Copper(I)‐Catalyzed Enantioselective Synthesis of Chiral Cyclohexenylallenes and Transfer of Axial to Center Chirality by Ytterbium (III) Catalyzed [4+2] Cycloaddition

Chiral cyclohexenylallenes are readily accessed from 1‐enynes, aldehydes and chiral secondary amines in good yields (up to 79 % yield) with excellent enantioselectivities (up to 99 % ee), through CuI catalyzed the formation of chiral propargylamine intermediates. Subsequent Yb(OTf) 3 catalyzed [4+2] cycloaddition reaction of cyclohexylallenes with the dienophiles tetracyanoethylene and diethyl acetylenedicarboxylate afforded the corresponding bicyclic products in 69–75 % yield and 84–90 % ee.