Substituted perhydrofuropyrans: easy preparation from 2-chloromethyl-3-(2-methoxyethoxy)propene through 3-methylene-1,6-diols

The reaction of 2-chloromethyl-3-(2-methoxyethoxy)prop-1-ene (1) 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 treatment with an epoxide [E2=R3R4C(O)CHR5] at 0 to 20°C leads, after hydrolysis, to the expected unsaturated diols 2. When some compounds 2 (2e–h) are successively hydroborated (BH3·THF) and oxidised (33% H2O2 and then PCC), the expected perhydrofuropyrans 3e–h are isolated directly.