Straight and versatile synthesis of substituted perhydrofuro[2,3-b]pyrans from 2-chloromethyl-3-(2-methoxyethoxy)propene

The reaction of 2-chloromethyl-3-(2-methoxyethoxy)propene 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 when subjected to successive hydroboration–oxidation and further oxidation, spontaneous cyclization occurs to furnish a series of differently substituted perhydrofuro[2,3-b]pyrans.