Straightforward synthesis of 1,7-dioxaspiro[4.4]nonanes

The reaction of 2-chloromethyl-3-(2-methoxyethoxy)prop-1-ene with an excess of lithium powder and a catalytic amount of naphthalene (2.5%) in the presence of a carbonyl compound (E1=R1R2CO) in THF at −78 to 0 °C, followed by the addition of an epoxide [E2=R3R4C(O)CHR5] at 0 to 20 °C leads, after hydrolysis, to the expected methylidenic diols. These diols, in the presence of iodine and silver(I) oxide in dioxane–water, undergo double intramolecular iodoetherification to give the corresponding 1,7-dioxaspiro[4.4]nonanes, which in addition can be easily oxidised to a variety of 1,7-dioxaspiro[4.4]nonan-6-ones.