Copper(I)-Catalyzed Asymmetric Conjugate Addition of 1,4-Dienes to β-Substituted Alkenyl Azaarenes

Chiral azaarene compounds are extremely important due to their prevalence in pharmaceutical ingredients. Herein, an array of chiral molecules bearing azaaryl groups is synthesized in moderate-to-excellent yields with moderate-to-excellent Z/E ratios, high dr, and excellent enantioselectivity by a copper(I)-catalyzed asymmetric conjugate addition of 1,4-dienes to (E)-beta- substituted alkenyl azaarenes. The reaction is carried out under mild proton-transfer conditions, which enjoys very high atom economy. Moreover, the reaction features a broad substrate scope on (E)-alpha,beta-unsaturated azaarenes as various azaarenes are well tolerated, such as benzothiazole, thiazole, N-methyl-benzimidazole, benzoxazole, quinoline, isoquinoline, pyrimidine, pyrazine, and triazine. Interestingly, the reaction with (Z)-alpha,beta-unsaturated azaarenes affords the same products in excellent results but with a reversed absolute configuration. DFT calculations indicate that the C-C bond-forming nucleophilic addition is a Z -/E- and enantioselectivities-determining step and provides a rationale for the origin of selectivities. At last, the synthetic utilities of the product are showcased by several transformations, including olefin metathesis, [4 + 2] cyclization, [2 + 1] cyclization, and cleavage of the benzothiazole ring.

Automated summary

Chiral azaarene compounds are synthesized through a copper(I)-catalyzed asymmetric conjugate addition reaction with (E)-beta-substituted alkenyl azaarenes as the substrate. The reaction shows good yields, Z/E ratios, and enantioselectivity. Various azaarenes can be used as substrates, and specific product outcomes depend on the configuration of the starting unsaturated azaarenes. DFT calculations provide insights into the selectivity-determining step and the origin of selectivities. The synthesized compounds have synthetic utility in various transformations.