Synthesis of Chiral 3H‐pyrrolo[1,2‐a]indoles via Organocatalytic Enantioselective Addition of Alkynyl Biphenyl Quinone Methides

Abstract An organocatalytic enantioselective reaction utilizing α‐[4‐(4‐hydroxyphenyl)phenyl]propargyl alcohols and 3‐substituted indoles has been successfully established for the synthesis of chiral 3 H ‐pyrrolo[1,2‐ a ]indoles. Through the assistance of an appropriate chiral phosphoric acid, a cascade sequence is facilitated, beginning with the dehydration of α‐[4‐(4‐hydroxyphenyl)phenyl]propargyl alcohols to form alkynyl 4,4’‐biphenyl quinone methides ( 4,4’‐BQMs ). Subsequently, 1,12‐addition of 3 H ‐pyrrolo[1,2‐ a ]indoles to these alkynyl 4,4’‐BQMs results in the formation of allenes, which are then protonated and regenerate 4,4’‐BQMs . Finally, an enantioselective intramolecular annulation of 4,4’‐BQMs occurs smoothly, leading to the production of a range of 3 H ‐pyrrolo[1,2‐ a ]indoles with high efficiency and asymmetric induction.