Highly Regio‐, Diastereo‐, and Enantioselective Assembly of Azepino[2,3‐b]indoles viaPalladium‐Catalyzed [4 + 3] Cycloaddition^†

Abstract

of main observation and conclusion A palladium-catalyzed asymmetric [4 + 3] cycloaddition of trimethylenemethanes and indoline-derived aza-dienes has been developed. The potential [3 + 2] side pathway was completely suppressed in the process. This protocol provides an efficient access to azepino[2,3-b]indoles bearing two vicinal stereocenters in generally excellent diastereo-and enantioselectivities (up to > 20 : 1 dr, 99% ee).

High-order dipolar annulations with metal-containing reactive dipoles

“…On the other hand, o -quinomethides ( o -QMs) and styryl-substituted o -QMs 15 were also employed as substrates with Trost's reaction conditions, and they delivered a series of benzo[ b ]oxepines bearing nitro-, CN, SO 2 Ph and quaternary carbon with high efficiency and enantioselectivity. Shortly after, similar transformations were further developed by the Shao group 28 and Deng group, 29,30 which demonstrate the generality of the Pd-catalyzed (3+4) annulation strategy for construction of 7-membered heterocycles.…”

Pd-catalyzed exclusively regioselective [5 + 4] cycloaddition for the construction of 1,5-di/ox-azonanes

“…The [5 + 4] cycloaddition reaction for the synthesis of nine-membered heterocycles has been tremendously stimulated by the above successful cases. Nevertheless, due to the inherent reactivity of α,β-unsaturated imines, 22,23 achieving regioselective control in the reaction remains an immense challenge. To prevent α,β-unsaturated imines from acting as two-atom synthons, it is common to incorporate a ring structure to constrain the conformation of α,β-unsaturated imines and leverage the aromatic driving force to promote the regioselectivity of α,β-unsaturated imines as four-atom synthons in the reaction.…”