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

The reaction of 2-chloromethyl-3-(2-methoxyethoxy)prop- I -ene with an excess of lithium powder and a catalytic amount of naphthalene (2.5%) in the presence of a carbonyl compound (E-1 = (RRCO)-R-1-C-2) in THF at -78 to 0degreesC, followed by the addition of an epoxide [E-2 = (RR4)-R-3 C(O)CHR5] at 0 to 20degreesC leads, after hydrolysis, to the expected methylidenic diols. These diols, in the presence of iodine and silver(l) 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. (C) 2003 Elsevier Ltd. All rights reserved.