1,4‐Dioxene

[543-75-9] C4H6O2 (MW 86.09) InChI = 1S/C4H6O2/c1-2-6-4-3-5-1/h1-2H,3-4H2 InChIKey = HIZVCIIORGCREW-UHFFFAOYSA-N (used to introduce carbonyl groups with varying degrees of oxygenation; Diels–Alder, [2 + 2] cycloaddition, and enol ether addition substrate; alcohol protecting group) Alternate Name: 2,3-dihydro-[1,4]-dioxine, dihydro-[1,4]-dioxin, 2,3-dihydrodioxine. Physical Data: bp 94 °C; d 1.0836 g cm−3 (20 °C). Solubility: soluble in organic solvents; insoluble in H2O. Analysis of Reagent Purity: 1H NMR (500 MHz, CDCl3) δ 5.89 (s, 2H), 4.00 (s, 4H); 13C NMR (125 MHz, CDCl3) ppm 126.7 (2C), 64.4 (2C).1 Preparative Methods: not commercially available. First identified in 1935,2 1,4-dioxene can be prepared through four reaction pathways. Photochlorination of p-dioxane followed by reductive dehalogenation using magnesium and iodine gives 1,4-dioxene after distillation.3 It has also been prepared by heating diethylene glycol at 230–250 °C in the presence of copper chromite and potassium hydrogen sulfate.4 Pyrolysis of the photoadduct of 9,10-phenanthrenequinone and p-dioxane at 230–250 °C gives 1,4-dioxene after purification by distillation.5 Finally, pyrolysis of 2-acetoxy-1,4-dioxane at 450 °C, which is formed from the reaction between lead(IV) acetate and p-dioxane, gives pure 1,4-dioxene.1 Handling, Storage, and Precautions: 1,4-dioxene can be stored for a significant period of time (years) if kept in a freezer. Storage in the presence of acids should be avoided as conversion to 2-hydroxydioxane, which is in equilibrium with 5-hydroxy-3-oxapentanal, occurs.6