Pd‐Catalyzed Enantioselective Construction of Isoindolo[2,1‐ a ]indoles

ABSTRACT

Isoindolo[2,1‐ a ]indoles are a class of important functionalized indole‐based heterocycles with significant utility in natural products, pharmaceuticals, and functional materials. Larock isoindolo[2,1‐ a ]indole synthesis is one of the most straightforward and efficient methods for the synthesis of isoindolo[2,1‐ a ]indole utilizing internal alkynes and imines derived from o ‐iodoanilines and aldehydes based on Larock indole synthesis. However, developing an asymmetric version for the construction of chiral isoindolo[2,1‐ a ]indoles has posed considerable challenges since its initial report in 1999. Herein, we report a first example of asymmetric Larock isoindolo[2,1‐ a ]indole synthesis by employing a chiral sulfinamide phosphine (Sadphos) ligand (Ming‐Phos) with modification. It allows rapid transformation of a wide range of substrates in good to excellent enantioselectivities, and provides a facile and straightforward access to chiral isoindolo[2,1‐ a ]indole fused heterocycles. Notably, these chiral isoindolo[2,1‐ a ]indole fused heterocycles exhibit bright fluorescence. The optical properties, including circular dichroism and quantum yield, are examined. The transformation offers a chiral highly conjugated system, which could have great potential applications in chiral optoelectronic materials.