Synthesis of 3,4‐Fused Tricyclic Indoles Using 3‐Alkylidene Indolines as Versatile Precursors

Diastereoselective Synthesis of Pyrroloquinolines via N-H Functionalization of Indoles with Vinyl Sulfonium Salts

A [2 + 4]/[1 + 2] annulation approach was successfully established to construct pyrroloquinoline-fused cyclopropane in a highly diastereoselective fashion (>20:1 dr). The tetracyclic 1,7-fused indoles were efficiently obtained from readily available starting materials under mild conditions. This methodology displays impressive substrate generality with two reaction components. The products resulting from this doubly annulative strategy are useful synthetic intermediates.

HOAc catalyzed three-component reaction for the synthesis of 3,3'-(arylmethylene)bis(1H-indoles)

An efficient HOAc catalyzed three-component reaction of 2-(arylethynyl)anilines with arylaldehydes has been achieved, which leads to the generation of 3,3'-(arylmethylene)bis(1H-indoles) with good to excellent yields and high regioselectivity under transition-metal-free conditions. Four new C-C and C-N bonds were effectively formed in a one-pot procedure. Subsequent research on the reaction mechanism indicated that the reaction likely involved the processes of intramolecular cyclization and cascade intermolecular dehydration condensation.

Asymmetric synthesis of tricyclic 6,5,5-fused polycycles by desymmetric Pauson-Khand reaction

A new rhodium(I)-BINAP-catalyzed enantioselective desymmetric Pauson-Khand (PK) reaction of prochiral 1,6-enynes with CO has been developed. Diverse tricyclic 6,5,5-fused bowl type polycycles with three continuous chiral centers were synthesized in...

Access to Polycyclic Indole-3,4-Fused Nine-Membered Ring via Cascade 1,6-Hydride Transfer/Cyclization

A cascade aldimine condensation/1,6-hydride transfer/Mannich-type cyclization of indole-derived phenylenediamine with aldehydes was developed for one-step construction of a polycyclic indole-3,4-fused skeleton. Aldehyde serves as a key to start the whole process, including 1,6-hydride transfer enabled δ-C(sp³)-H activation of the secondary amine. The challenges of construction of medium-sized rings are addressed via hydride transfer chemistry.

4-Aminoindoles as 1,4-bisnucleophiles for diversity-oriented synthesis of tricyclic indoles bearing 3,4-fused seven-membered rings

A straightforward access to tricyclic indoles bearing 3,4-fused seven-membered rings was established by using 4-aminoindoles as 1,4-bisnucleophiles in three-component reactions.