The Stereoselective Formation of Highly Substituted CF3‐Dihydropyrans as Versatile Building Blocks.

The enantioselective reaction of bromides (I) and (VI) with unsaturated aldehydes (II) followed by reduction or acetalization of intermediate aldehydes gives rise to alcohols (III) or acetals (VIII), which are readily converted into dihydropyran derivatives (V) and (X).