Chemical and spectroscopic properties of 2-formyl-1,4-benzodioxane and 3-keto-3,4-dihydro-2H-1,5-benzodioxepin

Abstract 2-Formyl-l,4-benzodioxane has been synthesized by an unambiguous route and proved different from the isomeric carbonyl compound, C 9 H 8 O 3 , previously isolated in the course of alkaline permanganate oxidation of a 2-hydroxymethyl-l,4-benzodioxane preparation. On the basis of N.M.R. spectrum, the structure of 3-keto-3,4-dihydro-2H-l,5-benzodioxepin has been established for the isomeric C 9 H 8 O 3 compound. Evidence is given that the benzodioxepin originated by oxidation of 3-hydroxy-3,4-dihydro-2H-l,5-benzodioxepin originally present as impurity in the 2-hydroxy methyl-1,4-benzodioxane preparation. Chemical and spectroscopic properties of the two isomeric compounds are discussed.