Enantioselective Catalysis on the Solid Phase: Synthesis of Natural Product‐Derived Tetrahydropyrans Employing the Enantioselective Oxa‐Diels–Alder Reaction

Aliphatic aldehydes were synthesized on a solid support and subjected to an enantioselectively catalyzed oxa‐Diels–Alder reaction with Danishefsky’s diene. Employing 5 mol % of a Cr(III)‐salen catalyst enantiomeric ratios up to>99 % and yields up to 40 % over five steps were achieved. Further elaboration of the polymer‐bound dihydropyrones was performed by subsequent conjugate cuprate addition, reduction of the ketone and transformation of the resulting alcohol to a carbamate yielding 2,4,6‐trisubstituted tetrahydropyrans after cleavage from the solid support.