Domino Strategy for the Stereoselective Construction of Angularly Fused Tricyclic Ethers

A stereoselective synthesis of decahydrofuro­[3,2-d]­isochromene derivatives has been achieved by the condensation of 2-cyclohexenylbutane-1,4-diol with aldehydes in the presence of a stochiometric amount of BF3·OEt2 in dichloromethane at −78 °C. Similarly, the condensation of 2-cyclopentenylbutan-1,4-diol with aldehydes provides the corresponding octahydro-2H-cyclopenta­[c]­furo­[2,3-d]­pyran derivatives in good yields with high diastereoselectivity. It is an elegant strategy for the quick construction of tricyclic architectures with four contiguous stereogenic centers in a single step. These tricyclic frameworks are the integral part of numerous natural products.