromosalicylaldehyde (10.3 g, 51.1 mmol) and potassium carbonate (7.0 g, 51.1 mmol) in 30 ml of 1,4-dioxane is treated with acrolein (4.3 g, 76.6 mmol). The mixture is heated at reflux for 2 hours and allowed to cool. This is partitioned between ether and water, and separated. The aqueous layer is extracted once with ether, and the organic phases are combined, dried (MgSO4) and evaporated. Flash chromatography (silica gel, 8% ethyl acetate/hexane) yields 6-bromo-2H-1-benzopyran-3-carboxaldehyde, m.p. 103°-104° C., which is converted to the final product as described above.

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