A novel synthesis of 4-methyl-1,3-dioxolane-4-carbaldehydes by epoxidationof 5-methyl-4H-1,3-dioxins and acid-catalyzed rearrangement

A straightforward procedure for the synthesis of 4-methyl-1,3-dioxolane-4-c arbaldehydes 2 is reported. The new procedure involves m-CPBA oxidation of 5-methyl-4H-1,3-dioxins 5 in dichloromethane to give 4-(m-chlorobenzoyloxy) -5-hydroxy-5-methyl-1,3-dioxanes 6 and acid-catalyzed rearrangement of 6 to carbaldehydes 2. By using commercially available m-CPBA the oxidation and rearrangement can be carried out as a one-pot reaction. The procedure is al so applicable to 4H-1,3-dioxins. Oxidation of 5 in methanol led to 4-methox y-5-hydroxy-1,3-dioxanes 7, which did not undergo acid-catalyzed rearrangem ent.