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. (Figure presented.).