“…Since the discovery by Danishefsky et al5a that Lewis acids catalyze the hetero‐Diels–Alder reaction between aldehydes and electron‐rich dienes such as 1‐methoxy‐3‐(trimethylsilyloxy)butadiene (Danishefsky’s diene; see Scheme , equation b), a variety of chiral Lewis acid catalysts have been developed 5b,6–17. It has been shown that different metal centers like Co II ,18,19 Cu II ,20,21 Rh II ,9,22B III ,23 Al III ,6,24,25 Cr III ,7,10,11,26 Eu III ,27 Yb III ,28,29 Mn IV ,10,26 and Ti IV[15,30,31] in combination with chiral ligands containing carboxamidate,9 BINOL,31–33 3,3′‐disubstituted BINOL,6,12,24 salen, [7,10,19,26,34] bisoxazoline,21,31,33,35 and triflylamide29 catalyze the HDA cycloaddition.…”