Structurally divergent enantioselective synthesis of benzofuran fused azocine derivatives and spiro-cyclopentanone benzofurans enabled by sequential catalysis

Abstract

An important objective in organic synthesis and medicinal chemistry is the capacity to access structurally varied and complex molecules rapidly and affordably from easily available starting materials. Herein, a protocol...

Recent advances in [4 + 4] annulation of conjugated heterodienes with 1,4-dipolar species for the synthesis of eight-membered heterocycles

“…25 In recent years, the assembly of the azocine skeleton through cascade transformations based on [4 + 4] annulation has evolved as a facile and powerful strategy for access to the related useful medium-sized N-heterocyclic molecules. 31,33,35,38,41,44,45,47,49,53…”

“…E )-catalyzed asymmetric catalytic addition reactions between aurones and conjugated ynones followed by the Lewis base-catalyzed switchable divergent annulation reactions (Scheme 9). 38 By using the two-step strategy, a variety of aurones and conjugated ynones bearing different substitution patterns successfully reacted to access benzofuran-fused azocines 65 and spiro-cyclopentanone benzofurans 66 in good to excellent yields with excellent enantiocontrol. In this work, computational investigations with DFT were conducted to further illustrate the origin of the enantioselectivity and divergence of the asymmetric product on switching the Lewis base catalysts.…”

Copper-Catalyzed Enantioselective 1,2-Allylation of Azadienes with Allylboronates

“…Subsequently, they presented some sophisticated examples of the Pd-catalyzed cycloadditions between azadienes and vinylethylene carbonates or vinyl oxetanes to access chiral nine- and ten-membered benzofuran-fused heterocycles . These azadienes can also serve as two-atom synthons to undergo [2 + 3] or [2 + 1] cycloaddition reactions. , Furthermore, such species can act as suitable Michael acceptors in conjugate addition reactions. − In 2018, Zhou’s group disclosed an organocatalytic asymmetric 1,4-conjugate addition of phosphites to azadienes . Later on, the enantioselective Michael additions of azadienes with tritylthiol, rhodanines, β,γ-unsaturated γ-lactones, 5 H -thiazol-4-ones, indoles, 2-naphthols, 3-homoacyl coumarin, α-thiocyanoindanones, difluoroenoxysilanes and PhMe 2 SiBpin were established by other groups to provide the 1,4-adducts in high yields with good to high stereoselectivities.…”