Tandem Prins and Friedel–Crafts Cyclizations for the Stereo­selective Synthesis of trans-Fused Hexahydro-1H-benzo[g]isochromene Derivatives

Abstract Aldehydes and ketones undergo smooth coupling with (4 E )-3-benzyl-5-phenylpent-4-en-1-ol in the presence of scandium(III) triflate (10 mol%) and 4-toluenesulfonic acid (30 mol%) to give the corresponding trans -fused hexahydro-1 H -benzo[ g ]isochromenes in good yields with excellent selectivity. This is the first example of the synthesis of a trans -fused hexahydro-1 H -benzo[ g ]isochromene derivatives from an aldehyde and (4 E )-3-benzyl-5-phenylpent-4-en-1-ol through tandem Prins and Friedel–Crafts cyclizations.