Asymmetric inverse-electron-demand 1,3-dipolar cycloadditions of cyclopentadienones and thiophene-1,1-dioxide with C,N-cyclic azomethine imines

The normal 1,3-dipolar cycloaddition between the carbonates of 4-hydroxy-2-cyclopentenones and C,N-cyclic azomethine imines can be switched to an inverse-electron-demand version under Pd(0) catalysis, by in situ generation of HOMO-raised eta(2)-Pd(0)-cyclopentadienone complexes. An array of fused heterocyclic architectures are constructed with high levels of diastereo and enantioselectivity, and diastereodivergent synthesis is well realised by tuning the bifunctional phosphine ligands. In addition, similar reaction with in situ formed thiophene-1,1-dioxide is compatible by using a chiral bisphosphine ligand, and the fused cyclic sulfone frameworks are afforded with high stereoselectivity.

Automated summary

In this study, the normal 1,3-dipolar cycloaddition between the carbonates of 4-hydroxy-2-cyclopentenones and C,N-cyclic azomethine imines was switched to an inverse-electron-demand version under Pd(0) catalysis. This transformation was achieved by in situ generation of HOMO-raised eta(2)-Pd(0)-cyclopentadienone complexes. The researchers constructed a variety of fused heterocyclic architectures with high levels of diastereo and enantioselectivity. Furthermore, diastereodivergent synthesis was realized by tuning the bifunctional phosphine ligands. A similar reaction with in situ formed thiophene-1,1-dioxide was also compatible by using a chiral bisphosphine ligand, leading to the formation of fused cyclic sulfone frameworks with high stereoselectivity.