Rh2(OAc)4-catalyzed reaction of 1,3-dioxanes with methyl diazoacetate

The reactions of methyl diazoacetate with 1,3-dioxanes in the presence of Rh2(OAc)4 afford 1,4-dioxepanes in up to 46% yields. The insertion of methoxycarbonylcarbene into the C—O bond occurs only in the case of 2-phenyl-1,3-dioxanes.