Distinctive Features of 3‐Acetyl‐ and 3‐Benzoyl‐Isocoumarins’ Interaction with Active Primary Amines

Abstract

Isoquinolones and isoquinolines are crucial natural and synthetic heterocyclic compounds exhibiting a range of biological activities. A less explored strategy for the recyclization of isocoumarins to isoquinolones involves the transformation of 1H‐isochromen‐1‐ones with a carbonyl group at position 3 using primary amines. This study presents a straightforward one‐pot protocol for the recyclization of 3‐acetyl‐ and 3‐benzoylisocoumarins into their corresponding isoquinolone derivatives using structurally diverse primary amines. This provides versatile and scalable routes for accessing a variety of 2‐R‐isoquinolin‐1(2H)‐ones. Interestingly, the acyl group also reacted with the hydroxyl group of 2‐aminoethanol, leading to the simultaneous formation of 3,4‐dihydro[1,4]oxazino[4,3‐b]isoquinolin‐6(1H)‐ones alongside lactone recyclization. Moreover, the recyclization process was accompanied by more complex alternative cyclizations, including an oxidative‐reductive stage. For instance, the recyclization of isocoumarins with benzylamine resulted in the formation of isochromeno[3,4‐c]pyrroles, whereas with glycine derivatives, 1,2‐dihydro‐6H‐pyrazino[1,2‐b]isoquinolin‐3,6(4H)‐diones were obtained.