One‐pot Synthesis of Isoquinoline‐Fused Isoquinolines via Intramolecular Hydroamination/Aza‐Claisen Type Rearrangement Cascade

A one‐pot, two‐step synthesis of isoquinoline‐fused isoquinolines from α‐amino acid esters and 2‐alkynyl benzaldehydes are reported. The strategy comprises an unconventional Pictet‐Spengler reaction between α‐amino acid esters and 2‐alkynyl benzaldehydes to give isoquinoline intermediates. Subsequent gold‐catalyzed intramolecular hydroamination furnishes isoquinoline‐fused isoquinolines. The scope of this strategy is further extended to prepare multisubstituted isoquinoline‐fused isoquinolines via subjecting the N‐allylated isoquinoline intermediates to gold‐catalyzed intramolecular hydroamination followed by aza‐Claisen type rearrangement.