Highly Stereoselective Synthesis of 2,6-<i>cis</i>-Substituted Tetrahydropyrans Using a One-Pot Sequential Catalysis

A catalytic highly diastereo- and enantioselective synthesis of 2,6-<i>cis</i>-substituted tetrahydropyrans was realized using a one-pot sequential catalysis involving Henry and oxa-Michael reactions. The nitroaldol products obtained in a highly enantioselective copper(II)-catalyzed Henry reaction between nitromethane and 7-oxo-hept-5-enals were subsequently treated with a catalytic amount of camphorsulfonic acid (CSA) to give the desired tetrahydropyran derivatives in excellent yields, diastereoselectivities (dr >99:1), and enantioselectivities (ee = 98–99%). The reaction can also be used for the high stereoselective synthesis of a <i>cis</i>-2,6-disubstituted morpholine