Rh(i)-Catalyzed enantioselective and scalable [4 + 2] cycloaddition of 1,3-dienes with dialkyl acetylenedicarboxylates†
An asymmetric intermolecular [4 + 2] cycloaddition of 1,3-dienes with dialkyl acetylenedicarboxylates, which was catalyzed by a rhodium(I)–chiral phosphoramidite complex, was developed. This protocol provided a highly enantioselective access to prepare carbonyl substituted cyclohexa-1,4-dienes with up to 96% yield and >99% ee. Notably, a cycloaddition on the 10 g scale gave the product in 92% yield and with 99% ee, which showed great potential for the scale-up synthesis of carbonyl substituted cyclohexa-1,4-dienes. In addition, oxidative aromatizations and hydrolysis of the products were also investigated.